Radiation-Tolerant Reconfigurable Readout System

• Radiation-tolerant reconfigurable readout systems are specialized electronic architectures that combine hardened components with modular, FPGA-driven data processing for reliable performance in high-radiation environments.
• They employ methods such as partial TMR, configuration scrubbing, and CRC checks to detect and correct radiation-induced errors, achieving metrics like 8.8 MRad tolerance and an SEU cross-section of (4.0 ± 0.7)×10⁻¹² cm².
• These systems are integral to collider experiments, space missions, and pixel detectors, offering scalability, remote firmware updates, and robust error mitigation for next-generation scientific instruments.

A radiation-tolerant reconfigurable readout system is a class of electronic data acquisition architecture intended for use in environments subject to high levels of ionizing radiation (e.g., space, accelerator experiments, X-ray astronomy) where both operational reliability and adaptability are essential. Such systems combine hardware-level resistance to cumulative and stochastic radiation effects—total ionizing dose (TID), single event upset (SEU), and single event effects (SEE)—with programmable or modular data processing capabilities using FPGAs, ASICs, or custom high-speed analog-digital converters. This article elaborates the principles, methods, design patterns, and empirical results underpinning the deployment of these systems as demonstrated in contemporary instrumentation for large physics experiments and space missions.

1. Radiation Effects and Mitigation Strategies

Radiation impacts digital circuits and analog front-end components primarily via TID (degradation of MOS devices) and SEE (SEUs, SEFIs, and SELs from ionizing particle hits). Characterization is routinely done via irradiation (gamma, neutron, proton, heavy ion) campaigns to determine dose limits and SEE cross sections. For instance, commercial off-the-shelf (COTS) ADCs such as the Texas Instruments ADS5272 maintain full functionality up to $8.8\;\textrm{MRad}$ (Si) and an SEU cross-section of $(4.0 \pm 0.7)\times 10^{-12}\;\textrm{cm}^2$ (Hu et al., 2014). FPGA-based systems, such as those using Kintex-7 or Actel ProASIC Plus, address SEU sensitivity in flip-flops and block RAM by employing mitigation techniques:

• Partial Triple Modular Redundancy (TMR): Triplicates key registers and logic, using majority voting to correct single upsets, formally expressed as $$voter = (x_1 \land x_2) \lor (x_1 \land x_3) \lor (x_2 \land x_3)$$ (Shen et al., 2014).
• Configuration scrubbing: Periodically compares operational configuration against a redundant copy and overwrites corrupted frames; scrubbing can be local (on-chip) or distributed (majority voting across modules) (Giordano et al., 2018, Giordano et al., 2020).
• CRC checksums: Detect and flag RAM corruption for subsequent reconfiguration or correction.
• Multi-domain reset: Provides selective reset of logic domains affected by SEU without disturbing global operation (Shen et al., 2014).
• Hardware screening/selection: Employ process technologies such as FD-SOI or flash-based FPGAs, inherently resistant to TID and SEU.

2. Architectures of Radiation-Tolerant Readout Chains

Readout system architectures are optimized for both reliability and reconfigurability:

• COTS ADC-based systems: After rigorous TID/SEE screening, top-performing ADCs (e.g., ADS5272, custom 12-bit pipeline/SAR ADCs) are integrated into digitizer boards. Interfacing drivers are qualified separately (up to 500 krad TID for AD8138).
• FPGA-centric systems: On-detector logic is increasingly migrated to FPGAs for reconfigurability. For example, the ATLAS TileCal demonstrator replaces ASICs with Kintex-7 FPGAs, enabling full-read out with redundancy: each calorimeter cell is read out by two modules, minimizing the effect of single-point failures (Åkerstedt et al., 2014).
• Hybrid systems: Dual-FPGA architectures pair SRAM-based FPGAs (high logic density, reconfigurable) with flash-based FPGAs dedicated to configuration scrubbing, communicating via radiation-tolerant GBT optical links (Yuan et al., 2020, Härringer et al., 5 Mar 2025).
• Optical data transmission: High-speed serial optical links (QSFP+, lpGBT) facilitate robust and immune data transfer. Redundant links and transmission-level CRCs further increase data integrity.

3. Real-Time Error Detection and Correction

Modern systems often integrate real-time radiation-induced error detection:

• LUT-based SEE detection: ADC outputs are compared in real time to pre-stored reference LUTs; deviations beyond thresholds trigger error flags, sample capture to DDR3, and later analysis (Hu et al., 2014).
• Firmware scrubbing in FPGAs: SRAM-based FPGAs are periodically read back, checked for upsets, and faulty bits are corrected. Enhanced algorithms employ redundant on-chip configuration or majority voting among modules for further protection (Giordano et al., 2020, Giordano et al., 2018).
• System-level resets/reconfiguration: Multi-domain resets allow recovery from SEU-induced logic errors without global power cycling, underpinning highly reliable autonomous operation in remote environments.

