Studies of laser-driven
magnetic reconnection
& collisionless shockwaves
Yutong Li
National Laboratory of Condensed Matter Physics
Institute of Physics, Chinese Academy of Sciences, Beijing
•
•
Session 1P2
• 5:30 - 5:45 pm Jiayong Zhong
• 5:45 - 6:00 pm Yutong Li
Session 2A2
• 12:15 - 12:30 pm Quan-Li Dong
April 30-May 4 HEDLA 2012
Our research team
National Lab. of
Condensed Matter
Physics, CAS
(Y. T. Li, Q. L. Dong, et al.)
National Astronomical
Observatories
(G. Zhao, J. Y. Zhong, F. L.
Wang, et al.)
Shanghai Jiao Tong U.
(J. Zhang, et al. )
National Laboratory on High Power Lasers and
Physics (J. Q. Zhu, et al.)
CAEP (W. D. Zheng, J. Y. Zhang, Y. K. Ding, et al)
Peking U. (X. G. Wang et al.)
ILE, Osaka U., Japan
(H. Takabe, H. Nishimura, Y. Sakawa, et al.)
Korea Atomic Energy Research Institute
(Yong-Joo Rhee, et al.)
Outline
• Laser- driven magnetic reconnection
(LDMR)
• Collisionless shockwaves formed by two
counter-streaming plasmas
Magnetic fields in laser-plasma interactions (~100T)
Toroidal B field
B field measured by proton
radiography
1.2 ns
C. K. Li et al., Phys. Rev. E. 80, 016407
Thermal electric source
B/t
~Texne
J. A. Stamper et al, PRL,
34,138 (1975)
Toroidal B fields are
 Mega Gauss (100 T)
 Concentrated on a hemispherical bubble
 Surrounding and expanding
Constructing LDMR
Magnetic reconnection occurs
 Magnetized plasmas encountered each other
 With oppositely pointed B-fields
Side view
Front view
LDMR examples
X-point
Gold
Yates et al., PRL, 49,1702 (1982)
X-ray emission
Nilson et al., PRL 97, 255001 (2006)
Optical probe
LDMR examples
Au foil or D 3He-filled capsule
Laser on from 0 – 1 ns
5 mm
0.04 ns
0.67 ns
1.42 ns
C. K. Li et al., PRL 99, 055001 (2007)
L. Willingale et al., PoP 17, 043104 (2010)
Proton probe
Magnetic reconnection jets in solar flares
MR model is used to explain the solar flare bursts.
Yohkoh/SXT
Astronomical observed evidence for MR model
--- loop-top hard x-ray source
Masuda, S, et al.
A loop-top hard X-ray source in a compact solar flare as
evidence for magnetic reconnection.
Nature 371, 495-497 (1994).
Can we simulate the astronomical x-ray
sources in lab.?
Shenguang II
Shenguang II Laser:
Pump: 8 beams(2kJ, 1ns, 3)
Probe: 9th beam (2 , 70 ps)
Optical shadowgraphy and
interferometry
X-ray imagers:
• Pinhole cameras
• framed camera
Modeling loop-top X-ray source with the MR jets
Laboratory
Solar flares
•
•
Jets in parallel with the target
surface are observed.
Similar hard x-ray source to the
astronomical is formed due to the
down jet interacting with another
target
J. Y. Zhong, et al., Nature Physics 6, 984 (2010)
Competition between MR and collision?
Diffusion structure of LDMR?
Particle acceleration by LDMR ?
― Competition between MR and collision
1. Changing the distance of two plasma bubbles
d
200 m
400 m
600 m
X-ray framing images for interaction of two plasma bubbles
d
2. Anti-parallel and parallel magnetic line of force
Anti-parallel
MR dominates
Parallel
Only collision
― The structures of diffusion region
Two- dimensional/3component Hall MHD
Simulations
• Ion diffusion region with the width of ~di
• Electron diffusion region with the width of ~10de
― Acceleration of particles in LDMR
High energy cosmic x-ray spectrum
MR?
― Electron measurements
430G EM
spectrometer
IP Stack
Spectral distribution
dN/dE (electron / keV)
spatial distribution
10
4
Th=520 keV
10
3
10
2
0
E >550 keV
200 400 600 800 1000 1200 1400
Electron energy (keV)
Dong et al PRL 2012 (accepted)
Outline
• Laser- driven magnetic reconnection
(LDMR)
• Collisionless shockwaves formed by two
counter-streaming plasmas
⇨ Generation of high-energy particles, origin of cosmic-ray
⇨ Acceleration by collisionless shocks
Supernova Remnant SN1006
Shell : Collisionless Shock
Two catalogues
In lab. collisionless shockwaves driven by
• High intensity relativistic laser pulses
(fs-ps, >1018W/cm2)
• High energy laser pulses (ns, kJ,
1015W/cm2)
Experiment Setup
SG II 8 laser beams with 2 kJ total energy, 1ns pulse duration, @ 3 
(351nm) to generate shocks
4 laser beams for generating shock
Pinhole camera 2
Pump
Pump
Neutral Filter
Imaging
Band pass filter
Glan prism
CH Target
9th beam
2 , 70ps, 50 mJ
Probe
2,
70 ps
CH Target
100um thick
Pump
Pumpprism 3°
Wollaston
CCD
Nomarski Interferometer
CCD
Pinhole camera 1
The distance between the targets was 4.5 mm.
The delay between the main beam and probe can be
changed from 0 ns to 13ns.
