A magnet as heavy as three African bush elephants with the size of a small van is boosting research for EUROfusion. After the successful delivery of a superconducting magnet, which weighs more than 17 tons, Magnum-PSI at EUROfusion’s Dutch Research Unit DIFFER is now the first facility to investigate material under ITER conditions.

Magnum-PSI is designed to expose candidate wall materials for ITER and its successors to the harsh conditions that can be expected inside future fusion reactors. As a superconducting machine, Magnum-PSI is capable of operating continuously. Hence, it will enable the first lifetime studies of fusion materials in a laboratory environment.

Hans van Eck, one of Magnum-PSI’s Group Leaders. Picture: DIFFER

Hans van Eck, one of Magnum-PSI’s Group Leaders. Picture: DIFFER

A tight and energetic beam

“The 2.5 tesla superconducting magnet is the key to the Magnum-PSI facility”, explains Hans van Eck, Head of Fusion Facilities and Instrumentation at DIFFER. The magnetic field it produces is used to guide the hot, charged particles in the plasma from Magnum-PSI’s cascaded arc source towards the target material in a tight, energetic beam. This replicates the conditions at the wall of a fusion reactor, where materials will face intense bombardments of heat and fast particles with power densities similar to those found at the surface of the sun.

Simulating the ITER divertor

Van Eck: “With the previous pulsed conventional magnet system, Magnum-PSI was only able to maintain those conditions for 10 to 20 seconds at a time, after which the copper coils needed to be cooled for 20 minutes. With this new superconducting magnet, the capabilities of Magnum-PSI are truly unique. Several other linear machines exist, around the world, with plasma fluxes that are lower by a factor of approximately 100. The length of a plasma pulse is currently limited by normal working day hours, so about eight hours per day. We are now really able explore how materials change during a sizable part of their lifetime in ITER and we can simulate that over the course of a couple of weeks.”

The new superconducting magnet for EUROfusion’s Dutch Research Unit being lowered in through the roof. Picture: DIFFER

The new superconducting magnet for EUROfusion’s Dutch Research Unit being lowered in through the roof. Picture: DIFFER

Lifetime studies

Magnum-PSI has already launched some experiments in its new superconducting configuration. The results from the first few months are really promising, as the machine operates according to specification. “We will be investigating a long-term exposure of tungsten this summer. For this reason, we are realising an extremely large plasma fluence corresponding to roughly one-tenth of that expected in the ITER divertor “, explains Hans van Eck.

Magnum-PSI and ITER divertor plasma conditions

Parameter Magnum-PSI ITER divertor
Electron density (m-3) 1019 – 1021 1019 – 1021
Ion flux density (m-2 s-1) 1023 – 1025 1024 – 1025
Magnetic field (T) 2.5 ~5
Energy flux density (MW m-2) >10 >10
Transient energy flux density* (GW m-2) 2 2-4

* Magnum-PSI is able to simulate ITER-like Edge Localised Modes – sudden energy bursts from the fusion plasma – using a modular capacitor bank