In order to set up a data base and diagnostic capability for understanding atomic hydrogen behaviour in pumped divertor plasmas, an experiment and a feasibility study using a novel laser-induced fluorescence (LIF) technique were performed. For the former, combined measurements of LIF tuned to Hα and emission intensities at Hα/Hβ were carried out on the compact helical system (CHS). The comparison of the measured data and a particle simulation code revealed atomic hydrogen behaviour quantitatively, providing a full estimate of toroidally and poloidally asymmetric distributions of hydrogen atoms. In order to supplement the data base around the pumped divertor region, the applicability of an LIF technique which uses two-photon excitation from the ground state was examined, based on the real optical constraints of the envisaged JET pumped divertor. It was concluded that it is feasible and the only remaining problem is not a serious one.
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