Development of detectors for antiprotonic atom spectroscopy with pulsed antiproton beam

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The purpose of this research is to make detailed plans and to develop suitable detectors for the experiments to be done at the pulsed low-energy antiproton source (CERN AD), which is to start operation in 1999. The results are as follows :1. When antiprotons are stopped in helium media, about 97% annihilate promptly (via multiple pion emission) while the rest 3% form antiprotonic helium atoms and become long lived. In order to measure the delayed annihilation time spectrum in strong pulsed beams, it is required to develop an analog recording method having a large enough dynamic range and good linearity.2. We chose Cherenkov counter as the annihilation detector, whose output is to be measured with a photomultiplier tube (PMT). We developed a new mesh-dynode type PMT with a gate so as to suppress the prompt signal, and studied in detail the gate operation and the output linearity. The output of the PMT is recorded on a digital oscilloscope.3. We simulated the behavior of the Cherenkov detector using the Monte Carlo method, and we also measured the response of a prototype detector at an electron synchrotron. The test experiment results were fed back to the simulation, so as to improve its reliability.4. The Cherekov detector with the newly developed PMT was found to satisfy all the requirements, and will be used in the experiments which start in 1999 at CERN AD.