315 research outputs found
A Radon Progeny Deposition Model
The next generation low-background detectors operating underground aim for
unprecedented low levels of radioactive backgrounds. Although the radioactive
decays of airborne radon (particularly Rn-222) and its subsequent progeny
present in an experiment are potential backgrounds, also problematic is the
deposition of radon progeny on detector materials. Exposure to radon at any
stage of assembly of an experiment can result in surface contamination by
progeny supported by the long half life (22 y) of Pb-210 on sensitive locations
of a detector. An understanding of the potential surface contamination from
deposition will enable requirements of radon-reduced air and clean room
environments for the assembly of low background experiments. It is known that
there are a number of environmental factors that govern the deposition of
progeny onto surfaces. However, existing models have not explored the impact of
some environmental factors important for low background experiments. A test
stand has been constructed to deposit radon progeny on various surfaces under a
controlled environment in order to develop a deposition model. Results from
this test stand and the resulting deposition model are presented.Comment: Proceedings of the Topical Workshop in Low Radioactivity Techniques,
(Sudbury, Canada) August 28-29, 201
Performance of Hamamatsu 64-anode photomultipliers for use with wavelength--shifting optical fibres
Hamamatsu R5900-00-M64 and R7600-00-M64 photomultiplier tubes will be used
with wavelength--shifting optical fibres to read out scintillator strips in the
MINOS near detector. We report on measurements of the gain, efficiency,
linearity, crosstalk, and dark noise of 232 of these PMTs, of which 219 met
MINOS requirements.Comment: 15 pages, 12 figures. Accepted by Nucl. Inst. Meth.
Fluorescence Efficiency and Visible Re-emission Spectrum of Tetraphenyl Butadiene Films at Extreme Ultraviolet Wavelengths
A large number of current and future experiments in neutrino and dark matter
detection use the scintillation light from noble elements as a mechanism for
measuring energy deposition. The scintillation light from these elements is
produced in the extreme ultraviolet (EUV) range, from 60 - 200 nm. Currently,
the most practical technique for observing light at these wavelengths is to
surround the scintillation volume with a thin film of Tetraphenyl Butadiene
(TPB) to act as a fluor. The TPB film absorbs EUV photons and reemits visible
photons, detectable with a variety of commercial photosensors. Here we present
a measurement of the re-emission spectrum of TPB films when illuminated with
128, 160, 175, and 250 nm light. We also measure the fluorescence efficiency as
a function of incident wavelength from 120 to 250 nm.Comment: 15 pages, 9 figures, Submitted to Nuclear Instruments and Methods in
Physics Research Section A: Accelerators, Spectrometers, Detectors and
Associated Equipmen
Four methods for determining the composition of trace radioactive surface contamination of low-radioactivity metal
Four methods for determining the composition of low-level uranium- and
thorium-chain surface contamination are presented. One method is the
observation of Cherenkov light production in water. In two additional methods a
position-sensitive proportional counter surrounding the surface is used to make
both a measurement of the energy spectrum of alpha particle emissions and also
coincidence measurements to derive the thorium-chain content based on the
presence of short-lived isotopes in that decay chain. The fourth method is a
radiochemical technique in which the surface is eluted with a weak acid, the
eluate is concentrated, added to liquid scintillator and assayed by recording
beta-alpha coincidences. These methods were used to characterize two `hotspots'
on the outer surface of one of the He-3 proportional counters in the Neutral
Current Detection array of the Sudbury Neutrino Observatory experiment. The
methods have similar sensitivities, of order tens of ng, to both thorium- and
uranium-chain contamination.Comment: 22 pages, 19 figure
The calibration of the Sudbury Neutrino Observatory using uniformly distributed radioactive sources
The production and analysis of distributed sources of 24Na and 222Rn in the
Sudbury Neutrino Observatory (SNO) are described. These unique sources provided
accurate calibrations of the response to neutrons, produced through
photodisintegration of the deuterons in the heavy water target, and to low
energy betas and gammas. The application of these sources in determining the
neutron detection efficiency and response of the 3He proportional counter
array, and the characteristics of background Cherenkov light from trace amounts
of natural radioactivity is described.Comment: 24 pages, 13 figure
Improving Photoelectron Counting and Particle Identification in Scintillation Detectors with Bayesian Techniques
Many current and future dark matter and neutrino detectors are designed to
measure scintillation light with a large array of photomultiplier tubes (PMTs).
The energy resolution and particle identification capabilities of these
detectors depend in part on the ability to accurately identify individual
photoelectrons in PMT waveforms despite large variability in pulse amplitudes
and pulse pileup. We describe a Bayesian technique that can identify the times
of individual photoelectrons in a sampled PMT waveform without deconvolution,
even when pileup is present. To demonstrate the technique, we apply it to the
general problem of particle identification in single-phase liquid argon dark
matter detectors. Using the output of the Bayesian photoelectron counting
algorithm described in this paper, we construct several test statistics for
rejection of backgrounds for dark matter searches in argon. Compared to simpler
methods based on either observed charge or peak finding, the photoelectron
counting technique improves both energy resolution and particle identification
of low energy events in calibration data from the DEAP-1 detector and
simulation of the larger MiniCLEAN dark matter detector.Comment: 16 pages, 16 figure
Estimation of GRB detection by FiberGLAST
FiberGLAST is one of several instrument concepts being developed for possible inclusion as the primary Gamma-ray Large Area Space Telescope (GLAST) instrument. The predicted FiberGLAST effective area is more than 12,000 cm2 for energies between 30 MeV and 300 GeV, with a field of view that is essentially flat from 0°–80°. The detector will achieve a sensitivity more than 10 times that of EGRET. We present results of simulations that illustrate the sensitivity of FiberGLAST for the detection of gamma-ray bursts
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