Design, installation and commissioning of new read-out electronics for HADES ECAL and diamond detectors for T0-reconstruction and beam diagnostics

Abstract

This work deals with the design, installation and commissioning of the front-end electronics for the newly installed HADES electromagnetic calorimeter (ECAL) detector at GSI Helmholtzzentrum fur Schwerionenforschung GmbH in Darmstadt. A Charge-to-Digital-Converter (QDC) and Time-to-Digital-Converter (TDC) based on a commercial FPGA (Field Programmable Gate Array) technology is used to read out 978 Photomultiplier tubes (PMT) of the ECAL. The charge measurement of the detector signals is based on a modified time-over-threshold (TOT) measuring method. In the context of this work the second generation of the PaDiWa-AMPS front-end board for the TRB3 (General Purpose Trigger and Readout Board - generation 3) was designed, tested in the laboratory and integrated into the HADES data acquisition infrastructure. The front-end achieves a time measurement precision of σₜ = 16 ps. The relative charge measurement precision for signal amplitudes above 1 V is below 0.5 %. A successful operation of the read-out system was shown during a four week physics production beam time with an 1.58A GeV Ag beam. A similar read-out concept is used to read out diamond based beam detectors in the HADES experiment. Those detectors are used as a trigger and for the T0 determination in the HADES time-of-flight measuring system, which is important for the particle identification. Beside this, they are used for online beam monitoring purposes. The requirement for the time precision of the sensors is about 50 ps. Currently the read-out system is adapted to new Ultra-Fast Silicon Detector (UFSD) technology which might replace the diamond detectors in the HADES experiment in the future. A UFSD prototype detector has been tested successfully with a proton beam. Furthermore, it is planned to use this technology as a diagnostic instrument for Energy Recovery Linac (ERL) operations of the electron accelerator S-DALINAC at TU Darmstadt in future. For further research and development of beam detectors a permanent multi-purpose detector test set-up was installed at the S-DALINAC. It allows tests of detectors with an electron beam with an energy up to 130 MeV and beam currents up to 20 µA. The set-up has been successfully commissioned and offers optimal conditions for future tests for research and development of beam detectors with a beam of minimum ionizing particles.