Bonn 2020 – wissenschaftliches Programm

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HK: Fachverband Physik der Hadronen und Kerne

HK 29: Instrumentation V

HK 29.3: Vortrag

Mittwoch, 1. April 2020, 14:45–15:00, J-HS C

Crystal Barrel Trigger Upgrade — •Peter Klassen for the CBELSA/TAPS collaboration — Helmholtz-Institut für Strahlen- und Kernphysik, Nussallee 14-16, 53115 Bonn

The excitation spectrum of baryons consists of many resonances, which contribute to distinct decay channels. In the CBELSA/TAPS experiment such resonances can be generated using real photons impinging on a polarizable target. The experimental setup is well-suited to observe their decays into final states with uncharged mesons and a proton. To improve the trigger efficiency for purely neutral reactions off neutrons the main calorimeter, the Crystal Barrel detector, was included into the first level trigger.

To achieve this, the frontend electronics were upgraded to an avalanche photo diode (APD) based readout, which allowed for the introduction of a previously non-existent Crystal Barrel timing branch. Core component of the timing branch is an FPGA-based, dual threshold discriminator board. At trigger level, the FPGA reduces the time walk of the digitized signals. These are afterwards processed by a free running clustering algorithm with a latency of 80 ns and an update rate of 5 ns. The cluster information is then passed on to the central experiment trigger. Furthermore, within the FPGA both thresholds are recorded by a multi-hit TDC for an improved offline time walk correction. In this talk the design and achieved performance of the new Crystal Barrel trigger will be presented.

Supported by the Deutsche Forschungsgemeischaft (SFB/TR16) and Schweizerischer Nationalfonds.