Sample records for accelerator driven experiment

  1. Electron acceleration in pulsed-power driven magnetic-reconnection experiments

    NASA Astrophysics Data System (ADS)

    Halliday, Jonathan; Hare, Jack; Lebedev, Sergey; Suttle, Lee; Bland, Simon; Clayson, Thomas; Tubman, Eleanor; Pikuz, Sergei; Shelkovenko, Tanya

    2017-10-01

    We present recent results from pulsed-power driven magnetic reconnection experiments, fielded on the MAGPIE generator (1.2 MA, 250 ns). The setup used in these experiments produces plasma inflows which are intrinsically magnetised; persist for many hydrodynamic time-scales; and are supersonic. Previous work has focussed on characterising the dynamics of bulk plasma flows, using a suite of diagnostics including laser interferometry, (imaging) Faraday rotation, and Thompson scattering. Measurements show the formation of a well defined, long lasting reconnection layer and demonstrate a power balance between the power into and out of the reconnection region. The work presented here focuses on diagnosing non-thermal electron acceleration by the reconnecting electric field. To achieve this, metal foils were placed in the path of accelerated electrons. Atomic transitions in the foil were collisionally exited by the electron beam, producing a characteristic X-Ray spectrum. This X-Ray emission was diagnosed using spherically bent crystal X-Ray spectrometry, filtered X-Ray pinhole imaging, and X-Ray sensitive PIN diodes.

  2. Laser-driven ion acceleration at BELLA

    NASA Astrophysics Data System (ADS)

    Bin, Jianhui; Steinke, Sven; Ji, Qing; Nakamura, Kei; Treffert, Franziska; Bulanov, Stepan; Roth, Markus; Toth, Csaba; Schroeder, Carl; Esarey, Eric; Schenkel, Thomas; Leemans, Wim

    2017-10-01

    BELLA is a high repetiton rate PW laser and we used it for high intensity laser plasma acceleration experiments. The BELLA-i program is focused on relativistic laser plasma interaction such as laser driven ion acceleration, aiming at establishing an unique collaborative research facility providing beam time to selected external groups for fundamental physics and advanced applications. Here we present our first parameter study of ion acceleration driven by the BELLA-PW laser with truly high repetition rate. The laser repetition rate of 1Hz allows for scanning the laser pulse duration, relative focus location and target thickness for the first time at laser peak powers of above 1 PW. Furthermore, the long focal length geometry of the experiment (f ∖65) and hence, large focus size provided ion beams of reduced divergence and unprecedented charge density. This work was supported by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

  3. Terahertz-driven linear electron acceleration

    PubMed Central

    Nanni, Emilio A.; Huang, Wenqian R.; Hong, Kyung-Han; Ravi, Koustuban; Fallahi, Arya; Moriena, Gustavo; Dwayne Miller, R. J.; Kärtner, Franz X.

    2015-01-01

    The cost, size and availability of electron accelerators are dominated by the achievable accelerating gradient. Conventional high-brightness radio-frequency accelerating structures operate with 30–50 MeV m−1 gradients. Electron accelerators driven with optical or infrared sources have demonstrated accelerating gradients orders of magnitude above that achievable with conventional radio-frequency structures. However, laser-driven wakefield accelerators require intense femtosecond sources and direct laser-driven accelerators suffer from low bunch charge, sub-micron tolerances and sub-femtosecond timing requirements due to the short wavelength of operation. Here we demonstrate linear acceleration of electrons with keV energy gain using optically generated terahertz pulses. Terahertz-driven accelerating structures enable high-gradient electron/proton accelerators with simple accelerating structures, high repetition rates and significant charge per bunch. These ultra-compact terahertz accelerators with extremely short electron bunches hold great potential to have a transformative impact for free electron lasers, linear colliders, ultrafast electron diffraction, X-ray science and medical therapy with X-rays and electron beams. PMID:26439410

  4. Terahertz-driven linear electron acceleration

    DOE PAGES

    Nanni, Emilio A.; Huang, Wenqian R.; Hong, Kyung-Han; ...

    2015-10-06

    The cost, size and availability of electron accelerators are dominated by the achievable accelerating gradient. Conventional high-brightness radio-frequency accelerating structures operate with 30–50 MeVm -1 gradients. Electron accelerators driven with optical or infrared sources have demonstrated accelerating gradients orders of magnitude above that achievable with conventional radio-frequency structures. However, laser-driven wakefield accelerators require intense femtosecond sources and direct laser-driven accelerators suffer from low bunch charge, sub-micron tolerances and sub-femtosecond timing requirements due to the short wavelength of operation. Here we demonstrate linear acceleration of electrons with keV energy gain using optically generated terahertz pulses. Terahertz-driven accelerating structures enable high-gradient electron/protonmore » accelerators with simple accelerating structures, high repetition rates and significant charge per bunch. As a result, these ultra-compact terahertz accelerators with extremely short electron bunches hold great potential to have a transformative impact for free electron lasers, linear colliders, ultrafast electron diffraction, X-ray science and medical therapy with X-rays and electron beams.« less

  5. Ultrashort laser pulse driven inverse free electron laser accelerator experiment

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

    Moody, J. T.; Anderson, S. G.; Anderson, G.

    In this paper we discuss the ultrashort pulse high gradient Inverse Free Electron laser accelerator experiment carried out at the Lawrence Livermore National Laboratory which demonstrated gra- dients exceeding 200 MV/m using a 4 TW 100 fs long 800 nm Ti:Sa laser pulse. Due to the short laser and electron pulse lengths, synchronization was determined to be one of the main challenges in this experiment. This made necessary the implementation of a single-shot, non destructive, electro-optic sampling based diagnostics to enable time-stamping of each laser accelerator shot with < 100 fs accuracy. The results of this experiment are expected tomore » pave the way towards the development of future GeV-class IFEL accelerators.« less

  6. Ultrashort laser pulse driven inverse free electron laser accelerator experiment

    DOE PAGES

    Moody, J. T.; Anderson, S. G.; Anderson, G.; ...

    2016-02-29

    In this paper we discuss the ultrashort pulse high gradient Inverse Free Electron laser accelerator experiment carried out at the Lawrence Livermore National Laboratory which demonstrated gra- dients exceeding 200 MV/m using a 4 TW 100 fs long 800 nm Ti:Sa laser pulse. Due to the short laser and electron pulse lengths, synchronization was determined to be one of the main challenges in this experiment. This made necessary the implementation of a single-shot, non destructive, electro-optic sampling based diagnostics to enable time-stamping of each laser accelerator shot with < 100 fs accuracy. The results of this experiment are expected tomore » pave the way towards the development of future GeV-class IFEL accelerators.« less

  7. Studying astrophysical particle acceleration with laser-driven plasmas

    NASA Astrophysics Data System (ADS)

    Fiuza, Frederico

    2016-10-01

    The acceleration of non-thermal particles in plasmas is critical for our understanding of explosive astrophysical phenomena, from solar flares to gamma ray bursts. Particle acceleration is thought to be mediated by collisionless shocks and magnetic reconnection. The microphysics underlying these processes and their ability to efficiently convert flow and magnetic energy into non-thermal particles, however, is not yet fully understood. By performing for the first time ab initio 3D particle-in-cell simulations of the interaction of both magnetized and unmagnetized laser-driven plasmas, it is now possible to identify the optimal parameters for the study of particle acceleration in the laboratory relevant to astrophysical scenarios. It is predicted for the Omega and NIF laser conditions that significant non-thermal acceleration can occur during magnetic reconnection of laser-driven magnetized plasmas. Electrons are accelerated by the electric field near the X-points and trapped in contracting magnetic islands. This leads to a power-law tail extending to nearly a hundred times the thermal energy of the plasma and that contains a large fraction of the magnetic energy. The study of unmagnetized interpenetrating plasmas also reveals the possibility of forming collisionless shocks mediated by the Weibel instability on NIF. Under such conditions, both electrons and ions can be energized by scattering out of the Weibel-mediated turbulence. This also leads to power-law spectra that can be detected experimentally. The resulting experimental requirements to probe the microphysics of plasma particle acceleration will be discussed, paving the way for the first experiments of these important processes in the laboratory. As a result of these simulations and theoretical analysis, there are new experiments being planned on the Omega, NIF, and LCLS laser facilities to test these theoretical predictions. This work was supported by the SLAC LDRD program and DOE Office of Science, Fusion

  8. Guided post-acceleration of laser-driven ions by a miniature modular structure

    PubMed Central

    Kar, Satyabrata; Ahmed, Hamad; Prasad, Rajendra; Cerchez, Mirela; Brauckmann, Stephanie; Aurand, Bastian; Cantono, Giada; Hadjisolomou, Prokopis; Lewis, Ciaran L. S.; Macchi, Andrea; Nersisyan, Gagik; Robinson, Alexander P. L.; Schroer, Anna M.; Swantusch, Marco; Zepf, Matt; Willi, Oswald; Borghesi, Marco

    2016-01-01

    All-optical approaches to particle acceleration are currently attracting a significant research effort internationally. Although characterized by exceptional transverse and longitudinal emittance, laser-driven ion beams currently have limitations in terms of peak ion energy, bandwidth of the energy spectrum and beam divergence. Here we introduce the concept of a versatile, miniature linear accelerating module, which, by employing laser-excited electromagnetic pulses directed along a helical path surrounding the laser-accelerated ion beams, addresses these shortcomings simultaneously. In a proof-of-principle experiment on a university-scale system, we demonstrate post-acceleration of laser-driven protons from a flat foil at a rate of 0.5 GeV m−1, already beyond what can be sustained by conventional accelerator technologies, with dynamic beam collimation and energy selection. These results open up new opportunities for the development of extremely compact and cost-effective ion accelerators for both established and innovative applications. PMID:27089200

  9. Absolute reactivity calibration of accelerator-driven systems after RACE-T experiments

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

    Jammes, C. C.; Imel, G. R.; Geslot, B.

    2006-07-01

    The RACE-T experiments that were held in november 2005 in the ENEA-Casaccia research center near Rome allowed us to improve our knowledge of the experimental techniques for absolute reactivity calibration at either startup or shutdown phases of accelerator-driven systems. Various experimental techniques for assessing a subcritical level were inter-compared through three different subcritical configurations SC0, SC2 and SC3, about -0.5, -3 and -6 dollars, respectively. The area-ratio method based of the use of a pulsed neutron source appears as the most performing. When the reactivity estimate is expressed in dollar unit, the uncertainties obtained with the area-ratio method were lessmore » than 1% for any subcritical configuration. The sensitivity to measurement location was about slightly more than 1% and always less than 4%. Finally, it is noteworthy that the source jerk technique using a transient caused by the pulsed neutron source shutdown provides results in good agreement with those obtained from the area-ratio technique. (authors)« less

  10. Particle acceleration in laser-driven magnetic reconnection

    DOE PAGES

    Totorica, S. R.; Abel, T.; Fiuza, F.

    2017-04-03

    Particle acceleration induced by magnetic reconnection is thought to be a promising candidate for producing the nonthermal emissions associated with explosive phenomena such as solar flares, pulsar wind nebulae, and jets from active galactic nuclei. Laboratory experiments can play an important role in the study of the detailed microphysics of magnetic reconnection and the dominant particle acceleration mechanisms. We have used two- and three-dimensional particle-in-cell simulations to study particle acceleration in high Lundquist number reconnection regimes associated with laser-driven plasma experiments. For current experimental conditions, we show that nonthermal electrons can be accelerated to energies more than an order ofmore » magnitude larger than the initial thermal energy. The nonthermal electrons gain their energy mainly from the reconnection electric field near the X points, and particle injection into the reconnection layer and escape from the finite system establish a distribution of energies that resembles a power-law spectrum. Energetic electrons can also become trapped inside the plasmoids that form in the current layer and gain additional energy from the electric field arising from the motion of the plasmoid. We compare simulations for finite and infinite periodic systems to demonstrate the importance of particle escape on the shape of the spectrum. Based on our findings, we provide an analytical estimate of the maximum electron energy and threshold condition for observing suprathermal electron acceleration in terms of experimentally tunable parameters. We also discuss experimental signatures, including the angular distribution of the accelerated particles, and construct synthetic detector spectra. Finally, these results open the way for novel experimental studies of particle acceleration induced by reconnection.« less

  11. Observation of 690 MV m -1 Electron Accelerating Gradient with a Laser-Driven Dielectric Microstructure

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

    Wootton, K. P.; Wu, Z.; Cowan, B. M.

    Acceleration of electrons using laser-driven dielectric microstructures is a promising technology for the miniaturization of particle accelerators. In this work, experimental results are presented of relativistic electron acceleration with 690±100 MVm -1 gradient. This is a record-high accelerating gradient for a dielectric microstructure accelerator, nearly doubling the previous record gradient. To reach higher acceleration gradients the present experiment employs 90 fs duration laser pulses.

  12. Controlling laser driven protons acceleration using a deformable mirror at a high repetition rate

    NASA Astrophysics Data System (ADS)

    Noaman-ul-Haq, M.; Sokollik, T.; Ahmed, H.; Braenzel, J.; Ehrentraut, L.; Mirzaie, M.; Yu, L.-L.; Sheng, Z. M.; Chen, L. M.; Schnürer, M.; Zhang, J.

    2018-03-01

    We present results from a proof-of-principle experiment to optimize laser driven protons acceleration by directly feeding back its spectral information to a deformable mirror (DM) controlled by evolutionary algorithms (EAs). By irradiating a stable high-repetition rate tape driven target with ultra-intense pulses of intensities ∼1020 W/ cm2, we optimize the maximum energy of the accelerated protons with a stability of less than ∼5% fluctuations near optimum value. Moreover, due to spatio-temporal development of the sheath field, modulations in the spectrum are also observed. Particularly, a prominent narrow peak is observed with a spread of ∼15% (FWHM) at low energy part of the spectrum. These results are helpful to develop high repetition rate optimization techniques required for laser-driven ion accelerators.

  13. Current driven instabilities of an electromagnetically accelerated plasma

    NASA Technical Reports Server (NTRS)

    Chouetri, E. Y.; Kelly, A. J.; Jahn, R. G.

    1988-01-01

    A plasma instability that strongly influences the efficiency and lifetime of electromagnetic plasma accelerators was quantitatively measured. Experimental measurements of dispersion relations (wave phase velocities), spatial growth rates, and stability boundaries are reported. The measured critical wave parameters are in excellent agreement with theoretical instability boundary predictions. The instability is current driven and affects a wide spectrum of longitudinal (electrostatic) oscillations. Current driven instabilities, which are intrinsic to the high-current-carrying magnetized plasma of the magnetoplasmadynmic (MPD) accelerator, were investigated with a kinetic theoretical model based on first principles. Analytical limits of the appropriate dispersion relation yield unstable ion acoustic waves for T(i)/T(e) much less than 1 and electron acoustic waves for T(i)/T(e) much greater than 1. The resulting set of nonlinear equations for the case of T(i)/T(e) = 1, of most interest to the MPD thruster Plasma Wave Experiment, was numerically solved to yield a multiparameter set of stability boundaries. Under certain conditions, marginally stable waves traveling almost perpendicular to the magnetic field would travel at a velocity equal to that of the electron current. Such waves were termed current waves. Unstable current waves near the upper stability boundary were observed experimentally and are in accordance with theoretical predictions. This provides unambiguous proof of the existence of such instabilites in electromagnetic plasma accelerators.

  14. Laser-driven ion acceleration: methods, challenges and prospects

    NASA Astrophysics Data System (ADS)

    Badziak, J.

    2018-01-01

    The recent development of laser technology has resulted in the construction of short-pulse lasers capable of generating fs light pulses with PW powers and intensities exceeding 1021 W/cm2, and has laid the basis for the multi-PW lasers, just being built in Europe, that will produce fs pulses of ultra-relativistic intensities ~ 1023 - 1024 W/cm2. The interaction of such an intense laser pulse with a dense target can result in the generation of collimated beams of ions of multi-MeV to GeV energies of sub-ps time durations and of extremely high beam intensities and ion fluencies, barely attainable with conventional RF-driven accelerators. Ion beams with such unique features have the potential for application in various fields of scientific research as well as in medical and technological developments. This paper provides a brief review of state-of-the art in laser-driven ion acceleration, with a focus on basic ion acceleration mechanisms and the production of ultra-intense ion beams. The challenges facing laser-driven ion acceleration studies, in particular those connected with potential applications of laser-accelerated ion beams, are also discussed.

  15. Beam-driven acceleration in ultra-dense plasma media

    DOE PAGES

    Shin, Young-Min

    2014-09-15

    Accelerating parameters of beam-driven wakefield acceleration in an extremely dense plasma column has been analyzed with the dynamic framed particle-in-cell plasma simulator, and compared with analytic calculations. In the model, a witness beam undergoes a TeV/m scale alternating potential gradient excited by a micro-bunched drive beam in a 10 25 m -3 and 1.6 x 10 28 m -3 plasma column. The acceleration gradient, energy gain, and transformer ratio have been extensively studied in quasi-linear, linear-, and blowout-regimes. The simulation analysis indicated that in the beam-driven acceleration system a hollow plasma channel offers 20 % higher acceleration gradient by enlargingmore » the channel radius (r) from 0.2 Ap to 0.6 .Ap in a blowout regime. This paper suggests a feasibility of TeV/m scale acceleration with a hollow crystalline structure (e.g. nanotubes) of high electron plasma density.« less

  16. Arc-driven rail accelerator research

    NASA Technical Reports Server (NTRS)

    Ray, Pradosh K.

    1987-01-01

    Arc-driven rail accelerator research is analyzed by considering wall ablation and viscous drag in the plasma. Plasma characteristics are evaluated through a simple fluid-mechanical analysis considering only wall ablation. By equating the energy dissipated in the plasma with the radiation heat loss, the average properties of the plasma are determined as a function of time and rate of ablation. Locations of two simultaneously accelerating arcs were determined by optical and magnetic probes and fron streak camera photographs. All three measurements provide consistent results.

  17. A New Type of Plasma Wakefield Accelerator Driven By Magnetowaves

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

    Chen, Pisin; /KIPAC, Menlo Park /Taiwan, Natl. Taiwan U.; Chang, Feng-Yin

    2011-09-12

    We present a new concept for a plasma wakefield accelerator driven by magnetowaves (MPWA). This concept was originally proposed as a viable mechanism for the 'cosmic accelerator' that would accelerate cosmic particles to ultra-high energies in the astrophysical setting. Unlike the more familiar plasma wakefield accelerator (PWFA) and the laser wakefield accelerator (LWFA) where the drivers, the charged-particle beam and the laser, are independently existing entities, MPWA invokes the high-frequency and high-speed whistler mode as the driver, which is a medium wave that cannot exist outside of the plasma. Aside from the difference in drivers, the underlying mechanism that excitesmore » the plasma wakefield via the ponderomotive potential is common. Our computer simulations show that under appropriate conditions, the plasma wakefield maintains very high coherence and can sustain high-gradient acceleration over many plasma wavelengths. We suggest that in addition to its celestial application, the MPWA concept can also be of terrestrial utility. A proof-of-principle experiment on MPWA would benefit both terrestrial and celestial accelerator concepts.« less

  18. First Observations of Laser-Driven Acceleration of Relativistic Electrons in a Semi-Infinite Vacuum Space

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

    Plettner, T.; Byer, R.L.; Smith, T.I.

    2006-02-17

    We have observed acceleration of relativistic electrons in vacuum driven by a linearly polarized visible laser beam incident on a thin gold-coated reflective boundary. The observed energy modulation effect follows all the characteristics expected for linear acceleration caused by a longitudinal electric field. As predicted by the Lawson-Woodward theorem the laser driven modulation only appears in the presence of the boundary. It shows a linear dependence with the strength of the electric field of the laser beam and also it is critically dependent on the laser polarization. Finally, it appears to follow the expected angular dependence of the inverse transitionmore » radiation process. experiment as the Laser Electron Accelerator Project (LEAP).« less

  19. Laser-ablation-based ion source characterization and manipulation for laser-driven ion acceleration

    NASA Astrophysics Data System (ADS)

    Sommer, P.; Metzkes-Ng, J.; Brack, F.-E.; Cowan, T. E.; Kraft, S. D.; Obst, L.; Rehwald, M.; Schlenvoigt, H.-P.; Schramm, U.; Zeil, K.

    2018-05-01

    For laser-driven ion acceleration from thin foils (∼10 μm–100 nm) in the target normal sheath acceleration regime, the hydro-carbon contaminant layer at the target surface generally serves as the ion source and hence determines the accelerated ion species, i.e. mainly protons, carbon and oxygen ions. The specific characteristics of the source layer—thickness and relevant lateral extent—as well as its manipulation have both been investigated since the first experiments on laser-driven ion acceleration using a variety of techniques from direct source imaging to knife-edge or mesh imaging. In this publication, we present an experimental study in which laser ablation in two fluence regimes (low: F ∼ 0.6 J cm‑2, high: F ∼ 4 J cm‑2) was applied to characterize and manipulate the hydro-carbon source layer. The high-fluence ablation in combination with a timed laser pulse for particle acceleration allowed for an estimation of the relevant source layer thickness for proton acceleration. Moreover, from these data and independently from the low-fluence regime, the lateral extent of the ion source layer became accessible.

  20. The LILIA (laser induced light ions acceleration) experiment at LNF

    NASA Astrophysics Data System (ADS)

    Agosteo, S.; Anania, M. P.; Caresana, M.; Cirrone, G. A. P.; De Martinis, C.; Delle Side, D.; Fazzi, A.; Gatti, G.; Giove, D.; Giulietti, D.; Gizzi, L. A.; Labate, L.; Londrillo, P.; Maggiore, M.; Nassisi, V.; Sinigardi, S.; Tramontana, A.; Schillaci, F.; Scuderi, V.; Turchetti, G.; Varoli, V.; Velardi, L.

    2014-07-01

    Laser-matter interaction at relativistic intensities opens up new research fields in the particle acceleration and related secondary sources, with immediate applications in medical diagnostics, biophysics, material science, inertial confinement fusion, up to laboratory astrophysics. In particular laser-driven ion acceleration is very promising for hadron therapy once the ion energy will attain a few hundred MeV. The limited value of the energy up to now obtained for the accelerated ions is the drawback of such innovative technique to the real applications. LILIA (laser induced light ions acceleration) is an experiment now running at LNF (Frascati) with the goal of producing a real proton beam able to be driven for significant distances (50-75 cm) away from the interaction point and which will act as a source for further accelerating structure. In this paper the description of the experimental setup, the preliminary results of solid target irradiation and start to end simulation for a post-accelerated beam up to 60 MeV are given.

  1. Experimental evidence of space charge driven resonances in high intensity linear accelerators

    DOE PAGES

    Jeon, Dong -O

    2016-01-12

    In the construction of high intensity accelerators, it is the utmost goal to minimize the beam loss by avoiding or minimizing contributions of various halo formation mechanisms. As a halo formation mechanism, space charge driven resonances are well known for circular accelerators. However, the recent finding showed that even in linear accelerators the space charge potential can excite the 4σ = 360° fourth order resonance [D. Jeon et al., Phys. Rev. ST Accel. Beams 12, 054204 (2009)]. This study increased the interests in space charge driven resonances of linear accelerators. Experimental studies of the space charge driven resonances of highmore » intensity linear accelerators are rare as opposed to the multitude of simulation studies. This paper presents an experimental evidence of the space charge driven 4σ ¼ 360° resonance and the 2σ x(y) – 2σ z = 0 resonance of a high intensity linear accelerator through beam profile measurements from multiple wire-scanners. Moreover, measured beam profiles agree well with the characteristics of the space charge driven 4σ = 360° resonance and the 2σ x(y) – 2σ z = 0 resonance that are predicted by the simulation.« less

  2. Laser-driven planar Rayleigh-Taylor instability experiments

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

    Glendinning, S.G.; Weber, S.V.; Bell, P.

    1992-08-24

    We have performed a series of experiments on the Nova Laser Facility to examine the hydrodynamic behavior of directly driven planar foils with initial perturbations of varying wavelength. The foils were accelerated with a single, frequency doubled, smoothed and temporally shaped laser beam at 0.8{times}10{sup 14} W/cm{sup 2}. The experiments are in good agreement with numerical simulations using the computer codes LASNEX and ORCHID which show growth rates reduced to about 70% of classical for this nonlinear regime.

  3. Plasma Radiation and Acceleration Effectiveness of CME-driven Shocks

    NASA Astrophysics Data System (ADS)

    Gopalswamy, N.; Schmidt, J. M.

    2008-05-01

    CME-driven shocks are effective radio radiation generators and accelerators for Solar Energetic Particles (SEPs). We present simulated 3 D time-dependent radio maps of second order plasma radiation generated by CME- driven shocks. The CME with its shock is simulated with the 3 D BATS-R-US CME model developed at the University of Michigan. The radiation is simulated using a kinetic plasma model that includes shock drift acceleration of electrons and stochastic growth theory of Langmuir waves. We find that in a realistic 3 D environment of magnetic field and solar wind outflow of the Sun the CME-driven shock shows a detailed spatial structure of the density, which is responsible for the fine structure of type II radio bursts. We also show realistic 3 D reconstructions of the magnetic cloud field of the CME, which is accelerated outward by magnetic buoyancy forces in the diverging magnetic field of the Sun. The CME-driven shock is reconstructed by tomography using the maximum jump in the gradient of the entropy. In the vicinity of the shock we determine the Alfven speed of the plasma. This speed profile controls how steep the shock can grow and how stable the shock remains while propagating away from the Sun. Only a steep shock can provide for an effective particle acceleration.

  4. Plasma radiation and acceleration effectiveness of CME-driven shocks

    NASA Astrophysics Data System (ADS)

    Schmidt, Joachim

    CME-driven shocks are effective radio radiation generators and accelerators for Solar Energetic Particles (SEPs). We present simulated 3 D time-dependent radio maps of second order plasma radiation generated by CME-driven shocks. The CME with its shock is simulated with the 3 D BATS-R-US CME model developed at the University of Michigan. The radiation is simulated using a kinetic plasma model that includes shock drift acceleration of electrons and stochastic growth theory of Langmuir waves. We find that in a realistic 3 D environment of magnetic field and solar wind outflow of the Sun the CME-driven shock shows a detailed spatial structure of the density, which is responsible for the fine structure of type II radio bursts. We also show realistic 3 D reconstructions of the magnetic cloud field of the CME, which is accelerated outward by magnetic buoyancy forces in the diverging magnetic field of the Sun. The CME-driven shock is reconstructed by tomography using the maximum jump in the gradient of the entropy. In the vicinity of the shock we determine the Alfven speed of the plasma. This speed profile controls how steep the shock can grow and how stable the shock remains while propagating away from the Sun. Only a steep shock can provide for an effective particle acceleration.

  5. Investigations into dual-grating THz-driven accelerators

    NASA Astrophysics Data System (ADS)

    Wei, Y.; Ischebeck, R.; Dehler, M.; Ferrari, E.; Hiller, N.; Jamison, S.; Xia, G.; Hanahoe, K.; Li, Y.; Smith, J. D. A.; Welsch, C. P.

    2018-01-01

    Advanced acceleration technologies are receiving considerable interest in order to miniaturize future particle accelerators. One such technology is the dual-grating dielectric structures, which can support accelerating fields one to two orders of magnitude higher than the metal RF cavities in conventional accelerators. This opens up the possibility of enabling high accelerating gradients of up to several GV/m. This paper investigates numerically a quartz dual-grating structure which is driven by THz pulses to accelerate electrons. Geometry optimizations are carried out to achieve the trade-offs between accelerating gradient and vacuum channel gap. A realistic electron bunch available from the future Compact Linear Accelerator for Research and Applications (CLARA) is loaded into an optimized 100-period dual-grating structure for a detailed wakefield study. A THz pulse is then employed to interact with this CLARA bunch in the optimized structure. The computed beam quality is analyzed in terms of emittance, energy spread and loaded accelerating gradient. The simulations show that an accelerating gradient of 348 ± 12 MV/m with an emittance growth of 3.0% can be obtained.

  6. Operation and reactivity measurements of an accelerator driven subcritical TRIGA reactor

    NASA Astrophysics Data System (ADS)

    O'Kelly, David Sean

    Experiments were performed at the Nuclear Engineering Teaching Laboratory (NETL) in 2005 and 2006 in which a 20 MeV linear electron accelerator operating as a photoneutron source was coupled to the TRIGA (Training, Research, Isotope production, General Atomics) Mark II research reactor at the University of Texas at Austin (UT) to simulate the operation and characteristics of a full-scale accelerator driven subcritical system (ADSS). The experimental program provided a relatively low-cost substitute for the higher power and complexity of internationally proposed systems utilizing proton accelerators and spallation neutron sources for an advanced ADSS that may be used for the burning of high-level radioactive waste. Various instrumentation methods that permitted ADSS neutron flux monitoring in high gamma radiation fields were successfully explored and the data was used to evaluate the Stochastic Pulsed Feynman method for reactivity monitoring.

  7. Current-driven plasma acceleration versus current-driven energy dissipation. I - Wave stability theory

    NASA Technical Reports Server (NTRS)

    Kelly, A. J.; Jahn, R. G.; Choueiri, E. Y.

    1990-01-01

    The dominant unstable electrostatic wave modes of an electromagnetically accelerated plasma are investigated. The study is the first part of a three-phase program aimed at characterizing the current-driven turbulent dissipation degrading the efficiency of Lorentz force plasma accelerators such as the MPD thruster. The analysis uses a kinetic theory that includes magnetic and thermal effects as well as those of an electron current transverse to the magnetic field and collisions, thus combining all the features of previous models. Analytical and numerical solutions allow a detailed description of threshold criteria, finite growth behavior, destabilization mechanisms and maximized-growth characteristics of the dominant unstable modes. The lower hybrid current-driven instability is implicated as dominant and was found to preserve its character in the collisional plasma regime.

  8. Editorial: Focus on Laser- and Beam-Driven Plasma Accelerators

    NASA Astrophysics Data System (ADS)

    Joshi, Chan; Malka, Victor

    2010-04-01

    The ability of short but intense laser pulses to generate high-energy electrons and ions from gaseous and solid targets has been well known since the early days of the laser fusion program. However, during the past decade there has been an explosion of experimental and theoretical activity in this area of laser-matter interaction, driven by the prospect of realizing table-top plasma accelerators for research, medical and industrial uses, and also relatively small and inexpensive plasma accelerators for high-energy physics at the frontier of particle physics. In this focus issue on laser- and beam-driven plasma accelerators, the latest advances in this field are described. Focus on Laser- and Beam-Driven Plasma Accelerators Contents Slow wave plasma structures for direct electron acceleration B D Layer, J P Palastro, A G York, T M Antonsen and H M Milchberg Cold injection for electron wakefield acceleration X Davoine, A Beck, A Lifschitz, V Malka and E Lefebvre Enhanced proton flux in the MeV range by defocused laser irradiation J S Green, D C Carroll, C Brenner, B Dromey, P S Foster, S Kar, Y T Li, K Markey, P McKenna, D Neely, A P L Robinson, M J V Streeter, M Tolley, C-G Wahlström, M H Xu and M Zepf Dose-dependent biological damage of tumour cells by laser-accelerated proton beams S D Kraft, C Richter, K Zeil, M Baumann, E Beyreuther, S Bock, M Bussmann, T E Cowan, Y Dammene, W Enghardt, U Helbig, L Karsch, T Kluge, L Laschinsky, E Lessmann, J Metzkes, D Naumburger, R Sauerbrey, M. Scḧrer, M Sobiella, J Woithe, U Schramm and J Pawelke The optimum plasma density for plasma wakefield excitation in the blowout regime W Lu, W An, M Zhou, C Joshi, C Huang and W B Mori Plasma wakefield acceleration experiments at FACET M J Hogan, T O Raubenheimer, A Seryi, P Muggli, T Katsouleas, C Huang, W Lu, W An, K A Marsh, W B Mori, C E Clayton and C Joshi Electron trapping and acceleration on a downward density ramp: a two-stage approach R M G M Trines, R Bingham, Z Najmudin

  9. Solid hydrogen target for laser driven proton acceleration

    NASA Astrophysics Data System (ADS)

    Perin, J. P.; Garcia, S.; Chatain, D.; Margarone, D.

    2015-05-01

    The development of very high power lasers opens up new horizons in various fields, such as laser plasma acceleration in Physics and innovative approaches for proton therapy in Medicine. Laser driven proton acceleration is commonly based on the so-called Target Normal Sheath Acceleration (TNSA) mechanisms: a high power laser is focused onto a solid target (thin metallic or plastic foil) and interact with matter at very high intensity, thus generating a plasma; as a consequence "hot" electrons are produced and move into the forward direction through the target. Protons are generated at the target rear side, electrons try to escape from the target and an ultra-strong quasi-electrostatic field (~1TV/m) is generated. Such a field can accelerate protons with a wide energy spectrum (1-200 MeV) in a few tens of micrometers. The proton beam characteristics depend on the laser parameters and on the target geometry and nature. This technique has been validated experimentally in several high power laser facilities by accelerating protons coming from hydrogenated contaminant (mainly water) at the rear of metallic target, however, several research groups are investigating the possibility to perform experiments by using "pure" hydrogen targets. In this context, the low temperature laboratory at CEA-Grenoble has developed a cryostat able to continuously produce a thin hydrogen ribbon (from 40 to 100 microns thick). A new extrusion concept, without any moving part has been carried out, using only the thermodynamic properties of the fluid. First results and perspectives are presented in this paper.

  10. Vibration isolation technology: Sensitivity of selected classes of experiments to residual accelerations

    NASA Technical Reports Server (NTRS)

    Alexander, J. Iwan D.

    1990-01-01

    The solution was sought of a 2-D axisymmetric moving boundary problem for the sensitivity of isothermal and nonisothermal liquid columns and the sensitivity of thermo-capillary flows to buoyancy driven convection caused by residual accelerations. The sensitivity of a variety of space experiments to residual accelerations are examined. In all the cases discussed, the sensitivity is related to the dynamic response of a fluid. In some cases the sensitivity can be defined by the magnitude of the response of the velocity field. This response may involve motion of the fluid associated with internal density gradients, or the motion of a free liquid surface. For fluids with internal density gradients, the type of acceleration to which the experiment is sensitive will depend on whether buoyancy driven convection must be small in comparison to other types of fluid motion (such as thermocapillary flow), or fluid motion must be suppressed or eliminated (such as in diffusion studies, or directional solidification experiments). The effect of the velocity on the composition and temperature field must be considered, particularly in the vicinity of the melt crystal interface. As far as the response to transient disturbances is concerned the sensitivity is determined by both the magnitude and frequency the acceleration and the characteristic momentum and solute diffusion times.

  11. Preferential enhancement of laser-driven carbon ion acceleration from optimized nanostructured surfaces

    PubMed Central

    Dalui, Malay; Wang, W.-M.; Trivikram, T. Madhu; Sarkar, Subhrangshu; Tata, Sheroy; Jha, J.; Ayyub, P.; Sheng, Z. M.; Krishnamurthy, M.

    2015-01-01

    High-intensity ultrashort laser pulses focused on metal targets readily generate hot dense plasmas which accelerate ions efficiently and can pave way to compact table-top accelerators. Laser-driven ion acceleration studies predominantly focus on protons, which experience the maximum acceleration owing to their highest charge-to-mass ratio. The possibility of tailoring such schemes for the preferential acceleration of a particular ion species is very much desired but has hardly been explored. Here, we present an experimental demonstration of how the nanostructuring of a copper target can be optimized for enhanced carbon ion acceleration over protons or Cu-ions. Specifically, a thin (≈0.25 μm) layer of 25–30 nm diameter Cu nanoparticles, sputter-deposited on a polished Cu-substrate, enhances the carbon ion energy by about 10-fold at a laser intensity of 1.2×1018  W/cm2. However, particles smaller than 20 nm have an adverse effect on the ion acceleration. Particle-in-cell simulations provide definite pointers regarding the size of nanoparticles necessary for maximizing the ion acceleration. The inherent contrast of the laser pulse is found to play an important role in the species selective ion acceleration. PMID:26153048

  12. Plasma wakefield acceleration experiments at FACET II

    NASA Astrophysics Data System (ADS)

    Joshi, C.; Adli, E.; An, W.; Clayton, C. E.; Corde, S.; Gessner, S.; Hogan, M. J.; Litos, M.; Lu, W.; Marsh, K. A.; Mori, W. B.; Vafaei-Najafabadi, N.; O'shea, B.; Xu, Xinlu; White, G.; Yakimenko, V.

    2018-03-01

    During the past two decades of research, the ultra-relativistic beam-driven plasma wakefield accelerator (PWFA) concept has achieved many significant milestones. These include the demonstration of ultra-high gradient acceleration of electrons over meter-scale plasma accelerator structures, efficient acceleration of a narrow energy spread electron bunch at high-gradients, positron acceleration using wakes in uniform plasmas and in hollow plasma channels, and demonstrating that highly nonlinear wakes in the ‘blow-out regime’ have the electric field structure necessary for preserving the emittance of the accelerating bunch. A new 10 GeV electron beam facility, Facilities for Accelerator Science and Experimental Test (FACET) II, is currently under construction at SLAC National Accelerator Laboratory for the next generation of PWFA research and development. The FACET II beams will enable the simultaneous demonstration of substantial energy gain of a small emittance electron bunch while demonstrating an efficient transfer of energy from the drive to the trailing bunch. In this paper we first describe the capabilities of the FACET II facility. We then describe a series of PWFA experiments supported by numerical and particle-in-cell simulations designed to demonstrate plasma wake generation where the drive beam is nearly depleted of its energy, high efficiency acceleration of the trailing bunch while doubling its energy and ultimately, quantifying the emittance growth in a single stage of a PWFA that has optimally designed matching sections. We then briefly discuss other FACET II plasma-based experiments including in situ positron generation and acceleration, and several schemes that are promising for generating sub-micron emittance bunches that will ultimately be needed for both an early application of a PWFA and for a plasma-based future linear collider.

  13. Plasma wakefield acceleration experiments at FACET II

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

    Joshi, C.; Adli, E.; An, W.

    During the past two decades of research, the ultra-relativistic beam-driven plasma wakefield accelerator (PWFA) concept has achieved many significant milestones. These include the demonstration of ultra-high gradient acceleration of electrons over meter-scale plasma accelerator structures, efficient acceleration of a narrow energy spread electron bunch at high-gradients, positron acceleration using wakes in uniform plasmas and in hollow plasma channels, and demonstrating that highly nonlinear wakes in the 'blow-out regime' have the electric field structure necessary for preserving the emittance of the accelerating bunch. A new 10 GeV electron beam facility, Facilities for Accelerator Science and Experimental Test (FACET) II, is currentlymore » under construction at SLAC National Accelerator Laboratory for the next generation of PWFA research and development. The FACET II beams will enable the simultaneous demonstration of substantial energy gain of a small emittance electron bunch while demonstrating an efficient transfer of energy from the drive to the trailing bunch. In this paper we first describe the capabilities of the FACET II facility. We then describe a series of PWFA experiments supported by numerical and particle-in-cell simulations designed to demonstrate plasma wake generation where the drive beam is nearly depleted of its energy, high efficiency acceleration of the trailing bunch while doubling its energy and ultimately, quantifying the emittance growth in a single stage of a PWFA that has optimally designed matching sections. Here, we briefly discuss other FACET II plasma-based experiments including in situ positron generation and acceleration, and several schemes that are promising for generating sub-micron emittance bunches that will ultimately be needed for both an early application of a PWFA and for a plasma-based future linear collider.« less

  14. Plasma wakefield acceleration experiments at FACET II

    DOE PAGES

    Joshi, C.; Adli, E.; An, W.; ...

    2018-01-12

    During the past two decades of research, the ultra-relativistic beam-driven plasma wakefield accelerator (PWFA) concept has achieved many significant milestones. These include the demonstration of ultra-high gradient acceleration of electrons over meter-scale plasma accelerator structures, efficient acceleration of a narrow energy spread electron bunch at high-gradients, positron acceleration using wakes in uniform plasmas and in hollow plasma channels, and demonstrating that highly nonlinear wakes in the 'blow-out regime' have the electric field structure necessary for preserving the emittance of the accelerating bunch. A new 10 GeV electron beam facility, Facilities for Accelerator Science and Experimental Test (FACET) II, is currentlymore » under construction at SLAC National Accelerator Laboratory for the next generation of PWFA research and development. The FACET II beams will enable the simultaneous demonstration of substantial energy gain of a small emittance electron bunch while demonstrating an efficient transfer of energy from the drive to the trailing bunch. In this paper we first describe the capabilities of the FACET II facility. We then describe a series of PWFA experiments supported by numerical and particle-in-cell simulations designed to demonstrate plasma wake generation where the drive beam is nearly depleted of its energy, high efficiency acceleration of the trailing bunch while doubling its energy and ultimately, quantifying the emittance growth in a single stage of a PWFA that has optimally designed matching sections. Here, we briefly discuss other FACET II plasma-based experiments including in situ positron generation and acceleration, and several schemes that are promising for generating sub-micron emittance bunches that will ultimately be needed for both an early application of a PWFA and for a plasma-based future linear collider.« less

  15. Plasmon-driven acceleration in a photo-excited nanotube

    DOE PAGES

    Shin, Young -Min

    2017-02-21

    A plasmon-assisted channeling acceleration can be realized with a large channel, possibly at the nanometer scale. Carbon nanotubes (CNTs) are the most typical example of nano-channels that can confine a large number of channeled particles in a photon-plasmon coupling condition. This paper presents a theoretical and numerical study on the concept of high-field charge acceleration driven by photo-excited Luttinger-liquid plasmons in a nanotube. An analytic description of the plasmon-assisted laser acceleration is detailed with practical acceleration parameters, in particular, with the specifications of a typical tabletop femtosecond laser system. Lastly, the maximally achievable acceleration gradients and energy gains within dephasingmore » lengths and CNT lengths are discussed with respect to laser-incident angles and CNT-filling ratios.« less

  16. Development of High-Gradient Dielectric Laser-Driven Particle Accelerator Structures

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

    Byer, Robert L.

    2013-11-07

    The thrust of Stanford's program is to conduct research on high-gradient dielectric accelerator structures driven with high repetition-rate, tabletop infrared lasers. The close collaboration between Stanford and SLAC (Stanford Linear Accelerator Center) is critical to the success of this project, because it provides a unique environment where prototype dielectric accelerator structures can be rapidly fabricated and tested with a relativistic electron beam.

  17. Accelerator driven sub-critical core

    DOEpatents

    McIntyre, Peter M; Sattarov, Akhdiyor

    2015-03-17

    Systems and methods for operating an accelerator driven sub-critical core. In one embodiment, a fission power generator includes a sub-critical core and a plurality of proton beam generators. Each of the proton beam generators is configured to concurrently provide a proton beam into a different area of the sub-critical core. Each proton beam scatters neutrons within the sub-critical core. The plurality of proton beam generators provides aggregate power to the sub-critical core, via the proton beams, to scatter neutrons sufficient to initiate fission in the sub-critical core.

  18. 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.

  19. Convectively driven decadal zonal accelerations in Earth's fluid core

    NASA Astrophysics Data System (ADS)

    More, Colin; Dumberry, Mathieu

    2018-04-01

    Azimuthal accelerations of cylindrical surfaces co-axial with the rotation axis have been inferred to exist in Earth's fluid core on the basis of magnetic field observations and changes in the length-of-day. These accelerations have a typical timescale of decades. However, the physical mechanism causing the accelerations is not well understood. Scaling arguments suggest that the leading order torque averaged over cylindrical surfaces should arise from the Lorentz force. Decadal fluctuations in the magnetic field inside the core, driven by convective flows, could then force decadal changes in the Lorentz torque and generate zonal accelerations. We test this hypothesis by constructing a quasi-geostrophic model of magnetoconvection, with thermally driven flows perturbing a steady, imposed background magnetic field. We show that when the Alfvén number in our model is similar to that in Earth's fluid core, temporal fluctuations in the torque balance are dominated by the Lorentz torque, with the latter generating mean zonal accelerations. Our model reproduces both fast, free Alfvén waves and slow, forced accelerations, with ratios of relative strength and relative timescale similar to those inferred for the Earth's core. The temporal changes in the magnetic field which drive the time-varying Lorentz torque are produced by the underlying convective flows, shearing and advecting the magnetic field on a timescale associated with convective eddies. Our results support the hypothesis that temporal changes in the magnetic field deep inside Earth's fluid core drive the observed decadal zonal accelerations of cylindrical surfaces through the Lorentz torque.

  20. Laser-driven dielectric electron accelerator for radiobiology researches

    NASA Astrophysics Data System (ADS)

    Koyama, Kazuyoshi; Matsumura, Yosuke; Uesaka, Mitsuru; Yoshida, Mitsuhiro; Natsui, Takuya; Aimierding, Aimidula

    2013-05-01

    In order to estimate the health risk associated with a low dose radiation, the fundamental process of the radiation effects in a living cell must be understood. It is desired that an electron bunch or photon pulse precisely knock a cell nucleus and DNA. The required electron energy and electronic charge of the bunch are several tens keV to 1 MeV and 0.1 fC to 1 fC, respectively. The smaller beam size than micron is better for the precise observation. Since the laser-driven dielectric electron accelerator seems to suite for the compact micro-beam source, a phase-modulation-masked-type laser-driven dielectric accelerator was studied. Although the preliminary analysis made a conclusion that a grating period and an electron speed must satisfy the matching condition of LG/λ = v/c, a deformation of a wavefront in a pillar of the grating relaxed the matching condition and enabled the slow electron to be accelerated. The simulation results by using the free FDTD code, Meep, showed that the low energy electron of 20 keV felt the acceleration field strength of 20 MV/m and gradually felt higher field as the speed was increased. Finally the ultra relativistic electron felt the field strength of 600 MV/m. The Meep code also showed that a length of the accelerator to get energy of 1 MeV was 3.8 mm, the required laser power and energy were 11 GW and 350 mJ, respectively. Restrictions on the laser was eased by adopting sequential laser pulses. If the accelerator is illuminated by sequential N pulses, the pulse power, pulse width and the pulse energy are reduced to 1/N, 1/N and 1/N2, respectively. The required laser power per pulse is estimated to be 2.2 GW when ten pairs of sequential laser pulse is irradiated.

  1. High-quality electron beam generation in a proton-driven hollow plasma wakefield accelerator

    NASA Astrophysics Data System (ADS)

    Li, Y.; Xia, G.; Lotov, K. V.; Sosedkin, A. P.; Hanahoe, K.; Mete-Apsimon, O.

    2017-10-01

    Simulations of proton-driven plasma wakefield accelerators have demonstrated substantially higher accelerating gradients compared to conventional accelerators and the viability of accelerating electrons to the energy frontier in a single plasma stage. However, due to the strong intrinsic transverse fields varying both radially and in time, the witness beam quality is still far from suitable for practical application in future colliders. Here we demonstrate the efficient acceleration of electrons in proton-driven wakefields in a hollow plasma channel. In this regime, the witness bunch is positioned in the region with a strong accelerating field, free from plasma electrons and ions. We show that the electron beam carrying the charge of about 10% of 1 TeV proton driver charge can be accelerated to 0.6 TeV with a preserved normalized emittance in a single channel of 700 m. This high-quality and high-charge beam may pave the way for the development of future plasma-based energy frontier colliders.

  2. Spectroscopic measurements of plasma emission light for plasma-based acceleration experiments

    NASA Astrophysics Data System (ADS)

    Filippi, F.; Anania, M. P.; Biagioni, A.; Chiadroni, E.; Cianchi, A.; Ferrario, M.; Mostacci, A.; Palumbo, L.; Zigler, A.

    2016-09-01

    Advanced particle accelerators are based on the excitation of large amplitude plasma waves driven by either electron or laser beams. Future experiments scheduled at the SPARC_LAB test facility aim to demonstrate the acceleration of high brightness electron beams through the so-called resonant Plasma Wakefield Acceleration scheme in which a train of electron bunches (drivers) resonantly excites wakefields into a preformed hydrogen plasma; the last bunch (witness) injected at the proper accelerating phase gains energy from the wake. The quality of the accelerated beam depends strongly on plasma density and its distribution along the acceleration length. The measurements of plasma density of the order of 1016-1017 cm-3 can be performed with spectroscopic measurements of the plasma-emitted light. The measured density distribution for hydrogen filled capillary discharge with both Balmer alpha and Balmer beta lines and shot-to-shot variation are here reported.

  3. Accelerator Driven Nuclear Energy: The Thorium Option

    ScienceCinema

    Raja, Rajendran

    2018-01-05

    Conventional nuclear reactors use enriched Uranium as fuel and produce nuclear waste which needs to be stored away for over 10,000 years.   At the current rate of use, existing sources of Uranium will last for 50-100 years.  We describe a solution to the problem that uses particle accelerators to produce fast neutrons that can be used to burn existing nuclear waste and produce energy.  Such systems, initially proposed by Carlo Rubbia and collaborators in the 1990's, are being seriously considered by many countries as a possible solution to the green energy problem.  Accelerator driven reactors operate in a sub-critical regime and, thus, are safer and can obtain energy from plentiful elements such as Thorium-232 and Uranium-238. What is missing is the high intensity (10MW) accelerator that produces 1 GeV protons. We will describe scenarios which if implemented will make such systems a reality.  

  4. Accelerator-driven Transmutation of Waste

    NASA Astrophysics Data System (ADS)

    Venneri, Francesco

    1998-04-01

    Nuclear waste from commercial power plants contains large quantities of plutonium, other fissionable actinides, and long-lived fission products that are potential proliferation concerns and create challenges for the long-term storage. Different strategies for dealing with nuclear waste are being followed by various countries because of their geologic situations and their views on nuclear energy, reprocessing and non-proliferation. The current United States policy is to store unprocessed spent reactor fuel in a geologic repository. Other countries are opting for treatment of nuclear waste, including partial utilization of the fissile material contained in the spent fuel, prior to geologic storage. Long-term uncertainties are hampering the acceptability and eventual licensing of a geologic repository for nuclear spent fuel in the US, and driving up its cost. The greatest concerns are with the potential for radiation release and exposure from the spent fuel for tens of thousands of years and the possible diversion and use of the actinides contained in the waste for weapons construction. Taking advantage of the recent breakthroughs in accelerator technology and of the natural flexibility of subcritical systems, the Accelerator-driven Transmutation of Waste (ATW) concept offers the United States and other countries the possibility to greatly reduce plutonium, higher actinides and environmentally hazardous fission products from the waste stream destined for permanent storage. ATW does not eliminate the need for, but instead enhances the viability of permanent waste repositories. Far from being limited to waste destruction, the ATW concept also brings to the table new technologies that could be relevant for next-generation power producing reactors. In the ATW concept, spent fuel would be shipped to the ATW site where the plutonium, transuranics and selected long-lived fission products would be destroyed by fission or transmutation in their first and only pass through the

  5. First-order particle acceleration in magnetically driven flows

    DOE PAGES

    Beresnyak, Andrey; Li, Hui

    2016-03-02

    In this study, we demonstrate that particles are regularly accelerated while experiencing curvature drift in flows driven by magnetic tension. Some examples of such flows include spontaneous turbulent reconnection and decaying magnetohydrodynamic turbulence, where a magnetic field relaxes to a lower-energy configuration and transfers part of its energy to kinetic motions of the fluid. We show that this energy transfer, which normally causes turbulent cascade and heating of the fluid, also results in a first-order acceleration of non-thermal particles. Since it is generic, this acceleration mechanism is likely to play a role in the production of non-thermal particle distribution inmore » magnetically dominant environments such as the solar chromosphere, pulsar magnetospheres, jets from supermassive black holes, and γ-ray bursts.« less

  6. Neutrino Physics with Accelerator Driven Subcritical Reactors

    NASA Astrophysics Data System (ADS)

    Ciuffoli, Emilio

    2017-09-01

    Accelerator Driven Subcritical System (ADS) reactors are being developed around the world, to produce energy and, at the same time, to provide an efficient way to dispose of and to recycle nuclear waste. Used nuclear fuel, by itself, cannot sustain a chain reaction; however in ADS reactors the additional neutrons which are required will be supplied by a high-intensity accelerator. This accelerator will produce, as a by-product, a large quantity of {\\bar{ν }}μ via muon Decay At Rest (µDAR). Using liquid scintillators, it will be possible to to measure the CP-violating phase δCP and to look for experimental signs of the presence of sterile neutrinos in the appearance channel, testing the LSND and MiniBooNE anomalies. Even in the first stage of the project, when the beam energy will be lower, it will be possible to produce {\\bar{ν }}e via Isotope Decay At Rest (IsoDAR), which can be used to provide competitive bounds on sterile neutrinos in the disappearance channel. I will consider several experimental setups in which the antineutrinos are created using accelerators that will be constructed as part of the China-ADS program.

  7. Modeling Particle Acceleration and Transport at a 2-D CME-Driven Shock

    NASA Astrophysics Data System (ADS)

    Hu, Junxiang; Li, Gang; Ao, Xianzhi; Zank, Gary P.; Verkhoglyadova, Olga

    2017-11-01

    We extend our earlier Particle Acceleration and Transport in the Heliosphere (PATH) model to study particle acceleration and transport at a coronal mass ejection (CME)-driven shock. We model the propagation of a CME-driven shock in the ecliptic plane using the ZEUS-3D code from 20 solar radii to 2 AU. As in the previous PATH model, the initiation of the CME-driven shock is simplified and modeled as a disturbance at the inner boundary. Different from the earlier PATH model, the disturbance is now longitudinally dependent. Particles are accelerated at the 2-D shock via the diffusive shock acceleration mechanism. The acceleration depends on both the parallel and perpendicular diffusion coefficients κ|| and κ⊥ and is therefore shock-obliquity dependent. Following the procedure used in Li, Shalchi, et al. (k href="#jgra53857-bib-0045"/>), we obtain the particle injection energy, the maximum energy, and the accelerated particle spectra at the shock front. Once accelerated, particles diffuse and convect in the shock complex. The diffusion and convection of these particles are treated using a refined 2-D shell model in an approach similar to Zank et al. (k href="#jgra53857-bib-0089"/>). When particles escape from the shock, they propagate along and across the interplanetary magnetic field. The propagation is modeled using a focused transport equation with the addition of perpendicular diffusion. We solve the transport equation using a backward stochastic differential equation method where adiabatic cooling, focusing, pitch angle scattering, and cross-field diffusion effects are all included. Time intensity profiles and instantaneous particle spectra as well as particle pitch angle distributions are shown for two example CME shocks.

  8. Laser-driven proton acceleration with nanostructured targets

    NASA Astrophysics Data System (ADS)

    Vallières, Simon; Morabito, Antonia; Veltri, Simona; Scisciò, Massimiliano; Barberio, Marianna; Antici, Patrizio

    2017-05-01

    Laser-driven particle acceleration has become a growing field of research, in particular for its numerous interesting applications. One of the most common proton acceleration mechanism that is obtained on typically available multi-hundred TW laser systems is based on the irradiation of thin solid metal foils by the intense laser, generating the proton acceleration on its rear target surface. The efficiency of this acceleration scheme strongly depends on the type of target used. Improving the acceleration mechanism, i.e. enhancing parameters such as maximum proton energy, laminarity, efficiency, monocromaticy, and number of accelerated particles, is heavily depending on the laser-to-target absorption, where obviously cheap and easy to implement targets are best candidates. In this work, we present nanostructured targets that are able to increase the absorption of light compared to what can be achieved with a classical solid (non-nanostructured) target and are produced with a method that is much simpler and cheaper than conventional lithographic processes. Several layers of gold nanoparticles were deposited on solid targets (aluminum, Mylar and multiwalled carbon nanotube buckypaper) and allow for an increased photon absorption. This ultimately permits to increase the laser-to-particle energy transfer, and thus to enhance the yield in proton production. Experimental characterization results on the nanostructured films are presented (UV-Vis spectroscopy and AFM), along with preliminary experimental proton spectra obtained at the JLF-TITAN laser facility at LLNL.

  9. 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.

  10. Novel target design for enhanced laser driven proton acceleration

    NASA Astrophysics Data System (ADS)

    Dalui, Malay; Kundu, M.; Tata, Sheroy; Lad, Amit D.; Jha, J.; Ray, Krishanu; Krishnamurthy, M.

    2017-09-01

    We demonstrate a simple method of preparing structured target for enhanced laser-driven proton acceleration under target-normal-sheath-acceleration scheme. A few layers of genetically modified, clinically grown micron sized E. Coli bacteria cell coated on a thin metal foil has resulted in an increase in the maximum proton energy by about 1.5 times and the total proton yield is enhanced by approximately 25 times compared to an unstructured reference foil at a laser intensity of 1019 W/cm2. Particle-in-cell simulations on the system shows that the structures on the target-foil facilitates anharmonic resonance, contributing to enhanced hot electron production which leads to stronger accelerating field. The effect is observed to grow as the number of structures is increased in the focal area of the laser pulse.

  11. Quasi-monoenergetic ion beam acceleration by laser-driven shock and solitary waves in near-critical plasmas

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

    Zhang, W. L.; Qiao, B., E-mail: bqiao@pku.edu.cn; Huang, T. W.

    2016-07-15

    Ion acceleration in near-critical plasmas driven by intense laser pulses is investigated theoretically and numerically. A theoretical model has been given for clarification of the ion acceleration dynamics in relation to different laser and target parameters. Two distinct regimes have been identified, where ions are accelerated by, respectively, the laser-induced shock wave in the weakly driven regime (comparatively low laser intensity) and the nonlinear solitary wave in the strongly driven regime (comparatively high laser intensity). Two-dimensional particle-in-cell simulations show that quasi-monoenergetic proton beams with a peak energy of 94.6 MeV and an energy spread 15.8% are obtained by intense laser pulsesmore » at intensity I{sub 0} = 3 × 10{sup 20 }W/cm{sup 2} and pulse duration τ = 0.5 ps in the strongly driven regime, which is more advantageous than that got in the weakly driven regime. In addition, 233 MeV proton beams with narrow spread can be produced by extending τ to 1.0 ps in the strongly driven regime.« less

  12. Direct numerical simulation of incompressible acceleration-driven variable-density turbulence

    NASA Astrophysics Data System (ADS)

    Gat, Ilana; Matheou, Georgios; Chung, Daniel; Dimotakis, Paul

    2015-11-01

    Fully developed turbulence in variable-density flow driven by an externally imposed acceleration field, e.g., gravity, is fundamental in many applications, such as inertial confinement fusion, geophysics, and astrophysics. Aspects of this turbulence regime are poorly understood and are of interest to fluid modeling. We investigate incompressible acceleration-driven variable-density turbulence by a series of direct numerical simulations of high-density fluid in-between slabs of low-density fluid, in a triply-periodic domain. A pseudo-spectral numerical method with a Helmholtz-Hodge decomposition of the pressure field, which ensures mass conservation, is employed, as documented in Chung & Pullin (2010). A uniform dynamic viscosity and local Schmidt number of unity are assumed. This configuration encapsulates a combination of flow phenomena in a temporally evolving variable-density shear flow. Density ratios up to 10 and Reynolds numbers in the fully developed turbulent regime are investigated. The temporal evolution of the vertical velocity difference across the shear layer, shear-layer growth, mean density, and Reynolds number are discussed. Statistics of Lagrangian accelerations of fluid elements and of vorticity as a function of the density ratio are also presented. This material is based upon work supported by the AFOSR, the DOE, the NSF GRFP, and Caltech.

  13. Ultraviolet radiation accelerates BRAF-driven melanomagenesis by targeting TP53

    PubMed Central

    Rae, Joel; Hogan, Kate; Ejiama, Sarah; Girotti, Maria Romina; Cook, Martin; Dhomen, Nathalie; Marais, Richard

    2014-01-01

    Cutaneous melanoma is epidemiologically linked to ultraviolet radiation (UVR), but the molecular mechanisms by which UVR drives melanomagenesis remain unclear1,2. The most common somatic mutation in melanoma is a V600E substitution in BRAF, which is an early event3. To investigate how UVR accelerates oncogenic BRAF-driven melanomagenesis, we used a V600EBRAF mouse model. In mice expressing V600EBRAF in their melanocytes, a single dose of UVR that mimicked mild sunburn in humans induced clonal expansion of the melanocytes, and repeated doses of UVR increased melanoma burden. We show that sunscreen (UVA superior: UVB SPF50) delayed the onset of UVR-driven melanoma, but only provided partial protection. The UVR-exposed tumours presented increased numbers of single nucleotide variants (SNVs) and we observed mutations (H39Y, S124F, R245C, R270C, C272G) in the Trp53 tumour suppressor in ~40% of cases. TP53 is an accepted UVR target in non-melanoma skin cancer, but is not thought to play a major role in melanoma4. However, we show that mutant Trp53 accelerated V600EBRAF-driven melanomagenesis and that TP53 mutations are linked to evidence of UVR-induced DNA damage in human melanoma. Thus, we provide mechanistic insight into epidemiological data linking UVR to acquired naevi in humans5. We identify TP53/Trp53 as a UVR-target gene that cooperates with V600EBRAF to induce melanoma, providing molecular insight into how UVR accelerates melanomagenesis. Our study validates public health campaigns that promote sunscreen protection for individuals at risk of melanoma. PMID:24919155

  14. Laser-driven acceleration of electrons in a partially ionized plasma channel.

    PubMed

    Rowlands-Rees, T P; Kamperidis, C; Kneip, S; Gonsalves, A J; Mangles, S P D; Gallacher, J G; Brunetti, E; Ibbotson, T; Murphy, C D; Foster, P S; Streeter, M J V; Budde, F; Norreys, P A; Jaroszynski, D A; Krushelnick, K; Najmudin, Z; Hooker, S M

    2008-03-14

    The generation of quasimonoenergetic electron beams, with energies up to 200 MeV, by a laser-plasma accelerator driven in a hydrogen-filled capillary discharge waveguide is investigated. Injection and acceleration of electrons is found to depend sensitively on the delay between the onset of the discharge current and the arrival of the laser pulse. A comparison of spectroscopic and interferometric measurements suggests that injection is assisted by laser ionization of atoms or ions within the channel.

  15. Laser-driven electron beam acceleration and future application to compact light sources

    NASA Astrophysics Data System (ADS)

    Hafz, N.; Jeong, T. M.; Lee, S. K.; Pae, K. H.; Sung, J. H.; Choi, I. W.; Yu, T. J.; Jeong, Y. U.; Lee, J.

    2009-07-01

    Laser-driven plasma accelerators are gaining much attention by the advanced accelerator community due to the potential these accelerators hold in miniaturizing future high-energy and medium-energy machines. In the laser wakefield accelerator (LWFA), the ponderomotive force of an ultrashort high intensity laser pulse excites a longitudinal plasma wave or bubble. Due to huge charge separation, electric fields created in the plasma bubble can be several orders of magnitude higher than those available in conventional microwave and RF-based accelerator facilities which are limited (up to ˜100 MV/m) by material breakdown. Therefore, if an electron bunch is injected into the bubble in phase with its field, it will gain relativistic energies within an extremely short distance. Here, in the LWFA we show the generation of high-quality and high-energy electron beams up to the GeV-class within a few millimeters of gas-jet plasmas irradiated by tens of terawatt ultrashort laser pulses. Thus we realize approximately four orders of magnitude acceleration gradients higher than available by conventional technology. As a practical application of the stable high-energy electron beam generation, we are planning on injecting the electron beams into a few-meters long conventional undulator in order to realize compact X-ray synchrotron (immediate) and FEL (future) light sources. Stable laser-driven electron beam and radiation devices will surely open a new era in science, medicine and technology and will benefit a larger number of users in those fields.

  16. Observation of Gigawatt-Class THz Pulses from a Compact Laser-Driven Particle Accelerator

    NASA Astrophysics Data System (ADS)

    Gopal, A.; Herzer, S.; Schmidt, A.; Singh, P.; Reinhard, A.; Ziegler, W.; Brömmel, D.; Karmakar, A.; Gibbon, P.; Dillner, U.; May, T.; Meyer, H.-G.; Paulus, G. G.

    2013-08-01

    We report the observation of subpicosecond terahertz (T-ray) pulses with energies ≥460μJ from a laser-driven ion accelerator, thus rendering the peak power of the source higher even than that of state-of-the-art synchrotrons. Experiments were performed with intense laser pulses (up to 5×1019W/cm2) to irradiate thin metal foil targets. Ion spectra measured simultaneously showed a square law dependence of the T-ray yield on particle number. Two-dimensional particle-in-cell simulations show the presence of transient currents at the target rear surface which could be responsible for the strong T-ray emission.

  17. New shielding material development for compact accelerator-driven neutron source

    NASA Astrophysics Data System (ADS)

    Hu, Guang; Hu, Huasi; Wang, Sheng; Han, Hetong; Otake, Y.; Pan, Ziheng; Taketani, A.; Ota, H.; Hashiguchi, Takao; Yan, Mingfei

    2017-04-01

    The Compact Accelerator-driven Neutron Source (CANS), especially the transportable neutron source is longing for high effectiveness shielding material. For this reason, new shielding material is researched in this investigation. The component of shielding material is designed and many samples are manufactured. Then the attenuation detection experiments were carried out. In the detections, the dead time of the detector appeases when the proton beam is too strong. To grasp the linear range and nonlinear range of the detector, two currents of proton are employed in Pb attenuation detections. The transmission ratio of new shielding material, polyethylene (PE), PE + Pb, BPE + Pb is detected under suitable current of proton. Since the results of experimental neutrons and γ-rays appear as together, the MCNP and PHITS simulations are applied to assisting the analysis. The new shielding material could reduce of the weight and volume compared with BPE + Pb and PE + Pb.

  18. PW-class laser-driven super acceleration systems in underdense plasmas

    NASA Astrophysics Data System (ADS)

    Yano, Masahiro; Zhidkov, Alexei; Kodama, Ryosuke

    2017-10-01

    Probing laser driven super-acceleration systems can be important tool to understand physics related to vacuum, space time, and particle acceleration. We show two proposals to probe the systems through Hawking-like effect using PW class lasers and x-ray free electron lasers. For that we study the interaction of ultrahigh intense laser pulses with intensity 1022 -1024 W/cm2 and underdense plasmas including ion motion and plasma radiation for the first time. While the acceleration w a0ωp /ωL in a wake is not maximal, the pulse propagation is much stable. The effect is that a constantly accelerated detector with acceleration w sees a boson's thermal bath at temperature ℏw / 2 πkB c . We present two designs for x-ray scattering from highly accelerated electrons produced in the plasma irradiated by intense laser pulses for such detection. Properly chosen observation angles enable us to distinguish spectral broadening from Doppler shift with a reasonable photon number. Also, ion motion and radiation damping on the interaction are investigated via fully relativistic 3D particle-in-cell simulation. We observe high quality electron bunches under super-acceleration when transverse plasma waves are excited by ponderomotive force producing plasma channel.

  19. Preliminary research on flow rate and free surface of the accelerator driven subcritical system gravity-driven dense granular-flow target

    PubMed Central

    Li, Xiaodong; Wan, Jiangfeng; Zhang, Sheng; Lin, Ping; Zhang, Yanshi; Yang, Guanghui; Wang, Mengke; Duan, Wenshan; Sun, Jian’an

    2017-01-01

    A spallation target is one of the three core parts of the accelerator driven subcritical system (ADS), which has already been investigated for decades. Recently, a gravity-driven Dense Granular-flow Target (DGT) is proposed, which consists of a cylindrical hopper and an internal coaxial cylindrical beam pipe. The research on the flow rate and free surface are important for the design of the target whether in Heavy Liquid Metal (HLM) targets or the DGT. In this paper, the relations of flow rate and the geometry of the DGT are investigated. Simulations based on the discrete element method (DEM) implementing on Graphics Processing Units (GPUs) and experiments are both performed. It is found that the existence of an internal pipe doesn’t influence the flow rate when the distance from the bottom of the pipe to orifice is large enough even in a larger system. Meanwhile, snapshots of the free surface formed just below the beam pipe are given. It is observed that the free surface is stable over time. The entire research is meaningful for the design of DGT. PMID:29095910

  20. Preliminary research on flow rate and free surface of the accelerator driven subcritical system gravity-driven dense granular-flow target.

    PubMed

    Li, Xiaodong; Wan, Jiangfeng; Zhang, Sheng; Lin, Ping; Zhang, Yanshi; Yang, Guanghui; Wang, Mengke; Duan, Wenshan; Sun, Jian'an; Yang, Lei

    2017-01-01

    A spallation target is one of the three core parts of the accelerator driven subcritical system (ADS), which has already been investigated for decades. Recently, a gravity-driven Dense Granular-flow Target (DGT) is proposed, which consists of a cylindrical hopper and an internal coaxial cylindrical beam pipe. The research on the flow rate and free surface are important for the design of the target whether in Heavy Liquid Metal (HLM) targets or the DGT. In this paper, the relations of flow rate and the geometry of the DGT are investigated. Simulations based on the discrete element method (DEM) implementing on Graphics Processing Units (GPUs) and experiments are both performed. It is found that the existence of an internal pipe doesn't influence the flow rate when the distance from the bottom of the pipe to orifice is large enough even in a larger system. Meanwhile, snapshots of the free surface formed just below the beam pipe are given. It is observed that the free surface is stable over time. The entire research is meaningful for the design of DGT.

  1. Particle Acceleration by Cme-driven Shock Waves

    NASA Technical Reports Server (NTRS)

    Reames, Donald V.

    1999-01-01

    In the largest solar energetic particle (SEP) events, acceleration occurs at shock waves driven out from the Sun by coronal mass ejections (CMEs). Peak particle intensities are a strong function of CME speed, although the intensities, spectra, and angular distributions of particles escaping the shock are highly modified by scattering on Alfven waves produced by the streaming particles themselves. Element abundances vary in complex ways because ions with different values of Q/A resonate with different parts of the wave spectrum, which varies with space and time. Just recently, we have begun to model these systematic variations theoretically and to explore other consequences of proton-generated waves.

  2. Research opportunities with compact accelerator-driven neutron sources

    NASA Astrophysics Data System (ADS)

    Anderson, I. S.; Andreani, C.; Carpenter, J. M.; Festa, G.; Gorini, G.; Loong, C.-K.; Senesi, R.

    2016-10-01

    Since the discovery of the neutron in 1932 neutron beams have been used in a very broad range of applications, As an aging fleet of nuclear reactor sources is retired the use of compact accelerator-driven neutron sources (CANS) is becoming more prevalent. CANS are playing a significant and expanding role in research and development in science and engineering, as well as in education and training. In the realm of multidisciplinary applications, CANS offer opportunities over a wide range of technical utilization, from interrogation of civil structures to medical therapy to cultural heritage study. This paper aims to provide the first comprehensive overview of the history, current status of operation, and ongoing development of CANS worldwide. The basic physics and engineering regarding neutron production by accelerators, target-moderator systems, and beam line instrumentation are introduced, followed by an extensive discussion of various evolving applications currently exploited at CANS.

  3. Experience-driven plasticity in binocular vision

    PubMed Central

    Klink, P. Christiaan; Brascamp, Jan W.; Blake, Randolph; van Wezel, Richard J.A.

