1. Modélisation non-linéaire des interactions ondes/plasma de bord Enabling Research CEA-05 L. COLAS (PI), L. LU, P. Tamain, IRFM E. Faudot, S. HEURAUX, IJL B. DESPRES, LJLL J. Jacquot, IPP Garching A. KRIVSKA, D. Van Eester, K. Crombe, F. Louche, ERM/KMS Brussels
9MW
Colloque prospective Fédération de recherche | L. COLAS
15 octobre 2015
CEA | 10 AVRIL 2012

2. Ion Cyclotron Range of Frequencies (ICRF) waves: the main heating method on WEST
40-60MHz; 12MW installed; up to 1000s
Goal: central heating / current drive
Launching: 3 phased arrays of poloidal current straps in SOL
Wave coupling: how much power to the core for IRF=1A? Losses in SOL?
IRF

3. ICRF launchers: active plasma-facing components
ICRF launchers are in the SOL…
~l/10 antenna: inefficient in vacuum
Coupling  minimal distance to cut-off
… hence undergo Plasma-Surface Interaction (PSI) …
Heat loads
Erosion
Impurity production
Active objects
Emitted RF fields  RF oscillation of sheaths
DC rectification  DC self-biasing of SOL
Locally enhanced PSI
Where?
How much?
Link with antenna design, RF setting?
Visible
~l/10
Important in high-Z long-pulse machine !
Infrared B0
CEA | 10 AVRIL 2012

4. Multi-scale modelling approach
Macro-scale antenna model
RF Wave excitation
Current straps
or RF Field map
Artifical wave damping
RF wave propagation & DC plasma biasing…
… Coupled by RF and DC sheath Boundary Conditions at shaped wall
Plasma
toroidal
poloidal
radial
wall
plasma
sheath
Micro-scale magnetized RF sheath models
Start simple
Upgrade  U-Lorraine
V(t)

5. Modular multi-physics modelling
[Colas’2012]
[Jacquot’2012]
Excitation
SSWICH
Self-consistent Sheaths & Waves for Ion Cyclotron Heating
RF Wave propagation
FEM
Iterative Solver
COMSOL
Start simple
Upgrade: input from
RF engineering
RF wave physics
RF Sheath physics
SOL physics
Applied maths
Sheath RF voltage
DC plasma
biasing
J. Jacquot et al
20th RF Top. Conf. June 27th 2013

6. SSWICH guides RF-sheath mitigation
limiter edge
limiter edge
Pcentral/Pouter = 2
IRF
IRF
Poloidal
Radial x x
Compare 2 ASDEX upgrade antennas
Figure of merit: DC plasma potential
SSWICH excited with RAPLICASOL RF solver [Jacquot2015]
Interpretation: compensation of weighted strap contributions to VRF
Poloidal
Radial
V. Bobkov | 43rd European Physical Society Conference on Plasma Physics | Leuven, Belgium | 8 July 2016 | Page 6

7. SSWICH: a unique tool in Europe with many prospects
WEST : challenge/opportunity for edge ICRF physics
Constraint models by measurements!
RF-induced W sources: need common work with SOLEDGE.
Future: guide design of more optimized antennas?
Other experimental opportunities
Tokamaks: ASDEX-Upgrade, JET, EAST…
RF sheath test beds:
ALINE (Nancy)
IShTAR (IPP Garching, MST2)
Implemented physics remains simple: input needed
RF wave physics  PhD L. LU, defense 02/12 (Nancy)
RF sheath physics  IJL (U. de Lorraine-CNRS)
SOL physics
Applied maths  B. Després (LJLL, next talk)
CEA | 10 AVRIL 2012

8. Spare
CEA | 10 AVRIL 2012

9. Adaptation of SSWICH for Aline simulationsy x
Aline: a cylindrical plasma device for basic RF sheath studies in ULorraine
[Faudot 2015]
RF electrode and probe
Collisional magnetized plasma
Argon or Helium plasma
ne : m-3
f : 10kHz-250MHz
B0 : 0-0.1T
Adapted SSWICH geometry
ULorraine public defence | 2 December 2016

10. RF simulations Using SSWICH-FW
Waves in Argon plasmas:
Lower hybrid wave: low density, 1015m-3
Helicon wave: high density, 1018m-3
Propagates along magnetic field, inside a resonance cone
θ=0.01o, kz=0.001 m-1
“Slow wave like”, Lower hybrid wave
By SSWICH-FW
“Fast wave like”, Helicon wave
By SSWICH-FW
ULorraine public defence | 2 December 2016

11. RF sheath simulations for Aline: preliminary results
Exp. floating potential map from probe measurement [courtesy S. Devaux]
DC plasma potential from simulation
By SSWICH-SW
LH wave is the main wave supported in Aline
Further improvement
More constraints on parameters, detailed density profile, collision frequency…
Include more physics: E×B drifts, 3D effects…
ULorraine public defence | 2 December 2016