In-situ measurement of trapped hydrogen by laser desorption in TEXTOR-94

First measurements on laser induced desorption of deuterium incorporated in a boron layer formed by plasma chemical vapor deposition on tungsten and g raphite limiter surfaces have been performed. A ruby laser (lambda = 694 nm ) with maximum energy of 50 J and a pulse length of about 0.5 ms was used a s a heat source. The desorbed deuterium was detected by mass spectroscopy a nd total pressure analysis in the residual gas. The amount of desorbed deut erium is about 10(17) D atoms cm(-2). The majority of the deuterium is rele ased during the first laser pulse. The limiter heads were investigated post -mortem by means of ion beam analysis to determine the spatial distribution of boron and deuterium and to investigate the effect of the laser pulse on the release of deuterium and sublimation of boron in the laser spot. All t he deuterium has been released by the laser pulse. The boron is sublimated partly from the graphite and removed nearly completely from the tungsten su rface.