No Arabic abstract
The Spherical gaseous detector (or Spherical Proportional Counter, SPC) is a novel type of par- ticle detector, with a broad range of applications. Its main features include a very low energy threshold independent of the volume (due to its very low capacitance), a good energy resolution, robustness and a single detection readout channel, in its simplest version. Applications range from radon emanation gas monitoring, neutron flux and gamma counting and spectroscopy to dark matter searches, in particular low mass WIMPs and coherent neutrino scattering measure- ment. Laboratories interested in these various applications share expertise within the NEWS (New Experiments With Sphere) network. SEDINE, a low background prototype installed at underground site of Laboratoire Souterrain de Modane is currently being operated and aims at measuring events at very low energy threshold, around 100 eV. We will present the energy cali- bration with 37Ar, the surface background reduction, the measurement of detector background at sub-keV energies, and show anticipated sensitivities for light dark matter search.
The main characteristics of a new concept of spherical gaseous detectors, with some details on its operation are first given. The very low energy threshold of such detector has led to investigations of its potential performance for dark matter particle searches, in particular low mass WIMPs : original methods for energy and fiducial volume calibration and background rejection are described and preliminary results obtained with a low radioactivity prototype operated in Laboratoire Souterrain de Modane (Frejus lab) are presented. Typical expected sensitivities in cross section for low mass WIMPs are also shown, and other applications briefly discussed.
Light dark matter in the context of dark sector theories is an attractive candidate for the dark matter thought to make up the bulk of the mass of our universe. We explore here the possibility of using a low-pressure, negative-ion, time projection chamber detector to search for light dark matter behind the beam dump of an electron accelerator. The sensitivity of a 10 m long detector is several orders of magnitude better than existing limits. This sensitivity includes regions of parameter space where light dark matter is predicted to have a required relic density consistent with measured dark matter density. Backgrounds at shallow depth will need to be considered carefully. However, several signatures exist, including a powerful directional signature, which will allow a detection even in the presence of backgrounds.
A direct WIMP (Weakly Interacting Massive Particle) detector with a neutron veto system is designed to better reject neutrons. An experimental configuration is studied in the present paper: a WIMP detectors with CsI(Na) target is placed inside a reactor neutrino detector. The neutrino detector is used as a neutron veto device. The neutron background for the experimental design has been estimated using the Geant4 simulation. The results show that the neutron background can decrease to O(0.01) events per year per tonne of CsI(Na). We calculate the sensitivity to spin-independent WIMP-nucleon elastic scattering. An exposure of one tonne $times$ year could reach a cross-section of about 3$times$$10^{-11}$ pb.
The aim of the presented work was to develop further techniques based on a Micromegas-TPC, in order to reach a high gas gain with good energy resolution, and to search for gas mixtures suitable for rare event detection. This paper focuses on xenon, which is convenient for the search of neutrinoless double beta decay in 136 Xe. Conversely, a small admixture of xenon to CF 4 can reduce attachment in the latter. This gas mixture would be suitable for dark matter searches and the study of solar and reactor neutrinos. Various configurations of the Micromegas plane were investigated and are described.
With the development of the Imaging Atmospheric Cherenkov Technique (IACT), Gamma-ray astronomy has become one of the most interesting and productive fields of astrophysics. Current IACT telescope arrays (MAGIC, H.E.S.S, VERITAS) use photomultiplier tubes (PMTs) to detect the optical/near-UV Cherenkov radiation emitted due to the interaction of gamma rays with the atmosphere. For the next generation of IACT experiments, the possibility of replacing the PMTs with Silicon photomultipliers (SiPMs) is being studied. Among the main drawbacks of SiPMs are their limited active area (leading to an increase in the cost and complexity of the camera readout) and their sensitivity to unwanted wavelengths. Here we propose a novel method to build a relatively low-cost pixel consisting of a SiPM attached to a PMMA disc doped with a wavelength shifter. This pixel collects light over a much larger area than a single standard SiPM and improves sensitivity to near-UV light while simultaneously rejecting background. We describe the design of a detector that could also have applications in other fields where detection area and cost are crucial. We present results of simulations and laboratory measurements of a pixel prototype and from field tests performed with a 7-pixel cluster installed in a MAGIC telescope camera.