Deuterium pellet fueling in type-III ELMy H-mode plasmas on EAST superconducting tokamak

Highlights: • Type-III ELMy H-mode plasmas have been fueled by pellets on EAST tokamak. • A string of small ELMs were induced after pellet injection from LFS at a low velocity. • The changed edge plasma parameters were proposed as the reason for the ELM modification. -- Abstract: Type-III ELMy H-mode plasmas are a valuable operating scenario, as they may simultaneously achieve fusion power gain of Q = 10 and acceptable steady-state and peak power fluxes to the plasma-facing components. It is important to investigate cryogenic deuterium pellet injection fueling in this kind of H-mode plasma since it has been chosen as a main plasma fueling technique for ITER. Recently, pellet fueling experiments have been successfully carried out on EAST, an ITER-like tokamak. A maximum electron density of 0.73 × n_GW has been obtained. It is found that ELM behavior was modified immediately and a string of small ELMs were induced when pellets were injected at a low velocity from ˜40 cm above the mid-plane on the low field side, which is different from the fact that pellets trigger signal ELMs in Type-I ELMy H-mode plasmas in other tokamaks. The decreased edge temperature caused by the cryogenic pellet was proposed as the reason for this ELM modification. These results will provide a useful reference for the pellet fueling in a Type-III ELMy H-mode plasma on ITER in the future.