Laser-plasma interactions in ignition targets for the National Ignition Facility

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Laser-plasma interactions in ignition targets for the National Ignition Facility Presented to: HEDS Summer School University of California, Los Angeles July 30, 009 D. E.

1 Laser-plasma interactions in ignition targets for the National Ignition Facility Presented to: HEDS Summer School University of California, Los Angeles July 30, 009 D. E. Hinkel This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC5-07NA7344. Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA

2 Introduction DE Hinkel HEDS SS 009!

Fusion is accomplished via gravitational,!

3 Fusion powers the sun and the stars and maybe one day our communities Fusing deuterium and tritium into a helium nucleus releases an energetic neutron! Fusion is accomplished via gravitational,! magnetic and inertial confinement Laboratory proof-of-principle experiments: more energy out than in DE Hinkel HEDS SS 009 3!

4 Inertial confinement fusion (ICF) relies on the inertia of the fuel to provide confinement INDIRECT DRIVE: laser energy is converted to x-ray energy by target x-rays bathe ICF capsule, heating it up -- it expands Laser Beams (enter through laser entrance hole (LEH) DT! Fuel Hohlraum (laser target) conservation of momentum: ablated shell expands outward, rest of shell (frozen DT) is forced inward fusion initiates in a central hot spot containing ~ 5% of the fuel, and a thermonuclear burn front propagates outward DE Hinkel HEDS SS 009 4!

5 So where do laser-plasma interactions (LPI) come into play? Plasma evolves into laser target by: -- radiation-driven blow-off -- direct laser ablation Energy Loss Title low of radiation Graph drive Energy Re-direction Title of Graph symmetry loss Laser Backscatter SBS: laser scatters off self-generated ion acoustic waves (iaws) SRS: laser scatters off self-generated electron plasma waves (epws) Beam spray: laser hotspots dig density wells -- refract, intensify & scatter light Beam bending: in transverse flow, light advects with density wells Crossed beam transfer: inner-to-outer energy transfer via scatter from mutually driven iaws Reduction of LPI optimizes laser-target coupling, thereby ensuring ignition conditions DE Hinkel HEDS SS 009 5!

6 Overview DE Hinkel HEDS SS 009 6!

7 Beams can self-focus (filament) filamentation is initiated by an intensity modulation (readily provided by laser beams) light refracts toward lower density: low light pressure! electron! density! v ph = ω 0 k 0 = c 1 n e n c Laser! hot! spot! high light pressure! laser light! self-focuses! low light pressure! self-focusing only occurs when refraction dominates over diffraction A laser beam must contain more power than a critical power to filament DE Hinkel HEDS SS 009 7!

Beam self-focusing leads to beam spray self-focusing : smaller transverse spatial structures in the beam smaller transverse spatial scales (in x-space) larger k x, k y (in k-space) larger k x, k y

8 Beam self-focusing leads to beam spray self-focusing : smaller transverse spatial structures in the beam smaller transverse spatial scales (in x-space) larger k x, k y (in k-space) larger k x, k y (in k-space) larger angular spreads laser beam propagation beam spray! is controlled beam spray occurs and is! accompanied by beam deflection Control of filamentation optimizes reproducibility of where laser energy deposition occurs in the target DE Hinkel HEDS SS 009 8!

9 Stimulated backscatter resonantly generates laser scatter off plasma waves incident laser light dispersion relation: ω 0 = ω pe + k 0 c reflected laser light dispersion relation: ω 1, = ω pe + k 1, c ion acoustic wave dispersion relation: ω iaw = k iaw C s electron plasma wave dispersion relation: ω epw = ω pe + 3k epw v e plasma wave! δn SBS occurs when: ω 0 = ω iaw + ω 1 SRS occurs when: k 0 = k iaw + k 1 ω 0 = ω + ω epw force! (A 1 A 0 ) current! δn u 0 k 0 = k + k epw reflected! wave A 1 Reducing backscatter optimizes laser energy deposition to the target DE Hinkel HEDS SS 009 9!

