Magnetized Target Fusion Driven by Plasma Liners

NASA Technical Reports Server (NTRS)

Thio, Y. C. Francis; Kirkpatrick, Ronald C.; Knapp, Charles E.; Rodgers, Stephen L. (Technical Monitor)

2002-01-01

Magnetized target fusion is an emerging, relatively unexplored approach to fusion for electrical power and propulsion application. The physical principles of the concept are founded upon both inertial confinement fusion (ICF) and magnetic confinement fusion (MCF). It attempts to combine the favorable attributes of both these orthogonal approaches to fusion, but at the same time, avoiding the extreme technical challenges of both by exploiting a fusion regime intermediate between them. It uses a material liner to compress, heat and contain the fusion reacting plasma (the target plasma) mentally. By doing so, the fusion burn could be made to occur at plasma densities as high as six orders of magnitude higher than conventional MCF such as tokamak, thus leading to an approximately three orders of magnitude reduction in the plasma energy required for ignition. It also uses a transient magnetic field, compressed to extremely high intensity (100's T to 1000T) in the target plasma, to slow down the heat transport to the liner and to increase the energy deposition of charged-particle fusion products. This has several compounding beneficial effects. It leads to longer energy confinement time compared with conventional ICF without magnetized target, and thus permits the use of much lower plasma density to produce reasonable burn-up fraction. The compounding effects of lower plasma density and the magneto-insulation of the target lead to greatly reduced compressional heating power on the target. The increased energy deposition rate of charged-particle fusion products also helps to lower the energy threshold required for ignition and increasing the burn-up fraction. The reduction in ignition energy and the compressional power compound to lead to reduced system size, mass and R&D cost. It is a fusion approach that has an affordable R&D pathway, and appears attractive for propulsion application in the nearer term.

Development and characterization of plasma targets for controlled injection of electrons into laser-driven wakefields

NASA Astrophysics Data System (ADS)

Kleinwaechter, Tobias; Goldberg, Lars; Palmer, Charlotte; Schaper, Lucas; Schwinkendorf, Jan-Patrick; Osterhoff, Jens

2012-10-01

Laser-driven wakefield acceleration within capillary discharge waveguides has been used to generate high-quality electron bunches with GeV-scale energies. However, owing to fluctuations in laser and plasma conditions in combination with a difficult to control self-injection mechanism in the non-linear wakefield regime these bunches are often not reproducible and can feature large energy spreads. Specialized plasma targets with tailored density profiles offer the possibility to overcome these issues by controlling the injection and acceleration processes. This requires precise manipulation of the longitudinal density profile. Therefore our target concept is based on a capillary structure with multiple gas in- and outlets. Potential target designs are simulated using the fluid code OpenFOAM and those meeting the specified criteria are fabricated using femtosecond-laser machining of structures into sapphire plates. Density profiles are measured over a range of inlet pressures utilizing gas-density profilometry via Raman scattering and pressure calibration with longitudinal interferometry. In combination these allow absolute density mapping. Here we report the preliminary results.

Development And Characterization Of A Liner-On-Target Injector For Staged Z-Pinch Experiments

NASA Astrophysics Data System (ADS)

Valenzuela, J. C.; Conti, F.; Krasheninnikov, I.; Narkis, J.; Beg, F.; Wessel, F. J.; Rahman, H. U.

2016-10-01

We present the design and optimization of a liner-on-target injector for Staged Z-pinch experiments. The injector is composed of an annular high atomic number (e.g. Ar, Kr) gas-puff and an on-axis plasma gun that delivers the ionized deuterium target. The liner nozzle injector has been carefully studied using Computational Fluid Dynamics (CFD) simulations to produce a highly collimated 1 cm radius gas profile that satisfies the theoretical requirement for best performance on the 1 MA Zebra current driver. The CFD simulations produce density profiles as a function of the nozzle shape and gas. These profiles are initialized in the MHD MACH2 code to find the optimal liner density for a stable, uniform implosion. We use a simple Snowplow model to study the plasma sheath acceleration in a coaxial plasma gun to help us properly design the target injector. We have performed line-integrated density measurements using a CW He-Ne laser to characterize the liner gas and the plasma gun density as a function of time. The measurements are compared with models and calculations and benchmarked accordingly. Advanced Research Projects Agency - Energy, DE-AR0000569.

Distribution of Fe atom density in a dc magnetron sputtering plasma source measured by laser-induced fluorescence imaging spectroscopy

NASA Astrophysics Data System (ADS)

Shibagaki, K.; Nafarizal, N.; Sasaki, K.; Toyoda, H.; Iwata, S.; Kato, T.; Tsunashima, S.; Sugai, H.

2003-10-01

Magnetron sputtering discharge is widely used as an efficient method for thin film fabrication. In order to achieve the optimized fabrication, understanding of the kinetics in plasmas is essential. In the present work, we measured the density distribution of sputtered Fe atoms using laser-induced fluorescence imaging spectroscopy. A dc magnetron plasma source with a Fe target was used. An area of 20 × 2 mm in front of the target was irradiated by a tunable laser beam having a planar shape. The picture of laser-induced fluorescence on the laser beam was taken using an ICCD camera. In this way, we obtained the two-dimensional image of the Fe atom density. As a result, it has been found that the Fe atom density observed at a distance of several centimeters from the target is higher than that adjacent to the target, when the Ar gas pressure was relatively high. It is suggested from this result that some gas-phase production processes of Fe atoms are available in the plasma. This work has been performed under the 21st Century COE Program by the Ministry of Education, Culture, Sports, Science and Technology in Japan.

Density and temperature characterization of long-scale length, near-critical density controlled plasma produced from ultra-low density plastic foam

PubMed Central

Chen, S. N.; Iwawaki, T.; Morita, K.; Antici, P.; Baton, S. D.; Filippi, F.; Habara, H.; Nakatsutsumi, M.; Nicolaï , P.; Nazarov, W.; Rousseaux, C.; Starodubstev, M.; Tanaka, K. A.; Fuchs, J.

2016-01-01

The ability to produce long-scale length (i.e. millimeter scale-length), homogeneous plasmas is of interest in studying a wide range of fundamental plasma processes. We present here a validated experimental platform to create and diagnose uniform plasmas with a density close or above the critical density. The target consists of a polyimide tube filled with an ultra low-density plastic foam where it was heated by x-rays, produced by a long pulse laser irradiating a copper foil placed at one end of the tube. The density and temperature of the ionized foam was retrieved by using x-ray radiography and proton radiography was used to verify the uniformity of the plasma. Plasma temperatures of 5–10 eV and densities around 1021 cm−3 are measured. This well-characterized platform of uniform density and temperature plasma is of interest for experiments using large-scale laser platforms conducting High Energy Density Physics investigations. PMID:26923471

Plasma block acceleration based upon the interaction between double targets and an ultra-intense linearly polarized laser pulse

NASA Astrophysics Data System (ADS)

Xu, Yanxia; Wang, Jiaxiang; Hora, Heinrich; Qi, Xin; Xing, Yifan; Yang, Lei; Zhu, Wenjun

2018-04-01

A new scheme of plasma block acceleration based upon the interaction between double targets and an ultra-intense linearly polarized laser pulse with intensity I ˜ 1022 W/cm2 is investigated via two-dimensional particle-in-cell simulations. The targets are composed of a pre-target of low-density aluminium plasma and an overdense main-target of hydrogen plasma. Through intensive parameter optimization, we have observed highly efficient plasma block accelerations with a monochromatic proton beam peaked at GeVs. The underlying mechanism is attributed to the enhancement of the charge separation field due to the properly selected pre-target.

Developing the science and technology for the Material Plasma Exposure eXperiment

NASA Astrophysics Data System (ADS)

Rapp, J.; Biewer, T. M.; Bigelow, T. S.; Caneses, J. F.; Caughman, J. B. O.; Diem, S. J.; Goulding, R. H.; Isler, R. C.; Lumsdaine, A.; Beers, C. J.; Bjorholm, T.; Bradley, C.; Canik, J. M.; Donovan, D.; Duckworth, R. C.; Ellis, R. J.; Graves, V.; Giuliano, D.; Green, D. L.; Hillis, D. L.; Howard, R. H.; Kafle, N.; Katoh, Y.; Lasa, A.; Lessard, T.; Martin, E. H.; Meitner, S. J.; Luo, G.-N.; McGinnis, W. D.; Owen, L. W.; Ray, H. B.; Shaw, G. C.; Showers, M.; Varma, V.; the MPEX Team

2017-11-01

Linear plasma generators are cost effective facilities to simulate divertor plasma conditions of present and future fusion reactors. They are used to address important R&D gaps in the science of plasma material interactions and towards viable plasma facing components for fusion reactors. Next generation plasma generators have to be able to access the plasma conditions expected on the divertor targets in ITER and future devices. The steady-state linear plasma device MPEX will address this regime with electron temperatures of 1-10 eV and electron densities of 1021{\\text{}}-1020 m-3 . The resulting heat fluxes are about 10 MW m-2 . MPEX is designed to deliver those plasma conditions with a novel Radio Frequency plasma source able to produce high density plasmas and heat electron and ions separately with electron Bernstein wave (EBW) heating and ion cyclotron resonance heating with a total installed power of 800 kW. The linear device Proto-MPEX, forerunner of MPEX consisting of 12 water-cooled copper coils, has been operational since May 2014. Its helicon antenna (100 kW, 13.56 MHz) and EC heating systems (200 kW, 28 GHz) have been commissioned and 14 MW m-2 was delivered on target. Furthermore, electron temperatures of about 20 eV have been achieved in combined helicon and ECH heating schemes at low electron densities. Overdense heating with EBW was achieved at low heating powers. The operational space of the density production by the helicon antenna was pushed up to 1.1 × 1020 m-3 at high magnetic fields of 1.0 T at the target. The experimental results from Proto-MPEX will be used for code validation to enable predictions of the source and heating performance for MPEX. MPEX, in its last phase, will be capable to expose neutron-irradiated samples. In this concept, targets will be irradiated in ORNL’s High Flux Isotope Reactor and then subsequently exposed to fusion reactor relevant plasmas in MPEX.

Experimental design to generate strong shear layers in a high-energy-density plasma

NASA Astrophysics Data System (ADS)

Harding, E. C.; Drake, R. P.; Aglitskiy, Y.; Gillespie, R. S.; Grosskopf, M. J.; Weaver, J. L.; Velikovich, A. L.; Visco, A.; Ditmar, J. R.

2010-06-01

The development of a new experimental system for generating a strong shear flow in a high-energy-density plasma is described in detail. The targets were designed with the goal of producing a diagnosable Kelvin-Helmholtz (KH) instability, which plays an important role in the transition turbulence but remains relatively unexplored in the high-energy-density regime. To generate the shear flow the Nike laser was used to drive a flow of Al plasma over a low-density foam surface with an initial perturbation. The interaction of the Al and foam was captured with a spherical crystal imager using 1.86 keV X-rays. The selection of the individual targets components is discussed and results are presented.

RF Sputtering for preparing substantially pure amorphous silicon monohydride

DOEpatents

Jeffrey, Frank R.; Shanks, Howard R.

1982-10-12

A process for controlling the dihydride and monohydride bond densities in hydrogenated amorphous silicon produced by reactive rf sputtering of an amorphous silicon target. There is provided a chamber with an amorphous silicon target and a substrate therein with the substrate and the target positioned such that when rf power is applied to the target the substrate is in contact with the sputtering plasma produced thereby. Hydrogen and argon are fed to the chamber and the pressure is reduced in the chamber to a value sufficient to maintain a sputtering plasma therein, and then rf power is applied to the silicon target to provide a power density in the range of from about 7 watts per square inch to about 22 watts per square inch to sputter an amorphous silicon hydride onto the substrate, the dihydride bond density decreasing with an increase in the rf power density. Substantially pure monohydride films may be produced.

Absorption of the laser radiation by the laser plasma with gas microjet targets

NASA Astrophysics Data System (ADS)

Borisevichus, D. A.; Zabrodskii, V. V.; Kalmykov, S. G.; Sasin, M. E.; Seisyan, R. P.

2017-01-01

An upper limit of absorption of the laser radiation in the plasma produced in a gas jet Xe target with the average density of (3-6) × 1018 cm-3 and the effective diameter of 0.7 mm is found. It is equal to ≈50% and remains constant under any variation in this range of densities. This result contradicts both theoretical assessments that have predicted virtually complete absorption and results of earlier experiments with the laser spark in an unlimited stationary Xe gas with the same density, where the upper limit of absorption was close to 100%. An analysis shows that nonlinearity of absorption and plasma nonequilibrium lead to the reduction of the absorption coefficient that, along with the limited size of plasma, can explain the experimental results.

RF sputtering for controlling dihydride and monohydride bond densities in amorphous silicon hydride

DOEpatents

Jeffery, F.R.; Shanks, H.R.

1980-08-26

A process is described for controlling the dihydride and monohydride bond densities in hydrogenated amorphous silicone produced by reactive rf sputtering of an amorphous silicon target. There is provided a chamber with an amorphous silicon target and a substrate therein with the substrate and the target positioned such that when rf power is applied to the target the substrate is in contact with the sputtering plasma produced thereby. Hydrogen and argon are fed to the chamber and the pressure is reduced in the chamber to a value sufficient to maintain a sputtering plasma therein, and then rf power is applied to the silicon target to provide a power density in the range of from about 7 watts per square inch to about 22 watts per square inch to sputter an amorphous solicone hydride onto the substrate, the dihydride bond density decreasing with an increase in the rf power density. Substantially pure monohydride films may be produced.

Experimental investigation of adiabatic compression and heating using collision of an MHD-driven jet with a gas target cloud for magnetized target fusion

NASA Astrophysics Data System (ADS)

Seo, Byonghoon; Li, Hui; Bellan, Paul

2017-10-01

We are studying magnetized target fusion using an experimental method where an imploding liner compressing a plasma is simulated by a high-speed MHD-driven plasma jet colliding with a gas target cloud. This has the advantage of being non-destructive so orders of magnitude more shots are possible. Since the actual density and temperature are much more modest than fusion-relevant values, the goal is to determine the scaling of the increase in density and temperature when an actual experimental plasma is adiabatically compressed. Two new-developed diagnostics are operating and providing data. The first new diagnostic is a fiber-coupled interferometer which measures line-integrated electron density not only as a function of time, but also as a function of position along the jet. The second new diagnostic is laser Thomson scattering which measures electron density and temperature at the location where the jet collides with the cloud. These diagnostics show that when the jet collides with a target cloud the jet slows down substantially and both the electron density and temperature increase. The experimental measurements are being compared with 3D MHD and hybrid kinetic numerical simulations that model the actual experimental geometry.

Magnetized Target Fusion Driven by Plasma Liners

NASA Technical Reports Server (NTRS)

Thio, Y. C. Francis; Eskridge, Richard; Smith, James; Lee, Michael; Richeson, Jeff; Schmidt, George; Knapp, Charles E.; Kirkpatrick, Ronald C.; Turchi, Peter J.; Rodgers, Stephen L. (Technical Monitor)

2001-01-01

Magnetized target fusion (MTF) attempts to combine the favorable attributes of magnetic confinement fusion (MCF) for energy confinement with the attributes of inertial confinement fusion (ICF) for efficient compression heating and wall-free containment of the fusing plasma. It uses a material liner to compress and contain a magnetized plasma. For practical applications, standoff drivers to deliver the imploding momentum flux to the target plasma remotely are required. Spherically converging plasma jets have been proposed as standoff drivers for this purpose. The concept involves the dynamic formation of a spherical plasma liner by the merging of plasma jets, and the use of the liner so formed to compress a spheromak or a field reversed configuration (FRC). For the successful implementation of the scheme, plasma jets of the requisite momentum flux density need to be produced. Their transport over sufficiently large distances (a few meters) needs to be assured. When they collide and merge into a liner, relative differences in velocity, density and temperature of the jets could give rise to instabilities in the development of the liner. Variation in the jet properties must be controlled to ensure that the growth rate of the instabilities are not significant over the time scale of the liner formation before engaging with the target plasma. On impact with the target plasma, some plasma interpenetration might occur between the liner and the target. The operating parameter space needs to be identified to ensure that a reasonably robust and conducting contact surface is formed between the liner and the target. A mismatch in the "impedance" between the liner and the target plasma could give rise to undesirable shock heating of the liner leading to increased entropy (thermal losses) in the liner. Any irregularities in the liner will accentuate the Rayleigh-Taylor instabilities during the compression of the target plasma by the liner.

Time-Space Position of Warm Dense Matter in Laser Plasma Interaction Process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, L F; Uschmann, I; Forster, E

2006-09-25

Laser plasma interaction experiments have been perform performed using an fs Titanium Sapphire laser. Plasmas have been generated from planar PMMA targets using single laser pulses with 3.3 mJ pulse energy, 50 fs pulse duration at 800 nm wavelength. Electron density distributions of the plasmas in different delay times have been characterized by means of Nomarski Interferometry. Experimental data were cautiously compared with relevant 1D numerical simulation. Finally these results provide a first experience of searching for the time-space position of the so-called warm dense plasma in an ultra fast laser target interaction process. These experiments aim to prepare nearmore » solid-density plasmas for Thomson scattering experiments using the short wavelength free-electron laser FLASH, DESY Hamburg.« less

Injector design for liner-on-target gas-puff experiments

NASA Astrophysics Data System (ADS)

Valenzuela, J. C.; Krasheninnikov, I.; Conti, F.; Wessel, F.; Fadeev, V.; Narkis, J.; Ross, M. P.; Rahman, H. U.; Ruskov, E.; Beg, F. N.

2017-11-01

We present the design of a gas-puff injector for liner-on-target experiments. The injector is composed of an annular high atomic number (e.g., Ar and Kr) gas and an on-axis plasma gun that delivers an ionized deuterium target. The annular supersonic nozzle injector has been studied using Computational Fluid Dynamics (CFD) simulations to produce a highly collimated (M > 5), ˜1 cm radius gas profile that satisfies the theoretical requirement for best performance on ˜1-MA current generators. The CFD simulations allowed us to study output density profiles as a function of the nozzle shape, gas pressure, and gas composition. We have performed line-integrated density measurements using a continuous wave (CW) He-Ne laser to characterize the liner gas density. The measurements agree well with the CFD values. We have used a simple snowplow model to study the plasma sheath acceleration in a coaxial plasma gun to help us properly design the target injector.

Injector design for liner-on-target gas-puff experiments.

PubMed

Valenzuela, J C; Krasheninnikov, I; Conti, F; Wessel, F; Fadeev, V; Narkis, J; Ross, M P; Rahman, H U; Ruskov, E; Beg, F N

2017-11-01

We present the design of a gas-puff injector for liner-on-target experiments. The injector is composed of an annular high atomic number (e.g., Ar and Kr) gas and an on-axis plasma gun that delivers an ionized deuterium target. The annular supersonic nozzle injector has been studied using Computational Fluid Dynamics (CFD) simulations to produce a highly collimated (M > 5), ∼1 cm radius gas profile that satisfies the theoretical requirement for best performance on ∼1-MA current generators. The CFD simulations allowed us to study output density profiles as a function of the nozzle shape, gas pressure, and gas composition. We have performed line-integrated density measurements using a continuous wave (CW) He-Ne laser to characterize the liner gas density. The measurements agree well with the CFD values. We have used a simple snowplow model to study the plasma sheath acceleration in a coaxial plasma gun to help us properly design the target injector.

Measurement of Two-Plasmon-Decay Dependence on Plasma Density Scale Length

NASA Astrophysics Data System (ADS)

Haberberger, D.

2013-10-01

An accurate understanding of the plasma scale-length (Lq) conditions near quarter-critical density is important in quantifying the hot electrons generated by the two-plasmon-decay (TPD) instability in long-scale-length plasmas. A novel target platform was developed to vary the density scale length and an innovative diagnostic was implemented to measure the density profiles above 1021 cm-3 where TPD is expected to have the largest growth. A series of experiments was performed using the four UV (351-nm) beams on OMEGA EP that varied the Lq by changing the radius of curvature of the target while maintaining a constant Iq/Tq. The fraction of laser energy converted to hot electrons (fhot) was observed to increase rapidly from 0.005% to 1% by increasing the plasma scale length from 130 μm to 300 μm, corresponding to target diameters of 0.4 mm to 8 mm. A new diagnostic was developed based on refractometry using angular spectral filters to overcome the large phase accumulation in standard interferometric techniques. The angular filter refractometer measures the refraction angles of a 10-ps, 263-nm probe laser after propagating through the plasma. An angular spectral filter is used in the Fourier plane of the probe beam, where the refractive angles of the rays are mapped to space. The edges of the filter are present in the image plane and represent contours of constant refraction angle. These contours are used to infer the phase of the probe beam, which are used to calculate the plasma density profile. In long-scale-length plasmas, the diagnostic currently measures plasma densities from ~1019 cm-3 to ~2 × 1021 cm-3. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944. In collaboration with D. H. Edgell, S. X. Hu, S. Ivancic, R. Boni, C. Dorrer, and D. H. Froula (Laboratory for Laser Energetics, U. of Rochester).

LPWA using supersonic gas jet with tailored density profile

NASA Astrophysics Data System (ADS)

Kononenko, O.; Bohlen, S.; Dale, J.; D'Arcy, R.; Dinter, M.; Erbe, J. H.; Indorf, G.; di Lucchio, L.; Goldberg, L.; Gruse, J. N.; Karstensen, S.; Libov, V.; Ludwig, K.; Martinez de La Ossa, A.; Marutzky, F.; Niroula, A.; Osterhoff, J.; Quast, M.; Schaper, L.; Schwinkendorf, J.-P.; Streeter, M.; Tauscher, G.; Weichert, S.; Palmer, C.; Horbatiuk, Taras

2016-10-01

Laser driven plasma wakefield accelerators have been explored as a potential compact, reproducible source of relativistic electron bunches, utilising an electric field of many GV/m. Control over injection of electrons into the wakefield is of crucial importance in producing stable, mono-energetic electron bunches. Density tailoring of the target, to control the acceleration process, can also be used to improve the quality of the bunch. By using gas jets to provide tailored targets it is possible to provide good access for plasma diagnostics while also producing sharp density gradients for density down-ramp injection. OpenFOAM hydrodynamic simulations were used to investigate the possibility of producing tailored density targets in a supersonic gas jet. Particle-in-cell simulations of the resulting density profiles modelled the effect of the tailored density on the properties of the accelerated electron bunch. Here, we present the simulation results together with preliminary experimental measurements of electron and x-ray properties from LPWA experiments using gas jet targets and a 25 TW, 25 fs Ti:Sa laser system at DESY.

Electron density measurement in gas discharge plasmas by optical and acoustic methods

NASA Astrophysics Data System (ADS)

Biagioni, A.; Anania, M. P.; Bellaveglia, M.; Chiadroni, E.; Cianchi, A.; Di Giovenale, D.; Di Pirro, G.; Ferrario, M.; Filippi, F.; Mostacci, A.; Pompili, R.; Shpakov, V.; Vaccarezza, C.; Villa, F.; Zigler, A.

2016-08-01

Plasma density represents a very important parameter for both laser wakefield and plasma wakefield acceleration, which use a gas-filled capillary plasma source. Several techniques can be used to measure the plasma density within a capillary discharge, which are mainly based on optical diagnostic methods, as for example the well-known spectroscopic method using the Stark broadening effect. In this work, we introduce a preliminary study on an alternative way to detect the plasma density, based on the shock waves produced by gas discharge in a capillary. Firstly, the measurements of the acoustic spectral content relative to the laser-induced plasmas by a solid target allowed us to understand the main properties of the acoustic waves produced during this kind of plasma generation; afterwards, we have extended such acoustic technique to the capillary plasma source in order to calibrate it by comparison with the stark broadening method.

High-energy-density plasma jet generated by laser-cone interaction

NASA Astrophysics Data System (ADS)

Ke, Y. Z.; Yang, X. H.; Ma, Y. Y.; Xu, B. B.; Ge, Z. Y.; Gan, L. F.; Meng, L.; Wang, S. W.; Kawata, S.

2018-04-01

The generation of high-energy-density (HED) plasma jet from a laser ablating thin cone target is studied theoretically and by numerical simulations. Theoretical analysis and 1D simulations show that a maximum kinetic energy conversion efficiency (CE) of 26% can be achieved when nearly 80% of the foil is ablated by laser. A HED plasma jet is generated when an intense laser (˜1015 W/cm2) irradiates the cone target, inducing a great enhancement of energy density compared to that of the planar target, which is attributed to the cumulative effect of the cone shape and the new generation mechanism of jet, i.e., laser directly accelerating the cone wall onto the axis. The characteristic of jet is influenced by the cone geometry, i.e., thickness and cone angle. It is found that a cone with a half opening angle around 70 ° and the optimized thickness (˜5 μm) can induce a jet with a high CE and long duration, whose peak energy density can reach 3.5 × 1015 erg/cm3. The results can be beneficial for laser-driven novel neutron sources and other fusion related experiments, where HED plasma jet can be applied.

Developing the science and technology for the Material Plasma Exposure eXperiment

DOE PAGES

Rapp, J.; Biewer, T. M.; Bigelow, T. S.; ...

2017-07-27

Linear plasma generators are cost effective facilities to simulate divertor plasma conditions of present and future fusion reactors. They are used to address important R&D gaps in the science of plasma material interactions and towards viable plasma facing components for fusion reactors. Next generation plasma generators have to be able to access the plasma conditions expected on the divertor targets in ITER and future devices. The steady-state linear plasma device MPEX will address this regime with electron temperatures of 1–10 eV and electron densities ofmore » $$10^{21}{\\text{}}\\!-\\!10^{20}$$ $${\\rm m}^{-3}$$. The resulting heat fluxes are about 10 MW $${\\rm m}^{-2}$$ . MPEX is designed to deliver those plasma conditions with a novel Radio Frequency plasma source able to produce high density plasmas and heat electron and ions separately with electron Bernstein wave (EBW) heating and ion cyclotron resonance heating with a total installed power of 800 kW. The linear device Proto-MPEX, forerunner of MPEX consisting of 12 water-cooled copper coils, has been operational since May 2014. Its helicon antenna (100 kW, 13.56 MHz) and EC heating systems (200 kW, 28 GHz) have been commissioned and 14 MW $${\\rm m}^{-2}$$ was delivered on target. Furthermore, electron temperatures of about 20 eV have been achieved in combined helicon and ECH heating schemes at low electron densities. Overdense heating with EBW was achieved at low heating powers. The operational space of the density production by the helicon antenna was pushed up to $$1.1 \\times 10^{20}$$ $${\\rm m}^{-3}$$ at high magnetic fields of 1.0 T at the target. Finally, the experimental results from Proto-MPEX will be used for code validation to enable predictions of the source and heating performance for MPEX. MPEX, in its last phase, will be capable to expose neutron-irradiated samples. In this concept, targets will be irradiated in ORNL's High Flux Isotope Reactor and then subsequently exposed to fusion reactor relevant plasmas in MPEX.« less

Developing the science and technology for the Material Plasma Exposure eXperiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rapp, J.; Biewer, T. M.; Bigelow, T. S.

Linear plasma generators are cost effective facilities to simulate divertor plasma conditions of present and future fusion reactors. They are used to address important R&D gaps in the science of plasma material interactions and towards viable plasma facing components for fusion reactors. Next generation plasma generators have to be able to access the plasma conditions expected on the divertor targets in ITER and future devices. The steady-state linear plasma device MPEX will address this regime with electron temperatures of 1–10 eV and electron densities ofmore » $$10^{21}{\\text{}}\\!-\\!10^{20}$$ $${\\rm m}^{-3}$$. The resulting heat fluxes are about 10 MW $${\\rm m}^{-2}$$ . MPEX is designed to deliver those plasma conditions with a novel Radio Frequency plasma source able to produce high density plasmas and heat electron and ions separately with electron Bernstein wave (EBW) heating and ion cyclotron resonance heating with a total installed power of 800 kW. The linear device Proto-MPEX, forerunner of MPEX consisting of 12 water-cooled copper coils, has been operational since May 2014. Its helicon antenna (100 kW, 13.56 MHz) and EC heating systems (200 kW, 28 GHz) have been commissioned and 14 MW $${\\rm m}^{-2}$$ was delivered on target. Furthermore, electron temperatures of about 20 eV have been achieved in combined helicon and ECH heating schemes at low electron densities. Overdense heating with EBW was achieved at low heating powers. The operational space of the density production by the helicon antenna was pushed up to $$1.1 \\times 10^{20}$$ $${\\rm m}^{-3}$$ at high magnetic fields of 1.0 T at the target. Finally, the experimental results from Proto-MPEX will be used for code validation to enable predictions of the source and heating performance for MPEX. MPEX, in its last phase, will be capable to expose neutron-irradiated samples. In this concept, targets will be irradiated in ORNL's High Flux Isotope Reactor and then subsequently exposed to fusion reactor relevant plasmas in MPEX.« less

Direct measurements of anode/cathode gap plasma in cylindrically imploding loads on the Z machine

NASA Astrophysics Data System (ADS)

Porwitzky, A.; Dolan, D. H.; Martin, M. R.; Laity, G.; Lemke, R. W.; Mattsson, T. R.

2018-06-01

By deploying a photon Doppler velocimetry based plasma diagnostic, we have directly observed low density plasma in the load anode/cathode gap of cylindrically converging pulsed power targets. The arrival of this plasma is temporally correlated with gross current loss and subtle power flow differences between the anode and the cathode. The density is in the range where Hall terms in the electromagnetic equations are relevant, but this physics is lacking in the magnetohydrodynamics codes commonly used to design, analyze, and optimize pulsed power experiments. The present work presents evidence of the importance of physics beyond traditional resistive magnetohydrodynamics for the design of pulsed power targets and drivers.

Computational modeling of joint U.S.-Russian experiments relevant to magnetic compression/magnetized target fusion (MAGO/MTF)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheehey, P.T.; Faehl, R.J.; Kirkpatrick, R.C.

1997-12-31

Magnetized Target Fusion (MTF) experiments, in which a preheated and magnetized target plasma is hydrodynamically compressed to fusion conditions, present some challenging computational modeling problems. Recently, joint experiments relevant to MTF (Russian acronym MAGO, for Magnitnoye Obzhatiye, or magnetic compression) have been performed by Los Alamos National Laboratory and the All-Russian Scientific Research Institute of Experimental Physics (VNIIEF). Modeling of target plasmas must accurately predict plasma densities, temperatures, fields, and lifetime; dense plasma interactions with wall materials must be characterized. Modeling of magnetically driven imploding solid liners, for compression of target plasmas, must address issues such as Rayleigh-Taylor instability growthmore » in the presence of material strength, and glide plane-liner interactions. Proposed experiments involving liner-on-plasma compressions to fusion conditions will require integrated target plasma and liner calculations. Detailed comparison of the modeling results with experiment will be presented.« less

Neutron yield when fast deuterium ions collide with strongly charged tritium-saturated dust particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akishev, Yu. S., E-mail: akishev@triniti.ru; Karal’nik, V. B.; Petryakov, A. V.

2017-02-15

The ultrahigh charging of dust particles in a plasma under exposure to an electron beam with an energy up to 25 keV and the formation of a flux of fast ions coming from the plasma and accelerating in the strong field of negatively charged particles are considered. Particles containing tritium or deuterium atoms are considered as targets. The calculated rates of thermonuclear fusion reactions in strongly charged particles under exposure to accelerated plasma ions are presented. The neutron generation rate in reactions with accelerated deuterium and tritium ions has been calculated for these targets. The neutron yield has been calculatedmore » when varying the plasma-forming gas pressure, the plasma density, the target diameter, and the beam electron current density. Deuterium and tritium-containing particles are shown to be the most promising plasmaforming gas–target material pair for the creation of a compact gas-discharge neutron source based on the ultrahigh charging of dust particles by beam electrons with an energy up to 25 keV.« less

Sn ion energy distributions of ns- and ps-laser produced plasmas

NASA Astrophysics Data System (ADS)

Bayerle, A.; Deuzeman, M. J.; van der Heijden, S.; Kurilovich, D.; de Faria Pinto, T.; Stodolna, A.; Witte, S.; Eikema, K. S. E.; Ubachs, W.; Hoekstra, R.; Versolato, O. O.

2018-04-01

Ion energy distributions arising from laser-produced plasmas of Sn are measured over a wide laser parameter space. Planar-solid and liquid-droplet targets are exposed to infrared laser pulses with energy densities between 1 J cm‑2 and 4 kJ cm‑2 and durations spanning 0.5 ps to 6 ns. The measured ion energy distributions are compared to two self-similar solutions of a hydrodynamic approach assuming isothermal expansion of the plasma plume into vacuum. For planar and droplet targets exposed to ps-long pulses, we find good agreement between the experimental results and the self-similar solution of a semi-infinite simple planar plasma configuration with an exponential density profile. The ion energy distributions resulting from solid Sn exposed to ns-pulses agrees with solutions of a limited-mass model that assumes a Gaussian-shaped initial density profile.

Improved Characteristics of Laser Source of Ions Using a Frequency Mode Laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khaydarov, R. T.

2008-04-07

We used a mass-spectrometric method to investigate the characteristics of laser-produced plasma ions depending on the nature of the target and on the parameters of the laser radiation. Experiments are carried out on porous Y{sub 2}O{sub 3} targets with different densities {rho}, subjected to a laser radiation, where the laser works in a frequency mode (v = l-12 Hz). We found that the laser frequency has a significant effect on the parameters of plasma ions: with increasing the frequency of the laser the charge, energy and intensity of ions increase for a given parameters of the target. This effect ismore » more pronounced for small densities of the target. We related these two effects to a non-linear ionization process in the plasma due to the formation of dense plasma volume inside the sample absorbing the laser radiation and to the change of the focusing conditions in the case of the frequency mode laser.« less

An innovative small angle slot divertor concept for long pulse advanced tokamaks

NASA Astrophysics Data System (ADS)

Guo, Houyang

2017-10-01

A new Small Angle Slot (SAS) divertor is being developed in DIII-D to address the challenge of efficient divertor heat dispersal at the relatively low plasma density required for non-inductive current drive in future advanced tokamaks. SAS features a small incident angle near the plasma strike point on the divertor target plate with a progressively opening slot. SOLPS (B2-Eirene) edge code analysis finds that SAS can achieve strong plasma cooling when the strike point is placed near the small angle target plate in the slot, leading to low electron temperature Te across the entire divertor target. This is enabled by strong coupling between a gas tight slot and directed neutral recycling by the small angle target to enhance neutral buildup near the target. SOLPS analysis reveals a strong correlation between Te and D2 density at the target for various divertor configurations including the flat target, slanted target, and lower single null divertor. The strong correlation suggests that achievement of low Te may reduce essentially to identifying the divertor baffle geometry that achieves the highest target gas density at a given upstream condition. The SAS divertor concept has recently been tested in DIII-D for a range of plasma configurations and conditions with precise control of slot strike point location. In confirmation of SOLPS predictions, a sharp transition is observed when the strike point is moved to the critical outer corner of SAS. A set of Langmuir probes imbedded in SAS show that the Te radial profile, which is peaked at the strike point when it is located away from the SAS corner, becomes low across the target when the strike point is located near the corner. With further increase in density, deep-slot detachment occurs with Te 1 eV, measured by the unique DIII-D divertor Thomson Scattering diagnostic. Work supported by US DOE under DE-FC02-04ER54698.

Plasma flow measurements in the Prototype-Material Plasma Exposure eXperiment (Proto-MPEX) and comparison with B2.5-Eirene modeling

NASA Astrophysics Data System (ADS)

Kafle, N.; Owen, L. W.; Caneses, J. F.; Biewer, T. M.; Caughman, J. B. O.; Donovan, D. C.; Goulding, R. H.; Rapp, J.

2018-05-01

The Prototype Material Plasma Exposure eXperiment (Proto-MPEX) at Oak Ridge National Laboratory is a linear plasma device that combines a helicon plasma source with additional microwave and radio frequency heating to deliver high plasma heat and particle fluxes to a target. Double Langmuir probes and Thomson scattering are being used to measure local electron temperature and density at various radial and axial locations. A recently constructed Mach-double probe provides the added capability of simultaneously measuring electron temperatures ( T e), electron densities ( n e), and Mach numbers (M). With this diagnostic, it is possible to infer the plasma flow, particle flux, and heat flux at different locations along the plasma column in Proto-MPEX. Preliminary results show Mach numbers of 0.5 (towards the dump plate) and 1.0 (towards the target plate) downstream from the helicon source, and a stagnation point (no flow) near the source for the case where the peak magnetic field was 1.3 T. Measurements of particle flow and ne and Te profiles are discussed. The extensive coverage provided by these diagnostics permits data-constrained B2.5-Eirene modeling of the entire plasma column, and comparison with results of modeling in the high-density helicon plasmas will be presented.

Ion propagation in an aluminum hollow cylinder target laser ion source

NASA Astrophysics Data System (ADS)

Saquilayan, Glynnis Mae Q.; Wada, Motoi

2018-01-01

Experimental results for the laser produced plasma in an aluminum hollow cylinder target are presented. Observing the plasma formation inside the cylinder, a high-speed camera captured the images of the plasma expanding towards the adjacent walls of target. The optical emission spectrum is obtained for the plasma inside the hollow cylinder and positive singly charged aluminum ions and neutrals are identified from emission spectral lines. Time dependent current signals of the Faraday cup displayed an enlarged signal intensity as the laser power density is increased up to 6.5 GW/cm2. Signal arrival times corresponding to fast ions appeared at the onset of the current waveforms when the laser power density exceeded 4.7 GW/cm2. For the mass analysis of plasma, an accelerating electric field was applied to separate the ions and the time-of-flight measurements showed positive ion signals with an identified peak to have an estimated mass of 350 amu.

Extreme plasma states in laser-governed vacuum breakdown.

PubMed

Efimenko, Evgeny S; Bashinov, Aleksei V; Bastrakov, Sergei I; Gonoskov, Arkady A; Muraviev, Alexander A; Meyerov, Iosif B; Kim, Arkady V; Sergeev, Alexander M

2018-02-05

Triggering vacuum breakdown at laser facility is expected to provide rapid electron-positron pair production for studies in laboratory astrophysics and fundamental physics. However, the density of the produced plasma may cease to increase at a relativistic critical density, when the plasma becomes opaque. Here, we identify the opportunity of breaking this limit using optimal beam configuration of petawatt-class lasers. Tightly focused laser fields allow generating plasma in a small focal volume much less than λ 3 and creating extreme plasma states in terms of density and produced currents. These states can be regarded to be a new object of nonlinear plasma physics. Using 3D QED-PIC simulations we demonstrate a possibility of reaching densities over 10 25  cm -3 , which is an order of magnitude higher than expected earlier. Controlling the process via initial target parameters provides an opportunity to reach the discovered plasma states at the upcoming laser facilities.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roy, Amitava; Harilal, Sivanandan S.; Hassan, Syed M.

We investigated the expansion dynamics of laser-produced plasmas expanding into an axial magnetic field. Plasmas were generated by focusing 1.064 µm Nd:YAG laser pulses onto a planar tin target in vacuum and allowed to expand into a 0.5 T magnetic-filed where field lines were aligned along the plume expansion direction. Gated images employing intensified CCD showed focusing of the plasma plume, which were also compared with results obtained using particle-in-cell modelling methods. The estimated density and temperature of the plasma plumes employing emission spectroscopy revealed significant changes in the presence and absence of the 0.5T magnetic field. In the presencemore » of the field, the electron temperature is increased with distance from the target, while the density showed opposite effects.« less

Laser Irradiated Foam Targets: Absorption and Radiative Properties

NASA Astrophysics Data System (ADS)

Salvadori, Martina; Luigi Andreoli, Pier; Cipriani, Mattia; Consoli, Fabrizio; Cristofari, Giuseppe; De Angelis, Riccardo; di Giorgio, Giorgio; Giulietti, Danilo; Ingenito, Francesco; Gus'kov, Sergey Yu.; Rupasov, Alexander A.

2018-01-01

An experimental campaign to characterize the laser radiation absorption of foam targets and the subsequent emission of radiation from the produced plasma was carried out in the ABC facility of the ENEA Research Center in Frascati (Rome). Different targets have been used: plastic in solid or foam state and aluminum targets. The activated different diagnostics allowed to evaluate the plasma temperature, the density distribution, the fast particle spectrum and the yield of the X-Ray radiation emitted by the plasma for the different targets. These results confirm the foam homogenization action on laser-plasma interaction, mainly attributable to the volume absorption of the laser radiation propagating in such structured materials. These results were compared with simulation absorption models of the laser propagating into a foam target.

Laser Beat-Wave Magnetization of a Dense Plasma

NASA Astrophysics Data System (ADS)

Yates, Kevin; Hsu, Scott; Montgomery, David; Dunn, John; Langendorf, Samuel; Pollock, Bradley; Johnson, Timothy; Welch, Dale; Thoma, Carsten

2017-10-01

We present results from the first of a series of experiments to demonstrate and characterize laser beat-wave magnetization of a dense plasma, motivated by the desire to create high-beta targets with standoff for magneto-inertial fusion. The experiments are being conducted at the Jupiter Laser Facility (JLF) at LLNL. The experiment uses the JLF Janus 1 ω (1053 nm) beam and a standalone Nd:YAG (1064 nm) to drive the beat wave, and the Janus 2 ω (526.5 nm) beam to ionize/heat a gas-jet target as well as to provide Thomson-scattering (TS) measurements of the target density/temperature and scattered light from the beat wave. Streaked TS data captured electron-plasma-wave and ion-acoustic-wave features utilizing either nitrogen or helium gas jets. Effects of initial gas density as well as laser intensity on target have been measured, with electron densities ranging from 1E18 to 1E19 cm-3 with temperatures of tens to hundreds of eV, near the desired range for optimal field generation. LSP simulations were run to aid experimental design and data interpretation. LANL LDRD Program.

Isochoric heating of low Z solid targets with sub 10 fs laser pulses

NASA Astrophysics Data System (ADS)

Osterholz, Jens

2004-11-01

The investigation of high density plasmas plays an important role for astrophysics, inertial confinement fusion and x-ray lasers. Therefore the generation of dense plasmas with ultra-intense laser pulses is a field of enormous topical interest. An upper limit of the maximum plasma density that can be achieved with this method, however, occurs due to the formation of a preplasma and the expansion of the plasma during the interaction [1,2]. Here we describe a novel approach that is based on a laser system that generates sub 10 fs pulses with a low prepulse energy. Isochoric heating is demonstrated with small Z solid targets. Time integrated XUV spectroscopy is used to investigate K-shell emission from the plasma. In the spectra, only the Ly α and He α lines are observed, whereas transitions from orbitals with principal quantum numbers n > 2 are not present. This series limit is explained by pressure ionisation in the dense plasma. The XUV spectra were simulated by two different models [3]. The first calculates the effect of pressure ionisation and the second calculates the line intensity ratios. Preliminary calculations suggest that the plasma density of the emitting region is close to solid density with an electron temperature of about 100eV. We conclude that our laser system is well suited for isochoric heating of solid targets and an efficient transfer of the laser energy to the dense region of the target is possible. In cooperation with: T. Fischer, F. Brandl, G. Pretzler and O. Willi, Heinrich-Heine-University Duesseldorf, Germany, S. J. Rose, University of Oxford, United Kingdom [1] D. Riley et al., PRL 69, 3739 (1992). [2] A. Saemann et al., PRL 82, 4843 (1999). [3] S. J. Rose, J Phys B: Atom Molec Opt Phys, 25, 1667 (1992), 31, 2129 (1998).

Affinity proteomic profiling of plasma for proteins associated to area-based mammographic breast density.

PubMed

Byström, Sanna; Eklund, Martin; Hong, Mun-Gwan; Fredolini, Claudia; Eriksson, Mikael; Czene, Kamila; Hall, Per; Schwenk, Jochen M; Gabrielson, Marike

2018-02-14

Mammographic breast density is one of the strongest risk factors for breast cancer, but molecular understanding of how breast density relates to cancer risk is less complete. Studies of proteins in blood plasma, possibly associated with mammographic density, are well-suited as these allow large-scale analyses and might shed light on the association between breast cancer and breast density. Plasma samples from 1329 women in the Swedish KARMA project, without prior history of breast cancer, were profiled with antibody suspension bead array (SBA) assays. Two sample sets comprising 729 and 600 women were screened by two different SBAs targeting a total number of 357 proteins. Protein targets were selected through searching the literature, for either being related to breast cancer or for being linked to the extracellular matrix. Association between proteins and absolute area-based breast density (AD) was assessed by quantile regression, adjusting for age and body mass index (BMI). Plasma profiling revealed linear association between 20 proteins and AD, concordant in the two sets of samples (p < 0.05). Plasma levels of seven proteins were positively associated and 13 proteins negatively associated with AD. For eleven of these proteins evidence for gene expression in breast tissue existed. Among these, ABCC11, TNFRSF10D, F11R and ERRF were positively associated with AD, and SHC1, CFLAR, ACOX2, ITGB6, RASSF1, FANCD2 and IRX5 were negatively associated with AD. Screening proteins in plasma indicates associations between breast density and processes of tissue homeostasis, DNA repair, cancer development and/or progression in breast cancer. Further validation and follow-up studies of the shortlisted protein candidates in independent cohorts will be needed to infer their role in breast density and its progression in premenopausal and postmenopausal women.

Contribution to the beam plasma material interactions during material processing with TEA CO2 laser radiation

NASA Astrophysics Data System (ADS)

Jaschek, Rainer; Konrad, Peter E.; Mayerhofer, Roland; Bergmann, Hans W.; Bickel, Peter G.; Kowalewicz, Roland; Kuttenberger, Alfred; Christiansen, Jens

1995-03-01

The TEA-CO2-laser (transversely excited atmospheric pressure) is a tool for the pulsed processing of materials with peak power densities up to 1010 W/cm2 and a FWHM of 70 ns. The interaction between the laser beam, the surface of the work piece and the surrounding atmosphere as well as gas pressure and the formation of an induced plasma influences the response of the target. It was found that depending on the power density and the atmosphere the response can take two forms. (1) No target modification due to optical break through of the atmosphere and therefore shielding of the target (air pressure above 10 mbar, depending on the material). (2) Processing of materials (air pressure below 10 mbar, depending on the material) with melting of metallic surfaces (power density above 0.5 109 W/cm2), hole formation (power density of 5 109 W/cm2) and shock hardening (power density of 3.5 1010 W/cm2). All those phenomena are usually linked with the occurrence of laser supported combustion waves and laser supported detonation waves, respectively for which the mechanism is still not completely understood. The present paper shows how short time photography and spatial and temporal resolved spectroscopy can be used to better understand the various processes that occur during laser beam interaction. The spectra of titanium and aluminum are observed and correlated with the modification of the target. If the power density is high enough and the gas pressure above a material and gas composition specific threshold, the plasma radiation shows only spectral lines of the background atmosphere. If the gas pressure is below this threshold, a modification of the target surface (melting, evaporation and solid state transformation) with TEA-CO2- laser pulses is possible and the material specific spectra is observed. In some cases spatial and temporal resolved spectroscopy of a plasma allows the calculation of electron temperatures by comparison of two spectral lines.

A novel method for fabrication of size-controlled metallic nanoparticles by laser ablation

NASA Astrophysics Data System (ADS)

Choudhury, Kaushik; Singh, R. K.; Ranjan, Mukesh; Kumar, Ajai; Srivastava, Atul

2017-12-01

Time resolved experimental investigation of laser produced plasma-induced shockwaves has been carried out in the presence of confining walls placed along the lateral directions using a Mach Zehnder interferometer in air ambient. Copper was used as target material. The primary and the reflected shock waves and their effects on the evolution of medium density and the plasma density have been studied. The reflected shock wave has been seen to be affecting the shape and density of the plasma plume in the confined geometry. The same experiments were performed with water and isopropyl alcohol as the ambient liquids and the produced nanoparticles were characterised for size and size distribution. Significant differences in the size and size distribution are seen in case of the nanoparticles produced from the ablation of the targets with and without confining boundary. The observed trend has been attributed to the presence of confining boundary and the way it affects the thermalisation time of the plasma plume. The experiments also show the effect of medium density on the mean size of the copper nanoparticles produced.

Enhanced ion acceleration in transition from opaque to transparent plasmas

NASA Astrophysics Data System (ADS)

Mishra, R.; Fiuza, F.; Glenzer, S.

2018-04-01

Using particle-in-cell simulations, we investigate ion acceleration in the interaction of high intensity lasers with plasmas which transition from opaque to transparent during the interaction process. We show that the highest ion energies are achieved when the laser traverses the target around the peak intensity and re-heats the electron population responsible for the plasma expansion, enhancing the corresponding sheath electric field. This process can lead to an increase of up to 2x in ion energy when compared with the standard Target Normal Sheath Acceleration in opaque targets under the same laser conditions. A theoretical model is developed to predict the optimal target areal density as a function of laser intensity and pulse duration. A systematic parametric scan for a wide range of target densities and thicknesses is performed in 1D, 2D and 3D and shown consistent with the theory and with recent experimental results. These results open the way for a better optimization of the ion energy in future laser–solid experiments.

Talbot-Lau x-ray deflectometer electron density diagnostic for laser and pulsed power high energy density plasma experiments (invited).

PubMed

Valdivia, M P; Stutman, D; Stoeckl, C; Mileham, C; Begishev, I A; Theobald, W; Bromage, J; Regan, S P; Klein, S R; Muñoz-Cordovez, G; Vescovi, M; Valenzuela-Villaseca, V; Veloso, F

2016-11-01

Talbot-Lau X-ray deflectometry (TXD) has been developed as an electron density diagnostic for High Energy Density (HED) plasmas. The technique can deliver x-ray refraction, attenuation, elemental composition, and scatter information from a single Moiré image. An 8 keV Talbot-Lau interferometer was deployed using laser and x-pinch backlighters. Grating survival and electron density mapping were demonstrated for 25-29 J, 8-30 ps laser pulses using copper foil targets. Moiré pattern formation and grating survival were also observed using a copper x-pinch driven at 400 kA, ∼1 kA/ns. These results demonstrate the potential of TXD as an electron density diagnostic for HED plasmas.

Talbot-Lau X-ray Deflectometer electron density diagnostic for laser and pulsed power high energy density plasma experiments

DOE PAGES

Valdivia, M. P.; Stutman, D.; Stoeckl, C.; ...

2016-04-21

Talbot-Lau X-ray Deflectometry has been developed as an electron density diagnostic for High Energy Density plasmas. The technique can deliver x-ray refraction, attenuation, elemental composition, and scatter information from a single Moiré image. An 8 keV Talbot-Lau interferometer was deployed using laser and x-pinch backlighters. Grating survival and electron density mapping was demonstrated for 25-29 J, 8-30 ps laser pulses using copper foil targets. Moire pattern formation and grating survival was also observed using a copper x-pinch driven at 400 kA, ~1 kA/ns. Lastly, these results demonstrate the potential of TXD as an electron density diagnostic for HED plasmas.

Using the Multipole Resonance Probe to Stabilize the Electron Density During a Reactive Sputter Process

NASA Astrophysics Data System (ADS)

Oberberg, Moritz; Styrnoll, Tim; Ries, Stefan; Bienholz, Stefan; Awakowicz, Peter

2015-09-01

Reactive sputter processes are used for the deposition of hard, wear-resistant and non-corrosive ceramic layers such as aluminum oxide (Al2O3) . A well known problem is target poisoning at high reactive gas flows, which results from the reaction of the reactive gas with the metal target. Consequently, the sputter rate decreases and secondary electron emission increases. Both parameters show a non-linear hysteresis behavior as a function of the reactive gas flow and this leads to process instabilities. This work presents a new control method of Al2O3 deposition in a multiple frequency CCP (MFCCP) based on plasma parameters. Until today, process controls use parameters such as spectral line intensities of sputtered metal as an indicator for the sputter rate. A coupling between plasma and substrate is not considered. The control system in this work uses a new plasma diagnostic method: The multipole resonance probe (MRP) measures plasma parameters such as electron density by analyzing a typical resonance frequency of the system response. This concept combines target processes and plasma effects and directly controls the sputter source instead of the resulting target parameters.

Third harmonic generation of a short pulse laser in a plasma density ripple created by a machining beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, C. S.; Tripathi, V. K.

An intense machining laser beam, impinged on a gas jet target, causes space periodic ionization of the gas and heats the electrons. The nonuniform plasma pressure leads to atomic density redistribution. When, after a suitable time delay, a second more intense laser pulse is launched along the periodicity wave vector q-vector, a plasma density ripple n{sub q} is instantly created, leading to resonant third harmonic generation when q=4{omega}{sub p}{sup 2}/(3{omega}c{gamma}{sub 0}), where {omega}{sub p} is the plasma frequency, {omega} is the laser frequency, and {gamma}{sub 0} is the electron Lorentz factor. The third harmonic is produced through the beating ofmore » ponderomotive force induced second harmonic density oscillations and the quiver velocity of electrons at the fundamental. The relativistic mass nonlinearity plays no role in resonant coupling. The energy conversion efficiency scales as the square of plasma density and square of depth of density ripple, and is {approx}0.2% for normalized laser amplitude a{sub o}{approx}1 in a plasma of 1% critical density with 20% density ripple. The theory explains several features of a recent experiment.« less

Small angle slot divertor concept for long pulse advanced tokamaks

NASA Astrophysics Data System (ADS)

Guo, H. Y.; Sang, C. F.; Stangeby, P. C.; Lao, L. L.; Taylor, T. S.; Thomas, D. M.

2017-04-01

SOLPS-EIRENE edge code analysis shows that a gas-tight slot divertor geometry with a small-angle (glancing-incidence) target, named the small angle slot (SAS) divertor, can achieve cold, dissipative/detached divertor conditions at relatively low values of plasma density at the outside midplane separatrix. SAS exhibits the following key features: (1) strong enhancement of the buildup of neutral density in a localized region near the plasma strike point on the divertor target; (2) spreading of the cooling front across the divertor target with the slot gradually flaring out from the strike point, thus effectively reducing both heat flux and erosion on the entire divertor target surface. Such a divertor may potentially provide a power and particle handling solution for long pulse advanced tokamaks.

Highly intensified emission of laser-accelerated electrons from a foil target through an additional rear laser plasma

NASA Astrophysics Data System (ADS)

Inoue, Shunsuke; Nakamiya, Yoshihide; Teramoto, Kensuke; Hashida, Masaki; Sakabe, Shuji

2018-04-01

Intensification of electrons escaping from an intense laser-produced plasma is demonstrated by using double femtosecond laser pulses. The electron density distribution at the rear surface of a laser-irradiated foil target is controlled by preirradiation to suppress sheath field growth and to expand the plasma into which the fast electrons are released. Consequently, the number of electrons escaping from the plasma that have an energy of 380 keV increases by a factor of 7. The experimental results are well explained by numerical simulations of a foil plasma with a preformed plasma and analytical evaluations considering the plasma expansion.

Simulated performance of the optical Thomson scattering diagnostic designed for the National Ignition Facility.

PubMed

Ross, J S; Datte, P; Divol, L; Galbraith, J; Froula, D H; Glenzer, S H; Hatch, B; Katz, J; Kilkenny, J; Landen, O; Manuel, A M; Molander, W; Montgomery, D S; Moody, J D; Swadling, G; Weaver, J

2016-11-01

An optical Thomson scattering diagnostic has been designed for the National Ignition Facility to characterize under-dense plasmas. We report on the design of the system and the expected performance for different target configurations. The diagnostic is designed to spatially and temporally resolve the Thomson scattered light from laser driven targets. The diagnostic will collect scattered light from a 50 × 50 × 200 μm volume. The optical design allows operation with different probe laser wavelengths. A deep-UV probe beam (λ 0 = 210 nm) will be used to Thomson scatter from electron plasma densities of ∼5 × 10 20 cm -3 while a 3ω probe will be used for plasma densities of ∼1 × 10 19 cm -3 . The diagnostic package contains two spectrometers: the first to resolve Thomson scattering from ion acoustic wave fluctuations and the second to resolve scattering from electron plasma wave fluctuations. Expected signal levels relative to background will be presented for typical target configurations (hohlraums and a planar foil).

Talbot-Lau x-ray deflectometer electron density diagnostic for laser and pulsed power high energy density plasma experiments (invited)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valdivia, M. P., E-mail: mpvaldivia@pha.jhu.edu; Stutman, D.; Stoeckl, C.

2016-11-15

Talbot-Lau X-ray deflectometry (TXD) has been developed as an electron density diagnostic for High Energy Density (HED) plasmas. The technique can deliver x-ray refraction, attenuation, elemental composition, and scatter information from a single Moiré image. An 8 keV Talbot-Lau interferometer was deployed using laser and x-pinch backlighters. Grating survival and electron density mapping were demonstrated for 25–29 J, 8–30 ps laser pulses using copper foil targets. Moiré pattern formation and grating survival were also observed using a copper x-pinch driven at 400 kA, ∼1 kA/ns. These results demonstrate the potential of TXD as an electron density diagnostic for HED plasmas.

Magnetized Target Fusion At General Fusion: An Overview

NASA Astrophysics Data System (ADS)

Laberge, Michel; O'Shea, Peter; Donaldson, Mike; Delage, Michael; Fusion Team, General

2017-10-01

Magnetized Target Fusion (MTF) involves compressing an initial magnetically confined plasma on a timescale faster than the thermal confinement time of the plasma. If near adiabatic compression is achieved, volumetric compression of 350X or more of a 500 eV target plasma would achieve a final plasma temperature exceeding 10 keV. Interesting fusion gains could be achieved provided the compressed plasma has sufficient density and dwell time. General Fusion (GF) is developing a compression system using pneumatic pistons to collapse a cavity formed in liquid metal containing a magnetized plasma target. Low cost driver, straightforward heat extraction, good tritium breeding ratio and excellent neutron protection could lead to a practical power plant. GF (65 employees) has an active plasma R&D program including both full scale and reduced scale plasma experiments and simulation of both. Although pneumatic driven compression of full scale plasmas is the end goal, present compression studies use reduced scale plasmas and chemically accelerated aluminum liners. We will review results from our plasma target development, motivate and review the results of dynamic compression field tests and briefly describe the work to date on the pneumatic driver front.

The magnetically driven plasma jet produces a pressure of 33 GPa on PTS

NASA Astrophysics Data System (ADS)

Xu, Qiang; Dan, Jiakun; Wang, Guilin; Guo, Shuai; Zhang, Siqun; Cai, Hongchun; Ren, Xiao; Wang, Kunlun; Zhou, Shaotong; Zhang, Zhaohui; Huang, Xianbin

2017-01-01

We report on experiments in which a magnetically driven plasma jet was used to hit a 500 μm thick planar aluminum target. The plasma jet was produced by using a 50 μm thick aluminum radial foil, which was subjected to 4 MA, 90 ns rising time current on the primary test stand pulsed power facility. The subsequent magnetic bubbles propagate with radial velocity reaching 200 km/s and an axial velocity of 230 km/s. After the plasma knocks onto the target, a shock forms in the target. When the shock gets to the backside of the target, we measure the velocity of the moving surface using dual laser heterodyne velocimetry. By using the Hugoniot relations, we know that the plasma jet produced a pressure of 33 GPa. According to the measured pressure and the velocity of the plasma jet, the density of the jet can be also roughly estimated.

Experimental validation of an analytical kinetic model for edge-localized modes in JET-ITER-like wall

NASA Astrophysics Data System (ADS)

Guillemaut, C.; Metzger, C.; Moulton, D.; Heinola, K.; O’Mullane, M.; Balboa, I.; Boom, J.; Matthews, G. F.; Silburn, S.; Solano, E. R.; contributors, JET

2018-06-01

The design and operation of future fusion devices relying on H-mode plasmas requires reliable modelling of edge-localized modes (ELMs) for precise prediction of divertor target conditions. An extensive experimental validation of simple analytical predictions of the time evolution of target plasma loads during ELMs has been carried out here in more than 70 JET-ITER-like wall H-mode experiments with a wide range of conditions. Comparisons of these analytical predictions with diagnostic measurements of target ion flux density, power density, impact energy and electron temperature during ELMs are presented in this paper and show excellent agreement. The analytical predictions tested here are made with the ‘free-streaming’ kinetic model (FSM) which describes ELMs as a quasi-neutral plasma bunch expanding along the magnetic field lines into the Scrape-Off Layer without collisions. Consequences of the FSM on energy reflection and deposition on divertor targets during ELMs are also discussed.

Optical shaping of gas targets for laser–plasma ion sources

DOE PAGES

Dover, N. P.; Cook, N.; Tresca, O.; ...

2016-02-09

In this paper, we report on the experimental demonstration of a technique to generate steep density gradients in gas-jet targets of interest to laser–plasma ion acceleration. By using an intentional low-energy prepulse, we generated a hydrodynamic blast wave in the gas to shape the target prior to the arrival of an intense COmore » $$_{2}$$($${\\it\\lambda}\\approx 10~{\\rm\\mu}\\text{m}$$) drive pulse. This technique has been recently shown to facilitate the generation of ion beams by shockwave acceleration (Trescaet al.,Phys. Rev. Lett., vol. 115 (9), 2015, 094802). Here, we discuss and introduce a model to understand the generation of these blast waves and discuss in depth the experimental realisation of the technique, supported by hydrodynamics simulations. With appropriate prepulse energy and timing, this blast wave can generate steepened density gradients as short as$$l\\approx 20~{\\rm\\mu}\\text{m}$$($1/e$), opening up new possibilities for laser–plasma studies with near-critical gaseous targets.« less

Splitter target for controlling magnetic reconnection in relativistic laser plasma interactions

NASA Astrophysics Data System (ADS)

Gu, Y. J.; Bulanov, S. S.; Korn, G.; Bulanov, S. V.

2018-04-01

The utilization of a conical target irradiated by a high power laser is proposed to study fast magnetic reconnection in relativistic plasma interactions. Such target, placed in front of the near critical density gas jet, splits the laser pulse, forming two parallel laser pulses in the 2D case and a donut shaped pulse in the 3D case. The magnetic annihilation and reconnection occur in the density downramp region of the subsequent gas jet. The magnetic field energy is converted into the particle kinetic energy. As a result, a backward accelerated electron beam is obtained as a signature of reconnection. The above mechanisms are demonstrated using particle-in-cell simulations in both 2D and 3D cases. Facilitating the synchronization of two laser beams, the proposed approach can be used in designing the corresponding experiments on studying fundamental problems of relativistic plasma physics.

Development of vacuum ultraviolet absorption spectroscopy system for wide measurement range of number density using a dual-tube inductively coupled plasma light source

NASA Astrophysics Data System (ADS)

Kuwahara, Akira; Matsui, Makoto; Yamagiwa, Yoshiki

2012-12-01

A vacuum ultraviolet absorption spectroscopy system for a wide measurement range of atomic number densities is developed. Dual-tube inductively coupled plasma was used as a light source. The probe beam profile was optimized for the target number density range by changing the mass flow rate of the inner and outer tubes. This system was verified using cold xenon gas. As a result, the measurement number density range was extended from the conventional two orders to five orders of magnitude.

Dependence of optimal initial density on laser parameters for multi-keV x-ray radiators generated by nanosecond laser-produced underdense plasma

NASA Astrophysics Data System (ADS)

Tu, Shao-yong; Yuan, Yong-teng; Hu, Guang-yue; Miao, Wen-yong; Zhao, Bin; Zheng, Jian; Jiang, Shao-en; Ding, Yong-kun

2016-01-01

Efficient multi-keV x-ray sources can be produced using nanosecond laser pulse-heated middle-Z underdense plasmas generated using gas or foam. Previous experimental results show that an optimal initial target density exists for efficient multi-keV x-ray emission at which the laser ionization wave is supersonic. Here we explore the influence of the laser intensity and the pulse duration on this optimal initial target density via a one-dimensional radiation hydrodynamic simulation. The simulation shows that the optimal initial density is sensitive to both the laser intensity and the pulse duration. However, the speed of the supersonic ionization wave at the end of the laser irradiation is always maintained at 1.5 to 1.7 times that of the ion acoustic wave under the optimal initial density conditions.

Enhanced ion acceleration in transition from opaque to transparent plasmas

DOE PAGES

Mishra, R.; Fiuza, F.; Glenzer, S.

2018-04-20

Using particle-in-cell simulations, we investigate ion acceleration in the interaction of high intensity lasers with plasmas which transition from opaque to transparent during the interaction process. We show that the highest ion energies are achieved when the laser traverses the target around the peak intensity and re-heats the electron population responsible for the plasma expansion, enhancing the corresponding sheath electric field. This process can lead to an increase of up to 2x in ion energy when compared with the standard Target Normal Sheath Acceleration in opaque targets under the same laser conditions. A theoretical model is developed to predict themore » optimal target areal density as a function of laser intensity and pulse duration. A systematic parametric scan for a wide range of target densities and thicknesses is performed in 1D, 2D and 3D and shown consistent with the theory and with recent experimental results. Thus, these results open the way for a better optimization of the ion energy in future laser–solid experiments.« less

Enhanced ion acceleration in transition from opaque to transparent plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mishra, R.; Fiuza, F.; Glenzer, S.

Using particle-in-cell simulations, we investigate ion acceleration in the interaction of high intensity lasers with plasmas which transition from opaque to transparent during the interaction process. We show that the highest ion energies are achieved when the laser traverses the target around the peak intensity and re-heats the electron population responsible for the plasma expansion, enhancing the corresponding sheath electric field. This process can lead to an increase of up to 2x in ion energy when compared with the standard Target Normal Sheath Acceleration in opaque targets under the same laser conditions. A theoretical model is developed to predict themore » optimal target areal density as a function of laser intensity and pulse duration. A systematic parametric scan for a wide range of target densities and thicknesses is performed in 1D, 2D and 3D and shown consistent with the theory and with recent experimental results. Thus, these results open the way for a better optimization of the ion energy in future laser–solid experiments.« less

Real-time interferometric diagnostics of rubidium plasma

NASA Astrophysics Data System (ADS)

Djotyan, G. P.; Bakos, J. S.; Kedves, M. Á.; Ráczkevi, B.; Dzsotjan, D.; Varga-Umbrich, K.; Sörlei, Zs.; Szigeti, J.; Ignácz, P.; Lévai, P.; Czitrovszky, A.; Nagy, A.; Dombi, P.; Rácz, P.

2018-03-01

A method of interferometric real-time diagnostics is developed and applied to rubidium plasma created by strong laser pulses in the femtosecond duration range at different initial rubidium vapor densities using a Michelson-type interferometer. A cosine fit with an exponentially decaying relative phase is applied to the obtained time-dependent interferometry signals to measure the density-length product of the created plasma and its recombination time constant. The presented technique may be applicable for real-time measurements of rubidium plasma dynamics in the AWAKE experiment at CERN, as well as for real-time diagnostics of plasmas created in different gaseous media and on surfaces of solid targets.

Experimental evidence of beam-foil plasma creation during ion-solid interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Prashant, E-mail: prashant@iuac.res.in; Nandi, Tapan

2016-08-15

Charge state evolution of the energetic projectile ions during the passage through thin carbon foils has been revisited using the X-ray spectroscopy technique. Contributions from the bulk and the solid surface in the charge changing processes have been segregated by measuring the charge state distribution of the projectile ions in the bulk of the target during the ion–solid interaction. Interestingly, the charge state distribution measured in the bulk exhibits Lorentzian profile in contrast to the well-known Gaussian structure observed using the electromagnetic methods and the theoretical predictions. The occurrence of such behavior is a direct consequence of the imbalance betweenmore » charge changing processes, which has been seen in various cases of the laboratory plasma. It suggests that the ion-solid collisions constitute high-density, localized plasma in the bulk of the solid target, called the beam-foil plasma. This condensed beam-foil plasma is similar to the high-density solar and stellar plasma which may have practical implementations in various fields, in particular, plasma physics and nuclear astrophysics. The present work suggests further modification in the theoretical charge state distribution calculations by incorporating the plasma coupling effects during the ion–solid interactions. Moreover, the multi-electron capture from the target exit surface has been confirmed through comparison between experimentally measured and theoretically predicted values of the mean charge state of the projectile ions.« less

Dense Plasma Focus - From Alternative Fusion Source to Versatile High Energy Density Plasma Source for Plasma Nanotechnology

NASA Astrophysics Data System (ADS)

Rawat, R. S.

2015-03-01

The dense plasma focus (DPF), a coaxial plasma gun, utilizes pulsed high current electrical discharge to heat and compress the plasma to very high density and temperature with energy densities in the range of 1-10 × 1010 J/m3. The DPF device has always been in the company of several alternative magnetic fusion devices as it produces intense fusion neutrons. Several experiments conducted on many different DPF devices ranging over several order of storage energy have demonstrated that at higher storage energy the neutron production does not follow I4 scaling laws and deteriorate significantly raising concern about the device's capability and relevance for fusion energy. On the other hand, the high energy density pinch plasma in DPF device makes it a multiple radiation source of ions, electron, soft and hard x-rays, and neutrons, making it useful for several applications in many different fields such as lithography, radiography, imaging, activation analysis, radioisotopes production etc. Being a source of hot dense plasma, strong shockwave, intense energetic beams and radiation, etc, the DPF device, additionally, shows tremendous potential for applications in plasma nanoscience and plasma nanotechnology. In the present paper, the key features of plasma focus device are critically discussed to understand the novelties and opportunities that this device offers in processing and synthesis of nanophase materials using, both, the top-down and bottom-up approach. The results of recent key experimental investigations performed on (i) the processing and modification of bulk target substrates for phase change, surface reconstruction and nanostructurization, (ii) the nanostructurization of PLD grown magnetic thin films, and (iii) direct synthesis of nanostructured (nanowire, nanosheets and nanoflowers) materials using anode target material ablation, ablated plasma and background reactive gas based synthesis and purely gas phase synthesis of various different types of nanostructured materials using DPF device will discussed to establish this device as versatile tool for plasma nanotechnology.

Dense blocks of energetic ions driven by multi-petawatt lasers

PubMed Central

Weng, S. M.; Liu, M.; Sheng, Z. M.; Murakami, M.; Chen, M.; Yu, L. L.; Zhang, J.

2016-01-01

Laser-driven ion accelerators have the advantages of compact size, high density, and short bunch duration over conventional accelerators. Nevertheless, it is still challenging to simultaneously enhance the yield and quality of laser-driven ion beams for practical applications. Here we propose a scheme to address this challenge via the use of emerging multi-petawatt lasers and a density-modulated target. The density-modulated target permits its ions to be uniformly accelerated as a dense block by laser radiation pressure. In addition, the beam quality of the accelerated ions is remarkably improved by embedding the target in a thick enough substrate, which suppresses hot electron refluxing and thus alleviates plasma heating. Particle-in-cell simulations demonstrate that almost all ions in a solid-density plasma of a few microns can be uniformly accelerated to about 25% of the speed of light by a laser pulse at an intensity around 1022 W/cm2. The resulting dense block of energetic ions may drive fusion ignition and more generally create matter with unprecedented high energy density. PMID:26924793

Plasma Source Development

NASA Astrophysics Data System (ADS)

Walker, Jonathan; Heinrich, Jonathon; Font, Gabriel; Ebersohn, Frans; Garrett, Michael

2017-10-01

A 100 kW class lanthanum-hexaboride plasma source is under continuing development for the Lockheed Martin Compact Fusion Reactor program. The current experiment, T4B, has become a test bed for plasma source operation with the goal of creating a high density plasma target for neutral beam heating. We present operation and performance of different plasma source geometries, results of plasma source coupling, and future plasma source development plans. ©2017 Lockheed Martin Corporation. All Rights Reserved.

Electron heating enhancement by frequency-chirped laser pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yazdani, E.; Afarideh, H., E-mail: hafarideh@aut.ac.ir; Sadighi-Bonabi, R., E-mail: Sadighi@sharif.ir

2014-09-14

Propagation of a chirped laser pulse with a circular polarization through an uprising plasma density profile is studied by using 1D-3V particle-in-cell simulation. The laser penetration depth is increased in an overdense plasma compared to an unchirped pulse. The induced transparency due to the laser frequency chirp results in an enhanced heating of hot electrons as well as increased maximum longitudinal electrostatic field at the back side of the solid target, which is very essential in target normal sheath acceleration regime of proton acceleration. For an applied chirp parameter between 0.008 and 0.01, the maximum amount of the electrostatic fieldmore » is improved by a factor of 2. Furthermore, it is noticed that for a chirped laser pulse with a₀=5, because of increasing the plasma transparency length, the laser pulse can penetrate up to about n{sub e}≈6n{sub c}, where n{sub c} is plasma critical density. It shows 63% increase in the effective critical density compared to the relativistic induced transparency regime for an unchirped condition.« less

Enhanced proton acceleration from an ultrathin target irradiated by laser pulses with plateau ASE.

PubMed

Wang, Dahui; Shou, Yinren; Wang, Pengjie; Liu, Jianbo; Li, Chengcai; Gong, Zheng; Hu, Ronghao; Ma, Wenjun; Yan, Xueqing

2018-02-07

We report a simulation study on proton acceleration driven by ultraintense laser pulses with normal contrast (10 7 -10 9 ) containing nanosecond plateau amplified spontaneous emission (ASE). It's found in hydrodynamic simulations that if the thickness of the targets lies in the range of hundreds nanometer matching the intensity and duration of ASE, the ablation pressure would push the whole target in the forward direction with speed exceeding the expansion velocity of plasma, resulting in a plasma density profile with a long extension at the target front and a sharp gradient at the target rear. When the main pulse irradiates the plasma, self-focusing happens at the target front, producing highly energetic electrons through direct laser acceleration(DLA) building the sheath field. The sharp plasma gradient at target rear ensures a strong sheath field. 2D particle-in-cell(PIC) simulations reveal that the proton energy can be enhanced by a factor of 2 compared to the case of using micrometer-thick targets.

Critical need for MFE: the Alcator DX advanced divertor test facility

NASA Astrophysics Data System (ADS)

Vieira, R.; Labombard, B.; Marmar, E.; Irby, J.; Wolf, S.; Bonoli, P.; Fiore, C.; Granetz, R.; Greenwald, M.; Hutchinson, I.; Hubbard, A.; Hughes, J.; Lin, Y.; Lipschultz, B.; Parker, R.; Porkolab, M.; Reinke, M.; Rice, J.; Shiraiwa, S.; Terry, J.; Theiler, C.; Wallace, G.; White, A.; Whyte, D.; Wukitch, S.

