The EDELWEISS-II Collaboration has completed a direct search for WIMP dark matter with an array of ten 400-g cryogenic germanium detectors in operation at the Laboratoire Souterrain de Modane. The ...combined use of thermal phonon sensors and charge collection electrodes with an interleaved geometry enables the efficient rejection of γ-induced radioactivity as well as near-surface interactions. A total effective exposure of 384 kg d has been achieved, mostly coming from fourteen months of continuous operation. Five nuclear recoil candidates are observed above 20 keV, while the estimated background is 3.0 events. The result is interpreted in terms of limits on the cross-section of spin-independent interactions of WIMPs and nucleons. A cross-section of 4.4×10−8 pb is excluded at 90%CL for a WIMP mass of 85 GeV. New constraints are also set on models where the WIMP-nucleon scattering is inelastic.
EMBRACE@Nançay is a prototype instrument consisting of an array of 4608 densely packed antenna elements creating a fully sampled, unblocked aperture. This technology is proposed for the Square ...Kilometre Array and has the potential of providing an extremely large field of view making it the ideal survey instrument. We describe the system, calibration procedures, and results from the prototype.
The final results of the EDELWEISS-I dark matter search using cryogenic heat-and-ionization Ge detectors are presented. The final data sample corresponds to an increase by a factor five in exposure ...relative to the previously published results. A recoil energy threshold of 13
keV or better was achieved with three 320
g detectors working simultaneously over four months of stable operation. Limits on the spin-independent cross-section for the scattering of a WIMP on a nucleon are derived from an accumulated fiducial exposure of 62
kg
day.
The final results of the EDELWEISS-I dark matter search using cryogenic heat-and-ionization Ge detectors are presented. The final data sample corresponds to an increase by a factor five in exposure ...relative to the previously published results. A recoil energy threshold of 13 keV or better was achieved with three 320g detectors working simultaneously over four months of stable operation. Limits on the spin-independent cross-section for the scattering of a WIMP on a nucleon are derived from an accumulated fiducial exposure of 62 kg.d.
This paper describes the first step in the development of a digital platform dedicated to primary radionuclide measurements. In order to validate the implementation of an on-line processing based on ...extendable dead-times, a FPGA-based digital system has been programmed for liquid scintillation counting. After a description of the hardware, TDCR (Triple to Double Coincidence Ratio) measurements are presented. Comparisons of activity measurements with the classical system operating at LNHB are used to validate the new system; coincidence counting differences observed when increasing the resolving time in the digital platform are discussed.
An overview of non-directional direct detection methods is given. The currently leading experiments for spin independent WIMPs interactions are using simultaneous measurement of two quantities for ...event-by-event background discrimination in cryogenic bolometers and noble gas like xenon. Besides these, several interesting techniques have been developped, each having a specific advantage concerning e.g. energy threshold lowering or strong immunity to ionizing radiations background. Technologies used and most recent results about spin-dependent and spin-independent cases are presented.
A multi-tiered data structure, analysis toolkit and data processing management system has been constructed using ROOT and CouchDB. This system is well suited for experiments that acquire many ...computer files of raw data over the course of months or years, that are distributed to different computing centers and further reduced in size by several steps of data processing. Data handling for experiments searching for rare events extracted from digitized pulse traces typically fit this description. An implementation of this system has been constructed for the EDELWEISS-III experiment and is described here in some detail. This solution may also serve as a prototype system for the proposed EURECA experiment.
The LNE-LNHB is engaged in a development program on digital instrumentation, the first step being the instrumentation of a NaI well-type detector set-up.
The prototype acquisition card and its ...technical specifications are presented together with the first comparison with the classical NIM-based acquisition chain, for counting rates up to 100
kcps. The digital instrumentation is shown to be counting-loss free in this range. This validates the main option adopted in this project, namely the implementation of an extending dead time with live-time measurement already successfully used in the MTR2 NIM module developed at LNE-LNHB.
This paper presents our interpretation and understanding of the different backgrounds in the EDELWEISS-I data sets. We analyze in detail the several populations observed, which include gammas, ...alphas, neutrons, thermal sensor events and surface events, and try to combine all data sets to provide a coherent picture of the nature and localization of the background sources. In light of this interpretation, we draw conclusions regarding the background suppression scheme for the EDELWEISS-II phase.
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