Transcript Advanced Accelerator Research & Development at JAERI-APRC Kazuhisa NAKAJIMA KEK

Advanced Accelerator Research &
Development at JAERI-APRC
Kazuhisa NAKAJIMA
KEK
JAERI-APRC
2nd ORION WORKSHOP
SLAC, Feb. 18-20, 2003
Japan Atomic Energy Research Center
Kansai Establishment
Advanced Photon Research Center
Spring-8 in Harima
Kyoto KEK in Tsukuba
Osaka
Tokyo
JAERI-KANSAI (West) in Kizu
関西
Director: Toshi Tajima
Colleagues of Laser Acceleration
Research Group
Kazuhisa NAKAJIMA
Masaki KANDO
Hideyuki KOTAKI
Shuji KONDOH
Shuhei KANAZAWA
Shinichi MASUDA
Takayuki HONMA
Outline
Progress of laser-driven accelerators
Recent topics on laser-plasma electron sources
Facility for laser acceleration research
at JAERI-APRC
Recent results on laser-plasma acceleration
Experiments
Prospects of laser accelerator developments
Direct Laser Field Accelerators
Particle velocity =Phase velocity < c
Grating Accelerator
Inverse Cherenkov Accelerator
Inverse Smith-Purcell Effect
Inverse FEL
VxB force
Laser
Beam 
l
Grating
Laser
Beam

Bu
l
lu
S
v ph c  1 nl S  cos 
n=integer
v
Gas
Axicon
v ph c  1 n cos 
Vacuum Beat Wave Accelerator
v ph c  1 - 1 - Z R1 Z R2 / kZ R1 
n=Refraction
Index of Gas
Laser Beam
2
Undulator
l  lu 1  K ; 2g
2
2
v c 1 - 1  K  g
2
Ponderomotive accelerator
Plasma
vg< c
Laser-driven Plasma Wave Accelerators
Laser Wake-Field Accelerator
L  lp
LWFA
Solitary wake accelerator
Plasma
vg< c
Plasma Beat Wave Accelerator
PBWA
w1 - w 2  w p
Self-Modulated LWFA
SM-LWFA
L > l p , P > Pc
Progress of Laser Acceleration Experiments
Laser-plasma acceleration experiments demonstrated
>200MeV, >100GeV/m electron acceleration.
1 PeV
Acceleration
mechanism
PWFA
ICF
PBWA
LWFA
SM-LWFA
Energy Gain
Conventional accelerator
energy frontier
Laser
Ponderomotive
Energy trend
1 TeV
1 GeV
1 MeV
SLAC
JAERI/KEK/UT
UCLA
KEK
ILE
KEK/ILE
BNL
ANL
1970 1980
LULI
LLNL
Michigan
RAL
NRL
MPI
GeV Laser
Acceleration
at JAERI-APRC
LULI
1990 2000 2010 2020
Year
Gas-Jet Plasma Cathode Experiments
A table-top accelerator
Gas jet LWFA experiment at LOA
Self-Modulated Laser Wake-Field
Acceleration experiment
at Univ. of Michigan
Forced Laser Wake-Field
Acceleration (?) experiment
(V.Malka et al.,SCIENCE,298,1596,2002)
Relativistic electron beam generation by
ultraintense laser-plasma interactions
Relativistic electron beam generation experiment at Univ. of Tokyo
He 20 atm (~2.8x10 19cm -3)
10
2
180mm
2.0 mm
Lower energy
electrons
E < 500keV
1.3 mm
I. P.
Nozzle
10
 ~30deg.
Ti:Sapphire
Plasma
~2mm
Self-channeling
Laser pulse
5 TW, 50fs
Intensity ~1.5x1019W/cm2
a0 ~3.0
1
Energetic
electron beam

~2deg.