    2010-01-01

    Summary Experience-driven neuronal plasticity allows the brain to adapt its functional connectivity to recent sensory input. Here we use binocular rivalry [1], an experimental paradigm where conflicting images are presented to the individual eyes, to demonstrate plasticity in the neuronal mechanisms that convert visual information from two separated retinas into single perceptual experiences. Perception during binocular rivalry tended to initially consist of alternations between exclusive representations of monocularly defined images, but upon prolonged exposure, mixture percepts became more prevalent. The completeness of suppression, reflected in the incidence of mixture percepts, plausibly reflects the strength of inhibition that likely plays a role in binocular rivalry [2]. Recovery of exclusivity was possible, but required highly specific binocular stimulation. Documenting the prerequisites for these observed changes in perceptual exclusivity, our experiments suggest experience-driven plasticity at interocular inhibitory synapses, driven by the (lack of) correlated activity of neurons representing the conflicting stimuli. This form of plasticity is consistent with a previously proposed, but largely untested, anti-Hebbian learning mechanism for inhibitory synapses in vision [3, 4]. Our results implicate experience-driven plasticity as one governing principle in the neuronal organization of binocular vision. PMID:20674360

  4. Rapid acceleration leads to rapid weakening in earthquake-like laboratory experiments

    NASA Astrophysics Data System (ADS)

    Chang, J. C.; Lockner, D. A.; Reches, Z.

    2012-12-01

    We simulated the slip of a fault-patch during a large earthquake by rapidly loading an experimental, ring-shaped fault with energy stored in a spinning flywheel. The flywheel abruptly delivers a finite amount of energy by spinning the fault-patch that spontaneously dissipates the energy without operator intervention. We conducted 42 experiments on Sierra White granite (SWG) samples, and 24 experiments on Kasota dolomite (KD) samples. Each experiment starts by spinning a 225 kg disk-shaped flywheel to a prescribed angular velocity. We refer to this experiment as an "earthquake-like slip-event" (ELSE). The strength-evolution in ELSE experiments is similar to the strength-evolution proposed for earthquake models and observed in stick-slip experiments. Further, we found that ELSE experiments are similar to earthquakes in at least three ways: (1) slip driven by the release of a finite amount of stored energy; (2) pattern of fault strength evolution; and (3) seismically observed values, such as average slip, peak-velocity and rise-time. By assuming that the measured slip, D, in ELSE experiments is equivalent to the average slip during an earthquake, we found that ELSE experiments (D = 0.003-4.6 m) correspond to earthquakes in moment-magnitude range of Mw = 4-8. In ELSE experiments, the critical-slip-distance, dc, has mean values of 2.7 cm and 1.2 cm for SWG and KD, that are much shorter than the 1-10 m in steady-state classical experiments in rotary shear systems. We attribute these dc values, to ELSE loading in which the fault-patch is abruptly loaded by impact with a spinning flywheel. Under this loading, the friction-velocity relations are strikingly different from those under steady-state loading on the same rock samples with the same shear system (Reches and Lockner, Nature, 2010). We further note that the slip acceleration in ELSE evolves systematically with fault strength and wear-rate, and that the dynamic weakening is restricted to the period of intense

  5. Compact beam transport system for free-electron lasers driven by a laser plasma accelerator

    DOE PAGES

    Liu, Tao; Zhang, Tong; Wang, Dong; ...

    2017-02-01

    Utilizing laser-driven plasma accelerators (LPAs) as a high-quality electron beam source is a promising approach to significantly downsize the x-ray free-electron laser (XFEL) facility. A multi-GeV LPA beam can be generated in several-centimeter acceleration distance, with a high peak current and a low transverse emittance, which will considerably benefit a compact FEL design. However, the large initial angular divergence and energy spread make it challenging to transport the beam and realize FEL radiation. In this paper, a novel design of beam transport system is proposed to maintain the superior features of the LPA beam and a transverse gradient undulator (TGU)more » is also adopted as an effective energy spread compensator to generate high-brilliance FEL radiation. As a result, theoretical analysis and numerical simulations are presented based on a demonstration experiment with an electron energy of 380 MeV and a radiation wavelength of 30 nm.« less

  6. Radiation reaction effect on laser driven auto-resonant particle acceleration

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

    Sagar, Vikram; Sengupta, Sudip; Kaw, P. K.

    2015-12-15

    The effects of radiation reaction force on laser driven auto-resonant particle acceleration scheme are studied using Landau-Lifshitz equation of motion. These studies are carried out for both linear and circularly polarized laser fields in the presence of static axial magnetic field. From the parametric study, a radiation reaction dominated region has been identified in which the particle dynamics is greatly effected by this force. In the radiation reaction dominated region, the two significant effects on particle dynamics are seen, viz., (1) saturation in energy gain by the initially resonant particle and (2) net energy gain by an initially non-resonant particlemore » which is caused due to resonance broadening. It has been further shown that with the relaxation of resonance condition and with optimum choice of parameters, this scheme may become competitive with the other present-day laser driven particle acceleration schemes. The quantum corrections to the Landau-Lifshitz equation of motion have also been taken into account. The difference in the energy gain estimates of the particle by the quantum corrected and classical Landau-Lifshitz equation is found to be insignificant for the present day as well as upcoming laser facilities.« less

  7. Space Acceleration Measurement System (SAMS)/Orbital Acceleration Research Experiment (OARE)

    NASA Technical Reports Server (NTRS)

    Hakimzadeh, Roshanak

    1998-01-01

    The Life and Microgravity Spacelab (LMS) payload flew on the Orbiter Columbia on mission STS-78 from June 20th to July 7th, 1996. The LMS payload on STS-78 was dedicated to life sciences and microgravity experiments. Two accelerometer systems managed by the NASA Lewis Research Center (LERC) flew to support these experiments, namely the Orbital Acceleration Research Experiment (OARE) and the Space Acceleration Measurements System (SAMS). In addition, the Microgravity Measurement Assembly (NOAA), managed by the European Space Research and Technology Center (ESA/ESTEC), and sponsored by NASA, collected acceleration data in support of the experiments on-board the LMS mission. OARE downlinked real-time quasi-steady acceleration data, which was provided to the investigators. The SAMS recorded higher frequency data on-board for post-mission analysis. The MMA downlinked real-time quasi-steady as well as higher frequency acceleration data, which was provided to the investigators. The Principal Investigator Microgravity Services (PIMS) project at NASA LERC supports principal investigators of microgravity experiments as they evaluate the effects of varying acceleration levels on their experiments. A summary report was prepared by PIMS to furnish interested experiment investigators with a guide to evaluate the acceleration environment during STS-78, and as a means of identifying areas which require further study. The summary report provides an overview of the STS-78 mission, describes the accelerometer systems flown on this mission, discusses some specific analyses of the accelerometer data in relation to the various activities which occurred during the mission, and presents plots resulting from these analyses as a snapshot of the environment during the mission. Numerous activities occurred during the STS-78 mission that are of interest to the low-gravity community. Specific activities of interest during this mission were crew exercise, radiator deployment, Vernier Reaction

  8. Bacterial cells enhance laser driven ion acceleration

    PubMed Central

    Dalui, Malay; Kundu, M.; Trivikram, T. Madhu; Rajeev, R.; Ray, Krishanu; Krishnamurthy, M.

    2014-01-01

    Intense laser produced plasmas generate hot electrons which in turn leads to ion acceleration. Ability to generate faster ions or hotter electrons using the same laser parameters is one of the main outstanding paradigms in the intense laser-plasma physics. Here, we present a simple, albeit, unconventional target that succeeds in generating 700 keV carbon ions where conventional targets for the same laser parameters generate at most 40 keV. A few layers of micron sized bacteria coating on a polished surface increases the laser energy coupling and generates a hotter plasma which is more effective for the ion acceleration compared to the conventional polished targets. Particle-in-cell simulations show that micro-particle coated target are much more effective in ion acceleration as seen in the experiment. We envisage that the accelerated, high-energy carbon ions can be used as a source for multiple applications. PMID:25102948

  9. Accelerator/Experiment Operations - FY 2014

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

    Czarapata, P.; Geer, S.; Geesaman, D.

    2014-10-01

    This Technical Memorandum (TM) summarizes the Fermilab accelerator and accelerator experiment operations for FY 2014. It is one of a series of annual publications intended to gather information in one place. In this case, the information concerns the FY 2014 MINOS and MINERvA experiments using the Main Injector Neutrino Beam (NuMI), the MiniBooNE experiment running in the Booster Neutrino Beam (BNB), and the SeaQuest experiment and Meson Test Beam (MTest) activities in the 120 GeV external Switchyard beam (SY120). Each section was prepared by the relevant authors, and was somewhat edited for inclusion in this summary.

  10. A beamline systems model for Accelerator-Driven Transmutation Technology (ADTT) facilities

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

    Todd, A.M.M.; Paulson, C.C.; Peacock, M.A.

    1995-10-01

    A beamline systems code, that is being developed for Accelerator-Driven Transmutation Technology (ADTT) facility trade studies, is described. The overall program is a joint Grumman, G.H. Gillespie Associates (GHGA) and Los Alamos National Laboratory effort. The GHGA Accelerator Systems Model (ASM) has been adopted as the framework on which this effort is based. Relevant accelerator and beam transport models from earlier Grumman systems codes are being adapted to this framework. Preliminary physics and engineering models for each ADTT beamline component have been constructed. Examples noted include a Bridge Coupled Drift Tube Linac (BCDTL) and the accelerator thermal system. A decisionmore » has been made to confine the ASM framework principally to beamline modeling, while detailed target/blanket, balance-of-plant and facility costing analysis will be performed externally. An interfacing external balance-of-plant and facility costing model, which will permit the performance of iterative facility trade studies, is under separate development. An ABC (Accelerator Based Conversion) example is used to highlight the present models and capabilities.« less

  11. A beamline systems model for Accelerator-Driven Transmutation Technology (ADTT) facilities

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

    Todd, Alan M. M.; Paulson, C. C.; Peacock, M. A.

    1995-09-15

    A beamline systems code, that is being developed for Accelerator-Driven Transmutation Technology (ADTT) facility trade studies, is described. The overall program is a joint Grumman, G. H. Gillespie Associates (GHGA) and Los Alamos National Laboratory effort. The GHGA Accelerator Systems Model (ASM) has been adopted as the framework on which this effort is based. Relevant accelerator and beam transport models from earlier Grumman systems codes are being adapted to this framework. Preliminary physics and engineering models for each ADTT beamline component have been constructed. Examples noted include a Bridge Coupled Drift Tube Linac (BCDTL) and the accelerator thermal system. Amore » decision has been made to confine the ASM framework principally to beamline modeling, while detailed target/blanket, balance-of-plant and facility costing analysis will be performed externally. An interfacing external balance-of-plant and facility costing model, which will permit the performance of iterative facility trade studies, is under separate development. An ABC (Accelerator Based Conversion) example is used to highlight the present models and capabilities.« less

  12. Comparing the new generation accelerator driven subcritical reactor system (ADS) to traditional critical reactors

    NASA Astrophysics Data System (ADS)

    Kemah, Elif; Akkaya, Recep; Tokgöz, Seyit Rıza

    2017-02-01

    In recent years, the accelerator driven subcritical reactors have taken great interest worldwide. The Accelerator Driven System (ADS) has been used to produce neutron in subcritical state by the external proton beam source. These reactors, which are hybrid systems, are important in production of clean and safe energy and conversion of radioactive waste. The ADS with the selection of reliability and robust target materials have been the new generation of fission reactors. In addition, in the ADS Reactors the problems of long-lived radioactive fission products and waste actinides encountered in the fission process of the reactor during incineration can be solved, and ADS has come to the forefront of thorium as fuel for the reactors.

  13. Laser driven ion accelerator

    DOEpatents

    Tajima, Toshiki

    2006-04-18

    A system and method of accelerating ions in an accelerator to optimize the energy produced by a light source. Several parameters may be controlled in constructing a target used in the accelerator system to adjust performance of the accelerator system. These parameters include the material, thickness, geometry and surface of the target.

  14. Recent advances in laser-driven neutron sources

    NASA Astrophysics Data System (ADS)

    Alejo, A.; Ahmed, H.; Green, A.; Mirfayzi, S. R.; Borghesi, M.; Kar, S.

    2016-11-01

    Due to the limited number and high cost of large-scale neutron facilities, there has been a growing interest in compact accelerator-driven sources. In this context, several potential schemes of laser-driven neutron sources are being intensively studied employing laser-accelerated electron and ion beams. In addition to the potential of delivering neutron beams with high brilliance, directionality and ultra-short burst duration, a laser-driven neutron source would offer further advantages in terms of cost-effectiveness, compactness and radiation confinement by closed-coupled experiments. Some of the recent advances in this field are discussed, showing improvements in the directionality and flux of the laser-driven neutron beams.

  15. Stochastic Acceleration of Ions Driven by Pc1 Wave Packets

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Sibeck, D. G.; Tel'nikhin, A. A.; Kronberg, T. K.

    2015-01-01

    The stochastic motion of protons and He(sup +) ions driven by Pc1 wave packets is studied in the context of resonant particle heating. Resonant ion cyclotron heating typically occurs when wave powers exceed 10(exp -4) nT sq/Hz. Gyroresonance breaks the first adiabatic invariant and energizes keV ions. Cherenkov resonances with the electrostatic component of wave packets can also accelerate ions. The main effect of this interaction is to accelerate thermal protons to the local Alfven speed. The dependencies of observable quantities on the wave power and plasma parameters are determined, and estimates for the heating extent and rate of particle heating in these wave-particle interactions are shown to be in reasonable agreement with known empirical data.

  16. The Strongest 40 keV Electron Acceleration By ICME-driven Shocks At 1 AU

    NASA Astrophysics Data System (ADS)

    Yang, L.; Wang, L.; Li, G.; Wimmer-Schweingruber, R. F.; He, J.; Tu, C. Y.; Bale, S. D.

    2017-12-01

    Here we present a comprehensive case study of the in situ electron acceleration at the two ICME-driven shocks observed by WIND/3DP on February 11, 2000 and July 22, 2004. For the 11 February 2000 shock (the 22 July 2004 shock), the shocked electrons in the downstream show significant flux enhancements over the ambient solar wind electrons at energies up to 40 keV (66 keV) with a 6.0 times (1.9 times) ehancment at 40 keV, the strongest among all the quasi-perpendicular (quasi-parallel) ICME-driven shocks observed by the WIND spacecraft at 1 AU from 1995 through 2014. We find that in both shocks, the shocked electron fluxes at 0.5-40 keV fit well to a double power-law spectrum, J ˜ E-β, bending up at ˜2 keV. In the downstream, these shocked electrons show stronger fluxes in the anti-sunward direction, but their enhancement over the ambient fluxes peaks near 90° pitch angle (PA). For the 11 February 2000 shock, the electron spectral index, β, appears to not vary with the electron PA, while for the 22 July 2004 shock, β roughly decreases from the anti-sunward PA direction to the sunward PA direction. All of these spectral indexes are strongly larger than the theoretical prediction of diffusive shock acceleration. At energies above (below) 2 keV, however, the shocked electron β is similar to the solar wind superhalo (halo) electrons observed at quiet times. These results suggest that the electron acceleration at the ICME-driven shocks at 1 AU may favor the shock drift acceleration, and the superthermal electrons accelerated by the interplanetary shocks may contribute to the formation of the halo and superhalo electron populations in the solar wind.

  17. Applications of compact accelerator-driven neutron sources: An updated assessment from the perspective of materials research in Italy

    DOE PAGES

    Andreani, C.; Anderson, I. S.; Carpenter, J. M.; ...

    2014-12-24

    In 2005 the International Atomic Energy Agency (IAEA) in Vienna published a report [1] on ‘Development Opportunities of Small and Medium Scale Accelerator Driven Neutron Sources’ which summarized the prospect of smaller sources in supporting the large spallation neutron sources for materials characterization and instrumentation, a theme advocated by Bauer, Clausen, Mank, and Mulhauser in previous publications [2-4]. In 2010 the Union for Compact Accelerator-driven Neutron Sources (UCANS) was established [5], galvanizing cross-disciplinary collaborations on new source and neutronics development and expanded applications based on both slow-neutron scattering and other neutron-matter interactions of neutron energies ranging from 10⁻⁶ to 10²more » MeV [6]. Here, we first cover the recent development of ongoing and prospective projects of compact accelerator-driven neutron sources (CANS) but concentrate on prospective accelerators currently proposed in Italy. Two active R&D topics, irradiation effects on electronics and cultural heritage studies, are chosen to illustrate the impact of state-of-the-art CANS on these programs with respect to the characteristics and complementarity of the accelerator and neutronics systems as well as instrumentation development.« less

  18. Pulsed power accelerator for material physics experiments

    DOE PAGES

    Reisman, D.  B.; Stoltzfus, B.  S.; Stygar, W.  A.; ...

    2015-09-01

    We have developed the design of Thor: a pulsed power accelerator that delivers a precisely shaped current pulse with a peak value as high as 7 MA to a strip-line load. The peak magnetic pressure achieved within a 1-cm-wide load is as high as 100 GPa. Thor is powered by as many as 288 decoupled and transit-time isolated bricks. Each brick consists of a single switch and two capacitors connected electrically in series. The bricks can be individually triggered to achieve a high degree of current pulse tailoring. Because the accelerator is impedance matched throughout, capacitor energy is delivered tomore » the strip-line load with an efficiency as high as 50%. We used an iterative finite element method (FEM), circuit, and magnetohydrodynamic simulations to develop an optimized accelerator design. When powered by 96 bricks, Thor delivers as much as 4.1 MA to a load, and achieves peak magnetic pressures as high as 65 GPa. When powered by 288 bricks, Thor delivers as much as 6.9 MA to a load, and achieves magnetic pressures as high as 170 GPa. We have developed an algebraic calculational procedure that uses the single brick basis function to determine the brick-triggering sequence necessary to generate a highly tailored current pulse time history for shockless loading of samples. Thor will drive a wide variety of magnetically driven shockless ramp compression, shockless flyer plate, shock-ramp, equation of state, material strength, phase transition, and other advanced material physics experiments.« less

  19. First staging of two laser accelerators.

    PubMed

    Kimura, W D; van Steenbergen, A; Babzien, M; Ben-Zvi, I; Campbell, L P; Cline, D B; Dilley, C E; Gallardo, J C; Gottschalk, S C; He, P; Kusche, K P; Liu, Y; Pantell, R H; Pogorelsky, I V; Quimby, D C; Skaritka, J; Steinhauer, L C; Yakimenko, V

    2001-04-30

    Staging of two laser-driven, relativistic electron accelerators has been demonstrated for the first time in a proof-of-principle experiment, whereby two distinct and serial laser accelerators acted on an electron beam in a coherently cumulative manner. Output from a CO2 laser was split into two beams to drive two inverse free electron lasers (IFEL) separated by 2.3 m. The first IFEL served to bunch the electrons into approximately 3 fs microbunches, which were rephased with the laser wave in the second IFEL. This represents a crucial step towards the development of practical laser-driven electron accelerators.

  20. 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.

  1. Laser-driven ion acceleration via target normal sheath acceleration in the relativistic transparency regime

    DOE PAGES

    Poole, P. L.; Obst, L.; Cochran, G. E.; ...

    2018-01-11

    Here we present an experimental study investigating laser-driven proton acceleration via target normal sheath acceleration (TNSA) over a target thickness range spanning the typical TNSA-dominant regime (~1 μm) down to below the onset of relativistic laser-transparency (<40 nm). This is done with a single target material in the form of freely adjustable films of liquid crystals along with high contrast (via plasma mirror) laser interaction (~2.65 J, 30 fs, I>1 x 10 21 W cm -2). Thickness dependent maximum proton energies scale well with TNSA models down to the thinnest targets, while those under ~40 nm indicate the influence ofmore » relativistic transparency on TNSA, observed via differences in light transmission, maximum proton energy, and proton beam spatial profile. Oblique laser incidence (45°) allowed the fielding of numerous diagnostics to determine the interaction quality and details: ion energy and spatial distribution was measured along the laser axis and both front and rear target normal directions; these along with reflected and transmitted light measurements on-shot verify TNSA as dominant during high contrast interaction, even for ultra-thin targets. Additionally, 3D particle-in-cell simulations qualitatively support the experimental observations of target-normal-directed proton acceleration from ultra-thin films.« less

  2. Laser-driven ion acceleration via target normal sheath acceleration in the relativistic transparency regime

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

    Poole, P. L.; Obst, L.; Cochran, G. E.

    Here we present an experimental study investigating laser-driven proton acceleration via target normal sheath acceleration (TNSA) over a target thickness range spanning the typical TNSA-dominant regime (~1 μm) down to below the onset of relativistic laser-transparency (<40 nm). This is done with a single target material in the form of freely adjustable films of liquid crystals along with high contrast (via plasma mirror) laser interaction (~2.65 J, 30 fs, I>1 x 10 21 W cm -2). Thickness dependent maximum proton energies scale well with TNSA models down to the thinnest targets, while those under ~40 nm indicate the influence ofmore » relativistic transparency on TNSA, observed via differences in light transmission, maximum proton energy, and proton beam spatial profile. Oblique laser incidence (45°) allowed the fielding of numerous diagnostics to determine the interaction quality and details: ion energy and spatial distribution was measured along the laser axis and both front and rear target normal directions; these along with reflected and transmitted light measurements on-shot verify TNSA as dominant during high contrast interaction, even for ultra-thin targets. Additionally, 3D particle-in-cell simulations qualitatively support the experimental observations of target-normal-directed proton acceleration from ultra-thin films.« less

  3. Coulomb-driven energy boost of heavy ions for laser-plasma acceleration.

    PubMed

    Braenzel, J; Andreev, A A; Platonov, K; Klingsporn, M; Ehrentraut, L; Sandner, W; Schnürer, M

    2015-03-27

    An unprecedented increase of kinetic energy of laser accelerated heavy ions is demonstrated. Ultrathin gold foils have been irradiated by an ultrashort laser pulse at a peak intensity of 8×10^{19}  W/  cm^{2}. Highly charged gold ions with kinetic energies up to >200  MeV and a bandwidth limited energy distribution have been reached by using 1.3 J laser energy on target. 1D and 2D particle in cell simulations show how a spatial dependence on the ion's ionization leads to an enhancement of the accelerating electrical field. Our theoretical model considers a spatial distribution of the ionization inside the thin target, leading to a field enhancement for the heavy ions by Coulomb explosion. It is capable of explaining the energy boost of highly charged ions, enabling a higher efficiency for the laser-driven heavy ion acceleration.

  4. Prognostics of Power Mosfets Under Thermal Stress Accelerated Aging Using Data-Driven and Model-Based Methodologies

    NASA Technical Reports Server (NTRS)

    Celaya, Jose; Saxena, Abhinav; Saha, Sankalita; Goebel, Kai F.

    2011-01-01

    An approach for predicting remaining useful life of power MOSFETs (metal oxide field effect transistor) devices has been developed. Power MOSFETs are semiconductor switching devices that are instrumental in electronics equipment such as those used in operation and control of modern aircraft and spacecraft. The MOSFETs examined here were aged under thermal overstress in a controlled experiment and continuous performance degradation data were collected from the accelerated aging experiment. Dieattach degradation was determined to be the primary failure mode. The collected run-to-failure data were analyzed and it was revealed that ON-state resistance increased as die-attach degraded under high thermal stresses. Results from finite element simulation analysis support the observations from the experimental data. Data-driven and model based prognostics algorithms were investigated where ON-state resistance was used as the primary precursor of failure feature. A Gaussian process regression algorithm was explored as an example for a data-driven technique and an extended Kalman filter and a particle filter were used as examples for model-based techniques. Both methods were able to provide valid results. Prognostic performance metrics were employed to evaluate and compare the algorithms.

  5. 9 GeV energy gain in a beam-driven plasma wakefield accelerator

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

    Litos, M.; Adli, E.; Allen, J. M.

    2016-02-15

    An electron beam has gained a maximum energy of 9 GeV per particle in a 1.3 m-long electron beam-driven plasma wakefield accelerator. The amount of charge accelerated in the spectral peak was 28.3 pC, and the root-mean-square energy spread was 5.0%. The mean accelerated charge and energy gain per particle of the 215 shot data set was 115 pC and 5.3 GeV, respectively, corresponding to an acceleration gradient of 4.0 GeV m -1 at the spectral peak. Moreover, the mean energy spread of the data set was 5.1%. Our results are consistent with the extrapolation of the previously reported energymore » gain results using a shorter, 36 cm-long plasma source to within 10%, evincing a non-evolving wake structure that can propagate distances of over a meter in length. Wake-loading effects were evident in the data through strong dependencies observed between various spectral properties and the amount of accelerated charge.« less

  6. The physics of sub-critical lattices in accelerator driven hybrid systems: The MUSE experiments in the MASURCA facility

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

    Chauvin, J. P.; Lebrat, J. F.; Soule, R.

    Since 1991, the CEA has studied the physics of hybrid systems, involving a sub-critical reactor coupled with an accelerator. These studies have provided information on the potential of hybrid systems to transmute actinides and, long lived fission products. The potential of such a system remains to be proven, specifically in terms of the physical understanding of the different phenomena involved and their modelling, as well as in terms of experimental validation of coupled systems, sub-critical environment/accelerator. This validation must be achieved through mock-up studies of the sub-critical environments coupled to a source of external neutrons. The MUSE-4 mock-up experiment ismore » planed at the MASURCA facility and will use an accelerator coupled to a tritium target. The great step between the generator used in the past and the accelerator will allow to increase the knowledge in hybrid physic and to decrease the experimental biases and the measurement uncertainties.« less

  7. The physics design of accelerator-driven transmutation systems

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

    Venneri, F.

    1995-10-01

    Nuclear systems under study in the Los Alamos Accelerator-Driven Transmutation Technology program (ADTT) will allow the destruction of nuclear spent fuel and weapons-return plutonium, as well as the production of nuclear energy from the thorium cycle, without a long-lived radioactive waste stream. The subcritical systems proposed represent a radical departure from traditional nuclear concepts (reactors), yet the actual implementation of ADTT systems is based on modest extrapolations of existing technology. These systems strive to keep the best that the nuclear technology has developed over the years, within a sensible conservative design envelope and eventually manage to offer a safe, lessmore » expensive and more environmentally sound approach to nuclear power.« less

  8. Vibration isolation technology: Sensitivity of selected classes of space experiments to residual accelerations

    NASA Technical Reports Server (NTRS)

    Alexander, J. Iwan D.; Zhang, Y. Q.; Adebiyi, Adebimpe

    1989-01-01

    Progress performed on each task is described. Order of magnitude analyses related to liquid zone sensitivity and thermo-capillary flow sensitivity are covered. Progress with numerical models of the sensitivity of isothermal liquid zones is described. Progress towards a numerical model of coupled buoyancy-driven and thermo-capillary convection experiments is also described. Interaction with NASA personnel is covered. Results to date are summarized and they are discussed in terms of the predicted space station acceleration environment. Work planned for the second year is also discussed.

  9. Transformer ratio saturation in a beam-driven wakefield accelerator

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

    Farmer, J. P.; Martorelli, R.; Pukhov, A.

    We show that for beam-driven wakefield acceleration, the linearly ramped, equally spaced train of bunches typically considered to optimise the transformer ratio only works for flat-top bunches. Through theory and simulation, we explain that this behaviour is due to the unique properties of the plasma response to a flat-top density profile. Calculations of the optimal scaling for a train of Gaussian bunches show diminishing returns with increasing bunch number, tending towards saturation. For a periodic bunch train, a transformer ratio of 23 was achieved for 50 bunches, rising to 40 for a fully optimised beam.

  10. Modeling laser-driven electron acceleration using WARP with Fourier decomposition

    DOE PAGES

    Lee, P.; Audet, T. L.; Lehe, R.; ...

    2015-12-31

    WARP is used with the recent implementation of the Fourier decomposition algorithm to model laser-driven electron acceleration in plasmas. Simulations were carried out to analyze the experimental results obtained on ionization-induced injection in a gas cell. The simulated results are in good agreement with the experimental ones, confirming the ability of the code to take into account the physics of electron injection and reduce calculation time. We present a detailed analysis of the laser propagation, the plasma wave generation and the electron beam dynamics.

  11. Modeling laser-driven electron acceleration using WARP with Fourier decomposition

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

    Lee, P.; Audet, T. L.; Lehe, R.

    WARP is used with the recent implementation of the Fourier decomposition algorithm to model laser-driven electron acceleration in plasmas. Simulations were carried out to analyze the experimental results obtained on ionization-induced injection in a gas cell. The simulated results are in good agreement with the experimental ones, confirming the ability of the code to take into account the physics of electron injection and reduce calculation time. We present a detailed analysis of the laser propagation, the plasma wave generation and the electron beam dynamics.

  12. Susceptibility of materials processing experiments to low-level accelerations

    NASA Technical Reports Server (NTRS)

    Naumann, R. J.

    1981-01-01

    The types of material processing experiments being considered for shuttle can be grouped into four categories: (1) contained solidification experiment; (2) quasicontainerless experiments; (3) containerless experiments; and (4) fluids experiments. Low level steady acceleration, compensated and uncompensated transient accelerations, and rotation induced flow factors that must be considered in the acceleration environment of a space vehicle whose importance depends on the type of experiment being performed. Some control of these factors may be exercised by the location and orientation of the experiment relative to shuttle and by the orbit vehicle attitude chosen for mission. The effects of the various residual accelerations can have serious consequence to the control of the experiment and must be factored into the design and operation of the apparatus.

  13. Sloshing dynamics modulated fluid angular momentum and moment fluctuations driven by orbital gravity gradient and jitter accelerations in microgravity

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Pan, H. L.

    1995-01-01

    The dynamical behavior of spacecraft propellant affected by the asymmetric combined gravity gradient and jitter accelerations, in particular the effect of surface tension on partially-filled rotating fluids applicable to a full-scale Gravity Probe-B Spacecraft dewar tank has been investigated. Three different cases of orbital accelerations: (1) gravity gradient-dominated, (2) equally weighted between gravity gradient and jitter, and (3) gravity jitter-dominated accelerations are studied. The results of slosh wave excitation along the liquid-vapor interface induced by gravity gradient-dominated accelerations provide a torsional moment with tidal motion of bubble oscillations in the rotating dewar. The results are clearly seen from the twisting shape of the bubble oscillations driven by gravity gradient-dominated acceleration. The results of slosh wave excitation along the liquid-vapor interface induced by gravity jitter-dominated acceleration indicate the results of bubble motion in a manner of down-and-up and leftward-and-rightward movement of oscillation when the bubble is rotating with respect to rotating dewar axis. Fluctuations of angular momentum, fluid moment and bubble mass center caused by slosh wave excitations driven by gravity gradient acceleration or gravity jitter acceleration are also investigated.

  14. 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.

  15. Climate-change-driven accelerated sea-level rise detected in the altimeter era.

    PubMed

    Nerem, R S; Beckley, B D; Fasullo, J T; Hamlington, B D; Masters, D; Mitchum, G T

    2018-02-27

    Using a 25-y time series of precision satellite altimeter data from TOPEX/Poseidon, Jason-1, Jason-2, and Jason-3, we estimate the climate-change-driven acceleration of global mean sea level over the last 25 y to be 0.084 ± 0.025 mm/y 2 Coupled with the average climate-change-driven rate of sea level rise over these same 25 y of 2.9 mm/y, simple extrapolation of the quadratic implies global mean sea level could rise 65 ± 12 cm by 2100 compared with 2005, roughly in agreement with the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report (AR5) model projections. Copyright © 2018 the Author(s). Published by PNAS.

  16. Wall-ablative laser-driven in-tube accelerator

    NASA Astrophysics Data System (ADS)

    Sasoh, Akihiro; Suzuki, Shingo; Matsuda, Atsushi

    2008-05-01

    The laser-driven in-tube accelerator in which the propellant is supplied from laser-ablated gas from the tube wall was developed. Proof-of concept demonstrations of vertical launch were successfully done. The device had a 25mm X 25mm square cross-section; two opposing walls were made of polyacetal and acted as the propellant, the other two acrylic window with guide grooves to the projectile. The upper end of the launch tube was connected to a vacuum chamber of an inner volume of 0.8 m2, in which the initial pressure was set to lower than 20 Pa. With plugging the bottom end of the launch tube, a momentum coupling coefficient exceeding 2.5 mN/W was obtained. Even with the bottom end connected to the same vacuum chamber through a different duct, the projectile was vertical launched successfully, obtaining 0.14 mN/W.

  17. Ultra-High Gradient Channeling Acceleration in Nanostructures: Design/Progress of Proof-of-Concept (POC) Experiments

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

    Shin, Young Min; Green, A.; Lumpkin, A. H.

    2016-09-16

    A short bunch of relativistic particles or a short-pulse laser perturbs the density state of conduction electrons in a solid crystal and excites wakefields along atomic lattices in a crystal. Under a coupling condition the wakes, if excited, can accelerate channeling particles with TeV/m acceleration gradients in principle since the density of charge carriers (conduction electrons) in solids n 0 = ~ 10 20 – 10 23 cm -3 is significantly higher than what can be obtained in gaseous plasma. Nanostructures have some advantages over crystals for channeling applications of high power beams. The dechanneling rate can be reduced andmore » the beam acceptance increased by the large size of the channels. For beam-driven acceleration, a bunch length with a sufficient charge density would need to be in the range of the plasma wavelength to properly excite plasma wakefields, and channeled particle acceleration with the wakefields must occur before the ions in the lattices move beyond the restoring threshold. In the case of the excitation by short laser pulses, the dephasing length is appreciably increased with the larger channel, which enables channeled particles to gain sufficient amounts of energy. This paper describes simulation analyses on beam- and laser (X-ray)-driven accelerations in effective nanotube models obtained from Vsim and EPOCH codes. Experimental setups to detect wakefields are also outlined with accelerator facilities at Fermilab and NIU. In the FAST facility, the electron beamline was successfully commissioned at 50 MeV and it is being upgraded toward higher energies for electron accelerator R&D. The 50 MeV injector beamline of the facility is used for X-ray crystal-channeling radiation with a diamond target. It has been proposed to utilize the same diamond crystal for a channeling acceleration POC test. Another POC experiment is also designed for the NIU accelerator lab with time-resolved electron diffraction. Recently, a stable generation of single

  18. Onset of turbulence in accelerated high-Reynolds-number flow

    NASA Astrophysics Data System (ADS)

    Zhou, Ye; Robey, Harry F.; Buckingham, Alfred C.

    2003-05-01

    of acceleration driven instability experiments: (1) classical, relatively low speed, constant acceleration RTI experiments; (2) shock tube, shockwave driven RMI flow mixing experiments; (3) laser target vaporization RTI and RMI mixing experiments driven at very high energy density. These last named experiments are of special interest as they provide scaleable flow conditions simulating those of astrophysical magnitude such as shock-driven hydrodynamic mixing in supernova evolution research.

  19. A gasdynamic gun driven by gaseous detonation

    NASA Astrophysics Data System (ADS)

    Li, Jinping; Chen, Hong; Zhang, Shizhong; Zhang, Xiaoyuan; Yu, Hongru

    2016-01-01

    A gasdynamic gun driven by gaseous detonation was developed to address the disadvantages of the insufficient driving capability of high-pressure gas and the constraints of gunpowder. The performance of this gasdynamic gun was investigated through experiments and numerical simulations. Much more powerful launching capability was achieved by this gun relative to a conventional high-pressure gas gun, owing to the use of the chemical energy of the driver gas. To achieve the same launching condition, the initial pressure required for this gun was an order of magnitude lower than that for a gun driven by high-pressure H2. Because of the presence of the detonation, however, a more complex internal ballistic process of this gun was observed. Acceleration of projectiles for this gun was accompanied by a series of impulse loads, in contrast with the smooth acceleration for a conventional one, which indicates that this gun should be used conditionally. The practical feasibility of this gun was verified by experiments. The experiments demonstrated the convenience of taking advantage of the techniques developed for detonation-driven shock tubes and tunnels.

  20. Simulations of laser-driven ion acceleration from a thin CH target

    NASA Astrophysics Data System (ADS)

    Park, Jaehong; Bulanov, Stepan; Ji, Qing; Steinke, Sven; Treffert, Franziska; Vay, Jean-Luc; Schenkel, Thomas; Esarey, Eric; Leemans, Wim; Vincenti, Henri

    2017-10-01

    2D and 3D computer simulations of laser driven ion acceleration from a thin CH foil using code WARP were performed. As the foil thickness varies from a few nm to μm, the simulations confirm that the acceleration mechanism transitions from the RPA (radiation pressure acceleration) to the TNSA (target normal sheath acceleration). In the TNSA regime, with the CH target thickness of 1 μ m and a pre-plasma ahead of the target, the simulations show the production of the collimated proton beam with the maximum energy of about 10 MeV. This agrees with the experimental results obtained at the BELLA laser facility (I 5 × 18 W / cm2 , λ = 800 nm). Furthermore, the maximum proton energy dependence on different setups of the initialization, i.e., different angles of the laser incidence from the target normal axis, different gradient scales and distributions of the pre-plasma, was explored. This work was supported by LDRD funding from LBNL, provided by the U.S. DOE under Contract No. DE-AC02-05CH11231, and used resources of the NERSC, a DOE office of Science User Facility supported by the U.S. DOE under Contract No. DE-AC02-05CH11231.

  1. Parametric investigations of target normal sheath acceleration experiments

    NASA Astrophysics Data System (ADS)

    Zani, Alessandro; Sgattoni, Andrea; Passoni, Matteo

    2011-10-01

    One of the most important challenges related to laser-driven ion acceleration research is to actively control some important ion beam features. This is a peculiar topic in the light of future possible technological applications. In the present work we make use of one theoretical model for target normal sheath acceleration in order to reproduce recent experimental parametric studies about maximum ion energy dependencies on laser parameters. The key role played by pulse energy and intensity is enlightened. Finally the effective dependence of maximum ion energy on intensity is evaluated using a combined theoretical approach, obtained by means of an analytical and a particle-in-cell numerical investigation.

  2. Laser-driven particle acceleration for radiobiology and radiotherapy: where we are and where we are going

    NASA Astrophysics Data System (ADS)

    Giulietti, Antonio

    2017-05-01

    Radiation therapy of tumors progresses continuously and so do devices, sharing a global market of about $ 4 billions, growing at an annual rate exceeding 5%. Most of the progress involves tumor targeting, multi-beam irradiation, reduction of damage on healthy tissues and critical organs, dose fractioning. This fast-evolving scenario is the moving benchmark for the progress of the laser-based accelerators towards clinical uses. As for electrons, both energy and dose requested by radiotherapy are available with plasma accelerators driven by lasers in the power range of tens of TW but several issues have still to be faced before getting a prototype device for clinical tests. They include capability of varying electron energy, stability of the process, reliability for medical users. On the other side hadron therapy, presently applied to a small fraction of cases but within an exponential growth, is a primary option for the future. With such a strong motivation, research on laser-based proton/ion acceleration has been supported in the last decade in order to get performances suitable to clinical standards. None of these performances has been achieved so far with laser techniques. In the meantime a rich crop of data have been obtained in radiobiological experiments performed with beams of particles produced with laser techniques. It is quite significant however that most of the experiments have been performed moving bio samples to laser labs, rather moving laser equipment to bio labs or clinical contexts. This give us the measure that laser community cannot so far provide practical devices usable by non-laser people.

  3. Plasma Accelerators Race to 10 GeV and Beyond

    NASA Astrophysics Data System (ADS)

    Katsouleas, Tom

    2005-10-01

    This paper reviews the concepts, recent progress and current challenges for realizing the tremendous electric fields in relativistic plasma waves for applications ranging from tabletop particle accelerators to high-energy physics. Experiments in the 90's on laser-driven plasma wakefield accelerators at several laboratories around the world demonstrated the potential for plasma wakefields to accelerate intense bunches of self-trapped particles at rates as high as 100 GeV/m in mm-scale gas jets. These early experiments offered impressive gradients but large energy spread (100%) and short interaction lengths. Major breakthroughs have recently occurred on both fronts. Three groups (LBL-US, LOA-France and RAL-UK) have now entered a new regime of laser wakefield acceleration resulting in 100 MeV mono-energetic beams with up to nanoCoulombs of charge and very small angular spread. Simulations suggest that current lasers are just entering this new regime, and the scaling to higher energies appears attractive. In parallel with the progress in laser-driven wakefields, particle-beam driven wakefield accelerators are making large strides. A series of experiments using the 30 GeV beam of the Stanford Linear Accelerator Center (SLAC) has demonstrated high-gradient acceleration of electrons and positrons in meter-scale plasmas. The UCLA/USC/SLAC collaboration has accelerated electrons beyond 1 GeV and is aiming at 10 GeV in 30 cm as the next step toward a ``plasma afterburner,'' a concept for doubling the energy of a high-energy collider in a few tens of meters of plasma. In addition to wakefield acceleration, these and other experiments have demonstrated the rich physics bounty to be reaped from relativistic beam-plasma interactions. This includes plasma lenses capable of focusing particle beams to the highest density ever produced, collective radiation mechanisms capable of generating high-brightness x-ray beams, collective refraction of particles at a plasma interface, and

  4. Study of an External Neutron Source for an Accelerator-Driven System using the PHITS Code

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

    Sugawara, Takanori; Iwasaki, Tomohiko; Chiba, Takashi

    A code system for the Accelerator Driven System (ADS) has been under development for analyzing dynamic behaviors of a subcritical core coupled with an accelerator. This code system named DSE (Dynamics calculation code system for a Subcritical system with an External neutron source) consists of an accelerator part and a reactor part. The accelerator part employs a database, which is calculated by using PHITS, for investigating the effect related to the accelerator such as the changes of beam energy, beam diameter, void generation, and target level. This analysis method using the database may introduce some errors into dynamics calculations sincemore » the neutron source data derived from the database has some errors in fitting or interpolating procedures. In this study, the effects of various events are investigated to confirm that the method based on the database is appropriate.« less

  5. Dynamics of electron injection and acceleration driven by laser wakefield in tailored density profiles

    DOE PAGES

    Lee, Patrick; Maynard, G.; Audet, T. L.; ...

    2016-11-16

    The dynamics of electron acceleration driven by laser wakefield is studied in detail using the particle-in-cell code WARP with the objective to generate high-quality electron bunches with narrow energy spread and small emittance, relevant for the electron injector of a multistage accelerator. Simulation results, using experimentally achievable parameters, show that electron bunches with an energy spread of ~11% can be obtained by using an ionization-induced injection mechanism in a mm-scale length plasma. By controlling the focusing of a moderate laser power and tailoring the longitudinal plasma density profile, the electron injection beginning and end positions can be adjusted, while themore » electron energy can be finely tuned in the last acceleration section.« less

  6. Efficient laser-driven proton acceleration from cylindrical and planar cryogenic hydrogen jets

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

    Obst, Lieselotte; Gode, Sebastian; Rehwald, Martin

    We report on recent experimental results deploying a continuous cryogenic hydrogen jet as a debris-free, renewable laser-driven source of pure proton beams generated at the 150 TW ultrashort pulse laser Draco. Efficient proton acceleration reaching cut-off energies of up to 20 MeV with particle numbers exceeding 109 particles per MeV per steradian is demonstrated, showing for the first time that the acceleration performance is comparable to solid foil targets with thicknesses in the micrometer range. Two different target geometries are presented and their proton beam deliverance characterized: cylindrical (Ø 5 μm) and planar (20 μm × 2 μm). In bothmore » cases typical Target Normal Sheath Acceleration emission patterns with exponential proton energy spectra are detected. Significantly higher proton numbers in laser-forward direction are observed when deploying the planar jet as compared to the cylindrical jet case. As a result, this is confirmed by two-dimensional Particle-in-Cell (2D3V PIC) simulations, which demonstrate that the planar jet proves favorable as its geometry leads to more optimized acceleration conditions.« less

  7. Efficient laser-driven proton acceleration from cylindrical and planar cryogenic hydrogen jets

    DOE PAGES

    Obst, Lieselotte; Gode, Sebastian; Rehwald, Martin; ...

    2017-08-31

    We report on recent experimental results deploying a continuous cryogenic hydrogen jet as a debris-free, renewable laser-driven source of pure proton beams generated at the 150 TW ultrashort pulse laser Draco. Efficient proton acceleration reaching cut-off energies of up to 20 MeV with particle numbers exceeding 109 particles per MeV per steradian is demonstrated, showing for the first time that the acceleration performance is comparable to solid foil targets with thicknesses in the micrometer range. Two different target geometries are presented and their proton beam deliverance characterized: cylindrical (Ø 5 μm) and planar (20 μm × 2 μm). In bothmore » cases typical Target Normal Sheath Acceleration emission patterns with exponential proton energy spectra are detected. Significantly higher proton numbers in laser-forward direction are observed when deploying the planar jet as compared to the cylindrical jet case. As a result, this is confirmed by two-dimensional Particle-in-Cell (2D3V PIC) simulations, which demonstrate that the planar jet proves favorable as its geometry leads to more optimized acceleration conditions.« less

  8. Accelerated Application Development: The ORNL Titan Experience

    DOE PAGES

    Joubert, Wayne; Archibald, Richard K.; Berrill, Mark A.; ...

    2015-05-09

    The use of computational accelerators such as NVIDIA GPUs and Intel Xeon Phi processors is now widespread in the high performance computing community, with many applications delivering impressive performance gains. However, programming these systems for high performance, performance portability and software maintainability has been a challenge. In this paper we discuss experiences porting applications to the Titan system. Titan, which began planning in 2009 and was deployed for general use in 2013, was the first multi-petaflop system based on accelerator hardware. To ready applications for accelerated computing, a preparedness effort was undertaken prior to delivery of Titan. In this papermore » we report experiences and lessons learned from this process and describe how users are currently making use of computational accelerators on Titan.« less

  9. Accelerated application development: The ORNL Titan experience

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

    Joubert, Wayne; Archibald, Rick; Berrill, Mark

    2015-08-01

    The use of computational accelerators such as NVIDIA GPUs and Intel Xeon Phi processors is now widespread in the high performance computing community, with many applications delivering impressive performance gains. However, programming these systems for high performance, performance portability and software maintainability has been a challenge. In this paper we discuss experiences porting applications to the Titan system. Titan, which began planning in 2009 and was deployed for general use in 2013, was the first multi-petaflop system based on accelerator hardware. To ready applications for accelerated computing, a preparedness effort was undertaken prior to delivery of Titan. In this papermore » we report experiences and lessons learned from this process and describe how users are currently making use of computational accelerators on Titan.« less

  10. Radiological Aspects of Heavy Metal Liquid Targets for Accelerator-Driven Systems as Intense Neutron Sources

    NASA Astrophysics Data System (ADS)

    Gai, E. V.; Ignatyuk, A. V.; Lunev, V. P.; Shubin, Yu. N.

    2001-11-01

    General problems arising in development of intense neutron sources as a part of accelerator-driven systems and first experience accumulated in IPPE during last several years are briefly discussed. The calculation and analysis of nuclear-physical properties of the targets, such as the accumulation of spallation reaction products, activity and heat release for various versions of heavy liquid metal targets were performed in IPPE. The sensitivity of the results of calculations to the various sets of nuclear data was considered. The main radiology characteristics of the lead-bismuth target, which is now under construction in the frame of ISTC Project # 559, are briefly described. The production of short-lived nuclides was estimated, the total activity and volatile nuclide accumulation, residual heat release, the energies of various decay modes were analysed.

  11. Accelerator-based neutrino oscillation experiments

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

    Harris, Deborah A.; /Fermilab

    2007-12-01

    Neutrino oscillations were first discovered by experiments looking at neutrinos coming from extra-terrestrial sources, namely the sun and the atmosphere, but we will be depending on earth-based sources to take many of the next steps in this field. This article describes what has been learned so far from accelerator-based neutrino oscillation experiments, and then describe very generally what the next accelerator-based steps are. In section 2 the article discusses how one uses an accelerator to make a neutrino beam, in particular, one made from decays in flight of charged pions. There are several different neutrino detection methods currently in use,more » or under development. In section 3 these are presented, with a description of the general concept, an example of such a detector, and then a brief discussion of the outstanding issues associated with this detection technique. Finally, section 4 describes how the measurements of oscillation probabilities are made. This includes a description of the near detector technique and how it can be used to make the most precise measurements of neutrino oscillations.« less

  12. Electrically Driven Liquid Film Boiling Experiment

    NASA Technical Reports Server (NTRS)

    Didion, Jeffrey R.

    2016-01-01

    This presentation presents the science background and ground based results that form the basis of the Electrically Driven Liquid Film Boiling Experiment. This is an ISS experiment that is manifested for 2021. Objective: Characterize the effects of gravity on the interaction of electric and flow fields in the presence of phase change specifically pertaining to: a) The effects of microgravity on the electrically generated two-phase flow. b) The effects of microgravity on electrically driven liquid film boiling (includes extreme heat fluxes). Electro-wetting of the boiling section will repel the bubbles away from the heated surface in microgravity environment. Relevance/Impact: Provides phenomenological foundation for the development of electric field based two-phase thermal management systems leveraging EHD, permitting optimization of heat transfer surface area to volume ratios as well as achievement of high heat transfer coefficients thus resulting in system mass and volume savings. EHD replaces buoyancy or flow driven bubble removal from heated surface. Development Approach: Conduct preliminary experiments in low gravity and ground-based facilities to refine technique and obtain preliminary data for model development. ISS environment required to characterize electro-wetting effect on nucleate boiling and CHF in the absence of gravity. Will operate in the FIR - designed for autonomous operation.

  13. Ultra-high gradient channeling acceleration in nanostructures: Design/progress of proof-of-concept (POC) experiments

    NASA Astrophysics Data System (ADS)

    Shin, Y. M.; Green, A.; Lumpkin, A. H.; Thurman-Keup, R. M.; Shiltsev, V.; Zhang, X.; Farinella, D. M.-A.; Taborek, P.; Tajima, T.; Wheeler, J. A.; Mourou, G.

    2017-03-01

    A short bunch of relativistic particles, or a short-pulse laser, perturb the density state of conduction electrons in a solid crystal and excite wakefields along atomic lattices in a crystal. Under a coupling condition between a driver and plasma, the wakes, if excited, can accelerate channeling particles with TeV/m acceleration gradients [1], in principle, since the density of charge carriers (conduction electrons) in solids n0 = 1020 - 1023 cm-3 is significantly higher than what was considered above in gaseous plasma. Nanostructures have some advantages over crystals for channeling applications of high power beams. The de-channeling rate can be reduced and the beam acceptance increased by the large size of the channels. For beam-driven acceleration, a bunch length with a sufficient charge density would need to be in the range of the plasma wavelength to properly excite plasma wakefields, and channeled particle acceleration with the wakefields must occur before the ions in the lattices move beyond the restoring threshold. In the case of the excitation by short laser pulses, the dephasing length is appreciably increased with the larger channel, which enables channeled particles to gain sufficient amounts of energy. This paper describes simulation analyses on beam- and laser (X-ray)-driven accelerations in effective nanotube models obtained from the Vsim and EPOCH codes. Experimental setups to detect wakefields are also outlined with accelerator facilities at Fermilab and Northern Illinois University (NIU). In the FAST facility, the electron beamline was successfully commissioned at 50 MeV, and it is being upgraded toward higher energies for electron accelerator R&D. The 50 MeV injector beamline of the facility is used for X-ray crystal-channeling radiation with a diamond target. It has been proposed to utilize the same diamond crystal for a channeling acceleration proof-of-concept (POC). Another POC experiment is also designed for the NIU accelerator lab with time

  14. Applications of High Intensity Proton Accelerators

    NASA Astrophysics Data System (ADS)

    Raja, Rajendran; Mishra, Shekhar

    2010-06-01

    Superconducting radiofrequency linac development at Fermilab / S. D. Holmes -- Rare muon decay experiments / Y. Kuno -- Rare kaon decays / D. Bryman -- Muon collider / R. B. Palmer -- Neutrino factories / S. Geer -- ADS and its potential / J.-P. Revol -- ADS history in the USA / R. L. Sheffield and E. J. Pitcher -- Accelerator driven transmutation of waste: high power accelerator for the European ADS demonstrator / J. L. Biarrotte and T. Junquera -- Myrrha, technology development for the realisation of ADS in EU: current status & prospects for realisation / R. Fernandez ... [et al.] -- High intensity proton beam production with cyclotrons / J. Grillenberger and M. Seidel -- FFAG for high intensity proton accelerator / Y. Mori -- Kaon yields for 2 to 8 GeV proton beams / K. K. Gudima, N. V. Mokhov and S. I. Striganov -- Pion yield studies for proton driver beams of 2-8 GeV kinetic energy for stopped muon and low-energy muon decay experiments / S. I. Striganov -- J-Parc accelerator status and future plans / H. Kobayashi -- Simulation and verification of DPA in materials / N. V. Mokhov, I. L. Rakhno and S. I. Striganov -- Performance and operational experience of the CNGS facility / E. Gschwendtner -- Particle physics enabled with super-conducting RF technology - summary of working group 1 / D. Jaffe and R. Tschirhart -- Proton beam requirements for a neutrino factory and muon collider / M. S. Zisman -- Proton bunching options / R. B. Palmer -- CW SRF H linac as a proton driver for muon colliders and neutrino factories / M. Popovic, C. M. Ankenbrandt and R. P. Johnson -- Rapid cycling synchrotron option for Project X / W. Chou -- Linac-based proton driver for a neutrino factory / R. Garoby ... [et al.] -- Pion production for neutrino factories and muon colliders / N. V. Mokhov ... [et al.] -- Proton bunch compression strategies / V. Lebedev -- Accelerator test facility for muon collider and neutrino factory R&D / V. Shiltsev -- The superconducting RF linac for muon

  15. Radiobiological effectiveness of laser accelerated electrons in comparison to electron beams from a conventional linear accelerator.

    PubMed

    Laschinsky, Lydia; Baumann, Michael; Beyreuther, Elke; Enghardt, Wolfgang; Kaluza, Malte; Karsch, Leonhard; Lessmann, Elisabeth; Naumburger, Doreen; Nicolai, Maria; Richter, Christian; Sauerbrey, Roland; Schlenvoigt, Hans-Peter; Pawelke, Jörg

    2012-01-01

    The notable progress in laser particle acceleration technology promises potential medical application in cancer therapy through compact and cost effective laser devices that are suitable for already existing clinics. Previously, consequences on the radiobiological response by laser driven particle beams characterised by an ultra high peak dose rate have to be investigated. Therefore, tumour and non-malignant cells were irradiated with pulsed laser accelerated electrons at the JETI facility for the comparison with continuous electrons of a conventional therapy LINAC. Dose response curves were measured for the biological endpoints clonogenic survival and residual DNA double strand breaks. The overall results show no significant differences in radiobiological response for in vitro cell experiments between laser accelerated pulsed and clinical used electron beams. These first systematic in vitro cell response studies with precise dosimetry to laser driven electron beams represent a first step toward the long term aim of the application of laser accelerated particles in radiotherapy.

  16. Laser-driven magnetic reconnection in the multi-plasmoid regime

    NASA Astrophysics Data System (ADS)

    Totorica, Samuel; Abel, Tom; Fiuza, Frederico

    2017-10-01

    Magnetic reconnection is a promising candidate mechanism for accelerating the nonthermal particles associated with explosive astrophysical phenomena. Laboratory experiments are starting to probe multi-plasmoid regimes of relevance for particle acceleration. We have performed two- and three-dimensional particle-in-cell (PIC) simulations to explore particle acceleration for parameters relevant to laser-driven reconnection experiments. We have extended our previous work to explore particle acceleration in larger system sizes. Our results show the transition to plasmoid-dominated acceleration associated with the merging and contraction of plasmoids that further extend the maximum energy of the power-law tail of the particle distribution. Furthermore, we have modeled Coulomb collisions and will discuss the influence of collisionality on the plasmoid formation, dynamics, and particle acceleration.

  17. Tailored electron bunches with smooth current profiles for enhanced transformer ratios in beam-driven acceleration

    DOE PAGES

    Lemery, F.; Piot, P.

    2015-08-03

    Collinear high-gradient O(GV/m) beam-driven wakefield methods for charged-particle acceleration could be critical to the realization of compact, cost-efficient, accelerators, e.g., in support of TeV-scale lepton colliders or multiple-user free-electron laser facilities. To make these options viable, the high accelerating fields need to be complemented with large transformer ratios >2, a parameter characterizing the efficiency of the energy transfer between a wakefield-exciting “drive” bunch to an accelerated “witness” bunch. While several potential current distributions have been discussed, their practical realization appears challenging due to their often discontinuous nature. In this paper we propose several alternative continuously differentiable (smooth) current profiles whichmore » support enhanced transformer ratios. We especially demonstrate that one of the devised shapes can be implemented in a photo-emission electron source by properly shaping the photocathode-laser pulse. We finally discuss a possible superconducting linear-accelerator concept that could produce shaped drive bunches at high-repetition rates to drive a dielectric-wakefield accelerator with accelerating fields on the order of ~60 MV/m and a transformer ratio ~5 consistent with a recently proposed multiuser free-electron laser facility.« less

  18. Tailored electron bunches with smooth current profiles for enhanced transformer ratios in beam-driven acceleration

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

    Lemery, F.; Piot, P.

    Collinear high-gradient O(GV/m) beam-driven wakefield methods for charged-particle acceleration could be critical to the realization of compact, cost-efficient, accelerators, e.g., in support of TeV-scale lepton colliders or multiple-user free-electron laser facilities. To make these options viable, the high accelerating fields need to be complemented with large transformer ratios >2, a parameter characterizing the efficiency of the energy transfer between a wakefield-exciting “drive” bunch to an accelerated “witness” bunch. While several potential current distributions have been discussed, their practical realization appears challenging due to their often discontinuous nature. In this paper we propose several alternative continuously differentiable (smooth) current profiles whichmore » support enhanced transformer ratios. We especially demonstrate that one of the devised shapes can be implemented in a photo-emission electron source by properly shaping the photocathode-laser pulse. We finally discuss a possible superconducting linear-accelerator concept that could produce shaped drive bunches at high-repetition rates to drive a dielectric-wakefield accelerator with accelerating fields on the order of ~60 MV/m and a transformer ratio ~5 consistent with a recently proposed multiuser free-electron laser facility.« less

  19. Feasibility of an XUV FEL Oscillator Driven by a SCRF Linear Accelerator

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

    Lumpkin, A. H.; Freund, H. P.; Reinsch, M.

    The Advanced Superconducting Test Accelerator (ASTA) facility is currently under construction at Fermi National Accelerator Laboratory. Using a1-ms-long macropulse composed of up to 3000 micropulses, and with beam energies projected from 45 to 800 MeV, the possibility for an extreme ultraviolet (XUV) free-electron laser oscillator (FELO) with the higher energy is evaluated. We have used both GINGER with an oscillator module and the MEDUSA/OPC code to assess FELO saturation prospects at 120 nm, 40 nm, and 13.4 nm. The results support saturation at all of these wavelengths which are also shorter than the demonstrated shortest wavelength record of 176 nmmore » from a storage-ring-based FELO. This indicates linac-driven FELOs can be extended into this XUV wavelength regime previously only reached with single-pass FEL configurations.« less

  20. Radiological Hazard of Spallation Products in Accelerator-Driven System

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

    Saito, M.; Stankovskii, A.; Artisyuk, V.

    The central issue underlying this paper is related to elucidating the hazard of radioactive spallation products that might be an important factor affecting the design option of accelerator-driven systems (ADSs). Hazard analysis based on the concept of Annual Limit on Intake identifies alpha-emitting isotopes of rare earths (REs) (dysprosium, gadolinium, and samarium) as the dominant contributors to the overall toxicity of traditional (W, Pb, Pb-Bi) targets. The matter is addressed from several points of view: code validation to simulate their yields, choice of material for the neutron producing targets, and challenging the beam type. The paper quantitatively determines the domainmore » in which the toxicity of REs exceeds that of polonium activation products broadly discussed now in connection with advertising lead-bismuth technology for the needs of ADSs.« less

  1. Relativistic klystron driven compact high gradient accelerator as an injector to an X-ray synchrotron radiation ring

    DOEpatents

    Yu, David U. L.

    1990-01-01

    A compact high gradient accelerator driven by a relativistic klystron is utilized to inject high energy electrons into an X-ray synchrotron radiation ring. The high gradients provided by the relativistic klystron enables accelerator structure to be much shorter (typically 3 meters) than conventional injectors. This in turn enables manufacturers which utilize high energy, high intensity X-rays to produce various devices, such as computer chips, to do so on a cost effective basis.

  2. Micron-size hydrogen cluster target for laser-driven proton acceleration

    NASA Astrophysics Data System (ADS)

    Jinno, S.; Kanasaki, M.; Uno, M.; Matsui, R.; Uesaka, M.; Kishimoto, Y.; Fukuda, Y.

    2018-04-01

    As a new laser-driven ion acceleration technique, we proposed a way to produce impurity-free, highly reproducible, and robust proton beams exceeding 100 MeV using a Coulomb explosion of micron-size hydrogen clusters. In this study, micron-size hydrogen clusters were generated by expanding the cooled high-pressure hydrogen gas into a vacuum via a conical nozzle connected to a solenoid valve cooled by a mechanical cryostat. The size distributions of the hydrogen clusters were evaluated by measuring the angular distribution of laser light scattered from the clusters. The data were analyzed mathematically based on the Mie scattering theory combined with the Tikhonov regularization method. The maximum size of the hydrogen cluster at 25 K and 6 MPa in the stagnation state was recognized to be 2.15 ± 0.10 μm. The mean cluster size decreased with increasing temperature, and was found to be much larger than that given by Hagena’s formula. This discrepancy suggests that the micron-size hydrogen clusters were formed by the atomization (spallation) of the liquid or supercritical fluid phase of hydrogen. In addition, the density profiles of the gas phase were evaluated for 25 to 80 K at 6 MPa using a Nomarski interferometer. Based on the measurement results and the equation of state for hydrogen, the cluster mass fraction was obtained. 3D particles-in-cell (PIC) simulations concerning the interaction processes of micron-size hydrogen clusters with high power laser pulses predicted the generation of protons exceeding 100 MeV and accelerating in a laser propagation direction via an anisotropic Coulomb explosion mechanism, thus demonstrating a future candidate in laser-driven proton sources for upcoming multi-petawatt lasers.

  3. Post-acceleration of laser driven protons with a compact high field linac

    NASA Astrophysics Data System (ADS)

    Sinigardi, Stefano; Londrillo, Pasquale; Rossi, Francesco; Turchetti, Giorgio; Bolton, Paul R.

    2013-05-01

    We present a start-to-end 3D numerical simulation of a hybrid scheme for the acceleration of protons. The scheme is based on a first stage laser acceleration, followed by a transport line with a solenoid or a multiplet of quadrupoles, and then a post-acceleration section in a compact linac. Our simulations show that from a laser accelerated proton bunch with energy selection at ~ 30MeV, it is possible to obtain a high quality monochromatic beam of 60MeV with intensity at the threshold of interest for medical use. In the present day experiments using solid targets, the TNSA mechanism describes accelerated bunches with an exponential energy spectrum up to a cut-off value typically below ~ 60MeV and wide angular distribution. At the cut-off energy, the number of protons to be collimated and post-accelerated in a hybrid scheme are still too low. We investigate laser-plasma acceleration to improve the quality and number of the injected protons at ~ 30MeV in order to assure efficient post-acceleration in the hybrid scheme. The results are obtained with 3D PIC simulations using a code where optical acceleration with over-dense targets, transport and post-acceleration in a linac can all be investigated in an integrated framework. The high intensity experiments at Nara are taken as a reference benchmarks for our virtual laboratory. If experimentally confirmed, a hybrid scheme could be the core of a medium sized infrastructure for medical research, capable of producing protons for therapy and x-rays for diagnosis, which complements the development of all optical systems.

  4. EDITORIAL: Laser and Plasma Accelerators Workshop, Kardamyli, Greece, 2009 Laser and Plasma Accelerators Workshop, Kardamyli, Greece, 2009

    NASA Astrophysics Data System (ADS)

    Bingham, Bob; Muggli, Patric

    2011-01-01

    The Laser and Plasma Accelerators Workshop 2009 was part of a very successful series of international workshops which were conceived at the 1985 Laser Acceleration of Particles Workshop in Malibu, California. Since its inception, the workshop has been held in Asia and in Europe (Kardamyli, Kyoto, Presqu'ile de Giens, Portovenere, Taipei and the Azores). The purpose of the workshops is to bring together the most recent results in laser wakefield acceleration, plasma wakefield acceleration, laser-driven ion acceleration, and radiation generation produced by plasma-based accelerator beams. The 2009 workshop was held on 22-26 June in Kardamyli, Greece, and brought together over 80 participants. (http://cfp.ist.utl.pt/lpaw09/). The workshop involved five main themes: • Laser plasma electron acceleration (experiment/theory/simulation) • Computational methods • Plasma wakefield acceleration (experiment/theory/simulation) • Laser-driven ion acceleration • Radiation generation and application. All of these themes are covered in this special issue of Plasma Physics and Controlled Fusion. The topic and application of plasma accelerators is one of the success stories in plasma physics, with laser wakefield acceleration of mono-energetic electrons to GeV energies, of ions to hundreds of MeV, and electron-beam-driven wakefield acceleration to 85 GeV. The accelerating electric field in the wake is of the order 1 GeV cm-1, or an accelerating gradient 1000 times greater than in conventional accelerators, possibly leading to an accelerator 1000 times smaller (and much more affordable) for the same energy. At the same time, the electron beams generated by laser wakefield accelerators have very good emittance with a correspondingly good energy spread of about a few percent. They also have the unique feature in being ultra-short in the femtosecond scale. This makes them attractive for a variety of applications, ranging from material science to ultra-fast time

  5. Molten salt considerations for accelerator-driven subcritical fission to close the nuclear fuel cycle

    NASA Astrophysics Data System (ADS)

    Sooby, Elizabeth; Adams, Marvin; Baty, Austin; Gerity, James; McIntyre, Peter; Melconian, Karie; Phongikaroon, Supathorn; Pogue, Nathaniel; Sattarov, Akhdiyor; Simpson, Michael; Tripathy, Prabhat; Tsevkov, Pavel

    2013-04-01

    The host salt selection, molecular modeling, physical chemistry, and processing chemistry are presented here for an accelerator-driven subcritical fission in a molten salt core (ADSMS). The core is fueled solely with the transuranics (TRU) and long-lived fission products (LFP) from used nuclear fuel. The neutronics and salt composition are optimized to destroy the transuranics by fission and the long-lived fission products by transmutation. The cores are driven by proton beams from a strong-focusing cyclotron stack. One such ADSMS system can destroy the transuranics in the used nuclear fuel produced by a 1GWe conventional reactor. It uniquely provides a method to close the nuclear fuel cycle for green nuclear energy.

  6. Accelerator/Experiment Operations - FY 2015

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

    Czarapata, P.

    2015-10-01

    This Technical Memorandum summarizes the Fermilab accelerator and experiment operations for FY 2015. It is one of a series of annual publications intended to gather information in one place. In this case, the information concerns the FY 2015 NOvA, MINOS+ and MINERvA experiments using the Main Injector Neutrino Beam (NuMI), the activities in the SciBooNE Hall using the Booster Neutrino Beam (BNB), and the SeaQuest experiment and Meson Test Beam (MTest) activities in the 120 GeV external Switchyard beam (SY120).

  7. Acceleration of on-axis and ring-shaped electron beams in wakefields driven by Laguerre-Gaussian pulses

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

    Zhang, Guo-Bo; Key Laboratory for Laser Plasmas; Chen, Min, E-mail: minchen@sjtu.edu.cn, E-mail: yanyunma@126.com

    2016-03-14

    The acceleration of electron beams with multiple transverse structures in wakefields driven by Laguerre-Gaussian pulses has been studied through three-dimensional (3D) particle-in-cell simulations. Under different laser-plasma conditions, the wakefield shows different transverse structures. In general cases, the wakefield shows a donut-like structure and it accelerates the ring-shaped hollow electron beam. When a lower plasma density or a smaller laser spot size is used, besides the donut-like wakefield, a central bell-like wakefield can also be excited. The wake sets in the center of the donut-like wake. In this case, both a central on-axis electron beam and a ring-shaped electron beam aremore » simultaneously accelerated. Further, reducing the plasma density or laser spot size leads to an on-axis electron beam acceleration only. The research is beneficial for some potential applications requiring special pulse beam structures, such as positron acceleration and collimation.« less

  8. Accelerator/Experiment Operations - FY 2016

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

    Blake, A.; Convery, M.; Geer, S.

    2016-10-01

    This Technical Memorandum summarizes the Fermilab accelerator and experiment operations for FY 2016. It is one of a series of annual publications intended to gather information in one place. In this case, the information concerns the FY 2016 NOvA, MINOS+ and MINERvA experiments using the Main Injector Neutrino Beam (NuMI), the MicroBooNE experiment and the activities in the SciBooNE Hall using the Booster Neutrino Beam (BNB), and the SeaQuest experiment, LArIAT experiment and Meson Test Beam activities in the 120 GeV external switchyard beam (SY120). Each section was prepared by the relevant authors, and was then edited for inclusion inmore » this summary.« less

  9. Compact Torus Acceleration and Injection Experiment

    NASA Astrophysics Data System (ADS)

    Fukumoto, Naoyuki; Fujiwara, Makoto; Nagata, Masayoshi; Uyama, Tadao; Oda, Yasushi; Azuma, Kingo

    1996-11-01

    The spheromak-type compact torus (CT) acceleration and injection experiment has been carried out using the Himeji Institute of Technology Compact Torus Injector (HIT-CTI). We explore the possibility of refueling, density control, current drive, and edge electric field control of tokamak plasma by means of CT injection. In last September the new HIT-CTI was built up to achieve higher speed (Vct>200 km/s) and higher density CT plasmoid by improving the capacitor bank system and eliminating the impurity and neutral particles. At initial formation discharge tests the gun for formation and compression successfully produced a CT plasmoid and injected it between electrodes for acceleration. (Initial velocity Vct.ini. 32 km/s, Bct 1 kG, Rct=5.5 cm). The formation capacitor bank will be upgraded to two 36 mF capacitors operating at 20 kV (14.4 kJ). The acceleration capacitor bank will be also upgraded to two 36 mF capacitors operating at 20 kV (14.4 kJ). The HIT-CTI will be optimized to obtain suitable CT parameters after acceleration (Bct>5 kG, Lct 20 cm, Vct>200 km/s). In the respect of CT parameter measurement magnetic probes and a He-Ne laser interferometer will be employed in order to measure the CT magnetic field, velocity, density, and length. CT acceleration experimental data on the HIT-CTI and the plan of CT injection experiment on the JFT-2M tokamak (JAERI) will be presented at the meeting.

  10. Demonstration of a positron beam-driven hollow channel plasma wakefield accelerator

    NASA Astrophysics Data System (ADS)

    Gessner, Spencer; Adli, Erik; Allen, James M.; An, Weiming; Clarke, Christine I.; Clayton, Chris E.; Corde, Sebastien; Delahaye, J. P.; Frederico, Joel; Green, Selina Z.; Hast, Carsten; Hogan, Mark J.; Joshi, Chan; Lindstrøm, Carl A.; Lipkowitz, Nate; Litos, Michael; Lu, Wei; Marsh, Kenneth A.; Mori, Warren B.; O'Shea, Brendan; Vafaei-Najafabadi, Navid; Walz, Dieter; Yakimenko, Vitaly; Yocky, Gerald

    2016-06-01

    Plasma wakefield accelerators have been used to accelerate electron and positron particle beams with gradients that are orders of magnitude larger than those achieved in conventional accelerators. In addition to being accelerated by the plasma wakefield, the beam particles also experience strong transverse forces that may disrupt the beam quality. Hollow plasma channels have been proposed as a technique for generating accelerating fields without transverse forces. Here we demonstrate a method for creating an extended hollow plasma channel and measure the wakefields created by an ultrarelativistic positron beam as it propagates through the channel. The plasma channel is created by directing a high-intensity laser pulse with a spatially modulated profile into lithium vapour, which results in an annular region of ionization. A peak decelerating field of 230 MeV m-1 is inferred from changes in the beam energy spectrum, in good agreement with theory and particle-in-cell simulations.

