The Mu2e Solenoid Cold Mass Position Monitor System

DOE PAGES

Strauss, Thomas; Feher, Sandor; Friedsam, Horst W.; ...

2018-01-23

The Mu2e experiment at Fermilab is designed to search for charged-lepton flavor violation by looking for muon to electron conversions in the field of the nucleus. The concept of the experiment is to generate a low momentum muon beam, stopping the muons in a target and measuring the momentum of the outgoing electrons. The implementation of this approach utilizes a complex magnetic field composed of graded solenoidal and toroidal fields. The location of the solenoid cold mass relative to external fiducials is needed for alignment as well as monitoring coil movements during cool down and magnet excitation. This study describesmore » a novel design of a Cold Mass Position Monitor System (CMPS) that will be implemented for the Mu2e experiment.« less

Effect of electron beam on the properties of electron-acoustic rogue waves

NASA Astrophysics Data System (ADS)

El-Shewy, E. K.; Elwakil, S. A.; El-Hanbaly, A. M.; Kassem, A. I.

2015-04-01

The properties of nonlinear electron-acoustic rogue waves have been investigated in an unmagnetized collisionless four-component plasma system consisting of a cold electron fluid, Maxwellian hot electrons, an electron beam and stationary ions. It is found that the basic set of fluid equations is reduced to a nonlinear Schrodinger equation. The dependence of rogue wave profiles and the associated electric field on the carrier wave number, normalized density of hot electron and electron beam, relative cold electron temperature and relative beam temperature are discussed. The results of the present investigation may be applicable in auroral zone plasma.

Kinetic interpretation of resonance phenomena in low pressure capacitively coupled radio frequency plasmas

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

Wilczek, Sebastian; Trieschmann, Jan; Eremin, Denis

Low pressure capacitive radio frequency (RF) plasmas are often described by equivalent circuit models based on fluid approaches that predict the self-excitation of resonances, e.g., high frequency oscillations of the total current in asymmetric discharges, but do not provide a kinetic interpretation of these effects. In fact, they leave important questions open: How is current continuity ensured in the presence of energetic electron beams generated by the expanding sheaths that lead to a local enhancement of the conduction current propagating through the bulk? How do the beam electrons interact with cold bulk electrons? What is the kinetic origin of resonancemore » phenomena? Based on kinetic simulations, we find that the energetic beam electrons interact with cold bulk electrons (modulated on a timescale of the inverse local electron plasma frequency) via a time dependent electric field outside the sheaths. This electric field is caused by the electron beam itself, which leaves behind a positive space charge, that attracts cold bulk electrons towards the expanding sheath. The resulting displacement current ensures current continuity by locally compensating the enhancement of the conduction current. The backflow of cold electrons and their interaction with the nonlinear plasma sheath cause the generation of multiple electron beams during one phase of sheath expansion and contribute to a strongly non-sinusoidal RF current. These kinetic mechanisms are the basis for a fundamental understanding of the electron power absorption dynamics and resonance phenomena in such plasmas, which are found to occur in discharges of different symmetries including perfectly symmetric plasmas.« less

2d axisymmetric "beam-bulk" modelling of the generation of runaway electrons by streamers.

NASA Astrophysics Data System (ADS)

Chanrion, Olivier; Bonaventura, Zdenek; Bourdon, Anne; Neubert, Torsten

2017-04-01

We present results from a 2d axisymmetric numerical model of streamers based on a "beam-bulk" approach which describes cold electrons with a fluid model and high energy electrons with a particle model. The interest is motivated by the generation of runaway electrons by streamers which may participate in the recently observed TGFs and which challenge the modelling. Runaway electrons are known to be generated from streamers when the electric field in its negative tip is of sufficient magnitude. After overtaking the streamer tip, runaways can affect the streamer propagation ahead and may produce high energy photons through the bremsstrahlung process. In conventional model of streamers, the evolution of the streamer discharge is mostly governed by cold electrons. By including runaway electrons, we model their production, their impact on the discharge propagation and can address their role in TGFs. Results of streamer propagation in leader electric field show that the runaway electrons accelerate the streamers, reduce the electric field in its tip and enlarge its radius by pre-ionizing the gas ahead. We observed that if we increase the electric field, the discharge is getting more diffuse, with a pattern driven by the increase in runaway induced ionisation.

Facile synthesis of ZnPc nanocubes: An electron emitting material for field emission display devices

NASA Astrophysics Data System (ADS)

Samanta, M.; Ghorai, U. K.; Mukherjee, M.; Howli, P.; Chattopadhyay, K. K.

2017-05-01

A simple low temperature water chemical route for synthesizing Zinc Phthalocyanine (ZnPc) nanostructures were reported here. The as-prepared samples were well analysed by X-ray diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM) technique. The plausible formation mechanism of cube like nanostructures was also explained here. Cold cathode emission properties of ZnPc nanocubes were studied by using an indigenously designed high vacuum system at anode to cathode distance 130 µm. The turn on field and enhancement factor is found to be 5.0 V/μm @ 1µA/cm2 and 1757 respectively. Cold cathode emission properties were further investigated theoretically by finite element method using ANSYS Maxwell simulation package. The obtained results strongly professed that ZnPc nanocubes can act as potential candidate for electron emitter for field emission display devices and many more.

Design and commissioning of an aberration-corrected ultrafast spin-polarized low energy electron microscope with multiple electron sources.

PubMed

Wan, Weishi; Yu, Lei; Zhu, Lin; Yang, Xiaodong; Wei, Zheng; Liu, Jefferson Zhe; Feng, Jun; Kunze, Kai; Schaff, Oliver; Tromp, Ruud; Tang, Wen-Xin

2017-03-01

We describe the design and commissioning of a novel aberration-corrected low energy electron microscope (AC-LEEM). A third magnetic prism array (MPA) is added to the standard AC-LEEM with two prism arrays, allowing the incorporation of an ultrafast spin-polarized electron source alongside the standard cold field emission electron source, without degrading spatial resolution. The high degree of symmetries of the AC-LEEM are utilized while we design the electron optics of the ultrafast spin-polarized electron source, so as to minimize the deleterious effect of time broadening, while maintaining full control of electron spin. A spatial resolution of 2nm and temporal resolution of 10ps (ps) are expected in the future time resolved aberration-corrected spin-polarized LEEM (TR-AC-SPLEEM). The commissioning of the three-prism AC-LEEM has been successfully finished with the cold field emission source, with a spatial resolution below 2nm. Copyright © 2017 Elsevier B.V. All rights reserved.

Magnetic Reconnection Dynamics in the Presence of Low-energy Ion Component: PIC Simulations of Hidden Particle Population

NASA Astrophysics Data System (ADS)

Khotyaintsev, Y. V.; Divin, A. V.; Toledo Redondo, S.; Andre, M.; Vaivads, A.; Markidis, S.; Lapenta, G.

2015-12-01

Magnetospheric and astrophysical plasmas are rarely in the state of thermal equilibrium. Plasma distribution functions may contain beams, supra-thermal tails, multiple ion and electron populations which are not thermalized over long time scales due to the lack of collisions between particles. In particular, the equatorial region of the dayside Earth's magnetosphere is often populated by plasma containing hot and cold ion components of comparable densities [Andre and Cully, 2012], and such ion distribution alters properties of the magnetic reconnection regions at the magnetopause [Toledo-Redondo et. al., 2015]. Motivated by these recent findings and also by fact that this region is one of the targets of the recently launched MMS mission, we performed 2D PIC simulations of magnetic reconnection in collisionless plasma with hot and cold ion components. We used a standard Harris current sheet, to which a uniform cold ion background is added. We found that introduction of the cold component modifies the structure of reconnection diffusion region. Diffusion region displays three-scale structure, with the cold Ion Diffusion Region (cIDR) scale appearing in-between the Electron Diffusion Region (EDR) and Ion Diffusion Region (IDR) scales. Structure and strength of the Hall magnetic field depends weakly on cold ion temperature or density, and is rather controlled by the conditions (B, n) upstream the reconnection region. The cold ions are accelerated predominantly transverse to the magnetic field by the Hall electric fields inside the IDR, leading to a large ion pressure anisotropy, which is unstable to ion Weibel-type or mirror-type mode. On the opposite, acceleration of cold ions is mostly field-aligned at the reconnection jet fronts downstream the X-line, producing intense ion phase-space holes there. Despite comparable reconnection rates produced , we find that the overall evolution of reconnection in presence of cold ion population is more dynamic compared to the case with a single hot ion component.

Optimization study of direct morphology observation by cold field emission SEM without gold coating.

PubMed

He, Dan; Fu, Cheng; Xue, Zhigang

2018-06-01

Gold coating is a general operation that is generally applied on non-conductive or low conductive materials, during which the morphology of the materials can be examined by scanning electron microscopy (SEM). However, fatal deficiencies in the materials can result in irreversible distortion and damage. The present study directly characterized different low conductive materials such as hydroxyapatite, modified poly(vinylidene fluoride) (PVDF) fiber, and zinc oxide nanopillar by cold field emission scanning electron microscopy (FE-SEM) without a gold coating. According to the characteristics of the low conductive materials, various test conditions, such as different working signal modes, accelerating voltages, electron beam spots, and working distances, were characterized to determine the best morphological observations of each sample. Copyright © 2018 Elsevier Ltd. All rights reserved.

Applying the cold plasma dispersion relation to whistler mode chorus waves: EMFISIS wave measurements from the Van Allen Probes

DOE PAGES

Hartley, D. P.; Chen, Y.; Kletzing, C. A.; ...

2015-01-26

Most theoretical wave models require the power in the wave magnetic field in order to determine the effect of chorus waves on radiation belt electrons. However, researchers typically use the cold plasma dispersion relation to approximate the magnetic wave power when only electric field data are available. In this study, the validity of using the cold plasma dispersion relation in this context is tested using Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) observations of both the electric and magnetic spectral intensities in the chorus wave band (0.1–0.9 f ce). Results from this study indicate that the calculatedmore » wave intensity is least accurate during periods of enhanced wave activity. For observed wave intensities >10⁻³ nT², using the cold plasma dispersion relation results in an underestimate of the wave intensity by a factor of 2 or greater 56% of the time over the full chorus wave band, 60% of the time for lower band chorus, and 59% of the time for upper band chorus. Hence, during active periods, empirical chorus wave models that are reliant on the cold plasma dispersion relation will underestimate chorus wave intensities to a significant degree, thus causing questionable calculation of wave-particle resonance effects on MeV electrons.« less

Cold atmospheric pressure plasma jets: Interaction with plasmid DNA and tailored electron heating using dual-frequency excitation

NASA Astrophysics Data System (ADS)

Niemi, K.; O'Neill, C.; Cox, L. J.; Waskoenig, J.; Hyland, W. B.; McMahon, S. J.; Reuter, S.; Currell, F. J.; Graham, W. G.; O'Connell, D.; Gans, T.

2012-05-01

Recent progress in plasma science and technology has enabled the development of a new generation of stable cold non-equilibrium plasmas operating at ambient atmospheric pressure. This opens horizons for new plasma technologies, in particular in the emerging field of plasma medicine. These non-equilibrium plasmas are very efficient sources for energy transport through reactive neutral particles (radicals and metastables), charged particles (ions and electrons), UV radiation, and electro-magnetic fields. The effect of a cold radio frequency-driven atmospheric pressure plasma jet on plasmid DNA has been investigated. The formation of double strand breaks correlates well with the atomic oxygen density. Taken with other measurements, this indicates that neutral components in the jet are effective in inducing double strand breaks. Plasma manipulation techniques for controlled energy delivery are highly desirable. Numerical simulations are employed for detailed investigations of the electron dynamics, which determines the generation of reactive species. New concepts based on nonlinear power dissipation promise superior strategies to control energy transport for tailored technological exploitations.

Two-dimensional array of cold-electron bolometers for high-sensitivity polarization measurements

NASA Astrophysics Data System (ADS)

Kuzmin, L. S.

2012-01-01

A new concept of a two-dimensional array of cold-electron bolometers with distributed dipole antennas in the focal plane for high-sensitivity polarization measurements is proposed. The concept gives a unique combination of high polarization resolution due to a large uniforms array of cold-electron bolometers and optimal matching with junction field effect transistor (JFET) amplifiers because of flexibility in direct-current connections. The noise characteristics are improved due to arriving-signal power distribution among numerous cold-electron bolometers and an increase in their response. This should lead to a significant increase in the sensitivity and dynamic range compared with competing alternative bolometer technologies. The reliability of the twodimensional array significantly increases due to a series-parallel connection of a large number of cold-electron bolometers. High polarization resolution should be ensured due to uniform covering of a substrate by a two-dimensional array over a large area and the absence of the beam compression to small lumped elements. The fundamental sensitivity limit of the cold-electron bolometer array is smaller than photon noise which is considered to be the ultimate level restricted by the background radiation. Estimates of noise of bolometers with the JFET reading system show the possibility of realizing the ultimate sensitivity below the photon-noise level 5 ・10-17 W/Hz1/2 at a frequency of 350 GHz for an optical load with a power of 5 pW. These parameters correspond to the requirements to the receiving system of a BOOMERanG balloon telescope.

Electron beam focusing system

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

Dikansky, N.; Nagaitsev, S.; Parkhomchuk, V.

1997-09-01

The high energy electron cooling requires a very cold electron beam. Thus, the electron beam focusing system is very important for the performance of electron cooling. A system with and without longitudinal magnetic field is presented for discussion. Interaction of electron beam with the vacuum chamber as well as with the background ions and stored antiprotons can cause the coherent electron beam instabilities. Focusing system requirements needed to suppress these instabilities are presented.

Performance of low-voltage STEM/TEM with delta corrector and cold field emission gun.

PubMed

Sasaki, Takeo; Sawada, Hidetaka; Hosokawa, Fumio; Kohno, Yuji; Tomita, Takeshi; Kaneyama, Toshikatsu; Kondo, Yukihito; Kimoto, Koji; Sato, Yuta; Suenaga, Kazu

2010-08-01

To reduce radiation damage caused by the electron beam and to obtain high-contrast images of specimens, we have developed a highly stabilized transmission electron microscope equipped with a cold field emission gun and spherical aberration correctors for image- and probe-forming systems, which operates at lower acceleration voltages than conventional transmission electron microscopes. A delta-type aberration corrector is designed to simultaneously compensate for third-order spherical aberration and fifth-order 6-fold astigmatism. Both were successfully compensated in both scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM) modes in the range 30-60 kV. The Fourier transforms of raw high-angle annular dark field (HAADF) images of a Si[110] sample revealed spots corresponding to lattice spacings of 111 and 96 pm at 30 and 60 kV, respectively, and those of raw TEM images of an amorphous Ge film with gold particles showed spots corresponding to spacings of 91 and 79 pm at 30 and 60 kV, respectively. Er@C(82)-doped single-walled carbon nanotubes, which are carbon-based samples, were successfully observed by HAADF-STEM imaging with an atomic-level resolution.

Optical properties of lamps with cold emission cathode

NASA Astrophysics Data System (ADS)

Kalenik, Jerzy; Czerwosz, ElŻbieta; Biernacki, Krzysztof; Rymarczyk, Joanna; Stepińska, Izabela

2016-12-01

A luminescent lamp was constructed and tested. Phosphor excited by electrons is the source of light. The source of electrons is field emission cathode. The cathode is covered with nickel-carbon layer containing carbon nanotubes that enhance electron emission from the cathode. Results of luminance measurements are presented. Luminance is high enough for lighting application.

Computational Investigation of Helical Traveling Wave Tube Transverse RF Field Forces

NASA Technical Reports Server (NTRS)

Kory, Carol L.; Dayton, James A.

1998-01-01

In a previous study using a fully three-dimensional (3D) helical slow-wave circuit cold- test model it was found, contrary to classical helical circuit analyses, that transverse FF electric fields have significant amplitudes compared with the longitudinal component. The RF fields obtained using this helical cold-test model have been scaled to correspond to those of an actual TWT. At the output of the tube, RF field forces reach 61%, 26% and 132% for radial, azimuthal and longitudinal components, respectively, compared to radial space charge forces indicating the importance of considering them in the design of electron beam focusing.

Arrays of Bundles of Carbon Nanotubes as Field Emitters

NASA Technical Reports Server (NTRS)

Manohara, Harish; Bronkowski, Michael

2007-01-01

Experiments have shown that with suitable choices of critical dimensions, planar arrays of bundles of carbon nanotubes (see figure) can serve as high-current-density field emitter (cold-cathode) electron sources. Whereas some hot-cathode electron sources must be operated at supply potentials of thousands of volts, these cold-cathode sources generate comparable current densities when operated at tens of volts. Consequently, arrays of bundles of carbon nanotubes might prove useful as cold-cathode sources in miniature, lightweight electron-beam devices (e.g., nanoklystrons) soon to be developed. Prior to the experiments, all reported efforts to develop carbon-nanotube-based field-emission sources had yielded low current densities from a few hundred microamperes to a few hundred milliamperes per square centimeter. An electrostatic screening effect, in which taller nanotubes screen the shorter ones from participating in field emission, was conjectured to be what restricts the emission of electrons to such low levels. It was further conjectured that the screening effect could be reduced and thus emission levels increased by increasing the spacing between nanotubes to at least by a factor of one to two times the height of the nanotubes. While this change might increase the emission from individual nanotubes, it would decrease the number of nanotubes per unit area and thereby reduce the total possible emission current. Therefore, to maximize the area-averaged current density, it would be necessary to find an optimum combination of nanotube spacing and nanotube height. The present concept of using an array of bundles of nanotubes arises partly from the concept of optimizing the spacing and height of field emitters. It also arises partly from the idea that single nanotubes may have short lifetimes as field emitters, whereas bundles of nanotubes could afford redundancy so that the loss of a single nanotube would not significantly reduce the overall field emission.

Comparison of free radicals formation induced by cold atmospheric plasma, ultrasound, and ionizing radiation.

PubMed

Rehman, Mati Ur; Jawaid, Paras; Uchiyama, Hidefumi; Kondo, Takashi

2016-09-01

Plasma medicine is increasingly recognized interdisciplinary field combining engineering, physics, biochemistry and life sciences. Plasma is classified into two categories based on the temperature applied, namely "thermal" and "non-thermal" (i.e., cold atmospheric plasma). Non-thermal or cold atmospheric plasma (CAP) is produced by applying high voltage electric field at low pressures and power. The chemical effects of cold atmospheric plasma in aqueous solution are attributed to high voltage discharge and gas flow, which is transported rapidly on the liquid surface. The argon-cold atmospheric plasma (Ar-CAP) induces efficient reactive oxygen species (ROS) in aqueous solutions without thermal decomposition. Their formation has been confirmed by electron paramagnetic resonance (EPR) spin trapping, which is reviewed here. The similarities and differences between the plasma chemistry, sonochemistry, and radiation chemistry are explained. Further, the evidence for free radical formation in the liquid phase and their role in the biological effects induced by cold atmospheric plasma, ultrasound and ionizing radiation are discussed. Copyright © 2016 Elsevier Inc. All rights reserved.

Influence of quantum effects on the parameters of a cold cathode with carbon nanotubes

NASA Astrophysics Data System (ADS)

Glukhova, O. E.; Kolesnikova, A. S.; Slepchenkov, M. M.

2016-01-01

We consider the effect of an external electric field on the parameters of a cold cathode on carbon nanotubes using the quantum-mechanical approach to the description of the interaction of the field with the atomic structure of nanoemitters. It is established for the first time that an increase in the length of the emitting edge of the tube in a field of 10-11 V/nm increases the field emission current of electrons by 3-10%. It is found that in a field of 11 V/nm and higher, atoms of the upper edge of a carbon nanotube are detached with the subsequent destruction of the atomic core.

Observations of Large-Amplitude, Parallel, Electrostatic Waves Associated with the Kelvin-Helmholtz Instability by the Magnetospheric Multiscale Mission

NASA Technical Reports Server (NTRS)

Wilder, F. D.; Ergun, R. E.; Schwartz, S. J.; Newman, D. L.; Eriksson, S.; Stawarz, J. E.; Goldman, M. V.; Goodrich, K. A.; Gershman, D. J.; Malaspina, D.;

Electron-acoustic solitons and double layers in the inner magnetosphere: ELECTRON-ACOUSTIC SOLITONS

DOE PAGES

Vasko, I. Y.; Agapitov, O. V.; Mozer, F. S.; ...

2017-05-28

The Van Allen Probes observe generally two types of electrostatic solitary waves (ESW) contributing to the broadband electrostatic wave activity in the nightside inner magnetosphere. ESW with symmetric bipolar parallel electric field are electron phase space holes. The nature of ESW with asymmetric bipolar (and almost unipolar) parallel electric field has remained puzzling. To address their nature, we consider a particular event observed by Van Allen Probes to argue that during the broadband wave activity electrons with energy above 200 eV provide the dominant contribution to the total electron density, while the density of cold electrons (below a few eV)more » is less than a few tenths of the total electron density. We show that velocities of the asymmetric ESW are close to velocity of electron-acoustic waves (existing due to the presence of cold and hot electrons) and follow the Korteweg-de Vries (KdV) dispersion relation derived for the observed plasma conditions (electron energy spectrum is a power law between about 100 eV and 10 keV and Maxwellian above 10 keV). The ESW spatial scales are in general agreement with the KdV theory. We interpret the asymmetric ESW in terms of electron-acoustic solitons and double layers (shocks waves).« less

Electron-acoustic solitons and double layers in the inner magnetosphere: ELECTRON-ACOUSTIC SOLITONS

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

Vasko, I. Y.; Agapitov, O. V.; Mozer, F. S.

The Van Allen Probes observe generally two types of electrostatic solitary waves (ESW) contributing to the broadband electrostatic wave activity in the nightside inner magnetosphere. ESW with symmetric bipolar parallel electric field are electron phase space holes. The nature of ESW with asymmetric bipolar (and almost unipolar) parallel electric field has remained puzzling. To address their nature, we consider a particular event observed by Van Allen Probes to argue that during the broadband wave activity electrons with energy above 200 eV provide the dominant contribution to the total electron density, while the density of cold electrons (below a few eV)more » is less than a few tenths of the total electron density. We show that velocities of the asymmetric ESW are close to velocity of electron-acoustic waves (existing due to the presence of cold and hot electrons) and follow the Korteweg-de Vries (KdV) dispersion relation derived for the observed plasma conditions (electron energy spectrum is a power law between about 100 eV and 10 keV and Maxwellian above 10 keV). The ESW spatial scales are in general agreement with the KdV theory. We interpret the asymmetric ESW in terms of electron-acoustic solitons and double layers (shocks waves).« less

Measurement-induced operation of two-ion quantum heat machines

NASA Astrophysics Data System (ADS)

Chand, Suman; Biswas, Asoka

2017-03-01

We show how one can implement a quantum heat machine by using two interacting trapped ions, in presence of a thermal bath. The electronic states of the ions act like a working substance, while the vibrational mode is modelled as the cold bath. The heat exchange with the cold bath is mimicked by the projective measurement of the electronic states. We show how such measurement in a suitable basis can lead to either a quantum heat engine or a refrigerator, which undergoes a quantum Otto cycle. The local magnetic field is adiabatically changed during the heat cycle. The performance of the heat machine depends upon the interaction strength between the ions, the magnetic fields, and the measurement cost. In our model, the coupling to the hot and the cold baths is never switched off in an alternative fashion during the heat cycle, unlike other existing proposals of quantum heat engines. This makes our proposal experimentally realizable using current tapped-ion technology.

Measurement-induced operation of two-ion quantum heat machines.

PubMed

Chand, Suman; Biswas, Asoka

2017-03-01

We show how one can implement a quantum heat machine by using two interacting trapped ions, in presence of a thermal bath. The electronic states of the ions act like a working substance, while the vibrational mode is modelled as the cold bath. The heat exchange with the cold bath is mimicked by the projective measurement of the electronic states. We show how such measurement in a suitable basis can lead to either a quantum heat engine or a refrigerator, which undergoes a quantum Otto cycle. The local magnetic field is adiabatically changed during the heat cycle. The performance of the heat machine depends upon the interaction strength between the ions, the magnetic fields, and the measurement cost. In our model, the coupling to the hot and the cold baths is never switched off in an alternative fashion during the heat cycle, unlike other existing proposals of quantum heat engines. This makes our proposal experimentally realizable using current tapped-ion technology.

Multi-field electron emission pattern of 2D emitter: Illustrated with graphene

NASA Astrophysics Data System (ADS)

Luo, Ma; Li, Zhibing

2016-11-01

The mechanism of laser-assisted multi-field electron emission of two-dimensional emitters is investigated theoretically. The process is basically a cold field electron emission but having more controllable components: a uniform electric field controls the emission potential barrier, a magnetic field controls the quantum states of the emitter, while an optical field controls electron populations of specified quantum states. It provides a highly orientational vacuum electron line source whose divergence angle over the beam plane is inversely proportional to square root of the emitter height. Calculations are carried out for graphene with the armchair emission edge, as a concrete example. The rate equation incorporating the optical excitation, phonon scattering, and thermal relaxation is solved in the quasi-equilibrium approximation for electron population in the bands. The far-field emission patterns, that inherit the features of the Landau bands, are obtained. It is found that the optical field generates a characteristic structure at one wing of the emission pattern.

Theoretical analysis of field emission from a metal diamond cold cathode emitter

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

Lerner, P.; Cutler, P.H.; Miskovsky, N.M.

Recently, Geis {ital et al.} [J. Vac. Sci. Technol. B {bold 14}, 2060 (1996)] proposed a cold cathode emitter based on a Spindt-type design using a diamond film doped by substitutional nitrogen. The device is characterized by high field emission currents at very low power. Two properties, the rough surface of the metallic injector and the negative electron affinity of the (111) surface of the diamond are essential for its operation. We present a first consistent quantitative theory of the operation of a Geis{endash}Spindt diamond field emitter. Its essential features are predicated on nearly {ital zero-field conditions} in the diamondmore » beyond the depletion layer, {ital quasiballistic transport} in the conduction band, and applicability of a modified {ital Fowler{endash}Nordheim equation} to the transmission of electrons through the Schottky barrier at the metal-diamond interface. Calculated results are in good qualitative and quantitative agreement with the experimental results of Geis {ital et al.} {copyright} {ital 1997 American Vacuum Society.}« less

Numerical implementation of a cold-ion, Boltzmann-electron model for nonplanar plasma-surface interactions

NASA Astrophysics Data System (ADS)

Holgate, J. T.; Coppins, M.

2018-04-01

Plasma-surface interactions are ubiquitous in the field of plasma science and technology. Much of the physics of these interactions can be captured with a simple model comprising a cold ion fluid and electrons which satisfy the Boltzmann relation. However, this model permits analytical solutions in a very limited number of cases. This paper presents a versatile and robust numerical implementation of the model for arbitrary surface geometries in cartesian and axisymmetric cylindrical coordinates. Specific examples of surfaces with sinusoidal corrugations, trenches, and hemi-ellipsoidal protrusions verify this numerical implementation. The application of the code to problems involving plasma-liquid interactions, plasma etching, and electron emission from the surface is discussed.

Ion gyroradius effects on particle trapping in kinetic Alfven waves along auroral field lines

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

Damiano, P. A.; Johnson, J. R.; Chaston, C. C.

In this study, a 2-D self-consistent hybrid gyrofluid-kinetic electron model is used to investigate Alfven wave propagation along dipolar magnetic field lines for a range of ion to electron temperature ratios. The focus of the investigation is on understanding the role of these effects on electron trapping in kinetic Alfven waves sourced in the plasma sheet and the role of this trapping in contributing to the overall electron energization at the ionosphere. This work also builds on our previous effort by considering a similar system in the limit of fixed initial parallel current, rather than fixed initial perpendicular electric field.more » It is found that the effects of particle trapping are strongest in the cold ion limit and the kinetic Alfven wave is able to carry trapped electrons a large distance along the field line yielding a relatively large net energization of the trapped electron population as the phase speed of the wave is increased. However, as the ion temperature is increased, the ability of the kinetic Alfven wave to carry and energize trapped electrons is reduced by more significant wave energy dispersion perpendicular to the ambient magnetic field which reduces the amplitude of the wave. This reduction of wave amplitude in turn reduces both the parallel current and the extent of the high-energy tails evident in the energized electron populations at the ionospheric boundary (which may serve to explain the limited extent of the broadband electron energization seen in observations). Here, even in the cold ion limit, trapping effects in kinetic Alfven waves lead to only modest electron energization for the parameters considered (on the order of tens of eV) and the primary energization of electrons to keV levels coincides with the arrival of the wave at the ionospheric boundary.« less

Ion gyroradius effects on particle trapping in kinetic Alfven waves along auroral field lines

DOE PAGES

Damiano, P. A.; Johnson, J. R.; Chaston, C. C.

2016-11-10

In this study, a 2-D self-consistent hybrid gyrofluid-kinetic electron model is used to investigate Alfven wave propagation along dipolar magnetic field lines for a range of ion to electron temperature ratios. The focus of the investigation is on understanding the role of these effects on electron trapping in kinetic Alfven waves sourced in the plasma sheet and the role of this trapping in contributing to the overall electron energization at the ionosphere. This work also builds on our previous effort by considering a similar system in the limit of fixed initial parallel current, rather than fixed initial perpendicular electric field.more » It is found that the effects of particle trapping are strongest in the cold ion limit and the kinetic Alfven wave is able to carry trapped electrons a large distance along the field line yielding a relatively large net energization of the trapped electron population as the phase speed of the wave is increased. However, as the ion temperature is increased, the ability of the kinetic Alfven wave to carry and energize trapped electrons is reduced by more significant wave energy dispersion perpendicular to the ambient magnetic field which reduces the amplitude of the wave. This reduction of wave amplitude in turn reduces both the parallel current and the extent of the high-energy tails evident in the energized electron populations at the ionospheric boundary (which may serve to explain the limited extent of the broadband electron energization seen in observations). Here, even in the cold ion limit, trapping effects in kinetic Alfven waves lead to only modest electron energization for the parameters considered (on the order of tens of eV) and the primary energization of electrons to keV levels coincides with the arrival of the wave at the ionospheric boundary.« less

The transverse magnetic field effect on steady-state solutions of the Bursian diode

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

Pramanik, Sourav; Chakrabarti, Nikhil; Ender, A. Ya.

2015-04-15

A study of steady-states of a planar vacuum diode driven by a cold electron beam (the Bursian diode) under an external transverse magnetic field is presented. The regime of no electrons turned around by a magnetic field only is under the consideration. The emitter electric field is evaluated as a characteristic function for the existence of solutions depending on the diode length, the applied voltage, and the magnetic field strength. At certain conditions, it is shown that a region of non-unique solutions exists in the Bursian diode when the magnetic field is absent. An expression for the maximum current transmittedmore » through the diode is derived. The external magnetic field is put forth to control fast electronic switches based on the Bursian diode.« less

Acquisition parameters optimization of a transmission electron forward scatter diffraction system in a cold-field emission scanning electron microscope for nanomaterials characterization.

PubMed

Brodusch, Nicolas; Demers, Hendrix; Trudeau, Michel; Gauvin, Raynald

2013-01-01

Transmission electron forward scatter diffraction (t-EFSD) is a new technique providing crystallographic information with high resolution on thin specimens by using a conventional electron backscatter diffraction (EBSD) system in a scanning electron microscope. In this study, the impact of tilt angle, working distance, and detector distance on the Kikuchi pattern quality were investigated in a cold-field emission scanning electron microscope (CFE-SEM). We demonstrated that t-EFSD is applicable for tilt angles ranging from -20° to -40°. Working distance (WD) should be optimized for each material by choosing the WD for which the EBSD camera screen illumination is the highest, as the number of detected electrons on the screen is directly dependent on the scattering angle. To take advantage of the best performances of the CFE-SEM, the EBSD camera should be close to the sample and oriented towards the bottom to increase forward scattered electron collection efficiency. However, specimen chamber cluttering and beam/mechanical drift are important limitations in the CFE-SEM used in this work. Finally, the importance of t-EFSD in materials science characterization was illustrated through three examples of phase identification and orientation mapping. © Wiley Periodicals, Inc.

Low-macroscopic field emission properties of wide bandgap copper aluminium oxide nanoparticles for low-power panel applications.

PubMed

Banerjee, Arghya Narayan; Joo, Sang W

2011-09-07

Field emission properties of CuAlO(2) nanoparticles are reported for the first time, with a low turn-on field of approximately 2 V µm(-1) and field enhancement factor around 230. The field emission process follows the standard Fowler-Nordheim tunnelling of cold electron emission. The emission mechanism is found to be a combination of low electron affinity, internal nanostructure and large field enhancement at the low-dimensional emitter tips of the nanoparticles. The field emission properties are comparable to the conventional carbon-based field emitters, and thus can become alternative candidate for field emission devices for low-power panel applications.

Low-macroscopic field emission properties of wide bandgap copper aluminium oxide nanoparticles for low-power panel applications

NASA Astrophysics Data System (ADS)

Narayan Banerjee, Arghya; Joo, Sang W.

2011-09-01

Field emission properties of CuAlO2 nanoparticles are reported for the first time, with a low turn-on field of approximately 2 V µm - 1 and field enhancement factor around 230. The field emission process follows the standard Fowler-Nordheim tunnelling of cold electron emission. The emission mechanism is found to be a combination of low electron affinity, internal nanostructure and large field enhancement at the low-dimensional emitter tips of the nanoparticles. The field emission properties are comparable to the conventional carbon-based field emitters, and thus can become alternative candidate for field emission devices for low-power panel applications.

Performance of a carbon nanotube field emission electron gun

NASA Astrophysics Data System (ADS)

Getty, Stephanie A.; King, Todd T.; Bis, Rachael A.; Jones, Hollis H.; Herrero, Federico; Lynch, Bernard A.; Roman, Patrick; Mahaffy, Paul

2007-04-01

A cold cathode field emission electron gun (e-gun) based on a patterned carbon nanotube (CNT) film has been fabricated for use in a miniaturized reflectron time-of-flight mass spectrometer (RTOF MS), with future applications in other charged particle spectrometers, and performance of the CNT e-gun has been evaluated. A thermionic electron gun has also been fabricated and evaluated in parallel and its performance is used as a benchmark in the evaluation of our CNT e-gun. Implications for future improvements and integration into the RTOF MS are discussed.

PIC-MCC analysis of electron multiplication in a cold-cathode Penning ion generator and its application to identify ignition voltage

NASA Astrophysics Data System (ADS)

Noori, H.; Ranjbar, A. H.; Mahjour-Shafiei, M.

2017-11-01

A cold-cathode Penning ion generator (PIG) has been developed in our laboratory to study the interaction of charged particles with matter. The ignition voltage was measured in the presence of the axial magnetic field in the range of 460-580 G. The performed measurements with stainless steel cathodes were in argon gas at pressure of 4 × 10-2 mbar. A PIC-MCC (particle-in-cell, Monte Carlo collision) technique has been used to calculate the electron multiplication coefficient M for various strength of axial magnetic field and applied voltage. An approach based on the coefficient M and the experimental values of the secondary electron emission coefficient γ, was proposed to determine the ignition voltages, theoretically. Applying the values of secondary coefficient γ leads to the average value of γM(V, B) to be = 1.05 ± 0.03 at the ignition of the PIG which satisfies the proposed ignition criterion. Thus, the ion-induced secondary electrons emitted from the cathode have dominant contribution to self-sustaining of the discharge process in a PIG.

Efficient cold cathode emission in crystalline-amorphous hybrid: Study on carbon nanotube-cadmium selenide system

NASA Astrophysics Data System (ADS)

Sarkar, S.; Banerjee, D.; Das, N. S.; Ghorai, U. K.; Sen, D.; Chattopadhyay, K. K.

2018-03-01

Cadmium Selenide (CdSe) quantum dot (QD) decorated amorphous carbon nanotubes (a-CNTs) hybrids have been synthesized by simple chemical process. The samples were characterized by field emission scanning and transmission electron microscopy, Fourier transformed infrared spectroscopy, Raman and UV-Vis spectroscopy. Lattice image obtained from transmission electron microscopic study confirms the successful attachment of CdSe QDs. It is seen that hybrid samples show an enhanced cold emission properties with good stability. The results have been explained in terms of increased roughness, more numbers of emitting sites and favorable band bending induced electron transport. ANSYS software based calculation has also supported the result. Also a first principle based study has been done which shows that due to the formation of hybrid structure there is a profound upward shift in the Fermi level, i.e. a decrease of work function, which is believed to be another key reason for the observed improved field emission performance.

Dust acoustic shock waves in magnetized dusty plasma

NASA Astrophysics Data System (ADS)

Yashika, GHAI; Nimardeep, KAUR; Kuldeep, SINGH; N, S. SAINI

2018-07-01

We have presented a theoretical study of the dust acoustic (DA) shock structures in a magnetized, electron depleted dusty plasma in the presence of two temperature superthermal ions. By deriving a Korteweg–de Vries–Burgers equation and studying its shock solution, we aim to highlight the effects of magnetic field and obliqueness on various properties of the DA shock structures in the presence of kappa-distributed two temperature ion population. The present model is motivated by the observations of Geotail spacecraft in the Earth's magnetotail and it is seen that the different physical parameters such as superthermality of the cold and hot ions, the cold to hot ion temperature ratio, the magnetic field strength, obliqueness and the dust kinematic viscosity greatly influence the dynamics of the shock structures so formed. The results suggest that the variation of superthermalities of the cold and hot ions have contrasting effects on both positive and negative polarity shock structures. Moreover, it is noted that the presence of the ambient magnetic field affects the dispersive properties of the medium and tends to make the shock structures less wide and more abrupt. The findings of present investigation may be useful in understanding the dynamics of shock waves in dusty plasma environments containing two temperature ions where the electrons are significantly depleted.

Contact discontinuities in a cold collision-free two-beam plasma

NASA Technical Reports Server (NTRS)

Kirkland, K. B.; Sonnerup, B. U. O.

1982-01-01

The structure of contact discontinuities in a collision-free plasma is examined using a model of a plasma which consists of two oppositely directed cold ion beams and a background of cold massless electrons such that exact charge neutrality is maintained and that the electric field is zero. The basic equations describing self-consistent equilibria are obtained for the more general situation where a net flow across the layer takes place and where the magnetic field has two nonzero tangential components but where the electric field remains zero. These equations are then specialized to the case of no net plasma flow where one of the tangential components is zero, and four different classes of sheets are obtained, all having thickness the order of the ion inertial length. The first class is for layers separating two identical plasma and magnetic field regions, the second is for an infinite array of parallel layers producing an undulated magnetic field, the third is for layers containing trapped ions in closed orbits which separate two vacuum regions with uniform identical magnetic fields, and the fourth is for layers which reflect a single plasma beam, leaving a vacuum with a reversed and compressed tangential field on the other side.

Magnetospheric Multiscale observations of large-amplitude, parallel, electrostatic waves associated with magnetic reconnection at the magnetopause

NASA Astrophysics Data System (ADS)

Ergun, R. E.; Holmes, J. C.; Goodrich, K. A.; Wilder, F. D.; Stawarz, J. E.; Eriksson, S.; Newman, D. L.; Schwartz, S. J.; Goldman, M. V.; Sturner, A. P.; Malaspina, D. M.; Usanova, M. E.; Torbert, R. B.; Argall, M.; Lindqvist, P.-A.; Khotyaintsev, Y.; Burch, J. L.; Strangeway, R. J.; Russell, C. T.; Pollock, C. J.; Giles, B. L.; Dorelli, J. J. C.; Avanov, L.; Hesse, M.; Chen, L. J.; Lavraud, B.; Le Contel, O.; Retino, A.; Phan, T. D.; Eastwood, J. P.; Oieroset, M.; Drake, J.; Shay, M. A.; Cassak, P. A.; Nakamura, R.; Zhou, M.; Ashour-Abdalla, M.; André, M.

2016-06-01

We report observations from the Magnetospheric Multiscale satellites of large-amplitude, parallel, electrostatic waves associated with magnetic reconnection at the Earth's magnetopause. The observed waves have parallel electric fields (E||) with amplitudes on the order of 100 mV/m and display nonlinear characteristics that suggest a possible net E||. These waves are observed within the ion diffusion region and adjacent to (within several electron skin depths) the electron diffusion region. They are in or near the magnetosphere side current layer. Simulation results support that the strong electrostatic linear and nonlinear wave activities appear to be driven by a two stream instability, which is a consequence of mixing cold (<10 eV) plasma in the magnetosphere with warm (~100 eV) plasma from the magnetosheath on a freshly reconnected magnetic field line. The frequent observation of these waves suggests that cold plasma is often present near the magnetopause.

Miniature quadrupole mass spectrometer having a cold cathode ionization source

DOEpatents

Felter, Thomas E.

2002-01-01

An improved quadrupole mass spectrometer is described. The improvement lies in the substitution of the conventional hot filament electron source with a cold cathode field emitter array which in turn allows operating a small QMS at much high internal pressures then are currently achievable. By eliminating of the hot filament such problems as thermally "cracking" delicate analyte molecules, outgassing a "hot" filament, high power requirements, filament contamination by outgas species, and spurious em fields are avoid all together. In addition, the ability of produce FEAs using well-known and well developed photolithographic techniques, permits building a QMS having multiple redundancies of the ionization source at very low additional cost.

Effects of electron pressure anisotropy on current sheet configuration

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

Artemyev, A. V., E-mail: aartemyev@igpp.ucla.edu; Angelopoulos, V.; Runov, A.

2016-09-15

Recent spacecraft observations in the Earth's magnetosphere have demonstrated that the magnetotail current sheet can be supported by currents of anisotropic electron population. Strong electron currents are responsible for the formation of very thin (intense) current sheets playing the crucial role in stability of the Earth's magnetotail. We explore the properties of such thin current sheets with hot isotropic ions and cold anisotropic electrons. Decoupling of the motions of ions and electrons results in the generation of a polarization electric field. The distribution of the corresponding scalar potential is derived from the electron pressure balance and the quasi-neutrality condition. Wemore » find that electron pressure anisotropy is partially balanced by a field-aligned component of this polarization electric field. We propose a 2D model that describes a thin current sheet supported by currents of anisotropic electrons embedded in an ion-dominated current sheet. Current density profiles in our model agree well with THEMIS observations in the Earth's magnetotail.« less

Studies on probe measurements in presence of magnetic field in dust containing hydrogen plasma

NASA Astrophysics Data System (ADS)

Kalita, Deiji; Kakati, Bharat; Kausik, Siddhartha Sankar; Saikia, Bipul Kumar; Bandyopadhyay, Mainak

2018-04-01

The accuracy of plasma parameters measured by Langmuir probe in presence of magnetic field is studied in our present work. It is observed that the ratio of electron to ion saturation current shows almost identical behavior with that of unmagnetized hydrogen plasma when r L > 10 r p (here r L : Larmor radius and r p : probe radius). At magnetic field strength, B = 594 gauss, the electron temperature ( T e ) shows an overestimated value up to 35-40%, whereas at B ≤ 37 gauss, T e shows around ≤10% overestimated value w.r.t. unmagnetized case. A bi-Maxwellian electron energy probability function is observed for entire magnetic field range for both pristine and dust containing hydrogen plasma. The bulk (cold) electron collection by the Langmuir probe is strongly suppressed whereas the higher energetic electron collection remains unaffected in presence of magnetic field. In presence of dust grains, it is found that the low energy electron population decreases even more than the magnetized plasma and the high-energy tail slightly increases compared to the pristine plasma.

On the application of quantum transport theory to electron sources.

PubMed

Jensen, Kevin L

2003-01-01

Electron sources (e.g., field emitter arrays, wide band-gap (WBG) semiconductor materials and coatings, carbon nanotubes, etc.) seek to exploit ballistic transport within the vacuum after emission from microfabricated structures. Regardless of kind, all sources strive to minimize the barrier to electron emission by engineering material properties (work function/electron affinity) or physical geometry (field enhancement) of the cathode. The unique capabilities of cold cathodes, such as instant ON/OFF performance, high brightness, high current density, large transconductance to capacitance ratio, cold emission, small size and/or low voltage operation characteristics, commend their use in several advanced devices when physical size, weight, power consumption, beam current, and pulse repletion frequency are important, e.g., RF power amplifier such as traveling wave tubes (TWTs) for radar and communications, electrodynamic tethers for satellite deboost/reboost, and electric propulsion systems such as Hall thrusters for small satellites. The theoretical program described herein is directed towards models to evaluate emission current from electron sources (in particular, emission from WBG and Spindt-type field emitter) in order to assess their utility, capabilities and performance characteristics. Modeling efforts particularly include: band bending, non-linear and resonant (Poole-Frenkel) potentials, the extension of one-dimensional theory to multi-dimensional structures, and emission site statistics due to variations in geometry and the presence of adsorbates. Two particular methodologies, namely, the modified Airy approach and metal-semiconductor statistical hyperbolic/ellipsoidal model, are described in detail in their present stage of development.

High-Temperature (940 °C) furnace in 18/20 T cold bore magnet

NASA Astrophysics Data System (ADS)

Wang, Ze; Hou, Yubin; Feng, Qiyuan; Dong, Hongliang; Lu, Qingyou

2018-01-01

We present a high-temperature furnace that can work continuously in an 18/20 T cold bore magnet. A specially designed liquid nitrogen (LN2) jacket is between the high-temperature parts of the furnace and the liquid helium in the magnet Dewar. With LN2 serving as the cooling medium, the calculated value of radiation received by the liquid helium (LHe) is as low as 0.004 W. The furnace can be put into LHe Dewar directly. Together with the magnet, the furnace can provide experimental conditions of a strong static magnetic field and temperatures up to 940 °C. A cobalt oxide synthesis in solution was carried out at 200 °C with and without a 15 T magnetic field for 8 h. Differences in material structure with the applied field were observed in transmission electron micrographs of the products. A Co film sample was treated at 900 °C with and without a 6.8 T magnetic field for 30 min. The scanning electron micrographs of the treated samples show that magnetic field had a clear effect on the heat treatment process. These two applications confirmed the performance of the furnace both in high magnetic field and at high temperature.

Field electron emission based on resonant tunneling in diamond/CoSi2/Si quantum well nanostructures

PubMed Central

Gu, Changzhi; Jiang, Xin; Lu, Wengang; Li, Junjie; Mantl, Siegfried

2012-01-01

Excellent field electron emission properties of a diamond/CoSi2/Si quantum well nanostructure are observed. The novel quantum well structure consists of high quality diamond emitters grown on bulk Si substrate with a nanosized epitaxial CoSi2 conducting interlayer. The results show that the main emission properties were modified by varying the CoSi2 thickness and that stable, low-field, high emission current and controlled electron emission can be obtained by using a high quality diamond film and a thicker CoSi2 interlayer. An electron resonant tunneling mechanism in this quantum well structure is suggested, and the tunneling is due to the long electron mean free path in the nanosized CoSi2 layer. This structure meets most of the requirements for development of vacuum micro/nanoelectronic devices and large-area cold cathodes for flat-panel displays. PMID:23082241

Field electron emission based on resonant tunneling in diamond/CoSi2/Si quantum well nanostructures.

PubMed

Gu, Changzhi; Jiang, Xin; Lu, Wengang; Li, Junjie; Mantl, Siegfried

2012-01-01

Excellent field electron emission properties of a diamond/CoSi(2)/Si quantum well nanostructure are observed. The novel quantum well structure consists of high quality diamond emitters grown on bulk Si substrate with a nanosized epitaxial CoSi(2) conducting interlayer. The results show that the main emission properties were modified by varying the CoSi(2) thickness and that stable, low-field, high emission current and controlled electron emission can be obtained by using a high quality diamond film and a thicker CoSi(2) interlayer. An electron resonant tunneling mechanism in this quantum well structure is suggested, and the tunneling is due to the long electron mean free path in the nanosized CoSi(2) layer. This structure meets most of the requirements for development of vacuum micro/nanoelectronic devices and large-area cold cathodes for flat-panel displays.

Breakdown voltage reliability improvement in gas-discharge tube surge protectors employing graphite field emitters

NASA Astrophysics Data System (ADS)

Žumer, Marko; Zajec, Bojan; Rozman, Robert; Nemanič, Vincenc

2012-04-01

Gas-discharge tube (GDT) surge protectors are known for many decades as passive units used in low-voltage telecom networks for protection of electrical components from transient over-voltages (discharging) such as lightning. Unreliability of the mean turn-on DC breakdown voltage and the run-to-run variability has been overcome successfully in the past by adding, for example, a radioactive source inside the tube. Radioisotopes provide a constant low level of free electrons, which trigger the breakdown. In the last decades, any concept using environmentally harmful compounds is not acceptable anymore and new solutions were searched. In our application, a cold field electron emitter source is used as the trigger for the gas discharge but with no activating compound on the two main electrodes. The patent literature describes in details the implementation of the so-called trigger wires (auxiliary electrodes) made of graphite, placed in between the two main electrodes, but no physical explanation has been given yet. We present experimental results, which show that stable cold field electron emission current in the high vacuum range originating from the nano-structured edge of the graphite layer is well correlated to the stable breakdown voltage of the GDT surge protector filled with a mixture of clean gases.

Method for analyzing the mass of a sample using a cold cathode ionization source mass filter

DOEpatents

Felter, Thomas E.

2003-10-14

An improved quadrupole mass spectrometer is described. The improvement lies in the substitution of the conventional hot filament electron source with a cold cathode field emitter array which in turn allows operating a small QMS at much high internal pressures then are currently achievable. By eliminating of the hot filament such problems as thermally "cracking" delicate analyte molecules, outgassing a "hot" filament, high power requirements, filament contamination by outgas species, and spurious em fields are avoid all together. In addition, the ability of produce FEAs using well-known and well developed photolithographic techniques, permits building a QMS having multiple redundancies of the ionization source at very low additional cost.

Wave Phenomena and Beam-Plasma Interactions at the Magnetopause Reconnection Region

NASA Astrophysics Data System (ADS)

Burch, J. L.; Webster, J. M.; Genestreti, K. J.; Torbert, R. B.; Giles, B. L.; Fuselier, S. A.; Dorelli, J. C.; Rager, A. C.; Phan, T. D.; Allen, R. C.; Chen, L.-J.; Wang, S.; Le Contel, O.; Russell, C. T.; Strangeway, R. J.; Ergun, R. E.; Jaynes, A. N.; Lindqvist, P.-A.; Graham, D. B.; Wilder, F. D.; Hwang, K.-J.; Goldstein, J.

2018-02-01

This paper reports on Magnetospheric Multiscale observations of whistler mode chorus and higher-frequency electrostatic waves near and within a reconnection diffusion region on 23 November 2016. The diffusion region is bounded by crescent-shaped electron distributions and associated dissipation just upstream of the X-line and by magnetic field-aligned currents and electric fields leading to dissipation near the electron stagnation point. Measurements were made southward of the X-line as determined by southward directed ion and electron jets. We show that electrostatic wave generation is due to magnetosheath electron beams formed by the electron jets as they interact with a cold background plasma and more energetic population of magnetospheric electrons. On the magnetosphere side of the X-line the electron beams are accompanied by a strong perpendicular electron temperature anisotropy, which is shown to be the source of an observed rising-tone whistler mode chorus event. We show that the apex of the chorus event and the onset of electrostatic waves coincide with the opening of magnetic field lines at the electron stagnation point.

Amorphous-diamond electron emitter

DOEpatents

Falabella, Steven

2001-01-01

An electron emitter comprising a textured silicon wafer overcoated with a thin (200 .ANG.) layer of nitrogen-doped, amorphous-diamond (a:D-N), which lowers the field below 20 volts/micrometer have been demonstrated using this emitter compared to uncoated or diamond coated emitters wherein the emission is at fields of nearly 60 volts/micrometer. The silicon/nitrogen-doped, amorphous-diamond (Si/a:D-N) emitter may be produced by overcoating a textured silicon wafer with amorphous-diamond (a:D) in a nitrogen atmosphere using a filtered cathodic-arc system. The enhanced performance of the Si/a:D-N emitter lowers the voltages required to the point where field-emission displays are practical. Thus, this emitter can be used, for example, in flat-panel emission displays (FEDs), and cold-cathode vacuum electronics.

THE LAUNCHING OF COLD CLOUDS BY GALAXY OUTFLOWS. II. THE ROLE OF THERMAL CONDUCTION

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

Brüggen, Marcus; Scannapieco, Evan

2016-05-01

We explore the impact of electron thermal conduction on the evolution of radiatively cooled cold clouds embedded in flows of hot and fast material as it occurs in outflowing galaxies. Performing a parameter study of three-dimensional adaptive mesh refinement hydrodynamical simulations, we show that electron thermal conduction causes cold clouds to evaporate, but it can also extend their lifetimes by compressing them into dense filaments. We distinguish between low column-density clouds, which are disrupted on very short times, and high-column density clouds with much longer disruption times that are set by a balance between impinging thermal energy and evaporation. Wemore » provide fits to the cloud lifetimes and velocities that can be used in galaxy-scale simulations of outflows in which the evolution of individual clouds cannot be modeled with the required resolution. Moreover, we show that the clouds are only accelerated to a small fraction of the ambient velocity because compression by evaporation causes the clouds to present a small cross-section to the ambient flow. This means that either magnetic fields must suppress thermal conduction, or that the cold clouds observed in galaxy outflows are not formed of cold material carried out from the galaxy.« less

Roles of hot electrons in generating upper-hybrid waves in the earth's radiation belt

DOE PAGES

Hwang, J.; Shin, D. K.; Yoon, P. H.; ...

2017-05-01

Electrostatic fluctuations near upper-hybrid frequency, which are sometimes accompanied by multiple-harmonic electron cyclotron frequency bands above and below the upper-hybrid frequency, are common occurrences in the Earth's radiation belt, as revealed through the twin Van Allen Probe spacecrafts. It is customary to use the upper-hybrid emissions for estimating the background electron density, which in turn can be used to determine the plasmapause locations, but the role of hot electrons in generating such fluctuations has not been discussed in detail. The present paper carries out detailed analyses of data from the Waves instrument, which is part of the Electric and Magneticmore » Field Instrument Suite and Integrated Science suite onboard the Van Allen Probes. Combined with the theoretical calculation, it is shown that the peak intensity associated with the upper-hybrid fluctuations might be predominantly determined by tenuous but hot electrons and that denser cold background electrons do not seem to contribute much to the peak intensity. This finding shows that upper-hybrid fluctuations detected during quiet time are not only useful for the determination of the background cold electron density but also contain information on the ambient hot electrons population as well.« less

Roles of hot electrons in generating upper-hybrid waves in the earth's radiation belt

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

Hwang, J.; Shin, D. K.; Yoon, P. H.

Electrostatic fluctuations near upper-hybrid frequency, which are sometimes accompanied by multiple-harmonic electron cyclotron frequency bands above and below the upper-hybrid frequency, are common occurrences in the Earth's radiation belt, as revealed through the twin Van Allen Probe spacecrafts. It is customary to use the upper-hybrid emissions for estimating the background electron density, which in turn can be used to determine the plasmapause locations, but the role of hot electrons in generating such fluctuations has not been discussed in detail. The present paper carries out detailed analyses of data from the Waves instrument, which is part of the Electric and Magneticmore » Field Instrument Suite and Integrated Science suite onboard the Van Allen Probes. Combined with the theoretical calculation, it is shown that the peak intensity associated with the upper-hybrid fluctuations might be predominantly determined by tenuous but hot electrons and that denser cold background electrons do not seem to contribute much to the peak intensity. This finding shows that upper-hybrid fluctuations detected during quiet time are not only useful for the determination of the background cold electron density but also contain information on the ambient hot electrons population as well.« less

Magnetospheric Multiscale Observations of Large-Amplitude Parallel, Electrostatic Waves Associated with Magnetic Reconnection at the Magnetopause

NASA Technical Reports Server (NTRS)

Ergun, R. E.; Holmes, J. C.; Goodrich, K. A.; Wilder, F. D.; Stawarz, J. E.; Eriksson, S.; Newman, D. L.; Schwartz, S. J.; Goldman, M. V.; Sturner, A. P.;

Measurements and modeling of radio frequency field structures in a helicon plasma

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

Lee, C. A.; Chen, Guangye; Arefiev, A. V.

2011-01-01

Measurements of the radio frequency (rf) field structure, plasma density, and electron temperature are presented for a 1 kW argon helicon plasma source. The measured profiles change considerably when the equilibrium magnetic field is reversed. The measured rf fields are identified as fields of radially localized helicon waves, which propagate in the axial direction. The rf field structure is compared to the results of two-dimensional cold plasma full-wave simulations for the measured density profiles. Electron collision frequency is adjusted in the simulations to match the simulated and measured field profiles. The resulting frequency is anomalously high, which is attributed tomore » the excitation of an ion-acoustic instability. The calculated power deposition is insensitive to the collision frequency and accounts for most of the power supplied by the rf-generator.« less

Actively controlling coolant-cooled cold plate configuration

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

Chainer, Timothy J.; Parida, Pritish R.

Cooling apparatuses are provided to facilitate active control of thermal and fluid dynamic performance of a coolant-cooled cold plate. The cooling apparatus includes the cold plate and a controller. The cold plate couples to one or more electronic components to be cooled, and includes an adjustable physical configuration. The controller dynamically varies the adjustable physical configuration of the cold plate based on a monitored variable associated with the cold plate or the electronic component(s) being cooled by the cold plate. By dynamically varying the physical configuration, the thermal and fluid dynamic performance of the cold plate are adjusted to, formore » example, optimally cool the electronic component(s), and at the same time, reduce cooling power consumption used in cooling the electronic component(s). The physical configuration can be adjusted by providing one or more adjustable plates within the cold plate, the positioning of which may be adjusted based on the monitored variable.« less

Kinetic Framework for the Magnetosphere-Ionosphere-Plasmasphere-Polar Wind System: Modeling Ion Outflow

NASA Astrophysics Data System (ADS)

Schunk, R. W.; Barakat, A. R.; Eccles, V.; Karimabadi, H.; Omelchenko, Y.; Khazanov, G. V.; Glocer, A.; Kistler, L. M.

2014-12-01

A Kinetic Framework for the Magnetosphere-Ionosphere-Plasmasphere-Polar Wind System is being developed in order to provide a rigorous approach to modeling the interaction of hot and cold particle interactions. The framework will include ion and electron kinetic species in the ionosphere, plasmasphere and polar wind, and kinetic ion, super-thermal electron and fluid electron species in the magnetosphere. The framework is ideally suited to modeling ion outflow from the ionosphere and plasmasphere, where a wide range for fluid and kinetic processes are important. These include escaping ion interactions with (1) photoelectrons, (2) cusp/auroral waves, double layers, and field-aligned currents, (3) double layers in the polar cap due to the interaction of cold ionospheric and hot magnetospheric electrons, (4) counter-streaming ions, and (5) electromagnetic wave turbulence. The kinetic ion interactions are particularly strong during geomagnetic storms and substorms. The presentation will provide a brief description of the models involved and discuss the effect that kinetic processes have on the ion outflow.

Electroluminescence and other diagnostic techniques for the study of hot-electron effects in compound semiconductor devices

NASA Astrophysics Data System (ADS)

Zanoni, Enrico; Meneghesso, Gaudenzio; Menozzi, Roberto

2000-03-01

Hot electron in III-V FETs can be indirectly monitored by measuring the current coming out from the gate when the device is biased at high electric fields. This negative current is due to the collection of holes generated by impact ionization in the gate-to drain region. Electroluminescence represents a powerful tool in order to characterize not only hot electrons but also material properties. By using spatially resolved emission microscopy it is possible to show that the light due to cold electron/hole recombination is emitted between the gate and the source (low electric field region), while the contribution due to hot electrons is emitted between the gate and the drain (high electric field region). Deep-traps created in the device by hot carriers can be analysed by means of drain current deep level transient spectroscopy and by transconductance frequency dispersion. Cathodoluminescence, optical beam induced current, X-ray spectroscopy, electron energy loss spectroscopy in combination with a transmission electron microscopy are powerful tools in order to identify and localize surface modification following hot-electron stress tests.

Method to fabricate portable electron source based on nitrogen incorporated ultrananocrystalline diamond (N-UNCD)

DOEpatents

Sumant, Anirudha V.; Divan, Ralu; Posada, Chrystian M.; Castano, Carlos H.; Grant, Edwin J.; Lee, Hyoung K.

2016-03-29

A source cold cathode field emission array (FEA) source based on ultra-nanocrystalline diamond (UNCD) field emitters. This system was constructed as an alternative for detection of obscured objects and material. Depending on the geometry of the given situation a flat-panel source can be used in tomography, radiography, or tomosynthesis. Furthermore, the unit can be used as a portable electron or X-ray scanner or an integral part of an existing detection system. UNCD field emitters show great field emission output and can be deposited over large areas as the case with carbon nanotube "forest" (CNT) cathodes. Furthermore, UNCDs have better mechanical and thermal properties as compared to CNT tips which further extend the lifetime of UNCD based FEA.

A field-emission based vacuum device for the generation of THz waves

NASA Astrophysics Data System (ADS)

Lin, Ming-Chieh

2005-03-01

Terahertz waves have been used to characterize the electronic, vibrational and compositional properties of solid, liquid and gas phase materials during the past decade. More and more applications in imaging science and technology call for the well development of THz wave sources. Amplification and generation of a high frequency electromagnetic wave are a common interest of field emission based devices. In the present work, we propose a vacuum electronic device based on field emission mechanism for the generation of THz waves. To verify our thinking and designs, the cold tests and the hot tests have been studied via the simulation tools, SUPERFISH and MAGIC. In the hot tests, two types of electron emission mechanisms are considered. One is the field emission and the other is the explosive emission. The preliminary design of the device is carried out and tested by the numerical simulations. The simulation results show that an electronic efficiency up to 4% can be achieved without employing any magnetic circuits.

DE 1 observations of theta aurora plasma source regions and Birkeland current charge carriers

NASA Technical Reports Server (NTRS)

Menietti, J. D.; Burch, J. L.

1987-01-01

Detailed analyses of the DE 1 high-altitude plasma instrument electron and ion data have been performed for four passes during which theta auroras were observed. The data indicate that the theta auroras occur on what appear to be closed field lines with particle signatures and plasma parameters that are quite similar to those of the magnetospheric boundary plasma sheet. The field-aligned currents computed from particle fluxes in the energy range 18-13 keV above the theta auroras are observed to be generally downward on the dawnside of the arcs with a narrower region of larger (higher density) upward currents on the duskside of the arcs. These currents are carried predominantly by field-aligned beams of accelerated cold electrons. Of particualr interest in regions of upward field-aligned current are downward electron beams at energies less than the inferred potential drop above the spacecraft.

Linear theory of plasma Čerenkov masers

NASA Astrophysics Data System (ADS)

Birau, M.

1996-11-01

A different theoretical model of Čerenkov instability in the linear amplification regime of plasma Čerenkov masers is developed. The model assumes a cold relativistic annular electron beam propagating through a column of cold dense plasma, the two bodies being immersed in an infinite magnetic guiding field inside a perfect cylindrical waveguide. In order to simplify the calculations, a radial rectangular distribution of plasma and beam density is assumed and only azimuthal symmetric modes are under investigation. The model's difference consists of taking into account the whole plasma and beam electromagnetic structures in the interpretation of the Čerenkov instability. This model leads to alternative results such as the possibility of emission at several frequencies. In addition, the electric field is calculated taking into account its radial phase dependence, so that a map of the field in the interaction region can be presented.

Nonlinear theory for axisymmetric self-similar two-dimensional oscillations of electrons in cold plasma with constant proton background

NASA Astrophysics Data System (ADS)

Osherovich, V. A.; Fainberg, J.

2018-01-01

We consider simultaneous oscillations of electrons moving both along the axis of symmetry and also in the direction perpendicular to the axis. We derive a system of three nonlinear ordinary differential equations which describe self-similar oscillations of cold electrons in a constant proton density background (np = n0 = constant). These three equations represent an exact class of solutions. For weak nonlinear conditions, the frequency spectra of electric field oscillations exhibit split frequency behavior at the Langmuir frequency ωp0 and its harmonics, as well as presence of difference frequencies at low spectral values. For strong nonlinear conditions, the spectra contain peaks at frequencies with values ωp0(n +m √{2 }) , where n and m are integer numbers (positive and negative). We predict that both spectral types (weak and strong) should be observed in plasmas where axial symmetry may exist. To illustrate possible applications of our theory, we present a spectrum of electric field oscillations observed in situ in the solar wind by the WAVES experiment on the Wind spacecraft during the passage of a type III solar radio burst.

Design of a 300-kV gas environmental transmission electron microscope equipped with a cold field emission gun.

PubMed

Isakozawa, Shigeto; Nagaoki, Isao; Watabe, Akira; Nagakubo, Yasuhira; Saito, Nobuhiro; Matsumoto, Hiroaki; Zhang, Xiao Feng; Taniguchi, Yoshifumi; Baba, Norio

2016-08-01

A new in situ environmental transmission electron microscope (ETEM) was developed based on a 300 kV TEM with a cold field emission gun (CFEG). Particular caution was taken in the ETEM design to assure uncompromised imaging and analytical performance of the TEM. Because of the improved pumping system between the gun and column, the vacuum of CFEG was largely improved and the probe current was sufficiently stabilized to operate without tip flashing for 2-3 h or longer. A high brightness of 2.5 × 10(9) A/cm(2) sr was measured at 300 kV, verifying the high quality of the CFEG electron beam. A specially designed gas injection-heating holder was used in the in situ TEM study at elevated temperatures with or without gas around the TEM specimen. Using this holder in a 10 Pa gas atmosphere and specimen temperatures up to 1000°C, high-resolution ETEM performance and analysis were achieved. © The Author 2016. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Radiation from Accelerated Particles in Shocks and Reconnections

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Zhang, B.; Niemiec, J.; Medvedev, M.; Hardee, P.; Mizuno, Y.; Nordlund, A.; Frederiksen, J. T.; Sol, H.; Pohl, M.;

Electron Spectrum of Nonlinear Cold Emission from a Metal under the Action of a Laser Shot

NASA Astrophysics Data System (ADS)

Golovinskii, P. A.; Mikhin, E. A.

2017-12-01

The nonlinear emission of electrons from a metal under the action of a femtosecond moderate-intensity laser pulse (laser shot) has been studied. A theoretical model of the process has been constructed based on the 1D nonstationary Schrödinger equation in the vacuum half-space with given boundary conditions for the electron wavefunction. This equation has been solved using the Laplace transformation. It has been assumed that the states of free electrons in a metal, which are described by the Sommerfeld theory of metals, are insignificantly influenced by the laser field. The energy spectrum of emitted electrons has been obtained, and its dependence on the parameters of the lased shot has been found. The calculated spectrum of nonlinear electron emission from a tungsten nanotip under the action of a 6.5-fs-long laser shot generating a field of 9.26 V/nm agrees with the experimental data.

Measurement of a density profile of a hot-electron plasma in RT-1 with three-chord interferometry

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

Saitoh, H.; Yano, Y.; Yoshida, Z.

2015-02-15

The electron density profile of a plasma in a magnetospheric dipole field configuration was measured with a multi-chord interferometry including a relativistic correction. In order to improve the accuracy of density reconstruction, a 75 GHz interferometer was installed at a vertical chord of the Ring Trap 1 (RT-1) device in addition to previously installed ones at tangential and another vertical chords. The density profile was calculated by using the data of three-chord interferometry including relativistic effects for a plasma consisting of hot and cold electrons generated by electron cyclotron resonance heating (ECH). The results clearly showed the effects of density peakingmore » and magnetic mirror trapping in a strongly inhomogeneous dipole magnetic field.« less

Simulation of electrostatic turbulence in the plasma sheet boundary layer with electron currents and bean-shaped ion beams

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Frank, L. A.; Huang, C. Y.

1988-01-01

Plasma data from ISEE-1 show the presence of electron currents as well as energetic ion beams in the plasma sheet boundary layer. Broadband electrostatic noise and low-frequency electromagnetic bursts are detected in the plasma sheet boundary layer, especially in the presence of strong ion flows, currents, and steep spacial gradients in the fluxes of few-keV electrons and ions. Particle simulations have been performed to investigate electrostatic turbulence driven by a cold electron beam and/or ion beams with a bean-shaped velocity distribution. The simulation results show that the counterstreaming ion beams as well as the counterstreaming of the cold electron beam and the ion beam excite ion acoustic waves with a given Doppler-shifted real frequency. However, the effect of the bean-shaped ion velocity distributions reduces the growth rates of ion acoustic instability. The simulation results also show that the slowing down of the ion bean is larger at the larger perpendicular velocity. The wave spectra of the electric fields at some points of the simulations show turbulence generated by growing waves.

