ELMs triggered from deuterium pellets injected into DIII-D and extrapolation to ITER

Fueling pellets have been found to trigger ELMs before they reach half way into the pedestal, which implies that the ITER requirement for pacing pellets to reach the top of the pedestal may be overly conservative. Pellets dropped from a vertical port on DIII-D with low speed and at a glancing angle with respect to the plasma surface do not have enough momentum to cross into the H-mode plasma and reliably trigger ELMs. This implies that pellets need to penetrate well inside the separatrix in ITER in order to guarantee triggering of an ELM. Future studies will elucidate just how far inside the separatrix the pellets need to penetrate. Pellet fueling of H-mode plasmas with RMP applied is a scenario under test for operation of ITER without strong type-I ELMs. Thus far testing on DIII-D has shown a return to a reduced amplitude ELMing state when strong pellet fueling is applied. Some cases with partial ELM suppression have led to fewer ELMs with the pellets. Thus further optimization of the RMP technique is needed to be able to fully suppress ELMs during pellet fueled H-mode scenarios for application to ITER.