Fast Ignition Program Overview

Pravesh Patel Associate Program Leader for Fast Ignition

Fusion Power Associates 31st Annual Meeting and Symposium Washington D.C. December 1-2, 2010

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Security, LLC, Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 LLNL-PRES-463260 Fast Ignition is an alternate approach to conventional ICF for achieving high gain target fusion

Fast Ignion . In CHS a high velocity isobaric implosion creates a high ρ, low T shell surrounding a high T, low ρ igniting hotspot . In FI a low velocity isochoric implosion assembles fuel to high ρ, and a separate short-pulse heats a small region to ignition temperature Lower velocity  Higher fuel mass  Higher gain 100

NIC Central Hot Spot Ignion

10 Target Gain

1 0.1 1 10 Laser Energy (MJ) Ignition requires using an ultraintense laser-generated electron beam to heat a small fuel region to >10 keV

. Long pulse laser must compress fuel to: ρ ~ 300 g/cm3 ρR ~ 2 g/cm2 NIF compatible geometry

Low-angle incidence IFE option . Short-pulse laser must heat core to 10 KeV: Energy ~ 20 kJ Δz ~ 40 µm τ ~ 20 ps

. Significantly reduced symmetry requirements (non-spherical implosion) means more flexible irradiation geometries attractive for IFE

S. Atzeni, POP 8, 3316 (1999) There are three principal scientific & design challenges for electron cone-guided fast ignition

1. Compress DT fuel to high ρ, ρR around cone tip; cone tip must 0.5-1.0 MJ, 20ns survive Gbar implosion pressure compression drive

100-200 kJ, 20 ps ignitor pulse 3. Relativistic electron transport in HED plasmas; collective 2. Relativistic laser interaction transport, filamentation, (I>1020 W/cm2) & electron extreme E&B fields; generation—beyond current code core heating & burn capabilities

. FI physics is extremely challenging—it encompasses ICF, relativistic laser interaction, particle beam transport in dense plasma—the fundamental science of all intense laser interactions with high energy density plasma

FI has attracted a large active research community with several joint University-National Laboratory programs

US FI Programs Intl. FI Programs

Electron FI Rutherford Appleton Lab LULI Universita di Roma University of Rochester Imperial College, UK General Atomics University of York, UK UCLA Queens Univ., Belfast MIT OFES CEA, France UCSD IST, Lisbon Ohio State University UPM, Madrid, … University of Nevada University of Texas ILSA LLNL ILE, Osaka University

Ion/Proton FI There are three principal scientific & design challenges for electron cone-guided fast ignition

1. Compress DT fuel to high ρ, ρR around cone tip; cone tip must 0.5-1.0 MJ, 20ns survive Gbar implosion pressure compression drive

100-200 kJ, 20 ps ignitor pulse 3. Relativistic electron transport in HED plasmas; collective transport, filamentation, 2. Relativistic laser interaction extreme E&B fields; core (I>1020 W/cm2) & electron heating & burn generation—beyond current code capabilities

. No code capability exists that can model this physics self-consistently

I. Predictive Simulation Capability II. Experimental Validation We embarked on a program to build a predictive simulation capability for FI and short-pulse HED physics

3D kinetic PIC (solves full Maxwell’s equations for fields and kinetic particles, with v. high spatial, temporal resolution)

LASNEX, HYDRA rad‐hydro codes implosion & burn

2D/3D rad-hydro PSC PIC code (hydrodynamics, laser absorpon radiation transport, ionization kinetics, burn, etc.) –leverages NNSA 3D hybrid transport code development (kinetic fast electrons ZUMA hybrid code with fluid background electron transport plasma) A new Hybrid-PIC scheme enables self-consistent modeling of FI laser interaction with high density plasma

density Laser ne>>100 ncrit Full-PIC Hybrid-PIC light &1! 2!+/3.4567896:!%&'!;51!%&'3+,-./0!<=!/04:9><7!.4567896:! Full&&1 Maxwell’s! 2!+/3.4567896:3!;51!?@!76A4.!.4567896:!+,-./0B! Hybrid reduced /41!C?@!D<5=4.!/:EF! equations field equations %&'()*+($,'&-$.*/0$1"2$*34$567$890:6$&;<$+4$=>$36+4?$@A+)B'*CD*;?+46E++$+-';&$A&;60;$*'6+6F5+)G$ ncrit ~100 ncrit s !"#$ !""#$

