21st IAEA Fusion Energy Conference Summary Innovative Concepts Confinement

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21st IAEA Fusion Energy ConferenceSummaryInnova
tive ConceptsConfinement performance

• Jerome PAMELA, EFDA
• With the kind support of A.Becoulet (CEA),
  D.Borba (EFDA) and R.Kamendje (EFDA)

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Innovative Concepts - Z-pinches- field
reversed configurations- spheromac formation by
steady helicity injection (HIT-SI) - magnetic
dipoles (or Ring Trap) SC rings levitated /
several seconds to minutes operation X
-Divertor concept proposed to enhance the
divertor thermal capacity
RT-1 / study of Jupiters magnetosphere
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Mirror experiments
GOL3 (RF) Te 2-4 keV ne 3 1020 m-3 nTt 1018
m-3 s keV Potential for testing PFCs (ELMs,
disrup. simulation) tbc. GDT (RF) Te 0.2 keV
ne 5 1019 m-3 With 4MW NB Agreement with
theory Hanbit (US) Test divertor stabilising
m-1 MHD flute-instab.
X-Ray Tomography
GAMMA 10 (Japan)
Turbulence
Ti Increase
With ExB Sheared Layer (b)
Without
ECH Produced Layer
Radial Transport Barrier
?i / ?i-classic
Diffusivity ?i
Suppress
Cylindrical ExB Sheared Flow due to off-axis ECH
Controls Radial Transport Barrier, which improves
Core Plasma confinement. ECH (250 kW) raises
Te0750 eV with Ti06.5 keV and Till02.5 keV
T. Cho et al. EX/P7-14 Phys. Rev. Lett. 97
(2006) 055001 Phys. Rev. Lett. 94 (2005) 085002
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Toroidal Magnetic Fusion DevicesMain recent
hardware improvements on Tokamaks

• AUG
• W-coverage extended to 85 of plasma facing
  components
• New integrated control and data acquisition
  system
• diagnostics
• MAST
• JET-type NB PINI
• Pellet injection
• Diagnostics and control systems
• Divertor upgrade
• NSTX
• Modified divertor PF coils (high d)
• Diagnostics and control
• C-Mod
• boronisation
• FTU
• Li Liquid Limiter

• EAST started
• JT60
• FST inserts
• JET
• MKII-HD Divertor (high delat, 40MW capability)
• NB heating
• Several diagnostics
• DIII-D
• NB reconfigured
• Lower divertor modification allowing balanced DN
  operation with imporved density control
• diagnostics

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EAST first plasma on 26 September 2006

• Largest operating fully SC Divertor tokamak
• Nominal parameters Bt3.5T, Ip 1MA, R1.75m,
  a0.4m, single/double null
• 4.5 s shots already achieved

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JT60-U ripple reduction by Ferritic Steel Tiles

• Installation of Ferritic Steel Tiles
• gt Reduction of fast ion losses
• by 1/21/3 at 1.6T

• Larger Pabs at given Pin
• gt smaller required NB units for given bN
• gt better flexibility in NBI combination
• gt better flexibility of torque profile
• Smaller inward Er
• gt less ctr-rotation

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AUG 85 W plasma facing components
? in 2005 thin W coating of - 4 guard
limiters at LFS (water cooled) - 8 ICRH antenna
side limiters - top of bottom PSL - roof
baffle ? in 2006 - upper and lower ICRH
limiters - W coated bottom target tiles (200
mm) ?full tungsten machine in 2007
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JET Divertor modified
Up to 32 MW plasma heating achieved recently
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DIII-D Reoriented NB box allows more relevant
balanced injection heating
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Transport/Confinement Physics Experiments
Specific Stellarator studies

• Comparison of quasi-helically symmetric (QHS)
  configuration to broken symmetric configurations
  on HSX / confirmation of improved confinement in
  QHS configuration
• Extensive Core Electron Root Confinement (CERC)
  studies in helical devices (CHS, LHD, TJ-II and
  W7-AS) / collisionality threshold depends on
  magnetic configuration and ECH power
• Studies of effective ripple on confinement
  (Heliotron-J, LHD)
• Other studies reported below

