EFDA-JET-PR(10)46

Feedback Control of the Sawtooth Period through Real Time Control of the Ion Cyclotron Resonance Frequency

Modification of the sawtooth period through Ion Cyclotron Heating and Current Drive (ICRF) has been demonstrated in a number of experiments. The effect has been seen to depend critically of the location of the ICRF absorption region with respect to the q = 1 flux surface. Consequently, for ICRF to be a viable tool for sawtooth control one must be able to control the ICRF absorption location in real time so as to follow variations in the location of the q = 1 surface. To achieve this, the JET ICRF system has been modified to allow the JET real time central controller to control the ICRF frequency. An algorithm for real time determination of the sawtooth period has been developed and a closed loop controller which modifies the ICRF frequency to bring the measured sawtooth period to the desired reference value has been implemented. The present paper shows the first experimental demonstration of closed loop sawtooth period control by real time variation of the ICRF frequency.
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EFDP10046 4.69 Mb