126 research outputs found
Gator: a low-background counting facility at the Gran Sasso Underground Laboratory
A low-background germanium spectrometer has been installed and is being
operated in an ultra-low background shield (the Gator facility) at the Gran
Sasso underground laboratory in Italy (LNGS). With an integrated rate of ~0.16
events/min in the energy range between 100-2700 keV, the background is
comparable to those of the world's most sensitive germanium detectors. After a
detailed description of the facility, its background sources as well as the
calibration and efficiency measurements are introduced. Two independent
analysis methods are described and compared using examples from selected sample
measurements. The Gator facility is used to screen materials for XENON, GERDA,
and in the context of next-generation astroparticle physics facilities such as
DARWIN.Comment: 14 pages, 6 figures, published versio
New Measurement of the Relative Scintillation Efficiency of Xenon Nuclear Recoils Below 10 keV
Liquid xenon is an important detection medium in direct dark matter
experiments, which search for low-energy nuclear recoils produced by the
elastic scattering of WIMPs with quarks. The two existing measurements of the
relative scintillation efficiency of nuclear recoils below 20 keV lead to
inconsistent extrapolations at lower energies. This results in a different
energy scale and thus sensitivity reach of liquid xenon dark matter detectors.
We report a new measurement of the relative scintillation efficiency below 10
keV performed with a liquid xenon scintillation detector, optimized for maximum
light collection. Greater than 95% of the interior surface of this detector was
instrumented with photomultiplier tubes, giving a scintillation yield of 19.6
photoelectrons/keV electron equivalent for 122 keV gamma rays. We find that the
relative scintillation efficiency for nuclear recoils of 5 keV is 0.14, staying
constant around this value up to 10 keV. For higher energy recoils we measure a
value around 20%, consistent with previously reported data. In light of this
new measurement, the XENON10 experiment's results on spin-independent
WIMP-nucleon cross section, which were calculated assuming a constant 0.19
relative scintillation efficiency, change from cm to
cm for WIMPs of mass 100 GeV/c, and from
cm to cm for WIMPs of mass 30
GeV/c.Comment: 8 pages, 8 figure
FlashCam: A fully digital camera for CTA telescopes
The future Cherenkov Telescope Array (CTA) will consist of several tens of
telescopes of different mirror sizes. CTA will provide next generation
sensitivity to very high energy photons from few tens of GeV to >100 TeV.
Several focal plane instrumentation options are currently being evaluated
inside the CTA consortium. In this paper, the current status of the FlashCam
prototyping project is described. FlashCam is based on a fully digital camera
readout concept and features a clean separation between photon detector plane
and signal digitization/triggering electronics.Comment: In Proceedings of the 2012 Heidelberg Symposium on High Energy
Gamma-Ray Astronomy. All CTA contributions at arXiv:1211.184
Study of nuclear recoils in liquid argon with monoenergetic neutrons
For the development of liquid argon dark matter detectors we assembled a
setup in the laboratory to scatter neutrons on a small liquid argon target. The
neutrons are produced mono-energetically (E_kin=2.45 MeV) by nuclear fusion in
a deuterium plasma and are collimated onto a 3" liquid argon cell operating in
single-phase mode (zero electric field). Organic liquid scintillators are used
to tag scattered neutrons and to provide a time-of-flight measurement. The
setup is designed to study light pulse shapes and scintillation yields from
nuclear and electronic recoils as well as from {\alpha}-particles at working
points relevant to dark matter searches. Liquid argon offers the possibility to
scrutinise scintillation yields in noble liquids with respect to the
populations of the two fundamental excimer states. Here we present experimental
methods and first results from recent data towards such studies.Comment: 9 pages, 8 figures, proceedings of TAUP 2011, to be published in
Journal of Physics: Conference Series (JCPS
FlashCam: a fully-digital camera for the medium-sized telescopes of the Cherenkov Telescope Array
The FlashCam group is currently preparing photomultiplier-tube based cameras
proposed for the medium-sized telescopes (MST) of the Cherenkov Telescope Array
(CTA). The cameras are designed around the FlashCam readout concept which is
the first fully-digital readout system for Cherenkov cameras, based on
commercial FADCs and FPGAs as key components for the front-end electronics
modules and a high performance camera server as back-end. This contribution
describes the progress of the full-scale FlashCam camera prototype currently
under construction, as well as performance results also obtained with earlier
demonstrator setups. Plans towards the production and implementation of
FlashCams on site are also briefly presented.Comment: 8 pages, 6 figures. In Proceedings of the 34th International Cosmic
Ray Conference (ICRC2015), The Hague, The Netherlands. All CTA contributions
at arXiv:1508.0589
3D Position Sensitive XeTPC for Dark Matter Search
The technique to realize 3D position sensitivity in a two-phase xenon time
projection chamber (XeTPC) for dark matter search is described. Results from a
prototype detector (XENON3) are presented.Comment: Presented at the 7th UCLA Symposium on "Sources and Detection of Dark
Matter and Dark Energy in the Universe
Constraints on inelastic dark matter from XENON10
It has been suggested that dark matter particles which scatter inelastically
from detector target nuclei could explain the apparent incompatibility of the
DAMA modulation signal (interpreted as evidence for particle dark matter) with
the null results from CDMS-II and XENON10. Among the predictions of
inelastically interacting dark matter are a suppression of low-energy events,
and a population of nuclear recoil events at higher nuclear recoil equivalent
energies. This is in stark contrast to the well-known expectation of a falling
exponential spectrum for the case of elastic interactions. We present a new
analysis of XENON10 dark matter search data extending to E keV
nuclear recoil equivalent energy. Our results exclude a significant region of
previously allowed parameter space in the model of inelastically interacting
dark matter. In particular, it is found that dark matter particle masses
GeV are disfavored.Comment: 8 pages, 4 figure
First Results from the XENON10 Dark Matter Experiment at the Gran Sasso National Laboratory
The XENON10 experiment at the Gran Sasso National Laboratory uses a 15 kg
xenon dual phase time projection chamber (XeTPC) to search for dark matter
weakly interacting massive particles (WIMPs). The detector measures
simultaneously the scintillation and the ionization produced by radiation in
pure liquid xenon, to discriminate signal from background down to 4.5 keV
nuclear recoil energy. A blind analysis of 58.6 live days of data, acquired
between October 6, 2006 and February 14, 2007, and using a fiducial mass of 5.4
kg, excludes previously unexplored parameter space, setting a new 90% C.L.
upper limit for the WIMP-nucleon spin-independent cross-section of 8.8 x
10^{-44} cm^2 for a WIMP mass of 100 GeV/c^2, and 4.5 x 10^{-44} cm^2 for a
WIMP mass of 30 GeV/c^2. This result further constrains predictions of
supersymmetric models.Comment: accepted for publication in Phys. Rev. Let
A search for light dark matter in XENON10 data
We report results of a search for light (<10 GeV) particle dark matter with
the XENON10 detector. The event trigger was sensitive to a single electron,
with the analysis threshold of 5 electrons corresponding to 1.4 keV nuclear
recoil energy. Considering spin-independent dark matter-nucleon scattering, we
exclude cross sections \sigma_n>3.5x10^{-42} cm^2, for a dark matter particle
mass m_{\chi}=8 GeV. We find that our data strongly constrain recent elastic
dark matter interpretations of excess low-energy events observed by CoGeNT and
CRESST-II, as well as the DAMA annual modulation signal.Comment: Manuscript identical to v2 (published version) but also contains
erratum. Note v3==v2 but without \linenumber
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