Fuelling and Diagnostics with Pellet Injection in the HL-1M Tokamak

Abstract

The pellet injection experiments for fuelling and diagnostics have been carried out on the HL-1M tokamak. The eight-pellet injector was installed on HL-1M. A reliable monitor-detector and camera system was set up to take initial pellet photographs and measure the initial pellet speed and size. High fuelling efficiency of 60%-100% and a density profile with a peaking factor of 1.8-2.0 were obtained. The maximum density close to 1014/cm3 in HL-1M was achieved with newly optimized combined fuelling techniques. Two typical models of pellet ablation have been utilized for simulative calculation of the ablation rates in HL-1M. In comparison with the distribution of the measured Hα emission intensity from the digital data of the CCD camera, the experimental result seems more optimistic for core fuelling than theoretical predictions by the two models. The safety factor profile q(r) has been extracted from the information provided by the CCD camera during the pellet injection. The reliability of the measured results depends mainly on the calibration of the imaging space position. Based on the calibration, the measured q-profile becomes more reasonable than those published previously for the same shot number and same photograph.