Uniformity of Glow Discharge Cleaning for CFETR Vacuum Chamber: A Simulation Study

The glow discharge cleaning(GDC) of vacuum chamber,for China Fusion Engineering Testing Reactor(CFETR) project,was mathematically modeled,theoretically analyzed and numerically simulated for design optimization of GDC setup.The influence of the discharge variables,including the He-pressure,current/position of anode and electrode-number,on the uniformity of ion-current density distribution was investigated.The simulated results included:first,an intense ionization occurs in the ionization zone closely above the anode,resulting in strong ion-sputtering of the wall nearby; second,as the single-electrode current increases,the ion-current density in the ionization zone significantly increases,bringing about a non-uniform ion-current density distribution; third,the electrode's radial position little affects the ion-current density distributions on the inner and outer walls; and finally,a lower pressure significantly reduces the non-uniformity and produces a small ion-current difference between the two walls.