The Enriched Xenon Observatory collaboration searches for neutrino-less double beta decay in 136Xe. The first phase of the experiment, EXO-200 has started taking data in 2011 and has already produced ...important physics results like the first observation of the allowed two-neutrino double beta decay in 136Xe. A massive effort for material screening has accompanied the design of EXO-200 and has produced a detector with very low background due to the residual radioactivity. The most recent data analysis campaign has provided a strong limit for the neutrino-less double beta decay in 136Xe. For the next phase ton-scale detector, the collaboration is investigating the options for employing a Ba ion tagging technique to provide complete suppression of the radioactive background.
The search for neutrinoless double beta decay requires increasingly advanced methods of background reduction. A bold approach to solving this problem, in experiments using
136
Xe, is to extract and ...identify the daughter
136
Ba ion produced by double beta decay. Tagging events in this manner allows for a virtually background-free verification of double beta decay signals. Various approaches are being pursued by the nEXO collaboration to achieve Ba-tagging. A Multi-Reflection Time-of-Flight Mass Spectrometer (MR TOF) has been designed and optimized as one of the ion-identification methods, where it will investigate the ion-extraction efficiency, as well as provide further identification of the Ba isotope. The envisioned mode of operation allows the MR TOF to achieve a quickly adjustable mass-range and resolution, with simulations suggesting that a mass-resolving power of 140,000 is within reach. This work will discuss the MR TOF design and the methods employed to simulate and optimize it.
EXO-200 is an experiment designed to search for double beta decay of super(136)Xe with a single-phase, liquid xenon detector. It uses an active mass of 110 kg of xenon enriched to 80.6% in the ...isotope 136 in an ultra-low background time projection chamber capable of simultaneous detection of ionization and scintillation. This paper describes the EXO-200 detector with particular attention to the most innovative aspects of the design that revolve around the reduction of backgrounds, the efficient use of the expensive isotopically enriched xenon, and the optimization of the energy resolution in a relatively large volume.
Characterization of large area APDs for the EXO-200 detector Neilson, R.; LePort, F.; Pocar, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2009, Letnik:
608, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Enriched Xenon Observatory (EXO)-200 uses 468 large area avalanche photodiodes (LAAPDs) for detection of scintillation light in an ultra-low-background liquid xenon (LXe) detector. We describe ...initial measurements of dark noise, gain and response to xenon scintillation light of LAAPDs at temperatures from room temperature to 169
K—the temperature of liquid xenon. We also describe the individual characterization of more than 800 LAAPDs for selective installation in the EXO-200 detector.
We report on the design, construction, and operation of a PID temperature controlled and vacuum tight camera casing. The camera casing contains a commercial digital camera and a lighting system. The ...design of the camera casing and its components are discussed in detail. Pictures taken by this cryo-camera while immersed in argon vapour and liquid nitrogen are presented. The cryo-camera can provide a live view inside cryogenic set-ups and allows to record video.
The PICASSO experiment reports an improved limit for the existence of cold dark matter WIMPs interacting via spin-dependent interactions with nuclei. The experiment is installed in the Sudbury ...Neutrino Observatory at a depth of 2070 m. With superheated C4F10 droplets as the active material, and an exposure of 1.98±0.19 kg day, no evidence for a WIMP signal was found. For a WIMP mass of 29 GeV/c2, limits on the spin-dependent cross section on protons of σp=1.31 pb and on neutrons of σn=21.5 pb have been obtained at 90% C.L. In both cases, some new parameter space in the region of WIMP masses below 20 GeV/c2 has now been ruled out. The results of these measurements are also presented in terms of limits on the effective WIMP-proton and neutron coupling strengths ap and an.
We present results of systematic studies of the radiation response of superheated liquid droplet detectors, which are used in the PICASSO dark matter search experiment. This detection technique is ...based on the phase transitions of superheated liquid Freon droplets dispersed and trapped in a polymerized gel. Phase transitions can be induced by nuclear recoils following particle interactions and, in particular, interactions with Weakly Interacting Massive Particles (WIMPs). These detectors are threshold devices since a minimal energy deposition is necessary to induce a phase transition and their sensitivity to various types of radiation depends strongly on the operating temperature and pressure. The sensitivity to neutrons,
α-particles and
γ-rays was determined as a function of these operating parameters and the results are compared with simulations. In particular, we present a complete characterization of the response of detector modules already in use for a dark matter search at the SNO site to detect WIMPs and discuss possible background sources.
A search for neutrinoless double-β decay (0νββ) in Xe136 is performed with the full EXO-200 dataset using a deep neural network to discriminate between 0νββ and background events. Relative to ...previous analyses, the signal detection efficiency has been raised from 80.8% to 96.4±3.0%, and the energy resolution of the detector at the Q value of Xe136 0νββ has been improved from σ/E=1.23% to 1.15±0.02% with the upgraded detector. Accounting for the new data, the median 90% confidence level 0νββ half-life sensitivity for this analysis is 5.0×1025 yr with a total Xe136 exposure of 234.1 kg yr. No statistically significant evidence for 0νββ is observed, leading to a lower limit on the 0νββ half-life of 3.5×1025 yr at the 90% confidence level.
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