Online program Overview Session: NSS-17

Abstract

Conventional readout electronics for silicon photomultiplier-coupled cesium iodide scintillation detectors are bulky, costly, and difficult to integrate into compact single-photon emission computed tomography systems. Prior sigma-delta modulation charge-to-digital converter implementations are limited to single-polarity operation or require firmware modification for polarity switching. We propose a configurable dual controlled discharging line sigma-delta readout circuit that simultaneously supports dual-polarity readout and high-precision single-polarity charge integration without firmware or hardware modification. The circuit employs a sigma-delta modulator directly integrating silicon photomultiplier charge, with two controlled discharging lines supporting dual-polarity mode for concurrent handling of both signal polarities, and single-polarity mode for fast baseline recovery and precise charge zeroing. Three CsI :Tl crystal configurations were evaluated against a commercial digitizer using Hamamatsu silicon photomultiplier arrays: a small unprocessed crystal with ²²Na and ¹³⁷Cs sources, a monolithic 50×50×8 mm³ crystal with ⁵⁷Co, and a laser-processed 25×25 pixel array under collimated and flood irradiation. On the small crystal, energy resolutions of 8.49% and 7.47% at 511 keV and 662 keV. On the monolithic crystal, the proposed circuit achieves 7.88% energy resolution at 122 keV versus 13.86% for the CAEN digitizer, a 1.76-fold improvement. On the laser-processed array, a 9% higher peak-to-valley ratio and superior energy resolution are obtained under collimated irradiation, with cleaner pixel separation under flood irradiation. The proposed dual- CDLs sigma-delta readout circuit outperforms commercial digitizers in energy resolution, event rate, and pixel separability across all configurations, offering a scalable, low-cost solution for next-generation SPECT systems.

Abstract

MeV gamma-ray astronomy provides an important observational window for studying cosmic nucleosynthesis, compact objects and high-energy transients. The MeV Astrophysical Spectroscopic Surveyor (MASS) is a 3-D position-sensitive CdZnTe (CZT) detector concept proposed for MeV gamma-ray detection. Its pathfinder payload, MASS-Cube, has been launched on September 5, 2025. To further improve the event reconstruction capability of CZT detectors, this work presents a readout system based on a waveform-sampling ASIC for the future upgrades of MASS-Cube. Preliminary test results show that the readout system can reliably acquire signal waveforms from the CZT detector. With a ¹³⁷Cs source, FWHM energy resolutions of 1.33% for single-interaction events and 0.69% for single-pixel spectrum were achieved at 662 keV. These results demonstrate the feasibility of the proposed readout chain and provide a foundation for future waveform-based 3-D position reconstruction and imaging optimization.

Abstract

The MALTA2 depleted monolithic active pixel sensor, implemented in 180 nm complementary metal-oxide-semiconductor imaging technology, has demonstrated hit detection efficiencies of up to 98% after neutron irradiation to 3 × 10¹⁵ 1 MeV n_eq/cm². Measurements at higher fluence motivate further sensor-characterization and test-beam studies, including planned investigations of UHD-modified samples. This contribution presents a new asynchronous oversampling readout developed to support these measurements through more stable sampling of MALTA2 hit signals. The system provides the readout basis for ongoing studies at the CERN Super Proton Synchrotron H6 beam line and future beam-test campaigns at KEK.

