242 research outputs found
First demonstration of THGEM/GAPD-matrix optical readout in two-phase Cryogenic Avalanche Detector in Ar
The multi-channel optical readout of a THGEM multiplier coupled to a matrix
of 3x3 Geiger-mode APDs (GAPDs) was demonstrated in a two-phase Cryogenic
Avalanche Detector (CRAD) in Ar. The GAPDs recorded THGEM-hole avalanches in
the Near Infrared (NIR). At an avalanche charge gain of 160, the yield of the
combined THGEM/GAPD-matrix multiplier amounted at ~80 photoelectrons per 20 keV
X-ray absorbed in the liquid phase. A spatial resolution of 2.5 mm (FWHM) has
been measured for the impinging X-rays. This technique has potential
applications in coherent neutrino-nucleus scattering and dark matter search
experiments.Comment: 4 pages, 6 figures. Presented at Vienna Conference of Instrumentation
(Feb 15-20, 2013, Vienna, Austria). Submitted to the Proceeding
MPGDs in Compton imaging with liquid-xenon
The interaction of radiation with liquid xenon, inducing both scintillation
and ionization signals, is of particular interest for Compton-sequences
reconstruction. We report on the development and recent results of a
liquid-xenon time-projection chamber, dedicated to a novel nuclear imaging
technique named "3 gamma imaging". In a first prototype, the scintillation is
detected by a vacuum photomultiplier tube and the charges are collected with a
MICROMEGAS structure; both are fully immersed in liquid xenon. In view of the
final large-area detector, and with the aim of minimizing dead-zones, we are
investigating a gaseous photomultiplier for recording the UV scintillation
photons. The prototype concept is presented as well as preliminary results in
liquid xenon. We also present soft x-rays test results of a gaseous
photomultiplier prototype made of a double Thick Gaseous Electron Multiplier
(THGEM) at normal temperature and pressure conditions.Comment: presented at MPGD09, CRETE, June 2009; to be published in JINST
Proceedings, PDF, 10 pages, 11 figure
On the operation of a Micropattern Gaseous UV-Photomultiplier in Liquid-Xenon
Operation results are presented of a UV-sensitive gaseous photomultiplier
(GPM) coupled through a MgF2 window to a liquid-xenon scintillator. It
consisted of a reflective CsI photocathode deposited on top of a THick Gaseous
Electron Multiplier (THGEM); further multiplication stages were either a second
THGEM or a Parallel Ionization Multiplier (PIM) followed by a MICROMEsh GAseous
Structure (MICROMEGAS). The GPM operated in gas-flow mode with non-condensable
gas mixtures. Gains of 10^4 were measured with a CsI-coated double-THGEM
detector in Ne/CH4 (95:5), Ne/CF4 (95:5) and Ne/CH4/CF4 (90:5:5), with soft
X-rays at 173 K. Scintillation signals induced by alpha particles in liquid
xenon were measured here for the first time with a double-THGEM GPM in He/CH4
(92.5:7.5) and a triple-structure THGEM/PIM/MICROMEGAS GPM in Ne/CH4 (90:10)
with a fast-current preamplifier.Comment: 12 pages, 9 figures, submitted to JINS
First Dark Matter Results from the XENON100 Experiment
The XENON100 experiment, in operation at the Laboratori Nazionali del Gran
Sasso in Italy, is designed to search for dark matter WIMPs scattering off 62
kg of liquid xenon in an ultra-low background dual-phase time projection
chamber. In this letter, we present first dark matter results from the analysis
of 11.17 live days of non-blind data, acquired in October and November 2009. In
the selected fiducial target of 40 kg, and within the pre-defined signal
region, we observe no events and hence exclude spin-independent WIMP-nucleon
elastic scattering cross-sections above 3.4 x 10^-44 cm^2 for 55 GeV/c^2 WIMPs
at 90% confidence level. Below 20 GeV/c^2, this result constrains the
interpretation of the CoGeNT and DAMA signals as being due to spin-independent,
elastic, light mass WIMP interactions.Comment: 5 pages, 5 figures. Matches published versio
Material screening and selection for XENON100
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.Comment: 8 pages, 1 figur
Dark Matter Results from 100 Live Days of XENON100 Data
We present results from the direct search for dark matter with the XENON100
detector, installed underground at the Laboratori Nazionali del Gran Sasso of
INFN, Italy. XENON100 is a two-phase time projection chamber with a 62 kg
liquid xenon target. Interaction vertex reconstruction in three dimensions with
millimeter precision allows to select only the innermost 48 kg as ultra-low
background fiducial target. In 100.9 live days of data, acquired between
January and June 2010, no evidence for dark matter is found. Three candidate
events were observed in a pre-defined signal region with an expected background
of 1.8 +/- 0.6 events. This leads to the most stringent limit on dark matter
interactions today, excluding spin-independent elastic WIMP-nucleon scattering
cross-sections above 7.0x10^-45 cm^2 for a WIMP mass of 50 GeV/c^2 at 90%
confidence level.Comment: 5 pages, 5 figures; matches accepted versio
Implications on Inelastic Dark Matter from 100 Live Days of XENON100 Data
The XENON100 experiment has recently completed a dark matter run with 100.9
live-days of data, taken from January to June 2010. Events in a 48kg fiducial
volume in the energy range between 8.4 and 44.6 keVnr have been analyzed. A
total of three events have been found in the predefined signal region,
compatible with the background prediction of (1.8 \pm 0.6) events. Based on
this analysis we present limits on the WIMP-nucleon cross section for inelastic
dark matter. With the present data we are able to rule out the explanation for
the observed DAMA/LIBRA modulation as being due to inelastic dark matter
scattering off iodine at a 90% confidence level.Comment: 3 pages, 3 figure
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