Search NASA⌕ Search

SEARCH · Search NASA

Results for “plasma switch”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Neutral gas analysis for JET DT operation

Neutral gas analysis, the measurement and evaluation of total and partial pressures, is a key technique to study the impact of neutral gas dynamics on retention, recycling and release processes of fuel or impurity species in fusion devices. At JET, the experiment closest to ITER in terms of operating parameters and size, various detectors and techniques for partial pressure and total pressure measurements are deployed together to characterise neutral gas dynamics during and after plasma operation on various toroidal and poloidal locations. An extensive modification of JET's sub-divertor neutral gas diagnostic system aims at retaining and extending established measurement capabilities in the forthcoming Deuterium-Tritium (DT) experiments (DTE2). To achieve DT compatibility, a separation of radiation-sensitive electronics from the sensor and adequate radiation shielding is required, as well as utilisation of a DT compatible differential pumping system with adjustable throughput to account for the strong pressure variation in the sub-divertor region. Finally, the sub-divertor neutral gas diagnostic will be equipped with multiple Residual Gas Analysers (RGAs), utilising quadrupole mass spectrometry and electrostatic ion-trap-principles, all operating with remote electronics located behind the biological radiation shield. These RGAs will record data in a fast selected discrete mass mode during plasma pulses (cycle ~2 s) and will automatically switch back to continuous data recording (cycle ~100 s) afterwards. They will be complemented by a newly improved Penning gauge spectroscopy configuration in particular supporting the He and D 2 separation relevant for DT operation. The distance between these devices and their associated control unit is typically 15m . A newly developed RGA with a cable length of 80 m, compatible with the ITER environment, will also be employed for the first time. Finally, this set-up and its operation in DTE2 will provide vital input to the development of the ITER divertor RGA in the most relevant environment currently available.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Turbulent Heating in Collisionless Low-beta Plasmas: Imbalance, Landau Damping, and Electron–Ion Energy Partition

An understanding of how turbulent energy is partitioned between ions and electrons in weakly collisional plasmas is crucial for modeling many astrophysical systems. Using theory and simulations of a four-dimensional reduced model of low-beta gyrokinetics (the “Kinetic Reduced Electron Heating Model”), we investigate the dependence of collisionless heating processes on plasma beta and imbalance (normalized cross-helicity). These parameters are important because they control the helicity barrier, the formation of which divides the parameter space into two distinct regimes with remarkably different properties. In the first, at lower beta and/or imbalance, the absence of a helicity barrier allows the cascade of injected power to proceed to small (perpendicular) scales, but its slow cascade rate makes it susceptible to significant electron Landau damping, in some cases leading to a marked steepening of the magnetic spectra on scales above the ion Larmor radius. In the second, at higher beta and/or imbalance, the helicity barrier halts the cascade, confining electron Landau damping to scales above the steep “transition-range” spectral break, resulting in dominant ion heating. We formulate quantitative models of these processes that compare well to simulations in each regime, and combine them with results of previous studies to construct a simple formula for the electron–ion heating ratio as a function of beta and imbalance. This model predicts a “winner takes all” picture of low-beta plasma heating, where a small change in the fluctuations' properties at large scales (the imbalance) can cause a sudden switch between electron and ion heating.

Interplanetary turbulence↗
NASA NTRS1982

Transient effects in beam-plasma interactions in a space simulation chamber stimulated by a fast pulse electron gun

Interest in the interaction of electron beams with plasma generated by ionization caused by the primary electron beam was stimulated by the need to develop special vacuum tubes to operate in the kMHz frequency region. The experiments of Getty and Smullin (1963) indicated that the interaction of an energetic electron beam with its self-produced plasma resulted in the emission of wave energy over a wide range of frequencies associated with cyclotron and longitudinal plasma instabilities. This enhanced the thermal plasma density in the vicinity of the beam, and the term Beam-Plasma Discharge (BPD) was employed to described this phenomenon. The present investigation is concerned with some of the transient phenomena associated with wave emission during the beam switch-on and switch-off periods. Results are presented on the changes in electron energy spectra on a time scale of tens of milliseconds following beam switch-on. The results are discussed in terms of the beam plasma discharge phenomenon.

