F. Casagrande

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.

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.

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.

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.

Improving the performance of the liquid argon TPC by doping with tetra-methyl-germanium

Abstract In order to recover the charge lost by electron-ion recombination, we doped pure liquid argon with a photosensitive hydrocarbon, tetra-methyl-germanium (TMG), in the 3 ton ICARUS TPC. A charge increase of 25% to 220% was observed for different electric fields and for energy densities ranging from 1.6 to 32 MeV/cm.

On atmospheric 39Ar and 42Ar abundance

Ar and 42Ar are possible sources of background in large volume argon based detectors for the study of low energy neutrino events, as proposed for the ICARUS experiment. The production of these nuclides from neutron capture by atmospheric argon is estimated by taking into account both cosmic rays and contributions from nuclear explosions.

The ICARUS R&D program and results

Abstract The 3 ton liquid-argon time-projection chamber for the ICARUS project has been in operation since May 1991 collecting events from cosmic rays and monocromatic gamma ray source. Recent results are reported as well as an overview of the possible physics applications of this promising technique.

A neural network approach for the TPC signal processing

Artificial neural networks may in some cases be alternatives to programmed computing. Since they offer a new important approach to information processing, we have investigated if the accuracy offered by this technique is good enough to extract physical information from the signals coming from a liquid argon time projection chamber. The results obtained implementing a neural network algorithm on a sequential scalar computer have been compared to those of a standard best-fit procedure on the same machine. This new method appears to be suited for the analysis of the events occurring in a very large detector, as that foreseen for the ICARUS experiment.