highlights of talk : e+e- pair laser production collisionless shocks
DESCRIPTION
Highlights of talk : e+e- pair laser production Collisionless shocks Colliding laser pulses accelerator. e+e- plasmas can be created by irradiating high-Z targets with ultra-intense lasers. LLNL PW-laser striking target. e+e-. Au. T hot =[(1+I l 2 /1.4.10 18 ) 1/2 -1]mc 2 - PowerPoint PPT PresentationTRANSCRIPT
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Highlights of talk :
1. e+e- pair laser production
1. Collisionless shocks
1. Colliding laser pulses accelerator
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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
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e+e-
e
(Liang & Wilks 1998)
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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
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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-)
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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
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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
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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
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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
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(Wilks & Liang 2002Unpublished)
Nakashima & Takabe 2002
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(Nakashima & Takabe 2002)
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Two-Sided PW Irradiation may create a pair fireball
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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
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Phase plot of e+e-component
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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
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QuickTime™ and a decompressor
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B
3D Simulations of Radiative Relativistic Collisionless Shocks
Movie by Noguchi
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Psyn
Ppic
Calibration of PIC calculation again analytic formula
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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
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ejecta e- shocked ambient e-
Prad of “shocked” ambient electron is lower than ejecta electron
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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
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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.
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ejecta e- shocked ambient e-
Prad of shocked ambient electron is comparable to the e+e- case
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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
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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
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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
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I=1021Wcm-2
=1μmInitial e+e- n=15ncr,
kT=2.6keV,thickness=0.5μm,
px
x
By
Ez
Jz
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Acceleration by colliding laser pulses appears almost identical to that generated by EM-dominated outflow
Poynting Jet Colliding laser pulses
to=40
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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
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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
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Momentum distribution approaches ~ -1 power-law and continuous increase of maximum energy with time
f(γ)
γ
-1
to=4000
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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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Elaser
Ee+e-
Maximum energy coupling reaches ~ 42%
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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
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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
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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
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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
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e+e- e-ion
f
γ γ
Electron energy spectrum is similar in e+e- and e-ion cases
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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-
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Conceptual experiment to study the CPA mechanism withThree PW lasers
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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