Raitt, W. J.↗
DOE OSTI2023

Ferroelectric Al1 − xBxN thin films integrated on Si

Ferroelectric Al0.93B0.07N thin films are prepared (100) Si substrates. The necessary c-axis out-of-plane orientation to observe macroscopic ferroelectric switching was achieved by implementing an initial Ar/N2 plasma treatment, followed by a thin layer of AlN to initiate the desired texture and a 150 nm W layer. The plasma treatment facilitates crystallinity enhancement of the AlN template layer, allowing for subsequent growth of highly oriented W and Al0.93B0.07N layers. The W layer exhibits random in-plane orientation and exclusive (110) out-of-plane orientation with a rocking curve width of 1.4°. When grown on these W surfaces, 175 nm thick Al0.93B0.07N films exhibit random in-plane orientation and exclusive (001) texture with rocking curve full-width-half-max values of 1.6° and RMS roughness values less than 1 nm. Polarization hysteresis measurements show robust hysteresis with coercive field values of 5.4 MV/cm and remanent polarization values of 136 μC/cm2. XPS depth profile analysis suggests that the plasma treatment converts the existing native oxide to a nitrogen rich oxynitride with approximate composition Si3O0.5N3.67. Cross-sectional TEM reveals that the oxynitride interlayer is amorphous and ∼3.4 nm thick, more than double the native oxide thickness measured by multiwavelength ellipsometry, implying that (oxy)nitride growth continues after conversion of the native oxide. This new family of ferroelectric wurtzites is interesting from an integration perspective given their chemical compatibility with mainstream semiconductors. Developing synthesis routes that promote needed texture while preserving compatible processing windows is an important step toward practical integration.

Physics↗
DOE OSTI2024

What next: Further implosion space exploration on the path to NIF extended yield capability

We present quantitative motivations and assessments of various proposed and ongoing directions to further improving yields and target gain of igniting indirect-drive implosions at the National Ignition Facility (NIF). These include increasing compression and confinement time, improving hohlraum and ablator efficiency, and further increasing peak power and laser energy. 1D hydroscaled simulations, augmented by analytic 1D theory, have been used to project yield improvements for each of these implosion optimization tracks, normalized to the best current performing 4 MJ shot. At current NIF capabilities of 2.2 MJ, 450 TW, we project several paths could reach 15 MJ yield levels. We also expect several key implosion physics questions will be addressed in attempting to reach this yield level. These include demonstrating to what extent lower adiabat designs leading to higher compression will increase gain and efficiency, and whether we can reduce residual kinetic energy and ablator-fuel mix that is probably limiting the current burn-up fraction. For an envisaged NIF upgrade to EL = 3 MJ at fixed 450 TW peak power, scaling capsule size and fuel thicknesses faster than pure hydroscaling should allow for yields that could reach up to 60–80 MJ, depending on the efficiency gains realized in increasing deuterium-tritium fuel thickness, reducing hohlraum losses, and switching to lower Z ablators. The laser-plasma instability and beam transmission scaling in these larger hohlraums is shown to be favorable if the spot size is increased with hohlraum scale.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1974

Electric and magnetic field observations during a substorm of 24 February 1970

A series of electric field measurements is reported which was obtained from the Injun 5 satellite along with a simultaneous magnetic disturbance observed in the interplanetary medium and on the ground during a magnetic substorm. The substorm analyzed took place on February 24, 1970. Prior to the onset of the substorm a greatly enhanced anti-sunward plasma flow was observed over the polar cap. The enhanced plasma flow occurred about 30 minutes after a switch in the direction of the interplanetary magnetic field from northward to southward. The electric fields across the polar cap immediately before and during the substorm were essentially unchanged indicating that an enhancement in the ionospheric conductivity rather than the electric field must be responsible for the large increase in the auroral electrojet current during the substorm.

