Highlights of talk : 1.e+e- pair laser production 1.Collisionless shocks 1.Colliding laser pulses...

Highlights of talk :

1. e+e- pair laser production

1. Collisionless shocks

1. Colliding laser pulses accelerator

e+e- plasmas can be created by irradiating high-Z targets with ultra-intense lasers

Fast ionsLaser

Au foil

1020 W/cm2

for 10 p Wilks et al., Phys. Plasmas 8, 542 (2001), Liang and Wilks, PRL (1998)

e+e-

Thot=[(1+I2/1.4.1018)1/2-1]mc2

Thot > mc2 when I2 >1018 Wcm-2

(<==> eE/m > c)

LLNL PW-laser striking target

Au

e+e-

e

(Liang & Wilks 1998)

Sample Laser Numbers

1 PW = 1 kJ / 1 ps

1 PW / (30 μm)2 = 1020 W/cm2

1020 W/cm2/ c~ 3.1016 er /gcm3 ~ 2.1022 e+ - /e cm3

S olidA u ion dens ity~ 6.1022 /cm3

n+/ne ~ 4.10-3

Bequipartition ~ 9.108 G

PAIR PRODUCTION BY SUPERTHERMALS ON HIGH-ZTARGET:

dN+/dt = (dN+/dt)eion + (dN+/dt)γion + (dN+/dt)γγ1 > 2 3

f or thi (n << 20 μm) lase r targe . ts HencedN+/ = dt (N+ + N-) < Nion (f(γ) vσeion )>

f(γ) is normalize dsupertherma l distr ibutionfunc tionandσeion ~ 1.4 10x –30 cm2 Z2 ( lnγ)3 f orγ >> 1

istride nt pai r produc tionc rosssec tion( +e ionË e+ion+γγ):Solving above equation:N+ = Z Nion {exp(Γt) – 1}/2 ~ ZNionΓt/2 for Γt << 1Ë N+/Ne ~ Γt/2 ~ 2 x 10–3 for t ~ 10 ps, I = 1020 Wcm-2

For Au: N+ ~ 1022 cm-3

e+e-)

B-H pair-production has larger cross-section than trident, but it depends on bremsstrahlung photon flux and optical

depth of the high-Z target

B-H

trident

(Nakashima & Takabe 2002 PoP)

20 40

Pair Creation Rate Rises Rapidly then plateaus above ~1020Wcm-2

1019W/cm2

1020W/cm2

Liang et al 1998

Nakashima & Takabe 2002f(E) approximates a truncated Maxwellian

2.1020W.cm-2

0.42 p s

e+e-

125μm Au

LLNL PW laser experiments confirm copious e+e-production

Cowan et al 2002

Trident dominates at early times and thin targets, but B-H dominates at late times and thick targetsdue to increasing bremsstrahlung photon density

Nakashima & Takabe 2002

(Wilks & Liang 2002Unpublished)

Nakashima & Takabe 2002

(Nakashima & Takabe 2002)

Two-Sided PW Irradiation may create a pair fireball

After lasers are turned off, e+e- plasmas expands relativistically, leaving the e-ion plasma behind.Charge-separation E-field is localized in the e-ionplasma region. It does not act on the e+e- plasma

(Liang & Wilks 2003)

e+e-

e-ion

ux

x

Ex

x

Phase plot of e+e-component

Weibel Instability in 3D using Quicksilver (Hastings & Liang 2007)e+e- colliding with e+e- at 0.9c head-on

Px vs x

By vs x

QuickTime™ and a decompressor

are needed to see this picture.

B

3D Simulations of Radiative Relativistic Collisionless Shocks

Movie by Noguchi

Psyn

Ppic

Calibration of PIC calculation again analytic formula

px

By*100

f(γ)

