Transcript Drive Laser Commissioning Results and Plans

Drive Laser Commissioning results
and plans
Philippe Hering
October 30, 2007
Outline
New oscillator
Improvements of laser performances
New transport beam line
Beam stabilization and diagnostics for the transport beam line
More remote control
October 30, 2007
Drive Laser Commissioning Results and Plans
1
Philippe Hering
[email protected]
Great Up Time!
20 weeks of commissioning
Three 8 hour downs – Hot swappable parts
available now
One 3 hour down during a night shift
2 hours per week for locking problems
98% up time !
October 30, 2007
Drive Laser Commissioning Results and Plans
2
Philippe Hering
[email protected]
New master oscillator from Femtolasers
• Narrower bandwidth requested to have higher spectral intensity and
get a better seeding in the Regen (before FWHM = 30 nm).
• Crystal is sealed in airtight cavity to avoid contamination (no more
weekly cleaning, endurance test made during > 200 hours).
• Remote starting capability.
• One pump mirror is remote controlled with picomotors.
October 30, 2007
Drive Laser Commissioning Results and Plans
3
Philippe Hering
[email protected]
New Femtolock driver for the oscillator
• Oscillator is first locked to 119 MHz and then to 476 MHz : no more
476 MHz bucket ambiguity.
• Lock button added to be lock always on the same bucket.
• RF- locking loop and lock button can be run remotely.
October 30, 2007
Drive Laser Commissioning Results and Plans
4
Philippe Hering
[email protected]
Reconfiguration of the stretcher
• Regarding the central wavelength of the Regen seeding beam.
• Grating and concave/convex mirrors reorientation.
12000
Stretcher output spectrum
Dazzler output spectrum
Spectrum intensity (a.u.)
10000
8000
6000
Central wavelength of the oscillator
4000
Central wavelength of the Regen seeding
2000
Bandwidth of the stretcher
0
740
745
750
755
760
765
770
775
780
Wavelength (nm)
October 30, 2007
Drive Laser Commissioning Results and Plans
5
Philippe Hering
[email protected]
New set-up of the Dazzler
• Single pass configuration (instead of two
before).
DAZZLER
• More accurate spectral shaping with the
Dazzler.
• After further studies from the vendor
(Fastlite), quadratic phase correction
cannot be added in a big amount and so 4th
and 6th orders are not possible.
 Only spectrum filtering is accurate for
our shaping purposes (FWHM < 4 nm).
October 30, 2007
Drive Laser Commissioning Results and Plans
6
Philippe Hering
[email protected]
• Pulse shaping with the Dazzler is made with the spectral filtering parameters : we fix the
central wavelength of the Regen seeding beam and shape the spectrum with a 3rd order
super-Gaussian. A “hole” in the spectrum can also be done to compensate spectrum
distortions in the amplifiers.
1.1
1
Super Gaussian Order 3
0.9
Specrtum Intensity (a.u.)
0.8
0.7
0.6
FWHM = 2 nm
0.5
0.4
0.3
0.2
0.1
0
754
755
756
757
758
759
Wavelength (nm )
October 30, 2007
Drive Laser Commissioning Results and Plans
7
Philippe Hering
[email protected]
760
761
762
Change in the REGEN cavity amplifier
Regen output spectrum with the new Dazzler set-up and edge mirror
8000
Dazzler output (Regen seeding)
Spectrum intensity (a.u)
7000
6000
5000
4000
3000
2000
1000
0
754
755
756
757
758
759
760
Wavelength (nm)
• The Lyot filter (wavelength tuning element)
has been removed.
• One of the end cavity mirror has been
changed with an “edge” mirror : low pass filter
coating cutting at ~750 nm.
• Remark : remaining modulations are coming
from the fibered input of the spectrometer.
October 30, 2007
Drive Laser Commissioning Results and Plans
8
Philippe Hering
[email protected]
761
762
Improvement of the temporal shape of the
pulse
• Ps pulse duration is obtained by adding quadratic phase with the
compressor (distance between gratings shorter than full compression).
• Super-Gaussian temporal profile is obtained with the Dazzler but only
with spectrum shaping (no more with phase orders).
•You can also dig a “hole” in the spectrum to compensate the spectrum
red shift in the multipass amplifiers after the Regen.
12000
11000
11000
Compressor output spectrum
with Dazzler hole OFF
10000
9000
9000
Spectrum intensity (a.u.)
Spectrum Intensity (a.u.)
10000
8000
7000
6000
5000
FWHM = 2 nm
4000
3000
8000
7000
6000
5000
3000
2000
1000
1000
755
756
757
758
759
760
761
0
754
762
Drive Laser Commissioning Results and Plans
755
756
757
758
759
Wavelength (nm)
Wavelength (nm)
October 30, 2007
FWHM = 2 nm
4000
2000
0
754
Compressor ouptut spectrum
with Dazzler hole ON
9
Philippe Hering
[email protected]
760
761
762
• We measure the temporal beam profile directly in the UV with our scanning crosscorrelator.
 A flat top spectrum in the IR doesn’t give a flat top temporal profile in the UV
because of saturation in the Tripler : asymmetric IR leads to flat top in the UV.
12000
11000
Compressor output spectrum
with Dazzler hole OFF
Spectrum Intensity (a.u.)