Gurnett, D. A.↗
NASA NTRS1974

Electric and magnetic field observations during a substorm on February 24, 1970

Description of a series of electric field measurements obtained from the Injun 5 satellite and simultaneous magnetic disturbances observed in the interplanetary medium and on the ground during a magnetic substorm. The substorm analyzed took place on Feb. 24, 1970. Prior to the onset of the substorm, a greatly enhanced antisunward plasma flow was observed over the polar cap. The enhanced plasma flow occurred about 30 minutes after a switch in the direction of the interplanetary magnetic field from northward to southward. The electric fields across the polar cap immediately before and during the substorm were essentially unchanged, and it is thus indicated that an enhancement in the ionospheric conductivity rather than the electric field must be responsible for the large increase in the auroral electrojet current during the substorm.

Gurnett, D. A.↗
NASA NTRS2003

High-Energy Two-Stage Pulsed Plasma Thruster

A high-energy (28 kJ per pulse) two-stage pulsed plasma thruster (MSFC PPT-1) has been constructed and tested. The motivation of this project is to develop a high power (approximately 500 kW), high specific impulse (approximately 10000 s), highly efficient (greater than 50%) thruster for use as primary propulsion in a high power nuclear electric propulsion system. PPT-1 was designed to overcome four negative characteristics which have detracted from the utility of pulsed plasma thrusters: poor electrical efficiency, poor propellant utilization efficiency, electrode erosion, and reliability issues associated with the use of high speed gas valves and high current switches. Traditional PPTs have been plagued with poor efficiency because they have not been operated in a plasma regime that fully exploits the potential benefits of pulsed plasma acceleration by electromagnetic forces. PPTs have generally been used to accelerate low-density plasmas with long current pulses. Operation of thrusters in this plasma regime allows for the development of certain undesirable particle-kinetic effects, such as Hall effect-induced current sheet canting. PPT-1 was designed to propel a highly collisional, dense plasma that has more fluid-like properties and, hence, is more effectively pushed by a magnetic field. The high-density plasma loading into the second stage of the accelerator is achieved through the use of a dense plasma injector (first stage). The injector produces a thermal plasma, derived from a molten lithium propellant feed system, which is subsequently accelerated by the second stage using mega-amp level currents, which eject the plasma at a speed on the order of 100 kilometers per second. Traditional PPTs also suffer from dynamic efficiency losses associated with snowplow loading of distributed neutral propellant. The twostage scheme used in PPT-I allows the propellant to be loaded in a manner which more closely approximates the optimal slug loading. Lithium propellant was chosen to test whether or not the reduced electrode erosion found in the Lithium Lorentz Force Accelerator (LiLFA) could also be realized in a pulsed plasma thruster. The use of the molten lithium dense plasma injector also eliminates the need for a gas valve and electrical switch; the injector design fulfills both roles, and uses no moving parts to provide, in principle, a highly reliable propellant feed and electrical switching system. Experimental results reported in this paper include: second-stage current traces, high-speed photographic and holographic imaging of the thruster exit plume, and internal mapping of the discharge chamber magnetic field from B-dot probe data. The magnetic field data is used to create a two-dimensional description of the evolution of the current sheet inside the thruster.

Markusic, Tom↗
NASA NTRS1980

Ion beams from laser-generated plasmas

The paper describes the space-charge-limited beams produced by the plasma blowoffs generated by 20-MW bursts of 1.06-micron radiation from an active Q-switched Nd:YAG laser. Laser power densities near 10 to the 11th/sq cm on solid targets generate thermalized plasma plumes which drift to a 15-kV gridded extraction gap where the ions are extracted, accelerated, and electrostatically focused; the spatially defined ion beams are then magnetically analyzed to determine the charge state content in the beams formed from carbon, aluminum, copper, and lead targets. This technique preserves time-of-flight (TOF) information in the plasma drift region, which permits plasma ion temperatures and mass flow velocities to be determined from the Maxwellian ion curve TOF shapes for the individual charge species.

