We present the first constraints on the spin-dependent, inelastic scattering cross section of weakly interacting massive particles (WIMPs) on nucleons from XENON100 data with an exposure of 7.64×103 ...kg·days. XENON100 is a dual-phase xenon time projection chamber with 62 kg of active mass, operated at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy and designed to search for nuclear recoils from WIMP-nucleus interactions. Here we explore inelastic scattering, where a transition to a low-lying excited nuclear state of Xe129 is induced. The experimental signature is a nuclear recoil observed together with the prompt deexcitation photon. We see no evidence for such inelastic WIMP-Xe129 interactions. A profile likelihood analysis allows us to set a 90% C.L. upper limit on the inelastic, spin-dependent WIMP-nucleon cross section of 3.3×10−38 cm2 at 100 GeV/c2. This is the most constraining result to date, and sets the pathway for an analysis of this interaction channel in upcoming, larger dual-phase xenon detectors.
The GERmanium Detector Array, Gerda, searches for neutrinoless double β decay in 76Ge using bare high-purity germanium detectors submerged in liquid argon. For the calibration of these detectors γ ...emitting sources have to be lowered from their parking position on the top of the cryostat over more than 5m down to the germanium crystals. With the help of Monte Carlo simulations, the relevant parameters of the calibration system were determined. It was found that three 228Th sources with an activity of 20kBq each at two different vertical positions will be necessary to reach sufficient statistics in all detectors in less than 4h of calibration time. These sources will contribute to the background of the experiment with a total of (1.07±0.04(stat)−0.19+0.13(sys))×10−4cts/(keVkgyr)) when shielded from below with 6cm of tantalum in the parking position.
Abstract
The selection of low-radioactive construction materials is of utmost importance for the success of low-energy rare event search experiments. Besides radioactive contaminants in the bulk, the ...emanation of radioactive radon atoms from material surfaces attains increasing relevance in the effort to further reduce the background of such experiments. In this work, we present the
$$^{222}$$
222
Rn emanation measurements performed for the XENON1T dark matter experiment. Together with the bulk impurity screening campaign, the results enabled us to select the radio-purest construction materials, targeting a
$$^{222}$$
222
Rn activity concentration of
$$10\,\mathrm{\,}\upmu \mathrm{Bq}/\mathrm{kg}$$
10
μ
Bq
/
kg
in
$$3.2\,\mathrm{t}$$
3.2
t
of xenon. The knowledge of the distribution of the
$$^{222}$$
222
Rn sources allowed us to selectively eliminate problematic components in the course of the experiment. The predictions from the emanation measurements were compared to data of the
$$^{222}$$
222
Rn activity concentration in XENON1T. The final
$$^{222}$$
222
Rn activity concentration of
$$(4.5\pm 0.1)\,\mathrm{\,}\upmu \mathrm{Bq}/\mathrm{kg}$$
(
4.5
±
0.1
)
μ
Bq
/
kg
in the target of XENON1T is the lowest ever achieved in a xenon dark matter experiment.
Background measurements in the Gran Sasso Underground Laboratory Haffke, M.; Baudis, L.; Bruch, T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2011, Letnik:
643, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The gamma background flux below 3000
keV in the Laboratori Nazionali del Gran Sasso (LNGS), Italy, has been measured using a 3
in. diameter NaI(Tl) detector at different underground positions: in ...hall A, hall B, the interferometer tunnel, and inside the Large Volume Detector (LVD). The integrated flux is 0.3–0.4
s
−1
cm
−2 at the first three locations, and is lower by two orders of magnitude inside LVD. With the help of Monte Carlo simulations for every location, the contribution of the individual primordial isotopes to the background has been determined. Using an 11
in. diameter NaI(Tl) detector, the background neutron flux in the LNGS interferometer tunnel has been estimated. Within the uncertainties, the result agrees with those from other neutron measurements in the main halls.
Dark matter and double beta decay experiments require extremely low radioactivity within the detector materials. For this purpose, the University of California, Los Angeles and Hamamatsu Photonics ...have developed the QUartz Photon Intensifying Detector (Q
upid), an ultra-low background photodetector based on the Hybrid Avalanche Photo Diode (HAPD) and entirely made of ultraclean synthetic fused silica. In this work we present the basic concept of the Q
upid and the testing measurements on Q
upids from the first production line.
Screening of radioactivity at the Gator facility in the Laboratori Nazionali del Gran Sasso has shown that the Q
upids safely fulfill the low radioactive contamination requirements for the next generation zero background experiments set by Monte Carlo simulations.
The quantum efficiency of the Q
upid at room temperature is
>
30
% at the xenon scintillation wavelength. At −100
°C, the Q
upid shows a leakage current smaller than 1
nA and a global gain of 10
5. In these conditions, the photocathode and the anode show
>
95
%
linearity up to
1
μ
A
for the cathode and 3
mA for the anode. The photocathode and collection efficiency are uniform to 80% over the entire surface. In parallel with single photon counting capabilities, the Q
upids have a good timing response: 1.8 ±0.1
ns rise time, 2.5 ±0.2
ns fall time, 4.20 ±0.05
ns (FWHM) pulse width, and 160 ±30
ps (FWHM) transit time spread.
The Q
upids have also been tested in a liquid xenon environment, and scintillation light from
57Co and
210Po radioactive sources was observed.
The selection of low-radioactive construction materials is of the utmost importance for rare-event searches and thus critical to the XENONnT experiment. Results of an extensive radioassay program are ...reported, in which material samples have been screened with gamma-ray spectroscopy, mass spectrometry, and
222
Rn emanation measurements. Furthermore, the cleanliness procedures applied to remove or mitigate surface contamination of detector materials are described. Screening results, used as inputs for a XENONnT Monte Carlo simulation, predict a reduction of materials background (
∼
17%) with respect to its predecessor XENON1T. Through radon emanation measurements, the expected
222
Rn activity concentration in XENONnT is determined to be 4.2 (
-
0.7
+
0.5
)
μ
Bq/kg, a factor three lower with respect to XENON1T. This radon concentration will be further suppressed by means of the novel radon distillation system.
A difficult task with many particle detectors focusing on interactions below approximately 100 keV is to perform a calibration in the appropriate energy range that adequately probes all regions of ...the detector. Because detector response can vary greatly in various locations within the device, a spatially uniform calibration is important. We present a new method for calibration of liquid xenon (LXe) detectors, using the short-lived (83m)Kr. This source has transitions at 9.4 and 32.1 keV, and as a noble gas like Xe, it disperses uniformly in all regions of the detector. Even for low source activities, the existence of the two transitions provides a method of identifying the decays that is free of background. We find that at decreasing energies, the LXe light yield increases, while the amount of electric field quenching is diminished. Additionally, we show that if any long-lived radioactive backgrounds are introduced by this method, they will present less than 67x10(-6) events kg(-1) day(-1) keV(-1) in the next generation of LXe dark matter direct detection searches.
XENON10 is the first two-phase xenon time projection chamber (TPC) developed within the XENON dark matter search program. The TPC, with an active liquid xenon (LXe) mass of about 14
kg, was installed ...at the Gran Sasso Underground Laboratory (LNGS) in Italy, and operated for more than one year, with excellent stability and performance. Results from a dark matter search with XENON10 have been published elsewhere. In this paper, we summarize the design and performance of the detector and its subsystems, based on calibration data using sources of gamma-rays and neutrons as well as background and Monte Carlo simulation data. The results on the detector’s energy threshold, position resolution, and overall efficiency show a performance that exceeds design specifications, in view of the very low energy threshold achieved (<10
keVr) and low background rate achieved.
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