No abstract available

No abstract available

[en] The behaviour of nearly-saturated superfluid helium films, several hundred Angstroms thick was investigated under zero gravity conditions in a small cryostat carried on a 0.3 m diameter, 3 m long sounding rocket, using a quartz microbalance technique. The flight provided 30 s of high acceleration, about 5 min. of zero gravity, and 90 s of mg acceleration. The temperature of the experiment ranged from 1.67 to 2.15 K. In contrast to ground test results, thick films uniformly distributed on all surfaces were observed in zero gravity. (author)

No abstract available

[en] Steady state flow rate and friction factor of superfluid helium (HeII) were measured under controlled experimental conditions. The driving pressure difference was due to the saturated vapour pressure difference and a small hydrostatic pressure head; it ranged from 1 to 35 mm Hg (0.13 to 4.7 kPa). Previous studies were restricted primarily to isothermal flow and small He II column height difference. In this study the temperature ranged from 1.5 K to T lambda. The stainless steel transfer tubes with 0.87 mm and 1.18 mm internal diameters were under an adiabatic condition. Several tube lengths were studied, the results were universal. For comparison, the transfer of He I was also investigated with the same apparatus. Characteristics on the flow rate and friction factor are presented and discussed. (author)

No abstract available

No abstract available

[en] Study of the hydrologic system at Yucca Mountain, Nevada, requires extraction of pore-water samples from unsaturated tuff bedrock. Two generations of compression cells have been designed and tested for extracting representative, unaltered pore-water samples from unsaturated tuff cores. The one-dimensional compression cell has a maximum compressive stress rating of 552 MPa. Results from 86 tests show that the minimum degree of saturation for successful extraction of pore water was about 14% for non welded tuff and about 61% for densely welded tuff. The high-pressure, one-dimensional compression cell has a maximum compressive stress rating of 827 MPa. Results from 109 tests show that the minimum degree of saturation for successful extraction of pore water was about 7.5% for non welded tuff and about 34% for densely welded tuff. Geochemical analyses show that, in general, there is a decrease in ion concentration of pore waters as extraction pressures increase. Only small changes in pore-water composition occur during the one-dimensional extraction test

[en] The initial results of experiments characterizing CuInSe₂ deposition by a hybrid sputtering-and-evaporation technique are presented. The method is demonstrated to yield films with compositions and structural properties comparable with those commonly accepted for polycrystalline CuInSe₂ over a large composition range at growth temperatures up to 450⁰C. Film compositions are uniform to with +-1 atomic percent and nonuniformities can be directly related to the deposition geometry. The Se flux is shown to play a major role in determining both the Se and the In contents of the films at elevated temperatures. The substrate properties also strongly affect the film composition. Layers deposited on sputtered Mo surfaces exhibit a lower In content than films on glass at all temperatures examined. Cu, In, and Se diffusion into the column boundaries of the Mo substrates was observed at all growth temperatures

[en] The evolution of microstructure in Mo-Cu thin films during annealing has been investigated by in situ sheet resistance measurements, ex situ x-ray diffraction, and in situ hot-stage as well as conventional transmission electron microscopy. Mo-Cu thin films, deposited on various glass substrates by magnetron sputtering at ∼30 degree C, were supersaturated solid solutions of Cu in Mo with a nanocrystalline microstructure. The as-deposited films had large compressive residual stresses owing to the low homologous deposition temperature and low Ar pressure during deposition. Annealing results showed two distinct sets of microstructural changes occurring in the temperature ranges between ∼300 and 500 degree C, and ∼525 and 810 degree C. In the lower-temperature range, anisotropic growth of nanocrystallites was accompanied by stress relaxation without any observable phase separation. At temperatures greater than ∼525 degree C, the metastable solid solution collapsed and Cu precipitated at the grain boundaries. Increasing temperature resulted in the coarsening of Cu precipitates and simultaneous growth of Mo grains. At temperatures greater than ∼700 degree C, phase separation and grain growth approached completion. copyright 1995 American Institute of Physics