10 LPI straddles a wide range of length and time scales -- so how do we analyze? macroscale Laser Hydrodynamic length and time scales are set by target size [O(mm)] and laser pulse length [O(ns)] environment -- plasma parameters and scale lengths Perform quick triage with gain analysis (newlip)! mesoscale LPI evolves on: µm length scales and ps time scales beam propagation Perform beam propagation simulations with pf3d! microscale wave-particle 0 wave-wave e - Detailed processes of LPI occur on light spatial and temporal scales kinetic effects Perform PIC/Vlasov simulations:! # determine energetic significance of nonlinearities! Our challenge: incorporate all necessary physics at all relevant length and time scales DE Hinkel HEDS SS !

11 Our approach uses a variety of tools macroscale Lasnex/Hydra Laser laser energy Radiation/Hydrodynamics simulations heat e - s make x-rays; hydro motion implosion & burn mesoscale pf3d incident laser propagation (paraxial) Wave propagation simulations fluid plasma model scattered light propagation (paraxial) microscale Z3/Bzohar/Vlasov Codes wave-particle 0 e - wave-wave Particle in cell (PIC) simulations particle phase space EM fields The goal: to develop a predictive capability for LPI DE Hinkel HEDS SS !

Rapidly increasing computer performance enables LPI calculations unimaginable twelve years ago Computer Performance by Year 1.00 Floating Log(Mflops) point ops / sec 10 16 10.00 8.00 10 1 6.00 4.

ASCI Blue TR ASCI White ASCI Blue SST Thunder ASCI Q ASCI Purple ASC Red Storm 004! massively parallel! nonlinear hydro! filamentation, SBS, SRS! saturation models! Blue Gene/L Blue Gene/P x x 5 mm 3!

12 Rapidly increasing computer performance enables LPI calculations unimaginable twelve years ago Computer Performance by Year 1.00 Floating Log(Mflops) point ops / sec ! serial code! linearized hydro! filamentation only! Cray Y/MP Cray J 90 Cray T3D ASCI Blue ID.05 x.05 x. mm 3! Cray T3E.05 x.05! x 5 mm 3! x x mm 3! ASCI Blue TR ASCI White ASCI Blue SST Thunder ASCI Q ASCI Purple ASC Red Storm 004! massively parallel! nonlinear hydro! filamentation, SBS, SRS! saturation models! Blue Gene/L Blue Gene/P x x 5 mm 3! ASC Sequoia 007! enhanced hydro! enhanced SRS model! optimized parallelization! Year Year Only in the last few years have we been able to simulate LPI of a quad of NIF beams DE Hinkel HEDS SS 009 1!

13 Today s supercomputers are the enabling technology for predictive LPI modeling Our computer time is provided by institutional, ASC, and weapons program resources DE Hinkel HEDS SS !

14 Macroscale: extract plasma profiles along the laser beam Electron Plasma Density At Peak Power Electron Temperature At Peak Power Black: CH NO liner! Red: CH WITH liner! n e /n c T e (kev) Black: CH NO liner! Red: CH WITH liner! spatial! gain! region! Distance From LEH (cm) Such profiles are used along with a 1D laser beam model to estimate beam spray and laser scatter DE Hinkel HEDS SS !

15 Mesoscale: use pf3d to simulate LPI pf3d numerically solves equations of the form: advection propagation absorption ( ) ( L +L +L ) adv prop abs A 0 = δn f A 0 + δn A A 1 + δn L A refraction SBS coupling SRS coupling A 0 Fields : incident laser A 1 : SBS; driven by δn A A 0 A : SRS; driven by δn L A 0 δn A (iaw): driven by δn L (epw): driven by Plasma Response A 0 A 1 A 0 A - both satisfy respective wave equations with nonlinear saturation terms and kinetically derived coefficients Background plasma: described by standard (nonlinear) fluid model couples to laser via ponderomotive (radiation) pressure, inverse brehmsstrahlung pf3d simulations couple paraxial wave propagation to a plasma fluid model DE Hinkel HEDS SS !

