Control of hydrogen content and fuel recycling for long pulse high performance plasma operation in EAST

The results show that long duration first wall baking and discharge cleaning in EAST provides the necessary clean vacuum environment with a high ultimate vacuum of 3.6 × 10−6 Pa and low outgassing rate of ~1.5 × 10−4 Pa m3 s−1 for plasma operation.

In-vessel cryopumps are found to provide an efficient method for particle recycling control in the divertor region to decrease global recycling coefficient (Rglobal) from ~1.0 to ~0.8 during ohmic heating plasmas, and it provides a high particle exhausting rate of 1020–1021 D-atoms s−1 in high-power plasma operations. Long duration silicon coating is found to be more powerful than baking and discharge cleaning, which reduces the H/(H + D) ratio gradually to a value as low as 8%, and lithium coating is more effective and more efficient than silicon coating, to further reduce the H/ (H + D) ratio to 3%.