The {nu}(bar sign){sub e} flux and spectrum have been measured at a distance of about 800 m from the reactors of the Palo Verde Nuclear Generating Station using a segmented Gd-loaded liquid ...scintillator detector. Correlated positron-neutron events from the reaction {nu}(bar sign){sub e}p{yields}e{sup +}n were recorded for a period of 200 d including 55 d with one of the three reactors off for refueling. Backgrounds were accounted for by making use of the reactor-on and reactor-off cycles, and also with a novel technique based on the difference between signal and background under reversal of the e{sup +} and n portions of the events. A detailed description of the detector calibration, background subtraction, and data analysis is presented here. Results from the experiment show no evidence for neutrino oscillations. {nu}(bar sign){sub e}{yields}{nu}(bar sign){sub x} oscillations were excluded at 90% C.L. for {delta}m{sup 2}>1.12x10{sup -3} eV{sup 2} for full mixing and sin{sup 2}2{theta}>0.21 for large {delta}m{sup 2}. These results support the conclusion that the observed atmospheric neutrino oscillations do not involve {nu}{sub e}. (c) 2000 The American Physical Society.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Anti-neutrino emission rates from nuclear reactors are determined from thermal power measurements and fission rate calculations. The uncertainties in these quantities for commercial power plants and ...their impact on the calculated interaction rates in detectors are examined. We discuss reactor-to-reactor correlations between the leading uncertainties, and their relevance to reactor experiments.
We describe the construction and calibration of a multi-channel liquid time projection chamber filled with Tetramethylsilane. Its charge readout system consists of 8 wires each in the X and Y ...directions. The chamber is also equipped with a light readout system consisting of a 5′′ photomultiplier tube coupled to the liquid volume through a viewport. The energy scale of the detector is calibrated using positron–electron pairs produced by 4.4 MeV gamma rays emitted from an AmBe source, using an external trigger on the positron annihilation gammas. The external trigger is then reconfigured to tag cosmic ray muons passing through the active Tetramethylsilane volume, which are used to measure the stopping power in Tetramethylsilane and the electron lifetime in the detector. We find a most-probable energy loss from minimum ionizing particles of Δp∕ds = (0.60 ± 0.01) MeV/cm. We also measure an electron lifetime of 43−21+680μs by measuring the most-probable energy loss as a function of drift time. For both measurements, the errors are statistical only. For both fast electron and muon signals, the photomultiplier tube detects prompt Cherenkov light, demonstrating the possibility of self-triggering of the detector. The room-temperature organic target medium, together with the self-triggering capabilities and long electron lifetimes reported in this work, make this an attractive technology to explore for rare event detectors or other applications in the area of radiation measurements.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
nEXO is a proposed experiment that will search for neutrinoless double-beta decay (0νββ) in 5-tonnes of liquid xenon (LXe), isotopically enriched in 136Xe . A technique called Ba-tagging is being ...developed as a potential future upgrade for nEXO to detect the 136Xe double-beta decay daughter isotope, 136Ba . An efficient Ba-tagging technique has the potential to boost nEXO’s 0νββ sensitivity by essentially suppressing non-double-beta decay background events. A conceptual approach for the extraction from the detector volume, trapping, and identification of a single Ba ion from 5 tonnes of LXe is presented, along with initial results from the commissioning of one of its subsystems, a quadrupole mass filter.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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.
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