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High Intensity Laser and Energetic Particle – Matter Interactions

Chuang Ren University of Rochester

Workshop on Scientific Opportunities in HEDLPAugust 26, 2008, Washington DC

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• Acknowledgement– J. Tonge & W. Mori (UCLA); L. O. Silva (IST); K.

Krushelnick (Michigan); A. Friedman (LLNL/LBNL); Y. Sentoku (UNR); J. Zuego (LLE)

high intensity

High energy content

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Introduction

• New laser/beam sources can explore new applications and fundamental physics problems

• Realizing these opportunities requires understanding in high intensity laser- and energetic particle-matter interactions– Ultra short pulse – plasma interaction (PWFA, new radiation

sources, QED, …)– kJ short pulse – relativistic plasmas interactions (FI,

collisionless shocks, proton accelerations…)– Energetic particle – matter interactions (FI, HIF, ….)

• Long-term healthy growth of the HEDLP field needs both curiosity-driven and application-driven research– Attract and retain new talents

Research program has put ultra short-pulse laser and beam physics at the Forefront of Science

Acceleration, Radiation Sources, Refraction, Medical Applications

Plasma Wakefield Accelerators Is a Major Driver behind the Field Plasma Wakefield Accelerators Is a Major Driver behind the Field of Ultra of Ultra SShort-Pulse Laser and Beam – Plasma Interactions

• Plasma ion channel exerts restoring force => space charge oscillations•Immobile ions & relativistic ‘cold’ electrons •Synchrotron radiation

Blowout RegimeRosenzweig et al. 1990, Puhkov and Meyer-ter-vehn 2002, Lu et al, 2006 and 2007

Driven by an electron beam Driven by a laser pulse

Large wake for a laser amplitude ao=eEo/moc ~ 1 or a beam density nb~ no

Laser and beam requirements on I, , P require 100TW to PW laser and beam (such as at SLAC) facilities

One-on-One Simulations Agree with Experiment

Nature 445 741 15-Feb-2007

E-167: Energy Doubling of the 42 GeV SLAC beam in a Plasma Wakefield

Full scale three-dimensionalparticle-in-cell simulations using the code QuickPIC identified that the energy gainSaturated due to head erosion

Validation: OSIRIS simulation of LBNL Nature experiment

Excellent agreement?

Total # of electrons:

Simulation: 1.7 109

Experiment: 2x109

Central energy:

Simulation: 90 MeV

Experiment: 86

Energy spread:

Simulation: 10 MeV

Experiment: 1.8 MeV

+10 GeV in uniform plasma

•Two regimes for laser propagation:

•Self-guiding propagation regime until 10 cm

•Depletion leads to diffraction after 10 cm

•Accelerating gradient in good agreement with theory

•QuickPIC: 0.8 GeV/cm

•Theoretical: 0.6 GeV/cm

Self-guiding: stronger self-channeling

Self-guiding: stronger self-channeling

Energy chirpadjust initial beam position

Energy chirpadjust initial beam position

@ 21.7 cm

@ 5.4 cm

5.4 cm

21.7 cm

Laser spot evolutionLaser spot evolution

Spectral evolutionSpectral evolution Phase-space evolutionPhase-space evolution

Diffraction: weaker self-channeling

Diffraction: weaker self-channeling

Main resultsMain results

Setup for -ray generation and photonuclear reaction production

- is direct laser interaction with nucleus possible?

14.8 MeV 238U(,fission)

1 10 1000

Cro

ss s

ecti

on

(mba

rn)

200

150

100

50

Incident -ray energy (MeV)

Samples 12C, 63Cu, 238UHe gas2.1019 e/cm340 TW, 30 fs,

I=1019 W/cm2

Supersonic nozzle100-150 MeV e-

Laser

Ta-converter

Cross-section 3 mm 238 U

70-75% of the -radiation in the relevant energy range (6-25 MeV) is contained within a half angle of ~9 degrees with respect to the incident electron direction. (Courtesy K. Krushelnick)

S. Reed et. al. APL 2006

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We have developed a systematic understanding of many LPI phenomena

• Fundamental processes such as SF & hosing are understood

• Mutual interactions btw laser beams---braided light

Braided Light, Ren et al., PRL’04

€

Pj

d2r r j

dτ 2= −

∂

∂r r j

[−kp

2

8k02

P1P2

W12 + W2

2exp(−

2d2

W12 + W2

2)]

d2 ≡ (r r 1 −

r r 2)2 = (X c1 − Xc2)2 + (Yc1 −Yc2)2, Pj ≡ A j

2W j2

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Future Ultra-High Intensity Lasers Can Test Fundamental Physics Laws

• Today’s laser has I~1022 W/cm2 (Michigan)– Electron radiation damping important

• Ambitious ILE/ELI projects aim at 1025 W/cm2 in 2014– 20 PW, 1024 W/cm2 beam in 2011

• At 1023 W/cm2, the Unruh effect can be tested (radiation from an accelerated vacuum)

• The Schwinger limit: 1030 W/cm2

– Spontaneous pair creation

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Upcoming kJ-class short pulses open up new LPI regimes of LPI

• Significant ion density modification• Density profiles dynamically determined

• Significant plasma heating• Relativistic electron temperatures• Laser absorption coupled to density profile evolution

• Many applications requires understanding of energetic particle – matter interactions

• Interactions with self-generated fields

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Propagation of high-intensity pulses in underdense plasmas

