102 research outputs found
A Compact 3H(p,gamma)4He 19.8-MeV Gamma-Ray Source for Energy Calibration at the Sudbury Neutrino Observatory
The Sudbury Neutrino Observatory (SNO) is a new 1000-tonne D2O Cerenkov solar
neutrino detector. A high energy gamma-ray source is needed to calibrate SNO
beyond the 8B solar neutrino endpoint of 15 MeV. This paper describes the
design and construction of a source that generates 19.8-MeV gamma rays using
the 3H(p,gamma)4He reaction (``pt''), and demonstrates that the source meets
all the physical, operational and lifetime requirements for calibrating SNO. An
ion source was built into this unit to generate and to accelerate protons up to
30 keV, and a high purity scandium tritide target with a scandium-tritium
atomic ratio of 1:2.0+/-0.2 was included. This pt source is the first
self-contained, compact, and portable high energy gamma-ray source (E>10 MeV).Comment: 33 pages (including 2 table, 12 figures) This is the revised
manuscript, accepted for publication in NIM A. This revision relfects minor
editorial changes from the previous versio
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
Determining the Drift Time of Charge Carriers in P-Type Point-Contact HPGe Detectors
An algorithm to measure the drift time of charge carriers in p-type point
contact (PPC) high-purity germanium (HPGe) detectors from the signals processed
with a charge-sensitive preamplifier is introduced. It is demonstrated that the
drift times can be used to estimate the distance of charge depositions from the
point contact and to characterize losses due to charge trapping. A correction
for charge trapping effects over a wide range of energies is implemented using
the measured drift times and is shown to improve the energy resolution by up to
30%.Comment: 16 pages, 8 figures, submitted to Nucl. Instrum. Meth.
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
Astroparticle Physics with a Customized Low-Background Broad Energy Germanium Detector
The MAJORANA Collaboration is building the MAJORANA DEMONSTRATOR, a 60 kg
array of high purity germanium detectors housed in an ultra-low background
shield at the Sanford Underground Laboratory in Lead, SD. The MAJORANA
DEMONSTRATOR will search for neutrinoless double-beta decay of 76Ge while
demonstrating the feasibility of a tonne-scale experiment. It may also carry
out a dark matter search in the 1-10 GeV/c^2 mass range. We have found that
customized Broad Energy Germanium (BEGe) detectors produced by Canberra have
several desirable features for a neutrinoless double-beta decay experiment,
including low electronic noise, excellent pulse shape analysis capabilities,
and simple fabrication. We have deployed a customized BEGe, the MAJORANA
Low-Background BEGe at Kimballton (MALBEK), in a low-background cryostat and
shield at the Kimballton Underground Research Facility in Virginia. This paper
will focus on the detector characteristics and measurements that can be
performed with such a radiation detector in a low-background environment.Comment: Submitted to NIMA Proceedings, SORMA XII. 9 pages, 4 figure
The Majorana Neutrinoless Double-Beta Decay Experiment
The proposed Majorana double-beta decay experiment is based on an array of
segmented intrinsic Ge detectors with a total mass of 500 kg of Ge isotopically
enriched to 86% in 76Ge. A discussion is given of background reduction by:
material selection, detector segmentation, pulse shape analysis, and
electro-formation of copper parts and granularity. Predictions of the
experimental sensitivity are given. For an experimental running time of 10
years over the construction and operation of Majorana, a half-life sensitivity
of ~4x10^27 y (neutrinoless) is predicted. This corresponds to an effective
Majorana mass of the electron neutrino of ~0.03-0.04 eV, according to recent
QRPA and RQRPA matrix element calculations.Comment: 10 pages, 7 figure
Gamma-induced background in the KATRIN main spectrometer
International audienceThe KArlsruhe TRItium Neutrino (KATRIN) experiment aims to make a model-independent determination of the effective electron antineutrino mass with a sensitivity of 0.2 eV/c 2 . It investigates the kinematics of β -particles from tritium β -decay close to the endpoint of the energy spectrum. Because the KATRIN main spectrometer (MS) is located above ground, muon-induced backgrounds are of particular concern. Coincidence measurements with the MS and a scintillator-based muon detector system confirmed the model of secondary electron production by cosmic-ray muons inside the MS. Correlation measurements with the same setup showed that about 12% of secondary electrons emitted from the inner surface are induced by cosmic-ray muons, with approximately one secondary electron produced for every 17 muon crossings. However, the magnetic and electrostatic shielding of the MS is able to efficiently suppress these electrons, and we find that muons are responsible for less than 17% (90% confidence level) of the overall MS background
The Sudbury Neutrino Observatory
The Sudbury Neutrino Observatory is a second generation water Cherenkov
detector designed to determine whether the currently observed solar neutrino
deficit is a result of neutrino oscillations. The detector is unique in its use
of D2O as a detection medium, permitting it to make a solar model-independent
test of the neutrino oscillation hypothesis by comparison of the charged- and
neutral-current interaction rates. In this paper the physical properties,
construction, and preliminary operation of the Sudbury Neutrino Observatory are
described. Data and predicted operating parameters are provided whenever
possible.Comment: 58 pages, 12 figures, submitted to Nucl. Inst. Meth. Uses elsart and
epsf style files. For additional information about SNO see
http://www.sno.phy.queensu.ca . This version has some new reference
The design, construction, and commissioning of the KATRIN experiment
The KArlsruhe TRItium Neutrino (KATRIN) experiment, which aims to make a direct and model-independent determination of the absolute neutrino mass scale, is a complex experiment with many components. More than 15 years ago, we published a technical design report (TDR) [1] to describe the hardware design and requirements to achieve our sensitivity goal of 0.2 eV at 90% C.L. on the neutrino mass. Since then there has been considerable progress, culminating in the publication of first neutrino mass results with the entire beamline operating [2]. In this paper, we document the current state of all completed beamline components (as of the first neutrino mass measurement campaign), demonstrate our ability to reliably and stably control them over long times, and present details on their respective commissioning campaigns
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