Example: Langmuir decay instability depletes epw of SRS daughter epw primary epw iaw LDI electron

16 Microscale: PIC simulations explore growth and saturation of laser-plasma instabilities Wave - Particle Interactions Example: electron trapping in epw de-tunes SRS Wave - Wave Interactions Example: Langmuir decay instability depletes epw of SRS daughter epw primary epw iaw LDI electron phase space PIC simulations guide development of reduced model saturation mechanisms DE Hinkel HEDS SS !

17 Microscale: PIC simulations can investigate novel LPI mechanisms Forward Scatter Spectrum Backscatter Spectrum ω 0 t RFS ω 0 t RBS BBS of RFS BBS ω/ω ω/ω 0 0 k inc ~ 0.9 k 0 k Lang ~ 0.6 k 0 k em ~ 0.3 k 0 RFS: BBS of RFS: k em ~ 0.3 k 0 k iaw ~ 0.6 k 0 k sc ~ 0.3 k 0 DE Hinkel HEDS SS !

18 Derivation of backscatter as calculated by pf3d DE Hinkel HEDS SS !

19 The pf3d equations are readily derived Use Maxwell equations Use the electron and ion continuity equations Use the electron and ion momentum equations Close the set of equations using the equation of state: p = Cn γ DE Hinkel HEDS SS !

20 We begin with Ampere s Law: B = 4π c J + 1 c E t or A = 4π c J + 1 c E t The current can be separated into a rotational and irrotational component: J J l + J t J t = 0 J l = 0 We will use the electron continuity equation: n e t + n e u e = 0 We will also use the electron momentum equation: mn e u e t + mn e u e u e + p e = en e E + 1 c u e B DE Hinkel HEDS SS 009 0!

21 We can further re-write Ampere s Law A = 4π c J + 1 c E t A A = 0 radiation/coulomb! gauge! 4π c J 1 c t φ + 1 c A t Re-group vector potential terms on the LHS: ( t c )A = c 4πJ t φ ( ) Use the continuity equation with ρ=n e q, J=n e qu as well as Poisson s equation: ρ ρ + J = 0 = 4π t t + 4π J l = ( 4πJ l t φ) = 0 ( t c )A = 4πcJ t DE Hinkel HEDS SS 009 1!

22 High frequency (electron motion) Now let s use the electron momentum equation: u mn e e + mn t e u e u e + p e = en e E + 1 c u e B Re-group terms: mn e t u e ea mc + mn u u + en e e e e c u A = p + en φ e e e or mn e t u l + u t ea mc + mn e ( ) mn e u e u t ea u e u e + u e u e mc = p + en φ e e Use the vector identity F F + F F = 1 F To find mn e u t l + u t ea mc u u ea e t mc = en φ mn e e u e DE Hinkel HEDS SS 009!

23 Electron response, cont. mn e u t l + u t ea mc u u ea e t mc = en φ mn e e u e Take the curl, and use, : ψ = 0 u l = 0 t q u e q = 0 q u t ea mc This is the vorticity eqn; if u t = ea mc at t=0, then it does for all time u t = ea mc So our set of equations is now: t : n e t + n e u e = 0 : u l t = e m φ p e 1 mn e u l + ea mc DE Hinkel HEDS SS 009 3!

24 Electron response, cont. We now have: n e t n e u l t u + ( n e u l )u l + n l e t = 0 = e m n φ p e e 1 mn e u l + ea mc Linearize:,,, n e = n 0 + n 1 u l = u l1 φ = φ 1 A = A 0 + A 1 n 1 u l + n 1 t 0 t = 0 n 0 u l1 t = e m n p 0 φ 1 1 m + n p 0 1 n 0 e ( mn 0 m c A 0 A 1 ) u l n 1 φ 1, 1, t ~ 1 n 0 n 1 φ 1 u λ 1 l1 n 0 t ~ 1 L O(λ/L) correction to n 1 n 1 etc. terms t 3v e ( + ω pe )n 1 = e ( m c A 0 A 1 ) where we have used p 1 = γn 1 T e = 3n 1 T e φ 4πen 1 ω pe 4πn 0e m DE Hinkel HEDS SS 009 4!