10000
9000
8000
7000
FWHM = 2 nm
6000
5000
4000
3000
2000
1000
0
754
755
756
757
758
759
760
761
762
Wavelength (nm)
BEFORE
Typical temporal shape during last commissioning
October 30, 2007
Drive Laser Commissioning Results and Plans
10
Philippe Hering
[email protected]
Improvement on the IR input spectrum shape for the Tripler has
increased UV yield :
 UV yield went up from <10% to >15% .
 To get the same UV energy in front of the clipping iris, we decided
to decrease the IR input ( ~18 mJ instead of ~28 mJ ): main IR
amplifier is running with less pumping energy. Save JEDI 2 diodes
(half of nominal current value) !!
 Safer operation of the Tripler at short pulse duration (<6 ps).
October 30, 2007
Drive Laser Commissioning Results and Plans
11
Philippe Hering
[email protected]
Beam quality
Typical beam image on the clipping iris
during last commissioning
Changes to be made :
• Work done on the pulse shaping has
improved a little the homogeneity of the
beam (to be investigated) ?
• Replacement of 6 mm thick fused-silica
dichroics in UV tripler by 2 mm thick MgF2
(to lower B-integral)
• Replacement of all Substrate transmissive
fused-silica optics by CaF2 (to lower
fluorescence and absorption).
Beam image on the clipping iris before transport after
working on the pulse shaping (Preliminary results !)
October 30, 2007
Drive Laser Commissioning Results and Plans
12
Philippe Hering
[email protected]
Beam stability on the cathode
Beam size on the cathode (on VCC camera)
Beam position on the cathode (on VCC camera)
Laser Beam on VCC camera
Jitter in x-axis = 35.4 m rms
Jiiter in y-axis = 39.2 m rms
Jitter in x-axis = 14.4 m rms
Jiiter in y-axis = 18.9 m rms
 Instabilities in the electron beam !
October 30, 2007
Drive Laser Commissioning Results and Plans
13
Philippe Hering
[email protected]
We move the BCS shutter onto the laser table : before it was attached to the side of the
table after the mirror folding the beam down through the transport tube.
We extended both ends of the vacuum transport tube : upstairs up to the laser table level
and downstairs down to the laser box cover.
Beam position on the cathode (on VCC camera)
Beam size on the cathode (on VCC camera)
Jitter in x-axis = 11 m rms
Jiiter in y-axis = 11 m rms
Jitter in x-axis = 3.6 m rms
Jiiter in y-axis = 4.7 m rms
 Improvement by a factor of 3 !
October 30, 2007
Drive Laser Commissioning Results and Plans
14
Philippe Hering
[email protected]
Shot-to-shot energy stability
Laser energy stability vs. time < 1.5% rms
1.1% charge stability at 1nC
October 30, 2007
Drive Laser Commissioning Results and Plans
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Philippe Hering
[email protected]
Original Transport Layout for 2007
Injector Commissioning
Zoom
Telescope
Vacuum
cell
Zoom
L4
Beam
shaper
F2=120
F3=-150
F4=F5=5000
F6=1500
L3
L1
Table in
the
tunnel
F1=200
L2
Virtual Powermeter
Cathode
Steering
system
Transport
tube
Camera
L5
Polarizer
Waveplate
Photocathode
Shutter
Active
Steering
Stabilization
L6
October 30, 2007
Drive Laser Commissioning Results and Plans
16
Philippe Hering
[email protected]
Changes in the Upstairs Layout
No Gaussian Beam Shaper
Adjustment of beam size on the cathode is accomplished
by changing the magnification of the input telescope and
the size of the imaged iris
First relay stage (L1 – L3) is removed.
Input telescope has 3X higher magnification
No vacuum cell is needed
Iris is the object plane of the L4 and L5 imaging system
Image of the L4-L5 system is virtual
L6 relay image the output of the L4 – L5 system to the
cathode 4:1. L6 has remote Z-adjustment
October 30, 2007
Drive Laser Commissioning Results and Plans
17
Philippe Hering
[email protected]
New Transport Layout
October 30, 2007
Drive Laser Commissioning Results and Plans
18
Philippe Hering
[email protected]
The iris diameter is adjusted by a
remotely controlled aperture wheel
•Wheel houses 12 apertures
•Beam sizes on cathode
• 0.25 - 2.0 mm
• Smaller diameters can be done
•Design allows for rapid change
for additional apertures
•Wheel is controlled via Epics
October 30, 2007
Drive Laser Commissioning Results and Plans
19
Philippe Hering
[email protected]
Option of Focusing the Beam on the Cathode
Removable Lens LCleaning F=3m
L4
Z-adjustment of L6 changes the
beam size on the cathode
Table in
the
tunnel
F4=F5=5000
F6=1500
Steering
system
Transport
tube
L5
Photocathode
Shutter
L6
October 30, 2007
Drive Laser Commissioning Results and Plans
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LCleaning
Philippe Hering
[email protected]
Active
Steering
Stabilization
No Major Changes to Vault Transport
C2
M4
L5
Cathode Cleaning Lens
M5
L6
C1
VC
UV plates for Cameras
M3
M2
Power Meter
M1
Cathode
October 30, 2007
Drive Laser Commissioning Results and Plans
21
Philippe Hering
[email protected]
Work in progress before next
commissioning
Vacuum Transport Cleaning
Layout and Alignment of New Optical Transport
Install New Controls Hardware
Power Meters
Cameras and UV plates
Iris Wheel
Beam quality still needs to be improved
Software Installation and Certification of Controls
Certification of Laser Operation
Training of Operators before LCLS restart
October 30, 2007
Drive Laser Commissioning Results and Plans
22
Philippe Hering
[email protected]