Experience with position-sensitive photomultipliers from the H1 forward proton spectrometer

For the H1 experiment at the HERA accelerator we built high resolution fiber detectors to measure very forward produced protons escaping the central H1 detector through the beam pipe. The fiber detectors were installed in movable vertical vacuum inserts, so-called Roman pots, touching the beam envelope at distances of 81 m and 90 m from the interaction point. The detection of the scintillation signals is performed by four position-sensitive photomultipliers H4139 per Roman pot. An approved upgrade program foresees the installation of additional stations at 63 m and 80 m. For the fiber readout another type of PSPM based on micro-channel plates is envisaged.