Quartz microbalance: a time resolved diagnostic to measure material deposition in JET

To promote solutions of key fusion problems like tritium retention and wall erosion, more measured data of carbon deposition in remote areas of fusion devices are needed. These data are essential to understand and model local and global particle fluxes and to make predictions for future devices like ITER. In spring 2000 the development of a new diagnostic, quartz microbalance (QMB), was started to measure quantitatively, in situ and time resolved (≤1 s) the material deposition in the sub divertor region of JET. Calibration work of mass and temperature characteristic was done at FZ-Jülich giving a layer mass sensitivity of Γmass=7.5×10−9 g/Hz and a temperature sensitivity of Γtemp(100 °C)≈0.09 °C/Hz. The commercially available QMB technique was adapted to the harsh constraints and requirements of JET. After implementation in March 2002 reliable and successful operation was demonstrated during the C5 campaign (∼1000 plasma pulses). First examples of measurements are presented.