2013-10-01

Three critical challenges must be met before a steady-state, power-producing fusion reactor can be realized: how to (1) safely handle extreme plasma exhaust power, (2) completely suppress material erosion at divertor targets and (3) do this while maintaining a burning plasma core. Advanced divertors such as ``Super X'' and ``X-point target'' may allow a fully detached, low temperature plasma to be produced in the divertor while maintaining a hot boundary layer around a clean plasma core - a potential game-changer for magnetic fusion. No facility currently exists to test these ideas at the required parallel heat flux densities. Alcator DX will be a national facility, employing the high magnetic field technology of Alcator combined with high-power ICRH and LHCD to test advanced divertor concepts at FNSF/DEMO power exhaust densities and plasma pressures. Its extended vacuum vessel contains divertor cassettes with poloidal field coils for conventional, snowflake, super-X and X-point target geometries. Divertor and core plasma performance will be explored in regimes inaccessible in conventional devices. Reactor relevant ICRF and LH drivers will be developed, utilizing high-field side launch platforms for low PMI. Alcator DX will inform the conceptual development and accelerate the readiness-for-deployment of next-step fusion facilities.

Simulated performance of the optical Thomson scattering diagnostic designed for the National Ignition Facility

DOE PAGES

Ross, J. S.; Datte, P.; Divol, L.; ...

2016-07-28

An optical Thomson scattering diagnostic has been designed for the National Ignition Facility to characterize under-dense plasmas. Here, we report on the design of the system and the expected performance for different target configurations. The diagnostic is designed to spatially and temporally resolve the Thomson scattered light from laser driven targets. The diagnostic will collect scattered light from a 50 × 50 × 200 μm volume. The optical design allows operation with different probe laser wavelengths. A deep-UV probe beam (λ 0 = 210 nm) will be used to Thomson scatter from electron plasma densities of ~5 × 10 20more » cm -3 while a 3ω probe will be used for plasma densities of ~1 × 10 19 cm -3. The diagnostic package contains two spectrometers: the first to resolve Thomson scattering from ion acoustic wave fluctuations and the second to resolve scattering from electron plasma wave fluctuations. Expected signal levels relative to background will be presented for typical target configurations (hohlraums and a planar foil).« less

Simulated performance of the optical Thomson scattering diagnostic designed for the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ross, J. S., E-mail: ross36@llnl.gov; Datte, P.; Divol, L.

2016-11-15

An optical Thomson scattering diagnostic has been designed for the National Ignition Facility to characterize under-dense plasmas. We report on the design of the system and the expected performance for different target configurations. The diagnostic is designed to spatially and temporally resolve the Thomson scattered light from laser driven targets. The diagnostic will collect scattered light from a 50 × 50 × 200 μm volume. The optical design allows operation with different probe laser wavelengths. A deep-UV probe beam (λ{sub 0} = 210 nm) will be used to Thomson scatter from electron plasma densities of ∼5 × 10{sup 20} cm{supmore » −3} while a 3ω probe will be used for plasma densities of ∼1 × 10{sup 19} cm{sup −3}. The diagnostic package contains two spectrometers: the first to resolve Thomson scattering from ion acoustic wave fluctuations and the second to resolve scattering from electron plasma wave fluctuations. Expected signal levels relative to background will be presented for typical target configurations (hohlraums and a planar foil).« less

The Material Plasma Exposure eXperiment (MPEX)

NASA Astrophysics Data System (ADS)

Rapp, J.; Biewer, T. M.; Bigelow, T. S.; Canik, J.; Caughman, J. B. O.; Duckworth, R. C.; Goulding, R. H.; Hillis, D. L.; Lore, J. D.; Lumsdaine, A.; McGinnis, W. D.; Meitner, S. J.; Owen, L. W.; Shaw, G. C.; Luo, G.-N.

2014-10-01

Next generation plasma generators have to be able to access the plasma conditions expected on the divertor targets in ITER and future devices. The Material Plasma Exposure eXperiment (MPEX) will address this regime with electron temperatures of 1--10 eV and electron densities of 1021--1020 m-3. The resulting heat fluxes are about 10 MW/m2. MPEX is designed to deliver those plasma conditions with a novel Radio Frequency plasma source able to produce high density plasmas and heat electron and ions separately with Electron Bernstein Wave (EBW) heating and Ion Cyclotron Resonance Heating (ICRH). Preliminary modeling has been used for pre-design studies of MPEX. MPEX will be capable to expose neutron irradiated samples. In this concept targets will be irradiated in ORNL's High Flux Isotope Reactor (HFIR) or possibly at the Spallation Neutron Source (SNS) and then subsequently (after a sufficient long cool-down period) exposed to fusion reactor relevant plasmas in MPEX. The current state of the pre-design of MPEX including the concept of handling irradiated samples will be presented. ORNL is managed by UT-Battelle, LLC, for the U.S. DOE under Contract DE-AC-05-00OR22725.

A contoured gap coaxial plasma gun with injected plasma armature.

PubMed

Witherspoon, F Douglas; Case, Andrew; Messer, Sarah J; Bomgardner, Richard; Phillips, Michael W; Brockington, Samuel; Elton, Raymond

2009-08-01

A new coaxial plasma gun is described. The long term objective is to accelerate 100-200 microg of plasma with density above 10(17) cm(-3) to greater than 200 km/s with a Mach number above 10. Such high velocity dense plasma jets have a number of potential fusion applications, including plasma refueling, magnetized target fusion, injection of angular momentum into centrifugally confined mirrors, high energy density plasmas, and others. The approach uses symmetric injection of high density plasma into a coaxial electromagnetic accelerator having an annular gap geometry tailored to prevent formation of the blow-by instability. The injected plasma is generated by numerous (currently 32) radially oriented capillary discharges arranged uniformly around the circumference of the angled annular injection region of the accelerator. Magnetohydrodynamic modeling identified electrode profiles that can achieve the desired plasma jet parameters. The experimental hardware is described along with initial experimental results in which approximately 200 microg has been accelerated to 100 km/s in a half-scale prototype gun. Initial observations of 64 merging injector jets in a planar cylindrical testing array are presented. Density and velocity are presently limited by available peak current and injection sources. Steps to increase both the drive current and the injected plasma mass are described for next generation experiments.

Target geometrical effects on the stagnation layer formed by colliding a pair of laser produced copper plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fallon, C., E-mail: colm.fallon5@mail.dcu.ie; Hayden, P.; Walsh, N.

We present the results of a time and space resolved optical-spectroscopic study of colliding plasmas formed at the front surfaces of flat and inclined Cu slab targets as a function of both the distance and the wedge angle between them for angles ranging from 100° to 180° (laterally colliding plasmas). The key parameters studied are stagnation layer density, temperature, duration, and kinetics of atomic/ionic spatial distributions and all have been found to vary significantly with wedge angle. It is found that the density and temperature of the stagnation layer decrease with increasing wedge angle. It is also found that themore » larger the wedge angle, the tighter and more well defined the stagnation layer formed.« less

Controlling dynamics of imploded core plasma for fast ignition

NASA Astrophysics Data System (ADS)

Nagatomo, H.; Johzaki, T.; Sunahara, A.; Shiraga, H.; Sakagami, H.; Cai, H.; Mima, K.

2010-08-01

In the Fast ignition, formation of highly compressed core plasma is one of critical issue. In this work, the effect hydrodynamic instability in cone-guided shell implosion is studied. Two-dimensional radiation hydrodynamic simulations are carried out where realistic seeds of Rayleigh-Taylor instability are imposed. Preliminary results suggest that the instability reduces implosion performance, such as implosion velocity, areal density, and maximum density. In perturbed target implosion, the break-up time of the tip of the cone is earlier than that of ideal unperturbed target implosion case. This is crucial matter for the Fast ignition because the pass for the heating laser is filled with plasma before the shot of heating laser. A sophisticated implosion design of stable and low in-flight aspect ratio is necessary for cone-guided shell implosion.

Simulation of laser interaction with ablative plasma and hydrodynamic behavior of laser supported plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tong Huifeng; Yuan Hong; Tang Zhiping

When an intense laser beam irradiates on a solid target, ambient air ionizes and becomes plasma, while part of the target rises in temperature, melts, vaporizes, ionizes, and yet becomes plasma. A general Godunov finite difference scheme WENO (Weighted Essentially Non-Oscillatory Scheme) with fifth-order accuracy is used to simulate 2-dimensional axis symmetrical laser-supported plasma flow field in the process of laser ablation. The model of the calculation of ionization degree of plasma and the interaction between laser beam and plasma are considered in the simulation. The numerical simulations obtain the profiles of temperature, density, and velocity at different times whichmore » show the evolvement of the ablative plasma. The simulated results show that the laser energy is strongly absorbed by plasma on target surface and that the velocity of laser supported detonation (LSD) wave is half of the ideal LSD value derived from Chapman-Jouguet detonation theory.« less

Progress in the Development of a High Power Helicon Plasma Source for the Materials Plasma Exposure Experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goulding, Richard Howell; Caughman, John B.; Rapp, Juergen

Proto-MPEX is a linear plasma device being used to study a novel RF source concept for the planned Material Plasma Exposure eXperiment (MPEX), which will address plasma-materials interaction (PMI) for nuclear fusion reactors. Plasmas are produced using a large diameter helicon source operating at a frequency of 13.56 MHz at power levels up to 120 kW. In recent experiments the helicon source has produced deuterium plasmas with densities up to ~6 × 1019 m–3 measured at a location 2 m downstream from the antenna and 0.4 m from the target. Previous plasma production experiments on Proto-MPEX have generated lower densitymore » plasmas with hollow electron temperature profiles and target power deposition peaked far off axis. The latest experiments have produced flat Te profiles with a large portion of the power deposited on the target near the axis. This and other evidence points to the excitation of a helicon mode in this case.« less

Propagation distance-resolved characteristics of filament-induced copper plasma

DOE PAGES

Ghebregziabher, Isaac; Hartig, Kyle C.; Jovanovic, Igor

2016-03-02

Copper plasma generated at different filament-copper interaction points was characterized by spectroscopic, acoustic, and imaging measurements. The longitudinal variation of the filament intensity was qualitatively determined by acoustic measurements in air. The maximum plasma temperature was measured at the location of peak filament intensity, corresponding to the maximum mean electron energy during plasma formation. The highest copper plasma density was measured past the location of the maximum electron density in the filament, where spectral broadening of the filament leads to enhanced ionization. Acoustic measurements in air and on solid target were correlated to reconstructed plasma properties. Lastly, optimal line emissionmore » is measured near the geometric focus of the lens used to produce the filament.« less

Ultraviolet Thomson Scattering from Direct-Drive Coronal Plasmas in Multilayer Targets

NASA Astrophysics Data System (ADS)

Henchen, R. J.; Goncharov, V. N.; Michel, D. T.; Follett, R. K.; Katz, J.; Froula, D. H.

2014-10-01

Ultraviolet (λ4 ω = 263 nm) Thomson scattering (TS) was used to probe ion-acoustic waves (IAW's) and electron plasma waves (EPW's) from direct-drive coronal plasmas. Fifty-nine drive beams (λ3 ω = 351 nm) illuminate a spherical target with a radius of ~ 860 μ m. A series of experiments studied the effect of higher electron temperature near the 3 ω quarter-critical surface (~ 2 . 5 ×1021 cm-3) on laser-plasma interactions resulting from a Si layer in the target. Electron temperatures and densities were measured from 150 to 400 μm from the initial target surface. Standard CH shells were compared to two-layered shells of CH and Si and three-layered shells of CH, Si, and CH. These multilayer targets have less hot-electron energy than standard CH shells as a result of higher electron temperature in the coronal plasmas. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Angular filter refractometry analysis using simulated annealing [An improved method for characterizing plasma density profiles using angular filter refractometry

DOE PAGES

Angland, P.; Haberberger, D.; Ivancic, S. T.; ...

2017-10-30

Here, a new method of analysis for angular filter refractometry images was developed to characterize laser-produced, long-scale-length plasmas using an annealing algorithm to iterative converge upon a solution. Angular filter refractometry (AFR) is a novel technique used to characterize the density pro files of laser-produced, long-scale-length plasmas. A synthetic AFR image is constructed by a user-defined density profile described by eight parameters, and the algorithm systematically alters the parameters until the comparison is optimized. The optimization and statistical uncertainty calculation is based on a minimization of themore » $$\\chi$$2 test statistic. The algorithm was successfully applied to experimental data of plasma expanding from a flat, laser-irradiated target, resulting in average uncertainty in the density profile of 5-10% in the region of interest.« less

Direct current dielectric barrier assistant discharge to get homogeneous plasma in capacitive coupled discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Du, Yinchang, E-mail: ycdu@mail.ustc.edu.cn; Max-Planck Institute for Extraterrestrial Physics, D-85748 Garching; Li, Yangfang

In this paper, we propose a method to get more homogeneous plasma in the geometrically asymmetric capacitive coupled plasma (CCP) discharge. The dielectric barrier discharge (DBD) is used for the auxiliary discharge system to improve the homogeneity of the geometrically asymmetric CCP discharge. The single Langmuir probe measurement shows that the DBD can increase the electron density in the low density volume, where the DBD electrodes are mounted, when the pressure is higher than 5 Pa. By this manner, we are able to improve the homogeneity of the plasma production and increase the overall density in the target volume. At last,more » the finite element simulation results show that the DC bias, applied to the DBD electrodes, can increase the homogeneity of the electron density in the CCP discharge. The simulation results show a good agreement with the experiment results.« less

Angular filter refractometry analysis using simulated annealing [An improved method for characterizing plasma density profiles using angular filter refractometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Angland, P.; Haberberger, D.; Ivancic, S. T.

Here, a new method of analysis for angular filter refractometry images was developed to characterize laser-produced, long-scale-length plasmas using an annealing algorithm to iterative converge upon a solution. Angular filter refractometry (AFR) is a novel technique used to characterize the density pro files of laser-produced, long-scale-length plasmas. A synthetic AFR image is constructed by a user-defined density profile described by eight parameters, and the algorithm systematically alters the parameters until the comparison is optimized. The optimization and statistical uncertainty calculation is based on a minimization of themore » $$\\chi$$2 test statistic. The algorithm was successfully applied to experimental data of plasma expanding from a flat, laser-irradiated target, resulting in average uncertainty in the density profile of 5-10% in the region of interest.« less

Characteristics of the three-half-turn-antenna-driven RF discharge in the Uragan-3M torsatron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grigor’eva, L. I.; Chechkin, V. V., E-mail: chechkin@ipp.kharkov.ua; Moiseenko, V. E.

In the ℓ = 3 Uragan-3M torsatron hydrogen plasma is produced by RF fields in the Alfvén range of frequencies (ω ≤ ω{sub ci}). The initial (target) plasma with the line-averaged density of units 10{sup 12} cm{sup −3} is produced by a frame antenna with a broad spectrum of generated parallel wavenumbers. After this, to heat the plasma and bring its density to ∼10{sup 13} cm{sup –3}, another, shorter wavelength three-half-turn antenna with large transverse currents is used. The behavior of the density, electron temperature, and loss of the plasma supported by the three-half-turn antenna is studied depending on themore » RF power fed to the antenna and initial values of the density and electron temperature supplied by the frame antenna.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biewer, Theodore M.; Bigelow, Tim S.; Caneses Marin, Juan F.

The Prototype Material Plasma Exposure Experiment at the Oak Ridge National Laboratory utilizes a variety of power systems to generate and deliver a high heat flux plasma onto the surface of material targets. In the experiments described here, a deuterium plasma is produced via a ~100 kW, 13.56 MHz RF helicon source, to which ~20 kW of 28 GHz microwave power is applied. The electron density and temperature profiles are measured using a Thomson scattering (TS) diagnostic, and indicate that the electron density is centrally peaked. In the core of the plasma column, the electron density is higher than themore » cut-off density (~0.9 × 1019 m -3) for the launched mixture of X- and O-mode electron cyclotron heating waves to propagate. TS measurements indicate electron temperature increases from ~5 eV to ~20 eV during 28 GHz power application when the neutral deuterium pressure is reduced below 0.13 Pa (~1 mTorr.).« less

First measurements of the temporal evolution of the plasma density in HiPIMS discharges using THz time domain spectroscopy

NASA Astrophysics Data System (ADS)

Meier, Steffen M.; Hecimovic, Ante; Tsankov, Tsanko V.; Luggenhölscher, Dirk; Czarnetzki, Uwe

2018-03-01

In this paper, the novel technique of THz time domain spectroscopy has been applied to obtain time-resolved measurements of the plasma density in the active zone of a HiPIMS discharge with a titanium target. The obtained peak values are in the range of 1012-1013 cm-3 for discharge current densities of 1-4 A cm-2 at 0.5 and 2 Pa argon pressure. The measured densities show good correlation with the discharge current and voltage and the intensity of various atomic and ionic lines. The well known phases of the discharge have been identified and related to the variation of the electron density. The measurement results show that the plasma density remains nearly constant during the runaway/self-sputtering phase. Based on that, it is conjectured that singly charged titanium ions are the dominant ion species during this phase.

The use of segmented cathodes to determine the spoke current density distribution in high power impulse magnetron sputtering plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poolcharuansin, Phitsanu; The Technological Plasma Research Unit, Department of Physics, Mahasarakham University, Maha Sarakham 44150; Estrin, Francis Lockwood

2015-04-28

The localized target current density associated with quasi-periodic ionization zones (spokes) has been measured in a high power impulse magnetron sputtering (HiPIMS) discharge using an array of azimuthally separated and electrical isolated probes incorporated into a circular aluminum target. For a particular range of operating conditions (pulse energies up to 2.2 J and argon pressures from 0.2 to 1.9 Pa), strong oscillations in the probe current density are seen with amplitudes up to 52% above a base value. These perturbations, identified as spokes, travel around the discharge above the target in the E×B direction. Using phase information from the angularly separated probes,more » the spoke drift speeds, angular frequencies, and mode number have been determined. Generally, at low HiPIMS pulse energies E{sub p} < 0.8 J, spokes appear to be chaotic in nature (with random arrival times), however as E{sub p} increases, coherent spokes are observed with velocities between 6.5 and 10 km s{sup −1} and mode numbers m = 3 or above. At E{sub p} > 1.8 J, the plasma becomes spoke-free. The boundaries between chaotic, coherent, and no-spoke regions are weakly dependent on pressure. During each HiPIMS pulse, the spoke velocities increase by about 50%. Such an observation is explained by considering spoke velocities to be determined by the critical ionization velocity, which changes as the plasma composition changes during the pulse. From the shape of individual current density oscillations, it appears that the leading edge of the spoke is associated with a slow increase in local current density to the target and the rear with a more rapid decrease. The measurements show that the discharge current density associated with individual spokes is broadly spread over a wide region of the target.« less

Long Scalelength Plasmas for LPI Studies at the Nike Laser

NASA Astrophysics Data System (ADS)

Weaver, J. L.; Oh, J.; Bates, J. W.; Schmitt, A. J.; Kehne, D. M.; Wolford, M. F.; Obenschain, S. P.; Serlin, V.; Lehmberg, R. H.; Follett, R. K.; Shaw, J. G.; Myatt, J. F.; McKenty, P. W.; Wei, M. S.; Reynolds, H.; Williams, J.; Tsung, F.

2017-10-01

Studies of laser plasma instabilities (LPI) at the Nike laser have mainly used short pulses, small focal spots, and solid plastic (CH) targets that have yielded maximum gradient scalelengths below 200 microns. The current experimental effort aims to produce larger volume plasmas with 5-10x reduction in the density and velocity gradients as a platform for SBS, SRS, and TPD studies. The next campaign will concentrate on the effects of wavelength shifting and bandwidth changes on CBET in low density (5-10 mg/cm3) CH foam targets. This poster will discuss the development of this new LPI target platform based on modelling with the LPSE code developed at LLE. The presentation will also discuss alternative target schemes (e.g. exploding foils) and improvements to the LPI diagnostic suite and laser operations; for example, a new set of etalons will be available for the next campaign that should double the range of available wavelength shifting. Upgrades to the scattered light spectrometers in general use for LPI studies will also be presented. Work supported by DoE/NNSA.

Simulation study of the sub-terawatt laser wakefield acceleration operated in self-modulated regime

NASA Astrophysics Data System (ADS)

Hsieh, C.-Y.; Lin, M.-W.; Chen, S.-H.

2018-02-01

Laser wakefield acceleration (LWFA) can be accomplished by introducing a sub-terawatt (TW) laser pulse into a thin, high-density gas target. In this way, the self-focusing effect and the self-modulation that happened on the laser pulse produce a greatly enhanced laser peak intensity that can drive a nonlinear plasma wave to accelerate electrons. A particle-in-cell model is developed to study sub-TW LWFA when a 0.6-TW laser pulse interacts with a dense hydrogen plasma. Gas targets having a Gaussian density profile or a flat-top distribution are defined for investigating the properties of sub-TW LWFA when conducting with a gas jet or a gas cell. In addition to using 800-nm laser pulses, simulations are performed with 1030-nm laser pulses, as they represent a viable approach to realize the sub-TW LWFA driven by high-frequency, diode-pumped laser systems. The peak density which allows the laser peak power PL˜2 Pc r of self-focusing critical power is favourable for conducting sub-TW LWFA. Otherwise, an excessively high peak density can induce an undesired filament effect which rapidly disintegrates the laser field envelope and violates the process of plasma wave excitation. The plateau region of a flat-top density distribution allows the self-focusing and the self-modulation of the laser pulse to develop, from which well-established plasma bubbles can be produced to accelerate electrons. The process of electron injection is complicated in such high-density plasma conditions; however, increasing the length of the plateau region represents a straightforward method to realize the injection and acceleration of electrons within the first bubble, such that an improved LWFA performance can be accomplished.

Laser opacity in underdense preplasma of solid targets due to quantum electrodynamics effects

NASA Astrophysics Data System (ADS)

Wang, W.-M.; Gibbon, P.; Sheng, Z.-M.; Li, Y.-T.; Zhang, J.

2017-07-01

We investigate how next-generation laser pulses at 10 -200 PW interact with a solid target in the presence of a relativistically underdense preplasma produced by amplified spontaneous emission (ASE). Laser hole boring and relativistic transparency are strongly restrained due to the generation of electron-positron pairs and γ -ray photons via quantum electrodynamics (QED) processes. A pair plasma with a density above the initial preplasma density is formed, counteracting the electron-free channel produced by hole boring. This pair-dominated plasma can block laser transport and trigger an avalanchelike QED cascade, efficiently transferring the laser energy to the photons. This renders a 1 -μ m scale-length, underdense preplasma completely opaque to laser pulses at this power level. The QED-induced opacity therefore sets much higher contrast requirements for such a pulse in solid-target experiments than expected by classical plasma physics. Our simulations show, for example, that proton acceleration from the rear of a solid with a preplasma would be strongly impaired.

The role of laser wavelength on plasma generation and expansion of ablation plumes in air

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hussein, A. E.; Department of Physics, McGill University, Montreal, Quebec H3A 0G4; Diwakar, P. K.

2013-04-14

We investigated the role of excitation laser wavelength on plasma generation and the expansion and confinement of ablation plumes at early times (0-500 ns) in the presence of atmospheric pressure. Fundamental, second, and fourth harmonic radiation from Nd:YAG laser was focused on Al target to produce plasma. Shadowgraphy, fast photography, and optical emission spectroscopy were employed to analyze the plasma plumes, and white light interferometry was used to characterize the laser ablation craters. Our results indicated that excitation wavelength plays a crucial role in laser-target and laser-plasma coupling, which in turn affects plasma plume morphology and radiation emission. Fast photographymore » and shadowgraphy images showed that plasmas generated by 1064 nm are more cylindrical compared to plasmas generated by shorter wavelengths, indicating the role of inverse bremsstrahlung absorption at longer laser wavelength excitation. Electron density estimates using Stark broadening showed higher densities for shorter wavelength laser generated plasmas, demonstrating the significance of absorption caused by photoionization. Crater depth analysis showed that ablated mass is significantly higher for UV wavelengths compared to IR laser radiation. In this experimental study, the use of multiple diagnostic tools provided a comprehensive picture of the differing roles of laser absorption mechanisms during ablation.« less

Influence of irradiation conditions on plasma evolution in laser-surface interaction

NASA Astrophysics Data System (ADS)

Hermann, J.; Boulmer-Leborgne, C.; Dubreuil, B.; Mihailescu, I. N.

1993-09-01

The plasma plume induced by pulsed CO2 laser irradiation of a Ti target at power densities up to 4×108 W cm-2 was studied by emission spectroscopy. Time- and space-resolved measurements were performed by varying laser intensity, laser temporal pulse shape, ambient gas pressure, and the nature of the ambient gas. Experimental results are discussed by comparison with usual models. We show that shock wave and plasma propagation depend critically on the ratio Ivap/Ii, Ivap being the intensity threshold for surface vaporization and Ii the plasma ignition threshold of the ambient gas. Spectroscopic diagnostics of the helium breakdown plasma show maximum values of electron temperature and electron density in the order of kTe˜10 eV and ne=1018 cm-3, respectively. The plasma cannot be described by local thermodynamic equilibrium modeling. Nevertheless, excited metal atoms appear to be in equilibrium with electrons, hence, they can be used like a probe to measure the electron temperature. In order to get information on the role of the plasma in the laser-surface interaction, Ti surfaces were investigated by microscopy after irradiation. Thus an enhanced momentum transfer from the plasma to the target due to the recoil pressure of the breakdown plasma could be evidenced.

Enhanced pair plasma generation in the relativistic transparency regime

NASA Astrophysics Data System (ADS)

Liu, W. Y.; Luo, W.; Yuan, T.; Yu, J. Y.; Chen, M.; Sheng, Z. M.

2017-10-01

Electron-positron ( e - e + ) pair plasma generation in the relativistic transparency regime in a thin foil with a fixed thickness irradiated by two counter-propagating laser pulses is investigated through multi-dimensional particle-in-cell simulations. It is shown that target transparency can significantly enhance the pair generation due to the formation of a stable standing wave. An optimum foil density of 200-280 n c (with nc being the critical plasma density of the incident laser at the wavelength of 1 μm) is found for enhanced e - e + pair generation for laser intensity around 10 PW. With such foil density, laser energy transformed to pair plasma formation is approximately four times higher than that with a foil density of 710 nc, while the laser energy transformed to γ-photons remains almost the same. Dense e - e + plasma with a density as high as 10 22 cm - 3 ( ≃ 10 n c ) can be produced accordingly. Comparison of pair plasma generation between cases with fundamental and double frequency driver lasers further demonstrates such an enhancement effect. It shows that when the duration of the laser pulse is relatively short, the double frequency driver can generate more pair plasmas due to the earlier excitation of relativistic transparency.

Electron Bernstein Wave Studies in MST

NASA Astrophysics Data System (ADS)

Seltzman, Andrew; Anderson, Jay; Forest, Cary; Nonn, Paul; Thomas, Mark; Reusch, Joshua; Hendries, Eric

2013-10-01

The overdense condition in a RFP prevents electromagnetic waves from propagating past the extreme edge. However use of the electron Bernstein wave (EBW) has the potential to heat and drive current in the plasma. MHD simulations have demonstrated that resistive tearing mode stability is very sensitive to the gradient in the edge current density profile, allowing EBW current drive to influence and potentially stabilize tearing mode activity. Coupling between the X-mode and Bernstein waves is strongly dependent on the edge density gradient. The effects on coupling of plasma density, magnetic field strength, antenna radial position and launch polarization have been examined. Coupling as high as 90% has been observed. Construction of a 450 kw RF source is complete and initial experimental results will be reported. The power and energy of this auxiliary system should be sufficient for several scientific purposes, including verifying mode conversion, EBW propagation and absorption in high beta plasmas. Target plasmas in the 300-400 kA range will be heated near the reversal surface, potentially allowing mode control, while target plasmas in the 250 kA range will allow heating near the core, allowing better observation of heating effects. Heating and heat pulse propagation experiments are planned, as well as probing the stability of parametric decay during mode conversion, at moderate injected power. Work supported by USDOE.

Studies of Ion Beam Charge Neutralization by Ferroelectric Plasma Sources

NASA Astrophysics Data System (ADS)

Stepanov, A.; Gilson, E. P.; Grisham, L.; Davidson, R. C.

2013-10-01

Space-charge forces limit the possible transverse compression of high perveance ion beams that are used in ion-beam-driven high energy density physics applications; the minimum radius to which a beam can be focused is an increasing function of perveance. The limit can be overcome if a plasma is introduced in the beam path between the focusing element and the target in order to neutralize the space charge of the beam. This concept has been implemented on the Neutralized Drift Compression eXperiment (NDCX) at LBNL using Ferroelectric Plasma Sources (FEPS). In our experiment at PPPL, we propagate a perveance-dominated ion beam through a FEPS to study the effect of the neutralizing plasma on the beam envelope and its evolution in time. A 30-60 keV space-charge-dominated Argon beam is focused with an Einzel lens into a FEPS located at the beam waist. The beam is intercepted downstream from the FEPS by a movable Faraday cup that provides time-resolved 2D current density profiles of the beam spot on target. We report results on: (a) dependence of charge neutralization on FEPS plasma density; (b) effects on beam emittance, and (c) time evolution of the beam envelope after the FEPS pulse. Research supported by the U.S. Department of Energy.

Stable quasi-monoenergetic ion acceleration from the laser-driven shocks in a collisional plasma

NASA Astrophysics Data System (ADS)

Bhadoria, Shikha; Kumar, Naveen; Keitel, Christoph H.

2017-10-01

Effect of collisions on the shock formation and subsequent ion acceleration from the laser-plasma interaction is explored by the means of particle-in-cell simulations. In this setup, the incident laser pushes the laser-plasma interface inside the plasma target through the hole-boring effect and generates hot electrons. The propagation of these hot electrons inside the target excites a return plasma current, leading to filamentary structures caused by the Weibel/filamentation instability. Weakening of the space-charge effects due to collisions results in the shock formation with a higher density jump than in a collisionless plasma. This results in the formation of a stronger shock leading to a stable quasi-monoenergetic acceleration of ions.

Changes in divertor conditions in response to changing core density with RMPs

DOE PAGES

Briesemeister, Alexis R.; Ahn, Joon -Wook; Canik, John M.; ...

2017-06-07

The effects of changes in core density on divertor electron temperature, density and heat flux when resonant magnetic perturbations (RMPs) are applied are presented, notably a reduction in RMP induced secondary radial peaks in the electron temperature profile at the target plate is observed when the core density is increased, which is consistent with modeling. RMPs is used here to indicated non-axisymmetric magnetic field perturbations, created using in-vessel control coils, which have components which has at least one but typically many resonances with the rotational transform of the plasma. RMPs are found to alter inter-ELM heat flux to the divertormore » by modifying the core plasma density. It is shown that applying RMPs reduces the core density and increases the inter-ELM heat flux to both the inner and outer targets. Using gas puffing to return the core density to the pre-RMP levels more than eliminates the increase in inter-ELM heat flux, but a broadening of the heat flux to the outer target remains. These measurements were made at a single toroidal location, but the peak in the heat flux profile was found near the outer strike point where simulations indicate little toroidal variation should exist and tangentially viewing diagnostics showed no evidence of strong asymmetries. In experiments where divertor Thomson scattering measurements were available it is shown that, local secondary peaks in the divertor electron temperature profile near the target plate are reduced as the core density is increased, while peaks in the divertor electron density profile near the target are increased. Furthermore, these trends observed in the divertor electron temperature and density are qualitatively reproduced by scanning the upstream density in EMC3-Eirene modeling. Measurements are presented showing that higher densities are needed to induce detachment of the outer strike point in a case where an increase in electron temperature, likely due to a change in MHD activity, is seen after RMPs are applied.« less

Changes in divertor conditions in response to changing core density with RMPs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Briesemeister, Alexis R.; Ahn, Joon -Wook; Canik, John M.

The effects of changes in core density on divertor electron temperature, density and heat flux when resonant magnetic perturbations (RMPs) are applied are presented, notably a reduction in RMP induced secondary radial peaks in the electron temperature profile at the target plate is observed when the core density is increased, which is consistent with modeling. RMPs is used here to indicated non-axisymmetric magnetic field perturbations, created using in-vessel control coils, which have components which has at least one but typically many resonances with the rotational transform of the plasma. RMPs are found to alter inter-ELM heat flux to the divertormore » by modifying the core plasma density. It is shown that applying RMPs reduces the core density and increases the inter-ELM heat flux to both the inner and outer targets. Using gas puffing to return the core density to the pre-RMP levels more than eliminates the increase in inter-ELM heat flux, but a broadening of the heat flux to the outer target remains. These measurements were made at a single toroidal location, but the peak in the heat flux profile was found near the outer strike point where simulations indicate little toroidal variation should exist and tangentially viewing diagnostics showed no evidence of strong asymmetries. In experiments where divertor Thomson scattering measurements were available it is shown that, local secondary peaks in the divertor electron temperature profile near the target plate are reduced as the core density is increased, while peaks in the divertor electron density profile near the target are increased. Furthermore, these trends observed in the divertor electron temperature and density are qualitatively reproduced by scanning the upstream density in EMC3-Eirene modeling. Measurements are presented showing that higher densities are needed to induce detachment of the outer strike point in a case where an increase in electron temperature, likely due to a change in MHD activity, is seen after RMPs are applied.« less

Proton acceleration by multi-terawatt interaction with a near-critical density hydrogen jet

NASA Astrophysics Data System (ADS)

Goers, Andy; Feder, Linus; Hine, George; Salehi, Fatholah; Woodbury, Daniel; Su, J. J.; Papadopoulos, Dennis; Zigler, Arie; Milchberg, Howard

2016-10-01

We investigate the high intensity laser interaction with thin, near critical density plasmas as a means of efficient acceleration of MeV protons. A promising mechanism is magnetic vortex acceleration, where the ponderomotive force of a tightly focused laser pulse drives a relativistic electron current which generates a strong azimuthal magnetic field. The rapid expansion of this azimuthal magnetic field at the back side of the target can accelerate plasma ions to MeV scale energies. Compared to typical ion acceleration experiments utilizing a laser- thin solid foil interaction, magnetic vortex acceleration in near critical density plasma may be realized in a high density gas jet, making it attractive for applications requiring high repetition rates. We present preliminary experiments studying laser-plasma interaction and proton acceleration in a thin (< 200 μm) near-critical density hydrogen gas jet delivering electron densities 1020 -1021 cm-3 . This research was funded by the United States Department of Energy and the Defense Advanced Research Projects Agency (DARPA) under Contract Number W911-NF-15-C-0217, issued by the Army Research Office.

Control of ultra-intense single attosecond pulse generation in laser-driven overdense plasmas.

PubMed

Liu, Qingcao; Xu, Yanxia; Qi, Xin; Zhao, Xiaoying; Ji, Liangliang; Yu, Tongpu; Wei, Luo; Yang, Lei; Hu, Bitao

2013-12-30

Ultra-intense single attosecond pulse (AP) can be obtained from circularly polarized (CP) laser interacting with overdense plasma. High harmonics are naturally generated in the reflected laser pulses due to the laser-induced one-time drastic oscillation of the plasma boundary. Using two-dimensional (2D) planar particle-in-cell (PIC) simulations and analytical model, we show that multi-dimensional effects have great influence on the generation of AP. Self-focusing and defocusing phenomena occur in front of the compressed plasma boundary, which lead to the dispersion of the generated AP in the far field. We propose to control the reflected high harmonics by employing a density-modulated foil target (DMFT). When the target density distribution fits the laser intensity profile, the intensity of the attosecond pulse generated from the center part of the plasma has a flatten profile within the center range in the transverse direction. It is shown that a single 300 attosecond (1 as = 10(-18)s) pulse with the intensity of 1.4 × 10(21) W cm(-2) can be naturally generated. Further simulations reveal that the reflected high harmonics properties are highly related to the modulated density distribution and the phase offset between laser field and the carrier envelope. The emission direction of the AP generated from the plasma boundary can be controlled in a very wide range in front of the plasma surface by combining the DMFT and a suitable driving laser.

Axial- and radial-resolved electron density and excitation temperature of aluminum plasma induced by nanosecond laser: Effect of the ambient gas composition and pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dawood, Mahmoud S.; Hamdan, Ahmad, E-mail: ahmad.ba.hamdan@gmail.com, E-mail: Joelle.margot@umontreal.ca; Margot, Joëlle, E-mail: ahmad.ba.hamdan@gmail.com, E-mail: Joelle.margot@umontreal.ca

2015-11-15

The spatial variation of the characteristics of an aluminum plasma induced by a pulsed nanosecond XeCl laser is studied in this paper. The electron density and the excitation temperature are deduced from time- and space- resolved Stark broadening of an ion line and from a Boltzmann diagram, respectively. The influence of the gas pressure (from vacuum up to atmospheric pressure) and compositions (argon, nitrogen and helium) on these characteristics is investigated. It is observed that the highest electron density occurs near the laser spot and decreases by moving away both from the target surface and from the plume center tomore » its edge. The electron density increases with the gas pressure, the highest values being occurred at atmospheric pressure when the ambient gas has the highest mass, i.e. in argon. The excitation temperature is determined from the Boltzmann plot of line intensities of iron impurities present in the aluminum target. The highest temperature is observed close to the laser spot location for argon at atmospheric pressure. It decreases by moving away from the target surface in the axial direction. However, no significant variation of temperature occurs along the radial direction. The differences observed between the axial and radial direction are mainly due to the different plasma kinetics in both directions.« less

Low-velocity ion stopping in a dense and low-temperature plasma target

NASA Astrophysics Data System (ADS)

Deutsch, Claude; Popoff, Romain

2007-07-01

We investigate the stopping specificities involved in the heating of thin foils irradiated by intense ion beams in the 0.3-3 MeV/amu energy range and in close vicinity of the Bragg peak. Considering a swiftly ionized target to eV temperatures before expansion while retaining solid-state density, a typical warm dense matter (WDM) situation thus arises. We stress low Vp stopping through ion diffusion in the given target plasma. This allows to include the case of a strongly magnetized target in a guiding center approximation. We also demonstrate that the ion projectile penetration depth in target is significantly affected by multiple scattering on target electrons. The given plasma target is taken weakly coupled with Maxwell electron either with no magnetic field ( B=0) or strongly magnetized ( B≠0). Dynamical coupling between ion projectiles energy losses and projectiles charge state will also be addressed.

Investigation of Zn and Cu prepulse plasmas relevant to collisional excitation x-ray lasers

NASA Astrophysics Data System (ADS)

Rus, B.; Zeitoun, P.; Mocek, T.; Sebban, S.; Kálal, M.; Demir, A.; Jamelot, G.; Klisnick, A.; Králiková, B.; Skála, J.; Tallents, G. J.

1997-11-01

This paper presents the results of a comparative experimental study of low-temperature Zn and Cu line plasmas created on slab targets by 400-ps laser pulse producing irradiance from 4×109 to 1011 W cm-2. The aim was to examine the nanosecond-scale postpulse evolution of plasmas created in conditions equivalent to those produced by prepulses in collisional x-ray lasers, of elements that have neighboring atomic numbers but very different material properties. The plasmas were interferometrically probed at 4 and 10 ns next to the driving pulse, using geometry that made it possible to obtain an authentic two-dimensional (2D) electron density pattern in the plane perpendicular to the plasma axis. VIS-IR spectroscopy and imaging were used to provide an indication of the electron temperature and volume of the plasma layer near the target. We observe that over the whole range of the applied irradiances the characteristics and/or the expansion history of the Zn and Cu plasmas are very different. For irradiance exceeding a threshold specific to each element the density patterns exhibit an unexpected structure characterized by symmetrical flanks strongly localized in space, suggesting plasma is generated in addition to that produced within the laser pulse duration. The results imply that during the postpulse time the energy coupling between the plasma and the target is substantial for the plasma flow that exhibits a complex 2D character. A comparison of the data and results of a 1.5D hydrodynamic simulation for 1011 W cm-2 is made, indicating reasons for problems of such models in the treatment of the plasmas in question, and thus in the treatment of small-prepulse action in some x-ray laser systems.

Combined experimental and theoretical description of direct current magnetron sputtering of Al by Ar and Ar/N2 plasma

NASA Astrophysics Data System (ADS)

Trieschmann, Jan; Ries, Stefan; Bibinov, Nikita; Awakowicz, Peter; Mráz, Stanislav; Schneider, Jochen M.; Mussenbrock, Thomas

2018-05-01

Direct current magnetron sputtering of Al by Ar and Ar/N2 low pressure plasmas was characterized by experimental and theoretical means in a unified consideration. Experimentally, the plasmas were analyzed by optical emission spectroscopy, while the film deposition rate was determined by weight measurements and laser optical microscopy, and the film composition by energy dispersive x-ray spectroscopy. Theoretically, a global particle and power balance model was used to estimate the electron temperature T e and the electron density n e of the plasma at constant discharge power. In addition, the sputtering process and the transport of the sputtered atoms were described using Monte Carlo models—TRIDYN and dsmcFoam, respectively. Initially, the non-reactive situation is characterized based on deposition experiment results, which are in agreement with predictions from simulations. Subsequently, a similar study is presented for the reactive case. The influence of the N2 addition is found to be twofold, in terms of (i) the target and substrate surface conditions (e.g., sputtering, secondary electron emission, particle sticking) and (ii) the volumetric changes of the plasma density n e governing the ion flux to the surfaces (e.g., due to additional energy conversion channels). It is shown that a combined experimental/simulation approach reveals a physically coherent and, in particular, quantitative understanding of the properties (e.g., electron density and temperature, target surface nitrogen content, sputtered Al density, deposited mass) involved in the deposition process.

NEUTRON SOURCE

DOEpatents

Foster, J.S. Jr.

1960-04-19

A compact electronic device capable of providing short time high density outputs of neutrons is described. The device of the invention includes an evacuated vacuum housing adapted to be supplied with a deuterium, tritium, or other atmosphere and means for establishing an electrical discharge along a path through the gas. An energized solenoid is arranged to constrain the ionized gas (plasma) along the path. An anode bearing adsorbed or adherent target material is arranged to enclose the constrained plasma. To produce neutrons a high voltage is applied from appropriate supply means between the plasma and anode to accelerate ions from the plasma to impinge upcn the target material, e.g., comprising deuterium.

Isochoric Heating of Solid-Density Matter with an Ultrafast Proton Beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Key, M H; Mackinnon, A J; Patel, P K

A new technique is described for the isochoric heating (i.e., heating at constant volume) of matter to high energy-density plasma states (>10{sup 5} J/g) on a picosecond timescale (10{sup -12} sec). An intense, collimated, ultrashort-pulse beam of protons--generated by a high-intensity laser pulse--is used to isochorically heat a solid density material to a temperature of several eV. The duration of heating is shorter than the timescale for significant hydrodynamic expansion to occur, hence the material is heated to a solid density warm dense plasma state. Using spherically-shaped laser targets a focused proton beam is produced and used to heat amore » smaller volume to over 20 eV. The technique described of ultrafast proton heating provides a unique method for creating isochorically heated high-energy density plasma states.« less

Stopping power in D6Li plasmas for target ignition studies

NASA Astrophysics Data System (ADS)

Cortez, Ross J.; Cassibry, Jason T.

2018-02-01

The ability to calculate the range of charged fusion products in a target is critical when estimating driver requirements. Additionally, charged particle ranges are a determining factor in the possibility that a burn front will propagate through the surrounding cold fuel layer, igniting the plasma. Performance parameters of the plasma, such as yield, gain, etc therefore rely on accurate knowledge of particle ranges and stopping power over a wide range of densities and temperatures. Further, this knowledge is essential in calculating ignition conditions for a given target design. In this paper, stopping power is calculated for DD and D6Li plasmas using a molecular dynamics based model. Emphasis is placed on solid D6Li which has been recently considered as a fuel option for fusion propulsion systems.

Dynamics of low- and high-Z metal ions emitted during nanosecond laser-produced plasmas

NASA Astrophysics Data System (ADS)

Elsied, Ahmed M.; Diwakar, Prasoon K.; Polek, Mathew; Hassanein, Ahmed

2016-11-01

Dynamics of metal ions during laser-produced plasmas was studied. A 1064 nm, Nd: YAG laser pulse was used to ablate pure Al, Fe, Co, Mo, and Sn samples. Ion flux and velocity were measured using Faraday cup ion collector. Time-of-flight measurements showed decreasing ion flux and ion velocity with increasing atomic weight, and heavy metal ion flux profile exhibited multiple peaks that was not observed in lighter metals. Slow peak was found to follow shifted Maxwell Boltzmann distribution, while the fast peak was found to follow Gaussian distribution. Ion flux angular distribution that was carried out on Mo and Al using fixed laser intensity 2.5 × 1010 W/cm2 revealed that the slow ion flux peaks at small angles, that is, close to normal to the target ˜0° independent of target's atomic weight, and fast ion flux for Mo peaks at large angles ˜40° measured from the target normal, while it completely absents for Al. This difference in spatial and temporal distribution reveals that the emission mechanism of the fast and slow ions is different. From the slow ion flux angular distribution, the measured plume expansion ratio (plume forward peaking) was 1.90 and 2.10 for Al and Mo, respectively. Moreover, the effect of incident laser intensity on the ion flux emission as well as the emitted ion velocity were investigated using laser intensities varying from 2.5 × 1010 W/cm2 to 1.0 × 1011 W/cm2. Linear increase of fast ion flux and velocity, and quadratic increase of slow ion flux and velocity were observed. For further understanding of plume dynamics, laser optical emission spectroscopy was used to characterize Sn plasma by measuring the temporal and spatial evolution of plasma electron density Ne and electron temperature Te. At 3.5 mm away from the target, plasma density showed slow decrease with time, however electron temperature was observed to decrease dramatically. The maximum plasma density and temperature occurred at 0.5 mm away from target and were measured to be 8.0 × 1017 cm-3 and 1.3 eV, respectively.

The current-density distribution in a pulsed dc magnetron deposition discharge

NASA Astrophysics Data System (ADS)

Vetushka, Alena; Bradley, James W.

2007-04-01

Using a carefully constructed magnetic probe (a B-dot probe) the spatial and temporal evolution of the perturbation in the magnetic field ΔB in an unbalanced pulsed dc magnetron has been determined. The plasma was run in argon at a pressure of 0.74 Pa and the plasma ions sputtered a pure graphite target. The pulse frequency and duty were set at 100 kHz and 55%, respectively. From the ΔB measurements (measured with magnitudes up to about 0.01 mT) the axial, azimuthal and radial components of the total current density j in the plasma bulk were determined. In the plasma 'on' phase, the axial current density jz has a maximum value of approximately 200 A m-2 above the racetrack region, while high values in the azimuthal current density jΦ are distributed in a region from 1 to 3 cm into the bulk plasma with jΦ exceeding 350 A m-2. In the 'off' phase of the plasma, jz decays almost instantaneously (at least within the 100 ns time-resolution of the ΔB measurements) as the electric field collapses; however, jΦ decays with a characteristic time constant of about 1 µs. This slow decay can be attributed to the presence of decaying Grad-B and curvature drifts, with their rates controlled by the decay in the plasma density. A comparison between axial and azimuthal current densities in the plasma 'on' time, when the plasma is being driven, strongly indicates that classical transport does not operate in the magnetron discharge.

LLE Review Quarterly Report (October - December 2007). Volume 113

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zuegel, Jonathan D.

2007-12-01

This volume of the LLE Review, covering October–December 2007, features “High-Intensity Laser–Plasma Interactions in the Refluxing Limit,” by P. M. Nilson, W. Theobald, J. Myatt, C. Stoeckl, M. Storm, O. V. Gotchev, J. D. Zuegel, R. Betti, D. D. Meyerhofer, and T. C. Sangster. In this article (p. 1), the authors report on target experiments using the Multi-Terawatt (MTW) Laser Facility to study isochoric heating of solid-density targets by fast electrons produced from intense, short-pulse laser irradiation. Electron refluxing occurs due to target-sheath field effects and contains most of the fast electrons within the target volume. This efficiently heats themore » solid-density plasma through collisions. X-ray spectroscopic measurements of absolute K α (x-radiation) photon yields and variations of the K β/K α b emission ratio both indicate that laser energy couples to fast electrons with a conversion efficiency of approximately 20%. Bulk electron temperatures of at least 200 eV are inferred for the smallest mass targets.« less

Non-Maxwellian electron distributions by direct laser acceleration in near-critical plasmas

NASA Astrophysics Data System (ADS)

Toncian, T.; Wang, C.; Arefiev, A.; McCary, E.; Meadows, A.; Blakeney, J.; Chester, C.; Roycroft, R.; Fu, H.; Yan, X. Q.; Schreiber, J.; Pomerantz, I.; Quevedo, H.; Dyer, G.; Gaul, E.; Ditmire, T.; Hegelich, B. M.

2015-11-01

The irradiation of few nm thick targets by a finite-contrast high-intensity short-pulse laser results in a strong pre-expansion of these targets at the arrival time of the main pulse. The targets will decompress to near and lower than critical electron densities plasmas extending over lengths of few micrometers. The laser-matter interaction of the main pulse with such a highly localized but inhomogeneous the target leads to the generation of a channel and further self focussing of the laser beam. As measured in a experiment conducted with the GHOST laser system at UT Austin, 2D PIC simulations predict Direct Laser Acceleration of non-Maxwellian electron distribution in the laser propagation direction for such targets. The hereby high density electron bunches have potential applications as injector beams for a further wakefield acceleration stage. This work was supported by NNSA cooperative agreement DE-NA0002008, the DARPA's PULSE program (12-63-PULSE-FP014) and the AFOSR (FA9550-14-1-0045).

Preliminary studies for a beam-generated plasma neutralizer test in NIO1

NASA Astrophysics Data System (ADS)

Sartori, E.; Veltri, P.; Balbinot, L.; Cavenago, M.; Veranda, M.; Antoni, V.; Serianni, G.

2017-08-01

The deployment of neutral beam injectors in future fusion plants is beset by the particularly poor efficiency of the neutralization process. Beam-generated plasma neutralizers were proposed as a passive and intrinsically safe scheme of efficient plasma neutralizers. The concept is based on the natural ionization of the gas target by the beam, and on a suitable confinement of the secondary plasma. The technological challenge of such a concept is the magnetic confinement of the secondary plasma: a proof-of-principle for the concept is needed. The possibility to test of such a system in the small negative ion beam system NIO1 is discussed in this paper. The constraints given by the facility are first discussed. A model of beam-gas interaction is developed to provide the charge-state of beam particles along the neutralizer, and to provide the source terms of plasma generation. By using a cylindrical model of plasma diffusion in magnetic fields, the ionization degree of the target is estimated. In the absence of magnetic fields the diffusion model is validated against experimental measurements of the space-charge compensation plasma in the drift region of NIO1. Finally, the feasibility study for a beam-generated plasma neutralizer in NIO is presented. The neutralizer length, required gas target thickness, and a very simple magnetic setup were considered, taking into account the integration in NIO1. For the basic design a low ionization degree (1%) is obtained, however a promising plasma density up to hundred times the beam density was calculated. The proposed test in NIO1 can be the starting point for studying advanced schemes of magnetic confinement aiming at ionization degrees in the order of 10%.

EFFECTS OF LASER RADIATION ON MATTER: Fast holographic cinematography of a laser plasma

NASA Astrophysics Data System (ADS)

Barikhin, B. A.; Ivanov, A. Yu; Nedolugov, V. I.

1990-11-01

A fast holographic cinematography method was used in an investigation of a laser plasma initiated at the surfaces of metal samples by pulses from a rhodamine laser. The time evolution of the electron densities and heavy-particle concentrations was determined and a study was made of the nature of motion of a shock wave front. A weak dependence of the evolution of the shock wave velocity on the target materials (aluminum, copper, zinc) was observed in the average power density range 10-25 MW/cm2. A faster increase in the dimensions of a refracting plasma region, compared with a luminous region, and strong expulsion of cold air by an erosion plasma were recorded.

Effect of Energetic Plasma Flux on Flowing Liquid Lithium Surfaces

NASA Astrophysics Data System (ADS)

Kalathiparambil, Kishor; Jung, Soonwook; Christenson, Michael; Fiflis, Peter; Xu, Wenyu; Szott, Mathew; Ruzic, David

2014-10-01

An operational liquid lithium system with steady state flow driven by thermo-electric magneto-hydrodynamic force and capable of constantly refreshing the plasma exposed surface have been demonstrated at U of I. To evaluate the system performance in reactor relevant conditions, specifically to understand the effect of disruptive plasma events on the performance of the liquid metal PFCs, the setup was integrated to a pulsed plasma generator. A coaxial plasma generator drives the plasma towards a theta pinch which preferentially heats the ions, simulating ELM like flux, and the plasma is further guided towards the target chamber which houses the flowing lithium system. The effect of the incident flux is examined using diagnostic tools including triple Langmuir probe, calorimeter, rogowski coils, Ion energy analyzers, and fast frame spectral image acquisition with specific optical filters. The plasma have been well characterized and a density of ~1021 m-3, with electron temperature ~10 - 20 eV is measured, and final plasma velocities of 34 - 74 kms-1 have been observed. Calorimetric measurements using planar molybdenum targets indicate a maximum plasma energy (with 6 kV plasma gun and 20 kV theta pinch) of 0.08 MJm-2 with plasma divergence effects resulting in marginal reduction of 40 +/- 23 J in plasma energy. Further results from the other diagnostic tools, using the flowing lithium targets and the planar targets coated with lithium will be presented. DOE DE-SC0008587.

Modeling of plasma distortions by laser-induced ablation spectroscopy (LIAS) and implications for the interpretation of LIAS measurements

NASA Astrophysics Data System (ADS)

Tokar, M. Z.; Gierse, N.; Philipps, V.; Samm, U.

2015-09-01

For the interpretation of the line radiation observed from laser induced ablation spectroscopy (LIAS) such parameters as the density and temperature of electrons within very compact clouds of atoms and singly charged ions of ablated material have to be known. Compared to the local plasma conditions prior to the laser pulse, these can be strongly changed during LIAS since new electrons are generated by the ionisation of particles ejected from the irradiated target. Because of their transience and spatial inhomogeneity it is technically difficult to measure disturbances induced in the plasma by LIAS. To overcome this uncertainty a numerical model has been elaborated, providing a self-consistent description for the spreading of ablated particles and accompanying modifications in the plasma. The results of calculations for LIAS performed on carbon-containing targets in Ohmic and additionally heated discharges in the tokamak TEXTOR are presented. Due to the increase in the electron density the ‘ionisation per photon’ ratio, S/XB factor, is significantly enhanced compared to unperturbed plasma conditions. The impact of the amount of material ablated and of the plasma conditions before LIAS on the level of the S/XB-enhancement is investigated.

Angular filter refractometry analysis using simulated annealing.

PubMed

Angland, P; Haberberger, D; Ivancic, S T; Froula, D H

2017-10-01

Angular filter refractometry (AFR) is a novel technique used to characterize the density profiles of laser-produced, long-scale-length plasmas [Haberberger et al., Phys. Plasmas 21, 056304 (2014)]. A new method of analysis for AFR images was developed using an annealing algorithm to iteratively converge upon a solution. A synthetic AFR image is constructed by a user-defined density profile described by eight parameters, and the algorithm systematically alters the parameters until the comparison is optimized. The optimization and statistical uncertainty calculation is based on the minimization of the χ 2 test statistic. The algorithm was successfully applied to experimental data of plasma expanding from a flat, laser-irradiated target, resulting in an average uncertainty in the density profile of 5%-20% in the region of interest.

Transport simulations of linear plasma generators with the B2.5-Eirene and EMC3-Eirene codes

DOE PAGES

Rapp, Juergen; Owen, Larry W.; Bonnin, X.; ...

2014-12-20

Linear plasma generators are cost effective facilities to simulate divertor plasma conditions of present and future fusion reactors. For this research, the codes B2.5-Eirene and EMC3-Eirene were extensively used for design studies of the planned Material Plasma Exposure eXperiment (MPEX). Effects on the target plasma of the gas fueling and pumping locations, heating power, device length, magnetic configuration and transport model were studied with B2.5-Eirene. Effects of tilted or vertical targets were calculated with EMC3-Eirene and showed that spreading the incident flux over a larger area leads to lower density, higher temperature and off-axis profile peaking in front of themore » target. In conclusion, the simulations indicate that with sufficient heating power MPEX can reach target plasma conditions that are similar to those expected in the ITER divertor. B2.5-Eirene simulations of the MAGPIE experiment have been carried out in order to establish an additional benchmark with experimental data from a linear device with helicon wave heating.« less

Inertial confinement fusion and fast ignitor studies

NASA Astrophysics Data System (ADS)

Willi, O.; Barringer, L.; Bell, A.; Borghesi, M.; Davies, J.; Gaillard, R.; Iwase, A.; MacKinnon, A.; Malka, G.; Meyer, C.; Nuruzzaman, S.; Taylor, R.; Vickers, C.; Hoarty, D.; Gobby, P.; Johnson, R.; Watt, R. G.; Blanchot, N.; Canaud, B.; Croso, H.; Meyer, B.; Miquel, J. L.; Reverdin, C.; Pukhov, A.; Meyer-ter-Vehn, J.

2000-03-01

Laser imprinting has been studied and, in particular, saturation of areal density perturbations induced by near single mode laser imprinting was observed. Several issues important for the foam buffered direct drive scheme have been investigated. These studies included measurements of the absolute levels of stimulated Brillouin and Raman scattering observed from laser irradiated low density foam targets, either bare or overcoated with a thin layer of gold. A novel scheme is proposed to increase the pressure in indirectly driven targets. By heating a foam supersonically that is attached to a solid target the pressure generated is not only the ablation pressure but also the combined pressure due to ablation at the foam-foil interface and the heated foam material. Planar brominated plastic foil targets overcoated with a low density foam were irradiated by a soft X ray pulse. The pressure was obtained by comparing the rear side trajectory of the driven target observed by soft X ray radiography with one dimensional radiation hydrodynamic simulations. Observations were also carried out of the transition from supersonic to subsonic propagation of an ionization front in low density chlorinated foam targets irradiated by an intense soft X ray pulse. The diagnostic for these measurements was K shell point projection absorption spectroscopy. In the fast ignitor area the channelling and guiding of picosecond laser pulses through underdense plasmas, preformed density channels and microtubes were investigated. It was observed that a large fraction of the incident laser energy can be propagated. Megagauss magnetic fields were measured, with a polarimetric technique, during and after propagation of intense picosecond pulses in preionized plasmas. Two types of toroidal fields, of opposite orientation, were detected. In addition, the production and propagation of an electron beam through solid glass targets irradiated at intensities above 1019W/cm2 were observed using optical probing techniques.

Observations of electron heating during 28 GHz microwave power application in proto-MPEX

DOE PAGES

Biewer, Theodore M.; Bigelow, Tim S.; Caneses Marin, Juan F.; ...

2018-02-01

The Prototype Material Plasma Exposure Experiment at the Oak Ridge National Laboratory utilizes a variety of power systems to generate and deliver a high heat flux plasma onto the surface of material targets. In the experiments described here, a deuterium plasma is produced via a ~100 kW, 13.56 MHz RF helicon source, to which ~20 kW of 28 GHz microwave power is applied. The electron density and temperature profiles are measured using a Thomson scattering (TS) diagnostic, and indicate that the electron density is centrally peaked. In the core of the plasma column, the electron density is higher than themore » cut-off density (~0.9 × 1019 m -3) for the launched mixture of X- and O-mode electron cyclotron heating waves to propagate. TS measurements indicate electron temperature increases from ~5 eV to ~20 eV during 28 GHz power application when the neutral deuterium pressure is reduced below 0.13 Pa (~1 mTorr.).« less

Observations of electron heating during 28 GHz microwave power application in proto-MPEX

NASA Astrophysics Data System (ADS)

Biewer, T. M.; Bigelow, T. S.; Caneses, J. F.; Diem, S. J.; Green, D. L.; Kafle, N.; Rapp, J.; Proto-MPEX Team

2018-02-01

The Prototype Material Plasma Exposure Experiment at the Oak Ridge National Laboratory utilizes a variety of power systems to generate and deliver a high heat flux plasma onto the surface of material targets. In the experiments described here, a deuterium plasma is produced via a ˜100 kW, 13.56 MHz RF helicon source, to which ˜20 kW of 28 GHz microwave power is applied. The electron density and temperature profiles are measured using a Thomson scattering (TS) diagnostic, and indicate that the electron density is centrally peaked. In the core of the plasma column, the electron density is higher than the cut-off density (˜0.9 × 1019 m-3) for the launched mixture of X- and O-mode electron cyclotron heating waves to propagate. TS measurements indicate electron temperature increases from ˜5 eV to ˜20 eV during 28 GHz power application when the neutral deuterium pressure is reduced below 0.13 Pa (˜1 mTorr.).

High-Density Lipoprotein-Targeted Therapy and Apolipoprotein A-I Mimetic Peptides.

PubMed

Uehara, Yoshinari; Chiesa, Giulia; Saku, Keijiro

2015-01-01

Numerous randomized clinical trials have established statins as the major standard therapy for atherosclerotic diseases because these molecules decrease the plasma level of low-density lipoprotein (LDL) cholesterol and moderately increase that of plasma high-density lipoprotein (HDL) cholesterol. The reverse cholesterol transport pathway, mediated by HDL particles, has a relevant antiatherogenic potential. An important approach to HDL-targeted therapy is optimization of the HDL-cholesterol level and enhanced removal of plasma cholesterol, together with the prevention and mitigation of inflammation related to atherosclerosis. Small-molecule inhibitors of cholesteryl ester transfer protein (CETP) increase the HDL-cholesterol level in subjects with normal or low HDL-cholesterol. However, CETP inhibitors do not seem to reduce the risk of atherosclerotic diseases. HDL therapies using reconstituted HDL, including apolipoprotein (Apo) A-I Milano, ApoA-I mimetics, or full-length ApoA-I, are dramatically effective in animal models. Of those, the ApoA-I-mimetic peptide called FAMP effectively removes cholesterol via the ABCA1 transporter and acts as an antiatherosclerotic agent by enhancing the biological functions of HDL without elevating the HDL-cholesterol level. Our review of the literature leads us to conclude that HDL-targeted therapies have significant atheroprotective potential and thus may effectively treat patients with cardiovascular diseases.

Relativistic Electron Beams, Forward Thomson Scattering, and ``Raman'' Scattering

NASA Astrophysics Data System (ADS)

Simon, A.

1999-11-01

Experiments at LLE (see abstract by D. Hicks at this meeting) show that surprisingly high potentials (+0.5 to 2.0 MV) develop in plasmas irradiated by high-energy lasers. The highly conducting plasma will be a near equipotential and should attract return-current electrons in a radial beam-like distribution, especially in the outer low-density regions. This will initiate the BOT instability, creating large plasma waves with phase velocities close to c. Coherent Thomson scattering of the interaction beam from these waves must occur primarily in the forward direction. This will appear to be ``backward SRS'' upon reflection from a critical surface. We will show that the resulting spectrum is fairly broad and at short wavelengths. Collisional absorption of the scattered EM wave limits the reflectivity to low values (depending on the density scale length). Thus, a distinct difference exists between the spectrum for thick targets (nc surface present) and thin targets (gasbags, etc., from which primarily a narrow absolute-SRS backward emission occurs, at the peak density). The thick-target, reflected-wave angular distribution will be concentrated in the backward direction. The corresponding plasma-wave k-vector will be a fraction of k_0. The variation of the spectrum with potential and angle will be discussed. Comparison will be made with recent results at LLE and LLNL. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460, UR, and NYSERDA.

A high sensitivity momentum flux measuring instrument for plasma thruster exhausts and diffusive plasmas.

PubMed

West, Michael D; Charles, Christine; Boswell, Rod W

2009-05-01

A high sensitivity momentum flux measuring instrument based on a compound pendulum has been developed for use with electric propulsion devices and radio frequency driven plasmas. A laser displacement system, which builds upon techniques used by the materials science community for surface stress measurements, is used to measure with high sensitivity the displacement of a target plate placed in a plasma thruster exhaust. The instrument has been installed inside a vacuum chamber and calibrated via two different methods and is able to measure forces in the range of 0.02-0.5 mN with a resolution of 15 microN. Measurements have been made of the force produced from the cold gas flow and with a discharge ignited using argon propellant. The plasma is generated using a Helicon Double Layer Thruster prototype. The instrument target is placed about 1 mean free path for ion-neutral charge exchange collisions downstream of the thruster exit. At this position, the plasma consists of a low density ion beam (10%) and a much larger downstream component (90%). The results are in good agreement with those determined from the plasma parameters measured with diagnostic probes. Measurements at various flow rates show that variations in ion beam velocity and plasma density and the resulting momentum flux can be measured with this instrument. The instrument target is a simple, low cost device, and since the laser displacement system used is located outside the vacuum chamber, the measurement technique is free from radio frequency interference and thermal effects. It could be used to measure the thrust in the exhaust of other electric propulsion devices and the momentum flux of ion beams formed by expanding plasmas or fusion experiments.

Differential Impact of Plasma Proteins on the Adhesion Efficiency of Vascular-Targeted Carriers (VTCs) in Blood of Common Laboratory Animals.

PubMed

Namdee, Katawut; Sobczynski, Daniel J; Onyskiw, Peter J; Eniola-Adefeso, Omolola

2015-12-16

Vascular-targeted carrier (VTC) interaction with human plasma is known to reduce targeted adhesion efficiency in vitro. However, the role of plasma proteins on the adhesion efficiency of VTCs in laboratory animals remains unknown. Here, in vitro blood flow assays are used to explore the effects of plasma from mouse, rabbit, and porcine on VTC adhesion. Porcine blood exhibited a strong negative plasma effect on VTC adhesion while no significant plasma effect was found with rabbit and mouse blood. A brush density poly(ethylene glycol) (PEG) on VTCs was effective at improving adhesion of microsized, but not nanosized, VTCs in porcine blood. Overall, the results suggest that porcine models, as opposed to mouse, can serve as better models in preclinical research for predicting the in vivo functionality of VTCs for use in humans. These considerations hold great importance for the design of various pharmaceutical products and development of reliable drug delivery systems.

Circulating plasma cholesteryl ester transfer protein activity and blood pressure tracking in the community

USDA-ARS?s Scientific Manuscript database

Clinical trials using cholesteryl ester transfer protein (CETP) inhibitors to raise high-density lipoprotein cholesterol (HDL-C) concentrations reported an 'off-target' blood pressure (BP) raising effect. We evaluated the relations of baseline plasma CETP activity and longitudinal BP change. One tho...

Diagnostics and results from coaxial plasma gun development for the PLX- α project

NASA Astrophysics Data System (ADS)

Case, A.; Brockington, S.; Cruz, E.; Witherspoon, F. D.

2016-10-01

We present results from the diagnostics used during development of the contoured gap coaxial plasma guns for the PLX- α project at LANL. Plasma-jet diagnostics include fast photodiodes for velocimetry, a ballistic pendulum for total plasmoid momentum, and interferometry for line integrated density. Deflectometry will be used for line integrated perpendicular density gradients. Time-resolved high-resolution spectroscopy using a novel detector and time-integrated survey spectroscopy are used for measurements of velocity and temperature, as well as impurities. We will also use a Faraday cup for density, fast imaging for plume geometry, and time-integrated imaging for overall light emission. Experimental results are compared to the desired target parameters for the plasma jets (up to n 2 ×1016cm-3 , v 50km / s , mass 5gm , radius = 4cm , and length 10cm). This work supported by the ARPA-E ALPHA Program.

Laser acceleration of protons using multi-ion plasma gaseous targets

DOE PAGES

Liu, Tung -Chang; Shao, Xi; Liu, Chuan -Sheng; ...

2015-02-01

We present a theoretical and numerical study of a novel acceleration scheme by applying a combination of laser radiation pressure and shielded Coulomb repulsion in laser acceleration of protons in multi-species gaseous targets. By using a circularly polarized CO₂ laser pulse with a wavelength of 10 μm—much greater than that of a Ti: Sapphire laser—the critical density is significantly reduced, and a high-pressure gaseous target can be used to achieve an overdense plasma. This gives us a larger degree of freedom in selecting the target compounds or mixtures, as well as their density and thickness profiles. By impinging such amore » laser beam on a carbon–hydrogen target, the gaseous target is first compressed and accelerated by radiation pressure until the electron layer disrupts, after which the protons are further accelerated by the electron-shielded carbon ion layer. An 80 MeV quasi-monoenergetic proton beam can be generated using a half-sine shaped laser beam with a peak power of 70 TW and a pulse duration of 150 wave periods.« less

Single-Shot Visualization of Evolving Laser Wakefields Using an All-Optical Streak Camera

NASA Astrophysics Data System (ADS)

Li, Zhengyan; Tsai, Hai-En; Zhang, Xi; Pai, Chih-Hao; Chang, Yen-Yu; Zgadzaj, Rafal; Wang, Xiaoming; Khudik, V.; Shvets, G.; Downer, M. C.

2014-08-01

We visualize ps-time-scale evolution of an electron density bubble—a wake structure created in atmospheric density plasma by an intense ultrashort laser pulse—from the phase "streak" that the bubble imprints onto a probe pulse that crosses its path obliquely. Phase streaks, recovered in one shot using frequency-domain interferometric techniques, reveal the formation, propagation, and coalescence of the bubble within a 3 mm long ionized helium gas target. 3D particle-in-cell simulations validate the observed density-dependent bubble evolution, and correlate it with the generation of a quasimonoenergetic ˜100 MeV electron beam. The results provide a basis for understanding optimized electron acceleration at a plasma density ne≈2×1019 cm-3, inefficient acceleration at lower density, and dephasing limits at higher density.

Volumetric Heating of Ultra-High Energy Density Relativistic Plasmas by Ultrafast Laser Irradiation of Aligned Nanowire Arrays

NASA Astrophysics Data System (ADS)

Bargsten, Clayton; Hollinger, Reed; Shlyaptsev, Vyacheslav; Pukhov, Alexander; Keiss, David; Townsend, Amanda; Wang, Yong; Wang, Shoujun; Prieto, Amy; Rocca, Jorge

2014-10-01

We have demonstrated the volumetric heating of near-solid density plasmas to keV temperatures by ultra-high contrast femtosecond laser irradiation of arrays of vertically aligned nanowires with an average density up to 30% solid density. X-ray spectra show that irradiation of Ni and Au nanowire arrays with laser pulses of relativistic intensities ionizes plasma volumes several micrometers in depth to the He-like and Co-like (Au 52 +) stages respectively. The penetration depth of the heat into the nanowire array was measured monitoring He-like Co lines from irradiated arrays in which the nanowires are composed of a Co segment buried under a selected length of Ni. The measurement shows the ionization reaches He-like Co for depth of up to 5 μm within the target. This volumetric plasma heating approach creates a new laboratory plasma regime in which extreme plasma parameters can be accessed with table-top lasers. Scaling to higher laser intensities promises to create plasmas with temperatures and pressures approaching those in the center of the sun. Work supported by the U.S Department of Energy, Fusion Energy Sciences and the Defense Threat Reduction Agency grant HDTRA-1-10-1-0079. A.P was supported by of DFG-funded project TR18.

Laser Imprint Reduction with a Short Shaping Laser Pulse Incident Upon a Foam-Plastic Target

DTIC Science & Technology

2002-12-01

Corporation, McLean, VA 22150, and Physics Department, Nuclear Research Center Negev , P. O. Box 9001, Beer Sheva, Israel Alexander L. Velikovich and...plasma oscillate rather than grow. Density tailoring seems to improve radiative performance of Z-pinch plasma radiation sources: For example, the cross...efficiency of the density profile shaping described above for laser imprint mitigation. We now use the the FAST2D hydrocode in a 2-D mode. The radiation

Nonequilibrium Nonideal Nanoplasma Generated by a Fast Single Ion in Condensed Matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faenov, A. Ya.; Kansai Photon Science Institut, Japan Atomic Energy Agency; Lankin, A. V.

A plasma model of relaxation of a medium in heavy ion tracks in condensed matter is proposed. The model is based on three assumptions: the Maxwell distribution of plasma electrons, localization of plasma inside the track nanochannel and constant values of the plasma electron density and temperature during the X-ray irradiation. It is demonstrated that the plasma relaxation model adequately describes the X-ray spectra observed upon interaction of a fast ion with condensed target. Preassumptions of plasma relaxation model are validated by the molecular dynamics modeling and simulation.

Plasma devices to guide and collimate a high density of MeV electrons.

PubMed

Kodama, R; Sentoku, Y; Chen, Z L; Kumar, G R; Hatchett, S P; Toyama, Y; Cowan, T E; Freeman, R R; Fuchs, J; Izawa, Y; Key, M H; Kitagawa, Y; Kondo, K; Matsuoka, T; Nakamura, H; Nakatsutsumi, M; Norreys, P A; Norimatsu, T; Snavely, R A; Stephens, R B; Tampo, M; Tanaka, K A; Yabuuchi, T

2004-12-23

The development of ultra-intense lasers has facilitated new studies in laboratory astrophysics and high-density nuclear science, including laser fusion. Such research relies on the efficient generation of enormous numbers of high-energy charged particles. For example, laser-matter interactions at petawatt (10(15) W) power levels can create pulses of MeV electrons with current densities as large as 10(12) A cm(-2). However, the divergence of these particle beams usually reduces the current density to a few times 10(6) A cm(-2) at distances of the order of centimetres from the source. The invention of devices that can direct such intense, pulsed energetic beams will revolutionize their applications. Here we report high-conductivity devices consisting of transient plasmas that increase the energy density of MeV electrons generated in laser-matter interactions by more than one order of magnitude. A plasma fibre created on a hollow-cone target guides and collimates electrons in a manner akin to the control of light by an optical fibre and collimator. Such plasma devices hold promise for applications using high energy-density particles and should trigger growth in charged particle optics.

First-principles thermal conductivity of warm-dense deuterium plasmas for inertial confinement fusion applications.

PubMed

Hu, S X; Collins, L A; Boehly, T R; Kress, J D; Goncharov, V N; Skupsky, S

2014-04-01

Thermal conductivity (κ) of both the ablator materials and deuterium-tritium (DT) fuel plays an important role in understanding and designing inertial confinement fusion (ICF) implosions. The extensively used Spitzer model for thermal conduction in ideal plasmas breaks down for high-density, low-temperature shells that are compressed by shocks and spherical convergence in imploding targets. A variety of thermal-conductivity models have been proposed for ICF hydrodynamic simulations of such coupled and degenerate plasmas. The accuracy of these κ models for DT plasmas has recently been tested against first-principles calculations using the quantum molecular-dynamics (QMD) method; although mainly for high densities (ρ > 100 g/cm3), large discrepancies in κ have been identified for the peak-compression conditions in ICF. To cover the wide range of density-temperature conditions undergone by ICF imploding fuel shells, we have performed QMD calculations of κ for a variety of deuterium densities of ρ = 1.0 to 673.518 g/cm3, at temperatures varying from T = 5 × 103 K to T = 8 × 106 K. The resulting κQMD of deuterium is fitted with a polynomial function of the coupling and degeneracy parameters Γ and θ, which can then be used in hydrodynamic simulation codes. Compared with the "hybrid" Spitzer-Lee-More model currently adopted in our hydrocode lilac, the hydrosimulations using the fitted κQMD have shown up to ∼20% variations in predicting target performance for different ICF implosions on OMEGA and direct-drive-ignition designs for the National Ignition Facility (NIF). The lower the adiabat of an imploding shell, the more variations in predicting target performance using κQMD. Moreover, the use of κQMD also modifies the shock conditions and the density-temperature profiles of the imploding shell at early implosion stage, which predominantly affects the final target performance. This is in contrast to the previous speculation that κQMD changes mainly the inside ablation process during the hot-spot formation of an ICF implosion.

