Development of an Ultrafast Accumulative X-ray Streak Camera
description
Transcript of Development of an Ultrafast Accumulative X-ray Streak Camera
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Development of an Ultrafast Accumulative X-ray Streak Camera
Mahendra Shakya , Jinyuan Liu, Bing Shan And Zenghu Chang
J.R.Macdonald Laboratory
Kansas State University, KS
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OBJECTIVE
To Design Camera With Resolution 100fs
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Motivation
• Study of physical process requires fast detector
• Auto correlation and Cross correlation require material with efficient non-linear effect.Not applicable for X-ray
• X-ray Streak Camera Provides Intensity, Time and Space information
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Streak Camera
Convert time into space
Mirror Film
Slit
t =x/v
x
vt
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X-ray Signal
CCD
Deflection Plate
Electrostatic Lens
Switch
AnodeCathode
Phosphor Screen
Slit2Slit1
Streak Tube
MCP
Laser Pulse GaAs
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1975 first demonstration
1990 2ps resolution
1996 0.5ps resolution in single-shot mode, Z.Chang (Appl.Phys.Lett.69,1(1996)
2001 0.7 ps in accumulation mode (G.A.Naylor, et al.) by improving laser stability
2002 0.8 ps (Belzile et al.) by using multiplephotoconductive switches
2003 Jinyuang Liu 590 fs in accumulation mode Appl. Phys Lett. 82, pp. 20 (2003, )
Developments
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Factors Affecting Temporal Resolution in Accumulative Mode
• Transit Time Dispersion Velocity distribution, Angular distribution
• Scanning Speed
t s= x/v x
• Timing Jitter
psE
t ps
63.2 E
V
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176fs 135fs
Au
E
Anode
Cathode
Collimating slit
psE
t ps
63.2
Effect of E field on Transit Time Dispersion
•Collimating Slit
10.6V/mm 13.75V/mm
•High electric field
tps Reduced By 23%
x Reduced 50%
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Factors Affecting Temporal Resolution in Accumulative Mode
• Transit Time Dispersion Velocity distribution, Angular distribution
• Scanning Speed
t s= x/v x
• Timing Jitter
psE
t ps
63.2 E
V
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rr oe148.1
re= radius of the electrode
r0= radius of the gap
Reducing x by Changing Electrode Geometry
The best focused static image width, x = 175 m(25pixels)
+/2+/2
-/2
-/2
ro
y x
re
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500 1000 1500 2000
0
10
20
30
40
50
FWHM 175m
Inte
nsity
mVb=0V , Vf = 85V, Laser energy = 60 J , 6600 Shots, Exposure time = 6s
Static Image
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Images with re/r0 = 1.9
FWHM, x = 560m
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Factors Affecting Temporal Resolution in Accumulative Mode
• Transit Time Dispersion Velocity distribution, Angular distribution
• Scanning Speed
t s= x/v x
• Timing Jitter
psE
t ps
63.2 E
V
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43200 43600 44000 44400
-200
-100
0
60 ps
Am
plit
ude
(V
)
Time (ps)
43200 43600 44000 44400
0
100
200
60psA
mp
litu
de
(V
)
Time(ps)
Effect Of Cables and Switch on Scanning Speed
RL
+V0 -V0
RLDP arm 1 DF arm 2
Es
GaAs switch
RbRb
2GHz cable, t = 90ps, 18GHz cable , t =60 ps
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49600 50000 50400 50800
-300
-200
-100
0
120ps
Am
plit
ud
e(V
)
Time(ps)
Deflection Plate Output With 18GHz Cables
+V0 -V0
RbRbRLRL
DP arm 1 DP arm 2Es
GaAs switch
t1/
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Factors Affecting Temporal Resolution in Accumulative Mode
• Transit Time Dispersion Velocity distribution, Angular distribution
• Scanning Speed
t s= x/v x
• Timing Jitter
psE
t ps
63.2 E
V
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0 20 40 60 80 1000
20
40
60
80
100
120
140
160
Ris
e tim
e A
mpl
itude
(V)
Laser Energy (J)
The pulse amplitude of GaAs switch changes with trigger laser energy
Photoconductive Switch
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Laser Energy Vs Pulse Amplitude of the Switch
0 20 40 60 80 1000
500
1000
1500
2000
2500
3000
Amplitude/Rise time fluctuation = 13.66%
Am
plitu
de/R
ise
time(
V/n
s)
Laser Energy
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f=150mmf=100mm
CCD
267nm
L1L2
800nm ,25 fs
Streak Camera Calibration Setup
STREAK CAMERA
GaAs
STREAK
CAMERA
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6000 7000 8000 9000 10000 11000
5.5
6.0
6.5
7.0
7.5
8.0
D Linear Fit of Data1_D
S
peed
X 1
08 m/s
ec
Cathode voltage (V)
Cathode Voltage Vs Scanning Speed
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40 50 60 70 80 90 100 110
80
90
100
110
120
130
140
S
pee
d(P
ixel
s/p
s)
Bias voltage(V)
Bias Voltage Vs Scanning Speed
Vf = 85V, Vc=8.5 kV, Laser Energy = 60 J
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6000 7000 8000 9000 10000 11000
0.5
0.6
0.7
0.8
0.9
1.0
Tem
po
ral R
eso
luti
on
(p
s)
Cathode Voltage (V)
Cathode Voltage Vs Temporal Resolution
Vb= 68.3V, Vf= 85V , Laser Energy = 60J, 6600 shots, Exposure time = 6.6sec
Temporal resolution
470fs at –8.5kV
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Electron Sweep Speed
Vb= 68.5V, Vc= -8.5kV, Vf= 8.5V, Laser Energy = 60J
0 500 1000 1500 2000 2500 3000 35001
2
3
4
5
6
7
Speed = 1.97c
1/speed = 1.7x10-9sec/m
time
(ps)
m
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0 1 2 3 4
0
5
10
15
20
25
30
FWHM 470fs
Inte
nsi
ty(a
rbitr
ary
)
time (ps)
Vc= -8.5kV, Vb= 68.3V, Vf= 85V,Exposure time = 6s, 6600 Shots.Laser energy = 60J
Time Resolution with Variable Slit
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-0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.00
50
100
150
200
250
Image with 400average frame FWHM = 500fs
Inte
nsi
ty (
arb
itra
ry)
Time (ps)
6600 Shots average sub-picosecond pulse width streak image, Exposition time= 6.6 sec, Vb= 68.3v,Vc=-11kV, Vf= 90 Laser Energy=60J
Intensity Vs Time at -11KV Cathode Voltage
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•Introducing variable slit to collimate electron beam
•Qudrupolens Geometry. Changed re /r0 from 1.9 to 1.147
Modification Made
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• High deflection sensitivity: 20 cm/kV
•Photoconductive Switch: 60ps rise and fall time
• Fast response time: 120 ps rise and fall time
• High scanning speed: 2c
•Current Status 470fs
• Camera Potential 200fs
Summary