2,260 research outputs found
The DRIFT Directional Dark Matter Detector and First Studies of the Head-Tail Effect
Measurement of the direction of the elastic nuclear recoil track and
ionization charge distribution along it, gives unique possibility for
unambiguous detection of the dark matter WIMP particle. Within current
radiation detection technologies only Time Projection Chambers filled with low
pressure gas are capable of such measurement. Due to the character of the
electronic and nuclear stopping powers of low energy nuclear recoils in the
gas, an asymmetric ionization charge distribution along their tracks may be
expected. Preliminary study of this effect, called Head-Tail, has been carried
out here using the SRIM simulation program for Carbon and Sulfur in 40 Torr
carbon disulfide, as relevant to the DRIFT detector. Investigations were
focused on ion tracks projected onto the axis of the initial direction of
motion in the energy range between 10 and 400 keV. Results indicate the likely
existence of an asymmetry influenced by two competing effects: the nature of
the stopping power and range straggling. The former tends to result in the Tail
being greater than the Head and the latter the reverse. It has been found that
for projected tracks the mean position of the ionization charge flows from
'head' to 'tail' with the magnitude depending on the ion type and its energy.Comment: To appear in the proceedings of Dark 2007 Sixth International
Heidelberg conference on "Dark Matter in Astro & Particle Physics", Sydney,
Australia 24th-28th September 200
The expected background spectrum in NaI dark matter detectors and the DAMA result
Detailed Monte Carlo simulations of the expected radioactive background rates
and spectra in NaI crystals are presented. The obtained spectra are then
compared to those measured in the DAMA/NaI and DAMA/LIBRA experiments. The
simulations can be made consistent with the measured DAMA spectrum only by
assuming higher than reported concentrations of some isotopes and even so leave
very little room for the dark matter signal. We conclude that any
interpretation of the annual modulation of the event rate observed by DAMA as a
dark matter signal, should include full consideration of the background
spectrum. This would significantly restrict the range of dark matter models
capable of explaining the modulation effect.Comment: 17 pages, 6 figure
Narrow muon bundles from muon pair production in rock
We revise the process of muon pair production by high-energy muons in rock
using the recently published cross-section. The three-dimensional Monte Carlo
code MUSIC has been used to obtain the characteristics of the muon bundles
initiated via this process. We have compared them with those of conventional
muon bundles initiated in the atmosphere and shown that large underground
detectors, capable of collecting hundreds of thousands of multiple muon events,
can discriminate statistically muon induced bundles from conventional ones.
However, we find that the enhancement of the measured muon decoherence function
over that predicted at small distances, recently reported by the MACRO
experiment, cannot be explained by the effect of muon pair production alone,
unless its cross-section is underestimated by a factor of 3.Comment: 10 pages, 1 table, 2 figures, to be published in Physics Letters
The Constitutionality of Section 9-103 of the Local Governmental and Governmental Employees Tort Immunity Act
Kirman and the Middle East: Paul Ward English\u27s City and Village in Iran: Settlement and Economy in the Kirman Basin
Measurement of the Scintillation Efficiency of Na Recoils in NaI(Tl) down to 10 keV Nuclear Recoil Energy relevant to Dark Matter Searches
We present preliminary results of measurements of the quenching factor for Na
recoils in NaI(Tl) at room temperature, made at a dedicated neutron facility at
the University of Sheffield. Measurements have been performed with a 2.45 MeV
mono-energetic neutron generator in the energy range from 10 keV to 100 keV
nuclear recoil energy. A BC501A liquid scintillator detector was used to tag
neutrons. Cuts on pulse-shape discrimination from the BC501A liquid
scintillator detector and neutron time-of-flight were performed on pulses
recorded by a digitizer with a 2 ns sampling time. Measured quenching factors
range from 19% to 26%, in agreement with other experiments. From pulse-shape
analysis, a mean time of pulses from electron and nuclear recoils are compared
down to 2 keV electron equivalent energy.Comment: to appear in Proc. 6th Int. Workshop on the Identification of Dark
Matter, 11-16 September 2006, Rhodes, Greece; 6 pages, 4 figures; corrected
preliminary theoretical estimation curve plotted in figure
The DRIFT Project: Searching for WIMPS with a Directional Detector
A low pressure time projection chamber for the detection of WIMPs is
discussed. Discrimination against Compton electron background in such a device
should be very good, and directional information about the recoil atoms would
be obtainable. If a full 3-D reconstruction of the recoil tracks can be
achieved, Monte Carlo studies indicate that a WIMP signal could be identified
with high confidence from as few as 30 detected WIMP-nucleus scattering events.Comment: 5 pages, 3 figures. Presented at Dark 98, Heidelberg, July 1998, and
to appear in conference proceeding
Modernization of the Walker River Irrigation District Water Gauges
The Irrigation Training and Research Center (ITRC) and Walker River Irrigation District (WRID) collaborated on WRID’s Water Gauge Improvement Project with support from the Bureau of Reclamation, U.S. Department of Interior in Carson City, Nevada. This paper presents a summary of the proposed plan and implementation for improving water gauges in WRID with strategic engineering recommendations for new hardware and control equipment; water management strategies; flow measurement devices; and integration of a new district-wide SCADA system. Field investigations and engineering analyses were carried out by the ITRC in 2009 to inspect existing WRID infrastructure, to review current operational procedures, and to interview district staff. This information was analyzed and compiled to summarize the scope of work for system improvements. The ITRC prioritized the order of engineering implementation and automation recommendations, provided planning-level cost estimates, and has assisted WRID in organizing implementation over the past five years
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