Physics and medical applications of cold atmospheric plasma

NASA Astrophysics Data System (ADS)

Keidar, Michael

2013-09-01

Recent progress in atmospheric plasmas led to the creation of cold plasmas with ion temperature close to room temperature. Varieties of novel plasma diagnostic techniques were applied in a quest to understand physics of cold plasmas. In particular it was established that the streamer head charge is about 108 electrons, the electrical field in the head vicinity is about 107 V/m, and the electron density of the streamer column is about 1019 m3. We have demonstrated the efficacy of cold plasma in a pre-clinical model of various cancer types (lung, bladder, breast, head, neck, brain and skin). Both in-vitro andin-vivo studies revealed that cold plasmas selectively kill cancer cells. We showed that: (a) cold plasma application selectively eradicates cancer cells in vitro without damaging normal cells. (b) Significantly reduced tumor size in vivo. Cold plasma treatment led to tumor ablation with neighbouring tumors unaffected. These experiments were performed on more than 10 mice with the same outcome. We found that tumors of about 5mm in diameter were ablated after 2 min of single time plasma treatment. The two best known cold plasma effects, plasma-induced apoptosis and the decrease of cell migration velocity can have important implications in cancer treatment by localizing the affected area of the tissue and by decreasing metastasic development. In addition, cold plasma treatment has affected the cell cycle of cancer cells. In particular, cold plasmainduces a 2-fold increase in cells at the G2/M-checkpoint in both papilloma and carcinoma cells at ~24 hours after treatment, while normal epithelial cells (WTK) did not show significant differences. It was shown that reactive oxygen species metabolism and oxidative stress responsive genes are deregulated. We investigated the production of reactive oxygen species (ROS) with cold plasma treatment as a potential mechanism for the tumor ablation observed.

Analysis and experimental study on formation conditions of large-scale barrier-free diffuse atmospheric pressure air plasmas in repetitive pulse mode

NASA Astrophysics Data System (ADS)

Li, Lee; Liu, Lun; Liu, Yun-Long; Bin, Yu; Ge, Ya-Feng; Lin, Fo-Chang

2014-01-01

Atmospheric air diffuse plasmas have enormous application potential in various fields of science and technology. Without dielectric barrier, generating large-scale air diffuse plasmas is always a challenging issue. This paper discusses and analyses the formation mechanism of cold homogenous plasma. It is proposed that generating stable diffuse atmospheric plasmas in open air should meet the three conditions: high transient power with low average power, excitation in low average E-field with locally high E-field region, and multiple overlapping electron avalanches. Accordingly, an experimental configuration of generating large-scale barrier-free diffuse air plasmas is designed. Based on runaway electron theory, a low duty-ratio, high voltage repetitive nanosecond pulse generator is chosen as a discharge excitation source. Using the wire-electrodes with small curvature radius, the gaps with highly non-uniform E-field are structured. Experimental results show that the volume-scaleable, barrier-free, homogeneous air non-thermal plasmas have been obtained between the gap spacing with the copper-wire electrodes. The area of air cold plasmas has been up to hundreds of square centimeters. The proposed formation conditions of large-scale barrier-free diffuse air plasmas are proved to be reasonable and feasible.

Cooled electronic system with liquid-cooled cold plate and thermal spreader coupled to electronic component

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

Chainer, Timothy J.; Graybill, David P.; Iyengar, Madhusudan K.

Apparatus and method are provided for facilitating cooling of an electronic component. The apparatus includes a liquid-cooled cold plate and a thermal spreader associated with the cold plate. The cold plate includes multiple coolant-carrying channel sections extending within the cold plate, and a thermal conduction surface with a larger surface area than a surface area of the component to be cooled. The thermal spreader includes one or more heat pipes including multiple heat pipe sections. One or more heat pipe sections are partially aligned to a first region of the cold plate, that is, where aligned to the surface tomore » be cooled, and partially aligned to a second region of the cold plate, which is outside the first region. The one or more heat pipes facilitate distribution of heat from the electronic component to coolant-carrying channel sections of the cold plate located in the second region of the cold plate.« less

Cooled electronic system with liquid-cooled cold plate and thermal spreader coupled to electronic component

DOEpatents

Chainer, Timothy J.; Graybill, David P.; Iyengar, Madhusudan K.; Kamath, Vinod; Kochuparambil, Bejoy J.; Schmidt, Roger R.; Steinke, Mark E.

2016-08-09

Apparatus and method are provided for facilitating cooling of an electronic component. The apparatus includes a liquid-cooled cold plate and a thermal spreader associated with the cold plate. The cold plate includes multiple coolant-carrying channel sections extending within the cold plate, and a thermal conduction surface with a larger surface area than a surface area of the component to be cooled. The thermal spreader includes one or more heat pipes including multiple heat pipe sections. One or more heat pipe sections are partially aligned to a first region of the cold plate, that is, where aligned to the surface to be cooled, and partially aligned to a second region of the cold plate, which is outside the first region. The one or more heat pipes facilitate distribution of heat from the electronic component to coolant-carrying channel sections of the cold plate located in the second region of the cold plate.

Cooled electronic system with liquid-cooled cold plate and thermal spreader coupled to electronic component

DOEpatents

Chainer, Timothy J.; Graybill, David P.; Iyengar, Madhusudan K.; Kamath, Vinod; Kochuparambil, Bejoy J.; Schmidt, Roger R.; Steinke, Mark E.

2016-04-05

Apparatus and method are provided for facilitating cooling of an electronic component. The apparatus includes a liquid-cooled cold plate and a thermal spreader associated with the cold plate. The cold plate includes multiple coolant-carrying channel sections extending within the cold plate, and a thermal conduction surface with a larger surface area than a surface area of the component to be cooled. The thermal spreader includes one or more heat pipes including multiple heat pipe sections. One or more heat pipe sections are partially aligned to a first region of the cold plate, that is, where aligned to the surface to be cooled, and partially aligned to a second region of the cold plate, which is outside the first region. The one or more heat pipes facilitate distribution of heat from the electronic component to coolant-carrying channel sections of the cold plate located in the second region of the cold plate.

High energy electron cooling

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

Parkhomchuk, V.

1997-09-01

High energy electron cooling requires a very cold electron beam. The questions of using electron cooling with and without a magnetic field are presented for discussion at this workshop. The electron cooling method was suggested by G. Budker in the middle sixties. The original idea of the electron cooling was published in 1966. The design activities for the NAP-M project was started in November 1971 and the first run using a proton beam occurred in September 1973. The first experiment with both electron and proton beams was started in May 1974. In this experiment good result was achieved very closemore » to theoretical prediction for a usual two component plasma heat exchange.« less

A new quasi-thermal trap model for solar flare hard X-ray bursts - An electrostatic trap model

NASA Technical Reports Server (NTRS)

Spicer, D. S.; Emslie, A. G.

1988-01-01

A new quasi-thermal trap model of solar flare hard X-ray bursts is presented. The new model utilizes the trapping ability of a magnetic mirror and a magnetic field-aligned electrostatic potential produced by differences in anisotropies of the electron and ion distribution function. It is demonstrated that this potential can, together with the magnetic mirror itself, effectively confine electrons in a trap, thereby enhancing their bremsstrahlung yield per electron. This analysis makes even more untenable models involving precipitation of the bremsstrahlung-producing electrons onto a cold target.

2D modeling of electromagnetic waves in cold plasmas

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

Crombé, K.; Van Eester, D.; Koch, R.

2014-02-12

The consequences of sheath (rectified) electric fields, resulting from the different mobility of electrons and ions as a response to radio frequency (RF) fields, are a concern for RF antenna design as it can cause damage to antenna parts, limiters and other in-vessel components. As a first step to a more complete description, the usual cold plasma dielectric description has been adopted, and the density profile was assumed to be known as input. Ultimately, the relevant equations describing the wave-particle interaction both on the fast and slow timescale will need to be tackled but prior to doing so was feltmore » as a necessity to get a feeling of the wave dynamics involved. Maxwell's equations are solved for a cold plasma in a 2D antenna box with strongly varying density profiles crossing also lower hybrid and ion-ion hybrid resonance layers. Numerical modelling quickly becomes demanding on computer power, since a fine grid spacing is required to capture the small wavelengths effects of strongly evanescent modes.« less

Cold and warm electrons at comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Eriksson, A. I.; Engelhardt, I. A. D.; André, M.; Boström, R.; Edberg, N. J. T.; Johansson, F. L.; Odelstad, E.; Vigren, E.; Wahlund, J.-E.; Henri, P.; Lebreton, J.-P.; Miloch, W. J.; Paulsson, J. J. P.; Simon Wedlund, C.; Yang, L.; Karlsson, T.; Jarvinen, R.; Broiles, T.; Mandt, K.; Carr, C. M.; Galand, M.; Nilsson, H.; Norberg, C.

2017-09-01

Context. Strong electron cooling on the neutral gas in cometary comae has been predicted for a long time, but actual measurements of low electron temperature are scarce. Aims: Our aim is to demonstrate the existence of cold electrons in the inner coma of comet 67P/Churyumov-Gerasimenko and show filamentation of this plasma. Methods: In situ measurements of plasma density, electron temperature and spacecraft potential were carried out by the Rosetta Langmuir probe instrument, LAP. We also performed analytical modelling of the expanding two-temperature electron gas. Results: LAP data acquired within a few hundred km from the nucleus are dominated by a warm component with electron temperature typically 5-10 eV at all heliocentric distances covered (1.25 to 3.83 AU). A cold component, with temperature no higher than about 0.1 eV, appears in the data as short (few to few tens of seconds) pulses of high probe current, indicating local enhancement of plasma density as well as a decrease in electron temperature. These pulses first appeared around 3 AU and were seen for longer periods close to perihelion. The general pattern of pulse appearance follows that of neutral gas and plasma density. We have not identified any periods with only cold electrons present. The electron flux to Rosetta was always dominated by higher energies, driving the spacecraft potential to order - 10 V. Conclusions: The warm (5-10 eV) electron population observed throughout the mission is interpreted as electrons retaining the energy they obtained when released in the ionisation process. The sometimes observed cold populations with electron temperatures below 0.1 eV verify collisional cooling in the coma. The cold electrons were only observed together with the warm population. The general appearance of the cold population appears to be consistent with a Haser-like model, implicitly supporting also the coupling of ions to the neutral gas. The expanding cold plasma is unstable, forming filaments that we observe as pulses.

Thermodynamic Study on Plasma Expansion along a Divergent Magnetic Field.

PubMed

Zhang, Yunchao; Charles, Christine; Boswell, Rod

2016-01-15

Thermodynamic properties are revisited for electrons that are governed by nonlocal electron energy probability functions in a plasma of low collisionality. Measurements in a laboratory helicon double layer experiment have shown that the effective electron temperature and density show a polytropic correlation with an index of γ_{e}=1.17±0.02 along the divergent magnetic field, implying a nearly isothermal plasma (γ_{e}=1) with heat being brought into the system. However, the evolution of electrons along the divergent magnetic field is essentially an adiabatic process, which should have a γ_{e}=5/3. The reason for this apparent contradiction is that the nearly collisionless plasma is very far from local thermodynamic equilibrium and the electrons behave nonlocally. The corresponding effective electron enthalpy has a conservation relation with the potential energy, which verifies that there is no heat transferred into the system during the electron evolution. The electrons are shown in nonlocal momentum equilibrium under the electric field and the gradient of the effective electron pressure. The convective momentum of ions, which can be assumed as a cold species, is determined by the effective electron pressure and the effective electron enthalpy is shown to be the source for ion acceleration. For these nearly collisionless plasmas, the use of traditional thermodynamic concepts can lead to very erroneous conclusions regarding the thermal conductivity.

Temperature Distribution within a Cold Cap during Nuclear Waste Vitrification

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

Dixon, Derek R.; Schweiger, Michael J.; Riley, Brian J.

2015-07-21

The kinetics of the feed-to-glass conversion affects the waste vitrification rate in an electric melter. The primary area of interest in this conversion process is the cold cap, a layer of reacting feed on top of molten glass. Knowing the temperature profile within a cold cap will help determine its characteristics and relate them to the rate of glass production. The work presented here provides an experimental determination of the temperature distribution within the cold cap. Since a direct measurement of the temperature field within the cold cap is impracticable, an indirect method was developed where the textural features inmore » a laboratory-made cold cap with a high-level waste feed were mapped as a function of position using optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. To correlate the temperature distribution to microstructures within the cold cap, microstructures were identified of individual feed samples that were heat treated to set temperatures between 400°C and 1200°C and quenched. The temperature distribution within the cold cap was then established by correlating cold-cap regions with the feed samples of nearly identical structures and was compared with the temperature profile from a mathematical model.« less

Cold plate

DOEpatents

Marroquin, Christopher M.; O'Connell, Kevin M.; Schultz, Mark D.; Tian, Shurong

2018-02-13

A cold plate, an electronic assembly including a cold plate, and a method for forming a cold plate are provided. The cold plate includes an interface plate and an opposing plate that form a plenum. The cold plate includes a plurality of active areas arranged for alignment over respective heat generating portions of an electronic assembly, and non-active areas between the active areas. A cooling fluid flows through the plenum. The plenum, at the non-active areas, has a reduced width and/or reduced height relative to the plenum at the active areas. The reduced width and/or height of the plenum, and exterior dimensions of cold plate, at the non-active areas allow the non-active areas to flex to accommodate surface variations of the electronics assembly. The reduced width and/or height non-active areas can be specifically shaped to fit between physical features of the electronics assembly.

Classical relativistic model for spin dependence in a magnetized electron gas

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

Melrose, D. B.; Mushtaq, A.; TPPD, PINSTECH, P. O. Nilore Islamabad 44000

2011-05-15

The response of a cold electron gas is generalized to include the spin of the electron described by the relativistically correct quasiclassical Bargmann-Michel-Telegdi (BMT) equation. The magnetization of the electron gas is assumed to be along the background magnetic field B and the spin-dependent contribution to the response tensor is proportional to the magnitude of the magnetization. The dispersion equation is shown to be quadratic in the refractive index squared, and dispersion curves for the two wave modes are plotted for cases where the magnetic field associated with magnetization is comparable with B. Two intrinsically spin-dependent wave modes are identified:more » one bounded by two resonances and the other by two cutoffs. The counterpart of the z mode can escape without encountering a resonance or a cutoff.« less

Electromagnetic cyclotron-loss-cone instability associated with weakly relativistic electrons

NASA Technical Reports Server (NTRS)

Wong, H. K.; Wu, C. S.; Ke, F. J.; Schneider, R. S.; Ziebell, L. F.

1982-01-01

The amplification of fast extraordinary mode waves at frequencies very close to the electron cyclotron frequency, due to the presence of a population of energetic electrons with a loss-cone type distribution, is studied. Low-energy background electrons are included in the analysis. Two types of loss-cone distribution functions are considered, and it is found that the maximum growth rates for both distribution functions are of the same order of magnitude. When the thermal effects of the energetic electrons are included in the dispersion equation, the real frequencies of the waves are lower than those obtained by using the cold plasma approximation. This effect tends to enhance the growth rate. An idealized case including a parallel electric field such that the distribution function of the trapped energetic electrons is modified is also considered. It is assumed that the parallel electric field can remove the low-energy background electrons away from the source region of radiation. Both these effects increase the growth rate.

Double layers in expanding plasmas and their relevance to the auroral plasma processes

NASA Astrophysics Data System (ADS)

Singh, Nagendra; Khazanov, George

2003-04-01

When a dense plasma consisting of a cold and a sufficiently warm electron population expands, a rarefaction shock forms [, 1978]. In the expansion of the polar wind in the magnetosphere, it has been previously shown that when a sufficiently warm electron population also exists, in addition to the usual cold ionospheric one, a discontinuity forms in the electrostatic potential distribution along the magnetic field lines [, 1984]. Despite the lack of spatial resolution and the assumption of quasi-neutrality in the polar wind models, such discontinuities have been called double layers (DLs). Recently similar discontinuities have been invoked to partly explain the auroral acceleration of electrons and ions in the upward current region [, 2000]. By means of one-dimensional Vlasov simulations of expanding plasmas, for the first time we make here the connection between (1) the rarefaction shocks, (2) the discontinuities in the potential distributions, and (3) DLs. We show that when plasmas expand from opposite directions into a deep density cavity with a potential drop across it and when the plasma on the high-potential side contains hot and cold electron populations, the temporal evolution of the potential and the plasma distribution generates evolving multiple double layers with an extended density cavity between them. One of the DLs is the rarefaction-shock (RFS) and it forms by the reflections of the cold electrons coming from the high-potential side; it supports a part of the potential drop approximately determined by the hot electron temperature. The other DLs evolve from charge separations arising either from reflection of ions coming from the low-potential side or stemming from plasma instabilities; they support the rest of the potential drop. The instabilities forming these additional double layers involve electron-ion (e-i) Buneman or ion-ion (i-i) two-stream interactions. The electron-electron two-stream interactions on the high-potential side of the RFS generate electron-acoustic waves, which evolve into electron phase-space holes. The ion population originating from the low-potential side and trapped by the RFS is energized by the e-i and i-i instabilities and it eventually precipitates into the high-potential plasma along with an electron beam. Applications of these findings to the auroral plasma physics are discussed.

Double Layers in Expanding Plasmas and Their Relevance to the Auroral Plasma Processes

NASA Technical Reports Server (NTRS)

Singh, Nagendra; Khazanov, George

2003-01-01

When a dense plasma consisting of a cold and a sufficiently warm electron population expands, a rarefaction shock forms [Bezzerides et al., 1978]. In the expansion of the polar wind in the magnetosphere, it has been previously shown that when a sufficiently warm electron population also exists, in addition to the usual cold ionospheric one, a discontinuity forms in the electrostatic potential distribution along the magnetic field lines [Barakat and Schunk, 1984]. Despite the lack of spatial resolution and the assumption of quasi-neutrality in the polar wind models, such discontinuities have been called double layers (DLs). Recently similar discontinuities have been invoked to partly explain the auroral acceleration of electrons and ions in the upward current region [Ergun et al., 2000]. By means of one-dimensional Vlasov simulations of expanding plasmas, for the first time we make here the connection between (1) the rarefaction shocks, (2) the discontinuities in the potential distributions, and (3) DLs. We show that when plasmas expand from opposite directions into a deep density cavity with a potential drop across it and when the plasma on the high-potential side contains hot and cold electron populations, the temporal evolution of the potential and the plasma distribution generates evolving multiple double layers with an ,extended density cavity between them. One of the DLs is the rarefaction-shock (RFS) and it forms by the reflections of the cold electrons coming from the high-potential side; it supports a part of the potential drop approximately determined by the hot electron temperature. The other DLs evolve from charge separations arising either from reflection of ions coming from the low-potential side or stemming from plasma instabilities; they support the rest of the potential drop. The instabilities forming these additional double layers involve electron-ion (e-i) Buneman or ion-ion (i-i) two-stream interactions. The electron-electron two-stream interactions on the high-potential side of the RFS generate electron-acoustic waves, which evolve into electron phase-space holes. The ion population originating from the low-potential side and trapped by the RFS is energized by the e-i and i-i instabilities and it eventually precipitates into the high-potential plasma along with an electron beam. Applications of these findings to the auroral plasma physics are discussed.

Radiation from Accelerated Particles in Shocks and Reconnections

NASA Technical Reports Server (NTRS)

Nishikawa, K. I.; Choi, E. J.; Min, K. W.; Niemiec, J.; Zhang, B.; Hardee, P.; Mizuno, Y.; Medvedev, M.; Nordlund, A.; Frederiksen, J.;

Cooled electronic system with thermal spreaders coupling electronics cards to cold rails

DOEpatents

Chainer, Timothy J; Gaynes, Michael A; Graybill, David P; Iyengar, Madhusudan K; Kamath, Vinod; Kochuparambil, Bejoy J; Schmidt, Roger R; Schultz, Mark D; Simco, Daniel P; Steinke, Mark E

2013-07-23

Liquid-cooled electronic systems are provided which include an electronic assembly having an electronics card and a socket with a latch at one end. The latch facilitates securing of the card within the socket or removal of the card from the socket. A liquid-cooled cold rail is disposed at the one end of the socket, and a thermal spreader couples the electronics card to the cold rail. The thermal spreader includes first and second thermal transfer plates coupled to first and second surfaces on opposite sides of the card, and thermally conductive extensions extending from end edges of the plates, which couple the respective transfer plates to the liquid-cooled cold rail. The thermally conductive extensions are disposed to the sides of the latch, and the card is securable within or removable from the socket using the latch without removing the cold rail or the thermal spreader.

A study on the steady-state solutions of a Bursian diode in the presence of transverse magnetic field, when the electrons of the injected beam are turned back partially or totally

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

Pramanik, Sourav; Chakrabarti, Nikhil; Kuznetsov, V. I.

2015-11-15

The properties of a steady-state planar vacuum diode driven by a cold electron beam have been investigated in the presence of an external transverse magnetic field, employing both the Eulerian and the Lagrangian formalism. With the help of a numerical scheme, the features of the steady-state solutions have been explored in the Eulerian frame, particularly for the case that corresponds to the potential distributions with a virtual cathode. However, exact analytical formulae for the potential and velocity profiles within the inter-electrode region have been derived with the Lagrangian description. In contrast to the previous work [Phys. Plasmas 22, 042110 (2015)],more » here we have emphasized the situation when electrons are reflected back to the emitter by the magnetic field. Both partial and complete reflection of the electrons due to the magnetic field have been taken into account. Using the emitter electric field as a characteristic parameter, steady-state solutions have been evaluated for specific values of diode length, applied voltage, and magnetic field strength. It has been shown that, due to the inclusion of the magnetic field, a new region of non-unique solutions appears. An external magnetic field seems to have a profound effect in controlling fast electronic switches based on the Bursian diode.« less

Overview of the electric propulsion plasma diagnostics suite for the VASIMR VX-200 testbed

NASA Astrophysics Data System (ADS)

Olsen, Christopher; Longmier, Benjamin; Ballenger, Maxwell; Squire, Jared; Glover, Tim; Carter, Mark; Bering, Edgar; Giambusso, Matthew

2012-10-01

Descriptions of the various plasma diagnostics and data analysis methods are given for instruments used in high power (> 100 kW) electric propulsion testing. These include planar Langmuir probes, an articulating retarding potential analyzer, a double Langmuir probe, a multi-axis magnetometer, a high frequency electric field probe, microwave interferometer, and momentum flux targets. These diagnostics have been used to measure the efficiencies of the thruster, plasma source, ion cyclotron resonance booster, and magnetic nozzle as well as used to explore physical phenomena in the plume such as ion/electron detachment, plasma turbulence, and magnetic field line stretching. Typical plume parameters range up to 10^13 cm-3 electron density, 1 kG applied magnetic fields, ion energies in excess of 150 eV, and cold electrons (2 -- 5 eV) with a spatial measurement range over 2 m.

The Earth's Plasmasphere

NASA Technical Reports Server (NTRS)

Gallagher, D. L.

2015-01-01

The Earth's plasmasphere is an inner part of the magneteosphere. It is located just outside the upper ionosphere located in Earth's atmosphere. It is a region of dense, cold plasma that surrounds the Earth. Although plasma is found throughout the magnetosphere, the plasmasphere usually contains the coldest plasma. Here's how it works: The upper reaches of our planet's atmosphere are exposed to ultraviolet light from the Sun, and they are ionized with electrons that are freed from neutral atmospheric particles. The results are electrically charged negative and positive particles. The negative particles are electrons, and the positive particles are now called ions (formerly atoms and molecules). If the density of these particles is low enough, this electrically charged gas behaves differently than it would if it were neutral. Now this gas is called plasma. The atmospheric gas density becomes low enough to support the conditions for a plasma around earth at about 90 kilometers above Earth's surface. The electrons in plasma gain more energy, and they are very low in mass. They move along Earth's magnetic field lines and their increased energy is enough to escape Earth's gravity. Because electrons are very light, they don't have to gain too much kinetic energy from the Sun's ultraviolet light before gravity loses its grip on them. Gravity is not all that holds them back, however. As more and more electrons begin to escape outward, they leave behind a growing net positive electric charge in the ionosphere and create a growing net negative electric charge above the ionosphere; an electric field begins to develop (the Pannekoek-Rosseland E-field). Thus, these different interacting charges result in a positively charged ionosphere and negatively charged region of space above it. Very quickly this resulting electric field opposed upward movement of the electrons out of the ionosphere. The electrons still have this increased energy, however, so the electric field doesn't just go away. Instead the ions react to the electric field and are attracted to it. They begin to move upward out of the ionosphere too. Since all this happens on a small scale, it simply looks like the electrons and ions move out of the ionosphere together. Ultimately the effect is that the lighter ions of hydrogen, helium and oxygen are able to escape from the ionosphere. For a planet like Earth with a strong planetary magnetic field, these outward moving particles remain trapped near the planet unless other processes further draw them away and into interplanetary space. As is always the case with nature, there is much more story to tell about this "upwardly mobile" plasma and these other processes. Over only a short time period of hours and days this escaping plasma can, in some places, build up in concentration until an equilibrium is reached where as much plasma flows inward into the ionosphere as flows outward. This "donut shaped" region of cold (about 1 electron volt in energy) plasma encircling the planet is called the plasmasphere. Because of space weather storms (kind of a generic phrase for those other processes) this cold and dense plasmaspheric plasma can actually end up all over the place. Generally, that region of space where plasma from the ionosphere has the time to build up to become identified as the plasmasphere rotates or nearly rotates with the Earth. That region shrinks in size with increased space weather activity and expands or refills during times of inactivity. As it shrinks with increasing activity, some of the plasmasphere is drawn away from its main body (plasmaspheric erosion) in the sunward direction toward the boundary in space between that region dominated by Earth's magnetic field and the much larger region dominated by the Sun's magnetic field. The region dominated by Earth's magnetic field is called the magnetosphere. The larger Sun dominated region is called the heliosphere.

A fluid description of plasma double-layers

NASA Technical Reports Server (NTRS)

Levine, J. S.; Crawford, F. W.

1979-01-01

The space-charge double-layer that forms between two plasmas with different densities and thermal energies was investigated using three progressively realistic models which are treated by fluid theory, and take into account four species of particles: electrons and ions reflected by the double-layer, and electrons and ions transmitted through it. The two plasmas are assumed to be cold, and the self-consistent potential, electric field and space-charge distributions within the double-layer are determined. The effects of thermal velocities are taken into account for the reflected particles, and the modifications to the cold plasma solutions are established. Further modifications due to thermal velocities of the transmitted particles are examined. The applicability of a one dimensional fluid description, rather than plasma kinetic theory, is discussed. Theoretical predictions are compared with double layer potentials and lengths deduced from laboratory and space plasma experiments.

Microstructure and mechanical behavior of pulsed laser surface melted AISI D2 cold work tool steel

NASA Astrophysics Data System (ADS)

Yasavol, N.; Abdollah-zadeh, A.; Ganjali, M.; Alidokht, S. A.

2013-01-01

D2 cold work tool steel (CWTS) was subjected to pulse laser surface melting (PLSM) at constant frequency of 20 Hz Nd: YAG laser with different energies, scanning rate and pulse durations radiated to the surface. Characterizing the PLSM, with optical and field emission scanning electron microscopy, electron backscattered diffraction and surface hardness mapping technique was used to evaluate the microhardness and mechanical behavior of different regions of melting pool. Increasing laser energy and reducing the laser scanning rate results in deeper melt pool formation. Moreover, PLSM has led to entirely dissolution of the carbides and re-solidification of cellular/dendritic structure of a fine scale surrounded by a continuous interdendritic network. This caused an increase in surface microhardness, 2-4 times over that of the base metal.

Particle-in-cell studies of fast-ion slowing-down rates in cool tenuous magnetized plasma

NASA Astrophysics Data System (ADS)

Evans, Eugene S.; Cohen, Samuel A.; Welch, Dale R.

2018-04-01

We report on 3D-3V particle-in-cell simulations of fast-ion energy-loss rates in a cold, weakly-magnetized, weakly-coupled plasma where the electron gyroradius, ρe, is comparable to or less than the Debye length, λDe, and the fast-ion velocity exceeds the electron thermal velocity, a regime in which the electron response may be impeded. These simulations use explicit algorithms, spatially resolve ρe and λDe, and temporally resolve the electron cyclotron and plasma frequencies. For mono-energetic dilute fast ions with isotropic velocity distributions, these scaling studies of the slowing-down time, τs, versus fast-ion charge are in agreement with unmagnetized slowing-down theory; with an applied magnetic field, no consistent anisotropy between τs in the cross-field and field-parallel directions could be resolved. Scaling the fast-ion charge is confirmed as a viable way to reduce the required computational time for each simulation. The implications of these slowing down processes are described for one magnetic-confinement fusion concept, the small, advanced-fuel, field-reversed configuration device.

Method of depositing multi-layer carbon-based coatings for field emission

DOEpatents

Sullivan, John P.; Friedmann, Thomas A.

1999-01-01

A novel field emitter device for cold cathode field emission applications, comprising a multi-layer resistive carbon film. The multi-layered film of the present invention is comprised of at least two layers of a resistive carbon material, preferably amorphous-tetrahedrally coordinated carbon, such that the resistivities of adjacent layers differ. For electron emission from the surface, the preferred structure comprises a top layer having a lower resistivity than the bottom layer. For edge emitting structures, the preferred structure of the film comprises a plurality of carbon layers, wherein adjacent layers have different resistivities. Through selection of deposition conditions, including the energy of the depositing carbon species, the presence or absence of certain elements such as H, N, inert gases or boron, carbon layers having desired resistivities can be produced. Field emitters made according the present invention display improved electron emission characteristics in comparison to conventional field emitter materials.

Method of depositing multi-layer carbon-based coatings for field emission

DOEpatents

Sullivan, J.P.; Friedmann, T.A.

1999-08-10

A novel field emitter device is disclosed for cold cathode field emission applications, comprising a multi-layer resistive carbon film. The multi-layered film of the present invention is comprised of at least two layers of a resistive carbon material, preferably amorphous-tetrahedrally coordinated carbon, such that the resistivities of adjacent layers differ. For electron emission from the surface, the preferred structure comprises a top layer having a lower resistivity than the bottom layer. For edge emitting structures, the preferred structure of the film comprises a plurality of carbon layers, wherein adjacent layers have different resistivities. Through selection of deposition conditions, including the energy of the depositing carbon species, the presence or absence of certain elements such as H, N, inert gases or boron, carbon layers having desired resistivities can be produced. Field emitters made according the present invention display improved electron emission characteristics in comparison to conventional field emitter materials. 8 figs.

Small amplitude two dimensional electrostatic excitations in a magnetized dusty plasma with q-distributed electrons

NASA Astrophysics Data System (ADS)

Khan, Shahab Ullah; Adnan, Muhammad; Qamar, Anisa; Mahmood, Shahzad

2016-07-01

The propagation of linear and nonlinear electrostatic waves is investigated in magnetized dusty plasma with stationary negatively or positively charged dust, cold mobile ions and non-extensive electrons. Two normal modes are predicted in the linear regime, whose characteristics are investigated parametrically, focusing on the effect of electrons non-extensivity, dust charge polarity, concentration of dust and magnetic field strength. Using the reductive perturbation technique, a Zakharov-Kuznetsov (ZK) type equation is derived which governs the dynamics of small-amplitude solitary waves in magnetized dusty plasma. The properties of the solitary wave structures are analyzed numerically with the system parameters i.e. electrons non-extensivity, concentration of dust, polarity of dust and magnetic field strength. Following Allen and Rowlands (J. Plasma Phys. 53:63, 1995), we have shown that the pulse soliton solution of the ZK equation is unstable, and have analytically traced the dependence of the instability growth rate on the nonextensive parameter q for electrons, dust charge polarity and magnetic field strength. The results should be useful for understanding the nonlinear propagation of DIA solitary waves in laboratory and space plasmas.

Filamentation instability in a quantum magnetized plasma

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

Bret, A.; and Instituto de Investigaciones Energeticas y Aplicaciones Industriales, Campus Universitario de Ciudad Real, 13071 Ciudad Real

2008-02-15

The filamentation instability occurring when a nonrelativistic electron beam passes through a quantum magnetized plasma is investigated by means of a cold quantum magnetohydrodynamic model. It is proved that the instability can be completely suppressed by quantum effects if and only if a finite magnetic field is present. A dimensionless parameter is identified that measures the strength of quantum effects. Strong quantum effects allow for a much smaller magnetic field to suppress the instability than in the classical regime.

Field Emission Enhancement and the Field-Screening Effect Reduction using Carbon Nanopipettes as Cold Cathodes

NASA Astrophysics Data System (ADS)

Safir, Abdelilah; Mudd, David; Yazdanpanah, Mehdi; Dobrokhotov, Vladimir; Sumanasekera, Gamini; Cohn, Robert

2008-03-01

In this work, we report a recent experimental study of high emission current densities exceeding 10mA/cm^2 and breakdown electric field lower than 5Volts/μm from novel cold cathodes such as conical shaped carbon nanopipettes (CNP). CNP were grown by CVD on Pt wire and have apex as sharp as 10nm with length between 3-6μm. The emission experiments were conducted under vacuum in a scanning electron microscope for individual CNP and in a dedicated chamber for bulk samples. CNP's conical bases and low density contribute significantly to the reduction of the screening effect and to the field emission enhancement. The experimental value for the field enhancement factor, γ, was about 867. Comparing emission results taken from CNP and aligned multiwall carbon nanotubes (MWNT) show that the ratio between γCNP and γMWNT is ˜1.6 which contributes to the reduction of screening effect. The emission from multilayers of graphene was also studied. High emission current (20μA) demonstrates promising emission properties of graphene.

A strained silicon cold electron bolometer using Schottky contacts

NASA Astrophysics Data System (ADS)

Brien, T. L. R.; Ade, P. A. R.; Barry, P. S.; Dunscombe, C.; Leadley, D. R.; Morozov, D. V.; Myronov, M.; Parker, E. H. C.; Prest, M. J.; Prunnila, M.; Sudiwala, R. V.; Whall, T. E.; Mauskopf, P. D.

2014-07-01

We describe optical characterisation of a strained silicon cold electron bolometer (CEB), operating on a 350 mK stage, designed for absorption of millimetre-wave radiation. The silicon cold electron bolometer utilises Schottky contacts between a superconductor and an n++ doped silicon island to detect changes in the temperature of the charge carriers in the silicon, due to variations in absorbed radiation. By using strained silicon as the absorber, we decrease the electron-phonon coupling in the device and increase the responsivity to incoming power. The strained silicon absorber is coupled to a planar aluminium twin-slot antenna designed to couple to 160 GHz and that serves as the superconducting contacts. From the measured optical responsivity and spectral response, we calculate a maximum optical efficiency of 50% for radiation coupled into the device by the planar antenna and an overall noise equivalent power, referred to absorbed optical power, of 1.1×10-16 W Hz-1/2 when the detector is observing a 300 K source through a 4 K throughput limiting aperture. Even though this optical system is not optimized, we measure a system noise equivalent temperature difference of 6 mK Hz-1/2. We measure the noise of the device using a cross-correlation of time stream data, measured simultaneously with two junction field-effect transistor amplifiers, with a base correlated noise level of 300 pV Hz-1/2 and find that the total noise is consistent with a combination of photon noise, current shot noise, and electron-phonon thermal noise.

Fabricating cooled electronic system with liquid-cooled cold plate and thermal spreader

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

Chainer, Timothy J.; Graybill, David P.; Iyengar, Madhusudan K.

Methods are provided for facilitating cooling of an electronic component. The method includes providing a liquid-cooled cold plate and a thermal spreader associated with the cold plate. The cold plate includes multiple coolant-carrying channel sections extending within the cold plate, and a thermal conduction surface with a larger surface area than a surface area of the component to be cooled. The thermal spreader includes one or more heat pipes including multiple heat pipe sections. One or more heat pipe sections are partially aligned to a first region of the cold plate, that is, where aligned to the surface to bemore » cooled, and partially aligned to a second region of the cold plate, which is outside the first region. The one or more heat pipes facilitate distribution of heat from the electronic component to coolant-carrying channel sections of the cold plate located in the second region of the cold plate.« less

Fabricating cooled electronic system with liquid-cooled cold plate and thermal spreader

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

Chainer, Timothy J.; Graybill, David P.; Iyengar, Madhusudan K.

Methods are provided for facilitating cooling of an electronic component. The methods include providing a liquid-cooled cold plate and a thermal spreader associated with the cold plate. The cold plate includes multiple coolant-carrying channel sections extending within the cold plate, and a thermal conduction surface with a larger surface area than a surface area of the component to be cooled. The thermal spreader includes one or more heat pipes including multiple heat pipe sections. One or more heat pipe sections are partially aligned to a first region of the cold plate, that is, where aligned to the surface to bemore » cooled, and partially aligned to a second region of the cold plate, which is outside the first region. The one or more heat pipes facilitate distribution of heat from the electronic component to coolant-carrying channel sections of the cold plate located in the second region of the cold plate.« less

Organic nanowire hierarchy over fabric platform for flexible cold cathode

NASA Astrophysics Data System (ADS)

Maiti, Soumen; Narayan Maiti, Uday; Pal, Shreyasi; Chattopadhyay, Kalyan Kumar

2013-11-01

Organic charge transfer (CT) complexes initiated a growing interest in modern electronic devices owing to their easy processability and unique characteristics. In this work, three-dimensional field emitters comprising metal-organic charge transfer complex nanostructures of AgTCNQ and CuTCNQ (TCNQ, 7,7,8,8-tetracyanoquinodimethane) over flexible fabric substrate are realized. Deliberate control over the reaction parameter during organic solid phase reaction leads to modification in structural parameters of the nanowires (i.e. length, diameter) as well as their arrangement atop the carbon fibers. The optimized arrays of AgTCNQ and CuTCNQ nanowires exhibit excellent field electron emission performance with very low turn-on (1.72 and 2.56 V μm-1) and threshold fields (4.21 and 6.33 V μm-1) respectively, which are comparable to those of the best organic field emitters reported to date. The underlying conducting carbon cloth with special woven-like geometry not only offers a flexible platform for nanowire growth, but also provides an additional field enhancement to ease the electron emission.

Fabrication of Gate-Electrode Integrated Carbon-Nanotube Bundle Field Emitters

NASA Technical Reports Server (NTRS)

Toda, Risaku; Bronikowski, Michael; Luong, Edward; Manohara, Harish

2008-01-01

A continuing effort to develop carbon-nanotube-based field emitters (cold cathodes) as high-current-density electron sources has yielded an optimized device design and a fabrication scheme to implement the design. One major element of the device design is to use a planar array of bundles of carbon nanotubes as the field-emission tips and to optimize the critical dimensions of the array (principally, heights of bundles and distances between them) to obtain high area-averaged current density and high reliability over a long operational lifetime a concept that was discussed in more detail in Arrays of Bundles of Carbon Nanotubes as Field Emitters (NPO-40817), NASA Tech Briefs, Vol. 31, No. 2 (February 2007), page 58. Another major element of the design is to configure the gate electrodes (anodes used to extract, accelerate, and/or focus electrons) as a ring that overhangs a recess wherein the bundles of nanotubes are located, such that by virtue of the proximity between the ring and the bundles, a relatively low applied potential suffices to generate the large electric field needed for emission of electrons.

Methods of determining electron concentrations in the magnetosphere from nose whistlers

NASA Technical Reports Server (NTRS)

Park, C. G.

1972-01-01

Whistler propagation in the magnetosphere was studied in detail to find accurate and economical means of determining the path latitude and the electron concentration along the path from whistler parameters of nose frequency and travel time at the nose. Longitudinal propagation in field aligned whistler ducts of cold plasma was assumed, and the earth's magnetic field was approximated by a centered dipole. The effects of whistler propagation in the earth-ionosphere waveguide and through the conjugate ionospheres were treated as small perturbations. Several alternative methods are described so that the most economical method may be chosen depending on the desired accuracy and the availability of a computer or a calculator.

Mu2e Transport Solenoid Cold-Mass Alignment Issues

DOE PAGES

Lopes, M.; Ambrosio, G.; Badgley, K.; ...

2017-01-05

The Muon-to-electron conversion experiment (Mu2e) at Fermilab is designed to explore charged lepton flavor violation. It is composed of three large superconducting solenoids: the Production Solenoid (PS), the Transport Solenoid (TS) and the Detector Solenoid (DS). The TS is formed by two magnets: TS upstream (TSu) and downstream (TSd). Each has its own cryostat and power supply. Tolerance sensitivity studies of the position and angular alignment of each coil in this magnet system were performed in the past with the objective to demonstrate that the magnet design meets all the field requirements. Furthermore, the alignment of the cold-masses is criticalmore » to maximize the transmission of muons and to avoid possible backgrounds that would reduce the sensitivity of the experiment. Each TS magnet cold-mass can be individually aligned. Here, we discuss implications of the alignment of the TS cold-masses in terms of the displacement of the magnetic center. Consideration of the practical mechanical limits are also presented.« less

Actively controlling coolant-cooled cold plate configuration

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

Chainer, Timothy J.; Parida, Pritish R.

A method is provided to facilitate active control of thermal and fluid dynamic performance of a coolant-cooled cold plate. The method includes: monitoring a variable associated with at least one of the coolant-cooled cold plate or one or more electronic components being cooled by the cold plate; and dynamically varying, based on the monitored variable, a physical configuration of the cold plate. By dynamically varying the physical configuration, the thermal and fluid dynamic performance of the cold plate are adjusted to, for example, optimally cool the one or more electronic components, and at the same time, reduce cooling power consumptionmore » used in cooling the electronic component(s). The physical configuration can be adjusted by providing one or more adjustable plates within the coolant-cooled cold plate, the positioning of which may be adjusted based on the monitored variable.« less

Phenomenological theory of laser-plasma interaction in ``bubble'' regime

NASA Astrophysics Data System (ADS)

Kostyukov, I.; Pukhov, A.; Kiselev, S.

2004-11-01

The electron trapping in the "bubble" regime of laser-plasma interaction as proposed by Pukhov and Meyer-ter-Vehn [A. Pukhov and J. Meyer-ter-Vehn, Appl. Phys. B 74, 355 (2002)] is studied. In this regime the laser pulse generates a solitary plasma electron cavity: the bubble. It is free from the cold plasma electrons and runs with nearly light velocity. The present work discusses the form of the bubble and the spatial distribution of electromagnetic fields within the cavity. We extend the one-dimensional electron capture theory to the three-dimensional case. It is shown that the bubble can trap plasma electrons. The trapping condition is derived and the trapping cross section is estimated. Electron motion in the self-generated electron bunch is investigated. Estimates for the maximum of electron bunch energy and the bunch density are provided.

Nonlinear excitations for the positron acoustic shock waves in dissipative nonextensive electron-positron-ion plasmas

NASA Astrophysics Data System (ADS)

Saha, Asit

2017-03-01

Positron acoustic shock waves (PASHWs) in unmagnetized electron-positron-ion (e-p-i) plasmas consisting of mobile cold positrons, immobile positive ions, q-nonextensive distributed electrons, and hot positrons are studied. The cold positron kinematic viscosity is considered and the reductive perturbation technique is used to derive the Burgers equation. Applying traveling wave transformation, the Burgers equation is transformed to a one dimensional dynamical system. All possible vector fields corresponding to the dynamical system are presented. We have analyzed the dynamical system with the help of potential energy, which helps to identify the stability and instability of the equilibrium points. It is found that the viscous force acting on cold mobile positron fluid is a source of dissipation and is responsible for the formation of the PASHWs. Furthermore, fully nonlinear arbitrary amplitude positron acoustic waves are also studied applying the theory of planar dynamical systems. It is also observed that the fundamental features of the small amplitude and arbitrary amplitude PASHWs are significantly affected by the effect of the physical parameters q e , q h , μ e , μ h , σ , η , and U. This work can be useful to understand the qualitative changes in the dynamics of nonlinear small amplitude and fully nonlinear arbitrary amplitude PASHWs in solar wind, ionosphere, lower part of magnetosphere, and auroral acceleration regions.

Particle-in-cell studies of fast-ion slowing-down rates in cool tenuous magnetized plasma

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

Evans, Eugene S.; Cohen, Samuel A.; Welch, Dale R.

We report on 3D-3V particle-in-cell simulations of fast-ion energy-loss rates in a cold, weakly-magnetized, weakly-coupled plasma where the electron gyroradius, ρe, is comparable to or less than the Debye length, λ De, and the fast-ion velocity exceeds the electron thermal velocity, a regime in which the electron response may be impeded. These simulations use explicit algorithms, spatially resolve ρ e and λ De, and temporally resolve the electron cyclotron and plasma frequencies. For mono-energetic dilute fast ions with isotropic velocity distributions, these scaling studies of the slowing-down time, τ s, versus fast-ion charge are in agreement with unmagnetized slowing-down theory;more » with an applied magnetic field, no consistent anisotropy between τs in the cross-field and field-parallel directions could be resolved. Scaling the fast-ion charge is confirmed as a viable way to reduce the required computational time for each simulation. In conclusion, the implications of these slowing down processes are described for one magnetic-confinement fusion concept, the small, advanced-fuel, field-reversed configuration device.« less

Particle-in-cell studies of fast-ion slowing-down rates in cool tenuous magnetized plasma

DOE PAGES

Evans, Eugene S.; Cohen, Samuel A.; Welch, Dale R.

2018-04-05

We report on 3D-3V particle-in-cell simulations of fast-ion energy-loss rates in a cold, weakly-magnetized, weakly-coupled plasma where the electron gyroradius, ρe, is comparable to or less than the Debye length, λ De, and the fast-ion velocity exceeds the electron thermal velocity, a regime in which the electron response may be impeded. These simulations use explicit algorithms, spatially resolve ρ e and λ De, and temporally resolve the electron cyclotron and plasma frequencies. For mono-energetic dilute fast ions with isotropic velocity distributions, these scaling studies of the slowing-down time, τ s, versus fast-ion charge are in agreement with unmagnetized slowing-down theory;more » with an applied magnetic field, no consistent anisotropy between τs in the cross-field and field-parallel directions could be resolved. Scaling the fast-ion charge is confirmed as a viable way to reduce the required computational time for each simulation. In conclusion, the implications of these slowing down processes are described for one magnetic-confinement fusion concept, the small, advanced-fuel, field-reversed configuration device.« less

Vacuum encapsulated hermetically sealed diamond amplified cathode capsule and method for making same

DOEpatents

Rao, Triveni; Walsh, John; Gangone, Elizabeth

2014-12-30

A vacuum encapsulated, hermetically sealed cathode capsule for generating an electron beam of secondary electrons, which generally includes a cathode element having a primary emission surface adapted to emit primary electrons, an annular insulating spacer, a diamond window element comprising a diamond material and having a secondary emission surface adapted to emit secondary electrons in response to primary electrons impinging on the diamond window element, a first cold-weld ring disposed between the cathode element and the annular insulating spacer and a second cold-weld ring disposed between the annular insulating spacer and the diamond window element. The cathode capsule is formed by a vacuum cold-weld process such that the first cold-weld ring forms a hermetical seal between the cathode element and the annular insulating spacer and the second cold-weld ring forms a hermetical seal between the annular spacer and the diamond window element whereby a vacuum encapsulated chamber is formed within the capsule.

Ion-acoustic supersolitons and double layers in plasmas with nonthermal electrons

NASA Astrophysics Data System (ADS)

Gao, D.-N.; Zhang, J.; Yang, Y.; Duan, W.-S.

2017-08-01

Supersoliton (SS) can be mainly featured in two ways, namely, by focusing on subsidiary maxima on its electric field or by meeting the requirement that the appropriate Sagdeev pseudopotential (SP) has three local extrema between the equilibrium conditions and its amplitude. In this paper, by using the SP method, double layers and ion-acoustic SSs are studied in a plasma with Maxwellian cold electrons, nonthermal hot electrons, and fluid ions. The existence of the SS regime in parameter space is obtained in a methodical fashion. The existence domains for positive solitary waves are also presented. It is found that there is no SSs at the acoustic speed.

Study of electron transport across the magnetic filter of NIO1 negative ion source

NASA Astrophysics Data System (ADS)

Veltri, P.; Sartori, E.; Cavenago, M.; Serianni, G.; Barbisan, M.; Zaniol, B.

2017-08-01

In the framework of the accompanying activities in support to the ITER NBI test facility, a relatively compact radiofrequency (RF) ion source, named NIO1 (Negative Ion Optimization, phase 1) was developed in Padua, Italy, in collaboration between Consorzio RFX and INFN. Negative hydrogen ions are formed in a cold, inductively coupled plasma with a 2MHz, 2.5 kW external antenna. A low electron energy is necessary to increase the survival probability of negative ions in the proximity of the extraction area. This goal is accomplished by means of a transversal magnetic field, confining the high energy electrons better than the colder electrons. In NIO1, this filter field can cover different topologies, exploiting different set of magnets and high current paths. In this contribution we study the property of the plasma in the vicinity of the extraction region for two different B field configurations. For this experiment the source was operated in pure volume conditions, in hydrogen and oxygen plasmas. The experimental data, measured by spectroscopic means, is interpreted also with the support of finite element analyses simulations of the magnetic field and a dedicated particle in cell (PIC) numerical model for the electron transport across it, including Coulomb and gas collisions.

Formation of Electrostatic Potential Drops in the Auroral Zone

NASA Technical Reports Server (NTRS)

Schriver, D.; Ashour-Abdalla, M.; Richard, R. L.

2001-01-01

In order to examine the self-consistent formation of large-scale quasi-static parallel electric fields in the auroral zone on a micro/meso scale, a particle in cell simulation has been developed. The code resolves electron Debye length scales so that electron micro-processes are included and a variable grid scheme is used such that the overall length scale of the simulation is of the order of an Earth radii along the magnetic field. The simulation is electrostatic and includes the magnetic mirror force, as well as two types of plasmas, a cold dense ionospheric plasma and a warm tenuous magnetospheric plasma. In order to study the formation of parallel electric fields in the auroral zone, different magnetospheric ion and electron inflow boundary conditions are used to drive the system. It has been found that for conditions in the primary (upward) current region an upward directed quasi-static electric field can form across the system due to magnetic mirroring of the magnetospheric ions and electrons at different altitudes. For conditions in the return (downward) current region it is shown that a quasi-static parallel electric field in the opposite sense of that in the primary current region is formed, i.e., the parallel electric field is directed earthward. The conditions for how these different electric fields can be formed are discussed using satellite observations and numerical simulations.

Propagation of Ion Solitary Pulses in Dense Astrophysical Electron-Positron-Ion Magnetoplasmas

NASA Astrophysics Data System (ADS)

Ata-Ur-Rahman; A. Khan, S.; Qamar, A.

2015-12-01

In this paper, we theoretically investigate the existence and propagation of low amplitude nonlinear ion waves in a dense plasma under the influence of a strong magnetic field. The plasma consists of ultra-relativistic and degenerate electrons and positrons and non-degenerate cold ions. Firstly, the appearance of two distinct linear modes and their evolution is studied by deriving a dispersion equation with the aid of Fourier analysis. Secondly, the dynamics of low amplitude ion solitary structures is investigated via a Korteweg-de Vries equation derived by employing a reductive perturbation method. The effects of various plasma parameters like positron concentration, strength of magnetic field, obliqueness of field, etc., are discussed in detail. At the end, analytical results are supplemented through numerical analysis by using typical representative parameters consistent with degenerate and ultra-relativistic magnetoplasmas of astrophysical regimes.

Hybrid fluid-particle simulation of whistler-mode waves in a compressed dipole magnetic field: Implications for dayside high-latitude chorus

NASA Astrophysics Data System (ADS)

da Silva, C. L.; Wu, S.; Denton, R. E.; Hudson, M. K.; Millan, R. M.

2017-01-01

In this work we present a methodology for simulating whistler-mode waves self-consistently generated by electron temperature anisotropy in the inner magnetosphere. We present simulation results using a hybrid fluid/particle-in-cell code that treats the hot, anisotropic (i.e., ring current) electron population as particles and the background (i.e., the cold and inertialess) electrons as fluid. Since the hot electrons are only a small fraction of the total population, warm (and isotropic) particle electrons are added to the simulation to increase the fraction of particles with mass, providing a more accurate characterization of the wave dispersion relation. Ions are treated as a fixed background of positive charge density. The plasma transport equations are coupled to Maxwell's equations and solved in a meridional plane (a 2-D simulation with 3-D fields). We use a curvilinear coordinate system that follows the topological curvature of Earth's geomagnetic field lines, based on an analytic expression for a compressed dipole magnetic field. Hence, we are able to simulate whistler wave generation at dawn (pure dipole field lines) and dayside (compressed dipole) by simply adjusting one scalar quantity. We demonstrate how, on the dayside, whistler-mode waves can be locally generated at a range of high latitudes, within pockets of minimum magnetic field, and propagate equatorward. The obtained dayside waves (in a compressed dipole field) have similar amplitude and frequency content to their dawn sector counterparts (in a pure dipole field) but tend to propagate more field aligned.

Ion-acoustic and electron-acoustic type nonlinear waves in dusty plasmas

NASA Astrophysics Data System (ADS)

Volosevich, A.-V.; Meister, C.-V.

2003-04-01

In the present work, two three-dimensional nonlinear theoretical models of electrostatic solitary waves are investigated within the frame of magnetohydrodynamics. Both times, a multi-component plasma is considered, which consists of hot electrons with a rather flexible distribution function, hot ions with Boltzmann-type distribution, and (negatively as well as positively charged) dust. Additionally, cold ion beams are taken into account in the model to study ion-acoustic structures (IAS), and cold electron beams are included into the model to investigate electron-acoustic structures (EAS). The numerical results of the considered theoretical models allow to make the following conclusions: 1) Electrostatic structures with negative potential (of rarefaction type) are formed both in the IAS model and in the EAS model, but structures with negative potential (of compressional type) are formed in the IAS model only. 2) The intervals of various plasma parameters (velocities of ion and electron beams, temperatures, densities of the plasma components, ions' masses), for which the existence of IAS and EAS solitary waves and structures is possible, are calculated. 3) Further, the parameters of the electrostatic structures (wave amplitudes, scales along and perpendicular to the magnetic field, velocities) are estimated. 4) The application of the present numerical simulation for multi-component plasmas to various astrophysical systems under different physical conditions is discussed.

Laboratory studies of magnetic anomaly effects on electric potential distributions near the lunar surface

NASA Astrophysics Data System (ADS)

Wang, X.; Robertson, S. H.; Horanyi, M.; NASA Lunar Science Institute: Colorado CenterLunar Dust; Atmospheric Studies

2011-12-01

The Moon does not have a global magnetic field, unlike the Earth, rather it has strong crustal magnetic anomalies. Data from Lunar Prospector and SELENE (Kaguya) observed strong interactions between the solar wind and these localized magnetic fields. In the laboratory, a configuration of a horseshoe permanent magnet below an insulating surface is used as an analogue of lunar crustal magnetic anomalies. Plasmas are created above the surface by a hot filament discharge. Potential distributions are measured with an emissive probe and show complex spatial structures. In our experiments, electrons are magnetized with gyro-radii r smaller than the distance from the surface d (r < d) and ions are un-magnetized with r > d. Unlike negative charging on surfaces with no magnetic fields, the surface potential at the center of the magnetic dipole is found close to the plasma bulk potential. The surface charging is dominated by the cold unmagnetized ions, while the electrons are shielded away. A potential minimum is formed between the center of the surface and the bulk plasma, most likely caused by the trapped electrons between the two magnetic mirrors at the cusps. The value of the potential minimum with respect to the bulk plasma potential decreases with increasing plasma density and neutral pressure, indicating that the mirror-trapped electrons are scattered by electron-electron and electron-neutral collisions. The potential at the two cusps are found to be more negative due to the electrons following the magnetic field lines onto the surface.

Electron-acoustic solitary waves in dense quantum electron-ion plasmas

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

Misra, A. P.; Shukla, P. K.; Bhowmik, C.

2007-08-15

A quantum hydrodynamic (QHD) model is used to investigate the propagation characteristics of nonlinear electron-acoustic solitary waves (EASWs) in a dense quantum plasma whose constituents are two groups of electrons: one inertial cold electrons and other inertialess hot electrons, and the stationary ions which form the neutralizing background. By using the standard reductive perturbation technique, a Kadomtsev-Petviashvili (KP) equation, which governs the dynamics of EASWs, is derived in both spherical and cylindrical geometry. The effects of cold electrons and the density correlations due to quantum fluctuations on the profiles of the amplitudes and widths of the solitary structures are examinedmore » numerically. The nondimensional parameter {delta}=n{sub c0}/n{sub h0}, which is the equilibrium density ratio of the cold to hot electron component, is shown to play a vital role in the formation of both bright and dark solitons. It is also found that the angular dependence of the physical quantities and the presence of cold electrons in a quantum plasma lead to the coexistence of some new interesting novel solitary structures quite distinctive from the classical ones.« less

Effect of parallel refraction on magnetospheric upper hybrid waves

NASA Technical Reports Server (NTRS)

Engel, J.; Kennel, C. F.

1984-01-01

Large amplitude (not less than 10 mV/m) electrostatic plasma waves near the upper hybrid (UH) frequency have been observed from 0 to 50 deg magnetic latitude (MLAT) during satellite plasma-pause crossings. A three-dimensional numerical ray-tracing calculation, based on an electron distribution measured during a GEOS 1 dayside intense upper-hybrid wave event, suggests how UH waves might achieve such large amplitudes away from the geomagnetic equator. Refractive effects largely control the wave amplification and, in particular, the unavoidable refraction due to parallel geomagnetic field gradients restricts growth to levels below those observed. However, a cold electron density gradient parallel to the field can lead to upper hybrid wave growth that can account for the observed emission levels.

Electron acoustic solitons in magneto-rotating electron-positron-ion plasma with nonthermal electrons and positrons

NASA Astrophysics Data System (ADS)

Jilani, K.; Mirza, Arshad M.; Iqbal, J.

2015-02-01

The propagation of electron acoustic solitary waves (EASWs) in a magneto-rotating electron-positron-ion (epi) plasma containing cold dynamical electrons, nonthermal electrons and positrons obeying Cairns' distribution have been explored in the stationary background of massive positive ions. Through the linear dispersion relation (LDR) the effects of nonthermal components, magnetic field and rotation have been analyzed, wherein, various limiting cases have been deduced from the LDR. For nonlinear analysis, Korteweg-de Vries (KdV) equation is obtained using the reductive perturbation technique. It is found that in the presence of nonthermal positrons both hump and dip type solitons appear to excite, the structural properties of these solitary waves change drastically with magneto-rotating effects. The present work may be employed to explore and to understand the formation of electron acoustic solitary structures in the space and laboratory plasmas with nonthermal electrons and positrons under magneto-rotating effects.

Carbon Nanotube Field Emitters Synthesized on Metal Alloy Substrate by PECVD for Customized Compact Field Emission Devices to Be Used in X-Ray Source Applications.

PubMed

Park, Sangjun; Gupta, Amar Prasad; Yeo, Seung Jun; Jung, Jaeik; Paik, Sang Hyun; Mativenga, Mallory; Kim, Seung Hoon; Shin, Ji Hoon; Ahn, Jeung Sun; Ryu, Jehwang

2018-05-29

In this study, a simple, efficient, and economical process is reported for the direct synthesis of carbon nanotube (CNT) field emitters on metal alloy. Given that CNT field emitters can be customized with ease for compact and cold field emission devices, they are promising replacements for thermionic emitters in widely accessible X-ray source electron guns. High performance CNT emitter samples were prepared in optimized plasma conditions through the plasma-enhanced chemical vapor deposition (PECVD) process and subsequently characterized by using a scanning electron microscope, tunneling electron microscope, and Raman spectroscopy. For the cathode current, field emission (FE) characteristics with respective turn on (1 μA/cm²) and threshold (1 mA/cm²) field of 2.84 and 4.05 V/μm were obtained. For a field of 5.24 V/μm, maximum current density of 7 mA/cm² was achieved and a field enhancement factor β of 2838 was calculated. In addition, the CNT emitters sustained a current density of 6.7 mA/cm² for 420 min under a field of 5.2 V/μm, confirming good operational stability. Finally, an X-ray generated image of an integrated circuit was taken using the compact field emission device developed herein.

Multi-walled carbon nanotubes decorated by platinum catalyst nanoparticles--examination and microanalysis using scanning and transmission electron microscopies.

PubMed

Guinel, M J-F; Brodusch, N; Verde-Gómez, Y; Escobar-Morales, B; Gauvin, R

2013-10-01

Carbon nanotubes (CNTs) decorated with platinum (Pt) nanoparticles (NPs) have been characterized using a cold field-emission scanning electron microscope (SEM) and a high resolution field-emission transmission electron microscope (TEM). With this particular composite material, the complementary nature of the two instruments was demonstrated. Although the long CNTs were found to be mostly bent and defective in some parts, the nucleation of Pt occurred randomly and uniformly covered the CNTs. The NPs displayed a large variation in size, were sometimes defective with twins and stacking faults, and were found to be faceted with the presence of surface steps. The shape and size of the NPs and the presence of defects may have significant consequences on the activity of the Pt catalyst material. Also, thin layers of platinum oxide were identified on the surface of some NPs. © 2013 The Authors Journal of Microscopy © 2013 Royal Microscopical Society.

Scrape-off layer tokamak plasma turbulence

NASA Astrophysics Data System (ADS)

Bisai, N.; Singh, R.; Kaw, P. K.

2012-05-01

Two-dimensional (2D) interchange turbulence in the scrape-off layer of tokamak plasmas and their subsequent contribution to anomalous plasma transport has been studied in recent years using electron continuity, current balance, and electron energy equations. In this paper, numerically it is demonstrated that the inclusion of ion energy equation in the simulation changes the nature of plasma turbulence. Finite ion temperature reduces floating potential by about 15% compared with the cold ion temperature approximation and also reduces the radial electric field. Rotation of plasma blobs at an angular velocity about 1.5×105 rad/s has been observed. It is found that blob rotation keeps plasma blob charge separation at an angular position with respect to the vertical direction that gives a generation of radial electric field. Plasma blobs with high electron temperature gradients can align the charge separation almost in the radial direction. Influence of high ion temperature and its gradient has been presented.

A theoretical study of electron multiplication coefficient in a cold-cathode Penning ion generator

NASA Astrophysics Data System (ADS)

Noori, H.; Ranjbar, A. H.; Rahmanipour, R.

2017-11-01

The discharge mechanism of a Penning ion generator (PIG) is seriously influenced by the electron ionization process. A theoretical approach has been proposed to formulate the electron multiplication coefficient, M, of a PIG as a function of the axial magnetic field and the applied voltage. A numerical simulation was used to adjust the free parameters of expression M. Using the coefficient M, the values of the effective secondary electron emission coefficient, γeff, were obtained to be from 0.09 to 0.22. In comparison to the experimental results, the average value of γeff differs from the secondary coefficient of clean and dirty metals by the factors 1.4 and 0.5, respectively.

Electrothermal energy conversion using electron gas volumetric change inside semiconductors

NASA Astrophysics Data System (ADS)

Yazawa, K.; Shakouri, A.

2016-07-01

We propose and analyze an electrothermal energy converter using volumetric changes in non-equilibrium electron gas inside semiconductors. The geometric concentration of electron gas under an electric field increases the effective pressure of the electrons, and then a barrier filters out cold electrons, acting like a valve. Nano- and micro-scale features enable hot electrons to arrive at the contact in a short enough time to avoid thermalization with the lattice. Key length and time scales, preliminary device geometry, and anticipated efficiency are estimated for electronic analogs of Otto and Brayton power generators and Joule-Thomson micro refrigerators on a chip. The power generators convert the energy of incident photons from the heat source to electrical current, and the refrigerator can reduce the temperature of electrons in a semiconductor device. The analytic calculations show that a large energy conversion efficiency or coefficient of performance may be possible.

Electrothermal energy conversion using electron gas volumetric change inside semiconductors

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

Yazawa, K.; Shakouri, A.

2016-07-25

We propose and analyze an electrothermal energy converter using volumetric changes in non-equilibrium electron gas inside semiconductors. The geometric concentration of electron gas under an electric field increases the effective pressure of the electrons, and then a barrier filters out cold electrons, acting like a valve. Nano- and micro-scale features enable hot electrons to arrive at the contact in a short enough time to avoid thermalization with the lattice. Key length and time scales, preliminary device geometry, and anticipated efficiency are estimated for electronic analogs of Otto and Brayton power generators and Joule-Thomson micro refrigerators on a chip. The powermore » generators convert the energy of incident photons from the heat source to electrical current, and the refrigerator can reduce the temperature of electrons in a semiconductor device. The analytic calculations show that a large energy conversion efficiency or coefficient of performance may be possible.« less

Flow Regime Transition in Inner Grooved Minichannel Cold Plates for Cooling Hybrid Electric Power Electronics

DTIC Science & Technology

2013-01-01

reentrant cavities) Corrugated or fluted tubes Screens Inner grooved tubes ( microfin tubes ) Fins Electrohydrodynamic field effect 3.1 Convective... microfin geometries, including 3-D geometries, but most commercial vendors continue to manufacture seamless tubes (46). Figure 6a shows the...enhancement technologies are compiled in table 4. Table 4. Comparison of leading refrigeration tube performance (42). Metric Microfin Tube Twisted

Energy and pitch angle-dispersed auroral electrons suggesting a time-variable, inverted-V potential structure

NASA Astrophysics Data System (ADS)

Arnoldy, R. L.; Lynch, K. A.; Austin, J. B.; Kintner, P. M.

1999-10-01

High temporal resolution electron detectors aboard the PHAZE II rocket flight have shown that the energy-dispersed, field-aligned bursts (FABs) are time coincident with pitch angle-dispersed electrons having energies at the maximum voltage of the inverted-V potential. This modulation of the energetic inverted-V electrons is superimposed upon an energy-diffused background resulting in a peak-to-valley ratio of ~2 for the pitch angle-dispersed electrons. Since the characteristic energy of the FABs, the order of an eV, is considerably less than that of the plasma sheet electrons (the order of a keV) presumably falling through the inverted-V potential to create the discrete aurora, the modulation mechanism has to be independent of the electron temperature. The mechanism must accelerate the cold electrons over a range of energies from the inverted-V energy down to a few tens of eV. It must do this at the same time it is creating a population of hot, pitch angle-dispersed electrons at the inverted-V energy. Both the energy dispersion of the FABs and the pitch angle dispersion of the inverted-V electrons can be used to determine a source height assuming both populations start from the same source region at the same time. These calculations give source heights between 3500 and 5300 km for various events and disagreement between the two methods the order of 20%, which is within the rather substantial error limits of both calculations. A simple mechanism of providing a common start time for both populations of electrons would be a turning on/off of a spatially limited (vertically), inverted-V potential. The energy-dispersed FABs can be reconstructed at rocket altitudes if one assumes that cold electrons are accelerated to an energy determined by how much of the inverted-V potential they fall through when it is turned on. Similarly, the pitch angle-dispersed, inverted-V electrons can be modeled at rocket altitudes if one assumes that the plasma sheet electrons falling through the entire potential drop all start to do so at the same time when the potential is turned on. The FABs seem to fluctuate at either ~10 Hz or near 100 Hz. An important constraint of the on/off mechanism is whether cold electrons (1 eV) can fill the inverted-V volume during the off cycle. The maximum vertical height of the 10 kV potential region for the 10 Hz events would be the order of 100 and 10 km for the 100 Hz events. To get 10 kV, these heights require parallel electric fields of 0.1 and 1 V/m respectively for the 10 and 100 Hz events assuming that the filling is along B from below the inverted-V potential. Alternative mechanisms are also discussed in the light of the data presented.

Method of fabricating a cooled electronic system

DOEpatents

Chainer, Timothy J; Gaynes, Michael A; Graybill, David P; Iyengar, Madhusudan K; Kamath, Vinod; Kochuparambil, Bejoy J; Schmidt, Roger R; Schultz, Mark D; Simco, Daniel P; Steinke, Mark E

2014-02-11

A method of fabricating a liquid-cooled electronic system is provided which includes an electronic assembly having an electronics card and a socket with a latch at one end. The latch facilitates securing of the card within the socket. The method includes providing a liquid-cooled cold rail at the one end of the socket, and a thermal spreader to couple the electronics card to the cold rail. The thermal spreader includes first and second thermal transfer plates coupled to first and second surfaces on opposite sides of the card, and thermally conductive extensions extending from end edges of the plates, which couple the respective transfer plates to the liquid-cooled cold rail. The extensions are disposed to the sides of the latch, and the card is securable within or removable from the socket using the latch without removing the cold rail or the thermal spreader.

