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Martino Gagliardi

Publications and source records attributed to Martino Gagliardi.

4 recordsLinked to original sources

Electron Collision Cross Sections in Tetrafluoropropene HFO1234ze(E) for Gas Mixtures in Resistive Plate Chambers

In recent years, there has been growing interest in tetrafluoropropene HFO1234ze(E) (C$_{3}$H$_{2}$F$_{4}$) for Resistive Plate Chambers (RPCs). This novel gas is considered a promising alternative to the standard mixtures currently used in RPCs, thanks to its low global warming potential. The knowledge of electron collision cross sections in C$_{3}$H$_{2}$F$_{4}$ enables reliable predictions of electron transport coefficients and reaction rates in C$_{3}$H$_{2}$F$_{4}$-based gas mixtures. This allows for optimizing the C$_{3}$H$_{2}$F$_{4}$-based gas mixtures to achieve the desired performance in RPCs. From measurements of electron transport coefficients and reaction rates, a complete set of scattering cross sections for electrons in C$_{3}$H$_{2}$F$_{4}$ has been derived. Validation of the electron collision cross sections is achieved through systematic comparisons of electron swarm parameters with experimental data in both pure C$_{3}$H$_{2}$F$_{4}$ and C$_{3}$H$_{2}$F$_{4}$/CO$_{2}$ gas mixtures. Given the influence of electron attachment in C$_{3}$H$_{2}$F$_{4}$ by the gas density, this work also includes precise calculations of the critical electric field strength in such mixtures. This set of cross sections has been further utilized to compute the effective ionization Townsend coefficient in gas mixtures containing C$_{3}$H$_{2}$F$_{4}$, potentially applicable for RPCs.

physics.plasm-ph↗

Performance and aging studies for the ALICE muon RPCs

The ALICE muon trigger (MTR) system consists of 72 Resistive Plate Chamber (RPC) detectors arranged in two stations, each composed of two planes with 18 RPCs per plane. The detectors are operated in maxi-avalanche mode using a mixture of 89.7% C$_2$H$_2$F$_4$, 10% i-C$_4$H$_{10}$ and 0.3% SF$_6$. A number of detector performance indicators, such as efficiency and dark current, have been monitored over time throughout the LHC Run2 (2015-18). While the efficiency showed very good stability, a steady increase in the absorbed dark current was observed. Since the end of 2018, the LHC has entered a phase of long shutdown, during which the ALICE experiment will be upgraded to cope with the next phase of data taking, expected in 2021. The MTR is undergoing a major upgrade of the front-end and readout electronics, and will change its functionalities, becoming a Muon Identifier. Only the replacement of the most irradiated RPCs is planned during the upgrade. It is therefore important to perform dedicated studies to gain further insights into the status of the detector. In particular, two RPCs were flushed with pure Ar gas for a prolonged period of time and a plasma was created by fully ionizing the gas. The output gas was analyzed using a Gas Chromatograph combined with a Mass Spectrometer and the possible presence of fluorinated compounds originating from the interaction of the plasma with the inner surfaces of the detector has been assessed using an Ion-Selective Electrode station. This contribution will include a detailed review of the ALICE muon RPC performance at the LHC. The procedure and results of the argon plasma test, described above, are also discussed.

physics.ins-det↗

Performance of the RPC-based ALICE muon trigger system at the LHC

The forward muon spectrometer of ALICE (A Large Ion Collider Experiment) is equipped with a trigger system made of four planes of Resistive Plate Chambers (RPC), arranged in two stations with two planes each, for a total area of about 140 m2 . The system provides single and di-muon triggers with suitable transverse momentum selection, optimised for the physics of quarkonia and open heavy flavour. In the first two years of data-taking at the Large Hadron Collider (2010 and 2011) the 72 RPCs were operated in highly saturated avalanche mode in both pp and Pb-Pb collisions. The integrated charge was about 1.3 mC/cm2 on average and 3.5 mC/cm2 for the most exposed detectors. This paper describes two main results. The first result is the determination of the RPC performance, with particular focus on the stability of the main detector parameters such as efficiency, dark current, and dark rate. The second result is the measurement of the muon trigger performance in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV, in terms of the reliability and stability of the trigger decision logic.

physics.ins-det↗