Filtering and Delay Compensation of Magnetic Field Caused by Eddy Current in Gyrotron With Flat-Top Pulsed Magnet

A new problem of eddy current effect affecting the magnetic field control is faced when the flat-top pulsed high magnetic field (FTPMF) is applied to the gyrotron. In this letter, the influences of eddy current on the regulation of FTPMF are analyzed. On the one hand, the eddy current can shield high-frequency ripples, such as a filter, which can be employed to improve the stability of FTPMF. But on the other hand, it causes a delay of magnetic field that shorts the span of flat top. This letter proves that a gyrotron can be equivalent to a first-order filter for the magnetic field, and the determining factors of its cutoff frequency are obtained. A method of compensating for the delay by current overshoot is proposed, and the delay is minimized by the prediction algorithm. Finally, the theoretical analysis is verified by experiments.