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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Characterization and controllability of radiated power via extrinsic impurity seeding in strongly negative triangularity plasmas in DIII-D

Experiments with extrinsic impurity seeding in strongly negative triangularity shapes in DIII-D achieved radiated power fractions (relative to input power) of up to ≈85% total radiation and ≈55% core radiation in steady-operating conditions. The relationship between core and total radiation was sensitive to impurity species and input power. Attempts to reach higher radiation levels via higher impurity flows resulted in radiative collapse disruptions. Nitrogen, neon, argon, and krypton were tested. Injection was by gas puffing, usually controlled by feeding back real-time estimates for core or total radiating fractions ($P_\textrm{rad} / P_\textrm{input}$). Argon and krypton were controlled by feeding back total radiating fraction, whereas neon was controlled by feeding back the core radiating fraction, due to the lower efficiency of neon as a divertor radiator. Nitrogen flows were pre-programmed. Reasonable total $P_\textrm{rad}$ control target following was achieved with argon or krypton. Control was more challenging with the neon/core radiation configuration, which was more prone to slow response and overshooting of the control target. Poor particle removal contributed to the control challenge: neon particle inventory within the last closed flux surface was roughly constant for up to 1 s (the longest duration tested) after neon injection was halted. However, separate experiments with laser-blow off of non-recycling impurities measured a short impurity confinement time, on the scale of the energy confinement time of ∼100 ms. Modeling with the Aurora impurity transport simulation matched experimental neon density profiles with full recycling (R = 1.0) and weak pumping but predicted rapid decreases in neon inventory if pumping were increased or recycling decreased. This indicates that changes outside the confined plasma (adding a well-placed pump) would improve controllability for all highly recycling species.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Power and isotope effects in the ITER baseline scenario with tungsten and tungsten-equivalent radiators in DIII-D

Abstract Experiments in DIII-D document the ITER Baseline Scenario (IBS) at q 95 ∼ 3 and P IN / P LH ∼ 1–2, in both deuterium and hydrogen utilizing Kr and Xe as Tungsten-equivalent radiators. The power threshold for H-mode operation ( P LH ) was determined experimentally without added impurities and found to be about a factor of two higher than the scaling law. In recent IBS experiments in deuterium, intrinsic levels of metals such as Tungsten (W) or molybdenum and inconel are present that reduce the pedestal pressure by 20%–25%. A complete radiative collapse of deuterium IBS plasmas occurs at W core concentrations C W = 10 −5 . Simulations show that for core temperatures expected for ITER, the plasmas would not have a radiative collapse at C W = 1 × 10 −5 , moreover Q = 8–10 would still be achieved for C W up to 3 × 10 −5 . In contrast to deuterium, the IBS in hydrogen is not affected by intrinsic high-Z impurities, indicating that hydrogen H-modes in ITER may not inform the D-T phase with respect to W accumulation and discharge survival. Compared to deuterium, the pedestal pressure in hydrogen is ∼25% lower, with much higher ELM frequency of 150 Hz, decreasing with input power. Krypton was injected in a matrix scan of input power and impurity flow in IBS hydrogen discharges. Krypton impurity density profiles in hydrogen are similar to deuterium plasmas, but at Kr flows that are 2–3 times higher for the same input power. Krypton is transported into the core and affects the whole radius; at the highest injection rates a radiative collapse occurs at core radiation fractions of 0.3–0.35, consistent with the expected maximum W radiation fraction for ITER core plasmas. Comparing the results with previous International Tokamak Physics Activity database studies of the IBS confirms that at higher radiation fraction due to high-Z impurities, a drop in H 98 of >10% is observed. On the other hand, the results using Kr as a W-equivalent radiator indicate that metal (W) devices at lower core temperatures than ITER may provide overly pessimistic performance extrapolations to ITER for deuterium-tritium operation. The new DIII-D results support a more attractive option for the ITER Research Plan with a short hydrogen phase for system commissioning, transitioning to deuterium operations as soon as possible to provide relevant conditions for deuterium-tritium operations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1980

A first roadmap for kryptology

Studies of the complex variations of the isotopic composition of xenon in the solar system have been christened 'xenology'. In the title of the present investigation, the word 'kryptology' is employed to indicate the primary objective of the reported studies. This objective is related to the prediction of the isotopic composition of krypton which comes from a number of specific locations of a supernova in association with the isotopic compositions of xenon from these locations. Krypton is a logical candidate for testing the stellar theory on geochemical grounds, taking into account also the point of view of nucleosynthesis, because the isotopes of xenon and krypton are formed by the same thermonuclear processes in stars. The data and arguments presented in the investigation show that the treatment by Heymann and Dziczkaniec (1979), although not wrong, is too simplistic, because it has ignored the possibility of holdup and arrest in Xe network.

