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Lee, R.

Publications and source records attributed to Lee, R..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Validation of magnetized gas-jet experiments to investigate the effects of an external magnetic field on laser-plasma instabilities

Laser-plasma instabilities (LPI) play a detrimental role in energy coupling to the target in inertial confinement fusion (ICF). The recent development of applied strong magnetic fields for use in ICF and laboratory astrophysics experiments has opened opportunities to investigate the role of external magnetic fields on LPIs. Recent numerical studies have shown that stimulated Raman scattering (SRS) can be mitigated by external magnetic fields in the kinetic regime of the instability and warrant systematic experimental studies to validate modelling. To this end, we design experiments at the OMEGA-EP laser facility to investigate the effect of an external perpendicular B-field of 5–30 T on the backscattered light spectrum from a gas-jet target. We present measurements from a proof-of-principle experiment, where the backward-SRS (BSRS) is in the kinetic regime, for which the magnetization is expected to produce the greatest effects on instability growth. New simulations motivated by this experiment are used to inform the proposal of an upgraded experimental design. Our simulation predictions show that the new design is suited to experimentally demonstrating BSRS mitigation by an external magnetic field, despite the magnetization effects on the hydrodynamics, as well as the inherent temporal and spatial variations in plasma conditions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Investigation of Surface Skidding Response of PBX 9501 and PBX 9502

Introduction: Assess the hazards of handling polymer bonder explosives(PBX) for the case of skidding with grit particles in the frictional interface. High explosive (HE) materials tested: PBX 9501 and 9502. High melting point materials at the skidding interface between HE and a substrate is known to increase the probability of ignition by creating hot spots not subject to reduced heating from the melting of HE material. Skidding occurred at peak forces of 6-26 kN normal force, and 0.6-3.4 kN of frictional force. Velocities for skidding range from 5-30 m/s, see figure 7. Sparse amounts of 300 μm silica grit is applied loosely to the HE surface before testing. Previous works have tested ignition by grit. Testing parameters include angle of impact, drop height, grit size, grit density, substrate material. This study focuses on pre ignition conditions and detailed thermal imaging of the frictional interface. Conclusions: Temperature hot spots were observed at high points in HE surface topology. These high points may be created by grit particles. Since these points impact first high frictional work is concentrated and quickly increases temperature. Small amounts of grit do not affect the overall frictional force but do concentrate the frictional work to create hot spots.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Electron acceleration at oblique angles via stimulated Raman scattering at laser irradiance >10 16 W cm –2 μm 2

The generation of hot, directional electrons via laser-driven stimulated Raman scattering (SRS) is a topic of great importance in inertial confinement fusion (ICF) schemes. Little recent research has been dedicated to this process at high laser intensity, in which back, side, and forward scatter simultaneously occur in high energy density plasmas, of relevance to, for example, shock ignition ICF. In this paper, we present an experimental and particle-in-cell (PIC) investigation of hot electron production from SRS in the forward and near-forward directions from a single speckle laser of wavelength λ 0 = 1.053μm, peak laser intensities in the range I 0 = 0.2–1.0×10 17 Wcm –2 and target electron densities between ne = 0.3–1.6% n c , where n c is the plasma critical density. As the intensity and density are increased, the hot electron spectrum changes from a sharp cutoff to an extended spectrum with a slope temperature T = 34 ± 1 keV and maximum measured energy of 350 keV experimentally. Multidimensional PIC simulations indicate that the high energy electrons are primarily generated from SRS-driven electron plasma wave phase fronts with k vectors angled ~50° with respect to the laser axis. These results are consistent with analytical arguments that the spatial gain is maximized at an angle which balances the tendency for the growth rate to be larger for larger scattered light wave angles until the kinetic damping of the plasma wave becomes important. The efficiency of generated high energy electrons drops significantly with a reduction in either laser intensity or target electron density, which is a result of the rapid drop in growth rate of Raman scattering at angles in the forward direction.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Single-molecule sequencing and Hi-C-based proximity-guided assembly of amaranth (Amaranthus hypochondriacus) chromosomes provide insights into genome evolution

