[en] Microcalorimeters (or bolometers) operated at temperatures below 100 mK allow individual counting of photons and electrons with a very low energy detection threshold. The physics is based on the pulse temperature increase of the target (or absorber) of the detector due to the complete absorption of both electrons and photons. Since this target can be constructed with a perfect 4-π geometry, a bolometer offers potentially a new method for absolute activity measurements of radionuclides emitting low-energy radiation. In this paper we present our first results of a feasibility study of activity standardization of a ⁵⁵Fe solution with a prototype 4-π bolometer

[en] Due to the intrinsic performances of cryogenic detectors such as energy resolution, LPRI has decided to use these devices to improve the quality of the radioactive measurements usually obtained with classical semiconductor detectors. A bolometer with a 10 μg tin absorber has been developed at IAS (Institut d'Astrophysique Spatiale) and has been tested in the cryogenic installation of LPRI; an energy resolution (full width half maximum, FWHM) of 39 eV has been obtained on the Kα line of Mn. Besides these good spectrometry results, an absolute activity measurement using bolometers is proposed by adapting an absorber geometry for 4 π counting

[en] A first characterization of a 1100 g sapphire bolometer, performed at sea level and at a working temperature of 40 mK, is presented. Despite perturbations coming from the high-radioactive background and cosmic rays, calibration spectra could be achieved with an internal α source and a ⁵⁷Co γ-ray source: the experimental threshold is 25 keV, while the FWHM resolution is 17.4 keV for the 122 keV peak. Possible heat release effects are discussed, and a new limit of 9x10^-14 W/g is obtained for sapphire

[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] Cryogenic detectors offer remarkably better energy resolutions than those achievable with conventional semiconductor or scintillation detectors. With the additional asset of a detection efficiency close to unity for low-energy X-ray photons and electrons, these detectors have the potential to perform X-ray, gamma and electron spectroscopy of a hitherto unknown quality, in particular at low energies. Two types of cryogenic detectors are described and the results of prototype detectors are presented

[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] 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

[en] The Rare Objects SEarch with Bolometers UndergrounD (ROSEBUD) experiment consists of three small sapphire bolometers with NTD-Ge sensors operating at 20 mK and attempts to directly detect low mass Weakly Interacting Massive Particles (WIMPs) through their scattering off Al and O nuclei. It has been recently installed in an ultralow background environment in the Canfranc Underground Laboratory (at 2450 m.w.e.) and the testing period is underway. The status and preliminary results of the experiment are reported in this paper

[en] An experiment to look for light WIMPs with sapphire bolometers is to be installed in the Canfranc Underground Laboratory (at 2450 m.w.e) in the Spanish Pyrenees. In the first stage two small 25g bolometers with NTD-Ge sensors, operating at 25 mK, with an energy threshold of 300eV and FWHM energy resolution of 120eV at 1.5keV will perform a background test experiment. The features of the bolometers, the radioactivity measurements of the components and the set-up and status of the experiment are reported