First-principles thermal conductivity of warm-dense deuterium plasmas for inertial confinement fusion applications

NASA Astrophysics Data System (ADS)

Hu, S. X.; Collins, L. A.; Boehly, T. R.; Kress, J. D.; Goncharov, V. N.; Skupsky, S.

2014-04-01

Thermal conductivity (κ) of both the ablator materials and deuterium-tritium (DT) fuel plays an important role in understanding and designing inertial confinement fusion (ICF) implosions. The extensively used Spitzer model for thermal conduction in ideal plasmas breaks down for high-density, low-temperature shells that are compressed by shocks and spherical convergence in imploding targets. A variety of thermal-conductivity models have been proposed for ICF hydrodynamic simulations of such coupled and degenerate plasmas. The accuracy of these κ models for DT plasmas has recently been tested against first-principles calculations using the quantum molecular-dynamics (QMD) method; although mainly for high densities (ρ > 100 g/cm3), large discrepancies in κ have been identified for the peak-compression conditions in ICF. To cover the wide range of density-temperature conditions undergone by ICF imploding fuel shells, we have performed QMD calculations of κ for a variety of deuterium densities of ρ = 1.0 to 673.518 g/cm3, at temperatures varying from T = 5 × 103 K to T = 8 × 106 K. The resulting κQMD of deuterium is fitted with a polynomial function of the coupling and degeneracy parameters Γ and θ, which can then be used in hydrodynamic simulation codes. Compared with the "hybrid" Spitzer-Lee-More model currently adopted in our hydrocode lilac, the hydrosimulations using the fitted κQMD have shown up to ˜20% variations in predicting target performance for different ICF implosions on OMEGA and direct-drive-ignition designs for the National Ignition Facility (NIF). The lower the adiabat of an imploding shell, the more variations in predicting target performance using κQMD. Moreover, the use of κQMD also modifies the shock conditions and the density-temperature profiles of the imploding shell at early implosion stage, which predominantly affects the final target performance. This is in contrast to the previous speculation that κQMD changes mainly the inside ablation process during the hot-spot formation of an ICF implosion.

Two-dimensional studies of relativistic electron beam plasma instabilities in an inhomogeneous plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shukla, Chandrasekhar; Das, Amita, E-mail: amita@ipr.res.in; Patel, Kartik

Relativistic electron beam propagation in plasma is fraught with several micro instabilities like two stream, filamentation, etc., in plasma. This results in severe limitation of the electron transport through a plasma medium. Recently, however, there has been an experimental demonstration of improved transport of Mega Ampere of electron currents (generated by the interaction of intense laser with solid target) in a carbon nanotube structured solid target [G. Chatterjee et al., Phys. Rev. Lett. 108, 235005 (2012)]. This then suggests that the inhomogeneous plasma (created by the ionization of carbon nanotube structured target) helps in containing the growth of the beammore » plasma instabilities. This manuscript addresses this issue with the help of a detailed analytical study and 2-D Particle-In-Cell simulations. The study conclusively demonstrates that the growth rate of the dominant instability in the 2-D geometry decreases when the plasma density is chosen to be inhomogeneous, provided the scale length 1/k{sub s} of the inhomogeneous plasma is less than the typical plasma skin depth (c/ω{sub 0}) scale. At such small scale lengths channelization of currents is also observed in simulation.« less

Plasma source development for fusion-relevant material testing

DOE PAGES

Caughman, John B. O.; Goulding, Richard H.; Biewer, Theodore M.; ...

2017-05-01

Plasma facing materials in the divertor of a magnetic fusion reactor will have to tolerate steady-state plasma heat fluxes in the range of 10 MW/m2 for ~107 sec, in addition to fusion neutron fluences, which can damage the plasma facing materials to high displacements per atom (dpa) of ~50 dpa . Material solutions needed for the plasma facing components are yet to be developed and tested. The Materials Plasma Exposure eXperiment (MPEX) is a newly proposed steady state linear plasma device that is designed to deliver the necessary plasma heat flux to a target for this material testing, including themore » capability to expose a-priori neutron damaged material samples to those plasmas. The requirements of the plasma source needed to deliver this plasma heat flux are being developed on the Proto-MPEX device, which is a linear high-intensity radio frequency (RF) plasma source that combines a high-density helicon plasma generator with electron and ion heating sections. It is being used to study the physics of heating over-dense plasmas in a linear configuration. The helicon plasma is operated at 13.56 MHz with RF power levels up to 120 kW. Microwaves at 28 GHz (~30 kW) are coupled to the electrons in the over-dense helicon plasma via Electron Bernstein Waves (EBW), and ion cyclotron heating at 7-9 MHz (~30 kW) is via a magnetic beach approach. High plasma densities >6x1019/m3 have been produced in deuterium, with electron temperatures that can range from 2 to >10 eV. Operation with on-axis magnetic field strengths between 0.6 and 1.4 T is typical. The plasma heat flux delivered to a target can be > 10 MW/m2, depending on the operating conditions.« less

Plasma source development for fusion-relevant material testing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Caughman, John B. O.; Goulding, Richard H.; Biewer, Theodore M.

Plasma facing materials in the divertor of a magnetic fusion reactor will have to tolerate steady-state plasma heat fluxes in the range of 10 MW/m2 for ~107 sec, in addition to fusion neutron fluences, which can damage the plasma facing materials to high displacements per atom (dpa) of ~50 dpa . Material solutions needed for the plasma facing components are yet to be developed and tested. The Materials Plasma Exposure eXperiment (MPEX) is a newly proposed steady state linear plasma device that is designed to deliver the necessary plasma heat flux to a target for this material testing, including themore » capability to expose a-priori neutron damaged material samples to those plasmas. The requirements of the plasma source needed to deliver this plasma heat flux are being developed on the Proto-MPEX device, which is a linear high-intensity radio frequency (RF) plasma source that combines a high-density helicon plasma generator with electron and ion heating sections. It is being used to study the physics of heating over-dense plasmas in a linear configuration. The helicon plasma is operated at 13.56 MHz with RF power levels up to 120 kW. Microwaves at 28 GHz (~30 kW) are coupled to the electrons in the over-dense helicon plasma via Electron Bernstein Waves (EBW), and ion cyclotron heating at 7-9 MHz (~30 kW) is via a magnetic beach approach. High plasma densities >6x1019/m3 have been produced in deuterium, with electron temperatures that can range from 2 to >10 eV. Operation with on-axis magnetic field strengths between 0.6 and 1.4 T is typical. The plasma heat flux delivered to a target can be > 10 MW/m2, depending on the operating conditions.« less

Helicon wave field measurements in Proto-MPEX

NASA Astrophysics Data System (ADS)

Caneses, Juan Francisco; Piotrowicz, Pawel; Goulding, Richard; Caughman, John; Showers, Missy; Kafle, Nischal; Rapp, Juergen; Campbell, Ian; Proto-MPEX Team

2016-10-01

A high density Deuterium discharge (ne 5e19 m-3, Te 4 eV) has been recently observed in ProtoMPEX (Prototype Material Plasma Exposure eXperiment). The discharge (100 kW, 13.56 MHz, D2, 700 G at the source, 1e4 G at the Target) begins with a low density plasma with hollow Te profile and transitions in about 100 ms to a high density mode with flat Te profile. It is believed that the transition to the high density mode is produced by a ``helicon resonance'' as evidenced by the centrally-peaked power deposition profile observed with IR imaging on a 2 mm thick metallic target plate. In this work, we present b-dot probe measurements of the radial helicon wavefields 30 cm downstream of the antenna during both the low and high density modes. In addition, we compare the experimental results with full wave simulations. This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy.

An automated design process for short pulse laser driven opacity experiments

DOE PAGES

Martin, M. E.; London, R. A.; Goluoglu, S.; ...

2017-12-21

Stellar-relevant conditions can be reached by heating a buried layer target with a short pulse laser. Previous design studies of iron buried layer targets found that plasma conditions are dominantly controlled by the laser energy while the accuracy of the inferred opacity is limited by tamper emission and optical depth effects. In this paper, we developed a process to simultaneously optimize laser and target parameters to meet a variety of design goals. We explored two sets of design cases: a set focused on conditions relevant to the upper radiative zone of the sun (electron temperatures of 200 to 400 eVmore » and densities greater than 1/10 of solid density) and a set focused on reaching temperatures consistent with deep within the radiative zone of the sun (500 to 1000 eV) at a fixed density. We found optimized designs for iron targets and determined that the appropriate dopant, for inferring plasma conditions, depends on the goal temperature: magnesium for up to 300 eV, aluminum for 300 to 500 eV, and sulfur for 500 to 1000 eV. The optimal laser energy and buried layer thickness increase with goal temperature. The accuracy of the inferred opacity is limited to between 11% and 31%, depending on the design. Finally, overall, short pulse laser heated iron experiments reaching stellar-relevant conditions have been designed with consideration of minimizing tamper emission and optical depth effects while meeting plasma condition and x-ray emission goals.« less

An automated design process for short pulse laser driven opacity experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin, M. E.; London, R. A.; Goluoglu, S.

Stellar-relevant conditions can be reached by heating a buried layer target with a short pulse laser. Previous design studies of iron buried layer targets found that plasma conditions are dominantly controlled by the laser energy while the accuracy of the inferred opacity is limited by tamper emission and optical depth effects. In this paper, we developed a process to simultaneously optimize laser and target parameters to meet a variety of design goals. We explored two sets of design cases: a set focused on conditions relevant to the upper radiative zone of the sun (electron temperatures of 200 to 400 eVmore » and densities greater than 1/10 of solid density) and a set focused on reaching temperatures consistent with deep within the radiative zone of the sun (500 to 1000 eV) at a fixed density. We found optimized designs for iron targets and determined that the appropriate dopant, for inferring plasma conditions, depends on the goal temperature: magnesium for up to 300 eV, aluminum for 300 to 500 eV, and sulfur for 500 to 1000 eV. The optimal laser energy and buried layer thickness increase with goal temperature. The accuracy of the inferred opacity is limited to between 11% and 31%, depending on the design. Finally, overall, short pulse laser heated iron experiments reaching stellar-relevant conditions have been designed with consideration of minimizing tamper emission and optical depth effects while meeting plasma condition and x-ray emission goals.« less

A spectroscopic study using line ratios of lithiumlike ions in a laser-produced plasma

NASA Astrophysics Data System (ADS)

Moreno, J. C.; Goldsmith, S.; Griem, H. R.

1989-02-01

Spectra of highly ionized titanium and calcium in the extreme ultraviolet region were observed in laser-produced plasmas using the OMEGA 24 beam (351 nm) laser system at the University of Rochester. The plasmas were produced using glass microballoon targets coated with a layer of a medium Z element and a layer of parylene (CH). Time-integrated electron temperatures and densities were obtained by comparing measured line intensity ratios of lithiumlike charge states of Ti and Ca to numerical calculations from a collisional-radiative model. The variation of line intensity ratios with electron density and temperature using the collisional-radiative model is discussed.

Characterization of X-ray emission from laser generated plasma

NASA Astrophysics Data System (ADS)

Cannavò, Antonino; Torrisi, Lorenzo; Ceccio, Giovanni; Cutroneo, Mariapompea; Calcagno, Lucia; Sciuto, Antonella; Mazzillo, Massimo

2018-01-01

X-ray emission from laser generated plasma was studied at low (1010 W/cm2) and high (1018 W/cm2) intensity using ns and fs laser, respectively. Plasma characteristics were controlled trough the laser parameters, the irradiation conditions and the target properties. The X-ray spectra were acquired using fast detection technique based on SiC diodes with different active regions. The X-ray yield increases with the atomic number of the target, both at low and high intensity, and a similar empirical law has been obtained. The X-ray emission mechanisms from plasma are correlated to the plasma temperature and density and to the Coulomb charge particle acceleration, due to the charge separation effects produced in the non-equilibrium plasma. Functional dependences, theoretical approaches and interpretation of possible mechanism will be presented and discussed.

Measurement of absolute laser energy absorption by nano-structured targets

NASA Astrophysics Data System (ADS)

Park, Jaebum; Tommasini, R.; London, R.; Bargsten, C.; Hollinger, R.; Capeluto, M. G.; Shlyaptsev, V. N.; Rocca, J. J.

2017-10-01

Nano-structured targets have been reported to allow the realization of extreme plasma conditions using table top lasers, and have gained much interest as a platform to investigate the ultra-high energy density plasmas (>100 MJ/cm3) . One reason for these targets to achieve extreme conditions is increased laser energy absorption (LEA). The absolute LEA by nano-structured targets has been measured for the first time and compared to that by foil targets. The experimental results, including the effects of target parameters on the LEA, will be presented. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52097NA27344, and funded by LDRD (#15-ERD-054).

Spectroscopic imaging of self-organization in high power impulse magnetron sputtering plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andersson, Joakim; Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543 Singapore; Ni, Pavel

Excitation and ionization conditions in traveling ionization zones of high power impulse magnetron sputtering plasmas were investigated using fast camera imaging through interference filters. The images, taken in end-on and side-on views using light of selected gas and target atom and ion spectral lines, suggest that ionization zones are regions of enhanced densities of electrons, and excited atoms and ions. Excited atoms and ions of the target material (Al) are strongly concentrated near the target surface. Images from the highest excitation energies exhibit the most localized regions, suggesting localized Ohmic heating consistent with double layer formation.

Spectroscopic imaging of self-organization in high power impulse magnetron sputtering plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543 Singapore, Singapore; Andersson, Joakim; Ni, Pavel

Excitation and ionization conditions in traveling ionization zones of high power impulse magnetron sputtering plasmas were investigated using fast camera imaging through interference filters. The images, taken in end-on and side on views using light of selected gas and target atom and ion spectral lines, suggest that ionization zones are regions of enhanced densities of electrons, and excited atoms and ions. Excited atoms and ions of the target material (Al) are strongly concentrated near the target surface. Images from the highest excitation energies exhibit the most localized regions, suggesting localized Ohmic heating consistent with double layer formation.

Characterization and optimization of the HyperV PLX- α coaxial-gun plasma jet

NASA Astrophysics Data System (ADS)

Case, Andrew; Brockington, Sam; Cruz, Edward; Witherspoon, F. Douglas

2017-10-01

We present results from characterizing and optimizing performance of the contoured gap coaxial plasma guns under development for the ARPA-E Accelerating Low-Cost Plasma Heating And Assembly (ALPHA) program. Plasma jet diagnostics include fast photodiodes for velocimetry and interferometry for line integrated density. Additionally we present results from spectroscopy, both time resolved high resolution spectroscopy using a novel detector and time integrated survey spectroscopy, for measurements of velocity and temperature as well as impurities. Fast imaging gives plume geometry and time integrated imaging gives overall light emission. Results from a novel long record length camera developed by HyperV will also be presented. Experimental results are compared to the desired target parameters for the plasma jets. The target values for the plasmoid are velocity of 50 km/s, mass of 3.5 mg, and length of 10 cm. The best results so far from the exploration of parameter space for gun operation are: 4 mg at >50 km/s, with a length of 10 cm. Peak axial density 34 cm downstream from the muzzle is 2 ×1016 cm-3. This work supported by the ARPA-E ALPHA Program under contract DE-AR0000566.

Particle-in-cell/Monte Carlo collisions treatment of an Ar/O2 magnetron discharge used for the reactive sputter deposition of TiOx films

NASA Astrophysics Data System (ADS)

Bultinck, E.; Bogaerts, A.

2009-10-01

The physical processes in an Ar/O2 magnetron discharge used for the reactive sputter deposition of TiOx thin films were simulated with a 2d3v particle-in-cell/Monte Carlo collisions (PIC/MCC) model. The plasma species taken into account are electrons, Ar+ ions, fast Arf atoms, metastable Arm* atoms, Ti+ ions, Ti atoms, O+ ions, O2+ ions, O- ions and O atoms. This model accounts for plasma-target interactions, such as secondary electron emission and target sputtering, and the effects of target poisoning. Furthermore, the deposition process is described by an analytical surface model. The influence of the O2/Ar gas ratio on the plasma potential and on the species densities and fluxes is investigated. Among others, it is shown that a higher O2 pressure causes the region of positive plasma potential and the O- density to be more spread, and the latter to decrease. On the other hand, the deposition rates of Ti and O are not much affected by the O2/Ar proportion. Indeed, the predicted stoichiometry of the deposited TiOx film approaches x=2 for nearly all the investigated O2/Ar proportions.

First-principles equation-of-state table of silicon and its effects on high-energy-density plasma simulations

NASA Astrophysics Data System (ADS)

Hu, S. X.; Gao, R.; Ding, Y.; Collins, L. A.; Kress, J. D.

2017-04-01

Using density-functional theory-based molecular-dynamics simulations, we have investigated the equation of state for silicon in a wide range of plasma density and temperature conditions of ρ =0.001 -500 g /c m3 and T =2000 -108K . With these calculations, we have established a first-principles equation-of-state (FPEOS) table of silicon for high-energy-density (HED) plasma simulations. When compared with the widely used SESAME-EOS model (Table 3810), we find that the FPEOS-predicted Hugoniot is ˜20% softer; for off-Hugoniot plasma conditions, the pressure and internal energy in FPEOS are lower than those of SESAME EOS for temperatures above T ≈ 1-10 eV (depending on density), while the former becomes higher in the low-T regime. The pressure difference between FPEOS and SESAME 3810 can reach to ˜50%, especially in the warm-dense-matter regime. Implementing the FPEOS table of silicon into our hydrocodes, we have studied its effects on Si-target implosions. When compared with the one-dimensional radiation-hydrodynamics simulation using the SESAME 3810 EOS model, the FPEOS simulation showed that (1) the shock speed in silicon is ˜10% slower; (2) the peak density of an in-flight Si shell during implosion is ˜20% higher than the SESAME 3810 simulation; (3) the maximum density reached in the FPEOS simulation is ˜40% higher at the peak compression; and (4) the final areal density and neutron yield are, respectively, ˜30% and ˜70% higher predicted by FPEOS versus the traditional simulation using SESAME 3810. All of these features can be attributed to the larger compressibility of silicon predicted by FPEOS. These results indicate that an accurate EOS table, like the FPEOS presented here, could be essential for the precise design of targets for HED experiments.

First-principles equation-of-state table of silicon and its effects on high-energy-density plasma simulations

DOE PAGES

Hu, S. X.; Gao, R.; Ding, Y.; ...

2017-04-21

Using density-functional theory–based molecular-dynamics simulations, we have investigated the equation of state for silicon in a wide range of plasma density and temperature conditions of ρ=0.001–500g/cm 3 and T=2000–10 8K. With these calculations, we have established a first-principles equation-of-state (FPEOS) table of silicon for high-energy-density (HED) plasma simulations. When compared with the widely used SESAME-EOS model (Table 3810), we find that the FPEOS-predicted Hugoniot is ~20% softer; for off-Hugoniot plasma conditions, the pressure and internal energy in FPEOS are lower than those of SESAME EOS for temperatures above T ≈ 1–10 eV (depending on density), while the former becomes highermore » in the low- T regime. The pressure difference between FPEOS and SESAME 3810 can reach to ~50%, especially in the warm-dense-matter regime. Implementing the FPEOS table of silicon into our hydrocodes, we have studied its effects on Si-target implosions. When compared with the one-dimensional radiation-hydrodynamics simulation using the SESAME 3810 EOS model, the FPEOS simulation showed that (1) the shock speed in silicon is ~10% slower; (2) the peak density of an in-flight Si shell during implosion is ~20% higher than the SESAME 3810 simulation; (3) the maximum density reached in the FPEOS simulation is ~40% higher at the peak compression; and (4) the final areal density and neutron yield are, respectively, ~30% and ~70% higher predicted by FPEOS versus the traditional simulation using SESAME 3810. All of these features can be attributed to the larger compressibility of silicon predicted by FPEOS. Furthermore, these results indicate that an accurate EOS table, like the FPEOS presented here, could be essential for the precise design of targets for HED experiments.« less

First-principles equation-of-state table of silicon and its effects on high-energy-density plasma simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, S. X.; Gao, R.; Ding, Y.

Using density-functional theory–based molecular-dynamics simulations, we have investigated the equation of state for silicon in a wide range of plasma density and temperature conditions of ρ=0.001–500g/cm 3 and T=2000–10 8K. With these calculations, we have established a first-principles equation-of-state (FPEOS) table of silicon for high-energy-density (HED) plasma simulations. When compared with the widely used SESAME-EOS model (Table 3810), we find that the FPEOS-predicted Hugoniot is ~20% softer; for off-Hugoniot plasma conditions, the pressure and internal energy in FPEOS are lower than those of SESAME EOS for temperatures above T ≈ 1–10 eV (depending on density), while the former becomes highermore » in the low- T regime. The pressure difference between FPEOS and SESAME 3810 can reach to ~50%, especially in the warm-dense-matter regime. Implementing the FPEOS table of silicon into our hydrocodes, we have studied its effects on Si-target implosions. When compared with the one-dimensional radiation-hydrodynamics simulation using the SESAME 3810 EOS model, the FPEOS simulation showed that (1) the shock speed in silicon is ~10% slower; (2) the peak density of an in-flight Si shell during implosion is ~20% higher than the SESAME 3810 simulation; (3) the maximum density reached in the FPEOS simulation is ~40% higher at the peak compression; and (4) the final areal density and neutron yield are, respectively, ~30% and ~70% higher predicted by FPEOS versus the traditional simulation using SESAME 3810. All of these features can be attributed to the larger compressibility of silicon predicted by FPEOS. Furthermore, these results indicate that an accurate EOS table, like the FPEOS presented here, could be essential for the precise design of targets for HED experiments.« less

Linear facing target sputtering of the epitaxial Ga-doped ZnO transparent contact layer on GaN-based light-emitting diodes

NASA Astrophysics Data System (ADS)

Shin, Hyun-Su; Lee, Ju-Hyun; Kwak, Joon-Seop; Lee, Hyun Hwi; Kim, Han-Ki

2013-10-01

In this study, we reported on the plasma damage-free sputtering of epitaxial Ga-doped ZnO (GZO) films on the p-GaN layer for use as a transparent contact layer (TCL) for GaN-based light-emitting diodes (LEDs) using linear facing target sputtering (LFTS). Effective confinement of high-density plasma between faced GZO targets and the substrate position located outside of the plasma region led to the deposition of the epitaxial GZO TCL with a low sheet resistance of 25.7 Ω/s and a high transmittance of 84.6% on a p-GaN layer without severe plasma damage, which was found using the conventional dc sputtering process. The low turn-on voltage of the GaN-based LEDs with an LFTS-grown GZO TCL layer that was grown at a longer target-to-substrate distance (TSD) indicates that the plasma damage of the GaN-LED could be effectively reduced by adjusting the TSD during the LFTS process.

Computer Simulation of Compression and Energy Release upon Laser Irradiation of Cylindrically Symmetric Target

NASA Astrophysics Data System (ADS)

Kuzenov, V. V.

2017-12-01

The paper is devoted to the theoretical and computational study of compression and energy release for magneto-inertial plasma confinement. This approach makes it possible to create new high-density plasma sources, apply them in materials science experiments, and use them in promising areas of power engineering.

Energy Density in Aligned Nanowire Arrays Irradiated with Relativistic Intensities: Path to Terabar Pressure Plasmas

NASA Astrophysics Data System (ADS)

Rocca, J.; Bargsten, C.; Hollinger, R.; Shylaptsev, V.; Wang, S.; Rockwood, A.; Wang, Y.; Keiss, D.; Capeluto, M.; Kaymak, V.; Pukhov, A.; Tommasini, R.; London, R.; Park, J.

2016-10-01

Ultra-high-energy-density (UHED) plasmas, characterized by energy densities >1 x 108 J cm-3 and pressures greater than a gigabar are encountered in the center of stars and in inertial confinement fusion capsules driven by the world's largest lasers. Similar conditions can be obtained with compact, ultra-high contrast, femtosecond lasers focused to relativistic intensities onto aligned nanowire array targets. Here we report the measurement of the key physical process in determining the energy density deposited in high aspect ratio nanowire array plasmas: the energy penetration. By monitoring the x-ray emission from buried Co tracer segments in Ni nanowire arrays irradiated at an intensity of 4 x 1019 W cm-2, we demonstrate energy penetration depths of several μm, leading to UHED plasmas of that size. Relativistic 3D particle-in-cell-simulations validated by these measurements predict that irradiation of nanostructures at increased intensity will lead to a virtually unexplored extreme UHED plasma regime characterized by energy densities in excess of 8 x 1010 J cm-3, equivalent to a pressure of 0.35 Tbar. This work was supported by the Fusion Energy Program, Office of Science of the U.S Department of Energy, and by the Defense Threat Reduction Agency.

Transparency of near-critical density plasmas under extreme laser intensities

NASA Astrophysics Data System (ADS)

Ji, Liangliang; Shen, Baifei; Zhang, Xiaomei

2018-05-01

We investigated transparency of near-critical plasma targets for highly intense incident lasers and discovered that beyond relativistic transparency, there exists an anomalous opacity regime, where the plasma target tend to be opaque at extreme light intensities. The unexpected phenomenon is found to originate from the trapping of ions under exotic conditions. We found out the propagation velocity and the amplitude of the laser-driven charge separation field in a large parameter range and derived the trapping probability of ions. The model successfully interpolates the emergence of anomalous opacity in simulations. The trend is more significant when radiation reaction comes into effect, leaving a transparency window in the intensity domain. Transparency of a plasma target defines the electron dynamics and thereby the emission mechanisms of gamma-photons in the ultra-relativistic regime. Our findings are not only of fundamental interest but also imply the proper mechanisms for generating desired electron/gamma sources.

Native and Reconstituted Plasma Lipoproteins in Nanomedicine: Physicochemical Determinants of Nanoparticle Structure, Stability, and Metabolism

PubMed Central

Pownall, Henry J.; Rosales, Corina; Gillard, Baiba K.; Ferrari, Mauro

2016-01-01

Although many acute and chronic diseases are managed via pharmacological means, challenges remain regarding appropriate drug targeting and maintenance of therapeutic levels within target tissues. Advances in nanotechnology will overcome these challenges through the development of lipidic particles, including liposomes, lipoproteins, and reconstituted high-density lipoproteins (rHDL) that are potential carriers of water-soluble, hydrophobic, and amphiphilic molecules. Herein we summarize the properties of human plasma lipoproteins and rHDL, identify the physicochemical determinants of lipid transfer between phospholipid surfaces, and discuss strategies for increasing the plasma half-life of lipoprotein- and liposome-associated molecules. PMID:27826368

Plasma Heating Simulation in the VASIMR System

NASA Technical Reports Server (NTRS)

Ilin, Andrew V.; ChangDiaz, Franklin R.; Squire, Jared P.; Carter, Mark D.

2005-01-01

The paper describes the recent development in the simulation of the ion-cyclotron acceleration of the plasma in the VASIMR experiment. The modeling is done using an improved EMIR code for RF field calculation together with particle trajectory code for plasma transport calculat ion. The simulation results correlate with experimental data on the p lasma loading and predict higher ICRH performance for a higher density plasma target. These simulations assist in optimizing the ICRF anten na so as to achieve higher VASIMR efficiency.

Upstream Density for Plasma Detachment with Conventional and Lithium Vapor-Box Divertors

NASA Astrophysics Data System (ADS)

Goldston, Rj; Schwartz, Ja

2016-10-01

Fusion power plants are likely to require detachment of the divertor plasma from material targets. The lithium vapor box divertor is designed to achieve this, while limiting the flux of lithium vapor to the main plasma. We develop a simple model of near-detachment to evaluate the required upstream plasma density, for both conventional and lithium vapor-box divertors, based on particle and dynamic pressure balance between up- and down-stream, at near-detachment conditions. A remarkable general result is found, not just for lithium-induced detachment, that the upstream density divided by the Greenwald-limit density scales as (P 5 / 8 /B 3 / 8) Tdet1 / 2 / (ɛcool + γTdet) , with no explicit size scaling. Tdet is the temperature just before strong pressure loss, 1/2 of the ionization potential of the dominant recycling species, ɛcool is the average plasma energy lost per injected hydrogenic and impurity atom, and γ is the sheath heat transmission factor. A recent 1-D calculation agrees well with this scaling. The implication is that the plasma exhaust problem cannot be solved by increasing R. Instead significant innovation, such as the lithium vapor box divertor, will be required. This work supported by DOE Contract No. DE-AC02-09CH11466.

Measurements of ion energies during plasma heating of the Proto-MPEX High Intensity Plasma Source

NASA Astrophysics Data System (ADS)

Caughman, J. B. O.; Goulding, R. H.; Biewer, T. M.; Bigelow, T. S.; Caneses, J.; Diem, S. J.; Green, D. L.; Isler, R. C.; Rapp, J.; Piotrowicz, P.; Beers, C. J.; Kafle, N.; Showers, M. A.

2017-10-01

The Prototype Materials Plasma Exposure eXperiment (Proto-MPEX) is a linear high-intensity RF plasma source that combines a high-density helicon plasma generator with ion and electron heating sections. It is being used to study the physics of heating over-dense plasmas in a linear configuration with the goal of delivering a plasma heat flux of 10 MW/m2 at a target. The helicon plasma is produced by coupling 13.56 MHz RF power at levels >100 kW. Additional heating is provided by ion cyclotron heating (ICH) ( 25 kW) and electron Bernstein wave (EBW) heating ( 25 kW) at 28 GHz. Measurements of the ion energy distribution with a retarding field energy analyzer (RFEA) show an increase in ion energies in the edge of the plasma when ICH is applied, which is consistent with COMSOL modeling of the power deposition from the antenna. Views of the target plate with an infrared camera show an increase in the surface temperature at large radii during ICH, and these areas map back to magnetic field lines near the antenna. The change in the power deposition at the target during ICH is compared with Thomson Scattering and RFEA measurements near the target. ORNL is managed by UT-Battelle, LLC, for the U.S. DOE under contract DE-AC-05-00OR22725.

Computational study of hot electron generation and energy transport in intense laser produced hot dense matter

NASA Astrophysics Data System (ADS)

Mishra, Rohini

Present ultra high power lasers are capable of producing high energy density (HED) plasmas, in controlled way, with a density greater than solid density and at a high temperature of keV (1 keV ˜ 11,000,000° K). Matter in such extreme states is particularly interesting for (HED) physics such as laboratory studies of planetary and stellar astrophysics, laser fusion research, pulsed neutron source etc. To date however, the physics in HED plasma, especially, the energy transport, which is crucial to realize applications, has not been understood well. Intense laser produced plasmas are complex systems involving two widely distinct temperature distributions and are difficult to model by a single approach. Both kinetic and collisional process are equally important to understand an entire process of laser-solid interaction. By implementing atomic physics models, such as collision, ionization, and radiation damping, self consistently, in state-of-the-art particle-in-cell code (PICLS) has enabled to explore the physics involved in the HED plasmas. Laser absorption, hot electron transport, and isochoric heating physics in laser produced hot dense plasmas are studied with a help of PICLS simulations. In particular, a novel mode of electron acceleration, namely DC-ponderomotive acceleration, is identified in the super intense laser regime which plays an important role in the coupling of laser energy to a dense plasma. Geometric effects on hot electron transport and target heating processes are examined in the reduced mass target experiments. Further, pertinent to fast ignition, laser accelerated fast electron divergence and transport in the experiments using warm dense matter (low temperature plasma) is characterized and explained.

Comparative proteomics evaluation of plasma exosome isolation techniques and assessment of the stability of exosomes in normal human blood plasma.

PubMed

Kalra, Hina; Adda, Christopher G; Liem, Michael; Ang, Ching-Seng; Mechler, Adam; Simpson, Richard J; Hulett, Mark D; Mathivanan, Suresh

2013-11-01

Exosomes are nanovesicles released by a variety of cells and are detected in body fluids including blood. Recent studies have highlighted the critical application of exosomes as personalized targeted drug delivery vehicles and as reservoirs of disease biomarkers. While these research applications have created significant interest and can be translated into practice, the stability of exosomes needs to be assessed and exosome isolation protocols from blood plasma need to be optimized. To optimize methods to isolate exosomes from blood plasma, we performed a comparative evaluation of three exosome isolation techniques (differential centrifugation coupled with ultracentrifugation, epithelial cell adhesion molecule immunoaffinity pull-down, and OptiPrep(TM) density gradient separation) using normal human plasma. Based on MS, Western blotting and microscopy results, we found that the OptiPrep(TM) density gradient method was superior in isolating pure exosomal populations, devoid of highly abundant plasma proteins. In addition, we assessed the stability of exosomes in plasma over 90 days under various storage conditions. Western blotting analysis using the exosomal marker, TSG101, revealed that exosomes are stable for 90 days. Interestingly, in the context of cellular uptake, the isolated exosomes were able to fuse with target cells revealing that they were indeed biologically active. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Saturn's Magnetospheric Plasma Flow Encountered by Titan

NASA Astrophysics Data System (ADS)

Sillanpää, I.

2017-09-01

Titan has been a major target of the ending Cassini mission to Saturn. 126 flybys have sampled, measured and observed a variety of Titan's features and processes from the surface features to atmospheric composition and upper atmospheric processes. Titan's interaction with the magnetospheric plasma flow it is mostly embedded in is highly dependent on the characteristics of the ambient plasma. The density, velocity and even the composition of the plasma flow can have great variance from flyby to flyby. Our purpose is the present the plasma flow conditions for all over 70 flybys of which we have Cassini Plasma Spectrometer (CAPS) measurements.

A novel experimental setup for energy loss and charge state measurements in dense moderately coupled plasma using laser-heated hohlraum targets

NASA Astrophysics Data System (ADS)

Ortner, A.; Schumacher, D.; Cayzac, W.; Frank, A.; Basko, M. M.; Bedacht, S.; Blazevic, A.; Faik, S.; Kraus, D.; Rienecker, T.; Schaumann, G.; Tauschwitz, An.; Wagner, F.; Roth, M.

2016-03-01

We report on a new experimental setup for ion energy loss measurements in dense moderately coupled plasma which has recently been developed and tested at GSI Darmstadt. A partially ionized, moderately coupled carbon plasma (ne ≤ 0.8• 1022 cm-3, Te = 15 eV, z = 2.5, Γ = 0.5) is generated by volumetrical heating of two thin carbon foils with soft X-rays. This plasma is then probed by a bunched heavy ion beam. For that purpose, a special double gold hohlraum target of sub-millimeter size has been developed which efficiently converts intense laser light into thermal radiation and guarantees a gold-free interaction path for the ion beam traversing the carbon plasma. This setup allows to do precise energy loss measurements in non-ideal plasma at the level of 10 percent solid-state density.

Progress in the characterization of diamond thin films prepared by a laser plasma discharge

NASA Astrophysics Data System (ADS)

Davanloo, F.; Juengerman, E. M.; Jander, D. R.; Lee, T. J.; Collins, C. B.

Progress in the characterization of diamond thin films produced by a unique laser plasma discharge source at practical growth rates of 0.7 micron/hr is reported. Optical properties, mass densities, and electrical resistivities of deposited films are given and their relationship to the power density of the laser at the graphite target is discussed. Examination of films with scanning tunneling microscopy show the clear prevalence of the structure recently predicted by Angus et al. (1990) in which sp3 clusters are bonded together with the carbon polytypes.

Features of plasma produced by excimer laser at low intensities

NASA Astrophysics Data System (ADS)

Vergunova, G. A.; Magunov, A. I.; Dyakin, V. M.; Faenov, A. Ya; Pikuz, T. A.; Skobelev, I. Yu; Batani, D.; Bossi, S.; Bernardinello, A.; Flora, F.; di Lazzaro, P.; Bollanti, S.; Lisi, N.; Letardi, T.; Reale, A.; Palladino, L.; Scafati, A.; Reale, L.; Osterheld, A. L.; Goldstein, W. H.

1997-04-01

A plasma, created at interaction of short-wavelength excimer laser radiation with flat targets was investigated (tlas = 12 ns, λlas = 0.308 μm, qlas = 4 - 8 × 1012 W/cm2) with the help of various x-ray spectroscopic methods. The comparison of shapes and intensities of some observable spectral lines of H-, He and Li-like ions of Na, Mg and Al with results of model calculations has allowed to determine space distributions of laser plasma parameters up to distances of 0.4 mm from the target surface. Comparison of obtained results with theoretical models of absorption of short-wavelength radiation in a plasma shows, that the absorption of short-wavelength laser radiation in a plasma (at considered values of laser flux density) is executed due to inverse bremsstrahlung process in the areas with Ne < Ne, crit..

Electron density measurements for plasma adaptive optics

NASA Astrophysics Data System (ADS)

Neiswander, Brian W.

Over the past 40 years, there has been growing interest in both laser communications and directed energy weapons that operate from moving aircraft. As a laser beam propagates from an aircraft in flight, it passes through boundary layers, turbulence, and shear layers in the near-region of the aircraft. These fluid instabilities cause strong density gradients which adversely affect the transmission of laser energy to a target. Adaptive optics provides corrective measures for this problem but current technology cannot respond quickly enough to be useful for high speed flight conditions. This research investigated the use of plasma as a medium for adaptive optics for aero-optics applications. When a laser beam passes through plasma, its phase is shifted proportionally to the electron density and gas heating within the plasma. As a result, plasma can be utilized as a dynamically controllable optical medium. Experiments were carried out using a cylindrical dielectric barrier discharge plasma chamber which generated a sub-atmospheric pressure, low-temperature plasma. An electrostatic model of this design was developed and revealed an important design constraint relating to the geometry of the chamber. Optical diagnostic techniques were used to characterize the plasma discharge. Single-wavelength interferometric experiments were performed and demonstrated up to 1.5 microns of optical path difference (OPD) in a 633 nm laser beam. Dual-wavelength interferometry was used to obtain time-resolved profiles of the plasma electron density and gas heating inside the plasma chamber. Furthermore, a new multi-wavelength infrared diagnostic technique was developed and proof-of-concept simulations were conducted to demonstrate the system's capabilities.

The effect of target materials on the propagation of atmospheric-pressure plasma jets

NASA Astrophysics Data System (ADS)

Ji, Longfei; Yan, Wen; Xia, Yang; Liu, Dongping

2018-05-01

The current study is focused on the effect of target materials (quartz plate, copper sheet, and quartz plate with a grounded copper sheet on the back) on the propagation of atmospheric-pressure helium plasma jets. The dynamics of ionization waves (IWs) and the relative amount of reactive oxygen species (OH and O) in the IW front were compared by using spatial and temporal images and relative optical emission spectroscopy. Our measurements show that the targets can significantly affect the propagation and intensity of the IWs. In addition, strong OH emission lines were detected when the IWs impinged upon the damp surface. Numerical simulations have been carried out to explain the experimental observation. The propagation velocity of IWs predicted by the simulation was in good agreement with the experimental results. Simulation results suggest that the density and velocity of IWs mainly depend on the electric field between the high voltage electrode tip and the target. Analysis indicates that the targets could change the electric field distribution between the high voltage electrode and targets and thus affect the dynamics and the density of the IWs, the generation of reactive oxygen species, and the corresponding sterilization efficiency.

Investigation of longitudinal proton acceleration in exploded targets irradiated by intense short-pulse laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gauthier, M.; CEA, DAM, DIF, 91297 Arpajon; Lévy, A.

2014-01-15

It was recently shown that a promising way to accelerate protons in the forward direction to high energies is to use under-dense or near-critical density targets instead of solids. Simulations have revealed that the acceleration process depends on the density gradients of the plasma target. Indeed, under certain conditions, the most energetic protons are predicted to be accelerated by a collisionless shock mechanism that significantly increases their energy. We report here the results of a recent experiment dedicated to the study of longitudinal ion acceleration in partially exploded foils using a high intensity (∼5 × 10{sup 18} W/cm{sup 2}) picosecond laser pulse. Wemore » show that protons accelerated using targets having moderate front and rear plasma gradients (up to ∼8 μm gradient length) exhibit similar maximum proton energy and number compared to proton beams that are produced, in similar laser conditions, from solid targets, in the well-known target normal sheath acceleration regime. Particle-In-Cell simulations, performed in the same conditions as the experiment and consistent with the measurements, allow laying a path for further improvement of this acceleration scheme.« less

Optimum hot electron production with low-density foams for laser fusion by fast ignition.

PubMed

Lei, A L; Tanaka, K A; Kodama, R; Kumar, G R; Nagai, K; Norimatsu, T; Yabuuchi, T; Mima, K

2006-06-30

We propose a foam cone-in-shell target design aiming at optimum hot electron production for the fast ignition. A thin low-density foam is proposed to cover the inner tip of a gold cone inserted in a fuel shell. An intense laser is then focused on the foam to generate hot electrons for the fast ignition. Element experiments demonstrate increased laser energy coupling efficiency into hot electrons without increasing the electron temperature and beam divergence with foam coated targets in comparison with solid targets. This may enhance the laser energy deposition in the compressed fuel plasma.

Supported plasma sputtering apparatus for high deposition rate over large area

DOEpatents

Moss, Ronald W.; McClanahan, Jr., Edwin D.; Laegreid, Nils

1977-01-01

A supported plasma sputtering apparatus is described having shaped electrical fields in the electron discharge region between the cathode and anode and the sputter region between the target and substrate while such regions are free of any externally applied magnetic field to provide a high deposition rate which is substantially uniform over a wide area. Plasma shaping electrodes separate from the anode and target shape the electrical fields in the electron discharge region and the sputter region to provide a high density plasma. The anode surrounds the target to cause substantially uniform sputtering over a large target area. In one embodiment the anode is in the form of an annular ring surrounding a flat target surface, such anode being provided with a ribbed upper surface which shields portions of the anode from exposure to sputtered material to maintain the electron discharge for a long stable operation. Several other embodiments accomplish the same result by using different anodes which either shield the anode from sputtered material, remove the sputtered coating on the anode by heating, or simultaneously mix sputtered metal from the auxiliary target with sputtered insulator from the main target so the resultant coating is conductive. A radio frequency potential alone or together with a D.C. potential, may be applied to the target for a greater sputtering rate.

Studies of Positron Generation from Ultraintense Laser-Matter Interactions

NASA Astrophysics Data System (ADS)

Williams, Gerald Jackson

Laser-produced pair jets possess unique characteristics that offer great potential for their use in laboratory-astrophysics experiments to study energetic phenomenon such as relativistic shock accelerations. High-flux, high-energy positron sources may also be used to study relativistic pair plasmas and useful as novel diagnostic tools for high energy density conditions. Copious amounts of positrons are produced with MeV energies from directly irradiating targets with ultraintense lasers where relativistic electrons, accelerated by the laser field, drive positron-electron pair production. Alternatively, laser wakefield accelerated electrons can produce pairs by the same mechanisms inside a secondary converter target. This dissertation describes a series of novel experiments that investigate the characteristics and scaling of pair production from ultraintense lasers, which are designed to establish a robust platform for laboratory-based relativistic pair plasmas. Results include a simple power-law scaling to estimate the effective positron yield for elemental targets for any Maxwellian electron source, typical of direct laser-target interactions. To facilitate these measurements, a solenoid electromagnetic coil was constructed to focus emitted particles, increasing the effective collection angle of the detector and enabling the investigation of pair production from thin targets and low-Z materials. Laser wakefield electron sources were also explored as a compact, high repetition rate platform for the production of high energy pairs with potential applications to the creation of charge-neutral relativistic pair plasmas. Plasma accelerators can produce low-divergence electron beams with energies approaching a GeV at Hz frequencies. It was found that, even for high-energy positrons, energy loss and scattering mechanisms in the target create a fundamental limit to the divergence and energy spectrum of the emitted positrons. The potential future application of laser-generated pairs was considered by exploring the feasibility of radiographing an imploding inertial confinement fusion capsule at ignition- relevant conditions. For an in-flight areal density of 0.02-0.2 g/cm2, currently available positron sources can make density and spatial measurements of deuterium-tritium fuel cores where additional complications of full-scale experiments are expected to reduce the measurement sensitivity.

X-ray imaging spectroscopic diagnostics on Nike

NASA Astrophysics Data System (ADS)

Aglitskiy, Y.; Karasik, M.; Serlin, V.; Weaver, J. L.; Oh, J.; Obenschain, S. P.; Ralchenko, Yu.

2017-10-01

Electron temperature and density diagnostics of the laser plasma produced within the focal spot of the NRL's Nike laser are being explored with the help of X-ray imaging spectroscopy. Spectra of He-like and H-like ions were taken by Nike focusing spectrometers in a range of lower (1.8 kev, Si XIV) and higher (6.7 kev, Fe XXV) x-ray energies. Data that were obtained with spatial resolution were translated into the temperature and density as functions of distance from the target. As an example electron density was determined from He-like satellites to Ly-alpha in Si XIV. The dielectronic satellites with intensity ratios that are sensitive to collisional transfer of population between different triplet groups of double-excited states 2l2l' in Si XIII were observed with high spatial and spectral resolution Lineouts taken at different axial distances from the planar Si target show changing spectral shapes due to the different electron densities as determined by supporting non-LTE simulations. These shapes are relatively insensitive to the plasma temperature which was measured using different spectral lines. This work was supported by the US DOE/NNSA.

Trains of electron micro-bunches in plasma wake-field acceleration

NASA Astrophysics Data System (ADS)

Lécz, Zsolt; Andreev, Alexander; Konoplev, Ivan; Seryi, Andrei; Smith, Jonathan

2018-07-01

Plasma-based charged particle accelerators have been intensively investigated in the past three decades due to their capability to open up new horizons in accelerator science and particle physics yielding electric field accelerating gradient more than three orders of magnitudes higher than in conventional devices. At the current stage the most advanced and reliable mechanism for accelerating electrons is based on the propagation of an intense laser pulse or a relativistic electron beam in a low density gaseous target. In this paper we concentrate on the electron beam-driven plasma wake-field acceleration and demonstrate using 3D PiC simulations that a train of electron micro-bunches with ∼10 fs period can be generated behind the driving beam propagating in a density down-ramp. We will discuss the conditions and properties of the micro-bunches generated aiming at understanding and study of multi-bunch mechanism of injection. It is show that the periodicity and duration of micro-bunches can be controlled by adjusting the plasma density gradient and driving beam charge.

Spatial structure of radio frequency ring-shaped magnetized discharge sputtering plasma using two facing ZnO/Al2O3 cylindrical targets for Al-doped ZnO thin film preparation

NASA Astrophysics Data System (ADS)

Sumiyama, Takashi; Fukumoto, Takaya; Ohtsu, Yasunori; Tabaru, Tatsuo

2017-05-01

Spatial structure of high-density radio frequency ring-shaped magnetized discharge plasma sputtering with two facing ZnO/Al2O3 cylindrical targets mounted in ring-shaped hollow cathode has been measured and Al-doped ZnO (AZO) thin film is deposited without substrate heating. The plasma density has a peak at ring-shaped hollow trench near the cathode. The radial profile becomes uniform with increasing the distance from the target cathode. A low ion current flowing to the substrate of 0.19 mA/cm2 is attained. Large area AZO films with a resistivity of 4.1 - 6.7×10-4 Ω cm can be prepared at a substrate room temperature. The transmittance is 84.5 % in a visible region. The surface roughnesses of AZO films are 0.86, 0.68, 0.64, 1.7 nm at radial positions of r = 0, 15, 30, 40 mm, respectively, while diffraction peak of AZO films is 34.26°. The grains exhibit a preferential orientation along (002) axis.

Nuclear Fusion Within Extremely Dense Plasma Enhanced by Quantum Particle Waves

NASA Astrophysics Data System (ADS)

Miao, Feng; Zheng, Xianjun; Deng, Baiquan

2015-05-01

Quantum effects play an enhancement role in p-p chain reactions occurring within stars. Such an enhancement is quantified by a wave penetration factor that is proportional to the density of the participating fuel particles. This leads to an innovative theory for dense plasma, and its result shows good agreement with independent data derived from the solar energy output. An analysis of the first Z-pinch machine in mankind's history exhibiting neutron emission leads to a derived deuterium plasma beam density greater than that of water, with plasma velocities exceeding 10000 km/s. Fusion power could be achieved by the intersection of four such pinched plasma beams with powerful head-on collisions in their common focal region due to the beam and target enhanced reaction. supported by the Fund for the Construction of Graduate Degree of China (No. 2014XWD-S0805)

Spoke rotation reversal in magnetron discharges of aluminium, chromium and titanium

NASA Astrophysics Data System (ADS)

Hecimovic, A.; Maszl, C.; Schulz-von der Gathen, V.; Böke, M.; von Keudell, A.

2016-06-01

The rotation of localised ionisation zones, i.e. spokes, in magnetron discharge are frequently observed. The spokes are investigated by measuring floating potential oscillations with 12 flat probes placed azimuthally around a planar circular magnetron. The 12-probe setup provides sufficient temporal and spatial resolution to observe the properties of various spokes, such as rotation direction, mode number and angular velocity. The spokes are investigated as a function of discharge current, ranging from 10 mA (current density 0.5 mA cm-2) to 140 A (7 A cm-2). In the range from 10 mA to 600 mA the plasma was sustained in DC mode, and in the range from 1 A to 140 A the plasma was pulsed in high-power impulse magnetron sputtering mode. The presence of spokes throughout the complete discharge current range indicates that the spokes are an intrinsic property of a magnetron sputtering plasma discharge. The spokes may disappear at discharge currents above 80 A for Cr, as the plasma becomes homogeneously distributed over the racetrack. Up to discharge currents of several amperes (the exact value depends on the target material), the spokes rotate in a retrograde \\mathbf{E}× \\mathbf{B} direction with angular velocity in the range of 0.2-4 km s-1. Beyond a discharge current of several amperes, the spokes rotate in a \\mathbf{E}× \\mathbf{B} direction with angular velocity in the range of 5-15 km s-1. The spoke rotation reversal is explained by a transition from Ar-dominated to metal-dominated sputtering that shifts the plasma emission zone closer to the target. The spoke itself corresponds to a region of high electron density and therefore to a hump in the electrical potential. The electric field around the spoke dominates the spoke rotation direction. At low power, the plasma is further away from the target and it is dominated by the electric field to the anode, thus retrograde \\mathbf{E}× \\mathbf{B} rotation. At high power, the plasma is closer to the target and it is dominated by the electric field pointing to the target, thus \\mathbf{E}× \\mathbf{B} rotation.

Spectral lines and characteristic of temporal variations in photoionized plasmas induced with laser-produced plasma extreme ultraviolet source

NASA Astrophysics Data System (ADS)

Saber, I.; Bartnik, A.; Wachulak, P.; Skrzeczanowski, W.; Jarocki, R.; Fiedorowicz, H.

2017-11-01

Spectral lines for Kr/Ne/H2 photoionized plasma in the ultraviolet and visible (UV/Vis) wavelength ranges have been created using a laser-produced plasma (LPP) EUV source. The source is based on a double-stream gas puff target irradiated with a commercial Nd:YAG laser. The laser pulses were focused onto a gas stream, injected into a vacuum chamber synchronously with the EUV pulses. Spectral lines from photoionization in neutral Kr/Ne/H2 and up to few charged states were observed. The intense emission lines were associated with the Kr transition lines. Experimental and theoretical investigations on intensity variations for some ionic lines are presented. A decrease in the intensity with the delay time between the laser pulse and the spectrum acquisition was revealed. Electron temperature and electron density in the photoionized plasma have been estimated from the characteristic emission lines. Temperature was obtained using Boltzmann plot method, assuming that the population density of atoms and ions are considered in a local thermodynamic equilibrium (LTE). Electron density was calculated from the Stark broadening profile. The temporal evaluation of the plasma and the way of optimizing the radiation intensity of LPP EUV sources is discussed.

Studies of ˜ps laser driven plasmas in line focus geometry

NASA Astrophysics Data System (ADS)

Tallents, G. J.; Al-Hadithi, Y.; Dwivedi, L.; Behjat, A.; Demir, A.; Holden, M.; Krishnan, J.; Zhang, J.; Key, M. H.; Neely, D.; Norreys, P. A.; Lewis, C. L. S.; MacPhee, A. G.

1995-05-01

Measurements of X-ray emission along linear plasmas produced in short pulse (2-12 ps) experiments using the Rutherford Appleton Laboratory glass (1.06 μm) and KrF (0.268 μm) lasers are interpreted to provide information about the uniformity and lateral and axial energy transport of X-ray laser gain media. For fiber targets, the difficulties of achieving uniform irradiation and accurate plasma length measurements are illustrated and discussed. For slab targets, it is shown that the ratio of the distance between the critical density surface and the ablation surface to the laser focal width controls lateral transport in a similar manner as for spot focus experiments.

Nonlocal heat transport and improved target design for x-ray heating studies at x-ray free electron lasers

NASA Astrophysics Data System (ADS)

Hoidn, Oliver; Seidler, Gerald T.

2018-01-01

The extremely high-power densities and short durations of single pulses of x-ray free electron lasers (XFELs) have opened new opportunities in atomic physics, where complex excitation-relaxation chains allow for high ionization states in atomic and molecular systems, and in dense plasma physics, where XFEL heating of solid-density targets can create unique dense states of matter having temperatures on the order of the Fermi energy. We focus here on the latter phenomena, with special emphasis on the problem of optimum target design to achieve high x-ray heating into the warm dense matter (WDM) state. We report fully three-dimensional simulations of the incident x-ray pulse and the resulting multielectron relaxation cascade to model the spatial energy density deposition in multicomponent targets, with particular focus on the effects of nonlocal heat transport due to the motion of high energy photoelectrons and Auger electrons. We find that nanoscale high-Z /low-Z multicomponent targets can give much improved energy density deposition in lower-Z materials, with enhancements reaching a factor of 100. This has three important benefits. First, it greatly enlarges the thermodynamic parameter space in XFEL x-ray heating studies of lower-Z materials. Second, it allows the use of higher probe photon energies, enabling higher-information content x-ray diffraction (XRD) measurements such as in two-color XFEL operations. Third, while this is merely one step toward optimization of x-ray heating target design, the demonstration of the importance of nonlocal heat transport establishes important common ground between XFEL-based x-ray heating studies and more traditional laser plasma methods.

Alfvén Waves Generated by Expanding Plasmas in the Laboratory and in Space

NASA Astrophysics Data System (ADS)

Gekelman, W.; Vanzeeland, M.; Vincena, S.; Pribyl, P.

2002-12-01

There are many situations, which occur in space (coronal mass ejections, supernovas), or are man-made (upper atmospheric detonations) in which a dense plasma expands into a background magnetized plasma, that can support Alfvén waves. The LArge Plasma Device (LAPD) is a machine, at UCLA, in which Alfvén waves propagation in homogeneous and inhomogeneous plasmas has been studied. These will be briefly reviewed. Then a new class of experiments which involve the expansion of a dense (initially, n/no>>1) laser-produced plasma into an ambient highly magnetized background plasma capable of supporting Alfvén waves will be presented. The 150 MW laser is pulsed at the same 1 Hz repetition rate as the plasma in a highly reproducible experiment. The laser beam impacts a solid target such that the initial plasma burst is directed either along or across the magnetic field. The interaction results in the production of intense shear and compressional Alfvén waves, as well as large density perturbations. The waves propagate away from the target and are observed to become plasma column resonances. The magnetic fields of the waves are obtained with a 3-axis inductive probe. Spatial patterns of the magnetic fields associated with the waves and density perturbations are measured at over {10}4 locations and will be shown in dramatic movies. These are used to estimate the coupling efficiency of the laser energy and kinetic energy of the dense plasma into wave energy. The wave generation mechanism is due to field aligned return currents, which replace fast electrons escaping the initial blast. Work supported by ONR, DOE, and NSF

Time-resolved compression of a capsule with a cone to high density for fast-ignition laser fusion

DOE PAGES

Theobald, W.; Solodov, A. A.; Stoeckl, C.; ...

2014-12-12

The advent of high-intensity lasers enables us to recreate and study the behaviour of matter under the extreme densities and pressures that exist in many astrophysical objects. It may also enable us to develop a power source based on laser-driven nuclear fusion. Achieving such conditions usually requires a target that is highly uniform and spherically symmetric. Here we show that it is possible to generate high densities in a so-called fast-ignition target that consists of a thin shell whose spherical symmetry is interrupted by the inclusion of a metal cone. Using picosecond-time-resolved X-ray radiography, we show that we can achievemore » areal densities in excess of 300 mg cm -2 with a nanosecond-duration compression pulse -- the highest areal density ever reported for a cone-in-shell target. Such densities are high enough to stop MeV electrons, which is necessary for igniting the fuel with a subsequent picosecond pulse focused into the resulting plasma.« less

Time-resolved compression of a capsule with a cone to high density for fast-ignition laser fusion.

PubMed

Theobald, W; Solodov, A A; Stoeckl, C; Anderson, K S; Beg, F N; Epstein, R; Fiksel, G; Giraldez, E M; Glebov, V Yu; Habara, H; Ivancic, S; Jarrott, L C; Marshall, F J; McKiernan, G; McLean, H S; Mileham, C; Nilson, P M; Patel, P K; Pérez, F; Sangster, T C; Santos, J J; Sawada, H; Shvydky, A; Stephens, R B; Wei, M S

2014-12-12

The advent of high-intensity lasers enables us to recreate and study the behaviour of matter under the extreme densities and pressures that exist in many astrophysical objects. It may also enable us to develop a power source based on laser-driven nuclear fusion. Achieving such conditions usually requires a target that is highly uniform and spherically symmetric. Here we show that it is possible to generate high densities in a so-called fast-ignition target that consists of a thin shell whose spherical symmetry is interrupted by the inclusion of a metal cone. Using picosecond-time-resolved X-ray radiography, we show that we can achieve areal densities in excess of 300 mg cm(-2) with a nanosecond-duration compression pulse--the highest areal density ever reported for a cone-in-shell target. Such densities are high enough to stop MeV electrons, which is necessary for igniting the fuel with a subsequent picosecond pulse focused into the resulting plasma.

RF magnetized ring-shaped plasma for target utilization obtained with circular magnet monopole arrangement

NASA Astrophysics Data System (ADS)

Amzad Hossain, Md.; Ohtsu, Yasunori

2018-01-01

We proposed a new setup for generating outer ring-shaped radio frequency (RF) magnetized plasma near the chamber wall using monopole magnet setups. Three monopole magnet setups with (a) R = 5 mm, (b) R = 20 mm, and (c) R = 35 mm were investigated, where R is the gap between the magnets in consecutive circles. The distributions of the two dimensional magnetic flux lines, the absolute value of the horizontal magnetic flux density, and the discharge voltage were investigated for the proposed setups to produce outer ring-shaped plasma. A highly luminous ring-shaped plasma was observed for the setup (a), whereas multi-ring discharges were observed for the setups (b) and (c). It was found that the electron temperature decreases with increasing gas pressure for all cases. The electron temperatures were 2.42, 1.71, and 1.15 eV at an Ar gas pressure of 4 Pa for setups (a), (b), and (c), respectively. The plasma density was approximately the same for setups (b) and (c) at all gas pressures. The highest plasma densities were 6.26 × 1015, 1.06 × 1016, and 1.11 × 1016 m-3 at 5 Pa for setups (a), (b), and (c), respectively. It was found that the electron mean free path was 41.4, 63.17, and 84.66 mm at an Ar gas pressure of 5 Pa for setups (a), (b), and (c), respectively. The electron neutral collision frequency for setup (a) was higher than those for setups (b) and (c) at a constant RF power of 40 W and an axial distance of z = 13 mm from the target surface. The radial profile of the ion saturation current for setup (b) was more uniform than those for setups (a) and (c).

EBW and Whistler propagation and damping in a linear device

NASA Astrophysics Data System (ADS)

Diem, S. J.; Caughman, J. B. O.; Harvey, R. W.; Petrov, Yu.

2011-10-01

Linear plasma devices are an economic method to study plasma-material interactions under high heat and particle fluxes. ORNL is developing a large cross section, high-density helicon plasma generator with additional resonant electron heating to study plasma-material interactions in ITER like conditions. The device will produce a heat flux of 10-20 MW/m2 and particle flux of 1024 /m2/s in a high recycling plasma near a target plate with a magnetic field of ~1 T. As part of this effort, heating of overdense plasma is being studied using a microwave-based plasma experiment. The plasma is initiated with a high-field launch of 18 GHz whistler waves producing a moderate-density plasma of ne ~1018 m-3. Electron heating of the overdense plasma can be provided by either whistler waves or EBW at 6 and 18 GHz. A modified GENRAY (GENRAY-C) ray-tracing code has been used to determine EBW and ECH whistler wave accessibility for these overdense plasmas. These results combined with emission measurements will be used to determine launcher designs and their placement. ORNL is managed by UT-Battelle, LLC, for the U.S. DOE under contract DE-AC-05-00OR22725.

Quasineutral plasma expansion into infinite vacuum as a model for parallel ELM transport

NASA Astrophysics Data System (ADS)

Moulton, D.; Ghendrih, Ph; Fundamenski, W.; Manfredi, G.; Tskhakaya, D.

2013-08-01

An analytic solution for the expansion of a plasma into vacuum is assessed for its relevance to the parallel transport of edge localized mode (ELM) filaments along field lines. This solution solves the 1D1V Vlasov-Poisson equations for the adiabatic (instantaneous source), collisionless expansion of a Gaussian plasma bunch into an infinite space in the quasineutral limit. The quasineutral assumption is found to hold as long as λD0/σ0 ≲ 0.01 (where λD0 is the initial Debye length at peak density and σ0 is the parallel length of the Gaussian filament), a condition that is physically realistic. The inclusion of a boundary at x = L and consequent formation of a target sheath is found to have a negligible effect when L/σ0 ≳ 5, a condition that is physically plausible. Under the same condition, the target flux densities predicted by the analytic solution are well approximated by the ‘free-streaming’ equations used in previous experimental studies, strengthening the notion that these simple equations are physically reasonable. Importantly, the analytic solution predicts a zero heat flux density so that a fluid approach to the problem can be used equally well, at least when the source is instantaneous. It is found that, even for JET-like pedestal parameters, collisions can affect the expansion dynamics via electron temperature isotropization, although this is probably a secondary effect. Finally, the effect of a finite duration, τsrc, for the plasma source is investigated. As is found for an instantaneous source, when L/σ0 ≳ 5 the presence of a target sheath has a negligible effect, at least up to the explored range of τsrc = L/cs (where cs is the sound speed at the initial temperature).

Characteristics of plasma plume in ultrafast laser ablation with a weakly ionized air channel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hou, Huaming; Yang, Bo; Mao, Xianglei

We report the influence of femtosecond (fs) laser weakly ionized air channel on characteristics of plasma induced from fs-laser ablation of solid Zr metal target. A novel method to create high temperature, low electron density plasma with intense elemental emission and weak bremsstrahlung emission was demonstrated. Weakly ionized air channel was generated as a result of a non-linear phenomenon. Two-dimensional time-resolved optical-emission images of plasma plumes were taken for plume dynamics analysis. Dynamic physical properties of filament channels were simulated. In particular, we investigated the influence of weakly ionized air channel on the evolution of solid plasma plume. Plasma plumemore » splitting was observed whilst longer weakly ionized air channel formed above the ablation spot. The domination mechanism for splitting is attributed to the long-lived underdense channel created by fs-laser induced weakly ionization of air. The evolutions of atomic/molecular emission intensity, peak broadening, and plasma temperature were analyzed, and the results show that the part of plasma entering weakly ionized air channel features higher initial temperature, lower electron density and faster decay.« less

Characteristics of plasma plume in ultrafast laser ablation with a weakly ionized air channel

DOE PAGES

Hou, Huaming; Yang, Bo; Mao, Xianglei; ...

2018-05-10

We report the influence of femtosecond (fs) laser weakly ionized air channel on characteristics of plasma induced from fs-laser ablation of solid Zr metal target. A novel method to create high temperature, low electron density plasma with intense elemental emission and weak bremsstrahlung emission was demonstrated. Weakly ionized air channel was generated as a result of a non-linear phenomenon. Two-dimensional time-resolved optical-emission images of plasma plumes were taken for plume dynamics analysis. Dynamic physical properties of filament channels were simulated. In particular, we investigated the influence of weakly ionized air channel on the evolution of solid plasma plume. Plasma plumemore » splitting was observed whilst longer weakly ionized air channel formed above the ablation spot. The domination mechanism for splitting is attributed to the long-lived underdense channel created by fs-laser induced weakly ionization of air. The evolutions of atomic/molecular emission intensity, peak broadening, and plasma temperature were analyzed, and the results show that the part of plasma entering weakly ionized air channel features higher initial temperature, lower electron density and faster decay.« less

Mechanism of equivalent electric dipole oscillation for high-order harmonic generation from grating-structured solid-surface by femtosecond laser pulse

NASA Astrophysics Data System (ADS)

Wang, Yang; Song, Hai-Ying; Liu, H. Y.; Liu, Shi-Bing

2017-07-01

We theoretically study high-order harmonic generation (HHG) from relativistically driven overdense plasma targets with rectangularly grating-structured surfaces by femtosecond laser pulses. Our particle-in-cell (PIC) simulations show that, under the conditions of low laser intensity and plasma density, the harmonics emit principally along small angles deviating from the target surface. Further investigation of the surface electron dynamics reveals that the electron bunches are formed by the interaction between the laser field and the target surface, giving rise to the oscillation of equivalent electric-dipole (OEED), which enhances specific harmonic orders. Our work helps understand the mechanism of harmonic emissions from grating targets and the distinction from the planar harmonic scheme.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Temporal and thermodynamic characteristics of plasma formation

NASA Astrophysics Data System (ADS)

Ignatavichyus, M. V.; Kazakyavichyus, É.; Orshevski, G.; Danyunas, V.

1991-11-01

An investigation was made of plasma formation accompanying the interaction with aluminum, iron, and VK-6 alloy targets of nanosecond radiation from a YAG:Nd3+ laser (Emax = 50 mJ, τ = 3-8 ns). The duration of the plasma formation process depended weakly on the laser radiation parameters [the power density was varied in the range 1-3 GW/cm2, the pulse rise time in the range 2-8 ns, or the rate of rise of the power density in the range (1-8) × 108 W · cm - 2 · ns -1]. A study was made of the establishment of a local thermodynamic equilibrium in a plasma jet excited by radiation from nanosecond and picosecond (E = 30 mJ, τ = 40 ps) lasers. The maximum of the luminescence from an aluminum plasma excited by picosecond laser radiation was found to correspond to a local thermodynamic equilibrium. A local thermodynamic equilibrium could be absent in the case of excitation by nanosecond laser radiation.

Investigating inertial confinement fusion target fuel conditions through x-ray spectroscopya)

NASA Astrophysics Data System (ADS)

Hansen, Stephanie B.

2012-05-01

Inertial confinement fusion (ICF) targets are designed to produce hot, dense fuel in a neutron-producing core that is surrounded by a shell of compressing material. The x-rays emitted from ICF plasmas can be analyzed to reveal details of the temperatures, densities, gradients, velocities, and mix characteristics of ICF targets. Such diagnostics are critical to understand the target performance and to improve the predictive power of simulation codes.

Stable dense plasma jets produced at laser power densities around 10{sup 14} W/cm{sup 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kasperczuk, A.; Pisarczyk, T.; Borodziuk, S.

2006-06-15

The results of investigations are presented that are connected with defocused laser beam-planar target interaction. Following the very large focus laser-plasma interaction experiments on the Nova [H. T. Powell, J. A. Caird, J. E. Murray, and C. E. Thompson, 1991 ICF Annual Report UCRL-LR-105820-91, p. 163 (1991)] and GEKKO-XII [C. Yamanaka, Y. Kato, Y. Izawa, K. Yoshida, T. Yamanaka, T. Sasaki, T. Nakatsuka, J. Kuroda, and S. Nakai, IEEE J. Quantum Electron. QE-17, 1639 (1981)] lasers, as well as on the National Ignition Facility (NIF) laser [W. J. Hogan, E. I. Moses, B. E. Warner, M. S. Sorem, and J.more » M. Soures, Nucl. Fusion 41, 567 (2001)] with generation of high Mach number jets, this paper is devoted to similar jet generation with very detailed measurements of density profiles by using high-power lasers at large focus conditions. The experiment was carried out with target materials of different mass densities (Al, Cu, Ag, Ta, and Pb) using the Prague Asterix Laser System (PALS) iodine laser [K. Jungwirth, A. Cejnarova, L. Juha, B. Kralikowa, J. Krasa, E. Krousky, P. Krupickova, L. Laska, K. Masek, A. Prag, O. Renner, K. Rohlena, B. Rus, J. Skala, P. Straka, and J. Ullschmied, Phys. Plasmas 8, 2495 (2001)]. The investigations were conducted for the laser radiation energy of 100 J at two wavelengths of 1.315 and 0.438 {mu}m (the first and third harmonics of laser radiation), pulse duration of 0.4 ns, and a focal spot radius of 300 {mu}m. Most of the experimental data were obtained by means of a three-frame laser interferometer and an x-ray streak camera; the crater parameters were obtained by using the crater replica technique. These investigations have shown that stable dense plasma jets can be produced in a simple configuration of laser beam-planar target interaction, provided that a proper target material is used.« less

Results from core-edge experiments in high Power, high performance plasmas on DIII-D

DOE PAGES

Petrie, T. W.; Fenstermacher, M. E.; Holcomb, C. T.; ...

2016-12-24

Here, significant challenges to reducing divertor heat flux in highly powered near-double null divertor (DND) hybrid plasmas, while still maintaining both high performance metrics and low enough density for application of RF heating, are identified. For these DNDs on DIII-D, the scaling of the peak heat flux at the outer target (q ⊥ P) ∝ [P SOL x I P] 0.92 for P SOL = 8-19 MW and I P = 1.0–1.4 MA, and is consistent with standard ITPA scaling for single-null H-mode plasmas. Two divertor heat flux reduction methods were tested. First, applying the puff-and-pump radiating divertor to DIII-Dmore » plasmas may be problematical at high power and H98 (≥ 1.5) due to improvement in confinement time with deuterium gas puffing which can lead to unacceptably high core density under certain conditions. Second, q ⊥ P for these high performance DNDs was reduced by ≈35% when an open divertor is closed on the common flux side of the outer divertor target (“semi-slot”) but also that heating near the slot opening is a significant source for impurity contamination of the core.« less

Interaction dynamics of high Reynolds number magnetized plasma flow on the CTIX plasma accelerator

NASA Astrophysics Data System (ADS)

Howard, Stephen James

The Compact Toroid Injection eXperiment, (CTIX), is a coaxial railgun that forms and accelerates magnetized plasma rings called compact toroids (CT's). CTIX consists of a pair of cylindrical coaxial electrodes with the region between them kept at high vacuum (2 m long, 15 cm outer diameter). Hydrogen is typically the dominant constituent of the CT plasma, however helium can also be used. The railgun effect that accelerates the CT can be accounted for by the Lorentz j x B force density created by the power input from a capacitor bank of roughly a Giga-Watt peak. The final velocity of the CT can be as high as 300 km/s, with an acceleration of about 3 billion times Earth's gravity. The compact toroid is able to withstand these forces because of a large internal magnetic field of about 1 Tesla. Understanding the nature of high speed flow of a magnetized plasma has been the primary challenge of this work. In this dissertation we will explore a sequence of fundamental questions regarding the plasma physics of CTIX. First we will go over some new results about the structure and dynamics of the compact toroid's magnetic field, and its electrical resistivity. Then we will present the results from a sequence of key experiments involving reconnection/compression and thermalization of the plasma during interaction of the CT with target magnetic fields of various geometries. Next, we look at the Doppler shift of a spectral line of the He II ion as a measurement of plasma velocity, and to gain insight into the ionization physics of helium in our plasma. These preliminary experiments provide the background for our primary experimental tool for investigating turbulence, a technique called Gas Puff Imaging (GPI) in which a cloud of helium can be used to enhance plasma brightness, allowing plasma density fluctuations to be imaged. We will conclude with an analysis of the images that show coherent density waves, as well as the transition to turbulence during the interaction with a wire target perturbation.

Experimental measurements of hydrodynamic instabilities on NOVA of relevance to astrophysics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Budil, K S; Cherfils, C; Drake, R P

1998-09-11

Large lasers such as Nova allow the possibility of achieving regimes of high energy densities in plasmas of millimeter spatial scales and nanosecond time scales. In those plasmas where thermal conductivity and viscosity do not play a significant role, the hydrodynamic evolution is suitable for benchmarking hydrodynamics modeling in astrophysical codes. Several experiments on Nova examine hydrodynamically unstable interfaces. A typical Nova experiment uses a gold millimeter-scale hohlraum to convert the laser energy to a 200 eV blackbody source lasting about a nanosecond. The x-rays ablate a planar target, generating a series of shocks and accelerating the target. The evolvingmore » area1 density is diagnosed by time-resolved radiography, using a second x-ray source. Data from several experiments are presented and diagnostic techniques are discussed.« less

Modeling dynamic plasmas driven by ultraintense nano-focused x-ray laser pulses in solid iron targets

NASA Astrophysics Data System (ADS)

Royle, Ryan; Sentoku, Yasuhiko; Mancini, Roberto

2017-10-01

The hard x-ray free electron laser has proven to be a valuable tool for high energy density (HED) physics as it is able to produce well-characterized samples of HED matter at exactly solid density and homogeneous temperatures. However, if the x-ray pulses are focused to sub-micron spot sizes, where peak intensities can exceed 1020 W/cm2, the plasmas driven by sources of non-thermal photoelectrons and Auger electrons can be highly dynamic and so cannot be modeled by atomic kinetics or fluid codes. We apply the 2D/3D particle-in-cell code, PICLS-which has been extended with numerous physics models to enable the simulation of XFEL-driven plasmas-to the modeling of such dynamic plasmas driven by nano-focused XFEL pulses in solid iron targets. In the case of the smallest focal spot investigated of just 100 nm in diameter, keV plasmas induce strong radial E-fields that accelerate keV ions radially as well as sheath fields that accelerate surface ions to hundreds of keV. The heated spot, which is initially larger than the laser spot due to the kinetic nature of the fast Auger electrons, expands as ion and electron waves propagate radially, leaving a low density region along the laser axis. This research was supported by the US DOE-OFES under Grant No. DE-SC0008827, the DOE-NNSA under Grant No. DE-NA0002075, and the JSPS KAKENHI under Grant No. JP15K21767.

Wave modeling in a cylindrical non-uniform helicon discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, L.; Hole, M. J.; Caneses, J. F.

