Upgraded Vacuum System for Long Pulse High Parameter Plasma Discharge in EAST

The vacuum system of Tokamak provides adequate vacuum, clean wall condition, real-time fuel injection and particle exhaust, which directly influences the high temperature performance. The vacuum system, as an important integral part of EAST, includes vacuum pumping system, plasma fueling system, wall conditioning system, vacuum measurement and control system. To realize the targets of long pulse and high parameter plasma discharges for EAST, some upgrades of the vacuum system have been conducted, including increased the number of pumps, increased the pumping speed and capacity of cryopumps, improved the reliability of SMBI and increased new divertor SMBI system to reduce gas injection delay time, increased ICRF cleaning power to >50 kW. Through these upgrades, it increases the pumping capability, improves the effect of wall conditioning, and results in a recorded pressure of 1.5×10⁻⁶ Pa in vacuum vessel. Based on these upgrades, some record plasmas, such as >400 s high confinement mode （H-mode）and 1056s long pulse plasma are successfully achieved in EAST, which provides a very important reference for vacuum system design and operation for ITER and future fusion reactor devices.