Jian-Hua Guo

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 DArk Matter Particle Explorer (DAMPE) is a spaceborne high-energy particle detector that surveys the γ -ray sky above ∼2 GeV with a peak acceptance of ∼0.2 m ² sr. With the 102 months of data collected by DAMPE, we show that the Fermi bubbles are detected at a significance of ∼26 σ and identify a GeV excess in the direction of the Galactic center at ∼7 σ confidence. Both spectra and morphology are consistent with those observed by the Fermi Large Area Telescope (Fermi-LAT) and the GeV excess component can be interpreted by dark matter annihilation with a mass of ∼50 GeV and a velocity-averaged cross section of ∼10 ⁻²⁶ cm ³ s ⁻¹ for the χ χ → b b ¯ channel. Our results thus provide the first independent detection of these two intriguing diffuse γ -ray sources besides Fermi-LAT.

The Giant Radio Array for Neutrino Detection (GRAND) is a proposed multi-messenger observatory of Ultra-High-Energy (UHE) particles of cosmic origin. Its main goal is to find the long-sought origin of UHE cosmic rays by detecting large numbers of them and the secondary particles created by their interactions like gamma rays and neutrinos. The GRAND Collaboration plans to achieve this using large arrays of radio antennas that look for the radio signals emitted by the air showers initiated by the interactions of the UHE particles in the atmosphere. Since 2023, three small-scale prototype GRAND arrays have been in operation: GRAND@Nançay in France, GRAND@Auger in Argentina, and GRANDProto300 in China. Together, their goal is to validate the detection principle of GRAND under prolonged field conditions, achieving efficient, autonomous radio-detection of air showers. We describe the hardware, software, layout, and operation of the GRAND prototypes. Using their data, we show a first characterization of the local electromagnetic environment of each site and a measurement of the Galactic synchrotron emission. Despite challenges, the successful operation of the prototypes confirms that the GRAND instrumentation is apt to address the goals of the experiment and lays the groundwork for its ensuing stages.

In this paper, we report the development of a low-power, 16-channel front-end readout application-specific integrated circuit (ASIC), named SiReadout-S, designed for the silicon microstrip detectors of the Very Large Area Gamma-ray Space Telescope (VLAST). Each readout channel measures the charge collected by the detector and provides trigger information. Each channel comprises a charge-sensitive amplifier, a leakage current compensation circuit, a polarity selection circuit, a CR-RC shaper, a multiple-feedback (MFB) filter, a sample-and-hold circuit, a discriminator, a time-sequence control circuit, and an output buffer. The SiReadout-S is implemented in a 180 nm mixed-signal CMOS process, and the prototype die measures 3.22 mm × 2.23 mm. For a typical positive charge input configuration, the electrical performance was characterized by an overall gain exceeding 6 mV/fC per channel, a core circuit power consumption of 298 μW per channel, a linearity error of less than 3%, a dynamic range of 220 fC, and a maximum channel-to-channel variation of 6.03%. The equivalent noise charge (ENC) for a typical channel is 671 e ^- at 0 pF plus 2.8 e ^- /pF. In integrated tests with a 16-channel silicon microstrip detector, the SiReadout-S test system achieved an energy resolution of 3.86% at the 5.486 MeV energy of ²⁴¹ Am source.

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.