H alpha line shape in front of the limiter in the HT-6M tokamak

The H-alpha line shape in front of the limiter in the HT-6M tokamak is anal ysed by multi-Gaussian fitting. The energy distribution of neutral hydrogen atoms reveals that H-alpha radiation is contributed by Franck-Condon atoms , atoms reflected at the limiter surface and charge exchange. Multi-Gaussia n fitting of the H-alpha spectral profile indicates contributions of 60% fr om reflection particles and 40% from molecule dissociation to recycling. Io n temperatures in central regions are obtained from the spectral width of c harge exchange components. Dissociation of hydrogen molecules and reflectio n of particles at the limiter surface are dominant in edge recycling. Reduc tion of particle reflection at the limiter surface is important for control ling edge recycling. The measured profiles of neutral hydrogen atom density are reproduced by a particle continuity equation and a simplified one dime nsional Monte Carlo simulation code.