Background: Amaranth (Amaranthus hypochondriacus) was a food staple among the ancient civilizations of Central and South America that has recently received increased attention due to the high nutritional value of the seeds, with the potential to help alleviate malnutrition and food security concerns, particularly in arid and semiarid regions of the developing world. Here, we present a reference-quality assembly of the amaranth genome which will assist the agronomic development of the species. Results: Utilizing single-molecule, real-time sequencing (Pacific Biosciences) and chromatin interaction mapping (Hi-C) to close assembly gaps and scaffold contigs, respectively, we improved our previously reported Illumina-based assembly to produce a chromosome-scale assembly with a scaffold N50 of 24.4 Mb. The 16 largest scaffolds contain 98% of the assembly and likely represent the haploid chromosomes (n = 16). To demonstrate the accuracy and utility of this approach, we produced physical and genetic maps and identified candidate genes for the betalain pigmentation pathway. The chromosome-scale assembly facilitated a genome-wide syntenic comparison of amaranth with other Amaranthaceae species, revealing chromosome loss and fusion events in amaranth that explain the reduction from the ancestral haploid chromosome number (n = 18) for a tetraploid member of the Amaranthaceae. Conclusions: The assembly method reported here minimizes cost by relying primarily on short-read technology and is one of the first reported uses of in vivo Hi-C for assembly of a plant genome. Our analyses implicate chromosome loss and fusion as major evolutionary events in the 2n = 32 amaranths and clearly establish the homoeologous relationship among most of the subgenome chromosomes, which will facilitate future investigations of intragenomic changes that occurred post polyploidization.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

Beamline HXN (03-ID, IVU 20): 25 mA Commissioning Radiation Survey Report

A comprehensive radiological survey of the Beamline HXN (03-ID, In-Vacuum Undulator) was conducted on February 27 and March 9, 2015 in accordance with the Beamline HXN (03-ID) Radiation Survey Plan [1]. The purpose of the survey is to verify the shielding integrity of the three, 03-ID beamline enclosures (03-ID-A, 03-ID-B, and 03-ID-C) and transport pipes between 03-ID-A and 03-ID-B, and between 03-ID-B and 03-ID-C. During the surveys the stored beam current varied between 20.75 and 23.15 mA,the ID-03 straight section vacuum was approximately 0.76 ntorr, and front-end slits were open near their hard stop limits.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Beamline CSX (23-ID, EPU 49): 25 mA Commissioning Radiation Survey Report

A comprehensive radiological survey of the Beamline CSX (23-ID-1) was conducted on March 27, 2015 in accordance with the Beamline CSX (23-ID, EPU 49) Radiation Survey Plan [1]. The purpose of the survey is to verify the shielding integrity of the 23-ID beamline First Optics Enclosure (FOE) and downstream beam pipe. At the time of this comprehensive survey, 23-ID-2 beamline was still undergoing technical commissioning and therefore Section II “23 ID-2 FOE, exclusion zone and downstream pipe” could not be completed. During the surveys the stored beam current varied between 21.43 mA and 23.51 mA, the 23-ID straight section vacuum was around 0.44 ntorr, and front-end slits were open near their hard stop limits.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Beamline CHX (11-ID, IVU 20): 25 mA Commissioning Radiation Survey Report

A comprehensive radiological survey of the Beamline CHX (11-ID, In-Vacuum Undulator) was conducted on March 12 and 13, 2015 in accordance with the Beamline CHX (11-ID) Radiation Survey Plan [1]. Some initial setup of the beamline and front end slits was needed and completed on March 09, 2015. The purpose of the survey was to verify the shielding integrity of the two 11-ID beamline enclosures (11-ID-A and 11-ID-B) and transport pipe between 11-ID-A and 11-ID-B.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Beamline SRX (05-ID, IVU 21): 25 mA Commissioning Radiation Survey Report

A comprehensive radiological survey of the Beamline SRX (05-ID, In-Vacuum Undulator) was conducted on March 20, 2015 in accordance with the Beamline SRX (05-ID) Radiation Survey Plan [1]. The purpose of the survey is to verify the shielding integrity of the 3, 05-ID beamline enclosures (05-ID-A, 05-ID-B and 05-ID-D) and the transport pipe in between 05-ID-A, 05-ID-B and 05-ID-D. Enclosure 05-ID-C currently has only a transport pipe connecting 05-ID-B and 05-ID-D, but will serve as the experimental end station as future branch line for the second IVU. During the surveys the stored beam current varied between 21.04 and 24.87 mA, the 05ID straight section vacuum was around 0.43 ntorr, andfront-end slits opened near their hard stop limits.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Beamline IXS (10-ID, IVU 22) 25 mA Commissioning Radiation Survey Report

