In-Vessel Components

The major in-vessel components are

  • divertor cassettes,
  • the inboard first wall,
  • the stabilizing baffle plate and outboard first wall,
  • fast plasma position control coils,
  • sector coils for resistive wall mode (RWM) control,
  • magnetic diagnostic coils,
  • error correction coils,
  • cryopanels for particle pumping.

Initially only a lower divertor will be installed, optimised to allow ITER-shape and high-triangularity plasmas. A fully equipped upper divertor is planned at the start of the extended research phase. A mono-block type CFC divertor armour is planned for the outboard side to withstand a heat load of ~15 MW/m2. This will be replaced with a flat tile type divertor armour during the initial research phases due to the smaller expected heat load once operation is better understood. The use of metallic divertor tiles is also being considered for the later research phases.

Full remote handling compatibility will be built up during the initial phases of operation, ready for full remote divertor tile replacement before the extended research phase.

 

Cryopanels will be installed behind the divertor to improve pumping capability. A water-cooled chevron is installed in front of the pumping hole to reduce heat load on the cryopanels.

Two in-vessel coils will be used for fast plasma position control. Independent power supplies will be connected to each coil block to control vertical and horizontal field at the same time.

The primary function of the stabilizing baffle plates is to enhance the ideal beta limit and to improve plasma positional stability. They have been designed as a double-wall structure and are covered with a bolted carbon-armoured first wall.

The sector coils for the RWM control will be installed around the openings of the stabilizing baffle plate facing the plasma to minimize the control response time. Since each sector coil has its own current leads, the magnetic field mode of m/n = 3/1 or 3/2 can be controlled depending on the configuration of the power supply connections.

Saddle coils (rectangular loops on the vacuum vessel) are included to manage slow or non-rotating MHD modes arising from any slight field misalignments after coil assembly. Three coils are located polodally at six toroidal locations.