25 Low frequency response: include ions, neglect electron inertia electrons: u t = ea mc 0 u l t = e m φ p e 1 mn e u l + ea mc eφ = m u l + ea mc + γt e ln n e ( ) + C n e = n 0 exp eφ T e m T e u l + ea mc, where ϒ=1 eφ Linearize: n 1 = n 1 0 m e T e T e m c A 0 A 1 ( ) Zn i 1 (neglect kλ d corrections; will account for them later) ions: n i t + n i u i = t + u i n + n u = d i i i dt n + n u = 0 i i i ion continuity eqn. du i dt = Ze M φ p i Mn i ion momentum eqn. d n i dt n i ( u i ) Ze M n i φ n i p i = 0 Mn i d dt of ion cont. eqn. + of ion mom. eqn. DE Hinkel HEDS SS 009 5!

26 Low frequency response, cont. Linearize ion equations: n i = n 0 Z + n i 1 u i = U 0 + u i1 φ = φ 1 d n i 1 n dt i 1 U 0 ( ) n 0 ( ) u i 1 O 1 k 0 L ( ) Z U 0 O 1 ( k 0 L) ( ) e M n 0 φ 1 p i 1 M + O 1 ( k 0 L ) = 0 d n i 1 dt p i 1 M = e M n 0 φ 1 p i1 ~ γt i n i1 = 3T i n i1 d n i 1 dt 3T i M n i 1 = e M n 0 φ 1 eφ Use the expression Zn i1 n 1 0 m e ( A : T e T e m c 0 A 1 ) d n i 1 dt ZT e + 3T i M n i 1 = n 0e Mmc A 0 A 1 and Zn i1 n 1 : ( t + U 0 ) ZT + 3T e i M n i 1 = Zn 0 e Mmc A 0 A 1 DE Hinkel HEDS SS 009 6!

27 Our final equation set: ( t c )A = 4πcJ t = 4πe m n e A not yet linearized t 3v e ( + ω pe )n 1 = e ( m c A 0 A 1 ) ( t + U 0 ) ZT + 3T e i M n i 1 = Zn 0 e Mmc A 0 A 1 frequency/wavenumber matching: ( k 0,ω 0 ) incident light wave ( k 1,ω 1 ) backscattered light wave (SBS) ( k,ω ) backscattered light wave (SRS) ( k A,ω A ) ion acoustic wave (iaw) ( ) electron plasma wave (epw) k L,ω L SBS: k 0 = k 1 + k A ω 0 = ω 1 + ω A SRS: k 0 = k + k L ω 0 = ω + ω L DE Hinkel HEDS SS 009 7!

28 We envelope out the wavenumber and frequency of each wave (almost) This leaves only the slowly varying portion of the variables: Let, where A = A 0 + A 1 + A { } e A 0 ˆ A b z 0(x,t)exp[ iω 0 t + i k 0 (z')dz' +c.c. 0 { } e A 1 ˆ A b z 1(x,t)exp[ iω 0 t i k 0 (z')dz' +c.c. L SBS: don t envelope out acoustic frequency { } e A ˆ A b (x,t)exp[ iω t i z k (z')dz' +c.c. L n 1 (x,t) = δn f (x,t) + 1 δn (x,t)exp i z k (z')dz' +i z k (z')dz' A L + c.c. + 1 δn (x,t)exp i z k (z')dz' +i z k (z')dz' iω t L 0 0 L L + c.c. DE Hinkel HEDS SS 009 8!

