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At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Pu2Re3Si5 by Materials Project

Pu2Re3Si5 crystallizes in the tetragonal P4/mnc space group. The structure is three-dimensional. Pu+3.50+ is bonded in a 9-coordinate geometry to nine Si4- atoms. There are a spread of Pu–Si bond distances ranging from 2.88–3.21 Å. There are two inequivalent Re+4.33+ sites. In the first Re+4.33+ site, Re+4.33+ is bonded to six Si4- atoms to form a mixture of distorted corner, edge, and face-sharing ReSi6 octahedra. The corner-sharing octahedral tilt angles are 48°. There are a spread of Re–Si bond distances ranging from 2.45–2.54 Å. In the second Re+4.33+ site, Re+4.33+ is bonded in a distorted hexagonal planar geometry to six Si4- atoms. There are four shorter (2.46 Å) and two longer (2.70 Å) Re–Si bond lengths. There are three inequivalent Si4- sites. In the first Si4- site, Si4- is bonded in a 9-coordinate geometry to three equivalent Pu+3.50+, four Re+4.33+, and two equivalent Si4- atoms. Both Si–Si bond lengths are 2.59 Å. In the second Si4- site, Si4- is bonded in a 11-coordinate geometry to four equivalent Pu+3.50+, three Re+4.33+, and four Si4- atoms. Both Si–Si bond lengths are 2.70 Å. In the third Si4- site, Si4- is bonded in a 9-coordinate geometry to four equivalent Pu+3.50+, four equivalent Re+4.33+, and one Si4- atom. The Si–Si bond length is 2.42 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ReIr3 by Materials Project

ReIr3 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Re is bonded to six equivalent Re and six equivalent Ir atoms to form ReRe6Ir6 cuboctahedra that share corners with six equivalent ReRe6Ir6 cuboctahedra, corners with six equivalent IrIr12 cuboctahedra, edges with six equivalent ReRe6Ir6 cuboctahedra, edges with eighteen IrRe3Ir9 cuboctahedra, faces with six equivalent ReRe6Ir6 cuboctahedra, and faces with twelve equivalent IrRe3Ir9 cuboctahedra. All Re–Re bond lengths are 2.74 Å. All Re–Ir bond lengths are 2.72 Å. There are five inequivalent Ir sites. In the first Ir site, Ir is bonded to three equivalent Re and nine Ir atoms to form IrRe3Ir9 cuboctahedra that share corners with twelve equivalent IrRe3Ir9 cuboctahedra, edges with six equivalent ReRe6Ir6 cuboctahedra, edges with eighteen IrRe3Ir9 cuboctahedra, faces with six equivalent ReRe6Ir6 cuboctahedra, and faces with twelve IrRe3Ir9 cuboctahedra. There are six shorter (2.74 Å) and three longer (2.78 Å) Ir–Ir bond lengths. In the second Ir site, Ir is bonded to twelve Ir atoms to form IrIr12 cuboctahedra that share corners with six equivalent ReRe6Ir6 cuboctahedra, corners with six equivalent IrIr12 cuboctahedra, edges with six equivalent ReRe6Ir6 cuboctahedra, edges with eighteen IrRe3Ir9 cuboctahedra, and faces with eighteen IrRe3Ir9 cuboctahedra. All Ir–Ir bond lengths are 2.74 Å. In the third Ir site, Ir is bonded to three equivalent Re and nine Ir atoms to form IrRe3Ir9 cuboctahedra that share corners with seventeen IrRe3Ir9 cuboctahedra, edges with six equivalent ReRe6Ir6 cuboctahedra, edges with sixteen IrRe3Ir9 cuboctahedra, faces with six equivalent ReRe6Ir6 cuboctahedra, and faces with fifteen IrRe3Ir9 cuboctahedra. All Ir–Re bond lengths are 2.72 Å. There are six shorter (2.74 Å) and three longer (2.78 Å) Ir–Ir bond lengths. In the fourth Ir site, Ir is bonded to sixteen Ir atoms to form IrIr16 cuboctahedra that share corners with six equivalent ReRe6Ir6 cuboctahedra, corners with sixteen IrRe3Ir9 cuboctahedra, edges with six equivalent ReRe6Ir6 cuboctahedra, edges with eighteen IrRe3Ir9 cuboctahedra, and faces with thirty-four IrRe3Ir9 cuboctahedra. There are a spread of Ir–Ir bond distances ranging from 2.74–5.49 Å. In the fifth Ir site, Ir is bonded to three equivalent Re and nine Ir atoms to form IrRe3Ir9 cuboctahedra that share corners with seventeen IrRe3Ir9 cuboctahedra, edges with six equivalent ReRe6Ir6 cuboctahedra, edges with sixteen IrRe3Ir9 cuboctahedra, faces with six equivalent ReRe6Ir6 cuboctahedra, and faces with fifteen IrIr16 cuboctahedra. All Ir–Re bond lengths are 2.72 Å. All Ir–Ir bond lengths are 2.74 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on ThReB4 by Materials Project

