Alignment of the TFTR bumper limiter

The TFTR (Tokamak Fusion Test Reactor) Bumper Limiter (BL) is an axisymmetric toroidal limiter mounted on the inner wall of the vacuum vessel. It subtends 120° poloidally and has a surface area of 22m². The plasma-facing surface consists of 1000 kg of graphite tiles mounted on water-cooled Inconel backing plates. During the initial installation in the Spring of 1985, the limiter surface was aligned to the toroidal magnetic field by mechanical and magnetic measurements to an estimated accuracy of ± 2 mm. The methods used to mechanically align the limiter are described, and evidence, based on machine operation with plasma, that the limiter is reasonably well aligned with the toroidal field is presented. Future work addressing the alignment of the total limiter to the toroidal field using mechanical and magnetic measurements and the replacement of a subset of the carbon tiles with carbon-carbon composite material is also discussed.