  11. The Strongest Acceleration of >40 keV Electrons by ICME-driven Shocks at 1 au

    NASA Astrophysics Data System (ADS)

    Yang, Liu; Wang, Linghua; Li, Gang; Wimmer-Schweingruber, Robert F.; He, Jiansen; Tu, Chuanyi; Tian, Hui; Bale, Stuart D.

    2018-01-01

    We present two case studies of the in-situ electron acceleration during the 2000 February 11 shock and the 2004 July 22 shock, with the strongest electron flux enhancement at 40 keV across the shock, among all the quasi-perpendicular and quasi-parallel ICME-driven shocks observed by the WIND 3DP instrument from 1995 through 2014 at 1 au. We find that for this quasi-perpendicular (quasi-parallel) shock on 2000 February 11 (2004 July 22), the shocked electron differential fluxes at ∼0.4–50 keV in the downstream generally fit well to a double-power-law spectrum, J ∼ E ‑β , with an index of β ∼ 3.15 (4.0) at energies below a break at ∼3 keV (∼1 keV) and β ∼ 2.65 (2.6) at energies above. For both shock events, the downstream electron spectral indices appear to be similar for all pitch angles, which are significantly larger than the index prediction by diffusive shock acceleration. In addition, the downstream electron pitch-angle distributions show the anisotropic beams in the anti-sunward-traveling direction, while the ratio of the downstream over ambient fluxes appears to peak near 90° pitch angles, at all energies of ∼0.4–50 keV. These results suggest that in both shocks, shock drift acceleration likely plays an important role in accelerating electrons in situ at 1 au. Such ICME-driven shocks could contribute to the formation of solar wind halo electrons at energies ≲2 keV, as well as the production of solar wind superhalo electrons at energies ≳2 keV in interplanetary space.

  12. Formation and acceleration of uniformly filled ellipsoidal electron bunches obtained via space-charge-driven expansion from a cesium-telluride photocathode

    NASA Astrophysics Data System (ADS)

    Piot, P.; Sun, Y.-E.; Maxwell, T. J.; Ruan, J.; Secchi, E.; Thangaraj, J. C. T.

    2013-01-01

    We report the experimental generation, acceleration, and characterization of a uniformly filled electron bunch obtained via space-charge-driven expansion (often referred to as “blow-out regime”) in an L-band (1.3-GHz) radiofrequency photoinjector. The beam is photoemitted from a cesium-telluride semiconductor photocathode using a short (<200fs) ultraviolet laser pulse. The produced electron bunches are characterized with conventional diagnostics and the signatures of their ellipsoidal character are observed. We especially demonstrate the production of ellipsoidal bunches with charges up to ˜0.5nC corresponding to a ˜20-fold increase compared to previous experiments with metallic photocathodes.

  13. Laser pulse shape design for laser-indirect-driven quasi-isentropic compression experiments

    NASA Astrophysics Data System (ADS)

    Xue, Quanxi; Jiang, Shaoen; Wang, Zhebin; Wang, Feng; Zhao, Xueqing; Ding, Yongkun

    2018-02-01

    Laser pulse shape design is a key work in the design of indirect-laser-driven experiments, especially for long pulse laser driven quasi-isentropic compression experiments. A method for designing such a laser pulse shape is given here. What's more, application experiments were performed, and the results of a typical shot are presented. At last of this article, the details of the application of the method are discussed, such as the equation parameter choice, radiation ablation pressure expression, and approximations in the method. The application shows that the method can provide reliable descriptions of the energy distribution in a hohlraum target; thus, it can be used in the design of long-pulse laser driven quasi-isentropic compression experiments and even other indirect-laser-driven experiments.

  14. Self-generated surface magnetic fields inhibit laser-driven sheath acceleration of high-energy protons.

    PubMed

    Nakatsutsumi, M; Sentoku, Y; Korzhimanov, A; Chen, S N; Buffechoux, S; Kon, A; Atherton, B; Audebert, P; Geissel, M; Hurd, L; Kimmel, M; Rambo, P; Schollmeier, M; Schwarz, J; Starodubtsev, M; Gremillet, L; Kodama, R; Fuchs, J

    2018-01-18

    High-intensity lasers interacting with solid foils produce copious numbers of relativistic electrons, which in turn create strong sheath electric fields around the target. The proton beams accelerated in such fields have remarkable properties, enabling ultrafast radiography of plasma phenomena or isochoric heating of dense materials. In view of longer-term multidisciplinary purposes (e.g., spallation neutron sources or cancer therapy), the current challenge is to achieve proton energies well in excess of 100 MeV, which is commonly thought to be possible by raising the on-target laser intensity. Here we present experimental and numerical results demonstrating that magnetostatic fields self-generated on the target surface may pose a fundamental limit to sheath-driven ion acceleration for high enough laser intensities. Those fields can be strong enough (~10 5  T at laser intensities ~10 21  W cm -2 ) to magnetize the sheath electrons and deflect protons off the accelerating region, hence degrading the maximum energy the latter can acquire.

  15. Self-generated surface magnetic fields inhibit laser-driven sheath acceleration of high-energy protons

    DOE PAGES

    Nakatsutsumi, M.; Sentoku, Y.; Korzhimanov, A.; ...

    2018-01-18

    High-intensity lasers interacting with solid foils produce copious numbers of relativistic electrons, which in turn create strong sheath electric fields around the target. The proton beams accelerated in such fields have remarkable properties, enabling ultrafast radiography of plasma phenomena or isochoric heating of dense materials. In view of longer-term multidisciplinary purposes (e.g., spallation neutron sources or cancer therapy), the current challenge is to achieve proton energies well in excess of 100 MeV, which is commonly thought to be possible by raising the on-target laser intensity. Here we present experimental and numerical results demonstrating that magnetostatic fields self-generated on the targetmore » surface may pose a fundamental limit to sheath-driven ion acceleration for high enough laser intensities. Those fields can be strong enough (~10 5 T at laser intensities ~10 21 W cm –2) to magnetize the sheath electrons and deflect protons off the accelerating region, hence degrading the maximum energy the latter can acquire.« less

  16. Self-generated surface magnetic fields inhibit laser-driven sheath acceleration of high-energy protons

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

    Nakatsutsumi, M.; Sentoku, Y.; Korzhimanov, A.

    High-intensity lasers interacting with solid foils produce copious numbers of relativistic electrons, which in turn create strong sheath electric fields around the target. The proton beams accelerated in such fields have remarkable properties, enabling ultrafast radiography of plasma phenomena or isochoric heating of dense materials. In view of longer-term multidisciplinary purposes (e.g., spallation neutron sources or cancer therapy), the current challenge is to achieve proton energies well in excess of 100 MeV, which is commonly thought to be possible by raising the on-target laser intensity. Here we present experimental and numerical results demonstrating that magnetostatic fields self-generated on the targetmore » surface may pose a fundamental limit to sheath-driven ion acceleration for high enough laser intensities. Those fields can be strong enough (~10 5 T at laser intensities ~10 21 W cm –2) to magnetize the sheath electrons and deflect protons off the accelerating region, hence degrading the maximum energy the latter can acquire.« less

  17. Demonstration of a positron beam-driven hollow channel plasma wakefield accelerator

    DOE PAGES

    Gessner, Spencer; Adli, Erik; Allen, James M.; ...

    2016-06-02

    Plasma wakefield accelerators have been used to accelerate electron and positron particle beams with gradients that are orders of magnitude larger than those achieved in conventional accelerators. In addition to being accelerated by the plasma wakefield, the beam particles also experience strong transverse forces that may disrupt the beam quality. Hollow plasma channels have been proposed as a technique for generating accelerating fields without transverse forces. In this study, we demonstrate a method for creating an extended hollow plasma channel and measure the wakefields created by an ultrarelativistic positron beam as it propagates through the channel. The plasma channel ismore » created by directing a high-intensity laser pulse with a spatially modulated profile into lithium vapour, which results in an annular region of ionization. A peak decelerating field of 230 MeV m -1 is inferred from changes in the beam energy spectrum, in good agreement with theory and particle-in-cell simulations.« less

  18. Demonstration of a positron beam-driven hollow channel plasma wakefield accelerator

    PubMed Central

    Gessner, Spencer; Adli, Erik; Allen, James M.; An, Weiming; Clarke, Christine I.; Clayton, Chris E.; Corde, Sebastien; Delahaye, J. P.; Frederico, Joel; Green, Selina Z.; Hast, Carsten; Hogan, Mark J.; Joshi, Chan; Lindstrøm, Carl A.; Lipkowitz, Nate; Litos, Michael; Lu, Wei; Marsh, Kenneth A.; Mori, Warren B.; O'Shea, Brendan; Vafaei-Najafabadi, Navid; Walz, Dieter; Yakimenko, Vitaly; Yocky, Gerald

    2016-01-01

    Plasma wakefield accelerators have been used to accelerate electron and positron particle beams with gradients that are orders of magnitude larger than those achieved in conventional accelerators. In addition to being accelerated by the plasma wakefield, the beam particles also experience strong transverse forces that may disrupt the beam quality. Hollow plasma channels have been proposed as a technique for generating accelerating fields without transverse forces. Here we demonstrate a method for creating an extended hollow plasma channel and measure the wakefields created by an ultrarelativistic positron beam as it propagates through the channel. The plasma channel is created by directing a high-intensity laser pulse with a spatially modulated profile into lithium vapour, which results in an annular region of ionization. A peak decelerating field of 230 MeV m−1 is inferred from changes in the beam energy spectrum, in good agreement with theory and particle-in-cell simulations. PMID:27250570

  19. Estimates of effects of residual acceleration on USML-1 experiments

    NASA Technical Reports Server (NTRS)

    Naumann, Robert J.

    1995-01-01

    The purpose of this study effort was to develop analytical models to describe the effects of residual accelerations on the experiments to be carried on the first U.S. Microgravity Lab mission (USML-1) and to test the accuracy of these models by comparing the pre-flight predicted effects with the post-flight measured effects. After surveying the experiments to be performed on USML-1, it became evident that the anticipated residual accelerations during the USML-1 mission were well below the threshold for most of the primary experiments and all of the secondary (Glovebox) experiments and that the only set of experiments that could provide quantifiable effects, and thus provide a definitive test of the analytical models, were the three melt growth experiments using the Bridgman-Stockbarger type Crystal Growth Furnace (CGF). This class of experiments is by far the most sensitive to low level quasi-steady accelerations that are unavoidable on space craft operating in low earth orbit. Because of this, they have been the drivers for the acceleration requirements imposed on the Space Station. Therefore, it is appropriate that the models on which these requirements are based are tested experimentally. Also, since solidification proceeds directionally over a long period of time, the solidified ingot provides a more or less continuous record of the effects from acceleration disturbances.

  20. Astrophysical particle acceleration mechanisms in colliding magnetized laser-produced plasmas

    DOE PAGES

    Fox, W.; Park, J.; Deng, W.; ...

    2017-08-11

    Significant particle energization is observed to occur in numerous astrophysical environments, and in the standard models, this acceleration occurs alongside energy conversion processes including collisionless shocks or magnetic reconnection. Recent platforms for laboratory experiments using magnetized laser-produced plasmas have opened opportunities to study these particle acceleration processes in the laboratory. Through fully kinetic particle-in-cell simulations, we investigate acceleration mechanisms in experiments with colliding magnetized laser-produced plasmas, with geometry and parameters matched to recent high-Mach number reconnection experiments with externally controlled magnetic fields. 2-D simulations demonstrate significant particle acceleration with three phases of energization: first, a “direct” Fermi acceleration driven bymore » approaching magnetized plumes; second, x-line acceleration during magnetic reconnection of anti-parallel fields; and finally, an additional Fermi energization of particles trapped in contracting and relaxing magnetic islands produced by reconnection. Furthermore, the relative effectiveness of these mechanisms depends on plasma and magnetic field parameters of the experiments.« less

  1. The FAST (FRC Acceleration Space Thruster) Experiment

    NASA Technical Reports Server (NTRS)

    Martin, Adam; Eskridge, R.; Lee, M.; Richeson, J.; Smith, J.; Thio, Y. C. F.; Slough, J.; Rodgers, Stephen L. (Technical Monitor)

    2001-01-01

    The Field Reverse Configuration (FRC) is a magnetized plasmoid that has been developed for use in magnetic confinement fusion. Several of its properties suggest that it may also be useful as a thruster for in-space propulsion. The FRC is a compact toroid that has only poloidal field, and is characterized by a high plasma beta = (P)/(B (sup 2) /2Mu0), the ratio of plasma pressure to magnetic field pressure, so that it makes efficient use of magnetic field to confine a plasma. In an FRC thruster, plasmoids would be repetitively formed and accelerated to high velocity; velocities of = 250 km/s (Isp = 25,000s) have already been achieved in fusion experiments. The FRC is inductively formed and accelerated, and so is not subject to the problem of electrode erosion. As the plasmoid may be accelerated over an extended length, it can in principle be made very efficient. And the achievable jet powers should be scalable to the MW range. A 10 kW thruster experiment - FAST (FRC Acceleration Space Thruster) has just started at the Marshall Space Flight Center. The design of FAST and the status of construction and operation will be presented.

  2. CANCELLED Microwave Ion Source and Beam Injection for anAccelerator-Driven Neut ron Source

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

    Vainionpaa, J.H.; Gough, R.; Hoff, M.

    2007-02-27

    An over-dense microwave driven ion source capable of producing deuterium (or hydrogen) beams at 100-200 mA/cm{sup 2} and with atomic fraction > 90% was designed and tested with an electrostatic low energy beam transport section (LEBT). This ion source was incorporated into the design of an Accelerator Driven Neutron Source (ADNS). The other key components in the ADNS include a 6 MeV RFQ accelerator, a beam bending and scanning system, and a deuterium gas target. In this design a 40 mA D{sup +} beam is produced from a 6 mm diameter aperture using a 60 kV extraction voltage. The LEBTmore » section consists of 5 electrodes arranged to form 2 Einzel lenses that focus the beam into the RFQ entrance. To create the ECR condition, 2 induction coils are used to create {approx} 875 Gauss on axis inside the source chamber. To prevent HV breakdown in the LEBT a magnetic field clamp is necessary to minimize the field in this region. Matching of the microwave power from the waveguide to the plasma is done by an autotuner. They observed significant improvement of the beam quality after installing a boron nitride liner inside the ion source. The measured emittance data are compared with PBGUNS simulations.« less

  3. Compact and tunable focusing device for plasma wakefield acceleration

    NASA Astrophysics Data System (ADS)

    Pompili, R.; Anania, M. P.; Chiadroni, E.; Cianchi, A.; Ferrario, M.; Lollo, V.; Notargiacomo, A.; Picardi, L.; Ronsivalle, C.; Rosenzweig, J. B.; Shpakov, V.; Vannozzi, A.

    2018-03-01

    Plasma wakefield acceleration, either driven by ultra-short laser pulses or electron bunches, represents one of the most promising techniques able to overcome the limits of conventional RF technology and allows the development of compact accelerators. In the particle beam-driven scenario, ultra-short bunches with tiny spot sizes are required to enhance the accelerating gradient and preserve the emittance and energy spread of the accelerated bunch. To achieve such tight transverse beam sizes, a focusing system with short focal length is mandatory. Here we discuss the development of a compact and tunable system consisting of three small-bore permanent-magnet quadrupoles with 520 T/m field gradient. The device has been designed in view of the plasma acceleration experiments planned at the SPARC_LAB test-facility. Being the field gradient fixed, the focusing is adjusted by tuning the relative position of the three magnets with nanometer resolution. Details about its magnetic design, beam-dynamics simulations, and preliminary results are examined in the paper.

  4. Transforming in-situ observations of CME-driven shock accelerated protons into the shock's reference frame.

    NASA Astrophysics Data System (ADS)

    Robinson, I. M.; Simnett, G. M.

    2005-07-01

    We examine the solar energetic particle event following solar activity from 14, 15 April 2001 which includes a "bump-on-the-tail" in the proton energy spectra at 0.99 AU from the Sun. We find this population was generated by a CME-driven shock which arrived at 0.99 AU around midnight 18 April. As such this population represents an excellent opportunity to study in isolation, the effects of proton acceleration by the shock. The peak energy of the bump-on-the-tail evolves to progressively lower energies as the shock approaches the observing spacecraft at the inner Lagrange point. Focusing on the evolution of this peak energy we demonstrate a technique which transforms these in-situ spectral observations into a frame of reference co-moving with the shock whilst making allowance for the effects of pitch angle scattering and focusing. The results of this transform suggest the bump-on-the-tail population was not driven by the 15 April activity but was generated or at least modulated by a CME-driven shock which left the Sun on 14 April. The existence of a bump-on-the-tail population is predicted by models in Rice et al. (2003) and Li et al. (2003) which we compare with observations and the results of our analysis in the context of both the 14 April and 15 April CMEs. We find an origin of the bump-on-the-tail at the 14 April CME-driven shock provides better agreement with these modelled predictions although some discrepancy exists as to the shock's ability to accelerate 100 MeV protons. Keywords. Solar physics, astrophysics and astronomy (Energetic particles; Flares and mass ejections) Space plasma physics (Transport processes)

  5. Generation of quasi-monoenergetic heavy ion beams via staged shock wave acceleration driven by intense laser pulses in near-critical plasmas

    NASA Astrophysics Data System (ADS)

    Zhang, W. L.; Qiao, B.; Shen, X. F.; You, W. Y.; Huang, T. W.; Yan, X. Q.; Wu, S. Z.; Zhou, C. T.; He, X. T.

    2016-09-01

    Laser-driven ion acceleration potentially offers a compact, cost-effective alternative to conventional accelerators for scientific, technological, and health-care applications. A novel scheme for heavy ion acceleration in near-critical plasmas via staged shock waves driven by intense laser pulses is proposed, where, in front of the heavy ion target, a light ion layer is used for launching a high-speed electrostatic shock wave. This shock is enhanced at the interface before it is transmitted into the heavy ion plasmas. Monoenergetic heavy ion beam with much higher energy can be generated by the transmitted shock, comparing to the shock wave acceleration in pure heavy ion target. Two-dimensional particle-in-cell simulations show that quasi-monoenergetic {{{C}}}6+ ion beams with peak energy 168 MeV and considerable particle number 2.1 × {10}11 are obtained by laser pulses at intensity of 1.66 × {10}20 {{W}} {{cm}}-2 in such staged shock wave acceleration scheme. Similarly a high-quality {{Al}}10+ ion beam with a well-defined peak with energy 250 MeV and spread δ E/{E}0=30 % can also be obtained in this scheme.

  6. Simulation of Fast Neutronics in an Accelerator-Driven Sub-Critical Core

    NASA Astrophysics Data System (ADS)

    Gwyn Rosaire, C.; Sattarov, Akhdiyor; McIntyre, Peter; Tsvetkov, Pavel

    2011-10-01

    Accelerator-driven subcritical fission in a molten salt core (ADSMS) is being developed as a technology for green nuclear power. ADSMS burns its fertile fuel to completion, it cannot melt down, and it destroys long-lived minor actinides. The ADSMS core consists of a vessel filled with a molten salt eutectic of UCl3 and NaCl. The fast neutronics of ADSMS makes possible two unique benefits: isobreeding, a steady-state equilibrium in which ^238U is bred to ^239Pu and the ^239Pu fissions, and destruction of minor actinides, in which fission of the intermediary nuclides dominates of breeding. Results of simulations of the fast neutronics in the ADSMS core will be presented.

  7. MEMS-based, RF-driven, compact accelerators

    NASA Astrophysics Data System (ADS)

    Persaud, A.; Seidl, P. A.; Ji, Q.; Breinyn, I.; Waldron, W. L.; Schenkel, T.; Vinayakumar, K. B.; Ni, D.; Lal, A.

    2017-10-01

    Shrinking existing accelerators in size can reduce their cost by orders of magnitude. Furthermore, by using radio frequency (RF) technology and accelerating ions in several stages, the applied voltages can be kept low paving the way to new ion beam applications. We make use of the concept of a Multiple Electrostatic Quadrupole Array Linear Accelerator (MEQALAC) and have previously shown the implementation of its basic components using printed circuit boards, thereby reducing the size of earlier MEQALACs by an order of magnitude. We now demonstrate the combined integration of these components to form a basic accelerator structure, including an initial beam-matching section. In this presentation, we will discuss the results from the integrated multi-beam ion accelerator and also ion acceleration using RF voltages generated on-board. Furthermore, we will show results from Micro-Electro-Mechanical Systems (MEMS) fabricated focusing wafers, which can shrink the dimension of the system to the sub-mm regime and lead to cheaper fabrication. Based on these proof-of-concept results we outline a scaling path to high beam power for applications in plasma heating in magnetized target fusion and in neutral beam injectors for future Tokamaks. This work was supported by the Office of Science of the US Department of Energy through the ARPA-e ALPHA program under contracts DE-AC02-05CH11231.

  8. Beyond injection: Trojan horse underdense photocathode plasma wakefield acceleration

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

    Hidding, B.; Rosenzweig, J. B.; Xi, Y.

    2012-12-21

    An overview on the underlying principles of the hybrid plasma wakefield acceleration scheme dubbed 'Trojan Horse' acceleration is given. The concept is based on laser-controlled release of electrons directly into a particle-beam-driven plasma blowout, paving the way for controlled, shapeable electron bunches with ultralow emittance and ultrahigh brightness. Combining the virtues of a low-ionization-threshold underdense photocathode with the GV/m-scale electric fields of a practically dephasing-free beam-driven plasma blowout, this constitutes a 4th generation electron acceleration scheme. It is applicable as a beam brightness transformer for electron bunches from LWFA and PWFA systems alike. At FACET, the proof-of-concept experiment 'E-210: Trojanmore » Horse Plasma Wakefield Acceleration' has recently been approved and is in preparation. At the same time, various LWFA facilities are currently considered to host experiments aiming at stabilizing and boosting the electron bunch output quality via a trojan horse afterburner stage. Since normalized emittance and brightness can be improved by many orders of magnitude, the scheme is an ideal candidate for light sources such as free-electron-lasers and those based on Thomson scattering and betatron radiation alike.« less

  9. Beryllium liner implosion experiments on the Z accelerator in preparation for magnetized liner inertial fusiona)

    NASA Astrophysics Data System (ADS)

    McBride, R. D.; Martin, M. R.; Lemke, R. W.; Greenly, J. B.; Jennings, C. A.; Rovang, D. C.; Sinars, D. B.; Cuneo, M. E.; Herrmann, M. C.; Slutz, S. A.; Nakhleh, C. W.; Ryutov, D. D.; Davis, J.-P.; Flicker, D. G.; Blue, B. E.; Tomlinson, K.; Schroen, D.; Stamm, R. M.; Smith, G. E.; Moore, J. K.; Rogers, T. J.; Robertson, G. K.; Kamm, R. J.; Smith, I. C.; Savage, M.; Stygar, W. A.; Rochau, G. A.; Jones, M.; Lopez, M. R.; Porter, J. L.; Matzen, M. K.

    2013-05-01

    Multiple experimental campaigns have been executed to study the implosions of initially solid beryllium (Be) liners (tubes) on the Z pulsed-power accelerator. The implosions were driven by current pulses that rose from 0 to 20 MA in either 100 or 200 ns (200 ns for pulse shaping experiments). These studies were conducted in support of the recently proposed Magnetized Liner Inertial Fusion concept [Slutz et al., Phys. Plasmas 17, 056303 (2010)], as well as for exploring novel equation-of-state measurement techniques. The experiments used thick-walled liners that had an aspect ratio (initial outer radius divided by initial wall thickness) of either 3.2, 4, or 6. From these studies, we present three new primary results. First, we present radiographic images of imploding Be liners, where each liner contained a thin aluminum sleeve for enhancing the contrast and visibility of the liner's inner surface in the images. These images allow us to assess the stability of the liner's inner surface more accurately and more directly than was previously possible. Second, we present radiographic images taken early in the implosion (prior to any motion of the liner's inner surface) of a shockwave propagating radially inward through the liner wall. Radial mass density profiles from these shock compression experiments are contrasted with profiles from experiments where the Z accelerator's pulse shaping capabilities were used to achieve shockless ("quasi-isentropic") liner compression. Third, we present "micro-Ḃ" measurements of azimuthal magnetic field penetration into the initially vacuum-filled interior of a shocked liner. Our measurements and simulations reveal that the penetration commences shortly after the shockwave breaks out from the liner's inner surface. The field then accelerates this low-density "precursor" plasma to the axis of symmetry.

  10. Beryllium liner implosion experiments on the Z accelerator in preparation for magnetized liner inertial fusion

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

    McBride, R. D.; Martin, M. R.; Lemke, R. W.

    Multiple experimental campaigns have been executed to study the implosions of initially solid beryllium (Be) liners (tubes) on the Z pulsed-power accelerator. The implosions were driven by current pulses that rose from 0 to 20 MA in either 100 or 200 ns (200 ns for pulse shaping experiments). These studies were conducted in support of the recently proposed Magnetized Liner Inertial Fusion concept [Slutz et al., Phys. Plasmas 17, 056303 (2010)], as well as for exploring novel equation-of-state measurement techniques. The experiments used thick-walled liners that had an aspect ratio (initial outer radius divided by initial wall thickness) of eithermore » 3.2, 4, or 6. From these studies, we present three new primary results. First, we present radiographic images of imploding Be liners, where each liner contained a thin aluminum sleeve for enhancing the contrast and visibility of the liner's inner surface in the images. These images allow us to assess the stability of the liner's inner surface more accurately and more directly than was previously possible. Second, we present radiographic images taken early in the implosion (prior to any motion of the liner's inner surface) of a shockwave propagating radially inward through the liner wall. Radial mass density profiles from these shock compression experiments are contrasted with profiles from experiments where the Z accelerator's pulse shaping capabilities were used to achieve shockless (“quasi-isentropic”) liner compression. Third, we present “micro-B-dot ” measurements of azimuthal magnetic field penetration into the initially vacuum-filled interior of a shocked liner. Our measurements and simulations reveal that the penetration commences shortly after the shockwave breaks out from the liner's inner surface. The field then accelerates this low-density “precursor” plasma to the axis of symmetry.« less

  11. Teaching experiences of second degree accelerated baccalaureate nursing faculty.

    PubMed

    Cangelosi, Pamela R

    2013-11-19

    Despite the extraordinary growth of accelerated second degree baccalaureate nursing programs, little research has been conducted about the experiences of faculty teaching these students. Using a hermeneutic phenomenological approach, this study explored the experiences of 14 accelerated second degree baccalaureate faculty from the eastern region of the United States. The data revealed that many faculty teaching second degree students feel unprepared and want guidance on how to teach these students, which was identified in the theme, Figuring It Out On My Own. This article describes this study and the implications of this theme for faculty recruitment and retention in accelerated second degree baccalaureate nursing programs.

  12. High-quality electron beams from beam-driven plasma accelerators by wakefield-induced ionization injection.

    PubMed

    Martinez de la Ossa, A; Grebenyuk, J; Mehrling, T; Schaper, L; Osterhoff, J

    2013-12-13

    We propose a new and simple strategy for controlled ionization-induced trapping of electrons in a beam-driven plasma accelerator. The presented method directly exploits electric wakefields to ionize electrons from a dopant gas and capture them into a well-defined volume of the accelerating and focusing wake phase, leading to high-quality witness bunches. This injection principle is explained by example of three-dimensional particle-in-cell calculations using the code OSIRIS. In these simulations a high-current-density electron-beam driver excites plasma waves in the blowout regime inside a fully ionized hydrogen plasma of density 5×10(17)cm-3. Within an embedded 100  μm long plasma column contaminated with neutral helium gas, the wakefields trigger ionization, trapping of a defined fraction of the released electrons, and subsequent acceleration. The hereby generated electron beam features a 1.5 kA peak current, 1.5  μm transverse normalized emittance, an uncorrelated energy spread of 0.3% on a GeV-energy scale, and few femtosecond bunch length.

  13. Petawatt pulsed-power accelerator

    DOEpatents

    Stygar, William A.; Cuneo, Michael E.; Headley, Daniel I.; Ives, Harry C.; Ives, legal representative; Berry Cottrell; Leeper, Ramon J.; Mazarakis, Michael G.; Olson, Craig L.; Porter, John L.; Wagoner; Tim C.

    2010-03-16

    A petawatt pulsed-power accelerator can be driven by various types of electrical-pulse generators, including conventional Marx generators and linear-transformer drivers. The pulsed-power accelerator can be configured to drive an electrical load from one- or two-sides. Various types of loads can be driven; for example, the accelerator can be used to drive a high-current z-pinch load. When driven by slow-pulse generators (e.g., conventional Marx generators), the accelerator comprises an oil section comprising at least one pulse-generator level having a plurality of pulse generators; a water section comprising a pulse-forming circuit for each pulse generator and a level of monolithic triplate radial-transmission-line impedance transformers, that have variable impedance profiles, for each pulse-generator level; and a vacuum section comprising triplate magnetically insulated transmission lines that feed an electrical load. When driven by LTD generators or other fast-pulse generators, the need for the pulse-forming circuits in the water section can be eliminated.

  14. Controllable robust laser driven ion acceleration from near-critical density relativistic self-transparent plasma

    NASA Astrophysics Data System (ADS)

    Liu, Bin; Meyer-Ter-Vehn, Juergen; Ruhl, Hartmut

    2017-10-01

    We introduce an alternative approach for laser driven self-injected high quality ion acceleration. We call it ion wave breaking acceleration. It operates in relativistic self-transparent plasma for ultra-intense ultra-short laser pulses. Laser propagating in a transparent plasma excites an electron wave as well as an ion wave. When the ion wave breaks, a fraction of ions is self-injected into the positive part of the laser driven wake. This leads to a superior ion pulse with peaked energy spectra; in particular in realistic three-dimensional geometry, the injection occurs localized close to the laser axis producing highly directed bunches. A theory is developed to investigate the ion wave breaking dynamics. Three dimensional Particle-in-Cell simulations with pure-gaussian laser pulses and pre-expanded near-critical density plasma targets have been done to verify the theoretical results. It is shown that hundreds of MeV, easily controllable and manipulable, micron-scale size, highly collimated and quasi-mono-energetic ion beams can be produced by using ultra-intense ultra-short laser pulses with total laser energies less than 10 Joules. Such ion beams may find important applications in tumour therapy. B. Liu acknowledges support from the Alexander von Humboldt Foundation. B. Liu and H. Ruhl acknowledge supports from the Gauss Centre for Supercomputing (GCS), and the Cluster-of-Excellence Munich Centre for Advanced Photonics (MAP).

  15. Energy Production and Transmutation of Nuclear Waste by Accelerator Driven Systems

    NASA Astrophysics Data System (ADS)

    Zhivkov, P. K.

    2018-05-01

    There is a significant amount of highly radiotoxic long-life nuclear waste (NW) produced by NPP (Nuclear Power Plants). Transmutation is a process which transforms NW into less radiotoxic nuclides with a shorter period of half-life by spallation neutrons or radiative capture of neutrons produced by ADS (Accelerator Driven System). In the processes of transmutation new radioactive nuclides are produced. ADS is big energy consumer equipment. It is a method for production of a high-flux and high-energy neutron field. All these processes occur in ADS simultaneously. ADS is able to transmute actinides and produce energy simultaneously. The article considers the energy production problems in ADS. Several ideas are developed regarding the solution of the global energy supply.

  16. Saclay Compact Accelerator-driven Neutron Sources (SCANS)

    NASA Astrophysics Data System (ADS)

    Marchix, A.; Letourneau, A.; Tran, HN; Chauvin, N.; Menelle, A.; Ott, F.; Schwindling, J.

    2018-06-01

    For next decade, the European neutron scattering community will face of important changes, as many facilities will close, strictly fission-based sources. This statement mainly concerns France with the planned closure of Orphee and ILL. At CEA-Saclay, the project SONATE has been launched in order to provide a high intensity neutron source in Saclay site, this project is based on Compact Accelerator-driven Neutron Sources technology coupled to high-intensity beams. The goal of SONATE is to develop a 50 kW target, aiming to produce at least a neutron yield of 1013 s-1 in pulse mode with a peak current of 100 mA. We have investigated in this document the best combinations of beam/target which would lead to this substantial neutron yields. Further investigations and tests have to be carry out, especially due to sparse data on thick target and such low-energy beams considered in this document. An intermediate step to the SONATE project is under test and development, called IPHI-NEUTRON, which would lead to provide a small-size neutron facility mainly devoted to neutron imagery for industry. This step is based on the existing 3 MeV proton beam, named IPHI. Best target candidates are Lithium and Beryllium, leading respectively to a neutron yield of about 2.1013 s-1 and 4.1012 s-1.

  17. Atwood's Machine: Experiments in an Accelerating Frame.

    ERIC Educational Resources Information Center

    Chee, Chia Teck; Hong, Chia Yee

    1999-01-01

    Experiments in an accelerating frame are hard to perform. Illustrates how simple computer software allows sufficiently rapid and accurate measurements to be made on an arrangement of weights and pulleys known as Atwood's machine. (Author/CCM)

  18. The accelerated residency program: the Marshall University family practice 9-year experience.

    PubMed

    Petrany, Stephen M; Crespo, Richard

    2002-10-01

    In 1989, the American Board of Family Practice (ABFP) approved the first of 12 accelerated residency programs in family practice. These experimental programs provide a 1-year experience for select medical students that combines the requirements of the fourth year of medical school with those of the first year of residency, reducing the total training time by 1 year. This paper reports on the achievements and limitations of the Marshall University accelerated residency program over a 9-year period that began in 1992. Several parameters have been monitored since the inception of the accelerated program and provide the basis for comparison of accelerated and traditional residents. These include initial resident characteristics, performance outcomes, and practice choices. A total of 16 students were accepted into the accelerated track from 1992 through 1998. During the same time period, 44 residents entered the traditional residency program. Accelerated resident tended to be older and had more career experience than their traditional counterparts. As a group, the accelerated residents scored an average of 30 points higher on the final in-training exams provided by the ABFP. All residents in both groups remained at Marshall to complete the full residency training experience, and all those who have taken the ABFP certifying exam have passed. Accelerated residents were more likely to practice in West Virginia, consistent with one of the initial goals for the program. In addition, accelerated residents were more likely to be elected chief resident and choose an academic career than those in the traditional group. Both groups opted for small town or rural practice equally. The Marshall University family practice 9-year experience with the accelerated residency track demonstrates that for carefully selected candidates, the program can provide an overall shortened path to board certification and attract students who excel academically and have high leadership potential

  19. 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

  20. Micro-Bubble Experiments at the Van de Graaff Accelerator

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

    Sun, Z. J.; Wardle, Kent E.; Quigley, K. J.

    In order to test and verify the experimental designs at the linear accelerator (LINAC), several micro-scale bubble ("micro-bubble") experiments were conducted with the 3-MeV Van de Graaff (VDG) electron accelerator. The experimental setups included a square quartz tube, sodium bisulfate solution with different concentrations, cooling coils, gas chromatography (GC) system, raster magnets, and two high-resolution cameras that were controlled by a LabVIEW program. Different beam currents were applied in the VDG irradiation. Bubble generation (radiolysis), thermal expansion, thermal convection, and radiation damage were observed in the experiments. Photographs, videos, and gas formation (O 2 + H 2) data were collected.more » The micro-bubble experiments at VDG indicate that the design of the full-scale bubble experiments at the LINAC is reasonable.« less

  1. High quality proton beams from hybrid integrated laser-driven ion acceleration systems

    NASA Astrophysics Data System (ADS)

    Sinigardi, Stefano; Turchetti, Giorgio; Rossi, Francesco; Londrillo, Pasquale; Giove, Dario; De Martinis, Carlo; Bolton, Paul R.

    2014-03-01

    We consider a hybrid acceleration scheme for protons where the laser generated beam is selected in energy and angle and injected into a compact linac, which raises the energy from 30 to 60 MeV. The laser acceleration regime is TNSA and the energy spectrum is determined by the cutoff energy and proton temperature. The dependence of the spectrum on the target properties and the incidence angle is investigated with 2D PIC simulations. We base our work on widely available technologies and on laser with a short pulse, having in mind a facility whose cost is approximately 15 M €. Using a recent experiment as the reference, we choose the laser pulse and target so that the energy spectrum obtained from the 3D PIC simulation is close to the one observed, whose cutoff energy was estimated to be over 50 MeV. Laser accelerated protons in the TNSA regime have wide energy spectrum and broad divergence. In this paper we compare three transport lines, designed to perform energy selection and beam collimation. They are based on a solenoid, a quadruplet of permanent magnetic quadrupoles and a chicane. To increase the maximum available energy, which is actually seen as an upper limit due to laser properties and available targets, we propose to inject protons into a small linac for post-acceleration. The number of selected and injected protons is the highest with the solenoid and lower by one and two orders of magnitude with the quadrupoles and the chicane respectively. Even though only the solenoid enables achieving to reach a final intensity at the threshold required for therapy with the highest beam quality, the other systems will be very likely used in the first experiments. Realistic start-to-end simulations, as the ones reported here, are relevant for the design of such experiments.

  2. Review of laser-driven ion sources and their applications.

    PubMed

    Daido, Hiroyuki; Nishiuchi, Mamiko; Pirozhkov, Alexander S

    2012-05-01

    For many years, laser-driven ion acceleration, mainly proton acceleration, has been proposed and a number of proof-of-principle experiments have been carried out with lasers whose pulse duration was in the nanosecond range. In the 1990s, ion acceleration in a relativistic plasma was demonstrated with ultra-short pulse lasers based on the chirped pulse amplification technique which can provide not only picosecond or femtosecond laser pulse duration, but simultaneously ultra-high peak power of terawatt to petawatt levels. Starting from the year 2000, several groups demonstrated low transverse emittance, tens of MeV proton beams with a conversion efficiency of up to several percent. The laser-accelerated particle beams have a duration of the order of a few picoseconds at the source, an ultra-high peak current and a broad energy spectrum, which make them suitable for many, including several unique, applications. This paper reviews, firstly, the historical background including the early laser-matter interaction studies on energetic ion acceleration relevant to inertial confinement fusion. Secondly, we describe several implemented and proposed mechanisms of proton and/or ion acceleration driven by ultra-short high-intensity lasers. We pay special attention to relatively simple models of several acceleration regimes. The models connect the laser, plasma and proton/ion beam parameters, predicting important features, such as energy spectral shape, optimum conditions and scalings under these conditions for maximum ion energy, conversion efficiency, etc. The models also suggest possible ways to manipulate the proton/ion beams by tailoring the target and irradiation conditions. Thirdly, we review experimental results on proton/ion acceleration, starting with the description of driving lasers. We list experimental results and show general trends of parameter dependences and compare them with the theoretical predictions and simulations. The fourth topic includes a review of

  3. Dogs lap using acceleration-driven open pumping

    PubMed Central

    Gart, Sean; Socha, John J.; Vlachos, Pavlos P.; Jung, Sunghwan

    2015-01-01

    Dogs lap because they have incomplete cheeks and cannot suck. When lapping, a dog’s tongue pulls a liquid column from the bath, suggesting that the hydrodynamics of column formation are critical to understanding how dogs drink. We measured lapping in 19 dogs and used the results to generate a physical model of the tongue’s interaction with the air–fluid interface. These experiments help to explain how dogs exploit the fluid dynamics of the generated column. The results demonstrate that effects of acceleration govern lapping frequency, which suggests that dogs curl the tongue to create a larger liquid column. Comparing lapping in dogs and cats reveals that, despite similar morphology, these carnivores lap in different physical regimes: an unsteady inertial regime for dogs and steady inertial regime for cats. PMID:26668382

  4. Accelerator-driven transmutation of spent fuel elements

    DOEpatents

    Venneri, Francesco; Williamson, Mark A.; Li, Ning

    2002-01-01

    An apparatus and method is described for transmuting higher actinides, plutonium and selected fission products in a liquid-fuel subcritical assembly. Uranium may also be enriched, thereby providing new fuel for use in conventional nuclear power plants. An accelerator provides the additional neutrons required to perform the processes. The size of the accelerator needed to complete fuel cycle closure depends on the neutron efficiency of the supported reactors and on the neutron spectrum of the actinide transmutation apparatus. Treatment of spent fuel from light water reactors (LWRs) using uranium-based fuel will require the largest accelerator power, whereas neutron-efficient high temperature gas reactors (HTGRs) or CANDU reactors will require the smallest accelerator power, especially if thorium is introduced into the newly generated fuel according to the teachings of the present invention. Fast spectrum actinide transmutation apparatus (based on liquid-metal fuel) will take full advantage of the accelerator-produced source neutrons and provide maximum utilization of the actinide-generated fission neutrons. However, near-thermal transmutation apparatus will require lower standing

  5. The Awful Truth About Zero-Gravity: Space Acceleration Measurement System; Orbital Acceleration Research Experiment

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Earth's gravity holds the Shuttle in orbit, as it does satellites and the Moon. The apparent weightlessness experienced by astronauts and experiments on the Shuttle is a balancing act, the result of free-fall, or continuously falling around Earth. An easy way to visualize what is happening is with a thought experiment that Sir Isaac Newton did in 1686. Newton envisioned a mountain extending above Earth's atmosphere so that friction with the air would be eliminated. He imagined a cannon atop the mountain and aimed parallel to the ground. Firing the cannon propels the cannonball forward. At the same time, Earth's gravity pulls the cannonball down to the surface and eventual impact. Newton visualized using enough powder to just balance gravity so the cannonball would circle the Earth. Like the cannonball, objects orbiting Earth are in continuous free-fall, and it appears that gravity has been eliminated. Yet, that appearance is deceiving. Activities aboard the Shuttle generate a range of accelerations that have effects similar to those of gravity. The crew works and exercises. The main data relay antenna quivers 17 times per second to prevent 'stiction,' where parts stick then release with a jerk. Cooling pumps, air fans, and other systems add vibration. And traces of Earth's atmosphere, even 200 miles up, drag on the Shuttle. While imperceptible to us, these vibrations can have a profound impact on the commercial research and scientific experiments aboard the Shuttle. Measuring these forces is necessary so that researchers and scientists can see what may have affected their experiments when analyzing data. On STS-107 this service is provided by the Space Acceleration Measurement System for Free Flyers (SAMS-FF) and the Orbital Acceleration Research Experiment (OARE). Precision data from these two instruments will help scientists analyze data from their experiments and eliminate outside influences from the phenomena they are studying during the mission.

  6. Small-scale laser based electron accelerators for biology and medicine: a comparative study of the biological effectiveness

    NASA Astrophysics Data System (ADS)

    Labate, Luca; Andreassi, Maria Grazia; Baffigi, Federica; Basta, Giuseppina; Bizzarri, Ranieri; Borghini, Andrea; Candiano, Giuliana C.; Casarino, Carlo; Cresci, Monica; Di Martino, Fabio; Fulgentini, Lorenzo; Ghetti, Francesco; Gilardi, Maria Carla; Giulietti, Antonio; Köster, Petra; Lenci, Francesco; Levato, Tadzio; Oishi, Yuji; Russo, Giorgio; Sgarbossa, Antonella; Traino, Claudio; Gizzi, Leonida A.

    2013-05-01

    Laser-driven electron accelerators based on the Laser Wakefield Acceleration process has entered a mature phase to be considered as alternative devices to conventional radiofrequency linear accelerators used in medical applications. Before entering the medical practice, however, deep studies of the radiobiological effects of such short bunches as the ones produced by laser-driven accelerators have to be performed. Here we report on the setup, characterization and first test of a small-scale laser accelerator for radiobiology experiments. A brief description of the experimental setup will be given at first, followed by an overview of the electron bunch characterization, in particular in terms of dose delivered to the samples. Finally, the first results from the irradiation of biological samples will be briefly discussed.

  7. Electrically Driven Thermal Management: Flight Validation, Experiment Development, Future Technologies

    NASA Technical Reports Server (NTRS)

    Didion, Jeffrey R.

    2018-01-01

    Electrically Driven Thermal Management is an active research and technology development initiative incorporating ISS technology flight demonstrations (STP-H5), development of Microgravity Science Glovebox (MSG) flight experiment, and laboratory-based investigations of electrically based thermal management techniques. The program targets integrated thermal management for future generations of RF electronics and power electronic devices. This presentation reviews four program elements: i.) results from the Electrohydrodynamic (EHD) Long Term Flight Demonstration launched in February 2017 ii.) development of the Electrically Driven Liquid Film Boiling Experiment iii.) two University based research efforts iv.) development of Oscillating Heat Pipe evaluation at Goddard Space Flight Center.

  8. Weibel instability mediated collisionless shocks using intense laser-driven plasmas

    NASA Astrophysics Data System (ADS)

    Palaniyappan, Sasi; Huang, Chengkun; Gautier, Donald; Fernandez, Juan; Ma, Wenjun; Schreiber, Jorg; LANL Collaboration; LMU Team

    2016-10-01

    The origin of cosmic rays remains a long-standing challenge in astrophysics and continues to fascinate physicists. It is believed that ``collisionless shocks'' - where the particle Coulomb mean free path is much larger that the shock transition - are a dominant source of energetic cosmic rays. These shocks are ubiquitous in astrophysical environments such as gamma-ray bursts, supernova remnants, pulsar wind nebula and coronal mass ejections from the sun. Several spacecraft observations have revealed acceleration of charged particles, mostly electrons, to very high energies with in the shock front. There is now also clear observational evidence that supernova remnant shocks accelerate both protons and electrons. The understanding of the microphysics behind collisionless shocks and their particle acceleration is tightly related with nonlinear basic plasma processes and remains a grand challenge. In this poster, we will present results from recent experiments at the LANL Trident laser facility studying collisionless shocks using intense ps laser (80J, 650 fs - peak intensity of 1020 W/cm2) driven near-critical plasmas using carbon nanotube foam targets. A second short pulse laser driven protons from few microns thick aluminum foil is used to image the laser-driven plasma.

  9. Laboratory flow experiments for visualizing carbon dioxide-induced, density-driven brine convection

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

    Kneafsey, T.; Pruess, K.

    2009-09-01

    Injection of carbon dioxide (CO{sub 2}) into saline aquifers confined by low-permeability cap rock will result in a layer of CO{sub 2} overlying the brine. Dissolution of CO{sub 2} into the brine increases the brine density, resulting in an unstable situation in which more-dense brine overlies less-dense brine. This gravitational instability could give rise to density-driven convection of the fluid, which is a favorable process of practical interest for CO{sub 2} storage security because it accelerates the transfer of buoyant CO{sub 2} into the aqueous phase, where it is no longer subject to an upward buoyant drive. Laboratory flow visualizationmore » tests in transparent Hele-Shaw cells have been performed to elucidate the processes and rates of this CO{sub 2} solute-driven convection (CSC). Upon introduction of CO{sub 2} into the system, a layer of CO{sub 2}-laden brine forms at the CO{sub 2}-water interface. Subsequently, small convective fingers form, which coalesce, broaden, and penetrate into the test cell. Images and time-series data of finger lengths and wavelengths are presented. Observed CO{sub 2} uptake of the convection system indicates that the CO{sub 2} dissolution rate is approximately constant for each test and is far greater than expected for a diffusion-only scenario. Numerical simulations of our system show good agreement with the experiments for onset time of convection and advancement of convective fingers. There are differences as well, the most prominent being the absence of cell-scale convection in the numerical simulations. This cell-scale convection observed in the experiments is probably initiated by a small temperature gradient induced by the cell illumination.« less

  10. Variable-pulse-shape pulsed-power accelerator

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

    Stoltzfus, Brian S.; Austin, Kevin; Hutsel, Brian Thomas

    A variable-pulse-shape pulsed-power accelerator is driven by a large number of independent LC drive circuits. Each LC circuit drives one or more coaxial transmission lines that deliver the circuit's output power to several water-insulated radial transmission lines that are connected in parallel at small radius by a water-insulated post-hole convolute. The accelerator can be impedance matched throughout. The coaxial transmission lines are sufficiently long to transit-time isolate the LC drive circuits from the water-insulated transmission lines, which allows each LC drive circuit to be operated without being affected by the other circuits. This enables the creation of any power pulsemore » that can be mathematically described as a time-shifted linear combination of the pulses of the individual LC drive circuits. Therefore, the output power of the convolute can provide a variable pulse shape to a load that can be used for magnetically driven, quasi-isentropic compression experiments and other applications.« less

  11. Neutron Source from Laser Plasma Acceleration

    NASA Astrophysics Data System (ADS)

    Jiao, Xuejing; Shaw, Joseph; McCary, Eddie; Downer, Mike; Hegelich, Bjorn

    2016-10-01

    Laser driven electron beams and ion beams were utilized to produce neutron sources via different mechanism. On the Texas Petawatt laser, deuterized plastic, gold and DLC foil targets of varying thickness were shot with 150 J , 150 fs laser pulses at a peak intensity of 2 ×1021W /cm2 . Ions were accelerated by either target normal sheath acceleration or Breakout Afterburner acceleration. Neutrons were produced via the 9Be(d,n) and 9Be(p,n) reactions when accelerated ions impinged on a Beryllium converter as well as by deuteron breakup reactions. We observed 2 ×1010 neutron per shot in average, corresponding to 5 ×1018n /s . The efficiencies for different targets are comparable. In another experiment, 38fs , 0.3 J UT3 laser pulse interacted with mixed gas target. Electrons with energy 40MeV were produced via laser wakefield acceleration. Neutron flux of 2 ×106 per shot was generated through bremsstrahlung and subsequent photoneutron reactions on a Copper converter.

  12. Microwave Driven Magnetic Plasma Accelerator Studies (CYCLOPS)

    NASA Technical Reports Server (NTRS)

    Crimi, G. F.; Eckert, A. C.; Miller, D. B.

    1967-01-01

    A microwave-driven cyclotron resonance plasma acceleration device was investigated using argon, krypton, xenon, and mercury as propellants. Limited ranges of propellant flow rate, input power, and magnetic field strength were used. Over-all efficiencies (including the 65% efficiency of the input polarizer) less than 10% were obtained for specific impulse values between 500 and 1500 sec. Power transfer efficiencies, however, approached 100% of the input power available in the right-hand component of the incident circularly polarized radiation. Beam diagnostics using Langmuir probes, cold gas mapping, r-f mapping and ion energy analyses were performed in conjunction with an engine operating in a pulsed mode. Measurements of transverse electron energies at the position of cyclotron resonant absorption yielded energy values more than an order of magnitude lower than anticipated. The measured electron energies were, however, consistent with the low values of average ion energy measured by retarding potential techniques. The low values of average ion energy were also consistent with the measured thrust values. It is hypothesized that ionization and radiation limit the electron kinetic energy to low-values thus limiting the energy which is finally transferred to the ion. Thermalization by electron-electron collision was also identified as an additional loss mechanism. The use of light alkali metals, which have relatively few low lying energy levels to excite, with the input power to mass ratio selected so as to limit the electron energies to less than the second ionization potential, is suggested. It is concluded, however, that the over-all efficiency for such propellants would be less than 40 per cent.

  13. Choosing experiments to accelerate collective discovery

    DOE PAGES

    Rzhetsky, Andrey; Foster, Jacob G.; Foster, Ian T.; ...

    2015-11-24

    Scientists perform a tiny subset of all possible experiments. What characterizes the experiments they choose? What are the consequences of those choices for the pace of scientific discovery? We model scientific knowledge as a network and science as a sequence of experiments designed to gradually uncover it. By analyzing millions of biomedical articles published over 30 y, we find that biomedical scientists pursue conservative research strategies exploring the local neighborhood of central, important molecules. Although such strategies probably serve scientific careers, we show that they slow scientific advance, especially in mature fields, where more risk and less redundant experimentation wouldmore » accelerate discovery of the network. Lastly, we also consider institutional arrangements that could help science pursue these more efficient strategies.« less

  14. Space experiments with particle accelerators (SEPAC): Description of instrumentation

    NASA Technical Reports Server (NTRS)

    Taylor, W. W. L.; Roberts, W. T.; Reasoner, D. L.; Chappell, C. R.; Baker, B. B.; Burch, J. L.; Gibson, W. C.; Black, R. K.; Tomlinson, W. M.; Bounds, J. R.

    1987-01-01

    SEPAC (Space Experiments with Particle Accelerators) flew on Spacelab 1 (SL 1) in November and December 1983. SEPAC is a joint U.S.-Japan investigation of the interaction of electron, plasma, and neutral beams with the ionosphere, atmosphere and magnetosphere. It is scheduled to fly again on Atlas 1 in August 1990. On SL 1, SEPAC used an electron accelerator, a plasma accelerator, and neutral gas source as active elements and an array of diagnostics to investigate the interactions. For Atlas 1, the plasma accelerator will be replaced by a plasma contactor and charge collection devices to improve vehicle charging meutralization. This paper describes the SEPAC instrumentation in detail for the SL 1 and Atlas 1 flights and includes a bibliography of SEPAC papers.

  15. Attosecond Thomson-scattering x-ray source driven by laser-based electron acceleration

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

    Luo, W.; College of Science, National University of Defense Technology, Changsha 410073; Zhuo, H. B.

    2013-10-21

    The possibility of producing attosecond x-rays through Thomson scattering of laser light off laser-driven relativistic electron beams is investigated. For a ≤200-as, tens-MeV electron bunch produced with laser ponderomotive-force acceleration in a plasma wire, exceeding 10{sup 6} photons/s in the form of ∼160 as pulses in the range of 3–300 keV are predicted, with a peak brightness of ≥5 × 10{sup 20} photons/(s mm{sup 2} mrad{sup 2} 0.1% bandwidth). Our study suggests that the physical scheme discussed in this work can be used for an ultrafast (attosecond) x-ray source, which is the most beneficial for time-resolved atomic physics, dubbed “attosecondmore » physics.”.« less

  16. Numerical and Experimental Investigation of the Effects of Acceleration Disturbances on Microgravity Experiments

    NASA Technical Reports Server (NTRS)

    Ramachandran, Narayanan

    2000-01-01

    Normal vibrational modes on large spacecraft are excited by crew activity, operating machinery, and other mechanical disturbances. Periodic engine burns for maintaining vehicle attitude and random impulse type disturbances also contribute to the acceleration environment of a Spacecraft. Accelerations from these vibrations (often referred to as g-jitter) are several orders of magnitude larger than the residual accelerations from atmospheric drag and gravity gradient effects. Naturally, the effects of such accelerations have been a concern to prospective experimenters wishing to take advantage of the microgravity environment offered by spacecraft operating in low Earth orbit and the topic has been studied extensively, both numerically and analytically. However, these studies have not produced a general theory that predicts the effects of multi-spectral periodic accelerations on a general class of experiments nor have they produced scaling laws that a prospective experimenter could use to assess how his/her experiment might be affected by this acceleration environment. Furthermore, there are no actual flight experimental data that correlates heat or mass transport with measurements of the periodic acceleration environment. The present investigation approaches this problem with carefully conducted terrestrial experiments and rigorous numerical modeling thereby providing comparative theoretical and experimental data. The modeling, it is hoped will provide a predictive tool that can be used for assessing experiment response to Spacecraft vibrations.

  17. Candidate molten salt investigation for an accelerator driven subcritical core

    NASA Astrophysics Data System (ADS)

    Sooby, E.; Baty, A.; Beneš, O.; McIntyre, P.; Pogue, N.; Salanne, M.; Sattarov, A.

    2013-09-01

    We report a design for accelerator-driven subcritical fission in a molten salt core (ADSMS) that utilizes a fuel salt composed of NaCl and transuranic (TRU) chlorides. The ADSMS core is designed for fast neutronics (28% of neutrons >1 MeV) to optimize TRU destruction. The choice of a NaCl-based salt offers benefits for corrosion, operating temperature, and actinide solubility as compared with LiF-based fuel salts. A molecular dynamics (MD) code has been used to estimate properties of the molten salt system which are important for ADSMS design but have never been measured experimentally. Results from the MD studies are reported. Experimental measurements of fuel salt properties and studies of corrosion and radiation damage on candidate metals for the core vessel are anticipated. A special thanks is due to Prof. Paul Madden for introducing the ADSMS group to the concept of using the molten salt as the spallation target, rather than a conventional heavy metal spallation target. This feature helps to optimize this core as a Pu/TRU burner.

  18. Benchmarking shielding simulations for an accelerator-driven spallation neutron source

    DOE PAGES

    Cherkashyna, Nataliia; Di Julio, Douglas D.; Panzner, Tobias; ...

    2015-08-09

    The shielding at an accelerator-driven spallation neutron facility plays a critical role in the performance of the neutron scattering instruments, the overall safety, and the total cost of the facility. Accurate simulation of shielding components is thus key for the design of upcoming facilities, such as the European Spallation Source (ESS), currently in construction in Lund, Sweden. In this paper, we present a comparative study between the measured and the simulated neutron background at the Swiss Spallation Neutron Source (SINQ), at the Paul Scherrer Institute (PSI), Villigen, Switzerland. The measurements were carried out at several positions along the SINQ monolithmore » wall with the neutron dosimeter WENDI-2, which has a well-characterized response up to 5 GeV. The simulations were performed using the Monte-Carlo radiation transport code Geant4, and include a complete transport from the proton beam to the measurement locations in a single calculation. An agreement between measurements and simulations is about a factor of 2 for the points where the measured radiation dose is above the background level, which is a satisfactory result for such simulations spanning many energy regimes, different physics processes and transport through several meters of shielding materials. The neutrons contributing to the radiation field emanating from the monolith were confirmed to originate from neutrons with energies above 1 MeV in the target region. The current work validates Geant4 as being well suited for deep-shielding calculations at accelerator-based spallation sources. We also extrapolate what the simulated flux levels might imply for short (several tens of meters) instruments at ESS.« less

  19. Accelerated ions from pulsed-power-driven fast plasma flow in perpendicular magnetic field

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

    Takezaki, Taichi, E-mail: ttakezaki@stn.nagaokaut.ac.jp; Takahashi, Kazumasa; Sasaki, Toru, E-mail: sasakit@vos.nagaokaut.ac.jp

    2016-06-15

    To understand the interaction between fast plasma flow and perpendicular magnetic field, we have investigated the behavior of a one-dimensional fast plasma flow in a perpendicular magnetic field by a laboratory-scale experiment using a pulsed-power discharge. The velocity of the plasma flow generated by a tapered cone plasma focus device is about 30 km/s, and the magnetic Reynolds number is estimated to be 8.8. After flow through the perpendicular magnetic field, the accelerated ions are measured by an ion collector. To clarify the behavior of the accelerated ions and the electromagnetic fields, numerical simulations based on an electromagnetic hybrid particle-in-cell methodmore » have been carried out. The results show that the behavior of the accelerated ions corresponds qualitatively to the experimental results. Faster ions in the plasma flow are accelerated by the induced electromagnetic fields modulated with the plasma flow.« less

  20. Accelerated Aging Experiments for Prognostics of Damage Growth in Composite Materials

    DTIC Science & Technology

    2011-09-01

    possible resource to collect such data is an accelerated aging platform. To that end this paper describes a fatigue cycling experiment with the goal to...possible resource to collect such data is an accelerated aging platform. To that end this paper describes a fatigue cycling experiment with the goal to...suffer from two damage types: matrix micro-cracks and inter- laminar delamination. When subject to fatigue loading matrix micro-cracks develop in the

  1. Rayleigh-Taylor mixing with time-dependent acceleration

    NASA Astrophysics Data System (ADS)

    Abarzhi, Snezhana

    2016-10-01

    We extend the momentum model to describe Rayleigh-Taylor (RT) mixing driven by a time-dependent acceleration. The acceleration is a power-law function of time, similarly to astrophysical and plasma fusion applications. In RT flow the dynamics of a fluid parcel is driven by a balance per unit mass of the rates of momentum gain and loss. We find analytical solutions in the cases of balanced and imbalanced gains and losses, and identify their dependence on the acceleration exponent. The existence is shown of two typical regimes of self-similar RT mixing-acceleration-driven Rayleigh-Taylor-type and dissipation-driven Richtymer-Meshkov-type with the latter being in general non-universal. Possible scenarios are proposed for transitions from the balanced dynamics to the imbalanced self-similar dynamics. Scaling and correlations properties of RT mixing are studied on the basis of dimensional analysis. Departures are outlined of RT dynamics with time-dependent acceleration from canonical cases of homogeneous turbulence as well as blast waves with first and second kind self-similarity. The work is supported by the US National Science Foundation.

  2. PEPSI-Dock: a detailed data-driven protein-protein interaction potential accelerated by polar Fourier correlation.

    PubMed

    Neveu, Emilie; Ritchie, David W; Popov, Petr; Grudinin, Sergei

    2016-09-01

    Docking prediction algorithms aim to find the native conformation of a complex of proteins from knowledge of their unbound structures. They rely on a combination of sampling and scoring methods, adapted to different scales. Polynomial Expansion of Protein Structures and Interactions for Docking (PEPSI-Dock) improves the accuracy of the first stage of the docking pipeline, which will sharpen up the final predictions. Indeed, PEPSI-Dock benefits from the precision of a very detailed data-driven model of the binding free energy used with a global and exhaustive rigid-body search space. As well as being accurate, our computations are among the fastest by virtue of the sparse representation of the pre-computed potentials and FFT-accelerated sampling techniques. Overall, this is the first demonstration of a FFT-accelerated docking method coupled with an arbitrary-shaped distance-dependent interaction potential. First, we present a novel learning process to compute data-driven distant-dependent pairwise potentials, adapted from our previous method used for rescoring of putative protein-protein binding poses. The potential coefficients are learned by combining machine-learning techniques with physically interpretable descriptors. Then, we describe the integration of the deduced potentials into a FFT-accelerated spherical sampling provided by the Hex library. Overall, on a training set of 163 heterodimers, PEPSI-Dock achieves a success rate of 91% mid-quality predictions in the top-10 solutions. On a subset of the protein docking benchmark v5, it achieves 44.4% mid-quality predictions in the top-10 solutions when starting from bound structures and 20.5% when starting from unbound structures. The method runs in 5-15 min on a modern laptop and can easily be extended to other types of interactions. https://team.inria.fr/nano-d/software/PEPSI-Dock sergei.grudinin@inria.fr. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e

  3. EDITORIAL: Laser and plasma accelerators Laser and plasma accelerators

    NASA Astrophysics Data System (ADS)

    Bingham, Robert

    2009-02-01

    This special issue on laser and plasma accelerators illustrates the rapid advancement and diverse applications of laser and plasma accelerators. Plasma is an attractive medium for particle acceleration because of the high electric field it can sustain, with studies of acceleration processes remaining one of the most important areas of research in both laboratory and astrophysical plasmas. The rapid advance in laser and accelerator technology has led to the development of terawatt and petawatt laser systems with ultra-high intensities and short sub-picosecond pulses, which are used to generate wakefields in plasma. Recent successes include the demonstration by several groups in 2004 of quasi-monoenergetic electron beams by wakefields in the bubble regime with the GeV energy barrier being reached in 2006, and the energy doubling of the SLAC high-energy electron beam from 42 to 85 GeV. The electron beams generated by the laser plasma driven wakefields have good spatial quality with energies ranging from MeV to GeV. A unique feature is that they are ultra-short bunches with simulations showing that they can be as short as a few femtoseconds with low-energy spread, making these beams ideal for a variety of applications ranging from novel high-brightness radiation sources for medicine, material science and ultrafast time-resolved radiobiology or chemistry. Laser driven ion acceleration experiments have also made significant advances over the last few years with applications in laser fusion, nuclear physics and medicine. Attention is focused on the possibility of producing quasi-mono-energetic ions with energies ranging from hundreds of MeV to GeV per nucleon. New acceleration mechanisms are being studied, including ion acceleration from ultra-thin foils and direct laser acceleration. The application of wakefields or beat waves in other areas of science such as astrophysics and particle physics is beginning to take off, such as the study of cosmic accelerators considered

  4. Accelerator driven reactors and nuclear waste management projects in the Czech Republic

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

    Janouch, Frantisek; Mach, Rostislav; Institute of Nuclear Physics, Rez near Prague

    1995-09-15

    The Czech Republic is almost the only country in the central Europe which continues with the construction of nuclear power reactors. Its small territory and dense population causes public worries concerning the disposal of the spent nuclear fuel. The Czech nuclear scientists and the power companies and the nuclear industries are therefore looking for alterative solutions. The Los Alamos ATW project had received a positive response in the Czech mass-media and even in the industrial and governmental quarters. The recent scientific symposium ''Accelerator driven reactors and nuclear waste management'' convened at the Liblice castle near Prague, 27-29.6. 1994 and sponsoredmore » by the Czech Energy Company CEZ, reviewed the competencies and experimental basis in the Czech republic and made the first attempt to formulate the national approach and to establish international collaboration in this area.« less

  5. Improved understanding of geologic CO{sub 2} storage processes requires risk-driven field experiments

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

    Oldenburg, C.M.

    2011-06-01

    The need for risk-driven field experiments for CO{sub 2} geologic storage processes to complement ongoing pilot-scale demonstrations is discussed. These risk-driven field experiments would be aimed at understanding the circumstances under which things can go wrong with a CO{sub 2} capture and storage (CCS) project and cause it to fail, as distinguished from accomplishing this end using demonstration and industrial scale sites. Such risk-driven tests would complement risk-assessment efforts that have already been carried out by providing opportunities to validate risk models. In addition to experimenting with high-risk scenarios, these controlled field experiments could help validate monitoring approaches to improvemore » performance assessment and guide development of mitigation strategies.« less

  6. Particle acceleration and transport at a 2D CME-driven shock using the HAFv3 and PATH Code

    NASA Astrophysics Data System (ADS)

    Li, G.; Ao, X.; Fry, C. D.; Verkhoglyadova, O. P.; Zank, G. P.

    2012-12-01

    We study particle acceleration at a 2D CME-driven shock and the subsequent transport in the inner heliosphere (up to 2 AU) by coupling the kinematic Hakamada-Akasofu-Fry version 3 (HAFv3) solar wind model (Hakamada and Akasofu, 1982, Fry et al. 2003) with the Particle Acceleration and Transport in the Heliosphere (PATH) model (Zank et al., 2000, Li et al., 2003, 2005, Verkhoglyadova et al. 2009). The HAFv3 provides the evolution of a two-dimensional shock geometry and other plasma parameters, which are fed into the PATH model to investigate the effect of a varying shock geometry on particle acceleration and transport. The transport module of the PATH model is parallelized and utilizes the state-of-the-art GPU computation technique to achieve a rapid physics-based numerical description of the interplanetary energetic particles. Together with a fast execution of the HAFv3 model, the coupled code gives us a possibility to nowcast/forecast the interplanetary radiation environment.

  7. Space Experiments with Particle Accelerators (SEPAC)

    NASA Technical Reports Server (NTRS)

    Obayashi, T.; Kawashima, N.; Kuriki, K.; Nagatomo, M.; Ninomiya, K.; Sasaki, S.; Ushirokawa, A.; Kudo, I.; Ejiri, M.; Roberts, W. T.

    1982-01-01

    Plans for SEPAC, an instrument array to be used on Spacelab 1 to study vehicle charging and neutralization, beam-plasma interaction in space, beam-atmospheric interaction exciting artificial aurora and airglow, and the electromagnetic-field configuration of the magnetosphere, are presented. The hardware, consisting of electron beam accelerator, magnetoplasma arcjet, neutral-gas plume generator, power supply, diagnostic package (photometer, plasma probes, particle analyzers, and plasma-wave package), TV monitor, and control and data-management unit, is described. The individual SEPAC experiments, the typical operational sequence, and the general outline of the SEPAC follow-on mission are discussed. Some of the experiments are to be joint ventures with AEPI (INS 003) and will be monitored by low-light-level TV.

  8. Considerations for Explosively Driven Conical Shock Tube Design: Computations and Experiments

    DTIC Science & Technology

    2017-02-16

    ARL-TR-7953 ● FEB 2017 US Army Research Laboratory Considerations for Explosively Driven Conical Shock Tube Design : Computations...The findings in this report are not to be construed as an official Department of the Army position unless so designated by other authorized...Considerations for Explosively Driven Conical Shock Tube Designs : Computations and Experiments by Joel B Stewart Weapons and Materials Research Directorate

  9. Absolute acceleration measurements on STS-50 from the Orbital Acceleration Research Experiment (OARE)

    NASA Technical Reports Server (NTRS)

    Blanchard, Robert C.; Nicholson, John Y.; Ritter, James R.

    1994-01-01

    Orbital Acceleration Research Experiment (OARE) data on Space Transportation System (STS)-50 have been examined in detail during a 2-day time period. Absolute acceleration levels have been derived at the OARE location, the orbiter center-of-gravity, and at the STS-50 spacelab Crystal Growth Facility. During the interval, the tri-axial OARE raw telemetered acceleration measurements have been filtered using a sliding trimmed mean filter in order to remove large acceleration spikes (e.g., thrusters) and reduce the noise. Twelve OARE measured biases in each acceleration channel during the 2-day interval have been analyzed and applied to the filtered data. Similarly, the in situ measured x-axis scale factors in the sensor's most sensitive range were also analyzed and applied to the data. Due to equipment problem(s) on this flight, both y- and z-axis sensitive range scale factors were determined in a separate process using orbiter maneuvers and subsequently applied to the data. All known significant low-frequency corrections at the OARE location (i.e., both vertical and horizontal gravity-gradient, and rotational effects) were removed from the filtered data in order to produce the acceleration components at the orbiter center-of-gravity, which are the aerodynamic signals along each body axis. Results indicate that there is a force being applied to the Orbiter in addition to the aerodynamic forces. The OARE instrument and all known gravitational and electromagnetic forces have been reexamined, but none produces the observed effect. Thus, it is tentatively concluded that the orbiter is creating the environment observed. At least part of this force is thought to be due to the Flash Evaporator System.

  10. KNMI DataLab experiences in serving data-driven innovations

    NASA Astrophysics Data System (ADS)

    Noteboom, Jan Willem; Sluiter, Raymond

    2016-04-01

    Climate change research and innovations in weather forecasting rely more and more on (Big) data. Besides increasing data from traditional sources (such as observation networks, radars and satellites), the use of open data, crowd sourced data and the Internet of Things (IoT) is emerging. To deploy these sources of data optimally in our services and products, KNMI has established a DataLab to serve data-driven innovations in collaboration with public and private sector partners. Big data management, data integration, data analytics including machine learning and data visualization techniques are playing an important role in the DataLab. Cross-domain data-driven innovations that arise from public-private collaborative projects and research programmes can be explored, experimented and/or piloted by the KNMI DataLab. Furthermore, advice can be requested on (Big) data techniques and data sources. In support of collaborative (Big) data science activities, scalable environments are offered with facilities for data integration, data analysis and visualization. In addition, Data Science expertise is provided directly or from a pool of internal and external experts. At the EGU conference, gained experiences and best practices are presented in operating the KNMI DataLab to serve data-driven innovations for weather and climate applications optimally.

  11. Longitudinal Dependence of SEP Peak Intensities as Evidence of CME-Driven Shock Particle Acceleration

    NASA Astrophysics Data System (ADS)

    Lario, D.; Roelof, E. C.; Decker, R. B.

