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At least 217 records · Page 12

Studies in Quantum Field Theory and Astroparticle Physics

OVERVIEW OF THE RESEARCH PLAN: Task 1: Theoretical Research in High Energy Physics Prof. Alford investigated the phases and properties of matter at the highest densities achieved in nature. His main focus was on quark matter and its manifestations and signatures in neutron stars. His work is directly relevant to both the Cosmic and the Energy Frontiers. Prof. Bender developed PT-symmetric quantum theory, which is a complex generalization of conventional Hermitian quantum theory. During the grant period, he constructed and analyzed new PT-symmetric field theoretic models that exhibit symmetry breaking. He also worked on other fundamental problems in theoretical physics. His work falls under the Intensity Frontier classification. Prof. Bernard continued to work on lattice gauge theory and associated issues in chiral perturbation theory. His research focused primarily on the calculation of weak matrix elements relevant to tests of the standard model and the search for new physics at the Intensity Frontier. This work included both direct numerical simulations in QCD and the development of theoretical tools to analyze the simulations and facilitate the comparison with Intensity-Frontier experiments. Prof. Ferrer continued working on dark matter and other topics in theoretical particle cosmology. His research focused on weakly interacting massive particles relevant to both the Cosmic and the Energy Frontiers, and on dark photons relevant to the Intensity Frontier. Prof. Ogilvie continued his work on lattice gauge theory and the phase structure of gauge theories. His research on the properties of confined, conformal and Higgs phases is relevant to the Energy Frontier, as well as addressing fundamental issues of broad theoretical interest. Task 2: Experimental Research at the Cosmic Frontier in High Energy Physics. Over the three year grant period, Profs. Buckley and Krawczynski continued research under the Cosmic Frontier. Prof. Buckley's group worked on two Cosmic Frontier projects (VERITAS and LZ), and conducted research in dark matter science and other areas of particle astrophysics. Buckley’s group worked on the conceptual design of the next generation ground-based gamma-ray experiment (CTA) and on the development of camera electronics for a 2-mirror SCT prototype telescope. Buckley's group also continued work on GaN photodetector detector development as part of the Instrumentation Frontier (Detector R&D) including work with the LAPPD group on the development robust amorphous photocathodes for very large area MCP-based photodetectors and ongoing development of deep UV photosensors for liquid Ar and Xenon Direct Dark matter detection. Prof. Krawczynski's group worked on two Cosmic Frontier topics: astrophysical tests of Lorentz Invariance and CPT symmetries at the Planck energy scale with the VERITAS gamma-ray experiment, and the search for dark matter particles with indirect detection experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Measurement of isospin mixing in {sup 80}Zr{sup *} at finite temperature

Isospin mixing induced by Coulomb interaction has been measured in the compound nucleus Z = N = 40 {sup 80}Zr at T{approx}2 MeV produced in a fusion-evaporation reaction. The observable sensitive to the isospin purity of the compound nucleus is the Giant Dipole Resonance {gamma} decay. The degree of mixing of the compound nucleus has been obtained via Statistical Model analysis of the measured {gamma} spectrum.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Predicted performance of a tangential viewing hard x-ray camera for the DIII-D high field side lower hybrid current drive experiment

High field side launch of lower hybrid current drive (LHCD) has improved accessibility and penetration over low field side launch on DIII-D. Simulations predict single pass absorption under a wide range of plasma conditions. Hard x-ray (HXR) measurement of LHCD generated fast electron bremsstrahlung (50–250 keV) will validate wave propagation and absorption. Emissivity profiles are recovered from one-dimensional inversion of HXR brightness to determine LH damping location, fast electron slowing down time, and some indication of the fast electron energy. The camera will be implemented by populating 32 tangential sightlines of the existing Gamma Ray Imager with Kromek SPEARTM Cadmium Zinc Telluride (CZT) detectors sensitive to 10–1000 keV photons with 10 keV energy resolution. Expected count rates allow for <0.5 ms time resolution. Pulses are processed using 50 ns shaping time Cremat CR-200 Gaussian shaping modules and are digitized by 25 MHz D-TACQ ACQ216 digitizers. The performance of the HXR camera is evaluated by comparing predicted fast electron density profiles and inverted synthetic brightnesses obtained from the ray-tracing/Fokker–Planck codes GENRAY/CQL3D. Inversions closely matched predicted fast electron profiles for a range of experimental parameters.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