&:=4.D<>4! . Hybrid treatment in dense region allows !!!!"#$%&'(! reduced spatial & temporal resolution !!!!)*#$%&'(! !!!!!EGG>HI! !!!!" $+,-./0(! !!!!!!CG!>HI! # . 1000x speed enhancement demonstrated in 2-D simulations

EC "GJK@EG LMI! >HIJ>4775!H4.!I/>.6:! B.I. Cohen et al., J. Comp. Phys. 229, 4591 (2010); A.J. Kemp et al., Phys. Plas. 17, 056702 (2010) Speed-up factor in 2D = 1/53!

PIC-Hybrid allows us to model cold solid-density plasma in 2D at an affordable resolution! For self-consistent transport and burn calculations we have linked a hybrid-PIC code with the ICF code, HYDRA

ZUMA: HYDRA: 3-D hybrid-PIC 3-D multiphysics relativistic radiation- electron hydrodynamics transport code ICF code

Two codes run in parallel: Energy, momentum dissimilar domains, deposition rates and meshes, and timesteops magnetic fields exchanged

Test case: 3-D relativistic electron beam injected into 50 g/cc DT plasma

Magnetic field Plasma temperature n n >2MeV We have performed>2MeV the first simulations of an FI ignitor /n /n c laser pulse at fullc spatial scale

. 200kcpu-hHot electron @2048 density, cpus on ATLAS electric ﬁeld along z Ez/E0 . Simulatelaser & 40electron µm diameter flux laser pulse for 2 ps duration 36 (a) . I=1.4x1020 W/cm2, 120x160 µm box, 50 cells/µm, 32e+32i ppc PIC.5.2D.1XL 40 80 40 z[z[!!m]m] 80 34 32 34 36 32 34 36 n /n h c -5 (b) (a) plot_electron_ene_pyz.i plot_electron_ene_pyz.i 32 -20 -20 80 plot_electron_ene_vdrift_ﬁg.i

EM field energy density EM field energy density / electric field along z 2D , L=3.5µm, 500fs E E0 36 (b) y[ y[ ! ! m] 0 0 0 m] m] ! 90% z[ 34/ 0 n>2MeV/nc P P 32 +20 +20 50% 40 -5 0 +5 DCT21M2-2 DCT21M2-2 +5 n n E P P E h h z / / / /n /n

-20 0 +20 /E P . These simulations P provide the first realistic electron source distributions for E 0 0 c c y[!m] 0 subsequent transport calculations 0 PIC.5.2D.1XL plot_electron_ene_vdrift_ﬁg.i . We observe high coupling efficiency but divergent beam due to µm-scale laser

self-focusingplot_electron_ene_pyz.i DCT21M2-2 In 2D radiation-hydrodynamic implosion designs we can keep cone tip intact and obtain small tip-core distance

Optimal fuel assembly Optimization parameters

1.5 Δz

1.0 r (mm)

0.5

200 g/cm3 0 160 µm -1.0 -0.5 0 0.5 1.0 z (mm)

. We use a single shock radiation drive . Peak ρ ~ 360 g/cc optimized for isochoric fuel assembly . Peak ρR ~ 1.36 g/cm2 . Optimize design to obtain max ρR prior . Cone-to-core Δz < 50 µm to shock breakout at cone tip . Target ignites with ~17 MJ yield We have recently begun performing fully integrated 2D/3D capsule implosion, core heating and burn simulations

. 3D simulation initialized with axisymmetric profiles at beginning of electron pulse . 47.7 million zones in HYDRA mesh with 100 million IMC photons run on 1024 processors . 36 millions zones in Zuma mesh – 1 µm resolution on each mesh

t = 0

t = 32.4 ns

Electron energy deposition rate

. We are now developing a self-consistent FI Point Design with a goal of gain>100 with 1 MJ total laser drive There are three principal scientific & design challenges for electron cone-guided fast ignition

1. Compress DT fuel to high ρ, ρR around cone tip; cone tip must 0.5-1.0 MJ, 20ns survive Gbar implosion pressure compression drive

