Streak Camera Characterization Using a
Femtosecond Ti: Sapphire Laser.
Mario Ferianis and Miltcho Danailov
Sincrotrone Trieste, S.S. 14 km, 163,5,34012 Trieste, ITALY
Abstract. At ELETTRA a Streak Camera system is in operation since 1999. Several
measurements have been performed so far on the diagnostic bending magnet beam line of the
Storage Ring. This instrument has been also widely used during the Storage Ring EEL
commissioning to fully characterize both the electron beam and the EEL radiation down to
190nm and pulse length of 7.7psFWHM- As the EEL pulse duration is approaching few
picoseconds, it becomes important to study the performance of the streak camera in this regime
which is very close to its temporal resolution limits. We therefore use the newly available
femtosecond TiiSapphire laser delivering sub-50fs pulses to fully characterize the Streak Camera
in short pulse operation. Using both infrared laser light and its second harmonic in the blue we
study the effects of incident light wavelength and bandwidth on the resolution, as well as the
linearity of the sweeps (linear single sweep and double sweep with synchroscan) on full-scale
extension. The results are presented in this paper, together with preliminary measurements of the
laser locking to the external Radio Frequency.
INTRODUCTION
Streak camera (SC) is a widely used diagnostic tool in the accelerator community
[1]. At ELETTRA a SC has been installed in 1999 [2], mainly intended as a diagnostic
tool for the storage ring (SR) longitudinal dynamics. The SC has been a fundamental
diagnostic tool for the commissioning of the European UV/VUV Storage Ring PEL
project at ELETTRA [3] and it is currently used for the further development of this
project. In some conditions, the length of the PEL pulses is approaching the temporal
limit of the camera; therefore it was important to find the operating conditions giving
the best temporal resolution.
Recently, the laser laboratory at ELETTRA has been equipped with a Ti:S
femtosecond laser and autocorrelator for laser pulse measurement, one of its main
applications being the development of a photo-cathode electron gun [4]. The
successful operation of such an electron gun will require highly stable synchronization
to the Radio Frequency signal driving the accelerating structures. A set of
measurements with the streak camera was devised with the purpose of characterizing
both the streak camera performances as well as to study the properties and parameters
of the frequency-locking unit. We present hereafter a set of measurements
demonstrating a sub-2ps resolution of the camera and sub-ps jitter in the timing of the
laser.
CP648, Beam Instrumentation Workshop 2002: Tenth Workshop, edited by G. A. Smith and T. Russo
© 2002 American Institute of Physics 0-7354-0103-9/02/$19.00
203
STREAK CAMERA MEASUREMENTS AT ELETTRA
STREAK CAMERA MEASUREMENTS AT ELETTRA
The streak camera at ELETTRA is installed on a bending magnet light port, which
The streak camera
ELETTRApurposes.
is installedThis
on ainstrument
bending magnet
lightdesigned
port, which
is specifically
used forat diagnostic
has been
and
is
specifically
used
for
diagnostic
purposes.
This
instrument
has
been
designed
and
manufactured by Photonetics (presently Optronis [5]) according to ELETTRA
manufactured (e.byg. Photonetics
[5]) according to ELETTRA
specifications
Synchroscan (presently
Frequency Optronis
of 250MHz).
specifications (e. g. Synchroscan Frequency of 250MHz).
Description of the Streak Camera
Description of the Streak Camera
The SC is equipped with two orthogonal deflection axis and with UV-graded input
TheThe
SC is
equipped
with twofrequency
orthogonalresponse
deflection
axis
and to
with
UV-graded
input
optics.
S20
photo-cathode
goes
down
200nm.
Thanks
to a
optics.
The
S20
photo-cathode
frequency
response
goes
down
to
200nm.
Thanks
to be
a
synchroscan frequency of 250MHz, consecutive bunches of a multibunch beam can
synchroscan
frequency
of
250MHz,
consecutive
bunches
of
a
multibunch
beam
can
be
acquired in single shot. The fastest deflection speeds are 25ps/mm in synchroscan
acquired in single shot. The fastest deflection speeds are 25ps/mm in synchroscan
mode
and 1 Ops/mm in single sweep mode. The ligth intensity at the input is reduced
mode and 10ps/mm in single sweep mode. The ligth intensity at the input is reduced
by a set of neutral density (N.D.) attenuators. A fast opto-electronic shutter [2], based
by a set of neutral density (N.D.) attenuators. A fast opto-electronic shutter [2], based
on a Pockels Cell, reduces the background light due to the undeflected photons (no
on a Pockels Cell, reduces the background light due to the undeflected photons (no
photo-cathode gating is used), which appear with the fastest secondary sweeps.
photo-cathode gating is used), which appear with the fastest secondary sweeps.
Measurements
Ring: Synchrotron
Synchrotron and
andFEL
EELRadiation
Radiation
Measurements on
on the
the Storage
Storage Ring:
The
current and
and bunch
bunch length
lengthvs.
vs.RF
RFcavity
cavityvoltage
voltage
Thetypical
typical bunch
bunch length
length vs.
vs. bunch
bunch current
dependancies
are
periodically
measured.
Longitudinal
multi
bunch
instabilities
dependancies are periodically measured. Longitudinal multi bunch instabilities
corresponding
operating conditions
conditions have
have been
been effectively
effectively
corresponding to
to different
different machine
machine operating
characterized
using
the
SC.