STS-37 Breakfast / Ingress / Launch & ISO Camera Views

The primary objective of the STS-37 mission was to deploy the Gamma Ray Observatory. The mission was launched at 9:22:44 am on April 5, 1991, onboard the space shuttle Atlantis. The mission was led by Commander Steven Nagel. The crew was Pilot Kenneth Cameron and Mission Specialists Jerry Ross, Jay Apt, and Linda Godwing. This videotape shows the crew having breakfast on the launch day, with the narrator introducing them. It then shows the crew's final preparations and the entry into the shuttle, while the narrator gives information about each of the crew members. The countdown and launch is shown including the shuttle separation from the solid rocket boosters. The launch is reshown from 17 different camera views. Some of the other camera views were in black and white.

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Properties of haze in the atmosphere of Triton

Voyager UV spectrometer measurements of CH4 and haze of the Triton atmosphere combined with the haze brightness profile determined by the narrow angle camera are used to infer a haze optical thickness of 0.024 at 1500 A and 0.0078 in the spectral range of the narrow angle camera centered at 4700A, rho/gamma = 0.36 +/- 0.1 g/cu cm (gamma is the quantum yield of condensate), and values of r(c) varying from 0.1 +/- 0.02 micron at 30 km to 0.15 +/- 0.03 micron near the surface. Other auxiliary properties of the haze are also determined. The value found for rho/gamma corresponds to a packing coefficient of 0.6 gamma if C2H4 is the main condensible species.

Krasnopolsky, V. A.↗

STS-37/Atlantis/GRO

The primary objective of the STS-37 mission was to deploy the Gamma Ray Observatory. The mission was launched at 9:22:44 am on April 5, 1991, onboard the space shuttle Atlantis. The mission was led by Commander Steven Nagel. The crew was Pilot Kenneth Cameron and Mission Specialists Jerry Ross, Jay Apt, and Linda Godwing. This videotape shows the crew having breakfast on the launch day. It then shows the crew's final preparations and the entry into the shuttle. The countdown and launch is shown including the shuttle separation from the solid rocket boosters. The launch is reshown from several different camera views. Some of the other camera views were in black and white. The deployment of the Gamma Ray Observatory is shown, including an unscheduled spacewalk to deploy the high gain antenna. The landing at Edwards Air Force Base is shown. The landing is also shown from several different cameras views.

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Upper Limits on TeV Gamma-Ray Emission from Active Galactic Nuclei

The results of a search for TeV gamma-ray emission from 35 active galactic nuclei (AGNS) using the Whipple Observatory High Resolution Atmospheric Cerenkov Camera are reported. Fifteen of these objects have been detected at GeV energies by the EGRET experiment on the Compton Gamma Ray Observatory. None of the 35 objects gave a signal at the 3 sigma level; Mrk 421 remains the only AGN detected at TeV energies. The absence of a TeV signal may imply a change in the primary source spectrum and/or the effect of absorption by pair production on intergalactic infrared photons.

