Abstract
Enhanced confinement has been achieved by the centre fuelling of pellet injection on the HL-2A tokamak. The energy confinement time increases from 50 ms to 140 ms after the pellet injection. Experimental results show that the improvement of the confinement is related to the decrease of the electron heat transport. Several phenomena which may lead to the improved confinement have been observed in the experiments. After the pellet injection the hollow electron temperature profile and the peaked electron density profile can be sustained for about 200 ms, but the improved confinement remains at about 500 ms. Sawtooth features and MHD modes have been observed by soft x-ray array and the Mirnov probes. The weak (or reversed) magnetic shear is thought to be an important cause of the low electron heat transport.