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Engineering

US to deliver "tough" electronics to ITER

6 Sep 2021 - US ITER
ITER, a machine that will imitate the sun, will also mimic the sun's extreme environment: intense heat, strong magnetic fields and radiation. A team at US ITER has been toughening up critical components of ITER's vacuum system so they can withstand those harsh conditions.
US_electronics2021-P04024-rev.jpg
The team involved in the development of radiation hardened electronics for US ITER includes (left to right): Frank Ivester, Shane Frank, Claudell Harvey, Nance Ericson and Kurt Vetter. Credit: ORNL
Neutrons, an energetic by-product of the fusion reactions in the ITER device, will not travel in docile single file as they leave the plasma. When running at full power, ITER's plasma is projected to generate billions and billions of neutrons*, each one with 14.1 MeV (mega-electron-volts) of energy. Shielding reduces the neutron flux, but neutrons are sub-atomic in size and can scatter and slip between the atoms in concrete. The shielding reduces the number of neutrons to about a million per second per square centimetre outside the protective bioshield.

"Five hundred megawatts of plasma power will be a sustained radiation environment that the fusion community hasn't experienced before," says US ITER's Kurt Vetter. Vetter leads the teams for electron cyclotron and ion cyclotron heating transmission lines and for instrumentation and controls.

Vetter's group has been designing and building the radiation hardened ("rad hard," for short) electronics supporting ITER's vacuum auxiliary system. The electronics will be mounted at 68 locations just outside a protective bioshield to monitor the vacuum system for leaks and other potential issues.

US ITER engineers are not the first to face this problem. Aviation and aerospace engineers need to design around the effects of cosmic radiation in the upper atmosphere and space. On Earth, numerous smaller fusion devices have contended with neutron-yielding plasmas. But radiation from those experiments is orders of magnitude smaller than what ITER will generate.  

Neutrons, while short-lived, are a source of both direct and indirect radiation immediately around the tokamak. ITER will restrict access to this area and further protects staff and instrumentation with a 3.2-metre-thick concrete bioshield. But some of these neutrons, and the gamma rays they spawn when interacting with the cooling water around the tokamak, can still threaten nearby equipment.

Consequently, sensitive components need to be rad hard—designed and built with years of radiation exposure in mind. That includes the vacuum auxiliary system components being delivered by US ITER.

* Their precise amount has been calculated. It is in excess of 1.77 multiplied by 10 followed by 27 zeros...

Continue reading the article on the US ITER website.

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