Kerrick, A. D.↗

Gamma Imaging and Mapping Advancements

The SRNL developed GrayQb{sup TM} gamma mapping system has been successfully deployed in field situations. Currently, to get the image from the GrayQb{sup TM} the internal Phosphor Storage Plate (PSP) used to capture radiation images must be recovered and scanned by a ScanX Scanner. Upgrades are being implemented which will enable the GrayQB{sup TM} to read the PSP using a camera and red LEDs then transmit results to a remote location. This will greatly reduce personnel interaction, increasing safety as well as eliminating the need for the ScanX. Upgrades have been based off of the MiniMax, a Los Alamos National Laboratory developed PSP reading device constructed with a Nikon DSLR and a red LED flash to obtain the images from the PSP. The electronics in the upgraded GrayQb{sup TM} need to be both functional and environmentally rugged. A PC/104 was chosen for its wider operational temperature range and its physical durability. The Sony α7 ii and the Mightex are the candidate cameras for the upgrades based on test results. PSPs were exposed to gamma radiation sources at SRS's Health Physics Instrumentation Calibration Laboratory (HPICL). PSPs were tested with both Am-241 and Cs-137. Linear intensity increased with dose verifying UV image simulations. Data collected enabled the PSP intensity to be referenced to a total dose. Further work includes design and implementation of a 3D printed housing for the new camera system. The housing will include the camera, light flash, PSP holders, tungsten dual pinhole, PC/104, dosimeter, and a battery or tethering option. Once the housing is finalized further testing at the HPICL facility is planned for early August. During this testing, the final housing design will capture both Am-241 and Cs-137 images.

3D PRINTING↗

Detection of the Crab Nebula with the 9.7 m prototype Schwarzschild-Couder telescope

The Schwarzschild-Couder Telescope (SCT) is a telescope concept proposed for the Cherenkov Telescope Array. It employs a dual-mirror optical design to remove comatic aberrations over an 8° field of view, and a high-density silicon photomultiplier camera (with a pixel resolution of 4 arcmin) to record Cherenkov emission from cosmic ray and gamma-ray initiated particle cascades in the atmosphere. Additionally, the prototype SCT (pSCT), comprising a 9.7 m diameter primary mirror and a partially instrumented camera with 1536 pixels, has been constructed at the Fred Lawrence Whipple Observatory. The telescope was inaugurated in January 2019, with commissioning continuing throughout 2019. We describe the first campaign of observations with the pSCT, conducted in January and February of 2020, and demonstrate the detection of gamma-ray emission from the Crab Nebula with a statistical significance of 8.6σ.

79 ASTRONOMY AND ASTROPHYSICS↗

High-Energy 3D Calorimeter for Use in Gamma-Ray Astronomy Based on Position-Sensitive Virtual Frisch-Grid CdZnTe Detectors

We will present a concept for a calorimeter based on a novel approach of 3D position-sensitive virtual Frisch-grid CdZnTe (hereafter CZT) detectors. This calorimeter aims to measure photons with energies from approximately 100 keV to 20 - 50 MeV . The expected energy resolution at 662 keV is better than 1% FWHM, and the photon interaction position-measurement accuracy is better than 1 mm in all 3 dimensions. Each CZT bar is a rectangular prism with typical cross-section from 5 x 5 to 7 x 7 mm2 and length of 2 - 4 cm. The bars are arranged in modules of 4 x 4 bars, and the modules themselves can be assembled into a larger array. The 3D virtual voxel approach solves a long-standing problem with CZT detectors associated with material imperfections that limit the performance and usefulness of relatively thick detectors (i.e., greater than 1 cm). Also, it allows us to use the standard (unselected) grade crystals, while achieving the energy resolution of the premium detectors and thus substantially reducing the cost of the instrument. Such a calorimeter can be successfully used in space telescopes that use Compton scattering of gamma rays, such as AMEGO, serving as part of its calorimeter and providing the position and energy measurement for Compton-scattered photons (like a focal plane detector in a Compton camera). Also, it could provide suitable energy resolution to allow for spectroscopic measurements of gamma ray lines from nuclear decays.

