LLNL Fast Ignition Program US-Japan Workshop San Diego, CA March 11, 2010

1. LLNL Fast Ignition ProgramUS-Japan WorkshopSan Diego, CAMarch 11, 2010 Cliff Chen on behalf of Pravesh Patel

2. Fast Ignition research programs have emerged at numerous universities and national labs across the US National FI Programs Intl. FI Programs Electron FI Rutherford Appleton Lab LULI Universita di Roma Imperial College, UK University of York, UK Queens Univ., Belfast CEA, France IST, Lisbon UPM, Madrid, … ILE, Osaka University University of Rochester General Atomics UCLA MIT UCSD Ohio State University University of Nevada University of Texas ILSA LLNL HEDLP Joint Program Ion/Proton FI • Fast Ignition in the US has effectively become a co-ordinated national effort • There are strong collaborations between the US, Europe, and Japan

3. Several options are being persued for delivering the required particle flux to the core Electrons (cone-guided) Electrons (laser channeling) Laser Protons Ions

4. NIF will enable integrated fast ignition experiments with the actual full-scale fuel assembly required for high gain 500 kJ NIF beams Scale 1 hohlraum 10kJ, 5ps ARC DT/CD capsule • We will measure & optimize coupling efficiency of an 10 kJ ignitor pulse to a full-scale fuel assembly to determine laser, physics, and target requirements for high gain FI

5. Major Program Elements:Point Design & Experimental Campaigns • Point Design • Hydro assembly 1D and 2D (LASNEX, HYDRA) • Laser interaction, electron generation (PSC, PICLS) • Electron transport and heating (LSP, ZUMA) • Burn, diagnostic signatures (LASNEX, HYDRA) • Experimental Campaigns • NIF Hydro campaigns • NIF Short-pulse campaigns • NIF Integrated campaigns • TITAN & OMEGA EP short-pulse campaigns • OMEGA EP integrated FI campaigns 500 kJ NIF beams 10kJ, 5ps ARC DT/CD capsule

6. In FI the core is heated to 10 keV using an intense particle beam generated by an ultrahigh power laser • Long pulse laser must compress fuel to: ~ 300 g/cm3 R ~ 2 g/cm2 • Short-pulse laser must heat core to 10 KeV: Energy~ 20 kJ • Dz ~ 40 µm • t~ 20 ps • High-intensity, short-pulse lasers (I > 1019 W/cm2) incident on a solid target can very efficiently accelerate intense beams of energetic electrons S. Atzeni, POP 8, 3316 (1999)

7. There are three principal design issues for electron cone-guided fast ignition [2] Laser-plasma interaction, fast electron generation [1] Fuel compression 10-100 kJ, 10 ps laser pulse 500 kJ, 20ns implosion [3] Electron transport in dense plasma • Fast Ignition physics is extremely challenging as it encompasses ICF, relativistic laser interaction, particle beam transport in dense plasma – fundamental science of all intense laser interactions with high energy density plasma • No code capability exists that can model this physics self-consistently

8. We are developing a new integrated code capability for simulating intense laser interaction with an HED plasma 3D rad-hydro code HYDRA (hydrodynamics, radiation, ionization kinetics, burn, etc.) shelf solid vacuum 3D kinetic PIC code PSC (solves full Maxwell’s equations for fields and kinetic particles, with v. high spatial, temporal resolution) 3D hybrid transport codes LSP & ZUMA (kinetic fast electrons with fluid background plasma)

9. There are three principal design issues for electron cone-guided fast ignition [2] Laser-plasma interaction, fast electron generation [1] Fuel compression 10-100 kJ, 10 ps laser pulse 500 kJ, 20ns implosion [3] Electron transport in dense plasma

10. [1] Fuel compression: we have developed optimal 1D isochoric compression designs in DT and CD

11. In 2D designs we must assemble the fuel around the cone tip – this is challenging at full-scale • Maintain 300g/cm3 and 2g/cm2 • Minimize ablation of cone wall and subsequent mixing (degrades yield) • Maintain integrity of cone tip from extreme pressure on-axis at stagnation • Minimize compressed core to cone tip distance (~100µm) to maximize fast electron coupling • This has been a major challenge—multiple radiation-hydrodynamics codes have been used to resolve physics and simulation issues

12. Typical simulation result with calculated single-shock DT radiation drive Very close to 1D performance over most of shell

13. Rev 1 hydro implosion design achieves good peak density and rR, but with slightly long transport distance 100 g/cm3 240 µm

14. There are three principal design issues for electron cone-guided fast ignition [2] Laser-plasma interaction, fast electron generation [1] Fuel compression 10-100 kJ, 10 ps laser pulse 500 kJ, 20ns implosion [3] Electron transport in dense plasma

15. [2] A Rev 1 electron source for NIF ARC is calculated with high resolution 2D PIC simulations • High-res explicit PIC, planar geometry, reduced spatial and temporal scales • Intensity equivalent to 4.3kJ, 5ps, 40µm diameter pulse 5 million cells 1 billion particles 81 hours on 128 cpus • Total conversion of light into electron energy flux is 60% • 50% of electron flux is in 80 deg opening angle

