937 research outputs found
Ion Drift Meter for Dynamics Explorer
The ion drift meter for Dynamics Explorer B is discussed. It measures two mutually perpendicular angles of arrival of thermal ions with respect to the sensor look directions. These angles lie in the vertical and horizontal planes and may be thought of as pitch and yaw in the conventional aerodynamic sense. The components of the ion drift velocity along vertical and horizontal axes through the spacecraft body are derived to first order from knowledge of the spacecraft velocity vector and more accurately with additional knowledge of the component of ion drift along the sensor look direction
Planar ion trap (retarding potential analyzer) experiment for atmosphere explorer
The retarding potential analyzer and drift meter were carried aboard all three Atmosphere Explorer spacecraft. These instruments measure the total thermal ion concentration and temperature, the bulk thermal ion velocity vector and some limited properties of the relative abundance of H(+), He(+), O(+) and molecular ions. These instruments functioned with no internal failures on all the spacecraft. On AE-E there existed some evidence for external surface contamination that damaged the integrity of the RPA sweep grids. This led to some difficulties in data reduction and interpretation that did not prove to be a disastrous problem. The AE-D spacecraft functioned for only a few months before it re-entered. During this time the satellite suffered from a nutation about the spin axis of about + or - 2 deg. This 2 deg modulation was superimposed upon the ion drift meter horizontal ion arrival angle output requiring the employment of filtering techniques to retrieve the real data
Direct WIMP identification: Physics performance of a segmented noble-liquid target immersed in a Gd-doped water veto
We evaluate background rejection capabilities and physics performance of a
detector composed of two diverse elements: a sensitive target (filled with one
or two species of liquefied noble gasses) and an active veto (made of Gd-doped
ultra-pure water). A GEANT4 simulation shows that for a direct WIMP search,
this device can reduce the neutron background to O(1) event per year per tonne
of material. Our calculation shows that an exposure of one tonne year
will suffice to exclude spin-independent WIMP-nucleon cross sections ranging
from pb to pb.Comment: 17 pages, 5 figures. Version accepted for publication in JCA
A Xenon Condenser with a Remote Liquid Storage Vessel
We describe the design and operation of a system for xenon liquefaction in
which the condenser is separated from the liquid storage vessel. The condenser
is cooled by a pulse tube cryocooler, while the vessel is cooled only by the
liquid xenon itself. This arrangement facilitates liquid particle detector
research by allowing easy access to the upper and lower flanges of the vessel.
We find that an external xenon gas pump is useful for increasing the rate at
which cooling power is delivered to the vessel, and we present measurements of
the power and efficiency of the apparatus.Comment: 22 pages, 7 figures Corrected typos in authors lis
Observation of the Dependence of Scintillation from Nuclear Recoils in Liquid Argon on Drift Field
We have exposed a dual-phase Liquid Argon Time Projection Chamber (LAr-TPC)
to a low energy pulsed narrowband neutron beam, produced at the Notre Dame
Institute for Structure and Nuclear Astrophysics to study the scintillation
light yield of recoiling nuclei in a LAr-TPC. A liquid scintillation counter
was arranged to detect and identify neutrons scattered in the LAr-TPC target
and to select the energy of the recoiling nuclei.
We report the observation of a significant dependence on drift field of
liquid argon scintillation from nuclear recoils of 11 keV. This observation is
important because, to date, estimates of the sensitivity of noble liquid TPC
dark matter searches are based on the assumption that electric field has only a
small effect on the light yield from nuclear recoils.Comment: v3 updated to reflect published version, including a set of plots for
49.9 keV dat
Measurement of Scintillation and Ionization Yield and Scintillation Pulse Shape from Nuclear Recoils in Liquid Argon
We have measured the scintillation and ionization yield of recoiling nuclei
in liquid argon as a function of applied electric field by exposing a
dual-phase liquid argon time projection chamber (LAr-TPC) to a low energy
pulsed narrow band neutron beam produced at the Notre Dame Institute for
Structure and Nuclear Astrophysics. Liquid scintillation counters were arranged
to detect and identify neutrons scattered in the TPC and to select the energy
of the recoiling nuclei. We report measurements of the scintillation yields for
nuclear recoils with energies from 10.3 to 57.3 keV and for median applied
electric fields from 0 to 970 V/cm. For the ionization yields, we report
measurements from 16.9 to 57.3 keV and for electric fields from 96.4 to 486
V/cm. We also report the observation of an anticorrelation between
scintillation and ionization from nuclear recoils, which is similar to the
anticorrelation between scintillation and ionization from electron recoils.
