Performance test of PPAC in different gases

A two-dimension position sensitive parallel-plate avalanche (PPAC) detector has been developed for RIBLL. The detector consists of one anode and two cathodes. In each cathode a resistance chain is used to readout position signals.. The detector has been tested in different operating gases with an a source. When the detector is at 7mb flowing rate of isobutane and + 500V on anode, the position resolution of 0.76mm is obtained. For 7mb C3F8 and + 595V on anode, the position resolution is 0.64mm. The efficiencies are around 99.1% in the cases of C3F8 and isobutane.