A high performance distillation system to remove krypton from xenon was constructed, and a purity level of Kr/Xe = ∼ 3 × 10 −12 was achieved. This development is crucial in facilitating high sensitivity low background experiments such as the search for dark matter in the universe.

The hydrogen absorption and thermal desorption behavior of Ni-Ti superelastic alloy immersed in neutral NaCl and NaF aqueous solutions at 25C under an applied cathodic potential for 2 h have been systematically investigated by hydrogen thermal desorption analysis. The critical potential for hydrogen absorption is independent of the type and concentration of solution. The amount of absorbed hydrogen increases with decreasing applied potential, although it is only slightly changed by the type of solution. The amount of hydrogen desorbed at low temperatures, for the alloy immersed in NaF solutions, is larger than those in NaCl solutions, suggesting that the type of solution affects the hydrogen states in the alloy. The present results indicate that for Ni-Ti superelastic alloy, compared with titanium and its alloys, the critical potential for hydrogen absorption is located in a more noble direction, and the amount of absorbed hydrogen is large in NaCl and NaF solutions. Thus, the hydrogen embrittlement of Ni-Ti superelastic alloy probably occurs more readily than those of titanium and its alloys in NaCl and NaF solutions.

Liquid xenon is a suitable material for a dark matter search. For future large scale experiments, single phase detectors are attractive due to their simple configuration and scalability. However, in order to reduce backgrounds, they need to fully rely on liquid xenon's self-shielding property. A prototype detector was developed at Kamioka Observatory to establish vertex and energy reconstruction methods and to demonstrate the self-shielding power against gamma rays from outside of the detector. Sufficient self-shielding power for future experiments was obtained.

The intensity of scintillation light emission from liquid xenon at room temperature was measured. The scintillation light yield at 1 deg. was measured to be 0.64 +/- 0.02 (stat.) +/- 0.06 (sys.) of that at -100 deg. Using the reported light yield at -100 deg. (46 photons/keV), the measured light yield at 1 deg. corresponds to 29 photons/keV. This result shows that liquid xenon scintillator gives high light yield even at room temperature.Comment: 16pages,12figure