Thin LG AD timing detectors for the ATLAS experiment.

Student thesis: Doctoral thesis


The Large Hadron Collider (LHC) with its 27 kilometer in circumference is the world's largest and most powerful particle accelerator. The LHC was designed to collide protons at 14 TeV energy at the center-of-mass. The design luminosity is 1034 cm2 s-1, which is achieved with 2808 circulating bunches, each with - 1011 protons. Bunches are spaced by 25ns, corresponding to a collision rate of 40 MHz at each of the four interaction points. The main priority of the European Strategy for P article Physics is the exploitation of the full potential of the LHC. An upgrade of the LHC to the high-luminosity LHC (HL-LHC) was planned for this purpose. The HL-LHC will require an upgrade of the machine and detectors with a view to collecting ten times more data than in the initial design, by around 2030. The major challenges for the high-luminosity phase are the occupancy, pile-up, high data rates, and radiation tolerance of the detectors. The increase in occupancy will be mitigated using higher granularity. Fast timing detectors with time resolution in the range of 30 ps will be used to reduce pile-up. Fur thermore , precision timing will provide additional physics capabilities. The purpose of the present thesis is the design, development and study of silicon detectors with high granularity and 30 ps time resolution suitable for the upgrade of the A Toroidal LHC Apparatus (ATLAS) experiment in the HL-LHC phase. Low Gain Avalanche Detectors (LGAD) have been proposed by RD50 collaboration as timing detectors for the Endcap Timing Layer (ETL) of ATLAS experiment. Three different strategies have been studied in order to fulfil with the high granularity, time resolution and radiation hardness specifications of devices for the ET L. The first strategy has consisted in detectors thickness reduction to decrease its collection time, rise time and intrinsic Landau noise. The second strategy has been the minimization of the capacitance developing strips and pixels with gain. Finally, the last strategy has lied in the use of other dopants to reduce radiation effects as boron removal. The structure of the thesis is as follows: chapter 2 introduces the major issues in the LHC upgrade, the CERN experiments, the required specifications of particle detectors for the HL­ LHC phase, their working principles, the measurement of time resolution, the microscopic and macroscopic radiation effects, and the state of the art in timing detectors; chapter 3 presents the technological and electrical simulation of the designed devices after the calibration of the technological simulation with the process characterization; chapter 4 gives an outline of the different device processes; chapter 5 presents the obtained results of unirradiated and irradiated devices; chapter 6 condenses the simulation, production and results of inverse Low Gain Avalanche Detectors (i-LGAD), and chapter 7 reports the conclusions and future work of the measured devices.
Date of Award6 Jun 2019
Original languageEnglish
SupervisorGiulio Pellegrini (Director), David Flores Gual (Director) & Luis Font Guiteras (Tutor)


  • Detectores para tracking; Particle tracking detectors; Detectores para timing; Iming detectors; Detectores resistentes a la radiación; Radiation-hard detectors

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