ThReB4 crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. Th is bonded in a 2-coordinate geometry to four equivalent Re and fourteen B atoms. There are two shorter (3.05 Å) and two longer (3.19 Å) Th–Re bond lengths. There are a spread of Th–B bond distances ranging from 2.76–2.86 Å. Re is bonded in a 10-coordinate geometry to four equivalent Th, one Re, and ten B atoms. The Re–Re bond length is 2.73 Å. There are a spread of Re–B bond distances ranging from 2.35–2.47 Å. There are three inequivalent B sites. In the first B site, B is bonded in a 3-coordinate geometry to four equivalent Th, two equivalent Re, and three B atoms. There is one shorter (1.76 Å) and two longer (1.88 Å) B–B bond length. In the second B site, B is bonded in a 9-coordinate geometry to four equivalent Th, two equivalent Re, and three B atoms. The B–B bond length is 1.92 Å. In the third B site, B is bonded in a 3-coordinate geometry to two equivalent Th, four equivalent Re, and three B atoms. The B–B bond length is 1.71 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Rhenium Isotope Reconnaissance of Uranium Ore Concentrates

Exploration of natural isotopic variations of the element rhenium (Re) is in its infancy, with initial studies revealing isotopic fractionation in a variety of geological materials. Here, in this work, we investigate Re isotope variation as a new geochemical tool, given its redox-sensitive properties and affinity for organic matter and sulfides. In this work, Re abundance and isotope ratio data were collected from uranium ore concentrates (UOCs) across a variety of depositional ages, locations, geologic settings, and deposit types. Ore types from which the UOC were derived include sandstone, unconformity, and quartz-pebble (QP) conglomerate. To isolate Re from the U-rich matrix of UOCs, a new purification method utilizing DGA ion exchange resin was developed. We found that UOCs exhibit a wide range of Re isotope ratios, with sandstone ore-derived UOCs having the isotopically lightest values, QP conglomerate ore-derived UOCs having the heaviest, and unconformity ore-derived UOCs in between (with some overlap with sandstone UOCs). The Re isotope ratio range observed in UOCs extends previously reported values by more than a factor of two. Industrial processing (e.g., incomplete recovery of Re from ore, contamination, fractionation during processing) may play a role in the isotopic variability in the UOCs. However, systematic differences between ore types suggest that the depositional setting is a significant factor. For nuclear forensic investigations, Re isotopic compositions combined with data from other isotopic systems provide geochemical signatures that can aid in provenance assessment of UOCs. Regardless of the specific causes for the wide range of Re isotope ratios in UOCs, these initial data indicate Re is a promising tool for nuclear forensic investigations on samples from early in the nuclear fuel cycle.

