The XENON100 dark matter experiment Aprile, E.; Arisaka, K.; Arneodo, F. ...
Astroparticle physics,
April 2012, 2012-4-00, 20120401, Letnik:
35, Številka:
9
Journal Article
Recenzirano
Odprti dostop
► XENON100 is currently one of the most sensitive experiments to detect WIMP dark matter. ► Detector design and active/passive shielding reduce the radioactive background level. ► The event vertex of ...an interaction is reconstructed with a few mm precision. ► All position dependent signal corrections are presented in the paper. ► An energy scale exploiting the light-charge anti-correlation leads to an energy resolution competitive with NaI(Tl) crystals.
The XENON100 dark matter experiment uses liquid xenon (LXe) in a time projection chamber (TPC) to search for xenon nuclear recoils resulting from the scattering of dark matter Weakly Interacting Massive Particles (WIMPs). In this paper we present a detailed description of the detector design and present performance results, as established during the commissioning phase and during the first science runs.
The active target of XENON100 contains 62kg of LXe, surrounded by an LXe veto of 99kg, both instrumented with photomultiplier tubes (PMTs) operating inside the liquid or in xenon gas. The LXe target and veto are contained in a low-radioactivity stainless steel vessel, embedded in a passive radiation shield and is installed underground at the Laboratori Nazionali del Gran Sasso (LNGS), Italy. The experiment has recently published results from a 100 live-days dark matter search. The ultimate design goal of XENON100 is to achieve a spin-independent WIMP-nucleon scattering cross section sensitivity of σ=2×10−45cm2 for a 100GeV/c2 WIMP.
► Material selection based on their intrinsic radioactive contaminations is crucial for low background experiments. ► We present detailed results from the material screening and selection campaign ...for the XENON100 dark matter experiment. ► The measurements were performed using low background gamma-ray spectrometry and mass spectrometry.
Results of the extensive radioactivity screening campaign to identify materials for the construction of XENON100 are reported. This dark matter search experiment is operated underground at Laboratori Nazionali del Gran Sasso (LNGS), Italy. Several ultra sensitive High Purity Germanium detectors (HPGe) have been used for gamma ray spectrometry. Mass spectrometry has been applied for a few low mass plastic samples. Detailed tables with the radioactive contaminations of all screened samples are presented, together with the implications for XENON100.
A technique to measure low intensity fast neutron flux has been developed. The design, calibrations, procedure for data analysis and interpretation of the results are discussed in detail. The ...technique has been applied to measure the neutron background from rock at the Boulby Underground Laboratory, a site used for dark matter and other experiments, requiring shielding from cosmic ray muons. The experiment was performed using a liquid scintillation detector. A 6.1
l volume stainless steel cell was filled with an in-house made liquid scintillator loaded with Gd to enhance neutron capture. A two-pulse signature (proton recoils followed by gammas from neutron capture) was used to identify the neutron events from much larger gamma background from PMTs. Suppression of gammas from the rock was achieved by surrounding the detector with high-purity lead and copper. Calibrations of the detector were performed with various gamma and neutron sources. Special care was taken to eliminate PMT afterpulses and correlated background events from the delayed coincidences of two pulses in the Bi-Po decay chain. A four month run revealed a neutron-induced event rate of 1.84
±
0.65(
stat.) events/day. Monte Carlo simulations based on the GEANT4 toolkit were carried out to estimate the efficiency of the detector and the energy spectra of the expected proton recoils. From comparison of the measured rate with Monte Carlo simulations the flux of fast neutrons from rock was estimated as (1.72
±
0.61(
stat.)
±
0.38(
syst.))
×
10
−6
cm
−2
s
−1 above 0.5
MeV.
First results are presented from an analysis of data from the DRIFT-IIa and DRIFT-IIb directional dark matter detectors at Boulby Mine in which alpha particle tracks were reconstructed and used to ...characterise detector performance—an important step towards optimising directional technology. The drift velocity in DRIFT-IIa was
59.3
±
0.2
(stat)
±
7.5
(sys)
ms
-
1
based on an analysis of naturally occurring alpha-emitting background. The drift velocity in DRIFT-IIb was
57
±
1
(stat)
±
3
(sys)
ms
-
1
determined by the analysis of alpha particle tracks from a
210Po source. Three-dimensional range reconstruction and range spectra were used to identify alpha particles from the decay of
222Rn,
218Po,
220Rn and
216Po. This study found that
(
22
±
2
)
%
of
218Po progeny (from
222Rn decay) did not plate out and remained suspended in the 40
Torr CS
2 gas fill until they decayed. A likely explanation for this is that some of the polonium progeny are produced in an uncharged state. For
216Po progeny (from
220Rn decay) the undeposited fraction was apparently much higher at
(
100
-
35
+
0
)
%
most likely due to a shorter lifetime, causing a larger fraction of the progeny to decay whilst drifting to the cathode plane. This explanation implies a much slower drift time for positively charged polonium progeny compared to
CS
2
-
ions.
Presented here are results of simulations of neutron background performed for a time projection chamber acting as a particle dark matter detector in an underground laboratory. The investigated ...background includes neutrons from rock and detector components, generated via spontaneous fission and (
α
,n) reactions, as well as those due to cosmic-ray muons. Neutrons were propagated to the sensitive volume of the detector and the nuclear recoil spectra were calculated. Methods of neutron background suppression were also examined and limitations to the sensitivity of a gaseous dark matter detector are discussed. Results indicate that neutrons should not limit sensitivity to WIMP-nucleon interactions down to a level of
(
1
-
3
)
×
10
-
8
pb in a 10
kg detector.
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