193 research outputs found
Removing krypton from xenon by cryogenic distillation to the ppq level
The XENON1T experiment aims for the direct detection of dark matter in a
cryostat filled with 3.3 tons of liquid xenon. In order to achieve the desired
sensitivity, the background induced by radioactive decays inside the detector
has to be sufficiently low. One major contributor is the -emitter
Kr which is an intrinsic contamination of the xenon. For the XENON1T
experiment a concentration of natural krypton in xenon Kr/Xe < 200
ppq (parts per quadrillion, 1 ppq = 10 mol/mol) is required. In this
work, the design of a novel cryogenic distillation column using the common
McCabe-Thiele approach is described. The system demonstrated a krypton
reduction factor of 6.410 with thermodynamic stability at process
speeds above 3 kg/h. The resulting concentration of Kr/Xe < 26 ppq
is the lowest ever achieved, almost one order of magnitude below the
requirements for XENON1T and even sufficient for future dark matter experiments
using liquid xenon, such as XENONnT and DARWIN
Measurement of the 2νββ decay half-life of 150Nd and a search for 0νββ decay processes with the full exposure from the NEMO-3 detector
We present results from a search for neutrinoless double-β (0νββ) decay using 36.6 g of the isotope
150Nd with data corresponding to a live time of 5.25 y recorded with the NEMO-3 detector. We construct a
complete background model for this isotope, including a measurement of the two-neutrino double-β decay
half-life of T2ν
1=2 ¼ ½9.34 0.22ðstatÞ þ0.62 −0.60 ðsystÞ × 1018 y for the ground state transition, which represents
the most precise result to date for this isotope. We perform a multivariate analysis to search for 0νββ decays
in order to improve the sensitivity and, in the case of observation, disentangle the possible underlying decay
mechanisms. As no evidence for 0νββ decay is observed, we derive lower limits on half-lives for several mechanisms involving physics beyond the standard model. The observed lower limit, assuming light
Majorana neutrino exchange mediates the decay, is T0ν
1=2 > 2.0 × 1022 y at the 90% C.L., corresponding to
an upper limit on the effective neutrino mass of hmνi < 1.6–5.3 eV
Development of methods for the preparation of radiopure <sup>82</sup>Se sources for the SuperNEMO neutrinoless double-beta decay experiment
A radiochemical method for producing 82Se sources with an ultra-low level of contamination of natural radionuclides (40K, decay products of 232Th and 238U) has been developed based on cation-exchange chromatographic purification with reverse removal of impurities. It includes chromatographic separation (purification), reduction, conditioning (which includes decantation, centrifugation, washing, grinding, and drying), and 82Se foil production. The conditioning stage, during which highly dispersed elemental selenium is obtained by the reduction of purified selenious acid (H2SeO3) with sulfur dioxide (SO2) represents the crucial step in the preparation of radiopure 82Se samples. The natural selenium (600 g) was first produced in this procedure in order to refine the method. The technique developed was then used to produce 2.5 kg of radiopure enriched selenium (82Se). The produced 82Se samples were wrapped in polyethylene (12 μm thick) and radionuclides present in the sample were analyzed with the BiPo-3 detector. The radiopurity of the plastic materials (chromatographic column material and polypropylene chemical vessels), which were used at all stages, was determined by instrumental neutron activation analysis. The radiopurity of the 82Se foils was checked by measurements with the BiPo-3 spectrometer, which confirmed the high purity of the final product. The measured contamination level for 208Tl was 8-54 μBq/kg, and for 214Bi the detection limit of 600 μBq/kg has been reached.</p
Analysis of test beam data taken with a prototype of TPC with resistive Micromegas for the T2K Near Detector upgrade
In this paper we describe the performance of a prototype of the High Angle
Time Projection Chambers (HA-TPCs) that are being produced for the Near
Detector (ND280) upgrade of the T2K experiment. The two HA-TPCs of ND280 will
be instrumented with eight Encapsulated Resistive Anode Micromegas (ERAM) on
each endplate, thus constituting in total 32 ERAMs. This innovative technique
allows the detection of the charge emitted by ionization electrons over several
pads, improving the determination of the track position. The TPC prototype has
been equipped with the first ERAM module produced for T2K and with the HA-TPC
readout electronics chain and it has been exposed to the DESY Test Beam in
order to measure spatial and dE/dx resolution. In this paper we characterize
the performances of the ERAM and, for the first time, we compare them with a
newly developed simulation of the detector response. Spatial resolution better
than 800 and dE/dx resolution better than 10% are observed for
all the incident angles and for all the drift distances of interest. All the
main features of the data are correctly reproduced by the simulation and these
performances fully fulfill the requirements for the HA-TPCs of T2K
Online Rn removal by cryogenic distillation in the XENON100 experiment
We describe the purification of xenon from traces of the radioactive noble gas radon using a cryogenic distillation column. The distillation column was integrated into the gas purification loop of the XENON100 detector for online radon removal. This enabled us to significantly reduce the constant ²²²Rn background originating from radon emanation. After inserting an auxiliary ²²²Rn emanation source in the gas loop, we determined a radon reduction factor of R>27 (95% C.L.) for the distillation column by monitoring the ²²²Rn activity concentration inside the XENON100 detector
DARWIN: towards the ultimate dark matter detector
DARk matter WImp search with liquid xenoN (DARWIN) will be an experiment forthe direct detection of dark matter using a multi-ton liquid xenon timeprojection chamber at its core. Its primary goal will be to explore theexperimentally accessible parameter space for Weakly Interacting MassiveParticles (WIMPs) in a wide mass-range, until neutrino interactions with thetarget become an irreducible background. The prompt scintillation light and thecharge signals induced by particle interactions in the xenon will be observedby VUV sensitive, ultra-low background photosensors. Besides its excellentsensitivity to WIMPs above a mass of 5 GeV/c2, such a detector with its largemass, low-energy threshold and ultra-low background level will also besensitive to other rare interactions. It will search for solar axions, galacticaxion-like particles and the neutrinoless double-beta decay of 136-Xe, as wellas measure the low-energy solar neutrino flux with <1% precision, observecoherent neutrino-nucleus interactions, and detect galactic supernovae. Wepresent the concept of the DARWIN detector and discuss its physics reach, themain sources of backgrounds and the ongoing detector design and R&D efforts
Characterization of Charge Spreading and Gain of Encapsulated Resistive Micromegas Detectors for the Upgrade of the T2K Near Detector Time Projection Chambers
An upgrade of the near detector of the T2K long baseline neutrino oscillation
experiment is currently being conducted. This upgrade will include two new Time
Projection Chambers, each equipped with 16 charge readout resistive Micromegas
modules. A procedure to validate the performance of the detectors at different
stages of production has been developed and implemented to ensure a proper and
reliable operation of the detectors once installed. A dedicated X-ray test
bench is used to characterize the detectors by scanning each pad individually
and to precisely measure the uniformity of the gain and the deposited energy
resolution over the pad plane. An energy resolution of about 10% is obtained. A
detailed physical model has been developed to describe the charge dispersion
phenomena in the resistive Micromegas anode. The detailed physical description
includes initial ionization, electron drift, diffusion effects and the readout
electronics effects. The model provides an excellent characterization of the
charge spreading of the experimental measurements and allowed the simultaneous
extraction of gain and RC information of the modules
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