    2014-05-01

    Multi-spacecraft observations of solar energetic particle (SEP) events allow us to estimate the longitudinal distributions of SEP peak intensities. By fitting a Gaussian functional form to the ensemble of SEP peak intensities measured by two or more spacecraft as a function of the longitudinal distance between the associated parent solar flare and the footpoint labels of the magnetic field lines connecting each spacecraft with the Sun, we found that such distributions are not centered at nominal well-connected flare longitudes but slightly offset to the west of the associated flare (Lario et al. 2006, 2013). We offer an interpretation of this result in terms of long-lived particle injection from shocks driven by the associated coronal mass ejections (CMEs). By assuming that (i) CME-driven shocks are centered on the longitude of the associated solar flare, (ii) the injection of shock accelerated particles maximizes at the nose of the shock which propagates radially outward from the Sun, and (iii) SEP particle injection from the shock starts at a certain distance above the solar surface, we infer an average radial distance where shocks are located when peak intensities in the prompt component of the SEP events are observed. We estimate the heliocentric distance of the CME-driven shock when particle injection from the shock maximizes and conclude that the injection of ˜20 MeV protons and near-relativistic electrons maximizes well inside ˜0.2 AU.

  12. Response of semicircular canal dependent units in vestibular nuclei to rotation of a linear acceleration vector without angular acceleration

    PubMed Central

    Benson, A. J.; Guedry, F. E.; Jones, G. Melvill

    1970-01-01

    1. Recent experiments have shown that rotation of a linear acceleration vector round the head can generate involuntary ocular nystagmus in the absence of angular acceleration. The present experiments examine the suggestion that adequate stimulation of the semicircular canals may contribute to this response. 2. Decerebrate cats were located in a stereotaxic device on a platform, slung from four parallel cables, which could be driven smoothly round a circular orbit without inducing significant angular movement of the platform. This Parallel Swing Rotation (PSR) generated a centripetal acceleration of 4·4 m/sec2 which rotated round the head at 0·52 rev/sec. 3. The discharge frequency of specifically lateral canal-dependent neural units in the vestibular nuclei of cats was recorded during PSR to right and left, and in the absence of motion. The dynamic responses to purely angular motion were also examined on a servo-driven turntable. 4. Without exception all proven canal-dependent cells examined (twenty-nine cells in nine cats) were more active during PSR in the direction of endolymph circulation assessed to be excitatory to the unit, than during PSR in the opposite direction. 5. The observed changes in discharge frequency are assessed to have been of a magnitude appropriate for the generation of the involuntary oculomotor response induced by the same stimulus in the intact animal. 6. The findings suggest that a linear acceleration vector which rotates in the plane of the lateral semicircular canals can be an adequate stimulus to ampullary receptors, though an explanation which invokes the modulation of canal cells by a signal dependent upon the sequential activation of macular receptors cannot be positively excluded. PMID:5501270

  13. 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.

  14. Mechanical engineering and design criteria for the Magnetically Insulated Transmission Experiment Accelerator

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

    Staller, G.E.; Hamilton, I.D.; Aker, M.F.

    1978-02-01

    A single-unit electron beam accelerator was designed, fabricated, and assembled in Sandia's Technical Area V to conduct magnetically insulated transmission experiments. Results of these experiments will be utilized in the future design of larger, more complex accelerators. This design makes optimum use of existing facilities and equipment. When designing new components, possible future applications were considered as well as compatibility with existing facilities and hardware.

  15. Rayleigh-Taylor mixing with space-dependent acceleration

    NASA Astrophysics Data System (ADS)

    Abarzhi, Snezhana

    2016-11-01

    We extend the momentum model to describe Rayleigh-Taylor (RT) mixing driven by a space-dependent acceleration. The acceleration is a power-law function of space coordinate, similarly to astrophysical and plasma fusion applications. In RT flow the dynamics of a fluid parcel is driven by a balance per unit mass of the rates of momentum gain and loss. We find analytical solutions in the cases of balanced and imbalanced gains and losses, and identify their dependence on the acceleration exponent. The existence is shown of two typical sub-regimes of self-similar RT mixing - the acceleration-driven Rayleigh-Taylor-type mixing and dissipation-driven Richtymer-Meshkov-type mixing with the latter being in general non-universal. Possible scenarios are proposed for transitions from the balanced dynamics to the imbalanced self-similar dynamics. Scaling and correlations properties of RT mixing are studied on the basis of dimensional analysis. Departures are outlined of RT dynamics with space-dependent acceleration from canonical cases of homogeneous turbulence as well as blast waves with first and second kind self-similarity. The work is supported by the US National Science Foundation.

  16. Fluid Physics in a Fluctuating Acceleration Environment

    NASA Technical Reports Server (NTRS)

    Thomson, J. Ross; Drolet, Francois; Vinals, Jorge

    1996-01-01

    We summarize several aspects of an ongoing investigation of the effects that stochastic residual accelerations (g-jitter) onboard spacecraft can have on experiments conducted in a microgravity environment. The residual acceleration field is modeled as a narrow band noise, characterized by three independent parameters: intensity (g(exp 2)), dominant angular frequency Omega, and characteristic correlation time tau. Realistic values for these parameters are obtained from an analysis of acceleration data corresponding to the SL-J mission, as recorded by the SAMS instruments. We then use the model to address the random motion of a solid particle suspended in an incompressible fluid subjected to such random accelerations. As an extension, the effect of jitter on coarsening of a solid-liquid mixture is briefly discussed, and corrections to diffusion controlled coarsening evaluated. We conclude that jitter will not be significant in the experiment 'Coarsening of solid-liquid mixtures' to be conducted in microgravity. Finally, modifications to the location of onset of instability in systems driven by a random force are discussed by extending the standard reduction to the center manifold to the stochastic case. Results pertaining to time-modulated oscillatory convection are briefly discussed.

  17. Subjective acceleration of time experience in everyday life across adulthood.

    PubMed

    John, Dennis; Lang, Frieder R

    2015-12-01

    Most people believe that time seems to pass more quickly as they age. Building on assumptions of socioemotional selectivity theory, we investigated whether awareness that one's future lifetime is limited is associated with one's experience of time during everyday activities across adulthood in 3 studies. In the first 2 studies (Study 1: N = 608; Study 2: N = 398), participants completed a web-based version of the day reconstruction method. In Study 3 (N = 392) participants took part in a newly developed tomorrow construction method, a web-based experimental method for assessing everyday life plans. Results confirmed that older adults' subjective interpretation of everyday episodes is that these episodes pass more quickly compared with younger adults. The subjective acceleration of time experience in old age was more pronounced during productive activities than during regenerative-consumptive activities. The age differences were partly related to limited time remaining in life. In addition, subjective acceleration of time experience was associated with positive evaluations of everyday activities. Findings suggest that subjective acceleration of time in older adults' daily lives reflects an adaptation to limitations in time remaining in life. (PsycINFO Database Record (c) 2015 APA, all rights reserved).

  18. Narrow bandwidth Laser-Plasma Accelerator driven Thomson photon source development

    NASA Astrophysics Data System (ADS)

    Geddes, C. G. R.; Tsai, H.-E.; Otero, G.; Liu, X.; van Tilborg, J.; Toth, Cs.; Vay, J.-L.; Lehe, R.; Schroeder, C. B.; Esarey, E.; Friedman, A.; Grote, D. P.; Leemans, W. P.

    2017-10-01

    Compact, high-quality photon sources at MeV energies can be provided by Thomson scattering of a laser from the electron beam of a Laser-Plasma Accelerator (LPA). Recent experiments and simulations demonstrate controllable LPAs in the energy range appropriate to MeV sources. Simulations indicate that high flux with narrow energy spread can be achieved via control of the scattering laser pulse shape and laser guiding, and that undesired background bremsstrahlung can be mitigated by plasma based deceleration of the electron beam after photon production. Construction of experiments and laser capabilities to combine these elements will be presented, along with initial operations, towards a compact photon source system. Work supported by US DOE NNSA DNN R&D and by Sc. HEP under contract DE-AC02-05CH11231.

  19. Space Experiments with Particle Accelerators: SEPAC

    NASA Technical Reports Server (NTRS)

    Burch, J. L.; Roberts, W. T.; Taylor, W. W. L.; Kawashima, N.; Marshall, J. A.; Moses, S. L.; Neubert, T.; Mende, S. B.; Choueiri, E. Y.

    1994-01-01

    The Space Experiments with Particle Accelerators (SEPAC), which flew on the Atmospheric Laboratory for Applications and Science (ATLAS) 1 mission, used new techniques to study natural phenomena in the Earth's upper atmosphere, ionosphere and magnetosphere by introducing energetic perturbations into the system from a high power electron beam with known characteristics. Properties of auroras were studied by directing the electron beam into the upper atmosphere while making measurements of optical emissions. Studies were also performed of the critical ionization velocity phenomenon.

  20. Accelerated approval of oncology products: a decade of experience.

    PubMed

    Dagher, Ramzi; Johnson, John; Williams, Grant; Keegan, Patricia; Pazdur, Richard

    2004-10-20

    We review the regulatory history of the accelerated approval process and summarize the U.S. Food and Drug Administration experience with accelerated approvals in oncology. The accelerated approval regulations, promulgated in 1992, allow approval of drugs for serious or life-threatening diseases on the basis of a surrogate endpoint that is reasonably likely to predict clinical benefit, such as survival or symptom benefit, pending completion of studies designed to confirm clinical benefit, referred to as phase 4 commitments, which are required to be conducted with due diligence. From 1992 to 2004, 22 applications involving anticancer drugs or biologics were approved. Of these 22 applications, accelerated approval was granted to 15 on the basis of findings from studies without an active comparator (i.e., single-arm studies or studies comparing two dose levels) and to the remaining seven on the basis of one or more randomized studies. Of the 22 approved applications, six (i.e., applications for dexrazoxane, irinotecan, capecitabine, docetaxel, imatinib mesylate, and oxaliplatin) have had one or more indications converted to regular approval. This review reports information that was presented at an Oncologic Drugs Advisory Committee meeting held in March 2003; it also presents a discussion of accelerated approval study designs, the study populations evaluated in the accelerated approval and confirmatory settings, and the integration of accelerated approval into a comprehensive drug development plan.

  1. Accelerated Learning: Undergraduate Research Experiences at the Texas A&M Cyclotron Institute

    NASA Astrophysics Data System (ADS)

    Yennello, S. J.

    The Texas A&M Cyclotron Institute (TAMU CI) has had an NSF funded Research Experiences for Undergraduates program since 2004. Each summer about a dozen students from across the country join us for the 10-week program. They are each imbedded in one of the research groups of the TAMU CI and given their own research project. While the main focus of their effort is their individual research project, we also have other activities to broaden their experience. For instance, one of those activities has been involvement in a dedicated group experiment. Because not every experimental group will run during those 10 weeks and the fact that some of the students are in theory research groups, a group research experience allows everyone to actually be involved in an experiment using the accelerator. In stark contrast to the REU students' very focused experience during the summer, Texas A&M undergraduates can be involved in research projects at the Cyclotron throughout the year, often for multiple years. This extended exposure enables Texas A&M students to have a learning experience that cannot be duplicated without a local accelerator. The motivation for the REU program was to share this accelerator experience with students who do not have that opportunity at their home institution.

  2. TEACHING PHYSICS: Atwood's machine: experiments in an accelerating frame

    NASA Astrophysics Data System (ADS)

    Teck Chee, Chia; Hong, Chia Yee

    1999-03-01

    Experiments in an accelerating frame are often difficult to perform, but simple computer software allows sufficiently rapid and accurate measurements to be made on an arrangement of weights and pulleys known as Atwood's machine.

  3. Essay: Robert H. Siemann As Leader of the Advanced Accelerator Research Department

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

    Colby, Eric R.; Hogan, Mark J.; /SLAC

    Robert H. Siemann originally conceived of the Advanced Accelerator Research Department (AARD) as an academic, experimental group dedicated to probing the technical limitations of accelerators while providing excellent educational opportunities for young scientists. The early years of the Accelerator Research Department B, as it was then known, were dedicated to a wealth of mostly student-led experiments to examine the promise of advanced accelerator techniques. High-gradient techniques including millimeter-wave rf acceleration, beam-driven plasma acceleration, and direct laser acceleration were pursued, including tests of materials under rf pulsed heating and short-pulse laser radiation, to establish the ultimate limitations on gradient. As themore » department and program grew, so did the motivation to found an accelerator research center that brought experimentalists together in a test facility environment to conduct a broad range of experiments. The Final Focus Test Beam and later the Next Linear Collider Test Accelerator provided unique experimental facilities for AARD staff and collaborators to carry out advanced accelerator experiments. Throughout the evolution of this dynamic program, Bob maintained a department atmosphere and culture more reminiscent of a university research group than a national laboratory department. His exceptional ability to balance multiple roles as scientist, professor, and administrator enabled the creation and preservation of an environment that fostered technical innovation and scholarship.« less

  4. Accelerator driven reactors and nuclear waste management projects in the Czech Republic

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

    Janouch, F.; Mach, R.

    1995-10-01

    The Czech Republic is almost the only country in the central Europe which continues with the construction of nuclear power reactors. Its small territory and dense population causes public worries concerning the disposal of the spent nuclear fuel. The Czech nuclear scientists and the power companies and the nuclear industries are therefore looking for alternative solutions. The Los Alamos ATW project had received a positive response in the Czech mass-media and even in the industrial and governmental quarters. The recent scientific symposium {open_quotes}Accelerator driven reactors and nuclear waste management{close_quotes} convened at the Liblice castle near Prague, 27-29. 6. 1994 andmore » sponsored by the Czech Energy Company CEZ, reviewed the competencies and experimental basis in the Czech republic and made the first attempt to formulate the national approach and to establish international collaboration in this area.« less

  5. Radiobiological study by using laser-driven proton beams

    NASA Astrophysics Data System (ADS)

    Yogo, A.; Sato, K.; Nishikino, M.; Mori, M.; Teshima, T.; Numasaki, H.; Murakami, M.; Demizu, Y.; Akagi, S.; Nagayama, S.; Ogura, K.; Sagisaka, A.; Orimo, S.; Nishiuchi, M.; Pirozhkov, A. S.; Ikegami, M.; Tampo, M.; Sakaki, H.; Suzuki, M.; Daito, I.; Oishi, Y.; Sugiyama, H.; Kiriyama, H.; Okada, H.; Kanazawa, S.; Kondo, S.; Shimomura, T.; Nakai, Y.; Tanoue, M.; Sugiyama, H.; Sasao, H.; Wakai, D.; Kawachi, T.; Nishimura, H.; Bolton, P. R.; Daido, H.

    2009-07-01

    Particle acceleration driven by high-intensity laser systems is widely attracting interest as a potential alternative to conventional ion acceleration, including ion accelerator applications to tumor therapy. Recent works have shown that a high intensity laser pulse can produce single proton bunches of a high current and a short pulse duration. This unique feature of laser-ion acceleration can lead to progress in the development of novel ion sources. However, there has been no experimental study of the biological effects of laser-driven ion beams. We describe in this report the first demonstrated irradiation effect of laser-accelerated protons on human lung cancer cells. In-vitro A549 cells are irradiated with a proton dose of 20 Gy, resulting in a distinct formation of γ-H2AX foci as an indicator of DNA double-strand breaks. This is a pioneering result that points to future investigations of the radiobiological effects of laser-driven ion beams. The laser-driven ion beam is apotential excitation source for time-resolved determination of hydroxyl (OH) radical yield, which will explore relationship between the fundamental chemical reactions of radiation effects and consequent biological processes.

  6. Spectral and spatial characterisation of laser-driven positron beams

    DOE PAGES

    Sarri, G.; Warwick, J.; Schumaker, W.; ...

    2016-10-18

    The generation of high-quality relativistic positron beams is a central area of research in experimental physics, due to their potential relevance in a wide range of scientific and engineering areas, ranging from fundamental science to practical applications. There is now growing interest in developing hybrid machines that will combine plasma-based acceleration techniques with more conventional radio-frequency accelerators, in order to minimise the size and cost of these machines. Here we report on recent experiments on laser-driven generation of high-quality positron beams using a relatively low energy and potentially table-top laser system. Lastly, the results obtained indicate that current technology allowsmore » to create, in a compact setup, positron beams suitable for injection in radio-frequency accelerators.« less

  7. Surface Tension Driven Convection Experiment (STDCE)

    NASA Technical Reports Server (NTRS)

    Ostrach, S.; Kamotani, Y.

    1996-01-01

    This document reports the results obtained from the Surface Tension Driven Convection Experiment (STDCE) conducted aboard the USML-1 Spacelab in 1992. The experiments used 10 cSt silicone oil placed in an open circular container that was 10 cm wide and 5 cm deep. Thermocapillary flow was induced by using either a cylindrical heater placed along the container centerline or by a CO2 laser. The tests were conducted under various power settings, laser beam diameters, and free surface shapes. Thermistors located at various positions in the test section recorded the temperature of the fluid, heater, walls, and air. An infrared imager was used to measure the free surface temperature. The flow field was studied by flow visualization and the data was analyzed by a PTV technique. The results from the flow visualization and the temperature measurements are compared with the numerical analysis that was conducted in conjunction with the experiment. The compared results include the experimental and numerical velocity vector plots, the streamline plots, the fluid temperature, and the surface temperature distribution.

  8. Surface Tension Driven Convection Experiment (STDCE)

    NASA Technical Reports Server (NTRS)

    Ostrach, Simon; Kamotani, Y.; Pline, A.

    1994-01-01

    Results are reported of the Surface Tension Driven Convection Experiment (STDCE) aboard the USML-1 (first United States Microgravity Laboratory) Spacelab which was launched on June 25, 1992. In the experiment 10 cSt silicone oil was placed in an open circular container which was 10 cm wide by 5 cm deep. The fluid was heated either by a cylindrical heater (1.11 cm dia.) located along the container centerline or by a CO2 laser beam to induce thermocapillary flow. The flow field was studied by flow visualization. Several thermistor probes were placed in the fluid to measure the temperature distribution. The temperature distribution along the liquid free surface was measured by an infrared imager. Tests were conducted over a range of heating powers, laser beam diameters, and free surface shapes. In conjunction with the experiments an extensive numerical modeling of the flow was conducted. In this paper some results of the velocity and temperature measurements with flat and curved free surfaces are presented and they are shown to agree well with the numerical predictions.

  9. Probing plasma wakefields using electron bunches generated from a laser wakefield accelerator

    NASA Astrophysics Data System (ADS)

    Zhang, C. J.; Wan, Y.; Guo, B.; Hua, J. F.; Pai, C.-H.; Li, F.; Zhang, J.; Ma, Y.; Wu, Y. P.; Xu, X. L.; Mori, W. B.; Chu, H.-H.; Wang, J.; Lu, W.; Joshi, C.

    2018-04-01

    We show experimental results of probing the electric field structure of plasma wakes by using femtosecond relativistic electron bunches generated from a laser wakefield accelerator. Snapshots of laser-driven linear wakes in plasmas with different densities and density gradients are captured. The spatiotemporal evolution of the wake in a plasma density up-ramp is recorded. Two parallel wakes driven by a laser with a main spot and sidelobes are identified in the experiment and reproduced in simulations. The capability of this new method for capturing the electron- and positron-driven wakes is also shown via 3D particle-in-cell simulations.

  10. High repetition rate laser-driven MeV ion acceleration at variable background pressures

    NASA Astrophysics Data System (ADS)

    Snyder, Joseph; Ngirmang, Gregory; Orban, Chris; Feister, Scott; Morrison, John; Frische, Kyle; Chowdhury, Enam; Roquemore, W. M.

    2017-10-01

    Ultra-intense laser-plasma interactions (LPI) can produce highly energetic photons, electrons, and ions with numerous potential real-world applications. Many of these applications will require repeatable, high repetition targets that are suitable for LPI experiments. Liquid targets can meet many of these needs, but they typically require higher chamber pressure than is used for many low repetition rate experiments. The effect of background pressure on the LPI has not been thoroughly studied. With this in mind, the Extreme Light group at the Air Force Research Lab has carried out MeV ion and electron acceleration experiments at kHz repetition rate with background pressures ranging from 30 mTorr to >1 Torr using a submicron ethylene glycol liquid sheet target. We present these results and provide two-dimensional particle-in-cell simulation results that offer insight on the thresholds for the efficient acceleration of electrons and ions. This research is supported by the Air Force Office of Scientific Research under LRIR Project 17RQCOR504 under the management of Dr. Riq Parra and Dr. Jean-Luc Cambier. Support was also provided by the DOD HPCMP Internship Program.

  11. Particle acceleration on a chip: A laser-driven micro-accelerator for research and industry

    NASA Astrophysics Data System (ADS)

    Yoder, R. B.; Travish, G.

    2013-03-01

    Particle accelerators are conventionally built from radio-frequency metal cavities, but this technology limits the maximum energy available and prevents miniaturization. In the past decade, laser-powered acceleration has been intensively studied as an alternative technology promising much higher accelerating fields in a smaller footprint and taking advantage of recent advances in photonics. Among the more promising approaches are those based on dielectric field-shaping structures. These ``dielectric laser accelerators'' (DLAs) scale with the laser wavelength employed and can be many orders of magnitude smaller than conventional accelerators; DLAs may enable the production of high-intensity, ultra-short relativistic electron bunches in a chip-scale device. When combined with a high- Z target or an optical-period undulator, these systems could produce high-brilliance x-rays from a breadbox-sized device having multiple applications in imaging, medicine, and homeland security. In our research program we have developed one such DLA, the Micro-Accelerator Platform (MAP). We describe the fundamental physics, our fabrication and testing program, and experimental results to date, along with future prospects for MAP-based light-sources and some remaining challenges. Supported in part by the Defense Threat Reduction Agency and National Nuclear Security Administration.

  12. Betatron x-ray radiation from laser-plasma accelerators driven by femtosecond and picosecond laser systems

    NASA Astrophysics Data System (ADS)

    Albert, F.; Lemos, N.; Shaw, J. L.; King, P. M.; Pollock, B. B.; Goyon, C.; Schumaker, W.; Saunders, A. M.; Marsh, K. A.; Pak, A.; Ralph, J. E.; Martins, J. L.; Amorim, L. D.; Falcone, R. W.; Glenzer, S. H.; Moody, J. D.; Joshi, C.

    2018-05-01

    A comparative experimental study of betatron x-ray radiation from laser wakefield acceleration in the blowout and self-modulated regimes is presented. Our experiments use picosecond duration laser pulses up to 150 J (self-modulated regime) and 60 fs duration laser pulses up to 10 J (blowout regime), for plasmas with electronic densities on the order of 1019 cm-3. In the self-modulated regime, where betatron radiation has been very little studied compared to the blowout regime, electrons accelerated in the wake of the laser pulse are subject to both the longitudinal plasma and transverse laser electrical fields. As a result, their motion within the wake is relatively complex; consequently, the experimental and theoretical properties of the x-ray source based on self-modulation differ from the blowout regime of laser wakefield acceleration. In our experimental configuration, electrons accelerated up to about 250 MeV and betatron x-ray spectra with critical energies of about 10-20 keV and photon fluxes between 108 and 1010 photons/eV Sr are reported. Our experiments open the prospect of using betatron x-ray radiation for applications, and the source is competitive with current x-ray backlighting methods on multi-kilojoule laser systems.

  13. Accelerated T1ρ acquisition for knee cartilage quantification using compressed sensing and data-driven parallel imaging: A feasibility study.

    PubMed

    Pandit, Prachi; Rivoire, Julien; King, Kevin; Li, Xiaojuan

    2016-03-01

    Quantitative T1ρ imaging is beneficial for early detection for osteoarthritis but has seen limited clinical use due to long scan times. In this study, we evaluated the feasibility of accelerated T1ρ mapping for knee cartilage quantification using a combination of compressed sensing (CS) and data-driven parallel imaging (ARC-Autocalibrating Reconstruction for Cartesian sampling). A sequential combination of ARC and CS, both during data acquisition and reconstruction, was used to accelerate the acquisition of T1ρ maps. Phantom, ex vivo (porcine knee), and in vivo (human knee) imaging was performed on a GE 3T MR750 scanner. T1ρ quantification after CS-accelerated acquisition was compared with non CS-accelerated acquisition for various cartilage compartments. Accelerating image acquisition using CS did not introduce major deviations in quantification. The coefficient of variation for the root mean squared error increased with increasing acceleration, but for in vivo measurements, it stayed under 5% for a net acceleration factor up to 2, where the acquisition was 25% faster than the reference (only ARC). To the best of our knowledge, this is the first implementation of CS for in vivo T1ρ quantification. These early results show that this technique holds great promise in making quantitative imaging techniques more accessible for clinical applications. © 2015 Wiley Periodicals, Inc.

  14. Experimental results from the VENUS-F critical reference state for the GUINEVERE accelerator driven system project

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

    Uyttenhove, W.; Baeten, P.; Ban, G.

    The GUINEVERE (Generation of Uninterrupted Intense Neutron pulses at the lead Venus Reactor) project was launched in 2006 within the framework of FP6 EUROTRANS in order to validate on-line reactivity monitoring and subcriticality level determination in Accelerator Driven Systems. Therefore the VENUS reactor at SCK.CEN in Mol (Belgium) was modified towards a fast core (VENUS-F) and coupled to the GENEPI-3C accelerator built by CNRS The accelerator can operate in both continuous and pulsed mode. The VENUS-F core is loaded with enriched Uranium and reflected with solid lead. A well-chosen critical reference state is indispensable for the validation of the on-linemore » subcriticality monitoring methodology. Moreover a benchmarking tool is required for nuclear data research and code validation. In this paper the design and the importance of the critical reference state for the GUINEVERE project are motivated. The results of the first experimental phase on the critical core are presented. The control rods worth is determined by the rod drop technique and the application of the Modified Source Multiplication (MSM) method allows the determination of the worth of the safety rods. The results are implemented in the VENUS-F core certificate for full exploitation of the critical core. (authors)« less

  15. Experimental results from the VENUS-F critical reference state for the GUINEVERE accelerator driven system project

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

    Uyttenhove, W.; Baeten, P.; Kochetkov, A.

    The GUINEVERE (Generation of Uninterrupted Intense Neutron pulses at the lead Venus Reactor) project was launched in 2006 within the framework of FP6 EUROTRANS in order to validate online reactivity monitoring and subcriticality level determination in accelerator driven systems (ADS). Therefore, the VENUS reactor at SCK.CEN in Mol, Belgium, was modified towards a fast core (VENUS-F) and coupled to the GENEPI-3C accelerator built by CNRS. The accelerator can operate in both continuous and pulsed mode. The VENUS-F core is loaded with enriched Uranium and reflected with solid lead. A well-chosen critical reference state is indispensable for the validation of themore » online subcriticality monitoring methodology. Moreover, a benchmarking tool is required for nuclear data research and code validation. In this paper, the design and the importance of the critical reference state for the GUINEVERE project are motivated. The results of the first experimental phase on the critical core are presented. The control rods worth is determined by the positive period method and the application of the Modified Source Multiplication (MSM) method allows the determination of the worth of the safety rods. The results are implemented in the VENUS-F core certificate for full exploitation of the critical core. (authors)« less

  16. Accelerating Vaccine Formulation Development Using Design of Experiment Stability Studies.

    PubMed

    Ahl, Patrick L; Mensch, Christopher; Hu, Binghua; Pixley, Heidi; Zhang, Lan; Dieter, Lance; Russell, Ryann; Smith, William J; Przysiecki, Craig; Kosinski, Mike; Blue, Jeffrey T

    2016-10-01

    Vaccine drug product thermal stability often depends on formulation input factors and how they interact. Scientific understanding and professional experience typically allows vaccine formulators to accurately predict the thermal stability output based on formulation input factors such as pH, ionic strength, and excipients. Thermal stability predictions, however, are not enough for regulators. Stability claims must be supported by experimental data. The Quality by Design approach of Design of Experiment (DoE) is well suited to describe formulation outputs such as thermal stability in terms of formulation input factors. A DoE approach particularly at elevated temperatures that induce accelerated degradation can provide empirical understanding of how vaccine formulation input factors and interactions affect vaccine stability output performance. This is possible even when clear scientific understanding of particular formulation stability mechanisms are lacking. A DoE approach was used in an accelerated 37(°)C stability study of an aluminum adjuvant Neisseria meningitidis serogroup B vaccine. Formulation stability differences were identified after only 15 days into the study. We believe this study demonstrates the power of combining DoE methodology with accelerated stress stability studies to accelerate and improve vaccine formulation development programs particularly during the preformulation stage. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  17. Modeling Laser-Driven Laboratory Astrophysics Experiments Using the CRASH Code

    NASA Astrophysics Data System (ADS)

    Grosskopf, Michael; Keiter, P.; Kuranz, C. C.; Malamud, G.; Trantham, M.; Drake, R.

    2013-06-01

    Laser-driven, laboratory astrophysics experiments can provide important insight into the physical processes relevant to astrophysical systems. The radiation hydrodynamics code developed by the Center for Radiative Shock Hydrodynamics (CRASH) at the University of Michigan has been used to model experimental designs for high-energy-density laboratory astrophysics campaigns on OMEGA and other high-energy laser facilities. This code is an Eulerian, block-adaptive AMR hydrodynamics code with implicit multigroup radiation transport and electron heat conduction. The CRASH model has been used on many applications including: radiative shocks, Kelvin-Helmholtz and Rayleigh-Taylor experiments on the OMEGA laser; as well as laser-driven ablative plumes in experiments by the Astrophysical Collisionless Shocks Experiments with Lasers (ACSEL) collaboration. We report a series of results with the CRASH code in support of design work for upcoming high-energy-density physics experiments, as well as comparison between existing experimental data and simulation results. This work is funded by the Predictive Sciences Academic Alliances Program in NNSA-ASC via grant DEFC52- 08NA28616, by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, grant number DE-FG52-09NA29548, and by the National Laser User Facility Program, grant number DE-NA0000850.

  18. Experiments on the Effects of Confining Pressure During Reaction-Driven Cracking

    NASA Astrophysics Data System (ADS)

    Skarbek, R. M.; Savage, H. M.; Kelemen, P. B.; Lambart, S.; Robinson, B.

    2016-12-01

    Cracking caused by reaction-driven volume increase is an important process in many geological settings. In particular, the interaction of brittle rocks with reactive fluids can create fractures that modify the permeability and reactive surface area, leading to a large variety of feedbacks. The conditions controlling reaction-driven cracking are poorly understood, especially at geologically relevant confining pressures. We conducted two sets of experiments to study the effects of confining pressure on cracking during the formation of gypsum from anhydrite CaSO4 + 2H2O = CaSO4•2H2O, and portlandite from calcium oxide CaO + H2O = Ca(OH)2. In the first set of experiments, we cold-pressed CaSO4, or CaO powder to form cylinders. Samples were confined in steel, and compressed with an axial load of 0.1 to 4 MPa. Water was allowed to infiltrate the initially unsaturated samples through the bottom face via capillary and Darcian flow across a micro-porous frit. The height of the sample was recorded during the experiment, and serves as a measure of volume change due to the hydration reaction. We also recorded acoustic emissions (AEs) using piezoelectric transducers (PZTs), to serve as a measure of cracking during an experiment. Experiments were stopped when the recorded volume change reached 80% - 100% of the stoichiometrically calculated volume change of the reaction. In a second set of experiments, we pressed CaSO4 powder to form cylinders 8.9 cm in length and 3.5 cm in diameter for testing in a tri-axial press with ports for fluid input and output, across the top and bottom faces of the sample. The tri-axial experiments were set up to investigate the reaction-driven cracking process for a range of confining pressures. Cracking during experiments was monitored using strain gauges and PZTs attached to the sample. We measured permeability during experiments by imposing a fluid pressure gradient across the sample. These experiments elucidate the role of cracking caused by

  19. Numerical modeling of laser-driven ion acceleration from near-critical gas targets

    NASA Astrophysics Data System (ADS)

    Tatomirescu, Dragos; Vizman, Daniel; d’Humières, Emmanuel

    2018-06-01

    In the past two decades, laser-accelerated ion sources and their applications have been intensely researched. Recently, it has been shown through experiments that proton beams with characteristics comparable to those obtained with solid targets can be obtained from gaseous targets. By means of particle-in-cell simulations, this paper studies in detail the effects of a near-critical density gradient on ion and electron acceleration after the interaction with ultra high intensity lasers. We can observe that the peak density of the gas jet has a significant influence on the spectrum features. As the gas jet density increases, so does the peak energy of the central quasi-monoenergetic ion bunch due to the increase in laser absorption while at the same time having a broadening effect on the electron angular distribution.

  20. Space Experiments with Particle Accelerators (SEPAC)

    NASA Technical Reports Server (NTRS)

    Taylor, William W. L.

    1994-01-01

    The scientific emphasis of this contract has been on the physics of beam ionosphere interactions, in particular, what are the plasma wave levels stimulated by the Space Experiments with Particle Accelerators (SEPAC) electron beam as it is ejected from the Electron Beam Accelerator (EBA) and passes into and through the ionosphere. There were two different phenomena expected. The first was generation of plasma waves by the interaction of the DC component of the beam with the plasma of the ionosphere, by wave particle interactions. The second was the generation of waves at the pulsing frequency of the beam (AC component). This is referred to as using the beam as a virtual antenna, because the beam of electrons is a coherent electrical current confined to move along the earth's magnetic field. As in a physical antenna, a conductor at a radio or TV station, the beam virtual antenna radiates electromagnetic waves at the frequency of the current variations. These two phenomena were investigated during the period of this contract.

  1. Stochastic acceleration of electrons from multiple uncorrelated plasma waves

    NASA Astrophysics Data System (ADS)

    Gee, David; Michel, Pierre; Wurtele, Jonathan

    2017-10-01

    One-dimensional theory puts a strict limit on the maximum energy attainable by an electron trapped and accelerated by an electron plasma wave (EPW). However, experimental measurements of hot electron distributions accelerated by stimulated Raman scattering (SRS) in ICF experiments typically show a thermal distribution with temperatures of the order of the kinetic energy of the resonant EPW's (Thot mvp2 , where vp is the phase velocity of the EPW's driven by SRS) and no clear cutoff at high energies. In this project, we are investigating conditions under which electrons can be stochastically accelerated by multiple uncorrelated EPW's, such as those generated by incoherent laser speckles in large laser spots like the ones used on NIF ( mm-size), and reproduce distributions similar to those observed in experiments. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

  2. Motion of Air Bubbles in Water Subjected to Microgravity Accelerations

    NASA Technical Reports Server (NTRS)

    DeLombard, Richard; Kelly, Eric M.; Hrovat, Kenneth; Nelson, Emily S.; Pettit, Donald R.

    2006-01-01

    The International Space Station (ISS) serves as a platform for microgravity research for the foreseeable future. A microgravity environment is one in which the effects of gravity are drastically reduced which then allows physical experiments to be conducted without the over powering effects of gravity. During his 6-month stay on the ISS, astronaut Donald R. Pettit performed many informal/impromptu science experiments with available equipment. One such experiment focused on the motion of air bubbles in a rectangular container nearly filled with de-ionized water. Bubbles were introduced by shaking and then the container was secured in place for several hours while motion of the bubbles was recorded using time-lapse photography. This paper shows correlation between bubble motion and quasi-steady acceleration levels during one such experiment operation. The quasi-steady acceleration vectors were measured by the Microgravity Acceleration Measurement System (MAMS). Essentially linear motion was observed in the condition considered here. Dr. Pettit also created other conditions which produced linear and circulating motion, which are the subjects of further study. Initial observations of this bubble motion agree with calculations from many microgravity physical science experiments conducted on shuttle microgravity science missions. Many crystal-growth furnaces involve heavy metals and high temperatures in which undesired acceleration-driven convection during solidification can adversely affect the crystal. Presented in this paper will be results showing correlation between bubble motion and the quasi-steady acceleration vector.

  3. Small Ground-Level Enhancement of 6 January 2014: Acceleration by CME-Driven Shock?

    NASA Astrophysics Data System (ADS)

    Li, C.; Miroshnichenko, L. I.; Sdobnov, V. E.

    2016-03-01

    Available spectral data for solar energetic particles (SEPs) measured near the Earth's orbit (GOES-13) and on the terrestrial surface (polar neutron monitors) on 6 January 2014 are analyzed. A feature of this solar proton event (SPE) and weak ground-level enhancement (GLE) is that the source was located behind the limb. For the purpose of comparison, we also use the Advanced Composition Explorer (ACE) data on sub-relativistic electrons and GOES-13 measurements of a strong and extended proton event on 8 - 9 January 2014. It was found that the surface observations at energies {>} 433 MeV and GOES-13 data at {>} 30 - {>} 700 MeV may be satisfactorily reconciled by a power-law time-of-maximum (TOM) spectrum with a characteristic exponential tail (cutoff). Some methodological difficulties of spectrum determination are discussed. Assuming that the TOM spectrum near the Earth is a proxy of the spectrum of accelerated particles in the source, we critically consider the possibility of shock acceleration to relativistic energies in the solar corona. Finally, it is suggested to interpret the observational features of this GLE under the assumption that small GLEs may be produced by shocks driven by coronal mass ejections. However, the serious limitations of such an approach to the problem of the SCR spectrum prevent drawing firm conclusions in this controversial field.

  4. A traveling-wave forward coupler design for a new accelerating mode in a silicon woodpile accelerator

    DOE PAGES

    Wu, Ziran; Lee, Chunghun H.; Wootton, Kent P.; ...

    2016-03-01

    Silicon woodpile photonic crystals provide a base structure that can be used to build a three-dimensional dielectric waveguide system for high-gradient laser driven acceleration. A new woodpile waveguide design that hosts a phase synchronous, centrally confined accelerating mode is proposed. Comparing with previously discovered silicon woodpile accelerating modes, this mode shows advantages in terms of better electron beam loading and higher achievable acceleration gradient. Several traveling-wave coupler design schemes developed for multi-cell RF cavity accelerators are adapted to the woodpile power coupler design for this new accelerating mode. Design of a forward coupled, highly efficient silicon woodpile accelerator is achieved.more » Simulation shows high efficiency of over 75% of the drive laser power coupled to this fundamental accelerating mode, with less than 15% backward wave scattering. The estimated acceleration gradient, when the coupler structure is driven at the damage threshold fluence of silicon at its operating 1.506 μm wavelength, can reach 185 MV/m. Lastly, a 17-layer woodpile waveguide structure was successfully fabricated, and the measured bandgap is in excellent agreement with simulation.« less

  5. A traveling-wave forward coupler design for a new accelerating mode in a silicon woodpile accelerator

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

    Wu, Ziran; Lee, Chunghun H.; Wootton, Kent P.

    Silicon woodpile photonic crystals provide a base structure that can be used to build a three-dimensional dielectric waveguide system for high-gradient laser driven acceleration. A new woodpile waveguide design that hosts a phase synchronous, centrally confined accelerating mode is proposed. Comparing with previously discovered silicon woodpile accelerating modes, this mode shows advantages in terms of better electron beam loading and higher achievable acceleration gradient. Several traveling-wave coupler design schemes developed for multi-cell RF cavity accelerators are adapted to the woodpile power coupler design for this new accelerating mode. Design of a forward coupled, highly efficient silicon woodpile accelerator is achieved.more » Simulation shows high efficiency of over 75% of the drive laser power coupled to this fundamental accelerating mode, with less than 15% backward wave scattering. The estimated acceleration gradient, when the coupler structure is driven at the damage threshold fluence of silicon at its operating 1.506 μm wavelength, can reach 185 MV/m. Lastly, a 17-layer woodpile waveguide structure was successfully fabricated, and the measured bandgap is in excellent agreement with simulation.« less

  6. Stress-Driven Melt Segregation and Organization in Partially Molten Rocks III: Annealing Experiments and Surface Tension-Driven Redistribution of Melt

    NASA Astrophysics Data System (ADS)

    Parsons, R.; Hustoft, J. W.; Holtzman, B. K.; Kohlstedt, D. L.; Phipps Morgan, J.

    2004-12-01

    As discussed in the two previous abstracts in this series, simple shear experiments on synthetic upper mantle-type rock samples reveal the segregation of melt into melt-rich bands separated by melt-depleted lenses. Here, we present new results from experiments designed to understand the driving forces working for and against melt segregation. To better understand the kinetics of surface tension-driven melt redistribution, we first deform samples at similar conditions (starting material, sample size, stress and strain) to produce melt-rich band networks that are statistically similar. Then the load is removed and the samples are statically annealed to allow surface tension to redistribute the melt-rich networks. Three samples of olivine + 20 vol% chromite + 4 vol% MORB were deformed at a confining pressure of 300 MPa and a temperature of 1523 K in simple shear at shear stresses of 20 - 55 MPa to shear strains of 3.5 and then statically annealed for 0, 10, or 100 h at the same P-T conditions. Melt-rich bands are fewer in number and appear more diffuse when compared to the deformed but not annealed samples. Bands with less melt tend to disappear more rapidly than more melt-rich ones. The melt fraction in the melt-rich bands decreased from 0.2 in the quenched sample to 0.1 in the sample annealed for 100 h. After deformation, the melt fraction in the melt-depleted regions are ~0.006; after static annealing for 100 h, this value increases to 0.02. These experiments provide new quantitative constraints on the kinetics of melt migration driven by surface tension. By quantifying this driving force in the same samples in which stress-driven distribution occurred, we learn about the relative kinetics of stress-driven melt segregation. The kinetics of both of these processes must be scaled together to mantle conditions to understand the importance of stress-driven melt segregation in the Earth, and to understand the interaction of this process with melt-rock reaction-driven

  7. Electron injection and acceleration in the plasma bubble regime driven by an ultraintense laser pulse combined with using dense-plasma wall and block

    NASA Astrophysics Data System (ADS)

    Zhao, Xue-Yan; Xie, Bai-Song; Wu, Hai-Cheng; Zhang, Shan; Hong, Xue-Ren; Aimidula, Aimierding

    2012-03-01

    An optimizing and alternative scheme for electron injection and acceleration in the wake bubble driven by an ultraintense laser pulse is presented. In this scheme, the dense-plasma wall with an inner diameter matching the expected bubble size is placed along laser propagation direction. Meanwhile, a dense-plasma block dense-plasma is adhered inward transversely at some certain position of the wall. Particle-in-cell simulations are performed, which demonstrate that the block plays an important role in the first electron injection and acceleration. The result shows that a collimated electron bunch with a total number of about 4.04×108μm-1 can be generated and accelerated stably to 1.61 GeV peak energy with 2.6% energy spread. The block contributes about 50% to the accelerated electron injection bunch by tracing and sorting statistically the source.

  8. Acceleration of a ground-state reaction by selective femtosecond-infrared-laser-pulse excitation

    NASA Astrophysics Data System (ADS)

    Stensitzki, Till; Yang, Yang; Kozich, Valeri; Ahmed, Ashour A.; Kössl, Florian; Kühn, Oliver; Heyne, Karsten

    2018-02-01

    Infrared (IR) excitation of vibrations that participate in the reaction coordinate of an otherwise thermally driven chemical reaction are believed to lead to its acceleration. Attempts at the practical realization of this concept have been hampered so far by competing processes leading to sample heating. Here we demonstrate, using femtosecond IR-pump IR-probe experiments, the acceleration of urethane and polyurethane formation due to vibrational excitation of the reactants for 1:1 mixtures of phenylisocyanate and cyclohexanol, and toluene-2,4-diisocyanate and 2,2,2-trichloroethane-1,1-diol, respectively. We measured reaction rate changes upon selective vibrational excitation with negligible heating of the sample and observed an increase of the reaction rate up to 24%. The observation is rationalized using reactant and transition-state structures obtained from quantum chemical calculations. We subsequently used IR-driven reaction acceleration to write a polyurethane square on sample windows using a femtosecond IR pulse.

  9. Materials Testing for an Accelerator-Driven Subcritical Molten Salt Fission System: A look at the Materials Science of Molten Salt Corrosion

    NASA Astrophysics Data System (ADS)

    Sooby, Elizabeth; Balachandran, Shreyas; Foley, David; Hartwig, Karl; McIntyre, Peter; Phongikaroon, Supathorn; Pogue, Nathaniel; Simpson, Michael; Tripathy, Prabhat

    2011-10-01

    For an accelerator-driven subcritical molten salt fission core to survive its 50+ year fuel life, the primary vessel, heat exchanger, and various internal components must be made of materials that resist corrosion and radiation damage in a high-temperature environment, (500-800 C). An experimental study of the corrosion behavior of candidate metals in contact with molten salt is being conducted at the Center for Advanced Energy Studies. Initial experiments have been run on Nb, Ta, Ni, two zirconium alloys, Hastelloy-N, and a series of steel alloys to form a base line for corrosion in both chloride and bromide salt. Metal coupons were immersed in LiCl-KCl or LiBr-KBr at 700 C in an inert-atmosphere. Salt samples were extracted on a time schedule over a 24-hr period. The samples were analyzed using inductively coupled plasma-mass spectrometry to determine concentrations of metals from corrosion. Preliminary results will be presented.

  10. Electrically Driven Single Phase Thermal Management: STP-H5 EHD Experiment

    NASA Technical Reports Server (NTRS)

    Didion, Jeffrey R.

    2016-01-01

    The Electrically Driven Single Phase Thermal Management: STP-H5 iEHDS Experiment is a technology demonstration of prototype proof of concept hardware to establish the feasilibilty and long term operation of this hardware. This is a structural thermal plate that will operate continuous as part of the STP-H5 ISEM experiment for up to 18 months. This presentation discusses the design, fabrication and environmental operational paramertes of the experiment hardware.

  11. Design of an electron-accelerator-driven compact neutron source for non-destructive assay

    NASA Astrophysics Data System (ADS)

    Murata, A.; Ikeda, S.; Hayashizaki, N.

    2017-09-01

    The threat of nuclear and radiological terrorism remains one of the greatest challenges to international security, and the threat is constantly evolving. In order to prevent nuclear terrorism, it is important to avoid unlawful import of nuclear materials, such as uranium and plutonium. Development of technologies for non-destructive measurement, detection and recognition of nuclear materials is essential for control at national borders. At Tokyo Institute of Technology, a compact neutron source system driven by an electron-accelerator has been designed for non-destructive assay (NDA). This system is composed of a combination of an S-band (2.856 GHz) RF-gun, a tungsten target to produce photons by bremsstrahlung, a beryllium target, which is suitable for use in generating neutrons because of the low threshold energy of photonuclear reactions, and a moderator to thermalize the fast neutrons. The advantage of this system can accelerate a short pulse beam with a pulse width less than 1 μs which is difficult to produce by neutron generators. The amounts of photons and neutron produced by electron beams were simulated using the Monte Carlo simulation code PHITS 2.82. When the RF-gun is operated with an average electron beam current of 0.1 mA, it is expected that the neutron intensities are 1.19 × 109 n/s and 9.94 × 109 n/s for incident electron beam energies of 5 MeV and 10 MeV, respectively.

  12. Accelerator-Reactor Coupling for Energy Production in Advanced Nuclear Fuel Cycles

    NASA Astrophysics Data System (ADS)

    Heidet, Florent; Brown, Nicholas R.; Haj Tahar, Malek

    This article is a review of several accelerator-reactor interface issues and nuclear fuel cycle applications of accelerator-driven subcritical systems. The systems considered here have the primary goal of energy production, but that goal is accomplished via a specific application in various proposed nuclear fuel cycles, such as breed-and-burn of fertile material or burning of transuranic material. Several basic principles are reviewed, starting from the proton beam window including the target, blanket, reactor core, and up to the fuel cycle. We focus on issues of interest, such as the impact of the energy required to run the accelerator and associated systems on the potential electricity delivered to the grid. Accelerator-driven systems feature many of the constraints and issues associated with critical reactors, with the added challenges of subcritical operation and coupling to an accelerator. Reliable accelerator operation and avoidance of beam trips are critically important. One interesting challenge is measurement of blanket subcriticality level during operation. We also review the potential benefits of accelerator-driven systems in various nuclear fuel cycle applications. Ultimately, accelerator-driven subcritical systems with the goal of transmutation of transuranic material have lower 100,000-year radioactivity than a critical fast reactor with recycling of uranium and plutonium.

  13. Developing the Systems Engineering Experience Accelerator (SEEA) Prototype and Roadmap

    DTIC Science & Technology

    2013-12-31

    information to be automatically presented without comment. 2.2.2 NEW FEATURES AND CAPABILITIES A number of new multiplayer capabilities were...2.4.1 OVERVIEW The EA game engine has two components: the runtime engine and the tools suite. The tools suite includes the Experience Development...the Learner. Figure 6: Experience Accelerator Logical Block Diagram The EARTE is a multiuser architecture for internet gaming . It has light

  14. Basic design considerations for free-electron lasers driven by electron beams from RF accelerators

    NASA Astrophysics Data System (ADS)

    Gover, A.; Freund, H.; Granatstein, V. L.; McAdoo, J. H.; Tang, C.-M.

    A design procedure and design criteria are derived for free-electron lasers driven by electron beams from RF accelerators. The procedure and criteria permit an estimate of the oscillation-buildup time and the laser output power of various FEL schemes: with waveguide resonator or open resonator, with initial seed-radiation injection or with spontaneous-emission radiation source, with a linear wiggler or with a helical wiggler. Expressions are derived for computing the various FEL parameters, allowing for the design and optimization of the FEL operational characteristics under ideal conditions or with nonideal design parameters that may be limited by technological or practical constraints. The design procedure enables one to derive engineering curves and scaling laws for the FEL operating parameters. This can be done most conveniently with a computer program based on flowcharts given in the appendices.

  15. Heat Transfer Experiments on a Pulse Detonation Driven Combustor

    DTIC Science & Technology

    2011-03-01

    steps that need to take place before such a hybrid is successfully developed. PDEs obtain their increased efficiency by means of detonation , a pressure...combustion in the Brayton cycle. A PDE utilizes detonations , which offer much higher pressures at the site of fuel ignition, generating less...HEAT TRANSFER EXPERIMENTS ON A PULSE DETONATION DRIVEN COMBUSTOR THESIS Nicholas C. Longo, Captain, USAF AFIT/GAE/ENY/11-M18

  16. Electrothermal instability growth in magnetically driven pulsed power liners

    NASA Astrophysics Data System (ADS)

    Peterson, Kyle J.; Sinars, Daniel B.; Yu, Edmund P.; Herrmann, Mark C.; Cuneo, Michael E.; Slutz, Stephen A.; Smith, Ian C.; Atherton, Briggs W.; Knudson, Marcus D.; Nakhleh, Charles

    2012-09-01

    This paper explores the role of electro-thermal instabilities on the dynamics of magnetically accelerated implosion systems. Electro-thermal instabilities result from non-uniform heating due to temperature dependence in the conductivity of a material. Comparatively little is known about these types of instabilities compared to the well known Magneto-Rayleigh-Taylor (MRT) instability. We present simulations that show electrothermal instabilities form immediately after the surface material of a conductor melts and can act as a significant seed to subsequent MRT instability growth. We also present the results of several experiments performed on Sandia National Laboratories Z accelerator to investigate signatures of electrothermal instability growth on well characterized initially solid aluminum and copper rods driven with a 20 MA, 100 ns risetime current pulse. These experiments show excellent agreement with electrothermal instability simulations and exhibit larger instability growth than can be explained by MRT theory alone.

  17. Arc-driven rail gun research

    NASA Technical Reports Server (NTRS)

    Ray, P. K.

    1984-01-01

    The equations describing the performance of an inductively-driven rail gun are analyzed numerically. Friction between the projectile and rails is included through an empirical formulation. The equations are applied to the experiment of Rashleigh and Marshall to obtain an estimate of energy distribution in rail guns as a function of time. The effect of frictional heat dissipation on the bore of the gun is calculated. The mechanism of plasma and projectile acceleration in a dc rail gun is described from a microscopic point of view through the establishment of the Hall field. The plasma conductivity is shown to be a tensor indicating that there is a small component of current parallel to the direction of acceleration. The plasma characteristics are evaluated as a function of plasma mass through a simple fluid mechanical analysis of the plasma. By equating the energy dissipated in the plasma with the radiation heat loss, the properties of the plasma are determined.

  18. Observation of multipactor suppression in a dielectric-loaded accelerating structure using an applied axial magnetic field

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

    Jing, C.; Konecny, R.; Antipov, S.

    2013-11-18

    Efforts by a number of institutions to develop a Dielectric-Loaded Accelerating (DLA) structure capable of supporting high gradient acceleration when driven by an external radio frequency source have been ongoing over the past decade. Single surface resonant multipactor has been previously identified as one of the major limitations on the practical application of DLA structures in electron accelerators. In this paper, we report the results of an experiment that demonstrated suppression of multipactor growth in an X-band DLA structure through the use of an applied axial magnetic field. This represents an advance toward the practical use of DLA structures inmore » many accelerator applications.« less

  19. The ram accelerator - A chemically driven mass launcher

    NASA Technical Reports Server (NTRS)

    Kaloupis, P.; Bruckner, A. P.

    1988-01-01

    The ram accelerator, a chemically propelled mass driver, is presented as a viable new approach for directly launching acceleration-insensitive payloads into low earth orbit. The propulsion principle is similar to that of a conventional air-breathing ramjet. The cargo vehicle resembles the center-body of a ramjet and travels through a tube filled with a pre-mixed fuel and oxidizer mixture. The launch tube acts as the outer cowling of the ramjet and the combustion process travels with the vehicle. Two drive modes of the ram accelerator propulsion system are described, which when used in sequence are capable of accelerating the vehicle to as high as 10 km/sec. The requirements are examined for placing a 2000 kg vehicle into a 500 km orbit with a minimum of on-board rocket propellant for circularization maneuvers. It is shown that aerodynamic heating during atmospheric transit results in very little ablation of the nose. An indirect orbital insertion scenario is selected, utilizing a three step maneuver consisting of two burns and aerobraking. An on-board propulsion system using storable liquid propellants is chosen in order to minimize propellant mass requirements, and the use of a parking orbit below the desired final orbit is suggested as a means to increase the flexibility of the mass launch concept. A vehicle design using composite materials is proposed that will best meet the structural requirements, and a preliminary launch tube design is presented.

  20. Experiment to Detect Accelerating Modes in a Photonic Bandgap Fiber

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

    England, R.J.; /SLAC; Colby, E.R.

    An experimental effort is currently underway at the E-163 test beamline at Stanford Linear Accelerator Center to use a hollow-core photonic bandgap (PBG) fiber as a high-gradient laser-based accelerating structure for electron bunches. For the initial stage of this experiment, a 50pC, 60 MeV electron beam will be coupled into the fiber core and the excited modes will be detected using a spectrograph to resolve their frequency signatures in the wakefield radiation generated by the beam. They will describe the experimental plan and recent simulation studies of candidate fibers.

  1. Experiences with Deriva: An Asset Management Platform for Accelerating eScience.

    PubMed

    Bugacov, Alejandro; Czajkowski, Karl; Kesselman, Carl; Kumar, Anoop; Schuler, Robert E; Tangmunarunkit, Hongsuda

    2017-10-01

    The pace of discovery in eScience is increasingly dependent on a scientist's ability to acquire, curate, integrate, analyze, and share large and diverse collections of data. It is all too common for investigators to spend inordinate amounts of time developing ad hoc procedures to manage their data. In previous work, we presented Deriva, a Scientific Asset Management System, designed to accelerate data driven discovery. In this paper, we report on the use of Deriva in a number of substantial and diverse eScience applications. We describe the lessons we have learned, both from the perspective of the Deriva technology, as well as the ability and willingness of scientists to incorporate Scientific Asset Management into their daily workflows.

  2. The LILIA experiment: Energy selection and post-acceleration of laser generated protons

    NASA Astrophysics Data System (ADS)

    Turchetti, Giorgio; Sinigardi, Stefano; Londrillo, Pasquale; Rossi, Francesco; Sumini, Marco; Giove, Dario; De Martinis, Carlo

    2012-12-01

    The LILIA experiment is planned at the SPARCLAB facility of the Frascati INFN laboratories. We have simulated the laser acceleration of protons, the transport and energy selection with collimators and a pulsed solenoid and the post-acceleration with a compact high field linac. For the highest achievable intensity corresponding to a = 30 over 108 protons at 30 MeV with a 3% spread are selected, and at least107 protons are post-accelerated up to 60 MeV. If a 10 Hz repetition rated can be achieved the delivered dose would be suitable for the treatment of small superficial tumors.

  3. Laser-driven injector of electrons for IOTA

    NASA Astrophysics Data System (ADS)

    Romanov, Aleksandr

    2017-03-01

    Fermilab is developing the Integrable Optics Test Accelerator (IOTA) ring for experiments on nonlinear integrable optics. The machine will operate with either electron beams of 150 MeV or proton beams of 2.5 MeV energies, respectively. The stability of integrable optics depends critically on the precision of the magnetic lattice, which demands the use of beam-based lattice measurements for optics correction. In the proton mode, the low-energy proton beam does not represent a good probe for this application; hence we consider the use of a low-intensity reverse-injected electron beam of matched momentum (70 MeV). Such an injector could be implemented with the use of laser-driven acceleration techniques. This report presents the consideration for a laser-plasma injector for IOTA and discusses the requirements determined by the ring design.

  4. Accelerator on a Chip

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

    England, Joel

    2014-06-30

    SLAC's Joel England explains how the same fabrication techniques used for silicon computer microchips allowed their team to create the new laser-driven particle accelerator chips. (SLAC Multimedia Communications)

  5. Accelerator on a Chip

    ScienceCinema

    England, Joel

    2018-01-16

    SLAC's Joel England explains how the same fabrication techniques used for silicon computer microchips allowed their team to create the new laser-driven particle accelerator chips. (SLAC Multimedia Communications)

  6. Development of a plasma driven permeation experiment for TPE

    DOE PAGES

    Buchenauer, Dean; Kolasinski, Robert; Shimada, Masa; ...

    2014-04-18

    Experiments on retention of hydrogen isotopes (including tritium) at temperatures less than 800 ?C have been carried out in the Tritium Plasma Experiment (TPE) at Idaho National Laboratory [1,2]. To provide a direct measurement of plasma driven permeation in plasma facing materials at temperatures reaching 1000 ?C, a new TPE membrane holder has been built to hold test specimens (=1 mm in thickness) at high temperature while measuring tritium permeating through the membrane from the plasma facing side. This measurement is accomplished by employing a carrier gas that transports the permeating tritium from the backside of the membrane to ionmore » chambers giving a direct measurement of the plasma driven tritium permeation rate. Isolation of the membrane cooling and sweep gases from TPE’s vacuum chamber has been demonstrated by sealing tests performed up to 1000 ?C of a membrane holder design that provides easy change out of membrane specimens between tests. Simulations of the helium carrier gas which transports tritium to the ion chamber indicate a very small pressure drop (~700 Pa) with good flow uniformity (at 1000 sccm). Thermal transport simulations indicate that temperatures up to 1000 ?C are expected at the highest TPE fluxes.« less

  7. rf breakdown measurements in electron beam driven 200 GHz copper and copper-silver accelerating structures

    DOE PAGES

    Dal Forno, Massimo; Dolgashev, Valery; Bowden, Gordon; ...

    2016-11-30

    This study explores the physics of vacuum rf breakdowns in subterahertz high-gradient traveling-wave accelerating structures. We present the experimental results of rf tests of 200 GHz metallic accelerating structures, made of copper and copper-silver. These experiments were carried out at the Facility for Advanced Accelerator Experimental Tests (FACET) at the SLAC National Accelerator Laboratory. The rf fields were excited by the FACET ultrarelativistic electron beam. The traveling-wave structure is an open geometry, 10 cm long, composed of two halves separated by a gap. The rf frequency of the fundamental accelerating mode depends on the gap size and can be changedmore » from 160 to 235 GHz. When the beam travels off axis, a deflecting field is induced in addition to the longitudinal field. We measure the deflecting forces by observing the displacement of the electron bunch and use this measurement to verify the expected accelerating gradient. Furthermore, we present the first quantitative measurement of rf breakdown rates in 200 GHz metallic accelerating structures. The breakdown rate of the copper structure is 10 –2 per pulse, with a peak surface electric field of 500 MV/m and a rf pulse length of 0.3 ns, which at a relatively large gap of 1.5 mm, or one wavelength, corresponds to an accelerating gradient of 56 MV/m. For the same breakdown rate, the copper-silver structure has a peak electric field of 320 MV/m at a pulse length of 0.5 ns. For a gap of 1.1 mm, or 0.74 wavelengths, this corresponds to an accelerating gradient of 50 MV/m.« less

  8. Rapid acceleration leads to rapid weakening in earthquake-like laboratory experiments

    USGS Publications Warehouse

    Chang, Jefferson C.; Lockner, David A.; Reches, Z.

    2012-01-01

    After nucleation, a large earthquake propagates as an expanding rupture front along a fault. This front activates countless fault patches that slip by consuming energy stored in Earth’s crust. We simulated the slip of a fault patch by rapidly loading an experimental fault with energy stored in a spinning flywheel. The spontaneous evolution of strength, acceleration, and velocity indicates that our experiments are proxies of fault-patch behavior during earthquakes of moment magnitude (Mw) = 4 to 8. We show that seismically determined earthquake parameters (e.g., displacement, velocity, magnitude, or fracture energy) can be used to estimate the intensity of the energy release during an earthquake. Our experiments further indicate that high acceleration imposed by the earthquake’s rupture front quickens dynamic weakening by intense wear of the fault zone.

  9. High Frequency, High Gradient Dielectric Wakefield Acceleration Experiments at SLAC and BNL

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

    Rosenzweig, James; /UCLA; Travish, Gil

    Given the recent success of >GV/m dielectric wakefield accelerator (DWA) breakdown experiments at SLAC, and follow-on coherent Cerenkov radiation production at the UCLA Neptune, a UCLA-USC-SLAC collaboration is now implementing a new set of experiments that explore various DWA scenarios. These experiments are motivated by the opportunities presented by the approval of FACET facility at SLAC, as well as unique pulse-train wakefield drivers at BNL. The SLAC experiments permit further exploration of the multi-GeV/m envelope in DWAs, and will entail investigations of novel materials (e.g. CVD diamond) and geometries (Bragg cylindrical structures, slab-symmetric DWAs), and have an over-riding goal ofmore » demonstrating >GeV acceleration in {approx}33 cm DWA tubes. In the nearer term before FACET's commissioning, we are planning measurements at the BNL ATF, in which we drive {approx}50-200 MV/m fields with single pulses or pulse trains. These experiments are of high relevance to enhancing linear collider DWA designs, as they will demonstrate potential for efficient operation with pulse trains.« less

  10. Simulations of material mixing in laser-driven reshock experiments

    NASA Astrophysics Data System (ADS)

    Haines, Brian M.; Grinstein, Fernando F.; Welser-Sherrill, Leslie; Fincke, James R.

    2013-02-01

    We perform simulations of a laser-driven reshock experiment [Welser-Sherrill et al., High Energy Density Phys. (unpublished)] in the strong-shock high energy-density regime to better understand material mixing driven by the Richtmyer-Meshkov instability. Validation of the simulations is based on direct comparison of simulation and radiographic data. Simulations are also compared with published direct numerical simulation and the theory of homogeneous isotropic turbulence. Despite the fact that the flow is neither homogeneous, isotropic nor fully turbulent, there are local regions in which the flow demonstrates characteristics of homogeneous isotropic turbulence. We identify and isolate these regions by the presence of high levels of turbulent kinetic energy (TKE) and vorticity. After reshock, our analysis shows characteristics consistent with those of incompressible isotropic turbulence. Self-similarity and effective Reynolds number assessments suggest that the results are reasonably converged at the finest resolution. Our results show that in shock-driven transitional flows, turbulent features such as self-similarity and isotropy only fully develop once de-correlation, characteristic vorticity distributions, and integrated TKE, have decayed significantly. Finally, we use three-dimensional simulation results to test the performance of two-dimensional Reynolds-averaged Navier-Stokes simulations. In this context, we also test a presumed probability density function turbulent mixing model extensively used in combustion applications.

  11. Experiments on vibration-driven stick-slip locomotion: A sliding bifurcation perspective

    NASA Astrophysics Data System (ADS)

    Du, Zhouwei; Fang, Hongbin; Zhan, Xiong; Xu, Jian

    2018-05-01

    Dry friction appears at the contact interface between two surfaces and is the source of stick-slip vibrations. Instead of being a negative factor, dry friction is essential for vibration-driven locomotion system to take effect. However, the dry-friction-induced stick-slip locomotion has not been fully understood in previous research, especially in terms of experiments. In this paper, we experimentally study the stick-slip dynamics of a vibration-driven locomotion system from a sliding bifurcation perspective. To this end, we first design and build a vibration-driven locomotion prototype based on an internal piezoelectric cantilever. By utilizing the mechanical resonance, the small piezoelectric deformation is significantly amplified to drive the prototype to achieve effective locomotion. Through identifying the stick-slip characteristics in velocity histories, we could categorize the system's locomotion into four types and obtain a stick-slip categorization diagram. In each zone of the diagram the locomotion exhibits qualitatively different stick-slip dynamics. Such categorization diagram is actually a sliding bifurcation diagram; crossing from one stick-slip zone to another corresponds to the triggering of a sliding bifurcation. In addition, a simplified single degree-of-freedom model is established, with the rationality of simplification been explained theoretically and numerically. Based on the equivalent model, a numerical stick-slip categorization is also obtained, which shows good agreement with the experiments both qualitatively and quantitatively. To the best of our knowledge, this is the first work that experimentally generates a sliding bifurcation diagram. The obtained stick-slip categorizations deepen our understanding of stick-slip dynamics in vibration-driven systems and could serve as a base for system design and optimization.

  12. Magnetohydrodynamic Particle Acceleration Processes: SSX Experiments, Theory, and Astrophysical Applications

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

    Brown, Michael R.

    2006-11-16

    Project Title: Magnetohydrodynamic Particle Acceleration Processes: SSX Experiments, Theory, and Astrophysical Applications PI: Michael R. Brown, Swarthmore College The purpose of the project was to provide theoretical and modeling support to the Swarthmore Spheromak Experiment (SSX). Accordingly, the theoretical effort was tightly integrated into the SSX experimental effort. During the grant period, Michael Brown and his experimental collaborators at Swarthmore, with assistance from W. Matthaeus as appropriate, made substantial progress in understanding the physics SSX plasmas.

  13. Accelerating Innovation Through Coopetition: The Innovation Learning Network Experience.

    PubMed

    McCarthy, Chris; Ford Carleton, Penny; Krumpholz, Elizabeth; Chow, Marilyn P

    Coopetition, the simultaneous pursuit of cooperation and competition, is a growing force in the innovation landscape. For some organizations, the primary mode of innovation continues to be deeply secretive and highly competitive, but for others, a new style of shared challenges, shared purpose, and shared development has become a superior, more efficient way of working to accelerate innovation capabilities and capacity. Over the last 2 decades, the literature base devoted to coopetition has gradually expanded. However, the field is still in its infancy. The majority of coopetition research is qualitative, primarily consisting of case studies. Few studies have addressed the nonprofit sector or service industries such as health care. The authors believe that this article may offer a unique perspective on coopetition in the context of a US-based national health care learning alliance designed to accelerate innovation, the Innovation Learning Network or ILN. The mission of the ILN is to "Share the joy and pain of innovation," accelerating innovation by sharing solutions, teaching techniques, and cultivating friendships. These 3 pillars (sharing, teaching, and cultivating) form the foundation for coopetition within the ILN. Through the lens of coopetition, we examine the experience of the ILN over the last 10 years and provide case examples that illustrate the benefits and challenges of coopetition in accelerating innovation in health care.

  14. Accelerated approval of oncology products: the food and drug administration experience.

    PubMed

    Johnson, John R; Ning, Yang-Min; Farrell, Ann; Justice, Robert; Keegan, Patricia; Pazdur, Richard

    2011-04-20

    We reviewed the regulatory history of the accelerated approval process and the US Food and Drug Administration (FDA) experience with accelerated approval of oncology products from its initiation in December 11, 1992, to July 1, 2010. The accelerated approval regulations allowed accelerated approval of products to treat serious or life-threatening diseases based on surrogate endpoints that are reasonably likely to predict clinical benefit. Failure to complete postapproval trials to confirm clinical benefit with due diligence could result in removal of the accelerated approval indication from the market. From December 11, 1992, to July 1, 2010, the FDA granted accelerated approval to 35 oncology products for 47 new indications. Clinical benefit was confirmed in postapproval trials for 26 of the 47 new indications, resulting in conversion to regular approval. The median time between accelerated approval and regular approval of oncology products was 3.9 years (range = 0.8-12.6 years) and the mean time was 4.7 years, representing a substantial time savings in terms of earlier availability of drugs to cancer patients. Three new indications did not show clinical benefit when confirmatory postapproval trials were completed and were subsequently removed from the market or had restricted distribution plans implemented. Confirmatory trials were not completed for 14 new indications. The five longest intervals from receipt of accelerated approval to July 1, 2010, without completion of trials to confirm clinical benefit were 10.5, 6.4, 5.5, 5.5, and 4.7 years. The five longest intervals between accelerated approval and successful conversion to regular approval were 12.6, 9.7, 8.1, 7.5, and 7.4 years. Trials to confirm clinical benefit should be part of the drug development plan and should be in progress at the time of an application seeking accelerated approval to prevent an ineffective drug from remaining on the market for an unacceptable time.

  15. Optimized operation of dielectric laser accelerators: Multibunch

    NASA Astrophysics Data System (ADS)

    Hanuka, Adi; Schächter, Levi

    2018-06-01

    We present a self-consistent analysis to determine the optimal charge, gradient, and efficiency for laser driven accelerators operating with a train of microbunches. Specifically, we account for the beam loading reduction on the material occurring at the dielectric-vacuum interface. In the case of a train of microbunches, such beam loading effect could be detrimental due to energy spread, however this may be compensated by a tapered laser pulse. We ultimately propose an optimization procedure with an analytical solution for group velocity which equals to half the speed of light. This optimization results in a maximum efficiency 20% lower than the single bunch case, and a total accelerated charge of 1 06 electrons in the train. The approach holds promise for improving operations of dielectric laser accelerators and may have an impact on emerging laser accelerators driven by high-power optical lasers.

  16. Proton shock acceleration using a high contrast high intensity laser

    NASA Astrophysics Data System (ADS)

    Gauthier, Maxence; Roedel, Christian; Kim, Jongjin; Aurand, Bastian; Curry, Chandra; Goede, Sebastian; Propp, Adrienne; Goyon, Clement; Pak, Art; Kerr, Shaun; Ramakrishna, Bhuvanesh; Ruby, John; William, Jackson; Glenzer, Siegfried

    2015-11-01

    Laser-driven proton acceleration is a field of intense research due to the interesting characteristics of this novel particle source including high brightness, high maximum energy, high laminarity, and short duration. Although the ion beam characteristics are promising for many future applications, such as in the medical field or hybrid accelerators, the ion beam generated using TNSA, the acceleration mechanism commonly achieved, still need to be significantly improved. Several new alternative mechanisms have been proposed such as collisionless shock acceleration (CSA) in order to produce a mono-energetic ion beam favorable for those applications. We report the first results of an experiment performed with the TITAN laser system (JLF, LLNL) dedicated to the study of CSA using a high intensity (5x1019W/cm2) high contrast ps laser pulse focused on 55 μm thick CH and CD targets. We show that the proton spectrum generated during the interaction exhibits high-energy mono-energetic features along the laser axis, characteristic of a shock mechanism.

  17. Neutron imaging with the short-pulse laser driven neutron source at the TRIDENT Laser Facility

    DOE PAGES

    Guler, Nevzat; Volegov, Petr Lvovich; Favalli, Andrea; ...