Heymann, D.↗
NASA NTRS1990

Improved Multiple-Species Cyclotron Ion Source

Use of pure isotope 86Kr instead of natural krypton in multiple-species ion source enables source to produce krypton ions separated from argon ions by tuning cylcotron with which source used. Addition of capability to produce and separate krypton ions at kinetic energies of 150 to 400 MeV necessary for simulation of worst-case ions occurring in outer space.

Soli, George A.↗
NASA NTRS1989

The determination of accurate dipole polarizabilities alpha and gamma for the noble gases

The static dipole polarizabilities alpha and gamma for the noble gases helium through xenon were determined using large flexible one-particle basis sets in conjunction with high-level treatments of electron correlation. The electron correlation methods include single and double excitation coupled-cluster theory (CCSD), an extension of CCSD that includes a perturbational estimate of connected triple excitations, CCSD(T), and second order perturbation theory (MP2). The computed alpha and gamma values are estimated to be accurate to within a few percent. Agreement with experimental data for the static hyperpolarizability gamma is good for neon and xenon, but for argon and krypton the differences are larger than the combined theoretical and experimental uncertainties. Based on our calculations, we suggest that the experimental value of gamma for argon is too low; adjusting this value would bring the experimental value of gamma for krypton into better agreement with our computed result. The MP2 values for the polarizabilities of neon, argon, krypton and zenon are in reasonabe agreement with the CCSD and CCSD(T) values, suggesting that this less expensive method may be useful in studies of polarizabilities for larger systems.

Rice, Julia E.↗
NASA NTRS2001

Radiation Effects on DC-DC Converters

In this work, several DC-DC converters were designed and built. The converters are Buck Buck-Boost, Cuk, Flyback, and full-bridge zero-voltage switched. The total ionizing dose radiation and single event effects on the converters were investigated. The experimental results for the TID effects tests show that the voltages of the Buck Buck-Boost, Cuk, and Flyback converters increase as total dose increased when using power MOSFET IRF250 as a switching transistor. The change in output voltage with total dose is highest for the Buck converter and the lowest for Flyback converter. The trend of increase in output voltages with total dose in the present work agrees with those of the literature. The trends of the experimental results also agree with those obtained from PSPICE simulation. For the full-bridge zero-voltage switch converter, it was observed that the dc-dc converter with IRF250 power MOSFET did not show a significant change of output voltage with total dose. In addition, for the dc-dc converter with FSF254R4 radiation-hardened power MOSFET, the output voltage did not change significantly with total dose. The experimental results were confirmed by PSPICE simulation that showed that FB-ZVS converter with IRF250 power MOSFET's was not affected with the increase in total ionizing dose. Single Event Effects (SEE) radiation tests were performed on FB-ZVS converters. It was observed that the FB-ZVS converter with the IRF250 power MOSFET, when the device was irradiated with Krypton ion with ion-energy of 150 MeV and LET of 41.3 MeV-square cm/mg, the output voltage increased with the increase in fluence. However, for Krypton with ion-energy of 600 MeV and LET of 33.65 MeV-square cm/mg, and two out of four transistors of the converter were permanently damaged. The dc-dc converter with FSF254R4 radiation hardened power MOSFET's did not show significant change at the output voltage with fluence while being irradiated by Krypton with ion energy of 1.20 GeV and LET of 25.97 MeV-square cm/mg. This might be due to fact that the device is radiation hardened.

Zhang, De-Xin↗
DOE OSTI2024

Solid Sorbent Cost Sensitivity Analysis: A Framework for UNF Reprocessing Sorbent Cost Comparison

Solid sorbents have been the subject of research and development across the U.S. Department of Energy national laboratory complex for many years. They are generally accepted as a safer alternative to cryogenic distillation for noble gas capture, and they present an easier pathway in development of long-term waste forms after iodine capture. As more types of sorbents have been proposed for capture of volatile radionuclides, it has become necessary to compare them based on performance and cost criteria. This report details cost and performance information for three promising sorbents and provides a cost sensitivity analysis. The goal of this analysis is to establish a framework which can be utilized to directly compare future sorbents, with differing properties, to the sorbents discussed in this report. Direct comparison is instrumental to making informed decisions to efficiently guide research and minimize laborious detours. In all cases, sorbent capacity is a major cost driver as it influences the mass of sorbent, operational footprint, and disposal cost requirements., However, sorbent price can greatly increase the cost of a capture technology. For sorbents used in krypton capture, the purity of krypton released to storage is the highest cost driver.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

