Our institute participated till the end of the project (January 31, 2009) in the EU Design Study “DIRAC­secondaryBeams” which was part of the technical developments for the new international research center FAIR at Darmstadt. We worked on the task PANDA1 within this design study. This sub-project aimed at the development of imaging Cherenkov detectors proposed for the DIRC (detection of internally reflected Cherenkov light) and for the forward RICH detector of PANDA.
We are studying the application of new matrix avalanche photo-detectors (SiPMs) operating in the Geiger-mode. This photo detector exhibits a high gain in the order of 10⁶ for single photons comparable with the gain of photomultipliers. The complexity of SiPMs is low (no vacuum tube, no high voltage supply necessary) and these devices are insensitive to magnetic fields.

The development of SiPMs is proceeding fast and new photon detectors optimized for short wavelengths and exhibiting high photo-detection efficiency are available. For the design study we tested the newest generation of SiPMs concerning dark count rate, sub-nanosecond timing resolution, temperature effects on gain and noise etc. In 2008 we continued the tests of various SiPMs using a test setup contained in a light-tight box (black box) with temperature stabilization. All optical components can be mounted on an optical table (breadboard) and operated inside the black box. We evaluated several kinds of SiPMs from different manufacturers with different sizes of cells, sensitive area and with different photo sensitivity. Proper temperature and bias voltage control of the device was found inevitable for a stable operation. Especially the SiPMs from Hamamatsu showed very strong temperature coefficient, significantly higher than the one from Photonique. Due to the temperature sensitivity for practical applications the temperature has to be stabilized and preferably the detectors have to be operated at low temperatures. Therefore, a cooling method using Peltier elements for SiPMs to be operated in vacuum – to avoid conden­sation of water vapor – was developed.

A fast pulsed blue laser system is used to evaluate the timing performance of the devices. We gained experience in operating SiPMs in beam: SiPMs in combination with a 16×16 scintillating fiber grid in 2 planes were used for a beam profile monitor for the FOPI experiment. This device was successfully operated in beam at GSI.