[en] We present a study of a 100 g low temperature Ge detector, allowing identification of surface events down to the energy threshold. The bolometer is fitted with segmented electrodes and two NbSi Anderson insulator thermometric layers. Analysis of the athermal signals amplitudes allows us to identify and reject all events occurring in the first millimeter under the electrodes

[en] We report the design of amorphous NbSi thin film bolometer thermometers on Silicon Nitride membranes. Due to the low-thermal conductivity of Si₃N₄, this material has several applications in millimeter wavelength bolometers and microcalorimetry. Compared to NTD-Ge thermometers, similar sensitivities are obtained with a 50 times lesser volume. The smallest realized films have a rectangular surface (100x400 μm²) and are 100 nm thick. Optimization of the thermometer shape, NbSi composition and electrical material contact is discussed. The goal of this development is to manufacture a complete array of bolometers by photolithography techniques

[en] We describe the digital acquisition systems used in the EDELWEISS experiment. In the EDELWEISS-I experiment, both charge and phonon signals are continuously digitized after preamplification and transferred to a computer using a high-speed DMA channel via a 1.5 Gbit/s optical fibre link, decoupling the detectors from the acquisition computer. Both phonon and charge triggers are defined numerically, without any analog triggering module, allowing a flexible filtering and trigger definition. The performances reached in this system are described, together with the improvements presently realized for the second phase of the experiment, EDELWEISS-II, involving up to 120 detectors

[en] We present a method allowing identification of near surface events in bulk cryogenic detector. It is based on amplitude effects in the athermal signal given by Anderson insulator thermometric layers. Applied to Ge detectors, the method may allow the rejection of near electrode events with incomplete charge collection, down to the energy threshold

[en] We present an analysis, supported by numerical simulations, of the heat and ionization yield for events with incomplete charge collection in low-temperature germanium detectors. A consistent explanation of the ionization and heat balance (including an incomplete Luke effect) at different collection voltages is obtained on the assumption that any carriers (electrons or holes) reaching the surface are trapped at surface states

[en] In order to measure the Cosmological Microwave Background (CMB), high performance 'bolometric cameras' similar to CCDs are currently developed. They are made out of thousands of pixels, each of which is a bolometer on its own. In order to meet the requirements for future CMB experiments - notably the measurement of the CMB B-mode polarization - the sensitivity of each pixel should be improved by one or two orders of magnitude compared to what now exists. Taking advantage of the solid-state properties of amorphous Nb_xSi_1-x thin films, we here present a proposal for a new bolometer structure that would increase the pixels' sensitivity, its response time and allow a simplification of the fabrication process. In this resistive detector (that can be either high impedance or TES) the three functions of a classical bolometer (wave absorption, temperature measurement and thermal decoupling) are achieved in a single Nb_xSi_1-x film. The frequency properties of this material allow the merger of the two first functions. The natural thermal decoupling between electrons and phonons at low temperature then makes it possible to use this single object as bolometer. This new type of detector solely uses the electronic properties of the Nb_xSi_1-x thin films and is free of any phononic mediation of the energy.

[en] The status of the EDELWEISS experiment (underground dark matter search with heat-ionisation bolometers) is reviewed. Auspicious results achieved with a prototype 70 g Ge heat-ionisation detector under a 2 V reverse bias tension are discussed. Based on gamma and neutron calibrations, a best-case rejection factor, over the 15-45 keV range, of 99.7% for gammas, with an acceptance of 94% for neutrons, is presented first. Some operational results of physical interest obtained under poor low radioactivity conditions follow. They include a raw event rate of around 30 events/day/kg/keV over the same energy range, and, after rejection of part of the background, lead to a conservative upper limit on the signal of approximately 1.6 events/day/kg/keV at a 90% confidence level. Performance degrading surface effects of the detector are speculated upon; and planned upgrades are summarized

[en] A new R&D on lithium molybdate scintillators has begun within a project CLYMENE (Czochralski growth of Li${}_2$MoO${}_4$ crYstals for the scintillating boloMeters used in the rare EveNts sEarches). One of the main goals of the CLYMENE is a realization of a Li${}_2$MoO${}_4$ crystal growth line to be complementary to the one recently developed by LUMINEU in view of a mass production capacity for CUPID, a next-generation tonne-scale bolometric experiment to search for neutrinoless double-beta decay. In the present paper we report the investigation of performance and radiopurity of 158-g and 13.5-g scintillating bolometers based on a first large-mass (230 g) Li${}_2$MoO${}_4$ crystal scintillator developed within the CLYMENE project. In particular, a good energy resolution (2–7 keV FWHM in the energy range of 0.2–5 MeV), one of the highest light yield (0.97 keV/MeV) amongst Li${}_2$MoO${}_4$ scintillating bolometers, an efficient alpha particles discrimination (10$\sigma$) and potentially low internal radioactive contamination (below 0.2–0.3 mBq/kg of U/Th, but 1.4 mBq/kg of ²¹⁰Po) demonstrate prospects of the CLYMENE in the development of high quality and radiopure Li${}_2$MoO${}_4$ scintillators for CUPID.

[en] The status of the EDELWEISS experiment is presented. First tests of a prototype detector of the '1 kg' stage show an event rate before rejection of ∼2 evt/kg/keV/day above E>20 keV, a factor ∼10 improvement compared to previous runs. An unexpected category of events is evidenced and used to interpret the 'bump' events observed by the UKDMC and Saclay NaI WIMP detection experiments. Finally, the short-term perspectives of the '1 kg' stage, which should allow to sample realistic SUSY models, and the main characteristics of the EDELWEISS-II experiment are described

[en] The status of the EDELWEISS experiment is presented. Data taking of two prototype detectors tested in the setup designed for the '1 kg' stage show an event rate before rejection of ∼2 evt/kg/keV/day above E > 20 keV, a factor ∼10 improvement compared to previous detectors. An unexpected category of events is evidenced which could explain the anomalous events observed by the UKDMC and Saclay NaI WIMP detection experiments