58 GEOSCIENCES↗
DOE OSTI2024

The Global Biogeochemical Cycle of Rhenium

Here, this paper is the first comprehensive synthesis of what is currently known about the different natural and anthropogenic fluxes of rhenium (Re) on Earth's surface. We highlight the significant role of anthropogenic mobilization of Re, which is an important consideration in utilizing Re in the context of a biogeochemical tracer or proxy. The largest natural flux of Re derives from chemical weathering and riverine transport to the ocean (dissolved = 62 × 10 6 g yr -1 and particulate = 5 × 10 6 g yr -1 ). This review reports a new global average [Re] of 16 ± 2 pmol L -1 , or 10 ± 1 pmol L -1 for the inferred pre-anthropogenic concentration without human impact, for rivers draining to the ocean. Human activity via mining (including secondary mobilization), coal combustion, and petroleum combustion mobilize approximately 560 × 10 6 g yr -1 Re, which is more than any natural flux of Re. There are several poorly constrained fluxes of Re that merit further research, including: submarine groundwater discharge, precipitation (terrestrial and oceanic), magma degassing, and hydrothermal activity. The mechanisms and the main host phases responsible for releasing (sources) or sequestrating (sinks) these fluxes remain poorly understood. This study also highlights the use of dissolved [Re] concentrations as a tracer of oxidation of petrogenic organic carbon, and stable Re isotopes as proxies for changes in global redox conditions.

58 GEOSCIENCES↗
DOE OSTI2020

Runaway electron transport in stochastic toroidal magnetic fields

Here, we study the transport and confinement properties of runaway electrons (RE) in the presence of magnetic fields with perturbations producing different levels of stochasticity. We use Kinetic Orbit Runaway Electron Code (KORC) [Carbajal et al. , Phys. Plasmas 24, 042512 (2017) and del-Castillo-Negrete et al. , Phys. Plasmas 25, 056104 (2018)] for simulating the full-orbit (FO) and guiding-center (GC) dynamics of RE in perturbed magnetic fields that exhibit magnetic islands. We extend previous works on this problem [Wingen et al. , Nucl. Fusion 46, 941 (2006); Izzo et al. , Nucl. Fusion 51, 063032 (2011); Papp et al. , Nucl. Fusion 51, 043004 (2011); V. Izzo and P. Parks, Phys. Plasmas 24, 060705 (2017); and Sommariva et al. , Nucl. Fusion 58, 016043 (2018)] by studying in detail full-orbit effects on the RE dynamics. We quantify FO effects on RE transport by performing one-to-one comparisons between FO and GC simulations. It is found that, for the magnetic field configurations considered, GC simulations predict twice the RE losses of FO simulations for 1 MeV and four times the RE losses of FO simulations for 25 MeV. Similarly, we show how different GC and FO dynamics of RE moving around magnetic islands can be, especially in the scenario where the RE Larmor radius is on the order of the size of the magnetic island. We also study the role of rotation of the magnetic islands on RE confinement, and we find that low-frequency toroidal rotation has no observable effect on RE transport in the cases considered. These results shed some light into the potential of avoidance or mitigation mechanisms based on magnetic perturbations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Numerical simulation of the hot-tail runaway electron production mechanism using CQL3D and comparison with Smith–Verwichte analytical model

Abstract The hot-tail mechanism of runaway electron (RE) production (Harvey et al 2000 Phys. Plasmas 7 4590) is the primary source of RE in the case of rapidly cooling tokamak plasma. Quantifying this mechanism is very important as it can provide most of the post-thermal-quench (TQ) current, or a seed current for the secondary source of RE through the avalanche mechanism. An analytic model which omits pitch-angle scattering is often used in literature for estimating the hot-tail RE density (Smith and Verwichte 2008 Phys. Plasmas 15 072502). In the present study, we use the CQL3D bounce-averaged Fokker–Planck code (Harvey and McCoy 1992 Proc. IAEA Technical Committee Meeting on Advances in Simulation and Modeling of Thermonuclear Plasmas p 527) to test the limits of validity of the model. In particular, we examine the cases of Z = 1 and Z = 18 ions, for sets of different initial temperature, density, electric field and the characteristic time of temperature decay. We show that for Z = 1 plasma, the ratio of RE density computed by CQL3D to that estimated from the model is within 0.6–6.0 in studied cases. For the Z = 18 case, this factor is systematically a much smaller number, typically 0.02–0.6. We suggest a simple correction to the model that narrows down the range of this ratio to 0.3–3.8 in all of the cases, including Z = 1 and Z = 18 plasmas.

