anti-Compton Detector Research Articles

Simulation of background reduction and Compton suppression in a low-background HPGe spectrometer at a surface laboratory

High-purity germanium (HPGe) detectors are well suited to analyse the radioactivity of samples. In order to reduce the environmental background for an ultra-low background HPGe spectrometer, low-activity lead and oxygen free copper are installed outside the probe to shield from gamma radiation, with an outer plastic scintillator to veto cosmic rays, and an anti-Compton detector to improve the peak-to-Compton ratio. Using Geant4 tools and taking into account a detailed description of the detector, we optimize the sizes of these detectors to reach the design requirements. A set of experimental data from an existing HPGe spectrometer was used to compare with the simulation. For the future low-background HPGe detector simulation, considering different thicknesses of BGO crystals and anti-coincidence efficiency, the simulation results show that the optimal BGO thickness is 5.5 cm, and the peak-to-Compton ratio of 40K is raised to 1000 when the anti-coincidence efficiency is 0.85. In the background simulation, 15 cm oxygen-free copper plus 10 cm lead can reduce the environmental gamma rays to 0.0024 cps/100 cm3 Ge (50 keV-2.8 MeV), which is about 10−5 of the environmental background.

Status and prospects of the China Dark Matter Experiment

The China Dark Matter Experiment (CDEX) pursues direct searches of light Weakly Interacting Massive Particles (WIMPs) at the China Jinping Underground Laboratory (CJPL), which is the deepest operating laboratory for astroparticle research in the world. Results from a prototype CDEX-0 20 g germanium detector array and CDEX-1 994 g pPCGe(p-type Point Contact Germanium) detector are reported. The new result from CDEX-1 pPCGe excludes the CoGeNT-2013 allowed region with an identical detector technique. CDEX-10 with a PCGearray of 10 kg target mass range enclosed in a liquid argon anti-Compton detector is being constructed and tested. The CDEX program evolves into the targets of "CDEX-1T Experiment". The CDEX-1T experiment will be located in CJPL-II which is under construction and will be finished by the end of 2016.

Measurement of intrinsic radioactive backgrounds from the 137Cs and U/Th chains in CsI(Tl) crystals**Supported by National Natural Science Foundation of China (11275107, 11175099)

The inorganic CsI(Tl) crystal scintillator is a candidate anti-compton detector for the China Dark matter Experiment. Studying the intrinsic radiopurity of the CsI(Tl) crystal is an issue of major importance. The timing, energy and spatial correlations, as well as the capability of pulse shape discrimination provide powerful methods for the measurement of intrinsic radiopurities. The experimental design, detector performance and event-selection algorithms are described. A total of 359×3 kg-days data from three prototypes of CsI(Tl) crystals were taken at China Jinping Underground Laboratory (CJPL), which offers a good shielding environment. The contamination levels of internal isotopes from 137Cs, 232Th and 238U series, as well as the upper bounds of 235U series are reported. Identification of the whole α peaks from U/Th decay chains and derivation of those corresponding quenching factors are achieved.

Application of the anti-Compton detector in neutron activation analysis techniques

In this work we report about performance of the cylindrical 3in.×3in. LaBr3 scintillation detector assembled with a BGO guard detector. This setup was optimized for the identification of explosive materials by means of fast neutron activation analysis.

Limits on light weakly interacting massive particles from the CDEX-1 experiment with ap-type point-contact germanium detector at the China Jinping Underground Laboratory

We report results of a search for light Dark Matter WIMPs with CDEX-1 experiment at the China Jinping Underground Laboratory, based on 53.9 kg-days of data from a p-type point-contact germanium detector enclosed by a NaI(Tl) crystal scintillator as anti-Compton detector. The event rate and spectrum above the analysis threshold of 475 eVee are consistent with the understood background model. Part of the allowed regions for WIMP-nucleus coherent elastic scattering at WIMP mass of 6-20 GeV are probed and excluded. Independent of interaction channels, this result contradicts the interpretation that the anomalous excesses of the CoGeNT experiment are induced by Dark Matter, since identical detector techniques are used in both experiments.