    2016-10-17

    Emerging approaches to short-pulse laser-driven neutron production offer a possible gateway to compact, low cost, and intense broad spectrum sources for a wide variety of applications. They are based on energetic ions, driven by an intense short-pulse laser, interacting with a converter material to produce neutrons via breakup and nuclear reactions. Recent experiments performed with the high-contrast laser at the Trident laser facility of Los Alamos National Laboratory have demonstrated a laser-driven ion acceleration mechanism operating in the regime of relativistic transparency, featuring a volumetric laser-plasma interaction. This mechanism is distinct from previously studied ones that accelerate ions at themore » laser-target surface. The Trident experiments produced an intense beam of deuterons with an energy distribution extending above 100 MeV. This deuteron beam, when directed at a beryllium converter, produces a forward-directed neutron beam with ~5x10 9 n/sr, in a single laser shot, primarily due to deuteron breakup. The neutron beam has a pulse duration on the order of a few nanoseconds with an energy distribution extending from a few hundreds of keV to almost 80 MeV. For the experiments on neutron-source spot-size measurements, our gated neutron imager was setup to select neutrons in the energy range of 2.5 to 35 MeV. The spot size of neutron emission at the converter was measured by two different imaging techniques, using a knife-edge and a penumbral aperture, in two different experimental campaigns. The neutron-source spot size is measured ~1 mm for both experiments. The measurements and analysis reported here give a spatial characterization for this type of neutron source for the first time. In addition, the forward modeling performed provides an empirical estimate of the spatial characteristics of the deuteron ion-beam. Finally, these experimental observations, taken together, provide essential yet unique data to benchmark and verify theoretical

  18. Neutron imaging with the short-pulse laser driven neutron source at the TRIDENT Laser Facility

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

    Guler, Nevzat; Volegov, Petr Lvovich; Favalli, Andrea

    Emerging approaches to short-pulse laser-driven neutron production offer a possible gateway to compact, low cost, and intense broad spectrum sources for a wide variety of applications. They are based on energetic ions, driven by an intense short-pulse laser, interacting with a converter material to produce neutrons via breakup and nuclear reactions. Recent experiments performed with the high-contrast laser at the Trident laser facility of Los Alamos National Laboratory have demonstrated a laser-driven ion acceleration mechanism operating in the regime of relativistic transparency, featuring a volumetric laser-plasma interaction. This mechanism is distinct from previously studied ones that accelerate ions at themore » laser-target surface. The Trident experiments produced an intense beam of deuterons with an energy distribution extending above 100 MeV. This deuteron beam, when directed at a beryllium converter, produces a forward-directed neutron beam with ~5x10 9 n/sr, in a single laser shot, primarily due to deuteron breakup. The neutron beam has a pulse duration on the order of a few nanoseconds with an energy distribution extending from a few hundreds of keV to almost 80 MeV. For the experiments on neutron-source spot-size measurements, our gated neutron imager was setup to select neutrons in the energy range of 2.5 to 35 MeV. The spot size of neutron emission at the converter was measured by two different imaging techniques, using a knife-edge and a penumbral aperture, in two different experimental campaigns. The neutron-source spot size is measured ~1 mm for both experiments. The measurements and analysis reported here give a spatial characterization for this type of neutron source for the first time. In addition, the forward modeling performed provides an empirical estimate of the spatial characteristics of the deuteron ion-beam. Finally, these experimental observations, taken together, provide essential yet unique data to benchmark and verify theoretical

  19. Application of Plasma Waveguides to High Energy Accelerators

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

    Milchberg, Howard M

    2013-03-30

    The eventual success of laser-plasma based acceleration schemes for high-energy particle physics will require the focusing and stable guiding of short intense laser pulses in reproducible plasma channels. For this goal to be realized, many scientific issues need to be addressed. These issues include an understanding of the basic physics of, and an exploration of various schemes for, plasma channel formation. In addition, the coupling of intense laser pulses to these channels and the stable propagation of pulses in the channels require study. Finally, new theoretical and computational tools need to be developed to aid in the design and analysismore » of experiments and future accelerators. Here we propose a 3-year renewal of our combined theoretical and experimental program on the applications of plasma waveguides to high-energy accelerators. During the past grant period we have made a number of significant advances in the science of laser-plasma based acceleration. We pioneered the development of clustered gases as a new highly efficient medium for plasma channel formation. Our contributions here include theoretical and experimental studies of the physics of cluster ionization, heating, explosion, and channel formation. We have demonstrated for the first time the generation of and guiding in a corrugated plasma waveguide. The fine structure demonstrated in these guides is only possible with cluster jet heating by lasers. The corrugated guide is a slow wave structure operable at arbitrarily high laser intensities, allowing direct laser acceleration, a process we have explored in detail with simulations. The development of these guides opens the possibility of direct laser acceleration, a true miniature analogue of the SLAC RF-based accelerator. Our theoretical studies during this period have also contributed to the further development of the simulation codes, Wake and QuickPIC, which can be used for both laser driven and beam driven plasma based acceleration

  20. MABE multibeam accelerator

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

    Hasti, D.E.; Ramirez, J.J.; Coleman, P.D.

    1985-01-01

    The Megamp Accelerator and Beam Experiment (MABE) was the technology development testbed for the multiple beam, linear induction accelerator approach for Hermes III, a new 20 MeV, 0.8 MA, 40 ns accelerator being developed at Sandia for gamma-ray simulation. Experimental studies of a high-current, single-beam accelerator (8 MeV, 80 kA), and a nine-beam injector (1.4 MeV, 25 kA/beam) have been completed, and experiments on a nine-beam linear induction accelerator are in progress. A two-beam linear induction accelerator is designed and will be built as a gamma-ray simulator to be used in parallel with Hermes III. The MABE pulsed power systemmore » and accelerator for the multiple beam experiments is described. Results from these experiments and the two-beam design are discussed. 11 refs., 6 figs.« less

  1. Acceleration during magnetic reconnection

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

    Beresnyak, Andrey; Li, Hui

    2015-07-16

    The presentation begins with colorful depictions of solar x-ray flares and references to pulsar phenomena. Plasma reconnection is complex, could be x-point dominated or turbulent, field lines could break due to either resistivity or non-ideal effects, such as electron pressure anisotropy. Electron acceleration is sometimes observed, and sometimes not. One way to study this complex problem is to have many examples of the process (reconnection) and compare them; the other way is to simplify and come to something robust. Ideal MHD (E=0) turbulence driven by magnetic energy is assumed, and the first-order acceleration is sought. It is found that dissipationmore » in big (length >100 ion skin depths) current sheets is universal and independent on microscopic resistivity and the mean imposed field; particles are regularly accelerated while experiencing curvature drift in flows driven by magnetic tension. One example of such flow is spontaneous reconnection. This explains hot electrons with a power-law tail in solar flares, as well as ultrashort time variability in some astrophysical sources.« less

  2. Effects of Experiment Location and Orbiter Attitude on the Residual Acceleration On-Board STS-73 (USML-2)

    NASA Technical Reports Server (NTRS)

    Hakimzadeh, Roshanak; McPherson, Kevin M.; Matisak, Brian P.; Wagar, William O.

    1997-01-01

    A knowledge of the quasi-steady acceleration environment on the NASA Space Shuttle Orbiter is of particular importance for materials processing experiments which are limited by slow diffusive processes. The quasi-steady (less than 1 HZ) acceleration environment on STS-73 (USML-2) was measured using the Orbital Acceleration Research Experiment (OARE) accelerometer. One of the facilities flown on USML-2 was the Crystal Growth Furnace (CGF), which was used by several Principal Investigators (PIS) to grow crystals. In this paper the OARE data mapped to the sample melt location within this furnace is presented. The ratio of the axial to radial components of the quasi-steady acceleration at the melt site is presented. Effects of Orbiter attitude on the acceleration data is discussed.

  3. Demonstration of acceleration of relativistic electrons at a dielectric microstructure using femtosecond laser pulses

    DOE PAGES

    Wootton, Kent P.; Wu, Ziran; Cowan, Benjamin M.; ...

    2016-06-02

    Acceleration of electrons using laser-driven dielectric microstructures is a promising technology for the miniaturization of particle accelerators. Achieving the desired GV m –1 accelerating gradients is possible only with laser pulse durations shorter than ~1 ps. In this Letter, we present, to the best of our knowledge, the first demonstration of acceleration of relativistic electrons at a dielectric microstructure driven by femtosecond duration laser pulses. Furthermore, using this technique, an electron accelerating gradient of 690±100 MV m –1 was measured—a record for dielectric laser accelerators.

  4. Flat electron beam sources for DLA accelerators

    DOE PAGES

    Ody, A.; Musumeci, P.; Maxson, J.; ...

    2016-10-26

    In this study we discuss the application of the flat beam transform to generate beams suitable for injection into slab-symmetric dielectric laser-driven accelerators (DLAs). A study of the focusing requirements to keep the particles within the tight apertures characterizing these accelerators shows the benefits of employing ultralow beam emittances. The slab geometry of the many dielectric accelerating structures strongly favors the use of flat beams with large ratio between vertical and horizontal emittances. We employ particle tracking simulations to study the application of the flat beam transform for two injector designs, a DC non relativistic photogun and a 1.6 cellmore » S-band RF photoinjector, obtaining in both cases emittance ratios between the horizontal and vertical plane in excess of 100 in agreement with simple analytical estimates. The 4 MeV RF photoinjector study-case can be directly applied to the UCLA Pegasus beamline and shows normalized emittances down to < 3 nm in the vertical dimension for beam charges up to 20 fC, enabling a two-stage DLA experiment.« less

  5. The Student Course Experience among Online, Accelerated, and Traditional Courses

    ERIC Educational Resources Information Center

    Bielitz, Colleen L.

    2016-01-01

    The demand by the public for a wider variety of course formats has led to complexity in determining a course's optimal delivery format as many faculty members still believe that online and accelerated courses do not offer students an equivalent experience to traditional face to face instruction. The purpose of this quantitative, comparative study…

  6. Accelerating gradient improvement using shape-tailor laser front in radiation pressure acceleration progress

    NASA Astrophysics Data System (ADS)

    Wang, W. P.; Shen, B. F.; Xu, Z. Z.

    2017-05-01

    The accelerating gradient of a proton beam is crucial for stable radiation pressure acceleration (RPA) because the multi-dimensional instabilities increase γ times slower in the relativistic region. In this paper, a shape-tailored laser is proposed to significantly accelerate the ions in a controllable high accelerating gradient. In this method, the fastest ions initially rest in the middle of the foil are controlled to catch the compressed electron layer at the end of the hole-boring stage, thus the light-sail stage can start as soon as possible. Then the compressed electron layer is accelerated tightly together with the fastest ions by the shaped laser intensity, which further increases the accelerating gradient in the light-sail stage. Such tailored pulse may be beneficial for the RPA driven by the 10-fs 10 petawatt laser in the future.

  7. Simulation prediction and experiment setup of vacuum laser acceleration at Brookhaven National Lab-Accelerator Test Facility

    NASA Astrophysics Data System (ADS)

    Shao, L.; Cline, D.; Ding, X.; Ho, Y. K.; Kong, Q.; Xu, J. J.; Pogorelsky, I.; Yakimenko, V.; Kusche, K.

    2013-02-01

    This paper presents the pre-experiment plan and prediction of the first stage of vacuum laser acceleration (VLA) collaborating by UCLA, Fudan University and ATF-BNL. This first stage experiment is a proof-of-principle to support our previously posted novel VLA theory. Simulations show that based on ATF's current experimental conditions the electron beam with initial energy of 15 MeV can get net energy gain from an intense CO2 laser beam. The difference in electron beam energy spread is observable by the ATF beam line diagnostics system. Further, this energy spread expansion effect increases along with an increase in laser intensity. The proposal has been approved by the ATF committee and the experiment will be our next project.

  8. Plasma Wakefield Acceleration of an Intense Positron Beam

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

    Blue, B

    2004-04-21

    The Plasma Wakefield Accelerator (PWFA) is an advanced accelerator concept which possess a high acceleration gradient and a long interaction length for accelerating both electrons and positrons. Although electron beam-plasma interactions have been extensively studied in connection with the PWFA, very little work has been done with respect to positron beam-plasma interactions. This dissertation addresses three issues relating to a positron beam driven plasma wakefield accelerator. These issues are (a) the suitability of employing a positron drive bunch to excite a wake; (b) the transverse stability of the drive bunch; and (c) the acceleration of positrons by the plasma wakemore » that is driven by a positron bunch. These three issues are explored first through computer simulations and then through experiments. First, a theory is developed on the impulse response of plasma to a short drive beam which is valid for small perturbations to the plasma density. This is followed up with several particle-in-cell (PIC) simulations which study the experimental parameter (bunch length, charge, radius, and plasma density) range. Next, the experimental setup is described with an emphasis on the equipment used to measure the longitudinal energy variations of the positron beam. Then, the transverse dynamics of a positron beam in a plasma are described. Special attention is given to the way focusing, defocusing, and a tilted beam would appear to be energy variations as viewed on our diagnostics. Finally, the energy dynamics imparted on a 730 {micro}m long, 40 {micro}m radius, 28.5 GeV positron beam with 1.2 x 10{sup 10} particles in a 1.4 meter long 0-2 x 10{sup 14} e{sup -}/cm{sup 3} plasma is described. First the energy loss was measured as a function of plasma density and the measurements are compared to theory. Then, an energy gain of 79 {+-} 15 MeV is shown. This is the first demonstration of energy gain of a positron beam in a plasma and it is in good agreement with the

  9. Helicon Plasma Injector and Ion Cyclotron Acceleration Development in the VASIMR Experiment

    NASA Technical Reports Server (NTRS)

    Squire, Jared P.; Chang, Franklin R.; Jacobson, Verlin T.; McCaskill, Greg E.; Bengtson, Roger D.; Goulding, Richard H.

    2000-01-01

    In the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) radio frequency (rf) waves both produce the plasma and then accelerate the ions. The plasma production is done by action of helicon waves. These waves are circular polarized waves in the direction of the electron gyromotion. The ion acceleration is performed by ion cyclotron resonant frequency (ICRF) acceleration. The Advanced Space Propulsion Laboratory (ASPL) is actively developing efficient helicon plasma production and ICRF acceleration. The VASIMR experimental device at the ASPL is called VX-10. It is configured to demonstrate the plasma production and acceleration at the 10kW level to support a space flight demonstration design. The VX-10 consists of three electromagnets integrated into a vacuum chamber that produce magnetic fields up to 0.5 Tesla. Magnetic field shaping is achieved by independent magnet current control and placement of the magnets. We have generated both helium and hydrogen high density (>10(exp 18) cu m) discharges with the helicon source. ICRF experiments are underway. This paper describes the VX-10 device, presents recent results and discusses future plans.

  10. Experiments in sensing transient rotational acceleration cues on a flight simulator

    NASA Technical Reports Server (NTRS)

    Parrish, R. V.

    1979-01-01

    Results are presented for two transient motion sensing experiments which were motivated by the identification of an anomalous roll cue (a 'jerk' attributed to an acceleration spike) in a prior investigation of realistic fighter motion simulation. The experimental results suggest the consideration of several issues for motion washout and challenge current sensory system modeling efforts. Although no sensory modeling effort is made it is argued that such models must incorporate the ability to handle transient inputs of short duration (some of which are less than the accepted latency times for sensing), and must represent separate channels for rotational acceleration and velocity sensing.

  11. A computational framework for estimating statistical power and planning hypothesis-driven experiments involving one-dimensional biomechanical continua.

    PubMed

    Pataky, Todd C; Robinson, Mark A; Vanrenterghem, Jos

    2018-01-03

    Statistical power assessment is an important component of hypothesis-driven research but until relatively recently (mid-1990s) no methods were available for assessing power in experiments involving continuum data and in particular those involving one-dimensional (1D) time series. The purpose of this study was to describe how continuum-level power analyses can be used to plan hypothesis-driven biomechanics experiments involving 1D data. In particular, we demonstrate how theory- and pilot-driven 1D effect modeling can be used for sample-size calculations for both single- and multi-subject experiments. For theory-driven power analysis we use the minimum jerk hypothesis and single-subject experiments involving straight-line, planar reaching. For pilot-driven power analysis we use a previously published knee kinematics dataset. Results show that powers on the order of 0.8 can be achieved with relatively small sample sizes, five and ten for within-subject minimum jerk analysis and between-subject knee kinematics, respectively. However, the appropriate sample size depends on a priori justifications of biomechanical meaning and effect size. The main advantage of the proposed technique is that it encourages a priori justification regarding the clinical and/or scientific meaning of particular 1D effects, thereby robustly structuring subsequent experimental inquiry. In short, it shifts focus from a search for significance to a search for non-rejectable hypotheses. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Magnetic Control of Solutal Buoyancy Driven Convection

    NASA Technical Reports Server (NTRS)

    Ramachandran, N.; Leslie, F. W.

    2003-01-01

    Volumetric forces resulting from local density variations and gravitational acceleration cause buoyancy induced convective motion in melts and solutions. Solutal buoyancy is a result of concentration differences in an otherwise isothermal fluid. If the fluid also exhibits variations in magnetic susceptibility with concentration then convection control by external magnetic fields can be hypothesized. Magnetic control of thermal buoyancy induced convection in ferrofluids (dispersions of ferromagnetic particles in a carrier fluid) and paramagnetic fluids have been demonstrated. Here we show the nature of magnetic control of solutal buoyancy driven convection of a paramagnetic fluid, an aqueous solution of Manganese Chloride hydrate. We predict the critical magnetic field required for balancing gravitational solutal buoyancy driven convection and validate it through a simple experiment. We demonstrate that gravity driven flow can be completely reversed by a magnetic field but the exact cancellation of the flow is not possible. This is because the phenomenon is unstable. The technique can be applied to crystal growth processes in order to reduce convection and to heat exchanger devices for enhancing convection. The method can also be applied to impose a desired g-level in reduced gravity applications.

  13. Bremsstrahlung hard x-ray source driven by an electron beam from a self-modulated laser wakefield accelerator

    NASA Astrophysics Data System (ADS)

    Lemos, N.; Albert, F.; Shaw, J. L.; Papp, D.; Polanek, R.; King, P.; Milder, A. L.; Marsh, K. A.; Pak, A.; Pollock, B. B.; Hegelich, B. M.; Moody, J. D.; Park, J.; Tommasini, R.; Williams, G. J.; Chen, Hui; Joshi, C.

    2018-05-01

    An x-ray source generated by an electron beam produced using a Self-Modulated Laser Wakefield Accelerator (SM-LWFA) is explored for use in high energy density science facilities. By colliding the electron beam, with a maximum energy of 380 MeV, total charge of >10 nC and a divergence of 64 × 100 mrad, from a SM-LWFA driven by a 1 ps 120 J laser, into a high-Z foil, an x/gamma-ray source was generated. A broadband bremsstrahlung energy spectrum with temperatures ranging from 0.8 to 2 MeV was measured with an almost 2 orders of magnitude flux increase when compared with other schemes using LWFA. GEANT4 simulations were done to calculate the source size and divergence.

  14. Consumer experiences in a consumer-driven health plan.

    PubMed

    Christianson, Jon B; Parente, Stephen T; Feldman, Roger

    2004-08-01

    To assess the experience of enrollees in a consumer-driven health plan (CDHP). Survey of University of Minnesota employees regarding their 2002 health benefits. Comparison of regression-adjusted mean values for CDHP and other plan enrollees: customer service, plan paperwork, overall satisfaction, and plan switching. For CDHP enrollees only, use of plan features, willingness to recommend the plan to others, and reports of particularly negative or positive experiences. There were significant differences in experiences of CDHP enrollees versus enrollees in other plans with customer service and paperwork, but similar levels of satisfaction (on a 10-point scale) with health plans. Eight percent of CDHP enrollees left their plan after one year, compared to 5 percent of enrollees leaving other plans. A minority of CDHP enrollees used online plan features, but enrollees generally were satisfied with the amount and quality of the information provided by the CDHP. Almost half reported a particularly positive experience, compared to a quarter reporting a particularly negative experience. Thirty percent said they would recommend the plan to others, while an additional 57 percent said they would recommend it depending on the situation. Much more work is needed to determine how consumer experience varies with the number and type of plan options available, the design of the CDHP, and the length of time in the CDHP. Research also is needed on the factors that affect consumer decisions to leave CDHPs.

  15. BOW SHOCK FRAGMENTATION DRIVEN BY A THERMAL INSTABILITY IN LABORATORY ASTROPHYSICS EXPERIMENTS

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

    Suzuki-Vidal, F.; Lebedev, S. V.; Pickworth, L. A.

    The role of radiative cooling during the evolution of a bow shock was studied in laboratory-astrophysics experiments that are scalable to bow shocks present in jets from young stellar objects. The laboratory bow shock is formed during the collision of two counterstreaming, supersonic plasma jets produced by an opposing pair of radial foil Z-pinches driven by the current pulse from the MAGPIE pulsed-power generator. The jets have different flow velocities in the laboratory frame, and the experiments are driven over many times the characteristic cooling timescale. The initially smooth bow shock rapidly develops small-scale nonuniformities over temporal and spatial scalesmore » that are consistent with a thermal instability triggered by strong radiative cooling in the shock. The growth of these perturbations eventually results in a global fragmentation of the bow shock front. The formation of a thermal instability is supported by analysis of the plasma cooling function calculated for the experimental conditions with the radiative packages ABAKO/RAPCAL.« less

  16. MeV electron acceleration at 1kHz with <10 mJ laser pulses

    NASA Astrophysics Data System (ADS)

    Salehi, Fatholah; Goers, Andy; Hine, George; Feder, Linus; Kuk, Donghoon; Kim, Ki-Yong; Milchberg, Howard

    2016-10-01

    We demonstrate laser driven acceleration of electrons at 1 kHz repetition rate with pC charge above 1MeV per shot using < 10 mJ pulse energies focused on a near-critical density He or H2 gas jet. Using the H2 gas jet, electron acceleration to 0.5 MeV in 10 fC bunches was observed with laser pulse energy as low as 1.3mJ . Using a near-critical density gas jet sets the critical power required for relativistic self-focusing low enough for mJ scale laser pulses to self- focus and drive strong wakefields. Experiments and particle-in-cell simulations show that optimal drive pulse duration and chirp for maximum electron bunch charge and energy depends on the target gas species. High repetition rate, high charge, and short duration electron bunches driven by very modest pulse energies constitutes an ideal portable electron source for applications such as ultrafast electron diffraction experiments and high rep. rate γ-ray production. This work is supported by the US Department of Energy, the National Science Foundation, and the Air Force Office of Scientific Research.

  17. X-ray driven channeling acceleration in crystals and carbon nanotubes

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

    Shin, Young-Min; Still, Dean A.; Shiltsev, Vladimir

    2013-12-01

    Acceleration of particles channeling in a crystal by means of diffracted x-rays via Bormann anomalous transmission was conceived for heavy ions and muons by Tajima and Cavenago [Phys. Rev. Lett. 59, 1440 (1987)], which potentially offers an appreciably high field gradient on the order of GV/cm. The theoretical model of the high gradient acceleration has been studied in two kinds of atomic structure, crystals and carbon nanotubes (CNTs), with analytic calculations and electromagnetic eigenmode simulations. A range of acceleration gradients and cutoffs of the x-ray power (the lowest power limit to overcome the Bremsstrahlung radiation losses) are characterized in termsmore » of the lattice constants, unit cell sizes, and photon energies. The parametric analysis indicates that the required x-ray power can be reduced to an order of megawatt by replacing crystals with CNTs. Eventually, the equivalent dielectric approximation of a multi-wall nanotube shows that 250–810 MeV muons can be synchronously coupled with x-rays of 0.65–1.32 keV in the accelerating structure.« less

  18. Laser acceleration of quasi-monoenergetic MeV ion beams.

    PubMed

    Hegelich, B M; Albright, B J; Cobble, J; Flippo, K; Letzring, S; Paffett, M; Ruhl, H; Schreiber, J; Schulze, R K; Fernández, J C

    2006-01-26

    Acceleration of particles by intense laser-plasma interactions represents a rapidly evolving field of interest, as highlighted by the recent demonstration of laser-driven relativistic beams of monoenergetic electrons. Ultrahigh-intensity lasers can produce accelerating fields of 10 TV m(-1) (1 TV = 10(12) V), surpassing those in conventional accelerators by six orders of magnitude. Laser-driven ions with energies of several MeV per nucleon have also been produced. Such ion beams exhibit unprecedented characteristics--short pulse lengths, high currents and low transverse emittance--but their exponential energy spectra have almost 100% energy spread. This large energy spread, which is a consequence of the experimental conditions used to date, remains the biggest impediment to the wider use of this technology. Here we report the production of quasi-monoenergetic laser-driven C5+ ions with a vastly reduced energy spread of 17%. The ions have a mean energy of 3 MeV per nucleon (full-width at half-maximum approximately 0.5 MeV per nucleon) and a longitudinal emittance of less than 2 x 10(-6) eV s for pulse durations shorter than 1 ps. Such laser-driven, high-current, quasi-monoenergetic ion sources may enable significant advances in the development of compact MeV ion accelerators, new diagnostics, medical physics, inertial confinement fusion and fast ignition.

  19. Laser-Driven Ion Acceleration from Plasma Micro-Channel Targets

    PubMed Central

    Zou, D. B.; Pukhov, A.; Yi, L. Q.; Zhou, H. B.; Yu, T. P.; Yin, Y.; Shao, F. Q.

    2017-01-01

    Efficient energy boost of the laser-accelerated ions is critical for their applications in biomedical and hadron research. Achiev-able energies continue to rise, with currently highest energies, allowing access to medical therapy energy windows. Here, a new regime of simultaneous acceleration of ~100 MeV protons and multi-100 MeV carbon-ions from plasma micro-channel targets is proposed by using a ~1020 W/cm2 modest intensity laser pulse. It is found that two trains of overdense electron bunches are dragged out from the micro-channel and effectively accelerated by the longitudinal electric-field excited in the plasma channel. With the optimized channel size, these “superponderomotive” energetic electrons can be focused on the front surface of the attached plastic substrate. The much intense sheath electric-field is formed on the rear side, leading to up to ~10-fold ionic energy increase compared to the simple planar geometry. The analytical prediction of the optimal channel size and ion maximum energies is derived, which shows good agreement with the particle-in-cell simulations. PMID:28218247

  20. Laser-Driven Ion Acceleration from Plasma Micro-Channel Targets

    NASA Astrophysics Data System (ADS)

    Zou, D. B.; Pukhov, A.; Yi, L. Q.; Zhou, H. B.; Yu, T. P.; Yin, Y.; Shao, F. Q.

    2017-02-01

    Efficient energy boost of the laser-accelerated ions is critical for their applications in biomedical and hadron research. Achiev-able energies continue to rise, with currently highest energies, allowing access to medical therapy energy windows. Here, a new regime of simultaneous acceleration of ~100 MeV protons and multi-100 MeV carbon-ions from plasma micro-channel targets is proposed by using a ~1020 W/cm2 modest intensity laser pulse. It is found that two trains of overdense electron bunches are dragged out from the micro-channel and effectively accelerated by the longitudinal electric-field excited in the plasma channel. With the optimized channel size, these “superponderomotive” energetic electrons can be focused on the front surface of the attached plastic substrate. The much intense sheath electric-field is formed on the rear side, leading to up to ~10-fold ionic energy increase compared to the simple planar geometry. The analytical prediction of the optimal channel size and ion maximum energies is derived, which shows good agreement with the particle-in-cell simulations.

  1. Analyzing radial acceleration with a smartphone acceleration sensor

    NASA Astrophysics Data System (ADS)

    Vogt, Patrik; Kuhn, Jochen

    2013-03-01

    This paper continues the sequence of experiments using the acceleration sensor of smartphones (for description of the function and the use of the acceleration sensor, see Ref. 1) within this column, in this case for analyzing the radial acceleration.

  2. Shock tube Multiphase Experiments

    NASA Astrophysics Data System (ADS)

    Middlebrooks, John; Allen, Roy; Paudel, Manoj; Young, Calvin; Musick, Ben; McFarland, Jacob

    2017-11-01

    Shock driven multiphase instabilities (SDMI) are unique physical phenomena that have far-reaching practical applications in engineering and science. The instability is present in high energy explosions, scramjet combustors, and supernovae events. The SDMI arises when a multiphase interface is impulsively accelerated by the passage of a shockwave. It is similar in development to the Richtmyer-Meshkov (RM) instability however, particle-to-gas coupling is the driving mechanism of the SDMI. As particle effects such as lag and phase change become more prominent, the SDMI's development begins to significantly deviate from the RM instability. We have developed an experiment for studying the SDMI in our shock tube facility. In our experiments, a multiphase interface is created using a laminar jet and flowed into the shock tube where it is accelerated by the passage of a planar shockwave. The interface development is captured using CCD cameras synchronized with planar laser illumination. This talk will give an overview of new experiments conducted to examine the development of a shocked cylindrical multiphase interface. The effects of Atwood number, particle size, and a second acceleration (reshock) of the interface will be discussed.

  3. Laser-driven x-ray and neutron source development for industrial applications of plasma accelerators

    NASA Astrophysics Data System (ADS)

    Brenner, C. M.; Mirfayzi, S. R.; Rusby, D. R.; Armstrong, C.; Alejo, A.; Wilson, L. A.; Clarke, R.; Ahmed, H.; Butler, N. M. H.; Haddock, D.; Higginson, A.; McClymont, A.; Murphy, C.; Notley, M.; Oliver, P.; Allott, R.; Hernandez-Gomez, C.; Kar, S.; McKenna, P.; Neely, D.

    2016-01-01

    Pulsed beams of energetic x-rays and neutrons from intense laser interactions with solid foils are promising for applications where bright, small emission area sources, capable of multi-modal delivery are ideal. Possible end users of laser-driven multi-modal sources are those requiring advanced non-destructive inspection techniques in industry sectors of high value commerce such as aerospace, nuclear and advanced manufacturing. We report on experimental work that demonstrates multi-modal operation of high power laser-solid interactions for neutron and x-ray beam generation. Measurements and Monte Carlo radiation transport simulations show that neutron yield is increased by a factor ~2 when a 1 mm copper foil is placed behind a 2 mm lithium foil, compared to using a 2 cm block of lithium only. We explore x-ray generation with a 10 picosecond drive pulse in order to tailor the spectral content for radiography with medium density alloy metals. The impact of using  >1 ps pulse duration on laser-accelerated electron beam generation and transport is discussed alongside the optimisation of subsequent bremsstrahlung emission in thin, high atomic number target foils. X-ray spectra are deconvolved from spectrometer measurements and simulation data generated using the GEANT4 Monte Carlo code. We also demonstrate the unique capability of laser-driven x-rays in being able to deliver single pulse high spatial resolution projection imaging of thick metallic objects. Active detector radiographic imaging of industrially relevant sample objects with a 10 ps drive pulse is presented for the first time, demonstrating that features of 200 μm size are resolved when projected at high magnification.

  4. Status of intense permanent magnet proton source for China-accelerator driven sub-critical system Linac.

    PubMed

    Wu, Q; Ma, H Y; Yang, Y; Sun, L T; Zhang, X Z; Zhang, Z M; Zhao, H Y; He, Y; Zhao, H W

    2016-02-01

    Two compact intense 2.45 GHz permanent magnet proton sources and their corresponding low energy beam transport (LEBT) system were developed successfully for China accelerator driven sub-critical system in 2014. Both the proton sources operate at 35 kV potential. The beams extracted from the ion source are transported by the LEBT, which is composed of two identical solenoids, to the 2.1 MeV Radio-Frequency Quadrupole (RFQ). In order to ensure the safety of the superconducting cavities during commissioning, an electrostatic-chopper has been designed and installed in the LEBT line that can chop the continuous wave beam into a pulsed one. The minimum width of the pulse is less than 10 μs and the fall/rise time of the chopper is about 20 ns. The performance of the proton source and the LEBT, such as beam current, beam profile, emittance and the impact to RFQ injection will be presented.

  5. Status of intense permanent magnet proton source for China-accelerator driven sub-critical system Linac

    NASA Astrophysics Data System (ADS)

    Wu, Q.; Ma, H. Y.; Yang, Y.; Sun, L. T.; Zhang, X. Z.; Zhang, Z. M.; Zhao, H. Y.; He, Y.; Zhao, H. W.

    2016-02-01

    Two compact intense 2.45 GHz permanent magnet proton sources and their corresponding low energy beam transport (LEBT) system were developed successfully for China accelerator driven sub-critical system in 2014. Both the proton sources operate at 35 kV potential. The beams extracted from the ion source are transported by the LEBT, which is composed of two identical solenoids, to the 2.1 MeV Radio-Frequency Quadrupole (RFQ). In order to ensure the safety of the superconducting cavities during commissioning, an electrostatic-chopper has been designed and installed in the LEBT line that can chop the continuous wave beam into a pulsed one. The minimum width of the pulse is less than 10 μs and the fall/rise time of the chopper is about 20 ns. The performance of the proton source and the LEBT, such as beam current, beam profile, emittance and the impact to RFQ injection will be presented.

  6. Analyses of transients for an 800 MW-class accelerator driven transmuter with fertile-free fuels

    NASA Astrophysics Data System (ADS)

    Maschek, Werner; Suzuki, Tohru; Chen, Xue-Nong; Rineiski, Andrei; Matzerath Boccaccini, Claudia; Mori, Magnus; Morita, Koji

    2006-06-01

    In the FUTURE Program, the development and application of fertile-free fuels for Accelerator Driven Transmuters (ADTs) has been advanced. To assess the reactor performance and safety behavior of an ADT with so-called dedicated fuels, various transient cases for an 800 MW-class Pb/Bi-cooled ADT were investigated using the SIMMER-III code. The FUTURE ADT also served as vehicle to develop and test ideas on a safety concept for such transmuters. After an extensive ranking procedure, a CERCER fuel with an MgO matrix and a CERMET fuel with a Mo-92 matrix were chosen. The transient scenarios shown here are: spurious beam trip (BT), unprotected loss of flow (ULOF) and unprotected blockage accident (UBA). Since the release of fission gas and helium after cladding failure could induce a significant positive reactivity, the gas-blowdown was investigated for the transient scenarios. The present analyses showed that power excursions could be avoided by the fuel sweep-out from the core under severe accident conditions.

  7. Advanced Accelerator Development Strategy Report: DOE Advanced Accelerator Concepts Research Roadmap Workshop

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

    None, None

    Over a full two day period, February 2–3, 2016, the Office of High Energy Physics convened a workshop in Gaithersburg, MD to seek community input on development of an Advanced Accelerator Concepts (AAC) research roadmap. The workshop was in response to a recommendation by the HEPAP Accelerator R&D Subpanel [1] [2] to “convene the university and laboratory proponents of advanced acceleration concepts to develop R&D roadmaps with a series of milestones and common down selection criteria towards the goal for constructing a multi-TeV e+e– collider” (the charge to the workshop can be found in Appendix A). During the workshop, proponentsmore » of laser-driven plasma wakefield acceleration (LWFA), particle-beam-driven plasma wakefield acceleration (PWFA), and dielectric wakefield acceleration (DWFA), along with a limited number of invited university and laboratory experts, presented and critically discussed individual concept roadmaps. The roadmap workshop was preceded by several preparatory workshops. The first day of the workshop featured presentation of three initial individual roadmaps with ample time for discussion. The individual roadmaps covered a time period extending until roughly 2040, with the end date assumed to be roughly appropriate for initial operation of a multi-TeV e+e– collider. The second day of the workshop comprised talks on synergies between the roadmaps and with global efforts, potential early applications, diagnostics needs, simulation needs, and beam issues and challenges related to a collider. During the last half of the day the roadmaps were revisited but with emphasis on the next five to ten years (as specifically requested in the charge) and on common challenges. The workshop concluded with critical and unanimous endorsement of the individual roadmaps and an extended discussion on the characteristics of the common challenges. (For the agenda and list of participants see Appendix B.)« less

  8. High power ring methods and accelerator driven subcritical reactor application

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

    Tahar, Malek Haj

    2016-08-07

    High power proton accelerators allow providing, by spallation reaction, the neutron fluxes necessary in the synthesis of fissile material, starting from Uranium 238 or Thorium 232. This is the basis of the concept of sub-critical operation of a reactor, for energy production or nuclear waste transmutation, with the objective of achieving cleaner, safer and more efficient process than today’s technologies allow. Designing, building and operating a proton accelerator in the 500-1000 MeV energy range, CW regime, MW power class still remains a challenge nowadays. There is a limited number of installations at present achieving beam characteristics in that class, e.g.,more » PSI in Villigen, 590 MeV CW beam from a cyclotron, SNS in Oakland, 1 GeV pulsed beam from a linear accelerator, in addition to projects as the ESS in Europe, a 5 MW beam from a linear accelerator. Furthermore, coupling an accelerator to a sub-critical nuclear reactor is a challenging proposition: some of the key issues/requirements are the design of a spallation target to withstand high power densities as well as ensure the safety of the installation. These two domains are the grounds of the PhD work: the focus is on the high power ring methods in the frame of the KURRI FFAG collaboration in Japan: upgrade of the installation towards high intensity is crucial to demonstrate the high beam power capability of FFAG. Thus, modeling of the beam dynamics and benchmarking of different codes was undertaken to validate the simulation results. Experimental results revealed some major losses that need to be understood and eventually overcome. By developing analytical models that account for the field defects, one identified major sources of imperfection in the design of scaling FFAG that explain the important tune variations resulting in the crossing of several betatron resonances. A new formula is derived to compute the tunes and properties established that characterize the effect of the field

  9. The Experimental Study of Rayleigh-Taylor Instability using a Linear Induction Motor Accelerator

    NASA Astrophysics Data System (ADS)

    Yamashita, Nicholas; Jacobs, Jeffrey

    2009-11-01

    The experiments to be presented utilize an incompressible system of two stratified miscible liquids of different densities that are accelerated in order to produce the Rayleigh-Taylor instability. Three liquid combinations are used: isopropyl alcohol with water, a calcium nitrate solution or a lithium polytungstate solution, giving Atwood numbers of 0.11, 0.22 and 0.57, respectively. The acceleration required to drive the instability is produced by two high-speed linear induction motors mounted to an 8 m tall drop tower. The motors are mounted in parallel and have an effective acceleration length of 1.7 m and are each capable of producing 15 kN of thrust. The liquid system is contained within a square acrylic tank with inside dimensions 76 x76x184 mm. The tank is mounted to an aluminum plate, which is driven by the motors to create constant accelerations in the range of 1-20 g's, though the potential exists for higher accelerations. Also attached to the plate are a high-speed camera and an LED backlight to provide continuous video of the instability. In addition, an accelerometer is used to provide acceleration measurements during each experiment. Experimental image sequences will be presented which show the development of a random three-dimensional instability from an unforced initial perturbation. Measurements of the mixing zone width will be compared with traditional growth models.

  10. Modeling pressure-driven assembly of polymer coated nanoparticles

    NASA Astrophysics Data System (ADS)

    Lane, J. Matthew D.; Salerno, K. Michael; Grest, Gary S.; Fan, Hongyou

    2017-06-01

    High-pressure experiments have successfully produced a variety of gold nanostructures by compressing polymer coated spherical nanoparticles. We apply atomistic simulation to understand the role of the soft polymer response in determining the pressure-driven assembly of gold nanostructures. Quasi-isentropic experiments have shown that 1D, 2D and 3D nanostructures can be formed and recovered from dynamic compression of fcc superlattices of alkanethiol-coated gold nanocrystals on Sandia's Veloce pulsed power accelerator. Molecular modeling has shown that the dimensionality of the final structures depends on the orientation of the superlattice and the uniaxial loading. We describe the role of coating ligand length and grafting density, on ligand migration and deformation processes during pressure-driven coalescence of the cores into permanent nanowires, nanosheets and 3D structures. The role of uniaxial vs isotropic pressure and the effects of compression along various superlattice orientations will be discussed. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  11. Accelerated Aging Experiments for Capacitor Health Monitoring and Prognostics

    NASA Technical Reports Server (NTRS)

    Kulkarni, Chetan S.; Celaya, Jose Ramon; Biswas, Gautam; Goebel, Kai

    2012-01-01

    This paper discusses experimental setups for health monitoring and prognostics of electrolytic capacitors under nominal operation and accelerated aging conditions. Electrolytic capacitors have higher failure rates than other components in electronic systems like power drives, power converters etc. Our current work focuses on developing first-principles-based degradation models for electrolytic capacitors under varying electrical and thermal stress conditions. Prognostics and health management for electronic systems aims to predict the onset of faults, study causes for system degradation, and accurately compute remaining useful life. Accelerated life test methods are often used in prognostics research as a way to model multiple causes and assess the effects of the degradation process through time. It also allows for the identification and study of different failure mechanisms and their relationships under different operating conditions. Experiments are designed for aging of the capacitors such that the degradation pattern induced by the aging can be monitored and analyzed. Experimental setups and data collection methods are presented to demonstrate this approach.

  12. Reduction of beam corkscrew motion on the ETAII linear induction accelerator

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

    Turner, W.C.; Allen, S.L.; Brand, H.R.

    1990-09-04

    The ETAII linear induction accelerator (6MeV, 3kA, 70ns) is designed to drive a microwave free electron laser (FEL) and demonstrate the front end accelerator technology for a shorter wavelength FEL. Performance to date has been limited by beam corkscrew motion that is driven by energy sweep and misalignment of the solenoidal focusing magnets. Modifications to the pulse power distribution system and magnetic alignment are expected to reduce the radius of corkscrew motion from its present value of 1 cm to less than 1 mm. The modifications have so far been carried out on the first 2.7 MeV (injector plus 20more » accelerator cells) and experiments are beginning. In this paper we will present calculations of central flux line alignment, beam corkscrew motion and beam brightness that are anticipated with the modified ETAII. 10 refs., 4 figs., 1 tab.« less

  13. ACCELERATION INTEGRATOR

    DOEpatents

    Pope, K.E.

    1958-01-01

    This patent relates to an improved acceleration integrator and more particularly to apparatus of this nature which is gyrostabilized. The device may be used to sense the attainment by an airborne vehicle of a predetermined velocitv or distance along a given vector path. In its broad aspects, the acceleration integrator utilizes a magnetized element rotatable driven by a synchronous motor and having a cylin drical flux gap and a restrained eddy- current drag cap deposed to move into the gap. The angular velocity imparted to the rotatable cap shaft is transmitted in a positive manner to the magnetized element through a servo feedback loop. The resultant angular velocity of tae cap is proportional to the acceleration of the housing in this manner and means may be used to measure the velocity and operate switches at a pre-set magnitude. To make the above-described dcvice sensitive to acceleration in only one direction the magnetized element forms the spinning inertia element of a free gyroscope, and the outer housing functions as a gimbal of a gyroscope.

  14. Accelerated model of lupus autoimmunity and vasculopathy driven by toll-like receptor 7/9 imbalance.

    PubMed

    Liu, Yudong; Seto, Nickie L; Carmona-Rivera, Carmelo; Kaplan, Mariana J

    2018-01-01

    Activation of endosomal toll-like receptor (TLR)7 or TLR9 has been proposed as a critical step for the initiation and development of SLE. Traditional spontaneous lupus models normally introduce multiple risk alleles, thereby adding additional confounding factors. In the induced lupus models, the role of TLR9 remains unclear. In the present study, we explored the role of an imbalance between TLR7 and TLR9 pathways in the pathogenesis of lupus and its associated vasculopathy using the imiquimod model in TLR9 KO/B6 background. Wild type (WT) and Tlr9 -/- mice were epicutaneously treated with imiquimod cream 5% on both ears three times per week for indicated times. At euthanasia, mice were analysed for organ involvement, endothelium-dependent vasorelaxation, serum autoantibodies, and innate and adaptive immune responses. Compared with the lupus-like phenotype that develops in imiquimod-treated WT mice, Tlr9 -/- mice exposed to imiquimod have increased severity of autoimmunity features and inflammatory phenotype that develops at earlier stages. These abnormalities are characterised by enhanced TLR7 expression and immune activation, increased immune complex deposition, Th1 T cells and dendritic cell kidney infiltration and significant impairments in endothelial function. Modulation of TLR7 expression was observed in the Tlr9 -/- mice. These findings further underscore the protective role of TLR9 in TLR7-driven autoimmunity and also in the development of vasculopathy, further strengthening the importance of tightly manipulating TLRs in putative therapeutic strategies. This study provides a new model of accelerated lupus phenotype driven by danger-associated molecular patterns.

  15. Erosion measurement techniques for plasma-driven railgun barrels

    NASA Astrophysics Data System (ADS)

    Jamison, K. A.; Niiler, Andrus

    1987-04-01

    Plasma-driven railguns are now in operation at several locations throughout the world. All share common problems in barrel erosion arising from the fact that the bore surface must contain a high temperature plasma armature which transmits the acceleration force to a projectile. The plasma temperature at the core of the armature is estimated to be 30 000 K or higher. Such conditions are erosive to most materials even when the exposure time is 100 μs or less. We have adapted two accelerator based techniques to aid in the study of this erosion. The first technique involves the collection and analysis of material ablated and left behind by the plasma. This analysis is based on the unfolding of the Rutherford backscattered (RBS) spectra of 1 MeV deuterons incident on residue collected from a railgun bore. The second technique is an erosion measurement involving thin layer activation (TLA) of surfaces. In this process, the copper rail surface is activated by 2.4 MeV protons creating a relatively thin (3 m) layer sparsely seeded with a long lived zinc isotope. Monitoring the decay of the activated sample before and after a firing can detect surface wear of about 0. 1 m. Results from the RBS and TLA experiments on the BRL plasma driven railgun are described.

  16. Accelerator Reactor Coupling for Energy Production in Advanced Nuclear Fuel Cycles

    DOE PAGES

    Brown, Nicholas R.; Heidet, Florent; Haj Tahar, Malek

    2016-01-01

    This article is a review of several accelerator–reactor interface issues and nuclear fuel cycle applications of acceleratordriven subcritical systems. The systems considered here have the primary goal of energy production, but that goal is accomplished via a specific application in various proposed nuclear fuel cycles, such as breed-and-burn of fertile material or burning of transuranic material. Several basic principles are reviewed, starting from the proton beam window including the target, blanket, reactor core, and up to the fuel cycle. We focus on issues of interest, such as the impact of the energy required to run the accelerator and associated systemsmore » on the potential electricity delivered to the grid. Accelerator-driven systems feature many of the constraints and issues associated with critical reactors, with the added challenges of subcritical operation and coupling to an accelerator. Reliable accelerator operation and avoidance of beam trips are critically important. One interesting challenge is measurement of blanket subcriticality level during operation. We also review the potential benefits of accelerator-driven systems in various nuclear fuel cycle applications. Ultimately, accelerator-driven subcritical systems with the goal of transmutation of transuranic material have lower 100,000-year radioactivity than a critical fast reactor with recycling of uranium and plutonium.« less

  17. Adult Learners' Experiences in Accelerated Degree-Completion Programs at Christian Colleges: Transactions and Transformations

    ERIC Educational Resources Information Center

    Decker, Allyn

    2017-01-01

    The aim of this qualitative study was to investigate the lived experiences of adult learners at 4 Christian colleges in Indiana who desired to pursue bachelor and associate degrees in accelerated programs. The growing trend of accelerated programming exists to meet the needs of a growing number of adults who believe that earning an academic…

  18. Evolution of sausage and helical modes in magnetized thin-foil cylindrical liners driven by a Z-pinch

    NASA Astrophysics Data System (ADS)

    Yager-Elorriaga, D. A.; Lau, Y. Y.; Zhang, P.; Campbell, P. C.; Steiner, A. M.; Jordan, N. M.; McBride, R. D.; Gilgenbach, R. M.

    2018-05-01

    In this paper, we present experimental results on axially magnetized (Bz = 0.5 - 2.0 T), thin-foil (400 nm-thick) cylindrical liner-plasmas driven with ˜600 kA by the Michigan Accelerator for Inductive Z-Pinch Experiments, which is a linear transformer driver at the University of Michigan. We show that: (1) the applied axial magnetic field, irrespective of its direction (e.g., parallel or anti-parallel to the flow of current), reduces the instability amplitude for pure magnetohydrodynamic (MHD) modes [defined as modes devoid of the acceleration-driven magneto-Rayleigh-Taylor (MRT) instability]; (2) axially magnetized, imploding liners (where MHD modes couple to MRT) generate m = 1 or m = 2 helical modes that persist from the implosion to the subsequent explosion stage; (3) the merging of instability structures is a mechanism that enables the appearance of an exponential instability growth rate for a longer than expected time-period; and (4) an inverse cascade in both the axial and azimuthal wavenumbers, k and m, may be responsible for the final m = 2 helical structure observed in our experiments. These experiments are particularly relevant to the magnetized liner inertial fusion program pursued at Sandia National Laboratories, where helical instabilities have been observed.

  19. Rarefaction-driven Rayleigh–Taylor instability. Part 2. Experiments and simulations in the nonlinear regime

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

    Morgan, R. V.; Cabot, W. H.; Greenough, J. A.

    Experiments and large eddy simulation (LES) were performed to study the development of the Rayleigh–Taylor instability into the saturated, nonlinear regime, produced between two gases accelerated by a rarefaction wave. Single-mode two-dimensional, and single-mode three-dimensional initial perturbations were introduced on the diffuse interface between the two gases prior to acceleration. The rarefaction wave imparts a non-constant acceleration, and a time decreasing Atwood number,more » $$A=(\\unicode[STIX]{x1D70C}_{2}-\\unicode[STIX]{x1D70C}_{1})/(\\unicode[STIX]{x1D70C}_{2}+\\unicode[STIX]{x1D70C}_{1})$$, where$$\\unicode[STIX]{x1D70C}_{2}$$and$$\\unicode[STIX]{x1D70C}_{1}$$are the densities of the heavy and light gas, respectively. Experiments and simulations are presented for initial Atwood numbers of$A=0.49$$,$$A=0.63$$,$$A=0.82$$and$$A=0.94$$. Nominally two-dimensional (2-D) experiments (initiated with nearly 2-D perturbations) and 2-D simulations are observed to approach an intermediate-time velocity plateau that is in disagreement with the late-time velocity obtained from the incompressible model of Goncharov (Phys. Rev. Lett., vol. 88, 2002, 134502). Reacceleration from an intermediate velocity is observed for 2-D bubbles in large wavenumber,$$k=2\\unicode[STIX]{x03C0}/\\unicode[STIX]{x1D706}=0.247~\\text{mm}^{-1}$$, experiments and simulations, where$$\\unicode[STIX]{x1D706}$is the wavelength of the initial perturbation. At moderate Atwood numbers, the bubble and spike velocities approach larger values than those predicted by Goncharov’s model. These late-time velocity trends are predicted well by numerical simulations using the LLNL Miranda code, and by the 2009 model of Mikaelian (Phys. Fluids., vol. 21, 2009, 024103) that extends Layzer type models to variable acceleration and density. Large Atwood number experiments show a delayed roll up, and exhibit a free-fall like behaviour. Finally, experiments initiated with three

  20. Rarefaction-driven Rayleigh–Taylor instability. Part 2. Experiments and simulations in the nonlinear regime

    DOE PAGES

    Morgan, R. V.; Cabot, W. H.; Greenough, J. A.; ...

    2018-01-12

    Experiments and large eddy simulation (LES) were performed to study the development of the Rayleigh–Taylor instability into the saturated, nonlinear regime, produced between two gases accelerated by a rarefaction wave. Single-mode two-dimensional, and single-mode three-dimensional initial perturbations were introduced on the diffuse interface between the two gases prior to acceleration. The rarefaction wave imparts a non-constant acceleration, and a time decreasing Atwood number,more » $$A=(\\unicode[STIX]{x1D70C}_{2}-\\unicode[STIX]{x1D70C}_{1})/(\\unicode[STIX]{x1D70C}_{2}+\\unicode[STIX]{x1D70C}_{1})$$, where$$\\unicode[STIX]{x1D70C}_{2}$$and$$\\unicode[STIX]{x1D70C}_{1}$$are the densities of the heavy and light gas, respectively. Experiments and simulations are presented for initial Atwood numbers of$A=0.49$$,$$A=0.63$$,$$A=0.82$$and$$A=0.94$$. Nominally two-dimensional (2-D) experiments (initiated with nearly 2-D perturbations) and 2-D simulations are observed to approach an intermediate-time velocity plateau that is in disagreement with the late-time velocity obtained from the incompressible model of Goncharov (Phys. Rev. Lett., vol. 88, 2002, 134502). Reacceleration from an intermediate velocity is observed for 2-D bubbles in large wavenumber,$$k=2\\unicode[STIX]{x03C0}/\\unicode[STIX]{x1D706}=0.247~\\text{mm}^{-1}$$, experiments and simulations, where$$\\unicode[STIX]{x1D706}$is the wavelength of the initial perturbation. At moderate Atwood numbers, the bubble and spike velocities approach larger values than those predicted by Goncharov’s model. These late-time velocity trends are predicted well by numerical simulations using the LLNL Miranda code, and by the 2009 model of Mikaelian (Phys. Fluids., vol. 21, 2009, 024103) that extends Layzer type models to variable acceleration and density. Large Atwood number experiments show a delayed roll up, and exhibit a free-fall like behaviour. Finally, experiments initiated with three

  1. Operational Characteristics of an Accelerator Driven Fissile Solution System

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

    Kimpland, Robert Herbert

    Operational characteristics represent the set of responses that a nuclear system exhibits during normal operation. Operators rely on this behavior to assess the status of the system and to predict the consequences of off-normal events. These characteristics largely refer to the relationship between power and system operating conditions. The static and dynamic behavior of a chain-reacting system, operating at sufficient power, is primarily governed by reactivity effects. The science of reactor physics has identified and evaluated a number of such effects, including Doppler broadening and shifts in the thermal neutron spectrum. Often these reactivity effects are quantified in the formmore » of feedback coefficients that serve as coupling coefficients relating the neutron population and the physical mechanisms that drive reactivity effects, such as fissile material temperature and density changes. The operational characteristics of such nuclear systems usually manifest themselves when perturbations between system power (neutron population) and system operating conditions arise. Successful operation of such systems requires the establishment of steady equilibrium conditions. However, prior to obtaining the desired equilibrium (steady-state) conditions, an approach from zero-power (startup) must occur. This operational regime may possess certain limiting system conditions that must be maintained to achieve effective startup. Once steady-state is achieved, a key characteristic of this operational regime is the level of stability that the system possesses. Finally, a third operational regime, shutdown, may also possess limiting conditions of operation that must be maintained. This report documents the operational characteristics of a “generic” Accelerator Driven Fissile Solution (ADFS) system during the various operational regimes of startup, steady-state operation, and shutdown. Typical time-dependent behavior for each operational regime will be illustrated, and

  2. Laser-driven electron beam and radiation sources for basic, medical and industrial sciences

    PubMed Central

    NAKAJIMA, Kazuhisa

    2015-01-01

    To date active research on laser-driven plasma-based accelerators have achieved great progress on production of high-energy, high-quality electron and photon beams in a compact scale. Such laser plasma accelerators have been envisaged bringing a wide range of applications in basic, medical and industrial sciences. Here inheriting the groundbreaker’s review article on “Laser Acceleration and its future” [Toshiki Tajima, (2010)],1) we would like to review recent progress of producing such electron beams due to relativistic laser-plasma interactions followed by laser wakefield acceleration and lead to the scaling formulas that are useful to design laser plasma accelerators with controllability of beam energy and charge. Lastly specific examples of such laser-driven electron/photon beam sources are illustrated. PMID:26062737

  3. Laser-driven electron beam and radiation sources for basic, medical and industrial sciences.

    PubMed

    Nakajima, Kazuhisa

    2015-01-01

    To date active research on laser-driven plasma-based accelerators have achieved great progress on production of high-energy, high-quality electron and photon beams in a compact scale. Such laser plasma accelerators have been envisaged bringing a wide range of applications in basic, medical and industrial sciences. Here inheriting the groundbreaker's review article on "Laser Acceleration and its future" [Toshiki Tajima, (2010)],(1)) we would like to review recent progress of producing such electron beams due to relativistic laser-plasma interactions followed by laser wakefield acceleration and lead to the scaling formulas that are useful to design laser plasma accelerators with controllability of beam energy and charge. Lastly specific examples of such laser-driven electron/photon beam sources are illustrated.

  4. Emittance Growth in the DARHT-II Linear Induction Accelerator

    DOE PAGES

    Ekdahl, Carl; Carlson, Carl A.; Frayer, Daniel K.; ...

    2017-10-03

    The dual-axis radiographic hydrodynamic test (DARHT) facility uses bremsstrahlung radiation source spots produced by the focused electron beams from two linear induction accelerators (LIAs) to radiograph large hydrodynamic experiments driven by high explosives. Radiographic resolution is determined by the size of the source spot, and beam emittance is the ultimate limitation to spot size. On the DARHT-II LIA, we measure an emittance higher than predicted by theoretical simulations, and even though this accelerator produces submillimeter source spots, we are exploring ways to improve the emittance. Some of the possible causes for the discrepancy have been investigated using particle-in-cell codes. Finally,more » the simulations establish that the most likely source of emittance growth is a mismatch of the beam to the magnetic transport, which can cause beam halo.« less

  5. Emittance Growth in the DARHT-II Linear Induction Accelerator

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

    Ekdahl, Carl; Carlson, Carl A.; Frayer, Daniel K.

    The dual-axis radiographic hydrodynamic test (DARHT) facility uses bremsstrahlung radiation source spots produced by the focused electron beams from two linear induction accelerators (LIAs) to radiograph large hydrodynamic experiments driven by high explosives. Radiographic resolution is determined by the size of the source spot, and beam emittance is the ultimate limitation to spot size. On the DARHT-II LIA, we measure an emittance higher than predicted by theoretical simulations, and even though this accelerator produces submillimeter source spots, we are exploring ways to improve the emittance. Some of the possible causes for the discrepancy have been investigated using particle-in-cell codes. Finally,more » the simulations establish that the most likely source of emittance growth is a mismatch of the beam to the magnetic transport, which can cause beam halo.« less

  6. Cancellation of residual spacecraft accelerations for zero-G space physics experiments

    NASA Technical Reports Server (NTRS)

    Stephens, J. B.

    1977-01-01

    The Drop Dynamics Module houses an acoustic positioning system which counteracts the effects of small accelerations of a spacecraft and thus allows long-term study of free-floating materials such as liquid drops. The acoustic positioning system provides an acoustic 'well' in the center of the experiment chamber. Data collection is by cinematographic photography. The module subsystems are discussed.

  7. Material processing of convection-driven flow field and temperature distribution under oblique gravity

    NASA Technical Reports Server (NTRS)

    Hung, R. J.

    1995-01-01

    A set of mathematical formulation is adopted to study vapor deposition from source materials driven by heat transfer process under normal and oblique directions of gravitational acceleration with extremely low pressure environment of 10(exp -2) mm Hg. A series of time animation of the initiation and development of flow and temperature profiles during the course of vapor deposition has been obtained through the numerical computation. Computations show that the process of vapor deposition has been accomplished by the transfer of vapor through a fairly complicated flow pattern of recirculation under normal direction gravitational acceleration. It is obvious that there is no way to produce a homogeneous thin crystalline films with fine grains under such a complicated flow pattern of recirculation with a non-uniform temperature distribution under normal direction gravitational acceleration. There is no vapor deposition due to a stably stratified medium without convection for reverse normal direction gravitational acceleration. Vapor deposition under oblique direction gravitational acceleration introduces a reduced gravitational acceleration in vertical direction which is favorable to produce a homogeneous thin crystalline films. However, oblique direction gravitational acceleration also induces an unfavorable gravitational acceleration along horizontal direction which is responsible to initiate a complicated flow pattern of recirculation. In other words, it is necessary to carry out vapor deposition under a reduced gravity in the future space shuttle experiments with extremely low pressure environment to process vapor deposition with a homogeneous crystalline films with fine grains. Fluid mechanics simulation can be used as a tool to suggest most optimistic way of experiment with best setup to achieve the goal of processing best nonlinear optical materials.

  8. Optimal moderator materials at various proton energies considering photon dose rate after irradiation for an accelerator-driven ⁹Be(p, n) boron neutron capture therapy neutron source.

    PubMed

    Hashimoto, Y; Hiraga, F; Kiyanagi, Y

    2015-12-01

    We evaluated the accelerator beam power and the neutron-induced radioactivity of (9)Be(p, n) boron neutron capture therapy (BNCT) neutron sources having a MgF2, CaF2, or AlF3 moderator and driven by protons with energy from 8 MeV to 30 MeV. The optimal moderator materials were found to be MgF2 for proton energies less than 10 MeV because of lower required accelerator beam power and CaF2 for higher proton energies because of lower photon dose rate at the treatment position after neutron irradiation. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. The Gift of Time: Today's Academic Acceleration Case Study Voices of Experience

    ERIC Educational Resources Information Center

    Scheibel, Susan Riley

    2010-01-01

    The purpose of this qualitative case study was to examine today's academic acceleration from the lived experience and perspectives of two young adults whose education was shortened, thereby allowing them the gift of time. Through personal interviews, parent interviews, and physical artifacts, the researcher gained a complex, holistic understanding…

  10. Laser-driven Ion Acceleration using Nanodiamonds

    NASA Astrophysics Data System (ADS)

    D'Hauthuille, Luc; Nguyen, Tam; Dollar, Franklin

    2016-10-01

    Interactions of high-intensity lasers with mass-limited nanoparticles enable the generation of extremely high electric fields. These fields accelerate ions, which has applications in nuclear medicine, high brightness radiography, as well as fast ignition for inertial confinement fusion. Previous studies have been performed with ensembles of nanoparticles, but this obscures the physics of the interaction due to the wide array of variables in the interaction. The work presented here looks instead at the interactions of a high intensity short pulse laser with an isolated nanodiamond. Specifically, we studied the effect of nanoparticle size and intensity of the laser on the interaction. A novel target scheme was developed to isolate the nanodiamond. Particle-in-cell simulations were performed using the EPOCH framework to show the sheath fields and resulting energetic ion beams.

  11. Generation of ultra-high-pressure shocks by collision of a fast plasma projectile driven in the laser-induced cavity pressure acceleration scheme with a solid target

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

    Badziak, J.; Rosiński, M.; Krousky, E.

    2015-03-15

    A novel, efficient method of generating ultra-high-pressure shocks is proposed and investigated. In this method, the shock is generated by collision of a fast plasma projectile (a macro-particle) driven by laser-induced cavity pressure acceleration (LICPA) with a solid target placed at the LICPA accelerator channel exit. Using the measurements performed at the kilojoule PALS laser facility and two-dimensional hydrodynamic simulations, it is shown that the shock pressure ∼ Gbar can be produced with this method at the laser driver energy of only a few hundred joules, by an order of magnitude lower than the energy needed for production of suchmore » pressure with other laser-based methods known so far.« less

  12. CFD Analysis and Design of Detailed Target Configurations for an Accelerator-Driven Subcritical System

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

    Kraus, Adam; Merzari, Elia; Sofu, Tanju

    2016-08-01

    High-fidelity analysis has been utilized in the design of beam target options for an accelerator driven subcritical system. Designs featuring stacks of plates with square cross section have been investigated for both tungsten and uranium target materials. The presented work includes the first thermal-hydraulic simulations of the full, detailed target geometry. The innovative target cooling manifold design features many regions with complex flow features, including 90 bends and merging jets, which necessitate three-dimensional fluid simulations. These were performed using the commercial computational fluid dynamics code STAR-CCM+. Conjugate heat transfer was modeled between the plates, cladding, manifold structure, and fluid. Steady-statemore » simulations were performed but lacked good residual convergence. Unsteady simulations were then performed, which converged well and demonstrated that flow instability existed in the lower portion of the manifold. It was established that the flow instability had little effect on the peak plate temperatures, which were well below the melting point. The estimated plate surface temperatures and target region pressure were shown to provide sufficient margin to subcooled boiling for standard operating conditions. This demonstrated the safety of both potential target configurations during normal operation.« less

  13. An investigation into the effectiveness of smartphone experiments on students’ conceptual knowledge about acceleration

    NASA Astrophysics Data System (ADS)

    Mazzella, Alessandra; Testa, Italo

    2016-09-01

    This study is a first attempt to investigate effectiveness of smartphone-based activities on students’ conceptual understanding of acceleration. 143 secondary school students (15-16 years old) were involved in two types of activities: smartphone- and non-smartphone activities. The latter consisted in data logging and ‘cookbook’ activities. For the sake of comparison, all activities featured the same phenomena, i.e., the motion on an inclined plane and pendulum oscillations. A pre-post design was adopted, using open questionnaires as probes. Results show only weak statistical differences between the smartphone and non-smartphone groups. Students who followed smartphone activities were more able to design an experiment to measure acceleration and to correctly describe acceleration in a free fall motion. However, students of both groups had many difficulties in drawing acceleration vector along the trajectory of the studied motion. Results suggest that smartphone-based activities may be effective substitutes of traditional experimental settings and represent a valuable aid for teachers who want to implement laboratory activities at secondary school level. However, to achieve a deeper conceptual understanding of acceleration, some issues need to be addressed: what is the reference system of the built-in smartphone sensor; relationships between smartphone acceleration graphs and experimental setup; vector representation of the measured acceleration.

  14. Accelerated model of lupus autoimmunity and vasculopathy driven by toll-like receptor 7/9 imbalance

    PubMed Central

    Liu, Yudong; Seto, Nickie L; Carmona-Rivera, Carmelo; Kaplan, Mariana J

    2018-01-01

    Objectives Activation of endosomal toll-like receptor (TLR)7 or TLR9 has been proposed as a critical step for the initiation and development of SLE. Traditional spontaneous lupus models normally introduce multiple risk alleles, thereby adding additional confounding factors. In the induced lupus models, the role of TLR9 remains unclear. In the present study, we explored the role of an imbalance between TLR7 and TLR9 pathways in the pathogenesis of lupus and its associated vasculopathy using the imiquimod model in TLR9 KO/B6 background. Methods Wild type (WT) and Tlr9-/- mice were epicutaneously treated with imiquimod cream 5% on both ears three times per week for indicated times. At euthanasia, mice were analysed for organ involvement, endothelium-dependent vasorelaxation, serum autoantibodies, and innate and adaptive immune responses. Results Compared with the lupus-like phenotype that develops in imiquimod-treated WT mice, Tlr9-/- mice exposed to imiquimod have increased severity of autoimmunity features and inflammatory phenotype that develops at earlier stages. These abnormalities are characterised by enhanced TLR7 expression and immune activation, increased immune complex deposition, Th1 T cells and dendritic cell kidney infiltration and significant impairments in endothelial function. Modulation of TLR7 expression was observed in the Tlr9-/- mice. Conclusions These findings further underscore the protective role of TLR9 in TLR7-driven autoimmunity and also in the development of vasculopathy, further strengthening the importance of tightly manipulating TLRs in putative therapeutic strategies. This study provides a new model of accelerated lupus phenotype driven by danger-associated molecular patterns. PMID:29765617

  15. 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

  16. Effects of Initial Conditions on Shock Driven Flows

    NASA Astrophysics Data System (ADS)

    Martinez, Adam A.; Mula, Swathi M.; Charonko, John; Prestridge, Kathy

    2017-11-01

    The spatial and temporal evolution of shock-driven, variable density flows, such as the Richtmyer Meshkov (RM) instability, are strongly influenced by the initial conditions (IC's) of the flow at the time of interaction with shockwave. We study the effects of the IC's on the Vertical Shock Tube (VST) and on flows from Mach =1.2 to Mach =9. Experiments at the VST are of an Air-SF6 (At =0.6) multimode interface. Perturbations are generated using a shear layer with a flapper plate. Planar Laser Induced Fluorescence (PLIF) is used to characterize the IC's. New experiments are occurring using the Powder Gun driver at LANL Proton Radiography (pRad) facility. Mach number up to M =9 accelerate a Xenon-Helium (At =0.94) interface that is perturbed using a membrane supported by different sized grids. This presentation focuses on how to design and characterize different types of initial conditions for experiments.

  17. Ablative Rayleigh-Taylor and Richtmyer-Meshkov Instabilities in Laser-Accelerated Colliding Foils

    NASA Astrophysics Data System (ADS)

    Aglitskiy, Y.; Metzler, N.; Karasik, M.; Serlin, V.; Weaver, J.; Obenschain, S. P.; Oh, J.; Schmitt, A. J.; Velikovich, A. L.; Zalesak, S. T.; Gardner, J. H.; Harding, E. C.

    2008-11-01

    In our experiments done on the Nike KrF laser, we study instability growth at shock-decelerated interfaces in planar colliding-foil experiments. We use streaked monochromatic (1.86 keV) x-ray face-on imaging diagnostics to measure the areal mass modulation growth caused by the instability. Higher x-ray energies up to 5.25 keV are used to follow the shock propagation as well as the 1D dynamics of the collision. While a laser-driven foil is accelerated towards the stationary low-density foam layer, an ablative RT instability develops. Having reached a high velocity, the foil hits the foam layer. The impact generates strong shocks in the plastic and in the foam. The reflected shock wave re-shocks the ablation front, its acceleration stops, and so does the observed RT growth. This is followed by areal mass oscillations due to the ablative RM instability and feedout mechanisms, of which the latter dominates.

  18. Rail accelerators for space transportation: An experimental investigation

    NASA Technical Reports Server (NTRS)

    Zana, L. M.; Kerslake, W. R.; Sturman, J. L.

    1986-01-01

    An experimental program was conducted at the Lewis Research Center with the objective of investigating the technical feasibility of rail accelerators for propulsion applications. Single-stage, plasma driven rail accelerators of small (4 by 6 mm) and medium (12.5 by 12.5 mm) bores were tested at peak accelerating currents of 50 to 450 kA. Streak-camera photography was used to provide a qualitative description of plasma armature acceleration. The effects of plasma blowby and varying bore pressure on the behavior of plasma armatures were studied.

  19. Laser Wakefield Acceleration: Structural and Dynamic Studies. Final Technical Report ER40954

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

    Downer, Michael C.

    2014-04-30

    is 10-15 seconds) in duration and 150 Joules in energy (equivalent to the muzzle energy of a small pistol bullet). This duration was well matched to the natural electron density oscillation period of plasma of 1/100 atmospheric density, enabling efficient excitation of a plasma wake, while this energy was sufficient to drive a high-amplitude wake of the right shape to produce an energetic, collimated electron beam. Continuing research is aimed at increasing electron energy even further, increasing the number of electrons captured and accelerated, and developing applications of the compact, multi-GeV accelerator as a coherent, hard x-ray source for materials science, biomedical imaging and homeland security applications. The second major advance under this project was to develop new methods of visualizing the laser-driven plasma wake structures that underlie laser-plasma accelerators. Visualizing these structures is essential to understanding, optimizing and scaling laser-plasma accelerators. Yet prior to work under this project, computer simulations based on estimated initial conditions were the sole source of detailed knowledge of the complex, evolving internal structure of laser-driven plasma wakes. In this project we developed and demonstrated a suite of optical visualization methods based on well-known methods such as holography, streak cameras, and coherence tomography, but adapted to the ultrafast, light-speed, microscopic world of laser-driven plasma wakes. Our methods output images of laser-driven plasma structures in a single laser shot. We first reported snapshots of low-amplitude laser wakes in Nature Physics in 2006. We subsequently reported images of high-amplitude laser-driven plasma “bubbles”, which are important for producing electron beams with low energy spread, in Physical Review Letters in 2010. More recently, we have figured out how to image laser-driven structures that change shape while propagating in a single laser shot. The latter

  20. Accelerator-driven Medical Sterilization to Replace Co-60 Sources

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

    Kroc, Thomas K.; Thangaraj, Jayakar C.T.; Penning, Richard T.

