Equilibrium coil magnetization begins

JT-60SA has 6 ring-shaped Equilibrium Field (EF) coils which will confine and shape the plasma. They are wound from niobium titanium cable-in-conduit superconductor.

Energization tests on the EF coils started on 19 September, beginning with the largest coil EF 1. EF 1 has a diameter of 12 m and weighs 30 tonnes, making it one of the largest pulsed magnets in the world.

The voltages and currents applied to the EF coils will be limited at first to avoid unnecessary risk. The first target is to commission the EF coils to ± 3 kA together with their base power supplies and Quench Protection Circuits (QPC).

The first tests for each EF coil are to confirm that an emergency stop can be reliably operated from both plus and minus 1 kA. That is, the QPC intervenes correctly to discharge the magnet and the power supply shuts down safely. This check is repeated whenever the current is increased, e.g. to plus and minus 3 kA. Then the control of the magnet is confirmed by applying current and voltage waveforms.