Recently,
a
new
measurement
activity
has
started
withthe
the
characterized using the SC. Recently, a new measurement activity has started with
synchrotron
light
pulses
directly
focused
onto
the
photo-cathode
(2x8mm)
to
acquire
synchrotron light pulses directly focused onto the photo-cathode (2x8mm) to acquire
also
(horizontal or
or vertical).
vertical).
alsothe
thetransverse
transverse bunch
bunch motion
motion (horizontal
FW HM = 7.7
170
180
Tim e (ps)
190
200
FIGURE 1.1. Example
Example of
of synchroscan
synchroscan single
FIGURE
single shot
shot acquisition:
acquisition: FEL
PEL radiation
radiation atat 196nm,
196nm, with
witha a
FWHM=7.7ps,vertical
vertical axis:
axis: 3.37ms
3.37ms full
full screen;
FWHM=7.7ps,
screen; horizontal
horizontal axis:
axis:441ps
441psfull
fullscreen.
screen.
Being the
the SR-FEL
SR-FEL located
located close
close to
Being
to the
the diagnostic
diagnostic bending
bending magnet,
magnet, the
the FEL
PEL
radiation (fig.
(fig. 1)
1) has
has been
been easily
easily driven
driven to
radiation
to the
the SC
SC input
input for
for direct
direct measurement
measurement[6].
[6].
204
FEMTOSECOND MEASUREMENT SET-UP
FEMTOSECOND
The streak
streak camera has been located on an optical table adjacent to the one of the
The
laser (see
(see figure
figure 2, left). Both tables are
are not isolated from
from ground
ground vibrations.
vibrations.
laser
The Femtosecond Laser
The source
source of
of ultrashort
ultrashort pulses
pulses is
is aa Kerr-lens
Kerr-lens Mode Locked (KLM)
(KLM) Ti:S laser
The
pumped
by
a
5W
continuous
wave
intracavity
frequency-doubled
Nd:YVC>44 laser
pumped by a 5W continuous wave intracavity
Nd:YVO
(Millenia, Spectra
Spectra Physics).
Physics). The
The 44 mm
mm long Ti:S crystal is placed in a standard X-fold
(Millenia,
cavity allowing
allowing for soft aperture KLM (details on the cavity design can be found e.g.
cavity
in [7]).
[7]). ItIt was
was normally used at
at 4.3W of pump
pump power
power giving
giving about 400mW average
in
in mode-locking
mode-locking regime.
regime. The
The cavity
cavity length was adjusted so as to provide a
power in
repetition rate
rate of
of 100MHz.
100MHz. Dispersion
Dispersion control
control was
was achieved with two intracavity fused
repetition
fused
silica prisms,
prisms, allowing
allowing for pulse duration in the 40fs range and bandwidth around
silica
40nm FWHM,
FWHM, centered
centered at
at 810nm.
810nm. A
A typical intensity autocorrelation trace (obtained
40nm
by aa FR-103
FR-103 autocorrelator,
autocorrelator, Femtochrome
Femtochrome Research,
Research, Inc)
Inc) is
is shown
shown on
on fig.
fig. 22 RIGHT
by
(scale 2µs/div).
2|is/div).
(scale
: 4
::
FIGURE 2.
2. LEFT:
LEFT: Picture
Picture of
of the
the measurement
measurement laboratory:
laboratory: in
in foreground,
foreground, the
the streak
streak camera
camera is
is visible
visible
FIGURE
with some
some of
of its
its optical
optical components;
components; the
the femto-second
femto-second laser
laser (black
(black box)
box) with
with its
its peripheral
peripheral units
units is
is
with
located on
on the
the second
second table,
table, in
in background.
background. RIGHT:
RIGHT: Plot
Plot of
of the
the autocorrelation
autocorrelation function
function corresponding
corresponding
located
to aa 42fs
42fsFWHM
pulse.
FWHM pulse.
to
Given the
the calibration
calibration factor
factor of
of the
the autocorrelator
autocorrelator (31fs/µs)
(31fs/|is) and
and assuming
assuming aa sech
sech22
Given
pulse shape
shape one
one obtains
obtains 42fs
42fs for
for the
the FWHM
FWHM duration
duration averaged
averaged over
over few
pulse
few hundred
hundred
pulses.
A
small
fraction
of
the
beam
was
reflected
by
a
glass
plate
and
directed
to the
the
pulses. A small fraction of the beam was reflected by a glass plate and directed to
Pockels
Cell
system
by
two
metallic
mirrors.
The
second-harmonic
was
generated
by
Pockels Cell system by two metallic mirrors. The second-harmonic was generated by aa
1mm thick
thick lithium
lithium triborate
triborate (LBO)
(LBO) crystal.
crystal. Due
Due to
to the
the narrow
narrow spectral
spectral acceptance
acceptance and
and
1mm
group-velocity mismatch
mismatch of
of this
this crystal
crystal the
the SH
SH pulses
pulses are
are estimated
estimated to
to be
be in
in the
150fs
group-velocity
the 150fs
range, which
which can
can still
still be
be considered
considered aa δ-function
8-function time
time signal
signal input
input for
for the
range,
the streak
streak
camera.
camera.
Even if
if the
the mode-locking
mode-locking mechanism
mechanism of
of the
the laser
laser is
is aa passive
passive one,
one, it
Even
it allows
allows the
the
synchronization of
of the
the laser
laser to
to an
an external
external RF
RF signal
signal by
by the
synchronization
the use
use of
of aa phase-locking
phase-locking
loop technique
technique [8].
[8]. This
This technique
technique is
is based
based on
on active
active control
control of
of the
the cavity
cavity length
length
loop
205
driven by an error signal provided by a phase detector: at this stage we have used a
Timing Stabilizer (CLX-1100, Time-Bandwidth Products). It implements the
frequency locking by acting on the back mirror position using fast piezo for fine
movement around a zero position adjusted by a picomotor drive. During normal
operation, the phase-noise measured at the output of the phase detector of the CLX1100 was in the range 0.6-5-lps.
