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Recent Progress in Laser Wakefield
Acceleration Experiments at APRI
Nasr. A. M. Hafz
Advanced Photonics Research Institute (APRI)
Gwangju Institute of Science and Technology (GIST), Korea
• Introduction
• Recent Results in the Field by other groups
• Recent Results at APRI
• Summary
Outlines
Laser interaction with an electron in vacuum
electron
ponderomotive force
C. A. Brau “Classical Electrodynamics”
218 /10 cmW& above
BVeEeF
218 /10 cmWI Plane wave
electron
electron
EeF
Longitudinal
Motion
Quiver Energy
]/[][106.8 210
0 cmWIma
00/)()( acmeAu
2/)1(]/)([)( 0
2
000 cmeAuz
2/)1(]/)([1)( 0
2
00 cmeA
Transverse
Motion
E
B
e
n
Electron motion
plasmaIntense
laser ion
electrons
Es
Charge separation
Plasma wave
Es
Wave breaking &
Electron acceleration
Excitation of Plasma Wakefield by Lasers
T. Tajima and J. Dawson-PRL 1979
1100 pL fs
Ions are immobile, plasma in stable
2
2
0
2
8Ef
p
p
Ponderomotive force
Electron acceleration in the Wakefield Bubble
Hafz et al., Nature Photonics, 2, 571, (2008).
p ~ 20 m
Plasma
Laser pulse
Femtosecond Electron bunches Wakefield Bubble
8.7 m
4.2
m Ma
ste
rO
scilla
tor
Stretcher
Regen. Amp.
Pre-Amp.
1st Main Amp. 2nd Main Amp.
Va
cuu
mC
om
pre
ssorPump Laser 2 Pump Laser 5
Pump Laser 4 Pump Laser 6
Pump Laser 3
Pu
mp
La
se
r 1
Pum
p L
aser 7
Pum
p L
aser 9
Pum
p L
aser 8
Pum
p L
aser 1
0
Pum
p L
aser 1
1P
um
p L
aser 1
2Pump Laser 13
Pump Laser 14
4. Pre-Amp.: 4 pass, 50 mJ, 130-mJ pump at 10 Hz
5. 1st Amp.: 4 pass, 1.8 J with 4.4-J pump at 10 Hz
(35 TW with direct pulse compression)
1. Master Oscillator: 20 fs, 6 nJ
2. Stretcher: 500 ps
3. Regen. Amp.: 1 mJ with 10-mJ pump at 1 kHz
(10 Hz after pulse picker)
6. 2nd Amp: 2 pass, 5.0 J with 12-J pump at 10 Hz
7. Compressor: 3.5 J, 32 fs, >100 TW at 10 Hz
Green pump lasers
Pump Laser 1: Nd:YLF (SHG), 527 nm,
10 mJ at 1 kHz (JADE series)
Pump Laser 2: Nd:YAG (SHG), 532 nm,
200 mJ at 10 Hz (COMP series)
Pump Laser 3-14: Nd:YAG (SHG), 532 nm,
1.2 J at 10 Hz (SAGA series)
100TW 30fs Ti:Sapphire Laser at UQBF, APRI, 2006
3.5 J, 32 fs, >100 TW at 10 Hz
http://apri.gist.ac.kr/
Pu
mp
po
we
r su
pp
lies
Pulse compressor
Target Chamber
Oscillator
Stretcher
Regenerative
Master Clock
Laser-Driven Electron Beams Before 2004 (Example: LOA Results)
(V. Malka, Science 2002)
Quasi-monoenergetic Electron Beams (2004-2007)
1 GeV in
Plasma
capillary
33 mm
Leemans et al., Nature Phys. 2, 696 (2006)
50 TW, 40 fs
30 TW, 30 fs
200 MeV in
Gas jets
Few mm
V. Malka
Our Recent Results
Self-modulated LWFA at KERI in 2003-2005
)( BVEeFLorenz
Laser: 2TW ~ 1ps
ND: Glass
Gas jet: 0.8 mm He and N
ICT: 1pC resolution
Magnet: up to 10 MeV
Al-foil: 16 um
Hafz, Hur, G. Kim, C. Kim, H. Suk, Phys. Rev. E, 73, 016405 (2006)
1.81.4 2.6 E (MeV)4 10
Laser beam
position
200
383
567
750
200pC
< 100 % dE/E (Energy Spread)
700 800 900 1000 1100
250
300
954 nm
0= 1054 nm
739.9 nm
858 nm
Inte
nsity
(a.
