36 research outputs found
Expected Performance of CryoArray
WIMP-nucleon cross sections below 10^(-9) pb may be probed by ton-scale
experiments with low thresholds and background rates ~20 events per year. An
array of cryogenic detectors ("CryoArray") could perform well enough to reach
this goal. Sufficient discrimination and background suppression of photons has
already been demonstrated. Reduction of neutron backgrounds may be achieved by
siting the experiment deep enough. Removal of the surface-electron backgrounds
alone has not yet been demonstrated, but the reductions required even for this
troublesome background are quite modest and appear achieveable.Comment: 4 pages, 2 figures. Talk at DM2002 Conference, Marina del Rey, CA,
Feb 20-22, 200
A New Model-Independent Method for Extracting Spin-Dependent Cross Section Limits from Dark Matter Searches
A new method is proposed for extracting limits on spin-dependent WIMP-nucleon
interaction cross sections from direct detection dark matter experiments. The
new method has the advantage that the limits on individual WIMP-proton and
WIMP-neutron cross sections for a given WIMP mass can be combined in a simple
way to give a model-independent limit on the properties of WIMPs scattering
from both protons and neutrons in the target nucleus. Extension of the
technique to the case of a target material consisting of several different
species of nuclei is discussed.Comment: 15 pages, 6 Encapsulated Postscript figure
Proposed low-energy absolute calibration of nuclear recoils in a dual-phase noble element TPC using D-D neutron scattering kinematics
We propose a new technique for the calibration of nuclear recoils in large noble element dual-phase time projection chambers used to search for WIMP dark matter in the local galactic halo. This technique provides an measurement of the low-energy nuclear recoil response of the target media using the measured scattering angle between multiple neutron interactions within the detector volume. The low-energy reach and reduced systematics of this calibration have particular significance for the low-mass WIMP sensitivity of several leading dark matter experiments. Multiple strategies for improving this calibration technique are discussed, including the creation of a new type of quasi-monoenergetic 272 keV neutron source. We report results from a time-of-flight based measurement of the neutron energy spectrum produced by an Adelphi Technology, Inc. DD108 neutron generator, confirming its suitability for the proposed nuclear recoil calibration.Peer Reviewe
The scintillation and ionization yield of liquid xenon for nuclear recoils
XENON10 is an experiment designed to directly detect particle dark matter. It
is a dual phase (liquid/gas) xenon time-projection chamber with 3D position
imaging. Particle interactions generate a primary scintillation signal (S1) and
ionization signal (S2), which are both functions of the deposited recoil energy
and the incident particle type. We present a new precision measurement of the
relative scintillation yield \leff and the absolute ionization yield Q_y, for
nuclear recoils in xenon. A dark matter particle is expected to deposit energy
by scattering from a xenon nucleus. Knowledge of \leff is therefore crucial for
establishing the energy threshold of the experiment; this in turn determines
the sensitivity to particle dark matter. Our \leff measurement is in agreement
with recent theoretical predictions above 15 keV nuclear recoil energy, and the
energy threshold of the measurement is 4 keV. A knowledge of the ionization
yield \Qy is necessary to establish the trigger threshold of the experiment.
The ionization yield \Qy is measured in two ways, both in agreement with
previous measurements and with a factor of 10 lower energy threshold.Comment: 8 pages, 9 figures. To be published in Nucl. Instrum. Methods
CDMS, Supersymmetry and Extra Dimensions
The CDMS experiment aims to directly detect massive, cold dark matter
particles originating from the Milky Way halo. Charge and lattice excitations
are detected after a particle scatters in a Ge or Si crystal kept at ~30 mK,
allowing to separate nuclear recoils from the dominating electromagnetic
background. The operation of 12 detectors in the Soudan mine for 75 live days
in 2004 delivered no evidence for a signal, yielding stringent limits on dark
matter candidates from supersymmetry and universal extra dimensions. Thirty Ge
and Si detectors are presently installed in the Soudan cryostat, and operating
at base temperature. The run scheduled to start in 2006 is expected to yield a
one order of magnitude increase in dark matter sensitivity.Comment: To be published in the proceedings of the 7th UCLA symposium on
sources and detection of dark matter and dark energy in the universe, Marina
del Rey, Feb 22-24, 200
Design and Performance of the XENON10 Dark Matter Experiment
XENON10 is the first two-phase xenon time projection chamber (TPC) developed
within the XENON dark matter search program. The TPC, with an active liquid