Timing and Synchronization Set-up
The main issues of the timing and synchronization system are:
• to provide the trigger and synchroscan signal to the streak camera
• to provide a stable reference signal to the laser timing synchronization system
• to assure the synchronization and the time stability of these signals at the
picosecond level
The allowed frequencies for the Synchroscan deflection unit range from 249.2MHz
to 251.0MHz; the frequency of the reference signal for the laser timing
synchronization system is 100MHz. Therefore, we decided to adopt a Master
Oscillator (Rhode&Schwartz SML02) frequency of 500.0MHz and to divide it by 5 to
obtain the 100MHz reference for the laser. The same Master Oscillator drives the
Synchroscan deflection Unit, after a "divide by 2" and a band-pass filtering for
increased spectral purity, as well as the long division chain (-5-(8640xM), M
programmable) generating the gate signals (=10Hz), used to form the trigger pulse and
for the Pockels Cell HV driver. The complex architecture of this timing system [2]
stems from the necessity of providing very low frequency, low jitter trigger signal to
the SC adopting, where possible, timing units already developed [9] at ELETTRA.
Only the Auxiliary Board has been specifically designed for the SC timing system.
DESCRIPTION OF THE MEASUREMENTS
The purpose of the measurement is the complete characterization of the streak
camera taking advantage of the femtosecond laser, which requires the synchronization
of the femtosecond laser to the Master Generator signal.
General Considerations
The Optronis streak camera is specified to have a resolution of 2pspwHM, in Single
Sweep mode. The femtosecond TiiSapphire laser delivers sub-50fs pulses at a
wavelength of 810nm, with a rate of 100MHz. It is easy to estimate that even after
propagation through the optical components (Pockels cell, camera optics, etc) the laser
pulse width remains below 300fs for both the fundamental and second harmonic
wavelengths. Therefore, the following statements hold:
i)
the laser pulse appears to the streak camera as a 8 function. As a
consequence, the laser pulse width cannot be measured, though its time
stability can be observed and measured
206
the
function will
will reveal
reveal its
its true
true time
time
the operation
operation of
of the
the streak
streak camera
camera with
with aa δ8 function
resolution
resolutionand
andhow
how itit isis affected
affected by
by different
different parameters
parameters
iii)
the
can be
be measured
measured
iii)
the time
time stability
stability (jitter)
(jitter) of
of the
the streak
streak camera
camera sweeping
sweeping can
provided
previously measured
measured in
in the
the same
same
provided the
the laser
laser pulse
pulse stability
stability has
has been
been previously
configuration
configuration by
by other
other means
means
The
to the
the incident
incident light
light
The effects
effects of
of the
the proper
proper setting
setting of
of the
the input
input optics
optics according
according to
wavelengths
in Focus
Focus Mode
Mode (deflection
(deflection
wavelengths have
have been
been observed,
observed, operating
operating the
the SC
SC in
stopped).The
Thetwo
two different
different modes
modes of
of operation
operation of
of the streak camera have been
stopped).
been tested:
tested:
synchroscanand
andsingle
single sweep.
sweep. Special
Special emphasis
emphasis has been given to the latter
synchroscan
latter as
as itit isis the
the
mostaccurate
accurateone
one(most
(most suited
suited to
to the
the femto-second
femto-second laser) and the most
most
most demanding
demanding for
for
thetriggering.
triggering. The
Themeasurements
measurements are
are summarized
summarized in
in Table
Table 1.
1._____________
the
ii)
ii)
Table1:1:summary
summaryofofthe
thestreak
streakcamera
camerameasurements
measurementswith
withthe
thefemto-second
femto-second laser
laser______
Table
Measuredquantity
quantity
Streak Camera
Camera
Notes
Measured
Streak
Varied
Notes
Mode // Single
Single shot
shot___parameter
Mode
parameter
Synchroscan
Resolution
D=200, 100 and 50um
Synchroscan
Pinhole diameter
1)1)Resolution
50µm
Synchroscan
Laser control loop
Laserlocking
lockingprocess
process
Synchroscan
2)2)Laser
sequence
sequence
open/close
Single sweep
sweep
Resolution
D=200, 50 and 30um
Single
Pinhole diameter
3)3)Resolution
30µm
Single sweep
sweep
Light intensity
intensity
Resolution
N. D. =0,
Single
Light
=0, 0.5
0.5 and
and 0.99
0.99
4)4)Resolution
Single sweep
sweep
Input wavelength
wavelength
Resolution
?t=810,A?t=40nm
Single
Input
4)4)Resolution
λ=810, ∆λ=40nm
?t=405nm,
λ=405nm, A?t=10nm
∆λ=10nm
Single sweep
sweep
Start of
of fast
fast ramp
ramp
JitterofofSweep
Sweepramp
ramp
Single
Start
5)5)Jitter
Accumulation= 1 0
Accumulation=10
Single sweep
sweep
Delayed Pulses
Accuracyand
and
Optical
Single
Delayed
Pulses
6)6)Accuracy
Optical Delay
Delay AL=
∆L=
Linearity
0,
1.5 and
Omm
Linearity
0, 1.5
and 3.
3.0mm
Data analysis
analysis
Data
Depending on
on the
the operation
operation mode,
mode, the
the output
output of
of aa fast
Depending
fast streak
streak camera
camera measurement
measurement
of
a
periodic
short
optical
pulse
is
an
image
with
one
or
several
spots,
of a periodic short optical pulse is an image with one or several spots, for
for single
single sweep
sweep
(see
fig.
3
right)
and
synchroscan
(see
fig.3
left)
respectively.
