Sawtooth control experiments were performed on HT-7 with a limiter configuration and on the Experimental Advanced Superconducting Tokamak (EAST) with a double null con-figuration. The sawtooth period can be modified by lower hybrid wave (LHW) and ion cyclotron resonance frequency (ICRF). Different sawtooth behavior was observed with the same plasma density, LHW power but different plasma currents on HT-7. There was a dwell time between LHW added and the sawtooth stabilization on HT-7 while the sawtooth stabilization immediately happened when LHW power was injected on EAST. The possible mechanism of the sawtooth control is discussed in this paper. All the experimental results have proved that power deposition of the radio frequency (RF) should be the key factor for sawtooth control.
Inward energy transport(pinch phenomenon)in the electron channel is observed in HT-7 plasmas using off-axis ion cyclotron resonance frequency(ICRF)heating.Experimental results and power balance transport analysis by TRANSP code are presented in this article.With the aids of GLF23 and Chang-Hinton transport models,which predict energy diffusivity in experimental conditions,the estimated electron pinch velocity is obtained by experimental data and is found reasonably comparable to the results in the previous study,such as Song on Tore Supra.Density scanning shows that the energy convective velocity in the electron channel has a close relation to density scale length,which is qualitatively in agreement with Wang’s theoretical prediction.The parametric dependence of electron energy convective velocity on plasma current is still ambiguous and is worthy of future research on EAST.
This paper reports for the first time an experimental study on the power deposition profile of the ion cyclotron range frequencies(ICRF)power depositing on electrons in HT-7.The fast Fourier transform(FFT)analysis and the break in slope(BIS)method are utilized to obtain the information of the power deposition.The results indicate that the electrons were heated directly,and the electrons absorbed around 20%of the input power of the discharge of interest.