Fission gas trapped in Chornobyl fuel microparticles reveals details of reactor operations

The isotopic ratios of fission gas would provide important source information of a nuclear fuel sample found in the environment. However, it is believed that during a reactor accident like Chornobyl all fission gas is lost and that the radioactive particles found in the Chornobyl Exclusion Zone today are depleted in gases by the initial explosion and subsequent fire. We disprove this hypothesis by detection and analysis of trapped krypton and xenon in these particles. Our analysis of krypton and xenon isotopes by noble gas mass spectroscopy in combination with resonance ionization mass spectrometry establishes that important information about reactor operations like age, neutron flux and plutonium fission fraction can still be reconstructed from individual micrometer-sized particles even after decades of weathering in the environment.

Chornobyl↗
DOE OSTI2025

Strength, deformation, and the fcc–hcp phase transition in condensed Kr and Xe to the 100 GPa pressure range

The rare gas solids exhibit systematic differences in crystal structure, phase transition conditions, bond strength, and other physical properties. The physical properties of heavy rare gas solids krypton and xenon are modified by the martensitic phase transition from face-centered cubic to hexagonal close packed structure over a broad pressure range. Crystal structure, strength, and plastic deformation of krypton and xenon have been investigated at 300 K using compression in the diamond-anvil cell with synchrotron angle-dispersive x-ray diffraction and complementary ruby fluorescence spectroscopy for Xe. Stacking faults indicative of the fcc–hcp phase transition are observed at pressures at and above 1.23 ± 0.05 and 1.9 ± 0.6 GPa in Kr and Xe, respectively. The transition remains incomplete in both solids to pressures greater than 100 GPa. Strength determined from stress measurements in Pt and ruby standards at pressures up to 111 GPa and complemented by observations of strain and texture measurements obtained by x-ray diffraction in the radial geometry to 100 GPa indicates similar or higher strength than Ar at all conditions, with significant stiffening at 15–20 GPa. Radial diffraction data reveal the persistence of broad highly textured fcc diffraction lines to 101 GPa in Xe, suggesting that the axial measurements may underestimate the metastable persistence of the fcc phase due to biased sampling of hcp crystallites resulting from preferred crystallite orientation. Kr and Xe are compared with He, Ne, and Ar for a systematic understanding of physical properties and phase equilibria of rare gas solids.

Compressive stress↗
NASA NTRS1971

Operation of an electron-bombardment ion source using various gases

An electron-bombardment ion thruster of the SERT 2 type was operated with xenon, krypton, argon, neon, nitrogen, helium, and carbon dioxide. The discharge performance with xenon, krypton, and argon was similar to that obtained previously with mercury. Mass spectrometer data indicated that the xenon contained no significant multiple ionization. Restriction of the beam area, with an associated decrease in discharge potential, was necessary to reduce multiple ionization with argon to a negligible level. This modification also resulted in more stable operation of the thruster. Performance with the remaining gases was poor because the basic thruster designed was optimized for operation with mercury.

Byers, D. C.↗
NASA NTRS1971

Electron-bombardment ion source operation using various gases.

Description of a modified flight-type SERT II ion thruster operated with xenon, krypton, argon, neon, nitrogen, helium, and carbon dioxide. The discharge performance with xenon, krypton, and argon was found to be similar to that obtained previously with mercury. Mass spectrometer data indicated that xenon could be operated efficiently with no significant multiple ionization. Restriction of the beam area, with an associated decrease in discharge potential, was necessary to reduce multiple ionization with argon to a negligible level. This modification also resulted in more stable operation of the thruster. Performance with the remaining gases was poor, but some future performance improvements may be realizable.

Byers, D. C.↗
NASA NTRS1973

Driving lamps by induction

An electrodeless lamp circuit with a coil surrounding a krypton lamp is driven by an RF input source. A coil surrounding a mercury lamp is tapped across the connection of the input central to the krypton-lamp coil. Each coil is connected in parallel with separate capacitors which form resonant circuits at the input frequency.

Laue, H. H.↗
NASA NTRS1972

Rare-gas analyses on neutron irradiated Apollo 12 samples.

