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Results for “Neutron Irradiation”

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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Electron trapping in neutron-irradiated silicon studied by space-charge-limited current.

The trapping and detrapping of electrons is studied through measurements of space-charge-limited current in the temperature range of 77 to 293 K in high-purity silicon after irradiation with 14-MeV neutrons. A model is developed which describes most of the results quantitatively and self-consistently, including dc characteristics. Two distinct trap levels exist: the fast levels lie at 0.14 (plus or minus 0.005) eV below the conduction band, and the slow levels lie at 0.47 (plus or minus 0.01) eV below the conduction band. At 77 K, injected free electrons are initially captured by the fast 0.14-eV traps and then sink into the deep 0.47-eV traps, predominantly without being reemitted into the band. Above approximately 110 K, the detrapping rate from the shallow traps becomes so fast that the deep traps dominate. The results also offer a direct verification of the simple model of space-charge-limited current dominated by shallow and deep traps.

Quat, V. T.↗
NASA NTRS1981

I-Xe dating - Intercomparisons of neutron irradiations and reproducibility of the Bjurbole standard

Previously unpublished data from the stepwise heating analysis of the Valecitos 1 (V1) Bjurbole standard are presented together with the results of an isotopic dilution measurement of a KI monitor included in the V1 irradiation package. The results of these analyses are compared with the values observed in other irradiations. Apparent I-Xe 'formation' ages are reproducible for three different samples of Bjurbole, suggesting isotopic homogeneity for initial iodine in the bulk material. The systematics of neutron capture in Xe-135 (produced from U-235 neutron fission) are examined and verified in irradiated BCR-1.

Hohenberg, C. M.↗
NASA NTRSDate not supplied

Identifying Neutron Irradiation in Space to Mitigate Bio-Medical Effects

Ubiquitous GCR high energy particles >1 GeV is primary concern • Medical effects compounded by ionizing dose of radiation from energetic particles- cancer, mutations, microbiome changes • Cancer induction and effects are irreversible after initiation • Long term space radiation exposure is cancer promoting but reversible Secondary GCR and Solar induced neutron spallation is a concern • Produced by interactions with space craft materials, EVA and planetary surfaces • Neutron Quality Factor is 10x that of beta, x-ray or gamma rays Space isn’t friendly to life or electronics! Real-time charged particle and EARLY neutron detection are required. Traveling fast or digging deep are the best protection. Nuclear space propulsion through LENR/LCF/Solid-State Fusion is a good bet!

space medicine↗
NASA NTRSDate not supplied

Identifying Neutron Irradiation in Space to Mitigate Bio-Medical Effects

One of the primary challenges to interplanetary human travel is mitigation of radiation expo-sure. As fast transit with LENR driven or conventional nuclear electric (NEP) or thermal propulsion (NTP) may be imminent, time and level of radiation exposure composingALARA (As Low as Rea-sonably Achievable) must be ascertained rapidly and precisely. Since acute physiological effects are difficult to detect, and chronic effects on crew health are delayed and potentially trans-generational, improved detection technologies will be game-changing and an essential element of the crew health monitoring and environmental protection toolkit.Secondary Galactic Cosmic Ray (GCR) induced neutrons are an additional hazard.

space medicine↗
NASA NTRS1967

Neutron irradiation of Am-241 effectively produces curium

Computer study was made on the production of multicurie amounts of highly alpha-active curium 242 from americium 241 irradiation. The information available includes curium 242 yields, curium composition, irradiation data, and production techniques and safeguards.

Anderson, R. W.↗
NASA NTRS1992

Irradiation By Neutrons And Annealing of SiGe Alloys

Heat treatment restores thermoelectric performance having deteriorated under irradiation by neutrons. Discovery suggests SiGe materials used in radioisotope thermoelectric generators and other applications up to fluences of 5.4 X 10(to the 19th power)cm(to the negative 2nd power) and operating at temperatures of 600 to 1,000 degrees C.

