Experiment Studies With The ECRH System On HL-2A Tokamak

As plasma temperature rises, the plasma resistivity decreases with the electron temperature as T_e^3/2, the ohmic heating becomes less important. Hence it is important to have auxiliary heating power in addition to the ohmic heating power to get high performance operation on tokamaks. For example, H-mode confinement regime can be obtained by delivering sufficient central heating power. There are several types of auxiliary heating and current drive, such as neutral beam injection, electron cyclotron resonance heating(ECRH),low hydride current drive,ion cyclotron resonance heating and so on. The work of this thesis is focused on the following: developing a high power (2MW) electron cyclotron resonance heating system on HL-2A tokamak to obtain the operational experience of the ECRH system and to learn the transmission engineering and measurement of the high power millimeter wave; increasing the plasma temperature; studying suppress of the magnetohydrodynamics instabilities by the ECRH system.Various experiments have been explored in HL-2A tokamak by the 2MW ECRH system under different experimental conditions: plasma current (250-350)kA, toroidal magnet field (2.2-2.6)T, line-averaged electron density (0.8-3.0)×10¹³cm^-3. In short 5830,toroidal magnet field Bt=2.43T, plasma current IP=300kA, line- averaged electron density ne = 1. 7×10^-13cm^-3, total power after MOU PEC=1.57MW, the central electron temperature Te was increased from 1.2KeV to 4.93KeV.Magnetohydrodynamics instabilities during ECRH have been studied in HL-2A tokamak. Snake-like oscillation of the soft X-ray suppressed by EC wave and fishbone instabilities driven by ECRH have been observed. Soft X-ray sawtooth activities during ECRH have been studied. Many types of sawtooth have been found such as giant sawtooth, inverted sawtooth, saturated sawtooth, compound sawtooth and so on. The results of this study have been shown that the power of EC wave and the evolution of the central electron temperature are correlated with different types of sawtooth activities. The effect of ECRH on Electron runaways has also been explored. These researches have provided some important experience and database for ITER- related research which will be undertaken on the HL-2A tokamak, for example, active control of instabilities.