Hokkaido University Proves Protons and Neutrons Cause Identical Error Rates in Semiconductors: World-First Discovery

The World-First Breakthrough in Semiconductor Reliability

Hokkaido University's latest collaboration with NTT has delivered a game-changing discovery in the field of semiconductor radiation hardness. Researchers have proven, for the first time globally, that protons and neutrons induce identical error rates in semiconductors across the critical high-energy spectrum dominant in space environments. This equivalence simplifies radiation testing dramatically, paving the way for more reliable electronics in satellites, spacecraft, and even ground-based systems exposed to cosmic rays.

Announced on February 27, 2026, the findings stem from meticulous experiments comparing soft error rates—or Single Event Upsets (SEUs)—caused by these particles. Soft errors occur when high-energy particles strike semiconductor memory cells, flipping bits and potentially crashing systems. In space, where protons from cosmic rays and solar activity prevail, ensuring device resilience is paramount for missions ranging from Earth observation to deep-space exploration.

This achievement not only cuts testing costs and time but also leverages existing neutron facilities, making radiation-hardened designs more accessible for Japan's burgeoning space sector. For professionals eyeing opportunities in this niche, platforms like higher-ed-jobs list roles in semiconductor engineering and space tech research.

Demystifying Radiation Hardness in Semiconductors

Semiconductor radiation hardness refers to a device's ability to withstand ionizing radiation without permanent damage or transient faults. Ionizing radiation, including protons, neutrons, heavy ions, and gamma rays, generates charge carriers in silicon lattices, leading to bit flips in memory or logic glitches in processors. Single Event Effects (SEEs) encompass SEUs (soft, recoverable) and Single Event Latchups (SELs, harder to recover).

Cosmic rays, galactic or solar-origin, pose the biggest threat. On Earth, atmospheric shielding converts most protons to secondary neutrons, causing aviation and data center outages. In orbit, unshielded protons dominate, with solar flares spiking fluxes by orders of magnitude. Historically, testing required separate proton beams (scarce, expensive) and neutron sources, complicating certification for Total Ionizing Dose (TID) and Displacement Damage Dose (DDD).

Hokkaido's work bridges this gap, showing that for energies above 20 MeV—covering over 80% of space proton spectra—the SEU cross-section (error probability per particle per area) matches neutrons precisely. This holds for sub-100-nm SRAM-based FPGAs, key in modern satellites.

Protons and Neutrons: Unveiling the Equivalence

The core revelation: protons (charged, direct ionization) and neutrons (neutral, nuclear reactions producing charged fragments) yield the same SEU rates in the 20-220 MeV range. Protons were tested at 10-65 MeV via TIARA and 70-220 MeV at Hokkaido University Hospital's proton therapy center—repurposed from cancer treatment beams. Neutrons used J-PARC's MLF NOBORU beamline, with a novel correction method enabling single-shot energy-resolved SER from 1 MeV to 100+ MeV.

Figure 3 from the study plots energy-dependent SEU cross-sections, converging post-20 MeV. Below, differences exist due to reaction thresholds, but space-relevant bands align perfectly. This debunks assumptions of proton superiority in direct effects, as nuclear recoils dominate both.

Published in IEEE Transactions on Nuclear Science (DOIs: 10.1109/TNS.2025.3646265, 10.1109/TNS.2025.3646262), the papers detail FPGA tests under full equipment casings for realism.Read the primary paper.

Innovative Experimental Approaches

Hokkaido's Neutron Beam Applied Science and Engineering Lab, led by Assoc. Prof. Hirotaka Sato, analyzed neutron fluxes via gold foil activation. Assoc. Prof. Seishin Takao from Quantum Beam Applied Medical Engineering Lab facilitated proton tests, adapting clinical accelerators— a clever dual-use innovation.

NTT's ultra-high-speed error detectors captured nanosecond-scale upsets, correlating time-of-flight data with errors. The neutron correction algorithm deconvolves beam spectra, yielding precise, continuous SER curves—world-first for broad energies in one run.

This builds on prior NTT-Hokkaido-Nagoya collaborations, like 2020's energy-resolved neutron SER at LANSCE and 2023's low-energy clarification.

Spotlight on Hokkaido University Researchers

Assoc. Prof. Hirotaka Sato's lab excels in accelerator-driven neutron sources, vital for SEE testing. His team's compact neutron facility at Hokkaido U has tested network gear since 2017. Seishin Takao's medical beam expertise enabled high-energy proton access, showcasing interdisciplinary prowess.

Hokkaido U's engineering graduate programs, including those in quantum beams and nuclear engineering, train talents for such feats. Aspiring researchers can explore university jobs in Japan or research positions via AcademicJobs.com.

Transforming Space Industry Reliability

Japan's space sector, valued at ¥4.3 trillion (2025), relies on semiconductors for JAXA satellites like H3 rockets and private ventures like ispace. Soft errors have downed missions; e.g., 2003 Mars Climate Orbiter lost to radiation glitches.

Neutron-only testing slashes costs 50-70%, as proton facilities like CERN are booked years ahead. NTT's "NTT C89" space brand eyes satellite constellations; this accelerates commercialization. Global market for rad-hard chips: $2.5B (2026 proj.), Japan holds 15% share via Renesas, Mitsubishi Electric.NTT Press Release

Solar Flares: Enhanced Preparedness

Solar flares eject GeV protons, overwhelming shields and spiking SEE rates 1000x. Past events like 2003 Halloween storms disrupted GPS. Hokkaido's method pre-evaluates full systems with neutrons, mimicking flare spectra.

ISS PEGASEUS experiments will validate in orbit, refining models for GEO/LEO sats.

Japan's Semiconductor Landscape and Higher Ed Role

Japan leads in rad-hard tech; Hokkaido U's cyclotron and proton center position it centrally. Ties to J-PARC, QST bolster neutron R&D. Amid US-China chip wars, domestic resilience grows—government's ¥10T semiconductor fund (2022-2030) funds such uni-industry links.

Universities like Hokkaido foster talent; career advice on rad-hard design is booming.

Challenges and Future Horizons

• Heavy ions remain; hybrid tests needed.
• Scale to AI chips, 2nm nodes.
• Commercial services via NTT expand globally.
• ISS validation, standards update (JEDEC89).

Prospects: rad-hard FPGAs for Artemis, Starlink-like nets. Hokkaido eyes more medical-beam repurposing.

Photo by Da-shika on Unsplash

Conclusion: Pioneering Reliable Space ICT

Hokkaido's protons-neutrons equivalence redefines rad hardness testing, boosting Japan's space ambitions. For jobs in this field, check Rate My Professor, higher-ed-jobs, career advice, university jobs, or post openings at post-a-job.