29 When we keep only resonant (phase-matched) contributions, we find: t c z ( + ω pe )b 0 exp iω 0 t + i k 0 (z')dz' 0 = 4πe m δn b + 1 f 0 δn b + 1 A 1 δn b L exp iω t + i 0 z 0 k (z')dz' 0 t c z ( + ω pe )b 1 exp iω 0 t i k 0 (z')dz' L = πe m δn * z Ab 0 exp iω 0 t i k 0 (z')dz' L t c z ( + ω pe )b exp iω t i k (z')dz' L = πe m δn * z Lb 0 exp iω t i k 0 (z')dz' L ( t + U 0 ) ZT e + 3T i M δn z z A exp i k 0 (z')dz' + i k 0 0 (z')dz' L = Zn 0e Mmc b 0 b * z z 1 exp i k 0 (z')dz' + i k 0 0 (z')dz' L t 3v e z z ( + ω pe )δn L exp iω L t + i k 0 (z')dz' + i k 0 (z')dz' L = n 0e m c b 0 b * z z exp iω L t + i k 0 (z')dz' + i k 0 (z')dz' L DE Hinkel HEDS SS 009 9!

30 Simplification of the light wave equations We have a differential operator of the form L em t c + ω pe z L em b 0 exp iω 0 t + k0(z')dz' = exp iω t + 0 z k (z')dz' 0 ω 0 iω 0 t + t + k 0 c ik 0 c z i( z k 0 )c [ + ω pe ]b 0 In the absence of density fluctuations (RHS=0), and with b 0 = C, a constant, we find: ω 0 = ω pe + k 0 c light wave dispersion relation in a uniform medium Similarly, for the SRS backscattered light we find: ω = ω pe + k c The dispersion relation for the SBS backscattered light is ω 1 = ω pe + k 1 c z L em b 0 exp iω 0 t + k0(z')dz' = exp iω 0t + z k 0 (z')dz' ω 0 iω 0 t + t + k 0 c ik 0 c z i( z k 0 )c [ + ω pe ]b 0 = ω pe k 0 c negligible; t << ω 0 DE Hinkel HEDS SS !

31 Simplification of the light wave equations, cont. incident! The wave equations for the incident and backscattered light reduce to: t + v g0 z + 1 zv g0 ( ) ic [ ] ω 0 b 0 = iπe δn mω f b 0 + δn A b 1 + δn L b 0 SBS! SRS! t + v g0 z + 1 zv g0 t + v g z + 1 zv g ( ) ic ( ) ic ω 0 b 1 = iπe δn mω A 0 * b 0 ω b = iπe δn mω L * b 0 v g0 k 0c ω 0 v g k c ω L b em 0 = iπe δn 0 mω f b 0 + δn A b 1 + δn L b 0 [ ] L b em 1 = iπe δn * 0 mω A b 0 0 OR L b em = iπe δn * mω L b 0 0 L em i t + v gi z + 1 ( zv gi ) ic ω i DE Hinkel HEDS SS !

32 Simplification of the plasma wave equations: Similar to the light wave equation(s), L epw δn L = in 0e 4ω L m c k * Lb 0 b L epw t + 3v ek L ω L z + 3 v e z k L ( ) 3iv e ω L L iaw δn A = Zn 0 e Mmc k * 0b 0 b 1 L iaw ( t + ik 0 U 0z ) + C s ( 4k 0 ik 0 z ) DE Hinkel HEDS SS 009 3!

33 Set of equations: L b em 0 = iπe δn 0 mω f b 0 + δn A b 1 + δn L b 0 [ ] L b em 1 = iπe δn * 0 mω A b 0 0 L em i t + v gi z + 1 ( v z g i ) ic ω i L b em = iπe δn * mω L b 0 0 L epw δn L = in 0 e 4ω L m c k * Lb 0 b L epw t + 3v ek L ω L z + 3 v e z k L ( ) 3iv e ω L L iaw δn A = Zn 0 e Mmc k * 0b 0 b 1 L iaw ( t + ik 0 U 0z ) + C s ( 4k 0 ik 0 z ) DE Hinkel HEDS SS !