    This report documents the results of a study prepared at the request of the Office of Radiological Security of the National Nuclear Security Administration (NNSA), as part of the Domestic Protect and Reduce mission by the Illinois Accelerator Research Center (IARC) of Fermi National Accelerator Laboratory. The study included a literature survey of over 80 relevant documents and articles including industry standards, regulatory documents, technical papers, a court case, previous task force reports and industry white papers. The team also conducted interviews or had conversations with over 40 individuals representing over a dozen organizations over the course of its 10-monthmore » program. This report summarizes our findings, addresses the specific questions posed to us by NNSA, and concludes with a list of actionable recommendations.« less

  1. The influence of data-driven versus conceptually-driven processing on the development of PTSD-like symptoms.

    PubMed

    Kindt, Merel; van den Hout, Marcel; Arntz, Arnoud; Drost, Jolijn

    2008-12-01

    Ehlers and Clark [(2000). A cognitive model of posttraumatic stress disorder. Behaviour Research and Therapy, 38, 319-345] propose that a predominance of data-driven processing during the trauma predicts subsequent PTSD. We wondered whether, apart from data-driven encoding, sustained data-driven processing after the trauma is also crucial for the development of PTSD. Both hypotheses were tested in two analogue experiments. Experiment 1 demonstrated that relative to conceptually-driven processing (n=20), data-driven processing after the film (n=14), resulted in more intrusions. Experiment 2 demonstrated that relative to the neutral condition (n=24) and the data-driven encoding condition (n=24), conceptual encoding (n=25) reduced suppression of intrusions and a trend emerged for memory fragmentation. The difference between the two encoding styles was due to the beneficial effect of induced conceptual encoding and not to the detrimental effect of data-driven encoding. The data support the viability of the distinction between data-driven/conceptually-driven processing for the understanding of the development of PTSD.

  2. Efficient modeling of laser-plasma accelerator staging experiments using INF&RNO

    NASA Astrophysics Data System (ADS)

    Benedetti, C.; Schroeder, C. B.; Geddes, C. G. R.; Esarey, E.; Leemans, W. P.

    2017-03-01

    The computational framework INF&RNO (INtegrated Fluid & paRticle simulatioN cOde) allows for fast and accurate modeling, in 2D cylindrical geometry, of several aspects of laser-plasma accelerator physics. In this paper, we present some of the new features of the code, including the quasistatic Particle-In-Cell (PIC)/fluid modality, and describe using different computational grids and time steps for the laser envelope and the plasma wake. These and other features allow for a speedup of several orders of magnitude compared to standard full 3D PIC simulations while still retaining physical fidelity. INF&RNO is used to support the experimental activity at the BELLA Center, and we will present an example of the application of the code to the laser-plasma accelerator staging experiment.

  3. Accelerating Translational Research through Open Science: The Neuro Experiment.

    PubMed

    Gold, E Richard

    2016-12-01

    Translational research is often afflicted by a fundamental problem: a limited understanding of disease mechanisms prevents effective targeting of new treatments. Seeking to accelerate research advances and reimagine its role in the community, the Montreal Neurological Institute (Neuro) announced in the spring of 2016 that it is launching a five-year experiment during which it will adopt Open Science-open data, open materials, and no patenting-across the institution. The experiment seeks to examine two hypotheses. The first is whether the Neuro's Open Science initiative will attract new private partners. The second hypothesis is that the Neuro's institution-based approach will draw companies to the Montreal region, where the Neuro is based, leading to the creation of a local knowledge hub. This article explores why these hypotheses are likely to be true and describes the Neuro's approach to exploring them.

  4. Start-to-end simulation of the shot-noise driven microbunching instability experiment at the Linac Coherent Light Source

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

    Qiang, J.; Ding, Y.; Emma, P.

    The shot-noise driven microbunching instability can significantly degrade electron beam quality in x-ray free electron laser light sources. Experiments were carried out at the Linac Coherent Light Source (LCLS) to study this instability. Here in this paper, we present start-to-end simulations of the shot-noise driven microbunching instability experiment at the LCLS using the real number of electrons. The simulation results reproduce the measurements quite well. A microbunching self-heating mechanism is also illustrated in the simulation, which helps explain the experimental observation.

  5. Start-to-end simulation of the shot-noise driven microbunching instability experiment at the Linac Coherent Light Source

    DOE PAGES

    Qiang, J.; Ding, Y.; Emma, P.; ...

    2017-05-23

    The shot-noise driven microbunching instability can significantly degrade electron beam quality in x-ray free electron laser light sources. Experiments were carried out at the Linac Coherent Light Source (LCLS) to study this instability. Here in this paper, we present start-to-end simulations of the shot-noise driven microbunching instability experiment at the LCLS using the real number of electrons. The simulation results reproduce the measurements quite well. A microbunching self-heating mechanism is also illustrated in the simulation, which helps explain the experimental observation.

  6. Lattice design of the integrable optics test accelerator and optical stochastic cooling experiment at Fermilab

    NASA Astrophysics Data System (ADS)

    Kafka, Gene

    The Integrable Optics Test Accelerator (IOTA) storage ring at Fermilab will serve as the backbone for a broad spectrum of Advanced Accelerator R&D (AARD) experiments, and as such, must be designed with significant flexibility in mind, but without compromising cost efficiency. The nonlinear experiments at IOTA will include: achievement of a large nonlinear tune shift/spread without degradation of dynamic aperture; suppression of strong lattice resonances; study of stability of nonlinear systems to perturbations; and studies of different variants of nonlinear magnet design. The ring optics control has challenging requirements that reach or exceed the present state of the art. The development of a complete self-consistent design of the IOTA ring optics, meeting the demands of all planned AARD experiments, is presented. Of particular interest are the precise control for nonlinear integrable optics experiments and the transverse-to-longitudinal coupling and phase stability for the Optical Stochastic Cooling Experiment (OSC). Since the beam time-of-flight must be tightly controlled in the OSC section, studies of second order corrections in this section are presented.

  7. Stellar winds driven by Alfven waves

    NASA Technical Reports Server (NTRS)

    Belcher, J. W.; Olbert, S.

    1973-01-01

    Models of stellar winds were considered in which the dynamic expansion of a corona is driven by Alfven waves propagating outward along radial magnetic field lines. In the presence of Alfven waves, a coronal expansion can exist for a broad range of reference conditions which would, in the absence of waves, lead to static configurations. Wind models in which the acceleration mechanism is due to Alfven waves alone and exhibit lower mass fluxes and higher energies per particle are compared to wind models in which the acceleration is due to thermal processes. For example, winds driven by Alfven waves exhibit streaming velocities at infinity which may vary between the escape velocity at the coronal base and the geometrical mean of the escape velocity and the speed of light. Upper and lower limits were derived for the allowed energy fluxes and mass fluxes associated with these winds.

  8. Transport calculations and accelerator experiments needed for radiation risk assessment in space.

    PubMed

    Sihver, Lembit

    2008-01-01

    The major uncertainties on space radiation risk estimates in humans are associated to the poor knowledge of the biological effects of low and high LET radiation, with a smaller contribution coming from the characterization of space radiation field and its primary interactions with the shielding and the human body. However, to decrease the uncertainties on the biological effects and increase the accuracy of the risk coefficients for charged particles radiation, the initial charged-particle spectra from the Galactic Cosmic Rays (GCRs) and the Solar Particle Events (SPEs), and the radiation transport through the shielding material of the space vehicle and the human body, must be better estimated Since it is practically impossible to measure all primary and secondary particles from all possible position-projectile-target-energy combinations needed for a correct risk assessment in space, accurate particle and heavy ion transport codes must be used. These codes are also needed when estimating the risk for radiation induced failures in advanced microelectronics, such as single-event effects, etc., and the efficiency of different shielding materials. It is therefore important that the models and transport codes will be carefully benchmarked and validated to make sure they fulfill preset accuracy criteria, e.g. to be able to predict particle fluence, dose and energy distributions within a certain accuracy. When validating the accuracy of the transport codes, both space and ground based accelerator experiments are needed The efficiency of passive shielding and protection of electronic devices should also be tested in accelerator experiments and compared to simulations using different transport codes. In this paper different multipurpose particle and heavy ion transport codes will be presented, different concepts of shielding and protection discussed, as well as future accelerator experiments needed for testing and validating codes and shielding materials.

  9. High Energy Density Physics and Exotic Acceleration Schemes

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

    Cowan, T.; /General Atomics, San Diego; Colby, E.

    2005-09-27

    The High Energy Density and Exotic Acceleration working group took as our goal to reach beyond the community of plasma accelerator research with its applications to high energy physics, to promote exchange with other disciplines which are challenged by related and demanding beam physics issues. The scope of the group was to cover particle acceleration and beam transport that, unlike other groups at AAC, are not mediated by plasmas or by electromagnetic structures. At this Workshop, we saw an impressive advancement from years past in the area of Vacuum Acceleration, for example with the LEAP experiment at Stanford. And wemore » saw an influx of exciting new beam physics topics involving particle propagation inside of solid-density plasmas or at extremely high charge density, particularly in the areas of laser acceleration of ions, and extreme beams for fusion energy research, including Heavy-ion Inertial Fusion beam physics. One example of the importance and extreme nature of beam physics in HED research is the requirement in the Fast Ignitor scheme of inertial fusion to heat a compressed DT fusion pellet to keV temperatures by injection of laser-driven electron or ion beams of giga-Amp current. Even in modest experiments presently being performed on the laser-acceleration of ions from solids, mega-amp currents of MeV electrons must be transported through solid foils, requiring almost complete return current neutralization, and giving rise to a wide variety of beam-plasma instabilities. As keynote talks our group promoted Ion Acceleration (plenary talk by A. MacKinnon), which historically has grown out of inertial fusion research, and HIF Accelerator Research (invited talk by A. Friedman), which will require impressive advancements in space-charge-limited ion beam physics and in understanding the generation and transport of neutralized ion beams. A unifying aspect of High Energy Density applications was the physics of particle beams inside of solids, which is

  10. Understanding hospital meal experiences by means of participant-driven-photo-elicitation.

    PubMed

    Justesen, Lise; Mikkelsen, Bent E; Gyimóthy, Szilvia

    2014-04-01

    A patients' hospital meal experiences can be complex and often difficult to capture using traditional methods. This study investigated patients' hospital meal experiences using participant-driven-photo-elicitation (PDPE). PDPE invites respondents to photograph their daily lives and combines this with interviews, which can provide deeper insight into multisensory experiences beyond verbal or written discourse. The sample consisted of eight hospitalised patients. Patients completed a photo-essay of their hospital meal experience during a single day at a Danish hospital and afterwards participated in an open-ended interview. Two inductive analytical approaches were selected to assess the patients' reflections on their hospital meal experiences. First, the interview transcripts were analysed using the Semiotic Analysis approach using qualitative data analysis software NVivo 9. Second, the 91 produced photographs and the participants' engagement with the photographs were analysed by means of a Reflexive Content Analysis. The study found that PDPE is a research method that can be used for expanding the conceptualisation of hospital meal experiences, revealing the significance of the meal context, materiality and memories beyond food per se. Copyright © 2013 Elsevier Ltd. All rights reserved.

  11. Overview of Heavy Ion Fusion Accelerator Research in the U. S.

    NASA Astrophysics Data System (ADS)

    Friedman, Alex

    2002-12-01

    This article provides an overview of current U.S. research on accelerators for Heavy Ion Fusion, that is, inertial fusion driven by intense beams of heavy ions with the goal of energy production. The concept, beam requirements, approach, and major issues are introduced. An overview of a number of new experiments is presented. These include: the High Current Experiment now underway at Lawrence Berkeley National Laboratory; studies of advanced injectors (and in particular an approach based on the merging of multiple beamlets), being investigated experimentally at Lawrence Livermore National Laboratory); the Neutralized (chamber) Transport Experiment being assembled at Lawrence Berkeley National Laboratory; and smaller experiments at the University of Maryland and at Princeton Plasma Physics Laboratory. The comprehensive program of beam simulations and theory is outlined. Finally, prospects and plans for further development of this promising approach to fusion energy are discussed.

  12. Process modelling for Space Station experiments

    NASA Technical Reports Server (NTRS)

    Alexander, J. Iwan D.; Rosenberger, Franz; Nadarajah, Arunan; Ouazzani, Jalil; Amiroudine, Sakir

    1990-01-01

    Examined here is the sensitivity of a variety of space experiments to residual accelerations. In all the cases discussed the sensitivity is related to the dynamic response of a fluid. In some cases the sensitivity can be defined by the magnitude of the response of the velocity field. This response may involve motion of the fluid associated with internal density gradients, or the motion of a free liquid surface. For fluids with internal density gradients, the type of acceleration to which the experiment is sensitive will depend on whether buoyancy driven convection must be small in comparison to other types of fluid motion, or fluid motion must be suppressed or eliminated. In the latter case, the experiments are sensitive to steady and low frequency accelerations. For experiments such as the directional solidification of melts with two or more components, determination of the velocity response alone is insufficient to assess the sensitivity. The effect of the velocity on the composition and temperature field must be considered, particularly in the vicinity of the melt-crystal interface. As far as the response to transient disturbances is concerned, the sensitivity is determined by both the magnitude and frequency of the acceleration and the characteristic momentum and solute diffusion times. The microgravity environment, a numerical analysis of low gravity tolerance of the Bridgman-Stockbarger technique, and modeling crystal growth by physical vapor transport in closed ampoules are discussed.

  13. Vortex Formation and Acceleration of a Fish-Inspired Robot Performing Starts from Rest

    NASA Astrophysics Data System (ADS)

    Devoria, Adam; Bapst, Jonathan; Ringuette, Matthew

    2009-11-01

    We investigate the unsteady flow of a fish-inspired robot executing starts from rest, with the objective of understanding the connection among the kinematics, vortex formation, and acceleration performance. Several fish perform ``fast starts,'' where the body bends into a ``C'' or ``S'' shape while turning (phase I), followed by a straightening of the body and caudal fin and a linear acceleration (phase II). The resulting highly 3-D, unsteady vortex formation and its relationship to the acceleration are not well understood. The self-propelled robotic model contains motor-driven joints with programmable motion to emulate phase II of a simplified C-start. The experiments are conducted in a water tank, and the model is constrained to 1 direction along rails. The velocity is measured using digital particle image velocimetry (DPIV) in multiple planes. Vortex boundaries are identified using the finite-time Lyapunov exponent, then the unsteady vortex circulation is computed. The thrust is estimated from the identified vortices, and correlated with the circulation and model acceleration for different kinematics.

  14. Acceleration ground test program to verify GAS payload No. 559 structure/support avionics and experiment structural integrity

    NASA Technical Reports Server (NTRS)

    Cassanto, John M.; Cassanto, Valerie A.

    1988-01-01

    Acceleration ground tests were conducted on the Get Away Special (GAS) payload 559 to verify the structural integrity of the structure/support avionics and two of the planned three flight experiments. The ITA (Integrated Test Area) Standardized Experiment Module (ISEM) structure was modified to accommodate the experiments for payload 559. The ISEM avionics consisted of a heavy duty sliver zinc power supply, three orthogonal-mounted low range microgravity accelerometers, a tri-axis high range accelerometer, a solid state recorder/programmer sequencer, and pressure and temperature sensors. The tests were conducted using the Gravitational Plant Physiology Laboratory Centrifuge of the University City Science Center in Philadelphia, PA. The launch-powered flight steady state acceleration profile of the shuttle was simulated from lift-off through jettison of the External Tank (3.0 g's). Additional tests were conducted at twice the nominal powered flight acceleration levels (6 g's) and an over-test condition of four times the powered flight loads to 12.6 g's. The present test program has demonstrated the value of conducting ground tests to verify GAS payload experiment integrity and operation before flying on the shuttle.

  15. EDITORIAL: Metrological Aspects of Accelerator Technology and High Energy Physics Experiments

    NASA Astrophysics Data System (ADS)

    Romaniuk, Ryszard S.; Pozniak, Krzysztof T.

    2007-08-01

    The subject of this special feature in Measurement Science and Technology concerns measurement methods, devices and subsystems, both hardware and software aspects, applied in large experiments of high energy physics (HEP) and superconducting RF accelerator technology (SRF). These experiments concern mainly the physics of elementary particles or the building of new machines and detectors. The papers present practical examples of applied solutions in large, contemporary, international research projects such as HERA, LHC, FLASH, XFEL, ILC and others. These machines are unique in their global scale and consist of extremely dedicated apparatus. The apparatus is characterized by very large dimensions, a considerable use of resources and a high level of overall technical complexity. They possess a large number of measurement channels (ranging from thousands to over 100 million), are characterized by fast of processing of measured data and high measurement accuracies, and work in quite adverse environments. The measurement channels cooperate with a large number of different sensors of momenta, energies, trajectories of elementary particles, electron, proton and photon beam profiles, accelerating fields in resonant cavities, and many others. The provision of high quality measurement systems requires the designers to use only the most up-to-date technical solutions, measurement technologies, components and devices. Research work in these demanding fields is a natural birthplace of new measurement methods, new data processing and acquisition algorithms, complex, networked measurement system diagnostics and monitoring. These developments are taking place in both hardware and software layers. The chief intention of this special feature is that the papers represent equally some of the most current metrology research problems in HEP and SRF. The accepted papers have been divided into four topical groups: superconducting cavities (4 papers), low level RF systems (8 papers

  16. Weibel instability mediated collisionless shocks using intense laser-driven plasmas

    NASA Astrophysics Data System (ADS)

    Palaniyappan, Sasikumar; Fiuza, Federico; Huang, Chengkun; Gautier, Donald; Ma, Wenjun; Schreiber, Jorg; Raymer, Abel; Fernandez, Juan; Shimada, Tom; Johnson, Randall

    2017-10-01

    The origin of cosmic rays remains a long-standing challenge in astrophysics and continues to fascinate physicists. It is believed that ``collisionless shocks'' - where the particle Coulomb mean free path is much larger that the shock transition - are a dominant source of energetic cosmic rays. These shocks are ubiquitous in astrophysical environments such as gamma-ray bursts, supernova remnants, pulsar wind nebula and coronal mass ejections from the sun. A particular type of electromagnetic plasma instability known as Weibel instability is believed to be the dominant mechanism behind the formation of these collisionless shocks in the cosmos. The understanding of the microphysics behind collisionless shocks and their particle acceleration is tightly related with nonlinear basic plasma processes and remains a grand challenge. In this poster, we will present results from recent experiments at the LANL Trident laser facility studying collisionless shocks using intense ps laser (80J, 650 fs - peak intensity of 1020 W/cm2) driven near-critical plasmas using carbon nanotube foam targets. A second short pulse laser driven protons from few microns thick gold foil is used to radiograph the main laser-driven plasma. Work supported by the LDRD program at LANL.

  17. Optimisation of composite metallic fuel for minor actinide transmutation in an accelerator-driven system

    NASA Astrophysics Data System (ADS)

    Uyttenhove, W.; Sobolev, V.; Maschek, W.

    2011-09-01

    A potential option for neutralization of minor actinides (MA) accumulated in spent nuclear fuel of light water reactors (LWRs) is their transmutation in dedicated accelerator-driven systems (ADS). A promising fuel candidate dedicated to MA transmutation is a CERMET composite with Mo metal matrix and (Pu, Np, Am, Cm)O 2-x fuel particles. Results of optimisation studies of the CERMET fuel targeting to increasing the MA transmutation efficiency of the EFIT (European Facility for Industrial Transmutation) core are presented. In the adopted strategy of MA burning the plutonium (Pu) balance of the core is minimized, allowing a reduction in the reactivity swing and the peak power form-factor deviation and an extension of the cycle duration. The MA/Pu ratio is used as a variable for the fuel optimisation studies. The efficiency of MA transmutation is close to the foreseen theoretical value of 42 kg TW -1 h -1 when level of Pu in the actinide mixture is about 40 wt.%. The obtained results are compared with the reference case of the EFIT core loaded with the composite CERCER fuel, where fuel particles are incorporated in a ceramic magnesia matrix. The results of this study offer additional information for the EFIT fuel selection.

  18. Fbxw7 Deletion Accelerates KrasG12D-Driven Pancreatic Tumorigenesis via Yap Accumulation.

    PubMed

    Zhang, Qiang; Zhang, Yaqing; Parsels, Joshua D; Lohse, Ines; Lawrence, Theodore S; Pasca di Magliano, Marina; Sun, Yi; Morgan, Meredith A

    2016-11-01

    Pancreatic cancers driven by KRAS mutations require additional mutations for tumor progression. The tumor suppressor FBXW7 is altered in pancreatic cancers, but its contribution to pancreatic tumorigenesis is unknown. To determine potential cooperation between Kras mutation and Fbxw7 inactivation in pancreatic tumorigenesis, we generated P48-Cre;LSL-Kras G12D ;Fbxw7 fl/fl (KFC fl/fl ) compound mice. We found that KFC fl/fl mice displayed accelerated tumorigenesis: all mice succumbed to pancreatic ductal adenocarcinoma (PDA) by 40 days of age, with PDA onset occurring by 2 weeks of age. PDA in KFC fl/fl mice was preceded by earlier onset of acinar-to-ductal metaplasia (ADM) and pancreatic intraepithelial neoplasia (PanIN) lesions, and associated with chromosomal instability and the accumulation of Fbxw7 substrates Yes-associated protein (Yap), c-Myc, and Notch. Using KFC fl/fl and FBXW7-deficient human pancreatic cancer cells, we found that Yap silencing attenuated growth promotion by Fbxw7 deletion. Our data demonstrate that Fbxw7 is a potent suppressor of Kras G12D -induced pancreatic tumorigenesis due, at least in part, to negative regulation of Yap. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  19. Optimization of Capsule Symmetry in Z-Pinch Driven Hohlraums

    NASA Astrophysics Data System (ADS)

    Vesey, R. A.; Cuneo, M.; Hanson, D.; Porter, J.; Mehlhorn, T.; Ruggles, L.; Simpson, W.; Vargas, M.; Hammer, J.; Landen, O.

    1999-11-01

    The uniformity of the radiation flux incident on the capsule is a critical issue for indirect drive fusion using the z-pinch driven hohlraum high-yield concept(J.H. Hammer et al., Phys. Plas. 6), 2129 (1999).. Experiments on the Z accelerator at Sandia have demonstrated the ability to diagnose the uniformity of the flux striking a foam ball (surrogate capsule)(P.A. Amendt et al., Phys. Plas. 4), 1862 (1997); S.G. Glendinning et al. Rev. Sci. Instrum. 70, 536 (1999).. These single-sided drive experiments have been modeled using radiosity and radiation-hydrodynamics codes, yielding agreement with the measured ablation rate vs. angle on the foam ball. Flux uniformity at the 1-2% level needed for high-convergence capsule implosions requires a 2-sided drive (top and bottom z-pinch) configuration. Constrained optimization methods have identified hohlraum geometries with improved symmetry.

  20. Turbulence Evolution and Shock Acceleration of Solar Energetic Particles

    NASA Technical Reports Server (NTRS)

    Chee, Ng K.

    2007-01-01

    We model the effects of self-excitation/damping and shock transmission of Alfven waves on solar-energetic-particle (SEP) acceleration at a coronal-mass-ejection (CME) driven parallel shock. SEP-excited outward upstream waves speedily bootstrap acceleration. Shock transmission further raises the SEP-excited wave intensities at high wavenumbers but lowers them at low wavenumbers through wavenumber shift. Downstream, SEP excitation of inward waves and damping of outward waves tend to slow acceleration. Nevertheless, > 2000 km/s parallel shocks at approx. 3.5 solar radii can accelerate SEPs to 100 MeV in < 5 minutes.

  1. Electron-Beam Dynamics for an Advanced Flash-Radiography Accelerator

    DOE PAGES

    Ekdahl, Carl

    2015-11-17

    Beam dynamics issues were assessed for a new linear induction electron accelerator being designed for multipulse flash radiography of large explosively driven hydrodynamic experiments. Special attention was paid to equilibrium beam transport, possible emittance growth, and beam stability. Especially problematic would be high-frequency beam instabilities that could blur individual radiographic source spots, low-frequency beam motion that could cause pulse-to-pulse spot displacement, and emittance growth that could enlarge the source spots. Furthermore, beam physics issues were examined through theoretical analysis and computer simulations, including particle-in-cell codes. Beam instabilities investigated included beam breakup, image displacement, diocotron, parametric envelope, ion hose, and themore » resistive wall instability. The beam corkscrew motion and emittance growth from beam mismatch were also studied. It was concluded that a beam with radiographic quality equivalent to the present accelerators at Los Alamos National Laboratory will result if the same engineering standards and construction details are upheld.« less

  2. Emittance Growth in the DARHT-II Linear Induction Accelerator

    NASA Astrophysics Data System (ADS)

    Ekdahl, Carl; Carlson, Carl A.; Frayer, Daniel K.; McCuistian, B. Trent; Mostrom, Christopher B.; Schulze, Martin E.; Thoma, Carsten H.

    2017-11-01

    The Dual-Axis Radiographic Hydrotest (DARHT) facility uses bremsstrahlung radiation source spots produced by the focused electron beams from two linear induction accelerators (LIAs) to radiograph large hydrodynamic experiments driven by high explosives. Radiographic resolution is determined by the size of the source spot, and beam emittance is the ultimate limitation to spot size. Some of the possible causes for the emittance growth in the DARHT LIA have been investigated using particle-in-cell (PIC) codes, and are discussed in this article. The results suggest that the most likely source of emittance growth is a mismatch of the beam to the magnetic transport, which can cause beam halo.

  3. Effect of polarization and focusing on laser pulse driven auto-resonant particle acceleration

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

    Sagar, Vikram; Sengupta, Sudip; Kaw, Predhiman

    2014-04-15

    The effect of laser polarization and focusing is theoretically studied on the final energy gain of a particle in the Auto-resonant acceleration scheme using a finite duration laser pulse with Gaussian shaped temporal envelope. The exact expressions for dynamical variables viz. position, momentum, and energy are obtained by analytically solving the relativistic equation of motion describing particle dynamics in the combined field of an elliptically polarized finite duration pulse and homogeneous static axial magnetic field. From the solutions, it is shown that for a given set of laser parameters viz. intensity and pulse length along with static magnetic field, themore » energy gain by a positively charged particle is maximum for a right circularly polarized laser pulse. Further, a new scheme is proposed for particle acceleration by subjecting it to the combined field of a focused finite duration laser pulse and static axial magnetic field. In this scheme, the particle is initially accelerated by the focused laser field, which drives the non-resonant particle to second stage of acceleration by cyclotron Auto-resonance. The new scheme is found to be efficient over two individual schemes, i.e., auto-resonant acceleration and direct acceleration by focused laser field, as significant particle acceleration can be achieved at one order lesser values of static axial magnetic field and laser intensity.« less

  4. Development of Safety Analysis Code System of Beam Transport and Core for Accelerator Driven System

    NASA Astrophysics Data System (ADS)

    Aizawa, Naoto; Iwasaki, Tomohiko

    2014-06-01

    Safety analysis code system of beam transport and core for accelerator driven system (ADS) is developed for the analyses of beam transients such as the change of the shape and position of incident beam. The code system consists of the beam transport analysis part and the core analysis part. TRACE 3-D is employed in the beam transport analysis part, and the shape and incident position of beam at the target are calculated. In the core analysis part, the neutronics, thermo-hydraulics and cladding failure analyses are performed by the use of ADS dynamic calculation code ADSE on the basis of the external source database calculated by PHITS and the cross section database calculated by SRAC, and the programs of the cladding failure analysis for thermoelastic and creep. By the use of the code system, beam transient analyses are performed for the ADS proposed by Japan Atomic Energy Agency. As a result, the rapid increase of the cladding temperature happens and the plastic deformation is caused in several seconds. In addition, the cladding is evaluated to be failed by creep within a hundred seconds. These results have shown that the beam transients have caused a cladding failure.

  5. Lattice design of the integrable optics test accelerator and optical stochastic cooling experiment at Fermilab

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

    Kafka, Gene

    2015-05-01

    The Integrable Optics Test Accelerator (IOTA) storage ring at Fermilab will serve as the backbone for a broad spectrum of Advanced Accelerator R&D (AARD) experiments, and as such, must be designed with signi cant exibility in mind, but without compromising cost e ciency. The nonlinear experiments at IOTA will include: achievement of a large nonlinear tune shift/spread without degradation of dynamic aperture; suppression of strong lattice resonances; study of stability of nonlinear systems to perturbations; and studies of di erent variants of nonlinear magnet design. The ring optics control has challenging requirements that reach or exceed the present state ofmore » the art. The development of a complete self-consistent design of the IOTA ring optics, meeting the demands of all planned AARD experiments, is presented. Of particular interest are the precise control for nonlinear integrable optics experiments and the transverse-to-longitudinal coupling and phase stability for the Optical Stochastic Cooling Experiment (OSC). Since the beam time-of- ight must be tightly controlled in the OSC section, studies of second order corrections in this section are presented.« less

  6. An Experiment in ''Less Time, More Options": A Study of Accelerated University Students.

    ERIC Educational Resources Information Center

    Litwin, James L.; And Others

    This study investigated the characteristics and experiences of 59 college students accelerated from their freshman to their junior year. The students showed high academic performance and few social problems, but questions of personal identity remained problematic; the best single predictor of academic success was found to be freshman grade-point…

  7. Experiments on 1,000 km/s flyer acceleration and collisions

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

    We will present results from follow-on experiments to the record-high velocities achieved using the ultra-uniform deep-uv drive of the Nike KrF laser [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. Such velocities may indicate a path to lower minimum energy required for central ignition. Still higher velocities and higher target densities are required for impact fast ignition. New results give velocity of >1,100 km/s achieved through improvements in pulseshaping. Variation of second foil parameters results in significant change in fusion neutron production on impact. In-flight target density is inferred from target heating upon collision via DD neutron time-of-flight ion temperature measurement. Availability of pressures generated by collisions of such highly accelerated flyers may provide an experimental platform for study of matter at extreme conditions. Work is supported by US DOE (NNSA).

  8. Characteristics of GeV Electron Bunches Accelerated by Intense Lasers in Vacuum

    NASA Astrophysics Data System (ADS)

    Wang, P. X.; Ho, Y. K.; Kong, Q.; Yuan, X. Q.; Cao, N.; Feng, L.

    This paper studies the characteristics of GeV electron bunches driven by ultra-intense lasers in vacuum based on the mechanism of capture and violent acceleration scenario [CAS, see, e.g. J. X. Wang et al., Phys. Rev. E58, 6575 (1998)], which shows an interesting prospect of becoming a new principle of laser-driven accelerators. It has been found that the accelerated GeV electron bunch is a macro-pulse composed of a lot of micro-pulses, which is analogous to the structure of the bunches produced by conventional linacs. The macro-pulse corresponds to the duration of the laser pulse while the micro-pulse corresponds to the periodicity of the laser wave. Therefore, provided that the incoming electron bunch with comparable sizes as that of the laser pulse synchronously impinges on the laser pulse, the total fraction of electrons captured and accelerated to GeV energy can reach more than 20%. These results demonstrate that the mechanisms of CAS is a relatively effective accelerator mechanism.

  9. STS-40 orbital acceleration research experiment flight results during a typical sleep period

    NASA Technical Reports Server (NTRS)

    Blanchard, Robert C.; Nicholson, John Y.; Ritter, James R.

    1992-01-01

    The Orbital Acceleration Research Experiment (OARE), an electrostatic accelerometer package with complete on-orbit calibration capabilities was flown aboard Shuttle on STS-40. The instrument is designed to measure and record the Shuttle aerodynamic acceleration environment from the free molecule flow regime through the rarefied flow transition into the hypersonic continuum regime. Because of its sensitivity, the OARE instrument detects aerodynamic behavior of the Shuttle while in low-earth orbit. A 2-h orbital time period on day seven of the mission, when the crew was asleep and other spacecraft activities were at a minimum, was examined. Examination of the model with the flight data shows the instrument to be sensitive to all major expected low-frequency acceleration phenomena; however, some erratic instrument bias behavior persists in two axes. In these axes, the OARE data can be made to match a comprehensive atmospheric-aerodynamic model by making bias adjustments and slight liner corrections for drift.

  10. SIN accelerator, operational experience and improvement programs

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

    Joho, W.; Olivo, M.; Stammbach, T.

    1977-06-01

    The SIN meson facility, in operation since 1974, consists of a 590 MeV ring cyclotron for protons and a 72 MeV injector cyclotron. The average beam current on target is presently about 50 ..mu..A, the peak being 112 ..mu..A. Extraction efficiency, once considered a severe handicap for cyclotrons, is now 99.6 to 99.9% for the ring cyclotron and about 90% for the injector. Many improvements in both accelerators allow single turn extraction in the ring cyclotron. The present current limit is given by the injector, while the ring itself could accept now a 600 ..mu..A beam, with 2 to 4more » mA as an ultimate limit. Some muon experiments require a pulsed beam with on-off times in the order of the lifetime of the muon. First trials with beam pulse frequencies of 200 and 400 kHz and a 50% duty cycle have been successful.« less

  11. A Stable High-Energy Electron Source from Laser Wakefield Acceleration

    NASA Astrophysics Data System (ADS)

    Zhang, Ping; Zhao, Baozhen; Liu, Cheng; Yan, Wenchao; Golovin, Grigory; Banerjee, Sudeep; Chen, Shouyuan; Haden, Daniel; Fruhling, Colton; Umstadter, Donald

    2016-10-01

    The stability of the electron source from laser wake-field acceleration (LWFA) is essential for applications, such as novel x-ray sources and fundamental experiments in high field physics. To obtain such a stable source, we used an optimal laser pulse and a novel gas nozzle. The high-power laser pulse on target was focused to a diffraction-limited spot by the use of adaptive wavefront correction and the pulse duration was transform limited by the use of spectral feedback control. An innovative design for the nozzle led to a stable, flat-top profile with diameters of 4 mm and 8 mm with a high Mach-number ( 6). In experiments to generate high-energy electron beams by LWFA, we were able to obtain reproducible results with beam energy of 800 MeV and charge >10 pC. Higher charge but broader energy spectrum resulted when the plasma density was increased. These developments have resulted in a laser-driven wakefield accelerator that is stable and robust. With this device, we show that narrowband high-energy x-rays beams can be generated by the inverse-Compton scattering process. This accelerator has also been used in recent experiments to study nonlinear effects in the interaction of high-energy electron beams with ultraintense laser pulses. This material is based upon work supported by NSF No. PHY-153700; US DOE, Office of Science, BES, # DE-FG02-05ER15663; AFOSR # FA9550-11-1-0157; and DHS DNDO # HSHQDC-13-C-B0036.

  12. Quasi-monoenergetic laser-plasma acceleration of electrons to 2 GeV

    PubMed Central

    Wang, Xiaoming; Zgadzaj, Rafal; Fazel, Neil; Li, Zhengyan; Yi, S. A.; Zhang, Xi; Henderson, Watson; Chang, Y.-Y.; Korzekwa, R.; Tsai, H.-E.; Pai, C.-H.; Quevedo, H.; Dyer, G.; Gaul, E.; Martinez, M.; Bernstein, A. C.; Borger, T.; Spinks, M.; Donovan, M.; Khudik, V.; Shvets, G.; Ditmire, T.; Downer, M. C.

    2013-01-01

    Laser-plasma accelerators of only a centimetre’s length have produced nearly monoenergetic electron bunches with energy as high as 1 GeV. Scaling these compact accelerators to multi-gigaelectronvolt energy would open the prospect of building X-ray free-electron lasers and linear colliders hundreds of times smaller than conventional facilities, but the 1 GeV barrier has so far proven insurmountable. Here, by applying new petawatt laser technology, we produce electron bunches with a spectrum prominently peaked at 2 GeV with only a few per cent energy spread and unprecedented sub-milliradian divergence. Petawatt pulses inject ambient plasma electrons into the laser-driven accelerator at much lower density than was previously possible, thereby overcoming the principal physical barriers to multi-gigaelectronvolt acceleration: dephasing between laser-driven wake and accelerating electrons and laser pulse erosion. Simulations indicate that with improvements in the laser-pulse focus quality, acceleration to nearly 10 GeV should be possible with the available pulse energy. PMID:23756359

  13. Helium-3 and helium-4 acceleration by high power laser pulses for hadron therapy

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

    Bulanov, S. S.; Esarey, E.; Schroeder, C. B.

    The laser driven acceleration of ions is considered a promising candidate for an ion source for hadron therapy of oncological diseases. Though proton and carbon ion sources are conventionally used for therapy, other light ions can also be utilized. Whereas carbon ions require 400 MeV per nucleon to reach the same penetration depth as 250 MeV protons, helium ions require only 250 MeV per nucleon, which is the lowest energy per nucleon among the light ions (heavier than protons). This fact along with the larger biological damage to cancer cells achieved by helium ions, than that by protons, makes thismore » species an interesting candidate for the laser driven ion source. Two mechanisms (magnetic vortex acceleration and hole-boring radiation pressure acceleration) of PW-class laser driven ion acceleration from liquid and gaseous helium targets are studied with the goal of producing 250 MeV per nucleon helium ion beams that meet the hadron therapy requirements. We show that He3 ions, having almost the same penetration depth as He4 with the same energy per nucleon, require less laser power to be accelerated to the required energy for the hadron therapy.« less

  14. Helium-3 and helium-4 acceleration by high power laser pulses for hadron therapy

    DOE PAGES

    Bulanov, S. S.; Esarey, E.; Schroeder, C. B.; ...

    2015-06-24

    The laser driven acceleration of ions is considered a promising candidate for an ion source for hadron therapy of oncological diseases. Though proton and carbon ion sources are conventionally used for therapy, other light ions can also be utilized. Whereas carbon ions require 400 MeV per nucleon to reach the same penetration depth as 250 MeV protons, helium ions require only 250 MeV per nucleon, which is the lowest energy per nucleon among the light ions (heavier than protons). This fact along with the larger biological damage to cancer cells achieved by helium ions, than that by protons, makes thismore » species an interesting candidate for the laser driven ion source. Two mechanisms (magnetic vortex acceleration and hole-boring radiation pressure acceleration) of PW-class laser driven ion acceleration from liquid and gaseous helium targets are studied with the goal of producing 250 MeV per nucleon helium ion beams that meet the hadron therapy requirements. We show that He3 ions, having almost the same penetration depth as He4 with the same energy per nucleon, require less laser power to be accelerated to the required energy for the hadron therapy.« less

  15. Alpha-Driven MHD and MHD-Induced Alpha Loss in TFTR DT Experiments

    NASA Astrophysics Data System (ADS)

    Chang, Zuoyang

    1996-11-01

    Theoretical calculation and numerical simulation indicate that there can be interesting interactions between alpha particles and MHD activity which can adversely affect the performance of a tokamak reactor (e.g., ITER). These interactions include alpha-driven MHD, like the toroidicity-induced-Alfven-eigenmode (TAE) and MHD induced alpha particle losses or redistribution. Both phenomena have been observed in recent TFTR DT experiments. Weak alpha-driven TAE activity was observed in a NBI-heated DT experiment characterized by high q0 ( >= 2) and low core magnetic shear. The TAE mode appears at ~30-100 ms after the neutral beam turning off approximately as predicted by theory. The mode has an amplitude measured by magnetic coils at the edge tildeB_p ~1 mG, frequency ~150-190 kHz and toroidal mode number ~2-3. It lasts only ~ 30-70 ms and has been seen only in DT discharges with fusion power level about 1.5-2.0 MW. Numerical calculation using NOVA-K code shows that this type of plasma has a big TAE gap. The calculated TAE frequency and mode number are close to the observation. (2) KBM-induced alpha particle loss^1. In some high-β, high fusion power DT experiments, enhanced alpha particle losses were observed to be correlated to the high frequency MHD modes with f ~100-200 kHz (the TAE frequency would be two-times higher) and n ~5-10. These modes are localized around the peak plasma pressure gradient and have ballooning characteristics. Alpha loss increases by 30-100% during the modes. Particle orbit simulations show the added loss results from wave-particle resonance. Linear instability analysis indicates that the plasma is unstable to the kinetic MHD ballooning modes (KBM) driven primarily by strong local pressure gradients. ----------------- ^1Z. Chang, et al, Phys. Rev. Lett. 76 (1996) 1071. In collaberation with R. Nazikian, G.-Y. Fu, S. Batha, R. Budny, L. Chen, D. Darrow, E. Fredrickson, R. Majeski, D. Mansfield, K. McGuire, G. Rewoldt, G. Taylor, R. White, K

  16. The acceleration of particles at propagating interplanetary shocks

    NASA Astrophysics Data System (ADS)

    Prinsloo, P. L.; Strauss, R. D. T.

    2017-12-01

    Enhancements of charged energetic particles are often observed at Earth following the eruption of coronal mass ejections (CMEs) on the Sun. These enhancements are thought to arise from the acceleration of those particles at interplanetary shocks forming ahead of CMEs, propagating into the heliosphere. In this study, we model the acceleration of these energetic particles by solving a set of stochastic differential equations formulated to describe their transport and including the effects of diffusive shock acceleration. The study focuses on how acceleration at halo-CME-driven shocks alter the energy spectra of non-thermal particles, while illustrating how this acceleration process depends on various shock and transport parameters. We finally attempt to establish the relative contributions of different seed populations of energetic particles in the inner heliosphere to observed intensities during selected acceleration events.

  17. Gyrokinetic theory of turbulent acceleration and momentum conservation in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Lu, WANG; Shuitao, PENG; P, H. DIAMOND

    2018-07-01

    Understanding the generation of intrinsic rotation in tokamak plasmas is crucial for future fusion reactors such as ITER. We proposed a new mechanism named turbulent acceleration for the origin of the intrinsic parallel rotation based on gyrokinetic theory. The turbulent acceleration acts as a local source or sink of parallel rotation, i.e., volume force, which is different from the divergence of residual stress, i.e., surface force. However, the order of magnitude of turbulent acceleration can be comparable to that of the divergence of residual stress for electrostatic ion temperature gradient (ITG) turbulence. A possible theoretical explanation for the experimental observation of electron cyclotron heating induced decrease of co-current rotation was also proposed via comparison between the turbulent acceleration driven by ITG turbulence and that driven by collisionless trapped electron mode turbulence. We also extended this theory to electromagnetic ITG turbulence and investigated the electromagnetic effects on intrinsic parallel rotation drive. Finally, we demonstrated that the presence of turbulent acceleration does not conflict with momentum conservation.

  18. Asymetrically driven implosion experiment on the Laser MégaJoule

    NASA Astrophysics Data System (ADS)

    Philippe, Franck; Seytor, Patricia; Tassin, Veronique; Rosch, Rudolf; Villette, Bruno

    2017-10-01

    We report on the results of the first implosion experiments performed on the Laser MégaJoule (LMJ) facility. Their main purpose was to study implosion with large polar asymmetries of incident radiative flux on a capsule, while preserving azimuthal symmetry, in the context of ICF. In these experiments, one quad of LMJ is focused axially on a gold shield inside a hohlraum. The shield effectively divides the hohlraum in two compartments, and a capsule placed in the second compartment is indirectly driven by the x-ray flux generated in the first one. The subsequent asymmetric implosion is backlit by an x-ray source generated by another quad of LMJ and imaged with an x-ray microscope coupled to a framing camera. Time-gated x-ray radiographs of the imploding capsule and diode array measurements of the hohlraum x-ray emission are found to be in good agreement with FCI2 radiative hydrodynamics simulations.

  19. Simulation Studies of the Dielectric Grating as an Accelerating and Focusing Structure

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

    Soong, Ken; Peralta, E.A.; Byer, R.L.

    A grating-based design is a promising candidate for a laser-driven dielectric accelerator. Through simulations, we show the merits of a readily fabricated grating structure as an accelerating component. Additionally, we show that with a small design perturbation, the accelerating component can be converted into a focusing structure. The understanding of these two components is critical in the successful development of any complete accelerator. The concept of accelerating electrons with the tremendous electric fields found in lasers has been proposed for decades. However, until recently the realization of such an accelerator was not technologically feasible. Recent advances in the semiconductor industry,more » as well as advances in laser technology, have now made laser-driven dielectric accelerators imminent. The grating-based accelerator is one proposed design for a dielectric laser-driven accelerator. This design, which was introduced by Plettner, consists of a pair of opposing transparent binary gratings, illustrated in Fig. 1. The teeth of the gratings serve as a phase mask, ensuring a phase synchronicity between the electromagnetic field and the moving particles. The current grating accelerator design has the drive laser incident perpendicular to the substrate, which poses a laser-structure alignment complication. The next iteration of grating structure fabrication seeks to monolithically create an array of grating structures by etching the grating's vacuum channel into a fused silica wafer. With this method it is possible to have the drive laser confined to the plane of the wafer, thus ensuring alignment of the laser-and-structure, the two grating halves, and subsequent accelerator components. There has been previous work using 2-dimensional finite difference time domain (2D-FDTD) calculations to evaluate the performance of the grating accelerator structure. However, this work approximates the grating as an infinite structure and does not accurately model a

  20. Free electron lasers driven by linear induction accelerators: High power radiation sources

    NASA Technical Reports Server (NTRS)

    Orzechowski, T. J.

    1989-01-01

    The technology of Free Electron Lasers (FELs) and linear induction accelerators (LIAs) is addressed by outlining the following topics: fundamentals of FELs; basic concepts of linear induction accelerators; the Electron Laser Facility (a microwave FEL); PALADIN (an infrared FEL); magnetic switching; IMP; and future directions (relativistic klystrons). This presentation is represented by viewgraphs only.

  1. Direct longitudinal laser acceleration of electrons in free space

    NASA Astrophysics Data System (ADS)

    Carbajo, Sergio; Nanni, Emilio A.; Wong, Liang Jie; Moriena, Gustavo; Keathley, Phillip D.; Laurent, Guillaume; Miller, R. J. Dwayne; Kärtner, Franz X.

    2016-02-01

    Compact laser-driven accelerators are pursued heavily worldwide because they make novel methods and tools invented at national laboratories widely accessible in science, health, security, and technology [V. Malka et al., Principles and applications of compact laser-plasma accelerators, Nat. Phys. 4, 447 (2008)]. Current leading laser-based accelerator technologies [S. P. D. Mangles et al., Monoenergetic beams of relativistic electrons from intense laser-plasma interactions, Nature (London) 431, 535 (2004); T. Toncian et al., Ultrafast laser-driven microlens to focus and energy-select mega-electron volt protons, Science 312, 410 (2006); S. Tokita et al. Single-shot ultrafast electron diffraction with a laser-accelerated sub-MeV electron pulse, Appl. Phys. Lett. 95, 111911 (2009)] rely on a medium to assist the light to particle energy transfer. The medium imposes material limitations or may introduce inhomogeneous fields [J. R. Dwyer et al., Femtosecond electron diffraction: "Making the molecular movie,", Phil. Trans. R. Soc. A 364, 741 (2006)]. The advent of few cycle ultraintense radially polarized lasers [S. Carbajo et al., Efficient generation of ultraintense few-cycle radially polarized laser pulses, Opt. Lett. 39, 2487 (2014)] has ushered in a novel accelerator concept [L. J. Wong and F. X. Kärtner, Direct acceleration of an electron in infinite vacuum by a pulsed radially polarized laser beam, Opt. Express 18, 25035 (2010); F. Pierre-Louis et al. Direct-field electron acceleration with ultrafast radially polarized laser beams: Scaling laws and optimization, J. Phys. B 43, 025401 (2010); Y. I. Salamin, Electron acceleration from rest in vacuum by an axicon Gaussian laser beam, Phys. Rev. A 73, 043402 (2006); C. Varin and M. Piché, Relativistic attosecond electron pulses from a free-space laser-acceleration scheme, Phys. Rev. E 74, 045602 (2006); A. Sell and F. X. Kärtner, Attosecond electron bunches accelerated and compressed by radially polarized laser

  2. Evaluation of laser-driven ion energies for fusion fast-ignition research

    NASA Astrophysics Data System (ADS)

    Tosaki, S.; Yogo, A.; Koga, K.; Okamoto, K.; Shokita, S.; Morace, A.; Arikawa, Y.; Fujioka, S.; Nakai, M.; Shiraga, H.; Azechi, H.; Nishimura, H.

    2017-10-01

    We investigate laser-driven ion acceleration using kJ-class picosecond (ps) laser pulses as a fundamental study for ion-assisted fusion fast ignition, using a newly developed Thomson-parabola ion spectrometer (TPIS). The TPIS has a space- and weight-saving design, considering its use in an laser-irradiation chamber in which 12 beams of fuel implosion laser are incident, and, at the same time, demonstrates sufficient performance with its detectable range and resolution of the ion energy required for fast-ignition research. As a fundamental study on laser-ion acceleration using a ps pulse laser, we show proton acceleration up to 40 MeV at 1 × 10^{19} W cm^{-2}. The energy conversion efficiency from the incident laser into protons higher than 6 MeV is 4.6%, which encourages the realization of fusion fast ignition by laser-driven ions.

  3. Surface Tension Driven Convection Experiment-2 (STDCE-2)

    NASA Technical Reports Server (NTRS)

    Masud, J.; Kamotani, Y.; Ostrach, S.

    1999-01-01

    Thermocapillary flows are known to become oscillatory (time-periodic), but how and when they become oscillatory in containers of unit-order aspect ratio are not yet fully understood. The present work is a part of our continuous effort to obtain a better understanding of the phenomenon. Thermocapillary flow experiments in normal gravity are limited to a narrow parametric range in order to minimize gravity and buoyancy effects, which is an important reason for our lack of full understanding of the oscillation phenomenon. One important unanswered question is what role, if any, free surface deformation plays in the oscillation mechanism. For that reason we performed thermocapillary flow experiments, called the Surface Tension Driven Convection Experiment-2 (STDCE-2), aboard the USML-2 Spacelab in 1995. The main objectives of the experiments were to investigate oscillatory thermocapillary flows in microgravity and to clarify the importance of free surface deformation in such flows. Steady and oscillatory thermocapillary flows were generated in cylindrical containers by employing two heating modes. A CO2 laser with adjustable power and beam diameter was used in the Constant Flux (CF) configuration to heat the free surface. The other configuration investigated in STDCE-2 was the Constant Temperature (CT) configuration in which a submerged cylindrical cartridge heater placed at the symmetry (axial) axis of the test container heated the fluid. Both heating modes cause non-uniform temperature distributions on the free surface, which generates thermocapillary flow. The flow field was investigated by flow visualization, and the temperature field was measured by thermistors and an infrared imager. The free surface shape and motion were measured by a Ronchi system. The hardware performed well and we were able to conduct more tests than originally planned. From the successful experiments a large amount of data was acquired. The analysis of the data is now nearly complete. Some

  4. An Experiment in "Less Time": A Study of Students Accelerated to Junior Status

    ERIC Educational Resources Information Center

    Litwin, James L.; And Others

    1975-01-01

    As the result of a time-shortened degree experiment, 31 end-of-year freshmen were accelerated to junior status. The students showed high academic performance and few social problems, but questions of personal identity remained problematic. The best single predictor of academic success in the junior year was the freshman grade point average.…

  5. Simulation of sloshing dynamics induced forces and torques actuated on dewar container driven by gravity gradient and jitter accelerations in microgravity

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Pan, H. L.

    1993-01-01

    Some experimental spacecraft use superconducting sensors for gyro read-out and so must be maintained at a very low temperature. The boil-off from the cryogenic liquid used to cool the sensors can also be used, as the Gravity Probe B (GP-B) spacecraft does, as propellant to maintain attitude control and drag-free operation of the spacecraft. The cryogenic liquid for such spacecraft is, however, susceptible to both slosh-like motion and non-axisymmetric configurations under the influence of various kinds of gravity jitter and gravity gradient accelerations. Hence, it is important to quantify the magnitude of the liquid-induced perturbations on the spacecraft. We use the example of the GP-B to investigate such perturbations by numerical simulations. For this spacecraft disturbances can be imposed on the liquid by atmospheric drag, spacecraft attitude control maneuvers, and the earth's gravity gradient. More generally, onboard machinery vibrations and crew motion can also create disturbances. Recent studies suggest that high frequency disturbances are relatively unimportant in causing liquid motions in comparison to low frequency ones. The results presented here confirm this conclusion. After an initial calibration period, the GP-B spacecraft rotates in orbit at 0.1 rpm about the tank symmetry axis. For this rotation rate, the equilibrium liquid free surface shape is a 'doughnut' configuration for all residual gravity levels of 10(exp -6) g(sub 0) or less, as shown by experiments and by numerical simulations; furthermore, the superfluid behavior of the 1.8 K liquid helium used in GP-B eliminates temperature gradients and therefore such effects as Marangoni convection do not have to be considered. Classical fluid dynamics theory is used as the basis of the numerical simulations here, since Mason's experiments show that the theory is applicable for cryogenic liquid helium in large containers. To study liquid responses to various disturbances, we investigate and simulate

  6. Dynamics of gas-driven eruptions: Experimental simulations using CO2-H2O-polymer system

    NASA Astrophysics Data System (ADS)

    Zhang, Youxue; Sturtevant, B.; Stolper, E. M.

    1997-02-01

    We report exploratory experiments simulating gas-driven eruptions using the CO2-H2O system at room temperature as an analog of natural eruptive systems. The experimental apparatus consists of a test cell and a large tank. Initially, up to 1.0 wt% of CO2 is dissolved in liquid water under a pressure of up to 735 kPa in the test cell. The experiment is initiated by suddenly reducing the pressure of the test cell to a typical tank pressure of 10 kPa. The following are the main results: (1) The style of the process depends on the decompression ratio. There is a threshold decompression ratio above which rapid eruption occurs. (2) During rapid eruption, there is always fragmentation at the liquid-vapor interface. Fragmentation may also occur in the flow interior. (3) Initially, the top of the erupting column ascends at a constant acceleration (instead of constant velocity). (4) Average bubble radius grows as t2/3. (5) When viscosity is 20 times that of pure water or greater, a static foam may be stable after expansion to 97% vesicularity. The experiments provide several insights into natural gas-driven eruptions, including (1) the interplay between bubble growth and ascent of the erupting column must be considered for realistic modeling of bubble growth during gas-driven eruptions, (2) buoyant rise of the bubbly magma is not necessary during an explosive volcanic eruption, and (3) CO2-driven limnic eruptions can be explosive. The violence increases with the initial CO2 content dissolved in water.

  7. Design and Construction of a Shock Tube Experiment for Multiphase Instability Experiments

    NASA Astrophysics Data System (ADS)

    Middlebrooks, John; Black, Wolfgang; Avgoustopoulos, Constantine; Allen, Roy; Kathakapa, Raj; Guo, Qiwen; McFarland, Jacob

    2016-11-01

    Hydrodynamic instabilities are important phenomena that have a wide range of practical applications in engineering and physics. One such instability, the shock driven multiphase instability (SDMI), arises when a shockwave accelerates an interface between two particle-gas mixtures with differing multiphase properties. The SDMI is present in high energy explosives, scramjets, and supernovae. A practical way of studying shock wave driven instabilities is through experimentation in a shock tube laboratory. This poster presentation will cover the design and data acquisition process of the University of Missouri's Fluid Mixing Shock Tube Laboratory. In the shock tube, a pressure generated shockwave is passed through a multiphase interface, creating the SDMI instability. This can be photographed for observation using high speed cameras, lasers, and advance imaging techniques. Important experimental parameters such as internal pressure and temperature, and mass flow rates of gases can be set and recorded by remotely controlled devices. The experimental facility provides the University of Missouri's Fluid Mixing Shock Tube Laboratory with the ability to validate simulated experiments and to conduct further inquiry into the field of shock driven multiphase hydrodynamic instabilities. Advisor.

  8. Reward priming eliminates color-driven affect in perception.

    PubMed

    Hu, Kesong

    2018-01-03

    Brain and behavior evidence suggests that colors have distinct affective properties. Here, we investigated how reward influences color-driven affect in perception. In Experiment 1, we assessed competition between blue and red patches during a temporal-order judgment (TOJ) across a range of stimulus onset asynchronies (SOAs). During the value reinforcement, reward was linked to either blue (version 1) or red (version 2) in the experiment. The same stimuli then served as test ones in the following unrewarded, unspeeded TOJ task. Our analysis showed that blue patches were consistently seen as occurring first, even when objectively appearing 2nd at short SOAs. This accelerated perception of blue over red was disrupted by prior primes related to reward (vs. neutral) but not perceptional (blue vs. red) priming. Experiment 2 replicated the findings of Experiment 1 while uncoupling action and stimulus values. These results are consistent with the blue-approach and red-avoidance motivation hypothesis and highlight an active nature of the association of reward priming and color processing. Together, the present study implies a link between reward and color affect and contributes to the understanding of how reward influences color affect in visual processing.

  9. Developing Large Scale Explosively Driven Flyer Experiments on Sand

    NASA Astrophysics Data System (ADS)

    Rehagen, Thomas; Kraus, Richard

    2017-06-01

    Measurements of the dynamic behavior of granular materials are of great importance to a variety of scientific and engineering applications, including planetary science, seismology, and construction and destruction. In addition, high quality data are needed to enhance our understanding of granular physics and improve the computational models used to simulate related physical processes. However, since there is a non-negligible grain size associated with these materials, experiments must be of a relatively large scale in order to capture the continuum response of the material and reduce errors associated with the finite grain size. We will present designs for explosively driven flyer experiments to make high accuracy measurements of the Hugoniot of sand (with a grain size of hundreds of microns). To achieve an accuracy of better than a few percent in density, we are developing a platform to measure the Hugoniot of samples several centimeters in thickness. We will present the target designs as well as coupled designs for the explosively launched flyer system. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

  10. Monodisperse granular flows in viscous dispersions in a centrifugal acceleration field

    NASA Astrophysics Data System (ADS)

    Cabrera, Miguel Angel; Wu, Wei

    2016-04-01

    Granular flows are encountered in geophysical flows and innumerable industrial applications with particulate materials. When mixed with a fluid, a complex network of interactions between the particle- and fluid-phase develops, resulting in a compound material with a yet unclear physical behaviour. In the study of granular suspensions mixed with a viscous dispersion, the scaling of the stress-strain characteristics of the fluid phase needs to account for the level of inertia developed in experiments. However, the required model dimensions and amount of material becomes a main limitation for their study. In recent years, centrifuge modelling has been presented as an alternative for the study of particle-fluid flows in a reduced scaled model in an augmented acceleration field. By formulating simple scaling principles proportional to the equivalent acceleration Ng in the model, the resultant flows share many similarities with field events. In this work we study the scaling principles of the fluid phase and its effects on the flow of granular suspensions. We focus on the dense flow of a monodisperse granular suspension mixed with a viscous fluid phase, flowing down an inclined plane and being driven by a centrifugal acceleration field. The scaled model allows the continuous monitoring of the flow heights, velocity fields, basal pressure and mass flow rates at different Ng levels. The experiments successfully identify the effects of scaling the plastic viscosity of the fluid phase, its relation with the deposition of particles over the inclined plane, and allows formulating a discussion on the suitability of simulating particle-fluid flows in a centrifugal acceleration field.

  11. Conceptual design of a pulsed-power accelerator optimized for megajoule-class 1-TPa dynamic-material-physics experiments

    DOE PAGES

    Stygar, William A.; Reisman, David B.; Stoltzfus, Brian S.; ...

    2016-07-07

    In this study, we have developed a conceptual design of a next-generation pulsed-power accelerator that is optmized for driving megajoule-class dynamic-material-physics experiments at pressures as high as 1 TPa. The design is based on an accelerator architecture that is founded on three concepts: single-stage electrical-pulse compression, impedance matching, and transit-time-isolated drive circuits. Since much of the accelerator is water insulated, we refer to this machine as Neptune. The prime power source of Neptune consists of 600 independent impedance-matched Marx generators. As much as 0.8 MJ and 20 MA can be delivered in a 300-ns pulse to a 16-mΩ physics load;more » hence Neptune is a megajoule-class 20-MA arbitrary waveform generator. Neptune will allow the international scientific community to conduct dynamic equation-of-state, phase-transition, mechanical-property, and other material-physics experiments with a wide variety of well-defined drive-pressure time histories. Because Neptune can deliver on the order of a megajoule to a load, such experiments can be conducted on centimeter-scale samples at terapascal pressures with time histories as long as 1 μs.« less

  12. Tales from the new frontier: pioneers' experiences with consumer-driven health care.

    PubMed

    Lo Sasso, Anthony T; Rice, Thomas; Gabel, Jon R; Whitmore, Heidi

    2004-08-01

    To conduct site visits to study the early experiences of firms offering consumer-driven health care (CDHC) plans to their employees and firms that provide CDHC products. A convenience sample of three firms offering CDHC products to their employees, one of which is also a large insurer, and one firm offering an early CDHC product to employers. We conducted onsite interviews of four companies during the spring and summer of 2003. These four cases were not selected randomly. We contacted organizations that already had a consumer-driven plan in place by January 2002 so as to provide a complete year's worth of experience with CDHC. The experience of the companies we visited indicated that favorable selection tends to result when a CDHC plan is introduced alongside traditional preferred provider organization (PPO) and health maintenance organization (HMO) plan offerings. Two sites demonstrated substantial cost-savings. Our case studies also indicate that the more mundane aspects of health care benefits are still crucial under CDHC. The size of the provider network accessible through the CDHC plan was critical, as was the role of premium contributions in the benefit design. Also, companies highlighted the importance of educating employees about new CDHC products: employees who understood the product were more likely to enroll. Our site visits suggest the peril (risk selection) and the promise (cost savings) of CDHC. At this point there is still far more that we do not know about CDHC than we do know. Little is known about the extent to which CDHC changes people's behavior, the extent to which quality of care is affected by CDHC, and whether web-based information and tools actually make patients become better consumers.

  13. Multipactor Physics, Acceleration, and Breakdown in Dielectric-Loaded Accelerating Structures

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

    Fischer, Richard P.; Gold, Steven H.

    2016-07-01

    The objective of this 3-year program is to study the physics issues associated with rf acceleration in dielectric-loaded accelerating (DLA) structures, with a focus on the key issue of multipactor loading, which has been found to cause very significant rf power loss in DLA structures whenever the rf pulsewidth exceeds the multipactor risetime (~10 ns). The experiments are carried out in the X-band magnicon laboratory at the Naval Research Laboratory (NRL) in collaboration with Argonne National Laboratory (ANL) and Euclid Techlabs LLC, who develop the test structures with support from the DoE SBIR program. There are two main elements inmore » the research program: (1) high-power tests of DLA structures using the magnicon output (20 MW @11.4 GHz), and (2) tests of electron acceleration in DLA structures using relativistic electrons from a compact X-band accelerator. The work during this period has focused on a study of the use of an axial magnetic field to suppress multipactor in DLA structures, with several new high power tests carried out at NRL, and on preparation of the accelerator for the electron acceleration experiments.« less

  14. RF conditioning and beam experiments on 400 keV RFQ accelerator at BARC

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

    Gupta, Shrikrishna; Rao, S.V.L.S.; Kumar, Rajesh, E-mail: sgupta@barc.gov.in

    2014-07-01

    A 400 keV Radio-frequency quadrupole accelerator (RFQ) has been designed, developed and tested at BARC. This will be used as a neutron generator (via D-T reaction). The RFQ operates at a resonant frequency of 350 MHz and needs an RF power of ∼ 60 kW to accelerate the deuteron beam to 400 keV within a length of 1.03 m. Though the RFQ is designed for deuteron beam, it was tested by accelerating both the proton and deuteron beams to their designed values of 200 and 400 keV respectively. The proton and deuteron beam experiments required peak RF power of approx.more » 15 kW and 60 kW respectively at 350 MHz. The RF power from the tetrode amplifier and coaxial transmission lines is coupled to the cavity by a coaxial loop coupler. As the coupler and cavity operated at vacuum of better than 2e-6 torr, extensive RF conditioning of the cavity and coupler was performed to reach at the desired power levels. (author)« less

  15. Motivation for proposed experimentation in the realm of accelerated E. M. systems: A preliminary design for an experiment

    NASA Technical Reports Server (NTRS)

    Post, E. J.

    1970-01-01

    An experiment, designed to determine the difference between fields-magnetic and electric-surrounding a uniformly moving charge as contrasted with the fields surrounding an accelerated charge, is presented. A thought experiment is presented to illustrate the process.

  16. Accelerators as Authentic Training Experiences for Nascent Entrepreneurs

    ERIC Educational Resources Information Center

    Miles, Morgan P.; de Vries, Huibert; Harrison, Geoff; Bliemel, Martin; de Klerk, Saskia; Kasouf, Chick J.

    2017-01-01

    Purpose: The purpose of this paper is to address the role of accelerators as authentic learning-based entrepreneurial training programs. Accelerators facilitate the development and assessment of entrepreneurial competencies in nascent entrepreneurs through the process of creating a start-up venture. Design/methodology/approach: Survey data from…

  17. Observation of the development of secondary features in a Richtmyer–Meshkov instability driven flow

    DOE PAGES

    Bernard, Tennille; Truman, C. Randall; Vorobieff, Peter; ...

    2014-09-10

    Richtmyer–Meshkov instability (RMI) has long been the subject of interest for analytical, numerical, and experimental studies. In comparing results of experiment with numerics, it is important to understand the limitations of experimental techniques inherent in the chosen method(s) of data acquisition. We discuss results of an experiment where a laminar, gravity-driven column of heavy gas is injected into surrounding light gas and accelerated by a planar shock. A popular and well-studied method of flow visualization (using glycol droplet tracers) does not produce a flow pattern that matches the numerical model of the same conditions, while revealing the primary feature ofmore » the flow developing after shock acceleration: the pair of counter-rotating vortex columns. However, visualization using fluorescent gaseous tracer confirms the presence of features suggested by the numerics; in particular, a central spike formed due to shock focusing in the heavy-gas column. Furthermore, the streamwise growth rate of the spike appears to exhibit the same scaling with Mach number as that of the counter-rotating vortex pair (CRVP).« less

  18. Adaptive Acceleration of Visually Evoked Smooth Eye Movements in Mice

    PubMed Central

    2016-01-01

    The optokinetic response (OKR) consists of smooth eye movements following global motion of the visual surround, which suppress image slip on the retina for visual acuity. The effective performance of the OKR is limited to rather slow and low-frequency visual stimuli, although it can be adaptably improved by cerebellum-dependent mechanisms. To better understand circuit mechanisms constraining OKR performance, we monitored how distinct kinematic features of the OKR change over the course of OKR adaptation, and found that eye acceleration at stimulus onset primarily limited OKR performance but could be dramatically potentiated by visual experience. Eye acceleration in the temporal-to-nasal direction depended more on the ipsilateral floccular complex of the cerebellum than did that in the nasal-to-temporal direction. Gaze-holding following the OKR was also modified in parallel with eye-acceleration potentiation. Optogenetic manipulation revealed that synchronous excitation and inhibition of floccular complex Purkinje cells could effectively accelerate eye movements in the nasotemporal and temporonasal directions, respectively. These results collectively delineate multiple motor pathways subserving distinct aspects of the OKR in mice and constrain hypotheses regarding cellular mechanisms of the cerebellum-dependent tuning of movement acceleration. SIGNIFICANCE STATEMENT Although visually evoked smooth eye movements, known as the optokinetic response (OKR), have been studied in various species for decades, circuit mechanisms of oculomotor control and adaptation remain elusive. In the present study, we assessed kinematics of the mouse OKR through the course of adaptation training. Our analyses revealed that eye acceleration at visual-stimulus onset primarily limited working velocity and frequency range of the OKR, yet could be dramatically potentiated during OKR adaptation. Potentiation of eye acceleration exhibited different properties between the nasotemporal and

  19. Energy research: accelerator builders eager to aid fusion work.

    PubMed

    Metz, W D

    1976-10-15

    Useful fusion energy may be generated by means of heavy ion accelerator driven implosions if the contraints dictated by the physics and economics of thermonuclear targets and reactors can be satisfied.

  20. Retuning the DARHT Axis-II Linear Induction Accelerator

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

    Ekdahl, Carl August Jr.; Schulze, Martin E.; Carlson, Carl A.

    2015-03-31

    The Dual-Axis Radiographic Hydrodynamic Test (DARHT) facility uses bremsstrahlung radiation source spots produced by the focused electron beams from two linear induction accelerators (LIAs) to radiograph large hydrodynamic experiments driven by high explosives. The Axis-II 1.7-kA, 1600-ns beam pulse is transported through the LIA by the magnetic field from 91 solenoids as it is accelerated to ~16.5 MeV. The magnetic field produced by the solenoids and 80 steering dipole pairs for a given set of magnet currents is known as the “tune” of the accelerator [1]. From June, 2013 through September, 2014 a single tune was used. This tune wasmore » based on measurements of LIA element positions made over several years [2], and models of solenoidal fields derived from actual field measurements [3] [4]. Based on the focus scan technique, changing the tune of the accelerator and downstream transport had no effect on the beam emittance, to within the uncertainties of the measurement. Beam sizes appear to have been overestimated in all prior measurements because of the low magnification of the imaging system. This has resulted in overestimates of emittance by ~50%. The high magnification imaging should be repeated with the old tune for direct comparison with the new tune. High magnification imaging with the new accelerator tune should be repeated after retuning the downstream to produce a much more symmetric beam to reduce the uncertainty of this measurement. Thus, these results should be considered preliminary until we can effect a new tune to produce symmetric spots at our imaging station, for high magnification images.« less

  1. Advanced Communications Technology Satellite (ACTS) Experiments Program - A market-driven approach to government/industry cooperation

    NASA Astrophysics Data System (ADS)

    Olmstead, Dean A.; Schertler, Ronald R.; Randall, Laura A.

    1992-03-01

    The Advanced Communications Technology Satellite (ACTS), now under development and scheduled for launch in early 1993, is the current focus of NASA's commercial communications satellite program. The full power of the key technologies on ACTS can only be realized if industry assumes an active role in the conduct of experiments and demonstrations. This paper discusses the current market-driven rationale behind the ACTS Experiments Program activities aimed at getting industry involved - a rationale that addresses industry concerns and responds to industry inputs.

  2. Experience-dependent enhancement of pitch-specific responses in the auditory cortex is limited to acceleration rates in normal voice range

    PubMed Central

    Krishnan, Ananthanarayan; Gandour, Jackson T.; Suresh, Chandan H.

