A two-dimensional readout pad-type annular Parallel Plate Avalanche Counter for heavy ion γ-ray coincidence measurements

Abstract: In order to perform particle-γ coincidence measurements in Coulomb excitation experiments, a two-dimensional readout pad-type annular Parallel Plate Avalanche Counter (PPAC) has been developed. The cathode consists of a multilayer Printed Circuit Board (PCB), enabling position readout in both the θ and ϕ directions via a delay-line module, which significantly reduces the complexity of the readout electronics. The sensitive area in the θ direction spans from a radius of 18 mm to 60 mm, with a step size of 1 mm, while the ϕ direction covers two sector regions from 6 ^◦ –174^◦ and 186^◦ –354^◦ . The detector was tested using a ²⁴¹Am α-source and exhibited an anode signal rise time of about 5 ns. With a source–detector distance of 36 mm, the angular resolution in both the θ and ϕ directions is better than 2^◦ , demonstrating that the PPAC meets the experimental requirements for both position and time resolution. Upon the completion of HIAF, this detector will be of great significance for the development of gas detectors used in high-intensity nuclear spectroscopy experiments.