xenon (LXe) mass of about 14 kg, was installed at the Gran Sasso underground
laboratory (LNGS) in Italy, and operated for more than one year, with excellent
stability and performance. Results from a dark matter search with XENON10 have
been published elsewhere. In this paper, we summarize the design and
performance of the detector and its subsystems, based on calibration data using
sources of gamma-rays and neutrons as well as background and Monte Carlo
simulations data. The results on the detector's energy threshold, energy and
position resolution, and overall efficiency show a performance that exceeds
design specifications, in view of the very low energy threshold achieved (<10
keVr) and the excellent energy resolution achieved by combining the ionization
and scintillation signals, detected simultaneously
The LUX Prototype Detector: Heat Exchanger Development
The LUX (Large Underground Xenon) detector is a two-phase xenon Time
Projection Chamber (TPC) designed to search for WIMP-nucleon dark matter
interactions. As with all noble element detectors, continuous purification of
the detector medium is essential to produce a large (1ms) electron lifetime;
this is necessary for efficient measurement of the electron signal which in
turn is essential for achieving robust discrimination of signal from background
events. In this paper we describe the development of a novel purification
system deployed in a prototype detector. The results from the operation of this
prototype indicated heat exchange with an efficiency above 94% up to a flow
rate of 42 slpm, allowing for an electron drift length greater than 1 meter to
be achieved in approximately two days and sustained for the duration of the
testing period.Comment: 12 pages, 9 figure
Deep Underground Science and Engineering Lab: S1 Dark Matter Working Group
A study of the current status of WIMP dark matter searches has been made in
the context of scientific and technical planning for a Deep Underground Science
and Engineering Laboratory (DUSEL) in the U.S. The table of contents follows:
1. Overview
2. WIMP Dark Matter: Cosmology, Astrophysics, and Particle Physics
3. Direct Detection of WIMPs
4. Indirect Detection of WIMPs
5. Dark Matter Candidates and New Physics in the Laboratory
6. Synergies with Other Sub-Fields
7. Direct Detection Experiments: Status and Future Prospects
8. Infrastructure
9. International Context
10. Summary and Outlook
11. AcknowledgmentsComment: Final working group report of 17 Feb 2007 updated to address reviewer
comments (Latex, 32 pages
The Majorana Neutrinoless Double-Beta Decay Experiment
The proposed Majorana double-beta decay experiment is based on an array of
segmented intrinsic Ge detectors with a total mass of 500 kg of Ge isotopically
enriched to 86% in 76Ge. A discussion is given of background reduction by:
material selection, detector segmentation, pulse shape analysis, and
electro-formation of copper parts and granularity. Predictions of the
experimental sensitivity are given. For an experimental running time of 10
years over the construction and operation of Majorana, a half-life sensitivity
of ~4x10^27 y (neutrinoless) is predicted. This corresponds to an effective
Majorana mass of the electron neutrino of ~0.03-0.04 eV, according to recent
QRPA and RQRPA matrix element calculations.Comment: 10 pages, 7 figure
An Ultra-Low Background PMT for Liquid Xenon Detectors
Results are presented from radioactivity screening of two models of
photomultiplier tubes designed for use in current and future liquid xenon
experiments. The Hamamatsu 5.6 cm diameter R8778 PMT, used in the LUX dark
matter experiment, has yielded a positive detection of four common radioactive
isotopes: 238U, 232Th, 40K, and 60Co. Screening of LUX materials has rendered
backgrounds from other detector materials subdominant to the R8778
contribution. A prototype Hamamatsu 7.6 cm diameter R11410 MOD PMT has also
been screened, with benchmark isotope counts measured at <0.4 238U / <0.3 232Th
/ <8.3 40K / 2.0+-0.2 60Co mBq/PMT. This represents a large reduction, equal to
a change of \times 1/24 238U / \times 1/9 232Th / \times 1/8 40K per PMT,
between R8778 and R11410 MOD, concurrent with a doubling of the photocathode
surface area (4.5 cm to 6.4 cm diameter). 60Co measurements are comparable
between the PMTs, but can be significantly reduced in future R11410 MOD units
through further material selection. Assuming PMT activity equal to the measured
90% upper limits, Monte Carlo estimates indicate that replacement of R8778 PMTs
with R11410 MOD PMTs will change LUX PMT electron recoil background
contributions by a factor of \times1/25 after further material selection for
60Co reduction, and nuclear recoil backgrounds by a factor of \times 1/36. The
strong reduction in backgrounds below the measured R8778 levels makes the
R11410 MOD a very competitive technology for use in large-scale liquid xenon
detectors.Comment: v2 updated to include content after reviewer comments (Sep 2012