Characterization of HV-MAPS for the Future LHCb Downstream Tracker and Development of the DAQ System MARS

Abstract

By the beginning of Run 5 of the Large Hadron Collider, the LHCb experiment will enter the High-Luminosity LHC era. An increase by one order of magnitude of the instantaneous luminosity from 1x10³³ cm⁻²s⁻¹ to 1x10³⁴ cm⁻²s⁻¹ will allow the collection of 300 f⁻¹ data over the lifetime of the experiment. The collected data enables the LHCb experiment to fully exploit its flavor physics potential, exploring physics beyond the Standard Model of particle physics and probing observables with unprecedented precision. <br/> As a consequence, the number of proton-proton interactions per bunch crossing will increase from 6 to 40. Efficient particle tracking in a harsh radiation environment is crucial to maintain and even improve the detector's performance. Therefore, all sub-detectors will undergo a major upgrade with the beginning of Long Shutdown 4. Radiation tolerant technologies, providing precise time information with high granularity are essential. <br/> A key element will be the new downstream tracking detector, referred to as Mighty-Tracker, consisting of a monolithic pixel detector, called Mighty-Pixel, in the innermost region close to the beam-pipe and a scintillating fiber detector, called Mighty-SciFi, in the outermost region. The hybrid solution offers high granularity, radiation tolerance and timing information while being cost-effective.<br/> For the Mighty-Pixel detector High-Voltage Monolithic Active Pixel Sensors, invented at the Karlsruher Institut für Technologie, are planned to be installed. The production sensor, MightyPix, will inherit the development of predecessor HV-MAPS designed for the Mu3e and ATLAS experiments. The following requirements are mandatory to ensure an efficient long-term operation of the detector: A radiation tolerance up to a fluence of 3x10¹⁴ MeVn_eqcm⁻² and 40 MRad with a time resolution of ≤ 3 ns and hit-efficiency of ≥ 99%. <br/> Characterization of prototype HV-MAPS, mainly the TelePix2 sensor, with focus on performance studies is one of the main topics of the presented thesis. To perform those, a new Data Acquisition System, mandatory for the evaluation of HV-MAPS in a laboratory and testbeam environment, has been developed. The development and commissioning of the Mighty ASIC Readout System MARS is the second topic of this thesis. <br/> Investigations of the performance of HV-MAPS, with emphasis on their time resolution, bias behavior and hit-efficiency in dependence of different kinds of radiation damage, will be presented. Therefore, several irradiation campaigns have been performed at the Bonn isochronous cyclotron and at a x-ray tube. Measurement procedures and obtained results will be discussed with respect to the Mighty-Pixel requirements. As a main result, the time resolution has been probed in terms of radiation tolerance. For all evaluated sensors the required time resolution of ≤ 3 ns could be fulfilled. In addition, a hit-efficiency of ≥ 99% up to a fluence of 1x10¹⁴ MeVn_eqcm⁻² and a dose of 40 MRad has been confirmed for TelePix2 - demonstrating the viability of HV-MAPS for the Mighty-Pixel.