u)
Wavelength (nm)
1.6x1019
2.4x1019
3.2x1019
4.0x1019
4.8x1019
2.4
2.8
3.2
3.6
4.0
4.4
Plasma density(cm-3)
En
erg
y (
Me
V)
Energy
100
200
300
400
Charge
Ch
arg
e (p
C)
Forward Raman Scattering
Self-modulated LWFA at KERI in 2003-2005
Hafz, Hur, G. Kim, C. Kim, H. Suk, Phys. Rev. E, 73, 016405 (2006)
Energy Spectrum from Nitrogen Plasma
Helium Plasma
Hafz, G. Kim, C. Kim, H. Suk, Int. J. Mod. Phys. B. 2007
Laser Wakefield Acceleration at APRI in 2006
Experimental Parameters
Plasma (He) density = 11019 cm-3
Laser pulse duration = 30 fs
Plasma length = 4 mm
Laser power ~ 20 & 40 TW
Spot size: 10 , 25, 30 m
Spherical mirror
(f= 75 or 100 cm)
4 mm slit nozzle
ICCD
LanexDipole magnet
0.8 T
Laser pulse
10 mm hole
M
37 cm
N. Hafz et al., Appl. Phys. Lett. 90, 151501 (2007)
LWFA in the f/2.5 focusing geometry: 10 m spot size
Deflection of electron beam
4 mm
Laser
Laser break up and filamentation
The f/2.5 focusing is very tight and it results in deflection and break up of the laser and electron beams.
Electron Beam
Profile
Laser-produced
Plasma
N. Hafz et al., Appl. Phys. Lett. 90, 151501 (2007)
Soft focusing
I ~ 5.61018 W/cm2
ne ~ 1 10 19 cm-3
Rayleigh Length ~ 1.7 mm
Gas jet length ~ 4 mm
Well collimated beam
Divergence 8 mrad
Electron beam spatial profile
B = 0
LWFA in the f/10 focusing geometry: 25 m spot size
Energy (MeV)
130 40 24
0 1313 2625 3500
0.6
0.8
1.0
1.2
1.4
1.6
Inte
ns
ity
(a
.u.)
Energy (MeV)40 130 24
105
4 mm
Laser
500 m long channel
LWFA in the f/10 focusing geometry
The f/10 focusing is relatively stable and it results in quai-monoenergetic electron beam generation.
Energy Spectrum
Laser-produced
Plasma
Charge = 20 pC
N. Hafz et al., APL, 90, 151501 (2007)
5
6
7
8
40
30070
Inte
ns
ity
(a
rb
.u)
Energy (M eV)145
3
4
5
5030
1.99 mm shift
Inte
ns
ity
(a
rb.u
)
Energy (MeV)330
Small mono-peaks
1.5 mm long channel= dephasing length25 m diameter
LWFA in the f/14 focusing geometry: 30 m spot size
N. Hafz et al., APL, 90, 151501 (2007)
Plasma channel
Energy Spectrum Energy Spectrum
Effect of Laser Spot Size on LWFA
A. Thomas et al. Phys. Rev. Lett. 98, 095004 (2007)
Laser Pulse
Wakefield
2
00
wz
Ld > cm
(ne~ 1018cm-3 is enough )
50 TW
35 fs
f#/21.4
fsa laser30,10
Uniform cm channel
Plasma Bubble
p
Gas jet
Long Rayleigh Range, several mm’s.
