Experimental Study for Pion Distribution in the Nuclear Surface

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The detector system was developed to study the coherent pion production, which will be sensitive to the short range component of the nuclear force. In this reaction, the virtual pion emitted from proton beam with kinetic energy 400 MeV will become real pion by scattered from nucleon through the propagation of nuclear medium. The construction of the prototype of detector system was completed, and the test experiment is scheduled in 2004.(1) Development of Gas Electron Multiplier (GEM) DetectorThe gas electron multiplier detector consists of cathode electrode, GEM electrodes, and readout board. The GEM electrode has very small holes, and the high voltage is applied on both sides of electrode. The rapid change of electric field near the hole causes the electron amplification. The produced electrons are collected into the strips fabricated on the readout board.We measured the gain dependence on the gas type and mixture, and found that we got a high gain with Ar + C4H1O, compared with Ar + C02.(2) Development of High Speed Readout ElectronicsThe readout card consists of the pre-amplifier, buffering, and multiplexer. The signals from many channels are amplified, and stored in the buffer. The buffered analogue signal is transferred to ADC module through the multiplexer with the speed of 10 MHz. The gain and shaping time can be adjusted by setting the value in the register of the readout card. We developed the electronics with Field Programmable G ate Array to load the data into the register to set the readout card.