Transducers and signal conditioners of the RFX new magnetic measurement system

RFX is the largest magnetic confinement fusion machine operating with the reversed field pinch (RFP) configuration. The RFX magnetic measurement system has been completely redesigned in order to meet the electromagnetic, mechanical and thermal requirements of the new toroidal assembly, with the thinner shell and the new system of coils for MHD modes control. In total, 744 independent measurements are available, 712 probes are placed in between the vacuum vessel and the new thin shell, where an air gap of only 6 mm thickness is available. Temperature can rise up to 200 degrees C and a voltage up to 2000 V can develop between shell and vessel during machine operation. To comply with such extreme requirements, specific techniques were developed for probes and connections. Conditioning electronics have been completely redesigned to improve accuracy and interferences immunity. Integrator drifts were lowered by an order of magnitude with respect to the previous system, and a new front-end was designed to cope with extended signal bandwidths and the presence of high frequency noise due to new powerful switching power supplies. Mechanical characteristics of conditioning channels were changed to improve modularity and reliability. This paper describes the design of all integral probes the tools and procedures adopted for installation and tests of the whole probe system, and the design and realisation of the conditioning electronics.