High laser power that leads to relativistic self-focusing
Long Dephasing Length, 1 cm, so higher electron energy
2)/(17)( pc GWP
ppd aL )/(2 222
0
]/[][106.8 22/110
0 cmWIma
Experiments in the bubble regime 2007
Experimental Scheme for Generation of Stable Electron Beams
Lens
LensLanex
Al filter
Up to 50 TW, 35 fs Laser Pulses
Nozzle
Gasjet
8-bit
CCD
12-bit
CCD
ElectronBeam
Top View Monitor
Side View Monitor
Filter
Filter
Spherical
Mirror
f =1.5 m
ICT
S
N
20 cm
Lens
Mirror
Band-pass
filter
Gated
ICCD
Electron Beam Energy Monitoring
Mirror
with Hole
B = 0.94 T
10 mm
5 mm channel
42 cm
Wave-front corrected
225 MeV Electron Beam Generation: 4 mm nozzle, 27 TW laser
Hafz, et al., Nat. Photon. 2, 571 (2008)
Quasi-momoenergetic
ReproducingLOA 2004-Nature
Input Parameters
Laser: 27 TW, 35 fs, 24 m (FWHM)
Plasma: 4 mm gas jet, Density: 71018 cm-3
Dephasing length= 3.1 mm
Electron Beam
Energy: 225 MeV, Charge: 100 pC
Divergence: 5.8 mrad (FWHM)
Energy Spread: 7 %
170-200 MeV Beams by 27 TW Laser Pulses
225
# 189
# 190
E peak =174 MeV
E spread= 32 %
E peak=192 MeV
E spread= 41%
# 191
Epeak = 190 MeV
E spread= 49 %
# 188
E peak=178 MeV
E spread= 33 %
27 TW, 35 fs, 24 m spot size
4 mm nozzle, no~ 7 1018cm-3,
Ld ~ 3.16 mm
Charge: 100 pC
Average Channel length ~ 3.5 mm
Mean Laser (J) = 36.8 TW
SD/Mean E = 4.6 %Intensity (arb.u.)
Div
erg
en
ce
An
gle
(m
rad
)
Electron Beam Energy (MeV)
Intensity (arb.u.)
Reproducible Quasi-monoenergetic Beams: 4 mm Gas Jet
Mean Energy = 236.9 MeV
SD/Mean E = 5 %
Hafz, et al., Nat. Photon. 2, 571 (2008)
Charge: 200 pC
Generation of 330±17MeV Electron Beams and 4 mm Gas Jet
Max
Hafz, et al., Nat. Photon. 2, 571 (2008)
Laser: 50TW, 35 fs, 24 m (FWHM)
Plasma: 4 mm gas jet
Density: 6.61018 cm-3
Dephasing length= 3.3 mm
Electron
Beam: Peak at 330 MeV, Max. at sub GeV,
Charge: ~500 pC
Divergence: few mrad (FWHM)
Energy Spread: ~ 30 %
Beam Energy Doubling
by doubling the
Laser power
Peak = 300±30 MeV
E spread = 50 %
# 582
Peak=320±25MeV
E spread = 31 %
# 583
Peak = 303±9 MeV
E spread= 30 %
# 584 # 586
Peak = 285±12 MeV
E spread= 42 %
50 TW, 35 fs, 24 m spot size, 4 mm nozzle, no~
6.5-6.8 1018cm-3,
Ld ~ 3.16 mm
320±25 MeV Beams by 50 TW Laser Pulses and 4 mm Gas Jet
Four successive shots with small change in density
1 Centimeter Gas Jet Results
Quasi-momoenergetic Electron Beams
Hafz, et al., Nat. Photon. 2, 571 (2008)
Laser: 50TW, 35 fs, 24 m (FWHM)
Plasma: 1 cm gas jet
Density: 3.41018 cm-3
Dephasing length 1 cm
Epeak1= 540 MeV, Emax1> 1 GeV,
Epeak2= 320 MeV,
E 2spread= 11%, E1spread= 30%,
Qpeak1=200 pC & Q peak2 = 20pC
5 mm Channel
Epeak= 480±60MeV
Espread= 23 %
# 328
Epeak= 480±15 MeV
Epeak= 320±10 MeV
# 330
Epeak= 500±20 MeV
Epeak= 330 MeV
# 333
Div
erg
ence
(mra
d)
Energy (MeV)
Epeak= 500±20 MeV
½ GeV Electron Beam Generation
50 TW, 35 fs, 24 m spot size, 10 mm nozzle,
no~ 3.4 1018cm-3,
Ld ~ 10 mm
# 327
5 mm Channel
R. Bingham et al., Plasma Phys. Cont. Fus_34, 557(1992)
Asymmetric laser pulse
with fast rising time
generates larger
wakefield intensity
Case 1: Low density 21018 cm -3
Case 2: High density 31019 cm -3
G X
e
i78.5 cm
40 cm
BP
L
M
Pb
d
l
2009 Experiment at APRI
Initial Laser-Plasma Parameters Experimental Scheme Laser pulse energy 0.8 0.9 J (= 800 nm, 50 nm FWHM)
Laser Spot size (FWHM) 25 µm.