2012-08-15

A radio frequency field solver based on Maxwell's equations and a cold plasma dielectric tensor is employed to describe wave phenomena observed in a cylindrical non-uniform helicon discharge. The experiment is carried out on a recently built linear plasma-material interaction machine: The magnetized plasma interaction experiment [Blackwell et al., Plasma Sources Sci. Technol. (submitted)], in which both plasma density and static magnetic field are functions of axial position. The field strength increases by a factor of 15 from source to target plate, and the plasma density and electron temperature are radially non-uniform. With an enhancement factor of 9.5 to themore » electron-ion Coulomb collision frequency, a 12% reduction in the antenna radius, and the same other conditions as employed in the experiment, the solver produces axial and radial profiles of wave amplitude and phase that are consistent with measurements. A numerical study on the effects of axial gradient in plasma density and static magnetic field on wave propagations is performed, revealing that the helicon wave has weaker attenuation away from the antenna in a focused field compared to a uniform field. This may be consistent with observations of increased ionization efficiency and plasma production in a non-uniform field. We find that the relationship between plasma density, static magnetic field strength, and axial wavelength agrees well with a simple theory developed previously. A numerical scan of the enhancement factor to the electron-ion Coulomb collision frequency from 1 to 15 shows that the wave amplitude is lowered and the power deposited into the core plasma decreases as the enhancement factor increases, possibly due to the stronger edge heating for higher collision frequencies.« less

Time-dependent spectroscopy of plasma plume under laser welding conditions

NASA Astrophysics Data System (ADS)

Hoffman, Jacek; Szymanski, Zygmunt

2004-07-01

Momentary emission spectra of iron and argon lines were measured in a plasma plume induced during welding with a continuous wave CO2 laser. Time-dependent spectra were registered using a fast gate, lens coupled microchannel plate image intensifier placed between a spectrograph and a 1254 silicon intensified target detector connected to an optical multichannel analyser. The results, together with the analysis of the colour images from a fast camera, show that in the case when argon is the shielding gas, two plasmas exist: the argon plasma and the iron plasma. It has been found that during strong bursts the plasma plume over the keyhole consists mainly of metal vapour, not being diluted by the shielding gas. No apparent mixing of the metal vapour and the shielding gas has been observed. The space-averaged electron densities determined from the Stark broadening of the 7503.87, 7514.65 Å Ar I lines amounts to (0.75-1.05) × 1023 m-3 depending on the distance from the surface. Assuming that argon is not mixed with the metal vapour and is in local thermodynamic equilibrium these electron densities correspond to the temperatures of 12-13 kK. At the peaks of strong vapour bursts the space-averaged electron densities determined from the Stark broadening of the 5383.37 Å Fe I line are (0.6-1) × 1023 m-3. Numerical simulations showed that the maximum densities in the plasma centre are considerably higher and amount to ~1.8 × 1023 m-3 and ~2.45 × 1023 m-3 in the case of the argon and metal plasma, respectively. Consequently the absorption of the laser beam in the plasma plume amounts to ~5% of the beam power in the case of argon and 10% in the case of metal plasma.

Shock wave acceleration of protons in inhomogeneous plasma interacting with ultrashort intense laser pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lecz, Zs.; Andreev, A.; Max-Born Institute, Berlin

The acceleration of protons, triggered by solitary waves in expanded solid targets is investigated using particle-in-cell simulations. The near-critical density plasma is irradiated by ultrashort high power laser pulses, which generate the solitary wave. The transformation of this soliton into a shock wave during propagation in plasma with exponentially decreasing density profile is described analytically, which allows to obtain a scaling law for the proton energy. The high quality proton bunch with small energy spread is produced by reflection from the shock-front. According to the 2D simulations, the mechanism is stable only if the laser pulse duration is shorter thanmore » the characteristic development time of the parasitic Weibel instability.« less

Plasma and Shock Generation by Indirect Laser Pulse Action

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kasperczuk, A.; Borodziuk, S.; Pisarczyk, T.

2006-01-15

In the paper the results of our experiment with flyer disks, accelerated to high velocities by the PALS iodine laser and subsequently creating craters when hitting massive targets , are presented. We have carried out experiments with the double targets consisted of a disk placed in front of a massive target part at distances of either 200 or 500 {mu}m. Both elements of the targets were made of Al. The following disk irradiation conditions were used: laser energy of 130 J, laser wavelength of 1.315 {mu}m, pulse duration of 0.4 ns, and laser spot diameter of 250 {mu}m. To measuremore » some plasma parameters and accelerated disk velocity a three frame interferometric system was used. Efficiency of crater creation by a disk impact was determined from the crater parameters, which were obtained by means of a crater replica technique. The experimental results concern two main stages: (a) ablative plasma generation and disk acceleration and (b) disk impact and crater creation. Spatial density distributions at different moments of plasma generation and expansion are shown. Discussion of the experimental results on the basis of a 2-D theoretical model of the laser -- solid target interaction is carried out.« less

Ultraviolet Thomson Scattering from Direct-Drive Coronal Plasmas

NASA Astrophysics Data System (ADS)

Henchen, R. J.; Goncharov, V. N.; Michel, D. T.; Follett, R. K.; Katz, J.; Froula, D. H.

2013-10-01

Ultraviolet (λ4 ω = 263 nm) Thomson scattering (TS) was used to probe ion-acoustic waves (IAW's) and electron plasma waves (EPW's) from direct-drive coronal plasmas. Fifty-nine drive beams (λ3 ω = 351 nm) illuminate a spherical target with a radius of ~860 μm. Advances in the ultraviolet (UV) TS diagnostic at the Omega Laser Facility provide the ability to detect deep UV photons (~190 nm) and allow access to scattered light from EPW's propagating near the 3 ω quarter-critical surface (~2.5 × 1021 cm-3) . A series of experiments studied the effects of ablator materials on coronal plasma conditions. Electron temperatures and densities were measured from 150 μm to 400 μm from the initial target surface. Standard CH shells were compared to three-layered shells consisting of Si doped CH, Si, and Be. Early analysis indicates that these multilayered targets have less hot-electron energy as a result of higher electron temperature in the coronal plasma. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Enhanced Laser-Driven Ion Acceleration by Superponderomotive Electrons Generated from Near-Critical-Density Plasma

NASA Astrophysics Data System (ADS)

Bin, J. H.; Yeung, M.; Gong, Z.; Wang, H. Y.; Kreuzer, C.; Zhou, M. L.; Streeter, M. J. V.; Foster, P. S.; Cousens, S.; Dromey, B.; Meyer-ter-Vehn, J.; Zepf, M.; Schreiber, J.

2018-02-01

We report on the experimental studies of laser driven ion acceleration from a double-layer target where a near-critical density target with a few-micron thickness is coated in front of a nanometer-thin diamondlike carbon foil. A significant enhancement of proton maximum energies from 12 to ˜30 MeV is observed when a relativistic laser pulse impinges on the double-layer target under linear polarization. We attributed the enhanced acceleration to superponderomotive electrons that were simultaneously measured in the experiments with energies far beyond the free-electron ponderomotive limit. Our interpretation is supported by two-dimensional simulation results.

Laser Driven Compression Equations of State and Hugoniot Pressure Measurements in Thick Solid Metallic Targets at ˜0.17-13 TW/cm2

NASA Astrophysics Data System (ADS)

Remo, John L.

2010-10-01

An electro-optic laser probe was developed to obtain parameters for high energy density equations of state (EoS), Hugoniot pressures (PH), and strain rates for high energy density laser irradiation intensity, I, experiments at ˜170 GW/cm2 (λ = 1064 nm) to ˜13 TW/cm2 (λ = 527 nm) on Al, Cu, Ti, Fe, Ni metal targets in a vacuum. At I ˜7 TW/cm2 front surface plasma pressures and temperatures reached 100's GPa and over two million K. Rear surface PH ranged from 7-120 GPa at average shock wave transit velocities 4.2-8.5 km/s, depending on target thickness and I. A surface plasma compression ˜100's GPa generated an impulsive radial expanding shock wave causing compression, rarefactions, and surface elastic and plastic deformations depending on I. A laser/fiber optic system measured rear surface shock wave emergence and particle velocity with ˜3 GHz resolution by monitoring light deflection from diamond polished rear surfaces of malleable metallic targets, analogous to an atomic force microscope. Target thickness, ˜0.5-2.9 mm, prevented front surface laser irradiation penetration, due to low radiation skin depth, from altering rear surface reflectivity (refractive index). At ˜10 TW electromagnetic plasma pulse noise generated from the target chamber overwhelmed detector signals. Pulse frequency analysis using Moebius loop antennae probed transient noise characteristics. Average shock (compression) and particle (rear surface displacement) velocity measurements determined rear surface PH and GPa) EoS that are compared with gas guns.

Particle-in-cell simulations of bounded plasma discharges applied to low pressure high density sources and positive columns

NASA Astrophysics Data System (ADS)

Kawamura, Emi

Particle-in-cell (PIC) simulations of bounded plasma discharges are attractive because the fields and the particle motion can be obtained self-consistently from first principles. Thus, we can accurately model a wide range of nonlocal and kinetic behavior. The only disadvantage is that PIC may be computationally expensive compared to other methods. Fluid codes, for example, may run faster but make assumptions about the bulk plasma velocity distributions and ignore kinetic effects. In Chapter 1, we demonstrate methods of accelerating PIC simulations of bounded plasma discharges. We find that a combination of physical and numerical methods makes run-times for PIC codes much more competitive with other types of codes. In processing plasmas, the ion energy distributions (IEDs) arriving at the wafer target are crucial in determining ion anisotropy and etch rates. The current trend for plasma reactors is towards lower gas pressure and higher plasma density. In Chapter 2, we review and analyze IEDs arriving at the target of low pressure high density rf plasma reactors. In these reactors, the sheath is typically collisionless. We then perform PIC simulations of collisionless rf sheaths and find that the key parameter governing the shape of the TED at the wafer is the ratio of the ion transit time across the sheath over the rf period. Positive columns are the source of illumination in fluorescent mercury-argon lamps. The efficiency of light production increases with decreasing gas pressure and decreasing discharge radius. Most current lamp software is based on the local concept even though low pressure lighting discharges tend to be nonlocal. In Chapter 3, we demonstrate a 1d3v radial PIC model to conduct nonlocal kinetic simulations of low pressure, small radius positive columns. When compared to other available codes, we find that our PIC code makes the least approximations and assumptions and is accurate and stable over a wider parameter range. We analyze the PIC simulation results in detail and find that the radial electron heat flow, which is neglected in local models, plays a major role in maintaining the global power balance. In Chapter 2, we focused on the sheaths of low pressure high density plasma reactors. In Chapter 4, we extend our study to the bulk and presheaths. Typical industrial plasma reactors often use gases with complex chemistries which tend to generate discharges containing negative ions. For high density electronegative plasmas with low gas pressure, we expect Coulomb collisions between positive and negative ions to dominate over collisions between ions and neutrals. We incorporate a Coulomb collision model into our PIC code to study the effect of this ion-ion Coulomb scattering. We find that the Coulomb collisions between the positive and negative ions significantly modify the negative ion flux, density and kinetic energy profiles.

Initial design for an experimental investigation of strongly coupled plasma behavior in the Atlas facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Munson, C.P.; Benage, J.F. Jr.; Taylor, A.J.

Atlas is a high current ({approximately} 30 MA peak, with a current risetime {approximately} 4.5 {micro}sec), high energy (E{sub stored} = 24 MJ, E{sub load} = 3--6 MJ), pulsed power facility which is being constructed at Los Alamos National Laboratory with a scheduled completion date in the year 2000. When operational, this facility will provide a platform for experiments in high pressure shocks (> 20 Mbar), adiabatic compression ({rho}/{rho}{sub 0} > 5, P > 10 Mbar), high magnetic fields ({approximately} 2,000 T), high strain and strain rates ({var_epsilon} > 200%, d{var_epsilon}/dt {approximately} 10{sup 4} to 10{sup 6} s{sup {minus}1}), hydrodynamicmore » instabilities of materials in turbulent regimes, magnetized target fusion, equation of state, and strongly coupled plasmas. For the strongly coupled plasma experiments, an auxiliary capacitor bank will be used to generate a moderate density (< 0.1 solid), relatively cold ({approximately} 1 eV) plasma by ohmic heating of a conducting material of interest such as titanium. This stargate plasma will be compressed against a central column containing diagnostic instrumentation by a cylindrical conducting liner that is driven radially inward by current from the main Atlas capacitor bank. The plasma is predicted to reach densities of {approximately} 1.1 times solid, achieve ion and electron temperatures of {approximately} 10 eV, and pressures of {approximately} 4--5 Mbar. This is a density/temperature regime which is expected to experience strong coupling, but only partial degeneracy. X-ray radiography is planned for measurements of the material density at discrete times during the experiments; diamond Raman measurements are anticipated for determination of the pressure. In addition, a neutron resonance spectroscopic technique is being evaluated for possible determination of the temperature (through low percentage doping of the titanium with a suitable resonant material). Initial target plasma formation experiments are being planned on an existing pulsed power facility at LANL and will be completed before the start of operation of Atlas.« less

LIF and fast imaging plasma jet characterization relevant for NTP biomedical applications

NASA Astrophysics Data System (ADS)

Riès, D.; Dilecce, G.; Robert, E.; Ambrico, P. F.; Dozias, S.; Pouvesle, J.-M.

2014-07-01

In the field of biomedical application, many publications report on non-thermal plasma jet potentialities for cell behaviour modifications in cancer treatment, wound healing or sterilization. However most previous plasma jet characterizations were performed when jets expend freely in air. Only recently has the influence of the targeted surface been properly considered. In this work, modifications induced by various types of targets, mimicking the biological samples, in the plasma propagation and production of hydroxyl radicals are evidenced through time-resolved intensified charge-coupled device imaging and laser-induced fluorescence (LIF) measurements. A LIF model, also specifically dedicated to estimate air and water penetration inside the jet, is used and proves to be well adapted to characterize the plasma jet under biomedical application conditions. It is shown that the plasma produced by the plasma gun counter-propagates after impinging the surface which, for the same operating parameters, leads to an increase of almost one order of magnitude in the maximum OH density (from ˜2 × 1013 cm-3 for open-air propagation to ˜1 × 1014 cm-3 for a grounded metal target). The nature of the target, especially its electrical conductivity, as well as gas flow rate and voltage amplitude are playing a key role in the production of hydroxyl radicals. The strong interplay between gas flow dynamics and plasma propagation is here confirmed by air and water distribution measurements. The need for a multi-diagnostic approach, as well as great care in setting up the in situ characterization of plasma jets, is here emphasized. Special attention must not only be paid to voltage amplitude and gas flow rate but also to the nature, humidity and conductivity of the target.

Time-Resolved Optical Emission Spectroscopy Diagnosis of CO2 Laser-Produced SnO2 Plasma

NASA Astrophysics Data System (ADS)

Lan, Hui; Wang, Xinbing; Zuo, Duluo

2016-09-01

The spectral emission and plasma parameters of SnO2 plasmas have been investigated. A planar ceramic SnO2 target was irradiated by a CO2 laser with a full width at half maximum of 80 ns. The temporal behavior of the specific emission lines from the SnO2 plasma was characterized. The intensities of Sn I and Sn II lines first increased, and then decreased with the delay time. The results also showed a faster decay of Sn I atoms than that of Sn II ionic species. The temporal evolutions of the SnO2 plasma parameters (electron temperature and density) were deduced. The measured temperature and density of SnO2 plasma are 4.38 eV to 0.5 eV and 11.38×1017 cm-3 to 1.1×1017 cm-3, for delay times between 0.1 μs and 2.2 μs. We also investigated the effect of the laser pulse energy on SnO2 plasma. supported by National Natural Science Foundation of China (No. 11304235) and the Director Fund of WNLO

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Formation of a plasma jet of multiply charged ions in the interaction of a laser plasma with an external pulsed magnetic field

NASA Astrophysics Data System (ADS)

Dyakin, V. M.; Pikuz, T. A.; Skobelev, I. Yu; Faenov, A. Ya; Wolowski, J.; Karpinski, L.; Kasperczuk, A.; Pisarczyk, T.

1994-12-01

A dense jet of a plasma consisting of multiply charged ions was generated in the interaction of a laser plasma with a strong external axial magnetic field. Images were formed by spectral lines and the soft x-ray spectrum range of the plasma jet was obtained with a large-aperture spectrograph containing a mica crystal bent to form a spherical surface with a radius of R = 10 cm. A tenfold increase in the density of the He-like Mg XI plasma, compared with a freely expanding plasma, was observed at a distance of 5 mm from the target.

Development of a Method for Local Electron Temperature and Density Measurements in the Divertor of the JET Tokamak

NASA Technical Reports Server (NTRS)

Jupen, C.; Meigs, A.; Bhatia, A. K.; Brezinsek, S.; OMullane, M.

2004-01-01

Plasma volume recombination in the divertor, a process in which charged particles recombine to neutral atoms, contributes to plasma detachment and hence cooling at the divertor target region. Detachment has been observed at JET and other tokamaks and is known to occur at low electron temperatures (T(sub e)<1 eV) and at high electron density (n(sub e)>10(exp 20)/m(exp 3)). The ability to measure such low temperatures is therefore of interest for modelling the divertor. In present work we report development of a new spectroscopic technique for investigation of local electron density (n(sub e)) and temperature (T,) in the outer divertor at JET.

Use of zooming and pulseshaping for acceleration to high velocities and fusion neutron production on the Nike laser

NASA Astrophysics Data System (ADS)

Karasik, Max; Weaver, J. L.; Aglitskiy, Y.; Kehne, D. M.; Zalesak, S. T.; Velikovich, A. L.; Oh, J.; Obenschain, S. P.; Arikawa, Y.

2011-10-01

We will present results from follow-on experiments to the record-high velocities of 1000 km/s achieved on Nike [Karasik et al, Phys. Plasmas 17, 056317(2010)], in which highly accelerated planar foils of deuterated polystyrene were made to collide with a witness foil to produce ~ 1 Gbar shock pressures and result in heating of matter to thermonuclear temperatures. Still higher velocities and higher target densities are required for impact fast ignition. The aim of these experiments is using the focal zoom capability of Nike and shaping the driving pulse to minimize shock heating of the accelerated target to achieve higher densities and velocities. In-flight target density is inferred from target heating upon collision via DD neutron time-of-flight ion temperature measurement. Work is supported by US DOE (NNSA) and Office of Naval Research. SAIC

High-current fast electron beam propagation in a dielectric target.

PubMed

Klimo, Ondrej; Tikhonchuk, V T; Debayle, A

2007-01-01

Recent experiments demonstrate an efficient transformation of high intensity laser pulse into a relativistic electron beam with a very high current density exceeding 10(12) A cm(-2). The propagation of such a beam inside the target is possible if its current is neutralized. This phenomenon is not well understood, especially in dielectric targets. In this paper, we study the propagation of high current density electron beam in a plastic target using a particle-in-cell simulation code. The code includes both ionization of the plastic and collisions of newborn electrons. The numerical results are compared with a relatively simple analytical model and a reasonable agreement is found. The temporal evolution of the beam velocity distribution, the spatial density profile, and the propagation velocity of the ionization front are analyzed and their dependencies on the beam density and energy are discussed. The beam energy losses are mainly due to the target ionization induced by the self-generated electric field and the return current. For the highest beam density, a two-stream instability is observed to develop in the plasma behind the ionization front and it contributes to the beam energy losses.

High-Energy-Density-Physics Studies for Inertial Confinement Fusion Applications

NASA Astrophysics Data System (ADS)

Hu, S. X.

2017-10-01

Accurate knowledge of the static, transport, and optical properties of high-energy-density (HED) plasmas is essential for reliably designing and understanding inertial confinement fusion (ICF) implosions. In the warm-dense-matter regime routinely accessed by low-adiabat ICF implosions, many-body strong-coupling and quantum electron degeneracy effects play an important role in determining plasma properties. The past several years have witnessed intense efforts to assess the importance of the microphysics of ICF targets, both theoretically and experimentally. On the theory side, first-principles methods based on quantum mechanics have been applied to investigate the properties of warm, dense plasmas. Specifically, self-consistent investigations have recently been performed on the equation of state, thermal conductivity, and opacity of a variety of ICF ablators such as polystyrene (CH), beryllium, carbon, and silicon over a wide range of densities and temperatures. In this talk, we will focus on the most-recent progress on these ab initio HED physics studies, which generally result in favorable comparisons with experiments. Upon incorporation into hydrocodes for ICF simulations, these first-principles ablator-plasma properties have produced significant differences over traditional models in predicting 1-D target performance of ICF implosions on OMEGA and direct-drive-ignition designs for the National Ignition Facility. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944. *In collaboration with L. A. Collins, T. R. Boehly, G. W. Collins, J. D. Kress, and V. N. Goncharov.

Targeted Proteomics and Absolute Protein Quantification for the Construction of a Stoichiometric Host-Pathogen Surface Density Model*

PubMed Central

Sjöholm, Kristoffer; Kilsgård, Ola; Teleman, Johan; Happonen, Lotta; Malmström, Lars; Malmström, Johan

2017-01-01

Sepsis is a systemic immune response responsible for considerable morbidity and mortality. Molecular modeling of host-pathogen interactions in the disease state represents a promising strategy to define molecular events of importance for the transition from superficial to invasive infectious diseases. Here we used the Gram-positive bacterium Streptococcus pyogenes as a model system to establish a mass spectrometry based workflow for the construction of a stoichiometric surface density model between the S. pyogenes surface, the surface virulence factor M-protein, and adhered human blood plasma proteins. The workflow relies on stable isotope labeled reference peptides and selected reaction monitoring mass spectrometry analysis of a wild-type strain and an M-protein deficient mutant strain, to generate absolutely quantified protein stoichiometry ratios between S. pyogenes and interacting plasma proteins. The stoichiometry ratios in combination with a novel targeted mass spectrometry method to measure cell numbers enabled the construction of a stoichiometric surface density model using protein structures available from the protein data bank. The model outlines the topology and density of the host-pathogen protein interaction network on the S. pyogenes bacterial surface, revealing a dense and highly organized protein interaction network. Removal of the M-protein from S. pyogenes introduces a drastic change in the network topology, validated by electron microscopy. We propose that the stoichiometric surface density model of S. pyogenes in human blood plasma represents a scalable framework that can continuously be refined with the emergence of new results. Future integration of new results will improve the understanding of protein-protein interactions and their importance for bacterial virulence. Furthermore, we anticipate that the general properties of the developed workflow will facilitate the production of stoichiometric surface density models for other types of host-pathogen interactions. PMID:28183813

SOLPS modeling of the effect on plasma detachment of closing the lower divertor in DIII-D

DOE PAGES

Sang, C. F.; Stangeby, P. C.; Guo, H. Y.; ...

2016-12-15

SOLPS modeling has been carried out to assess the effect of tightly closing the lower divertor in DIII-D, which at present is almost fully open, on the achievement of cold dissipative/detached divertor conditions. To isolate the impact of other factors on the divertor plasma solution and to make direct comparisons, most of the parameters including the meshes were kept as similar as possible. Only the neutral baffling was modified to compare a fully open divertor with a tightly closed one. The modeling shows that the tightly closed divertor greatly improves trapping of recycling neutrals, thereby increasing radiative and charge exchangemore » losses in the divertor and reducing the electron temperature T et and deposited power density q dep at the target plate. Furthermore, the closed structure enables the divertor plasma to enter into highly dissipative and detached divertor conditions at a significantly lower upstream density. The effects of divertor closure on the neutral density and pressure, and their correlation with the divertor plasma conditions are also demonstrated. The effect of molecular D 2- ion D + elastic collisions and neutral-neutral collisions on the divertor plasma solution are assessed.« less

A sensitive EUV Schwarzschild microscope for plasma studies with sub-micrometer resolution

DOE PAGES

Zastrau, U.; Rodel, C.; Nakatsutsumi, M.; ...

2018-02-05

We present an extreme ultraviolet (EUV) microscope using a Schwarzschild objective which is optimized for single-shot sub-micrometer imaging of laser-plasma targets. The microscope has been designed and constructed for imaging the scattering from an EUV-heated solid-density hydrogen jet. Here, imaging of a cryogenic hydrogen target was demonstrated using single pulses of the free-electron laser in Hamburg (FLASH) free-electron laser at a wavelength of 13.5 nm. In a single exposure, we observe a hydrogen jet with ice fragments with a spatial resolution in the sub-micrometer range. In situ EUV imaging is expected to enable novel experimental capabilities for warm dense mattermore » studies of micrometer-sized samples in laser-plasma experiments.« less

A sensitive EUV Schwarzschild microscope for plasma studies with sub-micrometer resolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zastrau, U.; Rodel, C.; Nakatsutsumi, M.

We present an extreme ultraviolet (EUV) microscope using a Schwarzschild objective which is optimized for single-shot sub-micrometer imaging of laser-plasma targets. The microscope has been designed and constructed for imaging the scattering from an EUV-heated solid-density hydrogen jet. Here, imaging of a cryogenic hydrogen target was demonstrated using single pulses of the free-electron laser in Hamburg (FLASH) free-electron laser at a wavelength of 13.5 nm. In a single exposure, we observe a hydrogen jet with ice fragments with a spatial resolution in the sub-micrometer range. In situ EUV imaging is expected to enable novel experimental capabilities for warm dense mattermore » studies of micrometer-sized samples in laser-plasma experiments.« less

Magnetic reconnection driven by Gekko XII lasers with a Helmholtz capacitor-coil target

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pei, X. X.; University of Chinese Academy of Sciences, Beijing 100049; Zhong, J. Y., E-mail: jyzhong@bnu.edu.cn, E-mail: gzhao@bao.ac.cn

2016-03-15

We demonstrate a novel plasma device for magnetic reconnection, driven by Gekko XII lasers irradiating a double-turn Helmholtz capacitor-coil target. Optical probing revealed an accumulated plasma plume near the magnetic reconnection outflow. The background electron density and magnetic field were measured to be approximately 10{sup 18 }cm{sup −3} and 60 T by using Nomarski interferometry and the Faraday effect, respectively. In contrast with experiments on magnetic reconnection constructed by the Biermann battery effect, which produced high beta values, our beta value was much lower than one, which greatly extends the parameter regime of laser-driven magnetic reconnection and reveals its potential in astrophysicalmore » plasma applications.« less

Design and engineering of a target for x-ray Thomson scattering measurements on matter at extreme densities and gigabar pressures

DOE PAGES

Boehm, K. -J.; Hash, N.; Barker, D.; ...

2016-06-24

Reconciling the experimental and system requirements during the development of a new target system is one of the most challenging tasks in the design and engineering of targets used in the National Ignition Facility. Targets for the GigaBar 3 campaign were meant to allow the detection of extremely weak Thomson scattering from matter at extreme densities in the face of very bright backlighter and laser entry hole plasma emissions. The problem was to shield the detector sufficiently while maintaining beamline and view clearances, and observing target mass restrictions. A new construction process, based on a rapid prototype frame structure, wasmore » used to develop this target. As a result, details of the design process for these targets are described, and lessons from this development for production and target assembly teams are discussed.« less

Dual Ion Species Plasma Expansion from Isotopically Layered Cryogenic Targets

NASA Astrophysics Data System (ADS)

Scott, G. G.; Carroll, D. C.; Astbury, S.; Clarke, R. J.; Hernandez-Gomez, C.; King, M.; Alejo, A.; Arteaga, I. Y.; Dance, R. J.; Higginson, A.; Hook, S.; Liao, G.; Liu, H.; Mirfayzi, S. R.; Rusby, D. R.; Selwood, M. P.; Spindloe, C.; Tolley, M. K.; Wagner, F.; Zemaityte, E.; Borghesi, M.; Kar, S.; Li, Y.; Roth, M.; McKenna, P.; Neely, D.

2018-05-01

A dual ion species plasma expansion scheme from a novel target structure is introduced, in which a nanometer-thick layer of pure deuterium exists as a buffer species at the target-vacuum interface of a hydrogen plasma. Modeling shows that by controlling the deuterium layer thickness, a composite H+/D+ ion beam can be produced by target normal sheath acceleration (TNSA), with an adjustable ratio of ion densities, as high energy proton acceleration is suppressed by the acceleration of a spectrally peaked deuteron beam. Particle in cell modeling shows that a (4.3 ±0.7 ) MeV per nucleon deuteron beam is accelerated, in a directional cone of half angle 9°. Experimentally, this was investigated using state of the art cryogenic targetry and a spectrally peaked deuteron beam of (3.4 ±0.7 ) MeV per nucleon was measured in a cone of half angle 7°-9°, while maintaining a significant TNSA proton component.

Observation of increased space-charge limited thermionic electron emission current by neutral gas ionization in a weakly-ionized deuterium plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hollmann, E. M.; Yu, J. H.; Doerner, R. P.

2015-09-14

The thermionic electron emission current emitted from a laser-produced hot spot on a tungsten target in weakly-ionized deuterium plasma is measured. It is found to be one to two orders of magnitude larger than expected for bipolar space charge limited thermionic emission current assuming an unperturbed background plasma. This difference is attributed to the plasma being modified by ionization of background neutrals by the emitted electrons. This result indicates that the allowable level of emitted thermionic electron current can be significantly enhanced in weakly-ionized plasmas due to the presence of large neutral densities.

Visualization of transient phenomena during the interaction of pulsed CO2 laser radiation with matter

NASA Astrophysics Data System (ADS)

Schmitt, R.; Hugenschmidt, Manfred

1996-05-01

Carbon-dioxide-lasers operating in the pulsed mode with energy densities up to several tens of J/cm2 and peak power densities in the multi-MW/cm2-range may cause fast heating and melting. Eventually quasi-explosive ejection, decomposition or vaporization of material can be observed. Surface plasmas are strongly influencing the energy transfer from the laser radiation field to any target. For optically transparent plastics, such as PMMA for example, only slowly expanding plasmas (LSC-waves) are ignited at fluences around 20 J/cm2, with a low level of self-luminosity. High brightness, supersonically expanding plasma jets (LSD-waves) are generated at the same fluences on glasses. Similar conditions were found for metals as well. From recordings with a high speed CCD-camera, interesting features concerning the initial plasma phases and temporal evolution were deduced. Additionally, information was obtained concerning the quasi explosive ejection of material for PMMA.

Effects of target plasma electron-electron collisions on correlated motion of fragmented protons.

PubMed

Barriga-Carrasco, Manuel D

2006-02-01

The objective of the present work is to examined the effects of plasma target electron-electron collisions on H2 + protons traversing it. Specifically, the target is deuterium in a plasma state with temperature Te=10 eV and density n=10(23) cm(-3), and proton velocities are vp=vth, vp=2vth, and vp=3vth, where vth is the electron thermal velocity of the target plasma. Proton interactions with plasma electrons are treated by means of the dielectric formalism. The interactions among close protons through plasma electronic medium are called vicinage forces. It is checked that these forces always screen the Coulomb explosions of the two fragmented protons from the same H2 + ion decreasing their relative distance. They also align the interproton vector along the motion direction, and increase the energy loss of the two protons at early dwell times while for longer times the energy loss tends to the value of two isolated protons. Nevertheless, vicinage forces and effects are modified by the target electron collisions. These collisions enhance the calculated self-stopping and vicinage forces over the collisionless results. Regarding proton correlated motion, when these collisions are included, the interproton vector along the motion direction overaligns at slower proton velocities (vp=vth) and misaligns for faster ones (vp=2vth, vp=3vth). They also contribute to a great extend to increase the energy loss of the fragmented H2 + ion. This later effect is more significant in reducing projectile velocity.

Minimizing scatter-losses during pre-heat for magneto-inertial fusion targets

NASA Astrophysics Data System (ADS)

Geissel, Matthias; Harvey-Thompson, Adam J.; Awe, Thomas J.; Bliss, David E.; Glinsky, Michael E.; Gomez, Matthew R.; Harding, Eric; Hansen, Stephanie B.; Jennings, Christopher; Kimmel, Mark W.; Knapp, Patrick; Lewis, Sean M.; Peterson, Kyle; Schollmeier, Marius; Schwarz, Jens; Shores, Jonathon E.; Slutz, Stephen A.; Sinars, Daniel B.; Smith, Ian C.; Speas, C. Shane; Vesey, Roger A.; Weis, Matthew R.; Porter, John L.

2018-02-01

The size, temporal and spatial shape, and energy content of a laser pulse for the pre-heat phase of magneto-inertial fusion affect the ability to penetrate the window of the laser-entrance-hole and to heat the fuel behind it. High laser intensities and dense targets are subject to laser-plasma-instabilities (LPI), which can lead to an effective loss of pre-heat energy or to pronounced heating of areas that should stay unexposed. While this problem has been the subject of many studies over the last decades, the investigated parameters were typically geared towards traditional laser driven Inertial Confinement Fusion (ICF) with densities either at 10% and above or at 1% and below the laser's critical density, electron temperatures of 3-5 keV, and laser powers near (or in excess of) 1 × 1015 W/cm2. In contrast, Magnetized Liner Inertial Fusion (MagLIF) [Slutz et al., Phys. Plasmas 17, 056303 (2010) and Slutz and Vesey, Phys. Rev. Lett. 108, 025003 (2012)] currently operates at 5% of the laser's critical density using much thicker windows (1.5-3.5 μm) than the sub-micron thick windows of traditional ICF hohlraum targets. This article describes the Pecos target area at Sandia National Laboratories using the Z-Beamlet Laser Facility [Rambo et al., Appl. Opt. 44(12), 2421 (2005)] as a platform to study laser induced pre-heat for magneto-inertial fusion targets, and the related progress for Sandia's MagLIF program. Forward and backward scattered light were measured and minimized at larger spatial scales with lower densities, temperatures, and powers compared to LPI studies available in literature.

Magnetized Target Fusion Collaboration. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slough, John

Nuclear fusion has the potential to satisfy the prodigious power that the world will demand in the future, but it has yet to be harnessed as a practical energy source. The entry of fusion as a viable, competitive source of power has been stymied by the challenge of finding an economical way to provide for the confinement and heating of the plasma fuel. It is the contention here that a simpler path to fusion can be achieved by creating fusion conditions in a different regime at small scale (~ a few cm). One such program now under study, referred tomore » as Magnetized Target Fusion (MTF), is directed at obtaining fusion in this high energy density regime by rapidly compressing a compact toroidal plasmoid commonly referred to as a Field Reversed Configuration (FRC). To make fusion practical at this smaller scale, an efficient method for compressing the FRC to fusion gain conditions is required. In one variant of MTF a conducting metal shell is imploded electrically. This radially compresses and heats the FRC plasmoid to fusion conditions. The closed magnetic field in the target plasmoid suppresses the thermal transport to the confining shell, thus lowering the imploding power needed to compress the target. The undertaking described in this report was to provide a suitable target FRC, as well as a simple and robust method for inserting and stopping the FRC within the imploding liner. The FRC must also survive during the time it takes for the metal liner to compress the FRC target. The initial work at the UW was focused on developing adequate preionization and flux trapping that were found to be essential in past experiments for obtaining the density, flux and most critically, FRC lifetime required for MTF. The timescale for testing and development of such a source can be rapidly accelerated by taking advantage of a new facility funded by the Department of Energy. At this facility, two inductive plasma accelerators (IPA) were constructed and tested. Recent experiments with these IPAs have demonstrated the ability to rapidly form, accelerate and merge two hypervelocity FRCs into a compression chamber. The resultant FRC that was formed was hot (T{sub ion} ~ 400 eV), stationary, and stable with a configuration lifetime several times that necessary for the MTF liner experiments. The accelerator length was less than 1 meter, and the time from the initiation of formation to the establishment of the final equilibrium was less than 10 microseconds. With some modification, each accelerator can be made capable of producing FRCs suitable for the production of the target plasma for the MTF liner experiment. Based on the initial FRC merging/compression results, the design and methodology for an experimental realization of the target plasma for the MTF liner experiment can now be defined. The construction and testing of the key components for the formation of the target plasma at the Air Force Research Laboratory (AFRL) will be performed on the IPA experiment, now at MSNW. A high density FRC plasmoid will be formed and accelerated out of each IPA into a merging/compression chamber similar to the imploding liner at AFRL. The properties of the resultant FRC plasma (size, temperature, density, flux, lifetime) will be obtained. The process will be optimized, and a final design for implementation at AFRL will be carried out. When implemented at AFRL it is anticipated that the colliding/merging FRCs will then be compressed by the liner. In this manner it is hoped that ultimately a plasma with ion temperatures reaching the 10 keV range and fusion gain near unity can be obtained.« less

Noninductive RF startup in CDX-U

NASA Astrophysics Data System (ADS)

Jones, B.; Majeski, R.; Efthimion, P.; Kaita, R.; Menard, J.; Munsat, T.; Takase, Y.

1998-11-01

For the spherical torus (ST) to prove viable as a reactor, it will be necessary to devise techniques for noninductive plasma startup. Initial studies of noninductive plasma initiation have been performed on CDX-U, using the 100 kW high harmonic fast wave (HHFW) system in combination with the 1 kW 2.45 GHz electron cyclotron heating system used for breakdown. Modest density (ne ~ 10^12 cm-3), low temperature (5 eV) plasmas were formed, but the density profile was peaked far off-axis, very near the HHFW antenna. High neutral fill pressures were also required. In upcoming experiments, up to 500 kW of low frequency RF power will utilized for heating and noninductive current drive in the mode conversion regime in a target noninductive plasma formed by a combination of 5.6 and 14 GHz ECH (40 kW total). Modeling will be presented which indicates that startup to plasma currents of 60 kA is feasible with this system.

Simulations of the interaction of intense petawatt laser pulses with dense Z-pinch plasmas : final report LDRD 39670.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Welch, Dale Robert; MacFarlane, Joseph John; Mehlhorn, Thomas Alan

We have studied the feasibility of using the 3D fully electromagnetic implicit hybrid particle code LSP (Large Scale Plasma) to study laser plasma interactions with dense, compressed plasmas like those created with Z, and which might be created with the planned ZR. We have determined that with the proper additional physics and numerical algorithms developed during the LDRD period, LSP was transformed into a unique platform for studying such interactions. Its uniqueness stems from its ability to consider realistic compressed densities and low initial target temperatures (if required), an ability that conventional PIC codes do not possess. Through several testmore » cases, validations, and applications to next generation machines described in this report, we have established the suitability of the code to look at fast ignition issues for ZR, as well as other high-density laser plasma interaction problems relevant to the HEDP program at Sandia (e.g. backlighting).« less

3D printing of gas jet nozzles for laser-plasma accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Döpp, A.; Guillaume, E.; Thaury, C.

2016-07-15

Recent results on laser wakefield acceleration in tailored plasma channels have underlined the importance of controlling the density profile of the gas target. In particular, it was reported that the appropriate density tailoring can result in improved injection, acceleration, and collimation of laser-accelerated electron beams. To achieve such profiles, innovative target designs are required. For this purpose, we have reviewed the usage of additive layer manufacturing, commonly known as 3D printing, in order to produce gas jet nozzles. Notably we have compared the performance of two industry standard techniques, namely, selective laser sintering (SLS) and stereolithography (SLA). Furthermore we havemore » used the common fused deposition modeling to reproduce basic gas jet designs and used SLA and SLS for more sophisticated nozzle designs. The nozzles are characterized interferometrically and used for electron acceleration experiments with the SALLE JAUNE terawatt laser at Laboratoire d’Optique Appliquée.« less

Simulating plasma production from hypervelocity impacts

NASA Astrophysics Data System (ADS)

Fletcher, Alex; Close, Sigrid; Mathias, Donovan

2015-09-01

Hypervelocity particles, such as meteoroids and space debris, routinely impact spacecraft and are energetic enough to vaporize and ionize themselves and as well as a portion of the target material. The resulting plasma rapidly expands into the surrounding vacuum. While plasma measurements from hypervelocity impacts have been made using ground-based technologies such as light gas guns and Van de Graaff dust accelerators, some of the basic plasma properties vary significantly between experiments. There have been both ground-based and in-situ measurements of radio frequency (RF) emission from hypervelocity impacts, but the physical mechanism responsible and the possible connection to the impact-produced plasma are not well understood. Under certain conditions, the impact-produced plasma can have deleterious effects on spacecraft electronics by providing a new current path, triggering an electrostatic discharge, causing electromagnetic interference, or generating an electromagnetic pulse. Multi-physics simulations of plasma production from hypervelocity impacts are presented. These simulations incorporate elasticity and plasticity of the solid target, phase change and plasma formation, and non-ideal plasma physics due to the high density and low temperature of the plasma. A smoothed particle hydrodynamics method is used to perform a continuum dynamics simulation with these additional physics. By examining a series of hypervelocity impacts, basic properties of the impact produced plasma plume (density, temperature, expansion speed, charge state) are determined for impactor speeds between 10 and 72 km/s. For a large range of higher impact speeds (30-72 km/s), we find the temperature is unvarying at 2.5 eV. We also find that the plasma plume is weakly ionized for impact speeds less than 14 km/s and fully ionized for impact speeds greater than 20 km/s, independent of impactor mass. This is the same velocity threshold for the detection of RF emission in recent Van de Graaff experiments, suggesting that the RF is correlated to the formation of fully ionized plasma.

Simulating plasma production from hypervelocity impacts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fletcher, Alex, E-mail: alexcf@stanford.edu; Close, Sigrid; Mathias, Donovan

2015-09-15

Hypervelocity particles, such as meteoroids and space debris, routinely impact spacecraft and are energetic enough to vaporize and ionize themselves and as well as a portion of the target material. The resulting plasma rapidly expands into the surrounding vacuum. While plasma measurements from hypervelocity impacts have been made using ground-based technologies such as light gas guns and Van de Graaff dust accelerators, some of the basic plasma properties vary significantly between experiments. There have been both ground-based and in-situ measurements of radio frequency (RF) emission from hypervelocity impacts, but the physical mechanism responsible and the possible connection to the impact-producedmore » plasma are not well understood. Under certain conditions, the impact-produced plasma can have deleterious effects on spacecraft electronics by providing a new current path, triggering an electrostatic discharge, causing electromagnetic interference, or generating an electromagnetic pulse. Multi-physics simulations of plasma production from hypervelocity impacts are presented. These simulations incorporate elasticity and plasticity of the solid target, phase change and plasma formation, and non-ideal plasma physics due to the high density and low temperature of the plasma. A smoothed particle hydrodynamics method is used to perform a continuum dynamics simulation with these additional physics. By examining a series of hypervelocity impacts, basic properties of the impact produced plasma plume (density, temperature, expansion speed, charge state) are determined for impactor speeds between 10 and 72 km/s. For a large range of higher impact speeds (30–72 km/s), we find the temperature is unvarying at 2.5 eV. We also find that the plasma plume is weakly ionized for impact speeds less than 14 km/s and fully ionized for impact speeds greater than 20 km/s, independent of impactor mass. This is the same velocity threshold for the detection of RF emission in recent Van de Graaff experiments, suggesting that the RF is correlated to the formation of fully ionized plasma.« less

Spectroscopic measurements of plasma plume induced during the laser deposition of the hydroxyapatite

NASA Astrophysics Data System (ADS)

Jedyński, M.; Szymański, Z.; Mróz, W.; Prokopiuk, A.; Jelinek, M.; Kocourek, T.

2004-03-01

Plasma plume induced by ArF exeimer laser ablation of a Ca10(PO4)6(OH)2 hydroxyapatite target during deposition process has been studied in different ambient conditions, i.e. in air or water vapour. ArF laser operated at the wavelength of 193 nm with the pulse energy of 300 mJ and 20 ns pulse duration. Spectroscopic measurements of the emission spectra of plasma plume have been made with the use of a fast gate, lens coupled micro-channel plate (MCP) image intensifier placed between a spectrograph and a 1254 silicon intensified target (SIT) detector connected to an optical multichannel analyser. The electron densities of 1022 ÷ 1023m-3 have been determined from the Stark broadening of Ca I lines as a function of the distance from the target. The expansion of the plasma plume has been studied using the time of flight method. The time-dependent radiation of the 422.673 nm Ca I and 393.366 nm Ca II lines has been, registered with the use of a monochromator and photomultiplier at various distances from the target. Velocities between 104 ÷ 103 m/s have been found. The velocity in air is several times higher than in the case with water vapour. The plasma plume dynamics is also different in both cases. In the presence of water vapour the spliting of the plasma plume appears.

Observations of temperature rise during electron cyclotron heating application in Proto-MPEX

NASA Astrophysics Data System (ADS)

Biewer, T. M.; Bigelow, T.; Caneses, J. F.; Diem, S. J.; Rapp, J.; Reinke, M.; Kafle, N.; Ray, H. B.; Showers, M.

2017-10-01

The Prototype Material Plasma Exposure eXperiment (Proto-MPEX) at ORNL utilizes a variety of power systems to generate and deliver a high heat flux plasma (1 MW/m2 for these discharges) onto the surface of material targets. In the experiments described here, up to 120 kW of 13.56 MHz ``helicon'' waves are combined with 20 kW of 28 GHz microwaves to produce Deuterium plasma discharges. The 28 GHz waves are launched in a region of the device where the magnetic field is axially varying near 0.8 T, resulting in the presence of a 2nd harmonic electron cyclotron heating (ECH) resonance layer that transects the plasma column. The electron density and temperature profiles are measured using a Thomson scattering (TS) diagnostic, and indicate that the electron density is radially peaked. In the core of the plasma column the electron density is higher than the cut-off density (0.9x1019 m-3) for ECH waves to propagate and O-X-B mode conversion into electron Bernstien waves (EBW) is expected. TS measurements indicate electron temperature increases during 28 GHz wave application, rising (from 5 eV to 20 eV) as the neutral Deuterium pressure is reduced below 1 mTorr. This work was supported by the US. D.O.E. contract DE-AC05-00OR22725.

Laser-induced plasmas in air studied using two-color interferometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Zefeng; Wu, Jian, E-mail: jxjawj@mail.xjtu.edu.cn; Li, Xingwen

2016-08-15

Temporally and spatially resolved density profiles of Cu atoms, electrons, and compressed air, from laser-induced copper plasmas in air, are measured using fast spectral imaging and two-color interferometry. From the intensified CCD images filtered by a narrow-band-pass filter centered at 515.32 nm, the Cu atoms expansion route is estimated and used to determine the position of the fracture surface between the Cu atoms and the air. Results indicate that the Cu atoms density at distances closer to the target (0–0.4 mm) is quite low, with the maximum density appearing at the edge of the plasma's core being ∼4.6 × 10{sup 24 }m{sup −3} at 304 ns.more » The free electrons are mainly located in the internal region of the plume, which is supposed to have a higher temperature. The density of the shock wave is (4–6) × 10{sup 25 }m{sup −3}, corresponding to air compression of a factor of 1.7–2.5.« less

Compton scattering measurements from dense plasmas

DOE PAGES

Glenzer, S. H.; Neumayer, P.; Doppner, T.; ...

2008-06-12

Here, Compton scattering techniques have been developed for accurate measurements of densities and temperatures in dense plasmas. One future challenge is the application of this technique to characterize compressed matter on the National Ignition Facility where hydrogen and beryllium will approach extremely dense states of matter of up to 1000 g/cc. In this regime, the density, compressibility, and capsule fuel adiabat may be directly measured from the Compton scattered spectrum of a high-energy x-ray line source. Specifically, the scattered spectra directly reflect the electron velocity distribution. In non-degenerate plasmas, the width provides an accurate measure of the electron temperatures, whilemore » in partially Fermi degenerate systems that occur in laser-compressed matter it provides the Fermi energy and hence the electron density. Both of these regimes have been accessed in experiments at the Omega laser by employing isochorically heated solid-density beryllium and moderately compressed beryllium foil targets. In the latter experiment, compressions by a factor of 3 at pressures of 40 Mbar have been measured in excellent agreement with radiation hydrodynamic modeling.« less

The COMMD Family Regulates Plasma LDL Levels and Attenuates Atherosclerosis Through Stabilizing the CCC Complex in Endosomal LDLR Trafficking.

PubMed

Fedoseienko, Alina; Wijers, Melinde; Wolters, Justina C; Dekker, Daphne; Smit, Marieke; Huijkman, Nicolette; Kloosterhuis, Niels; Klug, Helene; Schepers, Aloys; Willems van Dijk, Ko; Levels, Johannes H M; Billadeau, Daniel D; Hofker, Marten H; van Deursen, Jan; Westerterp, Marit; Burstein, Ezra; Kuivenhoven, Jan Albert; van de Sluis, Bart

2018-06-08

COMMD (copper metabolism MURR1 domain)-containing proteins are a part of the CCC (COMMD-CCDC22 [coiled-coil domain containing 22]-CCDC93 [coiled-coil domain containing 93]) complex facilitating endosomal trafficking of cell surface receptors. Hepatic COMMD1 inactivation decreases CCDC22 and CCDC93 protein levels, impairs the recycling of the LDLR (low-density lipoprotein receptor), and increases plasma low-density lipoprotein cholesterol levels in mice. However, whether any of the other COMMD members function similarly as COMMD1 and whether perturbation in the CCC complex promotes atherogenesis remain unclear. The main aim of this study is to unravel the contribution of evolutionarily conserved COMMD proteins to plasma lipoprotein levels and atherogenesis. Using liver-specific Commd1 , Commd6 , or Commd9 knockout mice, we investigated the relation between the COMMD proteins in the regulation of plasma cholesterol levels. Combining biochemical and quantitative targeted proteomic approaches, we found that hepatic COMMD1, COMMD6, or COMMD9 deficiency resulted in massive reduction in the protein levels of all 10 COMMDs. This decrease in COMMD protein levels coincided with destabilizing of the core (CCDC22, CCDC93, and chromosome 16 open reading frame 62 [C16orf62]) of the CCC complex, reduced cell surface levels of LDLR and LRP1 (LDLR-related protein 1), followed by increased plasma low-density lipoprotein cholesterol levels. To assess the direct contribution of the CCC core in the regulation of plasma cholesterol levels, Ccdc22 was deleted in mouse livers via CRISPR/Cas9-mediated somatic gene editing. CCDC22 deficiency also destabilized the complete CCC complex and resulted in elevated plasma low-density lipoprotein cholesterol levels. Finally, we found that hepatic disruption of the CCC complex exacerbates dyslipidemia and atherosclerosis in ApoE3*Leiden mice. Collectively, these findings demonstrate a strong interrelationship between COMMD proteins and the core of the CCC complex in endosomal LDLR trafficking. Hepatic disruption of either of these CCC components causes hypercholesterolemia and exacerbates atherosclerosis. Our results indicate that not only COMMD1 but all other COMMDs and CCC components may be potential targets for modulating plasma lipid levels in humans. © 2018 American Heart Association, Inc.

Efficient injection of radiation-pressure-accelerated sub-relativistic protons into laser wakefield acceleration based on 10 PW lasers

NASA Astrophysics Data System (ADS)

Liu, M.; Weng, S. M.; Wang, H. C.; Chen, M.; Zhao, Q.; Sheng, Z. M.; He, M. Q.; Li, Y. T.; Zhang, J.

2018-06-01

We propose a hybrid laser-driven ion acceleration scheme using a combination target of a solid foil and a density-tailored background plasma. In the first stage, a sub-relativistic proton beam can be generated by radiation pressure acceleration in intense laser interaction with the solid foil. In the second stage, this sub-relativistic proton beam is further accelerated by the laser wakefield driven by the same laser pulse in a near-critical-density background plasma with decreasing density profile. The propagating velocity of the laser front and the phase velocity of the excited wakefield wave are effectively lowered at the beginning of the second stage. By decreasing the background plasma density gradually from near critical density along the laser propagation direction, the wake travels faster and faster, while it accelerates the protons. Consequently, the dephasing between the protons and the wake is postponed and an efficient wakefield proton acceleration is achieved. This hybrid laser-driven proton acceleration scheme can be realized by using ultrashort laser pulses at the peak power of 10 PW for the generation of multi-GeV proton beams.

Laser-Plasma Interactions in Drive Campaign targets on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Hinkel, D. E.; Callahan, D. A.; Moody, J. D.; Amendt, P. A.; Lasinski, B. F.; MacGowan, B. J.; Meeker, D.; Michel, P. A.; Ralph, J.; Rosen, M. D.; Ross, J. S.; Schneider, M. B.; Storm, E.; Strozzi, D. J.; Williams, E. A.

2016-03-01

The Drive campaign [D A Callahan et al., this conference] on the National Ignition Facility (NIF) laser [E. I. Moses, R. N. Boyd, B. A. Remington, C. J. Keane, R. Al-Ayat, Phys. Plasmas 16, 041006 (2009)] has the focused goal of understanding and optimizing the hohlraum for ignition. Both the temperature and symmetry of the radiation drive depend on laser and hohlraum characteristics. The drive temperature depends on the coupling of laser energy to the hohlraum, and the symmetry of the drive depends on beam-to-beam interactions that result in energy transfer [P. A. Michel, S. H. Glenzer, L. Divol, et al, Phys. Plasmas 17, 056305 (2010).] within the hohlraum. To this end, hohlraums are being fielded where shape (rugby vs. cylindrical hohlraums), gas fill composition (neopentane at room temperature vs. cryogenic helium), and gas fill density (increase of ∼ 150%) are independently changed. Cylindrical hohlraums with higher gas fill density show improved inner beam propagation, as should rugby hohlraums, because of the larger radius over the capsule (7 mm vs. 5.75 mm in a cylindrical hohlraum). Energy coupling improves in room temperature neopentane targets, as well as in hohlraums at higher gas fill density. In addition cross-beam energy transfer is being addressed directly by using targets that mock up one end of a hohlraum, but allow observation of the laser beam uniformity after energy transfer. Ideas such as splitting quads into “doublets” by re-pointing the right and left half of quads are also being pursued. LPI results of the Drive campaign will be summarized, and analyses of future directions presented.

Transport modeling of convection dominated helicon discharges in Proto-MPEX with the B2.5-Eirene code

NASA Astrophysics Data System (ADS)

Owen, L. W.; Rapp, J.; Canik, J.; Lore, J. D.

2017-11-01

Data-constrained interpretative analyses of plasma transport in convection dominated helicon discharges in the Proto-MPEX linear device, and predictive calculations with additional Electron Cyclotron Heating/Electron Bernstein Wave (ECH/EBW) heating, are reported. The B2.5-Eirene code, in which the multi-fluid plasma code B2.5 is coupled to the kinetic Monte Carlo neutrals code Eirene, is used to fit double Langmuir probe measurements and fast camera data in front of a stainless-steel target. The absorbed helicon and ECH power (11 kW) and spatially constant anomalous transport coefficients that are deduced from fitting of the probe and optical data are additionally used for predictive simulations of complete axial distributions of the densities, temperatures, plasma flow velocities, particle and energy fluxes, and possible effects of alternate fueling and pumping scenarios. The somewhat hollow electron density and temperature radial profiles from the probe data suggest that Trivelpiece-Gould wave absorption is the dominant helicon electron heating source in the discharges analyzed here. There is no external ion heating, but the corresponding calculated ion temperature radial profile is not hollow. Rather it reflects ion heating by the electron-ion equilibration terms in the energy balance equations and ion radial transport resulting from the hollow density profile. With the absorbed power and the transport model deduced from fitting the sheath limited discharge data, calculated conduction limited higher recycling conditions were produced by reducing the pumping and increasing the gas fueling rate, resulting in an approximate doubling of the target ion flux and reduction of the target heat flux.

Hydrodynamic modeling of laser interaction with micro-structured targets

DOE PAGES

Velechovsky, Jan; Limpouch, Jiri; Liska, Richard; ...

2016-08-03

A model is developed for numerical simulations of laser absorption in plasmas made of porous materials, with particular interest in low-density foams. Laser absorption is treated on two spatial scales simultaneously. At the microscale, the expansion of a thin solid pore wall is modeled in one dimension and the information obtained is used in the macroscale fluid simulations for the description of the plasma homogenization behind the ionization front. This two-scale laser absorption model is implemented in the arbitrary Lagrangian–Eulerian hydrocode PALE. In conclusion, the numerical simulations of laser penetration into low-density foams compare favorably with published experimental data.

Ultrafast Kα x-ray Thomson scattering from shock compressed lithium hydride

DOE PAGES

Kritcher, A. L.; Neumayer, P.; Castor, J.; ...

2009-04-13

Spectrally and temporally resolved x-ray Thomson scattering using ultrafast Ti Kα x rays has provided experimental validation for modeling of the compression and heating of shocked matter. The coalescence of two shocks launched into a solid density LiH target by a shaped 6 ns heater beam was observed from rapid heating to temperatures of 2.2 eV, enabling tests of shock timing models. Here, the temperature evolution of the target at various times during shock progression was characterized from the intensity of the elastic scattering component. The observation of scattering from plasmons, electron plasma oscillations, at shock coalescence indicates a transitionmore » to a dense metallic plasma state in LiH. From the frequency shift of the measured plasmon feature the electron density was directly determined with high accuracy, providing a material compression of a factor of 3 times solid density. The quality of data achieved in these experiments demonstrates the capability for single shot dynamic characterization of dense shock compressed matter. Here, the conditions probed in this experiment are relevant for the study of the physics of planetary formation and to characterize inertial confinement fusion targets for experiments such as on the National Ignition Facility, Lawrence Livermore National Laboratory.« less

Laser-driven strong magnetostatic fields with applications to charged beam transport and magnetized high energy-density physics

NASA Astrophysics Data System (ADS)

Santos, Joao

2017-10-01

Powerful laser-plasma processes are explored to generate discharge currents of a few 100 kA in coil targets, yielding magnetostatic fields (B-fields) in the kTesla range. The B-fields are measured by proton-deflectometry and high-frequency bandwidth B-dot probes. According to our modeling, the quasi-static currents are provided from hot electron ejection from the laser-irradiated surface, accounting for the space charge neutralization and the plasma magnetization. The major control parameter is the laser irradiance Iλ2 . The B-fields ns-scale is long enough to magnetize secondary targets through resistive diffusion. We applied it in experiments of laser-generated relativistic electron transport into solid dielectric targets, yielding an unprecedented enhancement of a factor 5 on the energy-density flux at 60 µm depth, compared to unmagnetized transport conditions. These studies pave the ground for magnetized high-energy density physics investigations, related to laser-generated secondary sources of radiation and/or high-energy particles and their transport, to high-gain fusion energy schemes and to laboratory astrophysics. We acknowledge funding from French National Agency for Research (ANR), Grant TERRE ANR-2011-BS04-014, and from EUROfusion Consortium, European Union's Horizon 2020 research and innovation programme, Grant 633053.

High Intensity e-beam Diode Development for Flash X-ray Radiography

NASA Astrophysics Data System (ADS)

Oliver, Bryan

2007-11-01

A variety of electron beam diodes are being used and developed for the purpose of creating high-brightness, flash x-ray radiography sources. In these diodes, high energy (multi MeV), high current (multi kA), small spot (multi mm) electron beams are generated and stopped in high atomic number anode-targets (typically Ta or W). Beam stopping in the target creates copious amounts of bremsstrahlung radiation. In addition, beam heating of the target liberates material, either in the form of low density (˜10^12-10^14 cm-3) ion emission or higher density (> 10^15 cm-3) plasma. In all cases, beam/target collective effects dominate the diode and beam characteristics, affecting the radiation properties (dose and spot-size). Recent experiments at Sandia National Laboratories have demonstrated diodes capable of producing > 350 rad@m with 1.7mm FWHM x-ray source distributions. A review of our present theoretical understanding of the diode (s) operation and our experimental and simulation methods to investigate them will be presented. Emphasis will be given to e- beam sources used on state-of-the-art Inductive Voltage Adder (IVA) pulsed-power accelerators. In particular, the physics of magnetically pinched diodes (e.g. the rod-pinch [1,2]), gas-cell focusing diodes [3] and the magnetically immersed [4] diode will be discussed. Various proposed methods to optimize the x-ray intensity and the direction of future diode research will be discussed. [1] G. Cooperstein, et al., Phys. Plasmas 8, 4618 (2001).[2] B.V. Oliver et al., Phys. Plasmas 11, 3976 (2004)[3] B.V. Oliver, et al., IEEE Trans. on Plasma Science 33, 704 (2005).[4] M.G. Mazarakis, et al., Appl. Phys. Lett. 70, 832 (1997)

Optical diagnostics of laser-produced aluminium plasmas under water

NASA Astrophysics Data System (ADS)

Walsh, N.; Costello, J. T.; Kelly, T. J.

2017-06-01

We report on the findings of double-pulse studies performed on an aluminium target submerged in water using Nd:YAG laser pulses. Shadowgraphy measurements were performed to examine the dynamic behaviour of the cavitation bubble that eventually forms some considerable time post-plasma ignition. These measurements were used to inform subsequent investigations designed to probe the bubble environment. The results of time-resolved imaging from within the cavitation bubble following irradiation by a second laser pulse reveal the full dynamic evolution of a plasma formed in such an environment. Rapid displacement of the plasma plume in a direction normal to the target surface followed by a diffusive outwards expansion is observed and a qualitative model is proposed to explain the observed behaviour. Line profiles of several ionic and atomic species were observed within the irradiated cavitation bubble. Electron densities were determined using the Stark broadening of the Al II line at 466.3 nm and electron temperatures inferred using the ratio of the Al II (466.3 nm) and Al I (396.15 nm) lines. Evidence of self-reversal of neutral emission lines was observed at times corresponding to growth and collapse phases of the cavitation bubble suggesting high population density for ground state atoms during these times.

High-resolution measurements of the spatial and temporal evolution of megagauss magnetic fields created in intense short-pulse laser-plasma interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chatterjee, Gourab, E-mail: gourab@tifr.res.in; Singh, Prashant Kumar; Adak, Amitava

A pump-probe polarimetric technique is demonstrated, which provides a complete, temporally and spatially resolved mapping of the megagauss magnetic fields generated in intense short-pulse laser-plasma interactions. A normally incident time-delayed probe pulse reflected from its critical surface undergoes a change in its ellipticity according to the magneto-optic Cotton-Mouton effect due to the azimuthal nature of the ambient self-generated megagauss magnetic fields. The temporal resolution of the magnetic field mapping is typically of the order of the pulsewidth, limited by the laser intensity contrast, whereas a spatial resolution of a few μm is achieved by this optical technique. High-harmonics of themore » probe can be employed to penetrate deeper into the plasma to even near-solid densities. The spatial and temporal evolution of the megagauss magnetic fields at the target front as well as at the target rear are presented. The μm-scale resolution of the magnetic field mapping provides valuable information on the filamentary instabilities at the target front, whereas probing the target rear mirrors the highly complex fast electron transport in intense laser-plasma interactions.« less

Particle energization in magnetic reconnection in high-energy-density plasmas

NASA Astrophysics Data System (ADS)

Deng, W.; Fox, W.; Bhattacharjee, A.

2014-10-01

Significant particle energization is inferred to occur in many astrophysical environments and magnetic reconnection has been proposed to be the driver in many cases. Recent observation of magnetic reconnection in high-energy-density (HED) plasmas on the Vulcan, Omega and Shenguang laser facilities has opened up a new regime of reconnection study of great interest to laboratory and plasma astrophysics. In these experiments, plasma bubbles, excited by laser shots on solid targets and carrying magnetic fields, expand into one another, squeezing the opposite magnetic fields together to drive reconnection. 2D particle-in-cell (PIC) simulations have been performed to study the particle energization in such experiments. Two energization mechanisms have been identified. The first is a Fermi acceleration process between the expanding plasma bubbles, wherein the electromagnetic fields of the expanding plasma bounce particles, acting as moving walls. Particles can gain significant energy through multiple bounces between the bubbles. The second mechanism is a subsequent direct acceleration by electric field at the reconnection X-line when the bubbles collide into each other and drive reconnection.

Influence of the first wall material on the particle fuelling in ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Lunt, T.; Reimold, F.; Wolfrum, E.; Carralero, D.; Feng, Y.; Schmid, K.; the ASDEX Upgrade Team

2017-05-01

In the period from 2002 to 2007 the material of the plasma facing components (PFCs) of ASDEX Upgrade (AUG) was changed from carbon (C) to tungsten (W). Comparing the measured density profiles of low-density L-mode discharges with little or no gas puff before and after this modification, a significantly higher pedestal-top density was found for W PFCs together with a steeper gradient and a lower pedestal temperature. This change can be explained by larger particle- and energy reflection coefficients for D on W compared to D on C, as shown by EMC3-EIRENE simulations of AUG discharges in similar conditions on a computational grid extending to the main chamber first wall. In the simulations, a change of the wall material at fixed separatrix density indeed shows that for W PFCs more neutrals cross the separatrix, resulting in a steeper density gradient. Analysis of the source resolved and poloidally resolved neutral flux densities across the separatrix show a dominant contribution of the divertor targets to the fuelling profile in the simulation of the low density case. Increasing the density decreases the electron temperature at the target and therefore the potential drop in the electrostatic sheath as well as the energy of the ions impinging on the surface. Neutrals with ∼eV energies, able to reach the separatrix, are then only produced via molecular dissociation processes in the plasma volume independently of the PFC material. Also the contribution of the main chamber PFCs to the fuelling is observed to increase at higher densities.

Hydrodynamic study of plasma amplifiers for soft-x-ray lasers: a transition in hydrodynamic behavior for plasma columns with widths ranging from 20 μm to 2 mm.

PubMed

Oliva, Eduardo; Zeitoun, Philippe; Velarde, Pedro; Fajardo, Marta; Cassou, Kevin; Ros, David; Sebban, Stephan; Portillo, David; le Pape, Sebastien

2010-11-01

Plasma-based seeded soft-x-ray lasers have the potential to generate high energy and highly coherent short pulse beams. Due to their high density, plasmas created by the interaction of an intense laser with a solid target should store the highest amount of energy density among all plasma amplifiers. Our previous numerical work with a two-dimensional (2D) adaptive mesh refinement hydrodynamic code demonstrated that careful tailoring of plasma shapes leads to a dramatic enhancement of both soft-x-ray laser output energy and pumping efficiency. Benchmarking of our 2D hydrodynamic code in previous experiments demonstrated a high level of confidence, allowing us to perform a full study with the aim of the way for 10-100 μJ seeded soft-x-ray lasers. In this paper, we describe in detail the mechanisms that drive the hydrodynamics of plasma columns. We observed transitions between narrow plasmas, where very strong bidimensional flow prevents them from storing energy, to large plasmas that store a high amount of energy. Millimeter-sized plasmas are outstanding amplifiers, but they have the limitation of transverse lasing. In this paper, we provide a preliminary solution to this problem.

Fields in laser-ablated plasmas generalized to degenerate electrons and to Fermi energy in nuclei with change to quark-gluon plasma

NASA Astrophysics Data System (ADS)

Hora, Heinrich; Miley, George H.; Osman, Frederick; Hammerling, Peter X.

2004-09-01

The studies of laser ablation have lead to a new theory of nuclei, endothermic nuclei generation and quark-gluon plasmas. The surface of ablated plasma expanding into vacuum after high power laser irradiation of targets, contains an electric double layer having the thickness of the Debye length. This led to the discovery of surface tension of plasmas and to the internal dynamic electric fields in all inhomogeneous plasmas. The surface causes stabilization by short length surface waves smoothing the expanding plasma plume. Generalizing this to the degenerate electrons in a metal with the Fermi energy instead of the temperature, resulted in the surface tension of metals in agreement with measurements. Taking then the Fermi energy in the Debye length for nucleons results in a theory of nuclei with stable confinement of protons and neutrons just at the well known nuclear density, and in the Debye length equal to Hofstadter's decay of the nuclear surface. Increasing the nuclear density by a factor of 6 leads to the change of the Fermi energy into its relativistic branch where no surface energy is possible and the particle mass is not defined, permitting the quark-gluon plasma. Expansion of this higher density at the big band or in a supernova results in nucleation and element generation. The Boltzmann equilibrium permits the synthesis of nuclei even in the endothermic range limited to about uranium.

Consensus clinical recommendations for the management of plasma lipid disorders in the Middle East.

PubMed

Al Sayed, Nasreen; Al Waili, Khalid; Alawadi, Fatheya; Al-Ghamdi, Saeed; Al Mahmeed, Wael; Al-Nouri, Fahad; Al Rukhaimi, Mona; Al-Rasadi, Khalid; Awan, Zuhier; Farghaly, Mohamed; Hassanein, Mohamed; Sabbour, Hani; Zubaid, Mohammad; Barter, Philip

2016-12-15

Plasma lipid disorders are key risk factors for the development of atherosclerotic cardiovascular disease (ASCVD) and are prevalent in the Middle East, with rates increasing in recent decades. Despite this, no region-specific guidelines for managing plasma lipids exist and there is a lack of use of guidelines developed in other regions. A multidisciplinary panel of regional experts was convened to develop consensus clinical recommendations for the management of plasma lipids in the Middle East. The panel considered existing international guidelines and regional clinical experience to develop recommendations. The panel's recommendations include plasma lipid screening, ASCVD risk calculation and treatment considerations. The panel recommend that plasma lipid levels should be measured in all at-risk patients and at regular intervals in all adults from the age of 20years. A scoring system should be used to calculate ASCVD risk that includes known lipid and non-lipid risk factors. Primary treatment targets include low-density lipoprotein cholesterol and non-high-density lipoprotein cholesterol. Lifestyle modifications should be first-line treatment for all patients; the first-line pharmacological treatment targeting plasma lipids in patients at moderate-to-high risk of ASCVD is statin therapy, with a number of adjunctive or second-line agents available. Guidance is also provided on the management of underlying conditions and special populations; of particular pertinence in the region are familial hypercholesterolaemia, diabetes and metabolic dyslipidaemia. These consensus clinical recommendations provide practicing clinicians with comprehensive, region-specific guidance to improve the detection and management of plasma lipid disorders in patients in the Middle East. Copyright © 2016 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

Proton probing of a relativistic laser interaction with near-critical plasma

NASA Astrophysics Data System (ADS)

Willingale, Louise; Zulick, C.; Thomas, A. G. R.; Maksimchuk, A.; Krushelnick, K.; Nilson, P. M.; Stoeckl, C.; Sangster, T. C.; Nazarov, W.

2014-10-01

The Omega EP laser (1000 J in 10 ps pulses) was used to investigate a relativistic intensity laser interaction with near-critical density plasma using a transverse proton beam to diagnose the large electromagnetic fields generated. A very low density foam target mounted in a washer provided the near-critical density conditions. The fields from a scaled, two-dimensional particle-in-cell simulation were inputed into a particle-tracking code to create simulated proton probe images. This allows us to understand the origins of the complex features in the experimental images, including a rapidly expanding sheath field, evidence for ponderomotive channeling and fields at the foam-washer interface. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0002028.

High contrast ion acceleration at intensities exceeding 10{sup 21} Wcm{sup −2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dollar, F.; Zulick, C.; Matsuoka, T.

2013-05-15

Ion acceleration from short pulse laser interactions at intensities of 2×10{sup 21}Wcm{sup −2} was studied experimentally under a wide variety of parameters, including laser contrast, incidence angle, and target thickness. Trends in maximum proton energy were observed, as well as evidence of improvement in the acceleration gradients by using dual plasma mirrors over traditional pulse cleaning techniques. Extremely high efficiency acceleration gradients were produced, accelerating both the contaminant layer and high charge state ions from the bulk of the target. Two dimensional particle-in-cell simulations enabled the study of the influence of scale length on submicron targets, where hydrodynamic expansion affectsmore » the rear surface as well as the front. Experimental evidence of larger electric fields for sharp density plasmas is observed in simulation results as well for such targets, where target ions are accelerated without the need for contaminant removal.« less

Staged Z-pinch experiments on the Mega-Ampere current driver COBRA

NASA Astrophysics Data System (ADS)

Valenzuela, Julio; Banasek, Jacob; Byvank, Thomas; Conti, Fabio; Greenly, John; Hammer, David; Potter, William; Rocco, Sophia; Ross, Michael; Wessel, Frank; Narkis, Jeff; Rahman, Hafiz; Ruskov, Emil; Beg, Farhat

2017-10-01

Experiments were conducted on the Cornell's 1 MA, 100 ns current driver COBRA with the goal of better understanding the Staged Z-pinch physics and validating MHD codes. We used a gas injector composed of an annular (1.2 cm radius) high atomic number (e.g., Ar or Kr) gas-puff and an on-axis plasma gun that delivers the ionized hydrogen target. Liner implosion velocity and stability were studied using laser shadowgraphy and interferometry as well as XUV imaging. From the data, the signature of the MRT instability and zippering effect can be seen, but time integrated X-ray imaging show a stable target plasma. A key component of the experiment was the use of optical Thomson scattering (TS) diagnostics to characterize the liner and target plasmas. By fitting the experimental scattered spectra with synthetic data, electron and ion temperature as well as density can be obtained. Preliminary analysis shows significant scattered line broadening from the plasma on-axis ( 0.5 mm diameter) which can be explained by either a low temperature H plasma with Te =Ti =75eV, or by a hot plasma with Ti =3keV, Te =350eV if an Ar-H mixture is present with an Ar fraction higher than 10%. Funded by the Advanced Research Projects Agency - Energy, DE-AR0000569.

Improvement of Characteristics of Laser Source of Ions Using Two-Element Targets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khaydarov, R. T.

2006-12-04

Two-element plasma ions generated from porous (Ho2O3) and solid (PbMg) targets were studied depending on the target density {rho} and on the fraction of light (Mg) component of the target, using a mass-spectrometer. Oxygen ions with maximal charge is observed for small values of {rho}, while the heavy component of the target Ho has maximal charge for larger values of {rho}. The influence of {rho} to the energy spectra and intensity of plasma ions is also investigated. In the case of solid (PbMg) target the increase of the fraction of Mg leads to the widening of the energy spectra ofmore » Pb ions by more than a factor of two, while the intensity of Pb ions of all charge states does not depend on the Mg fraction. These effects are explained by the friction existing between light and heavy ions during their expansion away from the target.« less

Laser experiments to simulate coronal mass ejection driven magnetospheres and astrophysical plasma winds on compact magnetized stars

NASA Astrophysics Data System (ADS)

Horton, W.; Ditmire, T.; Zakharov, Yu. P.

2010-06-01

Laboratory experiments using a plasma wind generated by laser-target interaction are proposed to investigate the creation of a shock in front of the magnetosphere and the dynamo mechanism for creating plasma currents and voltages. Preliminary experiments are shown where measurements of the electron density gradients surrounding the obstacles are recorded to infer the plasma winds. The proposed experiments are relevant to understanding the electron acceleration mechanisms taking place in shock-driven magnetic dipole confined plasmas surrounding compact magnetized stars and planets. Exploratory experiments have been published [P. Brady, T. Ditmire, W. Horton, et al., Phys. Plasmas 16, 043112 (2009)] with the one Joule Yoga laser and centimeter sized permanent magnets.

Inhibition of miR-33a/b in non-human primates raises plasma HDL and lowers VLDL triglycerides.

