H-mode characterization for dominant ECR heating and comparison to dominant NBI or ICR heating F. Sommer PhD thesis advisor: Dr. Jörg Stober Academic advisor: Prof. Dr. Hartmut Zohm Advanced Course of EU PhD Network 29 Sep 2010 Max-Planck-Institut für Plasmaphysik Boltzmannstr. 2, 85748 Garching, Germany
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H-mode characterization for dominant ECR heating and comparison to dominant NBI or ICR heating F. Sommer PhD thesis advisor: Dr. Jörg Stober Academic advisor:
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H-mode characterization for dominant ECR heating and comparison to dominant
NBI or ICR heating
F. Sommer
PhD thesis advisor: Dr. Jörg Stober
Academic advisor: Prof. Dr. Hartmut Zohm
Advanced Course of EU PhD Network
29 Sep 2010
Max-Planck-Institut für Plasmaphysik
Boltzmannstr. 2, 85748 Garching, Germany
Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer 2
Outline
• NBI and ECR heating systems• Heat transport theory• H-mode heat transport characterization
– Te, Ti, profiles
• Further investigations and experiments• Summary and discussion
Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer 3
NBI – general introduction
• Beam of neutrals (H0, D0, T0, He0 ) injected into plasma with
– high power – up to 2.5 MW
– high (appropriate) energy – Ebeam > Ti,e
– Inside plasma neutrals collide with plasma ions & electrons
• H0 + H+ → H+ + H0 – CX
• H0 + H+ → H+ + H+ + e – Ionisation by ions
• H0 + e → H+ + 2 e – Ionisation by electrons
– exponential decay
Ebeam ~ 100 keV today
1 MeV for ITER
• Resulting fast ions are confined within the plasma by magnetic field
slowed down to thermal energies Coulomb collisions ions & electrons
transfer of beam power to plasma
mnA
E AUGD
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5.018
Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer 4
• critical energy: rate of energy loss to ions = rate of energy loss to electrons
• Ecr = 14.8 (kTe) [ (A3/2/Ai) ]2/3
– for pure D – beam: Ecr = 19 Te Ebeam/Ecr ~ 1 – 3
ITER: ENBI = 1MeV
E = 3,5 MeV
NBI – power deposition
Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer 5
NBI – layout
ASDEX Upgrade
neutraliser
ion dump
magnet
PINIs (4x)
box height:~ 4.5 m
cut through 1st injector – 10 MW at 60 kV
– arc sources pins have to be replaced quite often
– 10 MW at 93 kV– RF sources
simpler, cheaper, less maintenance
- pulse = 10 s
Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer 6
NBI – layout
• 2 Beamlines, each 4 ion sources
• SO-injector
• 2 radial beams
• 2 tangential beams
• NW-injector
• 2 tangential beams
• 2 off-axis deposition
• Also source of :
• particles edge: 1/10, but deep fuelling (not relevant for ITER)
• driven current
• plasma rotation (by NBI torque)
• CXRS
• efficiency factor of only 40 %
Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer 7
ECRH – principle
• Electron Cyclotron Maser Instability
• Electron gun: hollow e- beam
• Accelerated to relativistic speeds and focussed
• vII converted to v┴ inside resonant cavity (axial B-field)
• Interaction between e- and em wave
• Phase focus of e-
• Slowing down of e- by E transfer to
HF field
• Vgyrotron = 73 kV
Bgyrotron = 5.3 T
• Efficiency factor of 50 %
Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer 8
ECRH – layout
• fECRH ~ 140 GHz
• Electron cyclotron frequency fce(B = 2.5 T)= eB / (2me) = 70 GHz
• location determined by
– B 1/R
– fECR
– launching angle (mirror)
• Pold = 4 x 0.5MW for 2 s
• Pnew = 2 x 1 MW for 10 s
• Pfuture = 2 x 1 MW for 10 s
Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer 9
ECRH – advantages
• Localized (few cm) deposition
• Localized current drive
removal of NTMs by heating inside island structure
• Electron heating simulate reactor conditions
• Fast modulation ( 500 Hz) fast response in plasma
• Central heating enhanced impurity transport
Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer 10
Heat transport - theory
• Why are we interested in heat transport?
– High E low heat transport
– High central density low particle transport
– Low accumulation of impurities enhancement of impurity transport
• Heat transport is not governed by classical or neoclassical drive, but by micro instabilities and turbulent effects
– ITG, TEM, (ETG)
– Scale length ~ ion gyro radius << a
• qe(r) = - ne(r) · e(r) · Te(r)
• (r) = - D (r) · ne(r) + v · ne(r)
Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer 11
Heat transport - theory
• Gyro-Bohm scaling law in H-mode.
• Turbulence increases above a critical gradient length:
•
• S, 0, R/LTe, crit adjusted to experiment
stiffness of profiles
• Boundary condition at pol = 0.8 (H-mode pedestal)
GBTT
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L
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critee
02/3
,
e
e
T T
TR
L
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iLeGB T
ReB
TF
Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer 12
ASTRA
• Automated System for TRansport Analysis in a tokamak