LUX-ZEPLIN (LZ) is a second-generation direct dark matter experiment with spin-independent WIMP-nucleon scattering sensitivity above
1.4
×
10
-
48
cm
2
for a WIMP mass of
40
GeV
/
c
2
and a
1000
days
...exposure. LZ achieves this sensitivity through a combination of a large
5.6
t
fiducial volume, active inner and outer veto systems, and radio-pure construction using materials with inherently low radioactivity content. The LZ collaboration performed an extensive radioassay campaign over a period of six years to inform material selection for construction and provide an input to the experimental background model against which any possible signal excess may be evaluated. The campaign and its results are described in this paper. We present assays of dust and radon daughters depositing on the surface of components as well as cleanliness controls necessary to maintain background expectations through detector construction and assembly. Finally, examples from the campaign to highlight fixed contaminant radioassays for the LZ photomultiplier tubes, quality control and quality assurance procedures through fabrication, radon emanation measurements of major sub-systems, and bespoke detector systems to assay scintillator are presented.
The Large Underground Xenon (LUX) experiment Akerib, D.S.; Bai, X.; Bedikian, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2013, Letnik:
704
Journal Article
Recenzirano
Odprti dostop
The Large Underground Xenon (LUX) collaboration has designed and constructed a dual-phase xenon detector, in order to conduct a search for Weakly Interacting Massive Particles (WIMPs), a leading dark ...matter candidate. The goal of the LUX detector is to clearly detect (or exclude) WIMPS with a spin independent cross-section per nucleon of 2×10−46cm2, equivalent to ∼1event/100kg/month in the inner 100-kg fiducial volume (FV) of the 370-kg detector. The overall background goals are set to have <1 background events characterized as possible WIMPs in the FV in 300 days of running.
This paper describes the design and construction of the LUX detector.
We report on the design and performance of the LUX-ZEPLIN (LZ) “Screener”, a small liquid scintillator detector consisting of ≈23 kg of LAB-based gadolinium-loaded liquid scintillator (GdLS) to be ...used in the LZ Outer Detector. The Outer Detector will be filled with 17.3 tonnes of GdLS and will surround the central liquid xenon time projection chamber of LZ. Its primary function will be to tag neutron events in the liquid xenon which could mimic a WIMP dark matter signal. To meet the deadtime requirements for the Outer Detector, the radioimpurity levels in the GdLS must be kept below ≲0.07 mBq/kg. This background level corresponds to a rate of ≈50Hz above an energy threshold of 100 keV.
The Screener was operated in the ultra-low-background environment of the former LUX water shield in the Davis Laboratory at the Sanford Underground Research Facility for radioassay of the GdLS. Careful selection of detector materials and use of ultra-low-background PMTs allows the measurement of a variety of radioimpurities. The 14C/12C ratio in the scintillator is measured to be (2.83±0.06(stat.)±0.01(sys.))×10−17. Use of pulse shape discrimination allows the concentration of isotopes throughout the 238U, 235U, and 232Th chains to be measured by fitting the collected spectra from α and β events. We find that equilibrium is broken in the 238U and 232Th chains and that a significant portion of the contamination in the GdLS results from decays in the 227Ac subchain of the 235U series.
Predictions for the singles rate in the Outer Detector are presented. The rate from radioimpurities above 100 keV in the GdLS is estimated to be 97.9±6.4Hz, with 65.5±1.9Hz resulting from α-decays.
LUX-ZEPLIN (LZ) is a second-generation direct dark matter experiment with spin-independent WIMP-nucleon scattering sensitivity above 1.4 × 10-48 cm2 for a WIMP mass of 40 GeV/c 2 and a 1000 d ...exposure. LZ achieves this sensitivity through a combination of a large 5.6 t fiducial volume, active inner and outer veto systems, and radio-pure construction using materials with inherently low radioactivity content. The LZ collaboration performed an extensive radioassay campaign over a period of six years to inform material selection for construction and provide an input to the experimental background model against which any possible signal excess may be evaluated. The campaign and its results are described in this paper. We present assays of dust and radon daughters depositing on the surface of components as well as cleanliness controls necessary to maintain background expectations through detector construction and assembly. Finally, examples from the campaign to highlight fixed contaminant radioassays for the LZ photomultiplier tubes, quality control and quality assurance procedures through fabrication, radon emanation measurements of major sub-systems, and be spoke detector systems to assay scintillator are presented.
The Large Underground Xenon (LUX) experiment Akerib, D. S.; Bai, X.; Bedikian, S. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2012, Letnik:
704, Številka:
C
Journal Article
Recenzirano
Odprti dostop
The Large Underground Xenon (LUX) collaboration has designed and constructed a dual-phase xenon detector, in order to conduct a search for Weakly Interacting Massive Particles (WIMPs), a leading dark ...matter candidate. The goal of the LUX detector is to clearly detect (or exclude) WIMPS with a spin independent cross-section per nucleon of 2×10-46 cm2, equivalent to ∼1event/100kg/month in the inner 100-kg fiducial volume (FV) of the 370-kg detector. The overall background goals are set to have <1 background events characterized as possible WIMPs in the FV in 300 days of running. This paper describes the design and construction of the LUX detector.
BaBar silicon vertex tracker: Status and prospects Re, V.; Bondioli, M.; Bruinsma, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2006, Letnik:
569, Številka:
1
Journal Article
We report on the design and performance of the LUX-ZEPLIN (LZ) "Screener", a small liquid scintillator detector consisting of \(\approx 23\) kg of LAB-based gadolinium-loaded liquid scintillator ...(GdLS) to be used in the LZ Outer Detector. The Outer Detector will be filled with 17.3 tonnes of GdLS and will surround the central liquid xenon time projection chamber of LZ. Its primary function will be to veto neutron single-scatter events in the liquid xenon which could mimic a WIMP dark matter signal. To meet the requirements for the Outer Detector, the radioimpurity levels in the GdLS must be kept below \(\lesssim0.07\) mBq/kg. This background level corresponds to a rate of \(\approx50\) Hz above an energy threshold of 100 keV. The Screener was operated in the ultra-low-background environment of the former LUX water shield in the Davis Laboratory at the Sanford Underground Research Facility for radioassay of the GdLS. Careful selection of detector materials and use of ultra-low-background PMTs allows the measurement of a variety of radioimpurities. The \(^{14}\textrm{C}\)/\(^{12}\textrm{C}\) ratio in the scintillator is measured to be \((2.83\pm0.06\textrm{(stat.)}\pm0.01\textrm{(sys.)}) \times 10^{-17}\). Use of pulse shape discrimination allows the concentration of isotopes throughout the \(^{238}\textrm{U}\), \(^{235}\textrm{U}\), and \(^{232}\textrm{Th}\) chains to be measured by fitting the collected spectra from \(\alpha\) and \(\beta\) events. We find that equilibrium is broken in the \(^{238}\textrm{U}\) and \(^{232}\textrm{Th}\) chains and that a significant portion of the contamination in the GdLS results from decays in the \(^{227}\textrm{Ac}\) subchain of the \(^{235}\textrm{U}\) series. Predictions for the singles rate in the Outer Detector are presented. The rate from radioimpurities above 100 keV in the GdLS is estimated to be \(97.9\pm6.4\) Hz, with \(65.5\pm1.9\) Hz resulting from \(\alpha\)-decays.
PDF