PubMed

Rayner, Katey J; Esau, Christine C; Hussain, Farah N; McDaniel, Allison L; Marshall, Stephanie M; van Gils, Janine M; Ray, Tathagat D; Sheedy, Frederick J; Goedeke, Leigh; Liu, Xueqing; Khatsenko, Oleg G; Kaimal, Vivek; Lees, Cynthia J; Fernandez-Hernando, Carlos; Fisher, Edward A; Temel, Ryan E; Moore, Kathryn J

2011-10-19

Cardiovascular disease remains the leading cause of mortality in westernized countries, despite optimum medical therapy to reduce the levels of low-density lipoprotein (LDL)-associated cholesterol. The pursuit of novel therapies to target the residual risk has focused on raising the levels of high-density lipoprotein (HDL)-associated cholesterol in order to exploit its atheroprotective effects. MicroRNAs (miRNAs) have emerged as important post-transcriptional regulators of lipid metabolism and are thus a new class of target for therapeutic intervention. MicroRNA-33a and microRNA-33b (miR-33a/b) are intronic miRNAs whose encoding regions are embedded in the sterol-response-element-binding protein genes SREBF2 and SREBF1 (refs 3-5), respectively. These miRNAs repress expression of the cholesterol transporter ABCA1, which is a key regulator of HDL biogenesis. Recent studies in mice suggest that antagonizing miR-33a may be an effective strategy for raising plasma HDL levels and providing protection against atherosclerosis; however, extrapolating these findings to humans is complicated by the fact that mice lack miR-33b, which is present only in the SREBF1 gene of medium and large mammals. Here we show in African green monkeys that systemic delivery of an anti-miRNA oligonucleotide that targets both miR-33a and miR-33b increased hepatic expression of ABCA1 and induced a sustained increase in plasma HDL levels over 12 weeks. Notably, miR-33 antagonism in this non-human primate model also increased the expression of miR-33 target genes involved in fatty acid oxidation (CROT, CPT1A, HADHB and PRKAA1) and reduced the expression of genes involved in fatty acid synthesis (SREBF1, FASN, ACLY and ACACA), resulting in a marked suppression of the plasma levels of very-low-density lipoprotein (VLDL)-associated triglycerides, a finding that has not previously been observed in mice. These data establish, in a model that is highly relevant to humans, that pharmacological inhibition of miR-33a and miR-33b is a promising therapeutic strategy to raise plasma HDL and lower VLDL triglyceride levels for the treatment of dyslipidaemias that increase cardiovascular disease risk.

Accelerator based fusion reactor

NASA Astrophysics Data System (ADS)

Liu, Keh-Fei; Chao, Alexander Wu

2017-08-01

A feasibility study of fusion reactors based on accelerators is carried out. We consider a novel scheme where a beam from the accelerator hits the target plasma on the resonance of the fusion reaction and establish characteristic criteria for a workable reactor. We consider the reactions d+t\\to n+α,d+{{}3}{{H}\\text{e}}\\to p+α , and p+{{}11}B\\to 3α in this study. The critical temperature of the plasma is determined from overcoming the stopping power of the beam with the fusion energy gain. The needed plasma lifetime is determined from the width of the resonance, the beam velocity and the plasma density. We estimate the critical beam flux by balancing the energy of fusion production against the plasma thermo-energy and the loss due to stopping power for the case of an inert plasma. The product of critical flux and plasma lifetime is independent of plasma density and has a weak dependence on temperature. Even though the critical temperatures for these reactions are lower than those for the thermonuclear reactors, the critical flux is in the range of {{10}22}-{{10}24}~\\text{c}{{\\text{m}}-2}~{{\\text{s}}-1} for the plasma density {ρt}={{10}15}~\\text{c}{{\\text{m}}-3} in the case of an inert plasma. Several approaches to control the growth of the two-stream instability are discussed. We have also considered several scenarios for practical implementation which will require further studies. Finally, we consider the case where the injected beam at the resonance energy maintains the plasma temperature and prolongs its lifetime to reach a steady state. The equations for power balance and particle number conservation are given for this case.

Direct Laser Writing of Low-Density Interdigitated Foams for Plasma Drive Shaping [Direct Laser Writing of Low Density Nanostitched Foams for Plasma Drive Shaping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oakdale, James S.; Smith, Raymond F.; Forien, Jean -Baptiste

Monolithic porous bulk materials have many promising applications ranging from energy storage and catalysis to high energy density physics. High resolution additive manufacturing techniques, such as direct laser writing via two photon polymerization (DLW-TPP), now enable the fabrication of highly porous microlattices with deterministic morphology control. In this work, DLW-TPP is used to print millimeter-sized foam reservoirs (down to 0.06 g cm –3) with tailored density-gradient profiles, where density is varied by over an order of magnitude (for instance from 0.6 to 0.06 g cm –3) along a length of <100 µm. Taking full advantage of this technology, however, ismore » a multiscale materials design problem that requires detailed understanding of how the different length scales, from the molecular level to the macroscopic dimensions, affect each other. The design of these 3D-printed foams is based on the brickwork arrangement of 100 × 100 × 16 µm 3 log-pile blocks constructed from sub-micrometer scale features. A block-to-block interdigitated stitching strategy is introduced for obtaining high density uniformity at all length scales. Lastly, these materials are used to shape plasma-piston drives during ramp-compression of targets under high energy density conditions created at the OMEGA Laser Facility.« less

Direct Laser Writing of Low-Density Interdigitated Foams for Plasma Drive Shaping [Direct Laser Writing of Low Density Nanostitched Foams for Plasma Drive Shaping

DOE PAGES

Oakdale, James S.; Smith, Raymond F.; Forien, Jean -Baptiste; ...

2017-09-27

Monolithic porous bulk materials have many promising applications ranging from energy storage and catalysis to high energy density physics. High resolution additive manufacturing techniques, such as direct laser writing via two photon polymerization (DLW-TPP), now enable the fabrication of highly porous microlattices with deterministic morphology control. In this work, DLW-TPP is used to print millimeter-sized foam reservoirs (down to 0.06 g cm –3) with tailored density-gradient profiles, where density is varied by over an order of magnitude (for instance from 0.6 to 0.06 g cm –3) along a length of <100 µm. Taking full advantage of this technology, however, ismore » a multiscale materials design problem that requires detailed understanding of how the different length scales, from the molecular level to the macroscopic dimensions, affect each other. The design of these 3D-printed foams is based on the brickwork arrangement of 100 × 100 × 16 µm 3 log-pile blocks constructed from sub-micrometer scale features. A block-to-block interdigitated stitching strategy is introduced for obtaining high density uniformity at all length scales. Lastly, these materials are used to shape plasma-piston drives during ramp-compression of targets under high energy density conditions created at the OMEGA Laser Facility.« less

Infrared nanosecond laser-metal ablation in atmosphere: Initial plasma during laser pulse and further expansion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Jian; Wei, Wenfu; Li, Xingwen

2013-04-22

We have investigated the dynamics of the nanosecond laser ablated plasma within and after the laser pulse irradiation using fast photography. A 1064 nm, 15 ns laser beam was focused onto a target made from various materials with an energy density in the order of J/mm{sup 2} in atmosphere. The plasma dynamics during the nanosecond laser pulse were observed, which could be divided into three stages: fast expansion, division into the primary plasma and the front plasma, and stagnation. After the laser terminated, a critical moment when the primary plasma expansion transited from the shock model to the drag modelmore » was resolved, and this phenomenon could be understood in terms of interactions between the primary and the front plasmas.« less

Three-dimensional magnetohydrodynamical simulation of expanding magnetic flux ropes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arnold, L.; Dreher, J.; Grauer, R.

Three-dimensional, time-dependent numerical simulations of the dynamics of magnetic flux ropes are presented. The simulations are targeted towards an experiment previously conducted at California Institute of Technology [P. M. Bellan and J. F. Hansen, Phys. Plasmas 5, 1991 (1998)] which aimed at simulating solar prominence eruptions in the laboratory. The plasma dynamics is described by ideal magnetohydrodynamics using different models for the evolution of the mass density. The initial current distribution represents the situation at the plasma creation phase, while it is not increased during the simulation. Key features of the reported experimental observations like pinching of the current loop,more » its expansion and distortion into helical shape are reproduced in the numerical simulations. Details of the final structure depend on the choice of a specific model for the mass density.« less

Application of a high-density gas laser target to the physics of x-ray lasers and coronal plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pronko, J.G.; Kohler, D.

1996-05-31

An experiment has been proposed to investigate a photopumped x-ray laser approach using a novel, high-density, laser heated supersonic gas jet plasma to prepare the lasant plasma. The scheme uses the He- like sodium 1.10027 nm line to pump the He-like neon 1s-4p transition at 1.10003 nm with the lasing transitions between the n=4 to n=2,3 states and the n=3 to n=2 state at 5.8 nm, 23.0 nm, and 8.2 nm, respectively. The experiment had been proposed in 1990 and funding began Jan. 1991; however circumstances made it impossible to pursue the research over the past 5 years, and itmore » was decided not to pursue the research any further.« less

Structural Changes in the Vanadium Sample Surface Induced by Pulsed High-Temperature Deuterium Plasma and Deuterium Ion Fluxes

NASA Astrophysics Data System (ADS)

Borovitskaya, I. V.; Pimenov, V. N.; Gribkov, V. A.; Padukh, M.; Bondarenko, G. G.; Gaidar, A. I.; Paramonova, V. V.; Morozov, E. V.

2017-11-01

The structural changes in the vanadium sample surface are studied as functions of the conditions of irradiation by pulsed high-temperature deuterium plasma and deuterium ion fluxes in the Plasma Focus installation. It is found that processes of partial evaporation, melting, and crystallization of the surface layer of vanadium samples take place in the plasma flux power density range q = 108-1010 W/cm2 and the ion flux density range q = 1010-1012 W/cm2. The surface relief is wavelike. There are microcracks, gas-filled bubbles (blisters), and traces of fracture on the surface. The blisters are failed in the solid state. The character of blister fracture is similar to that observed during usual ion irradiation in accelerators. The samples irradiated at relatively low power density ( q = 107-108 W/cm2) demonstrate the ejection of microparticles (surface fragments) on the side facing plasma. This process is assumed to be due to the fact that the unloading wave formed in the sample-target volume reaches its irradiated surface. Under certain irradiation conditions (sample-anode distance, the number of plasma pulses), a block microstructure with block sizes of several tens of microns forms on the sample surfaces. This structure is likely to form via directional crack propagation upon cooling of a thin melted surface layer.

A study of the possibility of predicting the threshold of plasma formation on a metal surface by the optoacoustic method

NASA Astrophysics Data System (ADS)

Aver'ianov, N. E.; Baloshin, Iu. A.; Martiukhina, L. I.; Pavlishin, I. V.; Sud'Enkov, Iu. V.

1987-09-01

The amplitudes of the acoustic signals excited in metal reflectors by laser pulses are analyzed as a function of the energy density of target irradiation. It is shown that the slope of the resulting plot is related to the threshold of plasma generation near the specimen surface. Results are presented for the emission wavelengths of Nd-glass and CO2 lasers.

Triple probe interrogation of spokes in a HiPIMS discharge

NASA Astrophysics Data System (ADS)

Lockwood Estrin, F.; Karkari, S. K.; Bradley, J. W.

2017-07-01

Using a triple probe situated above the racetrack and inside the magnetic trap of a magnetron, rotating spoke-like structures have been clearly identified in a single HiPIMS pulse as periodic modulations of the electron temperature T e, electron density n e, ion saturation current I isat, floating potential V f and plasma potential V p. The spokes rotate in the E  ×  B direction with a velocity of ~8.8 km s-1. Defining the spoke shape from the footprint of the ion current, they deliver to flush-mounted probes embedded in the target, each spoke can be characterised by a dense but cool leading edge (n e ~ 2.0  ×  1019 m-3, T e ~ 2.1 eV) and a relatively hotter but more rarefied trailing edge (n e ~ 1  ×  1019 m-3, T e ~ 3.9 eV). Measurements of V p show a potential hump towards the rear of the spoke, separated from regions of the highest density, with plasma potentials up to 8 V more positive than the inter-spoke regions. Azimuthal electric fields of ~1 kV m-1 associated with these structures are calculated. Transforming the triple probe time-traces to functions of the azimuthal angle θ and assuming a Gaussian radial profile for the plasma parameters, 2D spatial maps of n e, T e and V p have been constructed as well as the target ion current density J p from the embedded probes. The phase relationship between T e, V p and n e can be clearly seen using this representation with n e leading T e and V p with a phase shift between them of ~50°. Regions of maximum ion current to the target, delivered by individual spokes, coincide with the overlap of regions of high n e and T e measured above the target at a height of 15 mm. Ions created at elevated positions above the target in the observed dense region will take several micro-seconds to reach that surface, so contributing to the target ion current in the following spokes.

Target dependent femtosecond laser plasma implantation dynamics in enabling silica for high density erbium doping

PubMed Central

Chandrappan, Jayakrishnan; Murray, Matthew; Kakkar, Tarun; Petrik, Peter; Agocs, Emil; Zolnai, Zsolt; Steenson, D.P.; Jha, Animesh; Jose, Gin

2015-01-01

Chemical dissimilarity of tellurium oxide with silica glass increases phase separation and crystallization tendency when mixed and melted for making a glass. We report a novel technique for incorporating an Er3+-doped tellurite glass composition into silica substrates through a femtosecond (fs) laser generated plasma assisted process. The engineered material consequently exhibits the spectroscopic properties of Er3+-ions, which are unachievable in pure silica and implies this as an ideal material for integrated photonics platforms. Formation of a well-defined metastable and homogeneous glass structure with Er3+-ions in a silica network, modified with tellurite has been characterized using high-resolution cross-sectional transmission electron microscopy (HRTEM). The chemical and structural analyses using HRTEM, Rutherford backscattering spectrometry (RBS) and laser excitation techniques, confirm that such fs-laser plasma implanted glasses may be engineered for significantly higher concentration of Er3+-ions without clustering, validated by the record high lifetime-density product 0.96 × 1019 s.cm−3. Characterization of planar optical layers and photoluminescence emission spectra were undertaken to determine their thickness, refractive indices and photoluminescence properties, as a function of Er3+ concentration via different target glasses. The increased Er3+ content in the target glass enhance the refractive index and photoluminescence intensity of the modified silica layer whilst the lifetime and thickness decrease. PMID:26370060

Surface heat flux feedback controlled impurity seeding experiments with Alcator C-Mod’s high-Z vertical target plate divertor: performance, limitations and implications for fusion power reactors

NASA Astrophysics Data System (ADS)

Brunner, D.; Wolfe, S. M.; LaBombard, B.; Kuang, A. Q.; Lipschultz, B.; Reinke, M. L.; Hubbard, A.; Hughes, J.; Mumgaard, R. T.; Terry, J. L.; Umansky, M. V.; The Alcator C-Mod Team

2017-08-01

The Alcator C-Mod team has recently developed a feedback system to measure and control surface heat flux in real-time. The system uses real-time measurements of surface heat flux from surface thermocouples and a pulse-width modulated piezo valve to inject low-Z impurities (typically N2) into the private flux region. It has been used in C-Mod to mitigate peak surface heat fluxes  >40 MW m-2 down to  <10 MW m-2 while maintaining excellent core confinement, H 98  >  1. While the system works quite well under relatively steady conditions, use of it during transients has revealed important limitations on feedback control of impurity seeding in conventional vertical target plate divertors. In some cases, the system is unable to avoid plasma reattachment to the divertor plate or the formation of a confinement-damaging x-point MARFE. This is due to the small operational window for mitigated heat flux in the parameters of incident plasma heat flux, plasma density, and impurity density as well as the relatively slow response of the impurity gas injection system compared to plasma transients. Given the severe consequences for failure of such a system to operate reliably in a reactor, there is substantial risk that the conventional vertical target plate divertor will not provide an adequately controllable system in reactor-class devices. These considerations motivate the need to develop passively stable, highly compliant divertor configurations and experimental facilities that can test such possible solutions.

Picosecond Streaked K-Shell Spectroscopy of Near Solid-Density Aluminum Plasmas

NASA Astrophysics Data System (ADS)

Stillman, C. R.; Nilson, P. M.; Ivancic, S. T.; Mileham, C.; Froula, D. H.; Golovkin, I. E.

2016-10-01

The thermal x-ray emission from rapidly heated solid targets containing a buried-aluminum layer was measured. The targets were driven by high-contrast 1 ω or 2 ω laser pulses at focused intensities up to 1 ×1019W/Wcm2 cm2 . A streaked x-ray spectrometer recorded the Al Heα and lithium-like satellite lines with 2-ps temporal resolution and moderate resolving power (E/E ΔE 700). Time-integrated measurements over the same spectral range were used to correct the streaked data for variations in photocathode sensitivity. Line widths and intensity ratios from the streaked data were interpreted using a collisional radiative atomic model to provide the average plasma conditions in the buried layer as a function of time. It was observed that the resonance line tends toward lower photon energies at high electron densities. The measured shifts will be compared to predicted shifts from Stark-operator calculations at the inferred plasma conditions. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944, the office of Fusion Energy Sciences Award Number DE-SC0012317, and the Stewardship Science Graduate Fellowship Grant Number DE-NA0002135.

Analysis of plasma-controlled laser evaporation of Al target in vacuum

NASA Astrophysics Data System (ADS)

Mazhukin, Vladimir I.; Nossov, Vadim V.; Smurov, Igor Y.

2004-04-01

The plasma-controlled evaporation of the Al target induced by the laser pulse with intensity of 8 x 108 W/cm2 and wavelength of 1.06 μm is analyzed with account for the two-dimensional effects. The self consistent model is applied, consisting of the heat transfer equation in condensed medium, the system of radiation gas dynamics in evaporated substance, and the Knudsen layer model at the two media boundary. It is established that the phase transition of the target surface is controlled by the two factors: the surface temperature that depends on the transmitted radiation intensity and the plasma pressure, governed by the expansion regime. The process comes through three characteristics stages -- the sonic evaporation at the beginning, the condensation during the period of plasma formation and initial expansion and, finally, the recommence of evaporation in subsonic regime after the partial brightening of the plasma. During the subsonic evaporation stage the vapor flow and the mass removal rate is much higher near the beam boundaries than in the center due to smaller plasma counter-pressure. The vapor plasma pattern is characterized by the dense hot zone near the surface where the deposition of laser energy occurs, and rapid decrease of density outside the zone due to three-dimensional expansion. The application of the laser beam of smaller radius at the same intensity leads to the formation of more rarefied and more transparent plasma, that allows to improve the mass removal efficiency.

Temporally resolved proton radiography of rapidly varying electric and magnetic fields in laser-driven capacitor coil targets

NASA Astrophysics Data System (ADS)

Morace, A.; Santos, J. J.; Bailly-Grandvaux, M.; Ehret, M.; Alpinaniz, J.; Brabetz, C.; Schaumann, G.; Volpe, L.

2017-02-01

Understanding the dynamics of rapidly varying electromagnetic fields in intense short pulse laser plasma interactions is of key importance to understand the mechanisms at the basis of a wide variety of physical processes, from high energy density physics and fusion science to the development of ultrafast laser plasma devices to control laser-generated particle beams. Target normal sheath accelerated (TNSA) proton radiography represents an ideal tool to diagnose ultrafast electromagnetic phenomena, providing 2D spatially and temporally resolved radiographs with temporal resolution varying from 2-3 ps to few tens of ps. In this work we introduce the proton radiography technique and its application to diagnose the spatial and temporal evolution of electromagnetic fields in laser-driven capacitor coil targets.

Parameter scaling toward high-energy density in a quasi-steady flow Z-pinch

NASA Astrophysics Data System (ADS)

Hughes, M. C.; Shumlak, U.; Nelson, B. A.; Golingo, R. P.; Claveau, E. L.; Doty, S. A.; Forbes, E. G.; Kim, B.; Ross, M. P.

2016-10-01

Sheared axial flows are utilized by the ZaP Flow Z-Pinch Experiment to stabilize MHD instabilities. The pinches formed are 50 cm long with radii ranging from 0.3 to 1.0 cm. The plasma is generated in a coaxial acceleration region, similar to a Marshall gun, which provides a steady supply of plasma for approximately 100 us. The power to the plasma is partially decoupled between the acceleration and pinch assembly regions through the use of separate power supplies. Adiabatic scaling of the Bennett relation gives targets for future devices to reach high-energy density conditions or fusion reactors. The applicability of an adiabatic assumption is explored and work is done experimentally to clarify the plasma compression process, which may be more generally polytropic. The device is capable of a much larger parameter space than previous machine iterations, allowing flexibility in the initial conditions of the compression process to preserve stability. This work is supported by DoE FES and NNSA.

Effects of ELMs on ITER divertor armour materials

NASA Astrophysics Data System (ADS)

Zhitlukhin, A.; Klimov, N.; Landman, I.; Linke, J.; Loarte, A.; Merola, M.; Podkovyrov, V.; Federici, G.; Bazylev, B.; Pestchanyi, S.; Safronov, V.; Hirai, T.; Maynashev, V.; Levashov, V.; Muzichenko, A.

2007-06-01

This paper is concerned with investigation of an erosion of the ITER-like divertor plasma facing components under plasma heat loads expected during the Type I ELMs in ITER. These experiments were carried out on plasma accelerator QSPA at the SRC RF TRINITI under EU/RF collaboration. Targets were exposed by series repeated plasma pulses with heat loads in a range of 0.5-1.5 MJ/m2 and pulse duration 0.5 ms. Erosion of CFC macrobrushes was determined mainly by sublimation of PAN-fibres that was less than 2.5 μm per pulse. The CFC erosion was negligible at the energy density less than 0.5 MJ/m2 and was increased to the average value 0.3 μm per pulse at 1.5 MJ/m2. The pure tungsten macrobrushes erosion was small in the energy range of 0.5-1.3 MJ/m2. The sharp growth of tungsten erosion and the intense droplet ejection were observed at the energy density of 1.5 MJ/m2.

Study of ablation and implosion stages in wire arrays using coupled ultraviolet and X-ray probing diagnostics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, A. A.; Ivanov, V. V.; Astanovitskiy, A. L.

2015-11-15

Star and cylindrical wire arrays were studied using laser probing and X-ray radiography at the 1-MA Zebra pulse power generator at the University of Nevada, Reno. The Leopard laser provided backlighting, producing a laser plasma from a Si target which emitted an X-ray probing pulse at the wavelength of 6.65 Å. A spherically bent quartz crystal imaged the backlit wires onto X-ray film. Laser probing diagnostics at the wavelength of 266 nm included a 3-channel polarimeter for Faraday rotation diagnostic and two-frame laser interferometry with two shearing interferometers to study the evolution of the plasma electron density at the ablation and implosionmore » stages. Dynamics of the plasma density profile in Al wire arrays at the ablation stage were directly studied with interferometry, and expansion of wire cores was measured with X-ray radiography. The magnetic field in the imploding plasma was measured with the Faraday rotation diagnostic, and current was reconstructed.« less

3φ Laser Beam Propagation in Inertial Confinement Plasmas*

NASA Astrophysics Data System (ADS)

Froula, Dustin

2006-10-01

A study of the relevant laser-plasma interaction processes in a long-scale length high-temperature transparent plasma has been performed using a new target platform to emulate the plasma conditions in an indirect drive fusion target. Recent experiments in this plasma emulator have demonstrated that for ignition relevant conditions (Te>3 keV, I < 2x10^15 W-cm-2) the 3φ laser light propagates through a high-density (5x10^20 cm-3) plasma with a peak transmission of 90%. Experiments have demonstrated an understanding of filamentation in these conditions that is consistent with theory increasing our confidence in our ability to execute the beam conditioning and focal spot designs for future ignition experiments. This target has been well characterized using Thomson-scattering where the peak electron temperature is shown to be 3.5 keV. The electron temperature measurements agree with HYDRA flux-limited radiation hydrodynamics calculations. Using a recently implemented 3φ transmitted beam diagnostic, the filamentation threshold has been experimentally measured for a beam that employs a continuous phase plate (CPP). For intensities above the threshold for filamentation, the beam was shown to spray. Defocusing the high-power laser beam reduced the backscatter while filamentation was not changed as predicted. Recent experiments investigating the importance of polarization and temporal smoothing of laser beams for propagation in this target platform will be presented. Detailed hydrodynamic and laser-plasma interaction simulations capture the stimulated Brillouin, stimulated Raman, and filamentation thresholds providing significant confidence that our models used for ignition designs can correctly predict the conditions where energy loss and beam propagation through the under dense NIF hohlraum plasmas will be small. ** Collaborators: L. Divol, S. H. Glenzer, J. S. Ross, N. Meezan, S. Prisbrey, S. Dixit.

Optimizing laser-driven proton acceleration from overdense targets

PubMed Central

Stockem Novo, A.; Kaluza, M. C.; Fonseca, R. A.; Silva, L. O.

2016-01-01

We demonstrate how to tune the main ion acceleration mechanism in laser-plasma interactions to collisionless shock acceleration, thus achieving control over the final ion beam properties (e. g. maximum energy, divergence, number of accelerated ions). We investigate this technique with three-dimensional particle-in-cell simulations and illustrate a possible experimental realisation. The setup consists of an isolated solid density target, which is preheated by a first laser pulse to initiate target expansion, and a second one to trigger acceleration. The timing between the two laser pulses allows to access all ion acceleration regimes, ranging from target normal sheath acceleration, to hole boring and collisionless shock acceleration. We further demonstrate that the most energetic ions are produced by collisionless shock acceleration, if the target density is near-critical, ne ≈ 0.5 ncr. A scaling of the laser power shows that 100 MeV protons may be achieved in the PW range. PMID:27435449

Refluxed electrons direct laser acceleration in ultrahigh laser and relativistic critical density plasma interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, J.; Science and Technology on Plasma Physics Laboratory, China Academy of Engineering Physics, P.O. Box 919-986, Mianyang 621900; Zhao, Z. Q.

2015-01-15

Refluxed electrons direct laser acceleration is proposed so as to generate a high-charge energetic electron beam. When a laser pulse is incident on a relativistic critical density target, the rising edge of the pulse heats the target and the sheath fields on the both sides of the target reflux some electrons inside the expanding target. These electrons can be trapped and accelerated due to the self-transparency and the negative longitudinal electrostatic field in the expanding target. Some of the electrons can be accelerated to energies exceeding the ponderomotive limit 1/2a{sub 0}{sup 2}mc{sup 2}. Effective temperature significantly above the ponderomotive scalingmore » is observed. Furthermore, due to the limited expanding length, the laser propagating instabilities are suppressed in the interaction. Thus, high collimated beams with tens of μC charge can be generated.« less

Dynamics and density distributions in a capillary-discharge waveguide with an embedded supersonic jet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matlis, N. H., E-mail: nmatlis@gmail.com; Gonsalves, A. J.; Steinke, S.

We present an analysis of the gas dynamics and density distributions within a capillary-discharge waveguide with an embedded supersonic jet. This device provides a target for a laser plasma accelerator which uses longitudinal structuring of the gas-density profile to enable control of electron trapping and acceleration. The functionality of the device depends sensitively on the details of the density profile, which are determined by the interaction between the pulsed gas in the jet and the continuously-flowing gas in the capillary. These dynamics are captured by spatially resolving recombination light from several emission lines of the plasma as a function ofmore » the delay between the jet and the discharge. We provide a phenomenological description of the gas dynamics as well as a quantitative evaluation of the density evolution. In particular, we show that the pressure difference between the jet and the capillary defines three regimes of operation with qualitatively different longitudinal density profiles and show that jet timing provides a sensitive method for tuning between these regimes.« less

Recent sheath physics studies on DIII-D

NASA Astrophysics Data System (ADS)

Watkins, J. G.; Labombard, B.; Stangeby, P. C.; Lasnier, C. J.; McLean, A. G.; Nygren, R. E.; Boedo, J. A.; Leonard, A. W.; Rudakov, D. L.

2015-08-01

A study to examine some current issues in the physics of the plasma sheath has been recently carried out in DIII-D low power Ohmic plasmas using both flush and domed Langmuir probes, divertor Thomson scattering (DTS), an infrared camera (IRTV), and a new calorimeter triple probe assembly mounted on the Divertor Materials Evaluation System (DIMES). The sheath power transmission factor was found to be consistent with the theoretically predicted value of 7 (±2) for low power plasmas. Using this factor, the three heat flux profiles derived from the LP, DTS, and calorimeter diagnostic measurements agree. Comparison of flush and domed Langmuir probes and divertor Thomson scattering indicates that proper interpretation of flush probe data to get target plate density and temperature is feasible and could potentially yield accurate measurements of target plate conditions where the probes are located.

Energy penetration into arrays of aligned nanowires irradiated with relativistic intensities: Scaling to terabar pressures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bargsten, Clayton; Hollinger, Reed; Capeluto, Maria Gabriela

Ultrahigh-energy density (UHED) matter, characterized by energy densities >1 × 10 8 J cm –3 and pressures greater than a gigabar, is encountered in the center of stars and inertial confinement fusion capsules driven by the world’s largest lasers. Similar conditions can be obtained with compact, ultrahigh contrast, femtosecond lasers focused to relativistic intensities onto targets composed of aligned nanowire arrays. We report the measurement of the key physical process in determining the energy density deposited in high-aspect-ratio nanowire array plasmas: the energy penetration. By monitoring the x-ray emission from buried Co tracer segments in Ni nanowire arrays irradiated atmore » an intensity of 4 × 10 19 W cm –2, we demonstrate energy penetration depths of several micrometers, leading to UHED plasmas of that size. As a result, relativistic three-dimensional particle-in-cell simulations, validated by these measurements, predict that irradiation of nanostructures at intensities of >1 × 10 22 W cm –2 will lead to a virtually unexplored extreme UHED plasma regime characterized by energy densities in excess of 8 × 10 10 J cm –3, equivalent to a pressure of 0.35 Tbar.« less

Energy Penetration into Arrays of Aligned Nanowires Irradiated with Relativistic Intensities: Scaling to Terabar Pressures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bargsten, Clayton; Hollinger, Reed; Capeluto, Maria Gabriela

Ultra-high-energy-density (UHED) matter, characterized by energy densities > 1 x 10 8 J cm -3 and pressures greater than a gigabar, is encountered in the center of stars and in inertial confinement fusion capsules driven by the world’s largest lasers. Similar conditions can be obtained with compact, ultra-high contrast, femtosecond lasers focused to relativistic intensities onto targets composed of aligned nanowire arrays. Here we report the measurement of the key physical process in determining the energy density deposited in high aspect ratio nanowire array plasmas: the energy penetration. By monitoring the x-ray emission from buried Co tracer segments in Nimore » nanowire arrays irradiated at an intensity of 4 x 10 19 W cm -2, we demonstrate energy penetration depths of several μm, leading to UHED plasmas of that size. Relativistic 3D particle-in-cell-simulations, validated by these measurements, predict that irradiation of nanostructures at intensities of > 1 x 10 22 W cm -2 will lead to a virtually unexplored extreme UHED plasma regime characterized by energy densities in excess of 8 x 10 10 J cm -3, equivalent to a pressure of 0.35 Tbar.« less

Energy penetration into arrays of aligned nanowires irradiated with relativistic intensities: Scaling to terabar pressures

DOE PAGES

Bargsten, Clayton; Hollinger, Reed; Capeluto, Maria Gabriela; ...

2017-01-11

Ultrahigh-energy density (UHED) matter, characterized by energy densities >1 × 10 8 J cm –3 and pressures greater than a gigabar, is encountered in the center of stars and inertial confinement fusion capsules driven by the world’s largest lasers. Similar conditions can be obtained with compact, ultrahigh contrast, femtosecond lasers focused to relativistic intensities onto targets composed of aligned nanowire arrays. We report the measurement of the key physical process in determining the energy density deposited in high-aspect-ratio nanowire array plasmas: the energy penetration. By monitoring the x-ray emission from buried Co tracer segments in Ni nanowire arrays irradiated atmore » an intensity of 4 × 10 19 W cm –2, we demonstrate energy penetration depths of several micrometers, leading to UHED plasmas of that size. As a result, relativistic three-dimensional particle-in-cell simulations, validated by these measurements, predict that irradiation of nanostructures at intensities of >1 × 10 22 W cm –2 will lead to a virtually unexplored extreme UHED plasma regime characterized by energy densities in excess of 8 × 10 10 J cm –3, equivalent to a pressure of 0.35 Tbar.« less

Energy penetration into arrays of aligned nanowires irradiated with relativistic intensities: Scaling to terabar pressures.

PubMed

Bargsten, Clayton; Hollinger, Reed; Capeluto, Maria Gabriela; Kaymak, Vural; Pukhov, Alexander; Wang, Shoujun; Rockwood, Alex; Wang, Yong; Keiss, David; Tommasini, Riccardo; London, Richard; Park, Jaebum; Busquet, Michel; Klapisch, Marcel; Shlyaptsev, Vyacheslav N; Rocca, Jorge J

2017-01-01

Ultrahigh-energy density (UHED) matter, characterized by energy densities >1 × 10 8 J cm -3 and pressures greater than a gigabar, is encountered in the center of stars and inertial confinement fusion capsules driven by the world's largest lasers. Similar conditions can be obtained with compact, ultrahigh contrast, femtosecond lasers focused to relativistic intensities onto targets composed of aligned nanowire arrays. We report the measurement of the key physical process in determining the energy density deposited in high-aspect-ratio nanowire array plasmas: the energy penetration. By monitoring the x-ray emission from buried Co tracer segments in Ni nanowire arrays irradiated at an intensity of 4 × 10 19 W cm -2 , we demonstrate energy penetration depths of several micrometers, leading to UHED plasmas of that size. Relativistic three-dimensional particle-in-cell simulations, validated by these measurements, predict that irradiation of nanostructures at intensities of >1 × 10 22 W cm -2 will lead to a virtually unexplored extreme UHED plasma regime characterized by energy densities in excess of 8 × 10 10 J cm -3 , equivalent to a pressure of 0.35 Tbar.

Energy penetration into arrays of aligned nanowires irradiated with relativistic intensities: Scaling to terabar pressures

PubMed Central

Bargsten, Clayton; Hollinger, Reed; Capeluto, Maria Gabriela; Kaymak, Vural; Pukhov, Alexander; Wang, Shoujun; Rockwood, Alex; Wang, Yong; Keiss, David; Tommasini, Riccardo; London, Richard; Park, Jaebum; Busquet, Michel; Klapisch, Marcel; Shlyaptsev, Vyacheslav N.; Rocca, Jorge J.

2017-01-01

Ultrahigh-energy density (UHED) matter, characterized by energy densities >1 × 108 J cm−3 and pressures greater than a gigabar, is encountered in the center of stars and inertial confinement fusion capsules driven by the world’s largest lasers. Similar conditions can be obtained with compact, ultrahigh contrast, femtosecond lasers focused to relativistic intensities onto targets composed of aligned nanowire arrays. We report the measurement of the key physical process in determining the energy density deposited in high-aspect-ratio nanowire array plasmas: the energy penetration. By monitoring the x-ray emission from buried Co tracer segments in Ni nanowire arrays irradiated at an intensity of 4 × 1019 W cm−2, we demonstrate energy penetration depths of several micrometers, leading to UHED plasmas of that size. Relativistic three-dimensional particle-in-cell simulations, validated by these measurements, predict that irradiation of nanostructures at intensities of >1 × 1022 W cm−2 will lead to a virtually unexplored extreme UHED plasma regime characterized by energy densities in excess of 8 × 1010 J cm−3, equivalent to a pressure of 0.35 Tbar. PMID:28097218

Target surface area effects on hot electron dynamics from high intensity laser–plasma interactions

DOE PAGES

Zulick, C.; Raymond, A.; McKelvey, A.; ...

2016-06-15

Reduced surface area targets were studied using an ultra-high intensity femtosecond laser in order to determine the effect of electron sheath field confinement on electron dynamics. X-ray emission due to energetic electrons was imaged using a K α imaging crystal. Electrons were observed to travel along the surface of wire targets, and were slowed mainly by the induced fields. Targets with reduced surface areas were correlated with increased hot electron densities and proton energies. Furthermore, Hybrid Vlasov–Fokker–Planck simulations demonstrated increased electric sheath field strength in reduced surface area targets.

Final report on the Magnetized Target Fusion Collaboration

DOE Office of Scientific and Technical Information (OSTI.GOV)

John Slough

Nuclear fusion has the potential to satisfy the prodigious power that the world will demand in the future, but it has yet to be harnessed as a practical energy source. The entry of fusion as a viable, competitive source of power has been stymied by the challenge of finding an economical way to provide for the confinement and heating of the plasma fuel. It is the contention here that a simpler path to fusion can be achieved by creating fusion conditions in a different regime at small scale (~ a few cm). One such program now under study, referred tomore » as Magnetized Target Fusion (MTF), is directed at obtaining fusion in this high energy density regime by rapidly compressing a compact toroidal plasmoid commonly referred to as a Field Reversed Configuration (FRC). To make fusion practical at this smaller scale, an efficient method for compressing the FRC to fusion gain conditions is required. In one variant of MTF a conducting metal shell is imploded electrically. This radially compresses and heats the FRC plasmoid to fusion conditions. The closed magnetic field in the target plasmoid suppresses the thermal transport to the confining shell, thus lowering the imploding power needed to compress the target. The undertaking to be described in this proposal is to provide a suitable target FRC, as well as a simple and robust method for inserting and stopping the FRC within the imploding liner. The timescale for testing and development can be rapidly accelerated by taking advantage of a new facility funded by the Department of Energy. At this facility, two inductive plasma accelerators (IPA) were constructed and tested. Recent experiments with these IPAs have demonstrated the ability to rapidly form, accelerate and merge two hypervelocity FRCs into a compression chamber. The resultant FRC that was formed was hot (T&ion ~ 400 eV), stationary, and stable with a configuration lifetime several times that necessary for the MTF liner experiments. The accelerator length was less than 1 meter, and the time from the initiation of formation to the establishment of the final equilibrium was less than 10 microseconds. With some modification, each accelerator was made capable of producing FRCs suitable for the production of the target plasma for the MTF liner experiment. Based on the initial FRC merging/compression results, the design and methodology for an experimental realization of the target plasma for the MTF liner experiment can now be defined. A high density FRC plasmoid is to be formed and accelerated out of each IPA into a merging/compression chamber similar to the imploding liner at AFRL. The properties of the resultant FRC plasma (size, temperature, density, flux, lifetime) are obtained in the reevant regime of interest. The process still needs to be optimized, and a final design for implementation at AFRL must now be carried out. When implemented at AFRL it is anticipated that the colliding/merging FRCs will then be compressed by the liner. In this manner it is hoped that ultimately a plasma with ion temperatures reaching the 10 keV range and fusion gain near unity can be obtained.« less

Active Control of Power Exhaust in Strongly Heated ASDEX Upgrade Plasmas

NASA Astrophysics Data System (ADS)

Dux, Ralph; Kallenbach, Arne; Bernert, Matthias; Eich, Thomas; Fuchs, Christoph; Giannone, Louis; Herrmann, Albrecht; Schweinzer, Josef; Treutterer, Wolfgang

2012-10-01

Due to the absence of carbon as an intrinsic low-Z radiator, and tight limits for the acceptable power load on the divertor target, ITER will rely on impurity seeding for radiative power dissipation and for generation of partial detachment. The injection of more than one radiating species is required to optimise the power removal in the main plasma and in the divertor region, i.e. a low-Z species for radiation in the divertor and a medium-Z species for radiation in the outer core plasma. In ASDEX Upgrade, a set of robust sensors, which is suitable to feedback control the radiated power in the main chamber and the divertor as well as the electron temperature at the target, has been developed. Different feedback schemes were applied in H-mode discharges with a maximum heating power of up to 23,W, i.e. at ITER values of P/R (power per major radius) to control all combinations of power flux into the divertor region, power flux onto the target or electron temperature at the target through injection of nitrogen as the divertor radiator and argon as the main chamber radiator. Even at the highest heating powers the peak heat flux density at the target is kept at benign values. The control schemes and the plasma behaviour in these discharges will be discussed.

Specular reflectivity and hot-electron generation in high-contrast relativistic laser-plasma interactions

NASA Astrophysics Data System (ADS)

Kemp, Gregory Elijah

Ultra-intense laser (> 1018 W/cm2) interactions with matter are capable of producing relativistic electrons which have a variety of applications in state-of-the-art scientific and medical research conducted at universities and national laboratories across the world. Control of various aspects of these hot-electron distributions is highly desired to optimize a particular outcome. Hot-electron generation in low-contrast interactions, where significant amounts of under-dense pre-plasma are present, can be plagued by highly non-linear relativistic laser-plasma instabilities and quasi-static magnetic field generation, often resulting in less than desirable and predictable electron source characteristics. High-contrast interactions offer more controlled interactions but often at the cost of overall lower coupling and increased sensitivity to initial target conditions. An experiment studying the differences in hot-electron generation between high and low-contrast pulse interactions with solid density targets was performed on the Titan laser platform at the Jupiter Laser Facility at Lawrence Livermore National Laboratory in Livermore, CA. To date, these hot-electrons generated in the laboratory are not directly observable at the source of the interaction. Instead, indirect studies are performed using state-of-the-art simulations, constrained by the various experimental measurements. These measurements, more-often-than-not, rely on secondary processes generated by the transport of these electrons through the solid density materials which can susceptible to a variety instabilities and target material/geometry effects. Although often neglected in these types of studies, the specularly reflected light can provide invaluable insight as it is directly influenced by the interaction. In this thesis, I address the use of (personally obtained) experimental specular reflectivity measurements to indirectly study hot-electron generation in the context of high-contrast, relativistic laser-plasma interactions. Spatial, temporal and spectral properties of the incident and specular pulses, both near and far away from the interaction region where experimental measurements are obtained, are used to benchmark simulations designed to infer dominant hot-electron acceleration mechanisms and their corresponding energy/angular distributions. To handle this highly coupled interaction, I employed particle-in-cell modeling using a wide variety of algorithms (verified to be numerically stable and consistent with analytic expressions) and physical models (validated by experimental results) to reasonably model the interaction's sweeping range of plasma densities, temporal and spatial scales, electromagnetic wave propagation and its interaction with solid density matter. Due to the fluctuations in the experimental conditions and limited computational resources, only a limited number of full-scale simulations were performed under typical experimental conditions to infer the relevant physical phenomena in the interactions. I show the usefulness of the often overlooked specular reflectivity measurements in constraining both high and low-contrast simulations, as well as limitations of their experimental interpretations. Using these experimental measurements to reasonably constrain the simulation results, I discuss the sensitivity of relativistic electron generation in ultra-intense laser plasma interactions to initial target conditions and the dynamic evolution of the interaction region.

First-principles investigations on ionization and thermal conductivity of polystyrene for inertial confinement fusion applications

DOE PAGES

Hu, S. X.; Collins, Lee A.; Goncharov, V. N.; ...

2016-04-14

Using quantum molecular-dynamics (QMD) methods based on the density functional theory, we have performed first-principles investigations on the ionization and thermal conductivity of polystyrene (CH) over a wide range of plasma conditions (ρ = 0.5 to 100 g/cm 3 and T = 15,625 to 500,000 K). The ionization data from orbital-free molecular-dynamics calculations have been fitted with a “Saha-type” model as a function of the CH plasma density and temperature, which exhibits the correct behaviors of continuum lowering and pressure ionization. The thermal conductivities (κ QMD) of CH, derived directly from the Kohn–Sham molecular-dynamics calculations, are then analytically fitted withmore » a generalized Coulomb logarithm [(lnΛ) QMD] over a wide range of plasma conditions. When compared with the traditional ionization and thermal conductivity models used in radiation–hydrodynamics codes for inertial confinement fusion simulations, the QMD results show a large difference in the low-temperature regime in which strong coupling and electron degeneracy play an essential role in determining plasma properties. Furthermore, hydrodynamic simulations of cryogenic deuterium–tritium targets with CH ablators on OMEGA and the National Ignition Facility using the QMD-derived ionization and thermal conductivity of CH have predicted –20% variation in target performance in terms of hot-spot pressure and neutron yield (gain) with respect to traditional model simulations.« less

Shock-wave proton acceleration from a hydrogen gas jet

NASA Astrophysics Data System (ADS)

Cook, Nathan; Pogorelsky, Igor; Polyanskiy, Mikhail; Babzien, Marcus; Tresca, Olivier; Maharjan, Chakra; Shkolnikov, Peter; Yakimenko, Vitaly

2013-04-01

Typical laser acceleration experiments probe the interaction of intense linearly-polarized solid state laser pulses with dense metal targets. This interaction generates strong electric fields via Transverse Normal Sheath Acceleration and can accelerate protons to high peak energies but with a large thermal spectrum. Recently, the advancement of high pressure amplified CO2 laser technology has allowed for the creation of intense (10^16 Wcm^2) pulses at λ˜10 μm. These pulses may interact with reproducible, high rep. rate gas jet targets and still produce plasmas of critical density (nc˜10^19 cm-3), leading to the transference of laser energy via radiation pressure. This acceleration mode has the advantage of producing narrow energy spectra while scaling well with pulse intensity. We observe the interaction of an intense CO2 laser pulse with an overdense hydrogen gas jet. Using two pulse optical probing in conjunction with interferometry, we are able to obtain density profiles of the plasma. Proton energy spectra are obtained using a magnetic spectrometer and scintillating screen.

Numerical analyses of baseline JT-60SA design concepts with the COREDIV code

NASA Astrophysics Data System (ADS)

Zagórski, R.; Gałązka, K.; Ivanova-Stanik, I.; Stępniewski, W.; Garzotti, L.; Giruzzi, G.; Neu, R.; Romanelli, M.

2017-06-01

JT-60SA reference design scenarios at high (#3) and low (#2) density have been analyzed with the help of the self-consistent COREDIV code. Simulations results for a standard C wall and full W wall have been compared in terms of the influence of impurities, both intrinsic (C, W) and seeded (N, Ar, Ne, Kr), on the radiation losses and plasma parameters. For scenario #3 in a C environment, the regime of detachment on divertor plates can be achieved with N or Ne seeding, whereas for the low density and high power scenario (#2), the C and seeding impurity radiation does not effectively reduce power to the targets. In this case, only an increase of either average density or edge density together with Kr seeding might help to develop conditions with strong radiation losses and semi-detached conditions in the divertor. The calculations show that, in the case of a W divertor, the power load to the plate is mitigated by seeding and the central plasma dilution is smaller compared to the C divertor. For the high density case (#3) with Ne seeding, operation in full detachment mode is predicted. Ar seems to be an optimal choice for the low-density high-power scenario #2, showing a wide operating window, whereas Ne leads to high plasma dilution at high seeding levels albeit not achieving semi-detached conditions in the divertor.

The FIELDS Instrument Suite for Solar Probe Plus Measuring the Coronal Plasma and Magnetic Field, Plasma Waves and Turbulence, and Radio Signatures of Solar Transients

NASA Technical Reports Server (NTRS)

Bale, S. D.; Goetz, K.; Harvey, P. R.; Turin, P.; Bonnell, J. W.; Dudok de Wit, T.; Ergun, R. E.; MacDowall, R. J.; Pulupa, M.; Choi, M. K.;

The FIELDS Instrument Suite for Solar Probe Plus: Measuring the Coronal Plasma and Magnetic Field, Plasma Waves and Turbulence, and Radio Signatures of Solar Transients.

PubMed

Bale, S D; Goetz, K; Harvey, P R; Turin, P; Bonnell, J W; de Wit, T Dudok; Ergun, R E; MacDowall, R J; Pulupa, M; Andre, M; Bolton, M; Bougeret, J-L; Bowen, T A; Burgess, D; Cattell, C A; Chandran, B D G; Chaston, C C; Chen, C H K; Choi, M K; Connerney, J E; Cranmer, S; Diaz-Aguado, M; Donakowski, W; Drake, J F; Farrell, W M; Fergeau, P; Fermin, J; Fischer, J; Fox, N; Glaser, D; Goldstein, M; Gordon, D; Hanson, E; Harris, S E; Hayes, L M; Hinze, J J; Hollweg, J V; Horbury, T S; Howard, R A; Hoxie, V; Jannet, G; Karlsson, M; Kasper, J C; Kellogg, P J; Kien, M; Klimchuk, J A; Krasnoselskikh, V V; Krucker, S; Lynch, J J; Maksimovic, M; Malaspina, D M; Marker, S; Martin, P; Martinez-Oliveros, J; McCauley, J; McComas, D J; McDonald, T; Meyer-Vernet, N; Moncuquet, M; Monson, S J; Mozer, F S; Murphy, S D; Odom, J; Oliverson, R; Olson, J; Parker, E N; Pankow, D; Phan, T; Quataert, E; Quinn, T; Ruplin, S W; Salem, C; Seitz, D; Sheppard, D A; Siy, A; Stevens, K; Summers, D; Szabo, A; Timofeeva, M; Vaivads, A; Velli, M; Yehle, A; Werthimer, D; Wygant, J R

2016-12-01

NASA's Solar Probe Plus (SPP) mission will make the first in situ measurements of the solar corona and the birthplace of the solar wind. The FIELDS instrument suite on SPP will make direct measurements of electric and magnetic fields, the properties of in situ plasma waves, electron density and temperature profiles, and interplanetary radio emissions, amongst other things. Here, we describe the scientific objectives targeted by the SPP/FIELDS instrument, the instrument design itself, and the instrument concept of operations and planned data products.

The FIELDS Instrument Suite for Solar Probe Plus. Measuring the Coronal Plasma and Magnetic Field, Plasma Waves and Turbulence, and Radio Signatures of Solar Transients

NASA Astrophysics Data System (ADS)

Bale, S. D.; Goetz, K.; Harvey, P. R.; Turin, P.; Bonnell, J. W.; Dudok de Wit, T.; Ergun, R. E.; MacDowall, R. J.; Pulupa, M.; Andre, M.; Bolton, M.; Bougeret, J.-L.; Bowen, T. A.; Burgess, D.; Cattell, C. A.; Chandran, B. D. G.; Chaston, C. C.; Chen, C. H. K.; Choi, M. K.; Connerney, J. E.; Cranmer, S.; Diaz-Aguado, M.; Donakowski, W.; Drake, J. F.; Farrell, W. M.; Fergeau, P.; Fermin, J.; Fischer, J.; Fox, N.; Glaser, D.; Goldstein, M.; Gordon, D.; Hanson, E.; Harris, S. E.; Hayes, L. M.; Hinze, J. J.; Hollweg, J. V.; Horbury, T. S.; Howard, R. A.; Hoxie, V.; Jannet, G.; Karlsson, M.; Kasper, J. C.; Kellogg, P. J.; Kien, M.; Klimchuk, J. A.; Krasnoselskikh, V. V.; Krucker, S.; Lynch, J. J.; Maksimovic, M.; Malaspina, D. M.; Marker, S.; Martin, P.; Martinez-Oliveros, J.; McCauley, J.; McComas, D. J.; McDonald, T.; Meyer-Vernet, N.; Moncuquet, M.; Monson, S. J.; Mozer, F. S.; Murphy, S. D.; Odom, J.; Oliverson, R.; Olson, J.; Parker, E. N.; Pankow, D.; Phan, T.; Quataert, E.; Quinn, T.; Ruplin, S. W.; Salem, C.; Seitz, D.; Sheppard, D. A.; Siy, A.; Stevens, K.; Summers, D.; Szabo, A.; Timofeeva, M.; Vaivads, A.; Velli, M.; Yehle, A.; Werthimer, D.; Wygant, J. R.

2016-12-01

NASA's Solar Probe Plus (SPP) mission will make the first in situ measurements of the solar corona and the birthplace of the solar wind. The FIELDS instrument suite on SPP will make direct measurements of electric and magnetic fields, the properties of in situ plasma waves, electron density and temperature profiles, and interplanetary radio emissions, amongst other things. Here, we describe the scientific objectives targeted by the SPP/FIELDS instrument, the instrument design itself, and the instrument concept of operations and planned data products.

Targeted Proteomics and Absolute Protein Quantification for the Construction of a Stoichiometric Host-Pathogen Surface Density Model.

PubMed

Sjöholm, Kristoffer; Kilsgård, Ola; Teleman, Johan; Happonen, Lotta; Malmström, Lars; Malmström, Johan

2017-04-01

Sepsis is a systemic immune response responsible for considerable morbidity and mortality. Molecular modeling of host-pathogen interactions in the disease state represents a promising strategy to define molecular events of importance for the transition from superficial to invasive infectious diseases. Here we used the Gram-positive bacterium Streptococcus pyogenes as a model system to establish a mass spectrometry based workflow for the construction of a stoichiometric surface density model between the S. pyogenes surface, the surface virulence factor M-protein, and adhered human blood plasma proteins. The workflow relies on stable isotope labeled reference peptides and selected reaction monitoring mass spectrometry analysis of a wild-type strain and an M-protein deficient mutant strain, to generate absolutely quantified protein stoichiometry ratios between S. pyogenes and interacting plasma proteins. The stoichiometry ratios in combination with a novel targeted mass spectrometry method to measure cell numbers enabled the construction of a stoichiometric surface density model using protein structures available from the protein data bank. The model outlines the topology and density of the host-pathogen protein interaction network on the S. pyogenes bacterial surface, revealing a dense and highly organized protein interaction network. Removal of the M-protein from S. pyogenes introduces a drastic change in the network topology, validated by electron microscopy. We propose that the stoichiometric surface density model of S. pyogenes in human blood plasma represents a scalable framework that can continuously be refined with the emergence of new results. Future integration of new results will improve the understanding of protein-protein interactions and their importance for bacterial virulence. Furthermore, we anticipate that the general properties of the developed workflow will facilitate the production of stoichiometric surface density models for other types of host-pathogen interactions. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

High Energy electron and proton acceleration by circularly polarized laser pulse from near critical density hydrogen gas target.

PubMed

Sharma, Ashutosh

2018-02-01

Relativistic electron rings hold the possibility of very high accelerating rates, and hopefully a relatively cheap and compact accelerator/collimator for ultrahigh energy proton source. In this work, we investigate the generation of helical shaped quasi-monoenergetic relativistic electron beam and high-energy proton beam from near critical density plasmas driven by petawatt-circularly polarized-short laser pulses. We numerically observe the efficient proton acceleration from magnetic vortex acceleration mechanism by using the three dimensional particle-in-cell simulations; proton beam with peak energy 350 MeV, charge ~10nC and conversion efficiency more than 6% (which implies 2.4 J proton beam out of the 40 J incident laser energy) is reported. We detailed the microphysics involved in the ion acceleration mechanism, which requires investigating the role of self-generated plasma electric and magnetic fields. The concept of efficient generation of quasi-monoenergetic electron and proton beam from near critical density gas targets may be verified experimentally at advanced high power - high repetition rate laser facilities e.g. ELI-ALPS. Such study should be an important step towards the development of high quality electron and proton beam.

Modification of ordinary-mode reflectometry system to detect lower-hybrid waves in Alcator C-Mod

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baek, S. G.; Shiraiwa, S.; Parker, R. R.

2012-10-15

Backscattering experiments to detect lower-hybrid (LH) waves have been performed in Alcator C-Mod, using the two modified channels (60 GHz and 75 GHz) of an ordinary-mode reflectometry system with newly developed spectral recorders that can continuously monitor spectral power at a target frequency. The change in the baseline of the spectral recorder during the LH wave injection is highly correlated to the strength of the X-mode non-thermal electron cyclotron emission. In high density plasmas where an anomalous drop in the lower hybrid current drive efficiency is observed, the observed backscattered signals are expected to be generated near the last closedmore » flux surface, demonstrating the presence of LH waves within the plasma. This experimental technique can be useful in identifying spatially localized LH electric fields in the periphery of high-density plasmas.« less

Perspectives on High-Energy-Density Physics

NASA Astrophysics Data System (ADS)

Drake, R. Paul

2008-11-01

Much of 21st century plasma physics will involve work to produce, understand, control, and exploit very non-traditional plasmas. High-energy density (HED) plasmas are often examples, variously involving strong Coulomb interactions and few particles per Debeye sphere, dominant radiation effects, strongly relativistic effects, or strongly quantum-mechanical behavior. Indeed, these and other modern plasma systems often fall outside the early standard theoretical definitions of ``plasma''. This presentation will focus on two types of HED plasmas that exhibit non-traditional behavior. Our first example will be the plasmas produced by extremely strong shock waves. Shock waves are present across the entire realm of plasma densities, often in space or astrophysical contexts. HED shock waves (at pressures > 1 Mbar) enable studies in many areas, from equations of state to hydrodynamics to radiation hydrodynamics. We will specifically consider strongly radiative shocks, in which the radiative energy fluxes are comparable to the mechanical energy fluxes that drive the shocks. Modern HED facilities can produce such shocks, which are also present in dense, energetic, astrophysical systems such as supernovae. These shocks are also excellent targets for advanced simulations due to their range of spatial scales and complex radiation transport. Our second example will be relativistic plasmas. In general, these vary from plasmas containing relativistic particle beams, produced for some decades in the laboratory, to the relativistic thermal plasmas present for example in pulsar winds. Laboratory HED relativistic plasmas to date have been those produced by laser beams of irradiance ˜ 10^18 to 10^22 W/cm^2 or by accelerator-produced HED electron beams. These have applications ranging from generation of intense x-rays to production of proton beams for radiation therapy to acceleration of electrons. Here we will focus on electron acceleration, a spectacular recent success and a rare example in which simplicity emerges from the complexity present in the plasma state.

First-principles investigations on ionization and thermal conductivity of polystyrene for inertial confinement fusion applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, S. X., E-mail: shu@lle.rochester.edu; Goncharov, V. N.; McCrory, R. L.

2016-04-15

Using quantum molecular-dynamics (QMD) methods based on the density functional theory, we have performed first-principles investigations of the ionization and thermal conductivity of polystyrene (CH) over a wide range of plasma conditions (ρ = 0.5 to 100 g/cm{sup 3} and T = 15 625 to 500 000 K). The ionization data from orbital-free molecular-dynamics calculations have been fitted with a “Saha-type” model as a function of the CH plasma density and temperature, which gives an increasing ionization as the CH density increases even at low temperatures (T < 50 eV). The orbital-free molecular dynamics method is only used to gauge the average ionization behavior of CH under the average-atommore » model in conjunction with the pressure-matching mixing rule. The thermal conductivities (κ{sub QMD}) of CH, derived directly from the Kohn–Sham molecular-dynamics calculations, are then analytically fitted with a generalized Coulomb logarithm [(lnΛ){sub QMD}] over a wide range of plasma conditions. When compared with the traditional ionization and thermal conductivity models used in radiation–hydrodynamics codes for inertial confinement fusion simulations, the QMD results show a large difference in the low-temperature regime in which strong coupling and electron degeneracy play an essential role in determining plasma properties. Hydrodynamic simulations of cryogenic deuterium–tritium targets with CH ablators on OMEGA and the National Ignition Facility using the QMD-derived ionization and thermal conductivity of CH have predicted ∼20% variation in target performance in terms of hot-spot pressure and neutron yield (gain) with respect to traditional model simulations.« less

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Pattern of the expansion of laser plasmas of various elements in a magnetic field

NASA Astrophysics Data System (ADS)

Bryunetkin, B. A.; Begimkulov, U. Sh; Dyakin, V. M.; Koldashov, G. A.; Repin, A. Yu; Stupitskiĭ, E. L.; Faenov, A. Ya

1993-02-01

The expansion of laser plasmas of the elements Be, Al, Cu, and Pb in a static transverse magnetic field B<=2.7 T has been studied experimentally. The plasma was produced by a ruby laser at a power density no greater than 1012 W/cm2. For all the elements, a characteristic "two-petal" expansion pattern is observed. At a certain distance from the target, the two petals coalesce into a narrow jet. The radius of curvature of the petals and the position of the coalescence point depend on the field strength and the atomic weight of the element.

Spectroscopic studies of Cr VI species in a laser produced plasma

NASA Astrophysics Data System (ADS)

Klemke, Nicolai; Nadarajan, Smijesh; Laban, Dane; Wood, James; Chetty, Dashavir; Kielpinski, David; Litvinyuk, Igor; Sang, Robert

2015-09-01

We present measurements characterizing a laser generated, highly ionized microplasma suitable to extend the cut-off energy of High Harmonic Generation (HHG) to energies up to 5 keV. The HHG process occurs when a strong ultrafast laser hits a gaseous target producing coherent radiation with a much higher photon energy than the driving laser. Commonly, noble gases are used and typical photon energies of several 100 eV are obtained. We plan to use Cr5+ species as the target for HHG as generated by a double pulse method: the first pulse creates the plasma, the second pulse is used to obtain the temperature required for Cr5+. Here, we present results on the optimization of plasma parameters such as the plasma temperature, the number density and the dynamics of Cr5+ by means of spectroscopic techniques in the optical and the XUV regime. This research is supported by Lockheed Martin and the Australian Research Council.

Quasi-monoenergetic ion generation by hole-boring radiation pressure acceleration in inhomogeneous plasmas using tailored laser pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weng, S. M., E-mail: weng-sm@ile.osaka-u.ac.jp; Murakami, M.; Azechi, H.

It is proposed that laser hole-boring at a steady speed in inhomogeneous overdense plasma can be realized by the use of temporally tailored intense laser pulses, producing high-fluence quasi-monoenergetic ion beams. A general temporal profile of such laser pulses is formulated for arbitrary plasma density distribution. As an example, for a precompressed deuterium-tritium fusion target with an exponentially increasing density profile, its matched laser profile for steady hole-boring is given theoretically and verified numerically by particle-in-cell simulations. Furthermore, we propose to achieve fast ignition by the in-situ hole-boring accelerated ions using a tailored laser pulse. Simulations show that the effectivemore » energy fluence, conversion efficiency, energy spread, and collimation of the resulting ion beam can be significantly improved as compared to those found with un-tailored laser profiles. For the fusion fuel with an areal density of 1.5 g cm{sup –2}, simulation indicates that it is promising to realize fast ion ignition by using a tailored driver pulse with energy about 65 kJ.« less

Multicomponent plasma expansion into vacuum with non-Maxwellian electrons

NASA Astrophysics Data System (ADS)

Elkamash, Ibrahem; Kourakis, Ioannis

2016-10-01

The expansion of a collisionless plasma into vacuum has been widely studied since the early works of Gurevich et al and Allen and coworkers. It has received momentum in recent years, in particular in the context of ultraintense laser pulse interaction with a solid target, in an effort to elucidate the generation of high energy ion beams. In most present day experiments, laser produced plasmas contain several ion species, due to increasingly complicated composite targets. Anderson et al have studied the isothermal expansion of a two-ion-species plasma. As in most earlier works, the electrons were assumed to be isothermal throughout the expansion. However, in more realistic situations, the evolution of laser produced plasmas into vacuum is mainly governed by nonthermal electrons. These electrons are characterized by particle distribution functions with high energy tails, which may significantly deviate from the Maxwellian distribution. In this paper, we present a theoretical model for plasma expansion of two component plasma with nonthermal electrons, modelled by a kappa-type distribution. The superthermal effect on the ion density, velocity and the electric field is investigated. It is shown that energetic electrons have a significant effecton the expansion dynamics of the plasma. This work was supported from CPP/QUB funding. One of us (I.S. Elkamash) acknowledges financial support by an Egyptian Government fellowship.

Increased heat dissipation with the X-divertor geometry facilitating detachment onset at lower density in DIII-D

NASA Astrophysics Data System (ADS)

Covele, B.; Kotschenreuther, M.; Mahajan, S.; Valanju, P.; Leonard, A.; Watkins, J.; Makowski, M.; Fenstermacher, M.; Si, H.

2017-08-01

The X-divertor geometry on DIII-D has demonstrated reduced particle and heat fluxes to the target, facilitating detachment onset at 10-20% lower upstream density and higher H-mode pedestal pressure than a standard divertor. SOLPS modeling suggests that this effect cannot be explained by an increase in total connection length alone, but rather by the addition of connection length specifically in the power-dissipating volume near the target, via poloidal flux expansion and flaring. However, poloidal flaring must work synergistically with divertor closure to most effectively reduce the detachment density threshold. The model also points to carbon radiation as the primary driver of power dissipation in divertors on the DIII-D floor, which is consistent with experimental observations. Sustainable divertor detachment at lower density has beneficial consequences for energy confinement and current drive efficiency for core operation, while simultaneously satisfying the exhaust requirements of the plasma-facing components.

On specular reflectivity measurements in high and low-contrast relativistic laser-plasma interactions

NASA Astrophysics Data System (ADS)

Kemp, G. E.; Link, A.; Ping, Y.; McLean, H. S.; Patel, P. K.; Freeman, R. R.; Schumacher, D. W.; Tiedje, H. F.; Tsui, Y. Y.; Ramis, R.; Fedosejevs, R.

2015-01-01

Using both experiment and 2D3V particle-in-cell (PIC) simulations, we describe the use of specular reflectivity measurements to study relativistic (Iλ2 > 1018 W/cm2ṡμm2) laser-plasma interactions for both high and low-contrast 527 nm laser pulses on initially solid density aluminum targets. In the context of hot-electron generation, studies typically rely on diagnostics which, more-often-than-not, represent indirect processes driven by fast electrons transiting through solid density materials. Specular reflectivity measurements, however, can provide a direct measure of the interaction that is highly sensitive to how the EM fields and plasma profiles, critical input parameters for modeling of hot-electron generation, evolve near the interaction region. While the fields of interest occur near the relativistic critical electron density, experimental reflectivity measurements are obtained centimeters away from the interaction region, well after diffraction has fully manifested itself. Using a combination of PIC simulations with experimentally inspired conditions and an analytic, non-paraxial, pulse propagation algorithm, we calculate reflected pulse properties, both near and far from the interaction region, and compare with specular reflectivity measurements. The experiment results and PIC simulations demonstrate that specular reflectivity measurements are an extremely sensitive qualitative, and partially quantitative, indicator of initial laser/target conditions, ionization effects, and other details of intense laser-matter interactions. The techniques described can provide strong constraints on many systems of importance in ultra-intense laser interactions with matter.

Progress in long scale length laser plasma interactions

NASA Astrophysics Data System (ADS)

Glenzer, S. H.; Arnold, P.; Bardsley, G.; Berger, R. L.; Bonanno, G.; Borger, T.; Bower, D. E.; Bowers, M.; Bryant, R.; Buckman, S.; Burkhart, S. C.; Campbell, K.; Chrisp, M. P.; Cohen, B. I.; Constantin, C.; Cooper, F.; Cox, J.; Dewald, E.; Divol, L.; Dixit, S.; Duncan, J.; Eder, D.; Edwards, J.; Erbert, G.; Felker, B.; Fornes, J.; Frieders, G.; Froula, D. H.; Gardner, S. D.; Gates, C.; Gonzalez, M.; Grace, S.; Gregori, G.; Greenwood, A.; Griffith, R.; Hall, T.; Hammel, B. A.; Haynam, C.; Heestand, G.; Henesian, M.; Hermes, G.; Hinkel, D.; Holder, J.; Holdner, F.; Holtmeier, G.; Hsing, W.; Huber, S.; James, T.; Johnson, S.; Jones, O. S.; Kalantar, D.; Kamperschroer, J. H.; Kauffman, R.; Kelleher, T.; Knight, J.; Kirkwood, R. K.; Kruer, W. L.; Labiak, W.; Landen, O. L.; Langdon, A. B.; Langer, S.; Latray, D.; Lee, A.; Lee, F. D.; Lund, D.; MacGowan, B.; Marshall, S.; McBride, J.; McCarville, T.; McGrew, L.; Mackinnon, A. J.; Mahavandi, S.; Manes, K.; Marshall, C.; Menapace, J.; Mertens, E.; Meezan, N.; Miller, G.; Montelongo, S.; Moody, J. D.; Moses, E.; Munro, D.; Murray, J.; Neumann, J.; Newton, M.; Ng, E.; Niemann, C.; Nikitin, A.; Opsahl, P.; Padilla, E.; Parham, T.; Parrish, G.; Petty, C.; Polk, M.; Powell, C.; Reinbachs, I.; Rekow, V.; Rinnert, R.; Riordan, B.; Rhodes, M.; Roberts, V.; Robey, H.; Ross, G.; Sailors, S.; Saunders, R.; Schmitt, M.; Schneider, M. B.; Shiromizu, S.; Spaeth, M.; Stephens, A.; Still, B.; Suter, L. J.; Tietbohl, G.; Tobin, M.; Tuck, J.; Van Wonterghem, B. M.; Vidal, R.; Voloshin, D.; Wallace, R.; Wegner, P.; Whitman, P.; Williams, E. A.; Williams, K.; Winward, K.; Work, K.; Young, B.; Young, P. E.; Zapata, P.; Bahr, R. E.; Seka, W.; Fernandez, J.; Montgomery, D.; Rose, H.

2004-12-01

The first experiments on the National Ignition Facility (NIF) have employed the first four beams to measure propagation and laser backscattering losses in large ignition-size plasmas. Gas-filled targets between 2 and 7 mm length have been heated from one side by overlapping the focal spots of the four beams from one quad operated at 351 nm (3ω) with a total intensity of 2 × 1015 W cm-2. The targets were filled with 1 atm of CO2 producing up to 7 mm long homogeneously heated plasmas with densities of ne = 6 × 1020 cm-3 and temperatures of Te = 2 keV. The high energy in an NIF quad of beams of 16 kJ, illuminating the target from one direction, creates unique conditions for the study of laser-plasma interactions at scale lengths not previously accessible. The propagation through the large-scale plasma was measured with a gated x-ray imager that was filtered for 3.5 keV x-rays. These data indicate that the beams interact with the full length of this ignition-scale plasma during the last ~1 ns of the experiment. During that time, the full aperture measurements of the stimulated Brillouin scattering and stimulated Raman scattering show scattering into the four focusing lenses of 3% for the smallest length (~2 mm), increasing to 10-12% for ~7 mm. These results demonstrate the NIF experimental capabilities and further provide a benchmark for three-dimensional modelling of the laser-plasma interactions at ignition-size scale lengths.

Flexible Al-doped ZnO films grown on PET substrates using linear facing target sputtering for flexible OLEDs

NASA Astrophysics Data System (ADS)

Jeong, Jin-A.; Shin, Hyun-Su; Choi, Kwang-Hyuk; Kim, Han-Ki

2010-11-01

We report the characteristics of flexible Al-doped zinc oxide (AZO) films prepared by a plasma damage-free linear facing target sputtering (LFTS) system on PET substrates for use as a flexible transparent conducting electrode in flexible organic light-emitting diodes (OLEDs). The electrical, optical and structural properties of LFTS-grown flexible AZO electrodes were investigated as a function of dc power. We obtained a flexible AZO film with a sheet resistance of 39 Ω/squ and an average transmittance of 84.86% in the visible range although it was sputtered at room temperature without activation of the Al dopant. Due to the effective confinement of the high-density plasma between the facing AZO targets, the AZO film was deposited on the PET substrate without plasma damage and substrate heating caused by bombardment of energy particles. Moreover, the flexible OLED fabricated on the AZO/PET substrate showed performance similar to the OLED fabricated on a ITO/PET substrate in spite of a lower work function. This indicates that LFTS is a promising plasma damage-free and low-temperature sputtering technique for deposition of flexible and indium-free AZO electrodes for use in cost-efficient flexible OLEDs.

Measurements of Electron Density Profiles of Plasmas Produced by Nike KrF Laser for Laser Plasma Instability (LPI) Research

NASA Astrophysics Data System (ADS)

Oh, Jaechul; Weaver, J. L.; Obenschain, S. P.; Schmitt, A. J.; Kehne, D. M.; Karasik, M.; Chan, L.-Y.; Serlin, V.; Phillips, L.

2013-10-01

Knowing spatial profiles of electron density (ne) in the underdense coronal region (n

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goto, Tetsuya; Matsuoka, Takaaki; Ohmi, Tadahiro

Novel magnetron-sputtering equipment, called rotation magnet sputtering (ROT-MS), was developed to overcome various disadvantages of current magnetron-sputtering equipment. Disadvantages include (1) very low target utilization of less than 20%, (2) difficulty in obtaining uniform deposition on the substrate, and (3) charge-up damages and ion-bombardment-induced damages resulting from very high electron temperature (>3 eV) and that the substrate is set at the plasma excitation region. In ROT-MS, a number of moving high-density plasma loops are excited on the target surface by rotating helical magnets, resulting in very high target utilization with uniform target erosion and uniform deposition on the substrate. Thismore » excellent performance can be principally maintained even if equipment size increases for very large-substrate deposition. Because strong horizontal magnetic fields (>0.05 T) are produced within a very limited region just at the target surface, very low electron-temperature plasmas (<2.5 eV for Ar plasma and <1 eV for direct-current-excited Xe plasma) are excited at the very limited region adjacent to the target surface with a combination of grounded plate closely mounted on the strong magnetic field region. Consequently, the authors can establish charge-up damage-free and ion-bombardment-induced damage-free processes. ROT-MS has been applied for thin-film formation of LaB{sub 6}, which is well known as a stable, low-work-function bulk-crystal material for electron emissions. The work function of the LaB{sub 6} film decreased to 2.8 eV due to enhanced (100)-orientation crystallinity and reduced resistivity realized by adjusting the flux of low-energy bombarding ions impinging on the depositing surface, which work very efficiently, improving the performance of the electron emission devices.« less

A hybrid electron cyclotron resonance metal ion source with integrated sputter magnetron for the production of an intense Al{sup +} ion beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weichsel, T., E-mail: tim.weichsel@fep.fraunhofer.de; Hartung, U.; Kopte, T.

2015-09-15

A metal ion source prototype has been developed: a combination of magnetron sputter technology with 2.45 GHz electron cyclotron resonance (ECR) ion source technology—a so called magnetron ECR ion source (MECRIS). An integrated ring-shaped sputter magnetron with an Al target is acting as a powerful metal atom supply in order to produce an intense current of singly charged metal ions. Preliminary experiments show that an Al{sup +} ion current with a density of 167 μA/cm{sup 2} is extracted from the source at an acceleration voltage of 27 kV. Spatially resolved double Langmuir probe measurements and optical emission spectroscopy were usedmore » to study the plasma states of the ion source: sputter magnetron, ECR, and MECRIS plasma. Electron density and temperature as well as Al atom density were determined as a function of microwave and sputter magnetron power. The effect of ECR heating is strongly pronounced in the center of the source. There the electron density is increased by one order of magnitude from 6 × 10{sup 9} cm{sup −3} to 6 × 10{sup 10} cm{sup −3} and the electron temperature is enhanced from about 5 eV to 12 eV, when the ECR plasma is ignited to the magnetron plasma. Operating the magnetron at constant power, it was observed that its discharge current is raised from 1.8 A to 4.8 A, when the ECR discharge was superimposed with a microwave power of 2 kW. At the same time, the discharge voltage decreased from about 560 V to 210 V, clearly indicating a higher plasma density of the MECRIS mode. The optical emission spectrum of the MECRIS plasma is dominated by lines of excited Al atoms and shows a significant contribution of lines arising from singly ionized Al. Plasma emission photography with a CCD camera was used to prove probe measurements and to identify separated plasma emission zones originating from the ECR and magnetron discharge.« less

The effect of pre-plasma formation under nonlocal transport conditions for ultra-relativistic laser-plasma interaction

NASA Astrophysics Data System (ADS)

Holec, M.; Nikl, J.; Vranic, M.; Weber, S.

