Japanese researchers aim to protect digital devices from cosmic rays

The Yomiuri Shimbun

By Takashi Maemura / Yomiuri Shimbun Staff WriterComputers dominate modern society, including smartphones, personal computers and control devices for machines, but they have an unexpected natural enemy: cosmic rays, high-speed particles raining down from outer space to Earth. Observers say cosmic rays can cause errors in computers, and various studies are under way at universities and major electronics manufacturers to address the issue.

Risk for modern world

Cosmic rays such as protons from the sun or far-off galaxies rain down ceaselessly on the Earth. They generate substances including neutrons and muons, a kind of elementary particle, when they collide with oxygen or nitrogen in the atmosphere.

When things like neutrons and muons come into contact with parts of computers, unexpected electricity is transmitted, leading to malfunctions called “soft errors,” in which systems do not work as designed.

Take as an example a device that malfunctions due to cosmic rays only once every 20 years. Assuming about 5 billion units of this device are used around the world, like smartphones or tablet devices, one estimate calculates that at least eight such units would experience soft errors every second. If self-driving cars and the transportation of goods via drones become widespread in the future, soft errors could cause unexpected accidents. Hence, this is a serious risk in modern society.

Since 2016, Hitachi Ltd. has conducted experiments to investigate the frequency of soft errors caused by neutrons. Hitachi assembled about 1,000 semiconductors that had been processed so as not to be affected by substances other than cosmic rays, waited for the incoming of neutrons, and investigated whether errors occurred.

According to Tadanobu Toba, 54, senior researcher at Hitachi, they confirmed 11 errors over about a month from January to February this year. “When the Internet of Things (IoT), which would connect everything to the internet, is realized, many devices could be affected,” Toba said.

A team comprising researchers from Kyushu University, Osaka University, the High Energy Accelerator Research Organization and other institutes announced this year that they had conducted an experiment using a device at the Japan Proton Accelerator Research Complex (J-PARC) in Tokai, Ibaraki Prefecture, and confirmed that the occurrence rate of soft errors is related to electric properties of muons.  

Safeguarding important parts

Engineers reportedly have implemented measures to prevent errors caused by cosmic rays with the “K” supercomputer, which boasts one of the highest performance levels in the world. This includes embedding a circuit that automatically detects and fixes soft errors in about 200,000 semiconductors, including the high-performance central processing unit (CPU).

Hideya Matsuyama, 56, an official of semiconductor manufacturer Socionext Inc. based in Yokohama, worked on measures to protect the K computer from cosmic rays. “Very high reliability is required [of the computer], so we had to take necessary measures,” Matsuyama said.

The introduction of dual systems is one effective measure to allow back-up systems to work even if errors occur. Such steps have been taken in transportation infrastructure, including railroads.

However, the introduction of such measures leads to increased costs. Furthermore, progress in nanotechnology has meant higher density of integrated circuits, which is said to be likely to cause errors.

“It’s necessary to clarify which measures are effective for which electronic devices, ” said Masanori Hashimoto, 43, professor of information systems engineering at Osaka University.Speech

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