Evolution of Wave Energy Deposition Profile in HT-7 Lower Hybrid Current Drive Experiment

Lower hybrid waves (LHWs) with a selected n_|| spectrum have been used to control the energy deposition profiles, and then the wave driven current profiles effectively in tokamak discharges. In our lower hybrid current drive experiment in HT-7 tokamak, it was found that the setup of the wave energy deposition profile is a graduation process. In the beginning phase of the wave injection duration, the waves (with different n_|| spectrum) deposit their energy almost all in the central region of the plasma column, even if their n_|| are very different. Up to around one hundred milliseconds, the wave energy deposition profiles just can take their corresponding shapes according to the n_|| spectrum of LHWs. It also shown that this evolution process is affected obviously by the LHW driven current profile, which has been formed early.