Differences of ICR cleanings in He, D2 and O2 for deposit removal and hydrogen release in HT-7

Hu, Jiansheng; Li, J.G.

doi:10.1016/j.jnucmat.2006.12.071

Cited by 11 publications

(3 citation statements)

References 28 publications

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“…GDC using He and D 2 sequentially has been used to enhance hydrogen release and help obtain clean walls. Also, it has been observed that D 2 -GDC has a higher removal rate for hydrogen than He-GDC by a factor of about 3-possibly due to isotopic exchange [27], as shown in figure 2. Using these techniques a significant amount of hydrogen was seen to be removed, which proved to be essential before beginning the plasma operation.…”

Section: Surface Cleaning Using Gdcmentioning

confidence: 96%

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Comparison of various wall conditionings on the reduction of H content and particle recycling in EAST

Zuo

Zhen

et al. 2011

Plasma Phys. Control. Fusion

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Reductions in H content and particle recycling are important for the improvement of ion cyclotron range of frequency (ICRF) minority heating efficiency and the enhancement of plasma performance of the EAST superconducting tokamak. During recent years several techniques of surface conditioning such as baking, glow discharge cleaning/ICRF discharge cleaning, surface coatings, such as boronization, siliconization and lithium coating, have all been attempted in order to reduce the H/(H+D) ratio and particle recycling in EAST. Even though boronization and siliconization were both reasonably effective methods to improve plasma performance, lithium coatings were observed to reduce the H content and particle recycling to levels low enough to allow the attainment of enhanced plasma parameters and operating modes on EAST. For example, by accomplishing lithium coating using either vacuum evaporation or the real-time injection of fine lithium powder, the H/(H+D) ratio could be routinely decreased to about 5%, which significantly improved ICRF minority heating efficiency during the autumn campaign of 2010. Due to the reduced H/(H+D) ratio and lower particle recycling, and a reduced H-mode power threshold, improved plasma confinement and the first EAST H-mode plasma were obtained. Furthermore, with increasing accumulation of deposited lithium, several new milestones of EAST performance, such as a 6.4 s-long H-mode, a 100 s-long plasma duration and a 1 MA plasma current, were achieved in the 2010 autumn campaign.

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Section: Surface Cleaning Using Gdcmentioning

confidence: 96%

“…To attempt a reduction in the H/(H+D) ratio, D 2 -ICRF was also applied for surface cleaning. But it also exhibited little ability to remove hydrogen from hydrogen-rich PFMs [27]. Using the D 2 -ICRF technique, it was difficult to reduce the H/(H+D) ratio to below 20%.…”

Section: Surface Cleanings Using Icrf In Between Dischargesmentioning

confidence: 99%

Comparison of various wall conditionings on the reduction of H content and particle recycling in EAST

Zuo

Zhen

et al. 2011

Plasma Phys. Control. Fusion

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“…ECR discharge cleaning was compared with ICR discharge cleaning with regard to removal rate of hydrogen. ICR discharge cleaning has been campaigned on the HT-7 tokamak many times, and the results of D 2 ICR discharge cleaning in spring 2005 [18] were taken into comparison. The total pressure taken for both ECR and ICR discharge cleaning for D 2 was (1-10) × 10 −2 Pa, but the powers were rather different: for ECR, the power was 5 kW with continuous injections, while ICR cleaning used higher powers of 20 and 40 kW with pulsed injections.…”

Section: Comparison With Icr Discharge Cleaningmentioning

confidence: 99%

ECR plasmas for wall conditioning of the HT-7 tokamak

Yu¹,

Gao²,

Shan³

et al. 2008

Phys. Scr.

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Electron cyclotron resonance (ECR) plasmas produced by radio frequency (RF) waves were investigated for wall conditioning, with a toroidal field of 0.066-0.088 T in the HT-7 superconducting tokamak. Effective wall conditioning was obtained. The influences of toroidal magnetic field, radio frequency (RF) powers, pressures and working gas species on removal rates have been investigated by the partial pressures of the relevant gases. It was shown that ECR plasmas were toroidally homogeneous on the HT-7 tokamak, and the radial position of ECR plasmas was controlled by adjusting the toroidal magnetic field. Moreover, ECR plasmas were more localized by imposing a vertical field. In the experiment, RF powers made little difference, whereas higher pressure brought better cleaning. It was also observed that ECR discharge cleaning in deuterium resulted in a higher removal rate than that in helium under similar parameters. It was shown that the removal rate of hydrogen in ECR discharge cleaning is 5-10 times lower than that in ion cyclotron resonance (ICR) discharge cleaning.

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