Moiseev, A.↗

THE CHANDRA HRC VIEW OF THE SUBARCSECOND STRUCTURES IN THE NUCLEAR REGION OF NGC 1068

We have obtained a high spatial resolution X-ray image of the nucleus of NGC 1068 using the High Resolution Camera (HRC-I) on board the Chandra X-ray Observatory, which provides an unprecedented view of the innermost 1 arcsec radius region of this galaxy. The HRC image resolves the narrow-line region into X-ray emission clumps matching bright emission-line clouds in the HST [OIII] {lambda}5007 images and allows comparison with subarcsecond-scale radio jet for the first time. Two distinct X-ray knots are revealed at 1.3-1.4 arcsec northeast and southwest of the nucleus. Based on the combined X-ray, [O III], and radio continuum morphology, we identify the locations of intense radio jet-cloud interaction. The [O III] to soft X-ray ratios show that some of these clouds are strongly affected by shock heating, whereas in other locations the jet simply thrusts through with no signs of strong interaction. This is further strengthened by the presence of a kT {approx} 1 keV collisionally ionized component in the ACIS spectrum of a shock-heated cloud HST-G. We estimate that the kinematic luminosity of the jet-driven shocks is 6 Multiplication-Sign 10{sup 38} erg s{sup -1}, a negligible fraction (10{sup -4}) of the estimated total jet power.

79 ASTRONOMY AND ASTROPHYSICS↗

Final Report DE-SC0020773

The DOE/NNSA sought development of innovative portable neutron/x-ray cameras for imaging and, when coupled with a portable source, also for radiography. This project focused on developing such a device that promises to have excellent resolution, while also providing neutron/gamma separation. We developed an Application Specific Integrated Circuit (ASIC) to be employed in conjunction with existing sensor technologies and modern assembly techniques. The concepts developed were a combination of new novel techniques and an innovative implementation of existing methods boosted by technological advances in ASIC performance.

61 RADIATION PROTECTION AND DOSIMETRY↗

Vesta's Elemental Composition

Many lines of evidence (e.g. common geochemistry, chronology, O-isotope trends, and the presence of different HED rock types in polymict breccias) indicate that the howardite, eucrite, and diogenite (HED) meteorites originated from a single parent body. Meteorite studies show that this protoplanet underwent igneous differentiation to form a metallic core, an ultramafic mantle, and a basaltic crust. A spectroscopic match between the HEDs and 4 Vesta along with a plausible mechanism for their transfer to Earth, perhaps as chips off V-type asteroids ejected from Vesta's southern impact basin, supports the consensus view that many of these achondritic meteorites are samples of Vesta's crust and upper mantle. The HED-Vesta connection was put to the test by the NASA Dawn mission, which spent a year in close proximity to Vesta. Measurements by Dawn's three instruments, redundant Framing Cameras (FC), a Visible-InfraRed (VIR) spectrometer, and a Gamma Ray and Neutron Detector (GRaND), along with radio science have strengthened the link. Gravity measurements by Dawn are consistent with a differentiated, silicate body, with a dense Fe-rich core. The range of pyroxene compositions determined by VIR overlaps that of the howardites. Elemental abundances determined by nuclear spectroscopy are also consistent with HED-compositions. Observations by GRaND provided a new view of Vesta inaccessible by telescopic observations. Here, we summarize the results of Dawn's geochemical investigation of Vesta and their implications.

Prettyman, T. H.↗

MOXE: An X-ray all-sky monitor for Soviet Spectrum-X-Gamma Mission

A Monitoring Monitoring X-Ray Equipment (MOXE) is being developed for the Soviet Spectrum-X-Gamma Mission. MOXE is an X-ray all-sky monitor based on array of pinhole cameras, to be provided via a collaboration between Goddard Space Flight Center and Los Alamos National Laboratory. The objectives are to alert other observers on Spectrum-X-Gamma and other platforms of interesting transient activity, and to synoptically monitor the X-ray sky and study long-term changes in X-ray binaries. MOXE will be sensitive to sources as faint as 2 milliCrab (5 sigma) in 1 day, and cover the 2 to 20 KeV band.

