ECH Absorbed Power Evaluation Method Compensated for Temporal Response of Diamagnetic Flux Measurements on LHD

Abstract

Evaluation methods of electron cyclotron resonance heating (ECH) power absorption are discussed. ECH power absorption can be evaluated from changes in the time derivative of the plasma stored energy. On the Large Helical Device (LHD), absorbed power is usually evaluated from the difference between the time derivative of the stored energy estimated from diamagnetic flux just before and after ECH injection. The temporal response of the diamagnetic flux measurement is slow with a time constant of several milliseconds because of uncompensated effects of image currents, and it affects the ECH absorbed power estimation. Therefore, a new method taking the slow response into account is developed. ECH power absorption has been evaluated from the plasma kinetic energy and compared with the power absorption evaluated by the new method. The evaluated power absorption values were approximately consistent with each other. Absorbed power evaluation using diamagnetic flux measurements is more accurate by taking the slow response into account.