(see fig. 3 right) and synchroscan (see fig.3 left) respectively.
441ps
sin g le la s e r
p u lse
6
c o n s e c u tiv e
la se r
p u ls e s
176ps
65ns
FIGURE 3. Streak Camera acquisitions of the femto-second laser. LEFT: synchroscan single shot of 6
FIGURE
3. Streak
Cameravertical
acquisitions
thefull
femto-second
laser. LEFT:
single RIGHT:
shot of 6
consecutive
laser pulses;
axis: of
65ns
screen; horizontal
axis: synchroscan
441ps full screen.
consecutive
laser
pulses;
vertical
axis:
65ns
full
screen;
horizontal
axis:
441ps
full
screen.
RIGHT:
single sweep shot of one laser pulse; horizontal axis: 176ps full screen.
single sweep shot of one laser pulse; horizontal axis: 176ps full screen.
Therefore, for each synchroscan acquisition, the average FWHM of the laser spots
Therefore, for each synchroscan acquisition, the average FWHM of the laser spots
has been computed. Then, the average FWHM values of different synchroscan
has been computed. Then, the average FWHM values of different synchroscan
207
acquisitions, relative to the same measurement set-up, have been averaged again. For
single sweep acquisitions the FWHM values from different acquisitions under the
same conditions have been averaged and the RMS computed. In fig. 4 the dispersion
for seven single-sweep single-shot acquisitions is shown: the average FWHM is equal
to 2.94ps, while the RMS of this distribution is 0.47ps.
DFWHM[ps] left axis AAmax [a.u.] right axis
FWHM [ps]
Amplitude[a.u.]
A
A
500
D
A
400
D
D
D
D
D
200
100
1
2
3
4
5
6
7
Single shot measurem ,nt: pinhole=50(im; MCP=790V
FIGURE 4. Plot of data dispersion for Single-Sweep single-shot acquisitions of the fs laser.
In fig. 5, a typical SC acquisition of laser pulse and its gaussian fit (a=1.3ps).
*
FIGURE 5. Streak Camera acquisition of laser pulse (circles) and its gaussian fit (triangles): a=1.3ps.
Results and discussion
The obtained results are in good agreement with the specifications provided by the
manufacturer: a comparison is reported in Table 2. In single sweep mode, as the
photoelectrons inside the streak tube experience only a single deflection, there is less
distorsion and the minimum resolution is achieved (resolution<2ps)._________
Table 2: summary of the measurement results and comparison with specification data____
Measured quantity
Streak Camera
Value
Specification data
Mode
Synchroscan
3.5ps FWHM
<3.5ps FWHM
Resolution
Single sweep
1.4psFWHM
<2ps FWHM
Resolution
Single sweep
Linearity
±1.25%
±5%
Single sweep
<5ps RMS
<5ps
Jitter
The beneficial reduction of pinhole diameter has been observed in both operating
modes (fig. 6 and 7): the reduction of the photocathode emitting area reduces the spot
size of the e-beam on the phosphor screen, and in addition minimizes the geometrical
aberrations inside the streak tube.
208
FWHM
[ps]
FWHM[ps]
FWHM
[ps][ps]
FWHM
8.000
8.000 ————————————————————————————————————
8.000
8.000
7.000
7.0007.000
7.000
6.000
6.000
6.000
6.000
5.000
5.000
^»***
5.000
5.000
^
4.0004.000
^***
4.0001
4.000
^«-^ ^-—***
h-—
3.000
3.000
3.000
3.000
2.000
2.000
2.000
5050
50 50
7070
70 70
**^
^1
yssss
90
110
130 150
150 170
170 190
190
90
110
130
90 90 110110 130130 150150 170170 190190
pinhole
diameter
[micron]
pinhole
diameter
[micron]
pinhole
diameter
[micron]
pinhole
diameter
[micron]
No.
Pinhole
Pinhole
No. of
of
No.
Pinhole
No.ofof
Pinhole
Synchroscan
Diameter
Diameter
Synchroscan
Diameter
Synchroscan
Diameter Synchroscan
Acquisitions
[um]
Acquisitions
[µm]
Acquisitions
Acquisitions
[µm]
[µm]
(see
(see Data
Data
(see
(seeData
Data
Analysis)
Analysis)
Analysis)
Analysis)
50
77
50
5050
77
(each
(each88spots)
spots)
(each8 8spots)
spots)
(each
100
44
100
100
4
100
4
(each888spots)
spots)
(each
spots)
(each
(each
8 spots)
200
200
200
200
4 444
(each
8spots)
spots)
(each
spots)
(each
(each
8 88spots)
AVG
AVG RMS
RMS
AVG
RMS
AVG
RMS
[ps]
[ps]
[ps]
[ps]
[ps]
[ps]
[ps]
[ps]
3.54
3.540.30 0.30
0.30
3.54 0.30
3.54
0.44 0.44
4.20
4.20
0.44
4.20
0.44
4.20
5.96
0.33 0.33
5.96
0.33
5.96
0.33
5.96
FIGURE
Plot
the
resolution
vs.
pinhole
diameter
insynchroscan
synchroscanmode.
mode.The
Thelinear
linearfitfit
FIGURE
6.6.6.Plot
Plot
ofof
the
resolution
vs.
pinhole
diameter
synchroscan
mode.
The
linear
fitis:is:
is:
FIGURE6.
Plotof
ofthe
theresolution
resolutionvs.
vs.pinhole
pinhole
diameterinin
in
synchroscan
mode.
The
linear
FIGURE
diameter
-3 3
-3 -3...
