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![Page 1: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/1.jpg)
Standard and Advanced TokamakOperation Scenarios for ITER
Hartmut Zohm
Max-Planck-Institut für Plasmaphysik, Garching, Germany
EURATOM Association
Lecture given at PhD Network Advanced Course, Garching, 06.10.2010
• What is a ‘tokamak (operational) scenario’?
• Short recap of fusion and tokamak physics
• Conventional scenarios
• Advanced scenarios
• Summary and conclusions
![Page 2: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/2.jpg)
What is a ‚tokamak scenario‘?
p = 1Ip = 800 kAfNI = 37%
p = 1Ip = 800 kAfNI = 14%
A tokamak (operational) scenario is a recipe to run a tokamak discharge
Plasma discharge characterised by
• external control parameters: Bt, R0, a, , , Pheat, D…
• integral plasma parameters: = 20<p>/B2, Ip = 2 j(r) r dr…
• plasma profiles: pressure p(r) = n(r)*T(r), current density j(r)
operational scenario best characterised by shape of p(r), j(r)
curr
en
t d
en
sity
(a
.u.)
curr
en
t d
en
sity
(a
.u.)
total j(r)noninductive j(r)
total j(r)noninductive j(r)
![Page 3: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/3.jpg)
Control of the profiles j(r)and p(r) is limited
• ohmic current coupled to temperature profile via ~ T3/2
inductive current profiles always peaked, q-profiles monotonic
• external heating systems drive current, but with limited efficiency (typically less than 0.1 A per 1 W under relevant conditions)…
• pressure gradient drives toroidal ‘bootstrap’ current: jbs ~ (r/R)1/2 p/Bpol
safety factor:
p
tor
pol
tor
IB
Rr
BB
Rr
q2
ITER simulation(CEA Cadarache)
![Page 4: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/4.jpg)
Control of the profiles j(r)and p(r) is limited
Pressure profile determined by combination of heating / fuellingprofile and radial transport coefficients
• ohmic heating coupled to temperature profile via ~T3/2
• external heating methods allow for some variation – ICRH/ECRH deposition determined by B-field, NBI has usually broad profile
• gas puff is peripheral source of particles, pellets further inside
but: under reactor-like conditions, dominant -heating ~ (nT)2
![Page 5: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/5.jpg)
Control of the profiles j(r)and p(r) is limited
Pressure profile determined by combination of heating / fuellingprofile and radial transport coefficients
• anomalous (turbulent) heat transport leads to ‘stiff’ temperature profiles (critical gradient length T/T) – except at the edge
• density profiles not stiff due to existence of ‘pinch’
![Page 6: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/6.jpg)
Control of the profiles j(r)and p(r) is limited
Stiffness can be overcome locally by sheared rotation
• edge transport barrier (H-mode)
• internal transport barrier (ITB)
![Page 7: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/7.jpg)
• What is a ‘tokamak (operational) scenario’?
• Short recap of fusion and tokamak physics
• Conventional scenarios
• Advanced scenarios
• Summary and conclusions
![Page 8: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/8.jpg)
Aim is to generate power, so
• Pfusion/Pheat (power needed to sustain plasma) should be high
• Pheat determined by thermal insulation:
E = Wplasma/Pheat (energy confinement time)
In present day experiments, Pheat comesfrom external heating systems
• Q = Pfus/Pext Pfus/Pheat ~ nTE
In a reactor, Pheat mainly by -(self)heating:
• Q = Pfus/Pext (ignited plasma)
The aim is to generate and sustain a plasma of T ~ several 10 keV, E ~ several seconds and n ~ 1020 particles / m3
Figure of merit for fusion performance nT
![Page 9: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/9.jpg)
Optimising nT means high pressure and, for given magnetic field,high = 20 <p> / B2
This quantity is limited by magneto-hydrodynamic (MHD) instabilities
‘Ideal’ MHD limit (ultimate limit, plasma unstable on Alfvén time scale ~ 10 s,only limited by inertia)
• ‘Troyon’ limit max ~ Ip/(aB), leads to definition of N = /(Ip/(aB))
• at fixed aB, shaping of plasma cross- section allows higher Ip (low q limit, see later) higher
