• M. Hüning, R. Jonas, J. Lund-Nielsen, F. Schmidt-Föhre
  DESY, Hamburg

The Positron Intensity Accumulator PIA at DESY is used to accumulate the intensity and damp down the emittance of the positrons produced in the Linac II before they are injected into DESY II. Up to 19 shots are collected and damped. During the damping process the (baseband) peak current is increased by about a factor 4. Therefore the signal from the circulating beam can be up to 80 times bigger than the injected beam and hence overload any first turn detectors. The injected beam however is bunched by the 3 GHz RF of the linac. By filtering the 3 GHz component of the antenna signal and subsequent demodulation it is possible to set up a BPM system detecting exclusively the injected beam.