Erosion and deposition behaviour of a-C:H layers in the private flux region of the JET MKII-HD divertor

• Published in: Journal of nuclear materials Vol. 390; pp. 148 - 151
• Main Authors: Esser, H.G., Kreter, A., Philipps, V., Widdowson, A.M., Coad, J.P., Stamp, M.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 15-06-2009; Elsevier
• Subjects: Applied sciences; Controled nuclear fusion plants; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fission nuclear power plants; Fuels; Installations for energy generation and conversion: thermal and electrical energy; Nuclear fuels; 52.55.Fa; 28.52.Fa; 52.40.Hf; Nuclear fusion reactor; Divertor; Quartz; Carbon; Plasma heating; Deposition; Erosion; Nuclear reactor
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2009.01.153

Material deposition was measured in the private flux region of JET by means of a quartz microbalance (QMB) for ∼11
900
s of successive plasma discharges with moderate additional heating (2–3
MW). The QMB was located under the load bearing septum replacement plate with a view towards the inner divertor. In total a ∼270
nm thick hydrogenated amorphous carbon layer was measured assuming a density of 1
g/cm
3 correlated with a fluence of 2.36
×
10
23 D
+ ions into a toroidal section of 1
cm length of the inner divertor. The area of the QMB in the private flux region was deposition dominated when the inner strike point position was on the vertical tiles, line-of-sight with the quartz crystal, and turned into erosion solely by moving the strike point from vertical tile 3 to horizontal tile 4. The most likely reason is a change of the C/D flux ratio of the particles impinging on QMB turning this area from a deposition to an erosion dominated region.