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LLNL Fast Ignition Program US-Japan Workshop San Diego, CA March 11, 2010. Cliff Chen on behalf of Pravesh Patel. Fast Ignition research programs have emerged at numerous universities and national labs across the US. National FI Programs. Intl. FI Programs. Electron FI.

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llnl fast ignition program us japan workshop san diego ca march 11 2010

LLNL Fast Ignition ProgramUS-Japan WorkshopSan Diego, CAMarch 11, 2010

Cliff Chen

on behalf of

Pravesh Patel

slide2
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
several options are being persued for delivering the required particle flux to the core
Several options are being persued for delivering the required particle flux to the core

Electrons (cone-guided)

Electrons (laser channeling)

Laser

Protons

Ions

slide4
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
major program elements point design experimental campaigns
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

slide6
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)

there are three principal design issues for electron cone guided fast ignition
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
slide8
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)

there are three principal design issues for electron cone guided fast ignition1
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

in 2d designs we must assemble the fuel around the cone tip this is challenging at full scale
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
typical simulation result with calculated single shock dt radiation drive
Typical simulation result with calculated single-shock DT radiation drive

Very close to 1D performance over most of shell

slide13
Rev 1 hydro implosion design achieves good peak density and rR, but with slightly long transport distance

100 g/cm3

240 µm

there are three principal design issues for electron cone guided fast ignition2
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

2 a rev 1 electron source for nif arc is calculated with high resolution 2d pic simulations
[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
there are three principal design issues for electron cone guided fast ignition3
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

3 transport core heating hybrid pic code lsp combines electron source and rad hydro data
[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)

we have produced the first transport calculations using realistic hydro and pic input calculations
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)

slide19
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

slide20
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)

slide21
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
we are benchmarking laser interaction and transport physics with experiments on titan and omega ep
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

slide23
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)

slide25
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)
experimental campaign fi can leverage the enormous capability for implosion tuning developed by nic
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

the integrated nif experiment will measure the fast electron coupling efficiency to the core
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

fi has two major goals establishing feasibility requirements for high gain demonstrating high gain
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)

slide30
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