A comprehensive radiological survey of the Beamline IXS (10-ID, In-Vacuum Undulator) was conducted on March 2 and 4, 2015 in accordance with the Beamline IXS (10-ID) Radiation Survey Plan [1]. The purpose of the survey is to verify the shielding integrity of the four 10-ID beamline enclosures (10-ID-A, 10-ID-B, 10-ID-C and 10-ID-D) and transport pipe between 10-ID-B and 10-ID-C. During the surveys the stored beam current varied between 24.83 and 21.77 mA, the ID-10 straight section vacuum was around 0.58 ntorr, and front-end slits open near their hard stop limits.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Beamline XPD (28-ID, DW 100) Commissioning Radiation Survey Report

A radiological survey of the Beamline XPD (28ID, Damping Wiggler) was conducted on February 19, 2015 between 0030 and 0320 in accordance with the Beamline XPD (28-ID) Radiation Survey Plan [1]. This comprehensive survey was limited in scope because the FE slits were not fully open and the filters were not ALL out.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Safety Integrity Level and Redundancy Requirements for the Top-Off Safety System

The purpose of this analysis is to evaluate the potential impacts resulting from the failure of the Top-Off Safety System (TOSS) and determine the minimum Safety Integrity Level (SIL) for the system. The TOSS consists of a series of apertures, interlocking monitors including current and voltage and electron beam stored current and other controls to ensure that the electron beam injected into the NSLS-II storage ring does not disturb the circulating electron beam and that the electron beam trajectory remains stable.

36 MATERIALS SCIENCE↗
DOE OSTI2013

2012 Annual Site Environmental Report

Brookhaven National Laboratory has one of the most diverse populations of reptiles and amphibians on Long Island. The photo on the front cover is of an eastern box turtle (Terrapene c. carolina) Other species present on the Labora tory site include the snapping turtle (Chelydra serpentine), the spotted turtle (Clemmys guttata), the painted turtle (Chrysemys p. picta), and the musk turtle (Sternotherus odoratus).

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2011

Material Development of Faraday Cup Grids for the Solar Probe Plus Mission

The Solar Probe Plus mission will launch a spacecraft to the Sun to study it's outer atmosphere. One of the instruments on board will be a Faraday Cup (FC) sensor. The FC will determine solar wind properties by measuring the current produced by ions striking a metal collector plate. It will be directly exposed to the Sun and will be subject to the temperature and radiation environment that exist within 10 solar radii. Conducting grids within the FC are biased up to 10 kV and are used to selectively transmit particles based on their energy to charge ratio. We report on the development of SiC grids. Tests were done on nitrogen-doped SiC starting disks obtained from several vendors, including annealing under vacuum at 1400 C and measurement of their electrical properties. SiC grids were manufactured using a photolithographic and plasma-etching process. The grids were incorporated into a prototype FC and tested in a simulated solar wind chamber. The energy cutoffs were measured for both proton and electron fluxes and met the anticipated sensor requirements.

Volz, M. P.↗
NASA NTRS2007

CALISTO: A Cryogenic Far-Infrared/Submillimeter Observatory

We present a design for a cryogenically cooled large aperture telescope for far-infrared astronomy in the wavelength range 30 micrometers to 300 micrometers. The Cryogenic Aperture Large Infrared Space Telescope Observatory, or CALISTO, is based on an off-axis Gregorian telescope having a 4 m by 6 m primary reflector. This can be launched using an Atlas V 511, with the only optical deployment required being a simple hinged rotation of the secondary reflector. The off-axis design, which includes a cold stop, offers exceptionally good performance in terms of high efficiency and minimum coupling of radiation incident from angles far off the direction of maximum response. This means that strong astronomical sources, such as the Milky Way and zodiacal dust in the plane of the solar system, add very little to the background. The entire optical system is cooled to 4 K to make its emission less than even this low level of astronomical emission. Assuming that detector technology can be improved to the point where detector noise is less than that of the astronomical background, we anticipate unprecedented low values of system noise equivalent power, in the vicinity of 10(exp -19) WHz(exp -0.5), through CALISTO's operating range. This will enable a variety of new astronomical investigations ranging from studies of objects in the outer solar system to tracing the evolution of galaxies in the universe throughout cosmic time.

Cryogenic Aperture Large Infrared Space Telescope ↗