MO+Ml*DIA
with:
M0=2.7;
Ml=16*10'
M0+M1*DIA
with:
M0=2.7;
M1=16*10
pinhole
pinhole
M0+M1*DIA
with:
M0=2.7;
M1=16*10
pinhole
M0+M1*DIA
with:
M0=2.7;
M1=16*10
.
pinhole
No.
of
AVG RMS
Pinhole
No.
AVG
RMS
FWHM[ps]
» meas
measdata
linear
fit
data
linear
Pinhole
AVG
RMS
FWHM
[ps][ps]
meas
data -9—
linear
FWHM
Pinhole
No.
ofof
AVG
meas
data
linear
fitfitfit
FWHM
[ps]
4.0004.000
4.000
Diameter
Single
[ps]
4.000
Diameter
Single
[ps]
[ps] [ps]
[ps]
[ps]
Diameter
Single
[ps]
[ps]
[um]
Sweep
Sweep
[µm]
[µm]
Sweep
[µm]
3500
3.500
3.5003.500
Acquisitions
Acquisitions
1
Acquisitions
^
(seeData
Data
(see
Data
3.000
3.000
3.000
(see
3.000
x""
Analysis)
Analysis)
Analysis)
2500
^
2.5002.500
200
17
3.54
2.500
0.30
3.54
200
0.30 0.30
3.54
200
1717
0.30
3.54
^
(each
1
spot)
spot)
(each
1
(each
1
spot)
^
2.000
2.000
2.000
50
0.75
1.702
0.75
1.702
0.75
1.702
5050
9 99
0.75
1.702
^
>
spot)
(each
1
spot)
(each
1
11.500
500 (each
1
spot)
1.500
IT
30
44
0.19
1.4
30
1.4 0.19
0.19
0.19
1.4
3030
44
1.4
1.000
1.000
(slit,
(each
1spot)
(slit,
(each
1spot)
spot)
1.000
(slit,
(each
spot)
(slit,
(each
11
50
100
150
200
100
150
200
0.8mm
5050
100
150
200
0.8mm
0 00
50
100
150
200
0.8mm
0.8mm
high)
high)
high)
FIGURE7.
Plotof
ofthe
theresolution
resolutionvs.
vs.pinhole
pinholediameter
diameter
single
sweep
mode.
The
linear
FIGURE
Plot
the
resolution
vs.
pinhole
diameterinin
insingle
singlesweep
sweepmode.
mode.The
Thelinear
linear
FIGURE
fitfitfit
is:is:is:
7.7.7.Plot
Plot
ofof
the
resolution
vs.
pinhole
-3 diameter in single sweep mode. The linear fit is:
-3-3 3..
M0+M1*DIA
with:
M0=1.1;
M1=10.9*10
pinhole
MO+Ml*DIA
with:
M0=l.l;
Ml=10.9*10M0+M1*DIA
pinholewith:
M0+M1*DIApinhole
with: M0=1.1;
M0=1.1;M1=10.9*10
M1=10.9*10 . .
pinhole
Theinfluence
influenceof
ofthe
thelight
lightintensity
intensityimpinging
impingingon
on
the
photocathode
was
studied
The
influence
of
the
light
intensity
impinging
onthe
thephotocathode
photocathodewas
wasstudied
studied
The
influence
of
the
light
intensity
impinging
on
the
photocathode
was
usingdifferent
different
N.D.
attenuators
in
front
of
the
input
optics,
while
keeping
the
same
using
different
N.D.
attenuators
in
front
of
the
input
optics,
while
keeping
the
same
using
N.D.
attenuators
in
front
of
the
input
optics,
while
keeping
the
different N.D. attenuators in front of the input optics, while keeping thesame
same
pinhole
and
MCP
voltage.
As
can
be
seen
in
fig.8,
there
is
an
improvment
at
low
input
pinholeand
andMCP
MCPvoltage.
voltage.As
Ascan
canbe
beseen
seeninin
infig.8,
fig.8,there
thereisis
isanan
animprovment
improvmentatat
atlow
lowinput
input
pinhole
and
MCP
voltage.
As
can
be
seen
fig.8,
there
improvment
low
input
light
levels,
which
canbebe
attributedtoto
reducedspace
space
charge
effects.
light
levels,
which
can
attributed
reduced
spacecharge
chargeeffects.
effects.
light
levels,
which
can
levels,
which
can
bebeattributed
attributed
totoreduced
reduced
space
charge
effects.
FW H M [ps]
FWHM
[ps]
FW
H
M
4.5
FW
H
M [ps]
[ps]
4.5
4.5 4.0
4.0
4.0 3.5
3.5
3.5 3.0
3.0
3.0 2.5
2.5
2.5 2.0
2.0
2.0 1.5
1.5
1.5 1.0
1.0
1.0 0.5
0.5
0.5 0.0
0.0
0
0.1
0.0
00
0.10.1
0
0.1
\:
0.2
0.20.2
0.2
0.3
0.4
0.30.3
0.40.4
0.4
N .0.3
D . value
N .ND. .Dvalue
.
value
N . D . value
0.5
0.50.5
0.5
0.6
0.60.6
0.6
No.
of
No.
of
No.
ofof
No.
Single
Single
Single
Single
Sweep
Sweep
Sweep
Sweep
Acquisitions
Acquisitions
Acquisitions
Acquisitions
ND=0.5;
ND=0.5;
ND=0.5;
ND=0.5;
9 acq.
9 9acq.
9acq.
acq.
ND=0;
ND=0;
ND=0;
ND=0;
7 acq.
7 7acq.
7acq.
acq.
