110 research outputs found
Optimization of light collection from crystal scintillators for cryogenic experiments
High light collection efficiency is an important requirement in any
application of scintillation detectors. The purpose of this study is to
investigate the possibility for improving this parameter in cryogenic
scintillation bolometers, which can be considered as a promising detectors in
experiments investigating neutrinoless double beta decay and dark matter.
Energy resolutions and relative pulse amplitudes of scintillation detectors
using ZnWO4 scintillation crystals of different shapes (cylinder 20 mm in
dimater by 20 mm and hexagonal prism with diagonal 20 mm and height 20 mm),
reflector materials and shapes, optical contact and surface properties
(polished and diffused) were measured at room temperature. Propagation of
optical photons in these experimental conditions was simulated using Geant4 and
ZEMAX codes. The results of the simulations are found to be in good agreement
with each other and with direct measurements of the crystals. This could be
applied to optimize the geometry of scintillation detectors used in the
cryogenic experiments.Comment: 12 pages, 8 figures, 1 Tabl
Impact of geometry on light collection efficiency of scintillation detectors for cryogenic rare event searches
Simulations of photon propagation in scintillation detectors were performed
with the aim to find the optimal scintillator geometry, surface treatment, and
shape of external reflector in order to achieve maximum light collection
efficiency for detector configurations that avoid direct optical coupling, a
situation that is commonly found in cryogenic scintillating bolometers in
experimental searches for double beta decay and dark matter. To evaluate the
light collection efficiency of various geometrical configurations we used the
ZEMAX ray-tracing software. It was found that scintillators in the shape of a
triangular prism with an external mirror shaped as truncated cone gives the
highest light collection efficiency. The results of the simulations were
confirmed by carrying out measurements of the light collection efficiencies of
CaWO4 crystal scintillators. A comparison of simulated and measured values of
light output shows good agreemen
Detection of the Natural Alpha Decay of Tungsten
The natural alpha decay of 180W has been unambiguously detected for the first
time. The alpha peak is found in a (gamma,beta and neutron)-free background
spectrum. This has been achieved by the simultaneous measurement of phonon and
light signals with the CRESST cryogenic detectors. A half-life of T1/2 = (1.8
+- 0.2) x 10^18 y and an energy release of Q = (2516.4 +- 1.1 (stat.) +- 1.2
(sys.)) keV have been measured. New limits are also set on the half-lives of
the other naturally occurring tungsten isotopes.Comment: Submitted to Physical Review C Revised versio
The CRESST Dark Matter Search
We present first competitive results on WIMP dark matter using the
phonon-light-detection technique. A particularly strong limit for WIMPs with
coherent scattering results from selecting a region of the phonon-light plane
corresponding to tungsten recoils. The observed count rate in the neutron band
is compatible with the rate expected from neutron background. CRESST is
presently being upgraded with a 66 channel SQUID readout system, a neutron
shield and a muon veto system. This results in a significant improvement in
sensitivity.Comment: 6 pages, 3 figures, to be published in the proceedings of the 5th
International Workshop on the Identification and Detection of Dark Matter IDM
2004, Edinburgh, Sept. 2004, World Scientifi
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