G. Piano Mortari

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.

The construction of the central detector for an experiment at the CERN p-p collider

Abstract The construction of a large (25 m 3 , 23 000 wires) drift chamber assembly with image readout to be used at the CERN p -p collider facility is reported. In this contribution the emphasis is mainly directed towards the mechanical and electrostatic design and on the implementation of the various control procedures.

Electronics and results for the central detector

Abstract The electronics systems for the readout of a large drift chamber (25 m3, 6110 sense wires) with image readout, to be used at the CERN p - p collider, is described. The system uses a flash analog-to-digital converter and is able to measure directly the drift time, the charge division, and the energy losses for many tracks on each wire. The results obtained with chamber and electronics prototypes are reported.

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.

A study of the factors affecting the electron lifetime in ultra-pure liquid argon

As part of the development program for the ICARUS experiment, which consists of a very large time projection chamber (TPC) filled with ultra-pure liquid Ar (LAr), we have carried out tests with different purifier systems, in order to evaluate the performance of the various parts and to improve the purification techniques developed so far. Electron lifetime τ in LAr has been determined with an improved method based on the measurement of the attenuation of a current due to an electron cloud, photoproduced by a laser pulse impinging on a metallic cathode and moving in a small drift chamber filled with the purified LAr. Results of the above-mentioned tests are reported. During these tests, we observed repeatedly and reproducibly an increase of τ that took place over a period of 10 to 20 h after liquefaction. Several tests performed in an attempt to elucidate this effect, suggest that the increase in τ is due to adsorption of electron-attaching impurities on the walls of the stainless steel container, a process governed by thermal diffusion. The electron lifetime monitoring system reported here was used to measure the electric field dependence of τ in purified LAr doped with O2 and CO2, for fields 100 V/cm < E < 800 V/cm: The results for O2 are consistent with published data.

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.

Argon purification in the liquid phase

Abstract In the R&D programme for the ICARUS experiment, we have developed a practical procedure to purify liquid argon in the liquid phase. Extreme purity is obtained, corresponding to an electronegative impurity concentration below 0.1 ppb of 0 2 equivalent. This corresponds to an electron lifetime in the range of several milliseconds equivalent to attenuation length of a few metres. The procedure has been tested up to flows of the order of 1000 litres of liquid per hour. The new technique makes it possible to operate very large amounts of ultrapure liquid argon as foreseen for the multikiloton ICARUS experiment at Gran Sasso.