No abstract available

No abstract available

[en] Published in summary form only

[en] Published in summary form only

No abstract available

[en] A Monte Carlo simulation of the propagation of relativistic solar flare protons in the interplanetary magnetic field was used to understand the intensity-time profiles and anisotropies for the GLEs on November 22, 1977 and May 7, 1978. Mean free path for pitch angle scattering of 0.5 AU and 5 AU, respectively, were deduced. The injection of the solar flare protons had an extended time structure that was found to be of similar shape as the x ray burst profiles in the bands 1-8 A and 0.5-4 A, respectively

[en] The Paul Scherrer Institut has initiated a project to develop a thermophotovoltaic (TPV) converter for residential heating applications. By economic reasons we have decided to design a thermophotovoltaic generator based on Si-cells and, accordingly, to make use of the selective emission properties of ytterbium containing emitter materials. In this contribution, we focus on the emitter materials and present results of an experimental study on the influence of ytterbium concentration on the emissive properties of ytterbium doped yttrium aluminum garnet (YAG) and yttria. The emitter materials were prepared by decomposition of nitrates and by co-precipitation methods with subsequent calcination at elevated temperatures. The polycrystalline materials are characterized by X-Ray diffraction (XRD), particle size distribution (PSD) measurements and Raman and fluorescence microscopy. The emissive properties of the Yb-doped materials have been measured at about 1400 K. Additionally, current-voltage (I endash V) curves of the Si-cells used in a prototype TPV generator have been recorded for selected emitter materials. copyright 1997 American Institute of Physics

[en] The need for precise characterization of dual-phase xenon detectors has grown as the technology has matured into a state of high efficacy for rare event searches. The Michigan Xenon detector was constructed to study the microphysics of particle interactions in liquid xenon across a large energy range in an effort to probe aspects of radiation detection in liquid xenon. We report the design and performance of a small 3D position sensitive dual-phase liquid xenon time projection chamber with high light yield (L_y"1"2"2=15.2 pe/keV at zero field), long electron lifetime (τ > 200 μs), and excellent energy resolution (σ/E = 1% for 1,333 keV gamma rays in a drift field of 200 V/cm). Liquid xenon time projection chambers with such high energy resolution may find applications not only in dark matter direct detection searches, but also in neutrinoless double beta decay experiments and other applications

[en] We present a new measurement of the cosmic-ray positron fraction at energies between 5 and 15 GeV with the balloon-borne HEAT-p-bar instrument in the spring of 2000. The data presented here are compatible with our previous measurements, obtained with a different instrument. The combined data from the three HEAT flights indicate a small positron flux of nonstandard origin above 5 GeV. We compare the new measurement with earlier data obtained with the HEAT-e^± instrument, during the opposite epoch of the solar cycle, and conclude that our measurements do not support predictions of charge sign dependent solar modulation of the positron abundance at 5 GeV

[en] Dual phase Xenon Time Projection Chambers (XeTPCs) are being used by several experiments as a promising technique for direct detection of dark matter. We report on the design and performance of a small 3-D sensitive dual phase XeTPC. The position resolution is 2 mm in the center of detector, limited by the hole size of the mesh at the proportional scintillation region. An energy resolution of 1.6%(σ/E) for 662 keV gamma rays is achieved in the very center of the detector by combining the ionization and scintillation signals at a drift field of 0.5 kV/cm. This represents the best energy resolution achieved among liquid xenon detectors to date. The energy resolution is only slightly dependent on the drift field. Better than 2% energy resolution (σ/E) for 662 keV gamma rays was achieved for drift fields between 100 V/cm and 2 kV/cm. If such a high position and energy resolution can be achieved in a large volume detector, the dual phase XeTPC will have potential applications in surveys of neutrinoless double-beta decay and in gamma ray imaging