[en] An improvement of the statistical and systematic uncertainty beyond the level achieved in GALLEX is an essential prerequisite for GNO. As major contributions to these errors are associated with the detection of the EC-decay of ⁷¹Ge in miniaturized gas counters, low-temperature calorimetric detectors (LTCs) might provide a promising alternative for a later phase of GNO. We report the status of our R and D project on optimization of LTCs for this application

[en] Using the proximity effect of iridium and gold we fabricate sensitive phase transition thermometers. In spite of problems with other material combinations iridium/gold thermometers show an excellent long-term stability. Up to now we reached transition temperatures in the range from 20 to 100 mK on different absorber materials for example silicon, germanium and sapphire. A study of detectors consisting of a dielectric sapphire absorber, an Ir/Au thermometer and an additional superconducting film is presented. In this case some phonons produced by an interaction in the absorber can break up Cooper-Pairs in the superconducting film. Some energy is stored in the quasiparticle system and reemitted into the absorber with a delay. The recombination phonons are again detected with the thermometer. From the pulse shape of the temperature signal the lifetime of the quasiparticles can be extracted. The results for aluminum and tantalum are presented

No abstract available

[en] We report on the results of the first underground dark matter search with light versus heat discrimination. It has been performed at the Canfranc Underground Laboratory in the frame of the Rare Objects SEarch with Bolometers UndergrounD (ROSEBUD) Collaboration with a double bolometer consisting of a 54 g scintillating CaWO₄ and a thin Ge (0.26 g) for light detection. Its capability to distinguish nuclear against electron recoils has been proved and applied to derive limits for weakly interacting massive particle (WIMP) dark matter candidates

[en] The ROSEBUD experiment for Direct Dark Matter detection settled in 1999 in the Canfranc Underground Laboratory. The first phase of the experiment was dedicated to the understanding and reduction of the radioactive background following successive removals of the radioimpure materials. Sapphire (25g, 50g) and germanium (67g) absorbers were used. Thresholds respectively lower than 1keV and 450 eV were achieved on these detectors. The second phase of the experiment plans to use scintillating bolometers to discriminate between recoiling nuclei and electrons. Prototypes using commercial CaWO₄ (54g ) and BGO (46g) were designed for this purpose. While internal contamination was found and identified in both targets, neutron calibrations revealed their high discrimination power. A 6 keV threshold on the heat channel of the BGO bolometer points out the interest of such a novel material, for Dark Matter research on neutralinos having spin-dependent or spin-independent interactions

[en] An experiment has been carried out at the Canfranc Underground Laboratory with a 54 g CaWO₄ scintillating bolometer in the frame of the ROSEBUD (Rare Objects SEarch with Bolometers UndergrounD) Collaboration. This detector has been developed in order to achieve a good particle discrimination capability by means of the simultaneous detection of light and heat with the goal of rejecting background in dark matter search. This Letter reports, as a byproduct of such development, improved limits on the lifetime for α decaying tungsten isotopes

[en] ANAIS (Annual Modulation with NaI's) is an experiment planned to investigate seasonal modulation effects in the signal of galactic WIMPs using up to 107 kg of NaI(Tl) in the Canfranc Underground Laboratory (Spain). A prototype using one single crystal (10.7 kg) is being developed before the installation of the complete experiment; the first results presented here show an average background level of 1.2 counts/(keV kg day) from threshold (E_thr ∼ 4 keV) up to 10 keV

[en] We are developing cryogenic detectors based on Ir/Au phase transition thermometers and superconducting aluminium tunnel junctions for different applications, where a high-energy resolution and a low detection threshold is required. These applications comprise low background experiments such as CRESST and GNO as well as high-energy resolution X-ray spectroscopy for astrophysics and fluorescence analysis where energy resolutions below 30 eV (FWHM) at 5.89 keV were achieved

[en] The sensitivity of an ultra low background Ge detector for the (ββ)_0ν decay of ⁷⁶Ge is estimated in two different experimental set-ups. The main difference between them is the inclusion or not of an active NaI shielding. We find that sensitivity of the Ge detector is not improved by this active shielding either for the O⁺-->O⁺ or the O⁺-->2⁺ (ββ)_0ν transitions. Our results provide a valuable information for future ⁷⁶Ge enriched experiments. (orig.)

[en] The ROSEBUD (Rare Objects SEarch with Bolometers UndergrounD) experiment consists of three small sapphire bolometers with NTD-Ge sensors operating at 20 mK in the Canfranc Underground Laboratory in an attempt to directly detect low mass Weakly Interacting Massive Particles (WIMPs) through their scattering off Al and O nuclei. We report in this paper the results of three runs (about 10 days each) performed along 1999 and the progressive background reduction obtained essentially from modifications in the cryostat. A new run is in progress to complete the first phase of the experiment