Abstract

A 6U CubeSat scheduled for launch in March 2027 will be equipped with a payload for in-orbit charged-particle spectroscopy, requiring on-board signal processing and feature extraction to comply with the narrow-band downlink. To satisfy these requirements, while testing and validating in a space environment a novel technology, an FPGA has been installed implementing the digital logic of the MAIA SoC. The solution is currently entering the testing phase. 
MAIA is a fully-programmable mixed-signal System-on-Chip for readout of particle detectors, targeting a 28 nm CMOS node. Each channel integrates selectable analog front-ends a 320 MSps 10-bit waveform sampling ADC, a programmable DSP for continuous-time signal conditioning, a feature extraction engine and four 1.28 Gbps data links. A global trigger unit with real-time pattern analysis capability is integrated as well. The system control is provided by a multi-core cv32e40p RISC-V CPU with radiation-tolerant lock-step operation support and DMA engine, implementing closed-loop real-time control of the signal processing parameters. A chiplet-compatible architecture enables cost-effective channel scaling and connection to external chips. The encapsulation of the UART and JTAG slow-control interfaces on a full-duplex 320 Mbps 8b10b-encoded data link allow remote control of the SoC when integrated in medium or large-scale experiments.
This approach based on high-level of programmability of the signal processing chain can reduce the cost with the respect to producing dedicated front-end ASICs in 110/65 nm for different experiments. All the features of the digital logic of MAIA SoC will be implemented on the satellite FPGA, while the analog front-end and the  ADCs will be replaced by the "MIZAR" chip. The payload will be characterized using a particle beam in the next months and the results will be presented at the conference, while the submission of the complete MAIA SoC to the foundry is planned for 2027.

Abstract

The POEMMA Balloon with Radio (PBR) is a NASA’s mission to achieve the dual purpose of detecting Ultra-High Energy Cosmic Rays (UHECRs) and performing neutrino astronomy. Planned to operate at stratospheric altitudes, this mission is equipped with two payloads, fluorescence light and Cherenkov light detectors respectively. To detect the latter, a new ASIC was designed in a commercial 65 nm CMOS technology. The Multi-channel Integrated Zone-sampling Analogue-memory based Readout (MIZAR) chip is a 64-channel ASIC developed to read out the signals generated in a tile of Silicon Photo-Multipliers (SiPMs). A single channel is made of 256 cells based on analog memories and working at the sampling frequency of 100 MHz. Each cell allows the local digitization of the events using a configurable Wilkinson Analog-to-Digital Converter (ADC) in the range 8-12 bits. When an event of interest is detected, MIZAR sends out to an FPGA a 64-bit hitmap. This raw information in used as first-level trigger and if it is validated the event is digitized, then the data is serialized through a dedicated Low Voltage Differential Signaling (LVDS) line at 200 MHz in Double Data Rate (DDR). This work describes the scientific context of the PBR mission and the design stages of the MIZAR ASIC. The general results of the test campaign in laboratory are shown, then a focus on the performances in terms of single photo-electron sensitivity and linearity are presented.

Abstract

The China Spallation Neutron Source (CSNS) is undergoing a beam power upgrade to 500 kW. This upgrade requires new detector readout systems for the Energy-Resolved Neutron Imaging (ERNI) instrument. We present CTPX1, a data-driven camera system based on the Timepix4 ASIC, designed to overcome the 80 Mhits/s bandwidth limit of legacy Timepix3 systems. The CTPX1 integrates a custom high-voltage bias supply with a noise floor below 1 mV, a thermoelectric cooling unit that maintains the sensor temperature within 0.1°C, and a  Zynq UltraScale+ FPGA-based readout system. The FPGA aggregates sixteen 5.12 Gbps serial links from the ASIC. The system provides a buffered mode for short data bursts up to 81.92 Gbps and a continuous streaming mode up to 64 Gbps via a QSFP+ interface. In high-flux X-ray tests, the system achieved a peak event rate of 1.17 Ghits/s without data loss. During neutron imaging tests at the CSNS BL-20 beamline, using a ⁶LiF/ZnS:Ag scintillator coupled with an image intensifier, the system obtained a spatial resolution of 55 µm. Furthermore, time-of-flight measurements on austenitic stainless steel successfully identified the Bragg edges corresponding to the expected fcc lattice planes. Quantitative energy calibration using X-ray fluorescence (XRF) also showed a highly linear ToT-to-energy relationship. These results indicate that the CTPX1 meets the high-throughput requirements for energy-resolved neutron imaging, making it a suitable candidate for the ERNI upgrade at CSNS-II. Future work will explore its application  at high-flux synchrotron light sources, such as HEPS.