34 What about damping? Damping: include the term mn e ν ei u e on the RHS of the momentum equation ν ei : electron-ion collision frequency L em i t + ν emi + v gi z + 1 ( zv gi ) ic ω i Light wave absorption (inverse bremsstrahlung): -- due to electron-ion collisions in plasma -- electron oscillatory motion in laser E-field is thermalized L epw t + ν epw + 3v ek L ω L z + 3 v e z k L ( ) 3iv e ω L Electron-plasma wave damping: -- collisionless + collisional L iaw ( t + ν iaw + ik 0 U 0z )( t + ik 0 U 0z ) + C s ( 4k 0 ik 0 z ) Ion-acoustic wave damping: -- collisionless + collisional DE Hinkel HEDS SS !

35 Final set of equations including damping: L b em 0 = iπe δn 0 mω f b 0 + δn A b 1 + δn L b 0 [ ] L b em 1 = iπe δn * 0 mω A b 0 0 L em i t + ν emi + v gi z + 1 ( v z g i ) ic ω i L b em = iπe δn * mω L b 0 0 L epw δn L = in 0 e 4ω L m c k * Lb 0 b L iaw δn A = Zn 0 e Mmc k * 0b 0 b 1 L epw t + ν epw + 3v ek L ω L z + 3 v e z k L ( ) 3iv e ω L L iaw ( t + ν iaw + ik 0 U 0z ) + C s ( 4k 0 ik 0 z ) DE Hinkel HEDS SS !

36 We enhance our linearized fluid equations by using kinetically derived coefficients where appropriate collisionless (Landau damping): incorporate into electron plasma and ion wave damping terms -- use kinetically derived values ion acoustic wave sound speed (C s ): -- use kinetically derived value DE Hinkel HEDS SS !

37 pf3d validation*: predictive modeling of Omega backscatter experiments, SBS Backscatter Linear gain SRS Backscatter Linear gain no PS 10 no PS SBS (%) 1 PS pf3d SRS (%) PS pf3d Intensity x10 15 (W-cm - ) Intensity x10 14 (W-cm - ) Quantitative LPI estimates are now routinely performed for ignition targets *R. L. Berger and L. Divol, LLNL DE Hinkel HEDS SS !

scattering *D. H. Froula et al., Phys. Rev. Lett. 100, 01500 (008); D.

38 pf3d validation: use OMEGA gas-filled hohlraums that reach NIF-like densities/temperatures* Plasma conditions characterized by Thomson scattering *D. H. Froula et al., Phys. Rev. Lett. 100, (008); D. H. Froula et al., Phys. Rev. Lett. 101, 1150 (008) DE Hinkel HEDS SS !

39 Some Facts About NIF and Some pf3d Results DE Hinkel HEDS SS !

40 The National Ignition Facility (NIF) is a 19 laser beam, state-of-the-art facility NIF is the first of its kind, delivering up to 1.8 MJ of blue laser light to the target chamber DE Hinkel HEDS SS !

41 The target: A hohlraum ( empty room ) ; converts laser energy to x-rays Measure the laser power into the hohlraum. Find the T RAD at which we can: Measure the backscattered light power reflected from the hohlraum. Demonstrate backscattered power < 15% on both cones. Measure the hard x- ray power and (photon) energy generated by hot electrons. Demonstrate hotelectron pre-heat is acceptable. Measure the x-ray flux and energy escaping from the LEH. Demonstrate acceptable radiation drive. Hohlraums provide the environment for capsule compression and burn DE Hinkel HEDS SS !

