Qiang Wan

We present the design and field validation of a prototype readout system for radio detection of extensive air showers in autonomous large-area arrays. Developed for future experiments, the system integrates high-throughput digitization, FPGA-based real-time signal processing and triggering, GPS-based time synchronization, and a modular data-acquisition framework. The hardware is centered on a three-channel digitizing and triggering board, which combines high-speed ADCs, an FPGA, an Arm-based processor, GPS timing modules, and dedicated power-management and communication interfaces. The firmware implements continuous data reception, buffering, event building, digital filtering for narrow-band radio-frequency interference mitigation, and coincidence-based trigger logic, while the DAQ software adopts a two-tier architecture for detection-unit control, data transmission, and online monitoring. The prototype was tested at the GRANDProto300 site near Dunhuang, China, using two adapted detection units. Periodic-trigger data show the expected 40–200 MHz band-pass response and an LST-dependent background variation in the 60–80 MHz band, consistent with Galactic synchrotron emission. A dedicated beacon transmitter was used to validate the triggering and timing performance. Pulsed 100 MHz signals were successfully detected, and the inter-board timing-difference distribution shows a standard deviation of 7.76 ns over a 10 min period. Four-day monitoring of temperature and supply voltage further demonstrates stable field operation. These results validate the prototype architecture and provide a basis for further development of autonomous radio detection units.

The next-generation DArk Matter Particle Explorer (DAMPE) — Very Large Area gamma-ray Space Telescope (VLAST) — will have gamma-ray detection capability in the MeV–GeV energy range. As one of VLAST's three sub-detectors, Silicon Tracker and low Energy gamma-ray Detector (STED) is designed to observe gamma-ray photons in the 1–100 MeV range, with excellent spatial resolution. STED replaces the traditional tungsten plates with CsI(Na) crystals, enabling measurement of MeV photons via the Compton effect and effectively improving the energy resolution for gamma rays below the GeV range. Wavelength shifting fibers, orthogonally coupled to the top and bottom surfaces of the CsI(Na) crystal, collect and transport scintillation light to SiPMs, whose outputs are read out by the front-end electronics (FEE). In this work, a FEE system is designed to read out 75 channels, with a sampling rate of 1 Gsps and a sampling depth of 1 μs. The standard deviation of the sampling time interval is 107.4 ps, the effective number of bits (ENOB) is 8.42 bits, and the noise is 0.556 mV (RMS), meeting a dynamic range of 0.8–50 pC. This paper presents the implementation of the FEE, including electronics design, firmware design and performance tests. The test results show that the FEE meets the readout requirements of the CsI(Na) detector.

As a successor to the DArk Matter Particle Explorer (DAMPE), the Very Large Area γ-rays Space Telescope (VLAST) is being designed to strengthen γ-ray observations and extend the cosmic ray nuclei measurements up to Zr (Z = 40) and even heavier ions. Consequently, a large dynamic range is required by the charge detector of VLAST to cover the measurements of cosmic ray particles from the proton to ultra-heavy ions. To achieve the requirements, a readout design based on the three dynodes signal extracted from the photomultiplier tube has been proposed. In addition, a prototype VLAST charge detector has been developed and tested with cosmic rays, pulse UV laser, and relativistic heavy ion beams to verify this design. The test results illustrate that the dynamic range readout design can easily cover the required dynamic range of about five orders of magnitude.