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Neutron detection technique

Description: The Sudbury Neutrino Observatory (SNO) has the ability to measure the total flux of all active flavors of neutrinos using the neutral current reaction, whose signature is a neutron. By comparing the rates of the neutral current reaction to the charged current reaction, which only detects electron neutrinos, one can test the neutrino oscillation hypothesis independent of solar models. It is necessary to understand the neutron detection efficiency of the detector to make use of the neutral current reaction. This report demonstrates a coincidence technique to identify neutrons emitted from the {sup 252}Cf neutron calibration source. The source releases on average four neutrons when a {sup 252}Cf nucleus spontaneously fissions. Each neutron is detected as a separate event when the neutron is captured by a deuteron, releasing a gamma ray of approximately 6.25 MeV. This gamma ray is in turn detected by the photomultiplier tube (PMT) array. By investigating the time and spatial separation between neutron-like events, it is possible to obtain a pure sample of neutrons for calibration study. Preliminary results of the technique applied to two calibration runs are presented.
Date: September 14, 2000
Creator: Oblath, N.S. & Poon, A.W.P.
Partner: UNT Libraries Government Documents Department

Study of the effects of D{sub 2}O circulation

Description: The Sudbury Neutrino Observatory (SNO) has been collecting data since November 1999. The study of whether or not the D{sub 2}O circulation affects the data is an important part of understanding how the SNO detector behaves. This report looks at several characteristics of the data to determine to what extent the D{sub 2}O circulation affects the data. We found that there is no evidence for any dependence of event rates in the cleaned data sets on the state of D{sub 2}O circulation.
Date: September 14, 2000
Creator: Oblath, N.S. & Poon, A.W.P.
Partner: UNT Libraries Government Documents Department

Development of a compact 20 MeV gamma-ray source for energy calibration at the Sudbury Neutrino Observatory

Description: The Sudbury Neutrino Observatory (SNO) is a real-time neutrino detector under construction near Sudbury, Ontario, Canada. SNO collaboration is developing various calibration sources in order to determine the detector response completely. This paper describes briefly the calibration sources being developed by the collaboration. One of these, a compact {sup 3}H(p,{gamma}){sup 4}He source, which produces 20-MeV {gamma}-rays, is described.
Date: December 31, 1995
Creator: Poon, A.W.P.; Browne, M.C.; Robertson, R.G.H.; Waltham, C.E. & Kherani, N.P.
Partner: UNT Libraries Government Documents Department

Evaluation of radioactive background rejection in 76Ge neutrino-lessdouble-beta decay experiments using a highly segmented HPGe detector

Description: A highly segmented coaxial HPGe detector was operated in a low background counting facility for over 1 year to experimentally evaluate possible segmentation strategies for the proposed Majorana neutrino-less double-beta decay experiment. Segmentation schemes were evaluated on their ability to reject multi-segment events while retaining single-segment events. To quantify a segmentation scheme's acceptance efficiency the percentage of peak area due to single segment events was calculated for peaks located in the energy region 911-2614 keV. Single interaction site events were represented by the double-escape peak from the 2614 keV decay in {sup 208}Tl located at 1592 keV. In spite of its prototypical nature, the detector performed well under realistic operating conditions and required only minimal human interaction. Though the energy resolution for events with interactions in multiple segments was impacted by inter-segment cross-talk, the implementation of a cross-talk correlation matrix restored acceptable resolution. Additionally, simulations utilizing the MaGe simulation package were performed and found to be in good agreement with experimental observations verifying the external nature of the background radiation.
Date: February 5, 2007
Creator: Chan, Yuen-Dat; Campbell, D.B.; Vetter, K.; Henning, R.; Lesko, K.; Chan, Y.D. et al.
Partner: UNT Libraries Government Documents Department

An array of low-background 3He proportional counters for theSudbury Neutrino Observatory

Description: An array of Neutral-Current Detectors (NCDs) has been builtin order to make a unique measurement of the total active ux of solarneutrinos in the Sudbury Neutrino Observatory (SNO). Data in the thirdphase of the SNO experiment were collected between November 2004 andNovember 2006, after the NCD array was added to improve theneutral-current sensitivity of the SNO detector. This array consisted of36 strings of proportional counters lled with a mixture of 3He and CF4gas capable of detecting the neutrons liberated by the neutrino-deuteronneutral current reaction in the D2O, and four strings lled with a mixtureof 4He and CF4 gas for background measurements. The proportional counterdiameter is 5 cm. The total deployed array length was 398 m. The SNO NCDarray is the lowest-radioactivity large array of proportional countersever produced. This article describes the design, construction,deployment, and characterization of the NCD array, discusses theelectronics and data acquisition system, and considers event signaturesand backgrounds.
Date: February 1, 2007
Creator: Amsbaugh, J.F.; Anaya, J.M.; Banar, J.; Bowles, T.J.; Browne,M.C.; Bullard, T.V. et al.
Partner: UNT Libraries Government Documents Department