4. Reconfigurability: Adaptation and Modularity

Reconfigurability enables adaptation to changing operational requirements or emerging faults:

• Firmware/algorithm updates: FPGA-based systems (Kintex Ultrascale, CertusPro-NX, etc.) support in-flight algorithm changes, tone reconfiguration for KID readout, or event-extraction logic for X-ray pixel arrays (Ogino et al., 15 Mar 2024, Bryan et al., 17 Sep 2025).
• Tunable hardware parameters: ADC power rails, bias voltages, and calibration constants can be adjusted (I²C or remote software control), aiding compensation for performance drifts post-irradiation (Andeen et al., 2019, Yuan et al., 2020).
• Remote configuration: Dedicated hardware/software chains (e.g., pa3jtag over GBT/SCA) enable reconfiguration of FPGAs in radiation zones via slow-control optical links, allowing upgrades and bug fixes during experiment runtime (Yuan et al., 2020).

5. Benchmark Performance and Empirical Results

Radiation-tolerant reconfigurable readout systems are characterized by extensive metrics:

System Component	Key Metric(s)	Radiation Qual.
ADS5272 ADC	TID up to 8.8 MRad(Si), 11.5 ENOB	$\sigma_{SEU} = (4.0 \pm 0.7)\times 10^{-12}$cm² (Hu et al., 2014)
12-bit pipeline ADC	67.9 dB SNDR, 11.0 ENOB, 50 mW/channel	2 MRad TID, $\sigma_{SEE}<10^{-12}$cm² (Kuppambatti et al., 2017)
CertusPro-NX FPGA TDC	10.9 ps LSB, 16-ch, $>$1 MHz/channel	100 krad TID, FD-SOI process (Bryce et al., 6 Dec 2024)
Kintex Ultrascale KID	7–15 mW/pix, ≥2 GHz BW, 10 kHz frame rate	Rad-hard, 20nm process, high transceiver count (Bryan et al., 17 Sep 2025)

Performance is commonly maintained or restored through digital calibration (e.g., foreground MDAC/SAR coefficient update), error monitoring and scrubbing periods, and modular dropout recovery (e.g., swap mini-drawer modules). Systems routinely demonstrate robustness to SEUs (SEU corrections per week, minimal unrecoverable errors), as well as TID radiation levels above their operational requirements (HL-LHC and beyond).

6. Applications and System-Level Implications

Radiation-tolerant reconfigurable readout systems enable reliable, high-speed, real-time data acquisition for:

• Collider Experiments: Upgrade readout chains for calorimeters (ATLAS LAr, CMS ECAL, ATLAS TileCal) digitize tens of thousands of channels with sub-200 ns latency, full trigger coverage, and robust error correction (Hu et al., 2014, Åkerstedt et al., 2014, Andeen et al., 2019, Härringer et al., 5 Mar 2025).
• Space Missions: Systems (Lattice CertusPro-NX TDC, Kintex Ultrascale KID readout) deliver wide bandwidth, low power operation with high detector count for time-of-flight or photon-counting cameras (Bryce et al., 6 Dec 2024, Bryan et al., 17 Sep 2025).
• Pixel Detectors: RD53A, RD53B chips offer per-pixel threshold/bias reconfiguration and maintain data integrity up to 500 Mrad, with tunable operating margins (Vogt, 2019, Dieter et al., 2021).
• Triggerless Data Acquisition: Muon identification systems with FE board FPGAs perform continuous real-time zero suppression and serialization, supporting high-rate streaming with high efficiency (Congedo, 2020).

7. Future Directions and System Integration

Ongoing developments focus on increasing the density of integration, logic resources, and power efficiency:

• Transition to smaller process nodes (20 nm FD-SOI, Kintex Ultrascale) to enhance radiation tolerance and reduce power requirement, supporting scaling to 100,000+ pixel arrays (HWO, future NASA missions) (Bryan et al., 17 Sep 2025).
• Enhanced configuration scrubbing (majority voting across modules, real-time correction) and soft error mitigation controllers contribute to continuous autonomous error recovery (Giordano et al., 2020).
• Expansion of modularity and remote reconfiguration to support in-flight firmware/hardware upgrades, mission adaptability, and risk reduction for long-duration scientific endeavors.

These advances position radiation-tolerant reconfigurable readout systems as the cornerstone for next-generation experiments in high-energy physics, astrophysics, and space exploration, providing both the reliability demanded by harsh environments and the flexibility required to adapt as experimental parameters or scientific objectives evolve.