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, Garching, Germany

Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer2 Outline NBI and ECR heating systems Heat transport theory H-mode heat transport characterization –T e, T i, profiles Further investigations and experiments Summary and discussion

Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer3 NBI – general introduction Beam of neutrals (H 0, D 0, T 0, He 0 ) injected into plasma with –high power –up to 2.5 MW –high (appropriate) energy –E beam > T i,e –Inside plasma neutrals collide with plasma ions & electrons H 0 + H + H + + H 0 –CX H 0 + H + H + + H + + e–Ionisation by ions H 0 + e H e –Ionisation by electrons –exponential decay E beam ~ 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

Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer4 critical energy: rate of energy loss to ions = rate of energy loss to electrons E cr = 14.8 (kT e ) [ (A 3/2 /A i ) ] 2/3 – for pure D – beam: E cr = 19 T e E beam /E cr ~ 1 – 3 ITER: E NBI = 1MeV E = 3,5 MeV NBI – power deposition

Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer5 NBI – layout ASDEX Upgrade neutraliser ion dump magnet PINIs (4x) box height: ~ 4.5 m cut through 1 st 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. Sommer6 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. Sommer7 ECRH – principle Electron Cyclotron Maser Instability Electron gun: hollow e - beam Accelerated to relativistic speeds and focussed v II 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 V gyrotron = 73 kV B gyrotron = 5.3 T Efficiency factor of 50 %

Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer8 ECRH – layout f ECRH ~ 140 GHz Electron cyclotron frequency f ce (B = 2.5 T)= eB / (2 m e ) = 70 GHz location determined by –B 1/R –f ECR –launching angle (mirror) P old = 4 x 0.5MW for 2 s P new = 2 x 1 MW for 10 s P future = 2 x 1 MW for 10 s

Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer9 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. Sommer10 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 q e (r) = - n e (r) · e (r) · T e (r) (r) = - D (r) · n e (r) + v · n e (r)

Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer11 Heat transport - theory Gyro-Bohm scaling law in H-mode. Turbulence increases above a critical gradient length: S, 0, R/L Te, crit adjusted to experiment stiffness of profiles Boundary condition at pol = 0.8 (H-mode pedestal)

Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer12 ASTRA Automated System for TRansport Analysis in a tokamak 2D equilibrium 1D (radial) profiles and transport equations of transport Modular build –Many implemented models –Easy inclusion of own models Equilibrium + radial profiles (T e, T i, n e, j, P heat,, P rad, …) q e,i, e,i, D n, … Equilibrium + radial profiles (n e, j, P heat,, P rad, …) + i,e,theory radial profiles (T e, T i )

Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer13 H-mode characterization 4 similar discharges: I p ~ 600 kA, B tor ~ 2.5 T, n e ~ 5 x 10 19, P NBI = 5 MW –Different heating power (P ECRH = 0, 0.5, 1.5 MW) –Different deposition location: P ECRH = 1 MW, pol = 0, 0.3, 0.6

Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer14 Power dependence of T e profiles with varying ECRH: 0.6 kA, 2.5 T, central ECRH n e = 5x10 19 H-mode characterization - T profiles

Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer15 Power dependence of T e profiles with varying ECRH deposition location: 0.6 kA, 2.5 T, P ECRH = 1.2 MW n e = 5x10 19 H-mode characterization - T profiles II R.M.McDermott et al 2010 EPS

Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer16 H-mode characterization - e profiles Electron and ion heat diffusion coefficients derived with ASTRA with varying heating power Transport dominated by ion heat transport (ITG)

Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer17 Increase of ECRH power (6 MW) Replacement of NBI in H-mode Higher current values up to I p ~ 1.2 MA Lower density values n e < 5x10 19 Increased influence of ECRH on e (TEM) due to decreased * Variation of R/L Te by variation of ECRH Dependence of ei on energy confinement time E Influence of central ECRH on pedestal Further experiments and investigations

Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer18 H-mode characterization – ECRH on edge Influence of ECRH power on edge profiles (T e, v tor, n e ) Analysis by Elisabeth Wolfrum

Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer19 Increase of ECRH power (6 MW) Replacement of NBI in H-mode Higher current values up to I p ~ 1.2 MA Lower density values n e < 5x10 19 Increased influence of ECRH on e (TEM) due to decreased * Variation of R/L Te by variation of ECRH Dependence of ei on energy confinement time E Influence of ECRH on pedestal Analysis of ICRH heated plasmas: torque e - /D + heating Further experiments and investigations

Advanced Course of EU PhD Network, 29 Sep 2010F. Sommer20 Difference between NBI and ECR heating its influence on transport Gyro-Bohm scaling law Examples of ECRH influence on heat transport Increase of available ECRH power increases the range of accessible parameter space to analyse heat transport. Thank You Summary and discussion