measurement of magnetic field in intense laser-matter interaction via relativistic electron...
TRANSCRIPT
Measurement of Magnetic fieldin intense laser-matter interactionvia Relativistic electron deflectometry
Osaka University
*N. Nakanii, H. Habara, K. A. Tanaka
University of California San Diego
T. Yabuuchi, H. Sawada, B.S. Paradkar, M.S. Wei, F.N. Beg
General Atomics
R.B. Stephens
University of Michigan
C. McGuffey, K. Krushelnick
* Also at University of California San Diego
Outline
• Motivation
• Laser-driven relativistic electron deflectometry
• Measurement of B field in intense laser-solid interaction– Long-pulse (ns) low-intensity (~ 1014 W/cm2)
• Proposed experiment• Integrated rad-hydro/hybrid PIC modeling
– Short-pulse (fs-ps) high-intensity (> 1018 W/cm2)• Experimental plan
• Summary
Outline
• Motivation
• Laser-driven relativistic electron deflectometry
• Measurement of B field in intense laser-solid interaction– Long-pulse (ns) low-intensity (~ 1014 W/cm2)
• Proposed experiment• Integrated rad-hydro/hybrid PIC modeling
– Short-pulse (fs-ps) high-intensity (> 1018 W/cm2)• Experimental plan
• Summary
Motivation
• Characterization of strong spontaneous magnetic (B) fields in intense laser-matter interaction is an important issue in High Energy Density (HED) sciences.
– Fast ignition (Electron energy transport)
– Generation of energetic electrons, ions, and x-rays
– and so on…
Strong spontaneous magnetic fields are generated in laser-matter interactions
• Long-pulse (ns) low-intense (-1014W/cm2) laser– ∇T x n in ablated plasma (dominantly)∇– 100 kGauss ~ MGauss
• Short-pulse (fs~ps) high-intense (>1018W/cm2) laser– ∇T x n∇
Ponderomotive force
Current of fast electrons
and etc…– Over 100 Mega-Gauss
€
∇T ×∇n
Outline
• Motivation
• Laser-driven relativistic electron deflectometry
• Measurement of B field in intense laser-solid interaction– Long-pulse (ns) low-intensity (~ 1014 W/cm2)
• Proposed experiment• Integrated rad-hydro/hybrid PIC modeling
– Short-pulse (fs-ps) high-intensity (> 1018 W/cm2)• Experimental plan
• Summary
Intense laser-driven electrons have advantages to diagnose B field with deflectometry method
Enough particle number for imaging
[Laser-solid] ~ 1011 with broad energy spread
[LWFA] > 108 with monoenergetic spectrum
Variable energies enable to detect wide-range B field
[Laser-solid] up to several ten MeV
[LWFA] up to 1 GeV
Ultrashort pulse duration can provide high temporal resolution
[Laser-solid] a few ps
[LWFA] several ten fs
Small source size can provide high spatial resolution
~ focal spot size
Relativistic electrons have advantages to measure B field in overdense plasmas
Relativistic electrons are penetrative in dense matter without significant energy loss in a short time
The electrons are susceptive to B field because they have the high velocity ~ c
€
F = q(E+ v ×B)
Laser-produced relativistic electrons are very useful for measuring the B field with deflectometry method
B field with wide range of strength or scale can be detected by using laser-produced electrons
Deflection angle
Changing the electron energy, different range of B field can be detected.
