The electromagnetic (e.m.) calorimeter of the ATLAS experiment for the Large Hadron Collider will be a sampling liquid argon accordion calorimeter. To achieve sufficient energy resolution, it is ...necessary to correct for the energy loss in the material upstream of the calorimeter. For this purpose, a separate presampler detector fixed on the inner face of the e.m. calorimeter, in the same cryostat, is being built by the ATLAS collaboration. Two presampler sectors have already been built and tested in their final version. The geometry of the detector and the various steps of its construction are reviewed. The hardware performance of the detector measured both at CERN and at the ISN-Grenoble (specific test bench) is discussed. It is concluded that the presampler will adequately fulfill its role for future operation at the CERN Large Hadron Collider.
The total charge response curve of an Am source placed in a liquid argon ionization cell has been measured. In a pure liquid argon sample (O concentration 0.1 ppm), it can be described by a ...semi-empirical formula which is derived from a model formerly elaborated by Thomas and Imel. The validity of this new formula was also tested in the case of oxygen-polluted liquid argon. The agreement with the data seems to indicate that the initial ion–electron pair recombination factor is not affected when the O concentration is smaller than 7 ppm. Further use of our recombination factor parameterization has been made to analyze data of liquid argon purity monitors utilizing Am sources with a sensitivity to O concentrations of 0.1 ppm. (Elsevier)
Pollution of liquid argon after neutron irradiation Andrieux, M.L.; Belymam, A.; Collot, J. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
2001, Letnik:
183, Številka:
3
Journal Article
Recenzirano
The purpose of the neutron facility installed at SARA is to investigate the behavior of various materials to be used in the ATLAS liquid argon calorimeter, when submitted to fast neutron radiation. ...The samples are placed in a liquid argon cryostat a few cm away from the neutron source. Various pieces of the electromagnetic calorimeter have been tested in order to evaluate the rate of pollution of the liquid and consequently the possible signal loss in energy measurements. The average fluence was equivalent to the maximum expected in the calorimeter in about 10 years. The most striking feature of the results is that the pollution is not due to oxygen, at least for most of it. Using a particular value of the absorption length derived from these data, a simulation was carried out and the energy signal loss in the calorimeter could be predicted. Within the limits of our present knowledge, the conclusion is that damages due to this pollution will not be a problem.
The effect of neutron radiation on light emitters and optical fibers at cryogenic temperatures (-184/spl deg/C) has been investigated as part of the development of an analogue optical link, intended ...for use at future high energy physics experiments. The LED's were also exposed to a gamma radiation dose of 3 Mrad. High radiance GaAs LED's, quantum-well LED's, quantum-well laser diodes and optical fibers have been exposed to neutron radiation reaching fluences of 10/sup 15/ neutrons/cm/sup 2/.
The total charge response curve of an
241
Am source placed in a liquid argon ionization cell has been measured. In a pure liquid argon sample (O
2
concentration
<0.1 ppm), it can be described by a ...semi-empirical formula which is derived from a model formerly elaborated by Thomas and Imel. The validity of this new formula was also tested in the case of oxygen-polluted liquid argon. The agreement with the data seems to indicate that the initial ion–electron pair recombination factor is not affected when the O
2
concentration is smaller than 7 ppm. Further use of our recombination factor parameterization has been made to analyze data of liquid argon purity monitors utilizing
241
Am sources with a sensitivity to O
2
concentrations of
∼0.1 ppm.
A fast neutron irradiation facility has been set up at the SARA cyclotron located in Grenoble. This facility provides the possibility to carry out fast neutron irradiation tests at both cryogenic and ...ambient temperatures. Neutrons are produced by stopping a 20.2 MeV deuteron beam in a 3 mm thick beryllium target. The angular distribution of the neutron flux and the energy spectra from 0° to 40° with respect to the deuteron beam axis were measured. A neutron fluence in the range of 10
14 cm
−2 is available per day, with a small gamma contamination and a small thermal neutron flux.
A fast neutron irradiation facility has been set up at the SARA cyclotron located in Grenoble. This facility provides the possibility to carry out fast neutron irradiation tests at both cryogenic and ...ambient temperatures. Neutrons are produced by stopping a 20.2MeV deuteron beam in a 3mm thick beryllium target. The angular distribution of the neutron flux and the energy spectra from 0 deg to 40 deg with respect to the deuteron beam axis were measured. A neutron fluence in the range of 10 exp 14 cm exp -2 is available per day, with a small gamma contamination and a small thermal neutron flux.
The cross sections for K
+ meson production in collisions of
36Ar on
12C,
natTi and
181Ta at an incident energy of 92 MeV per nucleon have been measured. A description of the set-up and of the method ...is given ; it is based on measurement of the muon decay of the positive kaon. At such a low incident energy the K
+ production seems to be more sensitive to the available energy in the center of mass of the nucleus-nucleus system than to the coulomb corrected incident energy normalized to the production threshold in a free nucleon-nucleon process.
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