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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.

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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Determination of primary energy in nucleus-nucleus collisions and the high P(sub)T tail of alpha-particles

A determination of primary energy is required in order to study the energy dependence of meson multiplicity in A-A collisions in cosmic rays. Various procedures which estimate the energy of a primary nucleus from its interaction were investigated. An average of two methods were used, one using the pions and wounded protons and the other using spectator protons and alpha particles. The high P sub T tail observed for Z = 2 fragments requires a modification of the latter method.

Freier, P. S.↗
DOE OSTI2020

Calculations of electronic excitation by protons and alpha particles in silicon

This paper presents an ab initio method of calculating the valence electron contribution to the stopping and interaction cross sections of swift ions in matter using linear response calculations of the dielectric function in crystals. We estimate the contribution to the stopping and cross sections by repeated electron capture and stripping of the projectile ion by the medium. We also predict the electronic stopping of protons and alpha particles in silicon and compare to measured values. The predictions generally agree with the data at ion speeds greater than 1 atomic unit. We find that electron capture and stripping is at most a small contribution to the stopping for both ions studied.

electron excitation, silicon, nuclear interactions↗
DOE OSTI2021

A Measurement of Proton, Deuteron, Triton and Alpha Particle Emission after Nuclear Muon Capture on Al, Si and Ti with the AlCap Experiment

Heavy charged particles after nuclear muon capture are an important nuclear physics background to the muon-to-electron conversion experiments Mu2e and COMET, which will search for charged lepton flavor violation at an unprecedented level of sensitivity. The AlCap experiment measured the yield and energy spectra of protons, deuterons, tritons, and alpha particles emitted after the nuclear capture of muons stopped in Al, Si, and Ti in the low energy range relevant for the muon-to-electron conversion experiments. Individual charged particle types were identified in layered silicon detector packages and their initial energy distributions were unfolded from the observed energy spectra. Detailed information on yields and energy spectra for all observed nuclei are presented in the paper.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Effects of Low-Dose Alpha-Particle Irradiation in Human Cells: The Role of Induced Genes and the Bystander Effect [Final Technical Report] (9/15/1998-5/31/2005)

This grant was designed to examine the cellular and molecular mechanisms for the bystander effect of radiation (initially described in this laboratory) whereby damage signals are passed from irradiated to non-irradiated cells in a population. These signals induce genetic effects including DNA damage, mutations and chromosomal aberrations in the nonirradiated cells. Experiments were carried out in cultured mammalian cells, primarily human diploid cells, irradiated with alpha particles. This research resulted in 17 publications in the refereed literature and is described in the Progress Report where it is keyed to the publication list. This project was initiated at the Harvard School of Public Health (HSPH) and continued in collaboration with students/fellows at Colorado State University (CSU) and the New Jersey Medical School (NJMS).

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2014

Fusion alpha-particle diagnostics for DT experiments on the joint European torus

JET equipped with ITER-like wall (a beryllium wall and a tungsten divertor) can provide auxiliary heating with power up to 35MW, producing a significant population of α-particles in DT operation. The direct measurements of alphas are very difficult and α-particle studies require a significant development of dedicated diagnostics. JET now has an excellent set of confined and lost fast particle diagnostics for measuring the α-particle source and its evolution in space and time, α-particle energy distribution, and α-particle losses. This paper describes how the above mentioned JET diagnostic systems could be used for α-particle measurements, and what options exist for keeping the essential α-particle diagnostics functioning well in the presence of intense DT neutron flux. Also, α-particle diagnostics for ITER are discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

Screening materials with the XIA UltraLo alpha particle counter at Southern Methodist University

Southern Methodist University houses one of five existing commercially available UltraLo 1800 production model alpha counters made by XIA LLC. The instrument has an electron drift chamber with a 707 cm{sup 2} or 1800 cm{sup 2} counting region which is determined by selecting the inner electrode size. The SMU team operating this device is part of the SuperCDMS screening working group, and uses the alpha counter to study the background rates from the decay of radon in materials used to construct the SuperCDMS experiment. We have studied four acrylic samples obtained from the MiniCLEAN direct dark matter search with the XIA instrument demonstrating its utility in low background experiments by investigating the plate-out of {sup 210}Pb and comparing the effectiveness of cleaning procedures in removing {sup 222}Rn progenies from the samples.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Development of ZnO Nanorod-Based Scintillators Grown Under a Low-Temperature Hydrothermal Method for Use in Alpha-Particle and Thermal Neutron Detectors