AVG
RMS
AVG RMS
RMS
AVG
AVG
RMS
[ps]
[ps] [ps]
[ps]
[ps]
[ps]
[ps]
[ps]
0.75
1.702
1.702
0.75
0.75
1.702
0.75
1.702
0.47
2.94
0.47
2.94
2.94
0.47 0.47
2.94
FIGURE 8. Resolution vs. N.D. attenuation in single sweep mode.
FIGURE
inin
single
sweep
mode.
FIGURE8.8.Resolution
Resolutionvs.vs.N.D.
N.D. attenuation
attenuation
single
sweep
mode.
8. Resolution
attenuationon
in temporal
single sweep
mode.
Next figureFIGURE
illustrates
the effectvs.ofN.D.
wavelength
resolution.
From these
Next
Nextfigure
figureillustrates
illustratesthe
theeffect
effectofof
ofwavelength
wavelengthon
ontemporal
temporalresolution.
resolution.From
Fromthese
these
Next
figure
illustrates
the
effect
wavelength
on
temporal
resolution.
From
these
preliminary (λ0=810nm and 405nm) measurements the effect of the larger
energy
preliminary
(λ
=810nm
and
405nm)
measurements
the
effect
of
the
larger
energy
preliminary
(^o=810nm
and
405nm)
measurements
the
effect
of
the
larger
energy
0
and
405nm)
measurements
the effect
of will
the larger
energy
preliminary
(λ0=810nm
spread induced
by higher
energy
photons
can be observed.
This test
be completed
spread
induced
by
energy
photons
can
be
This
spread
induced
byhigher
higher
energy
photons
can
beobserved.
observed.
Thistest
testwill
willbebe
becompleted
completed
spread
induced
higher
energy
can
be
observed.
This
test
will
completed
as soon
as the by
third
harmonic
of photons
the
fs laser
will
be
available.
as
soonas
thethird
thirdharmonic
harmonicof
thefsfsfslaser
laserwill
willbe
beavailable.
available.
asassoon
soon
asasthe
the
third
harmonic
ofofthe
the
laser
will
be
available.
209
«• FWHM
FWHM[ps]
[ps] m Amax
Amax[a.u.]
[a.u.]
FWHM [ps]
5
4.55
4
4.5
3.54
3
3.5
2.53
2
2.5
1.52
1.5
1
0.51
0.5
0
0200
200
200
Amax [a.u.]
p^/HM(@810nm)=2.63ps
FWHM(@810nm)=2.63ps
FV
/HM(@405nm)=3.41ps
FWHM(@405nm)=3.41ps
FWHM(@810nm)=2.63ps
- 1000
1000
900
900
1000
- 900
800
800
700
- 800
700
600
- 700
600
500
- 600
500
FWHM(@405nm)=3.41ps
1——
-
300
300
300
400
400
400
400
500
300
i——- 400
300
i - 300
200
200
500
500
500
600
600
700
700
600
700
800
800
800
100
- 200
100
00
- 100
900
9()00λ [nm]
Mnm]
No.of
of
AVG RMS
RMS
No.
AVG
Single
[ps]RMS
[ps]
No.
of
AVG
Single
[ps]
[ps]
Single
[ps]
[ps]
Sweep
Sweep
Sweep
Acquisitions
Acquisitions
Acquisitions
SlOnm:5acq
5acq 2.63
2.63 0.58
0.58
810nm:
0.58
810nm:
5acq
2.63
∆λ=40nm
A?t=40nm
∆λ=40nm
405nm:
7acq
405nm:
7acq 3.41
3.410.84
0.84
0.84
405nm:
7acq
3.41
∆λ=10nm
A^=10nm
∆λ=10nm
Diff
Diff
Diff
+29%
+29%
+29%
900λ [nm]
FIGURE9.9.Resolution
Resolution vs.
vs. input
input wavelengths.
wavelengths. N.D.=0
N.D.=0 (relative
FIGURE
(relative comparison).
comparison). Pinhole=50µm.
Pinhole=50urn.
FIGURE
9. Resolution
vs.
input
wavelengths.
N.D.=0
(relative
comparison).
Pinhole=50µm.
The
accuracy
and
the
linearity
of
the
fastest
single
The accuracy and the linearity of the fastest single sweep
sweep have
have been
been checked
checkedusing
using
The accuracy and the linearity of the fastest single sweep have been checked using
an optical
optical delay line.
line. The optical
optical path length
variation
∆L
(translation
stage/10µm
an
length variation
variation ∆L
AL(translation
(translationstage/10µm
stage/1 Ojim
an opticaldelay
delay line. The
The optical path
path length
resolution:
33fs)
was:
0mm,
1.5mm
and
3.0mm
yielding
a
delay
(2∆L)
between
pulses
resolution:
33fs)
was:
Omm,
1.5mm
and
3.0mm
yielding
a
delay
(2AL)
between
pulses
resolution:
33fs)
was:The
0mm,
1.5mm error
and 3.0mm
yielding
a delay
(2∆L) Due
between
pulses
of
0,
10ps
and
20ps.
maximum
is
2.5%
(0.7ps
over
27.8ps).
to
different
ofof0,0,lOps
and
20ps.
The
maximum
error
is
2.5%
(O.Vps
over
27.8ps).
Due
to
different
and 20ps. The maximum error is 2.5% (0.7ps over 27.8ps). Due to different
optical10ps
delays
most part
part of the
the sweep has
has been used
during
this
measurement
so
that
optical
used during
during this
thismeasurement
measurementso
sothat
that
opticaldelays
delaysmost
most part of
of the sweep
sweep has been
been used
we
checked
the
accuracy
and
the
linearity
as
well.
we
as well.
well.
wechecked
checkedthe
theaccuracy
accuracyand
and the
the linearity
linearity as
Average
Avg.
RMS
∆
Average Avg.
