We report the first measurements of the absolute ionization yield of nuclear recoils in liquid xenon, as a function of energy and electric-field. Independent experiments were carried out with two dualphase time projection chamber prototypes, developed for the XENON Dark Matter project. We find that the charge yield increases with decreasing recoil energy, and exhibits only a weak field dependence. These results are a first demonstration of the capability of dual phase xenon detectors to discriminate between electron and nuclear recoils, a key requirement for a sensitive dark matter search at recoil energies down to 20 keV. Introduction: Current evidence indicates that one quarter of the mass-energy density of the universe is composed of cold, non-baryonic dark matter, which has thus far been observed only through its gravitational interactions with normal matter. Its precise nature is undetermined, but weakly interacting massive particles (WIMPs) are an attractive candidate which may be detectable via rare elastic scattering interactions depositing a few tens of keV in target nuclei. For a review of the motivation for WIMPs, and current experimental WIMP searches, see [1]. The best limits, from CDMS, are <0.06 events/kg/day (in Ge) [2]. Improving the search sensitivity will require both larger detectors and lower radioactive backgrounds. An attractive method to achieve this uses liquid noble gas-based detectors, which promise to be readily scalable to the multi-ton scale. For the XENON experiment [3], we are developing a large volume liquid xenon (LXe) dual-phase time-projection-chamber (TPC) that features simultaneous measurement of recoil ionization and scintillation to determine the energy and 3-D localization on an event-by-event basis. Nuclear recoils from WIMPs (and neutrons) have denser tracks, and thus have been assumed to have greater electron-ion recombination than electron recoils, providing a basis for discrimination against radioactive background gammas and betas. However, ionization from these nuclear recoils has not been measured until now. In this report, we describe the first measurements of the ionization yield of low energy nuclear recoils in LXe and confirm the baseline discrimination capability of this technique.
XENON is a novel liquid xenon experiment concept for a sensitive dark matter search using a 1-tonne active target, distributed in an array of ten independent time projection chambers. The design relies on the simultaneous detection of ionization and scintillation signals in liquid xenon, with the goal of extracting as much information as possible on an event-by-event basis, while maintaining most of the target active. XENON is expected to have effective and redundant background identification and discrimination power, higher than 99.5%, and to achieve a very low threshold, on the order of 4 keV visible recoil energy. Based on this expectation and the 1-tonne mass of active xenon, we project a sensitivity of 0.0001 events/kg/day, after 3 yr operation in an appropriate underground location. The XENON experiment has been recently proposed to the National Science Foundation (NSF) for an initial development phase leading to the development of the 100 kg unit module.
Results of the extensive radioactivity screening campaign to identify materials for the construction of XENON100 are reported. This dark matter search experiment is operated underground at Laboratori Nazionali del Gran Sasso (LNGS), Italy. Several ultra sensitive High Purity Germanium detectors (HPGe) have been used for gamma ray spectrometry. Mass spectrometry has been applied for a few low mass plastic samples. Detailed tables with the radioactive contaminations of all screened samples are presented, together with the implications for XENON100. AbstractResults of the extensive radioactivity screening campaign to identify materials for the construction of XENON100 are reported. This Dark Matter search experiment is operated underground at Laboratori Nazionali del Gran Sasso (LNGS), Italy. Several ultra sensitive High Purity Germanium detectors (HPGe) have been used for gamma ray spectrometry. Mass spectrometry has been applied for a few low mass plastic samples. Detailed tables with the radioactive contaminations of all screened samples are presented, together with the implications for XENON100.
a b s t r a c t XENON10 is an experiment designed to directly detect particle dark matter. It is a dual phase (liquid/ gas) xenon time-projection chamber with 3D position imaging. Particle interactions generate a primary scintillation signal (S1) and ionization signal (S2), which are both functions of the deposited recoil energy and the incident particle type. We present a new precision measurement of the relative scintillation yield L eff and the absolute ionization yield Q y , for nuclear recoils in xenon. A dark matter particle is expected to deposit energy by scattering from a xenon nucleus. Knowledge of L eff is therefore crucial for establishing the energy threshold of the experiment; this in turn determines the sensitivity to particle dark matter. Our L eff measurement is in agreement with recent theoretical predictions above 15 keV nuclear recoil energy, and the energy threshold of the measurement is $4 keV.A knowledge of the ionization yield Q y is necessary to establish the trigger threshold of the experiment. The ionization yield Q y is measured in two ways, both in agreement with previous measurements and with a factor of 10 lower energy threshold.
The XENON experiment aims at the direct detection of dark matter in the form of WIMPs (Weakly Interacting Massive Particles) via their elastic scattering off Xe nuclei. A fiducial mass of 1000 kg, distributed in ten independent liquid xenon time projection chambers(LXeTPCs) will be used to probe the lowest interaction cross section predicted by SUSY models. The TPCs are operated in dual (liquid/gas) phase, to allow a measurement of nuclear recoils down to 16 keV energy, via simultaneous detection of the ionization, through secondary scintillation in the gas, and primary scintillation in the liquid. The distinct ratio of primary to secondary scintillation for nuclear recoils from WIMPs (or neutrons), and for electron recoils from background, is key to the event-by-event discrimination capability of XENON. A dual phase xenon prototype has been realized and is currently being tested, along with other prototypes dedicated to other measurements relevant to the XENON program. As part of the R&D phase, we will realize and move underground a first XENON module (XENON10) with at least 10 kg fiducial mass to measure the background rejection capability and to optimize the conditions for continuous and stable detector operation underground. We present some of the results from the ongoing R&D and summarize the expected performance of the 10 kg experiment, from Monte Carlo simulations. The main design features of the 100 kg detector unit(XENON100), with which we envisage to make up the 1 tonne sensitive mass of XENON1T will also be presented.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.