|XENON is a direct dark matter detection experiment using liquid xenon as the detector medium. The goal is to detect the small charge and light signal after a dark matter particle interacts with a xenon nucleus. The first module (XENON10) has been successfully operated at the Gran Sasso Undeground Laboratory (LNGS), in dark matter search mode from August 2006 to February 2007. The picture shows the XENON10 detector in its low-background shield.
First results on spin-independent WIMP-nucleon interactions have been submitted for publication in May 2007. No dark matter candidates have been detected, the sensitivity to WIMP-nucleon cross sections extending to about 4x10-8pb (4x10-44cm2) at a WIMP mass of 30 GeV/c2. The figure below shows the excluded region in the WIMP cross section-WIMP mass parameter space (region above the red curve), along with the CDMS-II 2005 results (blue curve), and predictions from the constraines MSSM (filled regions).
Currently, a slightly modified XENON10 version is under operation at the Gran Sasso Laboratory, and the construction of the next phase, XENON10+, is ongoing.
Our group is involved in operations at LNGS, in data processing and analysis, in Monte Carlo simulations of the expected gamma, alpha and neutron backgrounds, in material screening of detector and shield components with a high-purity Ge spectrometer, in the WIMP analysis for spin-dependent and spin-independent interactions, as well as in the design, construction and Monte Carlo simulations for the next phase. We are leading the collaboration wide Monte Carlo Working Group.
To measure the ionization and scintillation yield of nuclear recoils at low energies we have built a small dual-phase xenon chamber, which we plan to operate in a neutron beam. The picture below (left) shows the inner chamber, made of teflon and stainless steel grids. Additional pictures and information can be found on this site.
Our group has been operating a 2 kg high-purity Ge (HPGe) spectrometer at the Soudan Mine in Minnesota, to screen the detector and shield components for their U/Th/K/Co content. The results were used to construct a full background model of XENON10, and are guiding the construction of the next phase, Xenon10+. The above picture (right) shows the HPGe detector during its installation at Soudan in 2005, in the SOLO background facility. Currently the HPGe detector has been moved to the Gran Sasso Laboratory, where an improved shield, including an inner Cu layer and a nitrogen purged lock-chamber is under construction. The new setup will be used to screen materials for the future, larger scale experiment.
We are conducting Geant4 Monte Carlo simulation to predict the XENON10 internal and external backgrounds at LNGS, as well as gamma calibration source simulations. Pictures of the XENON10 geometry are shown below.
We are also involved in the design and construction of a first 100 kg liquid Xenon detector module. A 100 kg liquid Xenon detector would fit into the current XENON10 shield at LNGS.
XENON in the news:
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