Avg. RMS
RMS
LEFT AXIS [ps]: measured data (solid line) and expected values (dotted
Average
∆A
Pulse
Delay
On
Path
line) from micrometer readings; RIGHT AXIS [ps]: RMS on data (circles)
On
Pulse
Delay
Path
Pulse
Delay
On
Path
and ERROR from expected (crosses).
LEFT AXIS [ps]: measured data (solid line) and expected values (dotted
line)
from
micrometer
readings;
RIGHT
[ps]:expected
RMS onvalues
data (circles)
LEFT
AXIS
[ps]: measured
data
(solid AXIS
line) and
(dotted
and ERROR
from
expected
line) from micrometer
readings;
RIGHT
AXIS(crosses).
[ps]: RMS on data (circles)
and ERROR from expected (crosses).
2.00
40.00
2.00
40.00
35.00
S*
35.00
^
30.00
30.00
20.00
+
>**"
+
1.00
0.50
Length
Length
Length
[ps]
[ps]
[ps]
2.53
2.53
2.53
2.72
2.72
2.72
3.06
3.06
3.06
[ps]
[ps]
[ps]
17.8
17.8
17.8
28.50
28.50
28.50
37.76
37.76
37.76
Delay
Delay
Delay
[ps]
[ps]
[ps]
0.31
0.31
0.31
0.36
0.36
0.36
0.34
0.34
0.34
0.50
+
0.00
0.00
20.00
^
°
-0.50
15.00
15.00
1.50
1.00
^'
25.00
25.0025.00
1.50
Length
Length
Length
[mm]
[mm]
[mm]
0
00
1.5
1.5
1.5
3.0
3.0
3.0
1
15.00
i
2
1
3
2
3
-0.50
-0.50
FIGURE 10. Plot of the measured ∆T [ps] for three different optical lengths. Pinhole=200µm
FIGURE10.
10.Plot
Plotofofthe
themeasured
measuredAT
∆T [ps]
[ps] for
Pinhole=200µm
FIGURE
forthree
threedifferent
differentoptical
opticallengths.
lengths.
Pinhole=200um
Electrical Measurements on Timing and Laser Stability
ElectricalMeasurements
Measurements on
on Timing
Electrical
Timing and
andLaser
LaserStability
Stability
For
the
electrical
measurements,
listed
Table 3,
3, the 50GHz
50GHz TEK
TEK sampling
sampling scope
scope
Forthe
theelectrical
electricalmeasurements,
measurements, listed
listed in
in
For
in Table
Table 3, the
the 50GHz
TEK
sampling scope
CSA803A
has
been
used
with
the
25GHz
photodiode
(1411
by
New
Focus).
CSA803Ahas
hasbeen
beenused
used with
with the
the 25GHz
25GHz photodiode
CSA803A
photodiode(1411
(1411by
byNew
NewFocus).
Focus).
Table 3: summary
of the stability
measurements
Table 3: summary of the stability measurements
Table
3: summary of the stability
measurements
Scope
Scope
ScopeInput
Input
Scope Trigger
Trigger
Scope57.78kHz
Trigger
Scope
Input500MHz
RF
TCK,
RFMaster
Master500MHz
TCK, 57.78kHz
RF
Master
500MHz
TCK,
Laser
100MHz
reference
TCK,
Laser
100MHz
reference
TCK, 57.78kHz
57.78kHz
Laser
100MHz
reference
TCK,
25GHz
Photodiode
25GHz
Photodiode
TCK, 57.78kHz
57.78kHz
Measured Jitter
Jitter
Measured
Measured
Jitter
910fs, RMS
RMS
910fs,
910fs,
1.62ps,
RMS
1.62ps, RMS
1.62ps,RMS
660fs,
RMS
660fs,
RMS
660fs,
RMS
∼4ps,
PK-PK
∼4ps,
PK-PK
~4ps,
PK-PK
(estimated
from
(estimated from
(estimated
from
scope plot)
plot)
scope
scope plot)
Notes
Notes
Notestime
Accumulation
time
Accumulation
Accumulation
for
statistics
for statistics == time
forseconds
statistics =
30
seconds
30
25GHz
TCK,
57.78kHz
30 frequency
seconds
The
frequencyof
ofthe
the
25GHz
Photodiode
Streak
Camera
Trigger,
The
25GHzPhotodiode
Photodiode
Streak
Camera
Trigger,
25GHz Photodiode
Streak Camera
The frequency
of the
trigger
tothe
thescope
scope
10Hz
trigger
to
10Hz Trigger,
lOHz
trigger
to the
too low
low
forscope
an
isis too
for
an
is too
low for an
RMS
measurements
RMS
measurements
RMS
measurements
The
100MHz
laser
reference
The measured
measured jitter
jitter between
between the trigger TCK and the 100MHz
laser
reference
The ismeasured
jitterwhereas
betweenthethe
trigger
TCKtheand
thetrigger
100MHz
reference
signal
jitter
between
trigger
TCKlaser
and the
the
laser
signal
is 1.62psRMS,
1.62psRMS,
whereas
same
TCK
and
laser
signal
is
1.62psRMS,
whereas
the
jitter
between
the
same
trigger
TCK
and
the laser
light
pulse,
acquired
by
the
photodiode,
is
0.66ps
(fig.
11
left).
This
data
are
consistent
light pulse, acquired by the photodiode,
left). This data are consistent
light
acquired
by the
photodiode,
is 0.66ps
11 left). This
arefilters
consistent
with
the
pass
of
stabilization
loop of(fig.
the CLX1100
CLX1100
unit,data
which
filters
the
withpulse,
thelow
low
pass filter
filter
of the
the
stabilization
unit,
which
the
with
thefrequency
low pass filter
of
stabilization
loop of
unit, which filters the
“high”
jitter
is
100MHz signal.
signal.
