Etude de bruit de fond induit par les muons dans l'expérience ...

tel-00724955, version 1 - 23 Aug 2012
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78 The EDELWEISS-II experiment
The first phase of the EDELWEISS experiment successfully proved the detection
method of the heat-and-ionization Germanium crystals. However, the experimental
volume was limited to one liter. To significantly increase the size of the experiment,
the second phase of the experiment, EDELWEISS-II [137] uses a larger size dilution
cryostat which can house up to 120 detectors (∼ 30 kg), as described in Section 3.2.1.
Then, the shielding (Section 3.2) and the performance of the detectors (Section 3.1.3
and Section 3.1.4) have been improved. A muon veto detector (Section 3.3) and two
neutron counters (Section 3.4) have been built to further lower and understand the
background in the nuclear recoil band.
In this second phase of the experiment, the effective exposure time will be increased
by a factor 100, while the background rate should not exceed the level
of Γbg < 2 · 10 −3 kg·d to reach the aimed sensitivity goal. The goal is to achieve
a sensitivity of better than 10 −8 pb on the spin-independent WIMP-nucleon crosssection,
cf. Figure 3.16. After several commissioning runs in 2006 and improvements
on hardware components, data acquisition has started in 2007 with 28 bolometers
(∼ 9 kg).