A key stage in the commissioning of the UK’s new fusion device MAST Upgrade was reached last month with the first magnetic field produced inside the machine.

Before going into operation, all the machine’s power supplies have to be commissioned and coils connected. Although several of the power supplies had been tested with a dummy load (known as off-coil commissioning), this was the first time the power supplies were connected to the magnets inside the machine (on-coil commissioning).

In order for engineers to connect electric current to the machine, MAST Upgrade had to pass a High Voltage Inspection. This in itself is an important step on the way to ‘first plasma’, the moment when scientists will start to run experiments with hot plasma fuel.

On-coil commissioning allows engineers to measure the level of current with a range of independent diagnostics, including Rogowski coils (electrical devices for measuring the current). Although the commissioning has only been done to date with one pair of coils, it will soon be followed by the full suite of 24 coils.

Power supplies engineer Adam Kenny said: “The power supplies team were very pleased to see the first current on-coil. It is exciting to see all our hard work in preparing the new and existing power supplies for first plasma beginning to be seen.

Ioannis Katramados, MAST Upgrade on-coil responsible officer, said: “Getting current on a coil was both a very exciting moment and somewhat of a relief as well.”

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