We report the studies and optimization of scintillation light measurements in an updated version of the XEMIS1 prototype for the development of the XEMIS2 camera. A novel monolithic liquid xenon ...Compton camera, named XEMIS2 (XEnon Medical Imaging System), attempts to achieve low-activity small-animal imaging using the 3-gamma imaging technique. This emerging detector relies on the time projection chamber technique: it will be able to perform a simultaneous detection of the three γ-rays emitted by a specific radionuclide, such as scandium-44, and to produce a good quality image with a remarkable diminution of radiopharmaceutical activity at the same time. Vacuum Ultraviolet (VUV) scintillation light and ionization charge carriers generated from the recoiling particles within the detector are detected and used to reconstruct the interaction position and deposited energy. A cost-effective self-triggering scintillation signal read-out and data acquisition (DAQ) system has been developed to achieve a continuous data read-out with negligible electronics dead time. The DAQ prototype has been installed and qualified in an updated version of the XEMIS1 detector. It reaches the performance specifications in scintillation light measurements. Moreover, scintillation signals can also be used for the virtual segmentation of the monolithic detection volume through the matching algorithm of the scintillation and ionization signals based on the Light Collection Map (LCM). This spatial pre-localization of the physical events, called the virtual fiducialization of the active volume, is used to lower the detector occupancy rate when the administered activity is increased to lessen the examination time. The XEMIS1 experimental LCMs indicate that each PMT owns an individual field of view so as to segment the active volume virtually. The preparation work for the XEMIS2 camera operation has been completed in the updated XEMIS1 detector while the XEMIS2 scintillation light measurement system is under commissioning in Nantes Centre Hospitalier Universitaire.
•The XEMIS2 camera oriented to the whole-body small animal 3-gamma medical imaging is presented.•The XEMIS2 system is a monolithic liquid xenon Compton camera with a 24 cm axial field of view.•A cost-effective 16-channel self-triggering scintillation signal front-end read-out electronics named XSRETOT is reported.•The XEMIS1 experimental light collection maps can be used for the virtual segmentation of the monolithic detection volume.
We report on the response of liquid xenon to low energy electronic recoils below 15 keV from beta decays of tritium at drift fields of 92 V/cm, 154 V/cm and 366 V/cm using the XENON100 detector. A ...data-to-simulation fitting method based on Markov Chain Monte Carlo is used to extract the photon yields and recombination fluctuations from the experimental data. The photon yields measured at the two lower fields are in agreement with those from literature; additional measurements at a higher field of 366 V/cm are presented. The electronic and nuclear recoil discrimination as well as its dependence on the drift field and photon detection efficiency are investigated at these low energies. The results provide new measurements in the energy region of interest for dark matter searches using liquid xenon.
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 Formula omittedRn background originating from radon emanation. After inserting an auxiliary Formula omittedRn emanation source in the gas loop, we determined a radon reduction factor of Formula omitted (95% C.L.) for the distillation column by monitoring the Formula omittedRn activity concentration inside the XENON100 detector.
We present results of searches for vector and pseudoscalar bosonic super-weakly interacting massive particles (WIMPs), which are dark matter candidates with masses at the keV-scale, with the XENON100 ...experiment. XENON100 is a dual-phase xenon time projection chamber operated at the Laboratori Nazionali del Gran Sasso. A profile likelihood analysis of data with an exposure of 224.6 live days ×34 kg showed no evidence for a signal above the expected background. We thus obtain new and stringent upper limits in the (8–125) keV/c2 mass range, excluding couplings to electrons with coupling constants of gae>3×10−13 for pseudo-scalar and α′/α>2×10−28 for vector super-WIMPs, respectively. These limits are derived under the assumption that super-WIMPs constitute all of the dark matter in our galaxy.
The selection of low-radioactive construction materials is of utmost importance for the success of lowenergy 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 222Rn 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 222Rn activity concentration of 10 mu Bq/kg in 3.2 t of xenon. The knowledge of the distribution of the 222Rn 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 222Rn activity concentration in XENON1T. The final 222Rn activity concentration of (4.5 +/- 0.1) mu Bq/kg in the target of XENON1T is the lowest ever achieved in a xenon dark matter experiment.
Micromegas as a large microstrip detector for the COMPASS experiment Thers, D; Abbon, Ph; Ball, J ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2001, Volume:
469, Issue:
2
Journal Article
Peer reviewed
Open access
Recent results on the gaseous microstrip detector Micromegas which will be used to track particles in the COMPASS experiment at CERN are presented. Developments concerning its mechanical and ...electrical design, associated readout electronics and gas mixture were carried out. Particular attention was paid to the discharge phenomenon which affects this type of microstrip detector. The adequacy of the options finally retained, especially the SFE16 readout and the use of a Ne–C
2H
6–CF
4 gas mixture, was demonstrated in a set of beam tests performed on a
26×36
cm
2
prototype. Operating at a gain of ∼6400, full efficiency is reached along with a spatial resolution of
∼50
μm
and a timing accuracy of
8.5
ns
. Discharges are kept at a low rate, less than one per SPS spill in a COMPASS-like environment. Via a decoupling of the strips through individual capacitors their impact is greatly reduced. They generate a dead time on the full detector of
∼
3
ms
, affecting marginally the detection efficiency given their rate. The probability of discharge, at a given value of efficiency, is found to decrease with the mean value of the gas mixture atomic number. In view of these results, the commissioning of Micromegas for COMPASS is foreseen in the near future.
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![Online [Formula omitted]Rn ...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1434-6044/small "Online [Formula omitted]Rn removal by cryogenic distillation in the XENON100 experiment")
