An ultra-low background PMT for liquid xenon detectors Akerib, D.S.; Bai, X.; Bernard, E. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2013, Volume:
703
Journal Article
Peer reviewed
Open access
Results are presented from radioactivity screening of two models of photomultiplier tubes designed for use in current and future liquid xenon experiments. The Hamamatsu 5.6cm diameter R8778 PMT, used ...in the LUX dark matter experiment, has yielded a positive detection of four common radioactive isotopes: 238U, 232Th, 40K, and 60Co. Screening of LUX materials has rendered backgrounds from other detector materials subdominant to the R8778 contribution. A prototype Hamamatsu 7.6cm diameter R11410 MOD PMT has also been screened, with benchmark isotope counts measured at <0.4238U/<0.3232Th/<8.340K/2.0±0.2 60Co mBq/PMT. This represents a large reduction, equal to a change of ×124238U/×19232Th/×1840K per PMT, between R8778 and R11410 MOD, concurrent with a doubling of the photocathode surface area (4.5–6.4cm diameter). 60Co measurements are comparable between the PMTs, but can be significantly reduced in future R11410 MOD units through further material selection. Assuming PMT activity equal to the measured 90% upper limits, Monte Carlo estimates indicate that replacement of R8778 PMTs with R11410 MOD PMTs will change LUX PMT electron recoil background contributions by a factor of ×125 after further material selection for 60Co reduction, and nuclear recoil backgrounds by a factor of ×136. The strong reduction in backgrounds below the measured R8778 levels makes the R11410 MOD a very competitive technology for use in large-scale liquid xenon detectors.
LUX is a two-phase (liquid/gas) xenon time projection chamber designed to detect nuclear recoils from interactions with dark matter particles. Signals from the LUX detector are processed by ...custom-built analog electronics which provide properly shaped signals for the trigger and data acquisition (DAQ) systems. The DAQ is composed of commercial digitizers with firmware customized for the LUX experiment. Data acquisition systems in rare-event searches must accommodate high rate and large dynamic range during precision calibrations involving radioactive sources, while also delivering low threshold for maximum sensitivity. The LUX DAQ meets these challenges using real-time baseline suppression that allows for a maximum event acquisition rate in excess of 1.5kHz with virtually no deadtime. This paper describes the LUX DAQ and the novel acquisition techniques employed in the LUX experiment.
We developed particle identification (PID) in a CsI(Tl) crystal using digital pulse shape analysis. We present the details of the experiment, the data analysis, and the results. Four different ...methods of digital PID were applied to the same data set: (A) the rise-time inspection, (B) the sampling of the ADC waveform at the time of maximum waveform separation, (C) the charge comparison method with a rectangular integration window, and (D) the charge comparison method with a custom weight function. The performance of the methods A and B, which strongly depends on the bandwidth of the signal, is optimal when the bandwidth is reduced to about 0.5 MHz. The performance of the methods C and D can be only slightly improved by restricting the bandwidth. From among the four methods, the method A provides the poorest particle discrimination, while the method D provides the best. The algorithm D compares favorably with the analog charge comparison method, achieving very good proton/α-particle discrimination at energies as low as about 1 MeV, even though the measurements were carried out at the dynamic range of 35 MeV. Algorithms B, C, and D yield the PID index which is almost independent of particle energy, within the energy limits used in this work. Present results clearly show the power of digital electronics in achieving good particle identification for charged particles measured with large dynamic range.
The LUX dark matter search McKinsey, D N; Akerib, D; Bedikian, S ...
Journal of physics. Conference series,
01/2010, Volume:
203, Issue:
1
Journal Article
Peer reviewed
Open access
The Large Underground Xenon (LUX) experiment is a liquid xenon time projection chamber designed for extremely low levels of radioactive background in its fiducial volume. The overall liquid xenon ...mass is 300 kg, with a 100 kg fiducial mass. LUX is currently under construction, and integration of the full detector will begin in Fall 2009 at the Sanford Underground Science and Engineering Laboratory in South Dakota. The LUX sensitivity to the WIMP-nucleon spin-independent scattering cross-section will be 7 × 10-46 cm2 at 100 GeV after 300 days of low-background operation.
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, Volume:
704
Journal Article
Peer reviewed
Open access
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.
