Observation of hydrogen pellet ablation material flow by tomography

An H\alpha emission measurement array with 25 detection channels has been built on HL-1M tokamak. Reconstruction maps of H\alpha emission distribution in plasma cross-section have been obtained by using tomography, with a hydrogen pellet injected into the plasma. The dimension, the shape and the rotation characteristic of the cross-section of the pellet ablation material flow tube have been observed. These results have been analysed and explained tentatively by using the `tail' model and the linear expansion model.