Window-assisted nanosphere lithography for vacuum micro-nano-electronics

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

Li, Nannan; Institute of Electronic Engineering, Chinese Academy of Engineering Physics, Mianyang, 621900; Pang, Shucai

2015-04-15

Development of vacuum micro-nano-electronics is quite important for combining the advantages of vacuum tubes and solid-state devices but limited by the prevailing fabricating techniques which are expensive, time consuming and low-throughput. In this work, window-assisted nanosphere lithography (NSL) technique was proposed and enabled the low-cost and high-efficiency fabrication of nanostructures for vacuum micro-nano-electronic devices, thus allowing potential applications in many areas. As a demonstration, we fabricated high-density field emitter arrays which can be used as cold cathodes in vacuum micro-nano-electronic devices by using the window-assisted NSL technique. The details of the fabricating process have been investigated. This work provided amore » new and feasible idea for fabricating nanostructure arrays for vacuum micro-nano-electronic devices, which would spawn the development of vacuum micro-nano-electronics.« less

Numerical algorithms for cold-relativistic plasma models in the presence of discontinuties

NASA Astrophysics Data System (ADS)

Hakim, Ammar; Cary, John; Bruhwiler, David; Geddes, Cameron; Leemans, Wim; Esarey, Eric

2006-10-01

A numerical algorithm is presented to solve cold-relativistic electron fluid equations in the presence of sharp gradients and discontinuities. The intended application is to laser wake-field accelerator simulations in which the laser induces accelerating fields thousands of times those achievable in conventional RF accelerators. The relativistic cold-fluid equations are formulated as non-classical system of hyperbolic balance laws. It is shown that the flux Jacobian for this system can not be diagonalized which causes numerical difficulties when developing shock-capturing algorithms. Further, the system is shown to admit generalized delta-shock solutions, first discovered in the context of sticky-particle dynamics (Bouchut, Ser. Adv. Math App. Sci., 22 (1994) pp. 171--190). A new approach, based on relaxation schemes proposed by Jin and Xin (Comm. Pure Appl. Math. 48 (1995) pp. 235--276) and LeVeque and Pelanti (J. Comput. Phys. 172 (2001) pp. 572--591) is developed to solve this system of equations. The method consists of finding an exact solution to a Riemann problem at each cell interface and coupling these to advance the solution in time. Applications to an intense laser propagating in an under-dense plasma are presented.

Surface structure of neutron stars with high magnetic fields

NASA Technical Reports Server (NTRS)

Fushiki, I.; Gudmundsson, E. H.; Pethick, C. J.

1989-01-01

The equation of state of cold dense matter in strong magnetic fields is calculated in the Thomas-Fermi and Thomas-Fermi-Dirac approximations. For use in the latter calculation, a new expression is derived for the exchange energy of the uniform electron gas in a strong magnetic field. Detailed calculations of the density profile in the surface region of a neutron star are described for a variety of equations of state, and these show that the surface density profile is strongly affected by the magnetic field, irrespective of whether or not matter in a magnetic field has a condensed state bound with respect to isolated atoms. It is also shown that, as a consequence of the field dependence of the screening potential, magnetic fields can significantly increase nuclear reaction rates.

Electron acoustic solitary waves in a magnetized plasma with nonthermal electrons and an electron beam

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

Singh, S. V., E-mail: satyavir@iigs.iigm.res.in; Lakhina, G. S., E-mail: lakhina@iigs.iigm.res.in; University of the Western Cape, Belville

2016-08-15

A theoretical investigation is carried out to study the obliquely propagating electron acoustic solitary waves having nonthermal hot electrons, cold and beam electrons, and ions in a magnetized plasma. We have employed reductive perturbation theory to derive the Korteweg-de-Vries-Zakharov-Kuznetsov (KdV-ZK) equation describing the nonlinear evolution of these waves. The two-dimensional plane wave solution of KdV-ZK equation is analyzed to study the effects of nonthermal and beam electrons on the characteristics of the solitons. Theoretical results predict negative potential solitary structures. We emphasize that the inclusion of finite temperature effects reduces the soliton amplitudes and the width of the solitons increasesmore » by an increase in the obliquity of the wave propagation. The numerical analysis is presented for the parameters corresponding to the observations of “burst a” event by Viking satellite on the auroral field lines.« less

Mass ablation and magnetic flux losses through a magnetized plasma-liner wall interface

NASA Astrophysics Data System (ADS)

García-Rubio, F.; Sanz, J.

2017-07-01

The understanding of energy and magnetic flux losses in a magnetized plasma medium confined by a cold wall is of great interest in the success of magnetized liner inertial fusion (MagLIF). In a MagLIF scheme, the fuel is magnetized and subsonically compressed by a cylindrical liner. Magnetic flux conservation is degraded by the presence of gradient-driven transport processes such as thermoelectric effects (Nernst) and magnetic field diffusion. In previous publications [Velikovich et al., Phys. Plasmas 22, 042702 (2015)], the evolution of a hot magnetized plasma in contact with a cold solid wall (liner) was studied using the classical collisional Braginskii's plasma transport equations in one dimension. The Nernst term degraded the magnetic flux conservation, while both thermal energy and magnetic flux losses were reduced with the electron Hall parameter ωeτe with a power-law asymptotic scaling (ωeτe)-1/2. In the analysis made in the present paper, we consider a similar situation, but with the liner being treated differently. Instead of a cold solid wall acting as a heat sink, we model the liner as a cold dense plasma with low thermal conduction (that could represent the cryogenic fuel layer added on the inner surface of the liner in a high-gain MagLIF configuration). Mass ablation comes into play, which adds notably differences to the previous analysis. The direction of the plasma motion is inverted, but the Nernst term still convects the magnetic field towards the liner. Magnetization suppresses the Nernst velocity and improves the magnetic flux conservation. Thermal energy in the hot plasma is lost in heating the ablated material. When the electron Hall parameter is large, mass ablation scales as (ωeτe)-3/10, while both the energy and magnetic flux losses are reduced with a power-law asymptotic scaling (ωeτe)-7/10.

Microstructure refinement of cold-sprayed copper investigated by electron channeling contrast imaging.

PubMed

Zhang, Yinyin; Brodusch, Nicolas; Descartes, Sylvie; Chromik, Richard R; Gauvin, Raynald

2014-10-01

The electron channeling contrast imaging technique was used to investigate the microstructure of copper coatings fabricated by cold gas dynamic spray. The high velocity impact characteristics for cold spray led to the formation of many substructures, such as high density dislocation walls, dislocation cells, deformation twins, and ultrafine equiaxed subgrains/grains. A schematic model is proposed to explain structure refinement of Cu during cold spray, where an emphasis is placed on the role of dislocation configurations and twinning.

Vlf/elf radiation patterns of arbitrarily oriented electric and magnetic dipoles in a cold lossless multicomponent magnetoplasma.

NASA Technical Reports Server (NTRS)

Wang, T. N. C.; Bell, T. F.

1972-01-01

With the use of a power integral formulation, a study is made of the vlf/elf radiation patterns of arbitrarily oriented electric and magnetic dipoles in a cold lossless multicomponent magnetoplasma. Expressions for the ray patterns are initially developed that apply for arbitrary values of driving frequency, static magnetic-field strength, plasma density, and composition. These expressions are subsequently specialized to vlf/elf radiation in a plasma modeled on the magnetosphere. A series of representative pattern plots are presented for frequencies between the proton and electron gyrofrequencies. These patterns illustrate the fact that focusing effects that arise from the geometrical properties of the refractive index surface tend to dominate the radiation distribution over the entire range from the electron gyrofrequency to 4.6 times the proton gyrofrequency. It is concluded that focusing effects should be of significant importance in the design of a vlf/elf satellite transmitting system in the magnetosphere.

Experimental investigation of gas flow rate and electric field effect on refractive index and electron density distribution of cold atmospheric pressure-plasma by optical method, Moiré deflectometry

NASA Astrophysics Data System (ADS)

Khanzadeh, Mohammad; Jamal, Fatemeh; Shariat, Mahdi

2018-04-01

Nowadays, cold atmospheric-pressure (CAP) helium plasma jets are widely used in material processing devices in various industries. Researchers often use indirect and spectrometric methods for measuring the plasma parameters which are very expensive. In this paper, for the first time, characterization of CAP, i.e., finding its parameters such as refractive index and electron density distribution, was carried out using an optical method, Moiré deflectometry. This method is a wave front analysis technique based on geometric optics. The advantages of this method are simplicity, high accuracy, and low cost along with the non-contact, non-destructive, and direct measurement of CAP parameters. This method demonstrates that as the helium gas flow rate decreases, the refractive index increases. Also, we must note that the refractive index is larger in the gas flow consisting of different flow rates of plasma comparing with the gas flow without the plasma.

Cold denaturation induces inversion of dipole and spin transfer in chiral peptide monolayers

PubMed Central

Eckshtain-Levi, Meital; Capua, Eyal; Refaely-Abramson, Sivan; Sarkar, Soumyajit; Gavrilov, Yulian; Mathew, Shinto P.; Paltiel, Yossi; Levy, Yaakov; Kronik, Leeor; Naaman, Ron

2016-01-01

Chirality-induced spin selectivity is a recently-discovered effect, which results in spin selectivity for electrons transmitted through chiral peptide monolayers. Here, we use this spin selectivity to probe the organization of self-assembled α-helix peptide monolayers and examine the relation between structural and spin transfer phenomena. We show that the α-helix structure of oligopeptides based on alanine and aminoisobutyric acid is transformed to a more linear one upon cooling. This process is similar to the known cold denaturation in peptides, but here the self-assembled monolayer plays the role of the solvent. The structural change results in a flip in the direction of the electrical dipole moment of the adsorbed molecules. The dipole flip is accompanied by a concomitant change in the spin that is preferred in electron transfer through the molecules, observed via a new solid-state hybrid organic–inorganic device that is based on the Hall effect, but operates with no external magnetic field or magnetic material. PMID:26916536

Cold denaturation induces inversion of dipole and spin transfer in chiral peptide monolayers

NASA Astrophysics Data System (ADS)

Eckshtain-Levi, Meital; Capua, Eyal; Refaely-Abramson, Sivan; Sarkar, Soumyajit; Gavrilov, Yulian; Mathew, Shinto P.; Paltiel, Yossi; Levy, Yaakov; Kronik, Leeor; Naaman, Ron

2016-02-01

Chirality-induced spin selectivity is a recently-discovered effect, which results in spin selectivity for electrons transmitted through chiral peptide monolayers. Here, we use this spin selectivity to probe the organization of self-assembled α-helix peptide monolayers and examine the relation between structural and spin transfer phenomena. We show that the α-helix structure of oligopeptides based on alanine and aminoisobutyric acid is transformed to a more linear one upon cooling. This process is similar to the known cold denaturation in peptides, but here the self-assembled monolayer plays the role of the solvent. The structural change results in a flip in the direction of the electrical dipole moment of the adsorbed molecules. The dipole flip is accompanied by a concomitant change in the spin that is preferred in electron transfer through the molecules, observed via a new solid-state hybrid organic-inorganic device that is based on the Hall effect, but operates with no external magnetic field or magnetic material.

Inspection of Space Station Cold Plate Using Visual and Automated Holographic Techniques

NASA Technical Reports Server (NTRS)

Decker, Arthur J.; Melis, Matthew E.; Weiland, Kenneth E.

1999-01-01

Real-time holography has been used to confirm the presence of non-uniformity in the construction of an International Space Station cold plate. Ultrasonic C-scans have previously shown suspected areas of cooling fin disbonds. But both neural-net processed and visual holography did not evidence any progressive permanent changes resulting from 3000 pressurization and relaxation cycles of a Dash 8 cold plate. Neural-net and visual inspections were performed of characteristic patterns generated from electronic time-average holograms of the vibrating cold plate. Normal modes of vibration were excited at very low amplitudes for this purpose, The neural nets were trained to flag very small changes in the mode shapes as encoded in the characteristic patterns. Both the whole cold plate and a zoomed region were inspected. The inspections were conducted before, after, and during pressurization and relaxation cycles of the cold plate. A water-filled cold plate was pressurized to 120 psig (827 kPa) and relaxed for each cycle. Each cycle required 5 seconds. Both the artificial neural networks and the inspectors were unable to detect changes in the mode shapes of the relaxed cold plate. The cold plate was also inspected visually using real-time holography and double-exposure holography. Regions of non-uniformity correlating with the C-scans were apparent, but the interference patterns did not change after 3000 pressurization and relaxation cycles. These tests constituted the first practical application of a neural-net inspection technique developed originally with support from the Director's Discretionary Fund at the Glenn Research Center at Lewis Field.

A compilation of cold cases using scanning electron microscopy at the University of Rhode Island

NASA Astrophysics Data System (ADS)

Platek, Michael J.; Gregory, Otto J.

2015-10-01

Scanning electron microscopy combined with microchemical analysis has evolved into one of the most widely used instruments in forensic science today. In particular, the environmental scanning electron microscope (SEM) in conjunction with energy dispersive spectroscopy (EDS), has created unique opportunities in forensic science in regard to the examination of trace evidence; i.e. the examination of evidence without altering the evidence with conductive coatings, thereby enabling criminalists to solve cases that were previously considered unsolvable. Two cold cases were solved at URI using a JEOL 5900 LV SEM in conjunction with EDS. A cold case murder and a cold missing person case will be presented from the viewpoint of the microscopist and will include sample preparation, as well as image and chemical analysis of the trace evidence using electron microscopy and optical microscopy.

Laboratory plasma with cold electron temperature of the lower ionosphere

NASA Astrophysics Data System (ADS)

Dickson, Shannon; Robertson, Scott

2009-10-01

For the first time, plasma with cold electron temperatures less than 300K has been created continuously in the laboratory. The plasma is created in a cylindrical double-walled vacuum chamber in which the inner chamber (18cm in diameter and 30cm long) is wrapped in copper tubing through which vapor from liquid nitrogen flows, providing a cooling mechanism for the neutral gas. The inner chamber has two negatively-biased filaments for plasma generation and a platinum wire Langmuir probe for diagnostic measurements. Neutral gas pressures of 1.6mTorr and a total filament emission current of 2mA are used to obtain plasma densities near 4 x 10^8 cm-3. When carbon monoxide is used as the working gas, decreasing the neutral gas temperature also decreases the cold electron temperatures, yielding cold electrons with 21meV (240K) when the neutral CO is at 150K. The same experiment conducted with H2, He, or Ar results in a doubling of the cold electron temperatures, yielding 80meV (930K) when the neutral gas is at 150K. The lower electron temperature with CO is attributed to the asymmetric CO molecule having a nonzero electric dipole moment which increases the cross section for electron energy exchange. Nitric oxide, a dominant constituent of the ionosphere, has a similar dipole moment and collision cross section as carbon monoxide and is likely to be equally effective at cooling electrons.

Collimated Propagation of Fast Electron Beams Accelerated by High-Contrast Laser Pulses in Highly Resistive Shocked Carbon.

PubMed

Vaisseau, X; Morace, A; Touati, M; Nakatsutsumi, M; Baton, S D; Hulin, S; Nicolaï, Ph; Nuter, R; Batani, D; Beg, F N; Breil, J; Fedosejevs, R; Feugeas, J-L; Forestier-Colleoni, P; Fourment, C; Fujioka, S; Giuffrida, L; Kerr, S; McLean, H S; Sawada, H; Tikhonchuk, V T; Santos, J J

2017-05-19

Collimated transport of ultrahigh intensity electron current was observed in cold and in laser-shocked vitreous carbon, in agreement with simulation predictions. The fast electron beams were created by coupling high-intensity and high-contrast laser pulses onto copper-coated cones drilled into the carbon samples. The guiding mechanism-observed only for times before the shock breakout at the inner cone tip-is due to self-generated resistive magnetic fields of ∼0.5-1  kT arising from the intense currents of fast electrons in vitreous carbon, by virtue of its specific high resistivity over the range of explored background temperatures. The spatial distribution of the electron beams, injected through the samples at different stages of compression, was characterized by side-on imaging of hard x-ray fluorescence.

Experimental investigation of a 1 kA/cm² sheet beam plasma cathode electron gun.

PubMed

Kumar, Niraj; Pal, Udit Narayan; Pal, Dharmendra Kumar; Prajesh, Rahul; Prakash, Ram

2015-01-01

In this paper, a cold cathode based sheet-beam plasma cathode electron gun is reported with achieved sheet-beam current density ∼1 kA/cm(2) from pseudospark based argon plasma for pulse length of ∼200 ns in a single shot experiment. For the qualitative assessment of the sheet-beam, an arrangement of three isolated metallic-sheets is proposed. The actual shape and size of the sheet-electron-beam are obtained through a non-conventional method by proposing a dielectric charging technique and scanning electron microscope based imaging. As distinct from the earlier developed sheet beam sources, the generated sheet-beam has been propagated more than 190 mm distance in a drift space region maintaining sheet structure without assistance of any external magnetic field.

Photoassociation of cold (RbCs)2 tetramers in the ground electronic state

NASA Astrophysics Data System (ADS)

Gacesa, Marko; Côté, Robin

2017-04-01

We theoretically investigate prospects for photoassociative formation of cold (RbCs)2 tetramers from a pair of ultracold RbCs molecules. The long-range region of the potential energy surface (PES) of the lowest electronic state of (RbCs)2 can be affected by orienting both RbCs molecules by an external electric field. In fact, we find a long-range barrier that supports long-range shelf states for relative angles between the dimers' internuclear axes smaller than about 20°. We show that these shelf states can be populated by spontaneous decay from the first excited electronic state which can be efficiently populated by photoassociation from the scattering continuum at ultracold temperatures. The vibrationally excited ground-state tetramer molecules formed this way have sufficiently long lifetimes to allow experimental detection. Moreover, for the relative angles between the dimers close to 20°, the proposed approach may result in production of deeply bound tetramers. Partially supported by the NASA Postdoctoral Program at the NASA Ames Research Center, administered by USRA and the MURI US Army Research Office Grant No. W911NF-14-1-0378 (MG), and by the PIF program of the National Science Foundation Grant No. PHY-141556.

A study on the steady-state solutions of a relativistic Bursian diode in the presence of a transverse magnetic field

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

Pramanik, Sourav; Chakrabarti, Nikhil; Kuznetsov, V. I.

2016-08-15

A comprehensive study on the steady states of a planar vacuum diode driven by a cold relativistic electron beam in the presence of an external transverse magnetic field is presented. The regimes, where no electrons are turned around by the external magnetic field and where they are reflected back to the emitter by the magnetic field, are both considered in a generalized way. The problem is solved by two methods: with the Euler and the Lagrange formulation. Taking non-relativistic limit, the solutions are compared with the similar ones which were obtained for the Bursian diode with a non-relativistic electron beammore » in previous work [Pramanik et al., Phys. Plasmas 22, 112108 (2015)]. It is shown that, at a moderate value of the relativistic factor of the injected beam, the region of the ambiguous solutions located to the right of the SCL bifurcation point (space charge limit) in the non-relativistic regime disappears. In addition, the dependencies of the characteristic bifurcation points and the transmitted current on the Larmor frequency as well as on the relativistic factor are explored.« less

High-emission cold cathode

DOEpatents

Mancebo, L.

1974-01-29

A field-emission cathode having a multitude of field emission points for emitting a copious stream of electrons when subjected to a high field is described. The cathode is constructed by compressing a multitude of tungsten strips alternately arranged with molybdenum strips and copper ribbons or compressing alternately arranged copper plated tungsten and molybdenum strips, heating the arrangement to braze the tungsten and molybdenum strips together with the copper, machining and grinding the exposed strip edges of one side of the brazed arrangement to obtain a precisely planar surface, etching a portion of the molybdenum and copper to leave the edges of the tungsten strips protruding for electron emission, and subjecting the protruding edges of the tungsten strips to a high electric field to degas and roughen the surface to pnovide a large number of emitting points. The resulting structure is particularly useful as a cathode in a transversely excited gaseous laser where the cathode is mounted in a vacuum chamber for emitting electrons under the influence of a high electric field between the cathode and an extractor grid. The electrons pass through the extractor grid, a thin window in the wall of the laser chamber and into the laser chamber which is filled with a gaseous mixture of helium, nitrogen, and carbon dioxide. A second grid is mounted on the gaseous side of the window. The electrons pass into the laser chamber under the influence of a second electric field between the second grid and an anode in the laser chamber to raise selected gas atoms of the gaseous mixture to appropriately excited states so that a subsequent coherent light beam passing through the mixture transversely to the electron stream through windows in opposite ends of the laser chamber stimulates the excited atoms to amplify the beam. (Official Gazette)

Device physics vis-à-vis fundamental physics in Cold War America: the case of quantum optics.

PubMed

Bromberg, Joan Lisa

2006-06-01

Historians have convincingly shown the close ties U.S. physicists had with the military during the Cold War and have raised the question of whether this alliance affected the content of physics. Some have asserted that it distorted physics, shifting attention from fundamental problems to devices. Yet the papers of physicists in quantum electronics and quantum optics, fields that have been exemplary for those who hold the distortion thesis, show that the same scientists who worked on military devices simultaneously pursued fundamental and foundational topics. This essay examines one such physicist, Marlan O. Scully, with attention to both his extensive foundational studies and the way in which his applied and basic researches played off each other.

Selfconsistent vibrational and free electron kinetics for CO2 dissociation in cold plasmas

NASA Astrophysics Data System (ADS)

Capitelli, Mario

2016-09-01

The activation of CO2 by cold plasmas is receiving new theoretical interest thanks to two European groups. The Bogaerts group developed a global model for the activation of CO2 trying to reproduce the experimental values for DBD and microwave discharges. The approach of Pietanza et al was devoted to understand the dependence of electron energy distribution function (eedf) of pure CO2 on the presence of concentrations of electronically and vibrationally excited states taken as parameter. To understand the importance of the vibrational excitation in the dissociation process Pietanza et al compared an upper limit to the dissociation process from a pure vibrational mechanism (PVM) with the corresponding electron impact dissociation rate, the prevalence of the two models depending on the reduced electric field and on the choice of the electron molecule cross section database. Improvement of the Pietanza et al model is being considered by coupling the time dependent Boltzmann solver with the non equilibrium vibrational kinetics of asymmetric mode and with simplified plasma chemistry kinetics describing the ionization/recombination process and the excitation-deexcitation of a metastable level at 10.5eV. A new PVM mechanism is also considered. Preliminary results, for both discharge and post discharge conditions, emphasize the action of superelastic collisions involving both vibrationally and electronically excited states in affecting the eedf. The new results can be used to plan a road map for future developments of numerical codes for rationalizing existing experimental values, as well as, for indicating new experimental situations.

Experiences issues with plastic parts at cold temperatures

NASA Technical Reports Server (NTRS)

Sandor, Mike; Agarwal, Shri

2005-01-01

Missions to MARS/planets/asteroids require electronic parts to operate and survive at extreme cold conditions. At extreme cold temperatures many types of cold related failures can occur. Office 514 is currently evaluating plastic parts under various cold temperature conditions and applications. Evaluations, screens, and qualifications are conducted on flight parts.

Nonequilibrium Transport and the Bernoulli Effect of Electrons in a Two-Dimensional Electron Gas

NASA Astrophysics Data System (ADS)

Kaya, Ismet I.

2013-02-01

Nonequilibrium transport of charged carriers in a two-dimensional electron gas is summarized from an experimental point of view. The transport regime in which the electron-electron interactions are enhanced at high bias leads to a range of striking effects in a two-dimensional electron gas. This regime of transport is quite different than the ballistic transport in which particles propagate coherently with no intercarrier energy transfer and the diffusive transport in which the momentum of the electron system is lost with the involvement of the phonons. Quite a few hydrodynamic phenomena observed in classical gasses have the electrical analogs in the current flow. When intercarrier scattering events dominate the transport, the momentum sharing via narrow angle scattering among the hot and cold electrons lead to negative resistance and electron pumping which can be viewed as the analog of the Bernoulli-Venturi effect observed classical gasses. The recent experimental findings and the background work in the field are reviewed.

Interplanetary fast shock diagnosis with the radio receiver on Ulysses

NASA Technical Reports Server (NTRS)

Hoang, S.; Pantellini, F.; Harvey, C. C.; Lacombe, C.; Mangeney, A.; Meuer-Vernet, N.; Perche, C.; Steinberg, J.-L.; Lengyel-Frey, D.; Macdowall, R. J.

1992-01-01

The radio receiver on Ulysses records the quasi-thermal noise which allows a determination of the density and temperature of the cold (core) electrons of the solar wind. Seven interplanetary fast forward or reverse shocks are identified from the density and temperature profiles, together with the magnetic field profile from the Magnetometer experiment. Upstream of the three strongest shocks, bursts of nonthermal waves are observed at the electron plasma frequency f(peu). The more perpendicular the shock, the longer the time interval during which these upstream bursts are observed. For one of the strongest shocks we also observe two kinds of upstream electromagnetic radiation: radiation at 2 f(peu), and radiation at the downstream electron plasma frequency, which propagates into the less dense upstream regions.

Field emission from ZnS nanorods synthesized by radio frequency magnetron sputtering technique

NASA Astrophysics Data System (ADS)

Ghosh, P. K.; Maiti, U. N.; Jana, S.; Chattopadhyay, K. K.

2006-11-01

The field emission property of zinc sulphides nanorods synthesized in the thin film form on Si substrates has been studied. It is seen that ZnS nanorod thin films showed good field emission properties with a low-macroscopic turn-on field (2.9-6.3 V/μm). ZnS nanorods were synthesized by using radio frequency magnetron sputtering of a polycrystalline prefabricated ZnS target at a relatively higher pressure (10 -1 mbar) and at a lower substrate temperature (233-273 K) without using any catalyst. Transmission electron microscopic image showed the formation of ZnS nanorods with high aspect ratio (>60). The field emission data were analysed using Fowler-Nordhiem theory and the nearly straight-line nature of the F-N plots confirmed cold field emission of electrons. It was also found that the turn-on field decreased with the decrease of nanorod's diameters. The optical properties of the ZnS nanorods were also studied. From the measurements of transmittance of the films deposited on glass substrates, the direct allowed bandgap values have been calculated and they were in the range 3.83-4.03 eV. The thickness of the films was ˜600 nm.

Spontaneous evolution of rydberg atoms into an ultracold plasma

PubMed

Robinson; Tolra; Noel; Gallagher; Pillet

2000-11-20

We have observed the spontaneous evolution of a dense sample of Rydberg atoms into an ultracold plasma, in spite of the fact that each of the atoms may initially be bound by up to 100 cm(-1). When the atoms are initially bound by 70 cm(-1), this evolution occurs when most of the atoms are translationally cold, <1 mK, but a small fraction, approximately 1%, is at room temperature. Ionizing collisions between hot and cold Rydberg atoms and blackbody photoionization produce an essentially stationary cloud of cold ions, which traps electrons produced later. The trapped electrons rapidly collisionally ionize the remaining cold Rydberg atoms to form a cold plasma.

Effect of pullulan on the water distribution, microstructure and textural properties of rice starch gels during cold storage.

PubMed

Chen, Long; Tian, Yaoqi; Tong, Qunyi; Zhang, Zipei; Jin, Zhengyu

2017-01-01

The effects of pullulan on the water distribution, microstructure and textural properties of rice starch gels during cold storage were investigated by low field-nuclear magnetic resonance (LF-NMR), scanning electron microscope (SEM), and texture profile analysis (TPA). The addition of pullulan reduced the transversal relaxation time of rice starch gels during cold storage. The microstructure of rice starch gel with 0.5% pullulan was denser and more uniform compared with that of rice starch without pullulan in each period of storage time. With regard to textural properties, 0.01% pullulan addition did not significantly change the texture of rice starch gels, while 0.5% pullulan addition appeared to reduce the hardness and retain the springiness of rice starch gels (P⩽0.05). The restriction effects of pullulan on water mobility and starch retrogradation were hypothesized to be mainly responsible for the water retention, gel structure maintenance, and modification of the textural attributes of rice starch gels. Copyright © 2016 Elsevier Ltd. All rights reserved.

Investigations on the Behavior of HVOF and Cold Sprayed Ni-20Cr Coating on T22 Boiler Steel in Actual Boiler Environment

NASA Astrophysics Data System (ADS)

Bala, Niraj; Singh, Harpreet; Prakash, Satya; Karthikeyan, J.

2012-01-01

High temperature corrosion accompanied by erosion is a severe problem, which may result in premature failure of the boiler tubes. One countermeasure to overcome this problem is the use of thermal spray protective coatings. In the current investigation high velocity oxy-fuel (HVOF) and cold spray processes have been used to deposit commercial Ni-20Cr powder on T22 boiler steel. To evaluate the performance of the coatings in actual conditions the bare as well as the coated steels were subjected to cyclic exposures, in the superheater zone of a coal fired boiler for 15 cycles. The weight change and thickness loss data were used to establish kinetics of the erosion-corrosion. X-ray diffraction, surface and cross-sectional field emission scanning electron microscope/energy dispersive spectroscopy (FE-SEM/EDS) and x-ray mapping techniques were used to analyse the as-sprayed and corroded specimens. The HVOF sprayed coating performed better than its cold sprayed counterpart in actual boiler environment.

Two-fluid description of wave-particle interactions in strong Buneman turbulence

NASA Astrophysics Data System (ADS)

Che, H.

2014-06-01

To understand the nature of anomalous resistivity in magnetic reconnection, we investigate turbulence-induced momentum transport and energy dissipation while a plasma is unstable to the Buneman instability in force-free current sheets. Using 3D particle-in-cell simulations, we find that the macroscopic effects generated by wave-particle interactions in Buneman instability can be approximately described by a set of electron fluid equations. We show that both energy dissipation and momentum transport along electric current in the current layer are locally quasi-static, but globally dynamic and irreversible. Turbulent drag dissipates both the streaming energy of the current sheet and the associated magnetic energy. The net loss of streaming energy is converted into the electron component heat conduction parallel to the magnetic field and increases the electron Boltzmann entropy. The growth of self-sustained Buneman waves satisfies a Bernoulli-like equation that relates the turbulence-induced convective momentum transport and thermal momentum transport. Electron trapping and de-trapping drive local momentum transports, while phase mixing converts convective momentum into thermal momentum. The drag acts like a micro-macro link in the anomalous heating processes. The decrease of magnetic field maintains an inductive electric field that re-accelerates electrons, but most of the magnetic energy is dissipated and converted into the component heat of electrons perpendicular to the magnetic field. This heating process is decoupled from the heating of Buneman instability in the current sheets. Ion heating is weak but ions play an important role in assisting energy exchanges between waves and electrons. Cold ion fluid equations together with our electron fluid equations form a complete set of equations that describes the occurrence, growth, saturation and decay of the Buneman instability.

Oblique Propagation of Electrostatic Waves in a Magnetized Electron-Positron-Ion Plasma in the Presence of Heavy Particles

NASA Astrophysics Data System (ADS)

Sarker, M.; Hossen, M. R.; Shah, M. G.; Hosen, B.; Mamun, A. A.

2018-06-01

A theoretical investigation is carried out to understand the basic features of nonlinear propagation of heavy ion-acoustic (HIA) waves subjected to an external magnetic field in an electron-positron-ion plasma that consists of cold magnetized positively charged heavy ion fluids and superthermal distributed electrons and positrons. In the nonlinear regime, the Korteweg-de Vries (K-dV) and modified K-dV (mK-dV) equations describing the propagation of HIA waves are derived. The latter admits a solitary wave solution with both positive and negative potentials (for K-dV equation) and only positive potential (for mK-dV equation) in the weak amplitude limit. It is observed that the effects of external magnetic field (obliqueness), superthermal electrons and positrons, different plasma species concentration, heavy ion dynamics, and temperature ratio significantly modify the basic features of HIA solitary waves. The application of the results in a magnetized EPI plasma, which occurs in many astrophysical objects (e.g. pulsars, cluster explosions, and active galactic nuclei) is briefly discussed.

Optical Properties in Nonequilibrium Phase Transitions

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

Ao, T.; Lee, E.; Tam, H.

An open question about the dynamical behavior of materials is how phase transition occurs in highly nonequilibrium systems. One important class of study is the excitation of a solid by an ultrafast, intense laser. The preferential heating of electrons by the laser field gives rise to initial states dominated by hot electrons in a cold lattice. Using a femtosecond laser pump-probe approach, we have followed the temporal evolution of the optical properties of such a system. The results show interesting correlation to nonthermal melting and lattice disordering processes. They also reveal a liquid-plasma transition when the lattice energy density reachesmore » a critical value.« less

Optical Properties in Non-equilibrium Phase Transitions

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

Ao, T; Ping, Y; Widmann, K

An open question about the dynamical behavior of materials is how phase transition occurs in highly non-equilibrium systems. One important class of study is the excitation of a solid by an ultrafast, intense laser. The preferential heating of electrons by the laser field gives rise to initial states dominated by hot electrons in a cold lattice. Using a femtosecond laser pump-probe approach, we have followed the temporal evolution of the optical properties of such a system. The results show interesting correlation to non-thermal melting and lattice disordering processes. They also reveal a liquid-plasma transition when the lattice energy density reachesmore » a critical value.« less

Effect of excess superthermal hot electrons on finite amplitude ion-acoustic solitons and supersolitons in a magnetized auroral plasma

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

Rufai, O. R., E-mail: rrufai@csir.co.za; Bharuthram, R., E-mail: rbharuthram@uwc.ac.za; Singh, S. V., E-mail: satyavir@iigs.iigm.res.in

2015-10-15

The effect of excess superthermal electrons is investigated on finite amplitude nonlinear ion-acoustic waves in a magnetized auroral plasma. The plasma model consists of a cold ion fluid, Boltzmann distribution of cool electrons, and kappa distributed hot electron species. The model predicts the evolution of negative potential solitons and supersolitons at subsonic Mach numbers region, whereas, in the case of Cairn's nonthermal distribution model for the hot electron species studied earlier, they can exist both in the subsonic and supersonic Mach number regimes. For the dayside auroral parameters, the model generates the super-acoustic electric field amplitude, speed, width, and pulsemore » duration of about 18 mV/m, 25.4 km/s, 663 m, and 26 ms, respectively, which is in the range of the Viking spacecraft measurements.« less

High-Altitude Closed Magnetic Loops at Mars Observed by MAVEN

NASA Astrophysics Data System (ADS)

Xu, Shaosui; Mitchell, David; Luhmann, Janet; Ma, Yingjuan; Fang, Xiaohua; Harada, Yuki; Hara, Takuya; Brain, David; Weber, Tristan; Mazelle, Christian; DiBraccio, Gina A.

2017-11-01

With electron and magnetic field data obtained by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, we have identified closed magnetic field lines, with both foot points embedded in the dayside ionosphere, extending up to 6,200 km altitude into the Martian tail. This topology is deduced from photoelectrons produced in the dayside ionosphere being observed traveling both parallel and antiparallel to the magnetic field. At trapped-zone pitch angles (within a range centered on 90° where electrons magnetically reflect before interacting with the atmosphere), cases with either solar wind electrons or photoelectrons have been found, indicating different formation mechanisms for these closed loops. These large closed loops are present in MHD simulations. The case with field-aligned photoelectrons mixed with solar wind electrons having trapped-zone pitch angles is likely to be associated with reconnection, while the case with photoelectrons at all pitch angles is probably due to closed field lines being pulled tailward by the surrounding plasma flow. By utilizing an algorithm for distinguishing photoelectrons from solar wind electrons in pitch angle-resolved energy spectra, we systematically map the spatial distribution and occurrence rate of these closed magnetic loops over the region sampled by the MAVEN orbit. We find that the occurrence rate ranges from a few percent to a few tens of percent outside of the optical shadow and less than one percent within the shadow. These observations can be used to investigate the general magnetic topology in the tail, which is relevant to cold ion escape, reconnection, and flux ropes.

Analysis of cold worked holes for structural life extension

NASA Technical Reports Server (NTRS)

Wieland, David H.; Cutshall, Jon T.; Burnside, O. Hal; Cardinal, Joseph W.

1994-01-01

Cold working holes for improved fatigue life of fastener holes are widely used on aircraft. This paper presents methods used by the authors to determine the percent of cold working to be applied and to analyze fatigue crack growth of cold worked fastener holes. An elastic, perfectly-plastic analysis of a thick-walled tube is used to determine the stress field during the cold working process and the residual stress field after the process is completed. The results of the elastic/plastic analysis are used to determine the amount of cold working to apply to a hole. The residual stress field is then used to perform damage tolerance analysis of a crack growing out of a cold worked fastener hole. This analysis method is easily implemented in existing crack growth computer codes so that the cold worked holes can be used to extend the structural life of aircraft. Analytical results are compared to test data where appropriate.

Analytical model for fast reconnection in large guide field plasma configurations

NASA Astrophysics Data System (ADS)

Simakov, A. N.; Chacón, L.; Grasso, D.; Borgogno, D.; Zocco, A.

2009-11-01

Significant progress in understanding magnetic reconnection without a guide field was made recently by deriving quantitatively accurate analytical models for reconnection in electron [1] and Hall [2] MHD. However, no such analytical model is available for reconnection with a guide field. Here, we derive such an analytical model for the large-guide-field, low-β, cold-ion fluid model [3] with electron inertia, ion viscosity μ, and resistivity η. We find that the reconnection is Sweet-Parker-like when the Sweet-Parker layer thickness δSP> (ρs^4 + de^4)^1/4, with ρs and de the sound Larmor radius and electron inertial length. However, reconnection changes character otherwise, resulting in reconnection rates Ez/Bx^2 √2 η/μ (ρs^2 + de^2)/(ρsw) with Bx the upstream magnetic field and w the diffusion region length. Unlike the zero-guide-field case, μ plays crucial role in manifesting fast reconnection rates. If it represents the perpendicular viscosity [3], √η/μ ˜&-1circ;√(me/mi)(Ti/Te) and Ez becomes dissipation independent and therefore potentially fast.[0pt] [1] L. Chac'on, A. N. Simakov, and A. Zocco, PRL 99, 235001 (2007).[0pt] [2] A. N. Simakov and L. Chac'on, PRL 101, 105003 (2008).[0pt] [3] D. Biskamp, Magnetic reconnection in plasmas, Cambridge University Press, 2000.

Experimental investigation of a 1 kA/cm{sup 2} sheet beam plasma cathode electron gun

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

Kumar, Niraj, E-mail: niraj.ceeri@gmail.com; Narayan Pal, Udit; Prajesh, Rahul

In this paper, a cold cathode based sheet-beam plasma cathode electron gun is reported with achieved sheet-beam current density ∼1 kA/cm{sup 2} from pseudospark based argon plasma for pulse length of ∼200 ns in a single shot experiment. For the qualitative assessment of the sheet-beam, an arrangement of three isolated metallic-sheets is proposed. The actual shape and size of the sheet-electron-beam are obtained through a non-conventional method by proposing a dielectric charging technique and scanning electron microscope based imaging. As distinct from the earlier developed sheet beam sources, the generated sheet-beam has been propagated more than 190 mm distance inmore » a drift space region maintaining sheet structure without assistance of any external magnetic field.« less

Relativistic Laser Absorption and Magnetic Field Channel Formation in 3D PIC Simulation

NASA Astrophysics Data System (ADS)

Sentoku, Yasuhiko; Mima, Kunioki; Sheng, Zheng-Ming; Kaw, Predhiman; Nishihara, Katsunobu; Nishikawa, Kyoji

2000-10-01

We carried out 3D PIC simulations on overdense plasmas. On the surface of the plasmas, relativistic electrons are generated and transported into overdense plasmas. In the transport, it is found that energy is transferred to dense plasmas by convective cells. Namely, hot electron and cold electron return flows form convective cells through the magnetic instabilities (e.g. Weibel Instability). The heat flux associating with the convective cells and the anomalous stoppings in 3D simulations are compared with these in 2D simulations by Meyer-ter-Vehn etal. and Taguchi etal. [1] M. Honda, J. Meyer-ter-Vehn, and A. Pukhov, Phys. Plasmas 7, 1302, (2000). [2] ``Relativistic Electron Transport Simulation by 2D hybrid Simulation with Darwin Approximation." by T. Taguchi etal. (to be present in the poster of this conference)

Three dimensional fluid-kinetic model of a magnetically guided plasma jet

NASA Astrophysics Data System (ADS)

Ramos, Jesús J.; Merino, Mario; Ahedo, Eduardo

2018-06-01

A fluid-kinetic model of the collisionless plasma flow in a convergent-divergent magnetic nozzle is presented. The model combines the leading-order Vlasov equation and the fluid continuity and perpendicular momentum equation for magnetized electrons, and the fluid equations for cold ions, which must be solved iteratively to determine the self-consistent plasma response in a three-dimensional magnetic field. The kinetic electron solution identifies three electron populations and provides the plasma density and pressure tensor. The far downstream asymptotic behavior shows the anisotropic cooling of the electron populations. The fluid equations determine the electric potential and the fluid velocities. In the small ion-sound gyroradius case, the solution is constructed one magnetic line at a time. In the large ion-sound gyroradius case, ion detachment from magnetic lines makes the problem fully three-dimensional.

New Mixed Conductivity Mechanisms in the Cold Plasma Device Based on Silver-Modified Zeolite Microporous Electronic Materials

NASA Astrophysics Data System (ADS)

Koç, Sevgul Ozturk; Galioglu, Sezin; Ozturk, Seckin; Kurç, Burcu Akata; Koç, Emrah; Salamov, Bahtiyar G.

2018-02-01

We have analyzed the interaction between microdischarge and microporous zeolite electronic materials modified by silver (Ag0) nanoparticles (resistivity 1011 to 106 Ω cm) on the atmospheric pressure cold plasma generation in air. The generation and maintenance of stable cold plasma is studied according to the effect of the Ag0 nanoparticles. The role of charge carriers in mixed conductivity processes and electrical features of zeolite from low pressure to atmospheric pressure is analyzed in air microplasmas for both before and after breakdown regimes. The results obtained from the experiments indicate that Ag0 nanoparticles play a significant role in considerably reducing the breakdown voltage in plasma electronic devices with microporous zeolite electronic materials.

Observation of Hamiltonian chaos and its control in wave particle interaction

NASA Astrophysics Data System (ADS)

Doveil, F.; Macor, A.; Aïssi, A.

2007-12-01

Wave-particle interactions are central in plasma physics. They can be studied in a traveling wave tube (TWT) to avoid intrinsic plasma noise. This led to detailed experimental analysis of the self-consistent interaction between unstable waves and an either cold or warm beam. More recently a test cold electron beam has been used to observe its non-self-consistent interaction with externally excited wave(s). The velocity distribution function of the electron beam is recorded with a trochoidal energy analyzer at the output of the TWT. An arbitrary waveform generator is used to launch a prescribed spectrum of waves along the slow wave structure (a 4 m long helix) of the TWT. The nonlinear synchronization of particles by a single wave responsible for Landau damping is observed. The resonant velocity domain associated with a single wave is also observed, as well as the transition to large scale chaos when the resonant domains of two waves and their secondary resonances overlap. This transition exhibits a 'devil's staircase' behavior when increasing the excitation amplitude in agreement with numerical simulation. A new strategy for control of chaos by building barriers of transport which prevent electrons from escaping from a given velocity region as well as its robustness are successfully tested. The underlying concepts extend far beyond the field of electron devices and plasma physics.

Simulation of electrostatic turbulence in the plasma sheet boundary layer with electron currents and bean-shaped ion beams

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

Nishikawa, K.; Frank, L.A.; Huang, C.Y.

Plasma data from ISEE 1 show the presence of electron currents as well as energetic ion beams in the plasma sheet boundary layer. Broadband electrostatic noise and low-frequency electromagnetic bursts are detected in the plasma sheet boundary layer, especially in the presence of strong ion flows, currents, and steep spacial gradients in the fluxes of few-keV electrons and ions. Particle simulations have been performed to investigate electrostatic turbulence driven by a cold electron beam and/or ion beams with a bean-shaped velocity distribution. The simulation results show that the counterstreaming ion beams as well as the counterstreaming of the cold electronmore » beam and the ion beam excite ion acoustic waves with the Doppler-shifted real frequency ..omega..approx. = +- k/sub parallel/(c/sub s/-V/sub i//sub //sub parallel/). However, the effect of the bean-shaped ion velocity distributions reduces the growth rates of ion acoustic instability. The simulation results also show that the slowing down of the ion beam is larger at the larger perpendicular velocity. The wave spectra of the electric fields at some points for simulations show turbulence generated by growing waves. The frequency of these spectra ranges from ..cap omega../sub i/ to ..omega../sub p//sub e/, which is in qualitative agreement with the satellite data. copyright American Geophysical Union 1988« less

Two-dimensional Yukawa interactions from nonlocal Proca quantum electrodynamics

NASA Astrophysics Data System (ADS)

Alves, Van Sérgio; Macrı, Tommaso; Magalhães, Gabriel C.; Marino, E. C.; Nascimento, Leandro O.

2018-05-01

We derive two versions of an effective model to describe dynamical effects of the Yukawa interaction among Dirac electrons in the plane. Such short-range interaction is obtained by introducing a mass term for the intermediate particle, which may be either scalar or an abelian gauge field, both of them in (3 +1 ) dimensions. Thereafter, we consider that the fermionic matter field propagates only in (2 +1 ) dimensions, whereas the bosonic field is free to propagate out of the plane. Within these assumptions, we apply a mechanism for dimensional reduction, which yields an effective model in (2 +1 ) dimensions. In particular, for the gauge-field case, we use the Stueckelberg mechanism in order to preserve gauge invariance. We refer to this version as nonlocal-Proca quantum electrodynamics (NPQED). For both scalar and gauge cases, the effective models reproduce the usual Yukawa interaction in the static limit. By means of perturbation theory at one loop, we calculate the mass renormalization of the Dirac field. Our model is a generalization of Pseudo quantum electrodynamics (PQED), which is a gauge-field model that provides a Coulomb interaction for two-dimensional electrons. Possibilities of application to Fermi-Bose mixtures in mixed dimensions, using cold atoms, are briefly discussed.

Slowing and cooling of heavy or light (even with a tiny electric dipole moment) polar molecules using a novel, versatile electrostatic Stark decelerator.

PubMed

Wang, Qin; Hou, Shunyong; Xu, Liang; Yin, Jianping

2016-02-21

To meet some demands for realizing precise measurements of an electric dipole moment of electron (eEDM) and examining cold collisions or cold chemical physics, we have proposed a novel, versatile electrostatic Stark decelerator with an array of true 3D electric potential wells, which are created by a series of horizontally-oriented, U-shaped electrodes with time-sequence controlling high voltages (± HV) and two guiding electrodes with a constant voltage. We have calculated the 2D electric field distribution, the Stark shifts of the four lowest rotational sub-levels of PbF molecules in the X1(2)Π1/2(v = 0) electronic and vibrational ground states as well as the population in the different rotational levels. We have discussed the 2D longitudinal and transverse phase-space acceptances of PbF molecules in our decelerator. Subsequently, we have simulated the dynamic processes of the decelerated PbF molecules using the 3D Monte-Carlo method, and have found that a supersonic PbF beam with a velocity of 300 m s(-1) can be efficiently slowed to about 5 m s(-1), which will greatly enhance the sensitivities to research a parity violation and measure an eEDM. In addition, we have investigated the dependences of the longitudinal velocity spread, longitudinal temperature and bunching efficiency on both the number of guiding stages and high voltages, and found that after bunching, a cold packet of PbF molecules in the J = 7/2, MΩ = -7/4 state with a longitudinal velocity spread of 0.69 m s(-1) (corresponding to a longitudinal temperature of 2.35 mK) will be produced by our high-efficient decelerator, which will generate a high energy-resolution molecular beam for studying cold collision physics. Finally, our novel decelerator can also be used to efficiently slow NO molecules with a tiny electric dipole moment (EDM) of 0.16 D from 315 m s(-1) to 28 m s(-1). It is clear that our proposed new decelerator has a good slowing performance and experimental feasibility as well as wide applications in the field of precise measurements and cold molecule physics.

Thermoregulation in rats: Effects of varying duration of hypergravic fields

NASA Technical Reports Server (NTRS)

Horowitz, J. M.; Horwitz, B. A.

1980-01-01

The effects of hypergravitational fields on the thermoregulatory system of the rat are examined. The question underlying the investigation was whether the response of the rat to the one hour cold exposure depends only upon the amplitude of the hypergravic field during the period of cold exposure or whether the response is also dependent on the amplitude and duration of the hypergravic field prior to cold exposure. One hour of cold exposure applied over the last hour of either a 1, 4, 7, 13, 19, 25, or 37 hr period of 3G evoked a decrease in core temperature (T sub c) of about 3 C. However, when rats were subjected concurrently to cold and acceleration following 8 days at 3G, they exhibited a smaller fall in T sub c, suggesting partial recovery of the acceleration induced impairment of temperature regulation. In another series of experiments, the gravitational field profile was changed in amplitude in 3 different ways. Despite the different gravitational field profiles used prior to cold, the magnitude of the fall in T sub c over the 1 hr period of cold exposure was the same in all cases. These results suggest that the thermoregulatory impairment has a rapid onset, is a manifestation of an ongoing effect of hypergravity, and is not dependent upon the prior G profile.

Effects of Hot Limiter Biasing on Tokamak Runaway Discharges

NASA Astrophysics Data System (ADS)

Salar Elahi, A.; Ghoranneviss, M.; Ghanbari, M. R.

2013-10-01

In this research hot limiter biasing effects on the Runaway discharges were investigated. First wall of the tokamak reactors can affects serious damage due to the high energy runaway electrons during a major disruption and therefore its life time can be reduced. Therefore, it is important to find methods to decrease runaway electron generation and their energy. Tokamak limiter biasing is one of the methods for controlling the radial electric field and can induce a transition to an improved confinement state. In this article generation of runaway electrons and the energy they can obtain will be investigated theoretically. Moreover, in order to apply radial biasing an emissive limiter biasing is utilized. The biased limiter can apply +380 V in the status of cold and hot to the plasma and result in the increase of negative bias current in hot status. In fact, in this experiment we try to decrease the generation of runaway electrons and their energy by using emissive limiter biasing inserted on the IR-T1 tokamak. The mean energy of these electrons was obtained by spectroscopy of hard X-ray. Also, the plasma current center shift was measured from the vertical field coil characteristics in presence of limiter biasing. The calculation is made focusing on the vertical field coil current and voltage changes due to a horizontal displacement of plasma column.

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

Agafonov, A. I., E-mail: aai@isssph.kiae.ru

The inelastic scattering of cold neutrons by a ring leads to quantum jumps of a superconducting current which correspond to a decrease in the fluxoid quantum number by one or several units while the change in the ring energy is transferred to the kinetic energy of the scattered neutron. The scattering cross sections of transversely polarized neutrons have been calculated for a thin type-II superconductor ring, the thickness of which is smaller than the field penetration depth but larger than the electron mean free path.

Cold atmospheric plasma jet in an axial DC electric field

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

Lin, Li, E-mail: lilin@gwu.edu, E-mail: keidar@gwu.edu; Keidar, Michael, E-mail: lilin@gwu.edu, E-mail: keidar@gwu.edu

2016-08-15

Cold atmospheric plasma (CAP) jet is currently intensively investigated as a tool for new and potentially transformative cancer treatment modality. However, there are still many unknowns about the jet behavior that requires attention. In this paper, a helium CAP jet is tested in an electrostatic field generated by a copper ring. Using Rayleigh microwave scattering method, some delays of the electron density peaks for different ring potentials are observed. Meanwhile, a similar phenomenon associated with the bullet velocity is found. Chemical species distribution along the jet is analyzed based on the jet optical emission spectra. The spectra indicate that amore » lower ring potential, i.e., lower DC background electric field, can increase the amount of excited N{sub 2}, N{sub 2}{sup +}, He, and O in the region before the ring, but can decrease the amount of excited NO and HO almost along the entire jet. Combining all the results above, we discovered that an extra DC potential mainly affects the temporal plasma jet properties. Also, it is possible to manipulate the chemical compositions of the jet using a ring with certain electric potentials.« less

Field Emission Characteristics of Carbon Nanotubes and Their Applications in Sensors and Devices

NASA Astrophysics Data System (ADS)

Vaseashta, Ashok

2003-03-01

FIELD EMISSION CHARACTERISTICS OF CARBON NANOTUBES AND THEIR APPLICATIONS IN SENSORS AND DEVICES A. Vaseashta, C. Shaffer, M. Collins, A. Mwuara Dept of Physics, Marshall University, Huntington, WV V. Pokropivny Institute for Materials Sciences of NASU, Kiev, Ukraine. D. Dimova-Malinovska Bulgarian Academy of Sciences, Sofia, Bulgaria. The dimensionality of a system has profound influence on its physical behavior. With advances in technology over the past few decades, it has become possible to fabricate and study reduced-dimensional systems, such as carbon nanotubes (CNTs). Carbon nanotubes are especially promising candidate for cold cathode field emitter because of their electrical properties, high aspect ratio, and small radius of curvature at the tips. Electron emission from the carbon nanotubes was investigated. Based upon the field emission investigation of carbon nanotubes, several prototype devices have been suggested that operate with low swing voltages with sufficient high current densities. Characteristics that allow improved current stability and long lifetime operation for electrical and opto-electronics devices are presented. The aim of this brief overview is to illustrate the useful characteristics of carbon nanotubes and its possible application.

Nonlinear wave interaction in a plasma column

NASA Technical Reports Server (NTRS)

Larsen, J.

1972-01-01

Two particular cases of nonlinear wave interaction in a plasma column were investigated. The frequencies of the waves were on the order of magnitude of the electron plasma frequency, and ion motion was neglected. The nonlinear coupling of slow waves on a plasma column was studied by means of cold plasma theory, and the case of a plasma column surrounded by an infinite dielectric in the absence of a magnetic field was also examined. Nonlinear scattering from a plasma column in an electromagnetic field having it's magnetic field parallel to the axis of the column was investigated. Some experimental results on mode conversion in the presence of loss are presented along with some observations of nonlinear scattering, The effect of the earth's magnetic field and of discharge symmetry on the radiation pattern are discussed.

Expansion of a cold non-neutral plasma slab

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

Karimov, A. R.; Department of Electrophysical Facilities, National Research Nuclear University MEPhI, Kashirskoye shosse 31, Moscow 115409; Yu, M. Y., E-mail: myyu@zju.edu.cn

2014-12-15

Expansion of the ion and electron fronts of a cold non-neutral plasma slab with a quasi-neutral core bounded by layers containing only ions is investigated analytically and exact solutions are obtained. It is found that on average, the plasma expansion time scales linearly with the initial inverse ion plasma frequency as well as the degree of charge imbalance, and no expansion occurs if the cold plasma slab is stationary and overall neutral. However, in both cases, there can exist prominent oscillations on the electron front.

Amplification of a high-frequency electromagnetic wave by a relativistic plasma

NASA Technical Reports Server (NTRS)

Yoon, Peter H.

1990-01-01

The amplification of a high-frequency transverse electromagnetic wave by a relativistic plasma component, via the synchrotron maser process, is studied. The background plasma that supports the transverse wave is considered to be cold, and the energetic component whose density is much smaller than that of the background component has a loss-cone feature in the perpendicular momentum space and a finite field-aligned drift speed. The ratio of the background plasma frequency squared to the electron gyrofrequency squared is taken to be sufficiently larger than unity. Such a parameter regime is relevant to many space and astrophysical situations. A detailed study of the amplification process is carried out over a wide range of physical parameters including the loss-cone index, the ratio of the electron mass energy to the temperature of the energetic component, the field-aligned drift speed, the normalized density, and the wave propagation angle.

Multi-layer carbon-based coatings for field emission

DOEpatents

Sullivan, John P.; Friedmann, Thomas A.

1998-01-01

A multi-layer resistive carbon film field emitter device for cold cathode field emission applications. The multi-layered film of the present invention consists of at least two layers of a conductive carbon material, preferably amorphous-tetrahedrally coordinated carbon, where the resistivities of adjacent layers differ. For electron emission from the surface, the preferred structure can be a top layer having a lower resistivity than the bottom layer. For edge emitting structures, the preferred structure of the film can be a plurality of carbon layers, where adjacent layers have different resistivities. Through selection of deposition conditions, including the energy of the depositing carbon species, the presence or absence of certain elements such as H, N, inert gases or boron, carbon layers having desired resistivities can be produced.

Arbitrarily shaped high-coherence electron bunches from cold atoms

NASA Astrophysics Data System (ADS)

McCulloch, A. J.; Sheludko, D. V.; Saliba, S. D.; Bell, S. C.; Junker, M.; Nugent, K. A.; Scholten, R. E.

2011-10-01

Ultrafast electron diffractive imaging of nanoscale objects such as biological molecules and defects in solid-state devices provides crucial information on structure and dynamic processes: for example, determination of the form and function of membrane proteins, vital for many key goals in modern biological science, including rational drug design. High brightness and high coherence are required to achieve the necessary spatial and temporal resolution, but have been limited by the thermal nature of conventional electron sources and by divergence due to repulsive interactions between the electrons, known as the Coulomb explosion. It has been shown that, if the electrons are shaped into ellipsoidal bunches with uniform density, the Coulomb explosion can be reversed using conventional optics, to deliver the maximum possible brightness at the target. Here we demonstrate arbitrary and real-time control of the shape of cold electron bunches extracted from laser-cooled atoms. The ability to dynamically shape the electron source itself and to observe this shape in the propagated electron bunch provides a remarkable experimental demonstration of the intrinsically high spatial coherence of a cold-atom electron source, and the potential for alleviation of electron-source brightness limitations due to Coulomb explosion.

The effect of cold priming on the fitness of Arabidopsis thaliana accessions under natural and controlled conditions.

PubMed

Cvetkovic, Jelena; Müller, Klaus; Baier, Margarete

2017-03-09

Priming improves an organism's performance upon a future stress. To test whether cold priming supports protection in spring and how it is affected by cold acclimation, we compared seven Arabidopsis accessions with different cold acclimation potentials in the field and in the greenhouse for growth, photosynthetic performance and reproductive fitness in March and May after a 14 day long cold-pretreatment at 4 °C. In the plants transferred to the field in May, the effect of the cold pretreatment on the seed yield correlated with the cold acclimation potential of the accessions. In the March transferred plants, the reproductive fitness was most supported by the cold pretreatment in the accessions with the weakest cold acclimation potential. The fitness effect was linked to long-term effects of the cold pretreatment on photosystem II activity stabilization and leaf blade expansion. The study demonstrated that cold priming stronger impacts on plant fitness than cold acclimation in spring in accessions with intermediate and low cold acclimation potential.

Superconducting 112 MHz QWR electron gun

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

Belomestnykh, S.; Ben-Zvi, I.; Boulware, C.H.

Brookhaven National Laboratory and Niowave, Inc. have designed and fabricated a superconducting 112 MHz quarter-wave resonator (QWR) electron gun. The first cold test of the QWR cryomodule has been completed at Niowave. The paper describes the cryomodule design, presents the cold test results, and outline plans to upgrade the cryomodule. Future experiments include studies of different photocathodes and use for the coherent electron cooling proof-of-principle experiment. Two cathode stalk options, one for multi-alkali photocathodes and the other one for a diamond-amplified photocathode, are discussed. A quarter-wave resonator concept of superconducting RF (SRF) electron gun was proposed at BNL for electronmore » cooling hadron beams in RHIC. QWRs can be made sufficiently compact even at low RF frequencies (long wavelengths). The long wavelength allows to produce long electron bunches, thus minimizing space charge effects and enabling high bunch charge. Also, such guns should be suitable for experiments requiring high average current electron beams. A 112 MHz QWR gun was designed, fabricated, and cold-tested in collaboration between BNL and Niowave. This is the lowest frequency SRF gun ever tested successfully. In this paper we describe the gun design and fabrication, present the cold test results, and outline our plans. This gun will also serve as a prototype for a future SRF gun to be used for coherent electron cooling of hadrons in eRHIC.« less

Influence of the backreaction of streaming cosmic rays on magnetic field generation and thermal instability

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

Nekrasov, Anatoly K.; Shadmehri, Mohsen, E-mail: anekrasov@ifz.ru, E-mail: nekrasov.anatoly@gmail.com, E-mail: m.shadmehri@gu.ac.ir

2014-06-10

Using a multifluid approach, we investigate streaming and thermal instabilities of the electron-ion plasma with homogeneous cold cosmic rays propagating perpendicular to the background magnetic field. Perturbations are also considered to be across the magnetic field. The backreaction of cosmic rays resulting in strong streaming instabilities is taken into account. It is shown that, for sufficiently short wavelength perturbations, the growth rates can exceed the growth rate of cosmic-ray streaming instability along the magnetic field, found by Nekrasov and Shadmehri, which is in turn considerably larger than the growth rate of the Bell instability. The thermal instability is shown notmore » to be subject to the action of cosmic rays in the model under consideration. The dispersion relation for the thermal instability has been derived, which includes sound velocities of plasma and cosmic rays and Alfvén and cosmic-ray streaming velocities. The relation between these parameters determines the kind of thermal instability ranging from the Parker to the Field instabilities. The results obtained can be useful for a more detailed investigation of electron-ion astrophysical objects, such as supernova remnant shocks, galaxy clusters, and others, including the dynamics of streaming cosmic rays.« less

Cylindrical waveguide filled with radially inhomogeneous magnetized plasma as a microwave accelerating structure

NASA Astrophysics Data System (ADS)

Hedayatian, F.; Salem, M. K.; Saviz, S.

2018-01-01

In this study, microwave radiation is used to excite hybrid modes in a radially inhomogeneous cold plasma-filled cylindrical waveguide in the presence of external static magnetic field applied along the waveguide axis. The analytical expressions for EH0l field components, which accelerate an injected electron in the waveguide, are calculated. To study the effects of radial inhomogeneity on the electron dynamics and its acceleration, a model based on the Bessel-Fourier expansion is used while considering hybrid modes E H0 l(l =1 ,2 ,3 ,4 ) inside the waveguide, and the results are compared with the homogeneous plasma waveguide. The numerical results show that the field components related to the coupled EH0l modes are amplified due to radial inhomogeneity, which leads to an increase in the electron's energy gain. It is found that, if the waveguide is filled with radially inhomogeneous plasma, the electron acquires a higher energy gain while covering a shorter distance along the waveguide length (60 MeV energy gain in 1.1 cm distance along the waveguide length), so, a waveguide with a lesser length and a higher energy gain can be designed. The effects of radial inhomogeneity are studied on the deflection angle, the radial position, and the trajectory of an electron in the waveguide. The effects of the initial phase of the wave, injection point of the electron, and microwave power density are also investigated on the electron's energy gain. It is shown that the present model is applicable to both homogeneous and radially inhomogeneous plasma waveguides.

The Effects of Cold Stress on Photosynthesis in Hibiscus Plants

PubMed Central

Paredes, Miriam; Quiles, María José

2015-01-01

The present work studies the effects of cold on photosynthesis, as well as the involvement in the chilling stress of chlororespiratory enzymes and ferredoxin-mediated cyclic electron flow, in illuminated plants of Hibiscus rosa-sinensis. Plants were sensitive to cold stress, as indicated by a reduction in the photochemistry efficiency of PSII and in the capacity for electron transport. However, the susceptibility of leaves to cold may be modified by root temperature. When the stem, but not roots, was chilled, the quantum yield of PSII and the relative electron transport rates were much lower than when the whole plant, root and stem, was chilled at 10°C. Additionally, when the whole plant was cooled, both the activity of electron donation by NADPH and ferredoxin to plastoquinone and the amount of PGR5 polypeptide, an essential component of the cyclic electron flow around PSI, increased, suggesting that in these conditions cyclic electron flow helps protect photosystems. However, when the stem, but not the root, was cooled cyclic electron flow did not increase and PSII was damaged as a result of insufficient dissipation of the excess light energy. In contrast, the chlororespiratory enzymes (NDH complex and PTOX) remained similar to control when the whole plant was cooled, but increased when only the stem was cooled, suggesting the involvement of chlororespiration in the response to chilling stress when other pathways, such as cyclic electron flow around PSI, are insufficient to protect PSII. PMID:26360248

Hall-Effect Thruster Simulations with 2-D Electron Transport and Hydrodynamic Ions

NASA Technical Reports Server (NTRS)

Mikellides, Ioannis G.; Katz, Ira; Hofer, Richard H.; Goebel, Dan M.

2009-01-01

A computational approach that has been used extensively in the last two decades for Hall thruster simulations is to solve a diffusion equation and energy conservation law for the electrons in a direction that is perpendicular to the magnetic field, and use discrete-particle methods for the heavy species. This "hybrid" approach has allowed for the capture of bulk plasma phenomena inside these thrusters within reasonable computational times. Regions of the thruster with complex magnetic field arrangements (such as those near eroded walls and magnets) and/or reduced Hall parameter (such as those near the anode and the cathode plume) challenge the validity of the quasi-one-dimensional assumption for the electrons. This paper reports on the development of a computer code that solves numerically the 2-D axisymmetric vector form of Ohm's law, with no assumptions regarding the rate of electron transport in the parallel and perpendicular directions. The numerical challenges related to the large disparity of the transport coefficients in the two directions are met by solving the equations in a computational mesh that is aligned with the magnetic field. The fully-2D approach allows for a large physical domain that extends more than five times the thruster channel length in the axial direction, and encompasses the cathode boundary. Ions are treated as an isothermal, cold (relative to the electrons) fluid, accounting for charge-exchange and multiple-ionization collisions in the momentum equations. A first series of simulations of two Hall thrusters, namely the BPT-4000 and a 6-kW laboratory thruster, quantifies the significance of ion diffusion in the anode region and the importance of the extended physical domain on studies related to the impact of the transport coefficients on the electron flow field.

Interaction-induced conducting-non-conducting transition of ultra-cold atoms in one-dimensional optical lattices

NASA Astrophysics Data System (ADS)

Chien, Chih-Chun; Gruss, Daniel; Di Ventra, Massimiliano; Zwolak, Michael

2013-06-01

The study of time-dependent, many-body transport phenomena is increasingly within reach of ultra-cold atom experiments. We show that the introduction of spatially inhomogeneous interactions, e.g., generated by optically controlled collisions, induce negative differential conductance in the transport of atoms in one-dimensional optical lattices. Specifically, we simulate the dynamics of interacting fermionic atoms via a micro-canonical transport formalism within both a mean-field and a higher-order approximation, as well as with a time-dependent density-matrix renormalization group (DMRG). For weakly repulsive interactions, a quasi-steady-state atomic current develops that is similar to the situation occurring for electronic systems subject to an external voltage bias. At the mean-field level, we find that this atomic current is robust against the details of how the interaction is switched on. Further, a conducting-non-conducting transition exists when the interaction imbalance exceeds some threshold from both our approximate and time-dependent DMRG simulations. This transition is preceded by the atomic equivalent of negative differential conductivity observed in transport across solid-state structures.

Radial-Poloidal Mapping of the Energy Distribution of Electrons Accelerated by Lower Hybrid Waves in the Scrape-Off Layer

NASA Astrophysics Data System (ADS)

Gunn, J. P.; Petržílka, V.; Fuchs, V.; Ekedahl, A.; Goniche, M.; Hillaret, J.; Kočan, M.; Saint-Laurent, F.

2009-11-01

According to theory, Landau damping transfers the power carried by the high n//>50 components of the lower hybrid (LH) wave to thermal SOL electrons and stochastically accelerates them up to a few keV [1]. What amounts to a few percent of the injected LH power is thus transported along field lines and strikes plasma facing components, leading to the formation of well known "LH hot spots." We report on the first measurements of both the energy from 0 to 1 keV and the radial-poloidal distributions of the accelerated electrons using a retarding field analyzer. Two distinct electron populations are present : a cold, thermal population with temperatures between 10 and 30 eV, and a suprathermal component. Only partial attenuation of the electron flux was achieved at maximum applied voltage, indicating energies greater than 1 keV. Detailed 2D mapping of the hot spots was obtained by varying the safety factor stepwise during a single discharge. The radial width of the suprathermal electron beam at full power is rather large, at least about 5-6 cm, in contrast to Landau damping theory of the launched wave that predicts the radial width of the hot spots should not exceed a few millimetres [2]. The electron flux far from the grill is intermittent, with a typical burst rate of the order of 10 kHz.