A Search for Neutrinos from the Solar hep Reaction and the DiffuseSupernova Neutrino Background with the Sudbury Neutrino Observatory

Description: A search has been made for neutrinos from the hep reactionin the Sun and from the diffuse supernova neutrino background (DSNB)using data collected during the first operational phase of the SudburyNeutrino Observatory, with an exposure of 0.65 kilotonne-years. For thehep neutrino search, two events are observed in the effective electronenergy range of 14.3 MeV<Teff<20 MeV where 3.1 backgroundevents are expected. After accounting for neutrino oscillations, an upperlimit of 2.3 x 104 cm-2s-1 at the 90 percent confidence level is inferredon the integral total flux of hep neutrinos. For DSNB neutrinos, noevents are observed in the effective electron energy range of 21 MeV<Teff<35 MeV and, consequently, an upper limit on the nu e componentof the DSNB fluxin the neutrino energy range of 22.9 MeV<E nu<36.9 MeV of 70 cm-2-1 is inferred at the 90 percent confidence level.This is an improvement by a factor of 6.5 on the previous best upperlimit on the hep neutrino flux and by two orders of magnitude on theprevious upper limit on the nu e component of the DSNB flux.
Date: August 1, 2006
Creator: Aharmim, B.; Ahmed, S.N.; Anthony, A.E.; Beier, E.W.; Bellerive,A.; Bergevin, M. et al.
Partner: UNT Libraries Government Documents Department

Neutrino observations from the Sudbury Neutrino Observatory

Description: The Sudbury Neutrino Observatory (SNO) is a water imaging Cherenkov detector. Its usage of 1000 metric tons of D{sub 2}O as target allows the SNO detector to make a solar-model independent test of the neutrino oscillation hypothesis by simultaneously measuring the solar {nu}{sub e} flux and the total flux of all active neutrino species. Solar neutrinos from the decay of {sup 8}B have been detected at SNO by the charged-current (CC) interaction on the deuteron and by the elastic scattering (ES) of electrons. While the CC reaction is sensitive exclusively to {nu}{sub e}, the ES reaction also has a small sensitivity to {nu}{sub {mu}} and {nu}{sub {tau}}. In this paper, recent solar neutrino results from the SNO experiment are presented. It is demonstrated that the solar flux from {sup 8}B decay as measured from the ES reaction rate under the no-oscillation assumption is consistent with the high precision ES measurement by the Super-Kamiokande experiment. The {nu}{sub e} flux deduced from the CC reaction rate in SNO differs from the Super-Kamiokande ES results by 3.3{sigma}. This is evidence for an active neutrino component, in additional to {nu}{sub e}, in the solar neutrino flux. These results also allow the first experimental determination of the total active {sup 8}B neutrino flux from the Sun, and is found to be in good agreement with solar model predictions.
Date: September 24, 2001
Creator: Ahmad, Q.R.; Allen, R.C.; Andersen, T.C.; Anglin, J.D.; Barton,J.C.; Beier, E.W. et al.
Partner: UNT Libraries Government Documents Department

Measurement of the Cosmic Ray and Neutrino-Induced Muon Flux at the Sudbury Neutrino Observatory

Description: Results are reported on the measurement of the atmospheric neutrino-induced muon flux at a depth of 2 kilometers below the Earth's surface from 1229 days of operation of the Sudbury Neutrino Observatory (SNO). By measuring the flux of through-going muons as a function of zenith angle, the SNO experiment can distinguish between the oscillated and un-oscillated portion of the neutrino flux. A total of 514 muon-like events are measured between -1 {le} cos {theta}{sub zenith} 0.4 in a total exposure of 2.30 x 10{sup 14} cm{sup 2} s. The measured flux normalization is 1.22 {+-} 0.09 times the Bartol three-dimensional flux prediction. This is the first measurement of the neutrino-induced flux where neutrino oscillations are minimized. The zenith distribution is consistent with previously measured atmospheric neutrino oscillation parameters. The cosmic ray muon flux at SNO with zenith angle cos {theta}{sub zenith} &gt; 0.4 is measured to be (3.31 {+-} 0.01 (stat.) {+-} 0.09 (sys.)) x 10{sup -10} {micro}/s/cm{sup 2}.
Date: February 16, 2009
Creator: collaboration, SNO; Aharmim, B.; Ahmed, S.N.; Andersen, T.C.; Anthony, A.E.; Barros, N. et al.
Partner: UNT Libraries Government Documents Department