A New Analog Integrator for Magnetic Diagnostics on EAST

A new kind of analog integrator has been developed for a magnetic diagnostic system on the Experimental Advanced Superconducting Tokamak. Although the previous analog integrators are single-ended input, which has low common-mode rejection ratio (CMRR), a different kind of integrator, a difference integrator is introduced which has the same structure as a standard difference amplifier. The linear drift compensation method is used for determining the effective drift slope; then, the plasma control system uses the drift slope to rectify the integration signal in real time. To improve the maintainability and testability of the integrator system, a new integrator controller has been developed. The new controller uses an advanced reduced instruction set computing machine microcontroller and the lightweight IP protocol stack to realize the network control. The tests show that the upgraded integrator works well, its CMRR is high up to 125 dB when the common voltage is 1.5 V, and the processed integration drift is about 10 mV in 1000 s of integration when the time constant is 20 ms. The performance is much better than the previous integrator.