Pulse duration 37 fs (symmetric pulses)…
(Intensity 1.46 ×1018 W/cm2, a0 = 0.83).
Pulse duration 74 fs (asymmetric at the grating detuning of -200 µm)
(Intensity 7.5 ×1017 W/cm2 (Nonrelativistic ) a0 = 0.59).
Target: Gas Jet of Helium: 4 mm long
Density (very low): 10171018 cm-3.
Interaction length 3 ~ 4 mm.
a0 1, c ≤ w0 p
-0.3 -0.2 -0.1 0.0 0.1 0.2 0.30
100
200
0.0
0.2
0.4
0.6
0.8
1.0 FWHM
FW
HM
(fs
)
Detuning (mm)
No
rma
lize
d P
ea
k In
ten
sity
Peak Intensity
-150 -100 -50 0 50 100 150
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Inte
nsi
ty (
x10
16W
/cm
2)
Time (fs)
-150 -100 -50 0 50 100 150
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Inte
nsi
ty (
x10
16W
/cm
2)
Time (fs)
-150 -100 -50 0 50 100 150
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Inte
nsi
ty (
x10
16W
/cm
2)
Time (fs)
-150 -100 -50 0 50 100 150
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Inte
nsi
ty (
x10
16W
/cm
2)
Time (fs)
-150 -100 -50 0 50 100 150
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Inte
nsi
ty (
x10
16W
/cm
2)
Time (fs)
-150 -100 -50 0 50 100 150
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Inte
nsi
ty (
x10
16W
/cm
2)
Time (fs)
-150 -100 -50 0 50 100 150
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Inte
nsi
ty (
x10
16W
/cm
2)
Time (fs)
-150 -100 -50 0 50 100 150
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Inte
nsi
ty (
x10
16W
/cm
2)
Time (fs)
-150 -100 -50 0 50 100 150
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Inte
nsi
ty (
x10
16W
/cm
2)
Time (fs)
-150 -100 -50 0 50 100 150
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Inte
nsi
ty (
x10
16W
/cm
2)
Time (fs)
-150 -100 -50 0 50 100 150
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Inte
nsi
ty (
x10
16W
/cm
2)
Time (fs)
-250um
200um
-150um
-100um
-50um
0um
150um
100um
50um
200um
200um
Laser Pulse Compressor Detuning
-150 -100 -50 0 50 100 150
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Inte
nsi
ty (
x10
16W
/cm
2)
Time (fs)-150 -100 -50 0 50 100 150
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Inte
nsi
ty (
x10
16W
/cm
2)
Time (fs)
-150 -100 -50 0 50 100 150
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Inte
nsi
ty (
x10
16W
/cm
2)
Time (fs)
-250 m
- 200 m
0 m
Asymmetric Laser Pulses
50 fs FWHM
75 fs FWHM
37 fs FWHM
-0.5 -0.4 -0.3 -0.2 -0.1 0.0
0
20
40
60
80
100
Unstable
Weak
Less Stable
Weak
Grating detuning (mm)
Po
intin
g a
ng
le (
mra
d)
Laser Height = 3.25
Horizontal
Vertical
Stable
Bright
Pointing Angle Optimization
Hafz et al., Applied Physics Express 3(2010) 076401
Density: 10171018 cm-3
-500 -400 -300 -200 -1002
4
6
8
10
12
14
D
ive
rge
nce
(m
rad
)
Grating Detuning (m)
Horizontal
Vertical
Electron Beam Divergence
500 525 550 575 600 625 650 675
500
525
550
575
600
625
650
675
700
Horizontal Axis (pixels)
