Enhancement of electron injection using two auxiliary interfering-pulses in LWFAYan Yin (银燕 )

Department of Physics

National 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.

J. Faure, Y. Glinec, A. Pukhov et al., NATURE, 431, 541, 2004.

J. Faure, C. Rechatin, A. Norlin et al., NATURE, 444, 737, 2006.

W. P. Leemans, B. Nagler, A. J. Gonsalves et.al., Nature Phys., 2. 418, 2006.

I. Blumenfeld, C. E. Clayton, F. J. Decker et.al., Nature, 445,741, 2007.

N. A. M. Hafz, T.M. Jeong, I. W. Choi et.al., Nature Photonics, 2, 571, 2008.

H.-P. Schlenvoigt, K. Haupt, A. Debus et.al., 4, 130, 2008.

S. F. Martins, R. A. Fonseca, W. Lu et al., NATURE Phys. , 6, 311, 2010.

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 pulses

D. 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/

kv ph 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.