Physics↗
DOE OSTI2020

Materials Data on Sc2Re3Si4 by Materials Project

Sc2Re3Si4 crystallizes in the tetragonal P4_12_12 space group. The structure is three-dimensional. Sc3+ is bonded to seven Si4- atoms to form ScSi7 pentagonal bipyramids that share corners with four equivalent ReSi6 octahedra, corners with six equivalent ScSi7 pentagonal bipyramids, corners with five equivalent ReSi6 pentagonal pyramids, edges with three equivalent ScSi7 pentagonal bipyramids, edges with two equivalent ReSi6 pentagonal pyramids, faces with two equivalent ReSi6 octahedra, faces with two equivalent ScSi7 pentagonal bipyramids, and faces with four equivalent ReSi6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 41–50°. There are a spread of Sc–Si bond distances ranging from 2.71–2.93 Å. There are two inequivalent Re+3.33+ sites. In the first Re+3.33+ site, Re+3.33+ is bonded to six Si4- atoms to form ReSi6 octahedra that share corners with four equivalent ReSi6 octahedra, corners with eight equivalent ScSi7 pentagonal bipyramids, corners with six equivalent ReSi6 pentagonal pyramids, faces with four equivalent ScSi7 pentagonal bipyramids, and faces with four equivalent ReSi6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 49°. There are a spread of Re–Si bond distances ranging from 2.52–2.63 Å. In the second Re+3.33+ site, Re+3.33+ is bonded to six Si4- atoms to form distorted ReSi6 pentagonal pyramids that share corners with three equivalent ReSi6 octahedra, corners with five equivalent ScSi7 pentagonal bipyramids, corners with four equivalent ReSi6 pentagonal pyramids, edges with two equivalent ScSi7 pentagonal bipyramids, edges with four equivalent ReSi6 pentagonal pyramids, faces with two equivalent ReSi6 octahedra, and faces with four equivalent ScSi7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 37–46°. There are a spread of Re–Si bond distances ranging from 2.42–2.58 Å. There are two inequivalent Si4- sites. In the first Si4- site, Si4- is bonded in a 9-coordinate geometry to three equivalent Sc3+, five Re+3.33+, and one Si4- atom. The Si–Si bond length is 2.56 Å. In the second Si4- site, Si4- is bonded in a 9-coordinate geometry to four equivalent Sc3+, four Re+3.33+, and one Si4- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TlRe6Se8Cl3 by Materials Project

Re6TlSe8Cl3 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are six inequivalent Re3+ sites. In the first Re3+ site, Re3+ is bonded to four Se2- and one Cl1- atom to form a mixture of corner and edge-sharing ReSe4Cl square pyramids. There are a spread of Re–Se bond distances ranging from 2.52–2.56 Å. The Re–Cl bond length is 2.44 Å. In the second Re3+ site, Re3+ is bonded to five Se2- atoms to form a mixture of corner and edge-sharing ReSe5 square pyramids. There are a spread of Re–Se bond distances ranging from 2.54–2.67 Å. In the third Re3+ site, Re3+ is bonded to five Se2- atoms to form a mixture of corner and edge-sharing ReSe5 square pyramids. There are a spread of Re–Se bond distances ranging from 2.54–2.66 Å. In the fourth Re3+ site, Re3+ is bonded to five Se2- atoms to form ReSe5 square pyramids that share corners with three ReSe4Cl square pyramids and edges with five ReSe5 square pyramids. There are a spread of Re–Se bond distances ranging from 2.53–2.66 Å. In the fifth Re3+ site, Re3+ is bonded to four Se2- and one Cl1- atom to form ReSe4Cl square pyramids that share corners with two ReSe5 square pyramids and edges with four ReSe4Cl square pyramids. There are one shorter (2.54 Å) and three longer (2.55 Å) Re–Se bond lengths. The Re–Cl bond length is 2.43 Å. In the sixth Re3+ site, Re3+ is bonded to four Se2- and one Cl1- atom to form ReSe4Cl square pyramids that share corners with two ReSe5 square pyramids and edges with four ReSe4Cl square pyramids. There are a spread of Re–Se bond distances ranging from 2.53–2.57 Å. The Re–Cl bond length is 2.41 Å. Tl1+ is bonded in a 9-coordinate geometry to five Cl1- atoms. There are a spread of Tl–Cl bond distances ranging from 3.11–3.41 Å. There are eight inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 4-coordinate geometry to four Re3+ atoms. In the second Se2- site, Se2- is bonded in a 4-coordinate geometry to four Re3+ atoms. In the third Se2- site, Se2- is bonded in a 4-coordinate geometry to three Re3+ atoms. In the fourth Se2- site, Se2- is bonded in a 5-coordinate geometry to three Re3+ atoms. In the fifth Se2- site, Se2- is bonded in a 9-coordinate geometry to three Re3+ atoms. In the sixth Se2- site, Se2- is bonded in a 4-coordinate geometry to four Re3+ atoms. In the seventh Se2- site, Se2- is bonded in a 5-coordinate geometry to three Re3+ atoms. In the eighth Se2- site, Se2- is bonded in a 7-coordinate geometry to three Re3+ atoms. There are three inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a 2-coordinate geometry to one Re3+ and one Tl1+ atom. In the second Cl1- site, Cl1- is bonded in a 1-coordinate geometry to one Re3+ and two equivalent Tl1+ atoms. In the third Cl1- site, Cl1- is bonded in a 1-coordinate geometry to one Re3+ and two equivalent Tl1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HoFe11Re by Materials Project