    2015-01-01

    The aim of this study is to determine how pitch acceleration rates within and outside the normal pitch range may influence latency and amplitude of cortical pitch-specific responses (CPR) as a function of language experience (Chinese, English). Responses were elicited from a set of four pitch stimuli chosen to represent a range of acceleration rates (two each inside and outside the normal voice range) imposed on the high rising Mandarin Tone 2. Pitch-relevant neural activity, as reflected in the latency and amplitude of scalp-recorded CPR components, varied depending on language-experience and pitch acceleration of dynamic, time-varying pitch contours. Peak latencies of CPR components were shorter in the Chinese than the English group across stimuli. Chinese participants showed greater amplitude than English for CPR components at both frontocentral and temporal electrode sites in response to pitch contours with acceleration rates inside the normal voice pitch range as compared to pitch contours with acceleration rates that exceed the normal range. As indexed by CPR amplitude at the temporal sites, a rightward asymmetry was observed for the Chinese group only. Only over the right temporal site was amplitude greater in the Chinese group relative to the English. These findings may suggest that the neural mechanism(s) underlying processing of pitch in the right auditory cortex reflect experience-dependent modulation of sensitivity to acceleration in just those rising pitch contours that fall within the bounds of one’s native language. More broadly, enhancement of native pitch stimuli and stronger rightward asymmetry of CPR components in the Chinese group is consistent with the notion that long-term experience shapes adaptive, distributed hierarchical pitch processing in the auditory cortex, and reflects an interaction with higher-order, extrasensory processes beyond the sensory memory trace. PMID:26166727

  3. Self-injection of electrons in a laser-wakefield accelerator by using longitudinal density ripple

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

    Dahiya, Deepak; Sharma, A. K.; Sajal, Vivek

    By introducing a longitudinal density ripple (periodic modulation in background plasma density), we demonstrate self-injection of electrons in a laser-wakefield accelerator. The wakefield driven plasma wave, in presence of density ripple excites two side band waves of same frequency but different wave numbers. One of these side bands, having smaller phase velocity compared to wakefield driven plasma wave, preaccelerates the background plasma electrons. Significant number of these preaccelerated electrons get trapped in the laser-wakefield and further accelerated to higher energies.

  4. Experimental characterization of a coaxial plasma accelerator for a colliding plasma experiment

    NASA Astrophysics Data System (ADS)

    Wiechula, J.; Hock, C.; Iberler, M.; Manegold, T.; Schönlein, A.; Jacoby, J.

    2015-04-01

    We report experimental results of a single coaxial plasma accelerator in preparation for a colliding plasma experiment. The utilized device consisted of a coaxial pair of electrodes, accelerating the plasma due to J ×B forces. A pulse forming network, composed of three capacitors connected in parallel, with a total capacitance of 27 μF was set up. A thyratron allowed to switch the maximum applied voltage of 9 kV. Under these conditions, the pulsed currents reached peak values of about 103 kA. The measurements were performed in a small vacuum chamber with a neutral-gas prefill at gas pressures between 10 Pa and 14 000 Pa. A gas mixture of ArH2 with 2.8% H2 served as the discharge medium. H2 was chosen in order to observe the broadening of the Hβ emission line and thus estimate the electron density. The electron density for a single plasma accelerator reached peak values on the order of 1016 cm-3 . Electrical parameters, inter alia inductance and resistance, were determined for the LCR circuit during the plasma acceleration as well as in a short circuit case. Depending on the applied voltage, the inductance and resistance reached values ranging from 194 nH to 216 nH and 13 mΩ to 23 mΩ, respectively. Furthermore, the plasma velocity was measured using a fast CCD camera. Plasma velocities of 2 km/s up to 17 km/s were observed, the magnitude being highly correlated with gas pressure and applied voltage.

  5. Accelerations in Flight

    NASA Technical Reports Server (NTRS)

    Doolittle, J H

    1925-01-01

    This work on accelerometry was done at McCook Field for the purpose of continuing the work done by other investigators and obtaining the accelerations which occur when a high-speed pursuit airplane is subjected to the more common maneuvers. The accelerations obtained in suddenly pulling out of a dive with well-balanced elevators are shown to be within 3 or 4 per cent of the theoretically possible accelerations. The maximum acceleration which a pilot can withstand depends upon the length of time the acceleration is continued. It is shown that he experiences no difficulty under the instantaneous accelerations as high as 7.8 G., but when under accelerations in excess of 4.5 G., continued for several seconds, he quickly loses his faculties.

  6. Conceptual Design for Time-Resolved X-ray Diffraction in a Single Laser-Driven Compression Experiment

    NASA Astrophysics Data System (ADS)

    Benedetti, Laura Robin; Eggert, J. H.; Kilkenny, J. D.; Bradley, D. K.; Bell, P. M.; Palmer, N. E.; Rygg, J. R.; Boehly, T. R.; Collins, G. W.; Sorce, C.

    2017-06-01

    Since X-ray diffraction is the most definitive method for identifying crystalline phases of a material, it is an important technique for probing high-energy-density materials during laser-driven compression experiments. We are developing a design for collecting several x-ray diffraction datasets during a single laser-driven experiment, with a goal of achieving temporal resolution better than 1ns. The design combines x-ray streak cameras, for a continuous temporal record of diffraction, with fast x-ray imagers, to collect several diffraction patterns with sufficient solid angle range and resolution to identify crystalline texture. Preliminary experiments will be conducted at the Omega laser and then implemented at the National Ignition Facility. We will describe the status of the conceptual design, highlighting tradeoffs in the design process. We will also discuss the technical issues that must be addressed in order to develop a successful experimental platform. These include: Facility-specific geometric constraints such as unconverted laser light and target alignment; EMP issues when electronic diagnostics are close to the target; X-ray source requirements; and detector capabilities. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, LLNL-ABS-725146.

  7. Tales from the New Frontier: Pioneers' Experiences with Consumer-Driven Health Care

    PubMed Central

    Lo Sasso, Anthony T; Rice, Thomas; Gabel, Jon R; Whitmore, Heidi

    2004-01-01

    Objective To conduct site visits to study the early experiences of firms offering consumer-driven health care (CDHC) plans to their employees and firms that provide CDHC products. Data Sources/Study Setting A convenience sample of three firms offering CDHC products to their employees, one of which is also a large insurer, and one firm offering an early CDHC product to employers. Study Design We conducted onsite interviews of four companies during the spring and summer of 2003. These four cases were not selected randomly. We contacted organizations that already had a consumer-driven plan in place by January 2002 so as to provide a complete year's worth of experience with CDHC. Principal Findings The experience of the companies we visited indicated that favorable selection tends to result when a CDHC plan is introduced alongside traditional preferred provider organization (PPO) and health maintenance organization (HMO) plan offerings. Two sites demonstrated substantial cost-savings. Our case studies also indicate that the more mundane aspects of health care benefits are still crucial under CDHC. The size of the provider network accessible through the CDHC plan was critical, as was the role of premium contributions in the benefit design. Also, companies highlighted the importance of educating employees about new CDHC products: employees who understood the product were more likely to enroll. Conclusions Our site visits suggest the peril (risk selection) and the promise (cost savings) of CDHC. At this point there is still far more that we do not know about CDHC than we do know. Little is known about the extent to which CDHC changes people's behavior, the extent to which quality of care is affected by CDHC, and whether web-based information and tools actually make patients become better consumers. PMID:15230912

  8. Two-stage Electron Acceleration by 3D Collisionless Guide-field Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Buechner, J.; Munoz, P.

    2017-12-01

    We discuss a two-stage process of electron acceleration near X-lines of 3D collisionless guide-field magnetic reconnection. Non-relativistic electrons are first pre-accelerated by magnetic-field-aligned (parallel) electric fields. At the nonlinear stage of 3D guide-field magnetic reconnection electric and magnetic fields become filamentary structured due to streaming instabilities. This causes an additional curvature-driven electron acceleration in the guide-field direction. The resulting spectrum of the accelerated electrons follows a power law.

  9. Educating a Diverse Workforce: The Student of Color Experience in a Research University's Accelerated Undergraduate Nursing Program

    ERIC Educational Resources Information Center

    Johnson-Campbell, Tanisha

    2018-01-01

    This study is an investigation into a 15-month accelerated undergraduate nursing program and the minority student experience. Using a mixed methods approach, this research addressed the following questions: 1. What was the retention rate for students enrolled in the accelerated nursing bachelor's program and how did that differ by race? 2. What…

  10. Commercialization of an S-band standing-wave electron accelerator for industrial applications

    NASA Astrophysics Data System (ADS)

    Moon, Jin-Hyeok; Kwak, Gyeong-Il; Han, Jae-Ik; Lee, Gyu-Baek; Jeon, Seong-Hwan; Kim, Jae-Young; Hwang, Cheol-Bin; Lee, Gi-Yong; Kim, Young-Man; Park, Sung-Ju

    2016-09-01

    An electron accelerator system has been developed for use in industrial, as well as possible medical, applications. Based on our experiences achieved during prototype system development and various electron beam acceleration tests, we have built a stable and compact system for sales purposes. We have integrated a self-developed accelerating cavity, an E-gun pulse driver, a radio-frequency (RF) power system, a vacuum system, a cooling system, etc. into a frame with a size of 1800 × 1000 × 1500 mm3. The accelerating structure is a side-coupled standing-wave type operating in the π/2 mode (tuned to~3 GHz). The RF power is provided by using a magnetron driven by a solid-state modulator. The electron gun is a triode type with a dispenser cathode (diameter of 11 mm). The system is capable of delivering a maximum 900-W average electron beam power with tight focusing at the target. Until now, we have performed various electron beam tests and X-ray beam tests after having built the system, have completed the beam assessment for commercializations, and have been preparing full-fledged sales activity. This article reports on our system development processes and on some of our early test results for commercializations.

  11. Using a national archive of patient experience narratives to promote local patient-centered quality improvement: an ethnographic process evaluation of 'accelerated' experience-based co-design.

    PubMed

    Locock, Louise; Robert, Glenn; Boaz, Annette; Vougioukalou, Sonia; Shuldham, Caroline; Fielden, Jonathan; Ziebland, Sue; Gager, Melanie; Tollyfield, Ruth; Pearcey, John

    2014-10-01

    To evaluate an accelerated form of experience-based co-design (EBCD), a type of participatory action research in which patients and staff work together to improve quality; to observe how acceleration affected the process and outcomes of the intervention. An ethnographic process evaluation of an adapted form of EBCD was conducted, including observations, interviews, questionnaires and documentary analysis. Whilst retaining all components of EBCD, the adapted approach replaced local patient interviews with secondary analysis of a national archive of patient experience narratives to create national trigger films; shortened the timeframe; and employed local improvement facilitators. It was tested in intensive care and lung cancer in two English National Health Service (NHS) hospitals. A total of 96 clinical staff (primarily nursing and medical), and 63 patients and family members participated in co-design activities. The accelerated approach proved acceptable to staff and patients; using films of national rather than local narratives did not adversely affect local NHS staff engagement, and may have made the process less threatening or challenging. Local patients felt the national films generally reflected important themes although a minority felt they were more negative than their own experience. However, they served their purpose of 'triggering' discussion between patients and staff, and the resulting 48 co-design (improvement) activities across the four pathways were similar to those in EBCD, but achieved more quickly and at lower cost. Accelerated EBCD offers a rigorous and relatively cost-effective patient-centered quality improvement approach. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

  12. STS-40 orbital acceleration research experiment flight results during a typical sleep period

    NASA Technical Reports Server (NTRS)

    Blanchard, R. C.; Nicholson, J. Y.; Ritter, J. R.

    1992-01-01

    The Orbital Acceleration Research Experiment (OARE), an electrostatic accelerometer package with complete on-orbit calibration capabilities, was flown for the first time aboard the Space Shuttle on STS-40. This is also the first time an accelerometer package with nano-g sensitivity and a calibration facility has flown aboard the Space Shuttle. The instrument is designed to measure and record the Space Shuttle aerodynamic acceleration environment from the free molecule flow regime through the rarified flow transition into the hypersonic continuum regime. Because of its sensitivity, the OARE instrument defects aerodynamic behavior of the Space Shuttle while in low-earth orbit. A 2-hour orbital time period on day seven of the mission, when the crew was asleep and other spacecraft activities were at a minimum, was examined. During the flight, a 'trimmed-mean' filter was used to produce high quality, low frequency data which was successfully stored aboard the Space Shuttle in the OARE data storage system. Initial review of the data indicated that, although the expected precision was achieved, some equipment problems occurred resulting in uncertain accuracy. An acceleration model which includes aerodynamic, gravity-gradient, and rotational effects was constructed and compared with flight data. Examination of the model with the flight data shows the instrument to be sensitive to all major expected low frequency acceleration phenomena; however, some erratic instrument bias behavior persists in two axes. In these axes, the OARE data can be made to match a comprehensive atmospheric-aerodynamic model by making bias adjustments and slight linear corrections for drift. The other axis does not exhibit these difficulties and gives good agreement with the acceleration model.

  13. Method for generating a plasma wave to accelerate electrons

    DOEpatents

    Umstadter, D.; Esarey, E.; Kim, J.K.

    1997-06-10

    The invention provides a method and apparatus for generating large amplitude nonlinear plasma waves, driven by an optimized train of independently adjustable, intense laser pulses. In the method, optimal pulse widths, interpulse spacing, and intensity profiles of each pulse are determined for each pulse in a series of pulses. A resonant region of the plasma wave phase space is found where the plasma wave is driven most efficiently by the laser pulses. The accelerator system of the invention comprises several parts: the laser system, with its pulse-shaping subsystem; the electron gun system, also called beam source, which preferably comprises photo cathode electron source and RF-LINAC accelerator; electron photo-cathode triggering system; the electron diagnostics; and the feedback system between the electron diagnostics and the laser system. The system also includes plasma source including vacuum chamber, magnetic lens, and magnetic field means. The laser system produces a train of pulses that has been optimized to maximize the axial electric field amplitude of the plasma wave, and thus the electron acceleration, using the method of the invention. 21 figs.

  14. Method for generating a plasma wave to accelerate electrons

    DOEpatents

    Umstadter, Donald; Esarey, Eric; Kim, Joon K.

    1997-01-01

    The invention provides a method and apparatus for generating large amplitude nonlinear plasma waves, driven by an optimized train of independently adjustable, intense laser pulses. In the method, optimal pulse widths, interpulse spacing, and intensity profiles of each pulse are determined for each pulse in a series of pulses. A resonant region of the plasma wave phase space is found where the plasma wave is driven most efficiently by the laser pulses. The accelerator system of the invention comprises several parts: the laser system, with its pulse-shaping subsystem; the electron gun system, also called beam source, which preferably comprises photo cathode electron source and RF-LINAC accelerator; electron photo-cathode triggering system; the electron diagnostics; and the feedback system between the electron diagnostics and the laser system. The system also includes plasma source including vacuum chamber, magnetic lens, and magnetic field means. The laser system produces a train of pulses that has been optimized to maximize the axial electric field amplitude of the plasma wave, and thus the electron acceleration, using the method of the invention.

  15. Laser-driven three-stage heavy-ion acceleration from relativistic laser-plasma interaction.

    PubMed

    Wang, H Y; Lin, C; Liu, B; Sheng, Z M; Lu, H Y; Ma, W J; Bin, J H; Schreiber, J; He, X T; Chen, J E; Zepf, M; Yan, X Q

    2014-01-01

    A three-stage heavy ion acceleration scheme for generation of high-energy quasimonoenergetic heavy ion beams is investigated using two-dimensional particle-in-cell simulation and analytical modeling. The scheme is based on the interaction of an intense linearly polarized laser pulse with a compound two-layer target (a front heavy ion layer + a second light ion layer). We identify that, under appropriate conditions, the heavy ions preaccelerated by a two-stage acceleration process in the front layer can be injected into the light ion shock wave in the second layer for a further third-stage acceleration. These injected heavy ions are not influenced by the screening effect from the light ions, and an isolated high-energy heavy ion beam with relatively low-energy spread is thus formed. Two-dimensional particle-in-cell simulations show that ∼100MeV/u quasimonoenergetic Fe24+ beams can be obtained by linearly polarized laser pulses at intensities of 1.1×1021W/cm2.

  16. Commnity Petascale Project for Accelerator Science And Simulation: Advancing Computational Science for Future Accelerators And Accelerator Technologies

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

    Spentzouris, Panagiotis; /Fermilab; Cary, John

    The design and performance optimization of particle accelerators are essential for the success of the DOE scientific program in the next decade. Particle accelerators are very complex systems whose accurate description involves a large number of degrees of freedom and requires the inclusion of many physics processes. Building on the success of the SciDAC-1 Accelerator Science and Technology project, the SciDAC-2 Community Petascale Project for Accelerator Science and Simulation (ComPASS) is developing a comprehensive set of interoperable components for beam dynamics, electromagnetics, electron cooling, and laser/plasma acceleration modelling. ComPASS is providing accelerator scientists the tools required to enable the necessarymore » accelerator simulation paradigm shift from high-fidelity single physics process modeling (covered under SciDAC1) to high-fidelity multiphysics modeling. Our computational frameworks have been used to model the behavior of a large number of accelerators and accelerator R&D experiments, assisting both their design and performance optimization. As parallel computational applications, the ComPASS codes have been shown to make effective use of thousands of processors.« less

  17. The Origin Of Most Cosmic Rays: The Acceleration By E(parallel)

    NASA Astrophysics Data System (ADS)

    Colgate, Stirling A.; Li, H.

    2008-03-01

    We suggest a universal view of the origin of almost all cosmic rays. We propose that nearly every accelerated CRs was initially part of the parallel current that maintains most all force-free, twisted magnetic fields. We point out the greatest fraction of the free energy of magnetic fields in the universe likely resides in force-free fields as opposed to force-bounded ones, because the velocity of twisting, the ponder motive force, is small compared to local Alven speed. We suggest that these helical fields and the particles that they accelerate are distributed nearly uniformly and consequently are near space-filling with some notable exceptions. Charged particles are accelerated by the E( parallel to the magnetic field B) produced by the dissipation of the free energy of these fields by the progressive diffusive loss of "run-away" accelerated current-carrying charged particles from the "core" of the helical fields. Such diffusive loss is first identified as reconnection, but instead potentiates a much larger irreversible loss of highly accelerated anisotropic run-away current carrier particles. We suggest, as in fusion confinement experiments, that there exists a universal, highly robust, diffusion coefficient, D, resulting in D 1% of Bohm diffusion, as has been found in all confinement experiments, possibly driven by drift waves and, or collision-less, tearing modes. The consequential current carrier loss along the resulting tangled field lines is sufficient to account for the energy, number and spectrum of nearly all CR acceleration, both galactic as well as extra galactic. The spectrum is determined by a loss fraction dn/n -dE/E where dn D E-3/2 resulting in dn/dE = E/E0-2.5 up to 1022 ev. Only mass accretion onto SMBHs can supply the energy necessary, 1060 ergs, to fill the IGM with a CR spectrum of Γ 2.6. (Supported by the DOE)

  18. Particle drift model for Z-pinch-driven magneto-Rayleigh-Taylor instability

    NASA Astrophysics Data System (ADS)

    Dan, Jia Kun; Xu, Qiang; Wang, Kun Lun; Ren, Xiao Dong; Huang, Xian Bin

    2016-09-01

    A theoretical model of Z-pinch driven magneto-Rayleigh-Taylor instability is proposed based on the particle drift point of view, which can explain the helical instability structure observed in premagnetized imploding liner experiments. It is demonstrated that all possible drift motions, including polarization drift, gradient drift, and curvature drift, which can lead to charge separations, each will attribute to an effective gravity acceleration. Theoretical predictions given by this model are dramatically different from those given by previous theories which have been readily recovered in the theory presented here as a limiting case. The theory shows qualitative agreement with available experimental data of the pitch angle and provides certain predictions to be verified.

  19. Beam dynamics analysis of dielectric laser acceleration using a fast 6D tracking scheme

    NASA Astrophysics Data System (ADS)

    Niedermayer, Uwe; Egenolf, Thilo; Boine-Frankenheim, Oliver

    2017-11-01

    A six-dimensional symplectic tracking approach exploiting the periodicity properties of dielectric laser acceleration (DLA) gratings is presented. The longitudinal kick is obtained from the spatial Fourier harmonics of the laser field within the structure, and the transverse kicks are obtained using the Panofsky-Wenzel theorem. Additionally to the usual, strictly longitudinally periodic gratings, our approach is also applicable to periodicity chirped (subrelativistic) and tilted (deflection) gratings. In the limit of small kicks and short periods we obtain the 6D Hamiltonian, which allows, for example, to obtain matched beam distributions in DLAs. The scheme is applied to beam and grating parameters similar to recently performed experiments. The paper concludes with an outlook to laser based focusing schemes, which are promising to overcome fundamental interaction length limitations, in order to build an entire microchip-sized laser driven accelerator.

  20. First demonstration of an emulsion multi-stage shifter for accelerator neutrino experiments in J-PARC T60

    NASA Astrophysics Data System (ADS)

    Yamada, K.; Aoki, S.; Cao, S.; Chikuma, N.; Fukuda, T.; Fukuzawa, Y.; Gonin, M.; Hayashino, T.; Hayato, Y.; Hiramoto, A.; Hosomi, F.; Inoh, T.; Iori, S.; Ishiguro, K.; Kawahara, H.; Kim, H.; Kitagawa, N.; Koga, T.; Komatani, R.; Komatsu, M.; Matsushita, A.; Mikado, S.; Minamino, A.; Mizusawa, H.; Matsumoto, T.; Matsuo, T.; Morimoto, Y.; Morishima, K.; Morishita, M.; Naganawa, N.; Nakamura, K.; Nakamura, M.; Nakamura, Y.; Nakano, T.; Nakatsuka, Y.; Nakaya, T.; Nishio, A.; Ogawa, S.; Oshima, H.; Quilain, B.; Rokujo, H.; Sato, O.; Seiya, Y.; Shibuya, H.; Shiraishi, T.; Suzuki, Y.; Tada, S.; Takahashi, S.; Yokoyama, M.; Yoshimoto, M.

    2017-06-01

    We describe the first ever implementation of a clock-based, multi-stage emulsion shifter in an accelerator neutrino experiment. The system was installed in the neutrino monitoring building at the Japan Proton Accelerator Research Complex as part of a test experiment, T60, and stable operation was maintained for a total of 126.6 days. By applying time information to emulsion films, various results were obtained. Time resolutions of 5.3-14.7 s were evaluated in an operation spanning 46.9 days (yielding division numbers of 1.4-3.8×105). By using timing and spatial information, reconstruction of coincident events consisting of high-multiplicity and vertex-contained events, including neutrino events, was performed. Emulsion events were matched to events observed by INGRID, one of the on-axis near detectors of the T2K experiment, with high reliability (98.5%), and hybrid analysis of the emulsion and INGRID events was established by means of the multi-stage shifter. The results demonstrate that the multi-stage shifter can feasibly be used in neutrino experiments.

  1. Radiation pressure acceleration: The factors limiting maximum attainable ion energy

    DOE PAGES

    Bulanov, S. S.; Esarey, E.; Schroeder, C. B.; ...

    2016-04-15

    Radiation pressure acceleration (RPA) is a highly efficient mechanism of laser-driven ion acceleration, with near complete transfer of the laser energy to the ions in the relativistic regime. However, there is a fundamental limit on the maximum attainable ion energy, which is determined by the group velocity of the laser. The tightly focused laser pulses have group velocities smaller than the vacuum light speed, and, since they offer the high intensity needed for the RPA regime, it is plausible that group velocity effects would manifest themselves in the experiments involving tightly focused pulses and thin foils. However, in this case,more » finite spot size effects are important, and another limiting factor, the transverse expansion of the target, may dominate over the group velocity effect. As the laser pulse diffracts after passing the focus, the target expands accordingly due to the transverse intensity profile of the laser. Due to this expansion, the areal density of the target decreases, making it transparent for radiation and effectively terminating the acceleration. The off-normal incidence of the laser on the target, due either to the experimental setup, or to the deformation of the target, will also lead to establishing a limit on maximum ion energy.« less

  2. Light modulated electron beam driven radiofrequency emitter

    DOEpatents

    Wilson, M.T.; Tallerico, P.J.

    1979-10-10

    The disclosure relates to a light modulated electron beam-driven radiofrequency emitter. Pulses of light impinge on a photoemissive device which generates an electron beam having the pulse characteristics of the light. The electron beam is accelerated through a radiofrequency resonator which produces radiofrequency emission in accordance with the electron, hence, the light pulses.

  3. Conceptual design of a 15-TW pulsed-power accelerator for high-energy-density–physics experiments

    DOE PAGES

    Spielman, R. B.; Froula, D. H.; Brent, G.; ...

    2017-06-21

    We have developed a conceptual design of a 15-TW pulsed-power accelerator based on the linear-transformer-driver (LTD) architecture described by Stygar [W. A. Stygar et al., Phys. Rev. ST Accel. Beams 18, 110401 (2015)]. The driver will allow multiple, high-energy-density experiments per day in a university environment and, at the same time, will enable both fundamental and integrated experiments that are scalable to larger facilities. In this design, many individual energy storage units (bricks), each composed of two capacitors and one switch, directly drive the target load without additional pulse compression. Ten LTD modules in parallel drive the load. Each modulemore » consists of 16 LTD cavities connected in series, where each cavity is powered by 22 bricks connected in parallel. This design stores up to 2.75 MJ and delivers up to 15 TW in 100 ns to the constant-impedance, water-insulated radial transmission lines. The transmission lines in turn deliver a peak current as high as 12.5 MA to the physics load. To maximize its experimental value and flexibility, the accelerator is coupled to a modern, multibeam laser facility (four beams with up to 5 kJ in 10 ns and one beam with up to 2.6 kJ in 100 ps or less) that can provide auxiliary heating of the physics load. The lasers also enable advanced diagnostic techniques such as x-ray Thomson scattering and multiframe and three-dimensional radiography. In conclusion, the coupled accelerator-laser facility will be the first of its kind and be capable of conducting unprecedented high-energy-density-physics experiments.« less

  4. Conceptual design of a 15-TW pulsed-power accelerator for high-energy-density–physics experiments

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

    Spielman, R. B.; Froula, D. H.; Brent, G.

    We have developed a conceptual design of a 15-TW pulsed-power accelerator based on the linear-transformer-driver (LTD) architecture described by Stygar [W. A. Stygar et al., Phys. Rev. ST Accel. Beams 18, 110401 (2015)]. The driver will allow multiple, high-energy-density experiments per day in a university environment and, at the same time, will enable both fundamental and integrated experiments that are scalable to larger facilities. In this design, many individual energy storage units (bricks), each composed of two capacitors and one switch, directly drive the target load without additional pulse compression. Ten LTD modules in parallel drive the load. Each modulemore » consists of 16 LTD cavities connected in series, where each cavity is powered by 22 bricks connected in parallel. This design stores up to 2.75 MJ and delivers up to 15 TW in 100 ns to the constant-impedance, water-insulated radial transmission lines. The transmission lines in turn deliver a peak current as high as 12.5 MA to the physics load. To maximize its experimental value and flexibility, the accelerator is coupled to a modern, multibeam laser facility (four beams with up to 5 kJ in 10 ns and one beam with up to 2.6 kJ in 100 ps or less) that can provide auxiliary heating of the physics load. The lasers also enable advanced diagnostic techniques such as x-ray Thomson scattering and multiframe and three-dimensional radiography. In conclusion, the coupled accelerator-laser facility will be the first of its kind and be capable of conducting unprecedented high-energy-density-physics experiments.« less

  5. Impact of intermediate and high energy nuclear data on the neutronic safety parameters of MYRRHA accelerator driven system

    NASA Astrophysics Data System (ADS)

    Stankovskiy, Alexey; Çelik, Yurdunaz; Eynde, Gert Van den

    2017-09-01

    Perturbation of external neutron source can cause significant local power changes transformed into undesired safety-related events in an accelerator driven system. Therefore for the accurate design of MYRRHA sub-critical core it is important to evaluate the uncertainty of power responses caused by the uncertainties in nuclear reaction models describing the particle transport from primary proton energy down to the evaluated nuclear data table range. The calculations with a set of models resulted in quite low uncertainty on the local power caused by significant perturbation of primary neutron yield from proton interactions with lead and bismuth isotopes. The considered accidental event of prescribed proton beam shape loss causes drastic increase in local power but does not practically change the total core thermal power making this effect difficult to detect. In the same time the results demonstrate a correlation between perturbed local power responses in normal operation and misaligned beam conditions indicating that generation of covariance data for proton and neutron induced neutron multiplicities for lead and bismuth isotopes is needed to obtain reliable uncertainties for local power responses.

  6. Time of Flight based diagnostics for high energy laser driven ion beams

    NASA Astrophysics Data System (ADS)

    Scuderi, V.; Milluzzo, G.; Alejo, A.; Amico, A. G.; Booth, N.; Cirrone, G. A. P.; Doria, D.; Green, J.; Kar, S.; Larosa, G.; Leanza, R.; Margarone, D.; McKenna, P.; Padda, H.; Petringa, G.; Pipek, J.; Romagnani, L.; Romano, F.; Schillaci, F.; Borghesi, M.; Cuttone, G.; Korn, G.

    2017-03-01

    Nowadays the innovative high power laser-based ion acceleration technique is one of the most interesting challenges in particle acceleration field, showing attractive characteristics for future multidisciplinary applications, including medical ones. Nevertheless, peculiarities of optically accelerated ion beams make mandatory the development of proper transport, selection and diagnostics devices in order to deliver stable and controlled ion beams for multidisciplinary applications. This is the main purpose of the ELIMAIA (ELI Multidisciplinary Applications of laser-Ion Acceleration) beamline that will be realized and installed within 2018 at the ELI-Beamlines research center in the Czech Republic, where laser driven high energy ions, up to 60 MeV/n, will be available for users. In particular, a crucial role will be played by the on-line diagnostics system, recently developed in collaboration with INFN-LNS (Italy), consisting of TOF detectors, placed along the beamline (at different detection distances) to provide online monitoring of key characteristics of delivered beams, such as energy, fluence and ion species. In this contribution an overview on the ELIMAIA available ion diagnostics will be briefly given along with the preliminary results obtained during a test performed with high energy laser-driven proton beams accelerated at the VULCAN PW-laser available at RAL facility (U.K.).

  7. Research on Vacuum Laser Accelerator and Proof-of Principle Experiment

    NASA Astrophysics Data System (ADS)

    Shao, Lei

    BNL-ATF fit our project very well. The laser system at ATF is a short pulse CO2 laser. Under present ATF condition, the peak power of the CO2 laser is around 5J with pulse duration 5ps. Therefore the maximum laser intensity can reach a 0 ≈ 1.0. Such level of laser intensity is not sufficient to perform violent electron acceleration-CAS according to the threshold we defined. However this level intensity is already high enough to see basic proof-of-principle signal based on our extensive simulations with exact practical ATF experimental conditions. Another important factor is the electron beam condition. ATF uses photoinjector Radio Frequency (RF) gun system for electron beam. The working frequency is at constant level 2856MHz. Generally the electron beam deliver energy around 40MeV˜60MeV to the transport beam line. However as we mentioned before with relatively low laser intensity the electron initial energy is required to be lower as well correspondently. We tried best to tuned ATF electron beam energy down to 15MeV. With laser intensity around a 0 ≈ 1.0 and electron beam 15MeV, our simulation indicates to see energy spread expansion after interaction, and this effect increases while the laser intensity increases (even slightly change from a 0 ≈ 0.9 to 2.2). The experiment design is completed based on ATF beam line condition. The design and layout are presented. All the optical devices are acquired and machined. Installation and alignment have been done a few times for testing. (Abstract shortened by UMI.)

  8. Data Driven Trigger Design and Analysis for the NOvA Experiment

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

    Kurbanov, Serdar

    This thesis primarily describes analysis related to studying the Moon shadow with cosmic rays, an analysis using upward-going muons trigger data, and other work done as part of MSc thesis work conducted at Fermi National Laboratory. While at Fermilab I made hardware and software contributions to two experiments - NOvA and Mu2e. NOvA is a neutrino experiment with the primary goal of measuring parameters related to neutrino oscillation. This is a running experiment, so it's possible to provide analysis of real beam and cosmic data. Most of this work was related to the Data-Driven Trigger (DDT) system of NOvA. Themore » results of the Upward-Going muon analysis was presented at ICHEP in August 2016. The analysis demonstrates the proof of principle for a low-mass dark matter search. Mu2e is an experiment currently being built at Fermilab. Its primary goal is to detect the hypothetical neutrinoless conversion from a muon into an electron. I contributed to the production and tests of Cathode Strip Chambers (CSCs) which are required for testing the Cosmic Ray Veto (CRV) system for the experiment. This contribution is described in the last chapter along with a short description of the technical work provided for the DDT system of the NOvA experiment. All of the work described in this thesis will be extended by the next generation of UVA graduate students and postdocs as new data is collected by the experiment. I hope my eorts of have helped lay the foundation for many years of beautiful results from Mu2e and NOvA.« less

  9. "DIANA" - A New, Deep-Underground Accelerator Facility for Astrophysics Experiments

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

    Leitner, M.; Leitner, D.; Lemut, A.

    2009-05-28

    The DIANA project (Dakota Ion Accelerators for Nuclear Astrophysics) is a collaboration between the University of Notre Dame, University of North Carolina, Western Michigan University, and Lawrence Berkeley National Laboratory to build a nuclear astrophysics accelerator facility 1.4 km below ground. DIANA is part of the US proposal DUSEL (Deep Underground Science and Engineering Laboratory) to establish a cross-disciplinary underground laboratory in the former gold mine of Homestake in South Dakota, USA. DIANA would consist of two high-current accelerators, a 30 to 400 kV variable, high-voltage platform, and a second, dynamitron accelerator with a voltage range of 350 kV tomore » 3 MV. As a unique feature, both accelerators are planned to be equipped with either high-current microwave ion sources or multi-charged ECR ion sources producing ions from protons to oxygen. Electrostatic quadrupole transport elements will be incorporated in the dynamitron high voltage column. Compared to current astrophysics facilities, DIANA could increase the available beam densities on target by magnitudes: up to 100 mA on the low energy accelerator and several mA on the high energy accelerator. An integral part of the DIANA project is the development of a high-density super-sonic gas-jet target which can handle these anticipated beam powers. The paper will explain the main components of the DIANA accelerators and their beam transport lines and will discuss related technical challenges.« less

  10. Accelerating Particles with Plasma

    ScienceCinema

    Litos, Michael; Hogan, Mark

    2018-05-18

    Researchers at SLAC explain how they use plasma wakefields to accelerate bunches of electrons to very high energies over only a short distance. Their experiments offer a possible path for the future of particle accelerators.

  11. Dominance of hole-boring radiation pressure acceleration regime with thin ribbon of ionized solid hydrogen

    NASA Astrophysics Data System (ADS)

    Psikal, J.; Matys, M.

    2018-04-01

    Laser-driven proton acceleration from novel cryogenic hydrogen target of the thickness of tens of microns irradiated by multiPW laser pulse is investigated here for relevant laser parameters accessible in near future. It is demonstrated that the efficiency of proton acceleration from relatively thick hydrogen solid ribbon largely exceeds the acceleration efficiency for a thinner ionized plastic foil, which can be explained by enhanced hole boring (HB) driven by laser ponderomotive force in the case of light ions and lower target density. Three-dimensional particle-in-cell (PIC) simulations of laser pulse interaction with relatively thick hydrogen target show larger energies of protons accelerated in the target interior during the HB phase and reduced energies of protons accelerated from the rear side of the target by quasistatic electric field compared with the results obtained from two-dimensional PIC calculations. Linearly and circularly polarized multiPW laser pulses of duration exceeding 100 fs show similar performance in terms of proton acceleration from both the target interior as well as from the rear side of the target. When ultrashort pulse (∼30 fs) is assumed, the number of accelerated protons from the target interior is substantially reduced.

  12. A study of the feasibility of conducting the ELISE and EXL experiments at the ITEP accelerator complex

    NASA Astrophysics Data System (ADS)

    Bolshakov, A. E.; Golubev, A. A.; Zenkevich, P. R.; Kats, M. M.; Kolomiets, A. A.

    2014-09-01

    We report the results of a study into the feasibility of conducting the ELISE and EXL experiments on collisions of nuclei of radioactive fragments with electrons at the Institute for Theoretical and Experimental Physics (ITEP). A scheme for uranium ion acceleration in the ITEP accelerator complex is chosen, and it is shown that uranium ions may be accelerated with an intensity of ˜1 × 1011 ions/s as soon as the complex is modified and a new injector is constructed. The basic parameters of the modified complex are given, and a layout diagram indicating the positions of the target that serves to produce radioactive fragments, the separator, and the storage rings (CR, RESR, NESR, and ER) at the ITEP site is presented.

  13. First demonstration of multi-MeV proton acceleration from a cryogenic hydrogen ribbon target

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

    Kraft, Stephan; Obst, Lieselotte; Metzkes-Ng, Josefine

    We show efficient laser driven proton acceleration up to 14 MeV from a 50 μm thick cryogenic hydrogen ribbon. Pulses of the short pulse laser ELFIE at LULI with a pulse length of ≈ 350 fs at an energy of 8 J per pulse are directed onto the target. The results were then compared to proton spectra from metal and plastic foils with different thicknesses and show a similar good performance both in maximum energy as well as in proton number. Thus, this target type is a promising candidate for experiments with high repetition rate laser systems.

  14. First demonstration of multi-MeV proton acceleration from a cryogenic hydrogen ribbon target

    NASA Astrophysics Data System (ADS)

    Kraft, Stephan D.; Obst, Lieselotte; Metzkes-Ng, Josefine; Schlenvoigt, Hans-Peter; Zeil, Karl; Michaux, Sylvain; Chatain, Denis; Perin, Jean-Paul; Chen, Sophia N.; Fuchs, Julien; Gauthier, Maxence; Cowan, Thomas E.; Schramm, Ulrich

    2018-04-01

    We show efficient laser driven proton acceleration up to 14 MeV from a 62 μm thick cryogenic hydrogen ribbon. Pulses of the short pulse laser ELFIE at LULI with a pulse length of ≈350 fs at an energy of 8 J per pulse are directed onto the target. The results are compared to proton spectra from metal and plastic foils with different thicknesses and show a similarly good performance both in maximum energy as well as in proton number. Thus, this target type is a promising candidate for experiments with high repetition rate laser systems.

  15. First demonstration of multi-MeV proton acceleration from a cryogenic hydrogen ribbon target

    DOE PAGES

    Kraft, Stephan; Obst, Lieselotte; Metzkes-Ng, Josefine; ...

    2018-02-09

    We show efficient laser driven proton acceleration up to 14 MeV from a 50 μm thick cryogenic hydrogen ribbon. Pulses of the short pulse laser ELFIE at LULI with a pulse length of ≈ 350 fs at an energy of 8 J per pulse are directed onto the target. The results were then compared to proton spectra from metal and plastic foils with different thicknesses and show a similar good performance both in maximum energy as well as in proton number. Thus, this target type is a promising candidate for experiments with high repetition rate laser systems.

  16. Radiobiological Effectiveness of Ultrashort Laser-Driven Electron Bunches: Micronucleus Frequency, Telomere Shortening and Cell Viability.

    PubMed

    Andreassi, Maria Grazia; Borghini, Andrea; Pulignani, Silvia; Baffigi, Federica; Fulgentini, Lorenzo; Koester, Petra; Cresci, Monica; Vecoli, Cecilia; Lamia, Debora; Russo, Giorgio; Panetta, Daniele; Tripodi, Maria; Gizzi, Leonida A; Labate, Luca

    2016-09-01

    Laser-driven electron accelerators are capable of producing high-energy electron bunches in shorter distances than conventional radiofrequency accelerators. To date, our knowledge of the radiobiological effects in cells exposed to electrons using a laser-plasma accelerator is still very limited. In this study, we compared the dose-response curves for micronucleus (MN) frequency and telomere length in peripheral blood lymphocytes exposed to laser-driven electron pulse and X-ray radiations. Additionally, we evaluated the effects on cell survival of in vitro tumor cells after exposure to laser-driven electron pulse compared to electron beams produced by a conventional radiofrequency accelerator used for intraoperative radiation therapy. Blood samples from two different donors were exposed to six radiation doses ranging from 0 to 2 Gy. Relative biological effectiveness (RBE) for micronucleus induction was calculated from the alpha coefficients for electrons compared to X rays (RBE = alpha laser/alpha X rays). Cell viability was monitored in the OVCAR-3 ovarian cancer cell line using trypan blue exclusion assay at day 3, 5 and 7 postirradiation (2, 4, 6, 8 and 10 Gy). The RBE values obtained by comparing the alpha values were 1.3 and 1.2 for the two donors. Mean telomere length was also found to be reduced in a significant dose-dependent manner after irradiation with both electrons and X rays in both donors studied. Our findings showed a radiobiological response as mirrored by the induction of micronuclei and shortening of telomere as well as by the reduction of cell survival in blood samples and cancer cells exposed in vitro to laser-generated electron bunches. Additional studies are needed to improve preclinical validation of the radiobiological characteristics and efficacy of laser-driven electron accelerators in the future.

  17. Collaborative Data-Driven Decision Making: A Qualitative Study of the Lived Experiences of Primary Grade Classroom Teachers

    ERIC Educational Resources Information Center

    Ralston, Christine R.

    2012-01-01

    The purpose of this qualitative study was to describe the lived experiences of primary classroom teachers participating in collaborative data-driven decision making. Hermeneutic phenomenology served as the theoretical framework. Data were collected by conducting interviews with thirteen classroom teachers who taught in grades kindergarten through…

  18. Operation regimes of a dielectric laser accelerator

    NASA Astrophysics Data System (ADS)

    Hanuka, Adi; Schächter, Levi

    2018-04-01

    We investigate three operation regimes in dielectric laser driven accelerators: maximum efficiency, maximum charge, and maximum loaded gradient. We demonstrate, using a self-consistent approach, that loaded gradients of the order of 1 to 6 [GV/m], efficiencies of 20% to 80%, and electrons flux of 1014 [el/s] are feasible, without significant concerns regarding damage threshold fluence. The latter imposes that the total charge per squared wavelength is constant (a total of 106 per μm2). We conceive this configuration as a zero-order design that should be considered for the road map of future accelerators.

  19. Enhanced proton acceleration in an applied longitudinal magnetic field

    DOE PAGES

    Arefiev, A.; Toncian, T.; Fiksel, G.

    2016-10-31

    Using two-dimensional particle-in-cell simulations, we examine how an externally applied strong magnetic field impacts proton acceleration in laser-irradiated solid-density targets. We find that a kT-level external magnetic field can sufficiently inhibit transverse transport of hot electrons in a flat laser-irradiated target. While the electron heating by the laser remains mostly unaffected, the reduced electron transport during proton acceleration leads to an enhancement of maximum proton energies and the overall number of energetic protons. The resulting proton beam is much better collimated compared to a beam generated without applying a kT-level magnetic field. A factor of three enhancement of the lasermore » energy conversion efficiency into multi-MeV protons is another effect of the magnetic field. The required kT-level magnetic fields are becoming feasible due to a significant progress that has been made in generating magnetic fields with laser-driven coils using ns-long laser pulses. The possibility of improving characteristics of laser-driven proton beams using such fields is a strong motivation for further development of laser-driven magnetic field capabilities.« less

  20. Enhanced proton acceleration in an applied longitudinal magnetic field

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

    Arefiev, A.; Toncian, T.; Fiksel, G.

    Using two-dimensional particle-in-cell simulations, we examine how an externally applied strong magnetic field impacts proton acceleration in laser-irradiated solid-density targets. We find that a kT-level external magnetic field can sufficiently inhibit transverse transport of hot electrons in a flat laser-irradiated target. While the electron heating by the laser remains mostly unaffected, the reduced electron transport during proton acceleration leads to an enhancement of maximum proton energies and the overall number of energetic protons. The resulting proton beam is much better collimated compared to a beam generated without applying a kT-level magnetic field. A factor of three enhancement of the lasermore » energy conversion efficiency into multi-MeV protons is another effect of the magnetic field. The required kT-level magnetic fields are becoming feasible due to a significant progress that has been made in generating magnetic fields with laser-driven coils using ns-long laser pulses. The possibility of improving characteristics of laser-driven proton beams using such fields is a strong motivation for further development of laser-driven magnetic field capabilities.« less

  1. Goal-driven modulation of stimulus-driven attentional capture in multiple-cue displays.

    PubMed

    Richard, Christian M; Wright, Richard D; Ward, Lawrence M

    2003-08-01

    Six location-cuing experiments were conducted to examine the goal-driven control of attentional capture in multiple-cue displays. In most of the experiments, the cue display consisted of the simultaneous presentation of a red direct cue that was highly predictive of the target location (the unique cue) and three gray direct cues (the standard cues) that were not predictive of the location. The results indicated that although target responses were faster at all cued locations relative to uncued locations, they were significantly faster at the unique-cue location than at the standard-cue locations. Other results suggest that the faster responses produced by direct cues may be associated with two different components: an attention-related component that can be modulated by goal-driven factors and a nonattentional component that occurs in parallel at multiple direct-cue locations and is minimally affected by the same goal-driven factors.

  2. Multiple beam induction accelerators for heavy ion fusion

    NASA Astrophysics Data System (ADS)

    Seidl, Peter A.; Barnard, John J.; Faltens, Andris; Friedman, Alex; Waldron, William L.

    2014-01-01

    Induction accelerators are appealing for heavy-ion driven inertial fusion energy (HIF) because of their high efficiency and their demonstrated capability to accelerate high beam current (≥10 kA in some applications). For the HIF application, accomplishments and challenges are summarized. HIF research and development has demonstrated the production of single ion beams with the required emittance, current, and energy suitable for injection into an induction linear accelerator. Driver scale beams have been transported in quadrupole channels of the order of 10% of the number of quadrupoles of a driver. We review the design and operation of induction accelerators and the relevant aspects of their use as drivers for HIF. We describe intermediate research steps that would provide the basis for a heavy-ion research facility capable of heating matter to fusion relevant temperatures and densities, and also to test and demonstrate an accelerator architecture that scales well to a fusion power plant.

  3. Electron Acceleration and Ionization Production in High-Power Heating Experiments at HAARP

    NASA Astrophysics Data System (ADS)

    Mishin, E. V.; Pedersen, T.

    2012-12-01

    Recent ionospheric modification experiments with the 3.6 MW transmitter at the High Frequency Active Auroral Research Program (HAARP) facility in Alaska led to discovery of artificial ionization descending from the nominal interaction altitude in the background F-region ionosphere by ~60-80 km. Artificial ionization production is indicated by significant 427.8 nm emissions from the 1st negative band of N2+ and the appearance of transmitter-induced bottomside traces in ionosonde data during the periods of most intense optical emissions. However, the exact mechanisms producing the artificial plasmas remain to be determined. Yet the only existing theoretical models explain the development of artificial plasma as an ionizing wavefront moving downward due to ionization by electrons accelerated by HF-excited strong Langmuir turbulence (SLT) generated near the plasma resonance, where the pump frequency matches the plasma frequency. However, the observations suggest also the significance of interactions with upper hybrid and electron Bernstein waves near multiples of the electron gyrofrequency. We describe recent observations and discuss suitable acceleration mechanisms.

  4. Laser Acceleration of Ions for Radiation Therapy

    NASA Astrophysics Data System (ADS)

    Tajima, Toshiki; Habs, Dietrich; Yan, Xueqing

    Ion beam therapy for cancer has proven to be a successful clinical approach, affording as good a cure as surgery and a higher quality of life. However, the ion beam therapy installation is large and expensive, limiting its availability for public benefit. One of the hurdles is to make the accelerator more compact on the basis of conventional technology. Laser acceleration of ions represents a rapidly developing young field. The prevailing acceleration mechanism (known as target normal sheath acceleration, TNSA), however, shows severe limitations in some key elements. We now witness that a new regime of coherent acceleration of ions by laser (CAIL) has been studied to overcome many of these problems and accelerate protons and carbon ions to high energies with higher efficiencies. Emerging scaling laws indicate possible realization of an ion therapy facility with compact, cost-efficient lasers. Furthermore, dense particle bunches may allow the use of much higher collective fields, reducing the size of beam transport and dump systems. Though ultimate realization of a laser-driven medical facility may take many years, the field is developing fast with many conceptual innovations and technical progress.

  5. Analysis on weathering characteristics of volcanic rocks in Dokdo, Korea based on accelerated weatehring experiments

    NASA Astrophysics Data System (ADS)

    Woo, Ik; Song, Won-Kyong; Kim, Bok-Chul; Kang, Jinseok

    2010-05-01

    Dokdo consists of small volcanic islands located in the southern part of the East Sea. Accelerated weathering tests was performed to examine the physico-mechanical characteristics of volcanic rocks in Dokdo. Rock core specimens of trachyandesite, andesitic dyke and ash tuff were prepared, and double soxhlet extractors(DSE) and peristatic pumps were used for accelerating the weathering processes. The DSE was designed to perform cyclic leaching tests for rock core specimen using distilled water at seventy degrees centigrade. The core specimens which are classified according to pre-test weathering grades placed in the lower part of the DSE, and periodically exposed to hot distilled water at every ninety minutes. On the other hand the peristatic pumps were utilized to induce leaching by distilled or brine water at normal temperature. The physico-mechanical property changes including rock surface appearance, microscopic structure and rock strength were analyzed with the results obtained from both experiments performed for 120 days. The conducted research in this study have shown that the methodologies of artificial weathering experiments have strong capability to understand the weathering characteristics of the rocks effectively.

  6. Signature energetic analysis of accelerate electron beam after first acceleration station by accelerating stand of Joint Institute for Nuclear Research

    NASA Astrophysics Data System (ADS)

    Sledneva, A. S.; Kobets, V. V.

    2017-06-01

    The linear electron accelerator based on the LINAC - 800 accelerator imported from the Netherland is created at Joint Institute for Nuclear Research in the framework of the project on creation of the Testbed with an electron beam of a linear accelerator with an energy up to 250 MV. Currently two accelerator stations with a 60 MV energy of a beam are put in operation and the work is to put the beam through accelerating section of the third accelerator station. The electron beam with an energy of 23 MeV is used for testing the crystals (BaF2, CsI (native), and LYSO) in order to explore the opportunity to use them in particle detectors in experiments: Muon g-2, Mu2e, Comet, whose preparation requires a detailed study of the detectors properties such as their irradiation by the accelerator beams.

  7. Hot spots and dark current in advanced plasma wakefield accelerators

    DOE PAGES

    Manahan, G. G.; Deng, A.; Karger, O.; ...

    2016-01-29

    Dark current can spoil witness bunch beam quality and acceleration efficiency in particle beam-driven plasma wakefield accelerators. In advanced schemes, hot spots generated by the drive beam or the wakefield can release electrons from higher ionization threshold levels in the plasma media. Likewise, these electrons may be trapped inside the plasma wake and will then accumulate dark current, which is generally detrimental for a clear and unspoiled plasma acceleration process. The strategies for generating clean and robust, dark current free plasma wake cavities are devised and analyzed, and crucial aspects for experimental realization of such optimized scenarios are discussed.

  8. Demonstration of passive plasma lensing of a laser wakefield accelerated electron bunch

    DOE PAGES

    Kuschel, S.; Hollatz, D.; Heinemann, T.; ...

    2016-07-20

    We report on the first demonstration of passive all-optical plasma lensing using a two-stage setup. An intense femtosecond laser accelerates electrons in a laser wakefield accelerator (LWFA) to 100 MeV over millimeter length scales. By adding a second gas target behind the initial LWFA stage we introduce a robust and independently tunable plasma lens. We observe a density dependent reduction of the LWFA electron beam divergence from an initial value of 2.3 mrad, down to 1.4 mrad (rms), when the plasma lens is in operation. Such a plasma lens provides a simple and compact approach for divergence reduction well matchedmore » to the mm-scale length of the LWFA accelerator. The focusing forces are provided solely by the plasma and driven by the bunch itself only, making this a highly useful and conceptually new approach to electron beam focusing. Possible applications of this lens are not limited to laser plasma accelerators. Since no active driver is needed the passive plasma lens is also suited for high repetition rate focusing of electron bunches. As a result, its understanding is also required for modeling the evolution of the driving particle bunch in particle driven wake field acceleration.« less

  9. Transit Time and Normal Orientation of ICME-driven Shocks

    NASA Astrophysics Data System (ADS)

    Case, A. W.; Spence, H.; Owens, M.; Riley, P.; Linker, J.; Odstrcil, D.

    2006-12-01

    Interplanetary Coronal Mass Ejections (ICMEs) can drive shocks that accelerate particles to great energies. It is important to understand the acceleration, transport, and spectra of these particles in order to quantify this fundamental physical process operating throughout the cosmos. This understanding also helps to better protect astronauts and spacecraft in upcoming missions. We show that the ambient solar wind is crucial in determining characteristics of ICME-driven shocks, which in turn affect energetic particle production. We use a coupled 3-D MHD code of the corona and heliosphere to simulate ICME propagation from 30 solar radii to 1AU. ICMEs of different velocities are injected into a realistic solar wind to determine how the initial speed affects the shape and deceleration of the ICME-driven shock. We use shock transit time and shock normal orientation to quantify these dependencies. We also inject identical ICMEs into different ambient solar winds to quantify the effective drag force on an ICME.

  10. Reduction of angular divergence of laser-driven ion beams during their acceleration and transport

    NASA Astrophysics Data System (ADS)

    Zakova, M.; Pšikal, Jan; Margarone, Daniele; Maggiore, Mario; Korn, G.

    2015-05-01

    Laser plasma physics is a field of big interest because of its implications in basic science, fast ignition, medicine (i.e. hadrontherapy), astrophysics, material science, particle acceleration etc. 100-MeV class protons accelerated from the interaction of a short laser pulse with a thin target have been demonstrated. With continuing development of laser technology, greater and greater energies are expected, therefore projects focusing on various applications are being formed, e.g. ELIMAIA (ELI Multidisciplinary Applications of laser-Ion Acceleration). One of the main characteristic and crucial disadvantage of ion beams accelerated by ultra-short intense laser pulses is their large divergence, not suitable for the most of applications. In this paper two ways how to decrease beam divergence are proposed. Firstly, impact of different design of targets on beam divergence is studied by using 2D Particlein-cell simulations (PIC). Namely, various types of targets include at foils, curved foil and foils with diverse microstructures. Obtained results show that well-designed microstructures, i.e. a hole in the center of the target, can produce proton beam with the lowest divergence. Moreover, the particle beam accelerated from a curved foil has lower divergence compared to the beam from a flat foil. Secondly, another proposed method for the divergence reduction is using of a magnetic solenoid. The trajectories of the laser accelerated particles passing through the solenoid are modeled in a simple Matlab program. Results from PIC simulations are used as input in the program. The divergence is controlled by optimizing the magnetic field inside the solenoid and installing an aperture in front of the device.

  11. Vacuum electron acceleration by coherent dipole radiation

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

    Troha, A.L.; Van Meter, J.R.; Landahl, E.C.

    1999-07-01

    The validity of the concept of laser-driven vacuum acceleration has been questioned, based on an extrapolation of the well-known Lawson-Woodward theorem, which stipulates that plane electromagnetic waves cannot accelerate charged particles in vacuum. To formally demonstrate that electrons can indeed be accelerated in vacuum by focusing or diffracting electromagnetic waves, the interaction between a point charge and coherent dipole radiation is studied in detail. The corresponding four-potential exactly satisfies both Maxwell{close_quote}s equations and the Lorentz gauge condition everywhere, and is analytically tractable. It is found that in the far-field region, where the field distribution closely approximates that of a planemore » wave, we recover the Lawson-Woodward result, while net acceleration is obtained in the near-field region. The scaling of the energy gain with wave-front curvature and wave amplitude is studied systematically. {copyright} {ital 1999} {ital The American Physical Society}« less

  12. Autonomy and Non-autonomy of Angiogenic Cell Movements Revealed by Experiment-Driven Mathematical Modeling.

    PubMed

    Sugihara, Kei; Nishiyama, Koichi; Fukuhara, Shigetomo; Uemura, Akiyoshi; Arima, Satoshi; Kobayashi, Ryo; Köhn-Luque, Alvaro; Mochizuki, Naoki; Suda, Toshio; Ogawa, Hisao; Kurihara, Hiroki

    2015-12-01

    Angiogenesis is a multicellular phenomenon driven by morphogenetic cell movements. We recently reported morphogenetic vascular endothelial cell (EC) behaviors to be dynamic and complex. However, the principal mechanisms orchestrating individual EC movements in angiogenic morphogenesis remain largely unknown. Here we present an experiment-driven mathematical model that enables us to systematically dissect cellular mechanisms in branch elongation. We found that cell-autonomous and coordinated actions governed these multicellular behaviors, and a cell-autonomous process sufficiently illustrated essential features of the morphogenetic EC dynamics at both the single-cell and cell-population levels. Through refining our model and experimental verification, we further identified a coordinated mode of tip EC behaviors regulated via a spatial relationship between tip and follower ECs, which facilitates the forward motility of tip ECs. These findings provide insights that enhance our mechanistic understanding of not only angiogenic morphogenesis, but also other types of multicellular phenomenon. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  13. Acceleration Environment of the International Space Station

    NASA Technical Reports Server (NTRS)

    McPherson, Kevin; Kelly, Eric; Keller, Jennifer

    2009-01-01

    Measurement of the microgravity acceleration environment on the International Space Station has been accomplished by two accelerometer systems since 2001. The Microgravity Acceleration Measurement System records the quasi-steady microgravity environment, including the influences of aerodynamic drag, vehicle rotation, and venting effects. Measurement of the vibratory/transient regime, comprised of vehicle, crew, and equipment disturbances, has been accomplished by the Space Acceleration Measurement System-II. Until the arrival of the Columbus Orbital Facility and the Japanese Experiment Module, the location of these sensors, and therefore, the measurement of the microgravity acceleration environment, has been limited to within the United States Laboratory. Japanese Aerospace Exploration Agency has developed a vibratory acceleration measurement system called the Microgravity Measurement Apparatus which will be deployed within the Japanese Experiment Module to make distributed measurements of the Japanese Experiment Module's vibratory acceleration environment. Two Space Acceleration Measurement System sensors from the United States Laboratory will be re-deployed to support vibratory acceleration data measurement within the Columbus Orbital Facility. The additional measurement opportunities resulting from the arrival of these new laboratories allows Principal Investigators with facilities located in these International Space Station research laboratories to obtain microgravity acceleration data in support of their sensitive experiments. The Principal Investigator Microgravity Services project, at NASA Glenn Research Center, in Cleveland, Ohio, has supported acceleration measurement systems and the microgravity scientific community through the processing, characterization, distribution, and archival of the microgravity acceleration data obtained from the International Space Station acceleration measurement systems. This paper summarizes the PIMS capabilities available

  14. Battery-Powered RF Pre-Ionization System for the Caltech Magnetohydrodynamically-Driven Jet Experiment: RF Discharge Properties and MHD-Driven Jet Dynamics

    NASA Astrophysics Data System (ADS)

    Chaplin, Vernon H.

    This thesis describes investigations of two classes of laboratory plasmas with rather different properties: partially ionized low pressure radiofrequency (RF) discharges, and fully ionized high density magnetohydrodynamically (MHD)-driven jets. An RF pre-ionization system was developed to enable neutral gas breakdown at lower pressures and create hotter, faster jets in the Caltech MHD-Driven Jet Experiment. The RF plasma source used a custom pulsed 3 kW 13.56 MHz RF power amplifier that was powered by AA batteries, allowing it to safely float at 4-6 kV with the cathode of the jet experiment. The argon RF discharge equilibrium and transport properties were analyzed, and novel jet dynamics were observed. Although the RF plasma source was conceived as a wave-heated helicon source, scaling measurements and numerical modeling showed that inductive coupling was the dominant energy input mechanism. A one-dimensional time-dependent fluid model was developed to quantitatively explain the expansion of the pre-ionized plasma into the jet experiment chamber. The plasma transitioned from an ionizing phase with depressed neutral emission to a recombining phase with enhanced emission during the course of the experiment, causing fast camera images to be a poor indicator of the density distribution. Under certain conditions, the total visible and infrared brightness and the downstream ion density both increased after the RF power was turned off. The time-dependent emission patterns were used for an indirect measurement of the neutral gas pressure. The low-mass jets formed with the aid of the pre-ionization system were extremely narrow and collimated near the electrodes, with peak density exceeding that of jets created without pre-ionization. The initial neutral gas distribution prior to plasma breakdown was found to be critical in determining the ultimate jet structure. The visible radius of the dense central jet column was several times narrower than the axial current channel

  15. Safety and control of accelerator-driven subcritical systems

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

    Rief, H.; Takahashi, H.

    1995-10-01

    To study control and safety of accelertor driven nuclear systems, a one point kinetic model was developed and programed. It deals with fast transients as a function of reactivity insertion. Doppler feedback, and the intensity of an external neutron source. The model allows for a simultaneous calculation of an equivalent critical reactor. It was validated by a comparison with a benchmark specified by the Nuclear Energy Agency Committee of Reactor Physics. Additional features are the possibility of inserting a linear or quadratic time dependent reactivity ramp which may account for gravity induced accidents like earthquakes, the possibility to shut downmore » the external neutron source by an exponential decay law of the form exp({minus}t/{tau}), and a graphical display of the power and reactivity changes. The calculations revealed that such boosters behave quite benignly even if they are only slightly subcritical.« less

  16. Electromagnetic Safety of Spacecraft During Active Experiments with the Use of Plasma Accelerators and Ion Injectors

    NASA Astrophysics Data System (ADS)

    Plokhikh, Andrey; Popov, Garri; Shishkin, Gennady; Antropov, Nikolay; Vazhenin, Nikolay; Soganova, Galina

    Works under the development and application of stationary and pulsed plasma accelerators of charged particles conducted at the Moscow Aviation Institute and Research Institute of Applied Mechanics and Electrodynamics during over 40 years, active experiments on board meteorological rockets, artificial Earth satellites and "Mir" orbital station including [1], allowed to obtain data on the influence of pulsed and continuous plasma injection with the given parameters on the drop of energetic particles out of the radiation belts, efficiency of artificial excitation and propagation of electromagnetic waves in ELF and VLF ranges, and evolution of artificial plasma formations in different regions of ionosphere. Variation of the near-spacecraft electromagnetic environment related to the operation of plasma injectors was registered during active experiments along with the global electrodynamic processes. The measured electromagnetic fields are of rather high intensity and occupy frequency spectrum from some Hz to tens of GHz that may be of definite danger for the operation of spacecraft and its onboard systems. Analysis for the known test data is presented in the paper and methods are discussed for the diagnostics and modeling under laboratory conditions of radiative processes proceeding at the operation of plasma accelerators and ion injectors used while making active space experiments. Great attention is paid to the methodological and metrological bases for making radio measurements in vacuum chambers, design concept and hardware configuration of ground special-purpose instrumentation scientific complexes [2]. Basic requirements are formulated for the measurements and analysis of electromagnetic fields originating during the operation of plasma accelerators, including the radiative induced and conductive components inside the spacecraft, as well as the wave emission and excitation outside the spacecraft, in the ionosphere including. Measurement results for the intrinsic

  17. Microcharge neutralization transport experiments and simulations for ion-driven inertial confinement fusion

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

    Olson, C.L.; Hanson, D.L.; Poukey, J.W.

    Space charge neutralization for intense beams for inertial confinement fusion is usually assumed to be perfect. However, small charge clumps in the beam will not be totally charge neutralized, and the residual net minimum potential set by electron trapping (e{phi} {approx} {1/2}m{sub e}v{sup 2}{sub i}, where m{sub e} is the electron mass and v{sub i} is the ion velocity) may lead to a substantial microdivergence. Experiments on the SABRE accelerator and simulations with the IPROP computer code are being performed to assess this mechanism. The authors have successfully created a 5 mrad beam on the SABRE accelerator, by expanding themore » beam (a process consistent with Liouville`s theorem) and, by passing the beam through a plate with pinholes, they have created low divergence beamlets to study this mechanism. Results clearly show: (1) at low pressures, trapping does neutralize the beamlets, but only down to e{phi} {approx} {1/2}m{sub e}v{sup 2}{sub i}; and (2) at higher pressures ({approx} 0.1-1 Torr), plasma shielding does remove the effect.« less

  18. Public Data Set: Non-inductively Driven Tokamak Plasmas at Near-Unity βt in the Pegasus Toroidal Experiment

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

    Reusch, Joshua A.; Bodner, Grant M.; Bongard, Michael W.

    This public data set contains openly-documented, machine readable digital research data corresponding to figures published in J.A. Reusch et al., 'Non-inductively Driven Tokamak Plasmas at Near-Unity βt in the Pegasus Toroidal Experiment,' Phys. Plasmas 25, 056101 (2018).

  19. Time-dependent Electron Acceleration in Pulsar Wind Termination Shocks: Application to the 2011 April Crab Nebula Gamma-Ray Flare

    NASA Astrophysics Data System (ADS)

    Kroon, John J.; Becker, Peter A.; Finke, Justin D.

    2018-01-01

    The γ-ray flares from the Crab Nebula observed by AGILE and Fermi-LAT between 2007 and 2013 reached GeV photon energies and lasted several days. The strongest emission, observed during the 2011 April “superflare”, exceeded the quiescent level by more than an order of magnitude. These observations challenge the standard models for particle acceleration in pulsar wind nebulae, because the radiating electrons have energies exceeding the classical radiation-reaction limit for synchrotron emission. Particle-in-cell simulations have suggested that the classical synchrotron limit can be exceeded if the electrons also experience electrostatic acceleration due to shock-driven magnetic reconnection. In this paper, we revisit the problem using an analytic approach based on solving a fully time-dependent electron transport equation describing the electrostatic acceleration, synchrotron losses, and escape experienced by electrons in a magnetically confined plasma “blob” as it encounters and passes through the pulsar wind termination shock. We show that our model can reproduce the γ-ray spectra observed during the rising and decaying phases of each of the two sub-flare components of the 2011 April superflare. We integrate the spectrum for photon energies ≥slant 100 MeV to obtain the light curve for the event, which also agrees with the observations. We find that strong electrostatic acceleration occurs on both sides of the termination shock, driven by magnetic reconnection. We also find that the dominant mode of particle escape changes from diffusive escape to advective escape as the blob passes through the shock.

  20. Gravitational Acceleration Effects on Macrosegregation: Experiment and Computational Modeling

    NASA Technical Reports Server (NTRS)

    Leon-Torres, J.; Curreri, P. A.; Stefanescu, D. M.; Sen, S.

    1999-01-01

    Experiments were performed under terrestrial gravity (1g) and during parabolic flights (10-2 g) to study the solidification and macrosegregation patterns of Al-Cu alloys. Alloys having 2% and 5% Cu were solidified against a chill at two different cooling rates. Microscopic and Electron Microprobe characterization was used to produce microstructural and macrosegregation maps. In all cases positive segregation occurred next to the chill because shrinkage flow, as expected. This positive segregation was higher in the low-g samples, apparently because of the higher heat transfer coefficient. A 2-D computational model was used to explain the experimental results. The continuum formulation was employed to describe the macroscopic transports of mass, energy, and momentum, associated with the solidification phenomena, for a two-phase system. The model considers that liquid flow is driven by thermal and solutal buoyancy, and by solidification shrinkage. The solidification event was divided into two stages. In the first one, the liquid containing freely moving equiaxed grains was described through the relative viscosity concept. In the second stage, when a fixed dendritic network was formed after dendritic coherency, the mushy zone was treated as a porous medium. The macrosegregation maps and the cooling curves obtained during experiments were used for validation of the solidification and segregation model. The model can explain the solidification and macrosegregation patterns and the differences between low- and high-gravity results.

  1. Modeling and simulations of radiative blast wave driven Rayleigh-Taylor instability experiments

    NASA Astrophysics Data System (ADS)

    Shimony, Assaf; Huntington, Channing M.; Trantham, Matthew; Malamud, Guy; Elbaz, Yonatan; Kuranz, Carolyn C.; Drake, R. Paul; Shvarts, Dov

    2017-10-01

    Recent experiments at the National Ignition Facility measured the growth of Rayleigh-Taylor RT instabilities driven by radiative blast waves, relevant to astrophysics and other HEDP systems. We constructed a new Buoyancy-Drag (BD) model, which accounts for the ablation effect on both bubble and spike. This ablation effect is accounted for by using the potential flow model ]Oron et al PoP 1998], adding another term to the classical BD formalism: βDuA / u , where β the Takabe constant, D the drag term, uA the ablation velocity and uthe instability growth velocity. The model results are compared with the results of experiments and 2D simulations using the CRASH code, with nominal radiation or reduced foam opacity (by a factor of 1000). The ablation constant of the model, βb / s, for the bubble and for the spike fronts, are calibrated using the results of the radiative shock experiments. This work is funded by the Lawrence Livermore National Laboratory under subcontract B614207, and was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

  2. STUDIES OF A FREE ELECTRON LASER DRIVEN BY A LASER-PLASMA ACCELERATOR

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

    Montgomery, A.; Schroeder, C.; Fawley, W.

    A free electron laser (FEL) uses an undulator, a set of alternating magnets producing a periodic magnetic fi eld, to stimulate emission of coherent radiation from a relativistic electron beam. The Lasers, Optical Accelerator Systems Integrated Studies (LOASIS) group at Lawrence Berkeley National Laboratory (LBNL) will use an innovative laserplasma wakefi eld accelerator to produce an electron beam to drive a proposed FEL. In order to optimize the FEL performance, the dependence on electron beam and undulator parameters must be understood. Numerical modeling of the FEL using the simulation code GINGER predicts the experimental results for given input parameters. Amongmore » the parameters studied were electron beam energy spread, emittance, and mismatch with the undulator focusing. Vacuum-chamber wakefi elds were also simulated to study their effect on FEL performance. Energy spread was found to be the most infl uential factor, with output FEL radiation power sharply decreasing for relative energy spreads greater than 0.33%. Vacuum chamber wakefi elds and beam mismatch had little effect on the simulated LOASIS FEL at the currents considered. This study concludes that continued improvement of the laser-plasma wakefi eld accelerator electron beam will allow the LOASIS FEL to operate in an optimal regime, producing high-quality XUV and x-ray pulses.« less

  3. Proposal for an Accelerator R&D User Facility at Fermilab's Advanced Superconducting Test Accelerator (ASTA)

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

    Church, M.; Edwards, H.; Harms, E.

    2013-10-01

    Fermilab is the nation’s particle physics laboratory, supported by the DOE Office of High Energy Physics (OHEP). Fermilab is a world leader in accelerators, with a demonstrated track-record— spanning four decades—of excellence in accelerator science and technology. We describe the significant opportunity to complete, in a highly leveraged manner, a unique accelerator research facility that supports the broad strategic goals in accelerator science and technology within the OHEP. While the US accelerator-based HEP program is oriented toward the Intensity Frontier, which requires modern superconducting linear accelerators and advanced highintensity storage rings, there are no accelerator test facilities that support themore » accelerator science of the Intensity Frontier. Further, nearly all proposed future accelerators for Discovery Science will rely on superconducting radiofrequency (SRF) acceleration, yet there are no dedicated test facilities to study SRF capabilities for beam acceleration and manipulation in prototypic conditions. Finally, there are a wide range of experiments and research programs beyond particle physics that require the unique beam parameters that will only be available at Fermilab’s Advanced Superconducting Test Accelerator (ASTA). To address these needs we submit this proposal for an Accelerator R&D User Facility at ASTA. The ASTA program is based on the capability provided by an SRF linac (which provides electron beams from 50 MeV to nearly 1 GeV) and a small storage ring (with the ability to store either electrons or protons) to enable a broad range of beam-based experiments to study fundamental limitations to beam intensity and to develop transformative approaches to particle-beam generation, acceleration and manipulation which cannot be done elsewhere. It will also establish a unique resource for R&D towards Energy Frontier facilities and a test-bed for SRF accelerators and high brightness beam applications in support of the

  4. Accelerator Technology Division annual report, FY 1989

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

    Not Available

    1990-06-01

    This paper discusses: accelerator physics and special projects; experiments and injectors; magnetic optics and beam diagnostics; accelerator design and engineering; radio-frequency technology; accelerator theory and simulation; free-electron laser technology; accelerator controls and automation; and high power microwave sources and effects.