Vandersande, Jan W.↗
NASA NTRS1974

Effect of fast neutron, gamma-ray and combined radiations on the thermal decomposition of ammonium perchlorate single crystals

The thermal decomposition kinetics have been determined for ammonium perchlorate crystals subjected to a fast neutron irradiation or to a fast neutron irradiation followed by a gamma-ray irradiation. Qualitatively, the radiation induced changes are similar to those obtained in this and in previous studies, with samples exposed only to gamma rays. The induction period is shortened and the rate constants, obtained from an Avrami-Erofeyev kinetic analysis, are modified. The acceleratory period constant increases and the decay period constant decreases. When compared on an equal deposited energy basis, the fast neutron induced changes are appreciably larger than the gamma-ray induced changes. Some, or all, of the fast neutron induced effects might be attributable to the introduction of localized regions of concentrated radiation damage ('spikes') by lattice atom recoils which become thermal decomposition sites when the crystals are heated.

Herley, P. J.↗
NASA NTRS1982

s-process studies in the light of new experimental cross sections - Distribution of neutron fluences and r-process residuals

A best set of neutron-capture cross sections has been evaluated for the most important s-process isotopes. With this data base, s-process studies have been carried out using the traditional model which assumes a steady neutron flux and an exponential distribution of neutron irradiations. The calculated sigma-N curve is in excellent agreement with the empirical sigma-N-values of pure s-process nuclei. Simultaneously, good agreement is found between the difference of solar and s-process abundances and the abundances of pure r-process nuclei. The abundance pattern of the iron group elements where s-process results complement the abundances obtained from explosive nuclear burning is discussed. The results obtained from the traditional s-process model such as seed abundances, mean neutron irradiations, or neutron densities are compared to recent stellar model calculations which assume the He-burning shells of red giant stars as the site for the s-process.

Kaeppeler, F.↗
NASA NTRS1974

Total body calcium analysis

A technique to quantitate total body calcium in humans is developed. Total body neutron irradiation is utilized to produce argon 37. The radio argon, which diffuses into the blood stream and is excreted through the lungs, is recovered from the exhaled breath and counted inside a proportional detector. Emphasis is placed on: (1) measurement of the rate of excretion of radio argon following total body neutron irradiation; (2) the development of the radio argon collection, purification, and counting systems; and (3) development of a patient irradiation facility using a 14 MeV neutron generator. Results and applications are discussed in detail.

Lewellen, T. K.↗
NASA NTRS1988

Neutron effects on the electrical and switching characteristics of NPN bipolar power transistors

The use of nuclear reactors to generate electrical power for future space missions will require the electrical components used in the power conditioning, control, and transmission subsystem to operate in the associated radiation environments. An initial assessment of neutron irradiation on the electrical and switching characteristics of commercial high power NPN bipolar transistors was investigated. The results clearly show the detrimental effects caused by neutron irradiation on the electrical and switching characteristics of the NPN bipolar power transistor.

Frasca, Albert J.↗
NASA NTRS1983

Ar-39 recoil losses and presolar ages in Allende inclusions

Argon analyses were performed for five coarse-grained, Ca-Al-rich inclusions from the Allende meteorite. The samples were neutron-irradiated in evacuated ampuoles, and the Ar in the ampuoles and in the samples was analyzed. Up to 60 percent of Ar-39 was lost from the samples into the ampuoles due to recoil during neutron-irradiation; this loss resulted in substantial increases in the apparent Ar-40-Ar-39 ages of the samples. Substantial amounts of trapped Ar-36 of unknown origin were found in the inclusions, and the presence of trapped Ar-40 could not be ruled out. It is inferred that the interpretation of high Ar-40/K-40 ratios as very high (presolar) ages may be subject to question. It is noted that the degrees of Ar-39 recoil loss reported is comparable to recoil loss in terrestrial rocks and cannot be attributed to KCl contamination of the samples.

Villa, I. M.↗
NASA NTRS1990

Segmented Ge detectors and mechanical coolers for future gamma-ray astronomy instruments

The effectiveness of a segmented Ge detector in rejecting background events due to the beta decay of internal radioactivity is demonstrated by a laboratory experiment in which radioactivity was produced in the detector by neutron irradiation. A Cf-252 source of neutrons was used to produce, by neutron capture on Ge-74 in the detector itself, Ge-75, which decays by beta emission with a maximum energy of 1188 keV. Simultaneous spectra are taken of the activity in the detector under two conditions: a free spectrum in which all events in the detector are accumulated, and a gated spectrum in which events are accumulated only if they deposit energy in two or more segments. A comparison of the spectra shows that over 85 percent of the beta events are rejected, which is in good agreement with predictions.

Varnell, Larry S.↗