HoReFe11 crystallizes in the orthorhombic Imm2 space group. The structure is three-dimensional. Ho is bonded in a 12-coordinate geometry to one Re and nineteen Fe atoms. The Ho–Re bond length is 3.10 Å. There are a spread of Ho–Fe bond distances ranging from 3.01–3.24 Å. Re is bonded in a 1-coordinate geometry to one Ho and thirteen Fe atoms. There are a spread of Re–Fe bond distances ranging from 2.37–2.88 Å. There are six inequivalent Fe sites. In the first Fe site, Fe is bonded to two equivalent Ho, one Re, and nine Fe atoms to form a mixture of edge, corner, and face-sharing FeHo2Fe9Re cuboctahedra. There are a spread of Fe–Fe bond distances ranging from 2.34–2.60 Å. In the second Fe site, Fe is bonded to two equivalent Ho and ten Fe atoms to form a mixture of distorted edge, corner, and face-sharing FeHo2Fe10 cuboctahedra. There are four shorter (2.60 Å) and two longer (2.70 Å) Fe–Fe bond lengths. In the third Fe site, Fe is bonded to two equivalent Ho, two equivalent Re, and eight Fe atoms to form a mixture of distorted edge, corner, and face-sharing FeHo2Fe8Re2 cuboctahedra. There are two shorter (2.61 Å) and two longer (2.69 Å) Fe–Fe bond lengths. In the fourth Fe site, Fe is bonded to two equivalent Ho, one Re, and nine Fe atoms to form a mixture of distorted edge, corner, and face-sharing FeHo2Fe9Re cuboctahedra. All Fe–Fe bond lengths are 2.61 Å. In the fifth Fe site, Fe is bonded in a 1-coordinate geometry to one Ho, one Re, and twelve Fe atoms. All Fe–Fe bond lengths are 2.88 Å. In the sixth Fe site, Fe is bonded in a 12-coordinate geometry to one Ho, two equivalent Re, and eleven Fe atoms. The Fe–Fe bond length is 2.38 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Validating the rhenium proxy for rock organic carbon oxidation using weathering profiles

Chemical weathering over geological timescales acts as a source or sink of atmospheric carbon dioxide (CO 2 ), while influencing long-term redox cycling and atmospheric oxygen (O 2 ) at Earth's surface. There is a growing recognition that the oxidative weathering of rock organic carbon (OC petro ) can release more CO 2 than is locally drawn down by silicate weathering, and may vary due to changes in erosion and climate. The element rhenium (Re) has emerged as a proxy to track the oxidative weathering of OC petro , yet uncertainties in its application remain namely that we lack a systematic assessment of the comparative mobility of Re and OC petro during sedimentary rock weathering. Here we measure Re and OC petro loss across gradients in rock weathering at 9 global sites, spanning a range of initial OC petro values from ~0.2 % to >10 %. We use titanium to account for volume changes during weathering and assess Re and OC petro loss alongside major elements that reflect silicate (Na, Mg), carbonate (Ca, Mg) and sulfide (S) weathering. Across the dataset, Re loss is correlated with OC petro loss but not with loss of any other major element. Further, across the weathering profiles, the average molar ratio of OC petro to Re loss was 0.84 ± 0.15, with 8 out of 9 sites having a ratio >0.74. At one site (Marcellus Shale), the average ratio was lower at 0.58 ± 0.11. The excess loss of Re matches expectations that, typically, between ~0 and 20 % of the Re liberated by sedimentary rock weathering derives from silicate or sulfide phases, while some OC petro may be physically or chemically protected from weathering. Overall, our measurements provide validation for the Re proxy of OC petro oxidation and allow future work to further improve our knowledge of regional and global-scale rates of this important source of CO 2 in the geochemical carbon cycle.