  5. Data driven CAN node reliability assessment for manufacturing system

    NASA Astrophysics Data System (ADS)

    Zhang, Leiming; Yuan, Yong; Lei, Yong

    2017-01-01

    The reliability of the Controller Area Network(CAN) is critical to the performance and safety of the system. However, direct bus-off time assessment tools are lacking in practice due to inaccessibility of the node information and the complexity of the node interactions upon errors. In order to measure the mean time to bus-off(MTTB) of all the nodes, a novel data driven node bus-off time assessment method for CAN network is proposed by directly using network error information. First, the corresponding network error event sequence for each node is constructed using multiple-layer network error information. Then, the generalized zero inflated Poisson process(GZIP) model is established for each node based on the error event sequence. Finally, the stochastic model is constructed to predict the MTTB of the node. The accelerated case studies with different error injection rates are conducted on a laboratory network to demonstrate the proposed method, where the network errors are generated by a computer controlled error injection system. Experiment results show that the MTTB of nodes predicted by the proposed method agree well with observations in the case studies. The proposed data driven node time to bus-off assessment method for CAN networks can successfully predict the MTTB of nodes by directly using network error event data.

  6. Quasi-Steady Acceleration Direction Indicator in Three Dimensions

    NASA Technical Reports Server (NTRS)

    DeLombard, Richard; Nelson, Emily S.; Jules, Kenol

    2000-01-01

    Many materials processing and fluids physics experiments conducted in a microgravity environment require knowledge of the orientation of the low-frequency acceleration vector. This need becomes especially acute for space experiments such as directional solidification of a molten semiconductor, which is extremely sensitive to orientation and may involve tens of hours of operations of a materials furnace. These low-frequency acceleration data have been measured for many Shuttle missions with the Orbital Acceleration Research Experiment. Previous attempts at using fluid chambers for acceleration measurements have met with limited success due to pointing and vehicle attitude complications. An acceleration direction indicator is described, which is comprised of two orthogonal short cylinders of fluid, each with a small bubble. The motion and the position of the bubble within the chamber will indicate the direction of the acceleration experienced at the sensor location. The direction of the acceleration vector may then be calculated from these data. The frequency response of such an instrument may be tailored for particular experiments with the proper selection of fluid and gas parameters, surface type, and geometry. A three-dimensional system for sensing and displaying the low-frequency acceleration direction via an innovative technique described in this paper has advantages in terms of size, mass, and power compared with electronic instrumentation systems.

  7. Tau pathology does not affect experience-driven single-neuron and network-wide Arc/Arg3.1 responses.

    PubMed

    Rudinskiy, Nikita; Hawkes, Jonathan M; Wegmann, Susanne; Kuchibhotla, Kishore V; Muzikansky, Alona; Betensky, Rebecca A; Spires-Jones, Tara L; Hyman, Bradley T

    2014-06-10

    Intraneuronal neurofibrillary tangles (NFTs) - a characteristic pathological feature of Alzheimer's and several other neurodegenerative diseases - are considered a major target for drug development. Tangle load correlates well with the severity of cognitive symptoms and mouse models of tauopathy are behaviorally impaired. However, there is little evidence that NFTs directly impact physiological properties of host neurons. Here we used a transgenic mouse model of tauopathy to study how advanced tau pathology in different brain regions affects activity-driven expression of immediate-early gene Arc required for experience-dependent consolidation of long-term memories. We demonstrate in vivo that visual cortex neurons with tangles are as likely to express comparable amounts of Arc in response to structured visual stimulation as their neighbors without tangles. Probability of experience-dependent Arc response was not affected by tau tangles in both visual cortex and hippocampal pyramidal neurons as determined postmortem. Moreover, whole brain analysis showed that network-wide activity-driven Arc expression was not affected by tau pathology in any of the brain regions, including brain areas with the highest tangle load. Our findings suggest that intraneuronal NFTs do not affect signaling cascades leading to experience-dependent gene expression required for long-term synaptic plasticity.

  8. A scintillator-based online detector for the angularly resolved measurement of laser-accelerated proton spectra.

    PubMed

    Metzkes, J; Karsch, L; Kraft, S D; Pawelke, J; Richter, C; Schürer, M; Sobiella, M; Stiller, N; Zeil, K; Schramm, U

    2012-12-01

    In recent years, a new generation of high repetition rate (~10 Hz), high power (~100 TW) laser systems has stimulated intense research on laser-driven sources for fast protons. Considering experimental instrumentation, this development requires online diagnostics for protons to be added to the established offline detection tools such as solid state track detectors or radiochromic films. In this article, we present the design and characterization of a scintillator-based online detector that gives access to the angularly resolved proton distribution along one spatial dimension and resolves 10 different proton energy ranges. Conceived as an online detector for key parameters in laser-proton acceleration, such as the maximum proton energy and the angular distribution, the detector features a spatial resolution of ~1.3 mm and a spectral resolution better than 1.5 MeV for a maximum proton energy above 12 MeV in the current design. Regarding its areas of application, we consider the detector a useful complement to radiochromic films and Thomson parabola spectrometers, capable to give immediate feedback on the experimental performance. The detector was characterized at an electrostatic Van de Graaff tandetron accelerator and tested in a laser-proton acceleration experiment, proving its suitability as a diagnostic device for laser-accelerated protons.

  9. The IMISS-1 Experiment for Recording and Analysis of Accelerations in Orbital Flight

    NASA Astrophysics Data System (ADS)

    Sadovnichii, V. A.; Alexandrov, V. V.; Bugrov, D. I.; Lemak, S. S.; Pakhomov, V. B.; Panasyuk, M. I.; Petrov, V. L.; Yashin, I. V.

    2018-03-01

    The IMISS-1 experiment represents the second step in solving the problem of the creation of the gaze stabilization corrector. This device is designed to correct the effect of the gaze stabilization delay under microgravity. IMISS-1 continues research started by the Tat'yana-2 satellite. This research will be continued on board the International Space Station. At this stage we study the possibility of registration of angular and linear accelerations acting on the sensitive mass in terms of Low Earth Orbit flight, using MEMS sensors.

  10. High peak current acceleration of narrow divergence ions beams with the BELLA-PW laser

    NASA Astrophysics Data System (ADS)

    Steinke, Sven; Ji, Qing; Treffert, Franziska; Bulanov, Stepan; Bin, Jianhui; Nakamura, Kei; Gonsalves, Anthony; Toth, Csaba; Park, Jaehong; Roth, Markus; Esarey, Eric; Schenkel, Thomas; Leemans, Wim

    2017-10-01

    We present a parameter study of ion acceleration driven by the BELLA-PW laser. The laser repetition rate of 1Hz allowed for scanning the laser pulse duration, relative focus location and target thickness for the first time at laser peak powers of above 1 petawatt. Further, the long focal length geometry of the experiment (f\\65) and hence, large focus size provided ion beams of reduced divergence and unprecedented charge density. This work was supported by Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 and Laboratory Directed Research and Development (LDRD) funding from Lawrence Berkeley National Laboratory.

  11. Dynamic Monte Carlo simulations of radiatively accelerated GRB fireballs

    NASA Astrophysics Data System (ADS)

    Chhotray, Atul; Lazzati, Davide

    2018-05-01

    We present a novel Dynamic Monte Carlo code (DynaMo code) that self-consistently simulates the Compton-scattering-driven dynamic evolution of a plasma. We use the DynaMo code to investigate the time-dependent expansion and acceleration of dissipationless gamma-ray burst fireballs by varying their initial opacities and baryonic content. We study the opacity and energy density evolution of an initially optically thick, radiation-dominated fireball across its entire phase space - in particular during the Rph < Rsat regime. Our results reveal new phases of fireball evolution: a transition phase with a radial extent of several orders of magnitude - the fireball transitions from Γ ∝ R to Γ ∝ R0, a post-photospheric acceleration phase - where fireballs accelerate beyond the photosphere and a Thomson-dominated acceleration phase - characterized by slow acceleration of optically thick, matter-dominated fireballs due to Thomson scattering. We quantify the new phases by providing analytical expressions of Lorentz factor evolution, which will be useful for deriving jet parameters.

  12. Two-color ionization injection using a plasma beatwave accelerator

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

    Schroeder, C. B.; Benedetti, C.; Esarey, E.

    Two-color laser ionization injection is a method to generate ultra-low emittance (sub-100 nm transverse normalized emittance) beams in a laser-driven plasma accelerator. A plasma beatwave accelerator is proposed to drive the plasma wave for ionization injection, where the beating of the lasers effectively produces a train of long-wavelength pulses. The plasma beatwave accelerator excites a large amplitude plasma wave with low peak laser electric fields, leaving atomically-bound electrons with low ionization potential. A short-wavelength, low-amplitude ionization injection laser pulse (with a small ponderomotive force and large peak electric field) is used to ionize the remaining bound electrons at a wakemore » phase suitable for trapping, generating an ultra-low emittance electron beam that is accelerated in the plasma wave. Using a plasma beatwave accelerator for wakefield excitation, compared to short-pulse wakefield excitation, allows for a lower amplitude injection laser pulse and, hence, a lower emittance beam may be generated.« less

  13. Two-color ionization injection using a plasma beatwave accelerator

    DOE PAGES

    Schroeder, C. B.; Benedetti, C.; Esarey, E.; ...

    2018-01-10

    Two-color laser ionization injection is a method to generate ultra-low emittance (sub-100 nm transverse normalized emittance) beams in a laser-driven plasma accelerator. A plasma beatwave accelerator is proposed to drive the plasma wave for ionization injection, where the beating of the lasers effectively produces a train of long-wavelength pulses. The plasma beatwave accelerator excites a large amplitude plasma wave with low peak laser electric fields, leaving atomically-bound electrons with low ionization potential. A short-wavelength, low-amplitude ionization injection laser pulse (with a small ponderomotive force and large peak electric field) is used to ionize the remaining bound electrons at a wakemore » phase suitable for trapping, generating an ultra-low emittance electron beam that is accelerated in the plasma wave. Using a plasma beatwave accelerator for wakefield excitation, compared to short-pulse wakefield excitation, allows for a lower amplitude injection laser pulse and, hence, a lower emittance beam may be generated.« less

  14. First Experiments with Planar Wire Arrays on U Michigan's Linear Transformer Driver

    NASA Astrophysics Data System (ADS)

    Safronova, A. S.; Kantsyrev, V. L.; Weller, M. E.; Shrestha, I. K.; Shlyaptseva, V. V.; Cooper, M. C.; Lorance, M.; Stafford, A.; Patel, S. G.; Steiner, A. M.; Yager-Elorriaga, D. A.; Jordan, N. M.; Gilgenbach, R. M.

    2014-10-01

    For petawatt-class Z-pinch accelerators, a Linear Transformer Driver (LTD)-driven accelerator promises to be (at a given pinch current and implosion time) more efficient than the conventionally used Marx-driven accelerator. Because there exists almost no data on how wire arrays radiate on LTD-based machines in the USA, it is very important to perform radiation and plasma physics studies on this new type of generator. We report on the first outcome of the new partnership with University of Michigan (UM), which resulted in successful UNR-UM experiments on the low-impedance MAIZE generator with planar wire arrays (PWA). PWA is a novel wire array load that was introduced and tested in detail on high-impedance Zebra at UNR during the last years and found to be the most efficient radiator. Implosion of Al Double PWAs of different configurations were achieved on MAIZE, observed with a set of various diagnostics which include x-ray diode detectors, x-ray spectroscopy and imaging, and shadowgraphy. Al and Mg plasmas of more than 450 eV were studied in detail. Research supported by NNSA under DOE Cooperative Agreement DE-NA0001984. S. G. Patel and A. M. Steiner supported by Sandia National Laboratories. D. A. Yager-Elorriaga supported by NSF GF.

  15. Lightwave-driven quasiparticle collisions on a subcycle timescale

    NASA Astrophysics Data System (ADS)

    Langer, F.; Hohenleutner, M.; Schmid, C. P.; Poellmann, C.; Nagler, P.; Korn, T.; Schüller, C.; Sherwin, M. S.; Huttner, U.; Steiner, J. T.; Koch, S. W.; Kira, M.; Huber, R.

    2016-05-01

    Ever since Ernest Rutherford scattered α-particles from gold foils, collision experiments have revealed insights into atoms, nuclei and elementary particles. In solids, many-body correlations lead to characteristic resonances—called quasiparticles—such as excitons, dropletons, polarons and Cooper pairs. The structure and dynamics of quasiparticles are important because they define macroscopic phenomena such as Mott insulating states, spontaneous spin- and charge-order, and high-temperature superconductivity. However, the extremely short lifetimes of these entities make practical implementations of a suitable collider challenging. Here we exploit lightwave-driven charge transport, the foundation of attosecond science, to explore ultrafast quasiparticle collisions directly in the time domain: a femtosecond optical pulse creates excitonic electron-hole pairs in the layered dichalcogenide tungsten diselenide while a strong terahertz field accelerates and collides the electrons with the holes. The underlying dynamics of the wave packets, including collision, pair annihilation, quantum interference and dephasing, are detected as light emission in high-order spectral sidebands of the optical excitation. A full quantum theory explains our observations microscopically. This approach enables collision experiments with various complex quasiparticles and suggests a promising new way of generating sub-femtosecond pulses.

  16. Lightwave-driven quasiparticle collisions on a subcycle timescale.

    PubMed

    Langer, F; Hohenleutner, M; Schmid, C P; Poellmann, C; Nagler, P; Korn, T; Schüller, C; Sherwin, M S; Huttner, U; Steiner, J T; Koch, S W; Kira, M; Huber, R

    2016-05-12

    Ever since Ernest Rutherford scattered α-particles from gold foils, collision experiments have revealed insights into atoms, nuclei and elementary particles. In solids, many-body correlations lead to characteristic resonances--called quasiparticles--such as excitons, dropletons, polarons and Cooper pairs. The structure and dynamics of quasiparticles are important because they define macroscopic phenomena such as Mott insulating states, spontaneous spin- and charge-order, and high-temperature superconductivity. However, the extremely short lifetimes of these entities make practical implementations of a suitable collider challenging. Here we exploit lightwave-driven charge transport, the foundation of attosecond science, to explore ultrafast quasiparticle collisions directly in the time domain: a femtosecond optical pulse creates excitonic electron-hole pairs in the layered dichalcogenide tungsten diselenide while a strong terahertz field accelerates and collides the electrons with the holes. The underlying dynamics of the wave packets, including collision, pair annihilation, quantum interference and dephasing, are detected as light emission in high-order spectral sidebands of the optical excitation. A full quantum theory explains our observations microscopically. This approach enables collision experiments with various complex quasiparticles and suggests a promising new way of generating sub-femtosecond pulses.

  17. Relativistic Electron Acceleration with Ultrashort Mid-IR Laser Pulses

    NASA Astrophysics Data System (ADS)

    Feder, Linus; Woodbury, Daniel; Shumakova, Valentina; Gollner, Claudia; Miao, Bo; Schwartz, Robert; Pugžlys, Audrius; Baltuška, Andrius; Milchberg, Howard

    2017-10-01

    We report the first results of laser plasma wakefield acceleration driven by ultrashort mid-infrared laser pulses (λ = 3.9 μm , pulsewidth 100 fs, energy <20 mJ, peak power <1 TW), which enables near- and above-critical density interactions with moderate-density gas jets. We present thresholds for electron acceleration based on critical parameters for relativistic self-focusing and target width, as well as trends in the accelerated beam profiles, charge and energy spectra which are supported by 3D particle-in-cell simulations. These results extend earlier work with sub-TW self-modulated laser wakefield acceleration using near IR drivers to the Mid-IR, and enable us to capture time-resolved images of relativistic self-focusing of the laser pulse. This work supported by DOE (DESC0010706TDD, DESC0015516); AFOSR(FA95501310044, FA95501610121); NSF(PHY1535519); DHS.

  18. Mass sensitivity studies for an inductively driven railgun

    NASA Astrophysics Data System (ADS)

    Scanlon, J. J., III; Young, A. F.

    1991-01-01

    Those areas which result in substantial system mass reductions for an HPG (homopolar generator) driven EML (electromagnetic launcher) are identified. Sensitivity studies are performed by varying launch mass, peak acceleration, launcher efficiency, inductance gradient, injection velocity, barrel mass per unit length, fuel tankage and pump estimates, and component energy and power densities. Two major contributors to the system mass are the allowed number of shots per barrel versus the number required for the mission, and the barrel length. The effects of component performance parameters, such as friction coefficient, injection velocity, ablation coefficient, rail resistivity, armature voltage, peak acceleration, and inductance gradient on these two areas, are addressed.

  19. Experiences and emotions of faculty teaching in accelerated second baccalaureate degree nursing programs.

    PubMed

    Brandt, Cheryl L; Boellaard, Melissa R; Zorn, Cecelia R

    2013-07-01

    The number of accelerated second baccalaureate degree nursing (ASBSN) programs has mushroomed over recent decades, with more than 225 currently in existence. Scholars have described students and programs, but research examining the faculty experience is limited. The purpose of this study was to describe the experiences and emotions of faculty teaching students in ASBSN programs. Using a descriptive qualitative survey design, faculty (N = 138) from 25 randomly selected programs in 11 midwestern states were surveyed using an instrument developed for this study and distributed online. Ten themes emerged, including (a) Engaging With Motivated, Mature, and Diverse Students, (b) Students Choosing Nursing for the "Wrong Reasons," (c) Too Much Work, Too Little Time for Students and Faculty, (d) Amazement, (e) Pride, and (f) Frustration. These findings will help novice and seasoned ASBSN faculty interpret their experiences, strengthen precepting and mentoring activities, and support administrators in determining staffing plans and designing ASBSN programs. Copyright 2013, SLACK Incorporated.

  20. ATTO SECOND ELECTRON BEAMS GENERATION AND CHARACTERIZATION EXPERIMENT AT THE ACCELERATOR TEST FACILITY.

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

    ZOLOTOREV, M.; ZHOLENTS, A.; WANG, X.J.

    2002-02-01

    We are proposing an Atto-second electron beam generation and diagnostics experiment at the Brookhaven Accelerator Test facility (ATF) using 1 {micro}m Inverse Free Electron Laser (IFEL). The proposed experiment will be carried out by an BNL/LBNL collaboration, and it will be installed at the ATF beam line II. The proposed experiment will employ a one-meter long undulator with 1.8 cm period (VISA undulator). The electron beam energy will be 63 MeV with emittance less than 2 mm-mrad and energy spread less than 0.05%. The ATF photocathode injector driving laser will be used for energy modulation by Inverse Free Electron Lasermore » (IFEL). With 10 MW laser peak power, about 2% total energy modulation is expected. The energy modulated electron beam will be further bunched through either a drift space or a three magnet chicane into atto-second electron bunches. The attosecond electron beam bunches will be analyzed using the coherent transition radiation (CTR).« less

  1. Staging and laser acceleration of ions in underdense plasma

    NASA Astrophysics Data System (ADS)

    Ting, Antonio; Hafizi, Bahman; Helle, Michael; Chen, Yu-Hsin; Gordon, Daniel; Kaganovich, Dmitri; Polyanskiy, Mikhail; Pogorelsky, Igor; Babzien, Markus; Miao, Chenlong; Dover, Nicholas; Najmudin, Zulfikar; Ettlinger, Oliver

    2017-03-01

    Accelerating ions from rest in a plasma requires extra considerations because of their heavy mass. Low phase velocity fields or quasi-electrostatic fields are often necessary, either by operating above or near the critical density or by applying other slow wave generating mechanisms. Solid targets have been a favorite and have generated many good results. High density gas targets have also been reported to produce energetic ions. It is interesting to consider acceleration of ions in laser-driven plasma configurations that will potentially allow continuous acceleration in multiple consecutive stages. The plasma will be derived from gaseous targets, producing plasma densities slightly below the critical plasma density (underdense) for the driving laser. Such a plasma is experimentally robust, being repeatable and relatively transparent to externally injected ions from a previous stage. When optimized, multiple stages of this underdense laser plasma acceleration mechanism can progressively accelerate the ions to a high final energy. For a light mass ion such as the proton, relativistic velocities could be reached, making it suitable for further acceleration by high phase velocity plasma accelerators to energies appropriate for High Energy Physics applications. Negatively charged ions such as antiprotons could be similarly accelerated in this multi-staged ion acceleration scheme.

  2. Plasma production for electron acceleration by resonant plasma wave

    NASA Astrophysics Data System (ADS)

    Anania, M. P.; Biagioni, A.; Chiadroni, E.; Cianchi, A.; Croia, M.; Curcio, A.; Di Giovenale, D.; Di Pirro, G. P.; Filippi, F.; Ghigo, A.; Lollo, V.; Pella, S.; Pompili, R.; Romeo, S.; Ferrario, M.

    2016-09-01

    Plasma wakefield acceleration is the most promising acceleration technique known nowadays, able to provide very high accelerating fields (10-100 GV/m), enabling acceleration of electrons to GeV energy in few centimeter. However, the quality of the electron bunches accelerated with this technique is still not comparable with that of conventional accelerators (large energy spread, low repetition rate, and large emittance); radiofrequency-based accelerators, in fact, are limited in accelerating field (10-100 MV/m) requiring therefore hundred of meters of distances to reach the GeV energies, but can provide very bright electron bunches. To combine high brightness electron bunches from conventional accelerators and high accelerating fields reachable with plasmas could be a good compromise allowing to further accelerate high brightness electron bunches coming from LINAC while preserving electron beam quality. Following the idea of plasma wave resonant excitation driven by a train of short bunches, we have started to study the requirements in terms of plasma for SPARC_LAB (Ferrario et al., 2013 [1]). In particular here we focus on hydrogen plasma discharge, and in particular on the theoretical and numerical estimates of the ionization process which are very useful to design the discharge circuit and to evaluate the current needed to be supplied to the gas in order to have full ionization. Eventually, the current supplied to the gas simulated will be compared to that measured experimentally.

  3. Plasma Wake-field Acceleration in the Blow-out Regime

    NASA Astrophysics Data System (ADS)

    Barov, Nikolai; Rosenzweig, James

    1999-11-01

    Recent experiments at Argonne National Laboratory, investigating the blow-out regime of the plasma wake-field accelerator, are discussed. These experiments achieved stable underdense (beam denser than the ambient plasma density) beam transport, and measured average acceleration of 25 MV/m, corresponding to peak wave fields of over 60 MVm. A comparison of the results to simulation is given, and the physics of the system is discussed. Potential for improvements in performance and achieved acceleration gradient, as well as accelerated beam quality are examined within the context of the next generation of experiments at the Fermilab Test Facility. The status of these experiments will be given.

  4. Giant Acceleration of Diffusion Observed in a Single-Molecule Experiment on F(1)-ATPase.

    PubMed

    Hayashi, Ryunosuke; Sasaki, Kazuo; Nakamura, Shuichi; Kudo, Seishi; Inoue, Yuichi; Noji, Hiroyuki; Hayashi, Kumiko

    2015-06-19

    The giant acceleration (GA) of diffusion is a universal phenomenon predicted by the theoretical analysis given by Reimann et al. [Phys. Rev. Lett. 87, 010602 (2001)]. Here we apply the theory of the GA of diffusion to a single-molecule experiment on a rotary motor protein, F(1), which is a component of F(o)F(1) adenosine triphosphate synthase. We discuss the energetic properties of F(1) and identify a high energy barrier of the rotary potential to be 20k(B)T, with the condition that the adenosine diphosphates are tightly bound to the F(1) catalytic sites. To conclude, the GA of diffusion is useful for measuring energy barriers in nonequilibrium and single-molecule experiments.

  5. Giant Acceleration of Diffusion Observed in a Single-Molecule Experiment on F1-ATPase

    NASA Astrophysics Data System (ADS)

    Hayashi, Ryunosuke; Sasaki, Kazuo; Nakamura, Shuichi; Kudo, Seishi; Inoue, Yuichi; Noji, Hiroyuki; Hayashi, Kumiko

    2015-06-01

    The giant acceleration (GA) of diffusion is a universal phenomenon predicted by the theoretical analysis given by Reimann et al. [Phys. Rev. Lett. 87, 010602 (2001)]. Here we apply the theory of the GA of diffusion to a single-molecule experiment on a rotary motor protein, F1 , which is a component of Fo F1 adenosine triphosphate synthase. We discuss the energetic properties of F1 and identify a high energy barrier of the rotary potential to be 20 kBT , with the condition that the adenosine diphosphates are tightly bound to the F1 catalytic sites. To conclude, the GA of diffusion is useful for measuring energy barriers in nonequilibrium and single-molecule experiments.

  6. The High-Luminosity upgrade of the LHC: Physics and Technology Challenges for the Accelerator and the Experiments

    NASA Astrophysics Data System (ADS)

    Schmidt, Burkhard

    2016-04-01

    In the second phase of the LHC physics program, the accelerator will provide an additional integrated luminosity of about 2500/fb over 10 years of operation to the general purpose detectors ATLAS and CMS. This will substantially enlarge the mass reach in the search for new particles and will also greatly extend the potential to study the properties of the Higgs boson discovered at the LHC in 2012. In order to meet the experimental challenges of unprecedented pp luminosity, the experiments will need to address the aging of the present detectors and to improve the ability to isolate and precisely measure the products of the most interesting collisions. The lectures gave an overview of the physics motivation and described the conceptual designs and the expected performance of the upgrades of the four major experiments, ALICE, ATLAS, CMS and LHCb, along with the plans to develop the appropriate experimental techniques and a brief overview of the accelerator upgrade. Only some key points of the upgrade program of the four major experiments are discussed in this report; more information can be found in the references given at the end.

  7. Designing a Dielectric Laser Accelerator on a Chip

    NASA Astrophysics Data System (ADS)

    Niedermayer, Uwe; Boine-Frankenheim, Oliver; Egenolf, Thilo

    2017-07-01

    Dielectric Laser Acceleration (DLA) achieves gradients of more than 1GeV/m, which are among the highest in non-plasma accelerators. The long-term goal of the ACHIP collaboration is to provide relativistic (>1 MeV) electrons by means of a laser driven microchip accelerator. Examples of ’’slightly resonant” dielectric structures showing gradients in the range of 70% of the incident laser field (1 GV/m) for electrons with beta=0.32 and 200% for beta=0.91 are presented. We demonstrate the bunching and acceleration of low energy electrons in dedicated ballistic buncher and velocity matched grating structures. However, the design gradient of 500 MeV/m leads to rapid defocusing. Therefore we present a scheme to bunch the beam in stages, which does not only reduce the energy spread, but also the transverse defocusing. The designs are made with a dedicated homemade 6D particle tracking code.

  8. Flow accelerated organic coating degradation

    NASA Astrophysics Data System (ADS)

    Zhou, Qixin

    Applying organic coatings is a common and the most cost effective way to protect metallic objects and structures from corrosion. Water entry into coating-metal interface is usually the main cause for the deterioration of organic coatings, which leads to coating delamination and underfilm corrosion. Recently, flowing fluids over sample surface have received attention due to their capability to accelerate material degradation. A plethora of works has focused on the flow induced metal corrosion, while few studies have investigated the flow accelerated organic coating degradation. Flowing fluids above coating surface affect corrosion by enhancing the water transport and abrading the surface due to fluid shear. Hence, it is of great importance to understand the influence of flowing fluids on the degradation of corrosion protective organic coatings. In this study, a pigmented marine coating and several clear coatings were exposed to the laminar flow and stationary immersion. The laminar flow was pressure driven and confined in a flow channel. A 3.5 wt% sodium chloride solution and pure water was employed as the working fluid with a variety of flow rates. The corrosion protective properties of organic coatings were monitored inline by Electrochemical Impedance Spectroscopy (EIS) measurement. Equivalent circuit models were employed to interpret the EIS spectra. The time evolution of coating resistance and capacitance obtained from the model was studied to demonstrate the coating degradation. Thickness, gloss, and other topography characterizations were conducted to facilitate the assessment of the corrosion. The working fluids were characterized by Fourier Transform Infrared Spectrometer (FTIR) and conductivity measurement. The influence of flow rate, fluid shear, fluid composition, and other effects in the coating degradation were investigated. We conclude that flowing fluid on the coating surface accelerates the transport of water, oxygen, and ions into the coating, as

  9. Ion Acceleration by Flux Transfer Events in the Terrestrial Magnetosheath

    NASA Astrophysics Data System (ADS)

    Jarvinen, R.; Vainio, R.; Palmroth, M.; Juusola, L.; Hoilijoki, S.; Pfau-Kempf, Y.; Ganse, U.; Turc, L.; von Alfthan, S.

    2018-02-01

    We report ion acceleration by flux transfer events in the terrestrial magnetosheath in a global two-dimensional hybrid-Vlasov polar plane simulation of Earth's solar wind interaction. In the model we find that propagating flux transfer events created in magnetic reconnection at the dayside magnetopause drive fast-mode bow waves in the magnetosheath, which accelerate ions in the shocked solar wind flow. The acceleration at the bow waves is caused by a shock drift-like acceleration process under stationary solar wind and interplanetary magnetic field upstream conditions. Thus, the energization is not externally driven but results from plasma dynamics within the magnetosheath. Energetic proton populations reach the energy of 30 keV, and their velocity distributions resemble time-energy dispersive ion injections observed by the Cluster spacecraft in the magnetosheath.

  10. Designs and Plans for MAIZE: a 1 MA LTD-Driven Z-Pinch

    NASA Astrophysics Data System (ADS)

    Gilgenbach, R. M.; Gomez, M. R.; Zier, J.; Tang, W.; French, D. M.; Hoff, B. W.; Jordan, N.; Cruz, E.; Lau, Y. Y.; Fowler-Guzzardo, T.; Meisel, J.; Mazarakis, M. G.; Cuneo, M. E.; Johnston, M. D.; Mehlhorn, T. A.; Kim, A. A.; Sinebryukhov, V. A.

    2007-11-01

    We present designs and experimental plans of the first 1 MA z-pinch in the USA to be driven by a Linear Transformer Driver (LTD). The Michigan Accelerator for Inductive Z-pinch Experiments, (MAIZE), is based on the LTD developed at the Institute for High Current Electronics, utilizing 80 capacitors and 40 spark gap switches to deliver a 1 MA, 100 kV pulse with <100 ns risetime. Designs will be presented of a low-inductance MITL terminated in a wire-array z-pinch. Initial, planned experiments will evaluate the LTD driving time-changing inductance of imploding 4-16 wire-array z-pinches. Wire ablation dynamics, axial-correlations and instability development will be explored. *This work was supported by U. S. DoE through Sandia National Laboratories award number 240985 to the University of Michigan. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  11. A user-driven treadmill control scheme for simulating overground locomotion.

    PubMed

    Kim, Jonghyun; Stanley, Christopher J; Curatalo, Lindsey A; Park, Hyung-Soon

    2012-01-01

    Treadmill-based locomotor training should simulate overground walking as closely as possible for optimal skill transfer. The constant speed of a standard treadmill encourages automaticity rather than engagement and fails to simulate the variable speeds encountered during real-world walking. To address this limitation, this paper proposes a user-driven treadmill velocity control scheme that allows the user to experience natural fluctuations in walking velocity with minimal unwanted inertial force due to acceleration/deceleration of the treadmill belt. A smart estimation limiter in the scheme effectively attenuates the inertial force during velocity changes. The proposed scheme requires measurement of pelvic and swing foot motions, and is developed for a treadmill of typical belt length (1.5 m). The proposed scheme is quantitatively evaluated here with four healthy subjects by comparing it with the most advanced control scheme identified in the literature.

  12. Intense laser-driven ion beams in the relativistic-transparency regime: acceleration, control and applications

    NASA Astrophysics Data System (ADS)

    Fernandez, Juan C.

    2016-10-01

    Laser-plasma interactions in the novel regime of relativistically-induced transparency have been harnessed to generate efficiently intense ion beams with average energies exceeding 10 MeV/nucleon (>100 MeV for protons) at ``table-top'' scales. We have discovered and utilized a self-organizing scheme that exploits persisting self-generated plasma electric ( 0.1 TV/m) and magnetic ( 104 Tesla) fields to reduce the ion-energy (Ei) spread after the laser exits the plasma, thus separating acceleration from spread reduction. In this way we routinely generate aluminum and carbon beams with narrow spectral peaks at Ei up to 310 MeV and 220 MeV, respectively, with high efficiency ( 5%). The experimental demonstration has been done at the LANL Trident laser with 0.12 PW, high-contrast, 0.65 ps Gaussian laser pulses irradiating planar foils up to 250 nm thick. In this regime, Ei scales empirically with laser intensity (I) as I 1 / 2. Our progress is enabled by high-fidelity, massive computer simulations of the experiments. This work advances next-generation compact accelerators suitable for new applications. E . g ., a carbon beam with Ei 400 MeV and 10% energy spread is suitable for fast ignition (FI) of compressed DT. The observed scaling suggests that is feasible with existing target fabrication and PW-laser technologies, using a sub-ps laser pulse with I 2.5 ×1021 W/cm2. These beams have been used on Trident to generate warm-dense matter at solid-densities, enabling us to investigate its equation of state and mixing of heterogeneous interfaces purely by plasma effects distinct from hydrodynamics. They also drive an intense neutron-beam source with great promise for important applications such as active interrogation of shielded nuclear materials. Considerations on controlling ion-beam divergence for their increased utility are discussed. Funded by the LANL LDRD program.

  13. Particle Acceleration in Two Converging Shocks

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

    Wang, Xin; Wang, Na; Shan, Hao

    2017-06-20

    Observations by spacecraft such as ACE , STEREO , and others show that there are proton spectral “breaks” with energy E {sub br} at 1–10 MeV in some large CME-driven shocks. Generally, a single shock with the diffusive acceleration mechanism would not predict the “broken” energy spectrum. The present paper focuses on two converging shocks to identify this energy spectral feature. In this case, the converging shocks comprise one forward CME-driven shock on 2006 December 13 and another backward Earth bow shock. We simulate the detailed particle acceleration processes in the region of the converging shocks using the Monte Carlomore » method. As a result, we not only obtain an extended energy spectrum with an energy “tail” up to a few 10 MeV higher than that in previous single shock model, but also we find an energy spectral “break” occurring on ∼5.5 MeV. The predicted energy spectral shape is consistent with observations from multiple spacecraft. The spectral “break,” then, in this case is caused by the interaction between the CME shock and Earth’s bow shock, and otherwise would not be present if Earth were not in the path of the CME.« less

  14. Acceleration and evolution of a hollow electron beam in wakefields driven by a Laguerre-Gaussian laser pulse

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

    Zhang, Guo-Bo; College of Science, National University of Defense Technology, Changsha 410073; Chen, Min, E-mail: minchen@sjtu.edu.cn, E-mail: yanyunma@126.com

    2016-03-15

    We show that a ring-shaped hollow electron beam can be injected and accelerated by using a Laguerre-Gaussian laser pulse and ionization-induced injection in a laser wakefield accelerator. The acceleration and evolution of such a hollow, relativistic electron beam are investigated through three-dimensional particle-in-cell simulations. We find that both the ring size and the beam thickness oscillate during the acceleration. The beam azimuthal shape is angularly dependent and evolves during the acceleration. The beam ellipticity changes resulting from the electron angular momenta obtained from the drive laser pulse and the focusing forces from the wakefield. The dependence of beam ring radiusmore » on the laser-plasma parameters (e.g., laser intensity, focal size, and plasma density) is studied. Such a hollow electron beam may have potential applications for accelerating and collimating positively charged particles.« less

  15. DIFFUSIVE PARTICLE ACCELERATION IN SHOCKED, VISCOUS ACCRETION DISKS: GREEN'S FUNCTION ENERGY DISTRIBUTION

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

    Becker, Peter A.; Das, Santabrata; Le, Truong, E-mail: pbecker@gmu.edu, E-mail: sbdas@iitg.ernet.in, E-mail: truong.le@nhrec.org

    2011-12-10

    The acceleration of relativistic particles in a viscous accretion disk containing a standing shock is investigated as a possible explanation for the energetic outflows observed around radio-loud black holes. The energy/space distribution of the accelerated particles is computed by solving a transport equation that includes the effects of first-order Fermi acceleration, bulk advection, spatial diffusion, and particle escape. The velocity profile of the accreting gas is described using a model for shocked viscous disks recently developed by the authors, and the corresponding Green's function distribution for the accelerated particles in the disk and the outflow is obtained using a classicalmore » method based on eigenfunction analysis. The accretion-driven, diffusive shock acceleration scenario explored here is conceptually similar to the standard model for the acceleration of cosmic rays at supernova-driven shocks. However, in the disk application, the distribution of the accelerated particles is much harder than would be expected for a plane-parallel shock with the same compression ratio. Hence the disk environment plays a key role in enhancing the efficiency of the shock acceleration process. The presence of the shock helps to stabilize the disk by reducing the Bernoulli parameter, while channeling the excess binding energy into the escaping relativistic particles. In applications to M87 and Sgr A*, we find that the kinetic power in the jet is {approx}0.01 M-dot c{sup 2}, and the outflowing relativistic particles have a mean energy {approx}300 times larger than that of the thermal gas in the disk at the shock radius. Our results suggest that a standing shock may be an essential ingredient in accretion onto underfed black holes, helping to resolve the long-standing problem of the stability of advection-dominated accretion disks.« less

  16. Experiments on two- and three-dimensional vortex flows in lid-driven cavities

    NASA Astrophysics Data System (ADS)

    Siegmann-Hegerfeld, Tanja; Albensoeder, Stefan; Kuhlmann, Hendrik C.

    2009-11-01

    Vortex flows in one-sided lid-driven cavities with different cross-sectional aspect ratios (γ = 0.26 up to γ = 6.3) are investigated experimentally. In all cases the spanwise aspect ratio λ>>γ is very large and much larger than most previous experiments. Flow-structure visualizations will be presented together with quantitative LDA and PIV measurements. The experimental results are in good agreement with the critical data from numerical stability analyses and with nonlinear simulations. Experimentally, we find four different three-dimensional instabilities. Particular attention is paid to the so-called C4 mode which arises at large cross-sectional aspect ratios. When the spanwise aspect ratio is small the first bifurcation of the C4 mode is strongly imperfect.

  17. Do working memory-driven attention shifts speed up visual awareness?

    PubMed

    Pan, Yi; Cheng, Qiu-Ping

    2011-11-01

    Previous research has shown that content representations in working memory (WM) can bias attention in favor of matching stimuli in the scene. Using a visual prior-entry procedure, we here investigate whether such WM-driven attention shifts can speed up the conscious awareness of memory-matching relative to memory-mismatching stimuli. Participants were asked to hold a color cue in WM and to subsequently perform a temporal order judgment (TOJ) task by reporting either of two different-colored circles (presented to the left and right of fixation with a variable temporal interval) as having the first onset. One of the two TOJ circles could match the memory cue in color. We found that awareness of the temporal order of the circle onsets was not affected by the contents of WM, even when participants were explicitly informed that one of the TOJ circles would always match the WM contents. The null effect of WM on TOJs was not due to an inability of the memory-matching item to capture attention, since response times to the target in a follow-up experiment were improved when it appeared at the location of the memory-matching item. The present findings suggest that WM-driven attention shifts cannot accelerate phenomenal awareness of matching stimuli in the visual field.

  18. Buoyancy driven mixing of miscible fluids by volumetric energy deposition of microwaves.

    PubMed

    Wachtor, Adam J; Mocko, Veronika; Williams, Darrick J; Goertz, Matthew P; Jebrail, Farzaneh F

    2013-01-01

    An experiment that seeks to investigate buoyancy driven mixing of miscible fluids by microwave volumetric energy deposition is presented. The experiment involves the use of a light, non-polar fluid that initially rests on top of a heavier fluid which is more polar. Microwaves preferentially heat the polar fluid, and its density decreases due to thermal expansion. As the microwave heating continues, the density of the lower fluid eventually becomes less than that of the upper, and buoyancy driven Rayleigh-Taylor mixing ensues. The choice of fluids is crucial to the success of the experiment, and a description is given of numerous fluid combinations considered and characterized. After careful consideration, the miscible pair of toluene/tetrahydrofuran (THF) was determined as having the best potential for successful volumetric energy deposition buoyancy driven mixing. Various single fluid calibration experiments were performed to facilitate the development of a heating theory. Thereafter, results from two-fluid mixing experiments are presented that demonstrate the capability of this novel Rayleigh-Taylor driven experiment. Particular interest is paid to the onset of buoyancy driven mixing and unusual aspects of the experiment in the context of typical Rayleigh-Taylor driven mixing.

  19. Simultaneous operation of two soft x-ray free-electron lasers driven by one linear accelerator

    NASA Astrophysics Data System (ADS)

    Faatz, B.; Plönjes, E.; Ackermann, S.; Agababyan, A.; Asgekar, V.; Ayvazyan, V.; Baark, S.; Baboi, N.; Balandin, V.; von Bargen, N.; Bican, Y.; Bilani, O.; Bödewadt, J.; Böhnert, M.; Böspflug, R.; Bonfigt, S.; Bolz, H.; Borges, F.; Borkenhagen, O.; Brachmanski, M.; Braune, M.; Brinkmann, A.; Brovko, O.; Bruns, T.; Castro, P.; Chen, J.; Czwalinna, M. K.; Damker, H.; Decking, W.; Degenhardt, M.; Delfs, A.; Delfs, T.; Deng, H.; Dressel, M.; Duhme, H.-T.; Düsterer, S.; Eckoldt, H.; Eislage, A.; Felber, M.; Feldhaus, J.; Gessler, P.; Gibau, M.; Golubeva, N.; Golz, T.; Gonschior, J.; Grebentsov, A.; Grecki, M.; Grün, C.; Grunewald, S.; Hacker, K.; Hänisch, L.; Hage, A.; Hans, T.; Hass, E.; Hauberg, A.; Hensler, O.; Hesse, M.; Heuck, K.; Hidvegi, A.; Holz, M.; Honkavaara, K.; Höppner, H.; Ignatenko, A.; Jäger, J.; Jastrow, U.; Kammering, R.; Karstensen, S.; Kaukher, A.; Kay, H.; Keil, B.; Klose, K.; Kocharyan, V.; Köpke, M.; Körfer, M.; Kook, W.; Krause, B.; Krebs, O.; Kreis, S.; Krivan, F.; Kuhlmann, J.; Kuhlmann, M.; Kube, G.; Laarmann, T.; Lechner, C.; Lederer, S.; Leuschner, A.; Liebertz, D.; Liebing, J.; Liedtke, A.; Lilje, L.; Limberg, T.; Lipka, D.; Liu, B.; Lorbeer, B.; Ludwig, K.; Mahn, H.; Marinkovic, G.; Martens, C.; Marutzky, F.; Maslocv, M.; Meissner, D.; Mildner, N.; Miltchev, V.; Molnar, S.; Mross, D.; Müller, F.; Neumann, R.; Neumann, P.; Nölle, D.; Obier, F.; Pelzer, M.; Peters, H.-B.; Petersen, K.; Petrosyan, A.; Petrosyan, G.; Petrosyan, L.; Petrosyan, V.; Petrov, A.; Pfeiffer, S.; Piotrowski, A.; Pisarov, Z.; Plath, T.; Pototzki, P.; Prandolini, M. J.; Prenting, J.; Priebe, G.; Racky, B.; Ramm, T.; Rehlich, K.; Riedel, R.; Roggli, M.; Röhling, M.; Rönsch-Schulenburg, J.; Rossbach, J.; Rybnikov, V.; Schäfer, J.; Schaffran, J.; Schlarb, H.; Schlesselmann, G.; Schlösser, M.; Schmid, P.; Schmidt, C.; Schmidt-Föhre, F.; Schmitz, M.; Schneidmiller, E.; Schöps, A.; Scholz, M.; Schreiber, S.; Schütt, K.; Schütz, U.; Schulte-Schrepping, H.; Schulz, M.; Shabunov, A.; Smirnov, P.; Sombrowski, E.; Sorokin, A.; Sparr, B.; Spengler, J.; Staack, M.; Stadler, M.; Stechmann, C.; Steffen, B.; Stojanovic, N.; Sychev, V.; Syresin, E.; Tanikawa, T.; Tavella, F.; Tesch, N.; Tiedtke, K.; Tischer, M.; Treusch, R.; Tripathi, S.; Vagin, P.; Vetrov, P.; Vilcins, S.; Vogt, M.; de Zubiaurre Wagner, A.; Wamsat, T.; Weddig, H.; Weichert, G.; Weigelt, H.; Wentowski, N.; Wiebers, C.; Wilksen, T.; Willner, A.; Wittenburg, K.; Wohlenberg, T.; Wortmann, J.; Wurth, W.; Yurkov, M.; Zagorodnov, I.; Zemella, J.

    2016-06-01

    Extreme-ultraviolet to x-ray free-electron lasers (FELs) in operation for scientific applications are up to now single-user facilities. While most FELs generate around 100 photon pulses per second, FLASH at DESY can deliver almost two orders of magnitude more pulses in this time span due to its superconducting accelerator technology. This makes the facility a prime candidate to realize the next step in FELs—dividing the electron pulse trains into several FEL lines and delivering photon pulses to several users at the same time. Hence, FLASH has been extended with a second undulator line and self-amplified spontaneous emission (SASE) is demonstrated in both FELs simultaneously. FLASH can now deliver MHz pulse trains to two user experiments in parallel with individually selected photon beam characteristics. First results of the capabilities of this extension are shown with emphasis on independent variation of wavelength, repetition rate, and photon pulse length.

  20. Microgravity acceleration measurement and environment characterization science (17-IML-1)

    NASA Technical Reports Server (NTRS)

    1992-01-01

    The Space Acceleration Measurement System (SAMS) is a general purpose instrumentation system designed to measure the accelerations onboard the Shuttle Orbiter and Shuttle/Spacelab vehicles. These measurements are used to support microgravity experiments and investigation into the microgravity environment of the vehicle. Acceleration measurements can be made at locations remote from the SAMS main instrumentation unit by the use of up to three remote triaxial sensor heads. The prime objective for SAMS on the International Microgravity Lab (IML-1) mission will be to measure the accelerations experienced by the Fluid Experiment System (FES). The SAMS acceleration measurements for FES will be complemented by low level, low frequency acceleration measurements made by the Orbital Acceleration Research Experiment (OARE) installed on the shuttle. Secondary objectives for SAMS will be to measure accelerations at several specific locations to enable the acceleration transfer function of the Spacelab module to be analyzed. This analysis effort will be in conjunction with similar measurements analyses on other Spacelab missions.

  1. Relativistic Transparency Experiments at the Trident Laser

    NASA Astrophysics Data System (ADS)

    Cobble, J. A.; Palaniyappan, S.; Gautier, D. C.; Kim, Y. H.; Clark, D. D.; Johnson, R. P.; Shimada, T.; Fernandez, J. C.; Herrmann, H. W.

    2013-10-01

    With near-diffraction-limited irradiance of 3 × 1020 W/cm2 on target and prelase contrast better than 10-9, we have accessed the regime of relativistic transparency (RT) at the Trident Laser. The goal was to assess electron debris emitted from the target rear surface with phase-contrast imaging (PCI) and current density measurements (hence, the total electron current). Companion diagnostics show whether the experiments are in the target-normal-sheath-acceleration mode or in the RT regime. The superb laser contrast allows us to shoot targets as thin as 50 nm. PCI at 527 nm is temporally resolved to 600 fs. It has shown the evolution of electron behavior over tens of ps, including thermal electrons accompanying the ion jet, accelerated to many tens of MeV earlier in time. Faraday-cup measurements indicate the transfer of many uC of charge during the laser drive. As a ride-along experiment using a gas Cherenkov detector (GCD), we have detected gamma rays of energy >5 MeV. This radiation has a prompt component and a lesser source, driven by accelerated ions, that is time resolved by the GCD. The ion time of flight is compared to Thomson parabola data. Electron energy spectra are also collected. This work has been performed under the auspices of the US DOE contract number DE-AC52-06NA25396.

  2. Early Experiences Porting the NAMD and VMD Molecular Simulation and Analysis Software to GPU-Accelerated OpenPOWER Platforms

    PubMed Central

    Stone, John E.; Hynninen, Antti-Pekka; Phillips, James C.; Schulten, Klaus

    2017-01-01

    All-atom molecular dynamics simulations of biomolecules provide a powerful tool for exploring the structure and dynamics of large protein complexes within realistic cellular environments. Unfortunately, such simulations are extremely demanding in terms of their computational requirements, and they present many challenges in terms of preparation, simulation methodology, and analysis and visualization of results. We describe our early experiences porting the popular molecular dynamics simulation program NAMD and the simulation preparation, analysis, and visualization tool VMD to GPU-accelerated OpenPOWER hardware platforms. We report our experiences with compiler-provided autovectorization and compare with hand-coded vector intrinsics for the POWER8 CPU. We explore the performance benefits obtained from unique POWER8 architectural features such as 8-way SMT and its value for particular molecular modeling tasks. Finally, we evaluate the performance of several GPU-accelerated molecular modeling kernels and relate them to other hardware platforms. PMID:29202130

  3. SAMS Acceleration Measurements on MIR

    NASA Technical Reports Server (NTRS)

    Moskowitz, Milton E.; Hrovat, Kenneth; Finkelstein, Robert; Reckart, Timothy

    1997-01-01

    During NASA Increment 3 (September 1996 to January 1997), about 5 gigabytes of acceleration data were collected by the Space Acceleration Measurement System (SAMS) onboard the Russian Space Station, Mir. The data were recorded on 11 optical disks and were returned to Earth on STS-81. During this time, SAMS data were collected in the Priroda module to support the following experiments: the Mir Structural Dynamics Experiment (MiSDE) and Binary Colloidal Alloy Tests (BCAT). This report points out some of the salient features of the microgravity environment to which these experiments were exposed. Also documented are mission events of interest such as the docked phase of STS-81 operations, a Progress engine burn, attitude control thruster operation, and crew exercise. Also included are a description of the Mir module orientations, and the panel notations within the modules. This report presents an overview of the SAMS acceleration measurements recorded by 10 Hz and 100 Hz sensor heads. Variations in the acceleration environment caused by unique activities such as crew exercise and life-support fans are presented. The analyses included herein complement those presented in previous mission summary reports published by the Principal Investigator Microgravity Services (PIMS) group.

  4. Experimental and Numerical Investigation of Buoyancy Driven Convection During PDAMNA Thin Film Growth

    NASA Technical Reports Server (NTRS)

    Antar, Basil N.; Witherow, William K.; Paley, Mark S.; Curreri, Peter A. (Technical Monitor)

    2001-01-01

    This paper presents results from numerical simulations as well as laboratory experiments of buoyancy driven convection in an ampoule under varying heating and gravitational acceleration loadings. The modeling effort in this work resolves the large scale natural convective motion that occurs in the fluid during photodeposition of polydiacetelene films which is due to energy absorbed by the growth solution from a UV source. Consequently, the growth kinetics of the film are ignored in the model discussed here, and also a much simplified ampoule geometry is considered. The objective of this work is to validate the numerical prediction on the strength and structure of buoyancy driven convection that could occur under terrestrial conditions during nonlinear optical film growth. The validation is used to enable a reliable predictive capability on the nature and strength of the convective motion under low gravity conditions. The ampoule geometry is in the form of a parallelepiped with rectangular faces. The numerical results obtained from the solution to the Boussinesq equations show that natural convection will occur regardless of the orientation of the UV source with respect to the gravity vector. The least strong convective motion occurred with the UV beam directed at the top face of the parallelepiped. The strength of the convective motion was found to be almost linearly proportional to the total power of the UV source. Also, it was found that the strength of the convective motion decreased linearly with the gravity due to acceleration. The pattern of the convective flow on the other hand, depended on the source location.

  5. The effect of three surface conditions, speed and running experience on vertical acceleration of the tibia during running.

    PubMed

    Boey, Hannelore; Aeles, Jeroen; Schütte, Kurt; Vanwanseele, Benedicte

    2017-06-01

    Research has focused on parameters that are associated with injury risk, e.g. vertical acceleration. These parameters can be influenced by running on different surfaces or at different running speeds, but the relationship between them is not completely clear. Understanding the relationship may result in training guidelines to reduce the injury risk. In this study, thirty-five participants with three different levels of running experience were recruited. Participants ran on three different surfaces (concrete, synthetic running track, and woodchip trail) at two different running speeds: a self-selected comfortable speed and a fixed speed of 3.06 m/s. Vertical acceleration of the lower leg was measured with an accelerometer. The vertical acceleration was significantly lower during running on the woodchip trail in comparison with the synthetic running track and the concrete, and significantly lower during running at lower speed in comparison with during running at higher speed on all surfaces. No significant differences in vertical acceleration were found between the three groups of runners at fixed speed. Higher self-selected speed due to higher performance level also did not result in higher vertical acceleration. These results may show that running on a woodchip trail and slowing down could reduce the injury risk at the tibia.

  6. High-field plasma acceleration in a high-ionization-potential gas

    DOE PAGES

    Corde, S.; Adli, E.; Allen, J. M.; ...

    2016-06-17

    Plasma accelerators driven by particle beams are a very promising future accelerator technology as they can sustain high accelerating fields over long distances with high energy efficiency. They rely on the excitation of a plasma wave in the wake of a drive beam. To generate the plasma, a neutral gas can be field-ionized by the head of the drive beam, in which case the distance of acceleration and energy gain can be strongly limited by head erosion. In our research, we overcome this limit and demonstrate that electrons in the tail of a drive beam can be accelerated by upmore » to 27 GeV in a high-ionization-potential gas (argon), boosting their initial 20.35 GeV energy by 130%. Particle-in-cell simulations show that the argon plasma is sustaining very high electric fields, of ~150 GV m -1, over ~20 cm. Lastly, the results open new possibilities for the design of particle beam drivers and plasma sources.« less

  7. Dual-mass vibratory rate gyroscope with suppressed translational acceleration response and quadrature-error correction capability

    NASA Technical Reports Server (NTRS)

    Clark, William A. (Inventor); Juneau, Thor N. (Inventor); Lemkin, Mark A. (Inventor); Roessig, Allen W. (Inventor)

    2001-01-01

    A microfabricated vibratory rate gyroscope to measure rotation includes two proof-masses mounted in a suspension system anchored to a substrate. The suspension has two principal modes of compliance, one of which is driven into oscillation. The driven oscillation combined with rotation of the substrate about an axis perpendicular to the substrate results in Coriolis acceleration along the other mode of compliance, the sense-mode. The sense-mode is designed to respond to Coriolis accelerationwhile suppressing the response to translational acceleration. This is accomplished using one or more rigid levers connecting the two proof-masses. The lever allows the proof-masses to move in opposite directions in response to Coriolis acceleration. The invention includes a means for canceling errors, termed quadrature error, due to imperfections in implementation of the sensor. Quadrature-error cancellation utilizes electrostatic forces to cancel out undesired sense-axis motion in phase with drive-mode position.

  8. The Adelphi Experiment: Accelerating Social Work Education.

    ERIC Educational Resources Information Center

    Rosenblatt, Aaron; And Others

    The educational program adopted at Adelphi University School of Social Work provides students interested in obtaining the master's degree in social work with an opportunity to accelerate their professional education. As undergraduate students they can elect to major in social welfare, and if they do, some courses usually available only to graduate…

  9. On The Detection Of Footprints From Strong Electron Acceleration In High-Intensity Laser Fields, Including The Unruh Effect

    NASA Astrophysics Data System (ADS)

    Thirolf, P. G.; Habs, D.; Homma, K.; Hörlein, R.; Karsch, S.; Krausz, F.; Maia, C.; Osterhoff, J.; Popp, A.; Schmid, K.; Schreiber, J.; Schützhold, R.; Tajima, T.; Veisz, L.; Wulz, J.; Yamazaki, T.

    2010-04-01

    The ultra-high fields of high-power short-pulse lasers are expected to contribute to understanding fundamental properties of the quantum vacuum and quantum theory in very strong fields. For example, the neutral QED vacuum breaks down at the Schwinger field strength of 1.3 1018V/m, where a virtual e+e- pair gains its rest mass energy over a Compton wavelength and materializes as a real pair. At such an ultra-high field strength, an electron experiences an acceleration of as = 2 1028 g and hence fundamental phenomena such as the long predicted Unruh effect start to play a role. The Unruh effect implies that the accelerated electron experiences the vacuum as a thermal bath with the Unruh temperature. In its accelerated frame the electron scatters photons off the thermal bath, corresponding to the emission of an entangled pair of photons in the laboratory frame. In upcoming experiments with intense accelerating fields, we will encounter a set of opportunities to experimentally study the radiation from electrons under extreme fields. Even before the Unruh radiation detection, we should run into the copious Larmor radiation. The detection of Larmor radiation and its characterization themselves have never been experimentally carried out to the best of our knowledge, and thus this amounts to a first serious study of physics at extreme acceleration. For example, we can study radiation damping effects like the Landau-Lifshitz radiation. Furthermore, the experiment should be able to confirm or disprove whether the Larmor and Landau-Lifshitz radiation components may be enhanced by a collective (N2) radiation, if a tightly clumped cluster of electrons is accelerated. The technique of laser driven dense electron sheet formation by irradiating a thin DLC foil target should provide such a coherent electron cluster with a very high density. If and when such mildly relativistic electron sheets are realized, a counterpropagating second laser can interact with them coherently. Under

  10. Short-scale turbulent fluctuations driven by the electron-temperature gradient in the national spherical torus experiment.

    PubMed

    Mazzucato, E; Smith, D R; Bell, R E; Kaye, S M; Hosea, J C; LeBlanc, B P; Wilson, J R; Ryan, P M; Domier, C W; Luhmann, N C; Yuh, H; Lee, W; Park, H

    2008-08-15

    Measurements with coherent scattering of electromagnetic waves in plasmas of the National Spherical Torus Experiment indicate the existence of turbulent fluctuations in the range of wave numbers k perpendicular rho(e)=0.1-0.4, corresponding to a turbulence scale length nearly equal to the collisionless skin depth. Experimental observations and agreement with numerical results from a linear gyrokinetic stability code support the conjecture that the observed turbulence is driven by the electron-temperature gradient.

  11. JAERI R & D on accelerator-based transmutation under OMEGA program

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

    Takizuka, T.; Nishida, T.; Mizumoto, M.

    1995-10-01

    The overview of the Japanese long-term research and development program on nuclide partitioning and transmutation, called {open_quotes}OMEGA,{close_quotes} is presented. Under this national program, major R&D activities are being carried out at JAERI, PNC, and CRIEPI. Accelerator-based transmutation study at JAERI is focused on a dedicated transmutor with a subcritical actinide-fueled subcritical core coupled with a spallation target driven by a high intensity proton accelerator. Two types of system concept, solid system and molten-salt system, are discussed. The solid system consists of sodium-cooled tungsten target and metallic actinide fuel. The molten-salt system is fueled with molten actinide chloride that acts alsomore » as a target material. The proposed plant transmutes about 250 kg of minor actinide per year, and generates enough electricity to power its own accelerator. JAERI is proposing the development of an intense proton linear accelerator ETA with 1.5 GeV-10 mA beam for engineering tests of accelerator-based transmutation. Recent achievements in the accelerator development are described.« less

  12. Observation of acceleration and deceleration in gigaelectron-volt-per-metre gradient dielectric wakefield accelerators

    DOE PAGES

    O’Shea, B. D.; Andonian, G.; Barber, S. K.; ...

    2016-09-14

    There is urgent need to develop new acceleration techniques capable of exceeding gigaelectron-volt-per-metre (GeV m –1) gradients in order to enable future generations of both light sources and high-energy physics experiments. To address this need, short wavelength accelerators based on wakefields, where an intense relativistic electron beam radiates the demanded fields directly into the accelerator structure or medium, are currently under intense investigation. One such wakefield based accelerator, the dielectric wakefield accelerator, uses a dielectric lined-waveguide to support a wakefield used for acceleration. Here we show gradients of 1.347±0.020 GeV m –1 using a dielectric wakefield accelerator of 15 cmmore » length, with sub-millimetre transverse aperture, by measuring changes of the kinetic state of relativistic electron beams. We follow this measurement by demonstrating accelerating gradients of 320±17 MeV m –1. As a result, both measurements improve on previous measurements by and order of magnitude and show promise for dielectric wakefield accelerators as sources of high-energy electrons.« less

  13. Observation of acceleration and deceleration in gigaelectron-volt-per-metre gradient dielectric wakefield accelerators

    PubMed Central

    O'Shea, B. D.; Andonian, G.; Barber, S. K.; Fitzmorris, K. L.; Hakimi, S.; Harrison, J.; Hoang, P. D.; Hogan, M. J.; Naranjo, B.; Williams, O. B.; Yakimenko, V.; Rosenzweig, J. B.

    2016-01-01

    There is urgent need to develop new acceleration techniques capable of exceeding gigaelectron-volt-per-metre (GeV m−1) gradients in order to enable future generations of both light sources and high-energy physics experiments. To address this need, short wavelength accelerators based on wakefields, where an intense relativistic electron beam radiates the demanded fields directly into the accelerator structure or medium, are currently under intense investigation. One such wakefield based accelerator, the dielectric wakefield accelerator, uses a dielectric lined-waveguide to support a wakefield used for acceleration. Here we show gradients of 1.347±0.020 GeV m−1 using a dielectric wakefield accelerator of 15 cm length, with sub-millimetre transverse aperture, by measuring changes of the kinetic state of relativistic electron beams. We follow this measurement by demonstrating accelerating gradients of 320±17 MeV m−1. Both measurements improve on previous measurements by and order of magnitude and show promise for dielectric wakefield accelerators as sources of high-energy electrons. PMID:27624348

  14. Reduction of Effective Acceleration to Microgravity Levels

    NASA Technical Reports Server (NTRS)

    Downey, James P.

    2000-01-01

    Acceleration due to earth's gravity causes buoyancy driven convection and sedimentation in solutions. In addition. pressure gradients occur as a function of the height within a liquid column. Hence gravity effects both equilbria conditions and phase transitions as a result of hydrostatic pressure gradients. The affect of gravity on the rate of heat and man transfer in solutal processes can be particularly important in polymer processing due to the high sensitivity of polymeric materials to processing conditions. The term microgravity has been coined to describe an environment in which the affects of gravitational acceleration am greatly reduced. It may seem odd to talk in term of reducing the effects of gravitational acceleration since gravitational attraction is a basic property of matter. However, die presence of gravity on in situ processing or measurements can be negated by achieving conditions in which the laboratory, or more specifically the container of the experimental materials, a subjected to the same acceleration as the materials themselves. With regard to the laboratory reference frame, there is virtually no force on the experimental solutions. This is difficult to achieve but can be done. A short review of Newtonian physics provides an explanation on both how processes we affected by gravity and how microgravity conditions are achieved. The fact that fluids deform when subject to a force bid solids do not indicates that solids have a structure able to exert an opposing force that negates an externally applied force. Liquids deform when a force is applied, indicating that a liquid structure cannot completely negate an applied force. Just how easily a liquid resists deformation is related to its viscosity. Spaceflight provides an environment in which the laboratory reference frame i.e. the spacecraft and all the equipment therein an experiencing virtually identical forces. There is no solid foundation underneath such a laboratory, so the laboratory

  15. Ram accelerator direct space launch system - New concepts

    NASA Technical Reports Server (NTRS)

    Bogdanoff, David W.

    1992-01-01

    The ram accelerator, a chemically driven ramjet-in-tube device is a new option for direct launch of acceleration-insensitive payloads into earth orbit. The projectile is the centerbody of a ramjet and travels through a tube filled with a premixed fuel-oxidizer mixture. The tube acts as the cowl of the ramjet. A number of new concepts for a ram accelerator space launch system are presented. The velocity and acceleration capabilities of a number of ram accelerator drive modes, including several new modes, are given. Passive (fin) stabilization during atmospheric transit is investigated and found to be promising. Gasdynamic heating in-tube and during atmospheric transit is studied; the former is found to be severe, but may be alleviated by the selection of the most suitable drive modes, transpiration cooling, or a hydrogen gas core in the launch tube. To place the payload in earth orbit, scenarios using one impulse and three impulses (with an aeropass) and a new scenario involving an auxiliary vehicle are studied. The auxiliary vehicle scenario is found to be competitive regarding payload, and requires a much simpler projectile, but has the disadvantage of requiring the auxiliary vehicle.

  16. Experiments and Simulations on Magnetically Driven Implosions in High Repetition Rate Dense Plasma Focus

    NASA Astrophysics Data System (ADS)

    Caballero Bendixsen, Luis; Bott-Suzuki, Simon; Cordaro, Samuel; Krishnan, Mahadevan; Chapman, Stephen; Coleman, Phil; Chittenden, Jeremy

    2015-11-01

    Results will be shown on coordinated experiments and MHD simulations on magnetically driven implosions, with an emphasis on current diffusion and heat transport. Experiments are run at a Mather-type dense plasma focus (DPF-3, Vc: 20 kV, Ip: 480 kA, E: 5.8 kJ). Typical experiments are run at 300 kA and 0.33 Hz repetition rate with different gas loads (Ar, Ne, and He) at pressures of ~ 1-3 Torr, usually gathering 1000 shots per day. Simulations are run at a 96-core HP blade server cluster using 3GHz processors with 4GB RAM per node.Preliminary results show axial and radial phase plasma sheath velocity of ~ 1x105 m/s. These are in agreement with the snow-plough model of DPFs. Peak magnetic field of ~ 1 Tesla in the radial compression phase are measured. Electron densities on the order of 1018 cm-3 anticipated. Comparison between 2D and 3D models with empirical results show a good agreement in the axial and radial phase.

  17. Community Petascale Project for Accelerator Science and Simulation: Advancing Computational Science for Future Accelerators and Accelerator Technologies

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

    Spentzouris, P.; /Fermilab; Cary, J.

    The design and performance optimization of particle accelerators are essential for the success of the DOE scientific program in the next decade. Particle accelerators are very complex systems whose accurate description involves a large number of degrees of freedom and requires the inclusion of many physics processes. Building on the success of the SciDAC-1 Accelerator Science and Technology project, the SciDAC-2 Community Petascale Project for Accelerator Science and Simulation (ComPASS) is developing a comprehensive set of interoperable components for beam dynamics, electromagnetics, electron cooling, and laser/plasma acceleration modelling. ComPASS is providing accelerator scientists the tools required to enable the necessarymore » accelerator simulation paradigm shift from high-fidelity single physics process modeling (covered under SciDAC1) to high-fidelity multiphysics modeling. Our computational frameworks have been used to model the behavior of a large number of accelerators and accelerator R&D experiments, assisting both their design and performance optimization. As parallel computational applications, the ComPASS codes have been shown to make effective use of thousands of processors. ComPASS is in the first year of executing its plan to develop the next-generation HPC accelerator modeling tools. ComPASS aims to develop an integrated simulation environment that will utilize existing and new accelerator physics modules with petascale capabilities, by employing modern computing and solver technologies. The ComPASS vision is to deliver to accelerator scientists a virtual accelerator and virtual prototyping modeling environment, with the necessary multiphysics, multiscale capabilities. The plan for this development includes delivering accelerator modeling applications appropriate for each stage of the ComPASS software evolution. Such applications are already being used to address challenging problems in accelerator design and optimization. The Com

  18. VLF Wave Local Acceleration & ULF Wave Radial Diffusion: The Importance of K-Dependent PSD Analysis for Diagnosing the cause of Radiation Belt Acceleration.

    NASA Astrophysics Data System (ADS)

    Ozeke, L.; Mann, I. R.; Claudepierre, S. G.; Morley, S.; Henderson, M. G.; Baker, D. N.; Kletzing, C.; Spence, H. E.

    2017-12-01

    We present results showing the temporal evolution of electron Phase Space Density (PSD) in the outer radiation belt during the most intense geomagnetic storm of the last decade which occurred on March 17th 2015. Based on observations of growing local PSD peaks at fixed first and second adiabatic invariants of M=1000 MeV/G and K=0.18 G1/2Re respectively, previous studies argued that the outer radiation belt flux enhancement that occurred during this storm resulted from local acceleration driven by VLF waves. Here we show that the vast majority of the outer radiation belt consisted of electrons with much lower K-values than 0.18 G1/2Re, and that at these lower K-values there is no clear evidence of growing local PSD peaks consistent with that expected from local acceleration. Contrary to prior studies we show that the outer radiation belt flux enhancement is consistent with inward radial diffusion driven by ULF waves and present evidence that the growing local PSD peaks at K=0.18 G1/2Re and M=1000 MeV/G result from pitch-angle scattering of lower-K electrons to K=0.18 G1/2Re. In addition, we also show that the observed outer radiation belt flux enhancement during this geomagnetic storm can be reproduced using a radial diffusion model driven by measured ULF waves without including any local acceleration. These results highlight the importance of careful analysis of the electron PSD profiles as a function of L* over a range of fixed first, M and second K, adiabatic invariants to correctly determine the mechanism responsible for the electron flux enhancements observed in the outer radiation belt.

  19. Simultaneous operation of two soft x-ray free-electron lasers driven by one linear accelerator

    DOE PAGES

    Faatz, B.; Plönjes, E.; Ackermann, S.; ...

    2016-06-20

    Extreme-ultraviolet to x-ray free-electron lasers (FELs) in operation for scientific applications are up to now single-user facilities. While most FELs generate around 100 photon pulses per second, FLASH at DESY can deliver almost two orders of magnitude more pulses in this time span due to its superconducting accelerator technology. This makes the facility a prime candidate to realize the next step in FELs—dividing the electron pulse trains into several FEL lines and delivering photon pulses to several users at the same time. Hence, FLASH has been extended with a second undulator line and self-amplified spontaneous emission (SASE) is demonstrated inmore » both FELs simultaneously. Here, FLASH can now deliver MHz pulse trains to two user experiments in parallel with individually selected photon beam characteristics. First results of the capabilities of this extension are shown with emphasis on independent variation of wavelength, repetition rate, and photon pulse length.« less

  20. Stereo Imaging Velocimetry of Mixing Driven by Buoyancy Induced Flow Fields

    NASA Technical Reports Server (NTRS)

    Duval, W. M. B.; Jacqmin, D.; Bomani, B. M.; Alexander, I. J.; Kassemi, M.; Batur, C.; Tryggvason, B. V.; Lyubimov, D. V.; Lyubimova, T. P.

    2000-01-01

    Mixing of two fluids generated by steady and particularly g-jitter acceleration is fundamental towards the understanding of transport phenomena in a microgravity environment. We propose to carry out flight and ground-based experiments to quantify flow fields due to g-jitter type of accelerations using Stereo Imaging Velocimetry (SIV), and measure the concentration field using laser fluorescence. The understanding of the effects of g-jitter on transport phenomena is of great practical interest to the microgravity community and impacts the design of experiments for the Space Shuttle as well as the International Space Station. The aim of our proposed research is to provide quantitative data to the community on the effects of g-jitter on flow fields due to mixing induced by buoyancy forces. The fundamental phenomenon of mixing occurs in a broad range of materials processing encompassing the growth of opto-electronic materials and semiconductors, (by directional freezing and physical vapor transport), to solution and protein crystal growth. In materials processing of these systems, crystal homogeneity, which is affected by the solutal field distribution, is one of the major issues. The understanding of fluid mixing driven by buoyancy forces, besides its importance as a topic in fundamental science, can contribute towards the understanding of how solutal fields behave under various body forces. The body forces of interest are steady acceleration and g-jitter acceleration as in a Space Shuttle environment or the International Space Station. Since control of the body force is important, the flight experiment will be carried out on a tunable microgravity vibration isolation mount, which will permit us to precisely input the desired forcing function to simulate a range of body forces. To that end, we propose to design a flight experiment that can only be carried out under microgravity conditions to fully exploit the effects of various body forces on fluid mixing. Recent