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Results for “proton 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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Studies of proton-irradiated cometary-type ice mixtures

Cometary ice mixtures are studied in a laboratory experiment designed to simulate the temperature, pressure and radiation environments of the interstellar Oort cloud region, in order to test the hypothesized radiation synthesis mechanism for changing the characteristics of the outer few meters of a comet stored in the Oort cloud for 4.6 billion years. All experiments conducted confirm the synthesis of new molecular species in solid phase mixtures at 20 K. When CH4 is present in the irradiated ice mixture, long chained, voltaile hydrocarbon and CO2 are synthesized together with high molecular weight C compounds present in the room temperature residue. Due to radiation synthesis, about 1 percent of the ice was converted into a nonvolatile residue containing complicated C compounds not present in the blank samples. These results suggest that initial molecular abundances can be altered, and new species created, as a result of radiation synthesis. Irradiated mixtures exhibited thermoluminescence and pressure enhancements during warming, showing the synthesis of reactive species. Outbursts in new comets resulting from similar irradiation-induced exothermic activity would be expected to begin occurring at distances of the order of 100 AU.

Moore, M. H.↗
NASA NTRS1994

Performance, defect behavior and carrier enhancement in low energy, proton irradiated p+nn+ InP solar cells

The highest AMO efficiency (19.1 percent) InP solar cell consisted of an n+pp+ structure epitaxially grown on a p+ InP substrate. However, the high cost and relative fragility of InP served as motivation for research efforts directed at heteroepitaxial growth of InP on more viable substrates. The highest AMO efficiency (13.7 percent) for this type of cell was achieved using a GaAs substrate. Considering only cost and fracture toughness, Si would be the preferred substrate. The fact that Si is a donor in InP introduces complexities which are necessary in order to avoid the formation of an efficiency limiting counterdiode. One method used to overcome this problem lies in employing an n+p+ tunnel junction in contact with the cell's p region. A simpler method consists of using an n+ substrate and processing the cell in the p+ nn+ configuration. This eliminates the need for a tunnel junction. Unfortunately, the p/n configuration has received relatively little attention the best cell with this geometry having achieved an efficiency of 17 percent. Irradiation of these homoepitaxial cells, with 1 Mev electrons, showed that they were slightly more radiation resistant than diffused junction n/p cells. Additional p/n InP cells have been processed by some activity aimed at diffusion. Currently, there has been some activity aimed at producing heteroepitaxial p+nn+ InP cells using n+ Ge substrates. Since, like Si, Ge is an n-dopant in InP, use of this configuration obviates the need for a tunnel junction. Obviously, before attempting to process heteroepitaxial cells, one must produce a reasonably good homoepitaxial cell. In the present case we focus our attention on homoepitaxially on an n+ Ge substrate.

Weinberg, I.↗
DOE OSTI2024

Recovery of Neptunium-236g from Photon and Proton-Irradiated Actinide Targets

Neptunium-236g is a rare radionuclide used as a tracer for neptunium-237 analyses. The availability of 236gNp is limited and the viable production routes are costly, time consuming, and only produce trace quantities of the desired product. For this work, two known production methods were tested to determine product recovery, purity, and viability for use as a tracer. The first method utilizes a photon-irradiated 237Np target to produce 236gNp by the 237Np(?,n)?236Np reaction. The second method utilizes the 238U(d,4n) ?236Np reaction. These production routes were evaluated previously, and the former was considered ineffective without isotope separation and the latter was not well-characterized for the 236mNp/236gNp production ratio. Recent resurgence of electromagnetic isotope separation technology has enabled at least partial recovery of 236gNp from part-per-million abundance feeds produced by the photonuclear reaction. To address the lack of production data for the second method, a deuteron-irradiated depleted uranium target was chemically processed to recover and purify the Np for abundance and ratio analyses. The status and current analytical results for each production method are presented.

07 ISOTOPE AND RADIATION SOURCES↗