Priedhorsky, W.↗

MOXE - An X-ray all-sky monitor for the Soviet Spectrum-X-Gamma mission

A Monitoring X-Ray Equipment (MOXE) is being developed for the Soviet Spectrum-X-Gamma Mission. MOXE is an X-ray all-sky monitor based on array of pinhole cameras, to be provided via a collaboration between Goddard Space Flight Center and Los Alamos National Laboratory. The objectives are to alert other observers on Spectrum-X-Gamma and other platforms of interesting transient activity, and to synoptically monitor the X-ray sky and study long-term changes in X-ray binaries. MOXE will be sensitive to source as faint as 2 milliCrab (5 sigma) in 1 day, and cover the 2 to 20 KeV band.

Priedhorsky, W.↗

Detector Response Function and Directional Gamma-Ray Source Calculations for Polaris

A Directional Unfolded Source Term (DUST) method was developed to compute directionally resolved gamma-ray source terms based on back-projection spectra synthesized by Compton Cameras. Spectral features in the unprocessed spectra are indistinct primarily because the rotational angles for the conical projections cannot be determined, so probability distributions are constructed from overlapping cones. The DUST method uses an angular response function to compute a covariance matrix, which is used to process count rates in back-projection spectra by linear regression to partition the gamma-rays among several spatial regions. This method was applied to analyze data collected by the Polaris detector during an evaluation that was conducted at Oak Ridge National Laboratory (ORNL). The evaluation includes measurements of calibration sources with angular separations ranging from 1° to more than 50°. Measurements were also performed for cylindrical depleted uranium castings and a 137 Cs source inside a large polyethylene sphere. The DUST algorithm was able to differentiate gamma-rays emitted by 137 Cs and 60 Co when the sources were separated by less than 2°, but separation greater than 10° was required to isolate the 133 Ba emission from gamma-rays emitted by the other sources. The computed source terms were consistent with emission profiles from the calibration sources and from models of the spatially-extended sources. Methods for viewing radiation profiles were also evaluated because user input is required to select spatial regions of interest.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Study of the impact of resonant magnetic perturbation fields on gross tungsten erosion using DiMES samples in DIII-D

Here, an experiment was conducted in DIII-D to compare gross tungsten (W) erosion on samples exposed to outer strike point (OSP) sweeps in L-mode plasmas for three conditions. These included two phases of resonant magnetic perturbations (RMPs), and a set with no perturbations. Upon RMP application, lobe structures indicative of strike point splitting of the OSP were evident in divertor camera data and on Langmuir probes. Gross W erosion flux, ${{\rm{\Gamma }}}_{{\rm{W}}},$ inferred spectroscopically using the S/XB method applied to the 400.9 nm W-I line, was generally in the range ${{\rm{\Gamma }}}_{{\rm{W}}}/{{\rm{\Gamma }}}_{{\rm{D}}+,\perp }=2\times {10}^{-4}$ referenced to incident deuterium ion flux ${{\rm{\Gamma }}}_{{\rm{D}}+,\perp },$ and was increased in the RMP cases by no more than 30% of the level observed in unperturbed discharges. A large reduction in gross erosion (50%) was observed in the private flux region at the W sample for one specific toroidal phase of the RMP field.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Solar and galactic cosmic ray exposure of Surveyor 3 as determined from cosmogenic radionuclide measurements

The proton-produced Na-22 content of samples of Surveyor 3 TV camera, surface sampler scoop, and other components was determined by nondestructive gamma ray spectrometry. The contributions of the nine most prominent solar flares to Na-22 production were calculated to be 18 dpm/kg. The observed activity in the Surveyor 3 samples was 62 + or - dpm/kg. This indicates a galactic proton contribution of about 44 dpm/kg, which adjusted for spallation of Al gives a value of 42 dpm/kg. This is compared to measurements of 88 dpm/kg in the Lost City meteorite which had an orbit extending to 2.35 AU, with a 4 pi bombardment as compared to the 2 pi bombardment of the samples on the lunar surface. The agreement between Na-22 production in Surveyor 3 and the Lost City meteorite offers evidence that the galactic cosmic ray flux is almost the same at 1 Au and at 2.35 AU.

Rancitelli, L. A.↗