1. technology and computing

Status and Prospects of Nuclear Fusion
Using Magnetic Confinement
Hartmut Zohm
Max-Planck-Institut für Plasmaphysik, Garching, Germany
Invited Talk given at DPG Frühjahrstagung, AKE, Berlin, 17.03.2014
• Nuclear Fusion using Magnetic Confinement
• Fusion Roadmap and Roadmap Elements
• The German Contribution
• Summary and Conclusions
• Nuclear Fusion using Magnetic Confinement
• Fusion Roadmap and Roadmap Elements
• The German Contribution
• Summary and Conclusions
A simplistic view on a Fusion Power Plant
Pin = 50 MW
Pout = 2-3 GWth
(initiate and control
burn)
(aiming at 1 GWe)
The ‚amplifier‘ is a thermonuclear plasma burning hydrogen to helium
Centre of the sun: T ~ 15 Mio K, n  1032 m-3, p ~ 2.5 x 1011 bar
A bit closer look…
Pin = 50 MW
Pout = 2-3 GWth
(initiate and control
burn)
(aiming at 1 GWe)
3.5 MeV
a-heating
14.1 MeV
wall loading
Fusion reactor: magnetically confined plasma, D + T → He + n + 17.6 MeV
Centre of reactor: T = 250 Mio K, n = 1020 m-3, p = 8 bar
Schematic layout of a Fusion Power Plant
Magnetic confinement
The goal is to generate and sustain a plasma of 25 keV and 1020 m-3
This can be done in a toroidal system to avoid end losses
helical magnetic field lines to compensate particle drifts
Plasma can be confined in a magnetic field
'Stellarator': magnetic field exclusively produced by coils
Example: Wendelstein 7-X (IPP Greifswald)
Plasma can be confined in a magnetic field
'Tokamak': poloidal field component from current on plasma
Simple concept, but not inherently stationary!
Example: ASDEX Upgrade (IPP Garching)
The promise of fusion power plants
Supply of base load electricity (not dependent on externals)
• complementary to stochastic sources like wind or solar
Sustainable energy source (fusion fuel available for many 1000s of years)
• Deuterium e.g. from sea water
• T will be bred from Li in the innermost part of the reactor
Fusion energy will be environmentally friendly
• no CO2 emission
• no uncontrolled chain reaction
• radioactive waste (= structural materials) relatively short-lived
The road to Fusion Energy holds many challenges
Fusion plasma physics
• heat insulation of the confined plasma
• exhaust of heat and particles
• magnetohydrodynamic (MHD) stability of configuration
• self-heating of the plasma by fusion born a-particles
Fusion specific technology
• plasma heating
• fuel cycle including internal T-breeding from Li
• development of suitable materials in contact with plasma
The road to Fusion Energy holds many challenges
Fusion plasma physics
• heat insulation of the confined plasma
• exhaust of heat and particles
• magnetohydrodynamic (MHD) stability of configuration
• self-heating of the plasma by fusion born a-particles
Fusion specific technology
• plasma heating
• fuel cycle including internal T-breeding from Li
• development of suitable structural and first wall materials
• Nuclear Fusion using Magnetic Confinement
• Fusion Roadmap and Roadmap Elements
• The German Contribution
• Summary and Conclusions
The European Roadmap to Fusion Electricity
A step-ladder of fusion experiments to ITER
ASDEX Upgrade (IPP)
Major Radius
Volume
Fusion Power
1.65 m
14 m3
1.5 MW
(D-T equivalent)
JET (EU)
ITER
3m
80 m3
~ 16 MWth
(D-T)
6.2 m
800 m3
~ 400 MWth
(D-T)
The machine has to be big in order to have sufficient heat insulation (tE)
The step from ITER to DEMO
ITER = proof of principle for dominantly a-heated plasmas
DEMO = proof of principle for reliable large scale electricity production
DEMO must be larger: 6.2 m  8.5 m, 400 MW  ~ 2 GW
This brings new challenges for physics (and technology)
• higher density, higher pressure (stability!)
• higher power density (Pfus~R3, Atarget~ R)
• need for long pulse or steady state
(tokamak presently a pulsed system)
 We will not run out of work in near future!
• also alternative magnetic confinement
concepts must be studied
Tokamak
(ASDEX Upgrade, JET, ITER)
The step from ITER to DEMO
ITER = proof of principle for dominantly a-heated plasmas
DEMO = proof of principle for reliable large scale electricity production
DEMO must be larger: 6.2 m  7.5 m, 400 MW  ~ 2 GW
This brings new challenges for physics (and technology)
• higher density, higher pressure (stability!)
• higher power density (Pfus~R3, Atarget~ R)
• need for long pulse or steady state
(tokamak presently a pulse system)
 We will not run out of work in near future!
• also alternative magnetic confinement
concepts must be studied
Example: W7-X stellarator (IPP Greifswald)
Stellarator
(W7-X)
The Role of Stellarators in the EU Roadmap
 Using technology developed on a tokamak DEMO, stellarator can be
candidate for a Fusion Power Plant in the 2050s
• Nuclear Fusion using Magnetic Confinement
• Fusion Roadmap and Roadmap Elements
• The German Contribution
• Summary and Conclusions
German Fusion Programme: Combined Expertise
Stellarator Physics
and Technology
Plasma Wall
Interactions
Fusion
Technology
Tokamak
Physics and
Technology
Unique combination of physics and technology
Coordinated effort through ‚German DEMO Working Group‘
German DEMO Working Group: Roadmap Elements
7 Roadmap Elements that need to be tackled in any Roadmap
have been identified
 RE1: Consistent Tokamak Scenarios
 RE2: Consistent Stellarator Scenarios
 RE3: Enduring Exhaust of Power and Particles
 RE4: Safety – Public Accpetance and Licensing
 RE5: Sustainability – Tritium Self-sufficiency & Low Activation
 RE6: Economic Viability – Efficiency / Reliability / Availability
 RE7: Stellarator Specific Technology
The following examples highlight how these Roadmap Elements
bring together the expertise of Fusion Research in Germany
Tokamak Scenarios (RE1) / Economic Viability (RE6)
KIT, 1MW,
105 – 165 GHz
SP prototype
Mode for
237 GHz
coax gyrotron
Simulation of fully
noninductive DEMO
scenario
TE49,29
Brewster-angle
technology
(CVD Diamond
window)
 Realistic fully noninductive scenario may require substantial PCD
 Sets the goals for future gyrotron development at f > 200 GHz
 Issues of controllability must be incorporated from the start
Exhaust of Power and Particles (RE3)
W-divertor
in ITER
He-cooled
divertor
for DEMO
 Combined physics / technology requirements: P/Rsep  15 MW/m,
Ptarget  5 MW/m2, Te,div  5 eV
 Optimised technology solution may be He-cooled divertor
Stellarator Scenarios (RE2) & Technology (RE7)
Plasma Geometry
R ( s, u , v ) 
z ( s, u , v ) 
Modular Coils
/ Blanket
Island Divertor