D~10mm
E: up to ~40MeV
10
0
0
Emax ~ 40 MeV
Transverse emittance
~ 0.05 pmm・mrad
5
High quality electron beam
10
15
20
25
30
35
40
Energy [MeV]
by T. Hosokai
Facility for Laser Acceleration Research
Laser
CPA Ti:sapphire laser system
Peak power 100 TW
1 PW
Pulse duration 20 fs
Laser transport
Microtron with photocathode RF gun
Electron
Beam
Injector
Beam energy
150 MeV
Beam intensity 100 pC, 10-60 Hz
Bunch duration 10 ps
Norm. emittance <5 p mm-mrad
Beam line with laser energy modulation
and chicane section.
CPA Peak Power Toward the Petawatt
10 4
10 3
Peak Power (TW)
Petawatt
Nd:glass
Ti:sapphire
Cr:LiSAF
E
LLNL (single shot)
LLNL (single shot)
10 2
LLNL
ILE
10 1
LLNL
Limeil
CREOL
ENSTA
LLNL
JAERI (10 Hz)
LLNL
ISSP
ILE
JAERI
Stanford
10
UCSD
UC Be rk eley
0
WSU
Roc heste r
Stanford
10 -1
1988
1990
1992
ENSTA
1994
Year
1996
1998
2000
PW
Compressor
100 TW
Compressor
Air
Compressor
10 TW
Compressor
The 10-1000 TW Laser System
at JAERI-APRC
8 mJ
CW Nd:YVO4
1PW,25fs, 1Hz
100 TW, 20 fs, 10 Hz
Ti:Sapphire Laser System
at JAERI Advanced Photon
Research Center in Kyoto
4-Pass
Power amplifier
Booster
Amplifier
1Hz Pump Laser
(Under Development)
4-Pass
Pre-amplifier
Single-Shot
Nd:Glass Pump Laser
Oscillator Stretcher Regenarative
Amplifier
10-Hz
Nd:YAG
7 J, 10-Hz
Nd:YAG
10-Hz Nd:YAG
Laser Peak Intensity (Optical Measurements)
12m
12m
Spot Image
Amplifier Stage
Pre-amplifier
Power-amplifier
Pulse Energy
80 mJ
530 mJ
Pulse Width
(FWHM)
20 fs
25 fs
Spot Size
(FWHM)
7.0 m
6.4 m
Energy in 1/e 2
Spot Area (%)
74 %
53 %
Laser-focused
Peak Intensity
(Calculation)
5.9x10 18 W/cm 2
2.6x1019 W/cm 2
Schematic of the Petawatt Ti:Sapphire System
45 mJ Green Pump
Oscillator
10 fs
Stretcher
1 ns
Compressor
25 fs, 28 J, 1.1 PW
Regenerative Amplifier
8 mJ, 10 Hz
3-pass Booster Amplifier
~40 J, Single Shot
~70 J Green Pump
Additions for the petawatt
4-pass Preamplifier
320 mJ, 10 Hz
4-pass Power Amplifier
3.3 J, 10 Hz
6.4 J Green Pump
Major Petawatt Components
880-mm
cm diameter
Ti:Sapphire
Ti:sapphire
disk disk
40 cm compression grating
70-J green Nd:glass laser
Petawatt vacuum compressor
Offner Stretcher and Compressor with
Mixed Grating Scheme
J. Squier et al, Appl. Opt. ,vol. 37, 1638, 1998
1200 grooves/mm Offner Stretcher
Dazzler (planned)
1480 grooves /mm Tracy Compressor
Bandpass ~100 nm
Tables-Top Petawatt Ti:Sapphire Laser System
Oscillator
Stretcher
Regen
Pre - amp
100TW compressor
Power - amp
Nd : YAG
Nd : glass
Booster - amp
PW compressor
Optical table size ~ 90 m2
Pulse Compression and Beam Quality
Peak power
Autocorrelation trace
32.9 fs (FWHM)
18.1 J
1
Pulse duration
32.9 fs (FWHM)
Intensity (a. u.)