“high”
frequency
jitter that
thatthe
is eventually
eventually present
on the
the CLX1100
100MHz
"high" frequency jitter that is eventually present on the 100MHz signal.
210
:"K&
;VfQ£
FIGURE
25GHz photodiode
photodiode and
and the
the 50GHz
50GHz sampling
sampling scope.
scope.
FIGURE 11.
11. LEFT:
LEFT: Laser
Laser pulse
pulse acquired
acquired with
with the
the 25GHz
Jitter
=660fs. RIGHT:
RIGHT: same
same photodiode
photodiode signal
signal but
but with
with lOHz
10Hz trigger.
trigger.
RMS
JitterRM
s=660fs.
In
the same
same trigger
trigger signal
signal of
of the
the SC
SC has
has
In spite
spite of
of its
its ultra
ultra low
low frequency
frequency (10Hz),
(lOHz), the
been
used
to
reconstruct
the
photodiode
laser
pulse
(fig.11
right)
with
a
jitter=4ps
pk-pk
been used to reconstruct the photodiode laser pulse (fig. 11 right) with a jitter=4pspk-pk..
This
with the
the streak
streak camera
camera accumulation
accumulation mode
mode acquisitions
acquisitions showing
showing aa
This data
data together
together with
total
jitter
of
18.4ps
,
give
(subtracting
in
quadrature)
a
preliminary
value of
of
pk-pk
total jitter of 18.4pspk-pk, give (subtracting in quadrature) a preliminary value
jitter of
unit (<5ps
on the
the specs).
specs). As
As this
this is
is aa crucial
crucial
4.4ps
RMS jitter
RMS on
4.4pSRMs
of the
the streak
streak sweep
sweep unit
(<5pSRMs
point
this parameter
parameter will
will be
be fully
fully characterized
characterized vs.
vs. the
the
point for
for future
future applications
applications of
of the
the SC
SC this
trigger
parameters (tn
(trise
and
amplitude).
The
most
viable
option
for
reducing
it
to
trigger signal
signal parameters
and
amplitude).
The
most
viable
option
for
reducing
it
to
se
the
ramp.
the picosecond
picosecond level
level appears
appears the
the adoption
adoption of
of an
an optical
optical switch
switch enabled
enabled sweep
sweep ramp.
ACKNOWLEDGMENTS
ACKNOWLEDGMENTS
The
careful manuscript
manuscript reading,
reading, and
and to
to the
the
The Authors
Authors are
are grateful
grateful to
to D.
D. Bulfone,
Bulfone, for
for careful
Instrumentation
Instrumentation Group
Group people
people who
who helped
helped in
in setting
setting up
up this
this experiment.
experiment.
REFERENCES
REFERENCES
1.
of Streak
Streak Cameras
Cameras for
for Accelarators:
Accelarators: Features,
Features, Applications
Applications and
and Results,
Results,
1. Scheidt,
Scheidt, K.,
K., Review
Review of
Proceedings
Austria, 2000,
2000, pp.
pp. 182-186.
Proceedings of
of EPAC
EPAC 2000,
2000, Vienna
Vienna Austria,
182-186.
2.
Streak Camera:
Camera: Set-up
Set-up and
and First
First Results,
Results, Proceedings
Proceedings of
of DIP
DIPAC
1999,
2. Ferianis,
Ferianis, M.,
M., The
The ELETTRA
ELETTRA Streak
AC 1999,
Chester
pp. ..
Chester UK,
UK, 1999,
1999, pp.
3.
Ring FEL
FEL PROJECT
PROJECT at
at ELETTRA,
ELETTRA,
3. Walker,
Walker, R.P.
R.P. et
et al.,
al., The
The European
European UV/VUV
UV/VUV Storage
Storage Ring
Proceedings
Austria, 2000,
2000, pp.
pp. 93-97.
93-97.
Proceedings of
of EPAC
EPAC 2000,
2000, Vienna
Vienna Austria,
4.
of an
Integrated Photo-Injector
Photo-Injector for
for
4. G.D’Auria
G.D'Auria et
et al.,
al., The
The FABRE
FABRE Project:
Project: Design
Design and
and Construction
Construction of
an Integrated
Bright
Production, Proceedings
Proceedings of
of EPAC
EPAC 2000,
2000, Vienna
Vienna Austria,
Austria, 2000,
2000, pp.
pp. 1681-1683
1681-1683
Bright Electron
Electron Beam
Beam Production,
5.
Germany, http://www.optronis.com
http://www.optronis.com
5. Optronis
Optronis (former
(former Photonetics),
Photonetics), 77694
77694 Kehl
Kehl Germany,
6.
European storage
storage ring
ring FEL
FEL at
at ELETTRA
ELETTRA down
down to
to 190
190 nm,
nm,
6. M.
M. Trovo`
Trovov et
et al.,
al., Operation
Operation of
of the
the European
Proceedings
FEL Conference,
Conference, Darmstadt,
Darmstadt, Germany,
Germany, Aug.
Aug. 2001;
2001;
Proceedings of
of 23rd
23rd International
International FEL
7.
7. M.T.Asaki
M.T.Asaki et
et al,
al, Opt.Lett.
Opt.Lett. 18
18 (1993),
(1993), 977.
977.
8.
J.Quantum Electron.
Electron. 25
25 (1989),
(1989), 817
817
8. M.J.W.Rodwell
MJ.W.Rodwell et
et al,
al, IEEE
IEEE J.Quantum
9.
Timing System
System for
for the
the ELETTRA
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