• additionally, alsoN,max improves with shaping of poloidal cross-section
Optimisation of nT: ideal pressure limit
N=/(I/aB)=3.5
[%]
![Page 10: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/10.jpg)
Optimising nT means high pressure and, for given magnetic field,high = 20 <p> / B2
This quantity is limited by magneto-hydrodynamic (MHD) instabilities
‘Resistive’ MHD limit (on local current redistribution time scale ~ 100 ms)
ASDEX Upgrade
Optimisation of nT: resistive pressure limit
![Page 11: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/11.jpg)
Optimising nT means high pressure and, for given magnetic field,high = 20 <p> / B2
This quantity is limited by magneto-hydrodynamic (MHD) instabilities
‘Resistive’ MHD limit (on local current redistribution time scale ~ 100 ms)
• ‘Neoclassical Tearing Mode’ (NTM) driven by loss of bootstrap current within magnetic island
Optimisation of nT: resistive pressure limit
![Page 12: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/12.jpg)
Since T has an optimum value at ~ 20 keV, n should be as high as possible
• density is limited by disruptions due to excessive edge cooling
• empirical ‘Greenwald’ limit, nGr ~ Ip/(a2) high Ip helps to obtain high n
qedge = 2
1/q
edge
(no
rma
lise
d c
urr
en
t)
Optimisation of nT: density limit
![Page 13: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/13.jpg)
BUT: for given Bt, Ip is limited by current gradient driven MHD instabilities
Limit to safety factor q ~ (r/R) (Btor/Bpol)
• for q < 1, tokamak unconditionally unstable central ‘sawtooth’ instability
• for qedge 2, plasma tends to disrupt (external kink) – limits value of Ip
Hugill diagramfor TEXTOR JET
qedge = 2
normalised density
1/q
edge
(no
rma
lise
d c
urr
en
t)
Optimisation of nT: current limit
![Page 14: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/14.jpg)
Empirical confinement scalings show linear increase of with Ip
• note the power degradation (E decreases with Pheat!)
• ‘H-factor’ H measures the quality of confinement relative to the scaling
Optimisation of nT: confinement scaling
Empirical ITER 98(p,y) scaling:
E ~ H Ip0.93 Pheat
-0.63 Bt
0.15…
![Page 15: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/15.jpg)
N.B: for steady state tokamak operation, high Ip is not desirable:
Tokamak operation without transformer: current 100% noninductive
• external CD has low efficiency (remember less than 0.1 A per W)
• internal bootstrap current high for high jbs ~ (r/R)1/2 p/Bpol
fNI ~Ibs/Ip ~p/Bpol2 ~ pol
‘Advanced’ scenarios, which aim at steady state, need high , low Ip,have to make up for loss in E by increasing H
Without the ‘steady state’ boundary condition, a tokamak scenariois called ‘conventional’
N.B.2: ‘Long Pulse’ = stationary on all intrinsic time scales
‘Steady State’ = can be run forever
Tokamak optimisation: steady state operation
![Page 16: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/16.jpg)
• What is a ‘tokamak (operational) scenario’?
• Short recap of fusion and tokamak physics
• Conventional scenarios
• Advanced scenarios
• Summary and conclusions
![Page 17: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/17.jpg)
Standard scenario without special tailoring of geometry or profiles
• central current density usually limited by sawteeth
• temperature gradient sits at critical value over most of profile
• extrapolates to very large (R > 10 m, Ip > 30 MA) pulsed reactor
The (low confinement) L-mode scenario
![Page 18: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/18.jpg)
The (high confinement) H-mode scenario
With hot (low collisionality) conditions, edge transport barrier develops
• gives higher boundary condition for ‘stiff’ temperature profiles
• global confinement E roughly factor 2 better than L-mode
• extrapolates to more attractive (R ~ 8 m, Ip ~ 20 MA) pulsed reactor
![Page 19: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/19.jpg)
‘Hot’ (low collisionality) edge by divertor operation
• plasma wall interaction in well defined zone further away from core plasma
• possibility to decrease T, increase n along field lines (p=const.)