0.8
(after compression)
0.6
Beam Quality (before compression)
Horizontal plane
1.22 times diffraction limited
Vertical plane
1.15 times diffraction limited
0.4
0.2
0
-300
0.55 PW
-200
-100
0
100
Delay (fs)
200
300
Laser Acceleration Test Facility
Commissioning in 2000
Radiation safety permission
up to 2 GeV, 50 pA
Laser Transport
Microtron
150MeV Microtron
Chicane
Final Focus Doublet
IFEL
Undulator
100 TW
Laser Pulse
Spectrometer Magnet
Chicane
Plasma
Waveguide
Electron Spectrometer
High quality electron beam injectors
150 MeV Microtron
25 laps,
Magnetic field 1.23T
Bunch length <10ps
Norm.emittance
<5pmm-mrad
Transmission
efficiency < 92%
Electron Injector Section
S-band Accelerating Tube
1.1 m
Photocathode
RF gun
Max. charge 3nC,
QE~1.4x10-4,
Rep. rate 50Hz,
Stability <1%
Race-track Microtron
3.5 m
Beam Extraction Section
CCD Camera
150 MeV Photocathode - Microtron
Synchrotron radiation from an electron bunch in Microtron
Microtron
00-5-17
150MeV
120MeV
90MeV
60MeV
30MeV
Photocathode RF gun
25 th lap
20 th lap
15 th lap
10 th lap
5 th lap
All solid state
Nd:YLF laser
Performance of Photocathode RF Gun
RF Cavity
RF
1.6
Number of cell
Cu
Cathode
2856 MHz
Frequency
57 MΩ/m
Shunt impedance
Peak power
Pulse duration
Repetition rate
Laser
Wavelength
Energy
Energy stability
Pulse length
263 nm
200 µJ
0.5 %
6 ps
600
500
400
300
200
100
0.00
0
20
40
60
80 100 120 140 160
Phase (deg.)
8.6 MW
4 µs
50 Hz
All-solid-state laser for photocathode RF gun
All-solid-state Nd:YLF Laser
Output
Output energy of UV
Energy stability of UV
Pulse length of UV
200 µJ
< 0.5 %
6 ps
Oscillator
SESAM mode-locked Nd:YLF
Wavelength
1053 nm
Pulse length
12 ps (FWHM)
Repetition rate
79.3 MHz
Output power
> 100 mW
jitter
0.39 ps
Timing Stabilizer
Phase locked loop
with a reference signal
Regen
Laser-diode pumped Nd:YLF
Output energy
2 mJ
Repetition rate 100 Hz (max.)
Frequency Conversion
Green(527 nm) : SHG at 1053 nm
by KTP crystal
UV (263 nm) : SHG at 527 nm
by BBO
Beam charge and Transmission efficiency
Commissioning performance
• Charge 95 pC with 77 % transmission and 4% stability
• Transmission efficiency 92 % for 68 pC
• Repetition rate
10 Hz
Transmission efficiency of the conventional microtron with
thermionic electron gun is less than 10 %
Electron beam line for laser acceleration
Bunch Slicing Chicane
IFEL Undulator
シケイン
800
800
ダンプ
400
既存のライン
407.5
120
11
80
0
ステア
H
V
80
B E AM A T NE L 1=
1
A =- 2. 00 4
B= 5 .4 57
A = 1. 83 5
B= 3 7. 05
700
600
320
35
200
200
11
0
ステア
40
200
2500
95
155
11
レーザーステア
0
モニタ
for IFEL
200
7.5゜偏向電磁石
I=
0 .0 m A
W= 1 50 .0 0 00
15 0. 0 00 0 Me V
F RE Q= 2 86 0. 00 M H z
WL =
1 04 .8 2 m m
EM I TI =
0. 3 99
0. 1 79
10 96 . 13
EM I TO =
0. 3 99
0. 1 79
10 96 . 13
N1= 1
N 2 = 36
100
200
155
11
レーザー
0
モニタ ステア
for IFEL
95
アンジュレーター
