Front-End Electronics Design for the Transition Radiation Detector Prototype in the HERD

The high-energy cosmic radiation detection facility (HERD) is a part of the Chinese Cosmic Lighthouse Program in China space station (CSS), which is planned for launch in 2027. The HERD is expected to operate for ten years in orbit, and it will be able to indirectly detect dark matter, measure cosmic rays, and observe high-energy gamma rays. As a subdetector of the HERD, a transition radiation detector (TRD) has the main scientific goal of calibrating the electromagnetic calorimeter (CALO) at the TeV energy range, improving the measurement accuracy of the CALO, and detecting astronomical phenomena of high-energy gamma rays. In this work, we designed the front-end electronics (FEEs) as a standard readout unit for the TRD prototype in the HERD. The FEE uses four SAMPA application-specific integrated circuits (ASICs) for 128 detector signal readouts, realizing a high-speed, low-power, and high-reliability data acquisition system. The FEE receives trigger signals and serial commands from the back-end electronics (BEEs) using the universal asynchronous receiver transmitter (UART) protocol via an RS-422 bus and replies to the BEE, providing appropriate remote environmental and field-programmable gate array (FPGA) status parameters. In addition, the FEE sends detector scientific data and clock signals via a low-voltage differential signaling (LVDS) bus at 80 Mb/s with a dual-channel hot backup. According to the results of the electrical tests on the electronics, the channel’s root mean square (rms) noise is less than 1.7 fC, and the linearity is better than 0.2%. In addition, a beam test is performed on the super proton synchrotron (SPS) and proton synchrotron (PS) terminals of the European Organization for Nuclear Research (CERN) to verify the electronic performance of the proposed system. The results show that the proposed FEE can meet the readout requirements of the TRD prototype and can accurately obtain the energy spectrum of muons and electrons.