• high edge temperature gives access to edge transport barrier, if enough heating power is supplied (‘power threshold for H-mode’)
![Page 20: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/20.jpg)
Mechanism for edge transport barrier formation
• in a very narrow (~1 cm) layer at the edge very high plasma rotation develops (E = v x B several 10s of kV/m)
• sheared edge rotation tears turbulent eddies apart
• smaller eddy size leads to lower radial transport (D ~ r2/decor)
xB
![Page 21: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/21.jpg)
Stationary H-modes usually accompanied by ELMs
Edge Localised Modes (ELMs) regulate edge plasma pressure
• without ELMs, particle confinement ‚too good‘ – impurity accumulation
![Page 22: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/22.jpg)
Stationary H-modes usually accompanied by ELMs
But: ELMs may pose a serious threat to the ITER divertor
• large ‘type I ELMs’ may lead to too high divertor erosion
acceptable lifetimefor 1st ITER divertor
![Page 23: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/23.jpg)
-limit in H-modes usually set by NTMs
Present day tokamaks limited by (3,2) or (2,1) NTMs (latter disruptive)
• while onset N is acceptable in present day devices, it may be quite low in ITER due to unfavourable p
* scaling (rather than machine size)
![Page 24: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/24.jpg)
H-mode is ITER standard scenario for Q=10…
The design point allows for…
• …achieving Q=10 with conservative assumptions
• …incorporation of ‚moderate surprises‘
• …achieving ignition (Q ) if surprises are positive
H = E,ITER/E,predicted
Density lim
it
(Greenwald)
Access to edge transport barrier
Pressure drivenMHD instabilities
![Page 25: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/25.jpg)
…but some open issues remain…
Need to minimise ELM impact on divertor
• reduce power flow to divertor by radiative edge cooling
• special variants of the scenario (Quiescent H-mode, type II ELMs)
• ELM mitigation – pellet pacing or Resonant Magnetic Perturbations
Need to tackle NTM problem
• NTM suppression by Electron Cyclotron Current Drive demonstrated, but have to demonstrate that this can be used as reliable tool
![Page 26: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/26.jpg)
ELM control by pellet pacing
Injection of pellets triggers ELMs – allows to increase ELM frequency
• at the same time, ELM size decreases and peak power loads are mitigated
ASDEX Upgrade
![Page 27: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/27.jpg)
ELM control by Resonant Magnetic Perturbations
Static error field resonant in plasma edge can suppress ELMs
• removes ELM peaks but keeps discharge stationary with good confinement
• very promising, but physics needs to be understood to extrapolate to ITER
DIII-D
![Page 28: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/28.jpg)
Active control is possible by generating a localised helical current in the island to replace the missing bootstrap current
NTM control by Electron Cyclotron Current Drive
![Page 29: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/29.jpg)
Suppression of (2,1) NTM by ECCD
ASDEX Upgrade
![Page 30: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/30.jpg)
Current drive (PECRH / Ptotal = 10-20 %) results in removal
method has the potential for reactor applications
Suppression of (2,1) NTM by ECCD
ASDEX Upgrade
![Page 31: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/31.jpg)
• What is a ‘tokamak (operational) scenario’?
• Short recap of fusion and tokamak physics
• Conventional scenarios
• Advanced scenarios
• Summary and conclusions
![Page 32: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/32.jpg)
Advanced scenarios aim at stationary (transformerless) operation
• external CD has low efficiency (remember less than 0.1 A per W)
• internal bootstrap current high for high jbs ~ (r/R)1/2 p/Bpol
fNI ~Ibs/Ip ~p/Bpol2 ~ pol
Recipe to obtain high bootstrap fraction:
• low Bpol, i.e. high q – elevate or reverse q-profile (q=(r/R)(Btor/Bpol))
• eliminates NTMs (reversed shear, no low resonant q-surfaces)
• high pressure where Bpol is low, i.e. peaked p(r)
Both recipes tend to make discharge ideal MHD (kink) unstable!
In addition, jbs profile should be consistent with q-profile
Advanced tokamak – the problem of steady state
![Page 33: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/33.jpg)
A self-consistent solution is theoretically possible
• reversing q-profile suppresses turbulence – internal transport barrier (ITB)
• large bootstrap current at mid-radius supports reversed q-profile
Advanced tokamak – the problem of steady state
conventional
j(r)
q(r)
jbs(r)
p(r)
ASDEX Upgrade
![Page 34: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/34.jpg)
Broad current profile leads to low kink stability (low -limit):
• can partly be cured by close conducting shell, but kink instability then grows on resistive time scale of wall (Resistive Wall Mode RWM)
