N. Redaelli

Ageing measurements on glass RPCs

Resistive plate chambers (RPC) are widely used as active elements in particle physics detectors. A deterioration of RPC performance with time has been observed in several experiments, after operation at high temperature or with water contamination in the gas mixture, both for detectors with bakelite electrodes and for the ones with float-glass electrodes. We have developed a kind of RPCs suitable for large scale industrial production. Float-glass is employed as electrode material, and the screen-printing technique is used to apply the resistive coating on the electrodes. A dedicated intensive measurement program on these detectors has been carried out, to assess their long-term behavior and aging properties under different operational conditions.

Design and performance of the cooling system for the electromagnetic calorimeter of CMS

For the physics program of the CMS experiment at the LHC to be carried out successfully, excellent electromagnetic calorimetry is required. Given the thermal properties of CMS ECAL, keeping the constant term of the energy resolution below 0.5% needs its temperature to be stabilized at 18/spl deg/C within 0.05/spl deg/C. A prototype module of ECAL with the final cooling system has been tested at CERN to check its integration with the read-out electronics and verify that it complies with the severe thermal requirements. The thermal performance of the cooling system is reported here.

Performance of a test prototype for MONOLITH

Massive Observatory for Neutrino Oscillation or Limits on Their existence (MONOLITH) is the project of an experiment to study atmospheric neutrino oscillations with a massive magnetized iron detector. A 8 t prototype equipped with about 20 m 2 ofGlass RPCs has been realized and tested at LNGS with cosmic-ray muons. The capability to determine the muon direction, by means ofthe time-of-flight technique, is discussed. # 2001 Elsevier Science B.V. All rights reserved.

Analysis and interpretation of the performance degradation of glass Resistive Plate Chambers operated in streamer mode

The long-term stability of Resistive Plate Chambers (RPCs) with glass electrodes was studied for one year with a dedicated test station hosting about 10 m2 of detectors. RPCs were operated in streamer mode with a ternary gas mixture containing argon (27%), isobutane (9%) and tetrafluoroethane (64%). Environmental conditions were kept under control and, in particular, the water pollution in the gas, deemed responsible for the degradation of glass RPC performance, was monitored never to exceed 30 ppm in the exhaust line. Evidence for a substantial aging of the detectors was observed, resulting in a loss of efficiency correlated to an increased rate of spurious streamers. This can be ascribed to the chemical attack of the glass surface by hydrofluoric acid formed in the streamer process, as confirmed by detailed morphological and chemical analyses of the electrode surface. Our results strengthen the indication that the instability of glass RPCs in the long term is related to the use of fluorocarbons as quenching medium and is not due to external pollutants.

New large area glass RPC: development, production and performances

We report on a R&D program targeted to produce large area glass RPC detectors. Our aim has been to exploit as much as possible glass industry standard techniques. One of the most important steps we have introduced to reach the goal of fully automated production of large area detectors has been the use of screen silk printing technique for the resistive electrodes. A substantial number of prototypes detector have been produced: /spl ap/ 100 m/sup 2/. The detectors behavior as a function of the local particle rate has been tested at the DAFNE Test Beam Facility with 500 MeV electrons. Results concerning long term stability and ageing tests, presently going on by means of two cosmic ray telescopes in two different laboratories, will also be presented.

Baseline concept for a precise measurement of atmospheric neutrino oscillation

A high-density calorimeter, consisting of magnetized planes interleaved by Resistive Plates Chambers (RPCs, Ref. (1)) , as tracking and timing devices, is a good candidate for a new experiment on atmospheric neutrinos. With 34 kt of mass and in four years of data taking, this experiment will be sensitive to νμ→νx oscillation with Δm2>6×10−5 and large mixing, covering the region suggested by the SuperKamiokande results. Moreover, the experimental method will enable to measure the oscillation parameters from the modulation of the L/E spectrum (νμ disappearance). For >m2>3×10−3 eV2, this experiment can also establish whether the oscillation occurs into a tau or a sterile neutrino, by looking for an excess of muon-less events at high energies produced by upward-going tau neutrinos(ντ appearence).

A new high-density detector for atmospheric neutrinos. Towards neutrino stoichiometry

Abstract A high-density calorimeter, consisting of magnetised iron planes interleaved by RPCs, as tracking and timing devices, is a good candidate for a next generation experiment on atmospheric neutrinos. With 34 kt of mass and in four years of data taking, this experiment will be sensitive to v μ → v χ oscillation with Δm 2 > 6 × 10 −5 and mixing near to maximal and fuly cover the region of oscillation parameters suggested by Super-Kamiokande results. Moreover, the experimental method will enable to measure the oscillation parameters from the modulation of the L E spectrum ( v μ disappearance). For Δm 2 > 3 × 10 −3 eV 2 , this experiment can also establish whether the oscillation occurs into a tau or a sterile neutrino, by looking for an excess of muon-less events at high energies produced by upward-going tau neutrinos ( v τ appearance).