2029.5
TMP
40
200
20
95 80
モニタ
IFEL Modulation
Pulse
5 . 15 0 mm x
P
1. 21 1 m ra d
A = 7. 66 8
o w e r T r a c e
C OD E: TR AC E3 D v 61 b
DA T E: 1 1- 16 - 20 00
TI ME : 14 : 16 :5 7
2 .0 7 3 mm x
Laser-Plasma Accelerator
Z
700
600
320
35
700
11
0
ステア
700
11
0
ステア
200
95 80
モニタ
40
200
200
11
0
ステア
200
180
11
0
ステア
200
49 120
57
モニタ
143
CM
GV
370
50 50
120 49
モニモニ
80
タ タ
6
ICF114
Q
8 91 0
EBE
EBE
15
1118
67
EBE
19
20
2212
Final Focus
Quads
Focusing
8 1. 35 9 D eg x
5 3. 95 6 Ke V
N P 2= 3 6
mirror
Final focus
spot size
EBE
Q Q
Q Q
H:35m
24
25
26
27
2 8293 0 31
3233
33436
5
V:62m
RP
RP
1 1 113
24
1
120
TMP
TMP
Chicane
Q
500
120
排気
13 6 .1 D eg . ( Lo n gi tu di na l )
7
100
ICF70
可動ステージ
WI G
5
Electron
Spectrometer
B = 2 .9 40
832
600
1 8. 97 6 mr a d
22 5
29 9. 03 6 K eV
Q
A = 7. 67 9
132
5. 00 m m ( Ho ri z on ta l)
23 4
170
250
RP
Wake Pump Pulse
11 3. 38 2 D eg x
Q
250
TMP
RP
1
1100
250
300×300
×300
B= 2 .9 32
100TW,20fs
Laser Pulse
H
100
ICF253
1000
150
0
TMP
1
ICF203
RP
壁から 9.45m
V
1100
200
11
0
ステア
M AT CH I NG T YP E =
N P1 =
H
V
TMP
RP
Z
300
35
200
200
B EA M A T NE L2 = 3 6
A =- .8 55 7E - 02 B = 0. 30 92 E- 0 2
A =- .8 74 8E - 01 B = 0. 21 27 E- 0 1
ステア
80
700
600
320
23
Undulator
5. 00 m m ( Ve rt i ca l)
Beam Envelope
Le n gt h= 1 28 7 1. 41 mm
Laser and Beam Transports
Electron beam line
Laser transport
Acceleration
chamber
Spectrometer
Activities and Achievements
Brief History
1997
250 MeV LWFA experiment using 2TW, 90 fs T3 laser
with 17 MeV electron linac beam injection.
Wakefield measurements by the frequency domain interferometry.
Ovservations of a long self-channeling and abnormal blueshift.
50 Hz Photocathode RF gun developments by KEK/SHI/BNL
1998
2 cm capillary discharge plasma waveguide developments
1999
150 MeV Photocathode-Microtron developments
2000
Laser Acceleration Test Facility developments
2001
20 GeV/m laser wakefield measurement in a gas-jet plasma
2002
The first gas-jet plasma cathode experiment
1996
The world-highest laser acceleration
H. Dewa et al., NIM A410, 357, 1998
M. Kando et al., JJAP, 38, L967, 1999
17 MeV Electron Beam
Laser Pulse
2 TW, 90 fs
PMQ Doublet
Cu Collimator
Accelerated
Electrons
300 MeV
50 MeV
PMQ Triplet
17 MeV
OAP Mirror
f/10
Beam Dump
Alpha Magnet
Bending Magnet
B=2.6 kG
Scintillator Array
(32 ch)
The world-highest energy gain of
>250 MeV has been achieved by
LWFA experiments
using 2TW, 90fs T3 laser and
17 MeV electron linac.
Measured energy gain
spectrum
Schematic of Frequency Domain Interferometry
Plasma density oscillation measured by
frequency domain interferometer
.
0.00
He 2 Torr
Pump Peak Power 1 TW
ne  1.4 1017 cm-3
-0.05
ne  9.6  10 cm
16
-3
n 
l nc
 1.4 1016 cm -3
pL
n
-0.10
n
-0.15
 0.15
eEz  4 GeV/m
-0.20
T  360 fs
-0.25
0.02 rad.
-0.35
-0.40
0.8
0.9
(r
ad
.)