• can be counteracted by helical coils, but this needs sophisticated feedback
Position of ITB and minimum of q-profile must be well aligned
• needs active control of both p(r) and j(r) profiles – difficult with limited actuator set (and cross-coupling between the profiles)
Problems of the Advanced tokamak scenario
![Page 35: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/35.jpg)
RWM control by Resonant Magnetic Perturbations
Feedback control using RMPs shows possibility to exceed no-wall limit
• rotation plays a strong role in this process and has to be understood better (ITER is predicted to have very low rotation)
![Page 36: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/36.jpg)
Good performance can only be kept for several confinement times, notstationary on the current diffusion time (10 – 50 E in these devices)
Advanced Tokamak Stability is a tough Problem
duration/E
0.0
0.2
0.4
0.6
0.8
duration/E
Hybrid scenarios: Reversed shear scenarios
ITER reference (Q=10)
ITER advanced (Q=5)
QDB scenarios
40 60 80 0 20 40 60 800 20 40 60 80
JET, JT-60U
DIII-D
AUGDIII-DJT-60UJETTore Supra
Fus
ion
Per
form
ance
(~
nT E
)
![Page 37: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/37.jpg)
Control of ITB dynamics is nontrivial
Example: modelling of steady-state scenario in ITER – delicate internaldynamics that may be difficult to control with present actuator set
CRONOS Code (CEA)
![Page 38: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/38.jpg)
Hybrid operation aims at flat, elevated q-profile discharges with high q(0)
Not clear if this projects to steady state, but it will be very long pulse…
Reversed shear, ITB discharges
+ very large bootstrap fraction
+ steady state should be possible
- low -limit (kink, infernal, RWM)
- delicate to operate
Zero shear, ‘hybrid’ discharges
+ higher -limit (NTMs)
+ ‘easy’ to operate
- smaller bootstrap fraction
- have to elevate q(0) (also avoids sawteeth, NTMs)
0
1
2
3
4
5
0 0.5 1r/a
strong
weak
q-profiles
StandardH-mode
~ zero shear
Reversedshear
0
1
2
3
4
5
0 0.5 1r/a
strong
weak
q-profiles
StandardH-mode
~ zero shear
Reversedshear
A compromise: the ‚hybrid‘ scenario
![Page 39: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/39.jpg)
A ‘hybrid scenario’: the improved H-mode
0.1
0.3
0.5
0.7H89N/q95
2
0.1 0.3 0.5 0.7 0.9 1.1
(a/R)p
3-44-55-66-7
q-range
~ Bootstrap fraction
ITER
(sha
pe co
rrecte
d)
Improved H-mode (discovered on AUG) is best candidate for ‘hybrid’ operation
• projects to either longer pulses and/or higher fusion power in ITER
• flat central q-profile, avoid sawteeth – need some current profile control
Fus
ion
Per
form
ance
(~
nT E
)
![Page 40: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/40.jpg)
0.0
0.2
0.4
0.6
0.8
duration/E
H89 N
/q95
2
0.0
0.2
0.4
0.6
0.8
duration/E
H89 N
/q95
2
Hybrid scenarios: Reversed shear scenarios
ITER reference (Q=10)
ITER advanced (Q=5)
QDB scenarios
0 20 40 60 80 0 20 40 60 800 20 40 60 80
JET, JT-60U
DIII-D
AUGDIII-DJT-60UJETTore Supra
Presently, hybrid scenarios perform better in fusion power and pulse length
A ‘hybrid scenario’: the improved H-modeF
usio
n P
erfo
rman
ce (
~ n
T E
)
![Page 41: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/41.jpg)
• What is a ‘tokamak (operational) scenario’?
• Short recap of fusion and tokamak physics
• Conventional scenarios
• Advanced scenarios
• Summary and conclusions
![Page 42: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/42.jpg)
Summary and Conclusions
A variety of tokamak operational scenarios exists
• L-mode: low performance, pulsed operation, no need for profile control
• H-mode: higher performance, pulsed operation, MHD control needed
• Advanced modes: higher performance, steady state, needs profile control
0
1
2
3
4
5
0 0.5 1r/a
strong
weak
q-profiles
StandardH-mode
~ zero shear
Reversedshear
0
1
2
3
4
5
0 0.5 1r/a
strong
weak
q-profiles
StandardH-mode
~ zero shear
Reversedshear
L-modeH-mode
Advancedoperation
Saf
ety
fact
or
q
Hybrid
![Page 43: Standard and Advanced Tokamak Operation Scenarios for ITER Hartmut Zohm Max-Planck-Institut für Plasmaphysik, Garching, Germany EURATOM Association Lecture.](https://reader034.fdocuments.in/reader034/viewer/2022051215/56649cdc5503460f949a7033/html5/thumbnails/43.jpg)
Summary and Conclusions
ITER aims at operation in conventional and advanced scenarios
• demonstrating Q=10 in conventional (conservative) operation scenarios
• demonstrating long pulse (steady state) operation in ‚advanced‘ scenarios
One mission of ITER and the accompanying programme is to develop andverify an operational scenario for DEMO
• DEMO scenario must be a point design (no longer an experiment)
• actuators even more limited (e.g. maximum of 2 H&CD methods)
Scenario: Standard Low q Hybrid Advanced
Ip [MA] 15 17 13.8 9Bt [T] 5.3 5.3 5.3 5.18N 1.8 2.2 1.9 3Pfus [MW] 400 700 400 356Q 10 20 5.4 6tpulse [s] 400 100 1000 3000