360[deg]
180
90
10
1
0.1
0.01
0.001
1e-4
Trapped electrons
Deflection angle map with respect to e- energy and integrated B field along e- path
RelativisticNon-relativistic
€
θd =e
m0c
B × dlL
∫
m0c2 +ε km0c
2
⎛
⎝ ⎜
⎞
⎠ ⎟
2
−1
Integrated B fieldalong e- path
Kinetic energy
Outline
• Motivation
• Laser-driven relativistic electron deflectometry
• Measurement of B field in intense laser-solid interaction– Long-pulse (ns) low-intensity (~ 1014 W/cm2)
• Proposed experiment• Integrated rad-hydro/hybrid PIC modeling
– Short-pulse (fs-ps) high-intensity (> 1018 W/cm2)• Experimental plan
• Summary
Experiment to measure ns-laser-produced B fields with relativistic electron deflectometry is proposed
We demonstrated the feasibility of this relativistic electron deflectmetry using hybrid PIC (LSP) and rad-hydro code (h2d)
Schematic of proposed experiment
Electrons are produced in short pulse laser interaction with solid
10 MeV electrons with narrow-bandwidth (~0.3 MeV) are selected by a pair magnet and used as backlighter
Mesh provides initial spatial information of electron beam
Integrated rad-hydro/hybrid PIC modeling
Rad-hydro code (h2d):B field & Ablated plasma
profile
Z
R
Target
Long pulse
Ablated plasma& B field
0.1 Mega-Gauss toroidal B field generated around laser spot near the critical dense region
Laser (~ Titan long pulse @LLNL)• Energy 100J• Pulse width 1ns (square)• Wavelength 0.5um• Spot size 300um• Intensity 1.4x1014 W/cm2
Target• Polystyrene plane• Thickness 50umB field map at 1.5 ns after the laser
irradiation (2D Cylindrical geometry)
Integrated rad-hydro/hybrid PIC modeling
Hybrid PIC code (LSP): Deflection of probe
e- beam by the B field
e- source(10MeV)
LSP Simulation area
Z
Target
Long pulse
Ablated plasma& B field
Mesh(30um)
2mm 0.7mm
Electron bunch path w/o B field
Deflected electron path by B fieldRad-hydro code (h2d):
B field & Ablated plasma
profile
Electron bunches were passing through CH plasma and slightly deflected by the B field
Solid dense region
Corona plasma regionTe: 300 eV, Ti: 250 eV,Ave Z: 3.5
0.1334ps
0.5337ps 1.400ps 2.200ps
Track of electron bunches in LSP simulation
Integrated rad-hydro/hybrid PIC modeling
Shift
Target
Long pulse
Ablated plasma& B field
e- source(10MeV)
Detector
Shift
Z
Mesh(30um)
10cm
Extra calculations:e- distribution on
detectorDeflection angle
Rad-hydro code (h2d):B field & Ablated plasma
profile
Hybrid PIC code (LSP): Deflection of probe
e- beam by the B field
Electron bunches were slightly focused to center by the toroidal B field
• Deflection angle at the each point was calculated from the spike shift in the distribution on detector.
(b) w/o plasma and B field(a) w/ plasma and B field
Electron distribution on detector
Deflected
Integrated rad-hydro/hybrid PIC modeling
Shift
Target
Long pulse
Ablated plasma& B field
e- source(10MeV)
Detector
Shift
Z
Mesh(30um)
Extra calculation:e- distribution on
detectorDeflection angle
10cm
Reconstruction of integrated B field profile
Rad-hydro code (h2d):B field & Ablated plasma
profile
Hybrid PIC code (LSP): Deflection of probe
e- beam by the B field
0 0.01 0.02 0.03 0.04 0.05 0.060.0E+00
2.0E+00
4.0E+00
6.0E+00
8.0E+00
1.0E+01
0.0E+00
2.0E-01
4.0E-01
6.0E-01
8.0E-01
1.0E+00
1.2E+00
1.4E+00
1.6E+00 Integrated B fiield along z di-rection (Actual one from hydro simulation)
Deflection angle and Inte-grated B along electron path (Reconstructed)
R [cm]
Inte
gra
ted
B f
ield
[M
Ga
us
s u
m]
De
fle
cti
on
an
gle
[d
eg
]
Distribution of integrated B field reconstructed from deflection angle are comparable to actual one
€
B× dl =m0cθ de
m0c2 +ε km0c
2
⎛
⎝ ⎜
⎞
⎠ ⎟
2
−1L
∫
€
θd : deflection angle
ε k : kinetic energy
Deflection angles and profile of reconstructed integrated B field and actual one.
Outline
• Motivation
• Laser-driven relativistic electron deflectometry
• Measurement of B field in intense laser-solid interaction– Long-pulse (ns) low-intensity (~ 1014 W/cm2)
• Proposed experiment• Integrated rad-hydro/hybrid PIC modeling
– Short-pulse (fs-ps) high-intensity (> 1018 W/cm2)• Experimental plan
• Summary
Experiment to measure fs ultra-intense laser produced B fields with LWFA monoenegetic electrons
• Monoenergetic relativistic electron beam is created by laser wakefield acceleration with gas-jet.
• Deflected electrons pass through the hole of 2nd OAP and are detected • Temporal evolution of the B field can be observed by changing the
delay of optical delay unit with ultra-short time resolution
Summary
• We proposed a B field deflectometry experiment using laser-produced relativistic electrons
• We demonstrated the feasibility of electron deflectmetry to measure the B field produced in ns-laser-matter interaction using hybrid PIC (LSP) and rad-hydro code (h2d)
• Integrated magnetic field along electron path can be reconstructed from the deflected electron distribution on deflection
• Experiment for measuring B field in interaction of ultra-intense laser with solid will be performed soon
Acknowledgements
This work supported by
– Japan Society for the Promotion of Sciences (JSPS)
Research Fellowship DC1
– Global COE Program
Center for Electronic Device Innovation (CEDI)
– U.S. Department of Energy
DE-FG-02-05ER54834 (ACE)
– JSPS Core-to-Core Program
International Collaboration for High Energy Density Science (ICHEDS)