No abstract available

[en] Certain types of low-level radioactive waste (LLW) must be shipped in expensive special containers. It is therefore desirable to keep container utilization high. There must be a stock of containers sufficient to ship waste in a timely fashion, but one does not want to have containers sitting idle a significant fraction of the time. A computerized discrete event network model has been developed and is described in this report. The model allows an analyst to determine the effects of varying the increase in LLW, establishment of regional disposal, etc. on requirements for shipping containers

[en] Energy dependent electron emission (counts per second) between zero and 1.4 keV generated by the natural reactivity of uranium was measured by an electrostatic spectrometer with known acceptance angle and acceptance area. The electron intensity decreases continuously with energy, but at different rates in different energy regimes, suggesting that a variety of processes may be involved in producing the observed electron emission. The spectrum was converted to energy dependent electron flux (e-/cm² s) using the assumption that the emission has a cosine angular distribution. The flux decreased rapidly from ∼10⁶/cm²s to ∼10⁵/cm²s in the energy range from zero to 200 eV, and then more slowly from ∼10⁵/cm²s to ∼3*10⁴/cm² s in the range from 200 to 1400 eV. The energy dependent electron mean free path in gases together with literature cross sections for electron induced reactions were used to determine the number of ionization and dissociation reactions per cm²s within the inelastic mean free path of electrons, and found to be about 1.3*10⁸/cm²s and 1.5*10⁷/cm²s, respectively, for hydrogen. An estimate of the number of ionization and dissociation reactions occurring within the total range, rather than the mean free path of electrons in gases resulted in 6.2*10⁹/cm²s and 1.3*10⁹/cm²s, respectively. The total energy flux carried by electrons from the surface is suspiciously close to the total possible energy generated by one gram of uranium. A likely source of error is the assumption that the electron emission has a cosine distribution. Angular distribution measurements of the electron emission would check that assumption, and actual measurement of the total current emanating from the surface are needed to confirm the value of the current calculated in section II. These results must therefore be used with caution - until they are confirmed by other measurements.

[en] Energy dependent electron emission between zero and 1.4 keV generated by the natural reactivity of plutonium was measured by an electrostatic spectrometer with known acceptance angle and acceptance area. The electron spectral intensity decreases continuously except for a distinctive feature of unknown origin at approximately 180eV. The spectrum was converted to energy dependent electron flux (e/cm² s) using the assumption that the emission has a cosine angular distribution. The energy dependent electron mean free path in gases and literature cross sections for electron induced reactions were used to determine the number of ionization and dissociation reactions per cm² second, found to be about 8*10⁸/cm²s and 1.5*10⁸/cm²s, respectively, for hydrogen. These results are to be used with caution until complementary measurements can be made, e.g. independent measurement of the total emitted electron current, since the results here are based on the assumption that the electron emission has a cosine angular distribution. That is unlikely to be correct.

[en] Fused silica and Si-O_x coatings are of interest for use under high flux conditions of laser light. Si-O_x coatings are sputter deposited from silicon and fused quartz targets using planar magnetrons operated in the r.f. mode with a variable working-gas mixture of Argon-Oxygen. A series of coatings are prepared on optically flat, fused quartz substrates. Analysis of surface curvature reveals the deposition process conditions that minimize residual stress. Compressive stress levels that exceed 1.5 GPa can be reduced to less than 0.4 GPa for an optimum working-gas pressure. Characterization using Rutherford backscattering and X-ray photoelectron spectroscopy indicates that both the fused quartz and silicon targets can be used to sputter deposit coatings with the chemical bonding features of the fused-quartz substrate material

[en] X-ray photoelectron spectroscopy analysis was performed on ion beam sputter deposited films of indium tin oxide as a function of O₂ partial pressure during deposition. The oxygen partial pressure was varied over the range of 2.5 x 10^-6--4.0 x 10^-5 Torr. Changes in composition as well as in the deconvoluted In 3d₅/sub //₂, Sn 3d₅/sub //₂, and O 1s core level spectra were observed and correlated with the variation of the oxygen partial pressure during deposition. Results show that the films become increasingly stoichiometric as P/sub =/ is increased and that the excess oxygen introduced during deposition is bound predominantly to the Sn and has little or no effect on the In--O bonding

[en] Synchrotron radiation soft x-ray photoemission spectroscopy and reflection high-energy electron diffraction were used to investigate the structural and electronic properties at the ZnSe/CdTe(100) heterojunction interface. ZnSe overlayers were sequentially grown in steps on p-type CdTe(100) single crystals at 200 degree C. In situ photoemission measurements were acquired after each growth in order to observe changes in the valence band electronic structure as well as changes in the Cd 4d, Zn 3d, and Te 4d core lines. The results were used to correlate the interfacial chemistry with the electronic structure and to directly determine the ZnSe/CdTe heterojunction valence band discontinuity and the consequent heterojunction band diagram. Results of these measurements reveal that the valence band offset is ΔE_v=0.20 eV. copyright 1995 American Institute of Physics

No abstract available

[en] Interactions between the shallow acceptor boron and hydrogen in single crystal, polycrystalline, and amorphous Si are investigated. Low-temperature secondary ion mass spectrometry depth-compositional profiles indicate a definite interaction between the boron concentration and the hydrogen penetration in single crystals and at grain boundaries. The bonding of the H is identified to be directly to the Si rather than to the B, and is confirmed by infrared measurements. Electrical neutralization of the B by hydroxyl-group bonding is also reported at oxygen-rich Si grain boundaries. No similar relationships between P concentration and H penetration are observed. In amorphous Si material, the B-doping level has only a limited effect on the hydrogen penetration which seems to be controlled instead by structural diffusion mechanisms

[en] Basic material studies addressing the growth and processing of CdTe have resulted in dense, defect-free as-grown CdTe films on 7059 glass with initial grain sizes of ∼0.2 μm. Innovations in postdeposition processing (no CdCl₂) have resulted in films with >50 μm grain sizes. Scanning electron microscopy analyses confirm film density while concurrent cathodluminescence reveals a change in the recombination efficiency. Transmission electron microscopy analyses reveal that films grown below 300 degree C are defect-free, while films grown above 300 degree C contain defects. Photoluminescence lifetime measurements reveal a fivefold increase in lifetime following postdeposition processing of these films. These results were correlated with x-ray photoemission measurements of the Te 4d, Cd 4d, and valence band. This indicates that grain boundaries are the main factor limiting lifetimes. Based on these results, we have developed an understanding of the effects of oxygen and grain boundary oxides on postdeposition processing and enhanced grain growth