Ve
rtic
al A
xis
(p
ixe
ls)
0
2000
4000
6000
8000
10000
1.200E4
1.400E4
1.600E4
500 525 550 575 600 625 650 675
500
525
550
575
600
625
650
675
700 0
6250
1.250E4
1.875E4
2.500E4
3.125E4
3.750E4
4.375E4
5.000E4
500 525 550 575 600 625 650 675
500
525
550
575
600
625
650
675
700 0
3250
6500
9750
1.300E4
1.625E4
1.950E4
2.275E4
2.600E4
500 525 550 575 600 625 650 675
500
525
550
575
600
625
650
675
700 0
2250
4500
6750
9000
1.125E4
1.350E4
1.575E4
1.800E4
500 525 550 575 600 625 650 675
500
525
550
575
600
625
650
675
700 0
3500
7000
1.050E4
1.400E4
1.750E4
2.100E4
2.450E4
2.800E4
500 525 550 575 600 625 650 675
500
525
550
575
600
625
650
675
700 0
3250
6500
9750
1.300E4
1.625E4
1.950E4
2.275E4
2.600E4
500 525 550 575 600 625 650 675
500
525
550
575
600
625
650
675
700 0
3250
6500
9750
1.300E4
1.625E4
1.950E4
2.275E4
2.600E4
500 525 550 575 600 625 650 675
500
525
550
575
600
625
650
675
7000
10000
2.000E4
500 525 550 575 600 625 650 675
500
525
550
575
600
625
650
675
7000
10000
2.000E4
3.000E4
500 525 550 575 600 625 650 675
500
525
550
575
600
625
650
675
700 0
5625
1.125E4
1.688E4
2.250E4
2.813E4
3.375E4
3.938E4
4.500E4
500 525 550 575 600 625 650 675
500
525
550
575
600
625
650
675
700 0
1750
3500
5250
7000
8750
1.050E4
1.225E4
1.400E4
500 525 550 575 600 625 650 675
500
525
550
575
600
625
650
675
700 0
4375
8750
1.313E4
1.750E4
2.188E4
2.625E4
3.063E4
3.500E4
500 525 550 575 600 625 650 675
500
525
550
575
600
625
650
675
700 0
4375
8750
1.313E4
1.750E4
2.188E4
2.625E4
3.063E4
3.500E4
500 525 550 575 600 625 650 675
500
525
550
575
600
625
650
675
7000
1000
2000
3000
4000
5000
500 525 550 575 600 625 650 675
500
525
550
575
600
625
650
675
700 0
6250
1.250E4
1.875E4
2.500E4
3.125E4
3.750E4
4.375E4
5.000E4
500 525 550 575 600 625 650 675
500
525
550
575
600
625
650
675
700 0
2250
4500
6750
9000
1.125E4
1.350E4
1.575E4
1.800E4
500 525 550 575 600 625 650 675
500
525
550
575
600
625
650
675
700
1.96 mm 5 mrad
0
2000
4000
6000
8000
10000
1.200E4
1.400E4
1.600E4
10 mm= 25.4 mrad
500 525 550 575 600 625 650 675
500
525
550
575
600
625
650
675
700 0
5625
1.125E4
1.688E4
2.250E4
2.813E4
3.375E4
3.938E4
4.500E4
500 525 550 575 600 625 650 675
500
525
550
575
600
625
650
675
700 0
5000
10000
1.500E4
2.000E4
2.500E4
3.000E4
3.500E4
4.000E4
500 525 550 575 600 625 650 675
500
525
550
575
600
625
650
675
700 0
5000
10000
1.500E4
2.000E4
2.500E4
3.000E4
3.500E4
4.000E4
Electron Beam from 20 Successive Shots
Hafz et al., Applied Physics Express
3(2010) 076401
500 520 540 560 580 600 620 640
500
520
540
560
580
600
620
640
4 mrad
Ve
rtic
al (
pix
els
)
Horizontal (pixels)
Vertical
4 mrad
G X
e
i78.5 cm
40 cm
BP
L
M
Pb
d
l
Unambiguous Electron Beam Energy Measurement
Laser pulse length 74 fs (asymmetric)
(Intensity 7.5 ×1017 W/cm2
(Non-relativistic ) a0 = 0.59).
