Parallel Plate Avalanche Counter and Multi-step Parallel Plate Avalanche Counter

The parallel plate avalanche counter(PPAC) and the multi-step PPAC (MPPAC) with 100 mm×100 mm active area have been developed newly for RIBLL. Their performances are measured using α particles from the 3 components α source (5.155 MeV 239Pu, 5.486 MeV 241Am, 5.806 MeV 244Cm). For the PPAC filling 700 Pa isobutene and C 3F 8, 0.76 mm and 0.64 mm position resolution(FWHM) and 99.1% detection efficiencies are achieved. For MPPAC filling 650 Pa isobutene, 0.58 mm(FWHM) position resolution and much less than ±0.2 mm position linearity dispersion and 99.2% detection efficiencies are obtained.