| Popis: |
The first year operation of HL-1, a medium size, circular tokamak ( R =102 cm, a = 20 cm) was highlighted by the achievement of plasma current duration in excess of 600 ms ( I p = 100 kA). This is partially attributed to the low Z eff discharges made possible by wall conditioning using Taylor discharge cleaning in hydrogen (TDC), accompanied by baking. Approximately 30 h of TDC and PDC were required to obtain this low Z eff (- 2) tokamak discharges. During the initial clean-up of the wall, a great deal ( ∼ 50 monolayers) of O and C was removed. In this paper, we present: (1) a description of the TDC system and optimization of TDC operation, (2) some behaviour of the partial pressure of water vapour as function of filling pressure, plasma current, electron density (temperature), and discussion of the mechanism for removing oxygen with a simple model called the “three step model” to remove oxygen, compared with the experimental results. The sticking probability, P st is estimated to be around 0.3 for GH-39 steel bellows for clean conditions in HL-1. |