P
h
as
e
D
if
fe
re
n
ce
-0.30
1.0
1.1
Time (ps)
1.2
1.3
1.4
A long self-channeling and anomalous blue-shift
Thomson scattering image
at 1.8 TW, 20 Torr (He)
Anomalous blue-shift spectrum
at 20 Torr (He)
26.0
After propagation
25.5
105
213 mJ
24.5
24.0
20 Torr /1.8 TW/F/single
110 mJ
104
23.5
23.0
0
5
10
15
20
25
30
103
mm
30
50 mJ
20 T, 165 mJ
25
3
Intensity (a.u.)
mm
25.0
x10
original
20
40 mJ
102
730
Self-channeling
length ~ 2.5 cm
15
10
0
5
10
15
20
mm
25
750
760
770
780
790
800
810
Wavelength (nm)
5
0
740
6 mJ, Incident
30
(J. K. Koga et al., Phys. Plasmas,
7, 5223,2000)
Gas density measurement
for laser-plasma production
Gas Jet
Gas ：N2
Backing Pressure ：25atm.
Duration：1msec
Orifice : 0.8mm
IMAX(CCD)
Gate : 5msec
B eam S p litter
M irro r
H e-N e Laser
6 3 2 .8 n m
V acu u m
Ch am b er
G as Jet
S creen
M irro r
B eam S p litter
IM AX(CCD Cam era)
Mach-Zeｈnder
interferometer
Density measurement of the gas jet
Time-resolved gas jet density
measurement
He gas density distribution
1.2
1e+19
1.0
0.8
5e+18
0.6
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0.4
0.2
-0 . 5
0.0
0.5
x [mm]
Gas jet nozzle
0.8 mm diam.
He gas
Gas: N2
Backing Pressure: 25 atm
10 atm
Measurements of laser wakefields
Measurement of a laser wakefield
excited by a 2 TW, 50fs laser pulse
with frequency domain interferometer
20
15
Ez ~ 20 GV/m
10
probe1
probe2
Ez [GeV/m]
(H. Kotaki et al., Physics of Plasmas
Vol. 9, 1392, 2002.)
5
0
-5
-10
pump
tp
-15
n(t)
-20
0
50
 

N2 - N1 
c
150
Time [fs]
pl as ma
w pr
100
1/ 2
dL
 n 
N plasma  1 - e 
 nc 
1-
1 ne
2 nc
200
250
300
2-cm fast Z-pinch capillary optical guiding
The 2TW, 90fs laser pulse (> 1x1017 W/cm2) has been guided
over 2 cm in a Z-pinch capillary discharge plasma.
(T. Hosokai et al., Opt. Lett. 25,10, 2000)
Guided
Unguided
Gas inlet
Electrode
TMP
Streak /
CCD
Camera
Mirror
TMP
DC
40µm
(b)
Telescope
( x20 )
ND
Capillary
F# =12 Off Axis
Parabola
Mirror
(a)
Photo-diode
D=1mm
Channel
~70µm
TMP
Thyratron
axis
Ne
17
2nF x 4 ~20kV
400µm
Band Pass
Filter
-3
~5 x10 cm
Wall
Electron Density Profile
CCD Intensity (a.u.)
Ti-Sapphire
Laser
140
0
120
0
100
0
800
400µm
(c)
400µm
40µm
600
Guided Pulse
400
200
Unguided Pulse
60
120
180
240
Channel No.
