Welcome MAST Upgrade, a new fusion device !

First plasma in MAST-U © UKAEA

First plasma in MAST-U © UKAEA

On October 29th, 2020, MAST Upgrade, UK’s new fusion experimental device, came to life. Inside the machine’s vessel, hydrogen was heated into a plasma hotter than the temperature in the center of the Sun. The Swiss Plasma Center congratulates the MAST Upgrade team and looks forward to future scientific collaborations.

“MAST-U” is the result of a seven-year, £55-million upgrade to its predecessor, a device called the Mega Ampere Spherical Tokamak (MAST) that ran from December 1999 to September 2013 at Culham Centre for Fusion Energy (CCFE), Oxfordshire, England. "Fusion is coming and MAST Upgrade will take us closer to bringing plentiful, cleaner energy to people around the world. This experiment will break new ground and test technology that has never been tried before," says UK Atomic Energy Authority CEO Ian Chapman.

Spherical shape

© 2020 EPFL

MAST-U is of special interest because of its spherical shape. Its plasmas look more like a cored apple than a donut. This shape difference should make the multi-million degree plasma, held magnetically within, more stable – an important consideration for future fusion power plant designs, where plasmas will run for years instead of seconds. "The design of a spherical tokamak lets you get the same level of plasma confinement with a much smaller magnetic field," explains UKAEA media manager Nick Holloway. "If we get this right, we'll have another possible design for a fusion power plant." At the same time, MAST Upgrade is similar enough to mainstream tokamaks that results can be easily transferred between them.

Mitigating interactions between million-degree plasmas and vessel walls

MAST-U joins the Swiss Plasma Center’s fusion device, the "Tokamak à Configuration Variable" (TCV) and two other tokamaks in the collaborative, 28-nation EUROfusion research programme. “Congratulations to the entire MAST-Upgrade team for having achieved first plasma,” says Ambrogio Fasoli, EUROfusion Chair and Director of the Swiss Plasma Center at EPFL. “This device will help us verify the potential of innovative edge magnetic configurations for DEMO, the next big step after ITER. We are privileged to contribute to this crucial endeavour with our TCV tokamak, and look forward to future collaborations and fruitful exchanges with the MAST-Upgrade team.”

“We share a common goal: studying new plasma configurations,” explains physicist Yves Martin, Deputy to the Director at Swiss Plasma Center. “As we study different overall shapes and configurations of plasmas, researchers at MAST Upgrade will focus on new configurations of the region where plasma most interacts with the walls, called divertor like the Super-X, in order to find the best way to reduce the impact of hot plasma on the walls."

"These tokamaks all have their own specialties and unique insights they can deliver," says Sara Moradi, who coordinates EUROfusion's Medium Sized Tokamaks research. "Because they're smaller than JET and ITER, these setups are inherently more flexible, cheaper and quicker to modify. You can upgrade them in ways that are just not as feasible for a bigger machine."

Further enhancements

If all goes according to plan, MAST Upgrade will run for 10 experimental days in December, and continue its operation in 2021. Further enhancements are planned in 2023, including extra neutral beam heating, control upgrades, and a cryoplant to manage the heat load in the divertor.

"It is always genuinely exciting to witness the first flash of plasma in a new device. When this happens in a tokamak as novel and complex as MAST-Upgrade it is all the more rewarding not only to its own team, but to the entire European fusion community," shares Stefano Coda, Senior Scientist and Head of TCV Tokamak Physics at the Swiss Plasma Center at EPFL. “We have all been cheering MAST-Upgrade on for years! Here at TCV we have been especially impatient as our devices both include highly unorthodox and exploratory features and yet are very complementary - the obvious example being the Super-X divertor that we can study in two very different plasma configurations. I am looking forward to extensive collaboration and productive cross-pollination for years to come."