Development and initial operation of the pellet charge exchange diagnostic on LHD heliotron

An active corpuscular diagnostic with an artificially created localized target for the charge-exchange process has been developed and tested on a large helical device. The diagnostic is a combination of an impurity pellet injector and a natural diamond detector-based energy analyzer. High-energy particles neutralized at the pellet ablation cloud are detected while the pellet travels across the plasma column. Time-resolved atomic energy spectra translate into local measurements along the pellet trajectory. Thus, local parameters are obtained in the toroidally non-axis-symmetrical configuration. Physical basis, data interpretation, and the technical description of the diagnostic are given. The requirements to the analyzer geometry, electronics, and data acquisition needed to provide the desired spatial resolution are described. The initial experimental results are presented along with the other diagnostic data. The scope of experiments, possible comparisons with multichord passive charge-exchange measuremen...