A Combined Theoretical and Experimental Study of Dissociation of Charge Transfer States at the Donor-Acceptor Interface of Organic Solar Cells.

PubMed

Tscheuschner, Steffen; Bässler, Heinz; Huber, Katja; Köhler, Anna

2015-08-13

The observation that in efficient organic solar cells almost all electron-hole pairs generated at the donor-acceptor interface escape from their mutual coulomb potential remains to be a conceptual challenge. It has been argued that it is the excess energy dissipated in the course of electron or hole transfer at the interface that assists this escape process. The current work demonstrates that this concept is unnecessary to explain the field dependence of electron-hole dissociation. It is based upon the formalism developed by Arkhipov and co-workers as well as Baranovskii and co-workers. The key idea is that the binding energy of the dissociating "cold" charge-transfer state is reduced by delocalization of the hole along the polymer chain, quantified in terms of an "effective mass", as well as the fractional strength of dipoles existent at the interface in the dark. By covering a broad parameter space, we determine the conditions for efficient electron-hole dissociation. Spectroscopy of the charge-transfer state on bilayer solar cells as well as measurements of the field dependence of the dissociation yield over a broad temperature range support the theoretical predictions.

Colonization of Bacteria on the Surfaces of Cold-Sprayed Copper Coatings Alters Their Electrochemical Behaviors

NASA Astrophysics Data System (ADS)

Suo, Xinkun; Abdoli, Leila; Liu, Yi; Xia, Peng; Yang, Guanjun; Li, Hua

2017-04-01

Copper coatings were fabricated on stainless steel plates by cold spraying. Attachment and colonization of Bacillus sp. on their surfaces in artificial seawater were characterized, and their effects on anticorrosion performances of the coatings were examined. Attached bacteria were observed using field emission scanning electron microscopy. Electrochemical behaviors including potentiodynamic polarization and electrochemical impedance spectroscopy with/without bacterial attachment were evaluated using commercial electrochemical analysis station Modulab. Results show that Bacillus sp. opt to settle on low-lying spots of the coating surfaces in early stage, followed by recruitment and attachment of extracellular polymeric substances (EPS) secreted through metabolism of Bacillus sp. The bacteria survive with the protection of EPS. An attachment model is proposed to illustrate the bacterial behaviors on the surfaces of the coatings. Electrochemical data show that current density under Bacillus sp. environment decreases compared to that without the bacteria. Charge-transfer resistance increases markedly in bacteria-containing seawater, suggesting that corrosion resistance increases and corrosion rate decreases. The influencing mechanism of bacteria settlement on corrosion resistance of the cold-sprayed copper coatings was discussed and elucidated.

A COLD FLARE WITH DELAYED HEATING

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

Fleishman, Gregory D.; Pal'shin, Valentin D.; Lysenko, Alexandra L.

2016-05-10

Recently, a number of peculiar flares have been reported that demonstrate significant nonthermal particle signatures with low, if any, thermal emission, which implies a close association of the observed emission with the primary energy release/electron acceleration region. This paper presents a flare that appears “cold” at the impulsive phase, while displaying delayed heating later on. Using hard X-ray data from Konus- Wind , microwave observations by SSRT, RSTN, NoRH, and NoRP, context observations, and three-dimensional modeling, we study the energy release, particle acceleration, and transport, and the relationships between the nonthermal and thermal signatures. The flaring process is found tomore » involve the interaction between a small loop and a big loop with the accelerated particles divided roughly equally between them. Precipitation of the electrons from the small loop produced only a weak thermal response because the loop volume was small, while the electrons trapped in the big loop lost most of their energy in the coronal part of the loop, which resulted in coronal plasma heating but no or only weak chromospheric evaporation, and thus unusually weak soft X-ray emission. The energy losses of the fast electrons in the big tenuous loop were slow, which resulted in the observed delay of the plasma heating. We determined that the impulsively accelerated electron population had a beamed angular distribution in the direction of the electric force along the magnetic field of the small loop. The accelerated particle transport in the big loop was primarily mediated by turbulent waves, which is similar to other reported cold flares.« less

Monitoring the vaccine cold chain.

PubMed

Cheriyan, E

1993-11-01

Maintaining the vaccine cold chain is an essential part of a successful immunisation programme. A continuous electronic temperature monitor helped to identify breaks in the cold chain in the community and the study led to the issue of proper guidelines and replacement of faulty equipment.

A primer on clothing systems for cold-weather field work

USGS Publications Warehouse

Denner, Jon

1990-01-01

Conducting field work in cold weather is a demanding task. The most important safety consideration for field personnel is to maintain normal body temperature and avoid hypothermia.The human body adjusts to cold temperatures through different physiological processes. Heat production is enhanced by increases in the rates of basal metabolism, specific dynamic action, and physical exercise, and heat loss is reduced by vasoconstriction.Physiological adaptations alone are inadequate to stop rapid heat loss in cold temperatures. Additional insulation in the form of cold-weather clothing is necessary to retain heat.The most practical method of dressing for winter conditions is the layering system. Wearing multiple thin layers allows one to fine tune the insulation needed for different temperatures and activity levels.

Magnetic filter apparatus and method for generating cold plasma in semicoductor processing

DOEpatents

Vella, Michael C.

1996-01-01

Disclosed herein is a system and method for providing a plasma flood having a low electron temperature to a semiconductor target region during an ion implantation process. The plasma generator providing the plasma is coupled to a magnetic filter which allows ions and low energy electrons to pass therethrough while retaining captive the primary or high energy electrons. The ions and low energy electrons form a "cold plasma" which is diffused in the region of the process surface while the ion implantation process takes place.

Magnetic filter apparatus and method for generating cold plasma in semiconductor processing

DOEpatents

Vella, M.C.

1996-08-13

Disclosed herein is a system and method for providing a plasma flood having a low electron temperature to a semiconductor target region during an ion implantation process. The plasma generator providing the plasma is coupled to a magnetic filter which allows ions and low energy electrons to pass therethrough while retaining captive the primary or high energy electrons. The ions and low energy electrons form a ``cold plasma`` which is diffused in the region of the process surface while the ion implantation process takes place. 15 figs.

Robustness of the filamentation instability as shock mediator in arbitrarily oriented magnetic field

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

Bret, A.; Alvaro, E. Perez

2011-08-15

The filamentation instability (sometimes also referred to as ''Weibel'') is a key process in many astrophysical scenario. In the Fireball model for gamma ray bursts, this instability is believed to mediate collisionless shock formation from the collision of two plasma shells. It has been known for long that a flow aligned magnetic field can completely cancel this instability. We show here that in the general case where there is an angle between the field and the flow, the filamentation instability can never be stabilized, regardless of the field strength. The presented model analyzes the stability of two symmetric counter-streaming coldmore » electron/proton plasma shells. Relativistic effects are accounted for, and various exact analytical results are derived. This result guarantees the occurrence of the instability in realistic settings fulfilling the cold approximation.« less

SOI N-Channel Field Effect Transistors, CHT-NMOS80, for Extreme Temperatures

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Almad

2009-01-01

Extreme temperatures, both hot and cold, are anticipated in many of NASA space exploration missions as well as in terrestrial applications. One can seldom find electronics that are capable of operation under both regimes. Even for operation under one (hot or cold) temperature extreme, some thermal controls need to be introduced to provide appropriate ambient temperatures so that spacecraft on-board or field on-site electronic systems work properly. The inclusion of these controls, which comprise of heating elements and radiators along with their associated structures, adds to the complexity in the design of the system, increases cost and weight, and affects overall reliability. Thus, it would be highly desirable and very beneficial to eliminate these thermal measures in order to simplify system's design, improve efficiency, reduce development and launch costs, and improve reliability. These requirements can only be met through the development of electronic parts that are designed for proper and efficient operation under extreme temperature conditions. Silicon-on-insulator (SOI) based devices are finding more use in harsh environments due to the benefits that their inherent design offers in terms of reduced leakage currents, less power consumption, faster switching speeds, good radiation tolerance, and extreme temperature operability. Little is known, however, about their performance at cryogenic temperatures and under wide thermal swings. The objective of this work was to evaluate the performance of a new commercial-off-the-shelf (COTS) SOI parts over an extended temperature range and to determine the effects of thermal cycling on their performance. The results will establish a baseline on the suitability of such devices for use in space exploration missions under extreme temperatures, and will aid mission planners and circuit designers in the proper selection of electronic parts and circuits. The electronic part investigated in this work comprised of a CHT-NMOS80 high temperature N-channel MOSFET (metal-oxide semiconductor field-effect transistor) device that was manufactured by CISSOID. This high voltage, medium-power transistor is fabricated using SOI processes and is designed for extreme wide temperature applications such as geothermal well logging, aerospace and avionics, and automotive industry. It has a high DC current capability and is specified for operation in the temperature range of -55 C to +225 C

Relationship between directions of wave and energy propagation for cold plasma waves

NASA Technical Reports Server (NTRS)

Musielak, Zdzislaw E.

1986-01-01

The dispersion relation for plasma waves is considered in the 'cold' plasma approximation. General formulas for the dependence of the phase and group velocities on the direction of wave propagation with respect to the local magnetic field are obtained for a cold magnetized plasma. The principal cold plasma resonances and cut-off frequencies are defined for an arbitrary angle and are used to establish basic regimes of frequency where the cold plasma waves can propagate or can be evanescent. The relationship between direction of wave and energy propagation, for cold plasma waves in hydrogen atmosphere, is presented in the form of angle diagrams (angle between group velocity and magnetic field versus angle between phase velocity and magnetic field) and polar diagrams (also referred to as 'Friedrich's diagrams') for different directions of wave propagation. Morphological features of the diagrams as well as some critical angles of propagation are discussed.

Stormtime coupling of the ring current, plasmasphere, and topside ionosphere: Electromagnetic and plasma disturbances

NASA Astrophysics Data System (ADS)

Mishin, E. V.; Burke, W. J.

2005-07-01

We compare plasma and field disturbances observed in the ring current/plasmasphere overlap region and in the conjugate ionosphere during the magnetic storm of 5 June 1991. Data come from the Combined Release and Radiation Effects Satellite (CRRES) flying in a geostationary transfer orbit and three satellites of the Defense Meteorological Satellite Program (DMSP) series in Sun-synchronous polar orbits. In the region between ring current nose structures and the electron plasma sheet, CRRES detected wave-like features in local electric and magnetic fields, embedded in structured cold plasmas. Mapped to the ionosphere, these fields should reflect structuring within subauroral plasma streams (SAPS). Indeed, during the period of interest, DMSP F8, F9, and F10 satellites observed highly structured SAPS in the evening ionosphere at topside altitudes. They were collocated with precipitating ring current ions, enhanced fluxes of suprathermal electrons and ions, elevated electron temperatures, and irregular plasma density troughs. Overall, these events are similar to electromagnetic structures observed by DMSP satellites within SAPS during recent geomagnetic storms (Mishin et al., 2003, 2004). Their features can be explained in terms of Alfvén and fast magnetosonic perturbations. We developed a scenario for the formation of elevated electron temperatures at the equatorward side of the SAPS. It includes a lower-hybrid drift instability driven by diamagnetic currents, consistent with strong lower- and upper-hybrid plasma wave activity and intense fluxes of the low-energy electrons and ions near the ring current's inner edge.

A Parametric Study of the Cold Plasma Refilling Rate on the Plasmasphere and Inner Magnetosphere Dynamics during the 17-March-2013 and 28-June-2013 Magnetic Storms

NASA Astrophysics Data System (ADS)

Lemon, C.; Bishop, R. L.; Coster, A. J.; Nikoukar, R.; Chen, M.; Turner, D. L.; Roeder, J. L.; Shumko, M.; Payne, C.; Bhatt, R.

2017-12-01

Magnetosphere-ionosphere coupling is a complex process, and researchers must consider a number of factors: particle transport in the electric and magnetic fields drives plasma from the high latitude tail to the mid-latitude inner magnetosphere; particle precipitation into the ionosphere, which is frequently driven by wave-particle interactions, enhances the ionospheric conductivities; feedback of the ionospheric conductivities on the electric fields determines how well the convection electric field penetrates to the mid-latitude ionosphere; and the erosion and refilling of cold plasma in the plasmasphere substantially determines the mass of plasma on magnetospheric field lines and the subsequent wave environment that drives particle precipitation. While we model all of these processes, in this presentation we focus on the role of the plasmasphere and its role in M-I coupling. We present RCM-E simulations in which particle transport through self-consistent fields controls the drainage of the plasmasphere, an outflow model determines the plasmasphere refilling rate, and electron and ion precipitation influences the electric field by enhancing the ionospheric conductivity. The plasmasphere significantly affects the spatial structure of the wave environment and electron precipitation rates. This impacts the dynamics of the sub-auroral polarization stream (SAPS) in the pre-midnight region equatorward of the auroral boundary, which itself drives erosion of the plasmasphere through strong westward electric fields near the plasmapause. We present comparisons with Van Allen Probes, THEMIS, the Plasmasphere Data Assimilation (PDA) model, and line-of-sight observations from Millstone Hill ISR and space-based GPS receivers, showing how our modeled plasmasphere compares with observational data during the 17-March-2013 and 28-June-2013 magnetic storms. To better understand refilling, we focus particular attention on densities in the recently-depleted flux tubes in the plasmasphere trough. We compare several empirical models of the plasmasphere refilling rate to see which ones give the best agreement, and through parametric simulations we systematically investigate the effect of varying the local time and L dependence of the refilling rate.

Excitation of Plasma Waves in Aurora by Electron Beams

NASA Technical Reports Server (NTRS)

daSilva, C. E.; Vinas, A. F.; deAssis, A. S.; deAzevedo, C. A.

1996-01-01

In this paper, we study numerically the excitation of plasma waves by electron beams, in the auroral region above 2000 km of altitude. We have solved the fully kinetic dispersion relation, using numerical method and found the real frequency and the growth rate of the plasma wave modes. We have examined the instability properties of low-frequency waves such as the Electromagnetic Ion Cyclotron (EMIC) wave as well as Lower-Hybrid (LH) wave in the range of high-frequency. In all cases, the source of free energy are electron beams propagating parallel to the geomagnetic field. We present some features of the growth rate modes, when the cold plasma parameters are changed, such as background electrons and ions species (H(+) and O(+)) temperature, density or the electron beam density and/or drift velocity. These results can be used in a test-particle simulation code, to investigate the ion acceleration and their implication in the auroral acceleration processes, by wave-particle interaction.

Counterstreaming beams and flat-top electron distributions observed with Langmuir, Whistler, and compressional Alfvén waves in earth's magnetic tail.

PubMed

Teste, Alexandra; Parks, George K

2009-02-20

Relevant new clues to wave-particle interactions have been obtained in Earth's plasma sheet (PS). The plasma measurements made on Cluster spacecraft show that broadband (approximately 2-6 kHz) electrostatic emissions, in the PS boundary layer, are associated with cold counterstreaming electrons flowing at 5-12x10(3) km s(-1) through hot Maxwellian plasma. In the current sheet (CS), electromagnetic whistler mode waves (approximately 10-80 Hz) and compressional Alfvén waves (<2 Hz) are detected with flat-topped electron distributions whose cutoff speeds are approximately 15-17x10(3) km s(-1). These waves are damped in the central CS where |B|

Linear and nonlinear interactions of an electron beam with oblique whistler and electrostatic waves in the magnetosphere

NASA Astrophysics Data System (ADS)

Zhang, Y. L.; Matsumoto, H.; Omura, Y.

1993-12-01

Both linear and nonlinear interactions between oblique whistler, electrostatic, quasi-upper hybrid mode waves and an electron beam are studied by linear analyses and electromagnetic particle simulations. In addition to a background cold plasma, we assumed a hot electron beam drifting along a static magnetic field. Growth rates of the oblique whistler, oblique electrostatic, and quasi-upper hybrid instabilities were first calculated. We found that there are four kinds of unstable mode waves for parallel and oblique propagations. They are the electromagnetic whistler mode wave (WW1), the electrostatic whistler mode wave (WW2), the electrostatic mode wave (ESW), and the quasi-upper hybrid mode wave (UHW). A possible mechanism is proposed to explain the satellite observations of whistler mode chorus and accompanied electrostatic waves, whose amplitudes are sometimes modulated at the chorus frequency.

Role of Earth's plasmasphere in coupling of upper atmosphere

NASA Astrophysics Data System (ADS)

Singh, A. K.; Mishra, Sandhya; Dohare, S. K.

2010-02-01

The near-Earth space environment is a complex, ever changing system of magnetized plasmas whose behaviour has a profound impact upon our technology dependent society. The exploration of the cold, relatively dense, inner region of upper atmosphere (the plasmasphere) and its unexpectedly sharp outer boundary (the plasma pause) has proceeded through a combination of in-situ observations and ground based whistler observations. Studies have shown that plasmasphere is highly variable both spatially and temporally responding to changes in geomagnetic indices, ring current, penetration and shielding electric fields and subauroral electric fields. Consequently the plasmasphere exhibits erosion, emptying and refilling during active times. Infact, it is the electric field that plays one of the most important roles in coupling of upper atmosphere. The atmospheric dynamo is the main generator of the large-scale electric field in the upper atmosphere. It arises because of a special situation which electrons and ions move with different velocities across the magnetic field because of different collisions between electrons and neutral particles and ions with neutral particles. This process leads to charge separation and consequently to an electric field. In the present paper, storm/ quiet period VLF whistler data recorded at lower latitudes/mid latitudes are analyzed and attempt has been made to look at plasmasphere response on coupling of ionosphere and magnetosphere.

The 617 MHz-λ 850 μm correlation (cosmic rays and cold dust) in NGC 3044 and NGC 4157

NASA Astrophysics Data System (ADS)

Irwin, J. A.; Brar, R. S.; Saikia, D. J.; Henriksen, R. N.

2013-08-01

We present the first maps of NGC 3044 and NGC 4157 at λ 450 μm and λ 850 μm from the James Clerk Maxwell Telescope as well as the first maps at 617 MHz from the Giant Metrewave Radio Telescope. High-latitude emission has been detected in both the radio continuum and sub-mm for NGC 3044 and in the radio continuum for NGC 4157, including several new features. For NGC 3044, in addition, we find 617 MHz emission extending to the north of the major axis, beginning at the far ends of the major axis. One of these low-intensity features, more than 10 kpc from the major axis, has apparently associated emission at λ 20 cm and may be a result of in-disc activity related to star formation. The dust spectrum at long wavelengths required fitting with a two-temperature model for both galaxies, implying the presence of cold dust (Tc = 9.5 K for NGC 3044 and Tc = 15.3 K for NGC 4157). Dust masses are Md = 1.6 × 108 M⊙ and Md = 2.1 × 107 M⊙ for NGC 3044 and NGC 4157, respectively, and are dominated by the cold component. There is a clear correlation between the 617 MHz and λ 850 μm emission in the two galaxies. In the case of NGC 3044 for which the λ 850 μm data are strongly dominated by cold dust, this implies a relation between the non-thermal synchrotron emission and cold dust. The 617 MHz component represents an integration of massive star formation over the past 107-8 yr and the λ 850 μm emission represents heating from the diffuse interstellar radiation field (ISRF). The 617 MHz-λ 850 μm correlation improves when a smoothing kernel is applied to the λ 850 μm data to account for differences between the cosmic ray (CR) electron diffusion scale and the mean free path of an ISRF photon to dust. The best-fitting relation is L_{617_MHz} ∝ {L_{850μ m}}^{2.1 ± 0.2} for NGC 3044. If variations in the cold dust emissivity are dominated by variations in dust density, and the synchrotron emission depends on magnetic field strength (a function of gas density) as well as CR electron generation (a function of massive star formation rate and therefore density via the Schmidt law) then the expected correlation for NGC 3044 is L_{617_MHz} ∝ {L_{850μ m}}^{2.2}, in agreement with the observed correlation.

Nonlinear Electrostatic Steepening of Whistler Waves: The Guiding Factors and Dynamics in Inhomogeneous Systems

NASA Astrophysics Data System (ADS)

Agapitov, O.; Drake, J. F.; Vasko, I.; Mozer, F. S.; Artemyev, A.; Krasnoselskikh, V.; Angelopoulos, V.; Wygant, J.; Reeves, G. D.

2018-03-01

Whistler mode chorus waves are particularly important in outer radiation belt dynamics due to their key role in controlling the acceleration and scattering of electrons over a very wide energy range. The efficiency of wave-particle resonant interactions is defined by whistler wave properties which have been described by the approximation of plane linear waves propagating through the cold plasma of the inner magnetosphere. However, recent observations of extremely high-amplitude whistlers suggest the importance of nonlinear wave-particle interactions for the dynamics of the outer radiation belt. Oblique chorus waves observed in the inner magnetosphere often exhibit drastically nonsinusoidal (with significant power in the higher harmonics) waveforms of the parallel electric field, presumably due to the feedback from hot resonant electrons. We have considered the nature and properties of such nonlinear whistler waves observed by the Van Allen Probes and Time History of Events and Macroscale Interactions define during Substorms in the inner magnetosphere, and we show that the significant enhancement of the wave electrostatic component can result from whistler wave coupling with the beam-driven electrostatic mode through the resonant interaction with hot electron beams. Being modulated by a whistler wave, the electron beam generates a driven electrostatic mode significantly enhancing the parallel electric field of the initial whistler wave. We confirm this mechanism using a self-consistent particle-in-cell simulation. The nonlinear electrostatic component manifests properties of the beam-driven electron acoustic mode and can be responsible for effective electron acceleration in the inhomogeneous magnetic field.

Evaluation of using ferrofluid as an interface material for a field-reversible thermal connector

NASA Astrophysics Data System (ADS)

Yousif, Ahmed S.

The electrical functionality of an avionics chassis is limited due to heat dissipation limits. The limits arise due to the fact that components in an avionic computer boxes are packed very compactly, with the components mounted onto plug-in cards, and the harsh environment experienced by the chassis limits how heat can be dissipated from the cards. Convective and radiative heat transfer to the ambient are generally not possible. Therefore it is necessary to have heat transferred from the components conducted to the edge of the plug-in cards. The heat then needs to conduct from the card edge to a cold block that not only holds the card in place, but also removes the generated heat by some heat transfer fluid that is circulated through the cold block. The interface between the plug-in card and the cold block typically has a high thermal resistance since it is necessary for the card to have the capability to be re-workable, meaning that the card can be removed and then returned to the chassis. Reducing the thermal resistance of the interface is the objective of the current study and the topic of this thesis. The current design uses a pressure interface between the card and cold block. The contact pressure is increased through the addition of a wedgelock, which is a field-reversible mechanical connector. To use a wedgelock, the cold block has channels milled on the surface with widths that are larger than the thickness of the plug-in card and the un-expanded wedgelock. The card edge is placed in the channel and placed against one of the channel walls. A wedgelock is then placed between the card and the other channel wall. The wedgelock is then expanded by using either a screw or a lever. As the wedgelock expands it fills in the remaining channel gap and bears against the other face of the plug-in card. The majority of heat generated by the components on the plug-in card is forced to conduct from the card into the wall of the cold block, effectively a single sided, dry conduction heat transfer path. Having started as a student design competition named RevCon Challenge, work was performed to evaluate the use of new field-reversible thermal connectors. The new design proposed by the University of Missouri utilized oil based iron nanoparticles, commonly known as a ferrofluid, as a thermal interface material. By using a liquid type of interface material the channel gap can be reduced to a few micrometers, within machining tolerances, and heat can be dissipated off both sides of the card. The addition of nanoparticles improves the effective thermal conductivity of base fluid. The use of iron nanoparticles allows magnets to be used to hold the fluid in place, so the electronic cards may be easily inserted and removed while keeping the ferrofluid in the cold block channel. The ferrofluid-based design which was investigated has shown lower thermal resistance than the current wedgelock design. These results open the door for further development of electronic cards by using higher heat emitting components without compromising the simplicity of attaching/detaching cards from cooling plates.

Multi-layer carbon-based coatings for field emission

DOEpatents

Sullivan, J.P.; Friedmann, T.A.

1998-10-13

A multi-layer resistive carbon film field emitter device for cold cathode field emission applications is disclosed. The multi-layered film of the present invention consists of at least two layers of a conductive carbon material, preferably amorphous-tetrahedrally coordinated carbon, where the resistivities of adjacent layers differ. For electron emission from the surface, the preferred structure can be a top layer having a lower resistivity than the bottom layer. For edge emitting structures, the preferred structure of the film can be a plurality of carbon layers, where adjacent layers have different resistivities. Through selection of deposition conditions, including the energy of the depositing carbon species, the presence or absence of certain elements such as H, N, inert gases or boron, carbon layers having desired resistivities can be produced. 8 figs.

Structures with high number density of carbon nanotubes and 3-dimensional distribution

NASA Technical Reports Server (NTRS)

Chen, Zheng (Inventor); Tzeng, Yonhua (Inventor)

2002-01-01

A composite is described having a three dimensional distribution of carbon nanotubes. The critical aspect of such composites is a nonwoven network of randomly oriented fibers connected at their junctions to afford macropores in the spaces between the fibers. A variety of fibers may be employed, including metallic fibers, and especially nickel fibers. The composite has quite desirable properties for cold field electron emission applications, such as a relatively low turn-on electric field, high electric field enhancement factors, and high current densities. The composites of this invention also show favorable properties for other an electrode applications. Several methods, which also have general application in carbon nanotube production, of preparing these composites are described and employ a liquid feedstock of oxyhydrocarbons as carbon nanotube precursors.

Is there a field-theoretic explanation for precursor biopolymers?

PubMed

Rosen, Gerald

2002-08-01

A Hu-Barkana-Gruzinov cold dark matter scalar field phi may enter a weak isospin invariant derivative interaction that causes the flow of right-handed electrons to align parallel to (inverted delta phi). Hence, in the outer regions of galaxies where (inverted delta phi) is large, as in galactic halos, the derivative interaction may induce a chirality-imbued quantum chemistry. Such a chirality-imbued chemistry would in turn be conducive to the formation of abundant precursor biopolymers on interstellar dust grains, comets and meteors in galactic halo regions, with subsequent delivery to planets in the inner galactic regions where phi and (inverted delta phi) are concomitantly near zero and left-right symmetric terrestrial quantum chemistry prevails.

Solution for Minimizing Surface Heating Effect for Fast Open-Path CO2 Flux Measurements in Cold Environments

NASA Astrophysics Data System (ADS)

Hupp, J. R.; Burba, G. G.; McDermitt, D. K.; Anderson, D. J.; Eckles, R. D.

2010-12-01

Open-path design of the high speed gas analyzers is a well-established configuration widely used for measurements of CO2 fluxes and concentrations. This configuration has advantages and deficiencies. Advantages include excellent frequency response, long-term stability, low sensitivity to window contamination, low-power pump-free operation, and infrequent calibration requirements. Deficiencies include susceptibility to precipitation and icing, and a potential need for instrument surface heating correction in extremely cold environments. In spite of the deficiencies, open-path measurements often provide data coverage that would not have been possible using traditional closed-path approach. Data loss from precipitation and icing may not always be prevented for the open-path instruments, while heating effect does not pose a problem for CO2 flux in warm environments. Even in cold environments, the impact of heating on CO2 flux is much smaller than other well-known effects, such as Webb-Pearman-Leuning terms, or frequency response corrections for closed-path analyzers. Nonetheless, instrument surface heating effect in cold environments could be addressed scientifically, via developing the theoretical corrections, and instrumentally, via measuring fast integrated air temperature in the optical path, or via enclosing the open-path instrument into a low-power short-intake design. Here we provide an alternative way to minimize or eliminate open-path heating effect, achieved by minimizing or eliminating the temperature gradient between the instrument surface and ambient air. Open-path low temperature controlled design is discussed in comparison with two other approaches (e.g., traditional open-path design and closed-path design) in terms of their field performance for Eddy Covariance flux measurements in the cold. This study presents field data from a new open-path CO2/H2O gas analyzer, LI-7500A, based on the LI-7500 model modified to produce substantially less heat during extremely cold conditions. Two regiments of the temperature control for internal electronics were examined across a wide range of temperatures: (i) the traditional control temperature of about 30oC, and (ii) new regiment controlling parts of internal electronics at 5oC. When new 5oC regiment was activated, the following changes were observed: heat dissipation from the surface reduced several folds, surface-to-air temperature gradients reduced 2-50 times; and the number of false uptake hours were reduced by 3.5 times, to the same level as a closed-path standard. Significant advantage of the new regiment was also observed in the magnitude of CO2 fluxes, especially in cold weather below -10oC. At such cold temperatures, CO2 fluxes from a 30oC controlled LI-7500 were 19% below those of the closed-path standard, while fluxes from a 5oC controlled LI-7500A were, on average, within 1% of the standard. These are strong experimental evidence that open-path instrument heating can be substantially reduced or eliminated via such simple hardware based solution. This allows continued and expanded use of this ultimately lowest-power remote solution for fast gas measurements.

Drift turbulence, particle transport, and anomalous dissipation at the reconnecting magnetopause

NASA Astrophysics Data System (ADS)

Le, A.; Daughton, W.; Ohia, O.; Chen, L.-J.; Liu, Y.-H.; Wang, S.; Nystrom, W. D.; Bird, R.

2018-06-01

Using fully kinetic 3D simulations, the reconnection dynamics of asymmetric current sheets are examined at the Earth's magnetopause. The plasma parameters are selected to model MMS magnetopause diffusion region crossings with guide fields of 0.1, 0.4, and 1 of the reconnecting magnetosheath field. In each case, strong drift-wave fluctuations are observed in the lower-hybrid frequency range at the steep density gradient across the magnetospheric separatrix. These fluctuations give rise to cross-field electron particle transport. In addition, this turbulent mixing leads to significantly enhanced electron parallel heating in comparison to 2D simulations. We study three different methods of quantifying the anomalous dissipation produced by the drift fluctuations, based on spatial averaging, temporal averaging, and temporal averaging followed by integrating along magnetic field lines. A comparison of different methods reveals complications in identifying and measuring the anomalous dissipation. Nevertheless, the anomalous dissipation from short wavelength drift fluctuations appears weak for each case, and the reconnection rates observed in 3D are nearly the same as in 2D models. The 3D simulations feature a number of interesting new features that are consistent with recent MMS observations, including cold beams of magnetosheath electrons that penetrate into the hotter magnetospheric inflow, the related observation of decreasing temperature in regions of increasing total density, and an effective turbulent diffusion coefficient that agrees with predictions from quasi-linear theory.

Oblique ion-acoustic cnoidal waves in two temperature superthermal electrons magnetized plasma

NASA Astrophysics Data System (ADS)

Panwar, A.; Ryu, C. M.; Bains, A. S.

2014-12-01

A study is presented for the oblique propagation of ion acoustic cnoidal waves in a magnetized plasma consisting of cold ions and two temperature superthermal electrons modelled by kappa-type distributions. Using the reductive perturbation method, the nonlinear Korteweg de-Vries equation is derived, which further gives the solutions with a special type of cnoidal elliptical functions. Both compressive and rarefactive structures are found for these cnoidal waves. Nonlinear periodic cnoidal waves are explained in terms of plasma parameters depicting the Sagdeev potential and the phase curves. It is found that the density ratio of hot electrons to ions μ significantly modifies compressive/refractive wave structures. Furthermore, the combined effects of superthermality of cold and hot electrons κ c , κ h , cold to hot electron temperature ratio σ, angle of propagation and ion cyclotron frequency ωci have been studied in detail to analyze the height and width of compressive/refractive cnoidal waves. The findings in the present study could have important implications in understanding the physics of electrostatic wave structures in the Saturn's magnetosphere where two temperature superthermal electrons are present.

Optimising electron microscopy experiment through electron optics simulation.

PubMed

Kubo, Y; Gatel, C; Snoeck, E; Houdellier, F

2017-04-01

We developed a new type of electron trajectories simulation inside a complete model of a modern transmission electron microscope (TEM). Our model incorporates the precise and real design of each element constituting a TEM, i.e. the field emission (FE) cathode, the extraction optic and acceleration stages of a 300kV cold field emission gun, the illumination lenses, the objective lens, the intermediate and projection lenses. Full trajectories can be computed using magnetically saturated or non-saturated round lenses, magnetic deflectors and even non-cylindrical symmetry elements like electrostatic biprism. This multi-scale model gathers nanometer size components (FE tip) with parts of meter length (illumination and projection systems). We demonstrate that non-trivial TEM experiments requiring specific and complex optical configurations can be simulated and optimized prior to any experiment using such model. We show that all the currents set in all optical elements of the simulated column can be implemented in the real column (I2TEM in CEMES) and used as starting alignment for the requested experiment. We argue that the combination of such complete electron trajectory simulations in the whole TEM column with automatic optimization of the microscope parameters for optimal experimental data (images, diffraction, spectra) allows drastically simplifying the implementation of complex experiments in TEM and will facilitate the development of advanced use of the electron microscope in the near future. Copyright © 2017 Elsevier B.V. All rights reserved.

Strain Evolution in Cold-Warm Forged Steel Components Studied by Means of EBSD Technique

PubMed Central

Bonollo, Franco; Bassan, Fabio; Berto, Filippo

2017-01-01

Electron BackScatter Diffraction (EBSD) in conjunction with Field-Emission Environmental Scanning Electron Microscopy (FEG-ESEM) has been used to evaluate the microstructural and local plastic strain evolution in different alloys (AISI 1005, AISI 304L and Duplex 2205) deformed by a single-stage cold and warm forging process. The present work is aimed to describe the different behavior of the austenite and ferrite during plastic deformation as a function of different forging temperatures. Several topological EBSD maps have been measured on the deformed and undeformed states. Then, image quality factor, distributions of the grain size and misorientation have been analyzed in detail. In the austenitic stainless steel, the γ-phase has been found to harden more easily, then α-phase and γ-phase in AISI 1005 and in duplex stainless steel, sequentially. Compared to the high fraction of continuous dynamic recrystallized austenitic zones observed in stainless steels samples forged at low temperatures, the austenitic microstructure of samples forged at higher temperatures, 600–700 °C, has been found to be mainly characterized by large and elongated grains with some colonies of fine nearly-equiaxed grains attributed to discontinuous dynamic recrystallization. PMID:29258249

Inductive and electrostatic acceleration in relativistic jet-plasma interactions.

PubMed

Ng, Johnny S T; Noble, Robert J

2006-03-24

We report on the observation of rapid particle acceleration in numerical simulations of relativistic jet-plasma interactions and discuss the underlying mechanisms. The dynamics of a charge-neutral, narrow, electron-positron jet propagating through an unmagnetized electron-ion plasma was investigated using a three-dimensional, electromagnetic, particle-in-cell computer code. The interaction excited magnetic filamentation as well as electrostatic plasma instabilities. In some cases, the longitudinal electric fields generated inductively and electrostatically reached the cold plasma-wave-breaking limit, and the longitudinal momentum of about half the positrons increased by 50% with a maximum gain exceeding a factor of 2 during the simulation period. Particle acceleration via these mechanisms occurred when the criteria for Weibel instability were satisfied.

Electric dipole radiation at VLF in a uniform warm magneto-plasma.

NASA Technical Reports Server (NTRS)

Wang, T. N. C.; Bell, T. F.

1972-01-01

Use of a linear full electromagnetic wave theory to calculate the input impedance of an electric antenna embedded in a uniform, lossless, unbounded warm magnetoplasma, which is assumed to consist of warm electrons and cold ions. In calculating the dipole radiation resistance for the thermal modes and the thermally modified whistler mode the analysis includes the finite temperature only for the electrons. In deriving the formal solution of the warm plasma dipole input impedance a full-wave analysis is used and two antenna orientations are considered, parallel and perpendicular to the static magnetic field. A general dispersion equation governing the modes of propagation is derived and a detailed analysis is made of the propagation characteristics of these modes.

Compression of a mixed antiproton and electron non-neutral plasma to high densities

NASA Astrophysics Data System (ADS)

Aghion, Stefano; Amsler, Claude; Bonomi, Germano; Brusa, Roberto S.; Caccia, Massimo; Caravita, Ruggero; Castelli, Fabrizio; Cerchiari, Giovanni; Comparat, Daniel; Consolati, Giovanni; Demetrio, Andrea; Di Noto, Lea; Doser, Michael; Evans, Craig; Fanì, Mattia; Ferragut, Rafael; Fesel, Julian; Fontana, Andrea; Gerber, Sebastian; Giammarchi, Marco; Gligorova, Angela; Guatieri, Francesco; Haider, Stefan; Hinterberger, Alexander; Holmestad, Helga; Kellerbauer, Alban; Khalidova, Olga; Krasnický, Daniel; Lagomarsino, Vittorio; Lansonneur, Pierre; Lebrun, Patrice; Malbrunot, Chloé; Mariazzi, Sebastiano; Marton, Johann; Matveev, Victor; Mazzotta, Zeudi; Müller, Simon R.; Nebbia, Giancarlo; Nedelec, Patrick; Oberthaler, Markus; Pacifico, Nicola; Pagano, Davide; Penasa, Luca; Petracek, Vojtech; Prelz, Francesco; Prevedelli, Marco; Rienaecker, Benjamin; Robert, Jacques; Røhne, Ole M.; Rotondi, Alberto; Sandaker, Heidi; Santoro, Romualdo; Smestad, Lillian; Sorrentino, Fiodor; Testera, Gemma; Tietje, Ingmari C.; Widmann, Eberhard; Yzombard, Pauline; Zimmer, Christian; Zmeskal, Johann; Zurlo, Nicola; Antonello, Massimiliano

2018-04-01

We describe a multi-step "rotating wall" compression of a mixed cold antiproton-electron non-neutral plasma in a 4.46 T Penning-Malmberg trap developed in the context of the AEḡIS experiment at CERN. Such traps are routinely used for the preparation of cold antiprotons suitable for antihydrogen production. A tenfold antiproton radius compression has been achieved, with a minimum antiproton radius of only 0.17 mm. We describe the experimental conditions necessary to perform such a compression: minimizing the tails of the electron density distribution is paramount to ensure that the antiproton density distribution follows that of the electrons. Such electron density tails are remnants of rotating wall compression and in many cases can remain unnoticed. We observe that the compression dynamics for a pure electron plasma behaves the same way as that of a mixed antiproton and electron plasma. Thanks to this optimized compression method and the high single shot antiproton catching efficiency, we observe for the first time cold and dense non-neutral antiproton plasmas with particle densities n ≥ 1013 m-3, which pave the way for an efficient pulsed antihydrogen production in AEḡIS.

Ion distribution in the hot spot of an inertial confinement fusion plasma

NASA Astrophysics Data System (ADS)

Tang, Xianzhu; Guo, Zehua; Berk, Herb

2012-10-01

Maximizing the fusion gain of inertial confinement fusion (ICF) for inertial fusion energy (IFE) applications leads to the standard scenario of central hot spot ignition followed by propagating burn wave through the cold/dense assembled fuel. The fact that the hot spot is surrounded by cold but dense fuel layer introduces subtle plasma physics which requires a kinetic description. Here we perform Fokker-Planck calculations and kinetic PIC simulations for an ICF plasma initially in pressure balance but having large temperature gradient over a narrow transition layer. The loss of the fast ion tail from the hot spot, which is important for fusion reactivity, is quantified by Fokker-Planck models. The role of electron energy transport and the ambipolar electric field is investigated via kinetic simulations and the fluid moment models. The net effect on both hot spot ion temperature and the ion tail distribution, and hence the fusion reactivity, is elucidated.

Online Teaching Tool Simplifies Faculty Use of Multimedia and Improves Student Interest and Knowledge in Science

PubMed Central

Walsh, John P.; Chih-Yuan Sun, Jerry; Riconscente, Michelle

2011-01-01

Digital technologies can improve student interest and knowledge in science. However, researching the vast number of websites devoted to science education and integrating them into undergraduate curricula is time-consuming. We developed an Adobe ColdFusion– and Adobe Flash–based system for simplifying the construction, use, and delivery of electronic educational materials in science. The Online Multimedia Teaching Tool (OMTT) in Neuroscience was constructed from a ColdFusion-based online interface, which reduced the need for programming skills and the time for curriculum development. The OMTT in Neuroscience was used by faculty to enhance their lectures in existing curricula. Students had unlimited online access to encourage user-centered exploration. We found the OMTT was rapidly adapted by multiple professors, and its use by undergraduate students was consistent with the interpretation that the OMTT improved performance on exams and increased interest in the field of neuroscience. PMID:21885826

Atmospheric-Pressure Cold Plasmas Used to Embed Bioactive Compounds in Matrix Material for Active Packaging of Fruits and Vegetables

NASA Astrophysics Data System (ADS)

Fernandez, Sulmer; Pedrow, Patrick; Powers, Joseph; Pitts, Marvin

2009-10-01

Active thin film packaging is a technology with the potential to provide consumers with new fruit and vegetable products-if the film can be applied without deactivating bioactive compounds.Atmospheric pressure cold plasma (APCP) processing can be used to activate monomer with concomitant deposition of an organic plasma polymerized matrix material and to immobilize a bioactive compound all at or below room temperature.Aims of this work include: 1) immobilize an antimicrobial in the matrix; 2) determine if the antimicrobial retains its functionality and 3) optimize the reactor design.The plasma zone will be obtained by increasing the voltage on an electrode structure until the electric field in the feed material (argon + monomer) yields electron avalanches. Results will be described using Red Delicious apples.Prospective matrix precursors are vanillin and cinnamic acid.A prospective bioactive compound is benzoic acid.

Online teaching tool simplifies faculty use of multimedia and improves student interest and knowledge in science.

PubMed

Walsh, John P; Chih-Yuan Sun, Jerry; Riconscente, Michelle

2011-01-01

Digital technologies can improve student interest and knowledge in science. However, researching the vast number of websites devoted to science education and integrating them into undergraduate curricula is time-consuming. We developed an Adobe ColdFusion- and Adobe Flash-based system for simplifying the construction, use, and delivery of electronic educational materials in science. The Online Multimedia Teaching Tool (OMTT) in Neuroscience was constructed from a ColdFusion-based online interface, which reduced the need for programming skills and the time for curriculum development. The OMTT in Neuroscience was used by faculty to enhance their lectures in existing curricula. Students had unlimited online access to encourage user-centered exploration. We found the OMTT was rapidly adapted by multiple professors, and its use by undergraduate students was consistent with the interpretation that the OMTT improved performance on exams and increased interest in the field of neuroscience.

On the mechanism of X-ray production by dart leaders of lightning flashes

NASA Astrophysics Data System (ADS)

Cooray, Vernon; Dwyer, Joseph; Rakov, V.; Rahman, Mahbubur

2010-07-01

Radiation with energies up to about 250 keV associated with the dart leader phase of rocket-triggered lightning were reported by Dwyer et al. (2004). The mechanism of X-ray generation by dart leaders, however, is unknown at present. Recently, Cooray et al. (2009a) developed physical concepts and mathematical techniques necessary to calculate the electric field associated with the tip of dart leaders. We have utilized the results of these calculations together with the energy dependent frictional force on electrons, as presented by Moss et al. (2006), to evaluate the maximum energy an electron will receive in accelerating in the dart-leader-tip electric field. The main assumptions made in performing the calculations are: (a) the dart leader channel is straight and vertical; (b) the path of the electrons are straight inside the channel; and (c) the decay of the channel temperature is uniform along the length of the dart leader. In the calculation, we have taken into account the fact that the electric field is changing both in space and time and that the gas in the defunct return stroke channel is at atmospheric pressure and at elevated temperature (i.e. reduced gas density). The results of the calculation show that for a given dart leader current there is a critical defunct-return-stroke-channel temperature above which the cold electron runaway becomes feasible. For a typical dart leader, this temperature is around 2500 K. This critical temperature decreases with increase in dart leader current. Since the temperature of the defunct return stroke channel may lie in the range of 2000-4000 K, the results show that the electric field at the tip of dart leaders is capable of accelerating electrons to MeV energy levels.

Modeling of Inner Magnetosphere Coupling Processes

NASA Technical Reports Server (NTRS)

Khazanov, George V.

2011-01-01

The Ring Current (RC) is the biggest energy player in the inner magnetosphere. It is the source of free energy for Electromagnetic Ion Cyclotron (EMIC) wave excitation provided by a temperature anisotropy of RC ions, which develops naturally during inward E B convection from the plasmasheet. The cold plasmasphere, which is under the strong influence of the magnetospheric electric field, strongly mediates the RC-EMIC wave-particle-coupling process and ultimately becomes part of the particle and energy interplay. On the other hand, there is a strong influence of the RC on the inner magnetospheric electric and magnetic field configurations and these configurations, in turn, are important to RC dynamics. Therefore, one of the biggest needs for inner magnetospheric research is the continued progression toward a coupled, interconnected system with the inclusion of nonlinear feedback mechanisms between the plasma populations, the electric and magnetic fields, and plasma waves. As we clearly demonstrated in our studies, EMIC waves strongly interact with electrons and ions of energies ranging from approx.1 eV to approx.10 MeV, and that these waves strongly affect the dynamics of resonant RC ions, thermal electrons and ions, and the outer RB relativistic electrons. As we found, the rate of ion and electron scattering/heating in the Earth's magnetosphere is not only controlled by the wave intensity-spatial-temporal distribution but also strongly depends on the spectral distribution of the wave power. The latter is also a function of the plasmaspheric heavy ion content, and the plasma density and temperature distributions along the magnetic field lines. The above discussion places RC-EMIC wave coupling dynamics in context with inner magnetospheric coupling processes and, ultimately, relates RC studies with plasmaspheric and Superthermal Electrons formation processes as well as with outer RB physics.

Electronic Equipment Cold Plates

DTIC Science & Technology

1976-04-01

using fans or blowers to force the air through the cooling device». ^J^lJ^^i 5!°^ it ia ’«"^"o^ve. nonto«ic. nonfla—able, *nd possesses good ...Techniques GENERAL THERMAL CONTROL SYSTEMS AND THEIR REgUIREMENTS FLON DISTRIBUTION IN MANIFOLDS THE COLD PLATE IA ,! 1 3 S 12 15 33 32 32... IA .1 132 132 132 155 169 179 183 r (1) Air-Cooled Cold Plate No. (2) Air-Cooled Cold Plate No. (3) Air-cooled Cold Plate No. (4) Air-Cooled

Wave modeling in a cylindrical non-uniform helicon discharge

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

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

2012-08-15

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

Nonequilibrium dynamical mean-field theory

NASA Astrophysics Data System (ADS)

Freericks, James

2007-03-01

Dynamical mean-field theory (DMFT) is establishing itself as one of the most powerful approaches to the quantum many-body problem in strongly correlated electron materials. Recently, the formalism has been generalized to study nonequilibrium problems [1,2], such as the evolution of Bloch oscillations in a material that changes from a diffusive metal to a Mott insulator [2,3]. Using a real-time formalism on the Kadanoff-Baym-Keldysh contour, the DMFT algorithm can be generalized to the case of systems that are not time-translation invariant. The computational algorithm has a parallel implementation with essentially a linear scale up when running on thousands of processors. Results on the decay of Bloch oscillations, their change of character within the Mott insulator, and movies on how electrons redistribute themselves due to their response to an external electrical field will be presented. In addition to solid-state applications, this work also applies to the behavior of mixtures of light and heavy cold atoms in optical lattices. [1] V. M. Turkowski and J. K. Freericks, Spectral moment sum rules for strongly correlated electrons in time-dependent electric fields, Phys. Rev. B 075108 (2006); Erratum, Phys. Rev. B 73, 209902(E) (2006). [2] J. K. Freericks, V. M. Turkowski , and V. Zlati'c, Nonlinear response of strongly correlated materials to large electric fields, in Proceedings of the HPCMP Users Group Conference 2006, Denver, CO, June 26--29, 2006 edited by D. E. Post (IEEE Computer Society, Los Alamitos, CA, 2006), to appear. [3] J. K. Freericks, V. M. Turkowski, and V. Zlati'c, Nonequilibrium dynamical mean-field theory, submitted to Phys. Rev. Lett. cond-mat//0607053.

Effect of cold deformation on the recrystallization behavior of FePd alloy at the ordering temperature using electron backscatter diffraction

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

Lin, Hung-Pin; Chen, Yen-Chun; Chen, Delphic

2014-08-15

In this study, the evolution of the recrystallization texture and microstructure was investigated after annealing of 50% and 90% cold-rolled FePd alloy at 530 °C. The FePd alloy was produced by vacuum arc melting in an atmosphere of 97% Ar and 3% H{sub 2}. The specimens were cold rolled to achieve 50% and 90% reduction in thickness. Electron backscatter diffraction measurements were performed on the rolling direction–normal direction section. With increased deformation from 50% to 90%, recrystallized texture transition occurs. For the 50% cold-rolled alloy, the preferred orientation is (0 1 0) [11 0 1], which is close to themore » cubic orientation after 400 h of annealing. For the 90% cold-rolled alloy, the orientation changes to (0 5 4) [22–4 5] after 16 h of annealing. - Highlights: • Texture and microstructure in cold-rolled FePd alloy was investigated during annealing using EBSD. • The recrystallized texture of 50% cold-rolled FePd is (0 1 0) [11 0 1] at 530 °C for 400 hours. • The recrystallized texture of 90% cold-rolled FePd is changed to (0 5 4) [22–4 5] at 530 °C after 16 hours.« less

Field emission and photoluminescence characteristics of ZnS nanowires via vapor phase growth

NASA Astrophysics Data System (ADS)

Chang, Yongqin; Wang, Mingwei; Chen, Xihong; Ni, Saili; Qiang, Weijing

2007-05-01

Large-area ZnS nanowires were synthesized through a vapor phase deposition method. X-ray diffraction and electron microscopy results show that the products are composed of single crystalline ZnS nanowires with a cubic structure. The nanowires have sharp tips and are distributed uniformly on silicon substrates. The diameter of the bases is in the range of 320-530 nm and that of the tips is around 20-30 nm. The strong ultraviolet emission in the photoluminescence spectra also demonstrates that the ZnS nanowires are of high crystalline perfection. Field emission measurements reveal that the ZnS nanowires have a fairly low threshold field, which may be ascribed to their very sharp tips, rough surfaces and high crystal quality. The perfect field emission ability of the ZnS nanowires makes them a promising candidate for the fabrication of flexible cold cathodes.

Inductively guided circuits for ultracold dressed atoms

PubMed Central

Sinuco-León, German A.; Burrows, Kathryn A.; Arnold, Aidan S.; Garraway, Barry M.

2014-01-01

Recent progress in optics, atomic physics and material science has paved the way to study quantum effects in ultracold atomic alkali gases confined to non-trivial geometries. Multiply connected traps for cold atoms can be prepared by combining inhomogeneous distributions of DC and radio-frequency electromagnetic fields with optical fields that require complex systems for frequency control and stabilization. Here we propose a flexible and robust scheme that creates closed quasi-one-dimensional guides for ultracold atoms through the ‘dressing’ of hyperfine sublevels of the atomic ground state, where the dressing field is spatially modulated by inductive effects over a micro-engineered conducting loop. Remarkably, for commonly used atomic species (for example, 7Li and 87Rb), the guide operation relies entirely on controlling static and low-frequency fields in the regimes of radio-frequency and microwave frequencies. This novel trapping scheme can be implemented with current technology for micro-fabrication and electronic control. PMID:25348163

Heat to electricity conversion by cold carrier emissive energy harvesters

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

Strandberg, Rune

2015-12-07

This paper suggests a method to convert heat to electricity by the use of devices called cold carrier emissive energy harvesters (cold carrier EEHs). The working principle of such converters is explained and theoretical power densities and efficiencies are calculated for ideal devices. Cold carrier EEHs are based on the same device structure as hot carrier solar cells, but works in an opposite way. Whereas a hot carrier solar cell receives net radiation from the sun and converts some of this radiative heat flow into electricity, a cold carrier EEH sustains a net outflux of radiation to the surroundings whilemore » converting some of the energy supplied to it into electricity. It is shown that the most basic type of cold carrier EEHs have the same theoretical efficiency as the ideal emissive energy harvesters described earlier by Byrnes et al. In the present work, it is also shown that if the emission from the cold carrier EEH originates from electron transitions across an energy gap where a difference in the chemical potential of the electrons above and below the energy gap is sustained, power densities slightly higher than those given by Byrnes et al. can be achieved.« less

Investigation of a four-body coupling in the one-dimensional extended Penson-Kolb-Hubbard model

NASA Astrophysics Data System (ADS)

Ding, Hanqin; Ma, Xiaojuan; Zhang, Jun

2017-09-01

The experimental advances in cold fermion gases motivates the investigation of a one-dimensional (1D) correlated electronic system by incorporating a four-body coupling. Using the low-energy field theory scheme and focusing on the weak-coupling regime, we extend the 1D Penson-Kolb-Hubbard (PKH) model at half filling. It is found that the additional four-body interaction may significantly modify the quantum phase diagram, favoring the presence of the superconducting phase even in the case of two-body repulsions.

Effects of ethylene on photosystem II and antioxidant enzyme activity in Bermuda grass under low temperature.

PubMed

Hu, Zhengrong; Fan, Jibiao; Chen, Ke; Amombo, Erick; Chen, Liang; Fu, Jinmin

2016-04-01

The phytohormone ethylene has been reported to mediate plant response to cold stress. However, it is still debated whether the effect of ethylene on plant response to cold stress is negative or positive. The objective of the present study was to explore the role of ethylene in the cold resistance of Bermuda grass (Cynodon dactylon (L).Pers.). Under control (warm) condition, there was no obvious effect of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) or the antagonist Ag(+) of ethylene signaling on electrolyte leakage (EL) and malondialdehyde (MDA) content. Under cold stress conditions, ACC-treated plant leaves had a greater level of EL and MDA than the untreated leaves. However, the EL and MDA values were lower in the Ag(+) regime versus the untreated. In addition, after 3 days of cold treatment, ACC remarkably reduced the content of soluble protein and also altered antioxidant enzyme activity. Under control (warm) condition, there was no significant effect of ACC on the performance of photosystem II (PS II) as monitored by chlorophyll α fluorescence transients. However, under cold stress, ACC inhibited the performance of PS II. Under cold condition, ACC remarkably reduced the performance index for energy conservation from excitation to the reduction of intersystem electron acceptors (PI(ABS)), the maximum quantum yield of primary photochemistry (φP0), the quantum yield of electron transport flux from Q(A) to Q(B) (φE0), and the efficiency/probability of electron transport (ΨE0). Simultaneously, ACC increased the values of specific energy fluxes for absorption (ABS/RC) and dissipation (DI0/RC) after 3 days of cold treatment. Additionally, under cold condition, exogenous ACC altered the expressions of several related genes implicated in the induction of cold tolerance (LEA, SOD, POD-1 and CBF1, EIN3-1, and EIN3-2). The present study thus suggests that ethylene affects the cold tolerance of Bermuda grass by impacting the antioxidant system, photosystem II, as well as the CBF transcriptional regulatory cascade.

Field nanoemitter: One-dimension Al4C3 ceramics

NASA Astrophysics Data System (ADS)

Sun, Y.; Cui, H.; Gong, L.; Chen, Jian; Shen, P. K.; Wang, C. X.

2011-07-01

As a kind of ionic (or salt-like) carbide, Al4C3 hardly any active functions have been found except for structure material purposes. However, considering the unique characteristic features of its crystal structure, we think Al4C3 in fact might have huge potential for exhibiting active functionality on field-emission application. Herein, we report for the first time the catalyst-free synthesis and excellent field emission properties of Al4C3 one-dimension (1-D) nanostructures. The 1-D nanostructures acting as cold electron emitters display excellent field emission performance with the turn-on field as low as 1.4-2.0 V μm-1 and the threshold field down to 4.2-4.4 V μm-1. Such emitters are technologically useful, because they can be easily fabricated on large substrates, and the synthesis process is simple and broadly applicable. The findings conceptually provide new opportunities for the application of Al4C3 ceramic material in vacuum microelectronic devices.

Plasma properties of driver gas following interplanetary shocks observed by ISEE-3

NASA Technical Reports Server (NTRS)

Zwickl, R. D.; Asbridge, J. R.; Bame, S. J.; Feldman, W. C.; Gosling, J. T.; Smith, E. J.

1983-01-01

Plasma fluid parameters calculated from solar wind and magnetic field data to determine the characteristic properties of driver gas following a select subset of interplanetary shocks were studied. Of 54 shocks observed from August 1978 to February 1980, 9 contained a well defined driver gas that was clearly identifiable by a discontinuous decrease in the average proton temperature. While helium enhancements were present downstream of the shock in all 9 of these events, only about half of them contained simultaneous changes in the two quantities. Simultaneous with the drop in proton temperature the helium and electron temperature decreased abruptly. In some cases the proton temperature depression was accompanied by a moderate increase in magnetic field magnitude with an unusually low variance, by a small decrease in the variance of the bulk velocity, and by an increase in the ratio of parallel to perpendicular temperature. The cold driver gas usually displayed a bidirectional flow of suprathermal solar wind electrons at higher energies.

Low work function, stable thin films

DOEpatents

Dinh, Long N.; McLean, II, William; Balooch, Mehdi; Fehring, Jr., Edward J.; Schildbach, Marcus A.

2000-01-01

Generation of low work function, stable compound thin films by laser ablation. Compound thin films with low work function can be synthesized by simultaneously laser ablating silicon, for example, and thermal evaporating an alkali metal into an oxygen environment. For example, the compound thin film may be composed of Si/Cs/O. The work functions of the thin films can be varied by changing the silicon/alkali metal/oxygen ratio. Low work functions of the compound thin films deposited on silicon substrates were confirmed by ultraviolet photoelectron spectroscopy (UPS). The compound thin films are stable up to 500.degree. C. as measured by x-ray photoelectron spectroscopy (XPS). Tests have established that for certain chemical compositions and annealing temperatures of the compound thin films, negative electron affinity (NEA) was detected. The low work function, stable compound thin films can be utilized in solar cells, field emission flat panel displays, electron guns, and cold cathode electron guns.

Older Thinopyrum intermedium (Poaceae) plants exhibit superior photosynthetic tolerance to cold stress and greater increases in two photosynthetic enzymes under freezing stress compared with young plants

PubMed Central

Jaikumar, Nikhil S.; Snapp, Sieglinde S.; Sharkey, Thomas D.

2016-01-01

Effects of plant age on resource acquisition and stress tolerance processes is a largely unstudied subject in herbaceous perennials. In a field experiment, we compared rates of photosynthesis (A), ribulose-1,5-bisphosphate (RuBP) carboxylation capacity (V Cmax), maximum electron transport rate (J max), and triose phosphate utilization (TPU), as well as concentrations of Rubisco and sucrose-phosphate synthase (SPS) in 5-year-old and 2-year-old intermediate wheatgrass (Thinopyrum intermedium) under both optimal growing conditions and cold stress in early spring and autumn. This species is a relative of wheat undergoing domestication. An additional experiment compared photosynthetic rates in different cohorts at mid-season and under colder conditions. We hypothesized that photosynthetic capacity in older plants would be lower under favorable conditions but higher under cold stress. Our hypothesis was generally supported. Under cold stress, 5-year-old plants exhibited higher A, TPU, and temperature-adjusted V Cmax than younger plants, as well as 50% more SPS and 37% more Rubisco. In contrast, at mid-season, photosynthetic capacities in older plants were lower than in younger plants in one experiment, and similar in the other, independent of differences in water status. Both cohorts increased A, temperature-adjusted TPU and J max, [Rubisco], and [SPS] under cold stress, but changes were greater in older plants. Photosynthetic differences were largest at 1.2 ºC in very early spring, where older plants had 200% higher A and maintained up to 17% of their peak photosynthetic capacity. We find evidence of increased cold tolerance in older cohorts of wheatgrass, consistent with a growing body of research in woody perennials. PMID:27401911

A Robust High Current Density Electron Gun

NASA Astrophysics Data System (ADS)

Mako, F.; Peter, W.; Shiloh, J.; Len, L. K.

1996-11-01

Proof-of-principle experiments are proposed to validate a new concept for a robust, high-current density Pierce electron gun (RPG) for use in klystrons and high brightness electron sources for accelerators. This rugged, long-life electron gun avoids the difficulties associated with plasma cathodes, thermionic emitters, and field emission cathodes. The RPG concept employs the emission of secondary electrons in a transmission mode as opposed to the conventional mode of reflection, i.e., electrons exit from the back face of a thin negative electron affinity (NEA) material, and in the same direction as the incident beam. Current amplification through one stage of a NEA material could be over 50 times. The amplification is accomplished in one or more stages consisting of one primary emitter and one or more secondary emitters. The primary emitter is a low current density robust emitter (e.g., thoriated tungsten). The secondary emitters are thin NEA electrodes which emit secondary electrons in the same direction as the incident beam. Specific application is targeted for a klystron gun to be used by SLAC with a cold cathode at 30-40 amps/cm^2 output from the secondary emission stage, a ~2 μs pulse length, and ~200 pulses/second.

Monoenergetic acceleration of a target foil by circularly polarized laser pulse in RPA regime without thermal heating

NASA Astrophysics Data System (ADS)

Khudik, V.; Yi, S. A.; Siemon, C.; Shvets, G.

2012-12-01

A kinetic model of the monoenergetic acceleration of a target foil irradiated by the circularly polarized laser pulse is developed. The target moves without thermal heating with constant acceleration which is provided by chirping the frequency of the laser pulse and correspondingly increasing its intensity. In the accelerated reference frame, bulk plasma in the target is neutral and its parameters are stationary: cold ions are immobile while nonrelativistic electrons bounce back and forth inside the potential well formed by ponderomotive and electrostatic potentials. It is shown that a positive charge left behind of the moving target in the ion tail and a negative charge in front of the target in the electron sheath form a capacitor whose constant electric field accelerates the ions of the target. The charge separation is maintained by the radiation pressure pushing electrons forward. The scalings of the target thickness and electromagnetic radiation with the electron temperature are found.

Toward single mode, atomic size electron vortex beams.

PubMed

Krivanek, Ondrej L; Rusz, Jan; Idrobo, Juan-Carlos; Lovejoy, Tracy J; Dellby, Niklas

2014-06-01

We propose a practical method of producing a single mode electron vortex beam suitable for use in a scanning transmission electron microscope (STEM). The method involves using a holographic "fork" aperture to produce a row of beams of different orbital angular momenta, as is now well established, magnifying the row so that neighboring beams are separated by about 1 µm, selecting the desired beam with a narrow slit, and demagnifying the selected beam down to 1-2 Å in size. We show that the method can be implemented by adding two condenser lenses plus a selection slit to a straight-column cold-field emission STEM. It can also be carried out in an existing instrument, the monochromated Nion high-energy-resolution monochromated electron energy-loss spectroscopy-STEM, by using its monochromator in a novel way. We estimate that atom-sized vortex beams with ≥ 20 pA of current should be attainable at 100-200 keV in either instrument.

Dipole configuration for confinement of positrons and electron-positron plasma

NASA Astrophysics Data System (ADS)

Stenson, E. V.; Saitoh, H.; Horn-Stanja, J.; Hergenhahn, U.; Paschkowski, N.; Sunn Pedersen, T.; Stoneking, M. R.; Dickmann, M.; Singer, M.; Vohburger, S.; Hugenschmidt, C.; Schweikhard, L.; Danielson, J. R.; Surko, C. M.

2016-10-01

Laboratory creation and confinement of electron-positron plasmas, which are expected to exhibit atypical plasma physics characteristics, would enable tests of many theory and simulation predictions (e.g., the stabilization of anomalous transport mechanisms). This is the goal of APEX/PAX (A Positron-Electron eXperiment/Positron Accumulation eXperiment). Following demonstration of efficient (38%) E ×B injection and subsequent confinement (τ = 3-5 ms) of cold positrons in a dipole magnetic field, the system is undergoing upgrades from a supported permanent magnet to a supported HTSC (high-temperature superconductor) coil, then to a levitated HTSC coil suitable for the simultaneous confinement of electrons and positrons. This contribution will report on the design and testing of the new systems and subsystems (e.g., for cooling, excitation, and levitation) and, if available, on results of upcoming experiments using a ``rotating wall'' to generate inward particle flux deeper into the confinement region. on behalf of the APEX/PAX team and collaborators.

WEIBEL, TWO-STREAM, FILAMENTATION, OBLIQUE, BELL, BUNEMAN...WHICH ONE GROWS FASTER?

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

Bret, A.

2009-07-10

Many competing linear instabilities are likely to occur in astrophysical settings, and it is important to assess which one grows faster for a given situation. An analytical model including the main beam plasma instabilities is developed. The full three-dimensional dielectric tensor is thus explained for a cold relativistic electron beam passing through a cold plasma, accounting for a guiding magnetic field, a return electronic current, and moving protons. Considering any orientations of the wave vector allows to retrieve the most unstable mode for any parameters set. An unified description of the filamentation (Weibel), two-stream, Buneman, Bell instabilities (and more) ismore » thus provided, allowing for the exact determination of their hierarchy in terms of the system parameters. For relevance to both real situations and PIC simulations, the electron-to-proton mass ratio is treated as a parameter, and numerical calculations are conducted with two different values, namely 1/1836 and 1/100. In the system parameter phase space, the shape of the domains governed by each kind of instability is far from being trivial. For low-density beams, the ultra-magnetized regime tends to be governed by either the two-stream or the Buneman instabilities. For beam densities equaling the plasma one, up to four kinds of modes are likely to play a role, depending of the beam Lorentz factor. In some regions of the system parameters phase space, the dominant mode may vary with the electron-to-proton mass ratio. Application is made to solar flares, intergalactic streams, and relativistic shocks physics.« less

Modeling Transport of Relativistic Electrons through Warm-Dense Matter Using Collisional PIC

NASA Astrophysics Data System (ADS)

May, J.; McGuffey, C.; Yabuuchi, T.; Wei, Ms; Beg, F.; Mori, Wb

2017-10-01

In electron transport experiments performed on the OMEGA EP laser system, a relativistic electron beam was created by focusing a high intensity (eA /me c > 1) laser onto a gold (Au) foil. Behind the Au foil was a layer of plastic (CH) foam, with an initial density of 200mg /cm3 . Before the high intensity laser was switched on, this foam was either left unperturbed; or it was shocked using a lower intensity laser (eA /me c 10-4) with beam path perpendicular to the high intensity laser, which left the CH layer in a warm dense matter (WDM) state with temperature of 40 eV and density of 30mg /cm3 . The electron beam was imaged by observing the k- α signal from a copper foil on the far side from the Au. The result was that transport was decreased by an order of magnitude in the WDM compared to the cold foam. We have modeled this experiment using the PIC code OSIRIS, with also a Monte Carlo Coulomb collision package. Our simulations indicate that the main cause of the differences in transport is a collimating magnetic field in the higher density, cold foam, created by collisional resistivity. The plasma density of the Au layer, difficult to model fully in PIC, appears to effect the heat capacity and therefore temperature and resistivity of the target. The authors acknowledge the support of the Department of Energy under contract DE-NA 0001833 and the National Science Foundation under contract ACI 1339893.

Coherent control of the formation of cold heteronuclear molecules by photoassociation

NASA Astrophysics Data System (ADS)

de Lima, Emanuel F.

2017-01-01

We consider the formation of cold diatomic molecules in the electronic ground state by photoassociation of atoms of dissimilar species. A combination of two transition pathways from the free colliding pair of atoms to a bound vibrational level of the electronic molecular ground state is envisioned. The first pathway consists of a pump-dump scheme with two time-delayed laser pulses in the near-infrared frequency domain. The pump pulse drives the transition to a bound vibrational level of an excited electronic state, while the dump pulse transfers the population to a bound vibrational level of the electronic ground state. The second pathway takes advantage of the existing permanent dipole moment and employs a single pulse in the far-infrared domain to drive the transition from the unbound atoms directly to a bound vibrational level in the electronic ground state. We show that this scheme offers the possibility to coherently control the photoassociation yield by manipulating the relative phase and timing of the pulses. The photoassociation mechanism is illustrated for the formation of cold LiCs molecules.

Generation of auroral kilometric radiation by a finite-size source in a dipole magnetic field

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

Burinskaya, T. M., E-mail: tburinsk@iki.rssi.ru; Shevelev, M. M.

