Carbon deposition in the inner JET divertor measured by means of Quartz Microbalance

A Quartz Microbalance (QMB) system was implemented in the inner divertor region of JET in order to measure in situ and time resolved (minimum exposure time >= 0.1 s) material fluxes (mainly carbon) and layer deposition. The system has been developed to operate at temperatures up to 200 degrees C. The aim is to investigate carbon transport to the remote areas, and hence the tritium retention in dependence on plasma conditions. This question is still amajor concern for the ITER operation. The mass sensitivity of the system is S-m 1.5 x 10(-8) [g/Hzcm(2)]. First reliable measurements were made during the C5 campaign (March-May 2002; approximate to 1000 plasma discharges). The results presented are based on 74 selected exposures (694 s) under various conditions (strike point position, input power, neutral pressure, ELM frequency). Most influencing on the carbon deposition in the remote area seems to be the geometry i. e. the strike point position on the divertor tiles. In average 1.9 x 10(-4) C-atom are deposited per deuterium ion. owing into the inner divertor.