Pellet injection research on the HT-6M and HT-7 tokamaks

A multishot in situ pellet injection system has been constructed in the Ins titute of Plasma Physics. Single- and multi-pellet injection experiments we re performed on the HT-GM and superconducting HT-7 tokamaks. The system pro ved to be convenient and reliable to operate. Pellets were fired into ohmic ally and LHCD and ICRF heated plasmas. Single pellet injection in ohmic dis charge was found to increase the central density of HT-7 by about one half, while two pellet injection increased the central density in a step-like fa shion by one half with each shot. Peaking of the electron density profile a nd a hollow electron temperature profile were obtained.