2016-10-15

Generation, amplification, and propagation of auroral kilometric radiation in a narrow three-dimensional plasma cavity in which a weakly relativistic electron beam propagates is studied in the geometrical optics approximation. It is shown that the waves that start with a group velocity directed earthward and have optimal relation between the wave vector components determining the linear growth rate and the wave residence time inside the amplification region undergo the largest amplification. Taking into account the longitudinal velocity of fast electrons results in the shift of the instability domain toward wave vectors directed to the Earth and leads to a change inmore » the dispersion relation, due to which favorable conditions are created for the generation of waves with frequencies above the cutoff frequency for the cold background plasma at the wave generation altitude. The amplification factor for these waves is lower than for waves that have the same wave vectors but are excited by the electron beams with lower velocities along the magnetic field. For waves excited at frequencies below the cutoff frequency of the background plasma at the generation altitude, the amplification factor increases with increasing longitudinal electron velocity, because these waves reside for a longer time in the amplification region.« less

Analytic model of a laser-accelerated composite plasma target and its stability

NASA Astrophysics Data System (ADS)

Khudik, Vladimir; Shvets, Gennady

2013-10-01

A self-consistent analytical model of monoenergetic acceleration of a one and two-species ultrathin target irradiated by a circularly polarized laser pulse is developed. In the accelerated reference frame, the bulk plasma in the target is neutral and its parameters are assumed to be stationary. It is found that the structure of the target depends strongly on the temperatures of electrons and ions, which are both strongly influenced by the laser pulse pedestal. When the electron temperature is large, the hot electrons bounce back and forth inside the potential well formed by ponderomotive and electrostatic potentials while the heavy and light ions are forced-balanced by the electrostatic and non-inertial fields forming two separated layers. In the opposite limiting case when the ion temperature is large, the hot ions are trapped in the potential well formed by the ion-sheath's electric and non-inertial potentials while the cold electrons are forced-balanced by the electrostatic and ponderomotive fields. Using PIC simulations we have determined which scenario is realized in practice depending on the initial target structure and laser intensity. Target stability with respect to Rayleigh-Taylor instability will also be discussed. This work is supported by the US DOE grants DE-FG02-04ER41321 and DE-FG02-07ER54945.

Cassini measurements of cold plasma in the ionosphere of Titan.

PubMed

Wahlund, J E; Boström, R; Gustafsson, G; Gurnett, D A; Kurth, W S; Pedersen, A; Averkamp, T F; Hospodarsky, G B; Persoon, A M; Canu, P; Neubauer, F M; Dougherty, M K; Eriksson, A I; Morooka, M W; Gill, R; André, M; Eliasson, L; Müller-Wodarg, I

2005-05-13

The Cassini Radio and Plasma Wave Science (RPWS) Langmuir probe (LP) sensor observed the cold plasma environment around Titan during the first two flybys. The data show that conditions in Saturn's magnetosphere affect the structure and dynamics deep in the ionosphere of Titan. The maximum measured ionospheric electron number density reached 3800 per cubic centimeter near closest approach, and a complex chemistry was indicated. The electron temperature profiles are consistent with electron heat conduction from the hotter Titan wake. The ionospheric escape flux was estimated to be 10(25) ions per second.

PROTON HEATING BY PICK-UP ION DRIVEN CYCLOTRON WAVES IN THE OUTER HELIOSPHERE: HYBRID EXPANDING BOX SIMULATIONS

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

Hellinger, Petr; Trávníček, Pavel M., E-mail: petr.hellinger@asu.cas.cz

Using a one-dimensional hybrid expanding box model, we investigate properties of the solar wind in the outer heliosphere. We assume a proton–electron plasma with a strictly transverse ambient magnetic field and, aside from the expansion, we take into account the influence of a continuous injection of cold pick-up protons through the charge-exchange process between the solar wind protons and hydrogen of interstellar origin. The injected cold pick-up protons form a ring distribution function, which rapidly becomes unstable, and generate Alfvén cyclotron waves. The Alfvén cyclotron waves scatter pick-up protons to a spherical shell distribution function that thickens over that timemore » owing to the expansion-driven cooling. The Alfvén cyclotron waves heat solar wind protons in the perpendicular direction (with respect to the ambient magnetic field) through cyclotron resonance. At later times, the Alfvén cyclotron waves become parametrically unstable and the generated ion-acoustic waves heat protons in the parallel direction through Landau resonance. The resulting heating of the solar wind protons is efficient on the expansion timescale.« less

Reversal of Thermoelectric Current in Tubular Nanowires

NASA Astrophysics Data System (ADS)

Erlingsson, Sigurdur I.; Manolescu, Andrei; Nemnes, George Alexandru; Bardarson, Jens H.; Sanchez, David

2017-07-01

We calculate the charge current generated by a temperature bias between the two ends of a tubular nanowire. We show that in the presence of a transversal magnetic field the current can change sign; i.e., electrons can either flow from the hot to the cold reservoir, or in the opposite direction, when the temperature bias increases. This behavior occurs when the magnetic field is sufficiently strong, such that Landau and snaking states are created, and the energy dispersion is nonmonotonic with respect to the longitudinal wave vector. The sign reversal can survive in the presence of impurities. We predict this result for core-shell nanowires, for uniform nanowires with surface states due to the Fermi level pinning, and for topological insulator nanowires.

Energy-filtered cold electron transport at room temperature.

PubMed

Bhadrachalam, Pradeep; Subramanian, Ramkumar; Ray, Vishva; Ma, Liang-Chieh; Wang, Weichao; Kim, Jiyoung; Cho, Kyeongjae; Koh, Seong Jin

2014-09-10

Fermi-Dirac electron thermal excitation is an intrinsic phenomenon that limits functionality of various electron systems. Efforts to manipulate electron thermal excitation have been successful when the entire system is cooled to cryogenic temperatures, typically <1 K. Here we show that electron thermal excitation can be effectively suppressed at room temperature, and energy-suppressed electrons, whose energy distribution corresponds to an effective electron temperature of ~45 K, can be transported throughout device components without external cooling. This is accomplished using a discrete level of a quantum well, which filters out thermally excited electrons and permits only energy-suppressed electrons to participate in electron transport. The quantum well (~2 nm of Cr2O3) is formed between source (Cr) and tunnelling barrier (SiO2) in a double-barrier-tunnelling-junction structure having a quantum dot as the central island. Cold electron transport is detected from extremely narrow differential conductance peaks in electron tunnelling through CdSe quantum dots, with full widths at half maximum of only ~15 mV at room temperature.

Measurement and potential barrier evolution analysis of cold field emission in fracture fabricated Si nanogap

NASA Astrophysics Data System (ADS)

Banerjee, Amit; Hirai, Yoshikazu; Tsuchiya, Toshiyuki; Tabata, Osamu

2017-06-01

Cold field emission characteristics of a fracture fabricated Si nanogap (˜100 nm) were investigated with an ascending electric field (voltage) sweep. The nanogap was formed by controlled fracture of a free-standing silicon micro-beam along <111> direction by a microelectromechanical device, which results in flat, smooth, and conformal electrode pairs. This facilitates simultaneous large area emission, which gives rise to a significant current at low bias voltage, which usually remains indiscernible in nanogaps of this size. The measured emission current-voltage (I-V) characteristics clearly depict two distinct regimes: a linear (I ∝ V) regime at low bias voltage and a nonlinear [ln(I/V 2) ∝ V -1] regime at high bias voltage, separated by a transition point. We propose that the linear regime is owed to direct tunneling of electrons, whereas the nonlinear regime is due to Fowler-Nordheim type emission. This proposition essentially implies that the tunneling potential barrier gradually evolved from a rectangular shape to a triangular shape with increasing field (V). This type of evolution is usually observed in molecular size gaps. We have attempted to correlate the I-V curves acquired through the experiments with the electric field induced barrier shape evolution by numerical calculations involving standard quantum mechanics. The observed linear regime at low bias voltage (<5 V) in a relatively large size gap (˜100 nm) is attributed to the fabrication method adopted in this study. The reported study and the fabricated device are significant for developing a futuristic thermotunneling refrigerator that will find a wide range of application in nanoelectronic devices.

Growth of electron plasma waves above and below f(p) in the electron foreshock

NASA Technical Reports Server (NTRS)

Cairns, Iver H.; Fung, Shing F.

1988-01-01

This paper investigates the conditions required for electron beams to drive wave growth significantly above and below the electron plasma frequency, f(p), by numerically solving the linear dispersion equation. It is shown that kinetic growth well below f(p) may occur over a broad range of frequencies due to the beam instability, when the electron beam is slow, dilute, and relatively cold. Alternatively, a cold or sharp feature at low parallel velocities in the distribution function may drive kinetic growth significantly below f(p). Kinetic broadband growth significantly above f(p) is explained in terms of faster warmer beams. A unified qualitative theory for the narrow-band and broad-band waves is proposed.

Changes in chemical components in the freshwater apple snail, Pomacea canaliculata (Gastropoda: Ampullariidae), in relation to the development of its cold hardiness.

PubMed

Matsukura, Keiichiro; Tsumuki, Hisaaki; Izumi, Yohei; Wada, Takashi

2008-04-01

The apple snail, Pomacea canaliculata, is an invasive freshwater snail. It increases its cold hardiness before winter. However, the physiological mechanism of cold hardiness in molluscs is poorly understood, especially in freshwater molluscs. In this study, we examined the changes in low molecular weight compounds, glycogen and lipids, in the body of P. canaliculata in association with the development of cold hardiness. When snails without cold hardiness were experimentally cold-acclimated, the amount of glycerol, glutamine, and carnosine increased, while glycogen and phenylalanine decreased. Overwintering cold-tolerant snails collected from a drained paddy field in November also showed increased glycerol in their bodies with decreasing glycogen concentration, compared to summer snails collected from a submerged field. Water content also decreased during the cold acclimation, although the water loss was minimal. These results indicate that the freshwater snail, P. canaliculata enhances cold hardiness by accumulation of some kinds of low molecular weight compounds in its body as some insects do. However, the actual function of each low molecular compound is still unknown.

MitoQ blunts mitochondrial and renal damage during cold preservation of porcine kidneys.

PubMed

Parajuli, Nirmala; Campbell, Lia H; Marine, Akira; Brockbank, Kelvin G M; Macmillan-Crow, Lee Ann

2012-01-01

Cold preservation has greatly facilitated the use of cadaveric kidneys for transplantation but damage occurs during the preservation episode. It is well established that oxidant production increases during cold renal preservation and mitochondria are a key target for injury. Our laboratory has demonstrated that cold storage of renal cells and rat kidneys leads to increased mitochondrial superoxide levels and mitochondrial electron transport chain damage, and that addition of Mitoquinone (MitoQ) to the preservation solutions blunted this injury. In order to better translate animal studies, the inclusion of large animal models is necessary to develop safe preclinical protocols. Therefore, we tested the hypothesis that addition of MitoQ to cold storage solution preserves mitochondrial function by decreasing oxidative stress, leading to less renal tubular damage during cold preservation of porcine kidneys employing a standard criteria donor model. Results showed that cold storage significantly induced oxidative stress (nitrotyrosine), renal tubular damage, and cell death. Using High Resolution Respirometry and fresh porcine kidney biopsies to assess mitochondrial function we showed that MitoQ significantly improved complex II/III respiration of the electron transport chain following 24 hours of cold storage. In addition, MitoQ blunted oxidative stress, renal tubular damage, and cell death after 48 hours. These results suggested that MitoQ decreased oxidative stress, tubular damage and cell death by improving mitochondrial function during cold storage. Therefore this compound should be considered as an integral part of organ preservation solution prior to transplantation.

MitoQ Blunts Mitochondrial and Renal Damage during Cold Preservation of Porcine Kidneys

PubMed Central

Parajuli, Nirmala; Campbell, Lia H.; Marine, Akira; Brockbank, Kelvin G. M.; MacMillan-Crow, Lee Ann

2012-01-01

Cold preservation has greatly facilitated the use of cadaveric kidneys for transplantation but damage occurs during the preservation episode. It is well established that oxidant production increases during cold renal preservation and mitochondria are a key target for injury. Our laboratory has demonstrated that cold storage of renal cells and rat kidneys leads to increased mitochondrial superoxide levels and mitochondrial electron transport chain damage, and that addition of Mitoquinone (MitoQ) to the preservation solutions blunted this injury. In order to better translate animal studies, the inclusion of large animal models is necessary to develop safe preclinical protocols. Therefore, we tested the hypothesis that addition of MitoQ to cold storage solution preserves mitochondrial function by decreasing oxidative stress, leading to less renal tubular damage during cold preservation of porcine kidneys employing a standard criteria donor model. Results showed that cold storage significantly induced oxidative stress (nitrotyrosine), renal tubular damage, and cell death. Using High Resolution Respirometry and fresh porcine kidney biopsies to assess mitochondrial function we showed that MitoQ significantly improved complex II/III respiration of the electron transport chain following 24 hours of cold storage. In addition, MitoQ blunted oxidative stress, renal tubular damage, and cell death after 48 hours. These results suggested that MitoQ decreased oxidative stress, tubular damage and cell death by improving mitochondrial function during cold storage. Therefore this compound should be considered as an integral part of organ preservation solution prior to transplantation. PMID:23139796

Single Crystal Diamond Needle as Point Electron Source.

PubMed

Kleshch, Victor I; Purcell, Stephen T; Obraztsov, Alexander N

2016-10-12

Diamond has been considered to be one of the most attractive materials for cold-cathode applications during past two decades. However, its real application is hampered by the necessity to provide appropriate amount and transport of electrons to emitter surface which is usually achieved by using nanometer size or highly defective crystallites having much lower physical characteristics than the ideal diamond. Here, for the first time the use of single crystal diamond emitter with high aspect ratio as a point electron source is reported. Single crystal diamond needles were obtained by selective oxidation of polycrystalline diamond films produced by plasma enhanced chemical vapor deposition. Field emission currents and total electron energy distributions were measured for individual diamond needles as functions of extraction voltage and temperature. The needles demonstrate current saturation phenomenon and sensitivity of emission to temperature. The analysis of the voltage drops measured via electron energy analyzer shows that the conduction is provided by the surface of the diamond needles and is governed by Poole-Frenkel transport mechanism with characteristic trap energy of 0.2-0.3 eV. The temperature-sensitive FE characteristics of the diamond needles are of great interest for production of the point electron beam sources and sensors for vacuum electronics.

Single Crystal Diamond Needle as Point Electron Source

NASA Astrophysics Data System (ADS)

Kleshch, Victor I.; Purcell, Stephen T.; Obraztsov, Alexander N.

2016-10-01

Diamond has been considered to be one of the most attractive materials for cold-cathode applications during past two decades. However, its real application is hampered by the necessity to provide appropriate amount and transport of electrons to emitter surface which is usually achieved by using nanometer size or highly defective crystallites having much lower physical characteristics than the ideal diamond. Here, for the first time the use of single crystal diamond emitter with high aspect ratio as a point electron source is reported. Single crystal diamond needles were obtained by selective oxidation of polycrystalline diamond films produced by plasma enhanced chemical vapor deposition. Field emission currents and total electron energy distributions were measured for individual diamond needles as functions of extraction voltage and temperature. The needles demonstrate current saturation phenomenon and sensitivity of emission to temperature. The analysis of the voltage drops measured via electron energy analyzer shows that the conduction is provided by the surface of the diamond needles and is governed by Poole-Frenkel transport mechanism with characteristic trap energy of 0.2-0.3 eV. The temperature-sensitive FE characteristics of the diamond needles are of great interest for production of the point electron beam sources and sensors for vacuum electronics.

Low frequency solitons and double layers in a magnetized plasma with two temperature electrons

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

Rufai, O. R.; Bharuthram, R.; Singh, S. V.

2012-12-15

Finite amplitude non-linear ion-acoustic solitary waves and double layers are studied in a magnetized plasma with cold ions fluid and two distinct groups of Boltzmann electrons, using the Sagdeev pseudo-potential technique. The conditions under which the solitary waves and double layers can exist are found both analytically and numerically. We have shown the existence of negative potential solitary waves and double layers for subsonic Mach numbers, whereas in the unmagnetized plasma they can only in the supersonic Mach number regime. For the plasma parameters in the auroral region, the electric field amplitude of the solitary structures comes out to bemore » 49 mV/m which is in agreement of the Viking observations in this region.« less

Proposal for generating synthetic magnetic fields in hexagonal optical lattices

NASA Astrophysics Data System (ADS)

Tian, Binbin; Endres, Manuel; Pekker, David

2015-05-01

We propose a new approach to generating synthetic magnetic fields in ultra cold atom systems that does not rely on either Raman transitions nor periodic drive. Instead, we consider a hexagonal optical lattice produced by the intersection of three laser beams at 120 degree angles, where the intensity of one or more of the beams is spatially non-uniform. The resulting optical lattice remains hexagonal, but has spatially varying hopping matrix elements. For atoms near the Dirac points, these spatial variations appear as a gauge field, similar to the fictitious gauge field that is induced for for electrons in strained graphene. We suggest that a robust way to generate a gauge field that corresponds to a uniform flux is to aligning three gaussian beams to intersect in an equilateral triangle. Using realistic experimental parameters, we show how the proposed setup can be used to observe cyclotron motion of an atom cloud - the conventional Hall effect and distinct Landau levels - the integer quantum Hall effect.

Construction and Performance of a Superconducting Multipole Wiggler

NASA Astrophysics Data System (ADS)

Hwang, C. S.; Wang, B.; Chen, J. Y.; Chang, C. H.; Chen, H. H.; Fan, T. C.; Lin, F. Y.; Huang, M. H.; Chang, C. C.; Hsu, S. N.; Hsiung, G. Y.; Hsu, K. T.; Chen, J.; Chien, Y. C.; Chen, J. R.; Chen, C. T.

2004-05-01

A 3.2 Tesla superconducting multipole wiggler was designed and fabricated as an X-ray source. The magnet assembly, which consists of 32 pairs of racetrack NbTi superconducting coils with a periodic length of 60 mm, provides 28 effective poles. A 1.4056 m long elliptical cold-bore stainless steel beam duct with taper flanges and a wall thickness of 1 mm, was developed and constructed to fit the ultra-high vacuum condition for electron beam. The magnetic field strength was measured in liquid helium using a cryogenic Hall probe, revealing a field behavior very close to behavior consistent with the designed values. A Hall generator and the stretch wire methods are used to determine the transfer function of the peak field, the first and second integrated field distributions, and the good field region of the magnet. The quench protection of the magnet, the control algorithm for automatic filling of liquid helium, and the boil off rate of liquid helium and liquid nitrogen will also be discussed.

Strong Magnetic Field Fluctuations within Filamentary Auroral Density Cavities Interpreted as VLF Saucer Sources

NASA Technical Reports Server (NTRS)

Knudsen, D. L.; Kabirzadeh, R.; Burchill, J. K.; Pfaff, Robert F.; Wallis, D. D.; Bounds, S. R.; Clemmons, J. H.; Pincon, J.-L.

2012-01-01

The Geoelectrodynamics and Electro-Optical Detection of Electron and SuprathermalIon Currents (GEODESIC) sounding rocket encountered more than 100 filamentary densitycavities associated with enhanced plasma waves at ELF (3 kHz) and VLF (310 kHz)frequencies and at altitudes of 800990 km during an auroral substorm. These cavities weresimilar in size (20 m diameter in most cases) to so-called lower-hybrid cavities (LHCs)observed by previous sounding rockets and satellites; however, in contrast, many of theGEODESIC cavities exhibited up to tenfold enhancements in magnetic wave powerthroughout the VLF band. GEODESIC also observed enhancements of ELF and VLFelectric fields both parallel and perpendicular to the geomagnetic field B0 within cavities,though the VLF E field increases were often not as large proportionally as seen in themagnetic fields. This behavior is opposite to that predicted by previously published theoriesof LHCs based on passive scattering of externally incident auroral hiss. We argue thatthe GEODESIC cavities are active wave generation sites capable of radiating VLF wavesinto the surrounding plasma and producing VLF saucers, with energy supplied by cold,upward flowing electron beams composing the auroral return current. This interpretation issupported by the observation that the most intense waves, both inside and outside cavities,occurred in regions where energetic electron precipitation was largely inhibited orabsent altogether. We suggest that the wave-enhanced cavities encountered by GEODESICwere qualitatively different from those observed by earlier spacecraft because of thefortuitous timing of the GEODESIC launch, which placed the payload at apogee within asubstorm-related return current during its most intense phase, lasting only a few minutes.

Room temperature creep behavior of Ti–Nb–Ta–Zr–O alloy

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

Zhang, Wei-dong

The room temperature creep behavior and deformation mechanisms of a Ti–Nb–Ta–Zr–O alloy, which is also called “gum metal”, were investigated with the nanoindentation creep and conventional creep tests. The microstructure was observed with electron backscattered diffraction analysis (EBSD) and transmission electron microscopy (TEM). The results show that the creep stress exponent of the alloy is sensitive to cold deformation history of the alloy. The alloy which was cold swaged by 85% shows high creep resistance and the stress exponent is approximately equal to 1. Microstructural observation shows that creep process of the alloy without cold deformation is controlled by dislocationmore » mechanism. The stress-induced α' martensitic phase transformation also occurs. The EBSD results show that the grain orientation changes after the creep tests, and thus, the creep of the cold-worked alloy is dominated by the shear deformation of giant faults without direct assistance from dislocations. - Highlights: •Nanoindentation was used to investigate room temperature creep behavior of gum metal. •The creep stress exponent of gum metal is sensitive to the cold deformation history. •The creep stress exponent of cold worked gum metal is approximately equal to 1. •The creep of the cold-worked gum metal is governed by the shear deformation of giant faults.« less

Mechanisms of convective cloud organization by cold pools over tropical warm ocean during the AMIE/DYNAMO field campaign

DOE PAGES

Feng, Zhe; Hagos, Samson; Rowe, Angela K.; ...

2015-04-03

This paper investigates the mechanisms of convective cloud organization by precipitation-driven cold pools over the warm tropical Indian Ocean during the 2011 Atmospheric Radiation Measurement (ARM) Madden-Julian Oscillation (MJO) Investigation Experiment / Dynamics of the MJO (AMIE/DYNAMO) field campaign. A high-resolution regional model simulation is performed using the Weather Research and Forecasting model during the transition from suppressed to active phases of the November 2011 MJO. The simulated cold pool lifetimes, spatial extent and thermodynamic properties agree well with the radar and ship-borne observations from the field campaign. The thermodynamic and dynamic structures of the outflow boundaries of isolated andmore » intersecting cold pools in the simulation and the associated secondary cloud populations are examined. Intersecting cold pools last more than twice as long, are twice as large, 41% more intense (measured by buoyancy), and 62% deeper than isolated cold pools. Consequently, intersecting cold pools trigger 73% more convective clouds than isolated ones. This is possibly due to stronger outflows that enhance secondary updraft velocities by up to 45%. However, cold pool-triggered convective clouds grow into deep convection not because of the stronger secondary updrafts at cloud base, but rather due to closer spacing (aggregation) between clouds and larger cloud clusters that formed along the cold pool boundaries when they intersect. The close spacing of large clouds moistens the local environment and reduces entrainment drying, allowing the clouds to further develop into deep convection. Implications to the design of future convective parameterization with cold pool-modulated entrainment rates are discussed.« less

Structure of Ion Outflow in the Martian Magnetotail

NASA Astrophysics Data System (ADS)

McFadden, J. P.; Mitchell, D.; Luhmann, J. G.; Connerney, J. E. P.; Jakosky, B. M.

2017-12-01

The Suprathermal And Thermal Ion Composition (STATIC) sensor on the MAVEN spacecraft provides a detailed look at the structure of ion outflow in the Martian magnetotail including ion composition, energization, and flow. Mars' magnetotail contains a mixture of cold (<10 eV) nearly-stationary multi-species ions, tailward-moving cold multi-species ions, suprathermal ions of a few tens of eV, warm (about 100 eV) proton populations, and heavy (primarily O+) pickup ions at energies from 1 to 10 keV which may display several simultaneous peaks in energy flux. The cold tailward-moving ions represent a significant fraction of the Martian ion loss, perhaps comparable to loses from molecular oxygen dissociation. The suprathermal tail that accompanies the cold ions varies greatly and provides clues to ion escape. The warm protons, on first examination, appear to be of sheath origin, displaying a similar energy distribution and accompanied by a tenuous warm population at M/Q=2 (which could be either solar wind alphas or molecular hydrogen ions of ionospheric origin). STATIC produces a weak ghost peak at M/Q=11-12 when observing molecular hydrogen ions, but not alphas, often allowing the instrument to distinguish the source of protons. Measurements show the warm protons are of ionospheric origin in the central tail and transition to sheath plasma in the umbra. Energetic (1-10 keV) pickup oxygen in the magnetotail is produced on the nightside, near the pole where the IMF convection electric field points toward the planet, the same hemisphere where sputtering occurs. When two spectral peaks are observed, these tailward-moving ions differ in direction by relatively small angles (about 20 degrees). These peaks can persist for tens of minutes indicating approximately time-stationary acceleration, and therefore acceleration in potential fields. Magnetotail structure and geometry can be inferred not only from the local magnetic field, but also from the measured electron distributions which indicate source populations and connectivity (closed, open, or interplanetary). This paper will be used to describe the observed tail structure and the inferred acceleration structure.

Laser refrigeration of hydrothermal nanocrystals in physiological media.

PubMed

Roder, Paden B; Smith, Bennett E; Zhou, Xuezhe; Crane, Matthew J; Pauzauskie, Peter J

2015-12-08

Coherent laser radiation has enabled many scientific and technological breakthroughs including Bose-Einstein condensates, ultrafast spectroscopy, superresolution optical microscopy, photothermal therapy, and long-distance telecommunications. However, it has remained a challenge to refrigerate liquid media (including physiological buffers) during laser illumination due to significant background solvent absorption and the rapid (∼ ps) nonradiative vibrational relaxation of molecular electronic excited states. Here we demonstrate that single-beam laser trapping can be used to induce and quantify the local refrigeration of physiological media by >10 °C following the emission of photoluminescence from upconverting yttrium lithium fluoride (YLF) nanocrystals. A simple, low-cost hydrothermal approach is used to synthesize polycrystalline particles with sizes ranging from <200 nm to >1 μm. A tunable, near-infrared continuous-wave laser is used to optically trap individual YLF crystals with an irradiance on the order of 1 MW/cm(2). Heat is transported out of the crystal lattice (across the solid-liquid interface) by anti-Stokes (blue-shifted) photons following upconversion of Yb(3+) electronic excited states mediated by the absorption of optical phonons. Temperatures are quantified through analysis of the cold Brownian dynamics of individual nanocrystals in an inhomogeneous temperature field via forward light scattering in the back focal plane. The cold Brownian motion (CBM) analysis of individual YLF crystals indicates local cooling by >21 °C below ambient conditions in D2O, suggesting a range of potential future applications including single-molecule biophysics and integrated photonic, electronic, and microfluidic devices.

Laser refrigeration of hydrothermal nanocrystals in physiological media

PubMed Central

Roder, Paden B.; Smith, Bennett E.; Zhou, Xuezhe; Crane, Matthew J.; Pauzauskie, Peter J.

2015-01-01

Coherent laser radiation has enabled many scientific and technological breakthroughs including Bose–Einstein condensates, ultrafast spectroscopy, superresolution optical microscopy, photothermal therapy, and long-distance telecommunications. However, it has remained a challenge to refrigerate liquid media (including physiological buffers) during laser illumination due to significant background solvent absorption and the rapid (∼ps) nonradiative vibrational relaxation of molecular electronic excited states. Here we demonstrate that single-beam laser trapping can be used to induce and quantify the local refrigeration of physiological media by >10 °C following the emission of photoluminescence from upconverting yttrium lithium fluoride (YLF) nanocrystals. A simple, low-cost hydrothermal approach is used to synthesize polycrystalline particles with sizes ranging from <200 nm to >1 μm. A tunable, near-infrared continuous-wave laser is used to optically trap individual YLF crystals with an irradiance on the order of 1 MW/cm2. Heat is transported out of the crystal lattice (across the solid–liquid interface) by anti-Stokes (blue-shifted) photons following upconversion of Yb3+ electronic excited states mediated by the absorption of optical phonons. Temperatures are quantified through analysis of the cold Brownian dynamics of individual nanocrystals in an inhomogeneous temperature field via forward light scattering in the back focal plane. The cold Brownian motion (CBM) analysis of individual YLF crystals indicates local cooling by >21 °C below ambient conditions in D2O, suggesting a range of potential future applications including single-molecule biophysics and integrated photonic, electronic, and microfluidic devices. PMID:26589813

Advanced diesel electronic fuel injection and turbocharging

NASA Astrophysics Data System (ADS)

Beck, N. J.; Barkhimer, R. L.; Steinmeyer, D. C.; Kelly, J. E.

1993-12-01

The program investigated advanced diesel air charging and fuel injection systems to improve specific power, fuel economy, noise, exhaust emissions, and cold startability. The techniques explored included variable fuel injection rate shaping, variable injection timing, full-authority electronic engine control, turbo-compound cooling, regenerative air circulation as a cold start aid, and variable geometry turbocharging. A Servojet electronic fuel injection system was designed and manufactured for the Cummins VTA-903 engine. A special Servojet twin turbocharger exhaust system was also installed. A series of high speed combustion flame photos was taken using the single cylinder optical engine at Michigan Technological University. Various fuel injection rate shapes and nozzle configurations were evaluated. Single-cylinder bench tests were performed to evaluate regenerative inlet air heating techniques as an aid to cold starting. An exhaust-driven axial cooling air fan was manufactured and tested on the VTA-903 engine.

Design and investigations of the superconducting magnet system for the multipurpose superconducting electron cyclotron resonance ion source.

PubMed

Tinschert, K; Lang, R; Mäder, J; Rossbach, J; Spädtke, P; Komorowski, P; Meyer-Reumers, M; Krischel, D; Fischer, B; Ciavola, G; Gammino, S; Celona, L

2012-02-01

The production of intense beams of heavy ions with electron cyclotron resonance ion sources (ECRIS) is an important request at many accelerators. According to the ECR condition and considering semi-empirical scaling laws, it is essential to increase the microwave frequency together with the magnetic flux density of the ECRIS magnet system. A useful frequency of 28 GHz, therefore, requires magnetic flux densities above 2.2 T implying the use of superconducting magnets. A cooperation of European institutions initiated a project to build a multipurpose superconducting ECRIS (MS-ECRIS) in order to achieve an increase of the performances in the order of a factor of ten. After a first design of the superconducting magnet system for the MS-ECRIS, the respective cold testing of the built magnet system reveals a lack of mechanical performance due to the strong interaction of the magnetic field of the three solenoids with the sextupole field and the magnetization of the magnetic iron collar. Comprehensive structural analysis, magnetic field calculations, and calculations of the force pattern confirm thereafter these strong interactions, especially of the iron collar with the solenoidal fields. The investigations on the structural analysis as well as suggestions for a possible mechanical design solution are given.

Frequency sweep rates of rising tone electromagnetic ion cyclotron waves: Comparison between nonlinear theory and Cluster observation

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

He, Zhaoguo; University of Chinese Academy of Sciences, Beijing 100049; Zong, Qiugang, E-mail: qgzong@gmail.com

2014-12-15

Resonant pitch angle scattering by electromagnetic ion cyclotron (EMIC) waves has been suggested to account for the rapid loss of ring current ions and radiation belt electrons. For the rising tone EMIC wave (classified as triggered EMIC emission), its frequency sweep rate strongly affects the efficiency of pitch-angle scattering. Based on the Cluster observations, we analyze three typical cases of rising tone EMIC waves. Two cases locate at the nightside (22.3 and 22.6 magnetic local time (MLT)) equatorial region and one case locates at the duskside (18MLT) higher magnetic latitude (λ = –9.3°) region. For the three cases, the time-dependent wave amplitude,more » cold electron density, and cold ion density ratio are derived from satellite data; while the ambient magnetic field, thermal proton perpendicular temperature, and the wave spectral can be directly provided by observation. These parameters are input into the nonlinear wave growth model to simulate the time-frequency evolutions of the rising tones. The simulated results show good agreements with the observations of the rising tones, providing further support for the previous finding that the rising tone EMIC wave is excited through the nonlinear wave growth process.« less

Cold Antimatter Plasmas, and Aspirations for Cold Antihydrogen

DTIC Science & Technology

2002-06-24

comparison of any baryon and antibaryon by almost a factor of CP606, Non-Neutral Plasma Physics IV, edited by F. Anderegg et al. © 2002 American...antiprotons 3 _one-electron .1 eV quantum cyclotron 0.001 K FIGURE 1. Particle energies a million. An improved baryon CPT test (e.g. involving cold...more precise tests of CPT invariance with baryons and leptons than have been realized so far. The pursuit of cold antihydrogen thus began some time ago

An Investigation of Transonic Flow Fields Surrounding Hot and Cold Sonic Jets

NASA Technical Reports Server (NTRS)

Lee, George

1961-01-01

An investigation at free-stream Mach numbers of 0.90 t o 1.10 was made to determine (1) the jet boundaries and the flow fields around hot and cold jets, and (2) whether a cold-gas jet could adequately simulate the boundary and flow field of hot-gas jet. Schlieren photographs and static-pressure surveys were taken in the vacinity of a sonic jet which was operated over a range of jet pressure ratios of 1 to 6, specific heat ratios at the nozzle exit of 1.29 and 1.40, and jet temperatures up to 2600 R.

Parametric decay of plasma waves near the upper-hybrid resonance

DOE PAGES

Dodin, I. Y.; Arefiev, A. V.

2017-03-28

An intense X wave propagating perpendicularly to dc magnetic field is unstable with respect to a parametric decay into an electron Bernstein wave and a lower-hybrid wave. A modified theory of this effect is proposed that extends to the high-intensity regime, where the instability rate γ ceases to be a linear function of the incident-wave amplitude. An explicit formula for γ is derived and expressed in terms of cold-plasma parameters. Here, theory predictions are in reasonable agreement with the results of the particle-in-cell simulations presented in a separate publication.

Driving Force of Plasma Bullet in Atmospheric-Pressure Plasma

NASA Astrophysics Data System (ADS)

Yambe, Kiyoyuki; Masuda, Seiya; Kondo, Shoma

2018-06-01

When plasma is generated by applying high-voltage alternating current (AC), the driving force of the temporally and spatially varying electric field is applied to the plasma. The strength of the driving force of the plasma at each spatial position is different because the electrons constituting the atmospheric-pressure nonequilibrium (cold) plasma move at a high speed in space. If the force applied to the plasma is accelerated only by the driving force, the plasma will be accelerated infinitely. The equilibrium between the driving force and the restricting force due to the collision between the plasma and neutral particles determines the inertial force and the drift velocity of the plasma. Consequently, the drift velocity depends on the strength of the time-averaged AC electric field. The pressure applied by the AC electric field equilibrates with the plasma pressure. From the law of conservation of energy, the pressure equilibrium is maintained by varying the drift velocity of the plasma.

Observation of multi-channel non-local transport in J-TEXT plasmas

NASA Astrophysics Data System (ADS)

Shi, Yuejiang; Chen, Zhongyong; Yang, Zhoujun; Shi, Peng; Zhao, Kaijun; Diamond, Patrick H.; Kwon, JaeMin; Yan, Wei; Zhou, Hao; Pan, Xiaoming; Cheng, Zhifeng; Chen, Zhiping; Yang, SeongMoo; Zhang, Chi; Li, Da; Dong, Yunbo; Wang, Lu; Ding, YongHua; Liang, Yunfeng; Hahn, SangHee; Jhang, HoGun; Na, Yong-Su

2018-04-01

In cold pulse experiments in J-TEXT, not only are rapid electron temperature increases in the core observed, but also steep rises in the inner density are found. Moreover, some evidence of acceleration of the core toroidal rotation is also observed during the non-local transport process of electron temperature. These new findings of cold pulse experiments in J-TEXT suggest that turbulence spreading is a possible mechanism for the non-local transport dynamics.

A versatile substrate design for LEED and AES studies in uhv.

NASA Technical Reports Server (NTRS)

Holloway, P. H.; Hudson, J. B.

1972-01-01

A substrate design is described that incorporates a single crystal disk into an electrically isolated, electron bombardment heated mount. Electron and photon leakage from the bombarding filament are prevented, and LEED and AES may be used at elevated temperatures. A cold finger, thermally coupled to the mount, decreases the time lost between cleaning the crystal and cooling it to the desired observation temperature. The cold finger also allows observation at temperatures below ambient.

Spectroscopic method to study low charge state ion and cold electron population in ECRIS plasma

NASA Astrophysics Data System (ADS)

Kronholm, R.; Kalvas, T.; Koivisto, H.; Tarvainen, O.

2018-04-01

The results of optical emission spectroscopy experiments probing the cold electron population of a 14 GHz Electron Cyclotron Resonance Ion Source (ECRIS) are reported. The study has been conducted with a high resolution spectrometer and data acquisition setup developed specifically for the diagnostics of weak emission line characteristic to ECRIS plasmas. The optical emission lines of low charge state ions and neutral atoms of neon have been measured and analyzed with the line-ratio method. The aforementioned electron population temperature of the cold electron population (Te < 100 eV) is determined for Maxwell-Boltzmann and Druyvesteyn energy distributions to demonstrate the applicability of the method. The temperature was found to change significantly when the extraction voltage of the ion source is turned on/off. In the case of the Maxwellian distribution, the temperature of the cold electron population is 20 ± 10 eV when the extraction voltage is off and 40 ± 10 eV when it is on. The optical emission measurements revealed that the extraction voltage also affects both neutral and ion densities. Based on the rate coefficient analysis with the aforementioned temperatures, switching the extraction voltage off decreases the rate coefficient of neutral to 1+ ionization to 42% and 1+ to 2+ ionization to 24% of the original. This suggests that switching the extraction voltage on favors ionization to charge states ≥2+ and, thus, the charge state distributions of ECRIS plasmas are probably different with the extraction voltage on/off. It is therefore concluded that diagnostics results of ECRIS plasmas obtained without the extraction voltage are not depicting the plasma conditions in normal ECRIS operation.

Comet giacobini-zinner: plasma description.

PubMed

Bame, S J; Anderson, R C; Asbridge, J R; Baker, D N; Feldman, W C; Fuselier, S A; Gosling, J T; McComas, D J; Thomsen, M F; Young, D T; Zwickl, R D

1986-04-18

A strong interaction between the solar wind and comet Giacobini-Zinner was observed oh 11 September 1985 with the Los Alamos plasma electron experiment on the International Cometary Explorer (ICE) spacecraft. As ICE approached an intercept point 7800 kilometers behind the nucleus from the south and receded to the north, upstream phenomena due to the comet were observed. Periods of enhanced electron heat flux from the comet as well as almost continuous electron density fluctuations were measured. These effects are related to the strong electron heating observed in the cometary interaction region and to cometary ion pickup by the solar wind, respectively. No evidence for a conventional bow shock was found as ICE entered and exited the regions of strongest interaction of the solar wind with the cometary environment. The outer extent of this strong interaction zone was a transition region in which the solar wind plasma was heated, compressed, and slowed. Inside the inner boundary of the transition region was a sheath that enclosed a cold intermediate coma. In the transition region and sheath, small-scale enhancements in density were observed. These density spikes may be due to an instability associated with cometary ion pickup or to the passage of ICE through cometary ray structures. In the center of the cold intermediate coma a narrow, high-density core of plasma, presumably the developing plasma tail was found. In some ways this tail can be compared to the plasma sheet in Earth's magnetotail and to the current sheet in the tail at Venus. This type of configuration is expected in the double-lobe magnetic topology detected at the comet, possibly caused by the theoretically expected draping of the interplanetary magnetic field around its ionosphere.

NASA Cold Land Processes Experiment (CLPX 2002/03): Field measurements of snowpack properties and soil moisture

Treesearch

Kelly Elder; Don Cline; Glen E. Liston; Richard Armstrong

2009-01-01

A field measurement program was undertaken as part NASA's Cold Land Processes Experiment (CLPX). Extensive snowpack and soil measurements were taken at field sites in Colorado over four study periods during the two study years (2002 and 2003). Measurements included snow depth, density, temperature, grain type and size, surface wetness, surface roughness, and...

Energy-filtered cold electron transport at room temperature

PubMed Central

Bhadrachalam, Pradeep; Subramanian, Ramkumar; Ray, Vishva; Ma, Liang-Chieh; Wang, Weichao; Kim, Jiyoung; Cho, Kyeongjae; Koh, Seong Jin

2014-01-01

Fermi-Dirac electron thermal excitation is an intrinsic phenomenon that limits functionality of various electron systems. Efforts to manipulate electron thermal excitation have been successful when the entire system is cooled to cryogenic temperatures, typically <1 K. Here we show that electron thermal excitation can be effectively suppressed at room temperature, and energy-suppressed electrons, whose energy distribution corresponds to an effective electron temperature of ~45 K, can be transported throughout device components without external cooling. This is accomplished using a discrete level of a quantum well, which filters out thermally excited electrons and permits only energy-suppressed electrons to participate in electron transport. The quantum well (~2 nm of Cr2O3) is formed between source (Cr) and tunnelling barrier (SiO2) in a double-barrier-tunnelling-junction structure having a quantum dot as the central island. Cold electron transport is detected from extremely narrow differential conductance peaks in electron tunnelling through CdSe quantum dots, with full widths at half maximum of only ~15 mV at room temperature. PMID:25204839

Narrow Radiative Recombination Continua: A Signature of Ions Crossing the Contact Discontinuity of Astrophysical Shocks

NASA Technical Reports Server (NTRS)

Behar, Ehud; Nordon, Raanan; Soker, Noam; Kastner, Joel H.; Yu, Young Sam

2009-01-01

X-rays from planetary nebulae (PNs) are believed to originate from a shock driven into the fast stellar wind (v 1000 kilometers per second) as it collides with an earlier circumstellar slow wind (v 10 kilometers per second). In theory, the shocked fast wind (hot hubble) and the ambient cold nebula can remain separated by magnetic fields along a surface referred to as the contact discontinuity (CD) that inhibits diffusion and heat conduction. The CD region is extremely difficult to probe directly owing to its small size and faint emission. This has largely left the study of CDs, stellar-shocks, and the associated micro-physics in the realm of theory. This paper presents spectroscopic evidence for ions from the hot bubble (kT approximately equal to 100 eV) crossing the CD and penetrating the cold nebular gas (kT approximately equal to 1 eV). Specifically, a narrow radiative recombination continuum (RRC) emission feature is identified in the high resolution X-ray spectrum of the PN BD+30degree3639 indicating bare C VII ions are recombining with cool electrons at kT(sub e) = 1.7 plus or minus 1.3 eV. An upper limit to the flux of the narrow RRC of H-like C VI is obtained as well. The RRCs are interpreted as due to C ions from the hot bubble of BD+30degree3639 crossing the CD into the cold nebula, where they ultimately recombine with its cool electrons. The RRC flux ratio of C VII to C VI constrains the temperature jump across the CD to deltakT greater than 80 eV, providing for the first time direct evidence for the stark temperature disparity between the two sides of an astrophysical CD, and constraining the role of magnetic fields and heat conduction accordingly. Two colliding-wind binaries are noted to have similar RRCs suggesting a temperature jump and CD crossing by ions may be common feature of stellar wind shocks.

Plasmapause Location: Model Compared to Van Allen Probes Observations

NASA Astrophysics Data System (ADS)

Goldstein, J.; Baker, D. N.; Blake, J. B.; Funsten, H. O.; Jaynes, A. N.; Malaspina, D.; Reeves, G. D.; Spence, H. E.; Thaller, S. A.; Wygant, J. R.

2017-12-01

We study the evolution of the plasmapause for a multi-year period (January 2013 to January 2017) spanning much of the Van Allen Probes mission, by comparing the output of a plasmapause test particle simulation with the spacecraft potential measured by the Electric Field and Waves (EFW) suite. Consistent with previous results, we quantify the accuracy of the model by measuring the radial difference between real and virtual satellite encounters with the plasmapause boundary. We find that model performance is better on the nightside and during active periods, and worse on the duskside/dayside and during extended quiet intervals. For two case studies, we compare the plasmapause with the locations of relativistic electron flux peaks. For global context we use the test particle plasmaspheric index Fp [Goldstein et al., 2016], the fraction of a circular drift orbit inside the plasmapause, as a proxy for the globally integrated opportunity for losses in cold plasma. We find an inverse relationship between relativistic flux and the Fp index, consistent with increased likelihood of losses in cold plasma.

Cold Atmospheric-Pressure Plasmas Applied to Active Packaging of Fruits and Vegetables

NASA Astrophysics Data System (ADS)

Pedrow, Patrick; Fernandez, Sulmer; Pitts, Marvin

2008-10-01

Active packaging of fruits and vegetables uses films that absorb molecules from or contribute molecules to the produce. Applying uniform film to specific parts of a plant will enhance safe and economic adoption of expensive biofilms and biochemicals which would damage the plant or surrounding environment if misapplied. The pilot application will be to apply wax film to apples, replacing hot wax which is expensive and lowers the textural quality of the apple. The plasma zone will be obtained by increasing the voltage on an electrode structure until the electric field in the feed material (Argon + monomer) is sufficiently high to yield electron avalanches. The ``corona onset criterion'' is used to design the cold plasma reactor. The apple will be placed in a treatment chamber downstream from the activation zone. Key physical properties of the film will be measured. The deposition rate will be optimized in terms of economics and fruit surface quality for the purpose of determining if the technique is competitive in food processing plants.

Periodic multilayer magnetized cold plasma containing a doped semiconductor

NASA Astrophysics Data System (ADS)

Nayak, Chittaranjan; Saha, Ardhendu; Aghajamali, Alireza

2018-07-01

The present work is to numerically investigate the properties of the defect mode in a one-dimensional photonic crystal made of magnetized cold plasma, doped by semiconductor. The defect mode of such kind of multilayer structure is analyzed by applying the character matrix method to each individual layer. Numerical results illustrate that the defect mode frequency can be tuned by varying the external magnetic field, the electron density, and the thickness of the defect layer. Moreover, the behavior of the defect mode was found to be quite interesting when study the oblique incidence. It was found that for both right- and left-hand polarized transversal magnetic waves, the defect mode of the proposed defective structure disappears when the angle of incidence is larger than a particular oblique incidence. For the left-hand polarized transversal electric wave, however, an additional defect mode was noticed. The results lead to some new information concerning the designing of new types of tunable narrowband microwave filters.

Periodic multilayer magnetized cold plasma containing a doped semiconductor

NASA Astrophysics Data System (ADS)

Nayak, Chittaranjan; Saha, Ardhendu; Aghajamali, Alireza

2018-02-01

The present work is to numerically investigate the properties of the defect mode in a one-dimensional photonic crystal made of magnetized cold plasma, doped by semiconductor. The defect mode of such kind of multilayer structure is analyzed by applying the character matrix method to each individual layer. Numerical results illustrate that the defect mode frequency can be tuned by varying the external magnetic field, the electron density, and the thickness of the defect layer. Moreover, the behavior of the defect mode was found to be quite interesting when study the oblique incidence. It was found that for both right- and left-hand polarized transversal magnetic waves, the defect mode of the proposed defective structure disappears when the angle of incidence is larger than a particular oblique incidence. For the left-hand polarized transversal electric wave, however, an additional defect mode was noticed. The results lead to some new information concerning the designing of new types of tunable narrowband microwave filters.

THE EFFECT OF ANISOTROPIC VISCOSITY ON COLD FRONTS IN GALAXY CLUSTERS

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

ZuHone, J. A.; Markevitch, M.; Kunz, M. W.

2015-01-10

Cold fronts—contact discontinuities in the intracluster medium (ICM) of galaxy clusters—should be disrupted by Kelvin-Helmholtz (K-H) instabilities due to the associated shear velocity. However, many observed cold fronts appear stable. This opens the possibility of placing constraints on microphysical mechanisms that stabilize them, such as the ICM viscosity and/or magnetic fields. We performed exploratory high-resolution simulations of cold fronts arising from subsonic gas sloshing in cluster cores using the grid-based Athena MHD code, comparing the effects of isotropic Spitzer and anisotropic Braginskii viscosity (expected in a magnetized plasma). Magnetized simulations with full Braginskii viscosity or isotropic Spitzer viscosity reduced bymore » a factor f ∼ 0.1 are both in qualitative agreement with observations in terms of suppressing K-H instabilities. The rms velocity of turbulence within the sloshing region is only modestly reduced by Braginskii viscosity. We also performed unmagnetized simulations with and without viscosity and find that magnetic fields have a substantial effect on the appearance of the cold fronts, even if the initial field is weak and the viscosity is the same. This suggests that determining the dominant suppression mechanism of a given cold front from X-ray observations (e.g., viscosity or magnetic fields) by comparison with simulations is not straightforward. Finally, we performed simulations including anisotropic thermal conduction, and find that including Braginskii viscosity in these simulations does not significantly affect the evolution of cold fronts; they are rapidly smeared out by thermal conduction, as in the inviscid case.« less

Photosynthesis and Photosynthetic Electron Flow in the Alpine Evergreen Species Quercus guyavifolia in Winter

PubMed Central

Huang, Wei; Hu, Hong; Zhang, Shi-Bao

2016-01-01

Alpine evergreen broadleaf tree species must regularly cope with low night temperatures in winter. However, the effects of low night temperatures on photosynthesis in alpine evergreen broadleaf tree species are unclear. We measured the diurnal photosynthetic parameters before and after cold snap for leaves of Quercus guyavifolia growing in its native habitat at 3290 m. On 11 and 12 December 2013 (before cold snap), stomatal and mesophyll conductances (gs and gm), CO2 assimilation rate (An), and total electron flow through PSII (JPSII) at daytime were maintained at high levels. The major action of alternative electron flow was to provide extra ATP for primary metabolisms. On 20 December 2013 (after cold snap), the diurnal values of gs, gm, An, and JPSII at daytime largely decreased, mainly due to the large decrease in night air temperature. Meanwhile, the ratio of photorespiration and alternative electron flow to JPSII largely increased on 20 December. Furthermore, the high levels of alternative electron flow were accompanied with low rates of extra ATP production. A quantitative limitation analysis reveals that the gm limitation increased on 20 December with decreased night air temperature. Therefore, the night air temperature was an important determinant of stomatal/mesophyll conductance and photosynthesis. When photosynthesis is inhibited following freezing night temperatures, photorespiration and alternative electron flow are important electron sinks, which support the role of photorespiration and alternative electron flow in photoportection for alpine plants under low temperatures. PMID:27812359

Stationary to nonstationary transition in crossed-field devices

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

Marini, Samuel; Rizzato, Felipe B.; Pakter, Renato

2016-03-15

The previous results based on numerical simulations showed that a cold electron beam injected in a crossed field gap does not reach a time independent stationary state in the space charge limited regime [P. J. Christenson and Y. Y. Lau, Phys. Plasmas 1, 3725 (1994)]. In this work, the effect of finite injection temperature in the transition from stationary to nonstationary states is investigated. A fully kinetic model for the electron flow is derived and used to determine the possible stationary states of the system. It is found that although there is always a stationary solution for any set ofmore » parameters, depending on the injection temperature the electron flow becomes very sensitive to fluctuations and the stationary state is never reached. By investigating the nonlinear dynamics of a characteristic electron, a theory based on a single free parameter is constructed to predict when the transition between stationary and nonstationary states occurs. In agreement with the previous numerical results, the theory indicates that for vanishing temperatures the system never reaches the time independent stationary state in the space charge limited regime. Nevertheless, as the injection temperature is raised it is found a broad range of system parameters for which the stationary state is indeed attained. By properly adjusting the free parameter in the theory, one can be able to describe, to a very good accuracy, when the transition occurs.« less

Electronic interaction anisotropy between open-shell lanthanide atoms and helium from cold collision experiment

NASA Astrophysics Data System (ADS)

Krems, R. V.; Buchachenko, A. A.

2005-09-01

Based on measurements of the Zeeman relaxation in a cold gas of He3 [C. I. Hancox, S. C. Doret, M. I. Hummon, L. Luo, and J. M. Doyle, Nature (London) 431, 281 (2004)], we show that the electronic interaction anisotropy between rare-earth atoms with nonzero electronic orbital angular momenta and helium is extremely small. The interaction of the rare-earth atoms with He gives rise to several adiabatic potentials with different electronic symmetries. It is demonstrated that the energy splitting between these potentials does not exceed 0.09cm-1 at interatomic distances larger than the turning point for collisions at 0.8K, including the region of the van der Waals interaction minima.

External control of photonic bands in a magnetized cold plasma

NASA Astrophysics Data System (ADS)

Kumar, N.; Singh, P. P.; Suthar, B.; Kumar, A.; Thapa, K. B.

2018-05-01

In this analysis, the effect of external rectangle-wave-like periodic magnetic field, on photonic bandgaps (PBGs) exhibited by bulk cold plasma, has been illustrated. It is found that the forbidden gap for normal incidence decreases with a decrease in the thickness ratio for a constant magnetic field. A new gap appears for TM polarization at oblique incidence that is attributed to the Bragg's interference of plasma layers and this new gap width depends on the incident angle as well as the magnitude of the magnetic field. There is also a shifting in gap locations depending on the magnitude of the magnetic field. It is demonstrated that external parameters like magnetic field strength and the ratio of two parts of spatial period along with incident angle can tune the PBGs in a magnetized cold plasma.

Development and installation of an advanced beam guidance system on Viking`s 2.4 megawatt EB furnace

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

Motchenbacher, C.A.; Grosse, I.A.

1994-12-31

Viking Metallurgical is a manufacturer of titanium alloy and superalloy seamless ring forgings for the aerospace industry. For more than 20 years Viking has used electron beam cold hearth melting to recover titanium alloy scrap and to produce commercially pure titanium ingot for direct forging. In the 1970`s Viking pioneered electron beam cold hearth melting and in 1983 added a two-gun, 2.4 MW furnace. As part of Vikings efforts to improve process control we have commissioned and installed a new electron beam guidance system. The system is capable of generating virtually unlimited EB patterns resulting in improved melt control.

X-ray flares from runaway pair production in active galactic nuclei

NASA Technical Reports Server (NTRS)

Kirk, J. G.; Mastichiadis, A.

1992-01-01

The hard X-ray spectrum of AGNs is nonthermal, probably arising from an electron-positron pair cascade, with some emission reflected off relatively cold matter. There has been interest in models on which protons are accelerated and create relativistic electrons on interaction with a local radiation field. It is shown here that a sufficient column density of protons can lead to runaway pair production: photons generated by the relativistic pairs are the targets for the protons to produce more pairs. This can produce X-ray fluxes with the characteristics observed in AGN. The model predicts the maximum ratio of luminosity to source size as well as their spectrum in the early phases. The same mechanism may also be able to create the knots of synchrotron-radiating pair plasma seen in sources such as 3C273.

Energy absorption in cold inhomogeneous plasmas - The Herlofson paradox.

NASA Technical Reports Server (NTRS)

Crawford, F. W.; Harker, K. J.

1972-01-01

Confirmation of Barston's (1964) conclusions regarding the underlying mechanism of the Herlofson paradox by examining in detail several analytically tractable cases of delta-function and sinusoidal excitation. The effects of collisions and nonzero electron temperature in determining the steady state fields and dissipation are considered. Energy absorption without dissipation in plasmas is shown to be analogous to that occurring after application of a signal to a network of lossless resonant circuits. This analogy is pursued and is extended to cover Landau damping in a warm homogeneous plasma in which the resonating elements are the electron streams making up the velocity distribution. Some of the practical consequences of resonant absorption are discussed, together with a number of paradoxical plasma phenomena which can also be elucidated by considering a superposition of normal modes rather than a single Fourier component.

Advances/applications of MAGIC and SOS

NASA Astrophysics Data System (ADS)

Warren, Gary; Ludeking, Larry; Nguyen, Khanh; Smithe, David; Goplen, Bruce

1993-12-01

MAGIC and SOS have been applied to investigate a variety of accelerator-related devices. Examples include high brightness electron guns, beam-RF interactions in klystrons, cold-test modes in an RFQ and in RF sources, and a high-quality, flexible, electron gun with operating modes appropriate for gyrotrons, peniotrons, and other RF sources. Algorithmic improvements for PIC have been developed and added to MAGIC and SOS to facilitate these modeling efforts. Two new field algorithms allow improved control of computational numerical noise and selective control of harmonic modes in RF cavities. An axial filter in SOS accelerates simulations in cylindrical coordinates. The recent addition of an export/import feature now allows long devices to be modeled in sections. Interfaces have been added to receive electromagnetic field information from the Poisson group of codes and from EGUN and to send beam information to PARMELA for subsequent tracing of bunches through beam optics. Post-processors compute and display beam properties including geometric, normalized, and slice emittances, and phase-space parameters, and video. VMS, UNIX, and DOS versions are supported, with migration underway toward windows environments.

Design, Simulation and Experiments on the Recirculating Crossed-Field Planar Amplifier

NASA Astrophysics Data System (ADS)

Exelby, Steven; Greening, Geoffrey; Jordan, Nicholas; Packard, Drew; Lau, Yue Ying; Gilgenbach, Ronald; Simon, David; Hoff, Brad

2017-10-01

The Recirculating Planar Crossed-Field Amplifier (RPCFA) is the focus of simulation and experimental work. This amplifier, inspired by the Recirculating Planar Magnetron, is driven by the Michigan Electron Long Beam Accelerator (MELBA), configured to deliver a -300 kV, 1-10 kA, 0.3-1.0 µs pulse. For these parameters, a slow wave structure (SWS), cathode, and housing were designed using the finite element frequency domain code Ansys HFSS, and verified using the PIC code, MAGIC. Simulations of this device demonstrated amplification of 1.3 MW, 3 GHz signal to approximately 29 MW (13.5 dB) with nearly 53% electronic efficiency. Simulations have also shown the device is zero-drive stable, operates under a range of voltages, with bandwidth of 10%, on par with existing CFAs. The RPCFA SWS has been fabricated using 3D printing, while the rest of the device has been developed using traditional machining. Experimental RPCFA cold tube characteristics matched those from simulation. Experiments on MELBA have demonstrated zero-drive stability and amplifier experiments are underway. This work was supported by the AFOSR Grant FA9550-15-1-0097.

A Cryogenic Dc-Dc Power Converter for a 100 kW Synchronous HTS Generator at Liquid Nitrogen Temperatures

NASA Astrophysics Data System (ADS)

Bailey, Wendell; Wen, Hauming; Yang, Yifeng; Forsyth, Andrew; Jia, Chungjiang

A dc-dc converter has been developed for retrofitting inside the vacuum space of the HTS rotor of a synchronous generator. The heavy copper sections of the current leads used for energising the HTS field winding were replaced by cryogenic power electronics; consisting of the converter and a rotor control unit. The converter board was designed using an H-bridge configuration with two 5A rated wires connecting the cryogenic boards to the stator control board located on the outside of the generator and drawing power from a (5A, 50 V) dc power source. The robustness of converter board was well demonstrated when it was powered up from a cold start at 82K. When charging the field winding with moderate currents (30A), the heat in-leak to the 'cold' rotor core was only 2W. It continued to function down to 74K, surviving several quenches. However, the quench protection function failed when injecting 75A into the field winding, resulting in the burn out of one of the DC-link capacitors. The magnitudes of the critical currents measured with the original current leads were compared to the quench currents, which was defined as the current which triggered quench protection protocol. The difference between the two currents was rather large, (∼20A). However, additional measurements using a single HTS coil in liquid nitrogen found that this reduction should not be so dramatic and in the region of 4A. Our conclusions identified the converter's switching voltage and its operating frequency as two parameters, which could have contributed to lowering the quench current. Magnetic fields and eddy currents are expected to be more prominent the field winding and its impact on the converter also need further investigation.

Cryogenic properties of dispersion strengthened copper for high magnetic fields

NASA Astrophysics Data System (ADS)

Toplosky, V. J.; Han, K.; Walsh, R. P.; Swenson, C. A.

2014-01-01

Cold deformed copper matrix composite conductors, developed for use in the 100 tesla multi-shot pulsed magnet at the National High Magnetic Field Laboratory (NHMFL), have been characterized. The conductors are alumina strengthened copper which is fabricated by cold drawing that introduces high dislocation densities and high internal stresses. Both alumina particles and high density of dislocations provide us with high tensile strength and fatigue endurance. The conductors also have high electrical conductivities because alumina has limited solubility in Cu and dislocations have little scattering effect on conduction electrons. Such a combination of high strength and high conductivity makes it an excellent candidate over other resistive magnet materials. Thus, characterization is carried out by tensile testing and fully reversible fatigue testing. In tensile tests, the material exceeds the design criteria parameters. In the fatigue tests, both the load and displacement were measured and used to control the amplitude of the tests to simulate the various loading conditions in the pulsed magnet which is operated at 77 K in a non-destructive mode. In order to properly simulate the pulsed magnet operation, strain-controlled tests were more suitable than load controlled tests. For the dispersion strengthened coppers, the strengthening mechanism of the aluminum oxide provided better tensile and fatigue properties over convention copper.

Nonlinear oscillations and waves in multi-species cold plasmas

NASA Astrophysics Data System (ADS)

Verma, Prabal Singh

2016-12-01

The spatio-temporal evolution of nonlinear oscillations in multi-species plasma is revisited to provide more insight into the physics of phase mixing by constructing two sets of nonlinear solutions up to the second order. The first solution exhibits perfect oscillations in the linear regime and phase mixing appears only nonlinearly in the second order as a response to the ponderomotive forces. This response can be both direct and indirect. The indirect contribution of the ponderomotive forces appears through self-consistently generated low frequency fields. Furthermore, the direct and indirect contributions of the ponderomotive forces on the phase mixing process is explored and it is found that the indirect contribution is negligible in an electron-ion plasma and it disappears in the case of electron-positron plasma, yet represents an equal contribution in the electron-positron-ion plasma. However, the second solution does not exhibit any phase mixing due to the absence of ponderomotive forces but results in an undistorted nonlinear traveling wave. These investigations have relevance for laboratory/astrophysical multi-species plasma.

Development program on a cold cathode electron gun

NASA Technical Reports Server (NTRS)

Spindt, C. A.

1979-01-01

A prototype electron gun with a field emitter cathode capable of producing 95 mA in a 1/4 mm diameter beam at 12 kV was produced. Achievement of this goal required supporting studies in cathode fabrication, cathode performance, gun design, cathode mounting and gun fabrication. A series of empirical investigations advanced fabrication technology: More stable emitters were produced and multiple cone failure caused by chain reaction discharges were reduced. The cathode is capable of producing well over 95 mA, but a substantial collector development effort was required to demonstrate emission levels in the 100 mA region. Space charge problems made these levels difficult to achieve. Recommendations are made for future process and materials investigation. Electron gun designs were modeled and tested. A pair of two-electrode gun structures were fabricated and tested; one gun was delivered to NASA. Cathodes were pretested up to 100 mA at SRI and delivered to NASA for test in the gun structure.

Generation of low work function, stable compound thin films by laser ablation

DOEpatents

Dinh, Long N.; McLean, II, William; Balooch, Mehdi; Fehring, Jr., Edward J.; Schildbach, Marcus A.

2001-01-01

Generation of low work function, stable compound thin films by laser ablation. Compound thin films with low work function can be synthesized by simultaneously laser ablating silicon, for example, and thermal evaporating an alkali metal into an oxygen environment. For example, the compound thin film may be composed of Si/Cs/O. The work functions of the thin films can be varied by changing the silicon/alkali metal/oxygen ratio. Low work functions of the compound thin films deposited on silicon substrates were confirmed by ultraviolet photoelectron spectroscopy (UPS). The compound thin films are stable up to 500.degree. C. as measured by x-ray photoelectron spectroscopy (XPS). Tests have established that for certain chemical compositions and annealing temperatures of the compound thin films, negative electron affinity (NEA) was detected. The low work function, stable compound thin films can be utilized in solar cells, field emission flat panel displays, electron guns, and cold cathode electron guns.

Passage of the discharge current through the plasma-electrode interface in the electromagnetic rail accelerator channel

NASA Astrophysics Data System (ADS)

Zhukov, B. G.; Reznikov, B. I.; Kurakin, R. O.; Ponyaev, S. A.; Bobashev, S. V.

2016-11-01

We investigate the phenomena that accompany the acceleration of a free plasma piston (without a striker) in the electromagnetic rail accelerator channel filled with different gases (argon, helium). An intense glow appears in the shock-compressed layer (SCL) in the case of strong shock waves that produce a high electron concentration ( 1017-1018 cm-3) behind the front. We have proposed that explosive electron emission (EEE) ensures the high-intensity emission of electrons, the passage of a part of the discharge current through the SCL, and the glow of the SCL. The velocity of a shock wave for which the strong electric field in the Debye layer at the cathode causes EEE from its surface and the passage of the current in the SCL has been determined. It has been concluded that, for high velocities of the plasma, the EEE is a universal mechanism that ensure the passage of a strong current through the interface between the cold electrode and the plasma.

Carbon Nanotube-Based Digital Vacuum Electronics and Miniature Instrumentation for Space Exploration

NASA Technical Reports Server (NTRS)

Manohara, H.; Toda, R.; Lin, R. H.; Liao, A.; Mojarradi, M.

2010-01-01

JPL has developed high performance cold cathodes using arrays of carbon nanotube bundles that produce > 15 A/sq cm at applied fields of 5 to 8 V/micron without any beam focusing. They have exhibited robust operation in poor vacuums of 10(exp -6) to 10(exp -4) Torr- a typically achievable range inside hermetically sealed microcavities. Using these CNT cathodes JPL has developed miniature X-ray tubes capable of delivering sufficient photon flux at acceleration voltages of <20kV to perform definitive mineralogy on planetary surfaces; mass ionizers that offer two orders of magnitude power savings, and S/N ratio better by a factor of five over conventional ionizers. JPL has also developed a new class of programmable logic gates using CNT vacuum electronics potentially for Venus in situ missions and defense applications. These digital vacuum electronic devices are inherently high-temperature tolerant and radiation insensitive. Device design, fabrication and DC switching operation at temperatures up to 700 C are presented in this paper.

Development of a Two-Dimensional Hybrid-Kinetic Code for Simulations of Low-Altitude Auroral Flux-Tubes

NASA Astrophysics Data System (ADS)

Sydorenko, D.; Rankin, R.; Kabin, K.

2009-12-01

This paper presents initial results based on kinetic extensions of a nonlinear two-dimensional (2D) multi-fluid (three ion species and fluid electrons) MHD model that is designed to study propagation of shear Alfven waves in low-altitude auroral flux tubes. It is intended to use the model for scientific support of the “enhanced polar outflow probe” e-POP/CASSIOPE spacecraft mission (launch scheduled in 2010). Effects of gravity, thermal pressure, and geomagnetic field curvature are included, while the parallel electric field along geomagnetic field lines is calculated under the assumption of plasma quasineutrality. The model has been used successfully to study excitation of eigenmodes of the ionospheric Alfven resonator (IAR) by an Alfven wave packet injected from the magnetospheric end of the simulated plasma region. The formation of density cavities due to the ponderomotive force of standing oscillations in the IAR [Sydorenko, Rankin, and Kabin, 2008], and excitation of double layers and ion-acoustic wave packets, has been demonstrated. The kinetic extension of the multi-fluid code involves replacing the fluid electron model with a kinetic module that solves the simplified drift-kinetic Vlasov equation for the electron velocity distribution function (EVDF). To avoid undue complexity, it is assumed that (i) the electrons move only along geomagnetic field lines and (ii) the electron magnetic moment is conserved. As a result, the evolution of the EVDF is reduced to the problem of advection in 2D phase space “distance along the field line - velocity along the field line”. This problem is solved using a semi-Lagrangian algorithm [Staniforth and Cote, 1991]. The kinetic simulation starts from the initial equilibrium state similar to [Ergun et al., 2000]. The equilibrium assumes that the plasma consists of two electron populations: cold electrons with isotropic EVDF originating from the ionosphere, and hot anisotropic electrons with a loss-cone EVDF coming from the high-altitude end. The loss-cone distribution is prone to strong numerical dispersion, which is compensated by tracing the interface of the EVDF in the coordinate-velocity phase space. Ergun R. E., C. W. Carlson, J. P. McFadden, F. S. Mozer, and R. J. Strangeway (2000), Geophys. Res. Lett., 27, 4053-4056. Staniforth A. and J. Cote (1991), Mon. Wea. Rev., 119, 2206-2223 Sydorenko, D., R. Rankin, and K. Kabin (2008), J. Geophys. Res., 113, A10206, doi:10.1029/2008JA013579.

A primer on clothing systems for cold-weather field work

USGS Publications Warehouse

Denner, J.C.

