Results from first beam tests for the development of a RICH detector for CBM

In the CBM experiment at FAIR, electrons will be identified using a gaseous RICH detector positioned behind a system of silicon tracking stations. The concept of the RICH detector foresees an array of Multianode Photomultipliers (MAPMTs) as photodetector. First beam test data with a 2 GeV proton beam were recorded to investigate the Cherenkov light detection with a 64 channel Hamamatsu H8500 MAPMT. In the beam test a proximity focusing setup with a solid radiator was used together with a new self triggered readout electronics based on the n-XYTER ADC chip. The results of this beam test demonstrate that the new front end electronics is suited for the readout of the Hamamatsu H8500 MAPMT. It could be demonstrated that this MAPMT is able to detect single Cherenkov photons. Uncorrelated noise could be well separated from the signal using available timing information. The recorded number of MAPMT hits per beam event is consistent with the expectations.