58 GEOSCIENCES↗
DOE OSTI2023

In Situ High-Temperature Structural Analysis of High-Entropy Rare-Earth Sesquioxides

High-entropy rare-earth (RE) sesquioxides (RE 2 O 3 ) containing five cations in equimolar amounts have been investigated for a variety of applications, but little is known about their polymorphic behavior and coefficient of thermal expansion. Here, in this work, we evaluate the effect of the average ionic radius (AIR) on the polymorphism of high-entropy RE 2 O 3 . Powder samples of compositions 1 (Lu,Y,Ho,Nd,La) 2 O 3 (AIR = 0.938 Å) and 2 (Gd,Eu,Sm,Nd,La) 2 O 3 (AIR = 0.982 Å) were synthesized via a wet chemical method, and bead samples were prepared for aerodynamic levitation by melting the powders in a copper hearth. Structural transitions were monitored upon cooling from the melt to 1000 °C via in situ X-ray diffraction on aerodynamically levitated samples. The phase evolution was liquid, hexagonal H-type, and monoclinic B-type for composition 1 and liquid, cubic X-type, H-type, and B-type for composition 2. Based on their AIR, the general polymorphic transformations of the high-entropy RE 2 O 3 follow the trend of single-RE RE 2 O 3 , but the transition temperatures differ from those of single-RE RE 2 O 3 . The coefficient of thermal expansion values of the B-type phase of compositions 1 and 2 are similar to those of Gd 2 O 3 and previously published high-entropy RE 2 O 3 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Runaway electron seed formation at reactor-relevant temperature

Systematic variation of the pre-disruption core electron temperature (T e ) from 1 to 12 keV using an internal transport barrier scenario reveals a dramatic increase in the production of ‘seed’ runaway electrons (REs), ultimately accessing near-complete conversion of the pre-disruption current into sub-MeV RE current. Injected Ar pellets are observed to ablate more intensely and promptly as T e rises. At high T e , the observed ablation exceeds predictions from published thermal ablation models. Simultaneously, the thermal quench (TQ) is observed to significantly shorten with increasing T e —a surprising result. While the reason for the shorter TQ is not yet understood, candidate mechanisms include: insufficiently accurate thermal ablation models, enhanced ablation driven by the seed RE population, or significant parallel heat transport along stochastic fields. Kinetic modeling that self-consistently treats the plasma cooling via radiation, the induced electric field, and the formation of the seed RE is performed. Including the combined effect of the inherent dependence of hot-tail RE seeding on T e together with the shortened TQ, modeling recovers the progression towards near-complete conversion of the pre-disruption current to RE current as T e rises. Measurement of the HXR spectrum during the early current quench (CQ) reveals a trend of decreasing energy with pre-disruption T e . At the very highest T e (≈ 12 keV), ≈ 100% conversion of the thermal current to runaway current is found. The energy of this peculiar RE beam is inferred to be sub-MeV as it emits vanishingly few MeV hard x-rays (HXRs). These measurements demonstrate novel TQ dynamics as Te is varied and illustrate the limitations of treating the RE seed formation problem without considering the inter-related dependencies of the pellet ablation, radiative energy loss, and resultant variations of the TQ duration. Finally, if the observed shortening of the TQ with increasing T e extends to fusion-grade plasmas, than their propensity to form large quantities of RE seeds at high T e may be far worse than previously thought. Positively, the high T e scenario in DIII-D produces REs so prodigiously that it can serve as a meaningful new platform for demonstrating RE avoidance techniques.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Toroidal modeling of runaway electron loss due to 3-D fields in DIII-D and COMPASS