1993-01-01

Hypothermia in cold environments can be prevented by physiological adaptation and by the proper use of cold weather clothing. The human body adjusts to cold temperature by increasing the rates of basal metabolism, specific dynamic action, and physical exercise. Heat loss is reduced by vasoconstriction. Clothing systems for cold weather reduce loss by providing insulation and protection from the elements. Satisfactory cold- weather clothing is constructed of wool fabrics or the synthetic fibers polypropylene and polyester. Outerwear suitable for cold climates is insulated with down, high-loft polyester fiberfills, or the new synthetic thin insulators. (USGS)

Cold and heat strain during cold-weather field training with nuclear, biological, and chemical protective clothing.

PubMed

Rissanen, Sirkka; Rintamäki, Hannu

2007-02-01

The objective of this study was to quantify the thermal strain of soldiers wearing nuclear, biological, and chemical protective clothing during short-term field training in cold conditions. Eleven male subjects performed marching exercises at moderate and heavy activity levels for 60 minutes. Rectal temperature (Tre), skin temperatures, and heart rate were monitored. Ambient temperature (Ta) varied from -33 to 0 degrees C. Tre was affected by changes in metabolism, rather than in Ta. Tre increased above 38 degrees during heavy exercise even at -33 degrees C. The mean skin temperature decreased to tolerance level (25 degrees C) at Ta below -25 degrees C with moderate exercise. Finger temperature decreased below 15 degrees C (performance degradation) at Ta of -15 degrees C or cooler. The present results from the field confirm the previous results based on laboratory studies and show that risk of both heat and cold strain is evident, with cooling of extremities being most critical, while wearing nuclear, biological, and chemical protective clothing during cold-weather training.

Thales Cryogenics rotary cryocoolers for HOT applications

NASA Astrophysics Data System (ADS)

Martin, Jean-Yves; Cauquil, Jean-Marc; Benschop, Tonny; Freche, Sébastien

2012-06-01

Thales Cryogenics has an extensive background in delivering reliable linear and rotary coolers for military, civil and space programs. Recent work carried out at detector level enable to consider a higher operation temperature for the cooled detectors. This has a direct impact on the cooling power required to the cryocooler. In continuation of the work presented last year, Thales cryogenics has studied the operation and optimization of the rotary cryocoolers at high cold regulation temperature. In this paper, the performances of the Thales Cryogenics rotary cryocoolers at elevated cold regulation temperature will be presented. From these results, some trade-offs can be made to combine correct operation of the cryocooler on all the ambient operational range and maximum efficiency of the cryocooler. These trade-offs and the impact on MTTF of elevated cold regulation temperature will be presented and discussed. In correlation with the increase of the cold operation temperature, the cryocooler input power is significantly decreased. As a consequence, the cooler drive electronics own consumption becomes relatively important and must be reduced in order to minimize global input power to the cooling function (cryocooler and cooler drive electronics). Thales Cryogenics has developed a new drive electronics optimized for low input power requirements. In parallel, improvements on RM1 and RM2 cryocoolers have been defined and implemented. The main impacts on performances of these new designs will be presented. Thales cryogenics is now able to propose an efficient cooling function for application requiring a high cold regulation temperature including a range of tuned rotary coolers.

Studies on equatorial shock formation during plasmaspheric refilling

NASA Technical Reports Server (NTRS)

Singh, N.

1994-01-01

Investigations based on small-scale simulations of microprocesses occurring when a magnetic flux tube refills with a cold plasma are summarized. Results of these investigations are reported in the following attached papers: (1) 'Numerical Simulation of Filling a Magnetic Flux Tube with a Cold Plasma: The Role of Ion Beam-Driven Instabilities'; and (2) 'Numerical Simulation of Filling a Magnetic Flux Tube with a Cold Plasma: Effects of Magnetically Trapped Hot Plasma'. Other papers included are: 'Interaction of Field-Aligned Cold Plasma Flows with an Equatorially-Trapped Hot Plasma: Electrostatic Shock Formation'; and 'Comparison of Hydrodynamic and Semikinetic Treatments for a Plasma Flow along Closed Field Lines'. A proposal for further research is included.

Thermal Analysis of the NASA Integrated Vehicle Health Monitoring Experiment Technology for X-Vehicles (NITEX)

NASA Technical Reports Server (NTRS)

Hegab, Hisham E.

2002-01-01

The purpose of this project was to perform a thermal analysis for the NASA Integrated Vehicle Health Monitoring (IVHM) Technology Experiment for X-vehicles (NITEX). This electronics package monitors vehicle sensor information in flight and downlinks vehicle health summary information via telemetry. The experiment will be tested on the X-34 in an unpressurized compartment, in the vicinity of one of the vehicle's liquid oxygen tanks. The transient temperature profile for the electronics package has been determined using finite element analysis for possible mission profiles that will most likely expose the package to the most extreme hot and cold environmental conditions. From the analyses, it was determined that temperature limits for the electronics would be exceeded for the worst case cold environment mission profile. The finite element model used for the analyses was modified to examine the use of insulation to address this problem. Recommendations for insulating the experiment for the cold environment are presented, and were analyzed to determine their effect on a nominal mission profile.

Thermal Analysis Of The NASA Integrated Vehicle Health Monitoring Experiment Technology For X-Vehicles (NITEX)

NASA Technical Reports Server (NTRS)

Hegab, Hisham E.

2001-01-01

The purpose of this project was to perform a thermal analysis for the NASA Integrated Vehicle Health Monitoring (IVHM) Technology Experiment for X-vehicles (NITEX). This electronics package monitors vehicle sensor information in flight and downlinks vehicle health summary information via telemetry. The experiment will be tested on the X-34 in an unpressurized compartment, in the vicinity of one of the vehicle's liquid oxygen tanks. The transient temperature profile for the electronics package has been determined using finite element analysis for possible mission profiles that will most likely expose the package to the most extreme hot and cold environmental conditions. From the analyses, it was determined that temperature limits for the electronics would be exceeded for the worst case cold environment mission profile. The finite element model used for the analyses was modified to examine the use of insulation to address this problem. Recommendations for insulating the experiment for the cold environment are presented, and were analyzed to determine their effect on a nominal mission profile.

Cold Ionospheric Ions in the Magnetic Reconnection Outflow Region

NASA Astrophysics Data System (ADS)

Li, W. Y.; André, M.; Khotyaintsev, Yu. V.; Vaivads, A.; Fuselier, S. A.; Graham, D. B.; Toledo-Redondo, S.; Lavraud, B.; Turner, D. L.; Norgren, C.; Tang, B. B.; Wang, C.; Lindqvist, P.-A.; Young, D. T.; Chandler, M.; Giles, B.; Pollock, C.; Ergun, R.; Russell, C. T.; Torbert, R.; Moore, T.; Burch, J.

2017-10-01

Magnetosheath plasma usually determines properties of asymmetric magnetic reconnection at the subsolar region of Earth's magnetopause. However, cold plasma that originated from the ionosphere can also reach the magnetopause and modify the kinetic physics of asymmetric reconnection. We present a magnetopause crossing with high-density (10-60 cm-3) cold ions and ongoing reconnection from the observation of the Magnetospheric Multiscale (MMS) spacecraft. The magnetopause crossing is estimated to be 300 ion inertial lengths south of the X line. Two distinct ion populations are observed on the magnetosheath edge of the ion jet. One population with high parallel velocities (200-300 km/s) is identified to be cold ion beams, and the other population is the magnetosheath ions. In the deHoffman-Teller frame, the field-aligned magnetosheath ions are Alfvénic and move toward the jet region, while the field-aligned cold ion beams move toward the magnetosheath boundary layer, with much lower speeds. These cold ion beams are suggested to be from the cold ions entering the jet close to the X line. This is the first observation of the cold ionospheric ions in the reconnection outflow region, including the reconnection jet and the magnetosheath boundary layer.

Electron heating by intense short-pulse lasers propagating through near-critical plasmas

NASA Astrophysics Data System (ADS)

Debayle, A.; Mollica, F.; Vauzour, B.; Wan, Y.; Flacco, A.; Malka, V.; Davoine, X.; Gremillet, L.

2017-12-01

We investigate the electron heating induced by a relativistic-intensity laser pulse propagating through a near-critical plasma. Using particle-in-cell simulations, we show that a specific interaction regime sets in when, due to the energy depletion caused by the plasma wakefield, the laser front profile has steepened to the point of having a length scale close to the laser wavelength. Wave breaking and phase mixing have then occurred, giving rise to a relativistically hot electron population following the laser pulse. This hot electron flow is dense enough to neutralize the cold bulk electrons during their backward acceleration by the wakefield. This neutralization mechanism delays, but does not prevent the breaking of the wakefield: the resulting phase mixing converts the large kinetic energy of the backward-flowing electrons into thermal energy greatly exceeding the conventional ponderomotive scaling at laser intensities > {10}21 {{{W}}{cm}}-2 and gas densities around 10% of the critical density. We develop a semi-numerical model, based on the Akhiezer-Polovin equations, which correctly reproduces the particle-in-cell-predicted electron thermal energies over a broad parameter range. Given this good agreement, we propose a criterion for full laser absorption that includes field-induced ionization. Finally, we show that our predictions still hold in a two-dimensional geometry using a realistic gas profile.

Single Crystal Diamond Needle as Point Electron Source

PubMed Central

Kleshch, Victor I.; Purcell, Stephen T.; Obraztsov, Alexander N.

2016-01-01

Diamond has been considered to be one of the most attractive materials for cold-cathode applications during past two decades. However, its real application is hampered by the necessity to provide appropriate amount and transport of electrons to emitter surface which is usually achieved by using nanometer size or highly defective crystallites having much lower physical characteristics than the ideal diamond. Here, for the first time the use of single crystal diamond emitter with high aspect ratio as a point electron source is reported. Single crystal diamond needles were obtained by selective oxidation of polycrystalline diamond films produced by plasma enhanced chemical vapor deposition. Field emission currents and total electron energy distributions were measured for individual diamond needles as functions of extraction voltage and temperature. The needles demonstrate current saturation phenomenon and sensitivity of emission to temperature. The analysis of the voltage drops measured via electron energy analyzer shows that the conduction is provided by the surface of the diamond needles and is governed by Poole-Frenkel transport mechanism with characteristic trap energy of 0.2–0.3 eV. The temperature-sensitive FE characteristics of the diamond needles are of great interest for production of the point electron beam sources and sensors for vacuum electronics. PMID:27731379

Utilizing upper hybrid resonance for high density plasma production and negative ion generation in a downstream region

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

Sahu, Debaprasad; Bhattacharjee, Sudeep

2012-09-15

Localized wave-induced resonances are created by microwaves launched directly into a multicusp (MC) plasma device in the k Up-Tack B mode, where k is the wave vector and B is the static magnetic field. The resonance zone is identified as upper hybrid resonance (UHR), and lies r = {approx}22 mm away from the MC boundary. Measurement of radial wave electric field intensity confirms the right hand cutoff of the wave (r = 22.5-32.1 mm) located near the UHR zone. A sharp rise in the corresponding electron temperature in the resonance region by {approx}13 eV from its value away from resonancemore » at r = 0, is favorable for the generation of vibrationally excited molecules of hydrogen. A transverse magnetic filter allows cold electrons ({approx}1-2 eV) to pass into the downstream region where they generate negative ions by dissociative attachment. Measurements of electron energy distribution function (EEDF) support the viewpoint. H{sup -} current density of {approx}0.26 mA/cm{sup 2} is obtained at a wave power density of {approx}3 W/cm{sup 2} at 2.0 mTorr pressure, which agrees reasonably well with results obtained from a steady state model using particle balance equations.« less

New DMSP database of precipitating auroral electrons and ions

NASA Astrophysics Data System (ADS)

Redmon, Robert J.; Denig, William F.; Kilcommons, Liam M.; Knipp, Delores J.

2017-08-01

Since the mid-1970s, the Defense Meteorological Satellite Program (DMSP) spacecraft have operated instruments for monitoring the space environment from low Earth orbit. As the program evolved, so have the measurement capabilities such that modern DMSP spacecraft include a comprehensive suite of instruments providing estimates of precipitating electron and ion fluxes, cold/bulk plasma composition and moments, the geomagnetic field, and optical emissions in the far and extreme ultraviolet. We describe the creation of a new public database of precipitating electrons and ions from the Special Sensor J (SSJ) instrument, complete with original counts, calibrated differential fluxes adjusted for penetrating radiation, estimates of the total kinetic energy flux and characteristic energy, uncertainty estimates, and accurate ephemerides. These are provided in a common and self-describing format that covers 30+ years of DMSP spacecraft from F06 (launched in 1982) to F18 (launched in 2009). This new database is accessible at the National Centers for Environmental Information and the Coordinated Data Analysis Web. We describe how the new database is being applied to high-latitude studies of the colocation of kinetic and electromagnetic energy inputs, ionospheric conductivity variability, field-aligned currents, and auroral boundary identification. We anticipate that this new database will support a broad range of space science endeavors from single observatory studies to coordinated system science investigations.

Laser-Free Cold-Atom Gymnastics

NASA Astrophysics Data System (ADS)

Gould, Harvey; Feinberg, Benedict; Munger, Charles T., Jr.; Nishimura, Hiroshi

2017-01-01

We have performed beam transport simulations on ultra cold (2 μK) and cold (130 μK) neutral Cs atoms in the F = M = + 4 (magnetic weak-field seeking) ground state. We use inhomogeneous magnetic fields to focus and accelerate the atoms. Acceleration of neutral atoms by an inhomogeneous magnetic field was demonstrated by Stern and Gerlach in 1922. In the simulations, a two mm diameter cloud of atoms is released to fall under gravity. A magnetic coil focuses the falling atoms. After falling 41 cm, the atoms are reflected in the magnetic fringe field of a solenoid. They return to their starting height, about 0.7 s later, having passed a second time through the focusing coil. The simulations show that > 98 % of ultra cold Cs atoms and > 70 % of cold Cs atoms will survive at least 15 round trips (assuming perfect vacuum). More than 100 simulations were run to optimize coil currents and focusing coil diameter and height. Simulations also show that atoms can be launched into a fountain. An experimental apparatus to test the simulations, is being constructed. This technique may find application in atomic fountain clocks, interferometers, and gravitometers, and may be adaptable for use in microgravity. It may also work with Bose-Einstein condensates of paramagnetic atoms.

Older Thinopyrum intermedium (Poaceae) plants exhibit superior photosynthetic tolerance to cold stress and greater increases in two photosynthetic enzymes under freezing stress compared with young plants.

PubMed

Jaikumar, Nikhil S; Snapp, Sieglinde S; Sharkey, Thomas D

2016-08-01

Effects of plant age on resource acquisition and stress tolerance processes is a largely unstudied subject in herbaceous perennials. In a field experiment, we compared rates of photosynthesis (A), ribulose-1,5-bisphosphate (RuBP) carboxylation capacity (V Cmax), maximum electron transport rate (J max), and triose phosphate utilization (TPU), as well as concentrations of Rubisco and sucrose-phosphate synthase (SPS) in 5-year-old and 2-year-old intermediate wheatgrass (Thinopyrum intermedium) under both optimal growing conditions and cold stress in early spring and autumn. This species is a relative of wheat undergoing domestication. An additional experiment compared photosynthetic rates in different cohorts at mid-season and under colder conditions. We hypothesized that photosynthetic capacity in older plants would be lower under favorable conditions but higher under cold stress. Our hypothesis was generally supported. Under cold stress, 5-year-old plants exhibited higher A, TPU, and temperature-adjusted V Cmax than younger plants, as well as 50% more SPS and 37% more Rubisco. In contrast, at mid-season, photosynthetic capacities in older plants were lower than in younger plants in one experiment, and similar in the other, independent of differences in water status. Both cohorts increased A, temperature-adjusted TPU and J max, [Rubisco], and [SPS] under cold stress, but changes were greater in older plants. Photosynthetic differences were largest at 1.2 ºC in very early spring, where older plants had 200% higher A and maintained up to 17% of their peak photosynthetic capacity. We find evidence of increased cold tolerance in older cohorts of wheatgrass, consistent with a growing body of research in woody perennials. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Effect of cold rolling on the microstructural evolution of new β-typed Ti–6Mo–6V–5Cr–3Sn–2.5Zr alloys

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

Choi, Gwnaghyo; Lee, Kwangmin, E-mail: kmlee@jnu.a

A Ti–6Mo–6V–5Cr–3Sn–2.5Zr (wt.%) alloy was designed as a new metastable β-Ti alloy. The effect that cold rolling had on the microstructural evolution of the material was investigated via optical microscopy (OM), X-ray diffraction (XRD), electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM) measurements. A single β phase formed in the alloy after solution treatment at 780 °C for 30 min followed by water quenching. The solution-treated alloy was cold rolled with thickness reductions of 10%, 30%, 50% and 70%, and the hardness values increased as the thickness of the specimen decreased. The textures of the cold rolled specimen weremore » characterized according to the 〈110〉 partial parallel to the rolling direction as the rolling reduction increased. The crystallographic orientation showed principal α-fiber textures for (111)〈110〉 and (112)〈110〉. The cold deformation led to the appearance of martensite α″ phases, particularly stress-induced martensite (SIM) α″ phases. - Highlights: • Effect of cold rolling on new β-typed Ti-6Mo-6V-5Cr-3Sn-2.5Zr alloy was studied. • A single β phase was obtained after solution treatment at 780 °C for 30 min. • α-Fiber textures became dominated with the increase in cold rolling reduction. • A stress-induced α″ martensite was caused by cold rolling.« less

Influence of Electron Molecule Resonant Vibrational Collisions over the Symmetric Mode and Direct Excitation-Dissociation Cross Sections of CO2 on the Electron Energy Distribution Function and Dissociation Mechanisms in Cold Pure CO2 Plasmas.

PubMed

Pietanza, L D; Colonna, G; Laporta, V; Celiberto, R; D'Ammando, G; Laricchiuta, A; Capitelli, M

2016-05-05

A new set of electron-vibrational (e-V) processes linking the first 10 vibrational levels of the symmetric mode of CO2 is derived by using a decoupled vibrational model and inserted in the Boltzmann equation for the electron energy distribution function (eedf). The new eedf and dissociation rates are in satisfactory agreement with the corresponding ones obtained by using the e-V cross sections reported in the database of Hake and Phelps (H-P). Large differences are, on the contrary, found when the experimental dissociation cross sections of Cosby and Helm are inserted in the Boltzman equation. Comparison of the corresponding rates with those obtained by using the low-energy threshold energy, reported in the H-P database, shows differences up to orders of magnitude, which decrease with the increasing of the reduced electric field. In all cases, we show the importance of superelastic vibrational collisions in affecting eedf and dissociation rates either in the direct electron impact mechanism or in the pure vibrational mechanism.

Preservation of potassium balance is strongly associated with insect cold tolerance in the field: a seasonal study of Drosophila subobscura.

PubMed

MacMillan, Heath A; Schou, Mads F; Kristensen, Torsten N; Overgaard, Johannes

2016-05-01

There is interest in pinpointing genes and physiological mechanisms explaining intra- and interspecific variations in cold tolerance, because thermal tolerance phenotypes strongly impact the distribution and abundance of wild animals. Laboratory studies have highlighted that the capacity to preserve water and ion homeostasis is linked to low temperature survival in insects. It remains unknown, however, whether adaptive seasonal acclimatization in free-ranging insects is governed by the same physiological mechanisms. Here, we test whether cold tolerance in field-caught Drosophila subobscura is high in early spring and lower during summer and whether this transition is associated with seasonal changes in the capacity of flies to preserve water and ion balance during cold stress. Indeed, flies caught during summer were less cold tolerant, and exposure of these flies to sub-zero temperatures caused a loss of haemolymph water and increased the concentration of K(+) in the haemolymph (as in laboratory-reared insects). This pattern of ion and water balance disruption was not observed in more cold-tolerant flies caught in early spring. Thus, we here provide a field verification of hypotheses based on laboratory studies and conclude that the ability to maintain ion homeostasis is important for the ability of free-ranging insects to cope with chilling. © 2016 The Author(s).

Electronic circuit provides automatic level control for liquid nitrogen traps

NASA Technical Reports Server (NTRS)

Turvy, R. R.

1968-01-01

Electronic circuit, based on the principle of increased thermistor resistance corresponding to decreases in temperature provides an automatic level control for liquid nitrogen cold traps. The electronically controlled apparatus is practically service-free, requiring only occasional reliability checks.

Delta and gamma oscillations in operculo-insular cortex underlie innocuous cold thermosensation

PubMed Central

Vinding, Mikkel C.; Allen, Micah; Jensen, Troels Staehelin; Finnerup, Nanna Brix

2017-01-01

Cold-sensitive and nociceptive neural pathways interact to shape the quality and intensity of thermal and pain perception. Yet the central processing of cold thermosensation in the human brain has not been extensively studied. Here, we used magnetoencephalography and EEG in healthy volunteers to investigate the time course (evoked fields and potentials) and oscillatory activity associated with the perception of cold temperature changes. Nonnoxious cold stimuli consisting of Δ3°C and Δ5°C decrements from an adapting temperature of 35°C were delivered on the dorsum of the left hand via a contact thermode. Cold-evoked fields peaked at around 240 and 500 ms, at peak latencies similar to the N1 and P2 cold-evoked potentials. Importantly, cold-related changes in oscillatory power indicated that innocuous thermosensation is mediated by oscillatory activity in the range of delta (1–4 Hz) and gamma (55–90 Hz) rhythms, originating in operculo-insular cortical regions. We suggest that delta rhythms coordinate functional integration between operculo-insular and frontoparietal regions, while gamma rhythms reflect local sensory processing in operculo-insular areas. NEW & NOTEWORTHY Using magnetoencephalography, we identified spatiotemporal features of central cold processing, with respect to the time course, oscillatory profile, and neural generators of cold-evoked responses in healthy human volunteers. Cold thermosensation was associated with low- and high-frequency oscillatory rhythms, both originating in operculo-insular regions. These results support further investigations of central cold processing using magnetoencephalography or EEG and the clinical utility of cold-evoked potentials for neurophysiological assessment of cold-related small-fiber function and damage. PMID:28250150

Population kinetics on K alpha lines of partially ionized Cl atoms.

PubMed

Kawamura, Tohru; Nishimura, Hiroaki; Koike, Fumihiro; Ochi, Yoshihiro; Matsui, Ryoji; Miao, Wen Yong; Okihara, Shinichiro; Sakabe, Shuji; Uschmann, Ingo; Förster, Eckhart; Mima, Kunioki

2002-07-01

A population kinetics code was developed to analyze K alpha emission from partially ionized chlorine atoms in hydrocarbon plasmas. Atomic processes are solved under collisional-radiative equilibrium for two-temperature plasmas. It is shown that the fast electrons dominantly contribute to ionize the K-shell bound electrons (i.e., inner-shell ionization) and the cold electrons to the outer-shell bound ones. Ratios of K alpha lines of partially ionized atoms are presented as a function of cold-electron temperature. The model was validated by observation of the K alpha lines from a chlorinated plastic target irradiated with 1 TW Ti:sapphire laser pulses at 1.5 x 10(17) W/cm(2), inferring a plasma temperature of about 100 eV on the target surface.

Development of a hybrid chemical/mechanical heat pump

NASA Technical Reports Server (NTRS)

Grzyll, Lawrence R.; Silvestri, John J.; Scaringe, Robert P.

1991-01-01

The authors present the current development status of a hybrid chemical/mechanical heat pump for low-lift applications. The heat pump provides electronics cooling by evaporating a pure refrigerant from an absorbent/refrigerant mixture in a generator/cold plate. The current development focused on evaluation of absorbent/refrigerant pairs, corrosion testing, pump and compressor design, and electronic cold plate design. Two cycle configurations were considered. The first configuration utilized a standard mechanical compressor and pump. The second cycle configuration investigated pumps and compressors with non-moving parts. An innovative generator/cold plate design is also presented. The development to date shows that this cycle has about the same performance as standard vapor compression heat pumps with standard refrigerants but may have some performance and reliability advantages over vapor compression heat pumps.

Recovery and recrystalization kinetics of cold-worked Zircaloy-4 plate and tubing (LWBR Development Program)

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

Katz, O.M.

1968-02-01

Empirical kinetic equations were derived to describe the recovery region between 550 and 1020/sup 0/F for times to 4000 hours for 15 to 78% cold-worked Zircaloy-4 plate and tubing. The properties studied were electrical resistivity and X-ray line sharpening. Recrystallization kinetics were described with sigmoidal curves derived from X-ray intensity and microhardness data. Light, replica, and transmission electron microscopy and selected-area electron diffraction were used to postulate recovery and recrystallization mechanisms. From a structural aspect, the annealing process in cold-worked Zircaloy-4 is visualized as a dislocation climb and annihilation process to the limit allowed by the size of the deformationmore » subcells, a reorientation of the subgrain material into a recrystallization texture, a growth of reoriented cells located in the most highly worked bands, and a consumption of less favorably strained and/or oriented cells by the high-angle boundaries of the reoriented cells. Comparison of 15 and 73% cold-worked tubing showed the activation energy to be less (21 versus 60 kcal/mol) and the subcell size greater (8000A versus 1000A) for the 15% cold-worked material. (NSA 22: 21698)« less

A modified Bitter-type electromagnet and control system for cold atom experiments

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

Luan, Tian; Zhou, Tianwei; Chen, Xuzong, E-mail: xuzongchen@pku.edu.cn

2014-02-15

We present a modified Bitter-type electromagnet which features high magnetic field, fine electronic properties and efficient heat removal. The electromagnet is constructed from a stack of copper layers separated by mica layers that have the same shape. A distinctive design of cooling channels on the insulating layers and the parallel ducts between the layers ensures low resistance for cooling water to flow. A continuous current control system is also made to regulate the current through the electromagnet. In our experiment, versatile electromagnets are applied to generate magnetic field and gradient field. From our measurements, a peak magnetic field of 1000more » G and a peak gradient field of 80 G/cm are generated in the center of the apparatuses which are 7 cm and 5 cm away from the edge of each electromagnet with a current of 230 A and 120 A, respectively. With the effective feedback design in the current control system and cooling water flow of 3.8 l/min, the stability of the current through the electromagnets can reach 10{sup −5}.« less

Interchange Reconnection Associated with a Confined Filament Eruption: Implications for the Source of Transient Cold-dense Plasma in Solar Winds

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

Zheng, Ruisheng; Chen, Yao; Wang, Bing

The cold-dense plasma is occasionally detected in the solar wind with in situ data, but the source of the cold-dense plasma remains illusive. Interchange reconnections (IRs) between closed fields and nearby open fields are known to contribute to the formation of solar winds. We present a confined filament eruption associated with a puff-like coronal mass ejection (CME) on 2014 December 24. The filament underwent successive activations and finally erupted, due to continuous magnetic flux cancelations and emergences. The confined erupting filament showed a clear untwist motion, and most of the filament material fell back. During the eruption, some tiny blobsmore » escaped from the confined filament body, along newly formed open field lines rooted around the south end of the filament, and some bright plasma flowed from the north end of the filament to remote sites at nearby open fields. The newly formed open field lines shifted southward with multiple branches. The puff-like CME also showed multiple bright fronts and a clear southward shift. All the results indicate an intermittent IR existed between closed fields of the confined erupting filament and nearby open fields, which released a portion of filament material (blobs) to form the puff-like CME. We suggest that the IR provides a possible source of cold-dense plasma in the solar wind.« less

Structural Assembly for Cold Plate Cooling

NASA Technical Reports Server (NTRS)

Zaffetti, Mark A. (Inventor); Taddey, Edmund P. (Inventor)

2014-01-01

A device including a structural member having a heat spreader and an electronic device mounted directly to a first surface of the heat spreader of the structural member. The device also includes a cold plate mounted directly to the first surface of the heat spreader of the structural member.

Fabrication of gradient optical filter containing anisotropic Bragg nanostructure.

PubMed

Cho, Bomin; Um, Sungyong; Woo, Hee-Gweon; Sohn, Honglae

2011-08-01

New gradient optical filters containing asymmetric Bragg structure were prepared from the distributed Bragg reflector (DBR) porous silicon (PSi). Anisotropic DBR PSi displaying a rainbow-colored reflection was generated by using an asymmetric etching configuration. Flexible anisotropic DBR PSi composite films were obtained by casting of polymer solution onto anisotropic DBR PSi thin films. The surface and cross-sectional images images of anisotropic DBR PSi composite films obtained with cold field emission scanning electron microscope indicated that the average pore size and the thickness of porous layer decreased as the lateral distance increased. As lateral distance increased, the reflection resonance shifted to shorter wavelength.

Instrument Packages for the Cold, Dark, High Radiation Environments

NASA Technical Reports Server (NTRS)

Clark, P. E.; Millar, P. S.; Yeh, P. S.; Beamna, B.; Brigham, D.; Feng, S.

2011-01-01

We are developing a small cold temperature instrument package concept that integrates a cold temperature power system and radhard ultra low temperature ultra low power electronics components and power supplies now under development into a cold temperature surface operational version of a planetary surface instrument package. We are already in the process of developing a lower power lower tem-perature version for an instrument of mutual interest to SMD and ESMD to support the search for volatiles (the mass spectrometer VAPoR, Volatile Analysis by Pyrolysis of Regolith) both as a stand alone instrument and as part of an environmental monitoring package.

The effect of plasma density and emitter geometry on space charge limits for field emitter array electron charge emission into a space plasma

NASA Astrophysics Data System (ADS)

Morris, Dave; Gilchrist, Brian; Gallimore, Alec

2001-02-01

Field Emitter Array Cathodes (FEACs) are a new technology being developed for several potential spacecraft electron emission and charge control applications. Instead of a single hot (i.e., high powered) emitter, or a gas dependant plasma contactor, FEAC systems consist of many (hundreds or thousands) of small (micron level) cathode/gate pairs printed on a semiconductor wafer that effect cold field emission at relatively low voltages. Each individual cathode emits only micro-amp level currents, but a functional array is capable of amp/cm2 current densities. It is hoped that thus FEAC offers the possibility of a relatively low-power, simple to integrate, and inexpensive technique for the high level of current emissions that are required for an electrodynamic tether (EDT) propulsion mission. Space charge limits are a significant concern for the EDT application. Vacuum chamber tests and PIC simulations are being performed at the University of Michigan Plasmadynamics and Electric Propulsion Laboratory and Space Physics Research Laboratory to determine the effect of plasma density and emitter geometry on space charge limitations. The results of this work and conclusions to date of how to best mitigate space charge limits will be presented. .

New results on the generation of broadband electrostatic waves in the magnetotail

NASA Technical Reports Server (NTRS)

Grabbe, C. L.

1985-01-01

The theory of the generation of broadband electrostatic noise (BEN) in the magnetotail is extended through numerical solution of the dispersion relation under conditions that exist in the plasma sheet boundary layer. It is found that the low-frequency portion of the spectrum has a broad angular spectrum but a fairly sharp peak near 75 deg with respect to the magnetic field, while the high-frequency portion has a narrower angular spectrum that is strongly concentrated along the magnetic field line. These results are in excellent agreement with observations of the broadband wave spectrum and a recent measurement of the propagation direction. The effect of a second cold component of electrons is analyzed, and it is found that it can increase the upper cutoff frequency of BEN to the observed value at about the plasma frequency.

C2D8: An eight channel CCD readout electronics dedicated to low energy neutron detection

NASA Astrophysics Data System (ADS)

Bourrion, O.; Clement, B.; Tourres, D.; Pignol, G.; Xi, Y.; Rebreyend, D.; Nesvizhevsky, V. V.

2018-02-01

Position-sensitive detectors for cold and ultra-cold neutrons (UCN) are in use in fundamental research. In particular, measuring the properties of the quantum states of bouncing neutrons requires micro-metric spatial resolution. To this end, a Charge Coupled Device (CCD) coated with a thin conversion layer that allows a real time detection of neutron hits is under development at LPSC. In this paper, we present the design and performance of a dedicated electronic board designed to read-out eight CCDs simultaneously and operating under vacuum.

Cold Cathode Electron Beam Controlled CO2 Laser Performance.

DTIC Science & Technology

1974-10-01

Siegman (ref. 7), the cavity parameters are g, - 3/2, g2 3/4 so that 0he cavity will be confocal when the mirror separation is 2.5 m. The laser output was...E. Siegman , Laser Focus 7, 42, 1971. 8. W. F. Krupke and W. R. Sooy, IEEE Journal Quant. Elec. QE-5, 575, 1969. 9. 0. R. Wood, et al., Appl. Phys...U t AD/A-000 413 COLD CATHODE ELECTRON BEAM CONTROLLED C02 LASER PERFORMANCE Leslie L. McKee, 1II, et al Air Force Weapons Laboratory Kirtland Air

Deficit irrigation practices may alter Vitis vinifera L. resistance to cold injury: Empirical evidence from the field

USDA-ARS?s Scientific Manuscript database

Deficit irrigation reduces seasonal carbohydrate supply and decreases starch concentrations in vegetative tissues. The specific role of starch metabolism in conferring tolerance to cold is still poorly understood. A decrease in cold tolerance after sequential years of deficit irrigation would limit ...

21 CFR 1020.20 - Cold-cathode gas discharge tubes.

Code of Federal Regulations, 2010 CFR

2010-04-01

...) RADIOLOGICAL HEALTH PERFORMANCE STANDARDS FOR IONIZING RADIATION EMITTING PRODUCTS § 1020.20 Cold-cathode gas... discharge tubes designed to demonstrate the effects of a flow of electrons or the production of x-radiation... cathode. Exit beam means that portion of the radiation which passes through the aperture resulting from...

A simulation study of interactions of space-shuttle generated electron beams with ambient plasma and neutral gas

NASA Technical Reports Server (NTRS)

Winglee, Robert M.

1991-01-01

The objective was to conduct large scale simulations of electron beams injected into space. The study of the active injection of electron beams from spacecraft is important, as it provides valuable insight into the plasma beam interactions and the development of current systems in the ionosphere. However, the beam injection itself is not simple, being constrained by the ability of the spacecraft to draw current from the ambient plasma. The generation of these return currents is dependent on several factors, including the density of the ambient plasma relative to the beam density, the presence of neutrals around the spacecraft, the configuration of the spacecraft, and the motion of the spacecraft through the plasma. Two dimensional (three velocity) particle simulations with collisional processes included are used to show how these different and often coupled processes can be used to enhance beam propagation from the spacecraft. To understand the radial expansion mechanism of an electron beam injected from a highly charged spacecraft, two dimensional particle-in-cell simulations were conducted for a high density electron beam injected parallel to magnetic fields from an isolated equipotential conductor into a cold background plasma. The simulations indicate that charge build-up at the beam stagnation point causes the beam to expand radially to the beam electron gyroradius.

A simulation study of interactions of Space-Shuttle generated electron beams with ambient plasma and neutral gas

NASA Technical Reports Server (NTRS)

1991-01-01

The object was to conduct large scale simulations of electron beams injected into space. The study of active injection of electron beams from spacecraft is important since it provides valuable insight into beam-plasma interactions and the development of current systems in the ionosphere. However, the beam injection itself is not simple, being constrained by the ability of the spacecraft to draw return current from the ambient plasma. The generation of these return currents is dependent on several factors, including the density of the ambient plasma relative to the beam density, the presence of neutrals around the spacecraft, the configuration of the spacecraft, and the motion of the spacecraft through the plasma. Two dimensional particle simulations with collisional processes included are used to show how these different and often coupled processes can be utilized to enhance beam propagation from the spacecraft. To understand the radical expansion of mechanism of an electron beam from a highly charged spacecraft, two dimensional particle in cell simulations were conducted for a high density electron beam injected parallel to magnetic fields from an isolated equipotential conductor into a cold background plasma. The simulations indicate that charge buildup at the beam stagnation point causes the beam to expand radially to the beam electron gyroradius.

Collisionless Spectral Kinetic Simulation of Ideal Multipole Resonance Probe

NASA Astrophysics Data System (ADS)

Gong, Junbo; Wilczek, Sebastian; Szeremley, Daniel; Oberrath, Jens; Eremin, Denis; Dobrygin, Wladislaw; Schilling, Christian; Friedrichs, Michael; Brinkmann, Ralf Peter

2016-09-01

Active Plasma Resonance Spectroscopy denotes a class of industry-compatible plasma diagnostic methods which utilize the natural ability of plasmas to resonate on or near the electron plasma frequency ωpe. One particular realization of APRS with a high degree of geometric and electric symmetry is the Multipole Resonance Probe (MRP). The Ideal MRP(IMRP) is an even more symmetric idealization which is suited for theoretical investigations. In this work, a spectral kinetic scheme is presented to investigate the behavior of the IMRP in the low pressure regime. However, due to the velocity difference, electrons are treated as particles whereas ions are only considered as stationary background. In the scheme, the particle pusher integrates the equations of motion for the studied particles, the Poisson solver determines the electric field at each particle position. The proposed method overcomes the limitation of the cold plasma model and covers kinetic effects like collisionless damping.

Particle in cell simulation of instabilities in space and astrophysical plasmas

NASA Astrophysics Data System (ADS)

Tonge, John William

Several plasma instabilities relevant to space physics are investigated using the parallel PIC plasma simulation code P3arsec. This thesis addresses electrostatic micro-instabilities relevant to ion ring distributions, proceeds to electromagnetic micro-instabilities pertinent to streaming plasmas, and then to the stability of a plasma held in the field of a current rod. The physical relevance of each of these instabilities is discussed, a phenomenological description is given, and analytic and simulation results are presented and compared. Instability of a magnetized plasma with a portion of the ions in a velocity ring distribution around the magnetic field is investigated using simulation and analytic theory. The physics of this distribution is relevant to solar flares, x-ray emission by comets, and pulsars. Physical parameters, including the mass ratio, are near those of a solar flare in the simulation. The simulation and analytic results show agreement in the linear regime. In the nonlinear stage the simulation shows highly accelerated electrons in agreement with the observed spectrum of x-rays emitted by solar flares. A mildly relativistic streaming electron positron plasma with no ambient magnetic field is known to be unstable to electrostatic (two-stream/beam instability) and purely electromagnetic (Weibel) modes. This instability is relevant to highly energetic interstellar phenomena, including pulsars, supernova remnants, and the early universe. It is also important for experiments in which relativistic beams penetrate a background plasma, as in fast ignitor scenarios. Cold analytic theory is presented and compared to simulations. There is good agreement in the regime where cold theory applies. The simulation and theory shows that to properly characterize the instability, directions parallel and perpendicular to propagation of the beams must be considered. A residual magnetic field is observed which may be of astro-physical significance. The stability of a plasma in the magnetic field of a current rod is investigated for various temperature and density profiles. Such a plasma obeys similar physics to a plasma in a dipole magnetic field, while the current rod is much easier to analyze theoretically and realize in simulations. The stability properties of a plasma confined in a dipole field are important for understanding a variety of space phenomena and the Levitated Dipole eXperiment (LDX). Simple energy principle calculations and simulations with a variety of temperature and density profiles show that the plasma is stable to interchange for pressure profiles ∝ r-10/3. The simulations also show that the density profile will be stationary as long as density ∝ r -2 even though the temperature profile may not be stable.

Influence of Magnetic Topology on Mars' Ionospheric Structure

NASA Astrophysics Data System (ADS)

Adams, D.; Xu, S.; Mitchell, D. L.; Fillingim, M. O.; Lillis, R. J.; Andersson, L.; Fowler, C. M.; Benna, M.; Connerney, J. E. P.; Elrod, M. K.; Girazian, Z.; Vogt, M.

2017-12-01

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has been in Mars' orbit since September 2014 (>1 Mars year), and has collected particle and field data within the ionosphere over wide ranges of altitudes, latitudes, and local times. This study uses MAVEN data to (1) analyze the influence of magnetic topology on the day-side ionosphere and (2) identify the sources of the night-side ionosphere. On the day side, magnetic strength and elevation angle are commonly used as proxies for magnetic topology. In this study, we use pitch-angle-resolved suprathermal electron measurements by the Solar Wind Electron Analyzer (SWEA) to directly deduce the magnetic topology instead of using a proxy. On the night side, the main sources of ionospheric plasma are bulk transport and plasma pressure gradient flow from the day side, as well as in situ production by electron impact ionization (EII). Plasma transport at Mars is complicated by the presence of intense crustal magnetic fields. Closed crustal magnetic fields form isolated plasma environments ("miniature magnetospheres") that inhibit external sources of cold ionospheric plasma as well as suprathermal (ionizing) electrons. Inside these closed magnetic loops, we study how the plasma evolves with bulk flow transport as the only source. By comparing closed and non-closed magnetic configurations, the effects of pressure gradient flow and EII can be distinguished. Finally, the densities of O2+, O+, and NO+, as measured by the Neutral Gas and Ion Mass Spectrometer (NGIMS), are examined. Inside miniature magnetospheres on the night side, the abundances of these species are found to be primarily controlled by the different recombination rates, as there is little plasma created within these regions by EII or transported from the neighboring regions by plasma pressure gradient flow.

Generation of forerunner electron beam during interaction of ion beam pulse with plasma

NASA Astrophysics Data System (ADS)

Hara, Kentaro; Kaganovich, Igor D.; Startsev, Edward A.

2018-01-01

The long-time evolution of the two-stream instability of a cold tenuous ion beam pulse propagating through the background plasma with density much higher than the ion beam density is investigated using a large-scale one-dimensional electrostatic kinetic simulation. The three stages of the instability are investigated in detail. After the initial linear growth and saturation by the electron trapping, a portion of the initially trapped electrons becomes detrapped and moves ahead of the ion beam pulse forming a forerunner electron beam, which causes a secondary two-stream instability that preheats the upstream plasma electrons. Consequently, the self-consistent nonlinear-driven turbulent state is set up at the head of the ion beam pulse with the saturated plasma wave sustained by the influx of the cold electrons from upstream of the beam that lasts until the final stage when the beam ions become trapped by the plasma wave. The beam ion trapping leads to the nonlinear heating of the beam ions that eventually extinguishes the instability.

Dynamic Response of a Magnetized Plasma to AN External Source: Application to Space and Solid State Plasmas

NASA Astrophysics Data System (ADS)

Zhou, Huai-Bei

This dissertation examines the dynamic response of a magnetoplasma to an external time-dependent current source. To achieve this goal a new method which combines analytic and numerical techniques to study the dynamic response of a 3-D magnetoplasma to a time-dependent current source imposed across the magnetic field was developed. The set of the cold electron and/or ion plasma equations and Maxwell's equations are first solved analytically in (k, omega)^ace; inverse Laplace and 3 -D complex Fast Fourier Transform (FFT) techniques are subsequently used to numerically transform the radiation fields and plasma currents from the (k, omega) ^ace to the (r, t) space. The dynamic responses of the electron plasma and of the compensated two-component plasma to external current sources are studied separately. The results show that the electron plasma responds to a time -varying current source imposed across the magnetic field by exciting whistler/helicon waves and forming of an expanding local current loop, induced by field aligned plasma currents. The current loop consists of two anti-parallel field-aligned current channels concentrated at the ends of the imposed current and a cross-field current region connecting these channels. The latter is driven by an electron Hall drift. A compensated two-component plasma responds to the same current source as following: (a) For slow time scales tau > Omega_sp{i}{-1} , it generates Alfven waves and forms a non-local current loop in which the ion polarization currents dominate the cross-field current; (b) For fast time scales tau < Omega_sp{i}{-1} , the dynamic response of the compensated two-component plasma is the same as that of the electron plasma. The characteristics of the current closure region are determined by the background plasma density, the magnetic field and the time scale of the current source. This study has applications to a diverse range of space and solid state plasma problems. These problems include current closure in emf inducing tethered satellite systems (TSS), generation of ELF/VLF waves by ionospheric heating, current closure and quasineutrality in thin magnetopause transitions, and short electromagnetic pulse generation in solid state plasmas. The cross-field current in TSS builds up on a time scale corresponding to the whistler waves and results in local current closure. Amplitude modulated HF ionospheric heating generates ELF/VLF waves by forming a horizontal magnetic dipole. The dipole is formed by the current closure in the modified region. For thin transition the time-dependent cross-field polarization field at the magnetopause could be neutralized by the formation of field aligned current loops that close by a cross-field electron Hall current. A moving current source in a solid state plasma results in microwave emission if the speed of the source exceeds the local phase velocity of the helicon or Alfven waves. Detailed analysis of the above problems is presented in the thesis.

Cryogenic studies for the proposed CERN large hadron electron collider (LHEC)

NASA Astrophysics Data System (ADS)

Haug, F.; LHeC Study Team, The

2012-06-01

The LHeC (Large Hadron electron Collider) is a proposed future colliding beam facility for lepton-nucleon scattering particle physics at CERN. A new 60 GeV electron accelerator will be added to the existing 27 km circumference 7 TeV LHC for collisions of electrons with protons and heavy ions. Two basic design options are being pursued. The first is a circular accelerator housed in the existing LHC tunnel which is referred to as the "Ring-Ring" version. Low field normal conducting magnets guide the particle beam while superconducting (SC) RF cavities cooled to 2 K are installed at two opposite locations at the LHC tunnel to accelerate the beams. For this version in addition a 10 GeV re-circulating SC injector will be installed. In total four refrigerators with cooling capacities between 1.2 kW and 3 kW @ 4.5 K are needed. The second option, referred to as the "Linac-Ring" version consists of a race-track re-circulating energyrecovery type machine with two 1 km long straight acceleration sections. The 944 high field 2 K SC cavities dissipate 30 kW at CW operation. Eight 10 kW @ 4.5 K refrigerators are proposed. The particle detector contains a combined SC solenoid and dipole forming the cold mass and an independent liquid argon calorimeter. Cooling is done with two individual small sized cryoplants; a 4.5 K helium, and a 87 K liquid nitrogen plant.

Beam-plasma coupling physics in support of active experiments

NASA Astrophysics Data System (ADS)

Yakymenko, K.; Delzanno, G. L.; Roytershteyn, V.

2017-12-01

The recent development of compact relativistic accelerators might open up a new era of active experiments in space, driven by important scientific and national security applications. Examples include using electron beams to trace magnetic field lines and establish causality between physical processes occurring in the magnetosphere and those in the ionosphere. Another example is the use of electron beams to trigger waves in the near-Earth environment. Waves could induce pitch-angle scattering and precipitation of energetic electrons, acting as an effective radiation belt remediation scheme. In this work, we revisit the coupling between an electron beam and a magnetized plasma in the framework of linear cold-plasma theory. We show that coupling can occur through two different regimes. In the first, a non-relativistic beam radiates through whistler waves. This is well known, and was in fact the focus of many rockets and space-shuttle campaigns aimed at demonstrating whistler emissions in the eighties. In the second regime, the beam radiates through extraordinary (R-X) modes. Nonlinear simulations with a highly-accurate Vlasov code support the theoretical results qualitatively and demonstrate that the radiated power through R-X modes can be much larger than in the whistler regime. Test-particle simulations in the wave electromagnetic field will also be presented to assess the efficiency of these waves in inducing pitch-angle scattering via wave-particle interactions. Finally, the implications of these results for a rocket active experiment in the ionosphere and for a radiation belt remediation scheme will be discussed.

High density plasmas and new diagnostics: An overview (invited).

PubMed

Celona, L; Gammino, S; Mascali, D

2016-02-01

One of the limiting factors for the full understanding of Electron Cyclotron Resonance Ion Sources (ECRISs) fundamental mechanisms consists of few types of diagnostic tools so far available for such compact machines. Microwave-to-plasma coupling optimisation, new methods of density overboost provided by plasma wave generation, and magnetostatic field tailoring for generating a proper electron energy distribution function, suitable for optimal ion beams formation, require diagnostic tools spanning across the entire electromagnetic spectrum from microwave interferometry to X-ray spectroscopy; these methods are going to be implemented including high resolution and spatially resolved X-ray spectroscopy made by quasi-optical methods (pin-hole cameras). The ion confinement optimisation also requires a complete control of cold electrons displacement, which can be performed by optical emission spectroscopy. Several diagnostic tools have been recently developed at INFN-LNS, including "volume-integrated" X-ray spectroscopy in low energy domain (2-30 keV, by using silicon drift detectors) or high energy regime (>30 keV, by using high purity germanium detectors). For the direct detection of the spatially resolved spectral distribution of X-rays produced by the electronic motion, a "pin-hole camera" has been developed also taking profit from previous experiences in the ECRIS field. The paper will give an overview of INFN-LNS strategy in terms of new microwave-to-plasma coupling schemes and advanced diagnostics supporting the design of new ion sources and for optimizing the performances of the existing ones, with the goal of a microwave-absorption oriented design of future machines.

Study of Cold Coiling Spring Steel on Microstructure and Cold Forming Performance

NASA Astrophysics Data System (ADS)

Jiang, Y.; Liang, Y. L.; Ming, Y.; Zhao, F.

2017-09-01

Medium-carbon cold-coiling locomotive spring steels were treated by a novel Q-P-T (quenching-partitioning-tempering) process. Scanning electron microscopy (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD) were used to characterize the relevant parameters of the steel. Results show that the microstructure of tested steel treated by Q-P-T process is a complex microstructures composed of martensite, bainite and retained austenite. The volume fraction of retained austenite (wt.%) is up to 31%. After pre-deforming and tempering again at 310°C, the plasticity of samples treated by Q-P-T process is still well. Fracture images show that the Q-P-T samples are ductile fracture. It is attributed to the higher volume fraction of the retained austenite and the interactions between the multi-phases in Q-P-T processed sample.

The status of cold fusion

NASA Astrophysics Data System (ADS)

Storms, E.

This report attempts to update the status of the phenomenon of cold fusion. The new field is continuing to grow as a variety of nuclear reactions are discovered to occur in a variety of chemical environments at modest temperatures. However, it must be cautioned that most scientists consider cold fusion as something akin to UFO's, ESP, and numerology.

Prevention of Cold Damage to Container-Grown Longleaf Pine Roots

Treesearch

Richard W. Tinus; Mary Anne Sword; James P. Barnett

2002-01-01

When longleaf pine (Pinus palustris Mill.) seedlings are container-grown in open fields, their roots may be exposed to damaging, cold temperatures. Major losses in some nurseries have occurred. Between November 1996 and February 1997, we measured the cold hardiness of container-grown longleaf pine roots by measuring electrolyte leakage (a) of...

Filamentation instability in a quantum plasma

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

Bret, A.

2007-08-15

The growth rate of the filamentation instability triggered when a diluted cold electron beam passes through a cold plasma is evaluated using the quantum hydrodynamic equations. Compared with a cold fluid model, quantum effects reduce both the unstable wave vector domain and the maximum growth rate. Stabilization of large wave vector modes is always achieved, but significant reduction of the maximum growth rate depends on a dimensionless parameter that is provided. Although calculations are extended to the relativistic regime, they are mostly relevant to the nonrelativistic one.

New Results About the Earth’s Van Allen Radiation Belts

NASA Astrophysics Data System (ADS)

Baker, Daniel

2015-01-01

The first great scientific discovery of the Space Age was that the Earth is enshrouded in toroids, or 'belts', of very high-energy magnetically trapped charged particles. Early observations of the radiation environment clearly indicated that the Van Allen belts could be delineated into an inner zone dominated by high-energy protons and an outer zone dominated by high-energy electrons. Subsequent studies showed that electrons in the energy range 100 keV < E< 1 MeV often populated both the inner and outer zones with a pronounced 'slot' region relatively devoid of energetic electrons existing between them. This two-belt structure for the Van Allen moderate-energy electron component was explained as being due to strong interactions of electrons with electromagnetic waves just inside the cold plasma (plasmapause) boundary. The energy distribution, spatial extent and particle species makeup of the Van Allen belts has been subsequently explored by several space missions. However, recent observations by the NASA dual-spacecraft Van Allen Probes mission have revealed wholly unexpected properties of the radiation belts, especially at highly relativistic (E > 2 MeV) and ultra-relativistic (E > 5 MeV) kinetic energies. In this presentation we show using high spatial and temporal resolution data from the Relativistic Electron-Proton Telescope (REPT) experiment on board the Van Allen Probes that multiple belts can exist concurrently and that an exceedingly sharp inner boundary exists for ultra-relativistic electrons. Using additionally available Van Allen Probes data, we demonstrate that these remarkable features of energetic electrons are not due to a physical boundary within Earth's intrinsic magnetic field. Neither is it likely that human-generated electromagnetic transmitter wave fields might produce such effects. Rather, we conclude from these unique measurements that slow natural inward radial diffusion combined with weak, but persistent, wave-particle pitch angle scattering deep inside the Earth's magnetosphere can conspire to create an almost impenetrable barrier through which the most energetic Van Allen belt electrons cannot migrate.

Large low-field magnetoresistance in Fe3O4/molecule nanoparticles at room temperature

NASA Astrophysics Data System (ADS)

Yue, F. J.; Wang, S.; Lin, L.; Zhang, F. M.; Li, C. H.; Zuo, J. L.; Du, Y. W.; Wu, D.

2011-01-01

Acetic acid molecule-coated Fe3O4 nanoparticles, 450-650 nm in size, have been synthesized using a chemical solvothermal reduction method. Fourier transform infrared spectroscopy measurements confirm one monolayer acetic acid molecules chemically bond to the Fe3O4 nanoparticles. The low-field magnetoresistance (LFMR) of more than -10% at room temperature and -23% at 140 K is achieved with saturation field of less than 2 kOe. In comparison, the resistivity of cold-pressed bare Fe3O4 nanoparticles is six orders of magnitudes smaller than that of Fe3O4/molecule nanoparticles, and the LFMR ratio is one order of magnitude smaller. Our results indicate that the large LFMR in Fe3O4/molecule nanoparticles is associated with spin-polarized electrons tunnelling through molecules instead of direct nanoparticle contacts. These results suggest that magnetic oxide-molecule hybrid materials are an alternative type of materials to develop spin-based devices by a simple low-cost approach.

Sustaining Health and Performance in the Cold: Environmental Medicine Guidance for Cold-Weather Operation.

DTIC Science & Technology

1992-07-01

or vehicle should be suspected of possible CO poisoning. 4. DO NOT APPLY OINTMENTS , SNOW OR ICE TO THE BURN , 3. Proper field sanitation is very AND DO...susceptible to cold injuries, and the use of indoor stoves may lead to burns or suffocation. Operational problems often arise in cold weather. Heavy...potential for body heat to escape. When the skin is exposed to cold, the brain signals the blood vessels in the skin to tighten, and blood flow to the skin

Construction and characterization of the fringe field monochromator for a field emission gun

PubMed

Mook; Kruit

2000-04-01

Although some microscopes have shown stabilities sufficient to attain below 0.1 eV spectral resolution in high-resolution electron energy loss spectroscopy, the intrinsic energy width of the high brightness source (0.3-0.6 eV) has been limiting the resolution. To lower the energy width of the source to 50 meV without unnecessary loss of brightness, a monochromator has been designed consisting of a short (4 mm) fringe field Wien filter and a 150 nm energy selection slit (nanoslit) both to be incorporated in the gun area of the microscope. A prototype has been built and tested in an ultra-high-vacuum setup (10(-9) mbar). The monochromator, operating on a Schottky field emission gun, showed stable and reproducible operation. The nanoslits did not contaminate and the structure remained stable. By measuring the current through the slit structure a direct image of the beam in the monochromator could be attained and the monochromator could be aligned without the use of a microscope. Good dispersed imaging conditions were found indicating an ultimate resolution of 55 meV. A Mark II fringe field monochromator (FFM) was designed and constructed compatible with the cold tungsten field emitter of the VG scanning transmission microscope. The monochromator was incorporated in the gun area of the microscope at IBM T.J. Watson research center, New York. The monochromator was aligned on 100 kV and the energy distribution measured using the monochromator displayed a below 50 meV filtering capability. The retarding Wien filter spectrometer was used to show a 61 meV EELS system resolution. The FFM is shown to be a monochromator which can be aligned without the use of the electron microscope. This makes it directly applicable for scanning transmission microscopy and low-voltage scanning electron microscopy, where it can lower the resolution loss which is caused by chromatic blur of the spot.

A model of optical trapping cold atoms using a metallic nano wire with surface plasmon effect

NASA Astrophysics Data System (ADS)

Thi Phuong Lan, Nguyen; Thi Nga, Do; Viet, Nguyen Ai

2016-06-01

In this work, we construct a new model of optical trapping cold atoms with a metallic nano wire by using surface plasmon effect generated by strong field of laser beams. Using the skin effect, we send a strong oscillated electromagnetic filed through the surface of a metallic nano wire. The local field generated by evanescent effect creates an effective attractive potential near the surface of metallic nano wires. The consideration of some possible boundary and frequency conditions might lead to non-trivial bound state solution for a cold atom. We discus also the case of the laser reflection optical trap with shell-core design, and compare our model with another recent schemes of cold atom optical traps using optical fibers and carbon nanotubes.

Synthetic Spin-Orbit and Light Field Coupling in Ultra-cold Quantum Gases

NASA Astrophysics Data System (ADS)

Dong, Lin

Ultra-cold quantum gases subjected to light-induced synthetic gauge potentials have become an emergent field of theoretical and experimental studies. Because of the novel application of two-photon Raman transitions, ultra-cold neutral atoms behave like charged particles in magnetic field. The Raman coupling naturally gives rise to an effective spin-orbit interaction which couples the atoms center-of-mass motion to its selected pseudo-spin degrees of freedom. Combined with unprecedented controllability of interactions, geometry, disorder strength, spectroscopy, and high resolution measurement of momentum distribution, etc., we are truly in an exciting era of fulfilling and going beyond Richard Feynman's vision. of realizing quantum simulators to better understand the quantum mechanical nature of the universe, manifested immensely in the ultra-cold regimes. In this dissertation, we present a collection of theoretical progresses made by the doctoral candidate and his colleagues and collaborators. From the past few years of work, we mainly address three aspects of the synthetic spin-orbit and light field induced coupling in ultracold quantum gases: a) The ground-state physics of singleparticle system, two-body bound states, and many-body systems, all of which are subjected to spin-orbit coupling originated from synthetic gauge potentials; b) The symmetry breaking, topological phase transition and quench dynamics, which are conveniently offered by the realized experimental setup; c) The proposal and implications of light field induced dynamical spin-orbit coupling for atoms inside optical cavity. Our work represents an important advancement of theoretical understanding to the active research frontier of ultra-cold atom physics with spin-orbit coupling.

Dependence of electron beam instability growth rates on the beam-plasma system parameters

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

Strangeway, R.J.

1982-02-01

Electron beam instabilites are studied by using a simple model for an electron beam streaming through a cold plasma, the beam being of finite width perpendicular to the ambient magnetic field. Through considerations of finite geometry and the coldness of the beam and background plasma, an instability similar to the two stream instability is assumed to be the means for wave growth in the system. Having found the maximum growth rate for one set of beam-plasma system parameters, this maximum growth rate is traced as these parameters are varied. The parameters that describe the system are the beam velocity (v/submore » b/), electron gyrofrequency to ambient electron plasma frequency ratio (..cap omega../sub e//..omega../sub p/e), the beam to background number density ratio (n/sub b//n/sub a/), and the beam width (a). When ..cap omega../sub e//..omega../sub p/e>1, a mode with ..cap omega../sub e/<..omega..<..omega../sub u/hr is found to be unstable, where ..cap omega.. is the wave frequency and ..omega../sub u/hr is the upper hybrid resonance frequency. For low values of n/sub b//n/sub a/ and ..cap omega../sub e/<..omega../sub p/e, this mode is still present with ..omega../sub p/e<..omega..<..omega../sub u/hr. If the beam density is large, n/sub b//n/sub a/approx. =1, the instability occures for frequencies just above the electron gyrofrequency. This mode may well be that observed in laboratory plasma before the system undergoes the beam-plasma discharge. There is another instability present, which occurs for ..omega..approx. =..omega../sub p/e. The growth rates for this mode, which are generally larger than those found for the ..omega..approx. =..omega..uhr mode, are only weakly dependent on ..cap omega../sub d//..omega../sub p/e. That this mode is not always observed in the laboratory implies that some factors not considered in the present theory suppress this mode, specifically, finite beam length.« less

Strain softening during tension in cold drawn Cu–Ag alloys

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

Chang, L.L., E-mail: lilichang@sdu.edu.cn; Wen, S.; Li, S.L.

2015-10-15

Experiments were conducted on Cu–0.1wt.%Ag alloys to evaluate the influence of producing procedures and annealing conditions on microstructure evolution and mechanical properties of Cu–Ag alloys. Optical microscopy (OM), electron back-scattered diffraction (EBSD), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used for microstructural evaluation and mechanical properties were characterized by tensile tests. The results indicated that hot-extruded Cu–Ag alloys had a typical dynamic recrystallized microstructure with equiaxed grains. Cold drawing at room temperature leaded to partial recrystallized microstructure with a mixture of coarse and fine grains. The dominate {001}<100 > cubic texture formed during hot extrusion was changed tomore » be {112}<111 > copper texture by cold drawing. Strain softening occurred during room temperature tension of cold drawn Cu–Ag alloys with an average grain size of 13–19.7 μm. - Highlights: • Strain softening occurred during tension of Cu–Ag alloys with coarse grain size. • Work hardening was observed in hot-extruded and annealed Cu–0.1wt.%Ag alloys. • Strain softening was ascribed to dynamic recovery and dynamic recrystallization.« less

Extended spectrum SWIR camera with user-accessible Dewar

NASA Astrophysics Data System (ADS)

Benapfl, Brendan; Miller, John Lester; Vemuri, Hari; Grein, Christoph; Sivananthan, Siva

2017-02-01

Episensors has developed a series of extended short wavelength infrared (eSWIR) cameras based on high-Cd concentration Hg1-xCdxTe absorbers. The cameras have a bandpass extending to 3 microns cutoff wavelength, opening new applications relative to traditional InGaAs-based cameras. Applications and uses are discussed and examples given. A liquid nitrogen pour-filled version was initially developed. This was followed by a compact Stirling-cooled version with detectors operating at 200 K. Each camera has unique sensitivity and performance characteristics. The cameras' size, weight and power specifications are presented along with images captured with band pass filters and eSWIR sources to demonstrate spectral response beyond 1.7 microns. The soft seal Dewars of the cameras are designed for accessibility, and can be opened and modified in a standard laboratory environment. This modular approach allows user flexibility for swapping internal components such as cold filters and cold stops. The core electronics of the Stirlingcooled camera are based on a single commercial field programmable gate array (FPGA) that also performs on-board non-uniformity corrections, bad pixel replacement, and directly drives any standard HDMI display.

Preparation, melting behavior and thermal stability of poly(lactic acid)/poly(propylene carbonate) blends processed by vane extruder

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

Zou, Wei, E-mail: zw55624@163.com; Chen, Rongyuan; Zhang, Haichen

Poly (lactic acid) (PLA)/Poly (propylene carbonate) (PPC) blends were prepared by vane extruder which is a type of novel polymer processing extruder based on elongation force field. Scanning electron microscope (SEM), differential scanning calorimetry (DSC) and thermogravimetric (TG) were used respectively to analyze the compatibility, the melting behavior and thermal stability properties of PLA/PPC blends affected by the different content of PPC. The results showed that with the increase of the PPC content, the glass transition temperature of PLA was reduced, and the glass transition temperature of PPC was increased, which indicated that PLA and PPC had partial compatibility. Themore » cold crystallization temperature of PLA increased with the increase of the PPC content, which showed that PPC hindered the cold crystallization process of PLA. The addition of PPC had little impact on the melting process of PLA, and the melting temperature of PLA was almost kept the same value. Thermogravimetric analysis showed that the thermal stability of PPC was worse than that of PLA, the addition of PPC reduced the thermal stability of PLA.« less

Finalize field testing of cold climate heat pump (CCHP) based on tandem vapor injection compressors

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

Shen, Bo; Baxter, Van D.; Abdelaziz, Omar

2017-03-01

This report describes the system diagram and control algorithm of a prototype air-source cold climate heat pump (CCHP) using tandem vapor injection (VI) compressors. The prototype was installed in Fairbanks, Alaska and underwent field testing starting in 09/2016. The field testing results of the past six months, including compressor run time fractions, measured COPs and heating capacities, etc., are presented as a function of the ambient temperature. Two lessons learned are also reported.

Two-dimensional simulations of thermonuclear burn in ignition-scale inertial confinement fusion targets under compressed axial magnetic fields

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

Perkins, L. J.; Logan, B. G.; Zimmerman, G. B.

2013-07-15

We report for the first time on full 2-D radiation-hydrodynamic implosion simulations that explore the impact of highly compressed imposed magnetic fields on the ignition and burn of perturbed spherical implosions of ignition-scale cryogenic capsules. Using perturbations that highly convolute the cold fuel boundary of the hotspot and prevent ignition without applied fields, we impose initial axial seed fields of 20–100 T (potentially attainable using present experimental methods) that compress to greater than 4 × 10{sup 4} T (400 MG) under implosion, thereby relaxing hotspot areal densities and pressures required for ignition and propagating burn by ∼50%. The compressed fieldmore » is high enough to suppress transverse electron heat conduction, and to allow alphas to couple energy into the hotspot even when highly deformed by large low-mode amplitudes. This might permit the recovery of ignition, or at least significant alpha particle heating, in submarginal capsules that would otherwise fail because of adverse hydrodynamic instabilities.« less

Simulations of Cold Electroweak Baryogenesis: quench from portal coupling to new singlet field

NASA Astrophysics Data System (ADS)

Mou, Zong-Gang; Saffin, Paul M.; Tranberg, Anders

2018-01-01

We compute the baryon asymmetry generated from Cold Electroweak Baryogenesis, when a dynamical Beyond-the-Standard-Model scalar singlet field triggers the spinodal transition. Using a simple potential for this additional field, we match the speed of the quench to earlier simulations with a "by-hand" mass flip. We find that for the parameter subspace most similar to a by-hand transition, the final baryon asymmetry shows a similar dependence on quench time and is of the same magnitude. For more general parameter choices the Higgs-singlet dynamics can be very complicated, resulting in an enhancement of the final baryon asymmetry. Our results validate and generalise results of simulations in the literature and open up the Cold Electroweak Baryogenesis scenario to further model building.

Excitation of THz hybrid modes in an elliptical dielectric rod waveguide with a cold collisionless unmagnetized plasma column by an annular electron beam

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

Rahmani, Z., E-mail: z.rahmani@kashanu.ac.ir; Safari, S.; Heidari-Semiromi, E.

2016-06-15

The dispersion relation of electromagnetic waves propagating in an elliptical plasma waveguide with a cold collisionless unmagnetized plasma column and a dielectric rod is studied analytically. The frequency spectrum of the hybrid waves and the growth rate for excitation of the waves by a thin annular relativistic elliptical electron beam (TAREEB) is obtained. The effects of relative permittivity constant of dielectric rod, geometrical dimensions, plasma frequency, accelerating voltage, and current density of TAREEB on the growth rate and frequency spectra of the waveguide will be investigated.

Validity of field expedient devices to assess core temperature during exercise in the cold.

PubMed

Bagley, James R; Judelson, Daniel A; Spiering, Barry A; Beam, William C; Bartolini, J Albert; Washburn, Brian V; Carney, Keven R; Muñoz, Colleen X; Yeargin, Susan W; Casa, Douglas J

2011-12-01

Exposure to cold environments affects human performance and physiological function. Major medical organizations recommend rectal temperature (TREC) to evaluate core body temperature (TcORE) during exercise in the cold; however, other field expedient devices claim to measure TCORE. The purpose of this study was to determine if field expedient devices provide valid measures of TcRE during rest and exercise in the cold. Participants included 13 men and 12 women (age = 24 +/- 3 yr, height = 170.7 +/- 10.6 cm, mass = 73.4 +/- 16.7 kg, body fat = 18 +/- 7%) who reported being healthy and at least recreationally active. During 150 min of cold exposure, subjects sequentially rested for 30 min, cycled for 90 min (heart rate = 120-140 bpm), and rested for an additional 30 min. Investigators compared aural (T(AUR)), expensive axillary (T(AXLe)), inexpensive axillary (T(AXLi)), forehead (T(FOR)), gastrointestinal (T(GI)), expensive oral (T(ORLe)), inexpensive oral (T(ORLi)), and temporal (T(TEM)) temperatures to T(REc) every 15 min. Researchers used mean difference between each device and T(REC) (i.e., mean bias) as the primary criterion for validity. T(AUR), T(AXLe), T(AXLi), T(FOR), TORLe, T(ORLi), and TTEM provided significantly lower measures compared to T(REC) and fell below our validity criterion. T(GI) significantly exceeded T(REC) at three of eleven time points, but no significant difference existed between mean T(REC) and T(GI) across time. Only T(GI) achieved our validity criterion and compared favorably to T(REC). T(GI) offers a valid measurement with which to assess T(CORE) during rest and exercise in the cold; athletic trainers, mountain rescuers, and military medical personnel should avoid other field expedient devices in similar conditions.