2018-04-01

Interaction of high-power lasers with solid targets is in general strongly affected by the limited contrast available. The laser pre-pulse ionizes the target and produces a pre-plasma which can strongly modify the interaction of the main part of the laser pulse with the target. This is of particular importance for future experiments which will use laser intensities above 1021 W cm-2 and which are subject to the limited contrast. As a consequence the main part of the laser pulse will be modified while traversing the pre-plasma, interacting with it partially. A further complication arises from the fact that the interaction of a high-power pre-pulse with solid targets very often takes place under nonlocal transport conditions, i.e. the characteristic mean-free-path of the particles and photons is larger than the characteristic scale-lengths of density and temperature. The classical diffusion treatment of radiation and heat transport in the hydrodynamic model is then insufficient for the description of the pre-pulse physics. These phenomena also strongly modify the formation of the pre-plasma which in turn affects the propagation of the main laser pulse. In this paper nonlocal radiation-hydrodynamic simulations are carried out and serve as input for subsequent kinetic simulations of ultra-high intensity laser pulses interacting with the plasma in the ultra-relativistic regime. It is shown that the results of the kinetic simulations differ considerably whether a diffusive or nonlocal transport is used for the radiation-hydrodynamic simulations.

Study on electromagnetic plasma propulsion using rotating magnetic field acceleration scheme

NASA Astrophysics Data System (ADS)

Furukawa, T.; Takizawa, K.; Kuwahara, D.; Shinohara, S.

2017-04-01

As one of the electromagnetic plasma acceleration systems, we have proposed a rotating magnetic field (RMF) acceleration scheme to overcome the present problem of direct plasma-electrode interactions, leading to a short lifetime with a poor plasma performance due to contamination. In this scheme, we generate a plasma by a helicon wave excited by a radio frequency (rf) antenna which has no direct-contact with a plasma. Then, the produced plasma is accelerated by the axial Lorentz force fz = jθ × Br (jθ is an azimuthal current induced by RMF, and Br is an external radial magnetic field). Erosion of electrodes and contamination are not expected in this total system since RMF coils and an rf antenna do not have contact with the plasma directly. Here, we have measured the plasma parameters (electron density ne and axial ion velocity vi) to demonstrate this RMF acceleration scheme by the use of AC currents in two sets of opposing coils to generate a RMF. The maximum increasing rate Δvi /vi was ˜28% (maximum vi of ˜3 km/s), while the density increasing rate of Δne/ne is ˜ 70% in the case of a RMF current frequency fRMF of 3 MHz, which showed a better plasma performance than that with fRMF = 5 MHz. Moreover, thrust characteristics such as a specific impulse and a thrust efficiency were discussed, although a target plasma was not optimized.

Molecular formation in the stagnation region of colliding laser-produced plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Al-Shboul, K. F.; Hassan, S. M.; Harilal, S. S.

2016-10-27

The laser-produced colliding plasmas have numerous attractive applications and stagnation layer formed during collisions between plasmas is a useful system for understanding particle collisions and molecular formation in a controlled way. In this article, we explore carbon dimer formation and its evolutionary paths in a stagnation layer formed during the interaction of two laser-produced plasmas. Colliding laser produced plasmas are generated by splitting a laser beam into two sub-beams and then focus them into either a single flat (laterally colliding plasmas) or a V-shaped graphite targets (orthogonally colliding plasmas). The C2 formation in the stagnation region of both colliding plasmamore » schemes is investigated using optical spectroscopic means and compared with emission features from single seed plasma. Our results show that the collisions among the plasmas followed by the stagnation layer formation lead to rapid cooling causing enhanced carbon dimer formation. In addition, plasma electron temperature, density and C2 molecular temperature were measured for the stagnation zone and compared with seed plasma.« less

SOLAR HARD X-RAY SOURCE SIZES IN A BEAM-HEATED AND IONIZED CHROMOSPHERE

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Flannagain, Aidan M.; Gallagher, Peter T.; Brown, John C.

2015-02-01

Solar flare hard X-rays (HXRs) are produced as bremsstrahlung when an accelerated population of electrons interacts with the dense chromospheric plasma. HXR observations presented by Kontar et al. using the Ramaty High-Energy Solar Spectroscopic Imager have shown that HXR source sizes are three to six times more extended in height than those predicted by the standard collisional thick target model (CTTM). Several possible explanations have been put forward including the multi-threaded nature of flare loops, pitch-angle scattering, and magnetic mirroring. However, the nonuniform ionization (NUI) structure along the path of the electron beam has not been fully explored as amore » solution to this problem. Ionized plasma is known to be less effective at producing nonthermal bremsstrahlung HXRs when compared to neutral plasma. If the peak HXR emission was produced in a locally ionized region within the chromosphere, the intensity of emission will be preferentially reduced around this peak, resulting in a more extended source. Due to this effect, along with the associated density enhancement in the upper chromosphere, injection of a beam of electrons into a partially ionized plasma should result in an HXR source that is substantially more vertically extended relative to that for a neutral target. Here we present the results of a modification to the CTTM, which takes into account both a localized form of chromospheric NUI and an increased target density. We find 50 keV HXR source widths, with and without the inclusion of a locally ionized region, of ∼3 Mm and ∼0.7 Mm, respectively. This helps to provide a theoretical solution to the currently open question of overly extended HXR sources.« less

Specular Reflectivity and Hot-Electron Generation in High-Contrast Relativistic Laser-Plasma Interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kemp, Gregory Elijah

2013-01-01

Ultra-intense laser (> 1018 W/cm2) interactions with matter are capable of producing relativistic electrons which have a variety of applications in state-of-the-art scientific and medical research conducted at universities and national laboratories across the world. Control of various aspects of these hot-electron distributions is highly desired to optimize a particular outcome. Hot-electron generation in low-contrast interactions, where significant amounts of under-dense pre-plasma are present, can be plagued by highly non-linear relativistic laser-plasma instabilities and quasi-static magnetic field generation, often resulting in less than desirable and predictable electron source characteristics. High-contrast interactions offer more controlled interactions but often at the costmore » of overall lower coupling and increased sensitivity to initial target conditions. An experiment studying the differences in hot-electron generation between high and low-contrast pulse interactions with solid density targets was performed on the Titan laser platform at the Jupiter Laser Facility at Lawrence Livermore National Laboratory in Livermore, CA. To date, these hot-electrons generated in the laboratory are not directly observable at the source of the interaction. Instead, indirect studies are performed using state-of-the-art simulations, constrained by the various experimental measurements. These measurements, more-often-than-not, rely on secondary processes generated by the transport of these electrons through the solid density materials which can susceptible to a variety instabilities and target material/geometry effects. Although often neglected in these types of studies, the specularly reflected light can provide invaluable insight as it is directly influenced by the interaction. In this thesis, I address the use of (personally obtained) experimental specular reflectivity measurements to indirectly study hot-electron generation in the context of high-contrast, relativistic laser-plasma interactions.« less

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Emission of charged particles from the surface of a moving target acted on by cw CO2 laser radiation

NASA Astrophysics Data System (ADS)

Kuznetsov, S. I.; Petrov, A. L.; Shadrin, A. N.

1990-06-01

An experimental investigation was made of the emission of charged particles due to the irradiation of moving steel and graphite targets with cw CO2 laser radiation. The characteristics of the emission current signals were determined for different laser irradiation regimes. The maximum emission current density from the surface of a melt pool ( ~ 1.1 × 10 - 2 A/cm2) and the average temperature of the liquid metal (~ 2040 K) were measured for an incident radiation power density of 550 W and for horizontal and vertical target velocities of respectively ~ 1.5 mm/s and ~ 0.17 mm/s. The authors propose to utilize this phenomenon for monitoring the laser processing of materials.

X-ray opacity measurements in mid-Z dense plasmas with a new target design of indirect heating

NASA Astrophysics Data System (ADS)

Dozières, M.; Thais, F.; Bastiani-Ceccotti, S.; Blenski, T.; Fariaut, J.; Fölsner, W.; Gilleron, F.; Khaghani, D.; Pain, J.-C.; Reverdin, C.; Rosmej, F.; Silvert, V.; Soullié, G.; Villette, B.

2015-12-01

X-ray transmission spectra of copper, nickel and aluminum laser produced plasmas were measured at the LULI2000 laser facility with an improved target design of indirect heating. Measurements were performed in plasmas close to local thermodynamic equilibrium at temperatures around 25 eV and densities between 10-3g/cm3 and 10-2 g/cm3. This improved design provides several advantages, which are discussed in this paper. The sample is a thin foil of mid-Z material inserted between two gold cavities heated by two 300J, 2ω, nanosecond laser beams. A third laser beam irradiates a gold foil to create a spectrally continuous X-ray source (backlight) used to probe the sample. We investigate 2p-3d absorption structures in Ni and Cu plasmas as well as 1s-2p transitions in an additional Al plasma layer to infer the in-situ plasma temperature. Geometric and hydrodynamic calculations indicate that the improved geometry reduces spatial gradients during the transmission measurements. Experimental absorption spectra are in good agreement with calculations from the hybrid atomic physics code SCO-RCG.

Target electron collision effects on energy loss straggling of protons in an electron gas at any degeneracy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barriga-Carrasco, Manuel D.

2008-03-15

The purpose of the present paper is to describe the effects of target electron collisions on proton energy loss straggling in plasmas at any degeneracy. Targets are considered fully ionized so electronic energy loss is only due to the free electrons. The analysis is focused on targets with electronic density around solid values n{sub e}{approx_equal}10{sup 23} cm{sup -3} and with temperature around T{approx_equal}10 eV; these targets are in the limit of weakly coupled electron gases. These types of plasma targets have not been studied extensively, though they are very important for inertial confinement fusion. The energy loss straggling is obtainedmore » from an exact quantum-mechanical evaluation, which takes into account the degeneracy of the target plasma, and later it is compared with common classical and degenerate approximations. Then electron collisions in the exact quantum-mechanical straggling calculation are considered. Now the energy loss straggling is enhanced for energies smaller than the energy before the maximum, then decreases around this maximum, and finally tends to the same values with respect to noncollisional calculation. Differences with the same results but not taking into account these collisions are as far as 17% in the cases analyzed. As an example, proton range distributions have been calculated to show the importance of an accurate energy straggling calculation.« less

Fast Electron Deposition in Laser Shock Compressed Plastic Targets

NASA Astrophysics Data System (ADS)

Hall, T. A.; Ellwi, S.; Batani, D.; Bernardinello, A.; Masella, V.; Koenig, M.; Benuzzi, A.; Krishnan, J.; Pisani, F.; Djaoui, A.; Norreys, P.; Neely, D.; Rose, S.; Key, M. H.; Fews, P.

1998-08-01

We present the first results of fast electron deposition in a laser shock compressed plasma. The interaction of a 3 ps, 15 J laser pulse with solid polyethylene targets is used to produce fast electrons on one side of foil targets and a 2 ns duration laser pulse is used to drive a shock wave into the target from the opposite side. Kα emission from chlorine fluor buried layers is used to measure the electron transport. The hot electron range in the shock compressed plastic is found to be approximately twice as large as the range in the solid density plastic.

Debye sheath mechanism at laser plasma interaction and generalization to nuclear forces and quark-gluon plasma

NASA Astrophysics Data System (ADS)

Osman, Frederick; Ghahramani, Nader; Hora, Heinrich

2005-10-01

The studies of laser ablation have lead to a new theory of nuclei, endothermic nuclei generation, and quark-gluon plasmas. The surface of ablated plasma expanding into vacuum after high power laser irradiation of targets contains an electric double layer having the thickness of the Debye length. This led to the discovery of surface tension in plasmas, and led to the internal dynamic electric fields in all inhomogeneous plasmas. The surface tension causes stabilization by short length surface wave smoothing the expanding plasma plume and to stabilization against the Rayleigh Taylor instability. Generalizing this to the degenerate electrons in a metal with the Fermi energy instead of the temperature resulted in the first quantum theory of surface tension of metals in agreement with measurements. Taking the Fermi energy in the Debye length for nucleons results in a theory of nuclei with stable confinement of protons and neutrons just at the well-known nuclear density, and the Debye lengths equal to the Hofstadter decay of the nuclear surface. Increasing the nuclear density by a factor of 10 leads to a change of the Fermi energy into its relativistic branch where no surface energy is possible and the particle mass is not defined, permitting the quark gluon plasma. Expansion of this higher density at the big bang or in super-nova results in nucleation and element generation. The Boltzmann equilibrium permits the synthesis of nuclei even in the endothermic range, however with the limit to about uranium. A relation for the magic numbers leads to a quark structure of nuclear shells that can be understood as a duality property of nuclei with respect to nucleons and quarks

Optimization of the combined proton acceleration regime with a target composition scheme

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yao, W. P.; Graduate School, China Academy of Engineering Physics, Beijing 100088; Li, B. W., E-mail: li-baiwen@iapcm.ac.cn

A target composition scheme to optimize the combined proton acceleration regime is presented and verified by two-dimensional particle-in-cell simulations by using an ultra-intense circularly polarized (CP) laser pulse irradiating an overdense hydrocarbon (CH) target, instead of a pure hydrogen (H) one. The combined acceleration regime is a two-stage proton acceleration scheme combining the radiation pressure dominated acceleration (RPDA) stage and the laser wakefield acceleration (LWFA) stage sequentially together. Protons get pre-accelerated in the first stage when an ultra-intense CP laser pulse irradiating an overdense CH target. The wakefield is driven by the laser pulse after penetrating through the overdense CHmore » target and propagating in the underdense tritium plasma gas. With the pre-accelerate stage, protons can now get trapped in the wakefield and accelerated to much higher energy by LWFA. Finally, protons with higher energies (from about 20 GeV up to about 30 GeV) and lower energy spreads (from about 18% down to about 5% in full-width at half-maximum, or FWHM) are generated, as compared to the use of a pure H target. It is because protons can be more stably pre-accelerated in the first RPDA stage when using CH targets. With the increase of the carbon-to-hydrogen density ratio, the energy spread is lower and the maximum proton energy is higher. It also shows that for the same laser intensity around 10{sup 22} W cm{sup −2}, using the CH target will lead to a higher proton energy, as compared to the use of a pure H target. Additionally, proton energy can be further increased by employing a longitudinally negative gradient of a background plasma density.« less

Plasma diagnostic development and UHV testing for the ALPHA collaboration at Marquette University

NASA Astrophysics Data System (ADS)

Tharp, T. D.; Alpha Collaboration

2017-10-01

At Marquette, we are developing the next generation of nonneutral plasma diagnostics for the ALPHA experiment at CERN. ALPHA is building a new vertical experiment to test the gravitational interaction of antihydrogen with Earth. This expansion requires significant changes to the design of our plasma diagnostic suites: the next generation of tools must be able to measure plasmas from two directions, and must be capable of operating in a horizontal position. The diagnostic suite includes measurements of plasma density, shape, and temperature. The hardware used includes a MicroChannel Plate (MCP), a Faraday Cup, and an electron gun. In addition, we are building a vacuum chamber to test the viability of 3-d printed components for UHV compatibility, with target pressures of 10-10 mbar.

Demonstration of multi-generational growth of tungsten nanoparticles in hydrogen plasma using in situ laser extinction method

NASA Astrophysics Data System (ADS)

Ouaras, K.; Lombardi, G.; Hassouni, K.

2018-03-01

For the first time, we demonstrate that tungsten (W) nanoparticles (NPs) are created when a tungsten target is exposed to low-pressure, high density hydrogen plasma. The plasma was generated using a novel dual plasma system combining a microwave discharge and a pulsed direct-current (DC) discharge. The tungsten surface originates in the multi-generational formation of a significant population of 30-70 nm diameter particles when the W cathode is biased at ~  -1 kV and submitted to ~1020 m2 s-1 H+/H2+ /H3+ ions flux. The evidenced NPs formation should be taking into account as one of the consequence of the plasma surface interaction outcomes, especially for fusion applications.

Shell stability and conditions analyzed using a new method of extracting shell areal density maps from spectrally resolved images of direct-drive inertial confinement fusion implosions

DOE PAGES

Johns, H. M.; Mancini, R. C.; Nagayama, T.; ...

2016-01-25

In warm target direct-drive inertial confinement fusion implosion experiments performed at the OMEGA laser facility, plastic micro-balloons doped with a titanium tracer layer in the shell and filled with deuterium gas were imploded using a low-adiabat shaped laser pulse. Continuum radiation emitted in the core is transmitted through the tracer layer and the resulting spectrum recorded with a gated multi-monochromatic x-ray imager (MMI). Titanium K-shell line absorption spectra observed in the data are due to transitions in L-shell titanium ions driven by the backlighting continuum. The MMI data consist of an array of spectrally resolved images of the implosion. Thesemore » 2-D space-resolved titanium spectral features constrain the plasma conditions and areal density of the titanium doped region of the shell. The MMI data were processed to obtain narrow-band images and space resolved spectra of titanium spectral features. Shell areal density maps, ρL(x,y), extracted using a new method using both narrow-band images and space resolved spectra are confirmed to be consistent within uncertainties. We report plasma conditions in the titanium-doped region of electron temperature (Te) = 400 ± 28 eV, electron number density (N e) = 8.5 × 10 24 ± 2.5 × 10 24 cm –3, and average areal density = 86 ± 7 mg/cm 2. Fourier analysis of areal density maps reveals shell modulations caused by hydrodynamic instability growth near the fuel-shell interface in the deceleration phase. We observe significant structure in modes l = 2–9, dominated by l = 2. We extract a target breakup fraction of 7.1 ± 1.5% from our Fourier analysis. Furthermore, a new method for estimating mix width is evaluated against existing literature and our target breakup fraction. We estimate a mix width of 10.5 ±1 μm.« less

Characterization of high flux magnetized helium plasma in SCU-PSI linear device

NASA Astrophysics Data System (ADS)

Xiaochun, MA; Xiaogang, CAO; Lei, HAN; Zhiyan, ZHANG; Jianjun, WEI; Fujun, GOU

2018-02-01

A high-flux linear plasma device in Sichuan University plasma-surface interaction (SCU-PSI) based on a cascaded arc source has been established to simulate the interactions between helium and hydrogen plasma with the plasma-facing components in fusion reactors. In this paper, the helium plasma has been characterized by a double-pin Langmuir probe. The results show that the stable helium plasma beam with a diameter of 26 mm was constrained very well at a magnetic field strength of 0.3 T. The core density and ion flux of helium plasma have a strong dependence on the applied current, magnetic field strength and gas flow rate. It could reach an electron density of 1.2 × 1019 m-3 and helium ion flux of 3.2 × 1022 m-2 s-1, with a gas flow rate of 4 standard liter per minute, magnetic field strength of 0.2 T and input power of 11 kW. With the addition of -80 V applied to the target to increase the helium ion energy and the exposure time of 2 h, the flat top temperature reached about 530 °C. The different sizes of nanostructured fuzz on irradiated tungsten and molybdenum samples surfaces under the bombardment of helium ions were observed by scanning electron microscopy. These results measured in the SCU-PSI linear device provide a reference for International Thermonuclear Experimental Reactor related PSI research.

Interaction physics of multipicosecond Petawatt laser pulses with overdense plasma.

PubMed

Kemp, A J; Divol, L

2012-11-09

We study the interaction of intense petawatt laser pulses with overdense plasma over several picoseconds, using two- and three-dimensional kinetic particle simulations. Sustained irradiation with non-diffraction-limited pulses at relativistic intensities yields conditions that differ qualitatively from what is experimentally available today. Nonlinear saturation of laser-driven density perturbations at the target surface causes recurrent emissions of plasma, which stabilize the surface and keep absorption continuously high. This dynamics leads to the acceleration of three distinct groups of electrons up to energies many times the laser ponderomotive potential. We discuss their energy distribution for applications like the fast-ignition approach to inertial confinement fusion.

Genetics of Lipid and Lipoprotein Disorders and Traits.

PubMed

Dron, Jacqueline S; Hegele, Robert A

2016-01-01

Plasma lipids, namely cholesterol and triglyceride, and lipoproteins, such as low-density lipoprotein (LDL) and high-density lipoprotein, serve numerous physiological roles. Perturbed levels of these traits underlie monogenic dyslipidemias, a diverse group of multisystem disorders. We are on the verge of having a relatively complete picture of the human dyslipidemias and their components. Recent advances in genetics of plasma lipids and lipoproteins include the following: (1) expanding the range of genes causing monogenic dyslipidemias, particularly elevated LDL cholesterol; (2) appreciating the role of polygenic effects in such traits as familial hypercholesterolemia and combined hyperlipidemia; (3) accumulating a list of common variants that determine plasma lipids and lipoproteins; (4) applying exome sequencing to identify collections of rare variants determining plasma lipids and lipoproteins that via Mendelian randomization have also implicated gene products such as NPC1L1 , APOC3 , LDLR , APOA5 , and ANGPTL4 as causal for atherosclerotic cardiovascular disease; and (5) using naturally occurring genetic variation to identify new drug targets, including inhibitors of apolipoprotein (apo) C-III, apo(a), ANGPTL3, and ANGPTL4. Here, we compile this disparate range of data linking human genetic variation to plasma lipids and lipoproteins, providing a "one stop shop" for the interested reader.

Inductively Coupled Plasma and Electron Cyclotron Resonance Plasma Etching of InGaAlP Compound Semiconductor System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abernathy, C.R.; Hobson, W.S.; Hong, J.

1998-11-04

Current and future generations of sophisticated compound semiconductor devices require the ability for submicron scale patterning. The situation is being complicated since some of the new devices are based on a wider diversity of materials to be etched. Conventional IUE (Reactive Ion Etching) has been prevalent across the industry so far, but has limitations for materials with high bond strengths or multiple elements. IrI this paper, we suggest high density plasmas such as ECR (Electron Cyclotron Resonance) and ICP (Inductively Coupled Plasma), for the etching of ternary compound semiconductors (InGaP, AIInP, AlGaP) which are employed for electronic devices like heterojunctionmore » bipolar transistors (HBTs) or high electron mobility transistors (HEMTs), and photonic devices such as light-emitting diodes (LEDs) and lasers. High density plasma sources, opeiating at lower pressure, are expected to meet target goals determined in terms of etch rate, surface morphology, surface stoichiometry, selectivity, etc. The etching mechanisms, which are described in this paper, can also be applied to other III-V (GaAs-based, InP-based) as well as III-Nitride since the InGaAIP system shares many of the same properties.« less

Ion flux enhancements and oscillations in spatially confined laser produced aluminum plasmas

NASA Astrophysics Data System (ADS)

Singh, S. C.; Fallon, C.; Hayden, P.; Mujawar, M.; Yeates, P.; Costello, J. T.

2014-09-01

Ion signals from laser produced plasmas (LPPs) generated inside aluminum rectangular cavities at a fixed depth d = 2 mm and varying width, x = 1.0, 1.6, and 2.75 mm were obtained by spatially varying the position of a negatively biased Langmuir probe. Damped oscillatory features superimposed on Maxwellian distributed ion signals were observed. Depending on the distance of the probe from the target surface, three to twelve fold enhancements in peak ion density were observed via confinement of the LPP, generated within rectangular cavities of varying width which constrained the plasma plume to near one dimensional expansion in the vertical plane. The effects of lateral spatial confinement on the expansion velocity of the LPP plume front, the temperature, density and expansion velocity of ions, enhancement of ion flux, and ion energy distribution were recorded. The periodic behavior of ion signals was analyzed and found to be related to the electron plasma frequency and electron-ion collision frequency. The effects of confinement and enhancement of various ion parameters and expansion velocities of the LPP ion plume are explained on the basis of shock wave theory.

Evaluation of heat and particle controllability on the JT-60SA divertor

NASA Astrophysics Data System (ADS)

Kawashima, H.; Hoshino, K.; Shimizu, K.; Takizuka, T.; Ide, S.; Sakurai, S.; Asakura, N.

2011-08-01

The JT-60SA divertor design has been established on the basis of engineering requirements and physics analysis. Heat and particle fluxes under the full input power of 41 MW can give severe heat loads on the divertor targets, while the allowable heat load is limited below 15 MW/m2. Dependence of the heat flux mitigation on a D2 gas-puff is evaluated by SONIC simulations for high density (ne_ave ˜ 1 × 1020 m-3) high current plasmas. It is found that the peak heat load 10 MW/m2 with dense (ned > 4 × 1020 m-3) and cold (Ted, Tid ⩽ 1 eV) divertor plasmas are obtained at a moderate gas-puff of Γpuff = 15 × 1021 s-1. Divertor plasmas are controlled from attached to detached condition using the divertor pump with pumping-speed below 100 m3/s. In full non-inductive current drive plasmas with low density (ne_ave ˜ 5 × 1019 m-3), the reduction of divertor heat load is achieved with the Ar injection.

Low-energy plasma focus device as an electron beam source.

PubMed

Khan, Muhammad Zubair; Ling, Yap Seong; Yaqoob, Ibrar; Kumar, Nitturi Naresh; Kuang, Lim Lian; San, Wong Chiow

2014-01-01

A low-energy plasma focus device was used as an electron beam source. A technique was developed to simultaneously measure the electron beam intensity and energy. The system was operated in Argon filling at an optimum pressure of 1.7 mbar. A Faraday cup was used together with an array of filtered PIN diodes. The beam-target X-rays were registered through X-ray spectrometry. Copper and lead line radiations were registered upon usage as targets. The maximum electron beam charge and density were estimated to be 0.31 μC and 13.5 × 10(16)/m(3), respectively. The average energy of the electron beam was 500 keV. The high flux of the electron beam can be potentially applicable in material sciences.

Interaction of cw CO2 laser radiation with plasma near-metallic substrate surface

NASA Astrophysics Data System (ADS)

Azharonok, V. V.; Astapchik, S. A.; Zabelin, Alexandre M.; Golubev, Vladimir S.; Golubev, V. S.; Grezev, A. N.; Filatov, Igor V.; Chubrik, N. I.; Shimanovich, V. D.

2000-07-01

Optical and spectroscopic methods were used in studying near-surface plasma that is formed under the effect CW CO2 laser of (2- 5)x106W/cm2 power density upon stainless steel in He and Ar shielding gases. The variation of plume spatial structure with time has been studied, the outflow of gas-vapor jets from the interaction area has been characterized. The spectra of plasma plume pulsations have been obtained for the frequency range Δf = 0-1 MHz. The temperature and electron concentration of plasma plume have been found under radiation effect upon the target of stainless steel. Consideration has been given to the most probable mechanisms of CW laser radiation-metal non-stationary interaction.

Spatial measurement in rotating magnetic field plasma acceleration method by using two-dimensional scanning instrument and thrust stand

NASA Astrophysics Data System (ADS)

Furukawa, T.; Takizawa, K.; Yano, K.; Kuwahara, D.; Shinohara, S.

2018-04-01

A two-dimensional scanning probe instrument has been developed to survey spatial plasma characteristics in our electrodeless plasma acceleration schemes. In particular, diagnostics of plasma parameters, e.g., plasma density, temperature, velocity, and excited magnetic field, are essential for elucidating physical phenomena since we have been concentrating on next generation plasma propulsion methods, e.g., Rotating Magnetic Field plasma acceleration method, by characterizing the plasma performance. Moreover, in order to estimate the thrust performance in our experimental scheme, we have also mounted a thrust stand, which has a target type, on this movable instrument, and scanned the axial profile of the thrust performance in the presence of the external magnetic field generated by using permanent magnets, so as to investigate the plasma captured in a stand area, considering the divergent field lines in the downstream region of a generation antenna. In this paper, we will introduce the novel measurement instrument and describe how to measure these parameters.

Theoretical models of non-Maxwellian equilibria for one-dimensional collisionless plasmas

NASA Astrophysics Data System (ADS)

Allanson, O.; Neukirch, T.; Wilson, F.; Troscheit, S.

2016-12-01

It is ideal to use exact equilibrium solutions of the steady state Vlasov-Maxwell system to intialise collsionless simulations. However, exact equilibrium distribution functions (DFs) for a given macroscopic configuration are typically unknown, and it is common to resort to using `flow-shifted' Maxwellian DFs in their stead. These DFs may be consistent with a macrosopic system with the target number density and current density, but could well have inaccurate higher order moments. We present recent theoretical work on the `inverse problem in Vlasov-Maxwell equilibria', namely calculating an exact solution of the Vlasov equation for a specific given magnetic field. In particular, we focus on one-dimensional geometries in Cartesian (current sheets) coordinates.1. From 1D fields to Vlasov equilibria: Theory and application of Hermite Polynomials: (O. Allanson, T. Neukirch, S. Troscheit and F. Wilson, Journal of Plasma Physics, 82, 905820306 (2016) [28 pages, Open Access] )2. An exact collisionless equilibrium for the Force-Free Harris Sheet with low plasma beta: (O. Allanson, T. Neukirch, F. Wilson and S. Troscheit, Physics of Plasmas, 22, 102116 (2015) [11 pages, Open Access])3. Neutral and non-neutral collisionless plasma equilibria for twisted flux tubes: The Gold-Hoyle model in a background field (O. Allanson, F. Wilson and T. Neukirch, (2016)) (accepted, Physics of Plasmas)

Measurements of the K -Shell Opacity of a Solid-Density Magnesium Plasma Heated by an X-Ray Free-Electron Laser

DOE PAGES

Preston, T. R.; Vinko, S. M.; Ciricosta, O.; ...

2017-08-25

We present measurements of the spectrally resolved x rays emitted from solid-density magnesium targets of varying sub-μm thicknesses isochorically heated by an x-ray laser. The data exhibit a largely thickness independent source function, allowing the extraction of a measure of the opacity to K-shell x rays within well-defined regimes of electron density and temperature, extremely close to local thermodynamic equilibrium conditions. The deduced opacities at the peak of the Kα transitions of the ions are consistent with those predicted by detailed atomic-kinetics calculations.

Detailed characterization of laser-produced astrophysically-relevant jets formed via a poloidal magnetic nozzle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Higginson, D. P.; Revet, G.; Khiar, B.

We report that the collimation of astrophysically-relevant plasma ejecta in the form of narrow jets via a poloidal magnetic field is studied experimentally by irradiating a target situated in a 20 T axial magnetic field with a 40 J, 0.6 ns, 0.7 mm diameter, high-power laser. The dynamics of the plasma shaping by the magnetic field are studied over 70 ns and up to 20 mm from the source by diagnosing the electron density, temperature and optical self-emission. These show that the initial expansion of the plasma is highly magnetized, which leads to the formation of a cavity structure whenmore » the kinetic plasma pressure compresses the magnetic field, resulting in an oblique shock [A. Ciardi et al., Phys. Rev. Lett. 110, 025002 (2013)]. The resulting poloidal magnetic nozzle collimates the plasma into a narrow jet [B. Albertazzi et al., Science 346, 325 (2014)]. At distances far from the target, the jet is only marginally magnetized and maintains a high aspect ratio due to its high Mach-number (M~20) and not due to external magnetic pressure. The formation of the jet is evaluated over a range of laser intensities (10 12–10 13 W/cm 2), target materials and orientations of the magnetic field. Lastly, plasma cavity formation is observed in all cases and the viability of long-range jet formation is found to be dependent on the orientation of the magnetic field.« less

Detailed characterization of laser-produced astrophysically-relevant jets formed via a poloidal magnetic nozzle

DOE PAGES

Higginson, D. P.; Revet, G.; Khiar, B.; ...

2017-02-24

We report that the collimation of astrophysically-relevant plasma ejecta in the form of narrow jets via a poloidal magnetic field is studied experimentally by irradiating a target situated in a 20 T axial magnetic field with a 40 J, 0.6 ns, 0.7 mm diameter, high-power laser. The dynamics of the plasma shaping by the magnetic field are studied over 70 ns and up to 20 mm from the source by diagnosing the electron density, temperature and optical self-emission. These show that the initial expansion of the plasma is highly magnetized, which leads to the formation of a cavity structure whenmore » the kinetic plasma pressure compresses the magnetic field, resulting in an oblique shock [A. Ciardi et al., Phys. Rev. Lett. 110, 025002 (2013)]. The resulting poloidal magnetic nozzle collimates the plasma into a narrow jet [B. Albertazzi et al., Science 346, 325 (2014)]. At distances far from the target, the jet is only marginally magnetized and maintains a high aspect ratio due to its high Mach-number (M~20) and not due to external magnetic pressure. The formation of the jet is evaluated over a range of laser intensities (10 12–10 13 W/cm 2), target materials and orientations of the magnetic field. Lastly, plasma cavity formation is observed in all cases and the viability of long-range jet formation is found to be dependent on the orientation of the magnetic field.« less

Determining energy balance in the flaring chromosphere from oxygen V line ratios

NASA Astrophysics Data System (ADS)

Graham, D. R.; Fletcher, L.; Labrosse, N.

2015-12-01

Context. The impulsive phase of solar flares is a time of rapid energy deposition and heating in the lower solar atmosphere, leading to changes in the temperature and density structure of the region. Aims: We use an O v density diagnostic formed from the λ192 /λ248 line ratio, provided by the Hinode/EIS instrument, to determine the density of flare footpoint plasma at O v formation temperatures of ~2.5 × 105 K, giving a constraint on the properties of the heated transition region. Methods: Hinode/EIS rasters from 2 small flare events in December 2007 were used. Raster images were co-aligned to identify and establish the footpoint pixels, multiple-component Gaussian line fitting of the spectra was carried out to isolate the density diagnostic pair, and the density was calculated for several footpoint areas. The assumptions of equilibrium ionisation and optically-thin radiation for the O v lines used were assessed and found to be acceptable. For one of the events, properties of the electron distribution were deduced from earlier RHESSI hard X-ray observations. These were used to calculate the plasma heating rate delivered by an electron beam for 2 semi-empirical atmospheres under collisional thick-target assumptions. The radiative loss rate for this plasma was also calculated for comparison with possible energy input mechanisms. Results: Electron number densities of up to 1011.9 cm-3 were measured during the flare impulsive phase using the O v λ192 /λ248 diagnostic ratio. The heating rate delivered by an electron beam was found to exceed the radiative losses at this density, corresponding to a height of 450 km, and when assuming a completely ionised target atmosphere far exceed the losses but at a height of 1450-1600 km. A chromospheric thickness of 70-700 km was found to be required to balance a conductive input to the O v-emitting region with radiative losses. Conclusions: Electron densities have been observed in footpoint sources at transition region temperatures, comparable to previous results but with improved spatial information. The observed densities can be explained by heating of the chromosphere by collisional electrons, with O v formed at heights of 450-1600 km above the photosphere, depending on the atmospheric ionisation fraction.

Electromagnetic pulse (EMP) radiation by laser interaction with a solid H2 ribbon

NASA Astrophysics Data System (ADS)

De Marco, M.; Krása, J.; Cikhardt, J.; Velyhan, A.; Pfeifer, M.; Dudžák, R.; Dostál, J.; Krouský, E.; Limpouch, J.; Pisarczyk, T.; Kalinowska, Z.; Chodukowski, T.; Ullschmied, J.; Giuffrida, L.; Chatain, D.; Perin, J.-P.; Margarone, D.

2017-08-01

The electromagnetic pulses (EMPs) generated during the interaction of a focused 1.315-μm sub-nanosecond laser pulse with a solid hydrogen ribbon were measured. The strength and temporal characteristics of EMPs were found to be dependent on the target density. If a low density target is ionized during the interaction with the laser, and the plasma does not physically touch the target holder, the EMP is weaker in strength and shorter in time duration. It is shown that during the H2 target experiment, the EMP does not strongly affect the response of fast electronic devices. The measurements of the EMP were carried out by Rohde&Schwarz B-Probes, particularly sensitive in the frequency range from 30 MHz and 1 GHz. Numerical simulations of resonant frequencies of the target chamber used in the experiment at the Prague Asterix Laser System kJ-class laser facility elucidate the peaked structure of EMP frequency spectra in the GHz domain.

Atmospheric electromagnetic pulse propagation effects from thick targets in a terawatt laser target chamber.

PubMed

Remo, John L; Adams, Richard G; Jones, Michael C

2007-08-20

Generation and effects of atmospherically propagated electromagnetic pulses (EMPs) initiated by photoelectrons ejected by the high density and temperature target surface plasmas from multiterawatt laser pulses are analyzed. These laser radiation pulse interactions can significantly increase noise levels, thereby obscuring data (sometimes totally) and may even damage sensitive probe and detection instrumentation. Noise effects from high energy density (approximately multiterawatt) laser pulses (approximately 300-400 ps pulse widths) interacting with thick approximately 1 mm) metallic and dielectric solid targets and dielectric-metallic powder mixtures are interpreted as transient resonance radiation associated with surface charge fluctuations on the target chamber that functions as a radiating antenna. Effective solutions that minimize atmospheric EMP effects on internal and proximate electronic and electro-optical equipment external to the system based on systematic measurements using Moebius loop antennas, interpretations of signal periodicities, and dissipation indicators determining transient noise origin characteristics from target emissions are described. Analytic models for the effect of target chamber resonances and associated noise current and temperature in a probe diode laser are described.

Atmospheric electromagnetic pulse propagation effects from thick targets in a terawatt laser target chamber

NASA Astrophysics Data System (ADS)

Remo, John L.; Adams, Richard G.; Jones, Michael C.

2007-08-01

Generation and effects of atmospherically propagated electromagnetic pulses (EMPs) initiated by photoelectrons ejected by the high density and temperature target surface plasmas from multiterawatt laser pulses are analyzed. These laser radiation pulse interactions can significantly increase noise levels, thereby obscuring data (sometimes totally) and may even damage sensitive probe and detection instrumentation. Noise effects from high energy density (approximately multiterawatt) laser pulses (˜300-400 ps pulse widths) interacting with thick (˜1 mm) metallic and dielectric solid targets and dielectric-metallic powder mixtures are interpreted as transient resonance radiation associated with surface charge fluctuations on the target chamber that functions as a radiating antenna. Effective solutions that minimize atmospheric EMP effects on internal and proximate electronic and electro-optical equipment external to the system based on systematic measurements using Moebius loop antennas, interpretations of signal periodicities, and dissipation indicators determining transient noise origin characteristics from target emissions are described. Analytic models for the effect of target chamber resonances and associated noise current and temperature in a probe diode laser are described.

Atmospheric electromagnetic pulse propagation effects from thick targets in a terawatt laser target chamber

DOE PAGES

Remo, John L.; Adams, Richard G.; Jones, Michael C.

2007-08-16

Generation and effects of atmospherically propagated electromagnetic pulses (EMPs) initiated by photoelectrons ejected by the high density and temperature target surface plasmas from multiterawatt laser pulses are analyzed. These laser radiation pulse interactions can significantly increase noise levels, thereby obscuring data (sometimes totally) and may even damage sensitive probe and detection instrumentation. Noise effects from high energy density (approximately multiterawatt) laser pulses (~300–400 ps pulse widths) interacting with thick (~1 mm) metallic and dielectric solid targets and dielectric–metallic powder mixtures are interpreted as transient resonance radiation associated with surface charge fluctuations on the target chamber that functions as a radiatingmore » antenna. Effective solutions that minimize atmospheric EMP effects on internal and proximate electronic and electro-optical equipment external to the system based on systematic measurements using Moebius loop antennas, interpretations of signal periodicities, and dissipation indicators determining transient noise origin characteristics from target emissions are described. Analytic models for the effect of target chamber resonances and associated noise current and temperature in a probe diode laser are described.« less

Plasma measurement by optical visualization and triple probe method under high-speed impact

NASA Astrophysics Data System (ADS)

Sakai, T.; Umeda, K.; Kinoshita, S.; Watanabe, K.

2017-02-01

High-speed impact on spacecraft by space debris poses a threat. When a high-speed projectile collides with target, it is conceivable that the heat created by impact causes severe damage at impact point. Investigation of the temperature is necessary for elucidation of high-speed impact phenomena. However, it is very difficult to measure the temperature with standard methods for two main reasons. One reason is that a thermometer placed on the target is instantaneously destroyed upon impact. The other reason is that there is not enough time resolution to measure the transient temperature changes. In this study, the measurement of plasma induced by high-speed impact was investigated to estimate temperature changes near the impact point. High-speed impact experiments were performed with a vertical gas gun. The projectile speed was approximately 700 m/s, and the target material was A5052. The experimental data to calculate the plasma parameters of electron temperature and electron density were measured by triple probe method. In addition, the diffusion behavior of plasma was observed by optical visualization technique using high-speed camera. The frame rate and the exposure time were 260 kfps and 1.0 μs, respectively. These images are considered to be one proof to show the validity of plasma measurement. The experimental results showed that plasma signals were detected for around 70 μs, and the rising phase of the wave form was in good agreement with timing of optical visualization image when the plasma arrived at the tip of triple probe.

ECR Plasma Source for Heavy Ion Beam Charge Neutralization

NASA Astrophysics Data System (ADS)

Efthimion, P. C.; Gilson, E.; Grisham, L.; Davidson, R. C.; Yu, S.; Logan, B. G.

2002-11-01

Highly ionized plasmas are being considered as a medium for charge neutralizing heavy ion beams in order to focus beyond the space-charge limit. Calculations suggest that plasma at a density of 1 - 100 times the ion beam density and at a length ˜ 0.1-0.5 m would be suitable for achieving a high level of charge neutralization. An ECR source has been built at the Princeton Plasma Physics Laboratory (PPPL) to support a joint Neutralized Transport Experiment (NTX) at the Lawrence Berkeley National Laboratory (LBNL) to study ion beam neutralization with plasma. The ECR source operates at 13.6 MHz and with solenoid magnetic fields of 1-10 gauss. The goal is to operate the source at pressures ˜ 10-5 Torr at full ionization. The initial operation of the source has been at pressures of 10-4 - 10-1 Torr. Electron densities in the range of 10^8 - 10^11 cm-3 have been achieved. Low-pressure operation is important to reduce ion beam ionization. A cusp magnetic field has been installed to improve radial confinement and reduce the field strength on the beam axis. In addition, axial confinement is believed to be important to achieve lower-pressure operation. At moderate pressures (> 1 mTorr) the wave damping is collisional, and at low pressures (< 1 mTorr) there is a distinct electron cyclotron resonance. The source has recently been configured to operate with 2.45 GHz microwaves with similar results. At the present operating range the source can simulate the plasma produced by photo-ionization in the target chamber.

Advanced Thomson scattering system for high-flux linear plasma generator.

PubMed

van der Meiden, H J; Lof, A R; van den Berg, M A; Brons, S; Donné, A J H; van Eck, H J N; Koelman, P M J; Koppers, W R; Kruijt, O G; Naumenko, N N; Oyevaar, T; Prins, P R; Rapp, J; Scholten, J; Schram, D C; Smeets, P H M; van der Star, G; Tugarinov, S N; Zeijlmans van Emmichoven, P A

2012-12-01

An advanced Thomson scattering system has been built for a linear plasma generator for plasma surface interaction studies. The Thomson scattering system is based on a Nd:YAG laser operating at the second harmonic and a detection branch featuring a high etendue (f/3) transmission grating spectrometer equipped with an intensified charged coupled device camera. The system is able to measure electron density (n(e)) and temperature (T(e)) profiles close to the output of the plasma source and, at a distance of 1.25 m, just in front of a target. The detection system enables to measure 50 spatial channels of about 2 mm each, along a laser chord of 95 mm. By summing a total of 30 laser pulses (0.6 J, 10 Hz), an observational error of 3% in n(e) and 6% in T(e) (at n(e) = 9.4 × 10(18) m(-3)) can be obtained. Single pulse Thomson scattering measurements can be performed with the same accuracy for n(e) > 2.8 × 10(20) m(-3). The minimum measurable density and temperature are n(e) < 1 × 10(17) m(-3) and T(e) < 0.07 eV, respectively. In addition, using the Rayleigh peak, superimposed on the Thomson scattered spectrum, the neutral density (n(0)) of the plasma can be measured with an accuracy of 25% (at n(0) = 1 × 10(20) m(-3)). In this report, the performance of the Thomson scattering system will be shown along with unprecedented accurate Thomson-Rayleigh scattering measurements on a low-temperature argon plasma expansion into a low-pressure background.

The appearance and propagation of filaments in the private flux region in Mega Amp Spherical Tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harrison, J. R.; Fishpool, G. M.; Thornton, A. J.

2015-09-15

The transport of particles via intermittent filamentary structures in the private flux region (PFR) of plasmas in the MAST tokamak has been investigated using a fast framing camera recording visible light emission from the volume of the lower divertor, as well as Langmuir probes and IR thermography monitoring particle and power fluxes to plasma-facing surfaces in the divertor. The visible camera data suggest that, in the divertor volume, fluctuations in light emission above the X-point are strongest in the scrape-off layer (SOL). Conversely, in the region below the X-point, it is found that these fluctuations are strongest in the PFRmore » of the inner divertor leg. Detailed analysis of the appearance of these filaments in the camera data suggests that they are approximately circular, around 1–2 cm in diameter, but appear more elongated near the divertor target. The most probable toroidal quasi-mode number is between 2 and 3. These filaments eject plasma deeper into the private flux region, sometimes by the production of secondary filaments, moving at a speed of 0.5–1.0 km/s. Probe measurements at the inner divertor target suggest that the fluctuations in the particle flux to the inner target are strongest in the private flux region, and that the amplitude and distribution of these fluctuations are insensitive to the electron density of the core plasma, auxiliary heating and whether the plasma is single-null or double-null. It is found that the e-folding width of the time-average particle flux in the PFR decreases with increasing plasma current, but the fluctuations appear to be unaffected. At the outer divertor target, the fluctuations in particle and power fluxes are strongest in the SOL.« less

Experiments on the interaction of heavy ions with dense plasma at GSI-Darmstadt

NASA Astrophysics Data System (ADS)

Stöckl, C.; Boine-Frankenheim, O.; Geißel, M.; Roth, M.; Wetzler, H.; Seelig, W.; Iwase, O.; Spiller, P.; Bock, R.; Süß, W.; Hoffmann, D. H. H.

One of the main objectives of the experimental plasma physics activities at the Gesellschaft für Schwerionenforschung (GSI) are the interaction processes of heavy ions with dense ionized matter. Gas-discharge plasma targets were used for energy loss and charge state measurements in a regime of electron density and temperature up to 10 19 cm -3 and 20 eV, respectively. An improved model of the charge exchange processes in fully ionized hydrogen plasma, taking into account multiple excited electronic configurations which subsequently ionize, has removed the discrepancies of previous theoretical descriptions. The energy loss of the ion beam in partially ionized plasmas such as argon was found to agree very well with our simple theoretical model based on the modified Bethe-Bloch theory. A new setup with a 100 J/5 GW Nd-glass laser now provides access to density ranges up to 10 21 cm -3 and temperatures of up to 100 eV. First results of interaction experiments with laser-produced plasma are presented. To fully exploit the experimental possibilities of the new laser-plasma setup both improved charge state detection systems and better plasma diagnostics are indispensable. Present developments and future possibilities in these fields are presented. This paper summarizes the following contributions: Interaction of heavy-ion beams with laser plasma by C. Stöckl et al. Energy Loss of Heavy Ions in a laser-produced plasma by M. Roth et al. Charge state measurements of heavy ions passing a laser produced plasma with high time resolution by W. Süß et al. Plasma diagnostics for laser-produced plasma by O. Iwase et al. Future possibilities of plasma diagnostics at GSI by M. Geißel et al.

Spatial confinement effects on spectroscopic and morphological studies of nanosecond laser-ablated Zirconium

NASA Astrophysics Data System (ADS)

Hayat, Asma; Bashir, Shazia; Rafique, Muhammad Shahid; Ahmad, Riaz; Akram, Mahreen; Mahmood, Khaliq; Zaheer, Ali

2017-12-01

Spatial confinement effects on plasma parameters and surface morphology of laser ablated Zr (Zirconium) are studied by introducing a metallic blocker. Nd:YAG laser at various fluencies ranging from 8 J cm-2 to 32 J cm-2 was employed as an irradiation source. All measurements were performed in the presence of Ar under different pressures. Confinement effects offered by metallic blocker are investigated by placing the blocker at different distances of 6 mm, 8 mm and 10 mm from the target surface. It is revealed from LIBS analysis that both plasma parameters i.e. excitation temperature and electron number density increase with increasing laser fluence due to enhancement in energy deposition. It is also observed that spatial confinement offered by metallic blocker is responsible for the enhancement of both electron temperature and electron number density of Zr plasma. This is true for all laser fluences and pressures of Ar. Maximum values of electron temperature and electron number density without blocker are 12,600 K and 14 × 1017 cm-3 respectively whereas, these values are enhanced to 15,000 K and 21 × 1017 cm-3 in the presence of blocker. The physical mechanisms responsible for the enhancement of Zr plasma parameters are plasma compression, confinement and pronounced collisional excitations due to reflection of shock waves. Scanning Electron Microscope (SEM) analysis was performed to explore the surface morphology of laser ablated Zr. It reveals the formation of cones, cavities and ripples. These features become more distinct and well defined in the presence of blocker due to plasma confinement. The optimum combination of blocker distance, fluence and Ar pressure can identify the suitable conditions for defining the role of plasma parameters for surface structuring.

Converging shock wave focusing and interaction with a target

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nitishinskiy, M.; Efimov, S.; Antonov, O.

2016-04-15

Converging shock waves in liquids can be used efficiently in the research of the extreme state of matter and in various applications. In this paper, the recent results related to the interaction of a shock wave with plasma preliminarily formed in the vicinity of the shock wave convergence are presented. The shock wave is produced by the underwater electrical explosion of a spherical wire array. The plasma is generated prior to the shock wave's arrival by a low-pressure gas discharge inside a quartz capillary placed at the equatorial plane of the array. Analysis of the Stark broadening of H{sub α}more » and H{sub β} spectral lines and line-to-continuum ratio, combined with the ratio of the relative intensities of carbon C III/C II and silicon Si III/Si II lines, were used to determine the plasma density and temperature evolution. It was found that during the first ∼200 ns with respect to the beginning of the plasma compression by the shock wave and when the spectral lines are resolved, the plasma density increases from 2 × 10{sup 17 }cm{sup −3} to 5 × 10{sup 17 }cm{sup −3}, while the temperature remains at the same value of 3–4 eV. Further, following the model of an adiabatically imploding capillary, the plasma density increases >10{sup 19 }cm{sup −3}, leading to the continuum spectra obtained experimentally, and the plasma temperature >30 eV at radii of compression of ≤20 μm. The data obtained indicate that the shock wave generated by the underwater electrical explosion of a spherical wire array retains its uniformity during the main part of its convergence.« less

Neutron angular distribution in a plasma focus obtained using nuclear track detectors.

PubMed

Castillo-Mejía, F; Herrera, J J E; Rangel, J; Golzarri, J I; Espinosa, G

2002-01-01

The dense plasma focus (DPF) is a coaxial plasma gun in which a high-density, high-temperature plasma is obtained in a focused column for a few nanoseconds. When the filling gas is deuterium, neutrons can be obtained from fusion reactions. These are partially due to a beam of deuterons which are accelerated against the background hot plasma by large electric fields originating from plasma instabilities. Due to a beam-target effect, the angular distribution of the neutron emission is anisotropic, peaked in the forward direction along the axis of the gun. The purpose of this work is to illustrate the use of CR-39 nuclear track detectors as a diagnostic tool in the determination of the time-integrated neutron angular distribution. For the case studied in this work, neutron emission is found to have a 70% contribution from isotropic radiation and a 30% contribution from anisotropic radiation.

TIME EVOLUTION OF KELVIN–HELMHOLTZ VORTICES ASSOCIATED WITH COLLISIONLESS SHOCKS IN LASER-PRODUCED PLASMAS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuramitsu, Y.; Moritaka, T.; Mizuta, A.

2016-09-10

We report experimental results on Kelvin–Helmholtz (KH) instability and resultant vortices in laser-produced plasmas. By irradiating a double plane target with a laser beam, asymmetric counterstreaming plasmas are created. The interaction of the plasmas with different velocities and densities results in the formation of asymmetric shocks, where the shear flow exists along the contact surface and the KH instability is excited. We observe the spatial and temporal evolution of plasmas and shocks with time-resolved diagnostics over several shots. Our results clearly show the evolution of transverse fluctuations, wavelike structures, and circular features, which are interpreted as the KH instability andmore » resultant vortices. The relevant numerical simulations demonstrate the time evolution of KH vortices and show qualitative agreement with experimental results. Shocks, and thus the contact surfaces, are ubiquitous in the universe; our experimental results show general consequences where two plasmas interact.« less

Modelling of 13CH4 injection and local carbon deposition at the outer divertor of ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Aho-Mantila, L.; Airila, M. I.; Wischmeier, M.; Krieger, K.; Pugno, R.; Coster, D. P.; Chankin, A. V.; Neu, R.; Rohde, V.

2009-12-01

Numerical modelling of 13CH4 injection into the outer divertor plasma of the full tungsten, vertical target of ASDEX Upgrade is presented. The SOLPS5.0 code package is used to calculate a realistic scrape-off layer plasma background corresponding to L-mode discharges in the attached divertor plasma regime. The ERO code is then used for detailed modelling of the hydrocarbon break-up, re-deposition and re-erosion processes. The deposition patterns observed at two different poloidal locations are shown to strongly reflect the cross-field gradients in divertor plasma density and temperature, as well as the local plasma collisionality. Experimental results with forward and reversed BT, accompanied by numerical modelling, also point towards a significant poloidal hydrocarbon E×B drift in the divertor region.

Effects of laser-plasma instabilities on hydro evolution in an OMEGA-EP long-scale-length experiment

DOE PAGES

Li, J.; Hu, S. X.; Ren, C.

2017-02-28

Laser-plasma instabilities and hydro evolution of the coronal plasma in an OMEGA EP long-scale-length experiment with planar targets were studied with particle-in-cell (PIC) and hydrodynamic simulations. Plasma and laser conditions were first obtained in a two-dimensional DRACO hydro simulation with only inverse-bremsstrahlung absorption. Using these conditions, an OSIRIS PIC simulation was performed to study laser absorption and hot-electron generation caused by laser-plasma instabilities (LPIs) near the quarter-critical region. The obtained PIC information was subsequently coupled to another DRACO simulation to examine how the LPIs affect the overall hydrodynamics. Lastly, the results showed that the LPI-induced laser absorption increased the electronmore » temperature but did not significantly change the density scale length in the corona.« less

Effects of laser-plasma instabilities on hydro evolution in an OMEGA-EP long-scale-length experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, J.; Hu, S. X.; Ren, C.

Laser-plasma instabilities and hydro evolution of the coronal plasma in an OMEGA EP long-scale-length experiment with planar targets were studied with particle-in-cell (PIC) and hydrodynamic simulations. Plasma and laser conditions were first obtained in a two-dimensional DRACO hydro simulation with only inverse-bremsstrahlung absorption. Using these conditions, an OSIRIS PIC simulation was performed to study laser absorption and hot-electron generation caused by laser-plasma instabilities (LPIs) near the quarter-critical region. The obtained PIC information was subsequently coupled to another DRACO simulation to examine how the LPIs affect the overall hydrodynamics. Lastly, the results showed that the LPI-induced laser absorption increased the electronmore » temperature but did not significantly change the density scale length in the corona.« less

Modeling of combined effects of divertor closure and advanced magnetic configuration on detachment in DIII-D by SOLPS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Si, Hang; Guo, Houyang Y.; Covele, Brent

One of the major challenges facing the design and operation of next-step high-power steady-state fusion devices is to develop a divertor solution for handling power exhaust, while ensuring acceptable divertor target plate erosion, which necessitates access to divertor detachment at relative low main plasma densities compatible with current drive and high plasma confinement. Detailed modeling with SOLPS is carried out to examine the effect of divertor closure on detachment with the normal single null divertor (SD) configuration, as well as one of the advanced divertor configurations, such as x-divertor (XD) respectively. The SOLPS modeling for a high confinement plasma in DIII-D finds that increasing divertor closure with SD reduces the upstream separatrix density at the onset of detachment frommore » $$1.18\\times {{10}^{19}}\\,{{{\\rm m}}^{-3}}$$ to $$0.88\\times {{10}^{19}}\\,{{{\\rm m}}^{-3}}$$. Furthermore, coupling the divertor closure with XD further promotes the onset of divertor detachment at a still lower upstream separatrix density, down to the value of $$0.67\\times {{10}^{19}}\\,{{{\\rm m}}^{-3}}$$, thus, showing that divertor closure and advanced magnetic configuration can work synergistically to facilitate divertor detachment.« less

Modeling of combined effects of divertor closure and advanced magnetic configuration on detachment in DIII-D by SOLPS

DOE PAGES

Si, Hang; Guo, Houyang Y.; Covele, Brent; ...

2018-04-04

One of the major challenges facing the design and operation of next-step high-power steady-state fusion devices is to develop a divertor solution for handling power exhaust, while ensuring acceptable divertor target plate erosion, which necessitates access to divertor detachment at relative low main plasma densities compatible with current drive and high plasma confinement. Detailed modeling with SOLPS is carried out to examine the effect of divertor closure on detachment with the normal single null divertor (SD) configuration, as well as one of the advanced divertor configurations, such as x-divertor (XD) respectively. The SOLPS modeling for a high confinement plasma in DIII-D finds that increasing divertor closure with SD reduces the upstream separatrix density at the onset of detachment frommore » $$1.18\\times {{10}^{19}}\\,{{{\\rm m}}^{-3}}$$ to $$0.88\\times {{10}^{19}}\\,{{{\\rm m}}^{-3}}$$. Furthermore, coupling the divertor closure with XD further promotes the onset of divertor detachment at a still lower upstream separatrix density, down to the value of $$0.67\\times {{10}^{19}}\\,{{{\\rm m}}^{-3}}$$, thus, showing that divertor closure and advanced magnetic configuration can work synergistically to facilitate divertor detachment.« less

Turbulent Simulations of Divertor Detachment Based On BOUT + + Framework

NASA Astrophysics Data System (ADS)

Chen, Bin; Xu, Xueqiao; Xia, Tianyang; Ye, Minyou

2015-11-01

China Fusion Engineering Testing Reactor is under conceptual design, acting as a bridge between ITER and DEMO. The detached divertor operation offers great promise for a reduction of heat flux onto divertor target plates for acceptable erosion. Therefore, a density scan is performed via an increase of D2 gas puffing rates in the range of 0 . 0 ~ 5 . 0 ×1023s-1 by using the B2-Eirene/SOLPS 5.0 code package to study the heat flux control and impurity screening property. As the density increases, it shows a gradually change of the divertor operation status, from low-recycling regime to high-recycling regime and finally to detachment. Significant radiation loss inside the confined plasma in the divertor region during detachment leads to strong parallel density and temperature gradients. Based on the SOLPS simulations, BOUT + + simulations will be presented to investigate the stability and turbulent transport under divertor plasma detachment, particularly the strong parallel gradient driven instabilities and enhanced plasma turbulence to spread heat flux over larger surface areas. The correlation between outer mid-plane and divertor turbulence and the related transport will be analyzed. Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-675075.

LPI Thresholds in Longer Scale Length Plasmas Driven by the Nike Laser*

NASA Astrophysics Data System (ADS)

Weaver, J.; Oh, J.; Phillips, L.; Afeyan, B.; Seely, J.; Kehne, D.; Brown, C.; Obenschain, S.; Serlin, V.; Schmitt, A. J.; Feldman, U.; Holland, G.; Lehmberg, R. H.; McLean, E.; Manka, C.

2010-11-01

The Krypton-Fluoride (KrF) laser is an attractive driver for inertial confinement fusion due to its short wavelength (248nm), large bandwidth (1-3 THz), and beam smoothing by induced spatial incoherence. Experiments with the Nike KrF laser have demonstrated intensity thresholds for laser plasma instabilities (LPI) higher than reported for other high power lasers operating at longer wavelengths (>=351 nm). The previous Nike experiments used short pulses (350 ps FWHM) and small spots (<260 μm FWHM) that created short density scale length plasmas (Ln˜50-70 μm) from planar CH targets and demonstrated the onset of two-plasmon decay (2φp) at laser intensities ˜2x10^15 W/cm^2. This talk will present an overview of the current campaign that uses longer pulses (0.5-4.0 ns) to achieve greater density scale lengths (Ln˜100-200 μm). X-rays, emission near ^1/2φo and ^3/2φo harmonics, and reflected laser light have been monitored for onset of 2φp. The longer density scale lengths will allow better comparison to results from other laser facilities. *Work supported by DoE/NNSA and ONR.

Modeling of combined effects of divertor closure and advanced magnetic configuration on detachment in DIII-D by SOLPS

NASA Astrophysics Data System (ADS)

Si, H.; Guo, H. Y.; Covele, B.; Leonard, A. W.; Watkins, J. G.; Thomas, D.; Ding, R.

2018-05-01

One of the major challenges facing the design and operation of next-step high-power steady-state fusion devices is to develop a divertor solution for handling power exhaust, while ensuring acceptable divertor target plate erosion, which necessitates access to divertor detachment at relative low main plasma densities compatible with current drive and high plasma confinement. Detailed modeling with SOLPS is carried out to examine the effect of divertor closure on detachment with the normal single null divertor (SD) configuration, as well as one of the advanced divertor configurations, such as x-divertor (XD) respectively. The SOLPS modeling for a high confinement plasma in DIII-D finds that increasing divertor closure with SD reduces the upstream separatrix density at the onset of detachment from 1.18× {{10}19} {{m}-3} to 0.88× {{10}19} {{m}-3} . Moreover, coupling the divertor closure with XD further promotes the onset of divertor detachment at a still lower upstream separatrix density, down to the value of 0.67× {{10}19} {{m}-3} , thus, showing that divertor closure and advanced magnetic configuration can work synergistically to facilitate divertor detachment.

Temperature dependence of yields from multi-foil SPES target

NASA Astrophysics Data System (ADS)

Corradetti, S.; Biasetto, L.; Manzolaro, M.; Scarpa, D.; Andrighetto, A.; Carturan, S.; Prete, G.; Zanonato, P.; Stracener, D. W.

2011-10-01

The temperature dependence of neutron-rich isotope yields was studied within the framework of the HRIBF-SPES Radioactive Ion Beams (RIB) project. On-line release measurements of fission fragments from a uranium carbide target at ensuremath 1600 {}^{circ}C , ensuremath 1800 {}^{circ}C and ensuremath 2000 {}^{circ}C were performed at ORNL (USA). The fission reactions were induced by a 40MeV proton beam accelerated into a uranium carbide target coupled to a plasma ion source. The experiments allowed for tests of performance of the SPES multi-foil target prototype loaded with seven UC2/graphite discs (ratio C/ U = 4 with density about 4g/cm3.

Method and apparatus for reducing coherence of high-power laser beams

DOEpatents

Moncur, Norman K.; Mayer, Frederick J.

1978-01-01

Method and apparatus for reducing the coherence and for smoothing the power density profile of a collimated high-power laser beam in which the beam is focused at a point on the surface of a target fabricated of material having a low atomic number. The initial portion of the focused beam heats the material to form a hot reflective plasma at the material surface. The remaining, major portion of the focused beam is reflected by the plasma and recollected to form a collimated beam having reduced beam coherence.

LLE Review 118 (January-March 2009)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bittle, W., editor

2009-08-03

This issue has the following articles: (1) Applied Plasma Spectroscopy: Laser-Fusion Experiments; (2) Relativistic Electron-Beam Transport Studies Using High-Resolution, Coherent Transition Radiation Imaging; (3) Pressure-Driven, Resistive Magnetohydrodynamic Interchange Instabilities in Laser-Produced, High-Energy-Density Plasmas; (4) Extended Model for Polymer Cholesteric Liquid Crystal Flake Reorientation and Relaxation; (5) Modeling the Effects of Microencapsulation on the Electro-Optic Behavior of Polymer Cholesteric Liquid Crystal Flakes; (6) Capillarity and Dielectrophoresis of Liquid Deuterium; and (7) A Stable Mid-IR, GaSb-Based Diode Laser Source for Cryogenic Target Layering at the OMEGA Laser Facility.

Relativistic-electron-beam/target interaction in plasma channels

NASA Astrophysics Data System (ADS)

Halbleib, J. A., Sr.; Wright, T. P.

1980-08-01

A model describing the transport of relativistic electron beams in plasma channels and their subsequent interaction with solid targets is developed and applied to single-beam and multiple-beam configurations. For single beams the targets consist of planar tantalum foils and, in some cases, cusp fields on the transmission side of the foils are employed to improve beam/target coupling efficiency. In the multi-beam configurations, several beams are arranged in wagon-wheel fashion so as to converge upon cylindrical targets, consisting of either hollow tantalum or solid graphite cylinders, located at the hub. For 0.3-cm beam radii that are less than or equal to the channel radii, mean specific power depositions up to about 17 TW/g per MA of injected beam current are obtained for single beams; 12-beam results are typically an order-of-magnitude less. The corresponding enhancements are up to five times the collisional stopping power for either single or multiple beams. Substantial improvement is predicted for the multi-beam interaction should future channel technology permit transport at higher current densities in smaller channels.

Determination of the number density of excited and ground Zn atoms during rf magnetron sputtering of ZnO target

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maaloul, L.; Gangwar, R. K.; Stafford, L., E-mail: luc.stafford@umontreal.ca

2015-07-15

A combination of optical absorption spectroscopy (OAS) and optical emission spectroscopy measurements was used to monitor the number density of Zn atoms in excited 4s4p ({sup 3}P{sub 2} and {sup 3}P{sub 0}) metastable states as well as in ground 4s{sup 2} ({sup 1}S{sub 0}) state in a 5 mTorr Ar radio-frequency (RF) magnetron sputtering plasma used for the deposition of ZnO-based thin films. OAS measurements revealed an increase by about one order of magnitude of Zn {sup 3}P{sub 2} and {sup 3}P{sub 0} metastable atoms by varying the self-bias voltage on the ZnO target from −115 to −300 V. Over themore » whole range of experimental conditions investigated, the triplet-to-singlet metastable density ratio was 5 ± 1, which matches the statistical weight ratio of these states in Boltzmann equilibrium. Construction of a Boltzmann plot using all Zn I emission lines in the 200–500 nm revealed a constant excitation temperature of 0.33 ± 0.04 eV. In combination with measured populations of Zn {sup 3}P{sub 2} and {sup 3}P{sub 0} metastable atoms, this temperature was used to extrapolate the absolute number density of ground state Zn atoms. The results were found to be in excellent agreement with those obtained previously by actinometry on Zn atoms using Ar as the actinometer gas [L. Maaloul and L. Stafford, J. Vac. Sci. Technol., A 31, 061306 (2013)]. This set of data was then correlated to spectroscopic ellipsometry measurements of the deposition rate of Zn atoms on a Si substrate positioned at 12 cm away from the ZnO target. The deposition rate scaled linearly with the number density of Zn atoms. In sharp contrast with previous studies on RF magnetron sputtering of Cu targets, these findings indicate that metastable atoms play a negligible role on the plasma deposition dynamics of Zn-based coatings.« less

Increased heat dissipation with the X-divertor geometry facilitating detachment onset at lower density in DIII-D

DOE PAGES

Covele, Brent; Kotschenreuther, M.; Mahajan, S.; ...

2017-06-23

The X-Divertor geometry on DIII-D has demonstrated reduced particle and heat fluxes to the target, facilitating detachment onset at ~20% lower upstream density and higher H-mode pedestal pressure than a standard divertor. SOLPS modeling suggests that this effect cannot be explained by an increase in total connection length alone, but rather by the addition of connection length specifically in the power-dissipating volume near the target, via poloidal flux expansion and flaring. But, poloidal flaring must work synergistically with divertor closure to most effectively reduce the detachment density threshold. Furthermore, the model also points to carbon radiation as the primary drivermore » of power dissipation in divertors on the DIII-D floor, which is consistent with experimental observations. Sustainable divertor detachment at lower density has beneficial consequences for energy confinement and current drive efficiency in the core for advanced tokamak (AT) operation, while simultaneously satisfying the exhaust requirements of the plasma-facing components.« less

Increased heat dissipation with the X-divertor geometry facilitating detachment onset at lower density in DIII-D

DOE Office of Scientific and Technical Information (OSTI.GOV)

Covele, Brent; Kotschenreuther, M.; Mahajan, S.

The X-Divertor geometry on DIII-D has demonstrated reduced particle and heat fluxes to the target, facilitating detachment onset at ~20% lower upstream density and higher H-mode pedestal pressure than a standard divertor. SOLPS modeling suggests that this effect cannot be explained by an increase in total connection length alone, but rather by the addition of connection length specifically in the power-dissipating volume near the target, via poloidal flux expansion and flaring. But, poloidal flaring must work synergistically with divertor closure to most effectively reduce the detachment density threshold. Furthermore, the model also points to carbon radiation as the primary drivermore » of power dissipation in divertors on the DIII-D floor, which is consistent with experimental observations. Sustainable divertor detachment at lower density has beneficial consequences for energy confinement and current drive efficiency in the core for advanced tokamak (AT) operation, while simultaneously satisfying the exhaust requirements of the plasma-facing components.« less

X-ray Thomson scattering measurements of temperature and density from multi-shocked CH capsules

DOE PAGES

Fletcher, L. B.; Glenzer, S. H.; Kritcher, A.; ...

2013-05-24

Proof-of-principle measurements of the electron densities, temperatures, and ionization states of spherically compressed multi-shocked CH (polystyrene) capsules have been achieved using spectrally resolved x-ray Thomson scattering. A total energy of 13.5 kJ incident on target is used to compress a 70 μm thick CH shell above solid-mass density using three coalescing shocks. Separately, a laser-produced zinc He-α x-ray source at 9 keV delayed 200 ps-800 ps after maximum compression is used to probe the plasma in the non-collective scattering regime. The data show that x-ray Thomson scattering enables a complete description of the time-dependent hydrodynamic evolution of shock-compressed CH capsules,more » with a maximum measured density of ρ > 6 g cm –3. Additionally, the results demonstrate that accurate measurements of x-ray scattering from bound-free transitions in the CH plasma demonstrate strong evidence that continuum lowering is the primary ionization mechanism of carbon L-shell electrons.« less

Influence of damping on proton energy loss in plasmas of all degeneracies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barriga-Carrasco, Manuel D.

2007-07-15

The purpose of the present paper is to describe the effects of electron-electron collisions on the stopping power of plasmas of any degeneracy. Plasma targets are considered fully ionized so electronic stopping is only due to the free electrons. We focus our analysis on plasmas which electronic density is around solid values n{sub e}{approx_equal}10{sup 23} cm{sup -3} and which temperature is around T{approx_equal}10 eV; these plasmas are in the limit of weakly coupled plasmas. This type of plasma has not been studied extensively though it is very important for inertial confinement fusion. The electronic stopping is obtained from an exactmore » quantum mechanical evaluation, which takes into account the degeneracy of the target plasma, and later it is compared with common classical and degenerate approximations. Differences are around 30% in some cases which can produce bigger mistakes in further energy deposition and projectile range studies. Then we consider electron-electron collisions in the exact quantum mechanical electronic stopping calculation. Now the maximum stopping occurs at velocities smaller than for the calculations without considering collisions for all kinds of plasmas analyzed. The energy loss enhances for velocities smaller than the velocity at maximum while decreases for higher velocities. Latter effects are magnified with increasing collision frequency. Differences with the same results for the case of not taking into account collisions are around 20% in the analyzed cases.« less

Experimental results from plasma transport on Prototype-Material Plasma Exposure eXperiment and comparison with B2-Eirene modeling

NASA Astrophysics Data System (ADS)

Kafle, N.; Caneses, J. F.; Biewer, T. M.; Owen, L.; Showers, M.; Donovan, D.; Caughman, J. B.; Goulding, R. H.; Rapp, Juergen

2017-10-01

Proto-MPEX at ORNL is a linear plasma device that combines a helicon plasma source with additional microwave and RF heating to deliver high plasma heat and particle fluxes to a target. Double Langmuir probes and Thomson scattering are being used to measure local Te and ne at various radial and axial locations. A recently constructed Mach- double probe provides the added capability of simultaneously measuring Te, ne, and Mach number. With this diagnostic, it is possible to infer the plasma flow, particle flux, and convective heat flux at different locations along the plasma column in Proto-MPEX. Preliminary results show Mach numbers of 0.6 and 0.8 in either direction away from the helicon source, and no flow near the source for the case where the peak magnetic field was 1.0 T. In addition, the Thomson Scattering system has been upgraded to measure ne and Te profiles at two axial locations, upstream at the electron heating location and downstream close to the target. Measurements of particle flow and flux profiles, heat flux, and profiles of ne and Te will be discussed. The extensive coverage provided by these diagnostics permits data-constrained B2-Eirene modeling of the entire plasma column, and comparison with results of modeling of high density mode plasmas will be presented. Supported by the US. D.O.E. contract DE-AC05-00OR22725.

Influence of nitrogen admixture to argon on the ion energy distribution in reactive high power pulsed magnetron sputtering of chromium

NASA Astrophysics Data System (ADS)

Breilmann, W.; Maszl, C.; Hecimovic, A.; von Keudell, A.

2017-04-01

Reactive high power impulse magnetron sputtering (HiPIMS) of metals is of paramount importance for the deposition of various oxides, nitrides and carbides. The addition of a reactive gas such as nitrogen to an argon HiPIMS plasma with a metal target allows the formation of the corresponding metal nitride on the substrate. The addition of a reactive gas introduces new dynamics into the plasma process, such as hysteresis, target poisoning and the rarefaction of two different plasma gases. We investigate the dynamics for the deposition of chromium nitride by a reactive HiPIMS plasma using energy- and time-resolved ion mass spectrometry, fast camera measurements and temporal and spatially resolved optical emission spectroscopy. It is shown that the addition of nitrogen to the argon plasma gas significantly changes the appearance of the localized ionization zones, the so-called spokes, in HiPIMS plasmas. In addition, a very strong modulation of the metal ion flux within each HiPIMS pulse is observed, with the metal ion flux being strongly suppressed and the nitrogen molecular ion flux being strongly enhanced in the high current phase of the pulse. This behavior is explained by a stronger return effect of the sputtered metal ions in the dense plasma above the racetrack. This is best observed in a pure nitrogen plasma, because the ionization zones are mostly confined, implying a very high local plasma density and consequently also an efficient scattering process.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Covele, Brent; Kotschenreuther, M.; Mahajan, S.