16. There are three principal design issues for electron cone-guided fast ignition [2] Laser-plasma interaction, fast electron generation [1] Fuel compression 10-100 kJ, 10 ps laser pulse 500 kJ, 20ns implosion [3] Electron transport in dense plasma

17. [3] Transport & Core Heating: Hybrid-PIC code LSP combines electron source and rad-hydro data HYDRA simulation 200 Feedback for burn calculation, diagnostic signatures (neutrons, x-rays) 100 Radius (µm) PIC simulation of fast electron source 0 0 100 200 300 LSP simulation of fast electron heating Initial conditions 100 100 r Temp 380 g/cc, 150 eV 0 0 0 100 200 300 0 100 200 300 Distance (µm) Distance (µm)

18. We have produced the first transport calculations using realistic hydro and PIC input calculations 7640eV 126Gbar Temp Pressure 5% log lin PIC 150eV 0Gbar PIC q/2 100 100 Temp Pressure 21% • Coupling efficiency is lower than ideal - we need to better tailor electron source and/or reduce transport distance • Transport simulations can rapidly explore parameter space for optimal fuel assembly and electron source profiles 0 0 0 0 0 0 100 100 100 100 200 200 200 200 300 300 300 300 Distance (µm) Distance (µm) Distance (µm) Distance (µm)

19. Rev 2 design: Numerous improvements have led to large reduction in transport distance & intact cone tip Rev 1 Rev 2 100 g/cm3 240 µm 160 µm

20. Rev 2 design: Electron source PIC at larger scale, cone geometry, realistic ARC focal intensity profiles 10*Ne/Nc Reconstructed NIF ARC aberrated beam (PIC) NIF ARC 250mJ pre-pulse (HYDRA)

21. Rev 2 design will use a new hybrid-PIC code that combines PIC with a hybrid particle solver at high r Maxwell’s equations Hybrid field equations ne>>100 ncrit Laser light ~100 ncrit ncrit B.Cohen, A. Kemp, L. Divol(Phys. Plasmas 17: 056702, 2010) 210 x 60 um simulation box Energy density of elec>1MeV @ 500fs (and Poynting flux) P|| 500 eV Arbitrarily shaped boundaries between PIC/Hybrid 400 eV PIC region not shown 300 eV Te (eV) @ 500fs Cu Zeff =4.6 200 eV 100 eV 40 eV • The hybrid-PIC code enables us to model large, solid density targets with a realistic self-consistent electron distribution

22. We are benchmarking laser-interaction and transport physics with experiments on TITAN and OMEGA EP Short-pulse FI modeling Benchmarking experiments vacuum shelf solid X-ray spectrometer (Cu K) PSC 3-D explicit PIC Code TITAN 150J, 700 fs pulse Bremsstrahlung spectrometer LSP 3-D Hybrid Transport Code Cu K imager ZUMA 3-D Hybrid Transport Code 40µm  1mm long Cu wire Al cone

23. TITAN experiments are converging on the electron energy distribution using a combination of techniques Variable Al (μm) Bremsstrahlung Measurements Vacuum electron spectrum Buried Kα fluors 0 to 500 Al–Cu–Al 150 J, 0.5 ps 1020 Wcm-2 Electron spec 500 μm Al 10 μm Al 25 μm Ag 10 μm Cu TITAN Brems spec K yield -Bremsstrahlung sensitive to the internal electron distribution -Lower bound conversion efficiencies of 20-40% inferred -Limited spectral range (<700 keV) -Sensitivity to different parts of spectral range by changing fluor depth -Limited spectral resolution with low shot numbers -Large shot to shot variation in shallow depths -Dependent on transport model -High spectral resolution over a large energy range -Electrons affected by time-dependent target potentials -Strongly model dependent C.D. Chen, Phys. Plasmas 16:082705(2009)

24. Cone-wires are used to study the forward going energy flux in a conical geometry

25. K-alpha fluorescence imaging is being adapted to look at energy deposition in integrated experiments • LLE K-B was tested last week and is still being analyzed • Alberta is designing a new K-B with higher throughput (lower spatial resolution)

26. Compton radiography – we should get opportunity to try on cone-in-shell target in May

27. Experimental campaign: FI can leverage the enormous capability for implosion tuning developed by NIC Spherical capsule tuning Capsule and cone tuning Electron source tuning Integrated Coupling 2010-2011 2011-2012 2012-2013 2012-2014

28. The integrated NIF experiment will measure the fast electron coupling efficiency to the core X-ray radiography 500 kJ NIF beams X-ray radiography to measure density & R 10kJ, 5ps ARC High energy K-alpha imaging K x-ray imaging to measure 2D electron deposition

29. FI has two major goals: establishing feasibility/requirements for high gain & demonstrating high gain Establish the physics, target, and laser requirements for high gain FI—demonstrate compression, coupling efficiency, validated simulation capability, and high gain point design Implement a High Gain FI Demonstration Program (National FI Campaign)

30. Simulation tools & experiments over next few years will determine the architecture of a high gain facility NIF FI NIF FIREX II 500kJ compression 10 kJ ignitor HiPER