γ

Interaction of e+e- Poynting jet with cold ambient e+e- shows broad

(>> c/e, c/pe) transition region with 3-phase “Poynting shock”

ejecta

ambient

ejectaspectralevolution

ambientspectral evolution

γ

ejecta e- shocked ambient e-

Prad of “shocked” ambient electron is lower than ejecta electron

Propagation of e+e- Poynting jet into cold e-ion plasma: acceleration stalls after “swept-up” mass > few times ejecta mass. Poynting flux decays via mode conversion and particle acceleration

ejecta e+ ambient e- ambient ion

px/mc

By

x

By*100

pi*10

pi

ejecta e+

ejecta e-

ambient ion

ambient e-

γ

f(γ)-10pxe-10pxej

100pxi

100Ex

100By

Prad

Poynting shock in e-ion plasma is very complex with 5 phases and broad transition region(>> c/i, c/pe). Swept-up electrons are

accelerated by ponderomotive force. Swept-up ions are accelerated by charge separation electric fields.

ejecta e- shocked ambient e-

Prad of shocked ambient electron is comparable to the e+e- case

Examples of collisionless shocks: e+e- running into B=0 e+e- cold plasma ejecta hi-B, hi-γ weak-B, moderate γ B=0, low γ

swept-up

swept-up

swept-up

100By

ejecta

swept-up100By

100Ex

100By100Ex

-px swept-up

-pxswrpt-up

ejecta

When a single intense EM pulse irradiates an e+e- plasma,

it snowplows all upstream particles without penetrating

to=10 to=40

LLNL PW-laser striking target

By

px

By

px

thin slab of e+e-

plasma2 opposite EM pulses

It turns out that it can be achieved with two colliding linearly polarized EM pulses

irradiating a central thin e+e- plasma slab

How to create comoving J x B acceleration in the laboratory?

B B

I=1021Wcm-2

=1μmInitial e+e- n=15ncr,

kT=2.6keV,thickness=0.5μm,

px

x

By

Ez

Jz

Acceleration by colliding laser pulses appears almost identical to that generated by EM-dominated outflow

Poynting Jet Colliding laser pulses

to=40

x

Two colliding 85 fs long, 1021Wcm-2, =1μm, Gaussian laser pulse trains can accelerate

the e+e- energy to >1 GeV in 1ps or 300μm(Liang, POP 13, 064506, 2006)

637μm-637μm

Bypx

slope=0.8γ

x

Gev

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to = 40 to = 80™ QuickTime and a Graphics decompressor

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t o = 120 to = 160

Details of the inter-passage of the two pulse trains

ByEz

By

Particles are trapped and accelerated by multiple ponderomotive traps, EM energy is continuously transferred to particle energy

Notice decay of magnetic energy in pulse tail

to=4800

Px/100

By/100n/ncr

Momentum distribution approaches ~ -1 power-law and continuous increase of maximum energy with time

f(γ)

γ

-1

to=4000

degree

γ

1GeV

Highest energy particles are narrowly beamed at specificangle from forward direction of Poynting vector,

providing excellent energy-angle selectivity

to=4800

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are needed to see this picture.

QuickTime™ and aGraphics decompressor

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Elaser

Ee+e-

Maximum energy coupling reaches ~ 42%

n=0.025 n=9

If left and right pulses have unequal intensities,acceleration becomes asymmetric and sensitive to

plasma density, Here I<--=8.1020Wcm-2; I-->=1021Wcm-2

Pulses transmittedat max. compression

Pulses totally reflectedat max. compression

2D studies with finite laser spot size: D=8 μm

y

x

x

Bz

y

x

Eem

E e+e-

γ

(degrees)

y

x

px

x

Compression & Acceleration of overdense 0.5 μm thick e-ion plasma slab by 2-side irradiation of I=1021 Wcm-2 laser pulses

10*pi

pe

Acceleration of e-ion plasma by CLPA is sensitive to the plasma densityn=9 n=1

n=0.01 n=0.001

10pi

pe

100Ex 100Ex

1000Ex 10000Ex

10pi

10pi10pi

e+e- e-ion

f

γ γ

Electron energy spectrum is similar in e+e- and e-ion cases

y

x

y

x

px

x

Eem

Ee

Ei

γe 100γi

(degrees)

2D e-ion interaction with laser spot size D=8 μm

ion

e-

Conceptual experiment to study the CPA mechanism withThree PW lasers

e/pe

log<γ>

100 10 1 0.1 0.01

4

3

2

1

0

GRB

Galactic Black Holes

INTENSE LASERS

Phase space of laser plasmas overlaps most of relevant high energy astrophysics regimes

High-

Low-

PulsarWind

Blazar

Rpe/c

mi/me