Academic Research on the Inertial Confinement Thermonuclear Fusion in Europe
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ELI summer school, August 26 – 30, 2019 Academic research on the inertial confinement thermonuclear fusion in Europe V. T. Tikhonchuk Centre Lasers Intenses et Applications, University of Bordeaux – CNRS – CEA, Talence, France ELI-Beamlines, Institute of Physics, CSR, Dolní Břežany, Czech Republic Principles of initial confinement fusion for energy production (IFE) IFE is a pulsed process: the energy is released in periodic pellet explosions • Standard power plant produces 1 GW = 1 GJ/s: 1 GW = 10 explosions in 1 s = 250 kg TNT/s = 3 mg DT/s • Typical target mass is 1 mg corresponds to a sphere R = 1 mm at normal density ρ = 0.25 g/cc Ignition conditions are imposed by the Lawson criterion: ρR > 0.3 g/cm2 at T = 5 keV It cannot be satisfied at normal conditions: compression and heating are needed • compression of the total fuel mass by using the ablation pressure: recoil effect • heating of a small part of the fuel: creation of a spark (hot spot) • combustion of the residual fuel August 30, 2019 Academic research on ICF in Europe 2 Three steps of the ICF process: • compression of the total fuel mass by using the ablation pressure: recoil effect • heating of a small part of the fuel: creation of a spark (hot spot) • combustion of the residual fuel • implosion time 10 ns • driver energy 1 MJ • ignition time 30 ps • gain 300 • acceleration 1013g • final energy 50 kJ • radius 100 µm • fusion energy • pressure 100 Mbar • efficiency 5% • pressure 300 Gbar 300 MJ • implosion velocity ~ • energy 10 kJ 400 km/s August 30, 2019 Academic research on ICF in Europe 3 Two basic approaches: direct and indirect drive direct drive indirect drive ablator DT ice DT gas R R ~ 1 mm ~ 0.2 mm • indirect drive is motivated by the national defence programs: less efficient but considered to be more reliable • direct drive: academic program is motivated by energy production and modelling extreme states of matter in laboratory August 30, 2019 Academic research on ICF in Europe 4 Only few large scale laser installations exist in the world direct drive indirect drive OMEGA LMJ NIF 60-beams, 30 kJ, 30 TW 176-beams, 1.4 MJ, 400 TW 192-beams, 1.8 MJ, 500 TW direct drive: fast ignition Academic programs benefit a free access to the national MJ facilities on a competitive basis within ~15% of the GEKKO XII available shots 12-beams, 10 kJ, 10 TW SHENGUANG-III 48-beams, 180 kJ, 60 TW August 30, 2019 Academic research on ICF in Europe 5 Update on the indirect drive experiments Indirect Drive ignition experiments are conducted on NIF since 2009 Several approaches are considered: Major problems: • low adiabat (low foot) implosions (2010 – 2012) • low energy coupling to the hot spot • medium adiabat (high foot) implosions with plastic • hydrodynamic instability of the and HD carbon ablators imploding shell • low gas fill hohlraums (symmetry control) • low energy coupling to hohlraum O Hurricane et al, Phys Plasmas 2019 Significant progress but still far from ignition August 30, 2019 Academic research on ICF in Europe 6 Outline . Direct drive ignition program and role of the European scientific community . Alternative approaches to inertial fusion: fast and shock ignition . Recent developments in the fast ignition approach: magnetic guiding of electrons . Strong shock generation experiments in the planar and spherical geometry: role of hot electrons . Near future plans August 30, 2019 Academic research on ICF in Europe 7 Direct drive approach: more efficient energy deposition The ignition conditions impose a relation between the hot spot pressure and energy .⁄ By using relations between the energy pressure and radius: ~~/ ~~~/ the ignition criterion reads: Higher energy deposition in the hot spot with the direct drive approach results in lower compression ratio CR ~ 22 compared to CR ~30‐40 for the indirect drive R Betti et al, Phys Rev Lett 2015 SP Regan et al Nuclear Fusion 2019 August 30, 2019 Academic research on ICF in Europe 8 Program for the direct drive to 2020 The Rochester group is leading the International Direct Drive Program curves: scaled fusion yield for 1.9 MJ • Improve coupling of laser energy to the hot spot • Improve symmetry of implosions on OMEGA ) • Demonstrate scaled performance on NIF 14 (×10 yield neutron areal density (mg/cm2) Collaborations: • LLNL: LPI, target design, • NRL: imprint, CBET control V Goncharov et al PPCF 2018 • LANL: high Z, EoS, opacities V Gopalaswamy et al Nature 2019 • EUROPE: physics, alternative schemes August 30, 2019 Academic research on ICF in Europe 9 Alternative ignition schemes: fast and shock ignition Alternative ignition schemes separate the implosion and ignition phases: the implosion phase is common with the standard direct drive approach, but