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VERSION:2.0
PRODID:-//Memento EPFL//
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SUMMARY:Effect of RMPs on tokamak equilibrium and stability
DTSTART:20150610T103000
DTEND:20150610T113000
DTSTAMP:20260916T055302Z
UID:b78127a0c4757f327427100c57b1d470ba00e497530fd939fd8ea377
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. C.J. Ham\, CCFE\, Culham Science Center\, Abingdon\, UK\
 nNon-axisymmetric resonant magnetic perturbation (RMP) coils applied to mi
 tigate or suppress ELMs produce a very small field compared to the axisymm
 etric magnetic field and yet they cause significant changes to both the eq
 uilibrium and stability of the plasma. Non-axisymmetric simulations are sh
 edding new understanding on how these changes in stability influence the o
 bserved increase in ELM frequency or complete stabilization (suppression) 
 of ELMs.\nThe required non-axisymmetric equilibria have been modelled usin
 g stellarator equilibrium codes. We have compared the stochastic structure
 s and magnetic islands that form in HINT2 equilibria with VMEC\, where nes
 ted flux surfaces are assumed. It is observed that displacement at the X-p
 oint\, caused by the RMP field\, is correlated to density pump out. We cal
 culate the X-point displacement for an ITER equilibrium n=3 and n=4 RMPs a
 pplied. We also investigate potential experimental issues raised by applyi
 ng RMP fields.\nWe have also calculated Mercier stability and infinite-n b
 allooning stability using COBRA. We find that Mercier modes can become uns
 table at rational surfaces due to the applied RMP fields. The most unstabl
 e ballooning mode becomes more unstable with RMPs applied. This indicates 
 that RMPs act to destabilize ballooning modes and we would expect the ELM 
 frequency to increase i.e. ELM mitigation.\nThis work was part-funded by t
 he RCUK Energy Programme and the EU Horizon 2020 programme.
LOCATION:PPB 019
STATUS:CONFIRMED
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