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LHD study on the Confinement in High-b Regime
Degradation can be attributed to global
dependence on effective helical ripple to the
neoclassical transport not on MHD effect ?
Degradation in high b regime will be improved by
dynamic Rax control by vertical field in nearest
future
Outward shift of plasma by Shafranov shift causes
an increase of the effective helical ripple
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Transport/Confinement Physics Experiments
Rotation and Confinement
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Tore Supra toroidal rotation observed with ICRH
in correlation with confinement improvement
(L-Mode)

• Suggests sheared rotation
• Could explain confinement improvement through ITG
  and TE modes stabilization (Kinezero)

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JT60-U Pedestal parameters and confinement
improved with co-rotation in H-mode
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JET measured poloidal velocity in ITB

• Er and ExB shear much larger with measured Vq
• Weiland model with measured Vq (rather than
  neoclassical) matches experiment better

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DIII-D profiles with high / low rotation compared
to modelling confirm importance of ExB shear for
ITBs
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DIII-D Transport physics sensitive to applied
torque / Rotation
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Transport/Confinement Physics Experiments
Turbulent transport TEM, ITG, ETG
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LHD extensive parametric study of non-local Te
rise (cold pulse propagation) / anomalous
transport behaviour similar to that observed on
tokamaks / usefully extends experimental data
base to test ITG-based models
Larger dTe/dt
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ECH heated plasmas TCV Influence of plasma
triangularity on transport (L-mode)

• Gyro-fluid, gyro-kinetic models
• TEM dominant transport (mixing length) predicted
  to decrease with d, as observed

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AUG anomalous transport studies
Pure electron heating threshold for TEM at
R/LTe?3 (Similar observation on JET)
ITG-TEM transition (Er measured at r0.7) TEM
suppressed at high collisionality
Results reproduced by simulation (GS2)
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ECH heated plasmasT10 TEM dominates turbulent
transport at low collisionalities
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C-Mod TEM turbulence density fluctuation spectra
measured during ITB (ICRH heating) reproduced
by GS2 simulation
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NSTX new high resolution tangential microwave
scattering system (280 GHz) allows high
resolution of turbulence measurement

• Scattering system measures reduced dn/n from
  upper ITG/TEM to ETG kr ranges during H-mode
• Results consistent with modelling
• ITG/TEM stable during H-phase
• ETG modes could be important /
• Lower growth rate during H-mode

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Transport/Confinement Physics Experiments ETB
ITB studies
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Edge Transport Barrier Er transitions at plasma
edge in tokamaks and helical devices

• AUG Negative Er well observed at ETB, increases
  with confinement improvement
• - coincides with H-mode barrier gradient
• - Doppler reflectometry

AUG
AUG
CHS Negative radial electric field of Er 10
kV/m observed with ETB formation
CHS
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FTU ITBs in L-mode / reduced ion thermal
diffusivity
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JET Te modulation experiments show ITB as a
narrow layer with reduced heat diffusivity

• Modulated RF power deposited either side of ITB
  (at centre and at R3.6m)
• Heat wave propagates towards ITB from both sides
• Heat wave amplitude (red) damped strongly when
  wave reaches ITB
• Phase (blue) rises when heat wave approaches
  ITB, showing heat wave slows down

• ITB is a narrow layer with reduced heat
  diffusivity
• Indication of region with turbulence stabilised
  and loss of stiffness

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Transport/Confinement Physics Experiments ITB
studies role of rational q surfaces
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TJ-II role of low order rationals in core
transitions
SXR profiles

• CERC triggered by the n4/m2 rational
• Changes in both Te and Ti.
• The SXR tomography diagnostic shows a flattening
  of the profiles localized around ? 0.4 with a
  m2 poloidal structure.
• The rational must be inside the plasma to
  trigger the transition.