300
360
420
Jitter-free discharge system
of the plasma waveguide
T3
OPTICAL
DELAY
Marx Generator
High voltage~400kV
High impedance~20W
YAG
(Triger)
Charging
~10Hz
MARX
GENERATOR
MULTI
LTSG
Electron
beam
WATER
CAPACITOR
Water Capacitor
High voltage~400kV
Low inductance>30nH
High current~60kA(~3W)
Fast rising current~15ns
MULTI
LTSG
Plasma Channel
Front view of water capacitor
Trigger
Multi Laser Trigger
Spark Gap
Low jitter
Cylindrical current flow
Stabilization of
plasma channel
Laser trigger optics
Setup for the gas-jet plasma cathode
experiment
Inside view of the acceleration chamber
Electron detectors
Si(Li) , Faraday cup
Gas-Jet target 0.8mmφ
Laser Focus (spot 10m)
Extracting OAP with
a 5mmφ hole
Off-axis parabolic mirror
f=180mm
Measurement of pulse duration
Single-shot auto-correlation
measurement
02-11-13
02-11-14
SSA-BMI-021113 8:19:28 PM 02.11.13
SC1013.T XT
50
4.1
45
4.0
Ampl
40
Pulse width (fs)
Ampl. (V)
3.9
3.8
3.7
35
30
25
3.6
20
3.5
3.4
-4 10 -5
15
-2 10 -5
0
2 10 -5
4 10 -5
6 10 -5
10
-4000
-3500
Time (s)
Pulse width 30 fs (FWHM)
-3000
-2500
G2 (pulse readout)
-2000
-1500
Measurement of a spot size at focus
Peak focus intensity 7.3x1018 W/cm2 at 5 TW
Diffraction-limited focus
for a He-Ne reference laser
RDL~3.4 m, R~ 2.5x3.1 m
RMS spot radius for 50 % energy:
sx~5.3m, sy ~3.5m
5 TW (150
( 1 5 0 mJ
mJ/3
/300 fs
fs))のとき
のと き
0.0
15.0
Maximum intensity 5.4
5 .4 x10 18 W/cm2
2.5
17.5
5.0
20.0
7.5
3e18
10.0
Y (um)
y (m)
22.5
25.0
12.5
27.5
15.0
5e18
30.0
17.5
32.5
20.0
35.0
Focus for He-Ne 40mm diam.
22.5
15.0
17.5
20.0
22.5
25.0
27.5
30.0
32.5
x (m)
0e+00
35.0
0
5
10
15
20
X (um)
1e+18 2e+18 3e+18 4e+18 5e+18
_20021226_02_Cali_x
Intensity (W/cm2)
0
2500 5000 7500 10000 12500 15000
_20021224_01_LB5_s
25
Plasma and electron signals
62 mJ, I = 2.4 x 1018 W/cm2, a0=1.1, ne= 6.4 x 1019 cm-3
Focus at 0.29 mm
downstream
1.25
0.00
Focus at the center
of the nozzle
1.25
2.50
3.75
3.75
Y (mm)
2.50
5.00
2.50
3.75
5.00
5.00
6.25
6.25
7.50
7.50
7.50
8.75
8.75
8.75
1.25
2.50
3.75
5.00
X (mm)
6.25
7.50
8.75
0.00
1.25
2.50
3.75
5.00
X (mm)
6.25
7.50
8.75
0.00
100
100
0 2500 5000 75001000012500150001750020000
_20021226_07_LB5_s
bin width = 257 keV
Minimum energy
292keV
60
40
2000 4000 6000 8000 10000 12000
_20021226_09_LB5_s
Minimum energy
168keV
60
40
20
20
0
4
8
energy [MeV]
12
3.75
5.00
X (mm)
6.25
7.50
8.75
2000 4000 6000 8000 1000012000
_20021226_12_LB5_s
80
bin width = 164 keV
60
Minimum energy
-10keV
40
20
0
0
2.50
0
bin width = 237 keV
80
count
80
1.25
100
0
count
0.00
Focus at 0.77 mm
upstream
1.25
6.25
count
Y (mm)
0.00
Y (mm)
0.00
0
4
8
energy [MeV]
12
0
0
4
8
energy [MeV]
12
1D PIC simulation of electron acceleration
Laser pulse: Duration 30 fs, Intensity 6.8x1018W/cm2 (a0=1.8)
Plasma density distribution
3.6×1019cm-3
2.4×1019cm-3
x
0.15mm 0.1mm
2mm
Energy [MeV]
Accelerated electron bunch
140
120 Number of electrons
100 1.6x109 (0.26 nC)
80
60
40
20
0
2.10
2.12
2.14
2.16
x [mm]
2.18
2.20
Estimates of electron energy spectrum
Number of electrons
(/2.5×106)
1000
100
10
1
0
2.5
Number of electrons
All angles
20
×107
40
60 80
100
Energy [MeV]
120
140
Forward angle
2
-5.4 mrad<  <5.4 mrad
1.5
1
0.5
0
0
20
40
60
80
Energy [MeV]
100
120
140
Colliding pulse injection
Colliding pulse injection scheme
Simulation parameters
Pump pulse
Wavelength: 800 nm
Intensity: a0=1
Pulse duration: 50 fs
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ÅB
Injection pulse
Plasma density [cm-3]
Plasma density distribution in a gas jet
Intensity: a1= 0.3
Pulse duration: 50 fs
7×10 17
Plasma density
5×10 17
ne =7×1017 cm-3
0
0.15
0.75
0.25
Position [mm]
0.85
1.00
Simulation results of colliding pulse injection
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(1mm)
Quality of optically injected beam
Beam divergence
20
15
25
st =7.7 fs
10
5
0
3776
3784
3792
3800
3808
3816
umber of electrons [a.u.]