Target: Gas Jet of Helium: 4 mm long
Density (very low): 10171018 cm-3.
Interaction length 3 ~ 4 mm.
Electron Beam Energy at Optimum Detuning & Height
150 310 MeV
#1766
150 240 MeV
#1747
-500 -400 -300 -200 -100 0 100100
150
200
250
300
350
Original position
for shooting > 100 fs
75 fs
Range
37-40 fs Range
Grating Detuning (m)
Ele
ctro
n E
ne
rgy
(Me
V)
Electron Energy
Hafz et al., in preparation
Electron Beam Energy at Optimum Detuning & Height
0
2000
4000
6000
8000
10000
Electron Energy (MeV)
Sig
na
l Inte
nsi
ty (
arb
. un
its)
1754
380 2401801501200
4000
8000
12000
16000
1767
380 240180150120
Sig
na
l In
ten
sity
(a
rb. u
nits
)
Electron Energy (MeV)
500
1000
1500
2000
2500
3000
3500
4000
1748
380 240180150120
Electron Energy (MeV)
Sig
na
l Inte
nsi
ty (
arb
. un
its)
0
2000
4000
6000
8000
10000
12000
1765
380 240180150120
Sig
na
l Inte
nsi
ty (
arb
. un
its)
Electron Energy (MeV)
1000
2000
3000
4000
5000
1747
380 240180150120
Sig
na
l Inte
nsi
ty (
arb
. un
its)
Electron Energy (MeV)
0
4000
8000
12000
16000
1760S
ign
al I
nte
nsi
ty (
arb
. u
nits
)
Electron Energy (MeV)
120 150 180 240 380 0
2000
4000
6000
8000
1750
120 150 180 240 380
Sig
na
l In
ten
sity
(a
rb.
un
its)
Electron Energy (MeV)
0
4000
8000
12000
16000
1751
120 150 180 240 380
Electron Energy (MeV)
Sig
na
l Inte
nsi
ty (
arb
. un
its)
0
1000
2000
3000
4000
5000
6000
1762
380 240180150120
Sig
na
l Inte
nsi
ty (
arb
.u.)
Electron Energy (MeV)
0
4000
8000
12000
1749
380 240180150120
Sig
na
l In
ten
sity
(a
rb.
un
its)
Electron Energy (MeV)
0
2000
4000
6000
1759
380 240180150120
Electron Energy (MeV)
Sig
na
l In
ten
sity
(a
rb.
un
its)
0
4000
8000
12000
16000
Sig
na
l In
ten
sity
(a
rb.
un
its)
Electron Energy (MeV)
1761
380 2401801501200
2000
4000
6000
8000
10000
12000
1758
150120 180 240 380
Sig
na
l In
ten
sity
(a
rb. u
nits
)
Electron Energy (MeV)
0
2000
4000
6000
8000
10000
12000
14000
16000
1756
380 240180150120
Sig
na
l In
ten
sity
(a
rb.
un
its)
Electron Energy (MeV)
0
2000
4000
6000
8000
10000
12000
14000
16000
Electron Energy (MeV)
Sig
na
l In
ten
sity
(a
rb.u
.)