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JET ITB forms when qmin exists and approaches
(rather than reaches) an integer value
Te at various major radii, R, showing formation
of an ITB
ITB formation slightly ahead of Alfvén Cascades
(marking qmin integer)
Pulse No 61347
qmin reaches 2
Start of ITB formation
tAC-tITB (s)
Te (keV)
Case number
Time (s)

• Alfvén cascades seen simultaneously on
  microwave interferometer, O-mode
  interferometer, X-mode reflectometer and
  magnetic probe

• ITB formation starts before q2 surface enters
  plasma

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DIII-D similar observations / explained by GYRO
simulation (zonal flows)
Zonal flow structures with significant radial
extent / ExB shear flow needed
M.E.Austin, University of Texas
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Transport/Confinement Physics Experiments
Turbulence and Zonal Flows
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- a large number of experimental and
theoretical contributions- an overview by Pr.
Fujisawa
ZONAL FLOWS / A HIGHLIGHT
An example of extremely fruitful interaction
between Forward looking theoreticians Other
scientific Communities Smaller devices
of all type (tokamaks, helical devices
etc.) flexible and well diagnosed Larger
devices (driving specific
diagnostics improvements)
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Zonal Flow Experiments (Pr. Fujisawa Talk)
A challenge to experimentalists
- electric field or flow measurements in high
temporal and spatial resolution
More than a dozen papers have been published as a
PPCF cluster (2006).
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HL-2A , DIII-D, TJ-II - Toroidal structure of
Geodesic Acoustic Modes (GAMs) observed- GAM
interacts non-linearly with ambient turbulence
and drives forward cascade of energy to high
frequency- energy transfer between global
(parallel) flows and turbulence also observed on
helical devices
HL-2A
DIII-D
TJ-II
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CHS Energy partition between ZF and Turbulence
without/with ITB
CHS two Heavy Ion Beam Probes powerful core
plasma diagnostic
At a radius without mean Er-shear inside the
barrier
No ITB
Clear difference in energy partition
ITB
A larger fraction of zonal flows contributes to
confinement improvement inside the barrier!
Importance of zonal flows on confinement is
demonstrated.
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Extensive studies on several machinesAUG study
of parametric dependence of Geodesic Acoustic
Modes (GAMs)
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Transport/Confinement Physics Experiments
Scaling
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MAST and NSTX scaling studies
NSTX MAST in ITPA data base tE e1.03 as
compared to t98y,2 e0.58
Dedicated scans on NSTX show tE BT0.9 Ip0.4
? - ? interplay in H-mode
MAST-DIII-D comparison
Matching plasma shape, poloidal ?p, ?p and an/T2
provides a constraint on the exponents in the
power law scaling
Constraint is consistent with - gyro-Bohm
Scaling (x? -3) - weakly favourable
collisionality scaling (as observed in MAST
other devices) - ? - ? interplay in accord
with that derived from the database analysis
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Confinement in LHD Improved w.r.t. ISS95 scaling
Energy confinement time exceeding the ISS95
scaling
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scaling experiments in L mode favourable weak
dependence on b as seen in H-mode (JET DIII-D
20th FEC)

• Weak ? degradation. ? exponent -0.2
• ITER L-mode scaling -1.4
• Supported by density fluctuation measurements

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Transport/Confinement Physics Experiments
Density peaking
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Significant density peaking expected on ITER
TCV Stationary ELMy H-modes, eITBs Density
profiles are peaked despite pure electron heating
and no core source Te/Ti2 and bN2

• Peaking requires anomalous particle pinch /
  under investigation by theoreticians

n0/ltngtvol
ITER

• Scaling of density peaking to ITER
• ne0/ltnegt 1.4

Favourable for fusion power, bootstrap fraction,
density limit
?eff
Combined JET-AUG database on density peaking in
ITER Baseline ELMy H-modes / reduced
colinearities between physics variables