the ignition is non‐isobaric • shock ignition: the central hot spot pressure is boosted with a special intense laser spike (the scheme selected by the European ICF project HiPER, collaboration with LLE) • fast ignition: the ignition spark is initiated with an intense of electron or ion beam driven by a multi‐PW laser pulse (ILE, Osaka) Spike : Converging Shock v. 54, no.5 Hot Spot Fuel Major issues: Major issues: • transport of hot electrons or • generation of a strong converging ions to the core shock • high energy PW laser pulse • control of the hot electron preheat Review on alternative ignition schemes: Nuclear Fusion 54, No. 5, 2014 August 30, 2019 Academic research on ICF in Europe 10 Fast Ignition Approach August 30, 2019 Academic research on ICF in Europe 11 Fast ignition scheme: recent results Fast ignition approach requires less laser energy injected in the hot spot Central ignition Fast ignition ~~ (isobaric) (isochoric) High ρ (1000 g/cm3) Main fuel Low ρ (100 g/cm3) High ρ (a part of fuel) hot spark Fast ignition project with electron beams is led by the Japanese team, ILE, Osaka: The laser facility contains: • 12 beam 3.5 kJ ns GEKKO system • 4 beam 2.5 kJ ps LFEX R Kodama et al, Nature 2002 Nuclear Fusion 54, No. 5, 2014 Major issue: high energy & strong divergence of electrons August 30, 2019 Academic research on ICF in Europe 12 Magnetic field assisted fast ignition scheme GEKKO experimental campaigns in 2016 ‐ 2018 proposed three significant improvements in the integrated fast ignition experiment • A thin shell is replaced with a solid ball to improve the implosion stability 100 µm Gold cone • The LFEX contrast is strongly improved: suppression of super‐hot electrons • A capacity‐coil laser driven parallel magnetic field is applied for the electron guiding Bz S Sakata et al, Nature Comm 2018 August 30, 2019 Academic research on ICF in Europe 13 Solid ball compression The areal density of 100 mg/cm2 is achieved with a Gaussian GEKKO‐XII pulse and 200 µm diameter solid ball undriven -400ps #38964 #38989 -260ps -160ps #38989 Temporal evolution of ρR 100 μm 100 μm #38995 #38983 With a tailored laser pulse the areal density of 2.7 g/cm2 can be achieved on NIF X‐ray shadows of fuel core H Sawada et al. Appl Phys Lett 2016 August 30, 2019 Academic research on ICF in Europe 14 Strong magnetic field generation with a laser A capacitor‐coil target allows generation of magnetic fields ~ 5‐6 MG in a 1 mm3 volume current B In experiments on LULI200 and GEKKO‐XII a set of three complementary diagnostics has been used: • B‐dot probes • proton deflectometry • Faraday rotation J JSantos et al. NJP 2015 V T Tikhonchuk et al. Phys Rev E 2017 August 30, 2019 Academic research on ICF in Europe 15 Demonstration of the electron beam guiding Experiment on LULI2000 demonstrates an electron beam collimation in the magnetic field: CTR diagnostic of transmitted electrons 1.5×1019 W/cm2 w/out B‐field with B‐field • the electron beam width is reduced by 3 times • the electron peak density is raised by 12 times • smoothing of electron beam filaments • reduced emittance 2 times S Fujioka et al, Phys Plasmas 2016 M Bailly‐Grandvaux et al, Nature Comm. 2018 August 30, 2019 Academic research on ICF in Europe 16 Integrated experiment on fast ignition Experiment on GEKKO‐XII demonstrates good implosion and core heating up to 3 keV B-generation coil Cone Dense plasma core • 3 GEKKO beams for the magnetic field generation • 6 GEKKO beams for the ball compression • Core density of 6 ‐ 11 g/cm3 was obtained • 4 LFEX beams for the electron beam generation at the heating laser pulse injection timing • 3 GEKKO beams for the implosion diagnostics • Spectrum emitted from Li‐ and He‐like Cu ions indicates a 3 keV temperature of the • Cu‐doped oleic‐acid bead heated region • Coupling efficiency ~5 –8%, energy H Sawada et al, Appl Phys Lett 2016 deposition 50 J, pressure ~1 Gbar S Sakata et al, Nature Comm 2018 August 30, 2019 Academic research on ICF in Europe 17 Shock Ignition Approach August 30, 2019 Academic research on ICF in Europe 18 Shock Ignition scheme An intense laser spike launches a strong shock at the end of implosion phase which . provides a pressure boost in the central hot spot ~ ~ 200 TW 10 PW/cm2 Major issues: Laser Pulse • Strong shock generation • Control of high energy electrons • Definition of optimal ignition conditions • Effects of the irradiation anisotropy • Development of appropriate num. tools • Robust target design radius time Ignition V Shcherbakov, Sov J Plasma Phys 1983 R Betti et al. PRL 2007 X Ribeyre et al. PPCF 2009 August 30, 2019 Academic research on ICF in Europe 19 Shock pressure generation with hot electrons Spike pulse intensity ~ 1016 W/cm2 implies strong LPI effects: param. inst. & hot electrons Ablation pressure is evaluated from the quasi‐stationary energy flow balance / / ≅.