Assuming that the energy loss partitions into excitons and ion pairs from
Kr internal conversion electrons is comparable to that from Bi
conversion electrons, we obtained the numbers of excitons () and ion
pairs () and their ratio () produced by nuclear recoils from
16.9 to 57.3 keV. Motivated by arguments suggesting direction sensitivity in
LAr-TPC signals due to columnar recombination, a comparison of the light and
charge yield of recoils parallel and perpendicular to the applied electric
field is presented for the first time.Comment: v2 to reflect published versio
Snowmass CF1 Summary: WIMP Dark Matter Direct Detection
As part of the Snowmass process, the Cosmic Frontier WIMP Direct Detection
subgroup (CF1) has drawn on input from the Cosmic Frontier and the broader
Particle Physics community to produce this document. The charge to CF1 was (a)
to summarize the current status and projected sensitivity of WIMP direct
detection experiments worldwide, (b) motivate WIMP dark matter searches over a
broad parameter space by examining a spectrum of WIMP models, (c) establish a
community consensus on the type of experimental program required to explore
that parameter space, and (d) identify the common infrastructure required to
practically meet those goals.Comment: Snowmass CF1 Final Summary Report: 47 pages and 28 figures with a 5
page appendix on instrumentation R&
Radon backgrounds in the DEAP-1 liquid-argon-based Dark Matter detector
The DEAP-1 \SI{7}{kg} single phase liquid argon scintillation detector was
operated underground at SNOLAB in order to test the techniques and measure the
backgrounds inherent to single phase detection, in support of the
\mbox{DEAP-3600} Dark Matter detector. Backgrounds in DEAP are controlled
through material selection, construction techniques, pulse shape discrimination
and event reconstruction. This report details the analysis of background events
observed in three iterations of the DEAP-1 detector, and the measures taken to
reduce them.
The Rn decay rate in the liquid argon was measured to be between 16
and \SI{26}{\micro\becquerel\per\kilogram}. We found that the background
spectrum near the region of interest for Dark Matter detection in the DEAP-1
detector can be described considering events from three sources: radon
daughters decaying on the surface of the active volume, the expected rate of
electromagnetic events misidentified as nuclear recoils due to inefficiencies
in the pulse shape discrimination, and leakage of events from outside the
fiducial volume due to imperfect position reconstruction. These backgrounds
statistically account for all observed events, and they will be strongly
reduced in the DEAP-3600 detector due to its higher light yield and simpler
geometry
Nuclear recoil response of liquid xenon and its impact on solar 8B neutrino and dark matter searches
Knowledge of the ionization and scintillation responses of liquid xenon (LXe)
to nuclear recoils is crucial for LXe-based dark matter experiments. Current
calibrations carry large uncertainties in the low-energy region below
keV where signals from dark matter particles of 10 GeV/c masses are
expected. The coherent elastic neutrino-nucleus scattering (CENS) by solar
B neutrinos also results in a continuum of nuclear recoil events below 3.0
keV (99\% of events), which further complicates low-mass dark matter
searches in LXe experiments. In this paper, we describe a method to quantify
the uncertainties of low-energy LXe responses using published calibration data,
followed by case studies to evaluate the impact of yield uncertainties on
B searches and low-mass dark matter sensitivity in a typical ton-scale
LXe experiment. We conclude that naively omitting yield uncertainties leads to
overly optimistic limits by factor for a 6 GeV/c WIMP mass. Future
nuclear recoil light yield calibrations could allow experiments to recover this
sensitivity and also improve the accuracy of solar B flux measurements
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