Bootstrap current increment after siliconization on the HT-7 tokamak

We present some results for the estimation of the bootstrap current after siliconization on the HT-7 tokamak. After siliconization, the plasma pressure gradient and the electron temperature near the boundary are larger than before siliconization. These factors influence the ratio of the bootstrap current to the total plasma current which increases from several per cent to above 10%. The results are expected to explain the previous experimental phenomena that, after siliconization, the plasma current profile is broadened and the higher current can be obtained easily on the HT-7 tokamak experiment.