Statistical properties of the polarized emission of Planck Galactic cold clumps

NASA Astrophysics Data System (ADS)

Ristorcelli, Isabelle; Planck Collaboration

2015-08-01

The Galactic magnetic fields are considered as one of the key components regulating star formation, but their actual role on the dense cores formation and evolution remains today an open question.Dust polarized continuum emission is particularly well suited to probe the dense and cold medium and study the magnetic field structure. Such observations also provide tight constraints to better understand the efficiency of the dust alignment along the magnetic field lines, which in turn relate on our grasp to properly interpret the B-field properties.With the Planck all-sky survey of dust submillimeter emission in intensity and polarization, we can investigate the intermediate scales, between that of molecular cloud and of prestellar cores, and perform a statistical analysis on the polarization properties of cold clumps.Combined with the IRAS map at 100microns, the Planck survey has allowed to build the first all-sky catalogue of Galactic Cold Clumps (PGCC, Planck 2015 results XXVIII 2015). The corresponding 13188 sources cover a broad range in physical properties, and correspond to different evolutionary stages, from cold and starless clumps, nearby cores, to young protostellar objects still embedded in their cold surrounding cloud.I will present the main results of our polarization analysis obtained on different samples of sources from the PGCC catalogue, based on the 353GHz polarized emission measured with Planck. The statistical properties are derived from a stacking method, using optimized estimators for the polarization fraction and angle parameters. These properties are determined and compared according to the nature of the sources (starless or YSOs), their size or density range. Finally, I will present a comparison of our results with predictions from MHD simulations of clumps including radiative transfer and the dust radiative torque alignment mechanism.

Cryogenic Quenching Process for Electronic Part Screening

NASA Technical Reports Server (NTRS)

Sheldon, Douglas J.; Cressler, John

2011-01-01

The use of electronic parts at cryogenic temperatures (less than 100 C) for extreme environments is not well controlled or developed from a product quality and reliability point of view. This is in contrast to the very rigorous and well-documented procedures to qualify electronic parts for mission use in the 55 to 125 C temperature range. A similarly rigorous methodology for screening and evaluating electronic parts needs to be developed so that mission planners can expect the same level of high reliability performance for parts operated at cryogenic temperatures. A formal methodology for screening and qualifying electronic parts at cryogenic temperatures has been proposed. The methodology focuses on the base physics of failure of the devices at cryogenic temperatures. All electronic part reliability is based on the bathtub curve, high amounts of initial failures (infant mortals), a long period of normal use (random failures), and then an increasing number of failures (end of life). Unique to this is the development of custom screening procedures to eliminate early failures at cold temperatures. The ability to screen out defects will specifically impact reliability at cold temperatures. Cryogenic reliability is limited by electron trap creation in the oxide and defect sites at conductor interfaces. Non-uniform conduction processes due to process marginalities will be magnified at cryogenic temperatures. Carrier mobilities change by orders of magnitude at cryogenic temperatures, significantly enhancing the effects of electric field. Marginal contacts, impurities in oxides, and defects in conductor/conductor interfaces can all be magnified at low temperatures. The novelty is the use of an ultra-low temperature, short-duration quenching process for defect screening. The quenching process is designed to identify those defects that will precisely (and negatively) affect long-term, cryogenic part operation. This quenching process occurs at a temperature that is at least 25 C colder than the coldest expected operating temperature. This quenching process is the opposite of the standard burn-in procedure. Normal burn-in raises the temperature (and voltage) to activate quickly any possible manufacturing defects remaining in the device that were not already rejected at a functional test step. The proposed inverse burn-in or quenching process is custom-tailored to the electronic device being used. The doping profiles, materials, minimum dimensions, interfaces, and thermal expansion coefficients are all taken into account in determining the ramp rate, dwell time, and temperature.

The effect of various deformation processes on the corrosion behavior of casing and tubing carbon steels in sweet environment

NASA Astrophysics Data System (ADS)

Elramady, Alyaa Gamal

The aim of this research project is to correlate the plastic deformation and mechanical instability of casing steel materials with corrosion behavior and surface change, in order to identify a tolerable degree of deformation for casing steel materials. While the corrosion of pipeline and casing steels has been investigated extensively, corrosion of these steels in sweet environments with respect to plastic deformation due to bending, rolling, autofrettage, or handling needs more investigation. Downhole tubular expansion of pipes (casings) is becoming standard practice in the petroleum industry to repair damaged casings, shutdown perforations, and ultimately achieve mono-diameter wells. Tubular expansion is a cold-drawing metal forming process, which consists of running conical mandrels through casings either mechanically using a piston or hydraulically by applying a back pressure. This mechanism subjects the pipes to large radial plastic deformations of up to 30 pct. of the inner diameter. It is known that cold-working is a way of strengthening materials such as low carbon steel, but given that this material will be subjected to corrosive environments, susceptibility to stress corrosion cracking (SCC) should be investigated. This research studies the effect of cold-work, in the form of cold-rolling and cold-expansion, on the surface behavior of API 5CT steels when it is exposed to a CO2-containing environment. Cold-work has a pronounced influence on the corrosion behavior of both API 5CT K55 and P110 grade steels. The lowest strength grade steel, API 5CT K55, performed poorly in a corrosive environment in the slow strain rate test. The ductile material exhibited the highest loss in strength and highest susceptibility to stress corrosion cracking in a CO 2-containing environment. The loss in strength declined with cold-rolling, which can be ascribed to the surface compressive stresses induced by cold-work. On the other hand, API 5CT P110 grade steels showed higher susceptibility to SCC when they were cold-rolled and cold-expanded. The research found that surface compressive stresses have an effect on the SCC behavior of casing and tubing steels. The CO2 corrosion behavior and atomic processes at the corroding interface were investigated at laboratory temperature using electrochemical techniques. Cold-work was found to have an influence on the corrosion behavior of both API 5CT K55 and P110 grade steels. These behaviors were found to be material and process dependent. Surface evaluation techniques such as field emission scanning electron microscope (FE-SEM) and X-ray diffraction (XRD) analysis did not detect formation of a protective scale. X-ray diffraction and X-ray photoelectron spectroscopy (XPS) analysis both detected the appearance of a scale that was traced back to magnetite.

A novel microfluidic rapid freeze-quench device for trapping reactions intermediates for high field EPR analysis.

PubMed

Kaufmann, Royi; Yadid, Itamar; Goldfarb, Daniella

2013-05-01

Rapid freeze quench electron paramagnetic resonance (RFQ)-EPR is a method for trapping short lived intermediates in chemical reactions and subjecting them to EPR spectroscopy investigation for their characterization. Two (or more) reacting components are mixed at room temperature and after some delay the mixture is sprayed into a cold trap and transferred into the EPR tube. A major caveat in using commercial RFQ-EPR for high field EPR applications is the relatively large amount of sample needed for each time point, a major part of which is wasted as the dead volume of the instrument. The small sample volume (∼2μl) needed for high field EPR spectrometers, such as W-band (∼3.5T, 95GHz), that use cavities calls for the development of a microfluidic based RFQ-EPR apparatus. This is particularly important for biological applications because of the difficulties often encountered in producing large amounts of intrinsically paramagnetic proteins and spin labeled nucleic acid and proteins. Here we describe a dedicated microfluidic based RFQ-EPR apparatus suitable for small volume samples in the range of a few μl. The device is based on a previously published microfluidic mixer and features a new ejection mechanism and a novel cold trap that allows collection of a series of different time points in one continuous experiment. The reduction of a nitroxide radical with dithionite, employing the signal of Mn(2+) as an internal standard was used to demonstrate the performance of the microfluidic RFQ apparatus. Copyright © 2013 Elsevier Inc. All rights reserved.

Mean-field potential approach for thermodynamic properties of lanthanide: Europium as a prototype

NASA Astrophysics Data System (ADS)

Kumar, Priyank; Bhatt, N. K.; Vyas, P. R.; Gohel, V. B.

2018-03-01

In the present paper, a simple conjunction scheme [mean-field potential (MFP) + local pseudopotential] is used to study the thermodynamic properties of divalent lanthanide europium (Eu) at extreme environment. Present study has been carried out due to the fact that divalent nature of Eu arises because of stable half-filled 4f-shell at ambient condition, which has great influence on the thermodynamic properties at extreme environment. Due to such electronic structure, it is different from remaining lanthanides having incomplete 4f-shell. The presently computed results of thermodynamic properties of Eu are in good agreement with the experimental results. Looking to such success, it seems that the concept of MFP approach is successful to account contribution due to nuclear motion to the total Helmholtz free energy at finite temperatures and pressure-induced inter-band transfer of electrons for condensed state of matter. The local pseudopotential is used to evaluate cold energy and hence MFP accounts the s-p-d-f hybridization properly. Looking to the reliability and transferability along with its computational and conceptual simplicity, we would like to extend the present scheme for the study of thermodynamic properties of remaining lanthanides and actinides at extreme environment.

High-frequency Propagation through the Ionosphere from the Sura Heating Facility to the Orbiting CASSIOPE/e-POP Payload

NASA Astrophysics Data System (ADS)

James, H. G.; Frolov, V. L.; Padokhin, A. M.; Siefring, C. L.

2015-12-01

High-frequency pump waves have been transmitted from the Russian heating facility Sura to the Radio Receiver Instrument (RRI) in the e-POP payload on the Canadian small satellite CASSIOPE. This experiment has been carried out 24 times, under a variety of circumstances. In some cases, the ePOP VHF-UHF beacon CERTO was on, and ground receivers near Sura recorded total electron content. Subsequent tomographic processing has allowed the two-dimensional electron density distribution to be determined in the altitude-latitude space between Sura and CASSIOPE. We present some details from a night-time pass on 9 Sept. 2014 when the fixed pump frequency 4.3 MHz was slightly smaller than foF2 above Sura. This was an instance in which conversion between the O and Z cold plasma modes may have been required to achieve transmission. Explanation could be elaborated in terms of underdense, heater-created, field-aligned irregularities that are "artificial radio windows". The Sura heater radiation pattern maximum was tilted 12° south of the vertical, toward the terrestrial magnetic field axis, potentially enhancing the power transmitted through radio windows. The observations are interpreted in the light of competing concepts of transmission.

Modeling and simulation of the flow field in the electrolysis of magnesium

NASA Astrophysics Data System (ADS)

Sun, Ze; Zhang, He-Nan; Li, Ping; Li, Bing; Lu, Gui-Min; Yu, Jian-Guo

2009-05-01

A three-dimensional mathematical model was developed to describe the flow field in the electrolysis cell of the molten magnesium salt, where the model of the three-phase flow was coupled with the electric field force. The mathematical model was validated against the experimental data of the cold model in the electrolysis cell of zinc sulfate with 2 mol/L concentration. The flow field of the cold model was measured by particle image velocimetry, a non-intrusive visualization experimental technique. The flow field in the advanced diaphragmless electrolytic cell of the molten magnesium salt was investigated by the simulations with the mathematical model.

INDUCTION HEATING PROCESS FOR MELTING TITANIUM (COLD-WALL CRUCIBLES, SEGMENTED AND NON-SEGMENTED).

DTIC Science & Technology

system during melting tests. Three types of cold-wall crucibles were investigated. The first was a four-segment copper crucible , the second a non...segmented silicon bronze crucible, and the third a two-segment copper crucible coated with BeO. Attempts to melt titanium in an induction field in a cold

Identification of Sweet Sorghum accessions with seedling cold tolerance using both lab cold germination test and field early Spring planting evaluation

USDA-ARS?s Scientific Manuscript database

Cultivars with quick seedling emergence and stand establishment at early spring cold conditions may be planted early in the same region with an extended period of plant growth and can potentially increase either grain yield, stem sugar yield, or biomass production of sorghum. Planting cultivars with...

Degenerate pressure driven modified nucleus-acoustic waves in degenerate plasmas

NASA Astrophysics Data System (ADS)

Mamun, A. A.

2018-02-01

The existence of degenerate pressure driven modified nucleus-acoustic (DPDMNA) waves propagating in a cold degenerate quantum plasma (DQP) system [containing cold inertialess degenerate electron species (DES), cold inertial non-degenerate light nucleus species (LNS), and stationary heavy nucleus species (HNS)] is predicted for the first time. The DPDMNA waves (in which the mass density of the cold LNS provides the inertia and the cold inertialess DES gives rise to the restoring force) are new since they completely disappear if the degenerate pressure of the cold DES is neglected. It is found that the phase speed (Vp) of the DPDMNA waves decreases with the rise of the charge number density of the stationary HNS for both non-relativistic and ultra-relativistic DES, and that the ultra-relativistic DES does not have any effect on Vp when β = 1, where β = Λc/Λe with Λ e = ne 0 - 1 / 3 being the average inter-electron distance in the DQP system and Λc being the constant (˜10-10 cm) for the DES. However, the ultra-relativistic DES does have quite a significant effect on Vp for β ≫ 1 and β ≪ 1, and the ultra-relativistic effect significantly enhances (reduces) Vp for β ≫ 1 (β ≪ 1). The DPDMNA waves and their dispersion properties are expected to be useful in understanding the basic features of the electrostatic perturbation mode in space and laboratory DQP systems.

New DMSP Database of Precipitating Auroral Electrons and Ions.

PubMed

Redmon, Robert J; Denig, William F; Kilcommons, Liam M; Knipp, Delores J

2017-08-01

Since the mid 1970's, the Defense Meteorological Satellite Program (DMSP) spacecraft have operated instruments for monitoring the space environment from low earth orbit. As the program evolved, so to have the measurement capabilities such that modern DMSP spacecraft include a comprehensive suite of instruments providing estimates of precipitating electron and ion fluxes, cold/bulk plasma composition and moments, the geomagnetic field, and optical emissions in the far and extreme ultraviolet. We describe the creation of a new public database of precipitating electrons and ions from the Special Sensor J (SSJ) instrument, complete with original counts, calibrated differential fluxes adjusted for penetrating radiation, estimates of the total kinetic energy flux and characteristic energy, uncertainty estimates, and accurate ephemerides. These are provided in a common and self-describing format that covers 30+ years of DMSP spacecraft from F06 (launched in 1982) through F18 (launched in 2009). This new database is accessible at the National Centers for Environmental Information (NCEI) and the Coordinated Data Analysis Web (CDAWeb). We describe how the new database is being applied to high latitude studies of: the co-location of kinetic and electromagnetic energy inputs, ionospheric conductivity variability, field aligned currents and auroral boundary identification. We anticipate that this new database will support a broad range of space science endeavors from single observatory studies to coordinated system science investigations.

Langmuir vacuum and superconductivity

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

Veklenko, B. A.

It is shown that, in the 'jelly' model of cold electron-ion plasma, the interaction between electrons and the quantum electromagnetic vacuum of Langmuir waves involves plasma superconductivity with an energy gap proportional to the energy of the Langmuir quantum.

Synthetic Landau Levels and Spinor Vortex Matter on a Haldane Spherical Surface with a Magnetic Monopole.

PubMed

Zhou, Xiang-Fa; Wu, Congjun; Guo, Guang-Can; Wang, Ruquan; Pu, Han; Zhou, Zheng-Wei

2018-03-30

We present a flexible scheme to realize exact flat Landau levels on curved spherical geometry in a system of spinful cold atoms. This is achieved by applying the Floquet engineering of a magnetic quadrupole field to create a synthetic monopole field in real space. The system can be exactly mapped to the electron-monopole system on a sphere, thus realizing Haldane's spherical geometry for fractional quantum Hall physics. This method works for either bosons or fermions. We investigate the ground-state vortex pattern for an s-wave interacting atomic condensate by mapping this system to the classical Thompson's problem. The distortion and stability of the vortex pattern are further studied in the presence of dipolar interaction. Our scheme is compatible with the current experimental setup, and may serve as a promising route of investigating quantum Hall physics and exotic spinor vortex matter on curved space.

Solitary wave solutions of two-dimensional nonlinear Kadomtsev-Petviashvili dynamic equation in dust-acoustic plasmas

NASA Astrophysics Data System (ADS)

Seadawy, Aly R.

2017-09-01

Nonlinear two-dimensional Kadomtsev-Petviashvili (KP) equation governs the behaviour of nonlinear waves in dusty plasmas with variable dust charge and two temperature ions. By using the reductive perturbation method, the two-dimensional dust-acoustic solitary waves (DASWs) in unmagnetized cold plasma consisting of dust fluid, ions and electrons lead to a KP equation. We derived the solitary travelling wave solutions of the two-dimensional nonlinear KP equation by implementing sech-tanh, sinh-cosh, extended direct algebraic and fraction direct algebraic methods. We found the electrostatic field potential and electric field in the form travelling wave solutions for two-dimensional nonlinear KP equation. The solutions for the KP equation obtained by using these methods can be demonstrated precisely and efficiency. As an illustration, we used the readymade package of Mathematica program 10.1 to solve the original problem. These solutions are in good agreement with the analytical one.

Self-Adaptive System based on Field Programmable Gate Array for Extreme Temperature Electronics

NASA Technical Reports Server (NTRS)

Keymeulen, Didier; Zebulum, Ricardo; Rajeshuni, Ramesham; Stoica, Adrian; Katkoori, Srinivas; Graves, Sharon; Novak, Frank; Antill, Charles

2006-01-01

In this work, we report the implementation of a self-adaptive system using a field programmable gate array (FPGA) and data converters. The self-adaptive system can autonomously recover the lost functionality of a reconfigurable analog array (RAA) integrated circuit (IC) [3]. Both the RAA IC and the self-adaptive system are operating in extreme temperatures (from 120 C down to -180 C). The RAA IC consists of reconfigurable analog blocks interconnected by several switches and programmable by bias voltages. It implements filters/amplifiers with bandwidth up to 20 MHz. The self-adaptive system controls the RAA IC and is realized on Commercial-Off-The-Shelf (COTS) parts. It implements a basic compensation algorithm that corrects a RAA IC in less than a few milliseconds. Experimental results for the cold temperature environment (down to -180 C) demonstrate the feasibility of this approach.

Synthetic Landau Levels and Spinor Vortex Matter on a Haldane Spherical Surface with a Magnetic Monopole

NASA Astrophysics Data System (ADS)

Zhou, Xiang-Fa; Wu, Congjun; Guo, Guang-Can; Wang, Ruquan; Pu, Han; Zhou, Zheng-Wei

2018-03-01

We present a flexible scheme to realize exact flat Landau levels on curved spherical geometry in a system of spinful cold atoms. This is achieved by applying the Floquet engineering of a magnetic quadrupole field to create a synthetic monopole field in real space. The system can be exactly mapped to the electron-monopole system on a sphere, thus realizing Haldane's spherical geometry for fractional quantum Hall physics. This method works for either bosons or fermions. We investigate the ground-state vortex pattern for an s -wave interacting atomic condensate by mapping this system to the classical Thompson's problem. The distortion and stability of the vortex pattern are further studied in the presence of dipolar interaction. Our scheme is compatible with the current experimental setup, and may serve as a promising route of investigating quantum Hall physics and exotic spinor vortex matter on curved space.

Multi-field plasma sandpile model in tokamaks and applications

NASA Astrophysics Data System (ADS)

Peng, X. D.; Xu, J. Q.

2016-08-01

A multi-field sandpile model of tokamak plasmas is formulated for the first time to simulate the dynamic process with interaction between avalanche events on the fast/micro time-scale and diffusive transports on the slow/macro time-scale. The main characteristics of the model are that both particle and energy avalanches of sand grains are taken into account simultaneously. New redistribution rules of a sand-relaxing process are defined according to the transport properties of special turbulence which allows the uphill particle transport. Applying the model, we first simulate the steady-state plasma profile self-sustained by drift wave turbulences in the Ohmic discharge of a tokamak. A scaling law as f = a q0 b + c for the relation of both center-density n ( 0 ) and electron (ion) temperatures T e ( 0 ) ( T i ( 0 ) ) with the center-safety-factor q 0 is found. Then interesting work about the nonlocal transport phenomenon observed in tokamak experiments proceeds. It is found that the core electron temperature increases rapidly in response to the edge cold pulse and inversely it decreases in response to the edge heat pulse. The results show that the nonlocal response of core electron temperature depending on the amplitudes of background plasma density and temperature is more remarkable in a range of gas injection rate. Analyses indicate that the avalanche transport caused by plasma drift instabilities with thresholds is a possible physical mechanism for the nonlocal transport in tokamaks. It is believed that the model is capable of being applied to more extensive questions occurring in the transport field.

Field Investigation of an Air-Source Cold Climate Heat Pump

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

Shen, Bo; Abdelaziz, Omar; Rice, C Keith

In the U.S., there are approximately 2.6 million dwellings that use electricity for heating in cold and very cold regions with an annual energy consumption of 0.16 quads (0.17 EJ). A high performance cold climate heat pump (CCHP) would result in significant savings over current technologies (greater than 60% compared to electric resistance heating). We developed an air-source cold climate heat pump, which uses tandem compressors, with a single compressor rated for the building design cooling load, and running two compressors to provide, at -13 F (-25 C), 75% of rated heating capacity. The tandem compressors were optimized for heatingmore » operation and are able to tolerate discharge temperatures up to 280 F (138 C). A field investigation was conducted in the winter of 2015, in an occupied home in Ohio, USA. During the heating season, the seasonal COP was measured at 3.16, and the heat pump was able to operate down to -13 F (-25 C) and eliminate resistance heat use. The heat pump maintained an acceptable comfort level throughout the heating season. In comparison to a previous single-speed heat pump in the home, the CCHP demonstrated more than 40% energy savings in the peak heating load month. This paper illustrates the measured field performance, including compressor run time, frost/defrosting operations, distributions of building heating load and capacity delivery, comfort level, field measured COPs, etc.« less

Effect of Nb on Delayed Fracture Resistance of Ultra-High Strength Martensitic Steels

NASA Astrophysics Data System (ADS)

Song, Rongjie; Fonstein, Nina; Pottore, Narayan; Jun, Hyun Jo; Bhattacharya, Debanshu; Jansto, Steve

Ultra-high strength steels are materials of considerable interest for automotive and structural applications and are increasingly being used in those areas. Higher strength, however, makes steels more prone to hydrogen embrittlement (HE). The effects of Nb and other alloying elements on the hydrogen-induced delayed fracture resistance of cold rolled martensitic steels with ultra-high strength 2000 MPa were studied using an acid immersion test, thermal desorption analysis (TDA) and measuring of permeation. The microstructure was characterized by high resolution field emission Scanning Electron Microscopy (SEM) with Electron Backscattered Diffraction (EBSD) and Transmission Electron Microscopy (TEM). It was shown that the combined addition of Nb significantly improved the delayed fracture resistance of investigated steel. The addition of Nb to alloyed martensitic steels resulted in very apparent grain refinement of the prior austenite grain size. The Nb microalloyed steel contained a lower diffusible hydrogen content during thermal desorption analysis as compared to the base steel and had a higher trapped hydrogen amount after charging. The reason that Nb improved the delayed fracture resistance of steels can be attributed mostly to both hydrogen trapping and grain refinement.

PREFACE: XXV International Conference on Photonic, Electronic and Atomic Collisions

NASA Astrophysics Data System (ADS)

Becker, Uwe; Moshammer, Robert; Mokler, Paul; Ullrich, Joachim

2007-07-01

The XXVth ICPEAC in Freiburg marked a notable anniversary in collision physics: half a century ago the first conference in the series of International Conferences on the Physics of Electronic and Atomic Collisions (ICPEAC) was held in New York (1958). Since then, the development of electronic and atomic collision physics has seen tremendous progress. Starting during a time, when this field was regarded as somehow out-of-date, certainly not being in the main stream compared to particle and high-energy physics, it has expanded in a rather exceptional and unforeseen way. Over the years the original scope on electronic, atomic and heavy-ion collision physics was extended substantially to include upcoming expanding fields like synchrotron-radiation and strong-field laser-based atomic and molecular physics giving rise to a change of name to 'Photonic', Electronic and Atomic Collisions (ICPEAC) being used for the first time for the ICPEAC in Santa Fee in 2001. Nowadays, the ICPEAC has opened its agenda even more widely to other fields of atomic and molecular physics, such as interactions with clusters, bio-molecules and surfaces, to cold collisions, coherent control, femto- and attosecond physics and, with the Freiburg conference, to the application of free-electron lasers in the vacuum ultraviolet and soft x-ray regime, a field of potentially huge future impact in essentially all areas of science. In this larger context the XXVth ICPEAC in Freiburg with more than 800 participants set new standards. Representatives from all fields of Atomic, Molecular and Photon-based science came together and had very fruitful, inter-disciplinary discussions. This new forum of collision-based AMP physics will serve as a showcase example of future conferences, bridging not only the gap between different fields of collision physics but also, equally important, between different continents and cultures. The next ICPEAC is going to take place in Kalamazoo in North America, the one after that in Belfast back in Europe, and the subsequent one, 2013 in Lanzhou, will be the first one ever held in China. A great perspective for this ever-growing field of science! Uwe Becker (Fritz-Haber-Institut, Berlin) Robert Moshammer (Max-Planck-Institut für Kernphysik, Heidelberg) Paul Mokler (Gesellschaft für Schwerionenforschung, Darmstadt) Joachim Ullrich (Max-Planck-Institut für Kernphysik, Heidelberg) Editors Relaxed atmosphere for discussions during coffee breaks at ICPEAC XXV in Freiburg. The PDF file contains details of previous conferences, sponsors, exhibitors and committees.

Deacclimation may be crucial for winter survival of cereals under warming climate.

PubMed

Rapacz, Marcin; Jurczyk, Barbara; Sasal, Monika

2017-03-01

Climate warming can change the winter weather patterns. Warmer temperatures during winter result in a lower risk of extreme freezing events. On the other hand the predicted warm gaps during winter will decrease their freezing tolerance. Both contradict effects will affect winter survival but their resultant effect is unclear. In this paper, we demonstrate that climate warming may result in a decrease in winter survival of plants. A field study of winterhardiness of common wheat and triticale was established at 11 locations and repeated during three subsequent winters. The freezing tolerance of the plants was studied after controlled cold acclimation and de-acclimation using both plant survival analysis and chlorophyll fluorescence measurements. Cold deacclimation resistance was shown to be independent from cold acclimation ability. Further, cold deacclimation resistance appeared to be crucial for overwintering when deacclimation conditions occurred in the field. The shortening of uninterrupted cold acclimation may increase cold deacclimation efficiency, which could threaten plant survival during warmer winters. Measurements of chlorophyll fluorescence transient showed some differences triggered by freezing before and after deacclimation. We conclude that cold deacclimation resistance should be considered in the breeding of winter cereals and in future models of winter damage risk. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Magnetosheath-ionspheric plasma interactions in the cusp/cleft. 2: Mesoscale particle simulations

NASA Technical Reports Server (NTRS)

Winglee, R. M.; Menietti, J. D.; Lin, C. S.

1993-01-01

Ionospheric plasma flowing out from the cusp can be an important source of plasma to the magnetosphere. One source of free energy that can drive this outflow is the injection of magnetosheath plasma into the cusp. Two-dimensional (three velocity) mesoscale particle simulations are used to investigate the particle dynamics in the cusp during southward interplanetary magnetic field. This mesoscale model self-consistently incorporates (1) global influences such as the convection of plasma across the cusp, the action of the mirror force, and the injection of the magnetosheath plasma, and (2) wave-particle interactions which produce the actual coupling between the magnetosheath and ionospheric plasmas. It is shown that, because the thermal speed of the electrons is higher than the bulk motion of the magnetosheath plasma, an upward current is formed on the equatorward edge of the injection region with return currents on either side. However, the poleward return currents are the stronger due to the convection and mirroring of many of the magnetosheath electrons. The electron distribution in this latter region evolves from upward directed streams to single-sided loss cones or possibly electron conics. The ion distribution also shows a variety of distinct features that are produced by spatial and/or temporal effects associated with varying convection patterns and wave-particle interactions. On the equatorward edge the distribution has a downflowing magnetosheath component and an upflowing cold ionospheric component due to continuous convection of ionospheric plasma into the region. In the center of the magnetosheath region, heating from the development of an ion-ion streaming instability causes the suppression of the cold ionospheric component and the formation of downward ionospheric streams. Further poleward there is velocity filtering of ions with low pitch angles, so that the magnetosheath ions develop a ring-beam distribution and the ensuing wave instabilities generate downward ionospheric conics. These downward ionospheric components are eventually turned by the mirror force, leading to the production of upward conics at elevated energies throughout the region.

Analysis of the impact of modification of cold crucible design on the efficiency of the cold crucible induction furnace

NASA Astrophysics Data System (ADS)

Przylucki, R.; Golak, S.; Bulinski, P.; Smolka, J.; Palacz, M.; Siwiec, G.; Lipart, J.; Blacha, L.

2018-05-01

The article includes numerical simulation results for two induction furnace with cold crucible (IFCC). Induction furnaces differ in cold crucible design, while the inductor geometry was preserved for both variants. Numerical simulations were conducted as three dimensional one, with coupled analysis of electromagnetic, thermal and fluid dynamics fields. During the experiment, six calculation variants, differ in amount of molten titanium (three different weights of titanium for each type of cold crucible) were considered. Main parameters controlled during the calculations were: electrical efficiency of the IFCC and the meniscus shape of liquid metal.

Efficient pre-ionization by direct X-B mode conversion in VEST

NASA Astrophysics Data System (ADS)

Jo, JongGab; Lee, H. Y.; Kim, S. C.; Kim, S. H.; An, Y. H.; Hwang, Y. S.

2017-01-01

Pre-ionization experiments with pure toroidal field have been carried out in VEST (Versatile Experiment Spherical Torus) to investigate the feasibility of direct XB mode conversion from perpendicular LFS (Low Field Side) injection for efficient pre-ionization. Pre-ionization plasmas are studied by measuring the electron density and temperature profiles with respect to microwave power and toroidal field strength, and 2D full wave cold plasma simulation using the COMSOL Multiphysics is performed for the comparison. It is experimentally figured out that exceeding the threshold microwave power (>3 kW), the parametric decay and localized collisional heating is observed near the UHR (Upper Hybrid Resonance), and the efficient XB mode conversion can be achieved in both short density scale length (Ln) and magnetic scale length (LB) region positioned at outboard and inboard sides, respectively. From the 2D full wave simulations, the reflection and tunneling of X-wave near the R-cutoff layer according to the measured electron density profiles are analyzed with electric field polarization and power flow. Threshold electric field and wave power density for parametric decay are evaluated at least more than 4.8 × 104 V/m and 100 W/cm2, respectively. This study shows that efficient pre-ionization schemes using direct XB mode conversion can be realized by considering the key factors such as Ln, LB, and transmitted wave power at the UHR. Application to Ohmic start-up experiment is carried out to confirm the effect of the pre-ionization schemes on tokamak plasma start-up in VEST.

Control of tunneling in a double-well potential with chirped laser pulses

NASA Astrophysics Data System (ADS)

Vatasescu, Mihaela

2012-11-01

We investigate the use of chirped laser pulses to control the tunneling dynamics in the 0g-(6s,6p3/2) double well of Cs2 coupled with other electronic surfaces. The possibility to manipulate the tunneling dynamics appears in a pump-dump scheme designed to form deeply bound cold molecules by photoassociation of two cold cesium atoms in the 0g-(6s,6p3/2) electronic state coupled with a3Σu+ (6s,6s) electronic state. The dump pulse is acting on the 0g-(6s,6p3/2) barrier and can be used to control the tunneling and to capture population in the inner well in deep vibrational levels out of tunneling resonances.

Influence of Non-Maxwellian Particles on Dust Acoustic Waves in a Dusty Magnetized Plasma

NASA Astrophysics Data System (ADS)

M. Nouri, Kadijani; Zareamoghaddam, H.

2013-11-01

In this paper an investigation into dust acoustic solitary waves (DASWs) in the presence of superthermal electrons and ions in a magnetized plasma with cold dust grains and trapped electrons is discussed. The dynamic of both electrons and ions is simulated by the generalized Lorentzian (κ) distribution function (DF). The dust grains are cold and their dynamics are studied by hydrodynamic equations. The basic set of fluid equations is reduced to modified Korteweg-de Vries (mKdV) equation using Reductive Perturbation Theory (RPT). Two types of solitary waves, fast and slow dust acoustic soliton (DAS) exist in this plasma. Calculations reveal that compressive solitary structures are possibly propagated in the plasma where dust grains are negatively (or positively) charged. The properties of DASs are also investigated numerically.

Environment-Assisted Cracking in Custom 465 Stainless Steel

NASA Astrophysics Data System (ADS)

Lee, E. U.; Goswami, R.; Jones, M.; Vasudevan, A. K.

2011-02-01

The influence of cold work and aging on the environment-assisted cracking (EAC) behavior and mechanical properties of Custom 465 stainless steel (SS) was studied. Four sets of specimens were made and tested. All specimens were initially solution annealed, rapidly cooled, and refrigerated (SAR condition). The first specimen set was steel in the SAR condition. The second specimen set was aged to the H1000 condition. The third specimen set was 60 pct cold worked, and the fourth specimen set was 60 pct cold worked and aged at temperatures ranging from 755 K to 825 K (482 °C to 552 °C) for 4 hours in air. The specimens were subsequently subjected to EAC and mechanical testing. The EAC testing was conducted, using the rising step load (RSL) technique, in aqueous solutions of NaCl of pH 7.3 with concentrations ranging from 0.0035 to 3.5 pct at room temperature. The microstructure, dislocation substructure, and crack paths, resulting from the cold work, aging, or subsequent EAC testing, were examined by optical microscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The aging of the cold-worked specimens induced carbide precipitation within the martensite lath, but not at the lath or packet boundaries. In the aged specimens, as aging temperature rose, the threshold stress intensity for EAC (KIEAC), elongation, and fracture toughness increased, but the strength and hardness decreased. The KIEAC also decreased with increasing yield strength and NaCl concentration. In the SAR and H1000 specimens, the EAC propagated along the prior austenite grain boundary, while in the cold-worked and cold-worked and aged specimens, the EAC propagated along the martensite lath, and its packet and prior austenite grain boundaries. The controlling mechanism for the observed EAC was identified to be hydrogen embrittlement.

21 CFR 1020.20 - Cold-cathode gas discharge tubes.

Code of Federal Regulations, 2014 CFR

2014-04-01

... discharge tubes designed to demonstrate the effects of a flow of electrons or the production of x-radiation... electron flow is produced and sustained by ionization of contained gas atoms and ion bombardment of the... the ions of one sign produced in air when all electrons liberated by photons in a volume element of...

21 CFR 1020.20 - Cold-cathode gas discharge tubes.

Code of Federal Regulations, 2012 CFR

2012-04-01

... discharge tubes designed to demonstrate the effects of a flow of electrons or the production of x-radiation... electron flow is produced and sustained by ionization of contained gas atoms and ion bombardment of the... the ions of one sign produced in air when all electrons liberated by photons in a volume element of...

21 CFR 1020.20 - Cold-cathode gas discharge tubes.

Code of Federal Regulations, 2013 CFR

2013-04-01

... discharge tubes designed to demonstrate the effects of a flow of electrons or the production of x-radiation... electron flow is produced and sustained by ionization of contained gas atoms and ion bombardment of the... the ions of one sign produced in air when all electrons liberated by photons in a volume element of...

21 CFR 1020.20 - Cold-cathode gas discharge tubes.

Code of Federal Regulations, 2011 CFR

2011-04-01

... discharge tubes designed to demonstrate the effects of a flow of electrons or the production of x-radiation... electron flow is produced and sustained by ionization of contained gas atoms and ion bombardment of the... the ions of one sign produced in air when all electrons liberated by photons in a volume element of...

Observations of electron gyroharmonic waves and the structure of the Io torus. [jupiter 1 spacecraft radio astronomy experiment

NASA Technical Reports Server (NTRS)

Birmingham, T. J.; Alexander, J. K.; Desch, M. D.; Hubbard, R. F.; Pedersen, B. M.

1980-01-01

Narrow-banded emissions were observed by the Planetary Radio Astronomy experiment on the Voyager 1 spacecraft as it traversed the Io plasma torus. These waves occur between harmonics of the electron gyrofrequency and are the Jovian analogue of electrostatic emissions observed and theoretically studied for the terrestrial magnetosphere. The observed frequencies always include the component near the upper hybrid resonant frequency, (fuhr) but the distribution of the other observed emissions varies in a systematic way with position in the torus. A refined model of the electron density variation, based on identification of the fuhr line, is included. Spectra of the observed waves are analyzed in terms of the linear instability of an electron distribution function consisting of isotropic cold electrons and hot losscone electrons. The positioning of the observed auxiliary harmonics with respect to fuhr is shown to be an indicator of the cold to hot temperature ratio. It is concluded that this ratio increases systematically by an overall factor of perhaps 4 or 5 between the inner and outer portions of the torus.

Generation of forerunner electron beam during interaction of ion beam pulse with plasma

DOE PAGES

Hara, Kentaro; Kaganovich, Igor D.; Startsev, Edward A.

2018-01-01

The long-time evolution of the two-stream instability of a cold tenuous ion beam pulse propagating through the background plasma with density much higher than the ion beam density is investigated using a large-scale one-dimensional electrostatic kinetic simulation. The three stages of the instability are investigated in detail. After the initial linear growth and saturation by the electron trapping, a portion of the initially trapped electrons becomes detrapped and moves ahead of the ion beam pulse forming a forerunner electron beam, which causes a secondary two-stream instability that preheats the upstream plasma electrons. Consequently, the self-consistent nonlinear-driven turbulent state is setmore » up at the head of the ion beam pulse with the saturated plasma wave sustained by the influx of the cold electrons from upstream of the beam that lasts until the final stage when the beam ions become trapped by the plasma wave. Finally, the beam ion trapping leads to the nonlinear heating of the beam ions that eventually extinguishes the instability.« less

Generation of forerunner electron beam during interaction of ion beam pulse with plasma

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

Hara, Kentaro; Kaganovich, Igor D.; Startsev, Edward A.

The long-time evolution of the two-stream instability of a cold tenuous ion beam pulse propagating through the background plasma with density much higher than the ion beam density is investigated using a large-scale one-dimensional electrostatic kinetic simulation. The three stages of the instability are investigated in detail. After the initial linear growth and saturation by the electron trapping, a portion of the initially trapped electrons becomes detrapped and moves ahead of the ion beam pulse forming a forerunner electron beam, which causes a secondary two-stream instability that preheats the upstream plasma electrons. Consequently, the self-consistent nonlinear-driven turbulent state is setmore » up at the head of the ion beam pulse with the saturated plasma wave sustained by the influx of the cold electrons from upstream of the beam that lasts until the final stage when the beam ions become trapped by the plasma wave. Finally, the beam ion trapping leads to the nonlinear heating of the beam ions that eventually extinguishes the instability.« less

Explaining Cold-Pulse Dynamics in Tokamak Plasmas Using Local Turbulent Transport Models

NASA Astrophysics Data System (ADS)

Rodriguez-Fernandez, P.; White, A. E.; Howard, N. T.; Grierson, B. A.; Staebler, G. M.; Rice, J. E.; Yuan, X.; Cao, N. M.; Creely, A. J.; Greenwald, M. J.; Hubbard, A. E.; Hughes, J. W.; Irby, J. H.; Sciortino, F.

2018-02-01

A long-standing enigma in plasma transport has been resolved by modeling of cold-pulse experiments conducted on the Alcator C-Mod tokamak. Controlled edge cooling of fusion plasmas triggers core electron heating on time scales faster than an energy confinement time, which has long been interpreted as strong evidence of nonlocal transport. This Letter shows that the steady-state profiles, the cold-pulse rise time, and disappearance at higher density as measured in these experiments are successfully captured by a recent local quasilinear turbulent transport model, demonstrating that the existence of nonlocal transport phenomena is not necessary for explaining the behavior and time scales of cold-pulse experiments in tokamak plasmas.

Direct observation of turbulent magnetic fields in hot, dense laser produced plasmas.

PubMed

Mondal, Sudipta; Narayanan, V; Ding, Wen Jun; Lad, Amit D; Hao, Biao; Ahmad, Saima; Wang, Wei Min; Sheng, Zheng Ming; Sengupta, Sudip; Kaw, Predhiman; Das, Amita; Kumar, G Ravindra

2012-05-22

Turbulence in fluids is a ubiquitous, fascinating, and complex natural phenomenon that is not yet fully understood. Unraveling turbulence in high density, high temperature plasmas is an even bigger challenge because of the importance of electromagnetic forces and the typically violent environments. Fascinating and novel behavior of hot dense matter has so far been only indirectly inferred because of the enormous difficulties of making observations on such matter. Here, we present direct evidence of turbulence in giant magnetic fields created in an overdense, hot plasma by relativistic intensity (10(18) W/cm(2)) femtosecond laser pulses. We have obtained magneto-optic polarigrams at femtosecond time intervals, simultaneously with micrometer spatial resolution. The spatial profiles of the magnetic field show randomness and their k spectra exhibit a power law along with certain well defined peaks at scales shorter than skin depth. Detailed two-dimensional particle-in-cell simulations delineate the underlying interaction between forward currents of relativistic energy "hot" electrons created by the laser pulse and "cold" return currents of thermal electrons induced in the target. Our results are not only fundamentally interesting but should also arouse interest on the role of magnetic turbulence induced resistivity in the context of fast ignition of laser fusion, and the possibility of experimentally simulating such structures with respect to the sun and other stellar environments.

Characterizing convective cold pools: Characterizing Convective Cold Pools

DOE PAGES

Drager, Aryeh J.; van den Heever, Susan C.

2017-05-09

Cold pools produced by convective storms play an important role in Earth's climate system. However, a common framework does not exist for objectively identifying convective cold pools in observations and models. The present study investigates convective cold pools within a simulation of tropical continental convection that uses a cloud-resolving model with a coupled land-surface model. Multiple variables are assessed for their potential in identifying convective cold pool boundaries, and a novel technique is developed and tested for identifying and tracking cold pools in numerical model simulations. This algorithm is based on surface rainfall rates and radial gradients in the densitymore » potential temperature field. The algorithm successfully identifies near-surface cold pool boundaries and is able to distinguish between connected cold pools. Once cold pools have been identified and tracked, composites of cold pool evolution are then constructed, and average cold pool properties are investigated. Wet patches are found to develop within the centers of cold pools where the ground has been soaked with rainwater. These wet patches help to maintain cool surface temperatures and reduce cold pool dissipation, which has implications for the development of subsequent convection.« less

Characterizing convective cold pools: Characterizing Convective Cold Pools

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

Drager, Aryeh J.; van den Heever, Susan C.

Cold pools produced by convective storms play an important role in Earth's climate system. However, a common framework does not exist for objectively identifying convective cold pools in observations and models. The present study investigates convective cold pools within a simulation of tropical continental convection that uses a cloud-resolving model with a coupled land-surface model. Multiple variables are assessed for their potential in identifying convective cold pool boundaries, and a novel technique is developed and tested for identifying and tracking cold pools in numerical model simulations. This algorithm is based on surface rainfall rates and radial gradients in the densitymore » potential temperature field. The algorithm successfully identifies near-surface cold pool boundaries and is able to distinguish between connected cold pools. Once cold pools have been identified and tracked, composites of cold pool evolution are then constructed, and average cold pool properties are investigated. Wet patches are found to develop within the centers of cold pools where the ground has been soaked with rainwater. These wet patches help to maintain cool surface temperatures and reduce cold pool dissipation, which has implications for the development of subsequent convection.« less

Fungicides improve field performance of stored loblolly and longleaf pine seedlings

Treesearch

John C. Brissette

1996-01-01

Seedlings of loblolly and longleaf pine lifted in December, January, and February were treated with either benomyl or ridomil before cold storage. Along with an untreated control, they were planted after cold storage of less than 1 wk, 3 wk, and 6 wk. Survival was measured in mid-June after planting, and after 1 and 4 yr in the field. Total height was measured after 4...

Cold Water Cleaning and Sanitizing of Kitchenware in the Field

DTIC Science & Technology

1989-12-01

product would not be expected Product may result in irritat tact dermatitis have been rep benzalkonium chloride compoun mists or vapors may result in...CONSERVATION COLD WATER 19. ABSTRACT {Continue on reverse if necessary and identify by block number) In emergency situations in the field, where reduction ...MATERIAL: <CAS#) ! % Bv Wt. I TLV I PEL n-Alkyl Dimethyl Benzyl Ammonium Chloride (68424-85-1) Octyl decy I dimethyl

Optical Measurements of Strong Radio-Frequency Fields Using Rydberg Atoms

NASA Astrophysics Data System (ADS)

Miller, Stephanie Anne

There has recently been an initiative toward establishing atomic measurement standards for field quantities, including radio-frequency, millimeter-wave, and micro-wave electric fields. Current measurement standards are obtained using dipole antennas, which are fundamentally limited in frequency bandwidth (set by the physical size of the antenna) and accuracy (due to the metal perturbing the field during the measurement). Establishing an atomic standard rectifies these problems. My thesis work contributes to an ongoing effort towards establishing the viability of using Rydberg electromagnetically induced transparency (EIT) to perform atom-based measurements of radio-frequency (RF) fields over a wide range of frequencies and field strengths, focusing on strong-field measurements. Rydberg atoms are atoms with an electron excited to a high principal quantum number, resulting in a high sensitivity to an applied field. A model based on Floquet theory is implemented to accurately describe the observed atomic energy level shifts from which information about the field is extracted. Additionally, the effects due to the different electric field domains within the measurement volume are accurately modeled. Absolute atomic measurements of fields up to 296 V/m within a +/-0.35% relative uncertainty are demonstrated. This is the strongest field measured at the time of data publication. Moreover, the uncertainty is over an order of magnitude better than that of current standards. A vacuum chamber setup that I implemented during my graduate studies is presented and its unique components are detailed. In this chamber, cold-atom samples are generated and Rydberg atoms are optically excited within the ground-state sample. The Rydberg ion detection and imaging procedure are discussed, particularly the high magnification that the system provides. By analyzing the position of the ions, the spatial correlation g(2) (r) of Rydberg-atom distributions can be extracted. Aside from ion detection, EIT is implemented in the cold-atom samples. By measuring the timing of the probe photons exiting the EIT medium, the temporal correlation function g(2)(tau) can be extracted, yielding information about the timing between two different arbitrary photons. An experimental goal using this setup is to look at g(2)(tau) in conjunction with g(2)(r) for Rydberg atoms. Progress and preliminary measurements of ion detection and EIT spectra are presented including observed qualitative behaviors.

Investigating Approaches to Improving Appropriate Antibiotic Use Among Higher Risk Ethnic Groups

PubMed Central

Tice, Alan; Berthiaume, John T

2010-01-01

A field study with follow up investigations sought to: 1) determine whether cold packs (over-the-counter symptomtic treatments), coupled with in-office education, improve antibiotic-related knowledge, attitudes and behaviors more than in-office education alone in patient populations with high percentages of Asian Americans and Hawaiian/Pacific Islanders; 2) identify possible reasons for intervention outcomes as described by physicians who participated in the field study; and 3) explore potential future directions based on a large sample survey of physicians in the field study's highly ethnic county. The intervention resulted in a pre- to post-consultation decrease in perceived need for and an increase in knowledge about antibiotic risks but had no impact on frequency of reported receipt of an antibiotic prescription. Unexpectedly, in-office education alone was more effective in increasing knowledge than in-office education plus the cold pack. In-depth interviews of field study physicians and a large scale physician survey suggest that cold pack interventions targeting patient populations with high percentages of Asian Americans and Hawaiian/Pacific Islanders may be more likely to succeed if accompanied by mass public education regarding risks and physician training regarding effective ways to talk to patients. Use of in-office education with cold packs alone may not achieve desired results. PMID:21218376

Investigating approaches to improving appropriate antibiotic use among higher risk ethnic groups.

PubMed

Alden, Dana L; Tice, Alan D; Berthiaume, John T

2010-11-01

A field study with follow up investigations sought to: 1. determine whether cold packs (over-the-counter symptomtic treatments), coupled with in-office education, improve antibiotic-related knowledge, attitudes and behaviors more than in-office education alone in patient populations with high percentages of Asian Americans and Hawaiian/Pacific Islanders; 2. identify possible reasons for intervention outcomes as described by physicians who participated in the field study; and 3. explore potential future directions based on a large sample survey of physicians in the field study's highly ethnic county. The intervention resulted in a pre- to post-consultation decrease in perceived need for and an increase in knowledge about antibiotic risks but had no impact on frequency of reported receipt of an antibiotic prescription. Unexpectedly, in-office education alone was more effective in increasing knowledge than in-office education plus the cold pack. In-depth interviews of field study physicians and a large scale physician survey suggest that cold pack interventions targeting patient populations with high percentages of Asian Americans and Hawaiian/Pacific Islanders may be more likely to succeed if accompanied by mass public education regarding risks and physician training regarding effective ways to talk to patients. Use of in-office education with cold packs alone may not achieve desired results. Hawaii Medical Journal Copyright 2010.

SU-F-T-504: Non-Divergent Planning Method for Craniospinal Irradiation

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

Sperling, N; Bogue, J; Parsai, E

2016-06-15

Purpose: Traditional Craniospinal Irradiation (CSI) planning techniques require careful field placement to allow optimal divergence and field overlap at depth, and measurement of skin gap. The result of this is a necessary field overlap resulting in dose heterogeneity in the spinal canal. A novel, nondivergent field matching method has been developed to allow simple treatment planning and delivery without the need to measure skin gap. Methods: The CSI patient was simulated in the prone, and a plan was developed. Bilateral cranial fields were designed with couch and collimator rotation to eliminate divergence with the upper spine field and minimize anteriormore » divergence into the lenses. Spinal posterior-to-anterior fields were designed with the couch rotated to 90 degrees to allow gantry rotation to eliminate divergence at the match line, and the collimator rotated to 90 degrees to allow appropriate field blocking with the MLCs. A match line for the two spinal fields was placed and the gantry rotated to equal angles in opposite directions about the match line. Jaw positions were then defined to allow 1mm overlap at the match line to avoid cold spots. A traditional CSI plan was generated using diverging spinal fields, and a comparison between the two techniques was generated. Results: The non-divergent treatment plan was able to deliver a highly uniform dose to the spinal cord with a cold spot of only 95% and maximum point dose of 115.8%, as compared to traditional plan cold spots of 87% and hot spots of 132% of the prescription dose. Conclusion: A non-divergent method for planning CSI patients has been developed and clinically implemented. Planning requires some geometric manipulation in order to achieve an adequate dose distribution, however, it can help to manage cold spots and simplify the shifts needed between spinal fields.« less

Nonclassical storage and retrieval of a multiphoton pulse in cold Rydberg atoms

NASA Astrophysics Data System (ADS)

Tian, Xue-Dong; Liu, Yi-Mou; Bao, Qian-Qian; Wu, Jin-Hui; Artoni, M.; La Rocca, G. C.

2018-04-01

We investigate the storage and retrieval of a multiphoton probe field in cold Rydberg atoms with an effective method based on the superatom model. This probe field is found greatly attenuated in light intensity and two-photon correlation yet suffering little temporal broadening as a result of the partial dipole blockade of Rydberg excitation. In particular, the output field energy exhibits an intriguing saturation effect against the input field energy accompanied by an inhomogeneous nonclassical antibunching feature as a manifestation of the dynamic cooperative optical nonlinearity. Our numerical results are qualitatively consistent with those in a recent experiment and could be extended to pursue quantum information applications of nonclassical light fields.

The role of the large scale convection electric field in erosion of the plasmasphere during moderate and strong storms

NASA Astrophysics Data System (ADS)

Thaller, S. A.; Wygant, J. R.; Cattell, C. A.; Breneman, A. W.; Bonnell, J. W.; Kletzing, C.; De Pascuale, S.; Kurth, W. S.; Hospodarsky, G. B.; Bounds, S. R.

2015-12-01

The Van Allen Probes offer the first opportunity to investigate the response of the plasmasphere to the enhancement and penetration of the large scale duskward convection electric field in different magnetic local time (MLT) sectors. Using electric field measurements and estimates of the cold plasma density from the Van Allen Probes' Electric Fields and Waves (EFW) instrument, we study erosion of the plasmasphere during moderate and strong geomagnetic storms. We present the electric field and density data both on an orbit by orbit basis and synoptically, showing the behavior of the convection electric field and plasmasphere over a period of months. The data indicate that the large scale duskward electric field penetrates deep (L shell < 3) into the inner magnetosphere on both the dusk and dawn sides, but that the plasmasphere response on the dusk and dawn sides differ. In particular, significant (~2 orders of magnitude) decreases in the cold plasma density occur on the dawn side within hours of the onset of enhanced duskward electric field. In contrast, on the dusk side, the plasmapause is located at higher L shell than it is on the dawn side. In some cases, in the post-noon sector, cold plasma density enhancements accompany duskward electric field enhancements for the first orbit after the electric field enchantment, consistent with a duskside, sunward flowing, drainage plume.

How enhanced molecular ions in Cold EI improve compound identification by the NIST library.

PubMed

Alon, Tal; Amirav, Aviv

2015-12-15

Library-based compound identification with electron ionization (EI) mass spectrometry (MS) is a well-established identification method which provides the names and structures of sample compounds up to the isomer level. The library (such as NIST) search algorithm compares different EI mass spectra in the library's database with the measured EI mass spectrum, assigning each of them a similarity score called 'Match' and an overall identification probability. Cold EI, electron ionization of vibrationally cold molecules in supersonic molecular beams, provides mass spectra with all the standard EI fragment ions combined with enhanced Molecular Ions and high-mass fragments. As a result, Cold EI mass spectra differ from those provided by standard EI and tend to yield lower matching scores. However, in most cases, library identification actually improves with Cold EI, as library identification probabilities for the correct library mass spectra increase, despite the lower matching factors. This research examined the way that enhanced molecular ion abundances affect library identification probability and the way that Cold EI mass spectra, which include enhanced molecular ions and high-mass fragment ions, typically improve library identification results. It involved several computer simulations, which incrementally modified the relative abundances of the various ions and analyzed the resulting mass spectra. The simulation results support previous measurements, showing that while enhanced molecular ion and high-mass fragment ions lower the matching factor of the correct library compound, the matching factors of the incorrect library candidates are lowered even more, resulting in a rise in the identification probability for the correct compound. This behavior which was previously observed by analyzing Cold EI mass spectra can be explained by the fact that high-mass ions, and especially the molecular ion, characterize a compound more than low-mass ions and therefore carries more weight in library search identification algorithms. These ions are uniquely abundant in Cold EI, which therefore enables enhanced compound characterization along with improved NIST library based identification. Copyright © 2015 John Wiley & Sons, Ltd.

Reexamination of cold weather paving specifications for bituminous concrete.

DOT National Transportation Integrated Search

1978-01-01

The cold weather paving specification for bituminous concrete adopted in 1970 was reexamined to determine its effectiveness and any need for revisions. Density and temperature measurements were obtained on five field projects and observations were ma...

Thermal Bridge Effect of Aerated Concrete Block Wall in Cold Regions

NASA Astrophysics Data System (ADS)

Li, Baochang; Guo, Lirong; Li, Yubao; Zhang, Tiantian; Tan, Yufei

2018-01-01

As a self-insulating building material which can meet the 65 percent energy-efficiency requirements in cold region of China, aerated concrete blocks often go moldy, frost heaving, or cause plaster layer hollowing at thermal bridge parts in the extremely cold regions due to the restrictions of environmental climate and construction technique. L-shaped part and T-shaped part of aerated concrete walls are the most easily influenced parts by thermal bridge effect. In this paper, a field test is performed to investigate the scope of the thermal bridge effect. Moreover, a heat transfer calculation model for L-shaped wall and T-shaped wall is developed. According to the simulation results, the temperature fields of the thermal bridge affected regions are simulated and analyzed. The research outputs can provide theoretical basis for the application of aerated concrete wall in extremely cold regions.

Energy-Filtered Tunnel Transistor: A New Device Concept Toward Extremely-Low Energy Consumption Electronics

DTIC Science & Technology

2015-12-17

temperature . New device architecture that utilizes cold-electron transport for ultra-low energy consumption electronics has been designed in a configuration...the oxygen has also been found important for the SiC>2 sputter deposition. The sputter was carried out at room temperature . Our optimized process...have been pursued for two electronic devices, 1) room- temperature single-electron transistors, and 2) ultralow energy consumption transistors. For

Galactic cold cores. VI. Dust opacity spectral index

NASA Astrophysics Data System (ADS)

Juvela, M.; Demyk, K.; Doi, Y.; Hughes, A.; Lefèvre, C.; Marshall, D. J.; Meny, C.; Montillaud, J.; Pagani, L.; Paradis, D.; Ristorcelli, I.; Malinen, J.; Montier, L. A.; Paladini, R.; Pelkonen, V.-M.; Rivera-Ingraham, A.

2015-12-01

Context. The Galactic Cold Cores project has carried out Herschel photometric observations of 116 fields where the Planck survey has found signs of cold dust emission. The fields contain sources in different environments and different phases of star formation. Previous studies have revealed variations in their dust submillimetre opacity. Aims: The aim is to measure the value of dust opacity spectral index and to understand its variations spatially and with respect to other parameters, such as temperature, column density, and Galactic location. Methods: The dust opacity spectral index β and the dust colour temperature T are derived using Herschel and Planck data. The relation between β and T is examined for the whole sample and inside individual fields. Results: Based on IRAS and Planck data, the fields are characterised by a median colour temperature of 16.1 K and a median opacity spectral index of β = 1.84. The values are not correlated with Galactic longitude. We observe a clear T-β anti-correlation. In Herschel observations, constrained at lower resolution by Planck data, the variations follow the column density structure and βFIR can rise to ~2.2 in individual clumps. The highest values are found in starless clumps. The Planck 217 GHz band shows a systematic excess that is not restricted to cold clumps and is thus consistent with a general flattening of the dust emission spectrum at millimetre wavelengths. When fitted separately below and above 700 μm, the median spectral index values are βFIR ~ 1.91 and β(mm) ~ 1.66. Conclusions: The spectral index changes as a function of column density and wavelength. The comparison of different data sets and the examination of possible error sources show that our results are robust. However, β variations are partly masked by temperature gradients and the changes in the intrinsic grain properties may be even greater. Planck http://www.esa.int/Planck is a project of the European Space Agency - ESA - with instruments provided by two scientific consortia funded by ESA member states (in particular the lead countries: France and Italy) with contributions from NASA (USA), and telescope reflectors provided in a collaboration between ESA and a scientific consortium led and funded by Denmark.Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Table 3 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/584/A94Appendices are available in electronic form at http://www.aanda.org

Backward Raman Amplification in the Long-wavelength Infrared

DTIC Science & Technology

2016-12-29

mechanism for generating intense, broad bandwidth, long-wavelength infrared radiation. An electromagnetic finite-difference time-domain simulation...couples a finite-difference time-domain electromagnetic solver with a collisional, relativistic cold fluid plasma model [30]. The simulation domain... electromagnetic simulations coupled to a relativistic cold fluid plasma model with electron- ion collisions. Using a pump pulse that could be generated by a CO

Overexpression of Arabidopsis NADPH-dependent thioredoxin reductase C (AtNTRC) confers freezing and cold shock tolerance to plants

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

Moon, Jeong Chan; Lee, Sangmin; Shin, Su Young

Overexpression of AtNTRC (AtNTRC{sup OE}) in Arabidopsis thaliana led to a freezing and cold stress tolerance, whereas a knockout mutant (atntrc) showed a stress-sensitive phenotype. Biochemical analyses showed that the recombinant AtNTRC proteins exhibited a cryoprotective activity for malate dehydrogenase and lactic dehydrogenase. Furthermore, conclusive evidence of its interaction with nucleic acids in vitro is provided here on the basis of gel shift and electron microscopy analysis. Recombinant AtNTRC efficiently protected RNA and DNA from RNase A and metal catalyzed oxidation damage, respectively. The C-terminal thioredoxin domain is required for the nucleic acid–protein complex formation. From these results, it can bemore » hypothesized that AtNTRC, which is known to be an electron donor of peroxiredoxin, contributes the stability of macromolecules under cold stress. - Highlights: • AtNTRC has a cryoprotective activity in vitro. • Overexpression of AtNTRC increases tolerance to freezing and cold shock stresses. • Thioredoxin domain of AtNTRC protects nucleic acids in vitro. • AtNTRC inhibits protein aggregation under freezing stress in vitro.« less

Endocrine-metabolic responses to military field operations: Effects of cold and moderate altitude exposure

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

Floyd, E.; Hackney, A.C.; Hodgdon, J.A.

1991-03-11

Select endocrine-metabolic responses of US Marines to 4.5 day field operations (FOPS) in different environments were examined. Blood and urine samples were collected in the field immediately before and after FOPS at: (1) sea level, neutral temperatures (Ts) (SLN; n = 14), (2) sea level, cold Ts (SLC; n = 16), (3) 2,500 M altitude, neutral Ts (ALN; n = 16), and (4) 2,500 M altitude, cold Ts (ALC; n = 45). Measures examined were testosterone (T), cortisol (C), glucose (Glu), triglycerides (Tg), and urinary ketones (Uket). T decreased pre-post the FOPS in the cold conditions ({bar X}; 6.7 tomore » 5.5 hg/ml; n = 61) but did not change in neutral conditions. C increased pre-post FOPS at SLC (12.1 to 19.8 ug/dl, p < 0.01), ALN (9.3 to 13.9 ug/dl, p < 0.01), and ALC (16.7 to 19.0 ug/dl, p = 0.08). Normoglycemia was maintained under each condition. Tg decreased (p < 0.01) at SLC, ALN, and ALC ({bar X}{triangle}: {minus}59.1, {minus}102.2, {minus}93.3 mg/dl, respectively), but increased at SLN (+74.0 mg/dl). Uket increased post FOPS only at ALN and ALC ({bar X}{triangle}: 3.4 mg/dl and +11.3 mg/dl). The Uket increases were correlated to Tg decreases. Results suggest FOPS induces a slight endocrine stress response, which is augmented with moderate altitude or cold exposure. Furthermore FOPS at altitude, especially in the cold, seems to shift the body towards fat metabolism.« less

Atoms and Molecules Interacting with Light

NASA Astrophysics Data System (ADS)

van der Straten, Peter; Metcalf, Harold

2016-02-01

Part I. Atom-Light Interaction: 1. The classical physics pathway; Appendix 1.A. Damping force on an accelerating charge; Appendix 1.B. Hanle effect; Appendix 1.C. Optical tweezers; 2. Interaction of two-level atoms and light; Appendix 2.A. Pauli matrices for motion of the bloch vector; Appendix 2.B. The Ramsey method; Appendix 2.C. Echoes and interferometry; Appendix 2.D. Adiabatic rapid passage; Appendix 2.E Superposition and entanglement; 3. The atom-light interaction; Appendix 3.A. Proof of the oscillator strength theorem; Appendix 3.B. Electromagnetic fields; Appendix 3.C. The dipole approximation; Appendix 3.D. Time resolved fluorescence from multi-level atoms; 4. 'Forbidden' transitions; Appendix 4.A. Higher order approximations; 5. Spontaneous emission; Appendix 5.A. The quantum mechanical harmonic oscillator; Appendix 5.B. Field quantization; Appendix 5.C. Alternative theories to QED; 6. The density matrix; Appendix 6.A. The Liouville-von Neumann equation; Part II. Internal Structure: 7. The hydrogen atom; Appendix 7.A. Center-of-mass motion; Appendix 7.B. Coordinate systems; Appendix 7.C. Commuting operators; Appendix 7.D. Matrix elements of the radial wavefunctions; 8. Fine structure; Appendix 8.A. The Sommerfeld fine-structure constant; Appendix 8.B. Measurements of the fine structure 9. Effects of the nucleus; Appendix 9.A. Interacting magnetic dipoles; Appendix 9.B. Hyperfine structure for two spin =2 particles; Appendix 9.C. The hydrogen maser; 10. The alkali-metal atoms; Appendix 10.A. Quantum defects for the alkalis; Appendix 10.B. Numerov method; 11. Atoms in magnetic fields; Appendix 11.A. The ground state of atomic hydrogen; Appendix 11.B. Positronium; Appendix 11.C. The non-crossing theorem; Appendix 11.D. Passage through an anticrossing: Landau-Zener transitions; 12. Atoms in electric fields; 13. Rydberg atoms; 14. The helium atom; Appendix 14.A. Variational calculations; Appendix 14.B. Detail on the variational calculations of the ground state; 15. The periodic system of the elements; Appendix 15. A paramagnetism; Appendix 15.B. The color of gold; 16. Molecules; Appendix 16.A. Morse potential; 17. Binding in the hydrogen molecule; Appendix 17.A. Confocal elliptical coordinates; Appendix 17.B. One-electron two-center integrals; Appendix 17.C. Electron-electron interaction in molecular hydrogen; 18. Ultra-cold chemistry; Part III. Applications: 19. Optical forces and laser cooling; 20. Confinement of neutral atoms; 21. Bose-Einstein condensation; Appendix 21.A. Distribution functions; Appendix 21.B. Density of states; 22. Cold molecules; 23. Three level systems; Appendix 23.A. General Case for _1 , _2; 24. Fundamental physics; Part IV. Appendices: Appendix A. Notation and definitions; Appendix B. Units and notation; Appendix C. Angular momentum in quantum mechanics; Appendix D. Transition strengths; References; Index.

Nonlinear electron-acoustic rogue waves in electron-beam plasma system with non-thermal hot electrons

NASA Astrophysics Data System (ADS)

Elwakil, S. A.; El-hanbaly, A. M.; Elgarayh, A.; El-Shewy, E. K.; Kassem, A. I.

2014-11-01

The properties of nonlinear electron-acoustic rogue waves have been investigated in an unmagnetized collisionless four-component plasma system consisting of a cold electron fluid, non-thermal hot electrons obeying a non-thermal distribution, an electron beam and stationary ions. It is found that the basic set of fluid equations is reduced to a nonlinear Schrodinger equation. The dependence of rogue wave profiles on the electron beam and energetic population parameter are discussed. The results of the present investigation may be applicable in auroral zone plasma.

Cold in-place recycle phase III, mix design.

DOT National Transportation Integrated Search

2014-10-01

This projects purpose is to revise the UDOT accepted design methods for Cold In-Place Recycling so that they : better reflect field behavior and target the desirable attributes of the material. The previous design process failed to : adequately pr...

Mitofusin-2 protects against cold stress-induced cell injury in HEK293 cells

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

Zhang, Wenbin; Chen, Yaomin; Yang, Qun

2010-06-25

Mitochondrial impairment is hypothesized to contribute to cell injury during cold stress. Mitochondria fission and fusion are closely related in the function of the mitochondria, but the precise mechanisms whereby these processes regulate cell injury during cold stress remain to be determined. HEK293 cells were cultured in a cold environment (4.0 {+-} 0.1 {sup o}C) for 2, 4, 8, or 12 h. Western blot analyses showed that these cells expressed decreased fission-related protein Drp1 and increased fusion-related protein Mfn2 at 4 h; meanwhile, electron microscopy analysis revealed large and long mitochondrial morphology within these cells, indicating increased mitochondrial fusion. Withmore » silencing of Mfn2 but not of Mfn1 by siRNA promoted cold-stress-induced cell death with decreased ATP production in HEK293 cells. Our results show that increased expression of Mfn2 and mitochondrial fusion are important for mitochondrial function as well as cell survival during cold stress. These findings have important implications for understanding the mechanisms of mitochondrial fusion and fission in cold-stress-induced cell injury.« less

Cold Spray Repair of Martensitic Stainless Steel Components

NASA Astrophysics Data System (ADS)

Faccoli, M.; Cornacchia, G.; Maestrini, D.; Marconi, G. P.; Roberti, R.

2014-12-01

The possibility of using cold spray as repair technique of martensitic stainless steel components was evaluated through laboratory investigations. An austenitic stainless steel feedstock powder was chosen, instead of soft metals powders like nickel, copper, or aluminum, used for repairing components made in light alloy or cast iron. The present study directly compares the microstructure, the residual stresses, and the micro-hardness of repairs obtained by cold spray and by TIG welding, that is commonly used as repair technique in large steel components. XRD and optical metallographic analysis of the repairs showed that cold spray offers some advantages, inducing compressive residual stresses in the repair and avoiding alterations of the interface between repair and base material. For these reasons, a heat treatment after the cold spray repair is not required to restore the base material properties, whereas a post-weld heat treatment is needed after the welding repair. Cold spray repair also exhibits a higher micro-hardness than the welding repair. In addition, the cavitation erosion resistance of a cold spray coating was investigated through ultrasonic cavitation tests, and the samples worn surfaces were observed by scanning electron microscopy.