• Intense laser – underdense plasma interactions are important to– Fast ignition– Laser – solid experiments in general

due to pre-pulses

• Intense lasers cannot propagate as linear waves– Laser self-focusing and hosing– Transverse and longitudinal

denisty modification– Propagation via ponderomotive

push

channeling/hole-boring pulse

ignition pulse

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• Relativistic SF/Filament• Ponderomotive SF/Filament

– Micro channels created from laser filaments

• Central filament widening & shock launching– Laser snowplows away micron

channel walls to form a single channel

– Transverse expansion through high-mach-number shocks

• Vt~0.03c ~2Cs (at 500 keV)• Channel wider than laser width

– Laser hosing/channel branching seen

Stages of channeling process

Ela

ser

ni

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A preformed channel significantly improves the transmission of the ignition pulse

• The residual plasma is heated to relativistic temperatures– <>~12– Reduced nonlinear

interactions

0.0001

0.001

0.01

0.1

1

0 3 6 9 12

Pout/Pin

Time(ps)

10 2̂0W/cm2 with a T=6.5Mev

channel10 1̂9W/cm2 with a T=6.5Mev

channel

10 2̂0W/cm2 without a channel

10 1̂9W/cm2 without a channel

10 1̂9W/cm2 with a T=5kev

10 1̂9W/cm2 with a T=1kev

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LPI in Relativistic Plasmas Is a New Research Area

• Macro-size HEDLP plasmas (1 Gbar)• Relativistic pressure reduce electron

quiver momentum– Vosc/c=anp/ϒ(e+p) [Tzeng & Mori, prl’98]

• LPI needs to be studied in this new regime– SF & hosing

• Coupling with IAW, not EPW

Intense laser-overdense plasma interactions

X2

130µ

X1150µ

51µ41µ 20µ

laser

Flux diagnostic planes

44 0.8

• Isolated boundaries- we believe this is essential

– 100 nc Plasma

• 20 radius resistive core – particle drag Force = -k p -2 – passes low and high energy particles

(<50KeV, >10MeV)

• Box size 150 x130 – 5x108 cell – Grid size: 0.05 c/0 , 0.5 c/ p

– 4 electrons per cell, 109 particles– Te = 1.0 keV, mI= 3672me

• Duration 2.5ps +– 9104 time steps– 1 - 2 months real time

• 1-laser, W0 = 20 – Spot size matches core

High Intensity Laser DeliversPower to Core more Efficiently

Laser Intensity8x1020 W/cm2

2x1020 W/cm2

5x1019 W/cm2

8x1020 W/cm2 laser delivers:5x the Power of 2x1020 W/cm2 laser 50x the Power of 5x1019 W/cm2 laser

ScaledTo LaserIntensity

~ 50x

~ 10x

Net Electron Energy Flux Spectrum Peaks at Low Energy*

Through plane 0.8 m in front of core

Intensity8x1020 W/cm2

2x1020 W/cm2

5x1019 W/cm2

MeV

Scaled to laser power @ 2.5 ps

.25 MeV

.9 MeV

2.6 MeV

*compared to ponderomotivescaling

P1 (mec)

P2

(mec)

Energy is Transported in Hot Bulk

Distribution at 1.5 ps

TailHot Bulk

F (log(n))

P1 (mec)

laser

Sample Region

Peaks at -0.1 mec

80% - 90% of NET energy flux

0 10

6

-6-6

-10 200

Magnetic Filamentation and Formation of Shocks

• Weibel instability relaxes anisotropic particle distributions as well as filamenting currents.

• Magnetic fields reach over 100MG for high laser intensity runs - channeling usable 2 MeV energy electrons in x1 direction.

8x1020 W/cm2 @ 1 ps

Dynamics in the front surface of the Dynamics in the front surface of the targettargetDynamics in the front surface of the Dynamics in the front surface of the targettarget

Mass build up/compression & strong electric Mass build up/compression & strong electric fieldfieldFilamentation @ targetFilamentation @ target

t ~ 350 fs

Weibel instability

Return current

L. O. Silva | August 2008

L. O. Silva | August 2008

Electron dynamics different @ higher Electron dynamics different @ higher intensitiesintensitiesElectron dynamics different @ higher Electron dynamics different @ higher intensitiesintensities

II 00 =

5

x1

0 =

5

x1

021

21 W

/cm

W/c

m22 I

I 00

= 1

.25

x1

0 =

1.2

5x1

019

19 W

/cm

W/c

m22

return current e-

trapped e-

accelerated e-

e- from target front

accelerated e-

particle tracking

L. O. Silva | August 2008

L. O. Silva | August 2008

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Magnetic fields play the same role in the formation of laser-driven and relativistic shocks in GRB’s

• GRB afterglow requires magnetic fields– Weibel instabilities from colliding shells can provide

the B-field• PIC simulations of relativistic collisionless shocks

(Spitkovsky ‘08,γ~15) show the same importance of the B-field

• The key is to understand up- and down-stream particle distribution– Nonlinear evolution of current-driven instabilities

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• Understanding energy loss of heavy ions in matter– Loss to free e- understood– Difficulty is in calculating loss to bound e- with self-

consistent state (due to heating and collective effects)

– These effects tend to increase energy loss rate– Fusion only involves fixed charge-state particles

• Atomic physics is also important in laser-cone interactions

Ack: A. Friedman

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• Priority: LPI in plasmas of relativistic temperatures– Important to FI, lab astrophysics and basic science

• Laser absorption in self-consistent density profiles• Particle transport in self-generated fields

– Availability of kJ short pulse facilities– Peta-scale simulation capabilities to understand

experiments• 3D PIC simulations of 200×100×100 μm3 need 4 trillion cells

and a month on a peta-flop machine