Hughes, R. H.↗
DOE OSTI2025

Ferroelectric Al 1− x B x N sputtered thin films on n -type Si bottom electrodes

Ferroelectric Al 1−x B x N thin films are grown on highly doped and plasma treated (100) n-type Si. We demonstrate ferroelectricity for x = < 0.01, 0.02, 0.06, 0.08, 0.13, and 0.17 where the n-type Si is both the substrate and bottom electrode. Polarization hysteresis reveals remanent polarization values between 130 and 140 μC/cm 2 and coercive field values as low as 4 MV/cm at 1 Hz with low leakage. The highest resistivity and most saturating hysteresis occurs with B contents between x = 0.06 and 0.13. We also demonstrate the impact of substrate plasma treatment time on Al 1−x B x N crystallinity and switching. Cross-sectional transmission electron microscopy and electron energy loss spectra reveal an amorphous 3.5 nm SiN x layer at the Al 1−x B x N interface post-plasma treatment and deposition. The first ~ 5 nm of Al 1−x B x N is crystallographically defective. Using the n-type Si substrate, we demonstrate Al 1−x B x N thickness scaling to 25 nm via low-frequency hysteresis and CV. Serving as the bottom electrode and substrate, the n-type Si enables a streamlined growth process for Al 1−x B x N for a wide range of Al 1−x B x N compositions and layer thicknesses.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Current-Regulated Arc Modulator Optimization

n this study, the performance of a current-regulated arc modulator was investigated with a focus on its role in initiating and sustaining plasma discharge within the Magnetron Body of the LINAC system. The analysis centered on how switching components, circuit topology, and feedback loop architecture influence critical factors such as energy efficiency, discharge stability, and long-term plasma containment. Particular attention was given to variations in pulse termination behavior, as observed through oscilloscope traces, which revealed inconsistencies affecting the duty factor and cathode temperature. These fluctuations have downstream effects on the cesium-coated cathode surface, thereby impacting H⁻ ion production and beam reliability. Simulation-based testing in LTspice was used to evaluate noise suppression techniques and arc current regulation schemes, revealing how optimized snubber networks, improved pulse shaping, and feedback stability can mitigate modulator-induced noise. The results ide

Campos, Nathan↗
DOE OSTI2025

Development and Testing of a new Current-Regulated Arc Modulator for the LINAC

In this study, the performance of a current-regulated arc modulator was investigated with a focus on its role in initiating and sustaining plasma discharge within the Magnetron Body of the LINAC system. The analysis centered on how switching components, circuit topology, and feedback loop architecture influence critical factors such as energy efficiency, discharge stability, and long-term plasma containment. Particular attention was given to variations in pulse termination behavior, as observed through oscilloscope traces, which revealed inconsistencies affecting the duty factor and cathode temperature. These fluctuations have downstream effects on the cesium-coated cathode surface, thereby impacting H⁻ ion production and beam reliability. Simulation-based testing in LTspice was used to evaluate noise suppression techniques and arc current regulation schemes, revealing how optimized snubber networks, improved pulse shaping, and feedback stability can mitigate modulator-induced noise. The results identified hardware level parameters that significantly enhance discharge repeatability and improve overall plasma performance under operational conditions.

Campos, Nathan [Unlisted, US; Fermilab]↗
DOE OSTI2023

Mitigating dust particle contamination in an afterglow plasma by controlled lifting with a DC electric field

Abstract Particle contamination due to plasma processing motivates the design of a method of electrically lifting particles in a time interval after a plasma’s power is turned off. Small solid dust particles have electric charges that are not frozen until a late stage of the plasma afterglow. Beyond that time, before they fall to a surface below and cause defects, particles can be lifted in a controlled manner by applying an appropriate direct-current (DC) electric field, as we demonstrate experimentally. A few milliseconds after an argon plasma’s capacitively coupled radio-frequency power is switched off, a vertical DC electric field is applied. Thereafter, video imaging shows that the falling of the particles is slowed or stopped altogether, depending on the magnitude of the upward electric force.

Physics↗
NASA NTRS2000

Modeling of Optoelectronic Devices

Ultrafast modulation of semiconductor quantum well (QW) laser is of technological importance for information technology. Improvement by order(s) of magnitude in data transfer rate is possible as terahertz (THz) radiation is available for heating the laser at picosecond time scale. Optical gain modulation in the QW is achieved via temperature modulation of electron-hole plasma (EHP). Applications include free-space THz communication, optical switching, and pulse generation. The EHP in the semiconductor QW is described with a two-band model. Semiconductor Bloch equations with many-body effects are used to derive a hydrodynamical model for the active QW region. Because of ultrafast carrier-carrier scatterings in the order of 50 fs, EHP follows quasiequilibrium Fermi-Dirac distributions and THz field interacts incoherently with it. Carrier-longitudinal optical (LO) phonon scatterings and coherent laser-EHP interaction are treated microscopically in our physical model. A set of hydrodynamical equations for plasma density, temperature, and laser envelop amplitude are derived and Runge-Kutta method is adopted for numerical simulation. A typical 8 nm GaAs/Al(0.3)Ga(0.7) As single QW at 300 K is used. Additional information is contained in the original extended abstract.