. No code capability exists that can model this physics self-consistently

I. Predictive Simulation Capability II. Experimental Validation A new generation of facilities have come online capable of integrated tests of fast ignition physics

100kJ High Gain FI

10kJ

1kJ Vulcan PW TITAN LULI 2000 Gekko XII Texas

Short Pulse Energy Trident 100J Vulcan TAW Helen

LULI 100TW 10J 10J 100J 1kJ 10kJ 100kJ 1MJ 10MJ Long Pulse Energy A new generation of facilities have come online capable of integrated tests of fast ignition physics

100kJ High Gain FI

10kJ

1kJ Vulcan PW TITAN LULI 2000 Gekko XII Texas

Short Pulse Energy Trident 100J Vulcan TAW Helen

LULI 100TW 10J 10J 100J 1kJ 10kJ 100kJ 1MJ 10MJ Long Pulse Energy A new generation of facilities have come online capable of integrated tests of fast ignition physics

100kJ High Gain FI

10kJ FIREX I NIF ARC OMEGA EP

1kJ Vulcan PW TITAN LULI 2000 Gekko XII Texas

Short Pulse Energy Trident 100J Vulcan TAW Helen

LULI 100TW 10J 10J 100J 1kJ 10kJ 100kJ 1MJ 10MJ Long Pulse Energy TITAN: New benchmark quality experiments are combining with massively parallel full-scale PIC simulations TITAN: New benchmark quality experiments are combining with massively parallel full-scale PIC simulations

2& 9& !"#$%&'()*+*,&&&&&&&2& 2& 122& 9& 32 3 -./&012 &4567 8& :;$6<&=$*>#?)&!"#$%&'()*+*,&&&&&&&2& 2& 1& 122& @$5@6& 32 3 -./&012 &4567:;$6?%(*&0A1&B$C8&8& :;$6<&=$*>#?)& $*$%,)&=$*#>?)&0"<.<8& 2& 1& @$5@6& :;$6?%(*&0A1&B$C8& $*$%,)&=$*#>?)&0"<.<8&

. Predictive simulation capability is emerging for 2& 9& !"#$%&'()*+*,&&&&&&&2& 122& 32 3 relativistic laser interaction with HED plasma -./&012 &4567 8& :;$6<&=$*>#?)& 2& 1& @$5@6& :;$6?%(*&0A1&B$C8& $*$%,)&=$*#>?)&0"<.<8& A. G. MacPhee et al., PRL. 104, 055002 (2010)

2& 9& !"#$%&'()*+*,&&&&&&&2& 122& 32 3 -./&012 &4567 8& :;$6<&=$*>#?)& 2& 1& @$5@6& :;$6?%(*&0A1&B$C8& $*$%,)&=$*#>?)&0"<.<8& OMEGA EP: A robust experimental platform has been established for studying integrated FI physics

. First confirmation of fast electron core heating since original Osaka experiments . High laser and diagnostic performance of OMEGA EP makes it an ideal facility for studying FI physics, and validating integrated simulation codes NIF: First campaigns are planned to study full-scale compression of a cone-in-shell FI target

FI hydro-equivalent warm capsule Standard NIC hohlraum

. A series of experiments on NIF over the next 2-3 years can validate all key physics of FI compression at full hydrodynamic scale . Experimental techniques, tuning methodologies, diagnostics developed by the NIC directly apply to FI 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 DT/CD ARC capsule

. At 10 kJ, 5 ps ARC can be used to demonstrate efficient fast electron heating of a full scale hydro assembly, and thus, provide a high degree of confidence in a final high gain fast ignition point design We aim to demonstrate FI feasibility within the next 4-5 years through predictive simulation & experiment

. The last two years have seen tremendous progress in the :5";<=>$?@AB5$ development of large-scale predictive -+(C67(-'$&'(),$ simulation capability for FI—we are 8D/*',8'1$E$.F-1$

close to fully integrated simulations !"#$!%#$&'()$ *+,)-$+.,'-/0'1$ . We are applying these tools to develop and refine a fully self-consistent FI 2345$67.-8($&'()$ )*)&9-'1$9-+1,/'-9$ Point Design

. We now have the laser facilities required to experimentally validate all key physics of FI—relativistic laser interaction, full-scale fuel compression, and core-heating. The national and international research communities in FI are working toward this in a highly co-ordinated way