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,

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 The ‚amplifier‘ is a thermonuclear plasma burning hydrogen to helium Centre of the sun: T ~ 15 Mio K, n  m -3, p ~ 2.5 x bar P in = 50 MW (initiate and control burn) P out = 2-3 GW th (aiming at 1 GW e )

A bit closer look… Fusion reactor: magnetically confined plasma, D + T → He + n MeV Centre of reactor: T = 250 Mio K, n = m -3, p = 8 bar 3.5 MeV 14.1 MeV  -heating wall loading P in = 50 MW (initiate and control burn) P out = 2-3 GW th (aiming at 1 GW e )

Schematic layout of a Fusion Power Plant

The goal is to generate and sustain a plasma of 25 keV and m -3 This can be done in a toroidal system to avoid end losses helical magnetic field lines to compensate particle drifts Magnetic confinement

'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) Plasma can be confined in a magnetic field

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 CO 2 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  -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  -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

JET (EU) 3 m 80 m 3 ~ 16 MW th (D-T) ITER 6.2 m 800 m 3 ~ 400 MW th (D-T) Major Radius Volume Fusion Power ASDEX Upgrade (IPP) 1.65 m 14 m MW (D-T equivalent) A step-ladder of fusion experiments to ITER The machine has to be big in order to have sufficient heat insulation (  E )

ITER = proof of principle for dominantly  -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 (P fus ~R 3, A target ~ 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 The step from ITER to DEMO Tokamak (ASDEX Upgrade, JET, ITER)

ITER = proof of principle for dominantly  -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 (P fus ~R 3, A target ~ 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) The step from ITER to DEMO 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 Unique combination of physics and technology Coordinated effort through ‚German DEMO Working Group‘ Stellarator Physics and Technology Plasma Wall Interactions Fusion Tokamak Technology Physics and Technology

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)  Realistic fully noninductive scenario may require substantial P CD  Sets the goals for future gyrotron development at f > 200 GHz  Issues of controllability must be incorporated from the start KIT, 1MW, 105 – 165 GHz SP prototype Mode for 237 GHz coax gyrotron Brewster-angle technology (CVD Diamond window) TE 49,29 Simulation of fully noninductive DEMO scenario

Exhaust of Power and Particles (RE3)  Combined physics / technology requirements: P/R sep  15 MW/m, P target  5 MW/m 2, T e,div  5 eV  Optimised technology solution may be He-cooled divertor W-divertor in ITER He-cooled divertor for DEMO

Stellarator Scenarios (RE2) & Technology (RE7) Stellarator specifics are incorporated into tokamak systems codes Critical elements in physics and technology will be assessed 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. Plasma Geometry Modular Coils / Blanket Island Divertor

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. Plasma Geometry Modular Coils / Blanket Island Divertor Stellarator Scenarios (RE2) & Technology (RE7) Stellarator specifics are incorporated into tokamak systems codes Critical elements in physics and technology will be assessed

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. Plasma Geometry Modular Coils / Blanket Island Divertor Stellarator Scenarios (RE2) & Technology (RE7) 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

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  -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 Conclusions