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research article

Effects of magnetic ripple on 3D equilibrium and alpha particle confinement in the European DEMO

Pfefferle, D
•
Cooper, W A
•
Fasoli, A
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2016
Nuclear Fusion

An assessment of alpha particle confinement is performed in the European DEMO reference design. 3D MHD equilibria with nested flux-surfaces and single magnetic axis are obtained with the VMEC free-boundary code, thereby including the plasma response to the magnetic ripple created by the finite number of TF coils. Populations of fusion alphas that are consistent with the equilibrium profiles are evolved until slowing-down with the VENUS-LEVIS orbit code in the guiding-centre approximation. Fast ion losses through the last-closed flux-surface are numerically evaluated with two ripple models: (1) using the 3D equilibrium and (2) algebraically adding the non-axisymmetric ripple perturbation to the 2D equilibrium. By virtue of the small ripple field and its non-resonant nature, both models quantitatively agree. Differences are however noted in the toroidal location of particles losses on the last-closed flux-surface, which in the first case is 3D and in the second not. Superbanana transport, i.e. ripple-well trapping and separatrix crossing, is expected to be the dominant loss mechanism, the strongest effect on alphas being between 100â 200 KeV. Above this, stochastic ripple diffusion is responsible for a rather weak loss rate, as the stochastisation threshold is observed numerically to be higher than analytic estimates. The level of ripple in the current 18 TF coil design of the European DEMO is not found to be detrimental to fusion alpha confinement.

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Type
research article
DOI
10.1088/0029-5515/56/11/112002
Web of Science ID

WOS:000391393900002

Author(s)
Pfefferle, D
Cooper, W A
Fasoli, A
Graves, J P
Date Issued

2016

Publisher

IOP Science

Published in
Nuclear Fusion
Volume

56

Issue

11

Article Number

112002

Subjects

: alpha particle confinement

•

3D MHD equilibrium

•

stochastic ripple diffusion

•

ripple well trapping

•

neoclassical transport

•

energetic particle loss

URL

URL

https://crpplocal.epfl.ch/pinboard/jpapers/1600305.pdf
Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
SPC  
Available on Infoscience
July 22, 2016
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/128055
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