• Impact on impurities requires full assessment

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H-mode Core impurity peaking can be controlled
with central electron heating Transport of
impurities is turbulent
JET AUG
Turbulent transport models show peaking
dependence on Z and anomalous behaviour of high Z
impurities Transition ITG to TEM could
explain Ni peaking on JET
46

• Long pulses, steady state and
• Real Time Control (performance)

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JT60-U Fully Bootstrap-Driven Discharge

• Ip 510 kA was maintained for 1.3s with fBS
  1 (with net INB -35kA)
• Comment q95 still very high (gt10) gt higher
  current demonstration needed

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NSTX progress in current sustainment NBCD and
?p provide up to 65 of Ip

• Relative to 2004, High bN ? H89P now
  sustained 2 ? longer

Long Pulse Operation is a challenging issue for
STs
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LHD 54-Minute plasma operation
Record of input energy 1.6 GJ achieved on
LHD (Tore Supra 1 GJ at 20th FEC)
Rax 3.67-3.7m, B2.75T, PICRF 600-380 kW,
PECH110 kW
ALSO 31-minute long discharge with 680 kW ICRH
power, Te(0) and Ti (0) of 2 keV at ne of
0.8?1019m-3
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HT-7 steady state operation
Steady-state alternating current (AC) operation
Ip125kA ne(0) 1.5-2.51019m-3 Te 500 eV 30
seconds with LH 53 seconds w.o. LH
ALSO Steady state standard long pulse
achieved gt 6 minutes Ip60kA ne(0) 0.8-1 1019m-3
PLH 150kW
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JT60-U Real time qmin control with MSE
diagnostics and LHCD
Real time qmin control scheme
PNB (MW)
?N
LH
MSE
DPLH
r/a0.2
0.4
Te (keV)
qmin,ref
qMSE
qmin
0.6
jOH or jBS change

• Transport reduction at t12.4 s
• Time delay in response of qmin

PLH (MW)
MSE LH
command
qmin
ref.
Time (s)
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Tore Supra Integration of real time profile
control (LH power and n//) and InfraRed-avoidance
scheme
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JET Advanced Real Time Control Real Time
Control p(r) and q(r) profile reported at 20th
FEC gt New Dynamic-Model Approach for
Simultaneous Control of Distributed Magnetic and
Kinetic Parameters
4 actuators (NB, IC, LH PF) Dedicated
experiments to determine matrix
coefficients 2 time scale controller 2
feedback loops and one feed-forward (disturbance
rejection)
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• Not mentioned here Real Time Control of MHD
  modes (NTM, RWM)
• DIII-D, AUG, JT60-U, NSTX, RFX.
• (see Zohm Summary)

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Summary on Plasma Scenarios
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MST (Reversed Field Pinch) improved ion
confinement

• Improved-confinement RFP
• apply inductive current profile control ? reduce
  MHD activity
• reduced stochasticity, x10 confinement
  improvement, ?E 10 ms
• limitation inductive technique is transient
• gt Improved ion confinement
• sustained Ti 1 keV, ?E,i 10 ms
• fast ion confinement time gt 20 ms
• gt high ? operation with pellet injection
• ?tot 26

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LHD internal diffusion barrier (IDB) leading to
high density operation n(0)5 1020 m-3
Wp 1.1MJ, Pabs10MW ntET 4.4?1019m-3 s
keV b(0) 4.4 , ltbgt1.5 Rax 3.75m, B2.64T
Effective Core fueling by pellet injection
combined with Local Island Divertor (LID)
t1.36s
t1.136s
58
Towards more ITER-relevant conditions Advanced
H-mode (hybrid mode) on AUG
0.7 lt Ti0/Te0 lt 2.5 at high density Extension of
data base at low collisionality
59
Towards more ITER-relevant conditions DIII-D
High H-mode performance achieved with reduced
plasma rotation (balanced NB injection)
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H-ModeC-Mod performance improvement with
boronisation

• Improved pedestal results in improved global tE
  through profile stiffness
• Record pressure in tokamak
• ltpgt 1.8 atm
• at bN 1.74

