Fyzika tokamaků1: Úvod, opakování1 Tokamak Physics Jan Mlynář 8. Heating and current drive...
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Transcript of Fyzika tokamaků1: Úvod, opakování1 Tokamak Physics Jan Mlynář 8. Heating and current drive...
Fyzika tokamaků 1: Úvod, opakování 1
Tokamak PhysicsJan Mlynář
8. Heating and current drive
Neutral beam heating and current drive, ... to be continued
Neutral Beam Injection: principle
Ion source
Neutral
beam
Electricity -> other form(kinetic energy of particles)
Transport to plasma (outside part)
Neutraliser
Magnetic
filter
Beam duct
(inside part)
Accellerator
Ionisation Thermalisation
NBI Principle, in more detail
I E Day
Size matters – ITER beamline vs Torus
I E Day
power and pulse length for ITER
0
5
10
15
20
0 1000 2000 3000 4000 5000
pulse length (s)
po
wer
/be
amlin
e (M
W)
I E Day
Evolution from Present Status - ITER
Tokamak Physics 6
Neutral beam heating
8: Heating and current drive
= 2.9.1017
Tokamak Physics 7
Neutral beam heating
8: Heating and current drive
Tokamak Physics 8
Neutral beam heating
8: Heating and current drive
Tokamak Physics 9
Beam slowing
8: Heating and current drive
Tokamak Physics 10
Distribution function
8: Heating and current drive
Tokamak Physics 11
Beam current drive
8: Heating and current drive
Wave heating
Electricity -> other form(electromagnetic oscillations)
Transport to plasma (outside part)transmission linesantenna
(inside part)waves
Thermalisation
Antenna
Wave to particles
Resonance zone
R
Classification of waves
• phase velocity
– fast
– slow
• direction of propagation
– k parallel to B0: according to polarisation
(with respect to B0, in other fields of science –e.g. optics- wrt propagation direction)
• right -> direction of rotation of electrons
• left -> direction of rotation of ions
– k perpendicular to B0
• ordinary: E1 // B0
• extraordinary: E1 perp to B0
Tokamak Physics 14
Wave Heating
8: Heating and current drive
Review of Plasma Waves
Tokamak Physics 15
Wave Heating
8: Heating and current drive
Dielectric Tensor
Tokamak Physics 16
Wave Heating
8: Heating and current drive
Classification of waves
Tokamak Physics 17
Wave Heating
8: Heating and current drive
Resonances, Cut-offs
Tokamak Physics 18
Wave Heating
8: Heating and current drive
Resonances, Cut-offs
Tokamak Physics 19
Wave Heating
8: Heating and current drive
Energy flow
Tokamak Physics 20
Wave Heating: Ray tracing
8: Heating and current drive
Tokamak Physics 21
Wave Heating: Ray tracing
8: Heating and current drive
ASDEX-U
Tokamak Physics 22
Wave Heating: Ray tracing
8: Heating and current drive
Mode conversion
Boundary conditions
Tokamak Physics 23
Wave Heating: CMA diagram
8: Heating and current drive
In each region, the topological form of thephase velocity remain unchanged. Fast wave is outside (the wave front in vacuumwhich would always be a circle) slow wave is inside.E.g. in the top left region (high B, low n) the X/L wave is slow, the O/R wave is fast(X and O have k || B, L and R have k ┴ B)
Tokamak Physics 24
Ion Cyclotron Heating
8: Heating and current drive
ii
eB
m fast wave ~ tens of MHz
Plasma edge cutoff below 18 32 10 mn
heatingon harmonic frequencies
on minorities (e.g. on H in D plasmas)
Resonant layer is vertical at 1
TB R
Heating on harmonics vL
energies often higher than Ec
relaxation is mostly due to heating of electrons
Tokamak Physics 25
Ion Cyclotron Heating
8: Heating and current drive
Tokamak Physics 26
Ion Cyclotron Heating
8: Heating and current drive
Heating on minorities:
Decreases with increasing concentration, however,
new “ion-ion” hybrid resonance emerges.
May result in IBW (Ion Bernstein Wave)
can drive electrons
Disadvantage: strongly sensitive on minority concentration
ICRHadvantages: Economic, powerful, important ion heating
disadvantages: high E, problems with reflected power (ELMs),
(“coupling of waves to plasma”, in particular
problems with ELMs), non-directional.
Plasma edge – evanescent region (cutoff below )
i.e. “waves tunnels through”
The antenna produces a wide spectrum
wide spectrum of fast electrons due to
the Landau damping current drive
Tokamak Physics 27
Lower Hybrid Resonance
8: Heating and current drive
Slow wave at a small angle to B ~ GHz long path to the resonant region Landau damping along the path turns out
to be more important than LH itself
18 310 mn
k
Reminder: The current drive would not exist if
distribution of velocities of plasma particles were
flat. However, Maxwellian distribution is not flat,
which means wave can locally flatten the
distribution in the direction of the wave
propagation.
Tokamak Physics 28
Lower Hybrid Resonance
8: Heating and current drive
Mode converter
Equally split the RF power in 3 in the poloidal direction
1 input & 3 outputs WR-229 Conversion efficiency: 98.65 % Return Loss: -20.5dB
J. Hilairet
i
a ca
r mf
c ar ed h
i
a ca
r mf
c ar ed h
LH - Wave Propagation
Depends onne and B
Antenna structure
Tokamak Physics 31
Electron Cyclotron Resonance
8: Heating and current drive
~ 28 [T] GHz (~ mm)B
Advantages : no evanescent region
highly directional
highest achievable power density
Disadvantages: acts only on electrons
expensive
new technology (less reliable)
Highly directional profile controle.g. suppression of NTMs (mg. islands)
Tokamak Physics 32
Electron Cyclotron Resonance
8: Heating and current drive
Tokamak Physics 33
Electron Cyclotron Resonance
8: Heating and current drive
Tokamak Physics 34
Electron Cyclotron Resonance
8: Heating and current drive
Current Drive (ECCD)
Other applications of ECR:
3
1~
v
1) Fisch – Boozer
directional increase of decreases
2) Ohkawa
increase of pushes passing particles
into the trapped region (opposite direction to the Fisch - Boozer)
lower momentum loss
v
v
- plasma heating- current profile control for advanced regimes- transport studies via modulated ECRH- plasma start-up assistance - wall conditioning (ITER)
Tokamak Physics 35
Bulk and Tail Current Drive
8: Heating and current drive
Tokamak Physics 36
ITER ECR system
8: Heating and current drive
24 x 1 MW, 170 GHz gyrotrons
3 x 1 MW, 120 GHz gyrotrons for SUA
wave guide switch to …
equatorial or upper launcher
Tokamak Physics 37
ITER ECR Upper Port
8: Heating and current drive
• 3 ports with 8 beams in two rows• Main function: NTM (and sawtooth) control• Front steering
– In vertical direction to scan radial deposition
– Well focussed for optimised localization at q=3/2 and 2