  The impact of resonant magnetic perturbations (RMPs) on the power required to
access H-mode is examined experimentally on MAST. Applying RMP in n=2,3,4 and 6
configurations causes significant delays to the timing of the L-H transition at
low applied fields and prevents the transition at high fields. The experiment
was primarily performed at RMP fields sufficient to cause moderate increases in
ELM frequency, f mitigated/f natural~3. To obtain H-mode with RMPs at this
field, an increase of injected beam power is required of at least 50% for n=3
and n=4 RMP and 100% for n=6 RMP. In terms of power threshold, this corresponds
to increases of at least 20% for n=3 and n=4 RMPs and 60% for n=6 RMPs. This
'RMP affected' power threshold is found to increase with RMP magnitude above a
certain minimum perturbed field, below which there is no impact on the power
threshold. Extrapolations from these results indicate large increases in the
L-H power threshold will be required for discharges requiring large mitigated
ELM frequency.