This paper describes the conclusions that can be drawn from the data taken thus far with the PHOBOS detector at RHIC. In the most central Au
+
Au collisions at the highest beam energy, evidence is ...found for the formation of a very high energy density system whose description in terms of simple hadronic degrees of freedom is inappropriate. Furthermore, the constituents of this novel system are found to undergo a significant level of interaction. The properties of particle production at RHIC energies are shown to follow a number of simple scaling behaviors, some of which continue trends found at lower energies or in simpler systems. As a function of centrality, the total number of charged particles scales with the number of participating nucleons. When comparing Au
+
Au at different centralities, the dependence of the yield on the number of participants at higher
p
T
(
∼
4
GeV
/
c
) is very similar to that at low transverse momentum. The measured values of charged particle pseudorapidity density and elliptic flow were found to be independent of energy over a broad range of pseudorapidities when effectively viewed in the rest frame of one of the colliding nuclei, a property we describe as “extended longitudinal scaling”. Finally, the centrality and energy dependences of several observables were found to factorize to a surprising degree.
Observation of rotational curve of spiral galaxies shows that a large fraction (∼23%) of the mass density of the universe is unaccounted for. Such a significant percentage of missing dark matter ...suggests that the universe may consist of new types of elementary particles. A compelling explanation for the new particles is the existence of Weakly Interacting Massive Particles (WIMPs), which are non-baryonic particles characterized by particle physics theories beyond the Standard Model. WIMPs are believed to only interact through the weak force and gravity; hence the interaction cross section with ordinary matter is extremely small. Therefore, experimental techniques that combine low radioactivity, low energy thresholds, efficient discrimination against electronic recoil backgrounds, and scalability to large detector masses can only be performed at a deep underground environment where the interference of cosmic rays is obviated. In this paper, we report a cryogenic large liquid xenon detector for dark matter searches at Sanford Lab (Davis Cavern) in the Homestake Mine, USA. The goal of the large underground xenon (LUX) dual-phase detector is to clearly detect (or exclude) WIMPs with a spin independent cross-section per nucleon of 7 × 10−46 cm2, equivalent to ∼0.5 events/100 kg/month in an inner 100 kg fiducial volume (FV) of a 300 kg LXe detector.
Digital pulse processing is a signal processing technique in which detector (preamplifier output) signals are directly digitized and processed to extract quantities of interest. This approach has ...several significant advantages compared to traditional analog signal shaping. First, analyses can be developed which take pulse-by-pulse differences into account, as in making ballistic deficit compensations. Second, transient induced charge signals, which deposit no net charge on an electrode, can be analyzed to give, for example, information on the position of interaction within the detector. Third, deadtimes from transient overload signals are greatly reduced, from tens of μs to hundreds of ns. Fourth, signals are easily captured, so that more complex analyses can be postponed until the source event has been deemed “interesting”. Fifth, signal capture and processing may easily be based on coincidence criteria between different detectors or different parts of the same detector. XIAs recently introduced CAMAC module, the DGF-4C, provides many of these features for four input channels, including two levels of digital processing and a FIFO for signal capture for each signal channel. The first level of digital processing is “immediate”, taking place in a gate array at the 40 MHz digitization rate, and implements pulse detection, pileup inspection, trapezoidal energy filtering, and control of an external 25.6 μs long FIFO. The second level of digital processing is provided by a digital signal processor (DSP), where more complex algorithms can be implemented. To illustrate digital pulse processing’s possibilities, we describe the application of the DGF-4C to a series of experiments. The first, for which the DGF was originally developed, involves locating gamma-ray interaction sites within large segmented Ge detectors. The goal of this work is to attain spatial resolutions of order 2 mm
σ within 70 mm × 90 mm detectors. We show how pulse shape analysis allows ballistic deficit to be significantly reduced in these detectors. A second experiment involves studying exotic nuclei by observing their 1 MeV direct proton decays following implantation in a Si crossed stripe detector at 35 MeV. Whereas the implantation paralyzes analog electronics for almost 10 μs, the DGF allows the study of decay times as short as 1 μs. Initial energy and time resolution results are presented. Finally, we show how the DGF’s precise timing and coincidence capabilities lead to significant experimental simplifications in dealing with phoswich detectors, low background counting work, and trace Pb detection by coincident photon detection.
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