16 mm pf3d resolves the laser speckles (~8λ0 in transverse dimension) NIF laser beams are: -- spatially smoothed (speckly) --

42 The laser: a quad of beams propagated from outside of the target to the interior wall 300 Ignition Design Quad Intensity (W/cm) NIF laser beams are comprised of laser speckles.16 mm pf3d resolves the laser speckles (~8λ0 in transverse dimension) NIF laser beams are: -- spatially smoothed (speckly) -- temporally smoothed (speckles move around in time) -- polarization smoothed (split into two polarizations).16 mm Ignition whole beam propagation simulations: 147,000 bgp cpus DE Hinkel HEDS SS 009 4!

We analyze beam propagation at peak power, where LPI effects are maximum Ignition hohlraum circa peak power wall! LEH liner! H 4 He! gas! fill! wall! Be ablator! +! capsule!

43 We analyze beam propagation at peak power, where LPI effects are maximum Ignition hohlraum circa peak power wall! LEH liner! H 4 He! gas! fill! wall! Be ablator! +! capsule! 30 0 Quad Laser Quad Power (TW) Laser Power Vs Time 30 0 Quad LEH liner! H 4 He! gas! fill! CH! ablator! The quad of laser beams propagates 7.5 mm in this simulation DE Hinkel HEDS SS !

$6 laser beam refracts off the laser entrance hole (LEH) as it enters the target refraction causes intensification of the laser beam 7.$

44 The forward intensity pattern contains interesting features Ignition Design at 1 ns 8 ignition! capsule! 6 laser beam refracts off the laser entrance hole (LEH) as it enters the target refraction causes intensification of the laser beam 7.5 mm 4 x W/cm laser beam channels between the ablator and the wall LEH!.16 mm DE Hinkel HEDS SS !

plasma! SRS Reflectivity at 1 ns amplifies! in! gas-! fill!

45 SBS and SRS occur in different locations in the beam cross section SBS Reflectivity at 1 ns amplifies! in ablator! plasma! SRS Reflectivity at 1 ns amplifies! in! gas-! fill! plasma! x W/cm.5%! SBS! 7%! SRS! DE Hinkel HEDS SS !

SRS light at 1 ns Ø y Ø y Ø x Ø x This demonstrates the importance of

46 The angular distribution of the backscattered light has robust characteristics Angular Distribution SBS light at 1 ns Angular Distribution SRS light at 1 ns Ø y Ø y Ø x Ø x This demonstrates the importance of measuring the backscattered light both inside and outside of the lenses DE Hinkel HEDS SS !

47 A movie of the forward laser intensity: DE Hinkel HEDS SS !

48 A movie of the SRS light: DE Hinkel HEDS SS !

49 In summary: early ignition designs ( ) require five building-blocks for predicting LPI 1- A 3-dimensional wave based LPI simulation code based on linear plasma response theory (pf3d) - Using accurate hydrodynamic profiles 3- Using a realistic model of the laser spots CPU-days for pf3d DE Hinkel HEDS SS !

50 Prediction: Once we achieve ignition, designs will evolve and LPI will be predominantly nonlinear In preparation for LPI modeling beyond the time frame: -- we need to develop reduced model descriptions of microscale physics to be utilized at the mesoscale (in pf3d) We currently have an R&D project (led by David Strozzi) that is investigating this We are also developing the capability to perform massively parallel PIC simulations -- but computational resources are not sufficient to perform a PIC simulation of an entire NIF laser beam Our goal is to further develop our LPI modeling so that we can be predictive in the nonlinear LPI regime (note: this is hard!) DE Hinkel HEDS SS !

51 So, every now and then you can follow the rainbow to it s end at NIF NIF! Our pot of gold: achieving ignition This means we must learn to control LPI! DE Hinkel HEDS SS !

Modeling Laser-Plasma Interactions in MagLIF Experiment on NIF

Modeling Laser-Plasma Interactions in MagLIF Experiment on NIF Anomalous Absorption Meeting 5 May 2016 D. J. Strozzi, R. L. Berger, A. B. Sefkow, S. H. Langer, T. Chapman, B. Pollock, C. Goyon, J. Moody