The X-Divertor geometry on DIII-D has demonstrated reduced particle and heat fluxes to the target, facilitating detachment onset at ~20% lower upstream density and higher H-mode pedestal pressure than a standard divertor. SOLPS modeling suggests that this effect cannot be explained by an increase in total connection length alone, but rather by the addition of connection length specifically in the power-dissipating volume near the target, via poloidal flux expansion and flaring. But, poloidal flaring must work synergistically with divertor closure to most effectively reduce the detachment density threshold. Furthermore, the model also points to carbon radiation as the primary drivermore » of power dissipation in divertors on the DIII-D floor, which is consistent with experimental observations. Sustainable divertor detachment at lower density has beneficial consequences for energy confinement and current drive efficiency in the core for advanced tokamak (AT) operation, while simultaneously satisfying the exhaust requirements of the plasma-facing components.« less

Modelling of the reactive sputtering process with non-uniform discharge current density and different temperature conditions

NASA Astrophysics Data System (ADS)

Vašina, P; Hytková, T; Eliáš, M

2009-05-01

The majority of current models of the reactive magnetron sputtering assume a uniform shape of the discharge current density and the same temperature near the target and the substrate. However, in the real experimental set-up, the presence of the magnetic field causes high density plasma to form in front of the cathode in the shape of a toroid. Consequently, the discharge current density is laterally non-uniform. In addition to this, the heating of the background gas by sputtered particles, which is usually referred to as the gas rarefaction, plays an important role. This paper presents an extended model of the reactive magnetron sputtering that assumes the non-uniform discharge current density and which accommodates the gas rarefaction effect. It is devoted mainly to the study of the behaviour of the reactive sputtering rather that to the prediction of the coating properties. Outputs of this model are compared with those that assume uniform discharge current density and uniform temperature profile in the deposition chamber. Particular attention is paid to the modelling of the radial variation of the target composition near transitions from the metallic to the compound mode and vice versa. A study of the target utilization in the metallic and compound mode is performed for two different discharge current density profiles corresponding to typical two pole and multipole magnetics available on the market now. Different shapes of the discharge current density were tested. Finally, hysteresis curves are plotted for various temperature conditions in the reactor.

ICPP: Relativistic Plasma Physics with Ultra-Short High-Intensity Laser Pulses

NASA Astrophysics Data System (ADS)

Meyer-Ter-Vehn, Juergen

2000-10-01

Recent progress in generating ultra-short high-intensity laser pulses has opened a new branch of relativistic plasma physics, which is discussed in this talk in terms of particle-in-cell (PIC) simulations. These pulses create small plasma volumes of high-density plasma with plasma fields above 10^12 V/m and 10^8 Gauss. At intensities beyond 10^18 W/cm^2, now available from table-top systems, they drive relativistic electron currents in self-focussing plasma channels. These currents are close to the Alfven limit and allow to study relativistic current filamentation. A most remarkable feature is the generation of well collimated relativistic electron beams emerging from the channels with energies up to GeV. In dense matter they trigger cascades of gamma-rays, e^+e^- pairs, and a host of nuclear and particle processes. One of the applications may be fast ignition of compressed inertial fusion targets. Above 10^23 W/cm^2, expected to be achieved in the future, solid-density matter becomes relativistically transparent for optical light, and the acceleration of protons to multi-GeV energies is predicted in plasma layers less than 1 mm thick. These results open completely new perspectives for plasma-based accelerator schemes. Three-dimensional PIC simulations turn out to be the superior tool to explore the relativistic plasma kinetics at such intensities. Results obtained with the VLPL code [1] are presented. Different mechanisms of particle acceleration are discussed. Both laser wakefield and direct laser acceleration in plasma channels (by a mechanism similar to inverse free electron lasers) have been identified. The latter describes recent MPQ experimental results. [1] A. Pukhov, J. Plasma Physics 61, 425 - 433 (1999): Three-dimensional electromagnetic relativistic particle-in-cell code VLPL (Virtual Laser Plasma Laboratory).

Relationship between plasma parameters and film microstructure in radio frequency magnetron sputter deposition of barium strontium titanate

NASA Astrophysics Data System (ADS)

Panda, B.; Dhar, A.; Nigam, G. D.; Bhattacharya, D.; Ray, S. K.

1998-01-01

Radio frequency magnetron sputtered Ba0.8Sr0.2TiO3 thin films have been deposited on silicon and Si/SiO2/SiN/Pt substrates. The analysis of plasma discharge has been carried out using the Langmuir probe technique. Both the pressure and power have been found to influence the ion density and self-bias of the target. Introduction of oxygen into the discharge effectively decreases the ion density. The structural and electrical properties have been investigated using x-ray diffraction, atomic force microscopy of deposited films and capacitance-voltage, conductance-voltage, and current density-electric field characteristics of fabricated capacitors. The growth and orientation of the films have been found to depend upon the type of substrates and deposition temperatures. The <100> texture in the film is promoted at a pressure 0.25 Torr with a moderately high value of ion density and low ion bombardment energy. Films deposited on Si/SiO2/SiN/Pt substrate have shown higher dielectric constant (191) and lower leakage current density (2.8×10-6 A/cm2 at 100 kV/cm) compared to that on silicon.

Low-Energy Plasma Focus Device as an Electron Beam Source

PubMed Central

Seong Ling, Yap; Naresh Kumar, Nitturi; Lian Kuang, Lim; Chiow San, Wong

2014-01-01

A low-energy plasma focus device was used as an electron beam source. A technique was developed to simultaneously measure the electron beam intensity and energy. The system was operated in Argon filling at an optimum pressure of 1.7 mbar. A Faraday cup was used together with an array of filtered PIN diodes. The beam-target X-rays were registered through X-ray spectrometry. Copper and lead line radiations were registered upon usage as targets. The maximum electron beam charge and density were estimated to be 0.31 μC and 13.5 × 1016/m3, respectively. The average energy of the electron beam was 500 keV. The high flux of the electron beam can be potentially applicable in material sciences. PMID:25544952

Method of high-precision microsampled blood and plasma mass densitometry

NASA Technical Reports Server (NTRS)

Hinghofer-Szalkay, H.

1986-01-01

The reliability of the mechanical oscillator technique for blood and plasma density measurements on samples of volumes less than 0.1 ml is examined, and a precision of 0.001 g/l is found if plasma-isodensic heparin solution and siliconized densitometers are employed. Sources of measurement errors in the density determinations include storage of plasma samples, inhomogeneity of blood samples, and density reading before adequate temperature equilibration. In tests of plasma sample storage, the best reproducibility was obtained with samples kept at 4 C. Linear correlations were found between plasma density and plasma protein concentration, blood density and blood hemoglobin concentration, and erythrocyte density and MCHC.

Surface modification of platinum by laser-produced X-rays

NASA Astrophysics Data System (ADS)

Latif, Hamid; Shahid Rafique, M.; Khaleeq-ur-Rahaman, M.; Sattar, Abdul; Anjum, S.; Usman, A.; Zaheer, S.; Rawat, R. S.

2014-11-01

Laser-induced plasma is used as an X-ray source for the growth of hillocks like nanostructures on platinum surface. To generate X-rays, plasma is produced by Nd:YAG laser, which is operated at second harmonics (λ = 532 nm, E = 400 mJ). Analytical grade 5 N pure Al, Cu and W are used as laser targets for X-rays production. X-rays produced from Al, Cu and W plasmas are used to irradiate three analytical grade (5 N pure) platinum substrates, respectively, under the vacuum ∼10-4 torr. XRD analysis shows considerable structural changes in the exposed platinum. The decrement in reflection intensities, increment in dislocation line density, change in d-spacing and disturbance in the periodicity of planes evidently prove these structural changes. Atomic force microscope AFM topographic analysis of the platinum exposed to X-rays emitted from Al, Cu and W targets showed that nanometer-size hillocks are produced on the platinum surface irrespective of the source. It has also been observed that due to these hillocks, the roughness of the surface has increased. Conductivity of hillocks produced from X-rays produced by Al, Cu and W targets is compared and it is shown that the hillocks produced by Al target X-rays have better conductivity compared to the hillocks produced by X-rays from Cu and W targets.

Hydrodynamic instabilities at an oblique interface: Experiments and Simulations

NASA Astrophysics Data System (ADS)

Douglas-Mann, E.; Fiedler Kawaguchi, C.; Trantham, M. A.; Malamud, G.; Wan, W. C.; Klein, S. R.; Kuranz, C. C.

2017-10-01

Hydrodynamic instabilities are important phenomena that occur in high-energy-density systems, such as astrophysical systems and inertial confinement fusion experiments, where pressure, density, and velocity gradients are present. Using a 30 ns laser pulse from the Omega EP laser system, a steady shock wave is driven into a target. A Spherical Crystal Imager provides high-resolution x-ray radiographs to study the evolution of complex hydrodynamic structures. This experiment has a light-to-heavy interface at an oblique angle with a precision-machined perturbation. The incident shock wave deposits shear and vorticity at the interface causing the perturbation to grow via Richtmyer-Meshkov and Kelvin-Helmholtz processes. We present results from analysis of radiographic data and hydrodynamics simulations showing the evolution of the shock and unstable structure. This work is supported by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, Grant Number DE-NA0002956 and the National Science Foundation through the Basic Plasma Science and Engineering program and LILAC.

Review of ion energy and angular distributions in capacitively coupled RF plasma reactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawamura, E.; Lieberman, M.A.; Birdsall, C.K.

1995-12-31

The authors present a historical review and discussion of previous works on ion energy and angular distributions (IED and IAD) arriving at the target in the collisionless regime. This regime is of great interest to experimentalists and modelers studying the new generation of high density sources in which the sheath is much thinner than in the conventional RIE systems. The purpose of the review is to asses what has been done so far, and to clarify some issues about sheaths in high density systems. Having determined the important parameters, the authors show some particle-in-cell simulation results of a dually excitedmore » capacitively coupled plasma in which the sheath ions roughly see the scaling as in high density sources. The results show that when {tau}{sub ion}/{tau}{sub rf} < 1, the oscillating voltage and width of the rf sheath significantly affect the IEDs, where {tau}{sub ion} is the ion transit-time and {tau}{sub rf} is rf period.« less

2D imaging X-ray diagnostic for measuring the current density distribution in a wide-area electron beam produced in a multiaperture diode with plasma cathode

NASA Astrophysics Data System (ADS)

Kurkuchekov, V.; Kandaurov, I.; Trunev, Y.

2018-05-01

A simple and inexpensive X-ray diagnostic tool was designed for measuring the cross-sectional current density distribution in a low-relativistic pulsed electron beam produced in a source based on an arc-discharge plasma cathode and multiaperture diode-type electron optical system. The beam parameters were as follows: Uacc = 50–110 kV, Ibeam = 20–100 A, τbeam = 0.1–0.3 ms. The beam effective diameter was ca. 7 cm. Based on a pinhole camera, the diagnostic allows one to obtain a 2D profile of electron beam flux distribution on a flat metal target in a single shot. The linearity of the diagnostic system response to the electron flux density was established experimentally. Spatial resolution of the diagnostic was also estimated in special test experiments. The optimal choice of the main components of the diagnostic technique is discussed.

Anti-miR-33 therapy does not alter the progression of atherosclerosis in low-density lipoprotein receptor-deficient mice.

PubMed

Marquart, Tyler J; Wu, Judy; Lusis, Aldons J; Baldán, Ángel

2013-03-01

To determine the efficacy of long-term anti-miR-33 therapy on the progression of atherosclerosis in high-fat, high-cholesterol-fed Ldlr(-/-) mice. Ldlr(-/-) mice received saline, or control or anti-miR-33 oligonucleotides once a week for 14 weeks. The treatment was effective, as measured by reduced levels of hepatic miR-33 and increased hepatic expression of miR-33 targets. Analysis of plasma samples revealed an initial elevation in high-density lipoprotein cholesterol after 2 weeks of treatment that was not sustained by the end of the experiment. Additionally, we found a significant increase in circulating triglycerides in anti-miR-33-treated mice, compared with controls. Finally, examination of atheromata revealed no significant changes in the size or composition of lesions between the 3 groups. Prolonged silencing of miR-33 fails to maintain elevated plasma high-density lipoprotein cholesterol and does not prevent the progression of atherosclerosis in Ldlr(-/-) mice.

Novel diagnostics for direct measurements of radical densities in atmospheric pressure plasma jets

NASA Astrophysics Data System (ADS)

Wagenaars, Erik

2017-10-01

Atmospheric-pressure plasma jets (APPJs) are widely studied for potential applications in industry and healthcare, e.g. surface modification of plastics, plasma medicine and photoresist removal. These plasmas can operate in open air, remain at room temperature and still have a non-equilibrium chemistry. Even though the exact mechanisms through which APPJs affect target surfaces remain largely unknown, it is clear that reactive species play a pivotal role in the success of APPJs. Therefore, reactive species diagnostics of APPJs play an important role in further developing our understanding of the plasma chemistry and will enable increases in treatment efficacy. Two-photon Absorption Laser Induced Fluorescence (TALIF) is a well-known technique for the measurement of absolute densities of atomic radicals such as O, N and H. Unfortunately, application of this technique on APPJs that are operating under realistic conditions for applications, i.e. in open air and with complex admixtures, is not straightforward. The highly collisional environment of APPJs means that collisional quenching of the laser-excited state becomes significant and needs to be taken into account. For well-controlled atmospheres and simple admixtures the effect can be estimated using quenching coefficients, however under realistic operating conditions the identity and density of the quenching partners is unknown due to the complexity of the plasma chemistry. I will present a picosecond TALIF diagnostic which uses a sub-nanosecond laser and iCCD camera that allows the measurement of the quenching-affected fluorescence decay rate directly, enabling absolute measurements of O and N density maps in the open-air effluent of an APPJ. The author acknowledges his collaborators at UoY, A. West, J. Bredin, S. Schroeter, K. Niemi, T. Gans, J. Dedrick and D. O'Connell and support from the UK EPSRC (EP/K018388/1 & EP/H003797/1).

Hotspot ignition using a Z-pinch precursor plasma in a magneto-inertial ICF scheme

NASA Astrophysics Data System (ADS)

Chittenden, J. P.; Vincent, P.; Jennings, C. A.; Ciardi, A.

2006-01-01

Precursor plasma flow is a common feature of wire array Z-pinches. The precursor flow represents a fraction of the mass of the array which arrives on the axis early in time and remains confined at high density by the inertia of further material bombarding the axis. Later on, the main implosion of the Z-pinch then compresses this precursor to substantially higher density. We show that if the same system can be generated with a Deuterium-Tritium plasma then the precursor provides an ideal target for a cylindrical magneto-inertial ICF scheme. The implosion of the DT Z-pinch produces a dense, low temperature shell which compressively heats the precursor target to high temperatures and tamps its expansion. The azimuthal magnetic field in the hotspot is sufficient to reduce the Larmor radius for the alpha particles to much less than the hotspot size, which dramatically reduces the pR required for ignition. A computational analysis of this approach is presented, including a study of the thermonuclear burn wave propagation. The robustness of the scheme with respect to instabilities, confinement time and drive parameters is examined. The results indicate that a high energy gain can be achieved using Z-pinches with 50-100 MA currents and a few hundred nanosecond rise-times. This work was partially supported by the U.S. Department of Energy through cooperative agreement DE-FC03-02NA00057.

An improved current potential method for fast computation of stellarator coil shapes

NASA Astrophysics Data System (ADS)

Landreman, Matt

2017-04-01

Several fast methods for computing stellarator coil shapes are compared, including the classical NESCOIL procedure (Merkel 1987 Nucl. Fusion 27 867), its generalization using truncated singular value decomposition, and a Tikhonov regularization approach we call REGCOIL in which the squared current density is included in the objective function. Considering W7-X and NCSX geometries, and for any desired level of regularization, we find the REGCOIL approach simultaneously achieves lower surface-averaged and maximum values of both current density (on the coil winding surface) and normal magnetic field (on the desired plasma surface). This approach therefore can simultaneously improve the free-boundary reconstruction of the target plasma shape while substantially increasing the minimum distances between coils, preventing collisions between coils while improving access for ports and maintenance. The REGCOIL method also allows finer control over the level of regularization, it preserves convexity to ensure the local optimum found is the global optimum, and it eliminates two pathologies of NESCOIL: the resulting coil shapes become independent of the arbitrary choice of angles used to parameterize the coil surface, and the resulting coil shapes converge rather than diverge as Fourier resolution is increased. We therefore contend that REGCOIL should be used instead of NESCOIL for applications in which a fast and robust method for coil calculation is needed, such as when targeting coil complexity in fixed-boundary plasma optimization, or for scoping new stellarator geometries.

Low-temperature formation of c-axis-oriented aluminum nitride thin films by plasma-assisted reactive pulsed-DC magnetron sputtering

NASA Astrophysics Data System (ADS)

Takenaka, Kosuke; Satake, Yoshikatsu; Uchida, Giichiro; Setsuhara, Yuichi

2018-01-01

The low-temperature formation of c-axis-oriented aluminum nitride thin films was demonstrated by plasma-assisted reactive pulsed-DC magnetron sputtering. The effects of the duty cycle at the pulsed-DC voltage applied to the Al target on the properties of AlN films formed via inductively coupled plasma (ICP)-enhanced pulsed-DC magnetron sputtering deposition were investigated. With decreasing duty cycle at the target voltage, the peak intensity of AlN(0002) increased linearly. The surface roughness of AlN films decreased since there was an increase in film density owing to the impact of energetic ions on the films together with the enhancement of nitriding associated with the relative increase in N radical flux. The improvement of both the crystallinity and surface morphology of AlN films at low temperatures is considered to be caused by the difference between the relative flux values of ions and sputtered atoms.

Comprehensive genotyping in dyslipidemia: mendelian dyslipidemias caused by rare variants and Mendelian randomization studies using common variants.

PubMed

Tada, Hayato; Kawashiri, Masa-Aki; Yamagishi, Masakazu

2017-04-01

Dyslipidemias, especially hyper-low-density lipoprotein cholesterolemia and hypertriglyceridemia, are important causal risk factors for coronary artery disease. Comprehensive genotyping using the 'next-generation sequencing' technique has facilitated the investigation of Mendelian dyslipidemias, in addition to Mendelian randomization studies using common genetic variants associated with plasma lipids and coronary artery disease. The beneficial effects of low-density lipoprotein cholesterol-lowering therapies on coronary artery disease have been verified by many randomized controlled trials over the years, and subsequent genetic studies have supported these findings. More recently, Mendelian randomization studies have preceded randomized controlled trials. When the on-target/off-target effects of rare variants and common variants exhibit the same direction, novel drugs targeting molecules identified by investigations of rare Mendelian lipid disorders could be promising. Such a strategy could aid in the search for drug discovery seeds other than those for dyslipidemias.

Laser-driven proton and deuteron acceleration from a pure solid-density H2/D2 cryogenic jet

NASA Astrophysics Data System (ADS)

Kim, Jongjin; Gauthier, Maxence; Aurand, Bastian; Curry, Chandra; Goede, Sebastian; Goyon, Clement; Williams, Jackson; Kerr, Shaun; Ruby, John; Propp, Adrienne; Ramakrishna, Bhuvanesh; Pak, Art; Hazi, Andy; Glenzer, Siegfried; Roedel, Christian

2015-11-01

Laser-driven proton acceleration has become of tremendous interest for the fundamental science and the potential applications in tumor therapy and proton radiography. We have developed a cryogenic liquid hydrogen jet, which can deliver a self-replenishing target of pure solid-density hydrogen or deuterium. This allows for a target compatible with high-repetition-rate experiments and results in a pure hydrogen plasma, facilitating comparison with simulations. A new modification has allowed for the formation of jets with rectangular profiles, facilitating comparison with foil targets. This jet was installed at the Titan laser and driven by laser pulses of 40-60 J of 527 nm laser light in 1 ps. The resulting proton and deuteron spectra were measured in multiple directions with Thomson parabola spectrometers and RCF stacks. The spectral and angular information suggest contribution from both the TNSA and RPA acceleration mechanisms.

Neutron generator for BNCT based on high current ECR ion source with gyrotron plasma heating.

PubMed

Skalyga, V; Izotov, I; Golubev, S; Razin, S; Sidorov, A; Maslennikova, A; Volovecky, A; Kalvas, T; Koivisto, H; Tarvainen, O

2015-12-01

BNCT development nowadays is constrained by a progress in neutron sources design. Creation of a cheap and compact intense neutron source would significantly simplify trial treatments avoiding use of expensive and complicated nuclear reactors and accelerators. D-D or D-T neutron generator is one of alternative types of such sources for. A so-called high current quasi-gasdynamic ECR ion source with plasma heating by millimeter wave gyrotron radiation is suggested to be used in a scheme of D-D neutron generator in the present work. Ion source of that type was developed in the Institute of Applied Physics of Russian Academy of Sciences (Nizhny Novgorod, Russia). It can produce deuteron ion beams with current density up to 700-800 mA/cm(2). Generation of the neutron flux with density at the level of 7-8·10(10) s(-1) cm(-2) at the target surface could be obtained in case of TiD2 target bombardment with deuteron beam accelerated to 100 keV. Estimations show that it is enough for formation of epithermal neutron flux with density higher than 10(9) s(-1) cm(-2) suitable for BNCT. Important advantage of described approach is absence of Tritium in the scheme. First experiments performed in pulsed regime with 300 mA, 45 kV deuteron beam directed to D2O target demonstrated 10(9) s(-1) neutron flux. This value corresponds to theoretical estimations and proofs prospects of neutron generator development based on high current quasi-gasdynamic ECR ion source. Copyright © 2015 Elsevier Ltd. All rights reserved.

Chemistry of neutral species in the effluent of the micro atmospheric pressure plasma jet in water-helium admixture

NASA Astrophysics Data System (ADS)

Willems, Gert; Benedikt, Jan; von Keudell, Achim

2016-09-01

A thorough understanding and good control of produced neutral and charged species by cold atmospheric plasmas is essential for potential environmental and/or bio-medical applications. In this study we use the COST reference micro plasma jet (µ-APPJ), which is a radio-frequency capacitive coupled plasma source with 1 mm electrode distance, which has been operated in helium-water vapour mixture and has been studied as a potential source of hydroxyl radicals and hydrogen peroxide molecules. The water vapour concentration was up to 1.2%. Molecular Beam mass spectrometry is used as diagnostic tool. An absolute calibration of hydrogen peroxide was conducted using a double bubbler concept, because the ionization cross section for hydrogen peroxide is not available. Additionally the effluent chemistry was investigated by use of a 0D and 2D model. Absolute densities of hydrogen peroxide and hydroxyl radicals from atmospheric plasma will be presented. Their dependency on water vapour concentration in the carrier gas as well as distance to target have been investigated. The measured density is between 5E-13 cm-3 (2.4ppm) and 1.5E-14 cm-3 (7.2ppm) for both hydrogen peroxide molecules and hydroxyl radicals. The achieved results are in good agreement with other experiments.

Shock-Wave Acceleration of Protons on OMEGA EP

NASA Astrophysics Data System (ADS)

Haberberger, D.; Froula, D. H.; Pak, A.; Link, A.; Patel, P.; Fiuza, F.; Tochitsky, S.; Joshi, C.

2015-11-01

Recent experimental results using shock-wave acceleration (SWA) driven by a CO2 laser in a H2 gas-jet plasma have shown the possibility of producing proton beams with energy spreads <10% and with energies of up to 20 MeV using a modest peak laser power of 4 TW. Here we propose the investigation of the scaling of the SWA mechanism to higher laser powers using the 1- μm OMEGA EP Laser System at the Laboratory for Laser Energetics. The required tailored plasma profile is created by expanding a CH target using the thermal x-ray emission from a UV ablated material. The desired characteristics optimal for SWA are met: (a) peak plasma density is overcritical for the 1- μm main pulse and (b) the plasma profile exponentially decays over a long scale length on the rear side. Results will be shown using a 4 ω probe to experimentally characterize the plasma density profile. Scaling from simulations of the SWA mechanism shows that ion energies in the range of 100 MeV/amu are achievable with a focused a0 of 5 from the OMEGA EP Laser System. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Generation of warm dense matter using an argon based capillary discharge laser

NASA Astrophysics Data System (ADS)

Rossall, A. K.; Tallents, G. J.

2015-06-01

Argon based capillary discharge lasers operating in the extreme ultra violet (EUV) at 46.9 nm with output up to 0.5 mJ energy per pulse and repetition rates up to 10 Hz are capable of focused irradiances of 109-1012 W cm-2 and can be used to generate plasma in the warm dense matter regime by irradiating solid material. To model the interaction between such an EUV laser and solid material, the 2D radiative-hydrodynamic code POLLUX has been modified to include absorption via direct photo-ionisation, a super-configuration model to describe the ionization-dependent electronic configurations and a calculation of plasma refractive indices for ray tracing of the incident EUV laser radiation. A simulation study is presented, demonstrating how capillary discharge lasers of 1200 ps pulse duration can be used to generate warm dense matter at close to solid densities with temperatures of a few eV and energy densities up to 1 × 105 J cm-3. Plasmas produced by EUV laser irradiation are shown to be useful for examining the properties of warm dense matter as, for example, plasma emission is not masked by hotter, less dense plasma emission that occurs with visible/infra-red laser target irradiation.

Guiding of relativistic electron beams in dense matter by laser-driven magnetostatic fields.

PubMed

Bailly-Grandvaux, M; Santos, J J; Bellei, C; Forestier-Colleoni, P; Fujioka, S; Giuffrida, L; Honrubia, J J; Batani, D; Bouillaud, R; Chevrot, M; Cross, J E; Crowston, R; Dorard, S; Dubois, J-L; Ehret, M; Gregori, G; Hulin, S; Kojima, S; Loyez, E; Marquès, J-R; Morace, A; Nicolaï, Ph; Roth, M; Sakata, S; Schaumann, G; Serres, F; Servel, J; Tikhonchuk, V T; Woolsey, N; Zhang, Z

2018-01-09

Intense lasers interacting with dense targets accelerate relativistic electron beams, which transport part of the laser energy into the target depth. However, the overall laser-to-target energy coupling efficiency is impaired by the large divergence of the electron beam, intrinsic to the laser-plasma interaction. Here we demonstrate that an efficient guiding of MeV electrons with about 30 MA current in solid matter is obtained by imposing a laser-driven longitudinal magnetostatic field of 600 T. In the magnetized conditions the transported energy density and the peak background electron temperature at the 60-μm-thick target's rear surface rise by about a factor of five, as unfolded from benchmarked simulations. Such an improvement of energy-density flux through dense matter paves the ground for advances in laser-driven intense sources of energetic particles and radiation, driving matter to extreme temperatures, reaching states relevant for planetary or stellar science as yet inaccessible at the laboratory scale and achieving high-gain laser-driven thermonuclear fusion.

Advanced Thomson scattering system for high-flux linear plasma generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meiden, H. J. van der; Lof, A. R.; Berg, M. A. van den

2012-12-15

An advanced Thomson scattering system has been built for a linear plasma generator for plasma surface interaction studies. The Thomson scattering system is based on a Nd:YAG laser operating at the second harmonic and a detection branch featuring a high etendue (f /3) transmission grating spectrometer equipped with an intensified charged coupled device camera. The system is able to measure electron density (n{sub e}) and temperature (T{sub e}) profiles close to the output of the plasma source and, at a distance of 1.25 m, just in front of a target. The detection system enables to measure 50 spatial channels ofmore » about 2 mm each, along a laser chord of 95 mm. By summing a total of 30 laser pulses (0.6 J, 10 Hz), an observational error of 3% in n{sub e} and 6% in T{sub e} (at n{sub e}= 9.4 Multiplication-Sign 10{sup 18} m{sup -3}) can be obtained. Single pulse Thomson scattering measurements can be performed with the same accuracy for n{sub e} > 2.8 Multiplication-Sign 10{sup 20} m{sup -3}. The minimum measurable density and temperature are n{sub e} < 1 Multiplication-Sign 10{sup 17} m{sup -3} and T{sub e} < 0.07 eV, respectively. In addition, using the Rayleigh peak, superimposed on the Thomson scattered spectrum, the neutral density (n{sub 0}) of the plasma can be measured with an accuracy of 25% (at n{sub 0}= 1 Multiplication-Sign 10{sup 20} m{sup -3}). In this report, the performance of the Thomson scattering system will be shown along with unprecedented accurate Thomson-Rayleigh scattering measurements on a low-temperature argon plasma expansion into a low-pressure background.« less

Thomson scattering diagnostic for the measurement of ion species fraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ross, J S; Park, H S; Amendt, A

2012-05-01

Simultaneous Thomson scattering measurements of collective electron-plasma and ion-acoustic fluctuations have been utilized to determine ion species fraction from laser produced CH plasmas. The CH{sub 2} foil is heated with 10 laser beams, 500 J per beam, at the Omega Laser facility. Thomson scattering measurements are made 4 mm from the foil surface using a 30 J 2{omega} probe laser with a 1 ns pulse length. Using a series of target shots the plasma evolution is measured from 2.5 ns to 9 ns after the rise of the heater beams. Measuring the electron density and temperature from the electron-plasma fluctuationsmore » constrains the fit of the two-ion species theoretical form factor for the ion feature such that the ion temperature, plasma flow velocity and ion species fraction are determined. The ion species fraction is determined to an accuracy of {+-}0.06 in species fraction.« less

Plasma diagnostics of low pressure high power impulse magnetron sputtering assisted by electron cyclotron wave resonance plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stranak, Vitezslav; University of South Bohemia, Institute of Physics and Biophysics, Branisovska 31, 370 05 Ceske Budejovice; Herrendorf, Ann-Pierra

2012-11-01

This paper reports on an investigation of the hybrid pulsed sputtering source based on the combination of electron cyclotron wave resonance (ECWR) inductively coupled plasma and high power impulse magnetron sputtering (HiPIMS) of a Ti target. The plasma source, operated in an Ar atmosphere at a very low pressure of 0.03 Pa, provides plasma where the major fraction of sputtered particles is ionized. It was found that ECWR assistance increases the electron temperature during the HiPIMS pulse. The discharge current and electron density can achieve their stable maximum 10 {mu}s after the onset of the HiPIMS pulse. Further, a highmore » concentration of double charged Ti{sup ++} with energies of up to 160 eV was detected. All of these facts were verified experimentally by time-resolved emission spectroscopy, retarding field analyzer measurement, Langmuir probe, and energy-resolved mass spectrometry.« less

Discharge dynamics and plasma density recovery by on/off switches of additional gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Hyo-Chang, E-mail: lhc@kriss.re.kr; Department of Electrical Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04763; Kwon, Deuk-Chul

2016-06-15

Measurement of the plasma density is investigated to study plasma dynamics by adding reactive gas (O{sub 2}) or rare gas (He) in Ar plasmas. When the O{sub 2} or He gas is added, plasma density is suddenly decreased, while the plasma density recovers slowly with gas off. It is found that the recovery time is strongly dependent on the gas flow rate, and it can be explained by effect of gas residence time. When the He gas is off in the Ar plasma, the plasma density is overshot compared to the case of the O{sub 2} gas pulsing due tomore » enhanced ionizations by metastable atoms. Analysis and calculation for correlation between the plasma density dynamics and the gas pulsing are also presented in detail.« less

Opacity of iron, nickel, and copper plasmas in the x-ray wavelength range: Theoretical interpretation of 2p-3d absorption spectra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blenski, T.; Loisel, G.; Poirier, M.

2011-09-15

This paper deals with theoretical studies on the 2p-3d absorption in iron, nickel, and copper plasmas related to LULI2000 (Laboratoire pour l'Utilisation des Lasers Intenses, 2000J facility) measurements in which target temperatures were of the order of 20 eV and plasma densities were in the range 0.004-0.01 g/cm{sup 3}. The radiatively heated targets were close to local thermodynamic equilibrium (LTE). The structure of 2p-3d transitions has been studied with the help of the statistical superconfiguration opacity code sco and with the fine-structure atomic physics codes hullac and fac. A new mixed version of the sco code allowing one to treatmore » part of the configurations by detailed calculation based on the Cowan's code rcg has been also used in these comparisons. Special attention was paid to comparisons between theory and experiment concerning the term features which cannot be reproduced by sco. The differences in the spin-orbit splitting and the statistical (thermal) broadening of the 2p-3d transitions have been investigated as a function of the atomic number Z. It appears that at the conditions of the experiment the role of the term and configuration broadening was different in the three analyzed elements, this broadening being sensitive to the atomic number. Some effects of the temperature gradients and possible non-LTE effects have been studied with the help of the radiative-collisional code scric. The sensitivity of the 2p-3d structures with respect to temperature and density in medium-Z plasmas may be helpful for diagnostics of LTE plasmas especially in future experiments on the {Delta}n=0 absorption in medium-Z plasmas for astrophysical applications.« less

High-Q plasmas in the TFTR tokamak

NASA Astrophysics Data System (ADS)

Jassby, D. L.; Barnes, C. W.; Bell, M. G.; Bitter, M.; Boivin, R.; Bretz, N. L.; Budny, R. V.; Bush, C. E.; Dylla, H. F.; Efthimion, P. C.; Fredrickson, E. D.; Hawryluk, R. J.; Hill, K. W.; Hosea, J.; Hsuan, H.; Janos, A. C.; Jobes, F. C.; Johnson, D. W.; Johnson, L. C.; Kamperschroer, J.; Kieras-Phillips, C.; Kilpatrick, S. J.; LaMarche, P. H.; LeBlanc, B.; Mansfield, D. K.; Marmar, E. S.; McCune, D. C.; McGuire, K. M.; Meade, D. M.; Medley, S. S.; Mikkelsen, D. R.; Mueller, D.; Owens, D. K.; Park, H. K.; Paul, S. F.; Pitcher, S.; Ramsey, A. T.; Redi, M. H.; Sabbagh, S. A.; Scott, S. D.; Snipes, J.; Stevens, J.; Strachan, J. D.; Stratton, B. C.; Synakowski, E. J.; Taylor, G.; Terry, J. L.; Timberlake, J. R.; Towner, H. H.; Ulrickson, M.; von Goeler, S.; Wieland, R. M.; Williams, M.; Wilson, J. R.; Wong, K.-L.; Young, K. M.; Zarnstorff, M. C.; Zweben, S. J.

1991-08-01

In the Tokamak Fusion Test Reactor (TFTR) [Plasma Phys. Controlled Fusion 26, 11 (1984)], the highest neutron source strength Sn and D-D fusion power gain QDD are realized in the neutral-beam-fueled and heated ``supershot'' regime that occurs after extensive wall conditioning to minimize recycling. For the best supershots, Sn increases approximately as P1.8b. The highest-Q shots are characterized by high Te (up to 12 keV), Ti (up to 34 keV), and stored energy (up to 4.7 MJ), highly peaked density profiles, broad Te profiles, and lower Zeff. Replacement of critical areas of the graphite limiter tiles with carbon-fiber composite tiles and improved alignment with the plasma have mitigated the ``carbon bloom.'' Wall conditioning by lithium pellet injection prior to the beam pulse reduces carbon influx and particle recycling. Empirically, QDD increases with decreasing pre-injection carbon radiation, and increases strongly with density peakedness [ne(0)/] during the beam pulse. To date, the best fusion results are Sn=5×1016 n/sec, QDD=1.85×10-3, and neutron yield=4.0×1016 n/pulse, obtained at Ip=1.6-1.9 MA and beam energy Eb=95-103 keV, with nearly balanced co- and counter-injected beam power. Computer simulations of supershot plasmas show that typically 50%-60% of Sn arises from beam-target reactions, with the remainder divided between beam-beam and thermonuclear reactions, the thermonuclear fraction increasing with Pb. The simulations predict that QDT=0.3-0.4 would be obtained for the best present plasma conditions, if half the deuterium neutral beams were to be replaced by tritium beams. Somewhat higher values are calculated if D beams are injected into a predominantly tritium target plasma. The projected central beta of fusion alphas is 0.4%-0.6%, a level sufficient for the study of alpha-induced collective effects.

Spectral modification of shock accelerated ions using a hydrodynamically shaped gas target

DOE PAGES

Tresca, O.; Polyanskiy, M. N.; Dover, N. P.; ...

2015-08-28

We report on reproducible shock acceleration from irradiation of a λ=10 μm CO2 laser on optically shaped H2 and He gas targets. A low energy laser prepulse (I≲10 14 W cm –2) is used to drive a blast wave inside the gas target, creating a steepened, variable density gradient. This is followed, after 25 ns, by a high intensity laser pulse (I>10 16 W cm –2) that produces an electrostatic collisionless shock. Upstream ions are accelerated for a narrow range of prepulse energies. For long density gradients (≳40 μm), broadband beams of He + and H + were routinely produced,more » whilst for shorter gradients (≲20 μm), quasimonoenergetic acceleration of protons is observed. These measurements indicate that the properties of the accelerating shock and the resultant ion energy distribution, in particular the production of narrow energy spread beams, is highly dependent on the plasma density profile. These findings are corroborated by 2D particle-in-cell simulations.« less

A novel femtosecond-gated, high-resolution, frequency-shifted shearing interferometry technique for probing pre-plasma expansion in ultra-intense laser experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feister, S., E-mail: feister.7@osu.edu; Orban, C.; Innovative Scientific Solutions, Inc., Dayton, Ohio 45459

Ultra-intense laser-matter interaction experiments (>10{sup 18} W/cm{sup 2}) with dense targets are highly sensitive to the effect of laser “noise” (in the form of pre-pulses) preceding the main ultra-intense pulse. These system-dependent pre-pulses in the nanosecond and/or picosecond regimes are often intense enough to modify the target significantly by ionizing and forming a plasma layer in front of the target before the arrival of the main pulse. Time resolved interferometry offers a robust way to characterize the expanding plasma during this period. We have developed a novel pump-probe interferometry system for an ultra-intense laser experiment that uses two short-pulse amplifiersmore » synchronized by one ultra-fast seed oscillator to achieve 40-fs time resolution over hundreds of nanoseconds, using a variable delay line and other techniques. The first of these amplifiers acts as the pump and delivers maximal energy to the interaction region. The second amplifier is frequency shifted and then frequency doubled to generate the femtosecond probe pulse. After passing through the laser-target interaction region, the probe pulse is split and recombined in a laterally sheared Michelson interferometer. Importantly, the frequency shift in the probe allows strong plasma self-emission at the second harmonic of the pump to be filtered out, allowing plasma expansion near the critical surface and elsewhere to be clearly visible in the interferograms. To aid in the reconstruction of phase dependent imagery from fringe shifts, three separate 120° phase-shifted (temporally sheared) interferograms are acquired for each probe delay. Three-phase reconstructions of the electron densities are then inferred by Abel inversion. This interferometric system delivers precise measurements of pre-plasma expansion that can identify the condition of the target at the moment that the ultra-intense pulse arrives. Such measurements are indispensable for correlating laser pre-pulse measurements with instantaneous plasma profiles and for enabling realistic Particle-in-Cell simulations of the ultra-intense laser-matter interaction.« less

Characterization of cylindrically imploded magnetized plasma by spectroscopy and proton probing

NASA Astrophysics Data System (ADS)

Dozieres, M.; Forestier-Colleoni, P.; Wei, M. S.; Gourdain, P.-A.; Davies, J. R.; Fujioka, S.; Peebles, J.; Campbell, M.; Santos, J. J.; Batani, D.; McGuffey, C.; Beg, F. N.

2017-10-01

Understanding the role of magnetic field in relativistic electron beam transport and energy deposition is important for several applications including fast ignition inertial confinement fusion. We report the development of a cylindrically compressed target platform with externally applied magnetic fields on OMEGA. As a first step, we performed an experiment to characterize the imploded plasma and compressed field condition. The implosion of the target was performed using 36 UV beams (400 J per beam, 1.5 ns square pulse), and the magnetic field was measured by proton deflection using mono-energetic protons produced from D3He capsule implosion. The target was a CH foam cylinder doped with 1% chlorine in order to detect the time-resolved 1s-2p Cl absorption structures, using a gold foil as a broad band backlighter source. A Cu foil at the beginning of the foam cylinder and a Zn foil at the end, allowed us to measure the K α and the 1s-2p transitions of He-like and Li-like ions for both elements. The emission and absorption spectroscopic data are compared to atomic physics codes to determine the plasma temperature and density under the influence of the magnetic field. FOA-0001568.

Betatron x-ray radiation in the self-modulated wakefield acceleration regime (Conference Presentation)

NASA Astrophysics Data System (ADS)

Albert, Felicie

2017-05-01

Betatron x-ray radiation, driven by electrons from laser-wakefield acceleration, has unique properties to probe high energy density (HED) plasmas and warm dense matter. Betatron radiation is produced when relativistic electrons oscillate in the plasma wake of a laser pulse. Its properties are similar to those of synchrotron radiation, with a 1000 fold shorter pulse. This presentation will focus on the experimental challenges and results related to the development of betatron radiation in the self modulated regime of laser wakefield acceleration. We observed multi keV Betatron x-rays from a self-modulated laser wakefield accelerator. The experiment was performed at the Jupiter Laser Facility, LLNL, by focusing the Titan short pulse beam (4-150 J, 1 ps) onto the edge of a Helium gas jet at electronic densities around 1019 cm-3. For the first time on this laser system, we used a long focal length optic, which produced a laser normalized potential a0 in the range 1-3. Under these conditions, electrons are accelerated by the plasma wave created in the wake of the light pulse. As a result, intense Raman satellites, which measured shifts depend on the electron plasma density, were observed on the laser spectrum transmitted through the target. Electrons with energies up to 200 MeV, as well as Betatron x-rays with critical energies around 20 keV, were measured. OSIRIS 2D PIC simulations confirm that the electrons gain energy both from the plasma wave and from their interaction with the laser field.

Preparation of tris(8-hydroxyquinolinato)aluminum thin films by sputtering deposition using powder and pressed powder targets

NASA Astrophysics Data System (ADS)

Kawasaki, Hiroharu; Ohshima, Tamiko; Yagyu, Yoshihito; Ihara, Takeshi; Tanaka, Rei; Suda, Yoshiaki

2017-06-01

Tris(8-hydroxyquinolinato)aluminum (Alq3) thin films, for use in organic electroluminescence displays, were prepared by a sputtering deposition method using powder and pressed powder targets. Experimental results suggest that Alq3 thin films can be prepared using powder and pressed powder targets, although the films were amorphous. The surface color of the target after deposition became dark brown, and the Fourier transform infrared spectroscopy spectrum changed when using a pressed powder target. The deposition rate of the film using a powder target was higher than that using a pressed powder target. That may be because the electron and ion densities of the plasma generated using the powder target are higher than those when using pressed powder targets under the same deposition conditions. The properties of a thin film prepared using a powder target were almost the same as those of a film prepared using a pressed powder target.

Waves generated in the plasma plume of helicon magnetic nozzle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Nagendra; Rao, Sathyanarayan; Ranganath, Praveen

2013-03-15

Experimental measurements have shown that the plasma plume created in a helicon plasma device contains a conical structure in the plasma density and a U-shaped double layer (US-DL) tightly confined near the throat where plasma begins to expand from the source. Recently reported two-dimensional particle-in-cell simulations verified these density and US-DL features of the plasma plume. Simulations also showed that the plasma in the plume develops non-thermal feature consisting of radial ion beams with large densities near the conical surface of the density structure. The plasma waves that are generated by the radial ion beams affecting the structure of themore » plasma plume are studied here. We find that most intense waves persist in the high-density regions of the conical density structure, where the transversely accelerated ions in the radial electric fields in the plume are reflected setting up counter-streaming. The waves generated are primarily ion Bernstein modes. The nonlinear evolution of the waves leads to magnetic field-aligned striations in the fields and the plasma near the conical surface of the density structure.« less

Long life electrodes for large-area x-ray generators

NASA Technical Reports Server (NTRS)

Rothe, Dietmar E. (Inventor)

1991-01-01

This invention is directed to rugged, reliable, and long-life electrodes for use in large-area, high-current-density electron gun and x-ray generators which are employed as contamination-free preionizers for high-energy pulsed gas lasers. The electron source at the cathode is a corona plasma formed at the interface between a conductor, or semiconductor, and a high-permittivity dielectric. Detailed descriptions are provided of a reliable cold plasma cathode, as well as an efficient liquid-cooled electron beam target (anode) and x-ray generator which concentrates the x-ray flux in the direction of an x-ray window.

EFFECTS OF LASER RADIATION ON MATTER: Efficient surface-erosion plasma formation in air due to the action of pulse-periodic laser radiation

NASA Astrophysics Data System (ADS)

Min'ko, L. Ya; Chumakou, A. N.; Bosak, N. A.

1990-11-01

A study was made of the interaction of a series of periodic laser (λ = 1.06 μm) pulses with a number of materials (aluminum, copper, graphite, ebonite) in air at laser radiation power densities q = 107-109 W/cm2 and repetition frequencies f<=50 kHz. The radiation was concentrated in spots of ~ 10 - 2 cm2 area. Efficient formation of plasma as a result of laser erosion (q > 2 × 108 W/cm2, f>=5 kHz) was observed. A screening layer of an air plasma created by the first pulse of the series was expelled from the interaction zone and this was followed by erosion plasma formation under conditions of slight screening of the target during the action of the subsequent laser pulses.

Materials erosion and redeposition studies at the PISCES-facility: net erosion under redeposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hirooka, Y.; Goebel, D.M.; Conn, R.W.

1986-05-01

Simultaneous erosion and redeposition of copper and 304 stainless steel under controlled and continuous plasma (D,He,Ar) bombardment has been investigated in the PISCES-facility, which generates typical edge-plasma conditions of magnetic fusion devices. The plasma bombardment conditions are: incident ion flux in the range from 10/sup 17/ to 10/sup 18/ ions/sec/cm/sup 2/, ion bombarding energy of 100 eV, electron temperature in the range from 5 to 15 eV, plasma density in the range from 10/sup 11/ to 10/sup 13/ cm/sup -3/, target temperature in the range from 300 to 900K, and the total ion fluence in the range from 10/sup 20/more » to 10/sup 22/ ions/cm/sup 2/. The net erosion yield under redeposition is found to be significantly smaller than the classical sputtering yield data. A first-order modeling is attempted to interpret the erosion and redeposition behavior of materials under plasma bombardment. It is pointed out both theoretically and experimentally that the mean free path for electron impact ionization of the sputtered material is the key parameter to control the overall mechanism of erosion and redeposition. Strongly modified surface morphologies of bombarded targets are observed and indicate a retrapping effect.« less

[Dyslipidemias : Diagnostics and management].

PubMed

Sinning, D; Landmesser, U

2017-09-01

For disorders of lipid metabolism the risk-adapted adjustment of low-density lipoprotein (LDL) cholesterol remains the primary treatment target, as a causal role in minimizing the progression of ACVD has been shown. Because of their efficacy in reducing cardiovascular morbidity and mortality, statins are recommended as first-line pharmacological treatment in dyslipidemias. Additionally, ezetimibe and proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition have been shown to significantly reduce cardiovascular events in high-risk patients. Life style changes can improve the plasma lipid profile, particularly in the setting of hypertriglyceridemia. Evaluation of high-density lipoprotein (HDL) cholesterol and lipoprotein(a) provides further information when assessing the individual cardiovascular risk, but direct evidence that pharmacologically targeting HDL cholesterol or Lp(a) results in a reduction of cardiovascular events has not yet been shown.

Secondary antiproton production in relativistic plasmas

NASA Technical Reports Server (NTRS)

Dermer, C. D.; Ramaty, R.

1985-01-01

The possibility is investigated that the reported excess low energy antiproton component of the cosmic radiation results from proton-proton (p-p) interactions in relativistic plasmas. Because of both target and projectile motion in such plasmas, the antiproton production threshold in the frame of the plasma is much lower than the threshold of antiproton production in cosmic ray interactions with ambient matter. The spectrum of the resultant antiprotons therefore extends to much lower energy than in the cosmic ray case. The antiproton spectrum is calculated for relativistic thermal plasmas and the spectrum is estimated for relativistic nonthermal plasmas. As possible production sites, matter accreting onto compact objects located in the galaxy is considered. Possible overproduction of gamma rays from associated neutral pion production can be avoided if the site is optically thick to the photons but not to the antiprotons. A possible scenario involves a sufficiently large photon density that the neutral pion gamma rays are absorbed by photon-photon pair production. Escape of the antiprotons to the interstellar medium can be mediated by antineutron production.

Synergetic effects of double laser pulses for the formation of mild plasma in water: Toward non-gated underwater laser-induced breakdown spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sakka, Tetsuo; Institute of Sustainability Science, Kyoto University, Uji, Kyoto 611-0011; Tamura, Ayaka

2012-05-07

We experimentally study the dynamics of the plasma induced by the double-laser-pulse irradiation of solid target in water, and find that an appropriate choice of the pulse energies and pulse interval results in the production of an unprecedentedly mild (low-density) plasma, the emission spectra of which are very narrow even without the time-gated detection. The optimum pulse interval and pulse energies are 15-30 {mu}s and about {approx}1 mJ, respectively, where the latter values are much smaller than those typically employed for this kind of study. In order to clarify the mechanism for the formation of mild plasma we examine themore » role of the first and second laser pulses, and find that the first pulse produces the cavitation bubble without emission (and hence plasma), and the second pulse induces the mild plasma in the cavitation bubble. These findings may present a new phase of underwater laser-induced breakdown spectroscopy.« less

Observations of a field-aligned ion/ion-beam instability in a magnetized laboratory plasma

NASA Astrophysics Data System (ADS)

Heuer, P. V.; Weidl, M. S.; Dorst, R. S.; Schaeffer, D. B.; Bondarenko, A. S.; Tripathi, S. K. P.; Van Compernolle, B.; Vincena, S.; Constantin, C. G.; Niemann, C.; Winske, D.

2018-03-01

Collisionless coupling between super Alfvénic ions and an ambient plasma parallel to a background magnetic field is mediated by a set of electromagnetic ion/ion-beam instabilities including the resonant right hand instability (RHI). To study this coupling and its role in parallel shock formation, a new experimental configuration at the University of California, Los Angeles utilizes high-energy and high-repetition-rate lasers to create a super-Alfvénic field-aligned debris plasma within an ambient plasma in the Large Plasma Device. We used a time-resolved fluorescence monochromator and an array of Langmuir probes to characterize the laser plasma velocity distribution and density. The debris ions were observed to be sufficiently super-Alfvénic and dense to excite the RHI. Measurements with magnetic flux probes exhibited a right-hand circularly polarized frequency chirp consistent with the excitation of the RHI near the laser target. We compared measurements to 2D hybrid simulations of the experiment.

Observations of a field-aligned ion/ion-beam instability in a magnetized laboratory plasma

DOE PAGES

Heuer, P. V.; Weidl, M. S.; Dorst, R. S.; ...

2018-03-01

Collisionless coupling between super Alfvénic ions and an ambient plasma parallel to a background magnetic field is mediated by a set of electromagnetic ion/ion-beam instabilities including the resonant right hand instability (RHI). To study this coupling and its role in parallel shock formation, a new experimental configuration at the University of California, Los Angeles utilizes high-energy and high-repetition-rate lasers to create a super-Alfvénic field-aligned debris plasma within an ambient plasma in the Large Plasma Device. We used a time-resolved fluorescence monochromator and an array of Langmuir probes to characterize the laser plasma velocity distribution and density. The debris ions weremore » observed to be sufficiently super-Alfvénic and dense to excite the RHI. Measurements with magnetic flux probes exhibited a right-hand circularly polarized frequency chirp consistent with the excitation of the RHI near the laser target. To conclude, we compared measurements to 2D hybrid simulations of the experiment.« less

Collective behavior of silver plasma during pulsed laser ablation

NASA Astrophysics Data System (ADS)

Dildar, I. M.; Rehman, S.; Khaleeq-ur-Rahman, M.; Bhatti, K. A.; Shuaib, A.

2015-07-01

The present work reports an electrical investigation of silver plasma using a self-fabricated Langmuir probe in air and under a low vacuum (~10-3 torr). A silver target was irradiated with a Q-switched Nd:YAG laser with the wavelength 1.064 µm, energy 10 mJ, pulse duration 9-14 ns and power 1.1 MW. The collective behavior of a silver plasma plume is studied using a Langmuir probe as an electrical diagnostic technique. By applying different positive and negative voltages to the probe, the respective signals are collected on a four channels digital storage oscilloscope having a frequency of 500 MHz. An I-V curve helps to measure electron temperature and electron density directly and plasma frequency, response time, Debye length and number of particles in ‘Debye’s sphere’ indirectly using the theory of Langmuir probe and mathematical formulas. The floating potential is measured as negative for laser induced silver plasma in air and vacuum, following the theory of plasma.

Observations of a field-aligned ion/ion-beam instability in a magnetized laboratory plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heuer, P. V.; Weidl, M. S.; Dorst, R. S.

Collisionless coupling between super Alfvénic ions and an ambient plasma parallel to a background magnetic field is mediated by a set of electromagnetic ion/ion-beam instabilities including the resonant right hand instability (RHI). To study this coupling and its role in parallel shock formation, a new experimental configuration at the University of California, Los Angeles utilizes high-energy and high-repetition-rate lasers to create a super-Alfvénic field-aligned debris plasma within an ambient plasma in the Large Plasma Device. We used a time-resolved fluorescence monochromator and an array of Langmuir probes to characterize the laser plasma velocity distribution and density. The debris ions weremore » observed to be sufficiently super-Alfvénic and dense to excite the RHI. Measurements with magnetic flux probes exhibited a right-hand circularly polarized frequency chirp consistent with the excitation of the RHI near the laser target. To conclude, we compared measurements to 2D hybrid simulations of the experiment.« less

Laser Hole Boring into Overdense Plasma and Relativistic Electron Currents for Fast Ignition of ICF Targets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pukhov, A.; Meyer-ter-Vehn, J.

Laser hole boring and relativistic electron transport into plasma of 10 times critical density is studied by means of 2D particle-in-cell simulation. At intensities of I{sub 0}{lambda}{sup 2}=10{sup 20} W(cm){sup {minus}2} {mu}m{sup 2}, a channel 12{lambda} deep and 3{lambda} in diameter has formed after 200 laser cycles. The laser driven electron current carries up to 40{percent} of the incident laser power. When penetrating the overdense region, it breaks up into several filaments at early times, but is channeled into a single magnetized jet later on. These features are essential for fast ignition of targets for inertial confinement fusion (ICF). {copyright}more » {ital 1997} {ital The American Physical Society}« less

PCSK9: Regulation and Target for Drug Development for Dyslipidemia.

PubMed

Burke, Amy C; Dron, Jacqueline S; Hegele, Robert A; Huff, Murray W

2017-01-06

Proprotein convertase subtilisin/kexin type-9 (PCSK9) is a secreted zymogen expressed primarily in the liver. PCSK9 circulates in plasma, binds to cell surface low-density lipoprotein (LDL) receptors, is internalized, and then targets the receptors to lysosomal degradation. Studies of naturally occurring PCSK9 gene variants that caused extreme plasma LDL cholesterol (LDL-C) deviations and altered atherosclerosis risk unleashed a torrent of biological and pharmacological research. Rapid progress in understanding the physiological regulation of PCSK9 was soon translated into commercially available biological inhibitors of PCSK9 that reduced LDL-C levels and likely also cardiovascular outcomes. Here we review the swift evolution of PCSK9 from novel gene to drug target, to animal and human testing, and finally to outcome trials and clinical applications. In addition, we explore how the genetics-guided path to PCSK9 inhibitor development exemplifies a new paradigm in pharmacology. Finally, we consider some potential challenges as PCSK9 inhibition becomes established in the clinic.

High e+/e– ratio dense pair creation with 10 21W.cm –2 laser irradiating solid targets

DOE PAGES

Liang, E.; Clarke, T.; Henderson, A.; ...

2015-09-14

In this study, we report results of new pair creation experiments using ~100 Joule pulses of the Texas Petawatt Laser to irradiate solid gold and platinum targets, with intensities up to ~1.9 × 10 21 W.cm –2 and pulse durations as short as ~130 fs. Positron to electron (e+/e–) ratios >15% were observed for many thick disk and rod targets, with the highest e+/e– ratio reaching ~50% for a Pt rod. The inferred pair yield was ~ few ×10 10 with emerging pair density reaching ~10 15/cm 3 so that the pair skin depth becomes < pair jet transverse size.more » These results represent major milestones towards the goal of creating a significant quantity of dense pair-dominated plasmas with e+/e– approaching 100% and pair skin depth << pair plasma size, which will have wide-ranging applications to astrophysics and fundamental physics.« less

Global power balance on high density field reversed configurations for use in magnetized target fusion

NASA Astrophysics Data System (ADS)

Renneke, Richard M.

Field Reversed Configuration plasmas (FRCs) have been created in the Field Reversed Experiment-Liner (FRX-L) with density 2--6 x 10 22 m-3, total temperature 300--400 eV, and lifetime on the order of 10 micros. This thesis investigates global energy balance on high-density FRCs for the first time. The zero-dimensional approach to global energy balance developed by Rej and Tuszewski (Phys. Fluids 27, p. 1514, 1984) is utilized here. From the shots analyzed with this method, it is clear that energy loss from these FRCs is dominated by particle and thermal (collisional) losses. The percentage of radiative losses versus total loss is an order of magnitude lower than previous FRC experiments. This is reasonable for high density based on empirical scaling from the extensive database of tokamak plasma experiments. Ohmic dissipation, which heats plasma when trapped magnetic field decays to create electric field, is an important source of heating for the plasma. Ohmic heating shows a correlation with increasing the effective Lundquist number (S*). Empirical evidence suggest S* can be increased by lowering the density, which does not achieve the goals of FRX-L. A better way to improve ohmic heating is to trap more poloidal flux. This dissertation shows that FRX-L follows a semi-empirical scaling law which predicts plasma temperature gains for larger poloidal flux. Flux (tauφ) and particle (tauN) lifetimes for these FRCs were typically shorter than 10 micros. Approximately 1/3 of the particle and flux lifetimes for these FRCs did not scale with the usual tauN ≈ tauφ scaling of low-density FRCs, but instead showed tauN ≥ tau φ. However, scatter in the data indicates that the average performance of FRCs on FRX-L yields the typical (for FRCs) relationship tau N ≈ tauφ. Fusion energy gain Q was extrapolated for the shots analyzed in this study using a zero-dimensional scaling code with liner effects. The predicted Q is below the desired value of 0.1 (Schoenberg et al., LA-UR-98-2413, 1998). The situation predicted to lead to Q = 0.1 requires a larger plasma pressure than shown in the present data. This can be accomplished by increasing the plasma density (through larger fill pressure) and maintaining temperature with increased flux trapping. Larger Q and other benefits could be realized by raising the plasma pressure for future FRX-L shots. The innovation inherent in this work performed by the author is the extension of the global power balance model to include a time history of the plasma discharge. This extension required rigorous checking of the power balance model using internal density profiles provided by the multichord interferometer. Typical orders of the parameters calculated by the model are ˜500 MW total loss power, ˜100 MW ohmic heating power, and ˜200 MW total compression (input) power. Radiation was never measured above 5 MW, which is why it was deemed insignificant. It should be noted that these numbers are merely estimates and vary widely between shots.

Simulations of ion acceleration from ultrathin targets with the VEGA petawatt laser

NASA Astrophysics Data System (ADS)

Stockhausen, Luca C.; Torres, Ricardo; Conejero Jarque, Enrique

2015-05-01

The Spanish Pulsed Laser Centre (CLPU) is a new high-power laser facility for users. Its main system, VEGA, is a CPA Ti:Sapphire laser which, in its final phase, will be able to reach petawatt peak powers in pulses of 30 fs with a pulse contrast of 1 : 1010 at 1 ps. The extremely low level of pre-pulse intensity makes this system ideally suited for studying the laser interaction with ultrathin targets. We have used the particle-in-cell (PIC) code OSIRIS to carry out 2D simulations of the acceleration of ions from ultrathin solid targets under the unique conditions provided by VEGA, with laser intensities up to 1022Wcm-2 impinging normally on 5 - 40 nm thick overdense plasmas, with different polarizations and pre-plasma scale lengths. We show how signatures of the radiation pressure dominated regime, such as layer compression and bunch formation, are only present with circular polarization. By passively shaping the density gradient of the plasma, we demonstrate an enhancement in peak energy up to tens of MeV and monoenergetic features. On the contrary linear polarization at the same intensity level causes the target to blow up, resulting in much lower energies and broader spectra. One limiting factor of Radiation Pressure Acceleration is the development of Rayleigh-Taylor like instabilities at the interface of the plasma and photon fluid. This results in the formation of bubbles in the spatial profile of laser-accelerated proton beams. These structures were previously evidenced both experimentally and theoretically. We have performed 2D simulations to characterize this bubble-like structure and report on the dependency on laser and target parameters.

Progress in Direct-Drive Inertial Confinement Fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCrory, R.L.; Meyerhofer, D.D.; Betti, R.

Significant progress in direct-drive inertial confinement fusion (ICF) research has been made since the completion of the 60-beam, 30-kJ UV OMEGA Laser System [T. R. Boehly, Opt. Commun. 133, 495 (1997)] in 1995. A theory of ignition requirements, applicable to any ICF concept, has been developed. Detailed understanding of laser-plasma coupling, electron thermal transport, and hot-electron preheating has lead to the measurement of neutron-averaged areal densities of ~200 mg/cm^2 in cryogenic target implosions. These correspond to an estimated peak fuel density in excess of 100 g/cm^3 and are in good agreement with hydrodynamic simulations. The implosions were performed using anmore » 18-kJ drive pulse designed to put the converging fuel on an adiabat of two. The polar-drive concept will allow direct-drive-ignition research on the National Ignition Facility while it is configured for indirect drive. Advanced ICF ignition concepts—fast ignition [Tabak et al., Phys. Plasmas 1, 1626 (1994)] and shock ignition [R. Betti et al., Phys. Rev. Lett. 98, 155001 (2007)]—have the potential to significantly reduce ignition driver energies and/or provide higher target gain.« less

Progress in direct-drive inertial confinement fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCrory, R. L.; Meyerhofer, D. D.; Betti, R.

Significant progress in direct-drive inertial confinement fusion (ICF) research has been made since the completion of the 60-beam, 30-kJ{sub UV} OMEGA Laser System [Boehly, Opt. Commun. 133, 495 (1997)] in 1995. A theory of ignition requirements, applicable to any ICF concept, has been developed. Detailed understanding of laser-plasma coupling, electron thermal transport, and hot-electron preheating has lead to the measurement of neutron-averaged areal densities of {approx}200 mg/cm{sup 2} in cryogenic target implosions. These correspond to an estimated peak fuel density in excess of 100 g/cm{sup 3} and are in good agreement with hydrodynamic simulations. The implosions were performed using anmore » 18-kJ drive pulse designed to put the converging fuel on an adiabat of two. The polar-drive concept will allow direct-drive-ignition research on the National Ignition Facility while it is configured for indirect drive. Advanced ICF ignition concepts - fast ignition [Tabak et al., Phys. Plasmas 1, 1626 (1994)] and shock ignition [Betti et al., Phys. Rev. Lett. 98, 155001 (2007)] - have the potential to significantly reduce ignition driver energies and/or provide higher target gain.« less

Permanent alteration of PCSK9 with in vivo CRISPR-Cas9 genome editing.

PubMed

Ding, Qiurong; Strong, Alanna; Patel, Kevin M; Ng, Sze-Ling; Gosis, Bridget S; Regan, Stephanie N; Cowan, Chad A; Rader, Daniel J; Musunuru, Kiran

2014-08-15

Individuals with naturally occurring loss-of-function proprotein convertase subtilisin/kexin type 9 (PCSK9) mutations experience reduced low-density lipoprotein cholesterol levels and protection against cardiovascular disease. The goal of this study was to assess whether genome editing using a clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated system can efficiently introduce loss-of-function mutations into the endogenous PCSK9 gene in vivo. We used adenovirus to express CRISPR-associated 9 and a CRISPR guide RNA targeting Pcsk9 in mouse liver, where the gene is specifically expressed. We found that <3 to 4 days of administration of the virus, the mutagenesis rate of Pcsk9 in the liver was as high as >50%. This resulted in decreased plasma PCSK9 levels, increased hepatic low-density lipoprotein receptor levels, and decreased plasma cholesterol levels (by 35-40%). No off-target mutagenesis was detected in 10 selected sites. Genome editing with the CRISPR-CRISPR-associated 9 system disrupts the Pcsk9 gene in vivo with high efficiency and reduces blood cholesterol levels in mice. This approach may have therapeutic potential for the prevention of cardiovascular disease in humans. © 2014 American Heart Association, Inc.

Advanced Concept Exploration for Fast Ignition Science Program, Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stephens, Richard Burnite; McLean, Harry M.; Theobald, Wolfgang

The Fast Ignition (FI) Concept for Inertial Confinement Fusion (ICF) has the potential to provide a significant advance in the technical attractiveness of Inertial Fusion Energy reactors. FI differs from conventional “central hot spot” (CHS) target ignition by decoupling compression from heating: using a laser (or heavy ion beam or Z pinch) drive pulse (10’s of nanoseconds) to create a dense fuel and a second, much shorter (~10 picoseconds) high intensity pulse to ignite a small volume within the dense fuel. The physics of fast ignition process was the focus of our Advanced Concept Exploration (ACE) program. Ignition depends criticallymore » on two major issues involving Relativistic High Energy Density (RHED) physics: The laser-induced creation of fast electrons and their propagation in high-density plasmas. Our program has developed new experimental platforms, diagnostic packages, computer modeling analyses, and taken advantage of the increasing energy available at laser facilities to advance understanding of the fundamental physics underlying these issues. Our program had three thrust areas: • Understand the production and characteristics of fast electrons resulting from FI relevant laser-plasma interactions and their dependence on laser prepulse and laser pulse length. • Investigate the subsequent fast electron transport in solid and through hot (FI-relevant) plasmas. • Conduct and understand integrated core-heating experiments by comparison to simulations. Over the whole period of this project (three years for this contract), we have greatly advanced our fundamental understanding of the underlying properties in all three areas: • Comprehensive studies on fast electron source characteristics have shown that they are controlled by the laser intensity distribution and the topology and plasma density gradient. Laser pre-pulse induced pre-plasma in front of a solid surface results in increased stand-off distances from the electron origin to the high density target as well as large and erratic spread of the electron beam with increasing short pulse duration. We have demonstrated, using newly available higher contrast lasers, an improved energy coupling, painting a promising picture for FI feasibility. • Our detailed experiments and analyses of fast electron transport dependence on target material have shown that it is feasible to collimate fast electron beam by self-generated resistive magnetic fields in engineered targets with a rather simple geometry. Stable and collimated electron beam with spot size as small as 50-μm after >100-μm propagation distance (an angular divergence angle of 20°!) in solid density plasma targets has been demonstrated with FI-relevant (10-ps, >1-kJ) laser pulses Such collimated beam would meet the required heating beam size for FI. • Our new experimental platforms developed for the OMEGA laser (i.e., i) high resolution 8 keV backlighter platform for cone-in-shell implosion and ii) the 8 keV imaging with Cu-doped shell targets for detailed transport characterization) have enabled us to experimentally confirm fuel assembly from cone-in-shell implosion with record-high areal density. We have also made the first direct measurement of fast electron transport and spatial energy deposition in integrated FI experiments enabling the first experiment-based benchmarking of integrated simulation codes. Executing this program required a large team. It was managed as a collaboration between General Atomics (GA), Lawrence Livermore National Laboratory (LLNL), and the Laboratory for Laser Energetics (LLE). GA fulfills its responsibilities jointly with the University of California, San Diego (UCSD), The Ohio State University (OSU) and the University of Nevada at Reno (UNR). The division of responsibility was as follows: (1) LLE had primary leadership for channeling studies and the integrated energy transfer, (2) LLNL led the development of measurement methods, analysis, and deployment of diagnostics, and (3) GA together with UCSD, OSU and UNR studied the detailed energy-transfer physics. The experimental program was carried out using the Titan laser at the Jupiter Laser Facility at LLNL, the OMEGA and OMEGA EP lasers at LLE and the Texas Petawatt laser at the University of Texas, Austin. Modeling has been pursued on large computing facilities at LLNL, OSU, and UCSD using codes developed (by us and others) within the HEDLP program, commercial codes, and by leveraging existing simulations codes developed by the National Nuclear Security Administration ICF program. One important aspect of this program was the involvement and training of young scientists including postdoctoral fellows and graduate students. This project generated an impressive forty articles in high quality journals including nine (two under review) in Physical Review Letters during the three years of this grant and five graduate students completed their doctoral dissertations.« less

Wavefront-sensor-based electron density measurements for laser-plasma accelerators.

PubMed

Plateau, G R; Matlis, N H; Geddes, C G R; Gonsalves, A J; Shiraishi, S; Lin, C; van Mourik, R A; Leemans, W P

2010-03-01

Characterization of the electron density in laser produced plasmas is presented using direct wavefront analysis of a probe laser beam. The performance of a laser-driven plasma-wakefield accelerator depends on the plasma wavelength and hence on the electron density. Density measurements using a conventional folded-wave interferometer and using a commercial wavefront sensor are compared for different regimes of the laser-plasma accelerator. It is shown that direct wavefront measurements agree with interferometric measurements and, because of the robustness of the compact commercial device, offer greater phase sensitivity and straightforward analysis, improving shot-to-shot plasma density diagnostics.

Wavefront-sensor-based electron density measurements for laser-plasma accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Plateau, Guillaume; Matlis, Nicholas; Geddes, Cameron

2010-02-20

Characterization of the electron density in laser produced plasmas is presented using direct wavefront analysis of a probe laser beam. The performance of a laser-driven plasma-wakefield accelerator depends on the plasma wavelength, hence on the electron density. Density measurements using a conventional folded-wave interferometer and using a commercial wavefront sensor are compared for different regimes of the laser-plasma accelerator. It is shown that direct wavefront measurements agree with interferometric measurements and, because of the robustness of the compact commercial device, have greater phase sensitivity, straightforward analysis, improving shot-to-shot plasma-density diagnostics.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yanagawa, T.; Sakagami, H.; Nagatomo, H.

In inertial confinement fusion, the implosion process is important in forming a high-density plasma core. In the case of a fast ignition scheme using a cone-guided target, the fuel target is imploded with a cone inserted. This scheme is advantageous for efficiently heating the imploded fuel core; however, asymmetric implosion is essentially inevitable. Moreover, the effect of cone position and opening angle on implosion also becomes critical. Focusing on these problems, the effect of the asymmetric implosion, the initial position, and the opening angle on the compression rate of the fuel is investigated using a three-dimensional pure hydrodynamic code.

The distribution of the scattered laser light in laser-plate-target coupling

NASA Astrophysics Data System (ADS)

Xiao-bo, Nie; Tie-qiang, Chang; Dong-xian, Lai; Shen-ye, Liu; Zhi-jian, Zheng

1997-04-01

Theoretical and experimental studies of the angular distributions of scattered laser light in laser-Au-plate-target coupling are reported. A simple model that describes three-dimensional plasmas and scattered laser light is presented. The approximate shape of critical density surface has been given and the three-dimensional laser ray tracing is applied in the model. The theoretical results of the model are consistent with the experimental data for the scattered laser light in the polar angle range of 25° to 145° from the laser beam.

Laser-Plasma Interaction Experiments at Direct-Drive Ignition-Relevant Plasma Conditions at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Solodov, A. A.; Rosenberg, M. J.; Myatt, J. F.; Shaw, J. G.; Seka, W.; Epstein, R.; Short, R. W.; Follett, R. K.; Regan, S. P.; Froula, D. H.; Radha, P. B.; Michel, P.; Chapman, T.; Hohenberger, M.

2017-10-01

Laser-plasma interaction (LPI) instabilities, such as stimulated Raman scattering (SRS) and two-plasmon decay, can be detrimental for direct-drive inertial confinement fusion because of target preheat by the high-energy electrons they generate. The radiation-hydrodynamic code DRACO was used to design planar-target experiments at the National Ignition Facility that generated plasma and interaction conditions relevant to ignition direct-drive designs (IL 1015W/cm2 , Te > 3 keV, density gradient scale lengths of Ln 600 μm). Laser-energy conversion efficiency to hot electrons of 0.5% to 2.5% with temperature of 45 to 60 keV was inferred from the experiment when the laser intensity at the quarter-critical surface increased from 6 to 15 ×1014W/cm2 . LPI was dominated by SRS, as indicated by the measured scattered-light spectra. Simulations of SRS using the LPI code LPSE have been performed and compared with predictions of theoretical models. Implications for ignition-scale direct-drive experiments will be discussed. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Modeling Laser-Plasma Interactions at Direct-Drive Ignition-Relevant Plasma Conditions at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Solodov, A. A.; Rosenberg, M. J.; Myatt, J. F.; Epstein, R.; Seka, W.; Hohenberger, M.; Short, R. W.; Shaw, J. G.; Regan, S. P.; Froula, D. H.; Radha, P. B.; Bates, J. W.; Schmitt, A. J.; Michel, P.; Moody, J. D.; Ralph, J. E.; Turnbull, D. P.; Barrios, M. A.

2016-10-01

Laser-plasma interaction instabilities, such as two-plasmon decay (TPD) and stimulated Raman scattering (SRS), can be detrimental for direct-drive inertial confinement fusion because of target preheat by generated high-energy electrons. The radiation-hydrodynamics code DRACO has been used to design planar-target experiments that generate plasma and interaction conditions relevant to direct-drive-ignition designs (IL 1015 W / cm 2 , Te > 3 KeV density gradient scale lengths of Ln 600 μm) . The hot-electron temperature of 40to50keV and the fraction of laser energy converted to hot electrons of 0.5to were inferred based on comparing the simulated and experimentally observed x-ray emission when the laser intensity at the quarter-critical surface increased from 6 to 15 ×1014 W / cm 2 . The measured SRS energy was sufficient to explain the observed total energy in hot electrons. Implications for ignition-scale direct-drive experiments and hot-electron preheat mitigation using mid- Z ablators will be discussed. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Heat-Flux Measurements in Laser-Produced Plasmas Using Thomson Scattering from Electron Plasma Waves

NASA Astrophysics Data System (ADS)

Henchen, R. J.; Goncharov, V. N.; Cao, D.; Katz, J.; Froula, D. H.; Rozmus, W.

2017-10-01

An experiment was designed to measure heat flux in coronal plasmas using collective Thomson scattering. Adjustments to the electron distribution function resulting from heat flux affect the shape of the collective Thomson scattering features through wave-particle resonance. The amplitude of the Spitzer-Härm electron distribution function correction term (f1) was varied to match the data and determines the value of the heat flux. Independent measurements of temperature and density obtained from Thomson scattering were used to infer the classical heat flux (q = - κ∇Te) . Time-resolved Thomson-scattering data were obtained at five locations in the corona along the target normal in a blowoff plasma formed from a planar Al target with 1.5 kJ of 351-nm laser light in a 2-ns square pulse. The flux measured through the Thomson-scattering spectra is a factor of 5 less than the κ∇Te measurements. The lack of collisions of heat-carrying electrons suggests a nonlocal model is needed to accurately describe the heat flux. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Revealing plasma oscillation in THz spectrum from laser plasma of molecular jet.

PubMed

Li, Na; Bai, Ya; Miao, Tianshi; Liu, Peng; Li, Ruxin; Xu, Zhizhan

2016-10-03

Contribution of plasma oscillation to the broadband terahertz (THz) emission is revealed by interacting two-color (ω/2ω) laser pulses with a supersonic jet of nitrogen molecules. Temporal and spectral shifts of THz waves are observed as the plasma density varies. The former owes to the changing refractive index of the THz waves, and the latter correlates to the varying plasma frequency. Simulation of considering photocurrents, plasma oscillation and decaying plasma density explains the broadband THz spectrum and the varying THz spectrum. Plasma oscillation only contributes to THz waves at low plasma density owing to negligible plasma absorption. At the longer medium or higher density, the combining effects of plasma oscillation and absorption results in the observed low-frequency broadband THz spectra.

