Experiments have been performed on MAST using both external (n=1,2) and internal (n=3) resonant magnetic perturbation coils. ELM suppression has not been achieved even though vacuum modelling shows that either set of coils can produce a region for which the Chirikov parameter is greater than 1 wider than that required to produce ELM suppression in DIII-D. Hence having a certain width of the edge stochastic region may be a necessary criterion but is not a sufficient condition to ensure ELM suppression on any device. Although complete ELM suppression has not been achieved some effects on the ELMs have been observed including triggering ELMs in ELM free H-mode periods and increasing the ELM frequency in regularly ELMing discharges. In addition, large changes to the edge turbulence have been observed in L-mode discharges.
