Magnetic diagnostics for future tokamaks

Magnetic diagnostics are critical for future tokamaks such as the International Thermonuclear Experimental Reactor (ITER). Existing tokamaks use inductive coils and loops as magnetic sensors. The sensors are located outside the plasma boundary but within the plasma's external magnetic fields. The electrical signals from these sensors are integrated over time to determine the plasma shape and are used for plasma control. Present magnetic diagnostics are designed for plasmas lasting seconds to tens of seconds. In their present form, the inductive magnetic sensors and integrators; are not suitable for future tokamaks with their long duration plasmas lasting for 1000 s or more. Namely, magnetic diagnostics for future tokamaks require: (1) sensors that will not overheat due to plasma radiation heating, (2) sensor materials that can survive the neutron fluence, (3) sensors designed for the remote handling requirements, and (4) integrators that have a 1000 s measurement capability. This paper presents a high frequency inductive magnetic sensor being developed for ITER.