Abstract
We present an improved approach for detection of trace
amounts of
238
U by means of neutron activation analysis (NAA).
The analysis enhancement is obtained by utilizing γ-γ
coincidence ...counting. An empirical method for evaluating the
sensitivity gain in the presence of a large source-related
background is presented. A comparison of detection limits is made
between two counting schemes; namely, counting single gammas using
one HPGe detector versus counting coincident gammas using two HPGe
detectors placed face-to-face. A data-validated radiation transport
model, created in GEANT4 for a single HPGe detector, is extended to
handle the two-detector setup. In this counting scheme, a
238
U-detection sensitivity enhancement of about a factor of 8
is predicted for a sample of Saint-Gobain G3 Sapphire when compared
to the simpler singles counting approach.
ABSTRACT In the late stages of nuclear burning for massive stars (M > 8 M ), the production of neutrino-antineutrino pairs through various processes becomes the dominant stellar cooling mechanism. As ...the star evolves, the energy of these neutrinos increases and in the days preceding the supernova a significant fraction of emitted electron anti-neutrinos exceeds the energy threshold for inverse beta decay on free hydrogen. This is the golden channel for liquid scintillator detectors because the coincidence signature allows for significant reductions in background signals. We find that the kiloton-scale liquid scintillator detector KamLAND can detect these pre-supernova neutrinos from a star with a mass of 25 M at a distance less than 690 pc with 3 significance before the supernova. This limit is dependent on the neutrino mass ordering and background levels. KamLAND takes data continuously and can provide a supernova alert to the community.
Abstract
In this paper we describe the development, testing, and characterization of three
low-emission rate AmLi neutron sources. The sources are used to calibrate the nuclear recoil
response of the ...LUX-ZEPLIN (LZ) dark matter experiment. The sources' neutron emission rate was
measured using
3
He proportional tubes. The sources' gamma emissions were
characterized using a high-purity germanium (HPGe) detector. Source-validated
Geant4
Monte Carlo simulations allowed to calibrate the Ge and neutron detectors' responses.
Silicon Photomultipliers (SiPMs) are attractive candidates for light detectors for next generation liquid xenon double-beta decay experiments, like nEXO (next Enriched Xenon Observatory). In this ...paper we discuss the requirements that the SiPMs must satisfy in order to be suitable for nEXO and similar experiments, describe the two test setups operated by the nEXO collaboration, and present the results of characterization of SiPMs from several vendors. In particular, we find that the photon detection efficiency at the peak of xenon scintillation light emission (175-178 nm) approaches the nEXO requirements for tested FBK and Hamamatsu devices. Additionally, the nEXO collaboration performed radio-assay of several grams of bare FBK devices using neutron activation analysis, indicating levels of 40 K, 232 Th, and 238 U of the order of <; 0.15, (6.9 · 10 - 4 - 1.3 · 10 - 2 ), and <; 0.11 mBq/kg, respectively.
We present the results of a search for extraterrestrial electron antineutrinos (v sub(e)'s) in the energy range 8.3 MeV < Ev sub(e) < 31.8 MeV using the KamLAND detector. In an exposure of 4.53 ...kton-year, we identify 25 candidate events. All of the candidate events can be attributed to background, most importantly neutral current atmospheric neutrino interactions, setting an upper limit on the probability of super(8)B solar converting into v sub(e)'s at 5.3 x 10 super(-5) (90% CL), if we assume an undistorted v sub(e) shape. This limit corresponds to a solar v sub(e) flux of 93 cm super(-2) s super(-1) or an event rate of 1.6 events (kton - year) super(-1) above the energy threshold Ev sub(e) > or =, slanted 8.3 MeV. The present data also allows us to set more stringent limits on the diffuse supernova neutrino flux and on the annihilation rates for light dark matter particles.
The Palo Verde neutrino oscillation experiment, located at 750 and 890 m distance from the three reactors of the Palo Verde nuclear generating station, has collected data for a total of 350 days, 108 ...days with one of the reactors off for refueling. The neutrino signal and background were determined in two independent ways. The observed
v
e-flux is consistent with the absence of neutrino oscillations,
v
e α
v
x
oscillations are excluded, at the 90% c.l., for Δ
m
2 > 1.1 · 10
ṫ eV
2, at full mixing, and
sin
2θ < 0.17 at large Δ
m
2. The experiment has been concluded, the detector dismantled.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The Enriched Xenon Observatory (EXO) will search for double beta decays of
136Xe. We report the results of a systematic study of trace concentrations of radioactive impurities in a wide range of raw ...materials and finished parts considered for use in the construction of EXO-200, the first stage of the EXO experimental program. Analysis techniques employed, and described here, include direct gamma counting, alpha counting, neutron activation analysis, and high-sensitivity mass spectrometry.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
We report on the initial results from a measurement of the antineutrino flux and spectrum at a distance of about 800 m from the three reactors of the Palo Verde Nuclear Generating Station using a ...segmented gadolinium-loaded scintillation detector. We find that the antineutrino flux agrees with that predicted in the absence of oscillations excluding at 90% C.L. nu;(e)-nu;(x) oscillations with Deltam(2)>1.12x10(-3) eV(2) for maximal mixing and sin (2)2straight theta>0.21 for large Deltam(2). Our results support the conclusion that the atmospheric neutrino oscillations observed by Super-Kamiokande do not involve nu(e).
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
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