离子回旋频率波加热下的EAST等离子体锯齿行为研究

Sawtooth behavior of EAST plasma under ICRF heating

利用软X射线、中子注量检测诊断系统和偏振干涉仪(Polarimeter-interferometer,POINT)约束下的平衡反演算法(Equilibrium Fitting Algorithm,EFIT),对东方超环(Experimental Superconducting Tokamak,EAST)等离子体在离子回旋共振频率波(Ion Cyclotron Resonance Frequency wave,ICRF)在轴沉积加热下的锯齿周期,锯齿幅度,q=1面处等离子体压强梯度,q=1面的半径的变化情形进行了研究。研究发现,在轴沉积情况下,加入ICRF可以对锯齿起致稳作用(延长锯齿周期),锯齿周期与ICRF功率呈正相关;锯齿周期随着ICRF的加入或者ICRF功率的变化趋势,与锯齿幅度和q=1面处等离子体压强梯度变化趋势大体上一致;要改变q=1面半径,ICRF的功率可能需要到0.8 MW以上;在ICRF功率占比更高的加热条件下,锯齿周期和q=1面半径随着ICRF功率变化更敏感;EAST中ICRF产生的快离子和导致的q=1面半径的变化可能对锯齿行为有一定的影响。

[Background]Sawtooth oscillations are macroscopic instabilities in plasma.To better control the sawtooth oscillation in an advanced experimental superconducting tokamak(EAST)device,it is necessary to develop sawtooth controlling methods that help improve the confined performance of plasma in the EAST device.[Purpose]This study aims to analyze sawtooth behavior under the on-axis heating by ion cyclotron resonance frequency(ICRF)wave in the EAST device.[Methods]First of all,the soft X-ray integrated signal intensity data was used to analyze the sawtooth period and amplitude.The radius of q=1 surface and the plasma pressure gradient at q=1 surface were calculated using a soft X-ray intensity profile.Then the neutron yield flux was obtained from the neutron yield flux diagnostic data.Finally,the equilibrium reconstruction results of the equilibrium fitting algorithm(EFIT)were combined with polarimeter-interferometer(POINT)diagnostic data to investigate the relationship between the variation of ICRF and plasma current density.[Results]Experimental results show that the sawtooth period is positively correlated with the ICRF power,and the variation in sawtooth period is roughly same as that in sawtooth amplitude and plasma pressure gradient at q=1 surface.The ICRF power needs to exceed 0.8 MW to change the radius of q=1 surface.The sawtooth period and q=1 surface with ICRF power change are more sensitive under solely ICRF heating than under ICRF+lower hybrid wave(LHW)+electron cyclotron resonance heating(ECRH).[Conclusions]Sawtooth behavior of EAST plasma is affected by the fast ions produced by ICRF and the radius change of q=1 surface.