61
H-ModeJET type II ELMy H-mode, similar to
AUG with QDNalthough still at relatively low
current

• ELM behaviour constant over pulse
• Very fine scale activity - distinct ELMs almost
  indistinguishable

62
Advanced ModeseITB performance on TCV

• High confinement obtained with high bootstrap
  current fraction and bpol
• In eITB region ?ne/ne0.5?Te/Te (thermo-diffusive
  pinch)

63
Advanced ModesJT60-U High ?p ELMy H-mode plasma
improved by FSTs sustained for 23 s (12?R)
HH98(y,2)2.2 fBS36-45 q953.3 Ip 0.9 MA, BT
1.6 T
1
15
10
Ip (MA)
0.5
PNBI (MW)
5
0
0
q
3
?N, HH98(y,2)
2
?N
1
0
HH98(y,2)
4
3
ne (1019 m-3)
2
ID? (a.u.)
2
1
0
0
0
5
10
15
20
25
30
35
Time (s)
?R?0lt?gta2/12 D.R. Mikkelsen, Phys. Fluids B 1
(1989) 333.
64
Advanced ModesJET ITB plasmas with active ELM
control at gt30MW with neon seeding (60 radiated
power)
JET AT database quasi-stationary (?/?Egt10)
pulses at high ?N and high ?
bN
Target for JET-EP2 AT regimes with 45MW planned
power upgrades
ELM control with Neon (4-8s) PNBLHIC30 MW
Prad17MW B3.1T, I1.9MA, q955 Wdia5.6MJ, bN2
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Advanced ModesDIII-D High performance advanced
scenarios with reversed shear and high
non-inductive current fraction
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Hybrid Mode/ towards high performance AUG q95
range of advanced H-mode extended

• 1.2MA/2.0T q95 3.17
• NBI used with beta feedback,50 of NBI is
  off-axis.
• Central ICRF heating.
• ltnegt6.4x1019m-3, Ti0/Te01.4 ltnegt/nGW0.42,
  n/nITER2.
• H98(y,2) rises to 1.4 at bN2.9
• CW,core 2.5x10-5 (lt 10-4).
• Core MHD
• (1,1) fishbones.
• (4,3) NTMs.
• NO sawteeth.
• Early (3,2) NTM when bN 2.

20449
Ip (MA)
1.2
Da
0
PNBI (MW)
8
PICH (MW)
0
even n
odd n
3
bN
1
H98(y,2)
0
0
2
4
6
time (s)
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Hybrid Mode/ towards high performance JET
Hybrid modes at low q953 reach bN3
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ConclusionPhysics (transport and confinement)

• Density peaking
• significant peaking expected on ITER
• a puzzle to theory and modelling
• Weak (inverse) dependence of confinement on beta
  consolidating favourable to ITER
• A hot topic role of rational surfaces on ITB
  formation
• Could be linked to Zonal Flows
• Importance of rotation rotation shear confirmed
  / growing interest towards more ITER relevant
  rotation patterns
• Extensive studies of turbulence (TEM, ITG, ETG)
• Dramatic progress on physics of Zonal Flows and
  their interplay with turbulence

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Conclusion Plasma scenarios

• Stellarator
• LHD ne(0) 5 1020 m-3
• Tokamaks ITER relevant scenarios
• Real Time Control expanding getting more
  integrated
• Operation at more ITER relevant parameters
  (rotation, n, Te/Ti, n/nG)
• ELMy H-mode
• some progress towards type-II ELMy H-mode (low
  Ip yet / no scaling available)
• C-Mod 1.8 Atm in H-mode
• Progress on ITB regimes
• GH89bN/q295 up to 0.4, above ITER target, in
  steady state with dominant NI current
• Rapid developments on Hybrid regimes
• extension of operational space
• in particular demonstration at q95 3 (improved
  fusion performance)
• GH89bN/q295 gt 0.45 in steady state regimes with
  0.3-0.5 B.S. current
• - r, n, bN scans needed to develop scaling to
  ITER gt IN GENEVA !