7 research outputs found
First Results from the DRIFT-IIa Dark Matter Detector
Data from the DRIFT-IIa directional dark matter experiment are presented,
collected during a near continuous 6 month running period. A detailed
calibration analysis comparing data from gamma-ray, x-ray and neutron sources
to a GEANT4 Monte Carlo simulations reveals an efficiency for detection of
neutron induced recoils of 94+/-2(stat.)+/-5(sys.)%. Software-based cuts,
designed to remove non-nuclear recoil events, are shown to reject 60Co
gamma-rays with a rejection factor of better than 8x10-6 for all energies above
threshold. An unexpected event population has been discovered and is shown here
to be due to the alpha-decay of 222Rn daughter nuclei that have attached to the
central cathode. A limit on the flux of neutrons in the Boulby Underground
Laboratory is derived from analysis of unshielded and shielded data.Comment: 43 pages, 14 figures, submitted to Astroparticle Physic
Track Reconstruction and Performance of DRIFT Directional Dark Matter Detectors using Alpha Particles
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)] m/s based
on an analysis of naturally-occurring alpha-emitting background. The drift
velocity in DRIFT-IIb was [57 +/- 1 (stat) +/- 3 (sys)] m/s determined by the
analysis of alpha particle tracks from a Po-210 source. 3D range reconstruction
and energy spectra were used to identify alpha particles from the decay of
Rn-222, Po-218, Rn-220 and Po-216. This study found that (22 +/- 2)% of Po-218
progeny (from Rn-222 decay) are produced with no net charge in 40 Torr CS2. For
Po-216 progeny (from Rn-220 decay) the uncharged fraction is (100 +0 -35)%.Comment: 27 pages, 12 figures, 5 tables. Submitted to Nuclear Instruments and
Methods in Physics Research, Section A. Subj-class: Instrumentation and
Detector
The ZEPLIN II dark matter detector: data acquisition system and data reduction
ZEPLIN-II is a two-phase (liquid/gas) xenon dark matter detector searching
for WIMP-nucleon interactions. In this paper we describe the data acquisition
system used to record the data from ZEPLIN-II and the reduction procedures
which parameterise the data for subsequent analysis.Comment: 11 pages, 10 figure
The ZEPLIN II dark matter detector: data acquisition system and data reduction
ZEPLIN-II is a two-phase (liquid/gas) xenon dark matter detector searching
for WIMP-nucleon interactions. In this paper we describe the data acquisition
system used to record the data from ZEPLIN-II and the reduction procedures
which parameterise the data for subsequent analysis.Comment: 11 pages, 10 figure
Measurement of the Range Component Directional Signature in a DRIFT-II Detector using 252Cf Neutrons
The DRIFT collaboration utilizes low pressure gaseous detectors to search for
WIMP dark matter with directional signatures. A 252Cf neutron source was placed
on each of the principal axes of a DRIFT detector in order to test its ability
to measure directional signatures from the three components of very low energy
(~keV/amu) recoil ranges. A high trigger threshold and the event selection
procedure ensured that only sulfur recoils were analyzed. Sulfur recoils
produced in the CS2 target gas by the 252Cf source closely match those expected
from massive WIMP induced sulfur recoils. For each orientation of the source a
directional signal from the range components was observed, indicating that the
detector is directional along all 3 axes. An analysis of these results yields
an optimal orientation for DRIFT detectors when searching for a directional
signature from WIMPs. Additional energy dependent information is provided to
aid in understanding this effect.Comment: 14 pages, 1 Table, 8 Figure
Limits on spin-dependent WIMP-nucleon cross-sections from the first ZEPLIN-II data
The first underground data run of the ZEPLIN-II experiment has set a limit on
the nuclear recoil rate in the two-phase xenon detector for direct dark matter
searches. In this paper the results from this run are converted into the limits
on spin-dependent WIMP-proton and WIMP-neutron cross-sections. The minimum of
the curve for WIMP-neutron cross-section corresponds to 0.07 pb at a WIMP mass
of around 65 GeV.Comment: 12 pages, 2 figures, to be published in Physics Letters
The ZEPLIN III Detector; Results from Surface Calibrations
ZEPLIN-III is a direct dark-matter search instrument using liquid xenon as a target.Both the scintillation light and the ionisation charge are measured.The instrument has been built and it is currently being testing in a surface laboratory.We present results from some of the initial testing, including design thermal control system verification, photomultiplier calibration (including spectral measurements with 60 keV photons from 241Am) and two-phase operation showing simultaneous measurement of scintillation and charge and position reconstruction