Due to material properties such as sub-nanosecond decay time and high light output, ZnO-based scintillators are being developed as a radiation detector material. In this study, ZnO nanorods grown via a low temperature hydrothermal method were investigated using photoluminescence (PL) and α-particle testing. Vertically aligned ZnO nanorods of varying lengths were grown and tested. The ZnO nanorod scintillators were compared to a MOCVD grown ZnO scintillator. In conclusion, the low temperature hydrothermal method shows promising performance for low-cost growth of ZnO scintillators for use as α-particle detectors and as a part of thermal neutron detection systems if doped with or in contact with a thermal neutron radiator.

36 MATERIALS SCIENCE↗
NASA NTRS1995

Gas Pressure Gauge Based on Alpha-Particle Induced Ion Currents

The use of ionization currents for measuring pressure was first demonstrated in the late 1940's. The early gauges operated at high voltages and used rather large ion sources. The ionization gauge is actually a densitometer that is sensitive to the temperature and pressure of the gas in the chamber. This report describes the use of low voltages and small ion sources in the development of a prototype.

transducers gas pressure gauge alpha particles ion↗
DOE OSTI2016

Alpha particle response study of polycrstalline diamond radiation detector

Chemical vapor deposition has opened the possibility to grow high purity synthetic diamond at relatively low cost. This has opened up uses of diamond based detectors for wide range of applications. These detectors are most suitable for harsh environments where standard semiconductor detectors cannot work. In this paper, we present the fabrication details and performance study of polycrystalline diamond based radiation detector. Effect of different operating parameters such as bias voltage and shaping time for charge collection on the performance of detector has been studied.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Ab Initio Calculation of the Alpha-Particle Monopole Transition Form Factor

Here we present a parameter-free ab initio calculation of the α-particle monopole transition form factor in the framework of nuclear lattice effective field theory. We use a minimal nuclear interaction that was previously used to reproduce the ground state properties of light nuclei, medium-mass nuclei, and neutron matter simultaneously with no more than a few percent error in the energies and charge radii. The results for the monopole transition form factor are in good agreement with recent precision data from Mainz.

4He↗
DOE OSTI2023

Experiments on excitation of Alfvén eigenmodes by alpha-particles with bump-on-tail distribution in JET DTE2 plasmas

Dedicated experiments were performed in JET DTE2 plasmas for obtaining an α-particle bump-on-tail (BOT) distribution aiming at exciting Alfvén eigenmodes (AEs). Neutral beam injection-only heating with modulated power was used so that fusion-born α-particles were the only ions present in the MeV energy range in these DT plasmas. The beam power modulation on a time scale shorter than the α-particle slowing down time was chosen for modulating the α-particle source and thus sustaining a BOT in the α-particle distribution. High-frequency modes in the toroidicity-induced Alfven eigenmode (TAE) frequency range and multiple short-lived modes in a wider frequency range have been detected in these DT discharges with interferometry, soft x-ray cameras, and reflectometry. The modes observed were localised close to the magnetic axis and were not seen in the Mirnov coils. Analysis with the TRANSP and Fokker-Planck FIDIT codes confirms that α-particle distributions with BOT in energy were achieved during some time intervals in these discharges though no clear correlation was found between the times of the high-frequency mode excitation and the BOT time intervals. The combined magneto-hydrodynamic (MHD) and kinetic modelling studies show that the high-frequency mode in the TAE frequency range is best fitted with a TAE of toroidal mode number n= 9. This mode is driven mostly by the on-axis beam ions while the smaller drive due to the pressure gradient of α-particles allows overcoming the marginal stability and exciting the mode. The observed multiple short-lived modes in a wider frequency range are identified as the on-axis kinetic AEs predicted in Rosenbluth and Rutherford.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

