Manufacturing and commissioning of the new ex-vessel magnetic diagnostics system for JET

A new system of magnetic probes was installed during the 2005 shutdown and was commissioned during the 2005/2006 restart phase of JET. The system is made of traditional pick-up coils and Hall sensors, all located outside the vessel. Direct field measurements from Hall sensors are used to correct the drift of the integrators of the pick-up coils signals. This feature will be crucial for future ITER-like devices, where long-lasting flat top phases are expected, in a high neutron yield and a high temperature environment. After a general overview of the system, the paper describes the major manufacturing and installation issues, including the construction of the supports and probes as well as the acceptance tests before and after installation. The functional commissioning of the system includes the integration of the new signals in the JET Data Acquisition System and the analysis of several discharges with and without plasma. The critical aspects of the assessment of the reliability of the signals are shown and commented on.