S. Ventura

A three-ton liquid argon time projection chamber

Abstract We have constructed and operated a 3 ton liquid argon time projection chamber for the R&D programme of the ICARUS project. The chamber has been in op

Performance of a three-ton liquid argon time projection chamber

Abstract We have constructed and operated a 3 ton liquid argon time projection chamber as part of the R&D programme for the ICARUS project. We report on the analysis of events from cosmic rays and from radioactive sources collected from June 1991 to June 1993. We have systematically investigated the performance and the physical parameters of the detector. We present here the results obtained from the analysis of the cosmic rays data on the following items: the electron drift velocity, the electron lifetime, the free electron yield, the electron diffusion coefficient, the space resolution and the particle identification capability. The data from radioactive sources are used to study the energy resolution in the MeV range. The in depth understanding of the basic physics aspects of the liquid argon TPC allows us to conclude that such a detector can be built in large sizes and reliably operated over long periods of the time, providing a new instrument for physics experiments.

Detection of energy deposition down to the keV region using liquid xenon scintillation

Abstract A possible method for WIMPs detection using liquid xenon scintillation is discussed [1]. Background from cosmic and radioactive gamma rays at energies down to the keV region can be easily rejected by requiring the presence of proportional scintillation. The results from a basic test are presented and a prototype detector design is proposed.

Oxygen contamination in liquid Argon: combined effects on ionization electron charge and scintillation light

A dedicated test of the effects of Oxygen contamination in liquid Argon has been performed at the INFN-Gran Sasso Laboratory (LNGS, Italy) within the WArP R&D program. Two detectors have been used: the WArP2.3 lt prototype and a small (0.7 lt) dedicated detector, coupled with a system for the injection of controlled amounts of gaseous Oxygen. O2 contamination in LAr leads to depletion of both the free electron charge (via attachment process) and the scintillation light (via quenching and absorption mechanisms) available for ionization signal detection. Purpose of the test with the 0.7 lt detector was to detect the reduction of the long-lived component lifetime of the Argon scintillation light emission and of the overall light yield at increasing O2 concentration. Data from the WArP prototype were used for determining the behavior of both the ionization electron lifetime and the scintillation long-lived component lifetime at decreasing O2 concentration by the purification process activated in closed loop during the acquisition run. The electron lifetime measurements allowed to infer the O2 content of the Argon and correlate it with the long-lived scintillation lifetime data. The effects of Oxygen contamination on the scintillation light have been thus extensively measured over a wide range of O2 concentration, spanning from ~ 10−3 ppm up to ~ 10 ppm.

Scintillation efficiency of nuclear recoil in liquid xenon

Abstract We present the results of a test done with a Liquid Xenon (LXe) detector for “Dark Matter” search, exposed to a neutron beam to produce nuclear recoil events simulating those which would be generated by WIMPs elastic scattering. The aim of the experiment was to measure directly the scintillation efficiency of nuclear recoil. The nuclear recoil considered in the test was in the tens of keV range. The ratio of measured visible energy over the true recoil energy was evaluated to be about 20%, in good agreement with the theoretical predictions.

Performance of a liquid argon time projection chamber exposed to the CERN West Area Neutrino Facility neutrino beam

F. Arneodo, P. Benetti, M. Bonesini, A. Borio di Tigliole, B. Boschetti, A. Bueno, E. Calligarich, F. Casagrande, a D. Cavalli, F. Cavanna, P. Cennini, S. Centro, E. Cesana, D. Cline, A. Curioni, b I. De Mitri, C. De Vecchi, 2 R. Dolfini, A. Ferrari, A. Ghezzi, A . Guglielmi, J. Kisiel, G. Mannocchi, A. Mart́ınez de la Ossa, C. Matthey, F. Mauri, C. Montanari, S. Navas, P. Negri, M. Nicoletto, S. Otwinowski, M. Paganoni, O. Palamara, A. Pepato, L. Periale, G. Piano Mortari, P. Picchi, 5 F. Pietropaolo, A. Puccini, A. Pullia, S. Ragazzi, T. Rancati, A. Rappoldi, G.L. Raselli, N. Redaelli, E. Rondio, A. Rubbia, C. Rubbia, P.R. Sala, F. Sergiampietri, J. Sobczyk, S. Suzuki, 5, c T. Tabarelli de Fatis, M. Terrani, F. Terranova, A. Tonazzo, S. Ventura, C. Vignoli, H. Wang, and A. Zalewska

Detection of scintillation light in coincidence with ionizing tracks in a liquid argon time projection chamber

A system to detect light from liquid argon scintillation has been implemented in a small, ICARUS-like, liquid argon time projection chamber. The system, which uses a VUV-sensitive photomultiplier to collect the light, has recorded many ionizing tracks from cosmic-rays in coincidence with scintillation signals. Our measurements demonstrate that scintillation light detection can provide an effective method for absolute time measurement of events and eventually a useful trigger signal

Calibration of BC501A liquid scintillator cells with monochromatic neutron beams

Abstract The recoil proton energy response has been measured by exposing cylindrical cells, filled with BC501A BICRON liquid scintillator, to mono-energetic neutron reference fields. We determine the required calibration parameters and report the detailed procedures for the experimental data handling. A dedicated Monte Carlo simulation of the detector response and efficiency has been performed. It showed good agreement with the measured quantities. The results from this calibration are necessary for a detailed study of the neutron spectrum at the underground Gran Sasso Laboratory, with a neutron detector made of 32 liquid scintillator cells, like those used during the calibration.

A simple and effective purifier for liquid xenon

Abstract We describe a procedure to obtain ultra high electron lifetime in liquid xenon by means of a commercial Oxisorb cartridge and the distillation of the liquid. An improved ICARUS-type purity monitor chamber is described as well as details of the purification process. No charge attenuation is observed over the drifting distance (6 cm) at electric fields ranging from 800 down to 5 V/cm. This implies a free electron lifetime of at least several milliseconds. Results on the drift velocity dependence on the temperature are also reported.

Demonstration and comparison of photomultiplier tubes at liquid Argon temperature

Liquified noble gases are widely used as a target in direct Dark Matter searches. Signals from scintillation in the liquid, following energy deposition from the recoil nuclei scattered by Dark Matter particles (e.g. WIMPs), should be recorded down to very low energies by photosensors suitably designed to operate at cryogenic temperatures. Liquid Argon based detectors for Dark Matter searches currently implement photo multiplier tubes for signal read-out. In the last few years PMTs with photocathodes operating down to liquid Argon temperatures (87 K) have been specially developed with increasing Quantum Efficiency characteristics. The most recent of these, Hamamatsu Photonics Mod. R11065 with peak QE up to about 35%, has been extensively tested within the R&D program of the WArP Collaboration. During these testes the Hamamatsu PMTs showed superb performance and allowed obtaining a light yield around 7 phel/keVee in a Liquid Argon detector with a photocathodic coverage in the 12% range, sufficient for detection of events down to few keVee of energy deposition. This shows that this new type of PMT is suited for experimental applications, in particular for new direct Dark Matter searches with LAr-based experiments.