Calibration Of The Iter Outer Vessel Steady-State Magnetic Sensors

The outer vessel steady-state magnetic field sensors (OVSS), a subsystem of the ITER magnetic diagnostics, consists of 60 units that will be installed on the vacuum vessel outer shell. Each OVSS unit features a pair of Hall sensors with a sensing layer made of bismuth and an onboard thermocouple. Prior to the installation of the sensors on ITER, OVSS will be subject to the complex calibration process designed to satisfy the ITER requirement for the measurement accuracy of 4 mT (2 sigma) in the range of the magnetic field from 0 to 2.5 T.The calibration process includes the calibration of the onboard thermocouple, sensor controller calibration, measurement of tilt of each Hall sensor with respect to the OVSS housing, and the measurement of the sensitivity of Hall sensors as a function of temperature and magnetic field for the range of ITER-relevant magnetic fields and temperatures. The expected calibration error projected to the magnetic field measurement of 2.5 mT will allow to meet the required measurement accuracy.