Speaker
Description
The China Spallation Neutron Source (CSNS) is undergoing an upgrade to CSNS-II, targeting an increase in the proton beam power to 500 kW. This upgrade introduces stringent requirements for neutron detector readout electronics, including operation under vacuum conditions, higher neutron flux, increased counting rates, improved spatial resolution, and reduced power consumption. Conventional front-end readout systems based on discrete components suffer from high power dissipation and limited performance, making them unsuitable for future CSNS-II spectrometers.
To address these challenges, we have developed and experimentally characterized a prototype application-specific integrated circuit (ASIC), named HEROC (HElium-3 ReadOut Circuits), dedicated to position-sensitive Helium-3 tube neutron detectors. The ASIC provides an integrated, low-power analog front-end solution optimized for vacuum-compatible detector systems. Each channel integrates a charge-sensitive amplifier, pole-zero cancellation, shaping amplifier, and output buffer.
The fabricated HEROC prototype is an 8-channel ASIC and demonstrates an input dynamic range from 10 fC to 1.5 pC, with a counting rate of up to 500 kHz. Electrical measurements show an equivalent noise charge of 1130 electrons at an input capacitance of 15 pF, while the power consumption is less than 9.9 mW per channel, representing approximately a 90% reduction compared to the discrete-component front-end electronics previously used in the CSNS-I spectrometers. These characteristics make the ASIC suitable for high-rate and low-power neutron detection applications.
The ASIC was integrated into a prototype readout system including a data aggregation board equipped with an FPGA for data processing and a multi-channel ADC for signal digitization. Vacuum chamber measurements were performed to evaluate thermal behavior under vacuum conditions. After reaching stable operation, the ASIC temperature increased by less than 1 degree Celsius compared to operation in ambient air, indicating reliable performance with minimal thermal impact in vacuum environments.
Preliminary neutron beam tests were conducted at CSNS using two types of position-sensitive Helium-3 detectors with different geometries. Neutron charge spectra and time-of-flight distributions were successfully obtained. Using a slit collimator, the system achieved an optimal position resolution of 6 mm under nominal operating conditions. In addition, the ASIC-based readout system demonstrated stable operation with a counting rate of up to 125 kHz during the beam tests.
These results demonstrate that the HEROC ASIC effectively replaces traditional discrete-component front-end electronics, significantly reducing power consumption while enabling stable operation under vacuum and realistic neutron beam conditions. The ASIC-based readout system is a promising candidate for future implementation in CSNS-II spectrometer detectors, and further long-term beam tests are planned to fully evaluate its performance and stability.