CERN Accelerating science

Thesis
Report number	CERN-THESIS-2010-054
Title	Development of the Experiment Control System and Performance Study of the Muon Chambers for the LHCb Experiment
Author(s)	Antunes Nobrega, R (Sapienza, Università di Roma)
Publication	Roma : Sapienza, Università di Roma, 2010 - 159.
Thesis note	PhD : Roma, Sapienza, Università di Roma : 2010
Thesis supervisor(s)	Marinari, E ; Penso, G ; Pinci, D
Note	Presented on 21 Jan 2010
Subject category	Detectors and Experimental Techniques
Accelerator/Facility, Experiment	CERN LHC ; LHCb
Abstract	The work of this thesis practically opened three fronts of the LHCb muon system : the development of the control and monitoring system of the readout electronics; the study of noise and threshold of the detector; and the study of the performance of the muon chambers. The LHCb muon readout apparatus is made 1368 Multi-Wire Proportional Chambers (MWPC) and 24 Gas Electron Multiplier (GEM) chambers connected to approximately 7500 16-channel front-end boards, resulting in 120000 output channels. The large-scale of this system naturally led to a complex control and monitoring system made of about 600 microcontrollers which are directly connected to the front-end electronics and handled by six computers. The development of this control system was accomplished within this thesis; the microcontroller’s firmware and the high level software, operating on the six local computers, were implemented. Besides configuring and monitoring the on-chamber readout electronics, a set of calibration and debugging oriented procedures have been developed to measure the noise, the time align and to assess the connection chains of every single channel of the detector. The threshold and noise characteristics in particular were studied deeply since they are essential to achieve the requirements of the muon system of 95% of efficiency on triggering muon particles within a 25 ns time window, given by the bunch-crossing rate of the LHC. This work was fundam ental to calibrate and prepare the muon detector to receive the first proton beams collision and it will be used during the next years of operation of the LHCb experiment. In addition, before this thesis, the different chamber’s types of the muon detector had never been evaluated in detail. Therefore, a cosmir rays acquisition system was mounted in one of the laboratories of the “La Sapienza” University (Rome, Italy) and the performance of different MWPC types of the muon system were studied considering parameters as crosstalk, efficiency and response-time resolution. The obtained results validated the muon chambers’ designs showing that the muon detector can comply to the LHCb requirements. In this thesis, the LHCb and its muon system will be described in the Chapters 1 and 2, respectively. My contributions could be divided into three parts: The development of the control system of the detector readout electronics, presented in Chapter 3; the study of the threshold configuration and the noise characteristics of the different chamber’s types of the muon system, presented in Chapter 4; and the study of the performance of the MWPC applied to the muon detector, described in Chapter 5.

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