Overview on the target fabrication facilities at ELI-NP and ongoing strategies

NASA Astrophysics Data System (ADS)

Gheorghiu, C. C.; Leca, V.; Popa, D.; Cernaianu, M. O.; Stutman, D.

2016-10-01

Along with the development of petawatt class laser systems, the interaction between high power lasers and matter flourished an extensive research, with high-interest applications like: laser nuclear physics, proton radiography or cancer therapy. The new ELI-NP (Extreme Light Infrastructure - Nuclear Physics) petawatt laser facility, with 10PW and ~ 1023W/cm2 beam intensity, is one of the innovative projects that will provide novel research of fundamental processes during light-matter interaction. As part of the ELI-NP facility, Targets Laboratory will provide the means for in-house manufacturing and characterization of the required targets (mainly solid ones) for the experiments, in addition to the research activity carried out in order to develop novel target designs with improved performances. A description of the Targets Laboratory with the main pieces of equipment and their specifications are presented. Moreover, in view of the latest progress in the target design, one of the proposed strategies for the forthcoming experiments at ELI-NP is also described, namely: ultra-thin patterned foil of diamond-like carbon (DLC) coated with a carbon-based ultra-low density layer. The carbon foam which behaves as a near-critical density plasma, will allow the controlled-shaping of the laser pulse before the main interaction with the solid foil. Particular emphasis will be directed towards the target's design optimization, by simulation tests and tuning the key-properties (thickness/length, spacing, density foam, depth, periodicity etc.) which are expected to have a crucial effect on the laser-matter interaction process.

Morphology and characteristics of laser-induced aluminum plasma in argon and in air: A comparative study

NASA Astrophysics Data System (ADS)

Bai, Xueshi; Cao, Fan; Motto-Ros, Vincent; Ma, Qianli; Chen, Yanping; Yu, Jin

2015-11-01

In laser-induced breakdown spectroscopy (LIBS), ablation takes place in general in an ambient gas of the atmospheric pressure, often in air but also in noble gas such as argon or helium. The use of noble gas is known to significantly improve the performance of the technique. We investigate in this work the morphology and the characteristics of induced plasma in argon and in air. The purpose is to understand the mechanism of the analytical performance improvement by the use of argon ambient with respective to air ambient and the dependence on the other experimental parameters such as the laser fluence. The observation of plasma morphology in different ambient gases provides also information for better design of the detection system which optimizes the signal collection according to the used ambient gases. More specifically, the expansion of the plasma induced on an aluminum target with nanosecond infrared (1064 nm) laser pulse in two ambient gases, argon and the atmospheric air, has been studied with spectroscopic imaging at short delays and with emission spectroscopy at longer delays. With relatively low ablation laser fluence (65 J/cm2), similar morphologies have been observed in argon and in air over the early stage of plasma expansion, while diagnostics at longer delay shows stronger emission, higher electron density and temperature for plasma induced in argon. With higher ablation laser fluence (160 J/cm2) however, different expansion behaviors have been observed, with a stagnating aluminum vapor near the target surface in air while a propagating plume away from the target in argon. The craters left on the target surface show as well corresponding difference: in air, the crater is very shallow with a target surface chaotically affected by the laser pulse, indicating an effective re-deposition of the ablated material back to the crater; while in Ar a deeper crater is observed, indicating an efficient mass removal by laser ablation. At longer delays, a brighter, denser and hotter plasma is always observed in argon than in air as with lower ablation laser fluences. The observed different influences of the ambient gas on the plasma expansion behavior for different laser fluences are related to the different modes of laser-supported absorption waves, namely laser-supported combustion (LSC) wave and laser-supported detonation (LSD) wave.

High-efficiency acceleration in the laser wakefield by a linearly increasing plasma density

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, Kegong; Wu, Yuchi; Zhu, Bin

The acceleration length and the peak energy of the electron beam are limited by the dephasing effect in the laser wakefield acceleration with uniform plasma density. Based on 2D-3V particle in cell simulations, the effects of a linearly increasing plasma density on the electron acceleration are investigated broadly. Comparing with the uniform plasma density, because of the prolongation of the acceleration length and the gradually increasing accelerating field due to the increasing plasma density, the electron beam energy is twice higher in moderate nonlinear wakefield regime. Because of the lower plasma density, the linearly increasing plasma density can also avoidmore » the dark current caused by additional injection. At the optimal acceleration length, the electron energy can be increased from 350 MeV (uniform) to 760 MeV (linearly increasing) with the energy spread of 1.8%, the beam duration is 5 fs and the beam waist is 1.25 μm. This linearly increasing plasma density distribution can be achieved by a capillary with special gas-filled structure, and is much more suitable for experiment.« less

Preliminary scaling laws for plasma current, ion kinetic temperature, and plasma number density in the NASA Lewis bumpy torus plasma

NASA Technical Reports Server (NTRS)

Roth, J. R.

1976-01-01

Parametric variation of independent variables which may affect the characteristics of bumpy torus plasma have identified those which have a significant effect on the plasma current, ion kinetic temperature, and plasma number density, and those which do not. Empirical power law correlations of the plasma current, and the ion kinetic temperature and number density were obtained as functions of potential applied to the midplane electrode rings, the background neutral gas pressure, and the magnetic field strength. Additional parameters studied included the type of gas, the polarity of the midplane electrode rings, the mode of plasma operation, and the method of measuring the plasma number density. No significant departures from the scaling laws appear to occur at the highest ion kinetic temperatures or number densities obtained to date.

Long pulse high performance plasma scenario development for the National Spherical Torus Experiment

NASA Astrophysics Data System (ADS)

Kessel, C. E.; Bell, R. E.; Bell, M. G.; Gates, D. A.; Kaye, S. M.; LeBlanc, B. P.; Menard, J. E.; Phillips, C. K.; Synakowski, E. J.; Taylor, G.; Wilson, R.; Harvey, R. W.; Mau, T. K.; Ryan, P. M.; Sabbagh, S. A.

2006-05-01

The National Spherical Torus Experiment [Ono et al., Nucl. Fusion, 44, 452 (2004)] is targeting long pulse high performance, noninductive sustained operations at low aspect ratio, and the demonstration of nonsolenoidal startup and current rampup. The modeling of these plasmas provides a framework for experimental planning and identifies the tools to access these regimes. Simulations based on neutral beam injection (NBI)-heated plasmas are made to understand the impact of various modifications and identify the requirements for (1) high elongation and triangularity, (2) density control to optimize the current drive, (3) plasma rotation and/or feedback stabilization to operate above the no-wall β limit, and (4) electron Bernstein waves (EBW) for off-axis heating/current drive (H/CD). Integrated scenarios are constructed to provide the transport evolution and H/CD source modeling, supported by rf and stability analyses. Important factors include the energy confinement, Zeff, early heating/H mode, broadening of the NBI-driven current profile, and maintaining q(0) and qmin>1.0. Simulations show that noninductive sustained plasmas can be reached at IP=800 kA, BT=0.5 T, κ≈2.5, βN⩽5, β⩽15%, fNI=92%, and q(0)>1.0 with NBI H/CD, density control, and similar global energy confinement to experiments. The noninductive sustained high β plasmas can be reached at IP=1.0 MA, BT=0.35 T, κ≈2.5, βN⩽9, β⩽43%, fNI=100%, and q(0)>1.5 with NBI H/CD and 3.0 MW of EBW H/CD, density control, and 25% higher global energy confinement than experiments. A scenario for nonsolenoidal plasma current rampup is developed using high harmonic fast wave H/CD in the early low IP and low Te phase, followed by NBI H/CD to continue the current ramp, reaching a maximum of 480 kA after 3.4 s.

Onset of normal and inverse homoclinic bifurcation in a double plasma system near a plasma fireball

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitra, Vramori; Sarma, Bornali; Sarma, Arun

Plasma fireballs are generated due to a localized discharge and appear as a luminous glow with a sharp boundary, which suggests the presence of a localized electric field such as electrical sheath or double layer structure. The present work reports the observation of normal and inverse homoclinic bifurcation phenomena in plasma oscillations that are excited in the presence of fireball in a double plasma device. The controlling parameters for these observations are the ratio of target to source chamber (n{sub T}/n{sub S}) densities and applied electrode voltage. Homoclinic bifurcation is noticed in the plasma potential fluctuations as the system evolvesmore » from narrow to long time period oscillations and vice versa with the change of control parameter. The dynamical transition in plasma fireball is demonstrated by spectral analysis, recurrence quantification analysis (RQA), and statistical measures, viz., skewness and kurtosis. The increasing trend of normalized variance reflects that enhancing n{sub T}/n{sub S} induces irregularity in plasma dynamics. The exponential growth of the time period is strongly indicative of homoclinic bifurcation in the system. The gradual decrease of skewness and increase of kurtosis with the increase of n{sub T}/n{sub S} also reflect growing complexity in the system. The visual change of recurrence plot and gradual enhancement of RQA variables DET, L{sub max}, and ENT reflects the bifurcation behavior in the dynamics. The combination of RQA and spectral analysis is a clear evidence that homoclinic bifurcation occurs due to the presence of plasma fireball with different density ratios. However, inverse bifurcation takes place due to the change of fireball voltage. Some of the features observed in the experiment are consistent with a model that describes the dynamics of ionization instabilities.« less

Heavy ion charge-state distribution effects on energy loss in plasmas.

PubMed

Barriga-Carrasco, Manuel D

2013-10-01

According to dielectric formalism, the energy loss of the heavy ion depends on its velocity and its charge density. Also, it depends on the target through its dielectric function; here the random phase approximation is used because it correctly describes fully ionized plasmas at any degeneracy. On the other hand, the Brandt-Kitagawa (BK) model is employed to depict the projectile charge space distribution, and the stripping criterion of Kreussler et al. is used to determine its mean charge state [Q]. This latter criterion implies that the mean charge state depends on the electron density and temperature of the plasma. Also, the initial charge state of the heavy ion is crucial for calculating [Q] inside the plasma. Comparing our models and estimations with experimental data, a very good agreement is found. It is noticed that the energy loss in plasmas is higher than that in the same cold gas cases, confirming the well-known enhanced plasma stopping (EPS). In this case, EPS is only due to the increase in projectile effective charge Q(eff), which is obtained as the ratio between the energy loss of each heavy ion and that of the proton in the same plasma conditions. The ratio between the effective charges in plasmas and in cold gases is higher than 1, but it is not as high as thought in the past. Finally, another significant issue is that the calculated effective charge in plasmas Q(eff) is greater than the mean charge state [Q], which is due to the incorporation of the BK charge distribution. When estimations are performed without this distribution, they do not fit well with experimental data.

Electron cyclotron plasma startup in the GDT experiment

NASA Astrophysics Data System (ADS)

Yakovlev, D. V.; Shalashov, A. G.; Gospodchikov, E. D.; Solomakhin, A. L.; Savkin, V. Ya.; Bagryansky, P. A.

2017-01-01

We report on a new plasma startup scenario in the gas dynamic trap (GDT) magnetic mirror device. The primary 5 MW neutral beam injection (NBI) plasma heating system fires into a sufficiently dense plasma target (‘seed plasma’), which is commonly supplied by an arc plasma generator. In the reported experiments, a different approach to seed plasma generation is explored. One of the channels of the electron cyclotron resonance (ECR) heating system is used to ionize the neutral gas and build up the density of plasma to a level suitable for NBI capture. After a short transition of approximately 1 ms the discharge becomes essentially similar to a standard one initiated by the plasma gun. This paper presents the discharge scenario and experimental data on the seed plasma evolution during ECRH, along with the dependencies on incident microwave power, magnetic configuration and pressure of a neutral gas. The characteristics of the consequent high-power NBI discharge are studied and differences from the conventional scenario are discussed. A theoretical model describing the ECR breakdown and the seed plasma accumulation in a large-scale mirror trap is developed on the basis of the GDT experiment.

Diagnostics of RF magnetron sputtering plasma for synthesizing transparent conductive Indium-Zinc-Oxide film

NASA Astrophysics Data System (ADS)

Ohta, Takayuki; Inoue, Mari; Takota, Naoki; Ito, Masafumi; Higashijima, Yasuhiro; Kano, Hiroyuki; den, Shoji; Yamakawa, Koji; Hori, Masaru

2009-10-01

Transparent conductive Oxide film has been used as transparent conducting electrodes of optoelectronic devices such as flat panel display, solar cells, and so on. Indium-Zinc-Oxide (IZO) has been investigated as one of promising alternatives Indium Tin Oxide film, due to amorphous, no nodule and so on. In order to control a sputtering process with highly precise, RF magnetron sputtering plasma using IZO composite target was diagnosed by absorption and emission spectroscopy. We have developed a multi-micro hollow cathode lamp which can emit simultaneous multi-atomic lines for monitoring Zn and In densities simultaneously. Zn and In densities were measured to be 10^9 from 10^10 cm-3 at RF power from 40 to 100 W, pressure of 5Pa, and Ar flow rate of 300 sccm. The emission intensities of Zn, In, InO, and Ar were also observed.

Application of laser driven fast high density plasma blocks for ion implantation

NASA Astrophysics Data System (ADS)

Sari, Amir H.; Osman, F.; Doolan, K. R.; Ghoranneviss, M.; Hora, H.; Höpfl, R.; Benstetter, G.; Hantehzadeh, M. H.

2005-10-01

The measurement of very narrow high density plasma blocks of high ion energy from targets irradiated with ps-TW laser pulses based on a new skin depth interaction process is an ideal tool for application of ion implantation in materials, especially of silicon, GaAs, or conducting polymers, for micro-electronics as well as for low cost solar cells. A further application is for ion sources in accelerators with most specifications of many orders of magnitudes advances against classical ion sources. We report on near band gap generation of defects by implantation of ions as measured by optical absorption spectra. A further connection is given for studying the particle beam transforming of n-type semiconductors into p-type and vice versa as known from sub-threshold particle beams. The advantage consists in the use of avoiding aggressive or rare chemical materials when using the beam techniques for industrial applications.

Characteristics of the Secondary Divertor on DIII-D

NASA Astrophysics Data System (ADS)

Watkins, J. G.; Lasnier, C. J.; Leonard, A. W.; Evans, T. E.; Pitts, R.; Stangeby, P. C.; Boedo, J. A.; Moyer, R. A.; Rudakov, D. L.

2009-11-01

In order to address a concern that the ITER secondary divertor strike plates may be insufficiently robust to handle the incident pulses of particles and energy from ELMs, we performed dedicated studies of the secondary divertor plasma and scrape-off layer (SOL). Detailed measurements of the ELM energy and particle deposition footprint on the secondary divertor target plates were made with a fast IR camera and Langmuir probes and SOL profile and transport measurements were made with reciprocating probes. The secondary divertor and SOL conditions depended on changes in the magnetic balance and the core plasma density. Larger density resulted in smaller ELMs and the magnetic balance affected how many ELM particles coupled to the secondary SOL and divertor. Particularly striking are the images from a new fast IR camera that resolve ELM heat pulses and show spiral patterns with multiple peaks during ELMs in the secondary divertor.

Parametric scaling of neutral and ion excited state densities in an argon helicon source

NASA Astrophysics Data System (ADS)

McCarren, D.; Scime, E.

2016-04-01

We report measurements of the absolute density and temperature of ion and neutral excited states in an argon helicon source. The excited ion state density, which depends on ion density, electron density, and electron temperature, increases sharply with increasing magnetic field in the source. The neutral argon metastable density measurements are consistent with an increasing ionization fraction with increasing magnetic field strength. The ion temperature shows no evidence of increased heating with increasing magnetic field strength (which has only been observed in helicon sources operating at driving frequencies close to the lower hybrid frequency). The measurements were obtained through cavity ring down spectroscopy, a measurement technique that does not require the target excited state to be metastable or part of a fluorescence scheme; and is therefore applicable to any laser accessible atomic or ionic transition in a plasma.

A review on ab initio studies of static, transport, and optical properties of polystyrene under extreme conditions for inertial confinement fusion applications

NASA Astrophysics Data System (ADS)

Hu, S. X.; Collins, L. A.; Boehly, T. R.; Ding, Y. H.; Radha, P. B.; Goncharov, V. N.; Karasiev, V. V.; Collins, G. W.; Regan, S. P.; Campbell, E. M.

2018-05-01

Polystyrene (CH), commonly known as "plastic," has been one of the widely used ablator materials for capsule designs in inertial confinement fusion (ICF). Knowing its precise properties under high-energy-density conditions is crucial to understanding and designing ICF implosions through radiation-hydrodynamic simulations. For this purpose, systematic ab initio studies on the static, transport, and optical properties of CH, in a wide range of density and temperature conditions (ρ = 0.1 to 100 g/cm3 and T = 103 to 4 × 106 K), have been conducted using quantum molecular dynamics (QMD) simulations based on the density functional theory. We have built several wide-ranging, self-consistent material-properties tables for CH, such as the first-principles equation of state, the QMD-based thermal conductivity (κQMD) and ionization, and the first-principles opacity table. This paper is devoted to providing a review on (1) what results were obtained from these systematic ab initio studies; (2) how these self-consistent results were compared with both traditional plasma-physics models and available experiments; and (3) how these first-principles-based properties of polystyrene affect the predictions of ICF target performance, through both 1-D and 2-D radiation-hydrodynamic simulations. In the warm dense regime, our ab initio results, which can significantly differ from predictions of traditional plasma-physics models, compared favorably with experiments. When incorporated into hydrocodes for ICF simulations, these first-principles material properties of CH have produced significant differences over traditional models in predicting 1-D/2-D target performance of ICF implosions on OMEGA and direct-drive-ignition designs for the National Ignition Facility. Finally, we will discuss the implications of these studies on the current small-margin ICF target designs using a CH ablator.

Design of a novel high efficiency antenna for helicon plasma sources

NASA Astrophysics Data System (ADS)

Fazelpour, S.; Chakhmachi, A.; Iraji, D.

2018-06-01

A new configuration for an antenna, which increases the absorption power and plasma density, is proposed for helicon plasma sources. The influence of the electromagnetic wave pattern symmetry on the plasma density and absorption power in a helicon plasma source with a common antenna (Nagoya) is analysed by using the standard COMSOL Multiphysics 5.3 software. In contrast to the theoretical model prediction, the electromagnetic wave does not represent a symmetric pattern for the common Nagoya antenna. In this work, a new configuration for an antenna is proposed which refines the asymmetries of the wave pattern in helicon plasma sources. The plasma parameters such as plasma density and absorption rate for a common Nagoya antenna and our proposed antenna under the same conditions are studied using simulations. In addition, the plasma density of seven operational helicon plasma source devices, having a common Nagoya antenna, is compared with the simulation results of our proposed antenna and the common Nagoya antenna. The simulation results show that the density of the plasma, which is produced by using our proposed antenna, is approximately twice in comparison to the plasma density produced by using the common Nagoya antenna. In fact, the simulation results indicate that the electric and magnetic fields symmetry of the helicon wave plays a vital role in increasing wave-particle coupling. As a result, wave-particle energy exchange and the plasma density of helicon plasma sources will be increased.

High density operation with Lower Hybrid waves in FTU tokamak

NASA Astrophysics Data System (ADS)

Pericoli Ridolfini, V.; Mirizzi, F.; Panaccione, L.; Podda, S.

2001-10-01

Since April 2001 the lower hybrid (LH) radiofrequency system in FTU (6 gyrotrons @ f=8 GHz) can deliver to the plasma about 2 MW through two equal launchers with a reflection coefficient = 10%. This value is close to the target value of 2.2 MW (net power density of 6.2 kW/cm2 on the waveguides mouth) which could be reached after further conditioning of the grill and of the transmission lines. In high density plasmas (line density *1*1020 m-3), high magnetic field (BT=7.2 T), with PLH=2 MW we drive about 75% of the total current (Ip=500 kA) and stabilise fully the sawteeth activity. The central electron temperature Te0 increases from 1.6 to 3.3 keV (steady), and the neutron rate by about 10 times. Analysis of these pulses with effective electronic heating will be presented. In post-pellet plasmas ( *6*1020 m-3), good coupling of the LH is achieved with the launcher almost flush to the walls, due to the very dense scrape off-layer. The perturbation here induced by the pellet imposes a delay to the LH of only 20 ms. The exact location of the launcher is critical in these regimes, because the high N|| (parallel index of refraction) requested (N||>2.3) for a good penetration of the waves makes more problematic a good coupling all along the poloidal extension of the grill.

Observational Study of Ion Diffusion Region tailward of the Cusp: Polar and Cluster Observations in 1998-2008

NASA Astrophysics Data System (ADS)

Muzamil, F. M.; Farrugia, C. J.; Torbert, R. B.; Argall, M. R.; Wang, S.

2015-12-01

Asymmetries in plasma density and the presence of a guide field significantly alter the structure of the ion diffusion region (IDR) in symmetric, collisionless reconnection. These features have been shown by numerical simulations under moderate density asymmetries (~10), and theoretical analyses. However, very few studies have addressed these issues with in-situ observations. We have compiled a collection of Cluster and Polar crossings of the high-latitude magnetopause poleward of the cusp under northward interplanetary magnetic field in the years 1998-2008 when signatures of reconnection inside the IDR are observed. They encompass a wide range of density asymmetries (~10 to 1000), magnetic field asymmetries (~0.2 to 0.9), and guide fields (~10 to ~60 %). In this dedicated observational study, we target the following topics: (1) The alteration of the structure of the IDR -- i.e., its width, the non-colocation of stagnation and X-lines, jet outflow speed, and biasing of the reconnection outflow jet toward the magnetosphere -- as a function of increasing density asymmetry, and (2) the diamagnetic drift of the X-line. Further, focusing on IDR crossings during plasma flow reversals and/or near-simultaneous crossings on either side of the X-line by two spacecraft under steady ambient conditions, we report on the contrast in the Hall fields and the plasma behavior on the sunward versus the tailward sides of the X-line in its dependence on the strength of the guide field.

On the scaling of avaloids and turbulence with the average density approaching the density limit

NASA Astrophysics Data System (ADS)

Antar, G. Y.; Counsell, G.; Ahn, J.-W.

2005-08-01

This article is dedicated to the characterization of turbulent transport in the scrape-off layer of the Mega Ampère Spherical Tokamak [A. Sykes et al., Phys. Plasmas 8, 2101 (2001)] as a function of the average density (nL). The aim is to answer a renewed interest in this subject since the bursty character of turbulence in the scrape-off layer was shown to be caused by large-scale events with high radial velocity reaching about 1/10th of the sound speed called avaloids [G. Antar et al., Phys. Rev. Lett 87, 065001 (2001)]. With increasing density, turbulence and transport increase nonlinearly at the midplane while remaining almost unchanged in the target region. Using various and complementary statistical analyses, the existence of a "critical" density, at nL/nG≃0.35 is emphasized; nG is the Greenwald density. Both above and below this density, intermittency decreases and avaloids play a decreasing role in the particle radial transport. This is interpreted as caused by the interplay between avaloids and the surrounding turbulent structures which mix them more efficiently with increasing density as the level of the background turbulence increases. The scaling of the different quantities with respect to the normalized density is obtained. It reveals that not only the level of turbulence and transport increase, but also the radial velocity and length scales. This increases the coupling between the hot plasma edge and the cold scrape-off layer that may explain the disruptive instability occurring at high densities.

Lineshape measurements of He- β spectra on the ORION laser facility

DOE PAGES

Beiersdorfer, P.; Brown, G. V.; Shepherd, R.; ...

2016-10-25

Here, we have utilized a newly developed high-resolution X-ray spectrometer to measure the shapes of spectral lines produced from laser-irradiated targets on the Orion laser facility in the United Kingdom. We present measurements of the He-β spectra of chlorine and chromium from targets irradiated by either a long-pulse or a short-pulse laser beam. The experimental conditions provide a spread in plasma density ranging from about 10 19 to about 10 24 cm –3. We present spectral calculations that show that the relative intensities of the Li-like satellite lines can be used to infer the density in the lower range, especiallymore » if the lithiumlike satellite lines are well resolved. In addition, we use the Stark-broadened width of the He-β line to infer densities above about 10 22 cm –3. In the case of a short-pulse irradiated chromium foil, we find that the He-like chromium is produced at a density of almost 8 g/cm 3, i.e., solid density. In addition, we can infer the electron temperature from the observation of dielectronic recombination satellite lines.« less

FRX-L Research Status and Plans

NASA Astrophysics Data System (ADS)

Wurden, G. A.; Intrator, T. P.; Taccetti, J. M.; Furno, I. G.; Hsu, S. C.; Zhang, S. Y.; Degnan, J. H.; Grabowski, C.; Ruden, E. L.

2003-10-01

Our research plans for FRX-L, the field reversed configuration plasma injector at LANL for magnetized target fusion (MTF), have been planned for the next 4-year period. FRX-L has been successfully operating now for the last two years, although construction for both the machine and diagnostic sets is ongoing. Efforts in FY04 begin with continued improvements in the basic high density FRC parameters, through operation at increased magnetic fields and with the addition of a more effective main bank crowbar to reduce parasitic ringing in the high current main coil circuit. Translation experiments into a "fake" metal liner, perforated with diagnostic access ports, will start after designing and constructing the translation section. Another bank of capacitors will be added to power the additional guide and mirror coils. After demonstrating trapping of the plasma in the aluminum liner, and diagnosing sufficient plasma parameters (density, temperature, lifetime, purity), we will begin preparations for the integrated plasma/liner compression experiment at the Air Force Research Laboratory Shiva-Star machine in FY05. Construction of the new hardware will continue during FY06, and the first fusion-relevant demonstration of compression of plasma by an imploding metal liner is planned for FY07. Our MTF plans also include new initiatives with U of Washington, U of Wisconsin, and the University of New Mexico, in addition to ongoing theory ties to LLNL and GA.

Kinetic modeling of x-ray laser-driven solid Al plasmas via particle-in-cell simulation

NASA Astrophysics Data System (ADS)

Royle, R.; Sentoku, Y.; Mancini, R. C.; Paraschiv, I.; Johzaki, T.

2017-06-01

Solid-density plasmas driven by intense x-ray free-electron laser (XFEL) radiation are seeded by sources of nonthermal photoelectrons and Auger electrons that ionize and heat the target via collisions. Simulation codes that are commonly used to model such plasmas, such as collisional-radiative (CR) codes, typically assume a Maxwellian distribution and thus instantaneous thermalization of the source electrons. In this study, we present a detailed description and initial applications of a collisional particle-in-cell code, picls, that has been extended with a self-consistent radiation transport model and Monte Carlo models for photoionization and K L L Auger ionization, enabling the fully kinetic simulation of XFEL-driven plasmas. The code is used to simulate two experiments previously performed at the Linac Coherent Light Source investigating XFEL-driven solid-density Al plasmas. It is shown that picls-simulated pulse transmissions using the Ecker-Kröll continuum-lowering model agree much better with measurements than do simulations using the Stewart-Pyatt model. Good quantitative agreement is also found between the time-dependent picls results and those of analogous simulations by the CR code scfly, which was used in the analysis of the experiments to accurately reproduce the observed K α emissions and pulse transmissions. Finally, it is shown that the effects of the nonthermal electrons are negligible for the conditions of the particular experiments under investigation.

Preliminary scaling laws for plasma current, ion kinetic temperature, and plasma number density in the NASA Lewis Bumpy Torus plasma

NASA Technical Reports Server (NTRS)

Roth, J. R.

1976-01-01

Parametric variation of independent variables which may affect the characteristics of the NASA Lewis Bumpy Torus plasma have identified those which have a significant effect on the plasma current, ion kinetic temperature, and plasma number density, and those which do not. Empirical power-law correlations of the plasma current, and the ion kinetic temperature and number density were obtained as functions of the potential applied to the midplane electrode rings, the background neutral gas pressure, and the magnetic field strength. Additional parameters studied include the type of gas, the polarity of the midplane electrode rings (and hence the direction of the radial electric field), the mode of plasma operation, and the method of measuring the plasma number density. No significant departures from the scaling laws appear to occur at the highest ion kinetic temperatures or number densities obtained to date.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fang, Dongfan, E-mail: fangdongfan1208@126.com; Sun, Qizhi; Zhao, Xiaoming

A 633 nm laser interferometer has been designed based on a novel concept, which, without the acousto-optic modulator or the demodulator circuit, adopts the fibers to connect all elements except photodetectors and oscilloscope in this system to make it more compact, portable, and efficient. The noteworthy feature is to mathematically compare the two divided interference signals, which have the same phase-shift caused by the electron density but possess the different initial phase and low angular frequencies. It is possible to read the plasma density directly on the oscilloscope by our original mathematic demodulation method without a camera. Based on themore » Abel inversion algorithm, the radial electron density profiles versus time can be obtained by using the multi-chord system. The designed measurable phase shift ranges from 0 to 2π rad corresponding to the maximum line integral of electron density less than 3.5 × 10{sup 17} cm{sup −2}, and the phase accuracy is about 0.017 rad corresponding to the line integral of electron density accuracy of 1 × 10{sup 15} cm{sup −2}. After the construction of eight-chord interferometer, it will provide the detailed time resolved information of the spatial distribution of the electron density in the field-reversed configuration (FRC) plasma target produced by the “Yingguang-1” programmed-discharge device, which is being constructed in the Key Laboratory of Pulsed Power, China Academy of Engineering Physics.« less

Diagnostics of recombining laser plasma parameters based on He-like ion resonance lines intensity ratios

NASA Astrophysics Data System (ADS)

Ryazantsev, S. N.; Skobelev, I. Yu; Faenov, A. Ya; Pikuz, T. A.; Grum-Grzhimailo, A. N.; Pikuz, S. A.

2016-11-01

While the plasma created by powerful laser expands from the target surface it becomes overcooled, i.e. recombining one. Improving of diagnostic methods applicable for such plasma is rather important problem in laboratory astrophysics nowadays because laser produced jets are fully scalable to young stellar objects. Such scaling is possible because of the plasma hydrodynamic equations invariance under some transformations. In this paper it is shown that relative intensities of the resonance transitions in He-like ions can be used to measure the parameters of recombining plasma. Intensity of the spectral lines corresponding to these transitions is sensitive to the density in the range of 1016-1020 cm-3 while the temperature ranges from 10 to 100 eV for ions with nuclear charge Zn ∼ 10. Calculations were carried out for F VIII ion and allowed to determine parameters of plasma jets created by nanosecond laser system ELFIE (Ecole Polytechnique, France) for astrophysical phenomenon modelling. Obtained dependencies are quite universal and can be used for any recombining plasma containing He-like fluorine ions.

Directional power absorption in helicon plasma sources excited by a half-helix antenna

NASA Astrophysics Data System (ADS)

Afsharmanesh, Mohsen; Habibi, Morteza

2017-10-01

This paper deals with the investigation of the power absorption in helicon plasma excited through a half-helix antenna driven at 13.56 {{MHz}}. The simulations were carried out by means of a code, HELIC. They were carried out by taking into account different inhomogeneous radial density profiles and for a wide range of plasma densities, from {10}11 {{{cm}}}-3 to {10}13 {{{cm}}}-3. The magnetic field was 200, 400, 600 and 1000 {{G}}. A three-parameter function was used for generating various density profiles with different volume gradients, edge gradients and density widths. The density profile had a large effect on the efficient Trivelpiece-Gould (TG) and helicon mode excitation and antenna coupling to the plasma. The fraction of power deposition via the TG mode was extremely dependent on the plasma density near the plasma boundary. Interestingly, the obtained efficient parallel helicon wavelength was close to the anticipated value for Gaussian radial density profile. Power deposition was considerably asymmetric when the \\tfrac{n}{{B}0} ratio was more than a specific value for a determined density width. The longitudinal power absorption was symmetric at approximately {n}0={10}11 {{{cm}}}-3, irrespective of the magnetic field supposed. The asymmetry became more pronounced when the plasma density was {10}12 {{{cm}}}-3. The ratio of density width to the magnetic field was an important parameter in the power coupling. At high magnetic fields, the maximum of the power absorption was reached at higher plasma density widths. There was at least one combination of the plasma density, magnetic field and density width for which the RF power deposition at both side of the tube reached its maximum value.

Effect of the resonant magnetic perturbation on the plasma parameters in COMPASS tokamak’s divertor region

NASA Astrophysics Data System (ADS)

Dimitrova, M.; Cahyna, P.; Peterka, M.; Hasan, E.; Popov, Tsv K.; Ivanova, P.; Vasileva, E.; Panek, R.; Cavalier, J.; Seidl, J.; Markovic, T.; Havlicek, J.; Dejarnac, R.; Weinzettl, V.; Hacek, P.; Tomes, M.; the COMPASS Team; the EUROfusion MST1 Team

2018-02-01

The resonant magnetic perturbation (RMP) has proven to be a useful way to suppress edge-localized modes that under certain conditions can damage the device by the large power fluxes carried from the bulk plasma to the wall. The effect of RMP on the L-mode plasma parameters in the divertor region of the COMPASS tokamak was studied using the array of 39 Langmuir probes embedded into the divertor target. The current-voltage (IV) probe characteristics were processed by the first-derivative probe technique to obtain the plasma potential and the electron energy distribution function (EEDF) which was approximated by a bi-Maxwellian EEDF with a low-energy (4-6 eV) fraction and a high-energy (11-35 eV) one, the both factions having similar electron density. Clear splitting was observed during the RMP pulse in the low-field-side scrape-off-layer profiles of the floating potential U fl and the ion saturation current density J sat; these two quantities were obtained both by direct continuous measurement and by evaluation of the IV characteristics of probes with swept bias. The negative peaks of U fl induced by RMP spatially overlaps with the local minima of J sat (and n e) rather than with its local maxima which is partly caused by the spatial variation of the plasma potential and partly by the changed shape of the EEDF. The effective temperature of the whole EEDF is not correlated with the negative peaks of U fl, and the profile of the parallel power flux density shows secondary maxima due to RMP which mimic those of J sat.

XFEL resonant photo-pumping of dense plasmas and dynamic evolution of autoionizing core hole states

NASA Astrophysics Data System (ADS)

Rosmej, F. B.; Moinard, A.; Renner, O.; Galtier, E.; Lee, J. J.; Nagler, B.; Heimann, P. A.; Schlotter, W.; Turner, J. J.; Lee, R. W.; Makita, M.; Riley, D.; Seely, J.

2016-03-01

Similarly to the case of LIF (Laser-Induced Fluorescence), an equally revolutionary impact to science is expected from resonant X-ray photo-pumping. It will particularly contribute to a progress in high energy density science: pumped core hole states create X-ray transitions that can escape dense matter on a 10 fs-time scale without essential photoabsorption, thus providing a unique possibility to study matter under extreme conditions. In the first proof of principle experiment at the X-ray Free Electron Laser LCLS at SCLAC [Seely, J., Rosmej, F.B., Shepherd, R., Riley, D., Lee, R.W. Proposal to Perform the 1st High Energy Density Plasma Spectroscopic Pump/Probe Experiment”, approved LCLS proposal L332 (2010)] we have successfully pumped inner-shell X-ray transitions in dense plasmas. The plasma was generated with a YAG laser irradiating solid Al and Mg targets attached to a rotating cylinder. In parallel to the optical laser beam, the XFEL was focused into the plasma plume at different delay times and pump energies. Pumped X-ray transitions have been observed with a spherically bent crystal spectrometer coupled to a Princeton CCD. By using this experimental configuration, we have simultaneously achieved extremely high spectral (λ/δλ ≈ 5000) and spatial resolution (δx≈70 μm) while maintaining high luminosity and a large spectral range covered (6.90 - 8.35 Å). By precisely measuring the variations in spectra emitted from plasma under action of XFEL radiation, we have successfully demonstrated transient X- ray pumping in a dense plasma.

Plasma ignition and steady state simulations of the Linac4 H- ion source

NASA Astrophysics Data System (ADS)

Mattei, S.; Ohta, M.; Yasumoto, M.; Hatayama, A.; Lettry, J.; Grudiev, A.

2014-02-01

The RF heating of the plasma in the Linac4 H- ion source has been simulated using a particle-in-cell Monte Carlo collision method. This model is applied to investigate the plasma formation starting from an initial low electron density of 1012 m-3 and its stabilization at 1018 m-3. The plasma discharge at low electron density is driven by the capacitive coupling with the electric field generated by the antenna, and as the electron density increases the capacitive electric field is shielded by the plasma and induction drives the plasma heating process. Plasma properties such as e-/ion densities and energies, sheath formation, and shielding effect are presented and provide insight to the plasma properties of the hydrogen plasma.

Self-organization and self-limitation in high power impulse magnetron sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anders, Andre

The plasma over the racetrack in high power impulse magnetron sputtering develops in traveling ionization zones. Power densities can locally reach 10{sup 9} W/m{sup 2}, which is much higher than usually reported. Ionization zones move because ions are 'evacuated' by the electric field, exposing neutrals to magnetically confined, drifting electrons. Drifting secondary electrons amplify ionization of the same ionization zone where the primary ions came from, while sputtered and outgassing atoms are supplied to the following zone(s). Strong density gradients parallel to the target disrupt electron confinement: a negative feedback mechanism that stabilizes ionization runaway.

Overview of the electric propulsion plasma diagnostics suite for the VASIMR VX-200 testbed

NASA Astrophysics Data System (ADS)

Olsen, Christopher; Longmier, Benjamin; Ballenger, Maxwell; Squire, Jared; Glover, Tim; Carter, Mark; Bering, Edgar; Giambusso, Matthew

2012-10-01

Descriptions of the various plasma diagnostics and data analysis methods are given for instruments used in high power (> 100 kW) electric propulsion testing. These include planar Langmuir probes, an articulating retarding potential analyzer, a double Langmuir probe, a multi-axis magnetometer, a high frequency electric field probe, microwave interferometer, and momentum flux targets. These diagnostics have been used to measure the efficiencies of the thruster, plasma source, ion cyclotron resonance booster, and magnetic nozzle as well as used to explore physical phenomena in the plume such as ion/electron detachment, plasma turbulence, and magnetic field line stretching. Typical plume parameters range up to 10^13 cm-3 electron density, 1 kG applied magnetic fields, ion energies in excess of 150 eV, and cold electrons (2 -- 5 eV) with a spatial measurement range over 2 m.

Positron production by x rays emitted by betatron motion in a plasma wiggler.

PubMed

Johnson, D K; Auerbach, D; Blumenfeld, I; Barnes, C D; Clayton, C E; Decker, F J; Deng, S; Emma, P; Hogan, M J; Huang, C; Ischebeck, R; Iverson, R; Joshi, C; Katsouleas, T C; Kirby, N; Krejcik, P; Lu, W; Marsh, K A; Mori, W B; Muggli, P; O'Connell, C L; Oz, E; Siemann, R H; Walz, D; Zhou, M

2006-10-27

Positrons in the energy range of 3-30 MeV, produced by x rays emitted by betatron motion in a plasma wiggler of 28.5 GeV electrons from the SLAC accelerator, have been measured. The extremely high-strength plasma wiggler is an ion column induced by the electron beam as it propagates through and ionizes dense lithium vapor. X rays in the range of 1-50 MeV in a forward cone angle of 0.1 mrad collide with a 1.7 mm thick tungsten target to produce electron-positron pairs. The positron spectra are found to be strongly influenced by the plasma density and length as well as the electron bunch length. By characterizing the beam propagation in the ion column these influences are quantified and result in excellent agreement between the measured and calculated positron spectra.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frerichs, H.; Reiter, D.; Schmitz, O.

The impact of resonant magnetic perturbations (RMPs) on the plasma edge can be analyzed in detail by three dimensional computer simulations, which take the underlying magnetic field structure as input. Previously, the 'vacuum approximation' has been used to calculate the magnetic field structure although plasma response effects may result in a screening (or even an amplification) of the external perturbations. Simulation results for an ITER similar shape plasma at the DIII-D tokamak are presented for the full vacuum perturbation field and an ad hoc screening case in comparison to the unperturbed configuration. It is shown that the RMP induced helicalmore » patterns in the plasma edge and on the divertor target shrink once screening is taken into account. However, a flat temperature profile is still found in the 'open field line domain' inside the separatrix, while the 'density pump out effect' found in the vacuum RMP case is considerably weakened.« less

Laser ablated copper plasmas in liquid and gas ambient

NASA Astrophysics Data System (ADS)

Kumar, Bhupesh; Thareja, Raj K.

2013-05-01

The dynamics of copper ablated plasma plumes generated using laser ablation of copper targets in both liquid (de-ionized water) and gas (air) ambients is reported. Using time and space resolved visible emission spectroscopy (450-650 nm), the plasma plumes parameters are investigated. The electron density (ne) determined using Stark broadening of the Cu I (3d104d1 2D3/2-3d104p1 2P3/2 at 521.8 nm) line is estimated and compared for both plasma plumes. The electron temperature (Te) was estimated using the relative line emission intensities of the neutral copper transitions. Field emission scanning electron microscopy and energy dispersive x-ray spectral analysis of the ablated copper surface indicated abundance of spherical nanoparticles in liquid while those in air are amalgamates of irregular shapes. The nanoparticles suspended in the confining liquid form aggregates and exhibit a surface plasmon resonance at ˜590 nm.

Canonical angular momentum compression near the Brillouin limit

NASA Astrophysics Data System (ADS)

Jeong, E.; Gilson, E.; Fajans, J.

2000-10-01

Near the Brillouin limit, the angular momentum of a trapped, T=0, pure-electron plasma approaches zero. If the plasma expands axially, its density would appear to drop. However, the plasma's canonical angular momentum is not changed by an axial expansion, so the plasma must stay near the Brillouin limit; thus the plasma's density cannot change when it is expanded. The only way for the plasma density to remain constant as the plasma length increases is for the plasma radius to decrease. Dynamically, this decrease is caused by the polarization drift induced by a small decrease in the density. In this poster we present preliminary experimental evidence demonstrating this radial compression. This work was supported by the ONR.

High Current, High Density Arc Plasma as a New Source for WiPAL

NASA Astrophysics Data System (ADS)

Waleffe, Roger; Endrizzi, Doug; Myers, Rachel; Wallace, John; Clark, Mike; Forest, Cary; WiPAL Team

2016-10-01

The Wisconsin Plasma Astrophysics Lab (WiPAL) has installed a new array of nineteen plasma sources (plasma guns) on its 3 m diameter, spherical vacuum vessel. Each gun is a cylindrical, molybdenum, washer-stabilized, arc plasma source. During discharge, the guns are maintained at 1.2 kA across 100 V for 10 ms by the gun power supply establishing a high density plasma. Each plasma source is fired independently allowing for adjustable plasma parameters, with densities varying between 1018 -1019 m-3 and electron temperatures of 5-15 eV. Measurements were characterized using a 16 tip Langmuir probe. The plasma source will be used as a background plasma for the magnetized coaxial plasma gun (MCPG), the Terrestrial Reconnection Experiment (TREX), and as the plasma source for a magnetic mirror experiment. Temperature, density, and confinement results will be presented. This work is supported by the DoE and the NSF.

Enhanced electron yield from laser-driven wakefield acceleration in high-Z gas jets.

PubMed

Mirzaie, Mohammad; Hafz, Nasr A M; Li, Song; Liu, Feng; He, Fei; Cheng, Ya; Zhang, Jie

2015-10-01

An investigation of the electron beam yield (charge) form helium, nitrogen, and neon gas jet plasmas in a typical laser-plasma wakefield acceleration experiment is carried out. The charge measurement is made by imaging the electron beam intensity profile on a fluorescent screen into a charge coupled device which was cross-calibrated with an integrated current transformer. The dependence of electron beam charge on the laser and plasma conditions for the aforementioned gases are studied. We found that laser-driven wakefield acceleration in low Z-gas jet targets usually generates high-quality and well-collimated electron beams with modest yields at the level of 10-100 pC. On the other hand, filamentary electron beams which are observed from high-Z gases at higher densities reached much higher yields. Evidences for cluster formation were clearly observed in the nitrogen gas jet target, where we received the highest electron beam charge of ∼1.7 nC. Those intense electron beams will be beneficial for the applications on the generation of bright X-rays, gamma rays radiations, and energetic positrons via the bremsstrahlung or inverse-scattering processes.

Local palmitoylation cycles define activity-regulated postsynaptic subdomains

PubMed Central

Fukata, Yuko; Dimitrov, Ariane; Boncompain, Gaelle; Vielemeyer, Ole

2013-01-01

Distinct PSD-95 clusters are primary landmarks of postsynaptic densities (PSDs), which are specialized membrane regions for synapses. However, the mechanism that defines the locations of PSD-95 clusters and whether or how they are reorganized inside individual dendritic spines remains controversial. Because palmitoylation regulates PSD-95 membrane targeting, we combined a conformation-specific recombinant antibody against palmitoylated PSD-95 with live-cell super-resolution imaging and discovered subsynaptic nanodomains composed of palmitoylated PSD-95 that serve as elementary units of the PSD. PSD-95 in nanodomains underwent continuous de/repalmitoylation cycles driven by local palmitoylating activity, ensuring the maintenance of compartmentalized PSD-95 clusters within individual spines. Plasma membrane targeting of DHHC2 palmitoyltransferase rapidly recruited PSD-95 to the plasma membrane and proved essential for postsynaptic nanodomain formation. Furthermore, changes in synaptic activity rapidly reorganized PSD-95 nano-architecture through plasma membrane–inserted DHHC2. Thus, the first genetically encoded antibody sensitive to palmitoylation reveals an instructive role of local palmitoylation machinery in creating activity-responsive PSD-95 nanodomains, contributing to the PSD (re)organization. PMID:23836932

Interfacial Stability of Spherically Converging Plasma Jets for Magnetized Target Fusion

NASA Technical Reports Server (NTRS)

Thio, Y. C. Francis; Cassibry, Jason; Wu, S. T.; Eskridge, Richard; Smith, James; Lee, Michael; Rodgers, Stephen L. (Technical Monitor)

2000-01-01

A fusion propulsion scheme has been proposed that makes use of the merging of a spherical distribution of plasma jets to dynamically form a gaseous liner to implode a magnetized target to produce the fusion reaction. In this paper, a study is made of the interfacial stability of the interaction of these jets. Specifically, the Orr-Sommerfeld equation is integrated to obtain the growth rate of a perturbation to the primary flow at the interface between the colliding jets. The results lead to an estimate on the tolerances on the relative flow velocities of the merging plasma jets to form a stable, imploding liner. The results show that the maximum temporal growth rate of the perturbed flow at the jet interface is very small in comparison with the time to full compression of the liner. These data suggest that, as far as the stability of the interface between the merging jets is concerned, the formation of the gaseous liner can withstand velocity variation of the order of 10% between the neighboring jets over the density and temperature ranges investigated.

Three-dimensional modeling of the neutron spectrum to infer plasma conditions in cryogenic inertial confinement fusion implosions

NASA Astrophysics Data System (ADS)

Weilacher, F.; Radha, P. B.; Forrest, C.

2018-04-01

Neutron-based diagnostics are typically used to infer compressed core conditions such as areal density and ion temperature in deuterium-tritium (D-T) inertial confinement fusion (ICF) implosions. Asymmetries in the observed neutron-related quantities are important to understanding failure modes in these implosions. Neutrons from fusion reactions and their subsequent interactions including elastic scattering and neutron-induced deuteron breakup reactions are tracked to create spectra. It is shown that background subtraction is important for inferring areal density from backscattered neutrons and is less important for the forward-scattered neutrons. A three-dimensional hydrodynamic simulation of a cryogenic implosion on the OMEGA Laser System [Boehly et al., Opt. Commun. 133, 495 (1997)] using the hydrodynamic code HYDRA [Marinak et al., Phys. Plasmas 8, 2275 (2001)] is post-processed using the tracking code IRIS3D. It is shown that different parts of the neutron spectrum from the view can be mapped into different regions of the implosion, enabling an inference of an areal-density map. It is also shown that the average areal-density and an areal-density map of the compressed target can be reconstructed with a finite number of detectors placed around the target chamber. Ion temperatures are inferred from the width of the D-D and D-T fusion neutron spectra. Backgrounds can significantly alter the inferred ion temperatures from the D-D reaction, whereas they insignificantly influence the inferred D-T ion temperatures for the areal densities typical of OMEGA implosions. Asymmetries resulting in fluid flow in the core are shown to influence the absolute inferred ion temperatures from both reactions, although relative inferred values continue to reflect the underlying asymmetry pattern. The work presented here is part of the wide range of the first set of studies performed with IRIS3D. This code will continue to be used for post-processing detailed hydrodynamic simulations and interpreting observed neutron spectra in ICF implosions.

Interferometric analysis of laboratory photoionized plasmas utilizing supersonic gas jet targets.

NASA Astrophysics Data System (ADS)

Swanson, Kyle James; Ivanov, Vladimir; Mancini, Roberto; Mayes, Daniel C.

2018-06-01

Photoionized plasmas are an important component of active galactic nuclei, x-ray binary systems and other astrophysical objects. Laboratory produced photoionized plasmas have mainly been studied at large scale facilities, due to the need for high intensity broadband x-ray flux. Using supersonic gas jets as targets has allowed university scale pulsed power generators to begin similar research. The two main advantages of this approach with supersonic gas jets include: possibility of a closer location to the x-ray source and no attenuation related to material used for containment and or tamping. Due to these factors, this experimental platform creates a laboratory environment that more closely resembles astrophysical environments. This system was developed at the Nevada Terawatt Facility using the 1 MA pulsed power generator Zebra. Neon, argon, and nitrogen supersonic gas jets are produced approximately 7-8mm from the z-pinch axis. The high intensity broadband x-ray flux produced by the collapse of the z-pinch wire array implosion irradiates the gas jet. Cylindrical wire arrays are made with 4 and 8 gold 10µm thick wire. The z-pinch radiates approximately 12-16kj of x-ray energy, with x-ray photons under 1Kev in energy. The photoionized plasma is measured via x-ray absorption spectroscopy and interferometry. A Mach-Zehnder interferometer is used to the measure neutral density of the jet prior to the zebra shot at a wavelength of 266 nm. A dual channel air-wedge shearing interferometer is used to measure electron density of the ionized gas jet during the shot, at wavelengths of 532nm and 266nm. Using a newly developed interferometric analysis tool, average ionization state maps of the plasma can be calculated. Interferometry for nitrogen and argon show an average ionization state in the range of 3-8. Preliminary x-ray absorption spectroscopy collected show neon absorption lines. This work was sponsored in part by DOE Office of Science Grant DE-SC0014451.

Development and testing of a pulsed helium ion source for probing materials and warm dense matter studies

NASA Astrophysics Data System (ADS)

Ji, Q.; Seidl, P. A.; Waldron, W. L.; Takakuwa, J. H.; Friedman, A.; Grote, D. P.; Persaud, A.; Barnard, J. J.; Schenkel, T.

2016-02-01

The neutralized drift compression experiment was designed and commissioned as a pulsed, linear induction accelerator to drive thin targets to warm dense matter (WDM) states with peak temperatures of ˜1 eV using intense, short pulses (˜1 ns) of 1.2 MeV lithium ions. At that kinetic energy, heating a thin target foil near the Bragg peak energy using He+ ions leads to more uniform energy deposition of the target material than Li+ ions. Experiments show that a higher current density of helium ions can be delivered from a plasma source compared to Li+ ions from a hot plate type ion source. He+ beam pulses as high as 200 mA at the peak and 4 μs long were measured from a multi-aperture 7-cm-diameter emission area. Within ±5% variation, the uniform beam area is approximately 6 cm across. The accelerated and compressed pulsed ion beams can be used for materials studies and isochoric heating of target materials for high energy density physics experiments and WDM studies.

Development and testing of a pulsed helium ion source for probing materials and warm dense matter studies.

PubMed

Ji, Q; Seidl, P A; Waldron, W L; Takakuwa, J H; Friedman, A; Grote, D P; Persaud, A; Barnard, J J; Schenkel, T

2016-02-01

The neutralized drift compression experiment was designed and commissioned as a pulsed, linear induction accelerator to drive thin targets to warm dense matter (WDM) states with peak temperatures of ∼1 eV using intense, short pulses (∼1 ns) of 1.2 MeV lithium ions. At that kinetic energy, heating a thin target foil near the Bragg peak energy using He(+) ions leads to more uniform energy deposition of the target material than Li(+) ions. Experiments show that a higher current density of helium ions can be delivered from a plasma source compared to Li(+) ions from a hot plate type ion source. He(+) beam pulses as high as 200 mA at the peak and 4 μs long were measured from a multi-aperture 7-cm-diameter emission area. Within ±5% variation, the uniform beam area is approximately 6 cm across. The accelerated and compressed pulsed ion beams can be used for materials studies and isochoric heating of target materials for high energy density physics experiments and WDM studies.

Development and testing of a pulsed helium ion source for probing materials and warm dense matter studies

DOE PAGES

Ji, Q.; Seidl, P. A.; Waldron, W. L.; ...

2015-11-12

In this paper, the neutralized drift compression experiment was designed and commissioned as a pulsed, linear induction accelerator to drive thin targets to warm dense matter (WDM) states with peak temperatures of ~1 eV using intense, short pulses (~1 ns) of 1.2 MeV lithium ions. At that kinetic energy, heating a thin target foil near the Bragg peak energy using He + ions leads to more uniform energy deposition of the target material than Li + ions. Experiments show that a higher current density of helium ions can be delivered from a plasma source compared to Li + ions frommore » a hot plate type ion source. He + beam pulses as high as 200 mA at the peak and 4 μs long were measured from a multi-aperture 7-cm-diameter emission area. Within ±5% variation, the uniform beam area is approximately 6 cm across. Finally, the accelerated and compressed pulsed ion beams can be used for materials studies and isochoric heating of target materials for high energy density physics experiments and WDM studies.« less

Particle-in-cell simulations of electron beam control using an inductive current divider

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swanekamp, S. B.; Angus, J. R.; Cooperstein, G.

2015-11-15

Kinetic, time-dependent, electromagnetic, particle-in-cell simulations of the inductive current divider are presented. The inductive current divider is a passive method for controlling the trajectory of an intense, hollow electron beam using a vacuum structure that inductively splits the beam's return current. The current divider concept was proposed and studied theoretically in a previous publication [Swanekamp et al., Phys. Plasmas 22, 023107 (2015)]. A central post carries a portion of the return current (I{sub 1}), while the outer conductor carries the remainder (I{sub 2}) with the injected beam current given by I{sub b} = I{sub 1} + I{sub 2}. The simulations are in agreement withmore » the theory which predicts that the total force on the beam trajectory is proportional to (I{sub 2}−I{sub 1}) and the force on the beam envelope is proportional to I{sub b}. Independent control over both the current density and the beam angle at the target is possible by choosing the appropriate current-divider geometry. The root-mean-square (RMS) beam emittance (ε{sub RMS}) varies as the beam propagates through the current divider to the target. For applications where control of the beam trajectory is desired and the current density at the target is similar to the current density at the entrance foil, there is a modest 20% increase in ε{sub RMS} at the target. For other applications where the beam is pinched to a current density ∼5 times larger at the target, ε{sub RMS} is 2–3 times larger at the target.« less

Integration of uncooled scraper elements and its diagnostics into Wendelstein 7-X

DOE PAGES

Fellinger, Joris; Loesser, Doug; Neilson, Hutch; ...

2017-08-08

The modular stellarator Wendelstein 7-X in Greifswald (Germany) successfully started operation in 2015 with short pulse limiter plasmas. In 2017, the next operation phase (OP) OP1.2 will start once 10 uncooled test divertor units (TDU) with graphite armor will be installed. The TDUs allow for plasma pulses of 10 s with 8 MW heating. OP2, allowing for steady state operation, is planned for 2020 after the TDUs will be replaced by 10 water cooled CFC armored divertors. Due to the development of plasma currents like bootstrap currents in long pulse plasmas in OP2, the plasma could hit the edge ofmore » the divertor targets which has a reduced cooling capacity compared to the central part of the target tiles. To prevent overloading of these edges, a so-called scraper element can be positioned in front of the divertor, intersecting those strike lines that would otherwise hit the divertor edges. As a result, these edges are protected but as a drawback the pumping efficiency of neutrals is also reduced. As a test an uncooled scraper element with graphite tiles will be placed in two out of ten half modules in OP1.2. A decision to install ten water cooled scraper elements for OP2 is pending on the results of this test in OP1.2. To monitor the impact of the scraper element on the plasma, Langmuir probes are integrated in the plasma facing surface, and a neutral gas manometer measures the neutral density directly behind the plasma facing surface. Moreover, IR and VIS cameras observe the plasma facing surface and thermocouples monitor the temperatures of the graphite tiles and underlying support structure. This paper describes the integration of the scraper element and its diagnostics in Wendelstein 7-X.« less

Optimizing pulse shaping and zooming for acceleration to high velocities and fusion neutron production on the Nike laser

NASA Astrophysics Data System (ADS)

Karasik, Max; Weaver, J. L.; Aglitskiy, Y.; Zalesak, S. T.; Velikovich, A. L.; Oh, J.; Obenschain, S. P.; Arikawa, Y.; Watari, T.

2010-11-01

We will present results from follow-on experiments to the record-high velocities of 1000 km/s achieved on Nike [Karasik et al., Phys. Plasmas 17, 056317 (2010) ], in which highly accelerated planar foils of deuterated polystyrene were made to collide with a witness foil to produce extreme shock pressures and result in heating of matter to thermonuclear temperatures. Still higher velocities and higher target densities are required for impact fast ignition. The aim of these experiments is shaping the driving pulse to minimize shock heating of the accelerated target and using the focal zoom capability of Nike to achieve higher densities and velocities. Spectroscopic measurements of electron temperature achieved upon impact will complement the neutron time-of-flight ion temperature measurement. Work is supported by US DOE and Office of Naval Research.

LLE Review, Volume 57. Quarterly report, October--December 1993

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simon, A.

During this quarter, the visible fruits of long design labors on the OMEGA Upgrade began to appear. The target mirror structure was put in place, along with the target chamber itself. The laser bay structures were also installed, and the bay is now being prepared to receive optomechanical, control, and laser assemblies. Further details are in the OMEGA Upgrade Status Report in this issue. Theory and analysis of previous experiments continued during this reporting period. Articles contained herein describe an improved theory of the ablative Rayleigh-Taylor instability; a novel proposal for characterizing plasma-density profiles by using grid image refractometry; amore » much-improved treatment of the damping of ion sound waves in a mixture of light and heavy ions; and, finally, a new interpretation of measurements of 3/2-harmonic radiation emitted from the long-scale-length plasmas created in earlier OMEGA experiments.« less

Kilotesla Magnetic Field due to a Capacitor-Coil Target Driven by High Power Laser

PubMed Central

Fujioka, Shinsuke; Zhang, Zhe; Ishihara, Kazuhiro; Shigemori, Keisuke; Hironaka, Youichiro; Johzaki, Tomoyuki; Sunahara, Atsushi; Yamamoto, Naoji; Nakashima, Hideki; Watanabe, Tsuguhiro; Shiraga, Hiroyuki; Nishimura, Hiroaki; Azechi, Hiroshi

2013-01-01

Laboratory generation of strong magnetic fields opens new frontiers in plasma and beam physics, astro- and solar-physics, materials science, and atomic and molecular physics. Although kilotesla magnetic fields have already been produced by magnetic flux compression using an imploding metal tube or plasma shell, accessibility at multiple points and better controlled shapes of the field are desirable. Here we have generated kilotesla magnetic fields using a capacitor-coil target, in which two nickel disks are connected by a U-turn coil. A magnetic flux density of 1.5 kT was measured using the Faraday effect 650 μm away from the coil, when the capacitor was driven by two beams from the GEKKO-XII laser (at 1 kJ (total), 1.3 ns, 0.53 or 1 μm, and 5 × 1016 W/cm2). PMID:23378905

Final Report on DTRA Basic Research Project #BRCALL08-Per3-C-2-0006 "High-Z Non-Equilibrium Physics and Bright X-ray Sources with New Laser Targets"

DOE Office of Scientific and Technical Information (OSTI.GOV)

Colvin, Jeffrey D.

This project had two major goals. Final Goal: obtain spectrally resolved, absolutely calibrated x-ray emission data from uniquely uniform mm-scale near-critical-density high-Z plasmas not in local thermodynamic equilibrium (LTE) to benchmark modern detailed atomic physics models. Scientific significance: advance understanding of non-LTE atomic physics. Intermediate Goal: develop new nano-fabrication techniques to make suitable laser targets that form the required highly uniform non-LTE plasmas when illuminated by high-intensity laser light. Scientific significance: advance understanding of nano-science. The new knowledge will allow us to make x-ray sources that are bright at the photon energies of most interest for testing radiation hardening technologies,more » the spectral energy range where current x-ray sources are weak. All project goals were met.« less

Instability-driven electromagnetic fields in coronal plasmas

DOE PAGES

Manuel, M. J.-E.; Li, C. K.; Seguin, F. H.; ...

2013-04-15

Filamentary electromagnetic fields previously observed in the coronae of laser-driven spherical targets [F. H. S eguin et al., Phys. Plasma. 19, 012701 (2012)] have been further investigated in laser irradiated plastic foils. Face-on proton-radiography provides an axial view of these filaments and shows coherent cellular structure regardless of initial foil-surface conditions. The observed cellular fields are shown to have an approximately constant scale size of 210 lm throughout the plasma evolution. A discussion of possible field-generation mechanisms is provided and it is demonstrated that the likely source of the cellular field structure is the magnetothermal instability. Using predicted temperature andmore » density profiles, the fastest growing modes of this instability were found to be slowly varying in time and consistent with the observed cellular size.« less

Atomic rate coefficients in a degenerate plasma

NASA Astrophysics Data System (ADS)

Aslanyan, Valentin; Tallents, Greg

2015-11-01

The electrons in a dense, degenerate plasma follow Fermi-Dirac statistics, which deviate significantly in this regime from the usual Maxwell-Boltzmann approach used by many models. We present methods to calculate the atomic rate coefficients for the Fermi-Dirac distribution and present a comparison of the ionization fraction of carbon calculated using both models. We have found that for densities close to solid, although the discrepancy is small for LTE conditions, there is a large divergence from the ionization fraction by using classical rate coefficients in the presence of strong photoionizing radiation. We have found that using these modified rates and the degenerate heat capacity may affect the time evolution of a plasma subject to extreme ultraviolet and x-ray radiation such as produced in free electron laser irradiation of solid targets.

Hot-electron surface retention in intense short-pulse laser-matter interactions.

PubMed

Mason, R J; Dodd, E S; Albright, B J

2005-07-01

Implicit hybrid plasma simulations predict that a significant fraction of the energy deposited into hot electrons can be retained near the surface of targets with steep density gradients illuminated by intense short-pulse lasers. This retention derives from the lateral transport of heated electrons randomly emitted in the presence of spontaneous magnetic fields arising near the laser spot, from geometric effects associated with a small hot-electron source, and from E fields arising in reaction to the ponderomotive force. Below the laser spot hot electrons are axially focused into a target by the B fields, and can filament in moderate Z targets by resistive Weibel-like instability, if the effective background electron temperature remains sufficiently low. Carefully engineered use of such retention in conjunction with ponderomotive density profile steepening could result in a reduced hot-electron range that aids fast ignition. Alternatively, such retention may disturb a deeper deposition needed for efficient radiography and backside fast ion generation.

Neutral-depletion-induced axially asymmetric density in a helicon source and imparted thrust

NASA Astrophysics Data System (ADS)

Takahashi, Kazunori; Takao, Yoshinori; Ando, Akira

2016-02-01

The high plasma density downstream of the source is observed to be sustained only for a few hundreds of microsecond at the initial phase of the discharge, when pulsing the radiofrequency power of a helicon plasma thruster. Measured relative density of argon neutrals inside the source implies that the neutrals are significantly depleted there. A position giving a maximum plasma density temporally moves to the upstream side of the source due to the neutral depletion and then the exhausted plasma density significantly decreases. The direct thrust measurement demonstrates that the higher thrust-to-power ratio is obtained by using only the initial phase of the high density plasma, compared with the steady-state operation.

Laser-driven strong magnetostatic fields with applications to charged beam transport and magnetized high energy-density physics

NASA Astrophysics Data System (ADS)

Santos, J. J.; Bailly-Grandvaux, M.; Ehret, M.; Arefiev, A. V.; Batani, D.; Beg, F. N.; Calisti, A.; Ferri, S.; Florido, R.; Forestier-Colleoni, P.; Fujioka, S.; Gigosos, M. A.; Giuffrida, L.; Gremillet, L.; Honrubia, J. J.; Kojima, S.; Korneev, Ph.; Law, K. F. F.; Marquès, J.-R.; Morace, A.; Mossé, C.; Peyrusse, O.; Rose, S.; Roth, M.; Sakata, S.; Schaumann, G.; Suzuki-Vidal, F.; Tikhonchuk, V. T.; Toncian, T.; Woolsey, N.; Zhang, Z.

2018-05-01

Powerful nanosecond laser-plasma processes are explored to generate discharge currents of a few 100 kA in coil targets, yielding magnetostatic fields (B-fields) in excess of 0.5 kT. The quasi-static currents are provided from hot electron ejection from the laser-irradiated surface. According to our model, which describes the evolution of the discharge current, the major control parameter is the laser irradiance Ilasλlas2 . The space-time evolution of the B-fields is experimentally characterized by high-frequency bandwidth B-dot probes and proton-deflectometry measurements. The magnetic pulses, of ns-scale, are long enough to magnetize secondary targets through resistive diffusion. We applied it in experiments of laser-generated relativistic electron transport through solid dielectric targets, yielding an unprecedented 5-fold enhancement of the energy-density flux at 60 μm depth, compared to unmagnetized transport conditions. These studies pave the ground for magnetized high-energy density physics investigations, related to laser-generated secondary sources of radiation and/or high-energy particles and their transport, to high-gain fusion energy schemes, and to laboratory astrophysics.

Bohm criterion and plasma particle/power exhaust to and recycling at the wall

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Xianzhu; Guo, Zehua

The plasma particle and power exhaust to the divertor surface drives both particle and power recycling at the surface, which in return constrains the plasma density and temperature at the target and their profile further upstream. Both particle and power exhaust fluxes are mediated by the plasma sheath next to the divertor surface. In particular, the Bohm criterion constrains the ion exit flow speed, which enters directly into the particle flux and the kinetic flow energy component of the ion power flux, and indirectly into the electron power flux through the sheath potential drop. Here we give an overview onmore » how the Bohm speed is set in a general plasma and how it enters power exhaust and power recycling at the divertor surface, and the implication on the correct implementation of sheath boundary conditions in numerical codes. The cases of ideal and non-ideal Bohm speed are distinguished as a result of the physics discussion.« less

Bohm criterion and plasma particle/power exhaust to and recycling at the wall

DOE PAGES

Tang, Xianzhu; Guo, Zehua

2017-06-07

The plasma particle and power exhaust to the divertor surface drives both particle and power recycling at the surface, which in return constrains the plasma density and temperature at the target and their profile further upstream. Both particle and power exhaust fluxes are mediated by the plasma sheath next to the divertor surface. In particular, the Bohm criterion constrains the ion exit flow speed, which enters directly into the particle flux and the kinetic flow energy component of the ion power flux, and indirectly into the electron power flux through the sheath potential drop. Here we give an overview onmore » how the Bohm speed is set in a general plasma and how it enters power exhaust and power recycling at the divertor surface, and the implication on the correct implementation of sheath boundary conditions in numerical codes. The cases of ideal and non-ideal Bohm speed are distinguished as a result of the physics discussion.« less

Laser beat wave excitation of terahertz radiation in a plasma slab

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chauhan, Santosh; Parashar, Jetendra, E-mail: j.p.parashar@gmail.com

2014-10-15

Terahertz (THz) radiation generation by nonlinear mixing of lasers, obliquely incident on a plasma slab is investigated. Two cases are considered: (i) electron density profile is parabolic but density peak is below the critical density corresponding to the beat frequency, (ii) plasma boundaries are sharp and density is uniform. In both cases, nonlinearity arises through the ponderomotive force that gives rise to electron drift at the beat frequency. In the case of inhomogeneous plasma, non zero curl of the nonlinear current density gives rise to electromagnetic THz generation. In case of uniform plasma, the sharp density variation at the plasmamore » boundaries leads to radiation generation. In a slab width of less than a terahertz wavelength, plasma density one fourth of terahertz critical density, laser intensities ∼10{sup 17 }W/cm{sup 2} at 1 μm, one obtains the THz intensity ∼1 GW/cm{sup 2} at 3 THz radiation frequency.« less

High coupling efficiency of foam spherical hohlraum driven by 2ω laser light

NASA Astrophysics Data System (ADS)

Chen, Yao-Hua; Lan, Ke; Zheng, Wanguo; Campbell, E. M.

2018-02-01

The majority of solid state laser facilities built for laser fusion research irradiate targets with third harmonic light (0.35 μm) up-converted from the fundamental Nd wavelength at 1.05 μm. The motivation for this choice of wavelength is improved laser-plasma coupling. Significant disadvantages to this choice of wavelength are the reduced damage threshold of optical components and the efficiency of energy conversion to third harmonic light. Both these issues are significantly improved if second harmonic (0.53 μm) radiation is used, but theory and experiments have shown lower optical to x-ray energy conversion efficiency and increased levels of laser-plasma instabilities, resulting in reduced laser-target coupling. In this letter, we propose to use a 0.53 μm laser for the laser ignition facilities and use a low density foam wall to increase the coupling efficiency from the laser to the capsule and present two-dimensional radiation-hydrodynamic simulations of 0.53 μm laser light irradiating an octahedral-spherical hohlraum with a low density foam wall. The simulations show that the reduced optical depth of the foam wall leads to an increased laser-light conversion into thermal x-rays and about 10% higher radiation flux on the capsule than that achieved with 0.35 μm light irradiating a solid density wall commonly used in laser indirect drive fusion research. The details of the simulations and their implications and suggestions for wavelength scaling coupled with innovative hohlraum designs will be discussed.

Targeting Apolipoproteins in Magnetic Resonance Imaging

NASA Astrophysics Data System (ADS)

Sriram, Renuka; Lagerstedt, Jens O.; Samardzic, Haris; Kreutzer, Ulrike; Petrolova, Jitka; Xie, Hongtao; Kaysen, George A.; Voss, John C.; Desreux, Jean F.; Jue, Thomas

Maintaining normal physiological homeostasis depends upon a coordinated metabolism of both water-soluble and -insoluble substrates. In humans the body derives these molecules — such as glucose, amino acids, and fatty acids — from complex food matter. Water-soluble substrates can circulate readily in blood, while water-insoluble molecules — such as fatty acid, triacylglycerol, and cholesterol — require ampiphathic carriers to transport them from the site of biosynthesis (liver and intestine) to the target tissue. For fatty acid, albumin serves as the major transporter. For triacylglycerol and cholesterol, however, macromolecular complexes aggregate the hydrophobic molecules into the core and cover the surface with amphiphatic proteins and phospholipids to solubilize the particles in the lymphatic and circulatory systems. These macromolecules belong to a class of proteins, plasma lipoproteins, with specific functions and cellular targets. In the clinic these lipoproteins prognosticate the risk of cardiovascular disease (CVD). Lipoproteins divide usually into five major types: chylomicron, very-low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), low-density lipoprotein (LDL), and high-density lipoprotein (HDL). Each lipoprotein type exhibits characteristic density, size, and composition. As implied in the name, the density varies from the low-density chylomicron (<0.95 g/ml) to the high-density HDL (1.2 g/ml). Size also varies. The chylomicron has the largest diameter (75-1,200 nm), and HDL has the smallest (5-12 nm). The physical property variation arises from each lipoprotein's distinct composition. In a chylomicron, cholesterol, triacylglycerol, and phospholipid predominate and constitute about 90% of the particle. Protein constitutes only about 10%. In contrast, the smaller HDL has less cholesterol, triacylglycerol, and phospholipid (65% of the particle) but more protein (over 30%).

Turbulence and transport in high density, increased β LAPD plasmas

NASA Astrophysics Data System (ADS)

Rossi, Giovanni; Carter, Troy; Guice, Danny

2014-10-01

A new LaB6 cathode plasma source has recently been deployed on the Large Plasma Device (LAPD), allowing for the production of significantly higher plasma density (ne ~ 3 ×1013 cm-3) and temperature (Te ~ 12 eV and Ti ~ 6 eV). This source produces a smaller core plasma (~20cm diameter) that can be embedded in the lower temperature, lower density standard LAPD plasma (60 cm diameter, 1012 cm-3, Te ~ 5 eV, Ti ~ 1 eV). We will present first results from experiments exploring the nature of turbulence and transport produced by this high density core plasma. In contrast to the edge of the standard LAPD plasma, coherent fluctuations are observed in the edge of the high density core plasma. These coherent modes are dominant at low field (~400 G) with a transition to a more broadband spectrum at higher fields (~1 kG). The combination of increased density and temperature with lowered field in LAPD leads to significant increases in plasma β (in fact β ~ 1 can be achieved for B ~ 100 G). As the field is lowered, the strength of correlated magnetic fluctuations increases substantially.

Inertial fusion program and national laser users facility program

NASA Astrophysics Data System (ADS)

1995-01-01

This is the 1994 annual report for the University of Rochester, Laboratory for Laser Energetics. The report is presented as a series of research type reports. The titles emphasize the breadth of work carried out. They are: stability analysis of unsteady ablation fronts; characterization of laser-produced plasma density profiles using grid image refractometry; transport and sound waves in plasmas with light and heavy ions; three-halves-harmonic radiation from long-scale-length plasmas revisited; OMEGA upgrade status report; target imaging and backlighting diagnosis; effect of electron collisions on ion-acoustic waves and heat flow; particle-in-cell code simulations of the interaction of gaussian ultrashort laser pulses with targets of varying initial scale lengths; characterization of thick cryogenic fuel layers: compensation for the lens effect using convergent beam interferometry; compact, multijoule-output, Nd:Glass, large-aperture ring amplifier; atomic force microscopy observation of water-induced morphological changes in Y2O3 monolayer coatings; observation of longitudinal acceleration of electrons born in a high-intensity laser focus; spatial intensity nonuniformities of an OMEGA beam due to nonlinear beam propagation; calculated X-ray backlighting images of mixed imploded targets; evaluation of cosmic rays for use in the monitoring of the MEDUSA scintillator-photomultiplier diagnostic array; highly efficient second-harmonic generation of ultra-intense Nd:Glass laser pulses multiple cutoff wave numbers of the ablative Rayleigh-Taylor instability; ultrafast, all-silicon light modulator; angular dependence of the stimulated Brillouin scattering in homogeneous plasma; and femtosecond excited-state dynamics of a conjugated ladder polymer.