1757
380 240180150120
0
2000
4000
6000
8000
10000
12000
14000
1766
380 240180150120
Sig
na
l In
ten
sity
(a
rb.u
.)
Electron Energy (MeV)
0
5000
10000
15000
20000
25000
1755
380 240180150120
Sig
na
l In
ten
sity
(a
rb.u
.)
Electron Energy (MeV)
0
2000
4000
6000
8000
10000
12000
Sig
na
l In
ten
sity
(a
rb.u
.)
Electron Energy (MeV)
1753
380 240180150120
Mononenergetic Peaks at 380 MeV,
Mononenergetic Peaks at 210 MeV
SD in Energy is 40 MeV
Mean Energy is 255 MeV
Most frequent Energy is 240 MeV
For 20 Shots
At -200 m detuning
Hafz et al., in preparation
0
2000
4000
6000
8000
1763
Sig
na
l In
ten
sity
(a
rb.
un
its)
120 150 180 240 380
Electron Energy (MeV)
This is a Stable “Electron Beam Accelerator”
An initially non-relativistic interaction
producing highly relativistic electron beams
Laser pulse length 74 fs (asymmetric)
(Intensity 7.5 ×1017 W/cm2
(Non-relativistic ) a0 = 0.59).
Target: Gas Jet of Helium: 4 mm long
Density (very low): 10171018 cm-3.
Interaction length 3 ~ 4 mm.
Hafz et al., in preparation
0
4000
8000
12000
16000
1760
Sig
na
l In
ten
sity (
arb
. u
nits)
Electron Energy (MeV)
120 150 180 240 380
300 MeV per 3 mm 1 GeV per cm
(Nature Physics 2008)
0 100 200 300 400 500 600 70010
100
1000
Wa
vele
ng
th (
nm
)
Electron Beam Energy (MeV)
B
Undulator Parameters
Type Helical
Field Strength 0.5 Tesla
Length 95 cm
Period 2.4 cm
22
2
2 21
2
K
n
u
Undulator was designed through collaboration with KAERI, Quantum Optics Division
Magnet
Gas
Jet
~ 2m
Lanex
LanexLanex
Spectrometer
Gas Density = 1 atm
Laser Height = 3.25 mm
Laser ~ 12 TW, 74 fs
Grating Detuning = 200 m
Beam Profile
After Undulator
e-
UV-IR
Beam Profile
Before Undulator
Energy Spectrum
Undulator
Preliminary Undulator Experiment September 2009
Preliminary Undulator Experiment September 2009
43200 300 400 500 600 700 8000
5
10
15
20
2382
2394
2395
Inte
nsi
ty (
arb
. u
nits
)
wavelength (nm)
170 MeV
# 2382
~ 180 MeV
Beam Energy
# 2395
200 300 400 500 600 700 800
-0.5
0.0
0.5
1.0
1.5
2.0
Inte
nsi
ty (
arb
. u
nits
)
Wavelength (nm)
2356
2363
2365
# 2356
~ 170 MeV ~ 170 MeV
# 2365
Summary and Conclusion
- Using 2 TW class laser and 800 um gas jet we generated 5 MeV
quasimonoenergetic electron beam.
- Using 1 cm gas jet and < 50 TW, we have produced GeV-class
electron beams.
- By sing asymmetric laser pulses and low plasma density, we could
stabilize the electron beam pointing angle and produce highly
relativistic electron beam despite the fact that initial interaction
conditions were not relativistic.
- We have performed preliminary undulator radiation experiment
using 1 m helical undulator.
Dr. T. J. Yu (Laser)
Dr. V. Kulagin, and Uhm (Theory),
Dr. J. Lee (PI),
Dr. H. Suk (Capillary),
Dr. M. S. Hur and Dr. H. J. Lee (Simulations)
Acknowledgement
J. R. Cary (Univ. of Colorado)-Vorpal code
T. Hosokai (Tokyo Inst.Tech)-Gas jet
In Korea
Outside Korea
Thank you