Li, Jian-Zhong↗
DOE OSTI2020

Toroidal Field Reversing Switch

A motor-driven, high-current switch is being designed by Stäubli Electrical Connectors in collaboration with Princeton Plasma Physics Laboratory to reverse the DIII-D Toroidal field coil current. The existing field reversing procedure requires approximately 4 h of labor performed between run days to reconfigure the bus work, thus requiring a separate run day to complete experimental scans with both field directions. This typically results in different wall conditions which complicate the results or make them invalid. The proposed switch will complete the reversal process in approximately 4-5 min, between shots, so that wall conditions are not a factor, and easily fits within the 10-12 min DIII-D shot cycle. The switch is a compact design fitting into a 157.5 × 41 cm envelope. The switch uses two copper pins that slide between Stäubli MULTILAM contacts. The switch is rated for total current of 180-kA dc for 10 s with a 12-min repetition rate; the maximum operating coil current is 124-kA dc. The switch diagnostics include: voltage drop, current monitor, thermal monitors, position sensors, and motor torque. Here, the switch is rated for 300 cycles per year, and 3000 cycles overall before contact replacement, with contact inspection yearly. The design details and operation of the switch are covered in this article.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Spatiotemporal Plasma-Particle Characterization of Dry Aerosols Using Nanosecond, Femtosecond, and Filament Laser-Produced Plasmas

The ability to rapidly characterize dry aerosols in air using laser-induced breakdown spectroscopy (LIBS) with femtosecond laser pulses promises advancement towards real-time atmospheric sampling and standoff capabilities. Of particular interest is the ability to apply LIBS in the context of low-particle loaded environments where discrete particle interactions must be observed within the sampling volume of the laser-produced plasma (LPP). In this study, dry nanoparticles in suspension are generated from a standard solution and sampled in air using Q-switched nanosecond (ns-) pulses, short-focus (SF) femtosecond (fs-) pulses, and filaments. Short time-gated plasma images are captured to observe spatially and temporally varying discrete plasma-particle interactions, which is shown to influence early air breakdown behavior and subsequent plasma evolution. Along with images, photo-multiplier tube (PMT) measurements are conducted where strong spatiotemporal dependencies are exhibited by the collected emission signal on particle proximity and plasma expansion behavior. Finally, conditional analysis is performed on LIBS measurements to determine associated sampling probabilities and filter out spectra with poor or absent emission peaks with an adaptive threshold algorithm.

42 ENGINEERING↗
NASA NTRS2009

Electrostatic Switching in Vertically Oriented Nanotubes for Nonvolatile Memory Applications

We have demonstrated electrostatic switching in vertically oriented nanotubes or nanofibers, where a nanoprobe was used as the actuating electrode inside an SEM. When the nanoprobe was manipulated to be in close proximity to a single tube, switching voltages between 10 V - 40 V were observed, depending on the geometrical parameters. The turn-on transitions appeared to be much sharper than the turn-off transitions which were limited by the tube-to-probe contact resistances. In many cases, stiction forces at these dimensions were dominant, since the tube appeared stuck to the probe even after the voltage returned to 0 V, suggesting that such structures are promising for nonvolatile memory applications. The stiction effects, to some extent, can be adjusted by engineering the switch geometry appropriately. Nanoscale mechanical measurements were also conducted on the tubes using a custom-built anoindentor inside an SEM, from which preliminary material parameters, such as the elastic modulus, were extracted. The mechanical measurements also revealed that the tubes appear to be well adhered to the substrate. The material parameters gathered from the mechanical measurements were then used in developing an electrostatic model of the switch using a commercially available finite-element simulator. The calculated pull-in voltages appeared to be in agreement to the experimentally obtained switching voltages to first order.

plasma-enhanced chemical vapor deposition (PECVD).↗