The Design and Manufacture of the Enhanced Radial Field Amplifier (ERFA) for the JET Project
The JET plasma requires a radial magnetic field to control its vertical position and the bulk field is produced using relatively slow (line commutated) amplifiers. Should fast (possibly of order 100ms) disturbances arise, the plasma can move from its reference position very quickly and this must be controlled using a high speed amplifier. As part of a wider project to upgrade the plasma control system, a new, more powerful, Enhanced Radial Field Amplifier (ERFA) will be installed to replace the existing Fast Radial Field Amplifier (FRFA). The company JEMA has designed the ERFA and it comprises four series-connected Units with a total rated output voltage of ±12kV, in 3kV steps, and a maximum output current of ±5kA. The ERFA is being manufactured at JEMA's works during 2008 so that it can be installed, tested and then commissioned on the JET radial field load coils in spring 2009.