Speaker
Description
The GDOES (Glow Discharge Optical Emission Spectrometry) technique has been already used for investigation of erosion/re-deposition processes of W coated CFC tiles from JET. The challenge for GDOES was to measure the depth profile of deuterium together with the other elements from the W coatings exposed to JET plasmas. A tentative investigation using GDOES for deuterium analysis was performed by other authors, but the D depth profile was only qualitatively obtained.
Since reference samples for D calibration are not available on the market, these samples have been produced in our laboratory by High Power Impulse Magnetron Sputtering (HiPIMS) and Combined Magnetron Sputtering and Ion Implantation (CMSII). The D concentrations were measured by NRA (Nuclear Reaction Analysis) and ToF ERDA (Time of Flight Elastic Recoil Detection Analysis). Then these samples were used to calibrate the D channel of the GDOES machine.
Special samples cored from Tiles 1, 6 and 3, 7, 8 exposed in JET in the periods 2012-2014 and 2011-2014 respectively, were analyzed by GDOES and SEM. The following aspects can be emphasised:
- Be has contaminated both inner and outer divertor tiles.
- The thickness of the Be layer varies from about 2 microns on Tile 8 to about 44 microns on Tile 3.
- D penetrates into the coating, but its profile does not seem to follow that of Be. On Tile 3 where the Be deposition is very strong, the deuterium concentration is the lowest (0.2-0.6 at.%). On Tile 8 with the lowest Be deposition, the D concentration is highest (3.2 at.%).
- Small peaks of D have been detected at the interfaces.
- It is important to notice that the concentration of D found by GDOES is in very good agreement with that found by NRA (1 – 3.5 at.%).
