Nupix-H2: A MAPS With Multidimensional Measurements for the China Hyper-Nuclear Spectrometer

The high-intensity heavy ion accelerator facility (HIAF) is a high-intensity facility for advances in nuclear physics and related research fields. The China hyper-nuclear Spectrometer (CHNS), based on it, aims to investigate the properties of hypernuclei. We have designed a prototype monolithic active pixel sensor (MAPS) called Nupix-H2 for the CHNS with a 130-nm quadra-well process. This chip comprises $128\times 128$ pixels with a pitch of $28.705~\mu $ m, and it can measure the particle hit’s position, energy, and arrival time. Each pixel utilizes a charge sensitive amplifier (CSA) to achieve energy measurement, coupled with a comparator and a shared counter for 16 pixels to achieve time measurement. With a novel automatic reset scheme for each pixel, the Nupix-H2 can work continuously. It achieves an equivalent noise charge (ENC) of 29.7 e $^ - $ in the input range of up to 9k e $^ - $ , a maximum integral nonlinearity (INL) of 1.1% of the energy path output, and the conversion gain is approximately $57.7~\mu $ V/e $^ - $ . In addition, it can achieve a time resolution of ~25 ns.