Argon, krypton, and xenon from stepwise heating of five Apollo 12 rocks that had been irradiated to a neutron fluence of about 10 to the 19th neutrons/sq cm were analyzed mass-spectrometrically. The Ar40-Ar39 ages were determined and range from 3.18 plus or minus 0.06 x 10 to the 9th years to 3.32 plus or minus 0.06 x 10 to the 9th years. Trace elements Ba, Br, I, and U were measured via the neutron-induced reactions that produce isotopes of krypton and xenon. The following concentration ranges were observed: Ba, 46 to 70 ppm; Br, 48 to 146 ppb; I, 16 to 73 ppb; and U, 170 to 247 ppb.

Alexander, E. C., Jr.↗
NASA NTRS1976

The atmosphere of Mars near the surface - Isotope ratios and upper limits on noble gases

Several analyses of the Martian atmosphere have been carried out with the mass spectrometer in the molecular-analysis experiment. The ratios of abundant isotopes of carbon and oxygen are within 10 per cent of terrestrial values, whereas nitrogen-15 is considerably enriched on Mars. Argon-38 has been detected, and new limits on abundances of krypton and xenon have been set. The limit on krypton is sufficiently low to suggest that the inventories of volatile substances on Mars and on earth may be distinctly different.

Biemann, K.↗
NASA NTRS1978

Volumetric direct nuclear pumped laser

A volumetric direct nuclear pumped laser was developed in which the gas is a mixture of He-3 and a minority gas from the group of argon, krypton, xenon, chlorine and fluorine. The mixture of He-3 and the minority gas produces lasing with a minority gas concentration of from 0.01 to 10 percent argon, 1 percent krypton, 0.01 to 5 percent xenon and small concentrations of chlorine or fluorine.

Jalufka, N. W.↗
NASA NTRS1983

Quantum-chemical modeling of boron and noble gas dopants in silicon

The electron effects of the presence of boron and noble gas dopants in a model silicon lattice were investigated using a self-consistent charge extended Hueckel program. The extent of electronic interaction of the noble gas with the lattice is given by: Kr greater than Ar greater than Ne. Theoretically, boron diffusion in the presence of neon, argon or krypton was examined using a self-consistent charge extended Hueckel program. The net energy of interaction between boron and neon is strongly repulsive while argon-boron exhibits a region of relative stability; krypton exhibits behavior similar to argon though no region of stability was found for the range of separations used in the calculations. Finally, it is noted, from the relative energy of the topmost filled molecular orbital associated with boron (in an interstitial position), that activation of the boron does not require boron movement but can be accomplished by indirect transitions.

Aronowitz, S.↗
NASA NTRS1983

Development of a mass spectrometer system for the measurement of inert gases in meteorites

The study of the inert gases in meteorites has provided many clues as to the origin and evolution of the solar system. Particularly crucial and complex are the gases krypton and xenon. To accurately measure the isotopic compositions of these gases requires a mass spectrometer of high sensitivity and resolution. A previously unused and largely untested mass spectrometer system was brought to the point where it was ready for routine sample analyses. This involved, among other things, focusing the ion beam for optimal peak shape and sensitivity, documenting the instrument's response to a series of characteristic tests such as multplier gain checks, and interfacing the instrument to a computer to run the sample analyses. Following this testing and setting up, three iron meteorite samples were to be analyzed for argon, krypton, and xenon. The three samples were shown in prior work to possibly contain primordial heavy inert gases. Although these analyses have not yet been carried out, it is anticipated that they will be completed in the near future.

Palma, R. L.↗
NASA NTRS1988

A study of single and binary ion plasma expansion into laboratory-generated plasma wakes

Plasma expansion into the wake of a large rectangular plate immersed in a collisionless, supersonic plasma was investigated in laboratory experiments. The experimental conditions address both single ion and binary ion plasma flows for the case of a body whose size is large in comparison with the Debye length, when the potential difference between the body and the plasma is relatively small. A new plasma source was developed to generate equi-velocity, binary ion plasma flows, which allows access to new parameter space that have previously been unavailable for laboratory studies. Specifically, the new parameters are the ionic mass ratio and the ionic component density ratio. In a series of experiments, a krypton-neon plasma is employed where the ambient density ratio of neon to krypton is varied more than an order of magnitude. The expansion in both the single ion and binary ion plasma cases is limited to early times, i.e., a few ion plasma periods, by the combination of plasma density, plasma drift speed, and vacuum chamber size, which prevented detailed comparison with self-similar theory.

Wright, Kenneth Herbert, Jr.↗