Time [fs]
Energy spectrum
30
25
Ep =7.4 MeV
20
E/Ep = 3 %
10
5
0
7
sr’ = 0.0064
20
15
10
5
0
-0.02 -0.015 -0.01 -0.005 0
0.005 0.01 0.015 0.02
Beam radius sr = 15 m
Charge
26 pC
Peak current
1.3 kA
Normalized emittance
15
6.5
umber of electrons [a.u.]
umber of electrons [a.u.]
Pulse shape
7.5
Electron energy [MeV]
8
~1 pmm・mrad
Optical Bunch Slicing Injection
•The energy of relativistic electron bunch is optically
modulated with picosecomd synchronization.
•The sliced femtosecond electron beam will be injected into
the correct accelerating phase of laser wakefild with femtosecond synchronization.
The energy modulation scheme
•Inverse FEL mechanism at the resonance condition
Chicane
lu
E - E
Electron
bunch
E
g
Laser
pulse
1 K 2 2
lL 
lu
2
2g
lL
Undulator B0
Beam dump
•Laser Beat Wave Acceleration mechanism
Colinearly injected laser pulses of two different frequencies generate
accelerating beat wave forces.
Laser beat wave
l1 
EMeV  375 - 1P1TW 
l2 
Electron bunch
No undulator!
Bunch slicing experiments for production
of femtosecond synchrotron radiation
at ALS, LBNL
(CERN Courier 40,6,pp.31-32,2000)
Electron acceleration by standard
laser wakefield
Acceleration energy gain
Experimental parameters
Energy Gain [GeV]
Laser peak power
P = 100 TW
Pulse duration
t = 20 fs
Plasma density
ne = 7 x 1017 cm-3
Focus spot radius
r0 = 15 m
Acceleration energy gain
5
4
Pump depletion limit
3
Dephasing limit
2
Energy gain per cm
1
0
0
10
20
30
W = 2.4 GeV/cm
Focus spot radius
Relativistic self-channeling threshold
Pc = 42 TW
40
r0 [m]
50
LWFA Beam Tracking with /without Guiding
Laser and plasma parameters
laser peak power 100 TW(20 fs)
spot radius
30 m
laser strength
1.08
plasma density
1.51017 cm-3
Electron Injector
energy
spot radius
pulse length
tracking number
151 MeV
27 m20 m
2 ps
2000 e-
Injection Energy
No Guiding
100
Guiding (2.5cm)
Guiding(5.0cm)
Capillary Plasma Waveguide
Preionized gas
Discharge
Current
10
1
Ceramic Wall
0
200
400
600
Energy (MeV)
800
~ 1mm
Summary
Laser acceleration test facility (LATF) completed the high
quality electron beam injector consisting of the 150 MeV
photocathode- microtron and the beam line for laser acceleration
experiments using the 10 TW-1000 TW femtosecond laser pulses.
The first gas-jet plasma cathode experiment has generated
a collimated relativistic electrons (<100 MeV)with a relatively
small energy spread.
The facility will be opened for advanced accelerator R&D
to the world-wide community.