1,723 research outputs found
Gamma Ray Spectroscopy with Scintillation Light in Liquid Xenon
Scintillation light from gamma ray irradiation in liquid xenon is detected by
two Hamamatsu R9288 photomultiplier tubes (PMTs) immersed in the liquid. UV
light reflector material, PTFE, is used to optimize the light collection
efficiency. The detector gives a high light yield of 6 photoelectron per keV
(pe/keV), which allows efficient detection of the 122 keV gamma-ray line from
Co-57, with a measured energy resolution of (8.8+/-0.6)% (sigma). The best
achievable energy resolution, by removing the instrumental fluctuations, from
liquid xenon scintillation light is estimated to be around 6-8% (sigma) for
gamma-ray with energy between 662 keV and 122 keV
A Study of the LXeGRIT Detection Efficiency for MeV Gamma-Rays during the 2000 Balloon Flight Campaign
LXeGRIT - Liquid Xenon Gamma-Ray Imaging Telescope - is the first prototype
of a Compton telescope for \MeV \g-ray astrophysics based on a LXe time
projection chamber. One of the most relevant figures of merit for a Compton
telescope is the detection efficiency for \g-rays, which depends on diverse
contributions such as detector geometry and passive materials, trigger
efficiency, dead time, etc. A detailed study of the efficiency of the LXeGRIT
instrument, based both on laboratory measurements and Monte Carlo simulations,
is presented in this paper.Comment: 20 pages, 15 figures; submitted to NIM
XMASS
The XMASS detector is a large single phase liquid Xenon scintillator.After
its feasibility had been studied using a 100 kg size prototype detector, an 800
kg size detector is being built for dark matter search with the sensitivity of
region in spin-independent cross section. The results of
R\&D study for 800 kg detector, especially ultra low background technologies,
and the prospects of the experiment are described.Comment: 6 pages, 7 figures, for the proceedings of the 1st International
Workshop towards the Giant Liquid Argon Charge Imaging Experiment (GLA2010,
will be published in Journal of Physics, Conference Series (Editors: T.
Hasegawa and A. Rubbia)
Detection of liquid xenon scintillation light with a Silicon Photomultiplier
We have studied the feasibility of a silicon photomultiplier (SiPM) to detect
liquid xenon (LXe) scintillation light. The SiPM was operated inside a small
volume of pure LXe, at -95 degree Celsius, irradiated with an internal Am-241
alpha source. The gain of the SiPM at this temperature was estimated to be 1.8
x 10^6 with bias voltage at 52 V. Based on the geometry of the setup, the
quantum efficiency of the SiPM was estimated to be 22% at the Xe wavelength of
178 nm. The low excess noise factor, high single photoelectron detection
efficiency, and low bias voltage of SiPMs make them attractive alternative UV
photon detection devices to photomultiplier tubes (PMTs) for liquid xenon
detectors, especially for experiments requiring a very low energy detection
threshold, such as neutralino dark matter searches
Performance of a Large Area Avalanche Photodiode in a Liquid Xenon Ionization and Scintillation Chamber
Scintillation light produced in liquid xenon (LXe) by alpha particles,
electrons and gamma-rays was detected with a large area avalanche photodiode
(LAAPD) immersed in the liquid. The alpha scintillation yield was measured as a
function of applied electric field. We estimate the quantum efficiency of the
LAAPD to be 45%. The best energy resolution from the light measurement at zero
electric field is 7.5%(sigma) for 976 keV internal conversion electrons from
Bi-207 and 2.6%(sigma) for 5.5 MeV alpha particles from Am-241. The detector
used for these measurements was also operated as a gridded ionization chamber
to measure the charge yield. We confirm that using a LAAPD in LXe does not
introduce impurities which inhibit the drifting of free electrons.Comment: 13 pages, 8 figure
Naturality, unification and dark matter
We consider a model where electroweak symmetry breaking is driven by
Technicolor dynamics with minimal particle content required for walking
coupling and saturation of global anomalies. Furthermore, the model features
three additional Weyl fermions singlet under Technicolor interactions, which
provide for a one-loop unification of the Standard Model gauge couplings. Among
these extra matter fields exists a possible candidate for weakly interacting
dark matter. We evaluate the relic densities and find that they are sufficient
to explain the cosmological observations and avoid the experimental limits from
earth-based searches. Hence, we establish a non-supersymmetric framework where
hierarchy and naturality problems are solved, coupling constant unification is
achieved and a plausible dark matter candidate exists
Compton Imaging of MeV Gamma-Rays with the Liquid Xenon Gamma-Ray Imaging Telescope (LXeGRIT)
The Liquid Xenon Gamma-Ray Imaging Telescope (LXeGRIT) is the first
realization of a liquid xenon time projection chamber for Compton imaging of
MeV gamma-ray sources in astrophysics. By measuring the energy deposit and the
three spatial coordinates of individual gamma-ray scattering points, the
location of the source in the sky is inferred with Compton kinematics
reconstruction. The angular resolution is determined by the detector's energy
and spatial resolutions, as well as by the separation in space between the
first and second scattering. The imaging response of LXeGRIT was established
with gamma-rays from radioactive sources, during calibration and integration at
the Columbia Astrophysics Laboratory, prior to the 2000 balloon flight mission.
In this paper we describe in detail the various steps involved in imaging
sources with LXeGRIT and present experimental results on angular resolution and
other parameters which characterize its performance as a Compton telescope.Comment: 22 pages, 20 figures, submitted to NIM
A Monte Carlo analysis of the liquid xenon TPC as gamma ray telescope
Extensive Monte Carlo modeling of a coded aperture x ray telescope based on a high resolution liquid xenon TPC has been performed. Results on efficiency, background reduction capability and source flux sensitivity are presented. We discuss in particular the development of a reconstruction algorithm for events with multiple interaction points. From the energy and spatial information, the kinematics of Compton scattering is used to identify and reduce background events, as well as to improve the detector response in the few MeV region. Assuming a spatial resolution of 1 mm RMS and an energy resolution of 4.5 percent FWHM at 1 MeV, the algorithm is capable of reducing by an order of magnitude the background rate expected at balloon altitude, thus significantly improving the telescope sensitivity
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