Test of CsI (Tℓ) crystals for the dark matter search

Abstract

Searches for weakly interacting massive particles(WIMP) can be based on the detection of nuclear recoil energy in CsI(Tℓ) crystals. We demonstrate that low energy gamma rays down to few keV is detected with CsI(Tℓ) crystal detector. A clear peak at 6 keV is observed using X-ray source. Good energy resolution and linearity have been achieved down to X-ray region. In addition, we also show that alpha particles and gamma rays can be clearly separated using the different time characteristics of the crystal.

Nuclear recoil measurement in CsI(Tl) crystal for Cold Dark Matter detection

“…By optimizing the detector geometry and using green-extended photo-cathode, a detector with several kg modular mass and a light yield of a few photo-electron per keV can be realized [10,11]. The background from ambient radioactivity or intrinsic radio-purity is of course crucial to all low-background experiments.…”

“…Levels of better than the 10 −12 g/g level in concentration for the 238 U and 232 Th series have been demonstrated, assuming secular equilibrium. The potential problem of the internal 137 Cs contaminations can be overcome via selection of clear ore materials and careful chemical processing and purification treatment [10]. Figure 12 is the sensitivity plot for spin-independent WIMP interaction cross section per nucleon with a target mass of 1 ton of CsI(Tl).…”

“…An experiment towards 200 kg of CsI(Tl) crystal scintillators to study low energy neutrino interactions at the Kuo-Sheng power reactor is being pursued [7], while the adaptation of the crystal for Dark Matter searches are the focus of several on-going projects [8,9,10,11].…”

Reduction of coincident photomultiplier noise relevant to astroparticle physics experiments

“…WIMP search experiments use various techniques to distinguish between nuclear recoil events, expected from WIMP interactions, and background electron recoil events. In the case of NaI(Tl) crystals, such as used in NAIAD, and several other experiments, this discrimination is achieved using pulse shape analysis to identify nuclear recoils [6,7,8,9,10,11]. This is possible because in NaI(Tl), for instance, the scintillator time constant for nuclear recoil events is shorter (typically 170-200 ns) than for electron recoils (typically 240-300 ns).…”

The Texono Research Program on Neutrino and Astroparticle Physics

“…The measurements also provide the first confirmation of the Optical Model predictions on neutron elastic scatterings with a direct measurement on the nuclear recoils of heavy nuclei, as illustrated by the differential crosssection measurements of Figure 8b. A full scale Dark Matter experiment with CsI(Tl) crystals is being pursued by the KIMS Collaboration in South Korea [20].…”