Enhancement of electron injection using two auxiliary interfering-pulses in LWFAYan Yin (银燕 )
Department of PhysicsNational University of Defense Technology
Outline Laser Wakefield Accelerator (LWFA)
Trapping, Acceleration & Injection of Electrons
Enhancement of Electron Injection by Using two Auxiliary Interfering-Pulses in LWFA
Stage 1: Moving Electron Density Grating Formation in the Beating Field of Auxiliary Pulses
Stage 2: The Interfering-pulses Auxiliary LWFA (IPA-LWFA) scheme
LWFA: Background & Progress
E. Esarey, C. B. Schroeder, and W. P. Leemans, Rev.Mod.Phys., 81,001229(2009)
PBWA:
21
21
kkvp
S. P. D. Mangles et al., NATURE, 431, 535, 2004.
C. G. R. Geddes et al., NATURE, 431, 538, 2004.
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J. Faure, C. Rechatin, A. Norlin et al., NATURE, 444, 737, 2006.
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List but a few…..
Trapping & Acceleration of Electrons Rayleigh diffraction
Pump depletion, instability, …
Dephasing length:
ppdL 2
E. Esarey and M. Pilloff, Phys. Plasmas, 2, 1432 (1995)
Effects limiting acceleration Dephasing length
Rayleigh diffraction
Pump depletion, beam loading, instability, …
Electron boosted
Wake slow down
How does the election enter the acceleration phase of wakefield?
Injection of Electrons
Self-injection Optical injection
Ponderomotive injection Cold optical injection
Ionization injection Injection by density transition
Self-injection in bubble regime
S. Kalmykov et.al., Phys. Rev. Lett., 103, 135004 (2009)
V.Malka et.al., Nature Phys. 4,447(2008)
Ponderomotive injection by colliding pulsesD. Umstadter, J. K. Kim, and E. Dodd, Phys. Rev. Lett., 76, 2073(1996)
E. Esarey et. al., Phys. Rev. Lett., 79, 2682(1997)
H. Kotaki et.al., Phys. Plasmas, 11, 3296(2004)
J. Faure, C. Rechatin, A. Norlin et al., Nature, 444, 737, 2006.
H.Kotaki et.al., Phys. Rev. Lett., PRL 103, 194803 (2009)
Cold optical injection by using circularly polarized colliding pulses
X. Davoine et.al., Phys. Rev. Lett., 102, 065001(2009)
Enhanced self-injection of electrons by using two auxiliary interfering-pulses in LWFA
p
p
1 2
0
Auxiliary laser intensity: nonrelativistic ~1016W/cm2
Stage 1
Moving Electron Density Grating Formation in the Beating Field of
Auxiliary Pulses
From the set of two-stream fluid equations, the electron density modulation equation is obtained [1]:
[1] Z. M. Sheng, J. Zhang and D. Umstadter, Appl. Phys. B 77, 673 (2003).
Standing field
Quasi-charge-neutrality
Small velocity modulation
Z. M. Sheng, J. Zhang and D. Umstadter, Plasma density gratings induced by intersectinglaser pulses in underdense plasmas.Appl. Phys. B 77, 673 (2003).
Beating field
Especially, when
2 2
1 22 sin 2 sin sin 2e p pp
k c a an kx t t kx t
Spatial period:
Moving velocity:
k/
kvph 2/
1 0 2 00.8
085.021 aa
cnn 04.00 0p 2.0
1D PIC simulation:
0 50 150 200
90 92 94 96 98 1000.00
0.05
0.10
0.15
0.20
n e / n
cr
x / L
theoretical prediction
simulation results
0.57λ0 0.57 λ0
t=140T0
theoretical prediction
simulation results
0.113c 0.09c
Large velocity modulation of electrons
Pre-accelerated electrons are more easily trapped in the wakefield excited by the pu
mp laser
Stage 2
The Interfering-pulses Auxiliary LWFA (IPA-LWFA) scheme
1 0 2 00.8
0.21.0 021 aaacnn 04.00
1D PIC simulation:
0 50 150 200
Perpendicularly-polarized
It is the initial status of plasmas when the short
intense pump laser is incident.
IPA-LWFA LWFA
2D PIC simulation
2D PIC simulation
2D PIC simulation
2D PIC simulation
Summary
Efficient injection schemes are desired for electron acceleration
Moving electron density gratings can be generated by two low-intensity interfering pulses
Enhanced self-injection of electrons is obtained in the IPA-LWFA scheme.
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