1. Injector Drive Laser Technical Status
Sasha Gilevich
October 24, 2006
Outline
Injector Drive Laser
Temporal Shaping
Spatial Shaping
Photocathode Launch System

2. Laser Beam Specifications on the Cathode
Parameter
Nominal Spec
Tolerance
Central Wavelength
255nm
+/- 3nm
Pulse Energy
>0.4mJ
Continuously adjustable
<2% RMS variation (shot-to-shot)
Spatial Fluence Profile
Uniform (adjustable)
<20% (peak-to-peak)
Spot Radius
Adjustable from 0.6mm to 1.5mm
<4% (Shot-to-shot)
Centroid Position Stability
<10% radius (RMS)
Repetition Rate
120Hz, 60Hz, 30Hz, 10Hz, 1Hz
Temporal Power Profile
Slope adjustable from -10% to +20%
<8% peak-to-peak on the plateau
Profile FWHM
10 psec
(adjustable to from 5 to 20 psec)
< 2 % RMS
(over multiple shots)
Profile Rise/Fall time
1.0ps (10% to 90%)
Timing Jitter
< 0.25 psec (shot-to-shot)
with respect to the external RF source

3. Thales Laser System Specifications
Parameter
Nominal spec
Tolerance
Wavelength
255nm nom.
+/- 3nm
Pulse energy
> 2.5 mJ
< 2 % rms variation
Spatial fluence profile
Gaussian, M2<2
<10% peak-to-peak variation within the profile)
Pointing Stability
Less than 25 microradian
Rep rate
120Hz, 60Hz, 30Hz, 10Hz, 1Hz
Temporal power profile
Uniform
<8% peak-to-peak on the plateau
profile FWHM
10 psec adjustable from 5 to 20 psec
< 2 % (RMS over multiple shots)
Rise/fall time
1.0 psec (10% - 90%)
Timing jitter
< 0.25 psec (shot-to-shot)
MTBF
>5000 hours
With periodic maintenance

4. Thales Laser system Stretcher UV Conversion Dazzler Preamplifier
Compressor
Oscillator
Final Amplifier
Regen

5. Thales Laser System Performance
Pulse Energy
After compressor – 35mJ
UV output-2.8mJ
Energy jitter in UV – 1.1% (rms)
Spatial shape in IR – Gaussian, M2=1.5
Pointing Stability – 5 μrad
Timing Jitter – 0.21psec

6. Energy Jitter Measurements

7. Pointing Stability Measurements
Measured at the focal plane of the 0.8m focal length lens

8. Temporal Shaping Dazzler 45mm long 2 passes in the Dazzler
Beam size, collimation and alignment of the Dazzler are critical
Resolution of the Dazzler should be 0.3nm
0.3nm hole at 760nm

9. Using Dazzler to Shape the Spectrum
Spectrum after the compressor
Without Dazzler shaping
Dazzler spectrum has a hole
After the Dazzler
After the Compressor

10. Temporal Shaping and UV Conversion
UV Conversion process affects the temporal shape – Optimum crystal length is essential
IR Pulse
UV Pulse – SHG crystal 1mm long
UV Pulse – SHG crystal 0.5mm long

11. Temporal Pulse Shape
Streak Camera
Cross correlator

12. Temporal Pulse Shaping
The achieved temporal pulse shape meets physics requirements for the injector commissioning
Plan to improve the temporal shape
Replace the Lyot filter in the regen amplifier by the edge mirrors – this will reduce oscillations
Continue working on the Dazzler settings and the optimum UV conversion crystals lengths
Thales engineers are coming back in December-January to continue working on shaping
Plan B – to use stacking of Gaussian pulses
Design and parts for pulse stacking are in place

13. Spatial Beam Shaping – Newport Shaper
Converts Gaussian beam input to flat top output
Transmission >97%
High profile uniformity - 78% of input power is directed into the flat top with 15% RMS power variation
Collimated output beam allows use of conventional optics after beam shaping
Provides performance over large wavelength ranges
GBS-UV H

14. Spatial Shaping – work in progress
Spatial Shaper Output
Laser Output

15. Optical Design of the Transport and Launch System
System uses the aspheric beam shaper which transforms Gaussian beam into flat-top
Shaper output is relay-imaged with adjustable magnification to the photocathode through the transport tube
System allows continuous adjustment of the beam size on the photocathode
System includes active beam pointing stabilization
“Virtual Photocathode” is used for diagnostics

16. Transport System in the Laser Bay
Remotely Controlled Mirror
Lens
Shaper
Beam Size Adjustment
Shaper Input Adjustment
To Transport tube
Laser Output

17. Optical System next to the Photocathode
From Transport tube
Steering Stabilization Camera
Remotely Controlled Mirror
Lens
Virtual Cathode camera
Steering Stabilization Camera
Lead Block
Lens
Remotely Controlled Mirrors
Powermeter
Lead Blocks
Photocathode
In vacuum mirror

18. Photocathode Launch System
Virtual Cathode camera
To the cathode
Photocathode launch system has been assembled in the laser bay
The system will be tested before it goes into the vault

19. Drive Laser system was installed
Summary
Drive Laser system was installed
The system meets all specs except temporal and spatial shape
Thales engineers will come back to work on the temporal and spatial shape
All parts for the transport and photocathode launch system are in place
The system was assembled
Tests are underway

20. End of the Presentation

21. Back Up

22. Thales Laser – Factory Acceptance Test
Pump lasers
Jedi 1 running at 90mJ, Jedi 2 – 70mJ

23. Thales Laser – Factory Acceptance Test
Pump lasers – Shot-to-shot stability - 0.7%

24. Thales Laser – Factory Acceptance Test
Pump lasers – beam profile

25. Active Steering Stabilization
Two Steering Stabilization loops
Laser Bay
Steering Stabilization system was tested with He-Ne laser
Transport Tube
Table in the tunnel
Camera
From Virtual Cathode
Image plane F
Camera
To Photocathode

26. In Vacuum Mirror Metal mirror has laser optical quality
Mirror material: Ni Plate BeCu (Hardric Labs)
Flatness - λ/10
Scratch-Dig
Coating: 2 Options
Enhanced Al (R>95%)
High energy UV dielectric coating (ARO), R>99%