MUNU final results

The MUNU detector has been designed to study ν e ¯ e − elastic scattering at low energy. The central tracking detector is a 1 m3 Time Projection Chamber surrounded by an anti-Compton detector. In this paper the results from final analysis of the data recorded at 3-bar and 1-bar pressure are presented. At 3-bar a new upper limit on the neutrino magnetic moment μ ν 9 × 10 − 11 ( 7 × 10 − 11 ) μ B at 90 (68%) C.L. is derived. At 1-bar pressure electron tracks down to 80 keV are measured in the TPC. A 137Cs photopeak is reconstructed by measuring both the energy and direction of the Compton electrons in the TPC.

Search of neutrino magnetic moments with a high-purity germanium detector at the Kuo-Sheng nuclear power station

A search of neutrino magnetic moments was carried out at the Kuo-Sheng nuclear power station at a distance of 28 m from the 2.9 GW reactor core. With a high purity germanium detector of mass 1.06 kg surrounded by scintillating NaI(Tl) and CsI(Tl) crystals as anti-Compton detectors, a detection threshold of 5 keV and a background level of $1\text{ }\text{ }{\mathrm{kg}}^{\ensuremath{-}1}\text{ }{\mathrm{keV}}^{\ensuremath{-}1}\text{ }{\mathrm{day}}^{\ensuremath{-}1}$ near threshold were achieved. Details of the reactor neutrino source, experimental hardware, background understanding, and analysis methods are presented. Based on 570.7 and 127.8 days of Reactor ON and OFF data, respectively, at an average Reactor ON electron antineutrino flux of $6.4\ifmmode\times\else\texttimes\fi{}{10}^{12}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}2}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$, the limit on the neutrino magnetic moments of ${\ensuremath{\mu}}_{{\overline{\ensuremath{\nu}}}_{\mathrm{e}}}l7.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}{\ensuremath{\mu}}_{\mathrm{B}}$ at 90% confidence level was derived. Indirect bounds on the ${\overline{\ensuremath{\nu}}}_{\mathrm{e}}$ radiative decay lifetimes were inferred.

Final results on the neutrino magnetic moment from the MUNU experiment

The MUNU detector was designed to study ν¯ee− elastic scattering at low energy. The central component is a Time Projection Chamber filled with CF4 gas, surrounded by an anti-Compton detector. The experiment was carried out at the Bugey (France) nuclear reactor. In this Letter we present the final analysis of the data recorded at 3 bar and 1 bar pressure. Both the energy and the scattering angle of the recoil electron are measured. From the 3 bar data a new upper limit on the neutrino magnetic moment μeshort<9×10−11μB at 90% CL was derived. At 1 bar electron tracks down to 150 keV were reconstructed, demonstrating the potentiality of the experimental technique for future applications in low energy neutrino physics.

Results from the MUNU experiment on neutrino-electron scattering

The MUNU experiment studies electron antineutrino-electron elastic scattering. The detector is a time projection chamber surrounded by an anti-Compton detector. The distance between the reactor (serving as the neutrino source) and the detector is 18 m. Here, data are presented corresponding to 66.6-d live time reactor on and 16.7-d reactor off. The electron recoil spectrum obtained by using a visual scanning procedure is presented. The upper limit on the neutrino magnetic moment νπ<1.0×10−10πB is derived.

NEUTRINO MAGNETIC MOMENT RESULTS AT THE KUO-SHENG NUCLEAR POWER PLANT

A search of neutrino magnetic moment was carried out at the Kuo-Sheng Nuclear Power Station at a distance of 28 m from the 2.9 GW reactor core. With a high purity germanium detector of mass 1.06 kg surrounded by scintillating NaI(Tl) and CsI(Tl) crystals as anti-Compton detectors, a detection threshold of 5 keV and a background level of 1 kg -1 kev -1 day -1 at 12-60 keV were achieved. Based on 4712 and 1250 hours of Reactor ON and OFF data, respectively, the limits on the neutrino magnetic moment of [Formula: see text] at 90(68)% confidence level were derived. Indirect bounds of the [Formula: see text] radiative lifetime of [Formula: see text] can be inferred. The present status and future plans are discussed.