RADIOACTIVE POSITRON EMITTER PRODUCTION BY ENERGETIC ALPHA PARTICLES IN SOLAR FLARES

Measurements of the 0.511 MeV positron-annihilation line from solar flares are used to explore the flare process in general and ion acceleration in particular. In flares, positrons are produced primarily by the decay of radioactive positron-emitting isotopes resulting from nuclear interactions of flare-accelerated ions with ambient solar material. Kozlovsky et al. provided ion-energy-dependent production cross sections for 67 positron emitters evaluated from their threshold energies (some <1 MeV nucleon{sup –1}) to a GeV nucleon{sup –1}, incorporating them into a computer code for calculating positron-emitter production. Adequate cross-section measurements were available for proton reactions, but not for α-particle reactions where only crude estimates were possible. Here we re-evaluate the α-particle cross sections using new measurements and nuclear reaction codes. In typical large gamma-ray line flares, proton reactions dominate positron production, but α-particle reactions will dominate for steeper accelerated-ion spectra because of their relatively low threshold energies. With the accelerated-{sup 3}He reactions added previously, the code is now reliable for calculating positron production from any distribution of accelerated-ion energies, not just those of typical flares. We have made the code available in the online version of the Journal. We investigate which reactions, projectiles, and ion energies contribute to positron production. We calculate ratios of the annihilation-line fluence to fluences of other gamma-ray lines. Such ratios can be used in interpreting flare data and in determining which nuclear radiation is most sensitive for revealing acceleration of low-energy ions at the Sun.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Thermal Annealing Effect on Structure and Properties of Tungsten Surface Irradiated with High Fluence and Low Energy Alpha-Particles

The paper presents research into the surface morphology, helium cluster formation and mechanical properties of high-purity tungsten after the high fluence and low-energy helium ion implantation and subsequent annealing. Investigations are based on scanning electron and atomic force microscopy observations and thermal desorption measurements. Because of the local stresses appearing within the energy loss straggling of helium ions, atoms migrate at distances significantly increasing the ion projective range, and create mobile coalescence of helium atoms and immobile helium-vacancy clusters. The latter form helium bubbles in the energy loss straggling which cause the surface blistering. Local stresses induced by helium coalescence and helium-vacancy clusters beyond the energy loss straggling result in the material strengthening or hardness increase. Subsequent 600°С annealing provides the size growth of blisters on the metal surface irradiated with helium ions and high helium desorption due to the migration of mobile coalescence of helium atoms. With the increasing annealing temperature from 600 to 1000°С, the layer corresponding to the projective range of helium ions fully fractures due to the interstitial helium atoms releasing from immobile helium-vacancy clusters. After 1000°С annealing, the tungsten hardness returns to its initial value.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

GaAs Schottky Barrier Detectors for Alpha-Particle Spectrometry at Temperatures up to 120°C

GaAs Schottky barrier detectors for α particle spectrometry have been tested. Detectors had an input window area of 80 mm{sup 2} and a working barrier layer thickness of 40–50 μm. The energy resolution (FWHM) measured on 5.499 MeV α line of {sup 238}Pu source amounted to 17.5 keV at a generator peak width of 7.8 keV. In the measurements on a {sup 226}Ra source, detectors showed linear response and nearly 100% charge collection efficiency at reverse bias above 65 V for all energies of α particles emitted from the source. Tests for thermal stability showed that the proposed detectors can be used in alpha-spectrometry of radionuclides at temperatures up to 120°C.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1975

The energy spectra of protons and alpha particles above 300 keV/nucleon during quiet times

An unusual spectral feature and anomalously large abundance of helium between 0.6 and about 2 MeV/nucleon observed during the most quiet time periods in 1974 indicate the presence of low energy helium of an unknown origin. During these same quiet periods protons below 1.5 MeV and alphas below 0.6 MeV/nucleon have a power law energy spectrum with an index of -1.8 and the proton to alpha ratio is about 30. From these results and the measured anisotropy of these particles we conclude that the sun emits less than about 1 MeV particles continuously even during its most inactive periods.

Gloeckler, G.↗