Development and integration study of a new front-end electronics for the upgrade of the Resistive Plate Chamber detector for high radiation environment

The Resistive Plate Chamber (RPC) is a gaseous detector that, by means of a gas mixture as sensing material, reveals the passage of ionizing particles. Two resistive parallel planar electrodes are the basic RPC structure. The applied high voltage generates a strong electric field within the gas, providing directly an avalanche multiplication as soon as a free electron is generated, leading to the absence of any drift time. This unique feature makes it suitable for timing measurements. Moreover, the simple structure and the low cost materials allow its usage for large area applications. The upgrade of the Resistive Plate Chamber detector for the operation in high-background environments consists in the reduction of the operating voltage along with the capability to detect signals as small as 100 µV , moving part of the detector amplification to the Front-End electronics. A new Front-End (FE) electronics has been developed in this thesis project to reach this goal, exploiting a BJT-based preamplifier and a fast discriminator in SiGe BiCMOS technology to improve the detector time resolution and increasing its rate capability. The preamplifier, coupled to the 1-mm gap RPC, has a very low noise (1000 e − rms) and a peaking time of 100 ps. The discriminator has Time-Over-Threshold (TOT) measurement capability and a linear threshold response for signals as fast as 1 ns. The minimum effective threshold on the RPC signals, achievable by this system, is ∼ 100 µV . These RPCs represent a new generation of large area timing detectors, which integrate for the first time a highly performing FE electronics, granting a record time resolution of ∼ 350 ps on a single gas gap of 1 mm with 1.2 mm electrodes thickness. The entire development of this new FE electronics along with the detailed study of the FE integration within the RPC detector will be illustrated in this thesis. Moreover, the results of this new generation of RPC detectors will be shown, particularly in terms of charge threshold achieved (∼ 3 pC) by the electronics and, consequently, the improved detector rate capability (∼ 10 kHz/cm2 ). Furthermore, the application of this newly developed FE electronics is reported, precisely within the ATLAS experiment. The architecture of the present ATLAS Muon Spectrometer (MS) has been designed for a luminosity of 1034 cm−2 s −1 with a security factor of 5 with respect to the simulated background rate, now confirmed by the LHC Run 1 results. Since HL-LHC will have a 5 times higher luminosity and a one order of magnitude bigger background, the demand in terms of performance increases, being the detector operated in a much harsher conditions. The BI-BIS78 projects are part of the LHC Phase-1 and Phase-2 approved upgrades, in order to ensure the demands coming from the physics for the next 20 years. They consists in the installation of an entire new layer of RPC detectors inside the Inner Barrel of the ATLAS experiment. This will ensure higher redundancy and robustness of the trigger system, almost complete acceptance and an improved momentum selectivity. The BIS78 upgrade, scheduled for LHC Phase-1, is the pilot project for the BI RPCs installation. It aims at the installation of 10% of the BI RPCs in the transition region between the endcap and the Inner Barrel of 5 6 CONTENTS ATLAS experiment. This barrel region is the one with the highest background and for this reason is an excellent test bench for the BI upgrade. The BIS78 position will also help in the reduction of the fake muons produced upstream with respect to the cryostats. The BI RPCs represent a new generation of RPCs, basing their largely improved performance on the new and highly performing FE electronics. The BIS78 project, along with the performance achieved by such RPCs, will be shown in this thesis work.