Study of Impurity Control by Siliconization on HL-2A Tokamak
The plasma impurity and recycling could be effectively controlled by siliconization,which is a conventional wall conditioning method for HL-2A Tokamak.The recent progress of the siliconization system and the impurity control be-havior by siliconizaition on HL-2A are introduced.The siliconization system includes two subsytems:one is used for the of-fline siliconization experiment which employs glow discharge for coating,and the other one is used for the real-time sili-conization experiment which implements coating during plasma discharge.The experimental results show that the oxygen im-purity is significantly reduced after offline siliconization,but it will gradually increase following the plasma discharge experi-ment.The offline siliconization effect lasted for about 150 shots.In order to make further study,real-time siliconization was developed on HL-2A.The results show that carbon,oxygen and iron levels all drop during the real-time siliconization.The amounts of H2O and CO in the vacuum vessel were decreased after both the offline and real-time siliconization,while the real-time siliconization consumed less gas.The plasma performance of HL-2A was effectively improved by siliconization.The study provides an important technical support for the wall conditioning of the future steady-state operation fusion device.
wall conditioningoffline siliconizationreal-time siliconizationresidual gas mass spectraimpurity spectrum
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