Dust ion acoustic freak waves in a plasma with two temperature electrons featuring Tsallis distribution

NASA Astrophysics Data System (ADS)

Chahal, Balwinder Singh; Singh, Manpreet; Shalini; Saini, N. S.

2018-02-01

We present an investigation for the nonlinear dust ion acoustic wave modulation in a plasma composed of charged dust grains, two temperature (cold and hot) nonextensive electrons and ions. For this purpose, the multiscale reductive perturbation technique is used to obtain a nonlinear Schrödinger equation. The critical wave number, which indicates where the modulational instability sets in, has been determined precisely for various regimes. The influence of plasma background nonextensivity on the growth rate of modulational instability is discussed. The modulated wavepackets in the form of either bright or dark type envelope solitons may exist. Formation of rogue waves from bright envelope solitons is also discussed. The investigation indicates that the structural characteristics of these envelope excitations (width, amplitude) are significantly affected by nonextensivity, dust concentration, cold electron-ion density ratio and temperature ratio.

Lightweight, Rack-Mountable Composite Cold Plate/Shelves

NASA Technical Reports Server (NTRS)

Hurlbert, Kathryn M.; Ruemmele, Warren; Nguyen, Hai D.; Andish, Kambiz; McCalley, Sean

2004-01-01

Rack-mountable composite-material structural components that would serve as both shelves and cold plates for removing heat from electronic or other equipment mounted on the shelves have been proposed as lightweight alternatives to all-metal cold plate/shelves now in use. A proposed cold plate/shelf would include a highly thermally conductive face sheet containing oriented graphite fibers bonded to an aluminum honeycomb core, plus an extruded stainless-steel substructure containing optimized flow passages for a cooling fluid, and an inlet and outlet that could be connected to standard manifold sections. To maximize heat-transfer efficiency, the extruded stainless-steel substructure would be connected directly to the face sheet. On the basis of a tentative design, the proposed composite cold plate/shelf would weigh about 38 percent less than does an all-aluminum cold plate in use or planned for use in some spacecraft and possibly aircraft. Although weight is a primary consideration, the tentative design offers the additional benefit of reduction of thickness to half that of the all-aluminum version.

Possibility of the market expansion of large capacity optical cold archive

NASA Astrophysics Data System (ADS)

Matsumoto, Ikuo; Sakata, Emiko

2017-08-01

The field, IoT and Big data, which is activated by the revolution of ICT, has caused rapid increase of distribution data of various business application. As a result, data with low access frequency has been rapidly increasing into a huge scale that human has never experienced before. This data with low access frequency is called "cold data", and the storage for cold data is called "cold storage". In this situation, the specifications of storage including access frequency, response speed and cost is determined by the application's request.

Explaining Cold-Pulse Dynamics in Tokamak Plasmas Using Local Turbulent Transport Models

DOE PAGES

Rodriguez-Fernandez, P.; White, A. E.; Howard, N. T.; ...

2018-02-16

A long-standing enigma in plasma transport has been resolved by modeling of cold-pulse experiments conducted on the Alcator C-Mod tokamak. Controlled edge cooling of fusion plasmas triggers core electron heating on time scales faster than an energy confinement time, which has long been interpreted as strong evidence of nonlocal transport. Here, this Letter shows that the steady-state profiles, the cold-pulse rise time, and disappearance at higher density as measured in these experiments are successfully captured by a recent local quasilinear turbulent transport model, demonstrating that the existence of nonlocal transport phenomena is not necessary for explaining the behavior and timemore » scales of cold-pulse experiments in tokamak plasmas.« less

Explaining Cold-Pulse Dynamics in Tokamak Plasmas Using Local Turbulent Transport Models

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

Rodriguez-Fernandez, P.; White, A. E.; Howard, N. T.

A long-standing enigma in plasma transport has been resolved by modeling of cold-pulse experiments conducted on the Alcator C-Mod tokamak. Controlled edge cooling of fusion plasmas triggers core electron heating on time scales faster than an energy confinement time, which has long been interpreted as strong evidence of nonlocal transport. Here, this Letter shows that the steady-state profiles, the cold-pulse rise time, and disappearance at higher density as measured in these experiments are successfully captured by a recent local quasilinear turbulent transport model, demonstrating that the existence of nonlocal transport phenomena is not necessary for explaining the behavior and timemore » scales of cold-pulse experiments in tokamak plasmas.« less

Developmental arrest during embryonic development of the common chameleon (Chamaeleo chamaeleon) in Spain.

PubMed

Andrews, Robin M; Díaz-Paniagua, Carmen; Marco, Adolfo; Portheault, Alexandre

2008-01-01

Embryonic development of the common chameleon, Chamaeleo chamaeleon, was monitored from oviposition to hatching at a field site in southwestern Spain and in the laboratory under five experimental temperature regimes. Embryos were diapausing gastrulae at the time of oviposition; developmental arrest in the field continued as cold torpor during winter. Postarrest development in the field commenced in April, and hatching occurred in August, for a total incubation period of 10.5 mo. In the laboratory, one group of eggs was incubated at a constant warm (26 degrees C) temperature. The remaining treatments simulated field conditions and consisted of initial periods of warm temperature of 0, 27, 46, and 71 d, a subsequent 4-mo period of cold winter (16 degrees C) temperature, and a final period of warm (26 degrees C) temperature. Embryos in the constant warm temperature treatment were in diapause an average of 3 mo, with clutch means ranging from 2 to 4 mo. Hatching among clutches occurred over 2 mo. In contrast, for field and experimental eggs that experienced cold winter conditions, hatching within treatments occurred over 2-14 d; "winter" conditions synchronized development. The length of time between the end of cold conditions and hatching did not differ among treatments; development thus resumed as soon as temperature was suitable regardless of the initial period of warm temperature. Diapause in nature thus insures that embryos remain gastrulae after oviposition despite nest temperatures that may be warm enough to support development.

Efficient injection of an intense positron beam into a dipole magnetic field

NASA Astrophysics Data System (ADS)

Saitoh, H.; Stanja, J.; Stenson, E. V.; Hergenhahn, U.; Niemann, H.; Pedersen, T. Sunn; Stoneking, M. R.; Piochacz, C.; Hugenschmidt, C.

2015-10-01

We have demonstrated efficient injection and trapping of a cold positron beam in a dipole magnetic field configuration. The intense 5 eV positron beam was provided by the NEutron induced POsitron source MUniCh facility at the Heinz Maier-Leibnitz Zentrum, and transported into the confinement region of the dipole field trap generated by a supported, permanent magnet with 0.6 T strength at the pole faces. We achieved transport into the region of field lines that do not intersect the outer wall using the {E}× {B} drift of the positron beam between a pair of tailored plates that created the electric field. We present evidence that up to 38% of the beam particles are able to reach the intended confinement region and make at least a 180° rotation around the magnet where they annihilate on an insertable target. When the target is removed and the {E}× {B} plate voltages are switched off, confinement of a small population persists for on the order of 1 ms. These results lend optimism to our larger aims to apply a magnetic dipole field configuration for trapping of both positrons and electrons in order to test predictions of the unique properties of a pair plasma.

Design and measurement of a TE{sub 13} input converter for high order mode gyrotron travelling wave amplifiers

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

Wang, Yan; Liu, Guo, E-mail: liuguo@uestc.edu.cn; Shu, Guoxiang

2016-03-15

A technique to launch a circular TE{sub 13} mode to interact with the helical electron beam of a gyrotron travelling wave amplifier is proposed and verified by simulation and cold test in this paper. The high order (HOM) TE{sub 13} mode is excited by a broadband Y-type power divider with the aid of a cylindrical waveguide system. Using grooves and convex strips loaded at the lateral planes of the output cylindrical waveguide, the electric fields of the potential competing TE{sub 32} and TE{sub 71} modes are suppressed to allow the transmission of the dominant TE{sub 13} mode. The converter performancemore » for different structural dimensions of grooves and convex strips is studied in detail and excellent results have been achieved. Simulation predicts that the average transmission is ∼−1.8 dB with a 3 dB bandwidth of 7.2 GHz (91.5–98.7 GHz) and port reflection is less than −15 dB. The conversion efficiency to the TE{sub 32} and TE{sub 71} modes are, respectively, under −15 dB and −24 dB in the operating frequency band. Such an HOM converter operating at W-band has been fabricated and cold tested with the radiation boundary. Measurement from the vector network analyzer cold test and microwave simulations show a good reflection performance for the converter.« less

Tailoring the magnetic properties of new Fe-Ni-Co-Al-(Ta,Nb)-B superelastic rapidly quenched microwires

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

Borza, F., E-mail: fborza@phys-iasi.ro; Lupu, N.; Dobrea, V.

2015-05-07

Ferromagnetic Fe-Ni-Co-Al-(Ta,Nb)-B microwires with diameters from 170 μm to 50 μm, which possess both superelastic and good magnetic properties, have been prepared by rapid quenching from the melt using the in rotating water spinning technique followed by cold-drawing and ageing. The cold-drawing and annealing processes lead to the initialization of premartensitic phases as confirmed by the X-ray diffraction and scanning transmission electron microscopic investigations, more significantly in the 50 μm cold-drawn microwires. An increase in the coercive field and in the saturation magnetization has been obtained by annealing, more importantly in the case of Nb-containing alloy. Ageing by thermal or current annealing ledmore » to the initialization of the superelastic effect. High values of strain of up to 1.8%, very good repeatability under successive loading, and values of superelastic effect of up to 1.2% have been achieved. The structural analysis coupled with the stress-strain data suggests that these materials annealed at 800 °C have superelastic potential at reduced ageing times. The magnetic behavior was found to be easily tailored through both thermal and thermomagnetic treatments with changes in the magnetic parameters which can be contactless detected. The results are important for future applications where both mechanical and magnetic properties matter, i.e., sensing/actuating systems.« less

Dielectric tensor elements for the description of waves in rotating inhomogeneous magnetized plasma spheroids

NASA Astrophysics Data System (ADS)

Abdoli-Arani, A.; Ramezani-Arani, R.

2012-11-01

The dielectric permittivity tensor elements of a rotating cold collisionless plasma spheroid in an external magnetic field with toroidal and axial components are obtained. The effects of inhomogeneity in the densities of charged particles and the initial toroidal velocity on the dielectric permittivity tensor and field equations are investigated. The field components in terms of their toroidal components are calculated and it is shown that the toroidal components of the electric and magnetic fields are coupled by two differential equations. The influence of thermal and collisional effects on the dielectric tensor and field equations in the rotating plasma spheroid are also investigated. In the limiting spherical case, the dielectric tensor of a stationary magnetized collisionless cold plasma sphere is presented.

Dipole-dipole resonance line shapes in a cold Rydberg gas

NASA Astrophysics Data System (ADS)

Richards, B. G.; Jones, R. R.

2016-04-01

We have explored the dipole-dipole mediated, resonant energy transfer reaction, 32 p3 /2+32 p3 /2→32 s +33 s , in an ensemble of cold 85Rb Rydberg atoms. Stark tuning is employed to measure the population transfer probability as a function of the total electronic energy difference between the initial and final atom-pair states over a range of Rydberg densities, 2 ×108≤ρ ≤3 ×109 cm-3. The observed line shapes provide information on the role of beyond nearest-neighbor interactions, the range of Rydberg atom separations, and the electric field inhomogeneity in the sample. The widths of the resonance line shapes increase approximately linearly with the Rydberg density and are only a factor of 2 larger than expected for two-body, nearest-neighbor interactions alone. These results are in agreement with the prediction [B. Sun and F. Robicheaux, Phys. Rev. A 78, 040701(R) (2008), 10.1103/PhysRevA.78.040701] that beyond nearest-neighbor exchange interactions should not influence the population transfer process to the degree once thought. At low densities, Gaussian rather than Lorentzian line shapes are observed due to electric field inhomogeneities, allowing us to set an upper limit for the field variation across the Rydberg sample. At higher densities, non-Lorentzian, cusplike line shapes characterized by sharp central peaks and broad wings reflect the random distribution of interatomic distances within the magneto-optical trap (MOT). These line shapes are well reproduced by an analytic expression derived from a nearest-neighbor interaction model and may serve as a useful fingerprint for characterizing the position correlation function for atoms within the MOT.

Quenching of internally 'hot' H2 and N2 gases by collisions with ultracold electrons: a computational 'experiment'

NASA Astrophysics Data System (ADS)

Gianturco, F. A.

2008-11-01

Quantum mechanical methods are employed to obtain superelastic cross sections involving H2 and N2 molecules, in excited rotational states, colliding with electrons at the very low collision energies which are encountered in cold trap experiments. This computational analysis intends to explore the feasibility of cold electrons for the collisional quenching of molecular gases down to the nanokelvin regimes. The results are obtained using rigorous coupled-channel (CC) calculations in the laboratory frame of reference which allows one to correctly describe the cross section behaviour at ultralow energies. The results are analysed down to the ultracold region of validity of Wigner's law, where it is found that electron-driven collisions exhibit substantial efficiency for the quenching of rotational populations in molecular gases involving the title systems. This work is affectionately dedicated to Anna Giardini, a creative experimentalist and a long-time friend, on the occasion of her 'official' retirement.

Interaction of Intense Lasers with Plasmas

NASA Astrophysics Data System (ADS)

Shvets, Gennady

1995-01-01

This thesis addresses two important topics in nonlinear laser plasma physics: the interaction of intense lasers with a non thermal homogeneous plasma, the excitation of laser wakefields in hollow plasma channels, and the stability of channel guided propagation of laser pulses. In the first half of this thesis a new theoretical approach to the nonlinear interaction of intense laser pulses with underdense plasmas is developed. Unlike previous treatments, this theory is three-dimensional, relativistically covariant, and does not assume that a<<1, where a=eA/mc^2 is a dimensionless vector potential. This formalism borrows the diagrammatic techniques from quantum field theory, yet remains classical. This classical field theory, which treats cold plasma as a relativistic field interacting with the electromagnetic fields, introduces an artificial length scale which is smaller than any physically relevant spatial scale. By adopting a special (Arnowitt -Fickler) gauge, electromagnetic waves in a cold relativistic plasma are separated into "photons" and "plasmons" which are the relativistic extensions of electrostatic and electromagnetic waves in a cold stationary plasma. The field-theoretical formalism is applied to a variety of nonlinear problems including harmonic generation, parametric instabilities, and nonlinear corrections to the index of refraction. For the first time the rate of the second harmonic emission from a homogeneous plasma is calculated and its dependence on the polarization of the incident radiation is studied. An experimental check of this calculation is suggested, based on the predicted non-linear polarization rotation (the second harmonic is emitted polarized perpendicularly to polarization of the incident signal). The concept of renormalization is applied to the plasma and electromagnetic radiation (photons and plasmons). To the lowest order, this corresponds to relativistically correcting the electron mass for its oscillation in an intense EM field and to replacing the vacuum dispersion relation by the usual relativistic plasma dispersion relation. This renormalization procedure is then carried to higher order in epsilon=omega_sp{p} {2}a^2/[(1+a^2/2)^ {3/2}omega^2]. This yields the nonlinear modification of the index of refraction of a strong electromagnetic wave and the dispersion of a weak probe in the presence of the wave. In the second part of this thesis the stability of short laser pulses propagating through parabolic channels and the wake excitation of hollow plasma channels are studied. The stability of a channel guided short laser pulse propagation is analyzed for the first time. Perturbations to the laser pulse are shown to modify the ponderomotive pressure, which distorts the dielectric properties of the plasma channel. The channel perturbation then further distorts the laser pulse. A set of coupled mode equations is derived, and a matrix dispersion relation is obtained analytically. The ponderomotive excitation of wakefields in a hollow plasma channel by an intense laser pulse is studied analytically. An important finding is that the resonant absorption in the channel wall dissipates the accelerating wake, thereby introducing a finite quality factor of the hollow plasma channel and reducing the number of electron bunches that can be accelerated in the wake of a single laser pulse. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.) (Abstract shortened by UMI.).

Stopbands in the existence domains of acoustic solitons

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

Nsengiyumva, F., E-mail: franco.nseng@gmail.com; Hellberg, M. A., E-mail: hellberg@ukzn.ac.za; Mace, R. L., E-mail: macer@ukzn.ac.za

2014-10-15

A fully nonlinear Sagdeev pseudopotential approach is used to study the existence domain of fast mode ion-acoustic solitons in a three-species plasma composed of cold and warm adiabatic positive ion species and Boltzmann electrons. It is shown that for appropriate values of the cold-to-warm ion charge-to-mass ratio, μ, and the effective warm ion-to-electron temperature ratio, τ, there is a range in cold to warm ion charge density ratio, f, over which a stopband in soliton speed exists. Solitons do not propagate in the stopband, although they can occur for both higher and lower speeds. The stopbands are associated with amore » limiting curve of the existence domain that is double-valued in speed for a range of values of f. Analytical estimates of the upper and lower limits of τ and μ that support stopbands are found. It is suggested that, inter alia, the analysis should be applicable to the solar wind plasma.« less

Three dimensional dust-acoustic solitary waves in an electron depleted dusty plasma with two-superthermal ion-temperature

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

Borhanian, J.; Shahmansouri, M.

2013-01-15

A theoretical investigation is carried out to study the existence and characteristics of propagation of dust-acoustic (DA) waves in an electron-depleted dusty plasma with two-temperature ions, which are modeled by kappa distribution functions. A three-dimensional cylindrical Kadomtsev-Petviashvili equation governing evolution of small but finite amplitude DA waves is derived by means of a reductive perturbation method. The influence of physical parameters on solitary wave structure is examined. Furthermore, the energy integral equation is used to study the existence domains of the localized structures. It is found that the present model can be employed to describe the existence of positive asmore » well as negative polarity DA solitary waves by selecting special values for parameters of the system, e.g., superthermal index of cold and/or hot ions, cold to hot ion density ratio, and hot to cold ion temperature ratio. This model may be useful to understand the excitation of nonlinear DA waves in astrophysical objects.« less

Neural-Net Processed Characteristic Patterns for Measurement of Structural Integrity of Pressure Cycled Components

NASA Technical Reports Server (NTRS)

Decker, A. J.

2001-01-01

A neural-net inspection process has been combined with a bootstrap training procedure and electronic holography to detect changes or damage in a pressure-cycled International Space Station cold plate to be used for cooling instrumentation. The cold plate was excited to vibrate in a normal mode at low amplitude, and the neural net was trained by example to flag small changes in the mode shape. The NDE (nondestructive-evaluation) technique is straightforward but in its infancy; its applications are ad-hoc and uncalibrated. Nevertheless previous research has shown that the neural net can detect displacement changes to better than 1/100 the maximum displacement amplitude. Development efforts that support the NDE technique are mentioned briefly, followed by descriptions of electronic holography and neural-net processing. The bootstrap training procedure and its application to detection of damage in a pressure-cycled cold plate are discussed. Suggestions for calibrating and quantifying the NDE procedure are presented.

A mineralogical petrographic and geochemical study of samples from wells in the geothermal field of Milos Island (Greece)

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

Liakopoulos, A.

1991-01-01

This paper presents a study of hydrothermal alteration on Milos Island, Greece. Examination of cores and cuttings from the two drill sites, obtained from a depth of about 1100 m in Milos geothermal field, showed that the hydrothermal minerals occurring in the rock include: K-feldspar, albite, chlorite, talc, diopside, epidote, muscovite, tremolite, kaolinite, montmorillonite, alunite, anhydrite, gypsum, calcite, and opaque minerals. The chemical composition of the minerals (104 analyses) was determined with Electron Probe Microanalysis. The composition of the hydrothermal fluid was determined and correlated with the mineralogy. Isotopic ratios of C and O for one calcite sample taken frommore » 341 m depth were determined and used for geochemical calculations. A number of reactions feasible at the P-T conditions of the geothermal field are given to establish the chemical evolution of the hydrothermal fluid. The distribution of the hydrothermal minerals indicates the dilution of the K-, Na- Cl-rich hydrothermal fluid of the deep reservoir by a Ca-, Mg-rich cold water at a shallower level.« less

Cold air analgesia as pain reduction during photodynamic therapy of actinic keratoses.

PubMed

Stangeland, K Z; Kroon, S

2012-07-01

Photodynamic therapy (PDT) is an effective treatment for actinic keratoses and non-melanoma skin cancer. The main side effect of PDT is pain during the illumination. To assess the effect of cold air as pain relief during MAL-PDT for field cancerization on different body areas. A prospective, open, intra-individual right-left comparison study was performed in 43 patients with MAL-PDT as field cancerization. One area received cold air analgesia while the other did not. Pain was evaluated by numeric rating scale (NRS) during the illumination. The patients' received a questionnaire and recorded pain and postinflammatory symptoms on a visual analogue scale (VAS). We found a statistical significant difference in overall pain score at 3 and 9 minutes. The area receiving cold air during illumination had a mean NRS of 5.1 while the opposite side, not receiving cold air, had NRS of 6.1. At 9 minutes the side receiving cold air had mean NRS of 5.0, and the side without had 5.7. The pain difference on the chest was the most pronounced with a NRS of 5.2 without air and 3.5 with cold air. There was a significant difference in erythema immediately after, 1 h and 24 h after illumination. Small, open, not blinded study. The difference in pain was small. Cold air is an effective method for moderate pain relief. It is an easy, noninvasive method that can be used on all body parts. © 2011 The Authors. Journal of the European Academy of Dermatology and Venereology © 2011 European Academy of Dermatology and Venereology.

Detection of nerve agent stimulants based on photoluminescent porous silicon interferometer

NASA Astrophysics Data System (ADS)

Kim, Seongwoong; Cho, Bomin; Sohn, Honglae

2012-09-01

Porous silicon (PSi) exhibiting dual optical properties, both Fabry-Pérot fringe and photolumincence, was developed and used as chemical sensors. PSi samples were prepared by an electrochemical etch of p-type silicon under the illumination of 300-W tungsten lamp during the etch process. The surface of PSi was characterized by cold field-emission scanning electron microscope. PSi samples exhibited a strong visible orange photoluminescence at 610 nm with an excitation wavelength of 460 nm as well as Fabry-Pérot fringe with a tungsten light source. Both reflectivity and photoluminescence were simultaneously measured under the exposure of organophosphate vapors. An increase of optical thickness and quenching photoluminescences under the exposure of various organophosphate vapors were observed.

On the characteristics of obliquely propagating electrostatic structures in non-Maxwellian plasmas in the presence of ion pressure anisotropy

NASA Astrophysics Data System (ADS)

Adnan, Muhammad; Qamar, Anisa; Mahmood, Shahzad; Kourakis, Ioannis

2017-03-01

The dynamical characteristics of large amplitude ion-acoustic waves are investigated in a magnetized plasma comprising ions presenting space asymmetry in the equation of state and non-Maxwellian electrons. The anisotropic ion pressure is defined using the double adiabatic Chew-Golberger-Low theory. An excess in the superthermal component of the electron population is assumed, in agreement with long-tailed (energetic electron) distribution observations in space plasmas; this is modeled via a kappa-type distribution function. Large electrostatic excitations are assumed to propagate in a direction oblique to the external magnetic field. In the linear (small amplitude) regime, two electrostatic modes are shown to exist. The properties of arbitrary amplitude (nonlinear) obliquely propagating ion-acoustic solitary excitations are thus investigated via a pseudomechanical energy balance analogy, by adopting a Sagdeev potential approach. The combined effect of the ion pressure anisotropy and excess superthermal electrons is shown to alter the parameter region where solitary waves can exist. An excess in the suprathermal particles is thus shown to be associated with solitary waves, which are narrower, faster, and of larger amplitude. Ion pressure anisotropy, on the other hand, affects the amplitude of the solitary waves, which become weaker (in strength), wider (in spatial extension), and thus slower in comparison with the cold ion case.

Cold-loving microbes, plants, and animals—fundamental and applied aspects

NASA Astrophysics Data System (ADS)

Margesin, R.; Neuner, G.; Storey, K. B.

2007-02-01

Microorganisms, plants, and animals have successfully colonized cold environments, which represent the majority of the biosphere on Earth. They have evolved special mechanisms to overcome the life-endangering influence of low temperature and to survive freezing. Cold adaptation includes a complex range of structural and functional adaptations at the level of all cellular constituents, such as membranes, proteins, metabolic activity, and mechanisms to avoid the destructive effect of intracellular ice formation. These strategies offer multiple biotechnological applications of cold-adapted organisms and/or their products in various fields. In this review, we describe the mechanisms of microorganisms, plants, and animals to cope with the cold and the resulting biotechnological perspectives.

Cold resistant nickel-alloy steel

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

Legostaev, Yu.L.; Karchevskaya, N.I.; Karchevnikov, V.P.

1988-05-01

Low-alloy cold-resistant steel 10GNB was developed for the construction of ships and floating drill rigs. The optimal heat-treatment regime for the steel was refinement. Reducing the carbon content improved its weldability and toughness properties. Optical metallography and electron microscopy established that the optimal structure was a tempered martensitic-bainitic mixture with uniformly distributed particles of disperse special niobium carbides NbC. The substructure and the processes of carbide and carbonitride phase segregation were studied by transmission and extraction electron microscopy. In mechanical tests the steel exhibited high resistance to brittle failure. In terms of corrosion resistance the steel corresponds to the requirementsmore » set forth for shipbuilding steels.« less

International workshop on cold neutron sources

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

Russell, G.J.; West, C.D.

1991-08-01

The first meeting devoted to cold neutron sources was held at the Los Alamos National Laboratory on March 5--8, 1990. Cosponsored by Los Alamos and Oak Ridge National Laboratories, the meeting was organized as an International Workshop on Cold Neutron Sources and brought together experts in the field of cold-neutron-source design for reactors and spallation sources. Eighty-four people from seven countries attended. Because the meeting was the first of its kind in over forty years, much time was spent acquainting participants with past and planned activities at reactor and spallation facilities worldwide. As a result, the meeting had more ofmore » a conference flavor than one of a workshop. The general topics covered at the workshop included: Criteria for cold source design; neutronic predictions and performance; energy deposition and removal; engineering design, fabrication, and operation; material properties; radiation damage; instrumentation; safety; existing cold sources; and future cold sources.« less

Simulation and Characterization of a Miniaturized Scanning Electron Microscope

NASA Technical Reports Server (NTRS)

Gaskin, Jessica A.; Jerman, Gregory A.; Medley, Stephanie; Gregory, Don; Abbott, Terry O.; Sampson, Allen R.

2011-01-01

A miniaturized Scanning Electron Microscope (mSEM) for in-situ lunar investigations is being developed at NASA Marshall Space Flight Center with colleagues from the University of Alabama in Huntsville (UAH), Advanced Research Systems (ARS), the University of Tennessee in Knoxville (UTK) and Case Western Reserve University (CWRU). This effort focuses on the characterization of individual components of the mSEM and simulation of the complete system. SEMs can provide information on the size, shape, morphology and chemical composition of lunar regolith. Understanding these basic properties will allow us to better estimate the challenges associated with In-Situ Resource Utilization and to improve our basic science knowledge of the lunar surface (either precluding the need for sample return or allowing differentiation of unique samples to be returned to Earth.) The main components of the mSEM prototype includes: a cold field emission electron gun (CFEG), focusing lens, deflection/scanning system and backscatter electron detector. Of these, the electron gun development is of particular importance as it dictates much of the design of the remaining components. A CFEG was chosen for use with the lunar mSEM as its emission does not depend on heating of the tungsten emitter (lower power), it offers a long operation lifetime, is orders of magnitude brighter than tungsten hairpin guns, has a small source size and exhibits low beam energy spread.

Long pulse EBW start-up experiments in MAST

DOE PAGES

Shevchenko, V. F.; Baranov, Y. F.; Bigelow, T.; ...

2015-03-12

Start-up technique reported here relies on a double mode conversion (MC) for electron Bernstein wave (EBW) excitation. It consists of MC of the ordinary (O) mode, entering the plasma from the low field side of the tokamak, into the extraordinary (X) mode at a mirror-polarizer located at the high field side. The X mode propagates back to the plasma, passes through electron cyclotron resonance (ECR) and experiences a subsequent X to EBW MC near the upper hybrid resonance (UHR). Finally the excited EBW mode is totally absorbed at the Doppler shifted ECR. The absorption of EBW remains high even inmore » cold rarefied plasmas. Furthermore, EBW can generate significant plasma current giving the prospect of a fully solenoid-free plasma start-up. First experiments using this scheme were carried out on MAST [1]. Plasma currents up to 33 kA have been achieved using 28 GHz 100kW 90ms RF pulses. Recently experimental results were extended to longer RF pulses showing further increase of plasma currents generated by RF power alone. A record current of 73kA has been achieved with 450ms RF pulse of similar power. The current drive enhancement was mainly achieved due to RF pulse extension and further optimisation of the start-up scenario.« less

Long pulse EBW start-up experiments in MAST

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

Shevchenko, V. F.; Baranov, Y. F.; Bigelow, T.

Start-up technique reported here relies on a double mode conversion (MC) for electron Bernstein wave (EBW) excitation. It consists of MC of the ordinary (O) mode, entering the plasma from the low field side of the tokamak, into the extraordinary (X) mode at a mirror-polarizer located at the high field side. The X mode propagates back to the plasma, passes through electron cyclotron resonance (ECR) and experiences a subsequent X to EBW MC near the upper hybrid resonance (UHR). Finally the excited EBW mode is totally absorbed at the Doppler shifted ECR. The absorption of EBW remains high even inmore » cold rarefied plasmas. Furthermore, EBW can generate significant plasma current giving the prospect of a fully solenoid-free plasma start-up. First experiments using this scheme were carried out on MAST [1]. Plasma currents up to 33 kA have been achieved using 28 GHz 100kW 90ms RF pulses. Recently experimental results were extended to longer RF pulses showing further increase of plasma currents generated by RF power alone. A record current of 73kA has been achieved with 450ms RF pulse of similar power. The current drive enhancement was mainly achieved due to RF pulse extension and further optimisation of the start-up scenario.« less

Long Pulse EBW Start-up Experiments in MAST

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

Shevchenko, V. F.; Bigelow, Tim S; Caughman, J. B. O.

Start-up technique reported here relies on a double mode conversion (MC) for electron Bernstein wave (EBW) excitation. It consists of MC of the ordinary (0) mode, entering the plasma from the low field side of the tokamak, into the extraordinary (X) mode at a mirror-polarizer located at the high field side. The X mode propagates back to the plasma, passes through electron cyclotron resonance (ECR) and experiences a subsequent X to EBW MC near the upper hybrid resonance (UHR). Finally the excited EBW mode is totally absorbed at the Doppler shifted ECR. The absorption of EBW remains high even inmore » cold rarefied plasmas. Furthermore, EBW can generate significant plasma current giving the prospect of a fully solenoid-free plasma start-up. First experiments using this scheme were carried out on MAST [1]. Plasma currents up to 33 kA have been achieved using 28 GHz 100kW 90ms RF pulses. Recently experimental results were extended to longer RF pulses showing further increase of plasma currents generated by RF power alone. A record current of 73kA has been achieved with 450ms RF pulse of similar power. The current drive enhancement was mainly achieved due to RF pulse extension and further optimisation of the start-up scenario.« less

RNA interference of Arabidopsis beta-amylase8 prevents maltose accumulation upon cold shock and increases sensitivity of PSII photochemical efficiency to freezing stress.

PubMed

Kaplan, Fatma; Guy, Charles L

2005-12-01

It has been suggested that beta-amylase (BMY) induction during temperature stress in Arabidopsis could lead to starch-dependent maltose accumulation, and that maltose may contribute to protection of the electron transport chain and proteins in the chloroplast stroma during acute stress. A time-course transcript profiling analysis for cold shock at 4 degrees C revealed that BMY8 (At4g17090) was induced specifically in response to cold shock, while major induction was not observed for any of the other eight beta-amylases. A parallel metabolite-profiling analysis revealed a robust transient maltose accumulation during cold shock. BMY8 RNAi lines with lower BMY8 expression exhibited a starch-excess phenotype, and a dramatic decrease in maltose accumulation during a 6-h cold shock at 4 degrees C. The decreased maltose content was also accompanied by decreased glucose, fructose and sucrose content in the BMY8 RNAi plants, consistent with the roles of beta-amylase and maltose in transitory starch metabolism. BMY8 RNAi lines with reduced soluble sugar content exhibited diminished chlorophyll fluorescence as F(v)/F(m) ratio compared with wild type, suggesting that PSII photochemical efficiency was more sensitive to freezing stress. Together, carbohydrate analysis and freezing stress results of BMY8 RNAi lines indicate that increased maltose content, by itself or together through a maltose-dependent increase in other soluble sugars, contributes to the protection of the photosynthetic electron transport chain during freezing stress.

Parametric Study on the Tensile Properties of Ni-Based Alloy for a VHTR

NASA Astrophysics Data System (ADS)

Kim, Dong-Jin; Jung, Su Jin; Mun, Byung Hak; Kim, Sung Woo; Lim, Yun Soo

2015-01-01

A very high-temperature reactor (VHTR) has been studied among generation IV nuclear power plants owing to its many advantages such as high-electric efficiency and massive hydrogen production. The material used for the heat exchanger should sustain structural integrity for its life even though the material is exposed to a harsh environment at 1223 K (950 °C) in an impure helium coolant. Therefore, an enhancement of the material performance at high temperature gives a margin in determining the operating temperature and life time. This work is an effort to find an optimum combination of alloying elements and processing parameters to improve the material performance. The tensile property and microstructure for nickel-based alloys fabricated in a laboratory were evaluated as a function of the heat treatment, cold working, and grain boundary strengthener using a tension test at 1223 K (950 °C), scanning electron microscopy, and transmission electron microscopy. Elongation to rupture was increased by additional heat treatment and cold working, followed by additional heat treatment in the temperature range from 1293 K to 1383 K (1020 °C to 1110 °C) implying that the intergranular carbide contributes to grain boundary strengthening. The temperature at which the grain boundary is improved by carbide decoration was higher for a cold-worked specimen, which was described by the difference in carbide stability and carbide formation kinetics between no cold-worked and cold-worked specimens. Zr and Hf played a scavenging effect of harmful elements causing an increase in ductility.

[Bonding strength of resin and tooth enamel after teeth bleaching with cold plasma].

PubMed

Zhu, Meng-meng; Wang, Guo-min; Sun, Ke; Li, Ying-long; Pan, Jie

2016-02-18

To investigate the immediate bond strength and surface structure of resin and the tooth enamel which treated by cold plasma. In the study, 40 bovine incisors were divided into two equal parts. In this sense, all enamel adhesive samples were prepared and then randomly divided into 4 groups (n =20). group 1: acid + single bond 2+resin composite (control group); group 2:beyond bleaching+ acid+single bond 2+resin composite; group 3: treated by cold plasma for 5 minutes+ acid+single bond 2+resin composite; group 4: treated by cold plasma for 5 minutes+single bond 2+resin composite. Single bond 2 bonding system and Filtek Z250 resin were used in this experiment. The shear bond strength was tested by universal testing machine. The surface of the enamel in different processes was observed by scanning electron microscope (SEM). Statistical analyses by the single factor analysis of variance and multiple pairwise comparisons were performed with SPSS 17.0 . The shear bond strength of group 4 (8.60 MPa) was significantly lower than that of the other three groups (P<0.05). The shear bond strength of group 2 (17.89 MPa) was higher than that of group 4, but lower than group 1 and group 3 (P<0.05).There was no significant difference between group 1 (34.82 MPa) and group 3 (34.69 MPa). Scanning electron microscope indicated that the enamel treated by cold plasma had slight molten form, which was different from etched enamel surface.The fractured surface of group 3 was mix fracture, which was similar to the control group (group 1). Compared with the conventional clinic bleaching, immediate bond strength of resin-enamel that treated by cold plasma has not been affected.

Magnetic Field Effects and Electromagnetic Wave Propagation in Highly Collisional Plasmas.

NASA Astrophysics Data System (ADS)

Bozeman, Steven Paul

The homogeneity and size of radio frequency (RF) and microwave driven plasmas are often limited by insufficient penetration of the electromagnetic radiation. To investigate increasing the skin depth of the radiation, we consider the propagation of electromagnetic waves in a weakly ionized plasma immersed in a steady magnetic field where the dominant collision processes are electron-neutral and ion-neutral collisions. Retaining both the electron and ion dynamics, we have adapted the theory for cold collisionless plasmas to include the effects of these collisions and obtained the dispersion relation at arbitrary frequency omega for plane waves propagating at arbitrary angles with respect to the magnetic field. We discuss in particular the cases of magnetic field enhanced wave penetration for parallel and perpendicular propagation, examining the experimental parameters which lead to electromagnetic wave propagation beyond the collisional skin depth. Our theory predicts that the most favorable scaling of skin depth with magnetic field occurs for waves propagating nearly parallel to B and for omega << Omega_{rm e} where Omega_{rm e} is the electron cyclotron frequency. The scaling is less favorable for propagation perpendicular to B, but the skin depth does increase for this case as well. Still, to achieve optimal wave penetration, we find that one must design the plasma configuration and antenna geometry so that one generates primarily the appropriate angles of propagation. We have measured plasma wave amplitudes and phases using an RF magnetic probe and densities using Stark line broadening. These measurements were performed in inductively coupled plasmas (ICP's) driven with a standard helical coil, a reverse turn (Stix) coil, and a flat spiral coil. Density measurements were also made in a microwave generated plasma. The RF magnetic probe measurements of wave propagation in a conventional ICP with wave propagation approximately perpendicular to B show an increase in skin depth with magnetic field and a damping of the effect of B with pressure. The flat coil geometry which launches waves more nearly parallel to B allows enhanced wave penetration at higher pressures than the standard helical coil.

Cold Hardiness of the Black Soldier Fly (Diptera: Stratiomyidae).

PubMed

Spranghers, Thomas; Noyez, Annelies; Schildermans, Kristof; De Clercq, Patrick

2017-08-01

The black soldier fly, Hermetia illucens (L.), shows potential as a resource for animal feed. However, industrial production in regions where the insect is not native, like northwestern Europe, could lead to permanent establishment, which might entail environmental risks. In temperate climates, establishment depends on the insect's ability to overwinter. This study assessed the insect's cold hardiness by determining the supercooling point (SCP) and lower lethal time at 5 °C (LTime10,50,90) for different life stages. As diet or acclimation can influence cold hardiness, prepupae reared on different substrates and acclimated prepupae were tested in separate experiments. The SCP ranged from -7.3 °C for late-instar larvae to -13.7 °C for pupae. Prepupae reared on a highly nutritional substrate had a lower SCP compared with a control diet composed of chicken feed (-14.1 °C vs. -12.4 °C, respectively), whereas the SCP was unaffected by acclimation. Based on the LTime, prepupae and pupae were the most cold hardy life stages. Acclimated prepupae were most cold tolerant, with a LTime50 of 23 d. Based on an empirical relationship between LTime50 and field survival of various arthropods, it was predicted that H. illucens would survive about 47 d in the field during northwestern European winters. The results from this laboratory study suggest that H. illucens is rather unlikely to overwinter in northwestern Europe. However, caution is warranted given that diet and acclimation can influence the insect's cold hardiness and in the field the insect may survive in a diapausing state or in protected hibernacula. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Electron Heating by the Ion Cyclotron Instability in Collisionless Accretion Flows. I. Compression-driven Instabilities and the Electron Heating Mechanism

NASA Astrophysics Data System (ADS)

Sironi, Lorenzo; Narayan, Ramesh

2015-02-01

In systems accreting well below the Eddington rate, such as the central black hole in the Milky Way (Sgr A*), the plasma in the innermost regions of the disk is believed to be collisionless and have two temperatures, with the ions substantially hotter than the electrons. However, whether a collisionless faster-than-Coulomb energy transfer mechanism exists in two-temperature accretion flows is still an open question. We study the physics of electron heating during the growth of ion velocity-space instabilities by means of multidimensional, fully kinetic, particle-in-cell (PIC) simulations. A background large-scale compression—embedded in a novel form of the PIC equations—continuously amplifies the field. This constantly drives a pressure anisotropy P > P ∥ because of the adiabatic invariance of the particle magnetic moments. We find that, for ion plasma beta values β0i ~ 5-30 appropriate for the midplane of low-luminosity accretion flows (here, β0i is the ratio of ion thermal pressure to magnetic pressure), mirror modes dominate if the electron-to-proton temperature ratio is T 0e /T 0i >~ 0.2, whereas for T 0e /T 0i <~ 0.2 the ion cyclotron instability triggers the growth of strong Alfvén-like waves, which pitch-angle scatter the ions to maintain marginal stability. We develop an analytical model of electron heating during the growth of the ion cyclotron instability, which we validate with PIC simulations. We find that for cold electrons (β0e <~ 2 me /mi , where β0e is the ratio of electron thermal pressure to magnetic pressure), the electron energy gain is controlled by the magnitude of the E-cross-B velocity induced by the ion cyclotron waves. This term is independent of the initial electron temperature, so it provides a solid energy floor even for electrons starting with extremely low temperatures. On the other hand, the electron energy gain for β0e >~ 2 me /mi —governed by the conservation of the particle magnetic moment in the growing fields of the instability—is proportional to the initial electron temperature, and it scales with the magnetic energy of ion cyclotron waves. Our results have implications for two-temperature accretion flows as well as for solar wind and intracluster plasmas.

Diving into Cold Pools

NASA Astrophysics Data System (ADS)

van den Heever, S. C.; Grant, L. D.; Drager, A. J.

2017-12-01

Cold pools play a significant role in convective storm initiation, organization and longevity. Given their role in convective life cycles, recent efforts have been focused on improving the representation of cold pool processes within weather forecast models, as well as on developing cold pool parameterizations in order to better represent their impacts within global climate models. Understanding the physical processes governing cold pool formation, intensity and dissipation is therefore critical to these efforts. Cold pool characteristics are influenced by numerous factors, including those associated with precipitation formation and evaporation, variations in the environmental moisture and shear, and land surface interactions. The focus of this talk will be on the manner in which the surface characteristics and associated processes impact cold pool genesis and dissipation. In particular, the results from high-resolution modeling studies focusing on the role of sensible and latent heat fluxes, soil moisture and SST will be presented. The results from a recent field campaign examining cold pools over northern Colorado will also be discussed.

A Molecular Dynamics of Cold Neutral Atoms Captured by Carbon Nanotube Under Electric Field and Thermal Effect as a Selective Atoms Sensor.

PubMed

Santos, Elson C; Neto, Abel F G; Maneschy, Carlos E; Chen, James; Ramalho, Teodorico C; Neto, A M J C

2015-05-01

Here we analyzed several physical behaviors through computational simulation of systems consisting of a zig-zag type carbon nanotube and relaxed cold atoms (Rb, Au, Si and Ar). These atoms were chosen due to their different chemical properties. The atoms individually were relaxed on the outside of the nanotube during the simulations. Each system was found under the influence of a uniform electric field parallel to the carbon nanotube and under the thermal effect of the initial temperature at the simulations. Because of the electric field, the cold atoms orbited the carbon nanotube while increasing the initial temperature allowed the variation of the radius of the orbiting atoms. We calculated the following quantities: kinetic energy, potential energy and total energy and in situ temperature, molar entropy variation and average radius of the orbit of the atoms. Our data suggest that only the action of electric field is enough to generate the attractive potential and this system could be used as a selected atoms sensor.

The effects of return current and target charging in short pulse high intensity laser interactions

NASA Astrophysics Data System (ADS)

Beg, Farhat

2003-10-01

Since the introduction of the technique of chirped pulse amplification (CPA), peak laser intensities have increased dramatically. It is now possible to perform laser-plasma interaction experiments at intensities approaching 1021 Wcm-2. The electrons in the field of such lasers are highly relativistic (gamma 31) and the temperature of the hot electron distribution produced in a plasma at such extreme intensities can exceed 10 MeV. Since the resulting beam current exceeds the Alfvén limit, a neutralizing return current of cold plasma electrons moving in the opposite direction is produced. Another source of return current is that due to the escape of very energetic electrons from the target, which then creates a large electrostatic potential due to charge separation. These return currents can cause significant ohmic heating. We present results from experiments performed at Rutherford Appleton Laboratory using the VULCAN laser facility (I> 5 x1019 Wcm-2). Single wire targets were used and in some shots a secondary wire or foil was placed near the target. Three main observations were made: (i) generation of a Z-pinch in the wire due to the return current, (ii) optical transition radiation at 2w and (iii) proton emission from both the primary wire target and the secondary wire or foil. The Z-pinch was observed to be m=0 unstable. The current was estimated to be about 0.8 MA using simple energy balance considerations. Intense second harmonic emission due to coherent optical transition radiation from both the primary target and secondary objects was observed and is likely due to electron bunches accelerated by the ponderomotive jxB force of the laser. The proton emission from the secondary wire or foil was likely due to field emission of electrons from the these objects in response to the large potential produced from charging of the primary target. Results of simulations to model these interactions will also be presented.

What transmission electron microscopes can visualize now and in the future.

PubMed

Müller, Shirley A; Aebi, Ueli; Engel, Andreas

2008-09-01

Our review concentrates on the progress made in high-resolution transmission electron microscopy (TEM) in the past decade. This includes significant improvements in sample preparation by quick-freezing aimed at preserving the specimen in a close-to-native state in the high vacuum of the microscope. Following advances in cold stage and TEM vacuum technology systems, the observation of native, frozen hydrated specimens has become a widely used approach. It fostered the development of computer guided, fully automated low-dose data acquisition systems allowing matched pairs of images and diffraction patterns to be recorded for electron crystallography, and the collection of entire tilt-series for electron tomography. To achieve optimal information transfer to atomic resolution, field emission electron guns combined with acceleration voltages of 200-300 kV are now routinely used. The outcome of these advances is illustrated by the atomic structure of mammalian aquaporin-O and by the pore-forming bacterial cytotoxin ClyA resolved to 12 A. Further, the Yersinia injectisome needle, a bacterial pseudopilus and the binding of phalloidin to muscle actin filaments were chosen to document the advantage of the high contrast offered by dedicated scanning transmission electron microscopy (STEM) and/or the STEM's ability to measure the mass of protein complexes and directly link this to their shape. Continued progress emerging from leading research laboratories and microscope manufacturers will eventually enable us to determine the proteome of a single cell by electron tomography, and to more routinely solve the atomic structure of membrane proteins by electron crystallography.

Power Distribution for Cryogenic Instruments at 6-40K The James Webb Space Telescope Case

NASA Technical Reports Server (NTRS)

Rumler, Peter; Lundquist, Ray; Alvarez, Jose Lorenzo; Sincell, Jeff; Tuttle, Jim

2011-01-01

The Integrated Science Instrument Module (ISIM) of the James Webb Space Telescope (JWST) operates its instruments passively cooled at around 40 Kelvin (K), with a warm Instrument Electronic Compartment (IEC) at 300K attached to it. From the warm electronics all secondary signal and power harnesses have to bridge this 300-40K temperature difference and minimize the power dissipation and parasitic heat leak into the cold region. After an introduction of the ISIM with its instruments, the IEC with the electronics, and the harness architecture with a special radiator, this paper elaborates on the cryogenic wire selection and tests performed to establish current de-rating rules for different wire types. Finally failure modes are analyzed for critical instrument interfaces that could inject excessive currents and heat into the harness and cold side, and several solutions for the removal of such failures are presented.

Power Distribution For Cryogenic Instruments At 6-40K The James Webb Space Telescope Case

NASA Astrophysics Data System (ADS)

Rumler, Peter; Lundquist, Ray; Alvarez, Jose Lorenzo; Sincell, Jeff; Tuttle, Jim

2011-10-01

The Integrated Science Instrument Module (ISIM) of the James Webb Space Telescope (JWST) operates its instruments passively cooled at around 40 Kelvin (K), with a warm Instrument Electronic Compartment (IEC) at 300K attached to it. From the warm electronics all secondary signal and power harnesses have to bridge this 300-40K temperature difference and minimize the power dissipation and parasitic heat leak into the cold region. After an introduction of the ISIM with its instruments, the IEC with the electronics, and the harness architecture with a special radiator, this paper elaborates on the cryogenic wire selection and tests performed to establish current de-rating rules for different wire types. Finally failure modes are analyzed for critical instrument interfaces that could inject excessive currents and heat into the harness and cold side, and several solutions for the removal of such failures are presented.

Assessing the relative importance of environmental effects, carry-over effects and species differences in thermal stress resistance: a comparison of Drosophilids across field and laboratory generations.

PubMed

Schiffer, Michele; Hangartner, Sandra; Hoffmann, Ary A

2013-10-15

There is increasing interest in comparing species of related organisms for their susceptibility to thermal extremes in order to evaluate potential vulnerability to climate change. Comparisons are typically undertaken on individuals collected from the field with or without a period of acclimation. However, this approach does not allow the potential contributions of environmental and carry-over effects across generations to be separated from inherent species differences in susceptibility. To assess the importance of these different sources of variation, we here considered heat and cold resistance in Drosophilid species from tropical and temperate sites in the field and across two laboratory generations. Resistance in field-collected individuals tended to be lower when compared with F1 and F2 laboratory generations, and species differences in field flies were only weakly correlated to differences established under controlled rearing conditions, unlike in F1-F2 comparisons. This reflected large environmental effects on resistance associated with different sites and conditions experienced within sites. For the 8 h cold recovery assay there was no strong evidence of carry-over effects, whereas for the heat knockdown and 2 h cold recovery assays there was some evidence for such effects. However, for heat these were species specific in direction. Variance components for inherent species differences were substantial for resistance to heat and 8 h cold stress, but small for 2 h cold stress, though this may be a reflection of the species being considered in the comparisons. These findings highlight that inherent differences among species are difficult to characterise accurately without controlling for environmental sources of variation and carry-over effects. Moreover, they also emphasise the complex nature of carry-over effects that vary depending on the nature of stress traits and the species being evaluated.

21-cm lensing and the cold spot in the cosmic microwave background.

PubMed

Kovetz, Ely D; Kamionkowski, Marc

2013-04-26

An extremely large void and a cosmic texture are two possible explanations for the cold spot seen in the cosmic microwave background. We investigate how well these two hypotheses can be tested with weak lensing of 21-cm fluctuations from the epoch of reionization measured with the Square Kilometer Array. While the void explanation for the cold spot can be tested with Square Kilometer Array, given enough observation time, the texture scenario requires significantly prolonged observations, at the highest frequencies that correspond to the epoch of reionization, over the field of view containing the cold spot.

Analysis of Stress-Responsive Gene Expression in Cultivated and Weedy Rice Differing in Cold Stress Tolerance

PubMed Central

Pereira, Andy; Tseng, Te-Ming; Zimmer, Paulo Dejalma; Burgos, Nilda Roma

2015-01-01

Rice (Oryza sativa L.) cultivars show impairment of growth in response to environmental stresses such as cold at the early seedling stage. Locally adapted weedy rice is able to survive under adverse environmental conditions, and can emerge in fields from greater soil depth. Cold-tolerant weedy rice can be a good genetic source for developing cold-tolerant, weed-competitive rice cultivars. An in-depth analysis is presented here of diverse indica and japonica rice genotypes, mostly weedy rice, for cold stress response to provide an understanding of different stress adaptive mechanisms towards improvement of the rice crop performance in the field. We have tested a collection of weedy rice genotypes to: 1) classify the subspecies (ssp.) grouping (japonica or indica) of 21 accessions; 2) evaluate their sensitivity to cold stress; and 3) analyze the expression of stress-responsive genes under cold stress and a combination of cold and depth stress. Seeds were germinated at 25°C at 1.5- and 10-cm sowing depth for 10d. Seedlings were then exposed to cold stress at 10°C for 6, 24 and 96h, and the expression of cold-, anoxia-, and submergence-inducible genes was analyzed. Control plants were seeded at 1.5cm depth and kept at 25°C. The analysis revealed that cold stress signaling in indica genotypes is more complex than that of japonica as it operates via both the CBF-dependent and CBF-independent pathways, implicated through induction of transcription factors including OsNAC2, OsMYB46 and OsF-BOX28. When plants were exposed to cold + sowing depth stress, a complex signaling network was induced that involved cross talk between stresses mediated by CBF-dependent and CBF-independent pathways to circumvent the detrimental effects of stresses. The experiments revealed the importance of the CBF regulon for tolerance to both stresses in japonica and indica ssp. The mechanisms for cold tolerance differed among weedy indica genotypes and also between weedy indica and cultivated japonica ssp. as indicated by the up/downregulation of various stress-responsive pathways identified from gene expression analysis. The cold-stress response is described in relation to the stress signaling pathways, showing complex adaptive mechanisms in different genotypes. PMID:26230579

The role of local strains from prior cold work on stress corrosion cracking of α-brass in Mattsson's solution

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

Ulaganathan, Jaganathan, E-mail: jagan.ulaganathan@mail.utoronto.ca; Newman, Roger C., E-mail: roger.newman@utoronto.ca

2014-06-01

The dynamic strain rate ahead of a crack tip formed during stress corrosion cracking (SCC) under a static load is assumed to arise from the crack propagation. The strain surrounding the crack tip would be redistributed as the crack grows, thereby having the effect of dynamic strain. Recently, several studies have shown cold work to cause accelerated crack growth rates during SCC, and the slip-dissolution mechanism has been widely applied to account for this via a supposedly increased crack-tip strain rate in cold worked material. While these interpretations consider cold work as a homogeneous effect, dislocations are generated inhomogeneously withinmore » the microstructure during cold work. The presence of grain boundaries results in dislocation pile-ups that cause local strain concentrations. The local strains generated from cold working α-brass by tensile elongation were characterized using electron backscatter diffraction (EBSD). The role of these local strains in SCC was studied by measuring the strain distributions from the same regions of the sample before cold work, after cold work, and after SCC. Though, the cracks did not always initiate or propagate along boundaries with pre-existing local strains from the applied cold work, the local strains surrounding the cracked boundaries had contributions from both the crack propagation and the prior cold work. - Highlights: • Plastic strain localization has a complex relationship with SCC susceptibility. • Surface relief created by cold work creates its own granular strain localization. • Cold work promotes crack growth but several other factors are involved.« less

Catastrophic global-avalanche of a hollow pressure filament

NASA Astrophysics Data System (ADS)

van Compernolle, B.; Poulos, M. J.; Morales, G. J.

2017-10-01

New results are presented of a basic heat transport experiment performed in the Large Plasma Device at UCLA. A ring-shaped electron beam source injects low energy electrons along a strong magnetic field into a preexisting, large and cold plasma. The injected electrons are thermalized by Coulomb collisions within a short distance and provide an off-axis heat source that results in a long, hollow, cylindrical region of elevated plasma pressure. The off-axis source is active for a period long compared to the density decay time, i.e., as time progresses the power per particle increases. Two distinct regimes are observed to take place, an early regime dominated by multiple avalanches, identified as a sudden intermittent rearrangement of the pressure profile that repeats under sustained heating, and a second regime dominated by broadband drift-Alfvén fluctuations. The transition between the two regimes is sudden and global, both radially and axially. The initial regime is characterized by peaked density and temperature profiles, while only the peaked temperature profile survives in the second regime. Recent measurements at multiple axial locations provide new insight into the axial dynamics of the global avalanche. Sponsored by NSF Grant 1619505 and by DOE/NSF at BaPSF.

Hollow - cathode electrode for high-power, high-pressure discharge devices

DOEpatents

Chang, Jim J.; Alger, Terry W.

1995-01-01

Several different cold cathode configurations for a gas discharge device each having a plurality of grooves of selected spacing, depth and width to improve the emission of electrons in a gas discharge device. Each of the cold cathode configurations can be machined from a single piece of a selected material. Several of the configurations can be assembled with individual elements which is easily seen from the various figures.

Microstructure and Texture Development during Cold Rolling in UNS S32205 and UNS S32760 Duplex Stainless Steels

NASA Astrophysics Data System (ADS)

Kumar, Amit; Khatirkar, Rajesh Kisni; Chalapathi, Darshan; Kumar, Gulshan; Suwas, Satyam

2017-05-01

In the present study, microstructure and texture evolution during cold rolling in UNS S32205 and UNS S32760 duplex stainless steel was investigated. Both steels were unidirectionally cold rolled up to 80 pct thickness reduction. Scanning electron microscopy and electron backscattered diffraction (EBSD) were used for microstructural characterization, while X-ray diffraction (XRD) was used for the measurement of bulk texture. Strain-induced martensite (SIM) was identified and quantified with the help of magnetic measurements (B-H curve and magnetization saturation). With the increase in plastic strain, the grains became morphologically elongated along the rolling direction with the reduction in average band thickness and band spacing. SIM increased with the increase in deformation and was found to be a function of strain and the SFE of austenite. The increase in SIM was much more pronounced in UNS S32205 steel as compared to UNS S32760 steel. After cold rolling, strong α-fiber (RD//<110>) texture was developed in ferrite, while brass texture was dominant in austenite for both steels. The strength of texture components and fibers was stronger in UNS S32760 steel. Another significant feature was the development of weak γ-fiber (ND//<111>) in UNS S32760 steel at intermediate deformation.

Synoptic Meteorology during the SNOW-ONE-A Field Experiment.

DTIC Science & Technology

1983-05-01

AD ,34 888 SYNOPTIC METEOROLOGY DURING tHE SNOW-ONE A FIELD I EXPERIMENTIUP COLD REGIONS RESEARCH AND ENGINEERING LABHANOVER NN M A BILELLO MAY 83...PROGRAM ELEMENT. PROJECT. TASK U. S. Army Cold Regions Research and AREA & WORK UNIT NUMBERS Engineering Laboratory DA Project 4A762730AT42- Hanover, New...Hampshire 03755 B-El-5 It. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE Office of the Ch ief of Engineers May 1983 Washington, D.C. 20314 13

Bio/Nano Electronic Devices and Sensors

DTIC Science & Technology

2008-10-01

Microscopy and Microanalysis 2006 Meeting, Chicago, IL, July 30 - August 3, 2006 4) S. Khizroev, "Three-dimensional Magnetic Memory," presented at US Air...ABSTRACT This effort consists of five research thrusts: (1) Dense Memory Devices-(1)3-D magnetic recording was enhanced using patterned soft underlayers...and interlayer, (2) Cold cathode microwave generator and ceramic electron multiplier-ceramic multiplier using a novel secondary electron yield

High-Resolution Characterizations of Grain Boundary Damage and Stress Corrosion Cracks in Cold-Rolled Alloy 690

NASA Astrophysics Data System (ADS)

Bruemmer, S. M.; Olszta, M. J.; Toloczko, M. B.; Thomas, L. E.

Unidirectional cold rolling has been shown to promote intergranular stress corrosion cracking (IGSCC) in alloy 690 tested in PWR primary water. High-resolution scanning (SEM) and transmission electron microscopy (TEM) have been employed to investigate the microstructural reasons for this enhanced susceptibility in two stages, first examining grain boundary damage produced by cold rolling and second by characterization of stress corrosion crack tips. The degree of permanent grain boundary damage from cold rolling was found to depend directly on the initial IG precipitate distribution. Cold rolling to high levels of reduction was discovered to produce small IG voids and cracked carbides in alloys with a high density of grain boundary carbides. For the same degree of cold rolling, alloys with few IG carbides exhibited much less permanent damage. Although this difference in grain boundary damage appears to correlate with measured SCC growth rates, crack tip examinations reveal no interaction between the preexisting voids and cracked carbides with the propagation. In many cases, these features appeared to blunt propagation of IGSCC cracks. High-resolution characterizations are described for cold-rolled alloy 690 CRDM tubing and plate materials to gain insights into IGSCC mechanisms.

Ultracold neutral plasmas

NASA Astrophysics Data System (ADS)

Lyon, M.; Rolston, S. L.

2017-01-01

By photoionizing samples of laser-cooled atoms with laser light tuned just above the ionization limit, plasmas can be created with electron and ion temperatures below 10 K. These ultracold neutral plasmas have extended the temperature bounds of plasma physics by two orders of magnitude. Table-top experiments, using many of the tools from atomic physics, allow for the study of plasma phenomena in this new regime with independent control over the density and temperature of the plasma through the excitation process. Characteristic of these systems is an inhomogeneous density profile, inherited from the density distribution of the laser-cooled neutral atom sample. Most work has dealt with unconfined plasmas in vacuum, which expand outward at velocities of order 100 m/s, governed by electron pressure, and with lifetimes of order 100 μs, limited by stray electric fields. Using detection of charged particles and optical detection techniques, a wide variety of properties and phenomena have been observed, including expansion dynamics, collective excitations in both the electrons and ions, and collisional properties. Through three-body recombination collisions, the plasmas rapidly form Rydberg atoms, and clouds of cold Rydberg atoms have been observed to spontaneously avalanche ionize to form plasmas. Of particular interest is the possibility of the formation of strongly coupled plasmas, where Coulomb forces dominate thermal motion and correlations become important. The strongest impediment to strong coupling is disorder-induced heating, a process in which Coulomb energy from an initially disordered sample is converted into thermal energy. This restricts electrons to a weakly coupled regime and leaves the ions barely within the strongly coupled regime. This review will give an overview of the field of ultracold neutral plasmas, from its inception in 1999 to current work, including efforts to increase strong coupling and effects on plasma properties due to strong coupling.

Miniature Pulse Tube Cooler

NASA Astrophysics Data System (ADS)

Tward, E.; Nguyen, T.; Godden, J.; Toma, G.

2004-06-01

A high capacity miniature pulse tube cooler for space that is scaled from the High Efficiency Cryocooler (HEC) is being developed. The low mass (1.5 kg) integral pulse tube cryocooler can provide large cooling power over a wide temperature range (e.g., 5 W at 95 K). The cooler is designed to be compatible with the existing HEC flight electronics. A small back-to-back flexure compressor drives a pulse tube cold head which is integrated with the compressor. The cooler has been tested with both linear and coaxial cold heads. A description of the cooler and its performance in both linear and coaxial cold head versions is presented.

Test of the SO(6) selection rule in 196Pt using cold-neutron capture

NASA Astrophysics Data System (ADS)

Jolie, J.; Régis, J.-M.; Wilmsen, D.; Saed-Samii, N.; Pfeiffer, M.; Warr, N.; Blanc, A.; Jentschel, M.; Köster, U.; Mutti, P.; Soldner, T.; Simpson, G. S.; De France, G.; Urban, W.; Drouet, F.; Vancraeyenest, A.; Bruce, A. M.; Roberts, O. J.; Fraile, L. M.; Paziy, V.; Ignatov, A.; Kröll, Th.; Ivanova, D.; Kisyov, S.; Lalkovski, S.; Podolyak, Zs.; Regan, P. H.; Wilson, E.; Korten, W.; Ur, C. A.; Lica, R.; Marginean, N.

2015-02-01

At the PF1B cold-neutron beam line of the Institut Laue Langevin, the EXILL&FATIMA array, consisting of EXOGAM Ge detectors and fast LaBr3(Ce) scintillators, was used to perform fast electronic timing measurements after the 195Pt(n, γ) reaction using a highly collimated cold-neutron beam. An upper lifetime limit was obtained for the third 0+ state in 196Pt. As this state is the lowest state of the σ = N - 2 set of SO(6) states, the selection rule which forbids E2 transitions to the lower lying σ = N could be tested.

Three Distinct Deformation Behaviors of Cementite Lamellae in a Cold-Drawn Pearlitic Wire

NASA Astrophysics Data System (ADS)

Xin, Tuo; Liu, Guiju; Liang, Wenshuang; Cai, Rongsheng; Feng, Honglei; Li, Chen; Li, Jian; Wang, Yiqian

2018-03-01

High-resolution transmission electron microscopy is used to investigate the deformation behaviors of cementite lamellae in the heavily cold-drawn piano wires. Three distinct morphologies of cementite are observed, namely, complete lamella, partly-broken lamella and nearly-disappeared lamella. For the complete cementite lamella, it remains a single-crystalline structure. For the partly-broken cementite lamella, polycrystalline structure and neck-down region appear to release the residual strain. The lattice expansion of ferrite takes place in two perpendicular directions indicating that the carbon atoms dissolve from cementite into ferrite lattices. An orientation relationship is found between ferrite and cementite phases in the cold-drawn pearlitic wire.

The generalized accessibility and spectral gap of lower hybrid waves in tokamaks

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

Takahashi, Hironori

1994-03-01

The generalized accessibility of lower hybrid waves, primarily in the current drive regime of tokamak plasmas, which may include shifting, either upward or downward, of the parallel refractive index (n{sub {parallel}}), is investigated, based upon a cold plasma dispersion relation and various geometrical constraint (G.C.) relations imposed on the behavior of n{sub {parallel}}. It is shown that n{sub {parallel}} upshifting can be bounded and insufficient to bridge a large spectral gap to cause wave damping, depending upon whether the G.C. relation allows the oblique resonance to occur. The traditional n{sub {parallel}} upshifting mechanism caused by the pitch angle of magneticmore » field lines is shown to lead to contradictions with experimental observations. An upshifting mechanism brought about by the density gradient along field lines is proposed, which is not inconsistent with experimental observations, and provides plausible explanations to some unresolved issues of lower hybrid wave theory, including generation of {open_quote}seed electrons.{close_quote}« less

Next Generation Muon g-2 Experiments

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

Hertzog, David W.

2015-12-02

I report on the progress of two new muon anomalous magnetic moment experiments, which are in advanced design and construction phases. The goal of Fermilab E989 is to reduce the experimental uncertainty ofmore » $$a_\\mu$$ from Brookhaven E821 by a factor of 4; that is, $$\\delta a_\\mu \\sim 16 \\times 10^{-11}$$, a relative uncertainty of 140~ppb. The method follows the same magic-momentum storage ring concept used at BNL, and pioneered previously at CERN, but muon beam preparation, storage ring internal hardware, field measuring equipment, and detector and electronics systems are all new or upgraded significantly. In contrast, J-PARC E34 will employ a novel approach based on injection of an ultra-cold, low-energy, muon beam injected into a small, but highly uniform magnet. Only a small magnetic focusing field is needed to maintain storage, which distinguishes it from CERN, BNL and Fermilab. E34 aims to roughly match the previous BNL precision in their Phase~1 installation.« less

Aluminum/ammonia heat pipe gas generation and long term system impact for the Space Telescope's Wide Field Planetary Camera

NASA Technical Reports Server (NTRS)

Jones, J. A.

1983-01-01

In the Space Telescope's Wide Field Planetary Camera (WFPC) project, eight heat pipes (HPs) are used to remove heat from the camera's inner electronic sensors to the spacecraft's outer, cold radiator surface. For proper device functioning and maximization of the signal-to-noise ratios, the Charge Coupled Devices (CCD's) must be maintained at -95 C or lower. Thermoelectric coolers (TEC's) cool the CCD's, and heat pipes deliver each TEC's nominal six to eight watts of heat to the space radiator, which reaches an equilibrium temperature between -15 C to -70 C. An initial problem was related to the difficulty to produce gas-free aluminum/ammonia heat pipes. An investigation was, therefore, conducted to determine the cause of the gas generation and the impact of this gas on CCD cooling. In order to study the effect of gas slugs in the WFPC system, a separate HP was made. Attention is given to fabrication, testing, and heat pipe gas generation chemistry studies.

Toroidal nanotraps for cold polar molecules

DOE PAGES

Salhi, Marouane; Passian, Ali; Siopsis, George

2015-09-14

Electronic excitations in metallic nanoparticles in the optical regime that have been of great importance in surface-enhanced spectroscopy and emerging applications of molecular plasmonics, due to control and confinement of electromagnetic energy, may also be of potential to control the motion of nanoparticles and molecules. Here, we propose a concept for trapping polarizable particles and molecules using toroidal metallic nanoparticles. Specifically, gold nanorings are investigated for their scattering properties and field distribution to computationally show that the response of these optically resonant particles to incident photons permit the formation of a nanoscale trap when proper aspect ratio, photon wavelength, andmore » polarization are considered. However, interestingly the resonant plasmonic response of the nanoring is shown to be detrimental to the trap formation. The results are in good agreement with analytic calculations in the quasistatic limit within the first-order perturbation of the scalar electric potential. The possibility of extending the single nanoring trapping properties to two-dimensional arrays of nanorings is suggested by obtaining the field distribution of nanoring dimers and trimers.« less