Surface and Underground Ultra Low-Level Liquid Scintillation Spectrometry

Cosmic background and its variation have been removed in the Gran Sasso National Laboratory (National Institute of Nuclear Physics) by its 1400-m rock overburden. Stable, high-performance liquid scintillation counting conditions are obtained when any remaining variable components of the environmental background, such as radon, are eliminated. The ultra low-level liquid scintillation spectrometer Quantulus™ has an anti-Compton guard detector (guard for short) that allows monitoring of gamma radiation in the background. The guard detector efficiency in radiocarbon background reduction is 8% in the Gran Sasso National Laboratory, while 80% is observed in surface laboratories. Thus, atmospheric pressure variations in surface laboratories cause variation in cosmic radiation flux. The Quantulus anti-Compton detector is highly efficient in detecting cosmic radiation, and the sample count rate remains stable in long-term counting. Also, correlation of sample backgrounds with environmental gamma radiation in various laboratories is examined.

Neutrino magnetic moment results at the Kuo-Sheng Nuclear Power Plant

A search of neutrino magnetic moment was carried out at the Kuo-Sheng Nuclear Power Station at a distance of 28 m from the 2.9 GW reactor core. With a high purity germanium detector of mass 1.06 kg surrounded by scintillating NaI(Tl) and CsI(Tl) crystals as anti-Compton detectors, a detection threshold of 5 keV and a background level of 1 kg–1keV–1day–1 at 12-60 keV were achieved. Based on 4712 and 1250 hours of Reactor ON and OFF data, respectively, the limits on the neutrino magnetic moment of $\rm{ \rm{\mu_{\rm{\bar{\nu_e}}}} < 1.3(1.0) \times 10^{-10} ~ \rm{\mu_B}}$ at 90(68)% confidence level were derived. Indirect bounds of the $\rm{\bar{\nu_e}}$ radiative lifetime of mν3 τν > 2.8(4.8) × 1018 eV3 s can be inferred. The present status and future plans are discussed. PACS: 14.60.Lm Neutrino Properties — 13.40.Em Electric and Magnetic Moments

Limit on the electron neutrino magnetic moment from the kuo-sheng reactor neutrino experiment.

A search of neutrino magnetic moment was carried out at the Kuo-Sheng Nuclear Power Station at a distance of 28 m from the 2.9 GW reactor core. With a high purity germanium detector of mass 1.06 kg surrounded by scintillating NaI(Tl) and CsI(Tl) crystals as anti-Compton detectors, a detection threshold of 5 keV and a background level of 1 kg(-1) keV(-1) day(-1) at 12-60 keV were achieved. Based on 4712 and 1250 h of reactor ON and OFF data, respectively, the limit on the neutrino magnetic moment of mu(nu;(e))<1.3x10(-10)mu(B) at 90% confidence level was derived. An indirect bound of the nu;(e) radiative lifetime of m(3)(nu)tau(nu)>2.8x10(18) eV(3) s can be inferred.

Weak γ rays from the electron-capture decay of194Au

We present \ensuremath{\gamma}-ray energies and intensities of 34 new weak transitions in the electron-capture decay of ${}^{194}\mathrm{Au}.$ These \ensuremath{\gamma} rays were detected in singles experiments with high-purity Ge and anti-Compton detectors, and in \ensuremath{\gamma}-\ensuremath{\gamma} coincidence experiments, with the HERA array of Ge detectors. Their placements in the decay scheme confirm levels in ${}^{194}\mathrm{Pt}$ at 1373.9 and 1737.3 keV observed in the electron-capture decay of ${}^{194}\mathrm{Au}.$