qed in ultra-intense laser

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QED IN ULTRA-INTENSE LASER

FIELDS

TOM HEINZL

PIF2010, KEK, TSUKUBA

24 NOVEMBER 2010

With: N. Iji, K. Langfeld (UoP), C. Harvey, A. Ilderton, M. Marklund (Ume), A. Wipf (Jena),H. Schwoerer (Stellenbosch), B. Kmpfer, R. Sauerbrey, D. Seipt (FZD)


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Outline

1. Introduction

2. Strong Fields: Theory

3. rong e s: xamp es1. Nonlinear Compton Scattering

2. Laser Pair Production

3. Vacuum Birefringence4. Conclusion and Outlook


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Introduction


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50 Years of Laser Development

Important parameter:

dim.less amplitude

Energy gain of

across laser wavelength

: relativistic

(adapted from Mourou, Tajima, Bulanov, RMP 78, 2006)


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Regime of Extremes Current magnitudes:

Power

Largest e.m. fields currently available in lab

But: fields pulsedand alternating

Electric field

Magnetic field


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Laser Projects CLF Vulcan 10 PW

1023 Wcm-2

Construction by 2014 (?)

Bud et: 20 M ?

ELI

>100 PW (Exawatt ?)

>1025 Wcm-2

Budget: several 100 M

Construction by 2016 (?)

Building (projected)


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2. Strong Fields: Theory


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Modelling a laser In order of increasing complexity:

Plane wave Infinite (IPW)

Pulsed (PPW)

w

z0

Finite T-duration Infinite transverse extension

Gaussian beam:

Finite transverse waist w

Finite longitudinal extensionz0

T


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Plane waves: peculiarities Null wave vector

Electromagnetic field only dependent on invariant phase

Null:

No intrinsic invariant scale!

Need (probe) momentum to build invariants

E.g. (TH, A. Ilderton, Opt. Comm. 2009)


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Charge in IPW Solution of Lorentz force eq.: rapid quiver motion

(momentum ) Charge acquires quasi-momentum

Longitudinal addition consequence:

Effective mass squared

The basic intensity effect!

(Sengupta 1951, Kibble 1964)


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Strong-field QED Probe photons

Volkov soln of Dirac eqn in PWfield (Volkov 1935)

ec rons resse y aser p o ons---------

Volkov electron:

Build transition amps between Volkov electrons from

Feynman rules (`Furry picture)


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Main issues

Intensity dependence of elementary processes

see below

Finite (beam) size effects (see below )

Beyond plane waves (? )


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Exploring intensity dependence High intensity ( ) = uncharted region of

standard modelenergy

Hi h-intensit QED

all-optical

Backscattered

(5 GeV )

100 102 103 106

1Vulcan

1PW

10PW

ELISLAC


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3.1 Nonlinear Compton Scattering (NLC)3. Strong Fields: Examples


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NLC scattering Expand Furry picture Feynman diagram

Sum over all processes of the type

Schott 1912; Nikishov/Ritus 1964,

Brown/Kibble 1964, Goldman 1964

emission


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NLC: main features No energy threshold!

Classical limit: Thomson ( ) For : frequency upshift

Used for

X-ray generation

Nonlinearity:

Terawatt laser pulse(a0 = 0.05)

Electron Bunch

(e = 235)

Femtosecondgamma-ray pulse

(0.78 MeV)

T-REX, LLNL (2008)


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NLC cont

d

For high intensity,

modified Compton edge

In particular:

Higher harmonics: n >1 (nonlinear)

Overall blueshift maintained as long as Redshift of n=1 edge


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NLC spectrum: maina0 effects

Linear Compton

edge

Higher

harmonics, n >1

Red-shift

C. Harvey, TH, A. Ilderton,

PRA 79, 2009


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a0 dependence (lab)

Tuning a0similar to changing frame: when

inverse Compton Compton C. Harvey, TH, A. Ilderton, PRA 79, 2009


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Finite Size Effects

Strongly focussed: Weakly focussed:

laser

ee

laser


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Finite Size NL Thomson Spectra

Strongly focussed: Weakly focussed:

= 0 mrad

= 5 mrad

= 10 mrad

TH, D. Seipt, B. Kmpfer, PRA 81, 2010


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3.2 Laser Pair Production (PP)3. Strong Fields: Examples


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Stimulated PP

Obtained from NLC via crossing

Main new feature: energy threshold

Experiment SLAC E-144 (1995): combine bothprocesses ...


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SLAC E-144 (Bula et al. 96, Burke et al. 97)

Two stages: NLC

stimulated PP

New development: prediction of pair cascades(Bell, Kirk et al.; Narozhny, Fedotov, Ruhl et al.)

Gil Eisner, Photonics Spectra 1997


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Stimulated PP: finite-size effects

IPW:

triple-diff rate = deltacomb

above threshold ( )

PPW: dependence on cycles

per pulse,

Sub-threshold signals

IPW approached for

TH, A. Ilderton, M. Marklund, 2010


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Wave train vs. pulse: vs.

Spectrum = fingerprint of pulse!


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Spontaneous (vacuum) PP (G. Dunnes talk)

Feynman diagram

vacvacuum

breakdown

Im = 0~

Nonzero for , (Schwinger 1951)

Identically zero for pure (no work done)

Identically zero for PW ( compensates )


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3.3 Vacuum Birefringence (VB)3. Strong Fields: Examples


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Heisenberg, Euler 1936

...even in situations where the [photon] energy is

not sufficient for matter production, its virtual

possibility will result in a polarization of thevacuum and hence in an alteration of Maxwells

equations.


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Optical Theorem (Kramers-Kronig)

Total PP rate can be obtained via

Virtual dipoles feel presence of

Re : change of polarisation state diagonalisation of (for X-fields = PW )

two nontrivial eigenvalues

Vacuum polarisation


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Vacuum birefringence (Brezin, Itzykson 1970)

Calcite crystal

wo n ces o re rac on (Toll 1952)

Dim.less (small) parameters:

Field strength:

Probe frequency

fine structure const


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Experiment: measure ellipticity

Phase retardation of e+


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Analysis

ellipticity (squared)

ower aw suppresse

Optimal scenario @ ELI

large intensity:

large probe frequency (X-ray, ):

New record in polarisation purity: @ 6 keV(Marx et al., Opt. Comm., 2010)


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for : 3 GeV @ ELI, 10 GeV @ Vulcan10PW

Large-birefringence via NLC

(Toll 1952

TH, O. Schrder

NB: SLAC E-144 had

Shore 2007)

(K. Langfeld)

Anomalous dispersion Absorption PP


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Summary

Stimulated PP

vacuum PP

NL Compton/Thomson

Vacuum birefringence


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Conclusion

Laser power approaching exawatt regime

Extreme field physics Schwinger limit: QED Experiments planned or under way

-ray genera on:

Theory ( dependence) :

Ok for plane wave models

Challenge: incorporate realistic laser beam model Finite size effects

Beyond plane waves

Numerical approaches


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for your attention

Thank you very much...

qed in ultra-intense laser

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