Experiment results（4+0 laser beams )
Density jump
The ion mean free
path is ~25-35mm，
far larger than the
density jump
region (100um)
Collisionless shock
5 ns
9 ns
Experiment results （4+4 laser beams )
Density jump
1 ns
2 ns
Plasma filaments
3 ns
5 ns
A 2D hydrodynamic code was used to
simulate the CH plasma generation
-3
Electron density (cm )
Simulation
Experiment
6.00E+019
4.00E+019
2.00E+019
0.00E+000
0
500
1000
1500
2000
2500
Distance (um)
Electron density distribution along the Distribution of the electron to
center of the target
ion temperature ratio
Te is much higher than Ti
The linear dispersion relation of the electrostatic mode:
2
 2  (kc)2   kDs
(vth2 , s s Z ( s )  2(Vd , s sin  )2 (1   s Z ( s )))  0
s
The linear growth rate of the
electrostatic ion-ion instability
The linear growth rate of the
electromagnetic Weibel-type instability
1)The strength of electrostatic (ES) instability is larger than the Weibel
(EM) instability at the beginning. 2)The wavelength of ES is smaller than
that of EM.
Discussions
•From calculation and PIC simulations, it is deduced
that the density jump at early time was probably an
electrostatic collisionless shock.
•The wavelength of Weibel type instability is much
closer to the size of the filaments observed at later time
(for example, 5 ns). The filaments may be caused by
the Weibel instability.
X. Liu, et al., New J. Phys. 13, 093001 (2011)
Instabilities induced by two non-identical plasmas
（a）
Probe ( t2)
100 μm
150 μm
CH
3
beams
(t1)
4 beams
(t0)
350 μm
2 mm
4.5mm
（b）
t0
1 ns
1.5 ns
t1
1 ns
2.0 ns
t2
120 ps
Rayleigh-Taylor instability?
Summary
With high power laser facility,
•
•
•
Spatial- and temporal-resolved structure and
particle acceleration of LDMR have been
observed
Shock waves and instabilities have been
investigated in the interaction of two counterstreaming plasmas
In future experiment , We will concentrate on the
acceleration physics related to MR, shocks and
jets.
Thanks!
Two plasmas in different systems
Rm = 5108
Solar flare
Plasmas
Parameters
Scaling Law
Ideal
MHD
equations
Laser
Plasmas
Laser
Plasmas
Rm = 4000
(before
scaling)solar
(After scaling)solar
flare
flare
109-2-10
-1010-1
Length (cm)     v  10
0, -1
t
2-10
10
-103-9
Time (s)
10-9
10-10
1
 v

B B
, -37-10
1
10
Pressure (Pa)   v  v 107 p 
10
-1011
4
 t

10919-10
-101121
Density (cm-3) B
1019-1020
 vv
t
102-1023
Velocity (km s-1)
102
10-10
r激光  ar太阳 , p激光  cp太阳 , 激光  b太阳 , B激光  c B太阳,
Magnetic field (G)
106
10-100
106-7
v激光  a
c
b
v太阳 , t激光  a t太阳
b
c
Contributors
China
J. Zhang, Y. T. Li, Q. L. Dong, Y. Zhang, S. J. Wang, X. Liu, Z.
M. Sheng, et al.,
Institute of Physics (IOP), CAS
Shanghai Jiao Tong University (STJU)
G. Zhao, J. Y. Zhong, F. L. Wang, J. R. Shi, H. G. Wei, L. Di, et
al., National Astronomical Observatories
J. Y. Zhang, Y. K. Ding, B. H. Zhang, L. Zhang, Y. J. Tang, et al,
Research Center for Laser Fusion, CAEP
J. Q. Zhu, Y. Gu, et al., ，National Laboratory on High Power
Lasers and Physics, Shanghai
Japan
H. Takabe, H. Nishimura, S. Fujioka, Y. Sakawa, T. Kato, Y.
Kuramitsu et al., Institute of Laser Engineering, Osaka University
Korea
Yong-Joo Rhee, et al., Korea Atomic Energy Research Institute
无碰撞冲击波的实验室研究
□ 实验中的等离子体凸变区域尺度约为350μm
□ 由 ii 
4
mi2v12
4 e4 Z 4 nLn12
计算对流等离子体中离子平均自由程为110cm
□ 2 ns时密度变化主要是由于两个等离子体之间的无碰撞机制产生的
PIC simulation of collisionless shocks
wall
0.9 c
Reflection of the plasma by the wall
⇨ Production of counter-streaming plasma
simulation by T. Kato
Number density
Upstream region
Downstream region
Mass Ratio: mp/me = 20
Velocity: V = 0.9c
Transition region
Magnetic field is ~1% of the
kinetic energy of the bulk plasma
in the upstream region
Magnetic field
Electric field
x
Strong magnetic field in the
transition region provides an
effective dissipation
Kato, T. N. & Takabe, H. 2008, ApJ, 681, L93
Kato, T. N. & Takabe, H. 2010, Phys. Plasmas, 17, 032114
Comparison of the dimensionless parameters of the shock in a
SNR with the experimental
Parameters
SNR
Expt.
2×106
4×102
Euler number, Eu
18
28
Mach number, M
16
14
Reynolds number,
Re
1013
2.5×106
Peclet number, Pe
1011
4.5×103
Collisionality, ζ
X. Liu, et al., New J. Phys. 13, 093001 (2011)