The 3-D field induced relativistic runaway electron (RE) loss has been simulated for DIII-D, COMPASS and ITER plasmas, utilizing the MARS-F code incorporated with the recently developed and updated RE orbit module (REORBIT). Modeling shows effectively 100% loss of a post-disruption, high-current runaway beam in DIII-D, due to the 1 kG level of magnetic field perturbation produced by a fast growing n = 1 resistive kink instability. The RE loss is shown to be independent of the particle energy or the initial location of particles in the configuration space. Applied resonant magnetic perturbation (RMP) fields from in-vessel coils are not effective for RE beam mitigation in DIII-D, but do produce finite (>10%) RE loss in COMPASS, consistent with experimental observations in above two devices. The major reasons for this difference in RE control by RMP between these two devices are (i) the coil proximity to the RE beam and (ii) the effective coil current scaling versus the machine size and the toroidal magnetic field. About 10% RE loss fraction is also predicted for an ITER 15 MA scenario with pre-disruption plasma, highlighting the role of the plasma response. Up to 30% loss is computed, however, by artificially scaling the equilibrium pressure to zero. This is due to the more resistive plasma response and stronger resulting field line stochasticity. Distributions of the lost REs to the limiting surface show poloidally peaked profile near the high-field-side in both DIII-D and COMPASS, covering about 100o poloidal angle. Higher perturbation field level and/or higher particle energy also result in REs being lost to the low-field-side of the limiting surface of these two devices, increasing the effective wetted area. Finally, for the modeled ITER plasmas, the applied RMP field, with optimal poloidal spectrum that maximizes the edge localized mode control, leads to REs being lost to the lower divertor region of the limiting surface within a narrow poloidal band.

3-D field↗
DOE OSTI2020

Materials Data on Be2Re by Materials Project

Be2Re is Hexagonal Laves structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Be sites. In the first Be site, Be is bonded to six equivalent Be and six equivalent Re atoms to form a mixture of face, edge, and corner-sharing BeBe6Re6 cuboctahedra. All Be–Be bond lengths are 2.20 Å. All Be–Re bond lengths are 2.57 Å. In the second Be site, Be is bonded to six Be and six equivalent Re atoms to form a mixture of face, edge, and corner-sharing BeBe6Re6 cuboctahedra. There are two shorter (2.16 Å) and two longer (2.22 Å) Be–Be bond lengths. There are two shorter (2.56 Å) and four longer (2.57 Å) Be–Re bond lengths. Re is bonded in a 12-coordinate geometry to twelve Be and four equivalent Re atoms. There are three shorter (2.68 Å) and one longer (2.69 Å) Re–Re bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Re3B by Materials Project

Re3B crystallizes in the orthorhombic Cmcm space group. The structure is two-dimensional and consists of two Re3B sheets oriented in the (0, 1, 0) direction. there are two inequivalent Re sites. In the first Re site, Re is bonded in a 2-coordinate geometry to three equivalent B atoms. There are two shorter (2.25 Å) and one longer (2.59 Å) Re–B bond lengths. In the second Re site, Re is bonded in a distorted L-shaped geometry to two equivalent B atoms. Both Re–B bond lengths are 2.22 Å. B is bonded in a 6-coordinate geometry to eight Re atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Re2P by Materials Project

Re2P crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Re sites. In the first Re site, Re is bonded in a 1-coordinate geometry to three equivalent P atoms. There are one shorter (2.39 Å) and two longer (2.57 Å) Re–P bond lengths. In the second Re site, Re is bonded in a 2-coordinate geometry to four equivalent P atoms. There are two shorter (2.35 Å) and two longer (2.75 Å) Re–P bond lengths. P is bonded in a 7-coordinate geometry to seven Re atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al(CuRe)2 by Materials Project

Al(ReCu)2 crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Re is bonded in a 11-coordinate geometry to five equivalent Re, six equivalent Cu, and four equivalent Al atoms. There are one shorter (2.74 Å) and four longer (3.13 Å) Re–Re bond lengths. There are two shorter (2.58 Å) and four longer (2.64 Å) Re–Cu bond lengths. All Re–Al bond lengths are 2.95 Å. Cu is bonded in a 2-coordinate geometry to six equivalent Re and two equivalent Al atoms. Both Cu–Al bond lengths are 2.30 Å. Al is bonded in a square co-planar geometry to eight equivalent Re and four equivalent Cu atoms.

36 MATERIALS SCIENCE↗