New advances and developments on the RPC top wall of the HADES experiment at GSI

Abstract

Summary Ph.D Thesis Gas Ionisation Detectors are widely used in nuclear and particle physics experiments. In the beginning of the XXI century a new type was developed by P.Fonte et al. called Timing Resistive Plate Chambers (RPC). In this work we analyse the performance of the RPC TOF Wall detector installed at the HADES spectrometer at GSI, Darmstadt, Germany. Moreover we explore the feasibility of such a detector to contribute for tracing particles by using the TimTrack method. Finally we analyse the Cosmic Ray data taken during the commissioning of the detector before its final installation in the spectrometer. The timing RPC technology became widely used very fast as the provided accuracy of the time measurement and the relatively low cost made them a good substitute for other time of fligh detectors as scintillators coupled to photomultipliers. The physical background which lies underneath is mainly related to gas ionisation processes. The existing theoretical background is revised and compared with experimental data. Heavy Ion collision produced at the HADES experiment at the SIS18 facility (GSI, Darmstadt) bring the opportunity to carry out a deep analysis of the performance of the RPC TOF wall with a broad spectra of momenta, together with the particle identification and tracking provided by the spectrometer. Moreover, during the commissioning of the RPCs, done in 2009, hundreds of millions of Cosmic Ray events were recorded with a granularity and a time resolution never reached before at the Earth surface, offering an outstanding opportunity to analyse the spatial and temporal microstructure of cosmic ray air showers. The present work examined several aspects related to the RPC TOF wall of the HADES spectrometer. The techniques used for the performance analysis, synchronisation, and calibration were revised, some of them improved and, in case of absence, were developed specifically. Moreover a deep analysis of the measured variables (time and avalanche charge) has shown some new effects which may open the door for future developments regarding energy measurement and particle identification. A tracking method called TimTrack was extended to drift chambers and successfully tested in the HADES spectrometer as a proof of concept. Finally, the Cosmic Ray analysis has shown that a relatively small detector but with high granularity and high time resolution can access new parameters to explore and measure the interaction between the Cosmic Radiation and the Earth atmosphere. This work follows previous works done in RPC and gas ionisation done by R. Santonico, R. Cardarelli, P. Fonte, C. Lippman, W.Riegler and H. Bichsel. The TimTrack tracking method is based on works of J.A. Garzón and finally the Cosmic Ray analysis among others refers to the ideas of J. Linsley.