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HK: Fachverband Physik der Hadronen und Kerne

HK 45: Postersession

HK 45.25: Poster

Mittwoch, 16. März 2016, 18:30–20:30, S1/05 22-24

Studies on an Automated Gain Stabilisation for the new APD Read-Out of the Crystal Barrel Calorimeter — •Peter Pauli for the CBELSA/TAPS collaboration — HISKP Bonn, Germany

For the investigation of the nucleon spectrum it is not enough to measure only cross sections because of the large overlap of resonances. To disentangle these resonances, a partial wave analysis is needed. To find unambiguous solutions it is necessary to measure (double) polarisation observables. The CBELSA/TAPS experiment is an important tool to measure these observables in meson photoproduction off nucleons. To achieve a high efficiency in purely neutral reactions it is important to implement the main calorimeter into the first level trigger. To do so it is necessary to replace the current PIN photo diodes with new avalanche photo diodes (APDs). The new read-out is able to provide a timing signal that is fast enough to use it as a trigger while it does not impair the energy resolution of the calorimeter compared to the previous system. A drawback of APDs is their temperature dependency. To provide a stable gain throughout varying running conditions it is vital to monitor the temperature change and correct it if necessary.

The poster shows an approach to ensure temperature stability where the temperature is monitored via a temperature sensitive NTC thermistor and the gain is adjusted via changes of the high voltage supply of the APDs. This method proved successful while it is easy to implement in all 1320 CsI(Tl) crystals of the calorimeter.

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