( s) cos( mu  Nnv)

m 0 n   nmax
 V , A, reff
mmax nmax

z
(
s
)
sin(
mu

Nnv
)
  m,n

m  0 n   nmax
mmax
nmax
 R
m,n
Plasma geometry described
by Fourier coefficients of
LCFS obtained from VMEC.
Existing coil design of Helias
5-B builds model basis which
is scaled as input.
Model relates power crossing
separatrix to effective wetted
area to estimate heat load.
• Stellarator specifics are incorporated into tokamak systems codes
• Critical elements in physics and technology will be assessed
Stellarator Scenarios (RE2) & Technology (RE7)
Plasma Geometry
R ( s, u , v ) 
z ( s, u , v ) 
Modular Coils
/ Blanket
Island Divertor

( s) cos( mu  Nnv)

m 0 n   nmax
 V , A, reff
mmax nmax

z
(
s
)
sin(
mu

Nnv
)
  m,n

m  0 n   nmax
mmax
nmax
 R
m,n
Plasma geometry described
by Fourier coefficients of
LCFS obtained from VMEC.
Existing coil design of Helias
5-B builds model basis which
is scaled as input.
Model relates power crossing
separatrix to effective wetted
area to estimate heat load.
• Stellarator specifics are incorporated into tokamak systems codes
• Critical elements in physics and technology will be assessed
Stellarator Scenarios (RE2) & Technology (RE7)
Plasma Geometry
R ( s, u , v ) 
z ( s, u , v ) 
Modular Coils
/ Blanket
Island Divertor

( s) cos( mu  Nnv)

m 0 n   nmax
 V , A, reff
mmax nmax

z
(
s
)
sin(
mu

Nnv
)
  m,n

m  0 n   nmax
mmax
nmax
 R
m,n
Plasma geometry described
by Fourier coefficients of
LCFS obtained from VMEC.
Existing coil design of Helias
5-B builds model basis which
is scaled as input.
Model relates power crossing
separatrix to effective wetted
area to estimate heat load.
• Stellarator specifics are incorporated into tokamak systems codes
• Critical elements in physics and technology will be assessed
• Nuclear Fusion using Magnetic Confinement
• Fusion Roadmap and Roadmap Elements
• The German Contribution
• Summary and Conclusions
Conclusions
Significant progress of understanding in all basic areas of Nuclear Fusion
research by developing plasma physics and technology base
• core plasma parameters sufficient for generation of fusion energy
• technical systems mature for controlling thermonuclear plasma
Nuclear Fusion research is ready for the next step
• ITER will be built in an international effort
• will allow qualitatitvely new studies: exploring plasmas with
dominant a-heating
The step to DEMO and a Fusion Power Plant builds on ITER but must
be prepared in due time
• adress physics and technology in an integrated way
• bring in the stellarator line in a consistent manner