Injector Drive Laser Update

1
Injector Drive Laser Update

• Facilities Advisory Committee Meeting
• October 27, 2005

• Project Status
• Drive Laser
• Change in the Gun design
• Launch System Design
• Transport tubes Installation
• Response to the April FAC recommendations
• Summary

2
Project Status

• The contract for the Drive Laser was awarded to
  Thales Lasers.
• Design review was held October 18 - 20
• Construction of the S20 drive laser facility is
  underway.
• Old building has been demolished
• Requirements to the electrical and water systems
  were defined based on the Thales laser system
  requirements
• Design of the electrical system is near
  completion.
• Beneficial occupancy is planned for February 2006
• The Laser safety system design is underway.
• The laser safety review planned at the end of
  November

3
Project Status

• The laser beam transport tubes were installed.
• Tubes passed the leak check
• Design of the optical tables completed.
  Procurement process started
• Design of the active beam steering stabilization
  system started.
• The system will be tested in Build. 407
• Parts for the test were defined and ordered
• Optical Design of the Launch System for normal
  incidence completed
• The draft of the Drive laser Commissioning
  schedule is put together
• Schedule is being synchronized with the
  commissioning schedule for the gun

4
Project Status

• RD effort is underway.
• LLNL completed modeling of the UV temporal pulse
  shaping. The UV conversion modeling code was
  completed and run on a number of cases. It was
  shown that to obtain efficient, temporally
  uniform UV pulses that we need to convert the IR
  beam to a spatial flat-top before frequency
  conversion.
• The temporal diagnostics designs were finished.
  For UV and blue measurements TG FROG was
  proposed. Orders were placed.
• ANL performed spatial shaping of broadband IR
  pulses using the Newport aspheric beam shaper.
  Optimum shaping conditions were defined. It was
  shown that extent of the bandwidth significantly
  affects the quality of shaping
• Work to arrange the collaboration with INFN and
  Elettra started

5
Thales Drive Laser System
150ps 80mW 119MHz
119MHz 400mW
1.5mx3.75m footprint (4.5x11.5)
Femtolasers Oscillator Femtosource Scientific
20s (chirped mirrors)
Stretcher
DAZZLER
20 mJ, 120 Hz
RGA Regen Amp
5W, 119MHZ
Spectra Physics MILLENIA Vs
JEDI 1 100 mJ,120 Hz
1mJ, 120Hz
Pre-Amp 4-pass Bowtie
Amplifiers are not cryo-cooled IR stability
lt1rms (short term)
80 mJ, 120 Hz
gt20mJ, 120Hz
Amplifier 2-pass Bowtie
JEDI 2 100 mJ,120 Hz
To cathode
Compressor
THG
gt25mJ, 120Hz
gt2.5mJ, 120Hz
gt40mJ, 120Hz
100 mJ, 120 Hz
6
Thales Drive Laser System

• General Set-up

7
Cathode Launch System Design

• Grazing incidence vs. normal incidence

• Grazing incidence
• Advantages
• No in-vacuum mirrorgt no wake
• Requires no space in gun-to-linac region
• Increased QE for P-polarization
• Disadvantages
• Requires grating to tilt the beam without
  introducing temporal slew and to produce round
  beam. Grating has less than 50 efficiency
• Large bandwidth with grating causes chromatic
  aberration
• Dispersed beam requires large optics (expensive!)
• Limited/complicated adjustment of beam size on
  cathode
• Low damage threshold of grating in UV

8
Cathode Launch System Design

• Grazing incidence vs. normal incidence

• Normal incidence
• Advantages
• Simple launch optics
• Launch optics allow continuous variation the beam
  size on the cathode
• Easy to preserve required temporal shape
• Disadvantages
• In-vacuum mirror causes transverse wake
• Lower QE
• Requires space in the gun-to-linac region
• In-vacuum mirror requires careful design

9
Normal vs Grazing Incidence

• Grazing incidence optics add risk to laser
  shaping
• Wakes from dual in-vacuum mirrors tolerable

We have changed the design to normal incidence
10
Preliminary Gun Design for Normal Incidence

• Layout of Laser from Injection Mirror to Cathode

gun solenoid
cathode
laser injection cross
vacuum valve
drawing compliments of R.F. Boyce T. Osier
11
Optical Design of the Transport and Launch System

• System uses the aspheric beam shaper which
  transforms Gaussian beam into flat-top
• System allows continuous adjustment of the beam
  size on the photocathode
• Spatial Shaper and Zoom system for beam diameter
  adjustment are located in the laser bay upstairs
• Shaper output is imaged with adjustable
  magnification to the input of the relay system
  that images it to the photocathode through the
  transport tube

12
Layout
Vacuum cell
Zoom
Beam shaper UV converter
Virtual Cathode
Transport tube
Table in the tunnel
Steering system
Photocathode
Active Steering Stabilization
13
Beam Profile on the CathodeZEMAX Modeling
14
Beam Profile on the CathodeZEMAX Modeling
15
Adjustment of the Beam Diameter
16
Beam Size on the vacuum mirror
10mm
10mm
10mm
Radius on the cathode 1.5mm
Radius on the cathode 0.6mm
Size of the vacuum mirror 14mm
17
Photocathode Launch System

• Optical system provides flat-top beam on the
  cathode
• System allows continuous adjustment of the beam
  radius on the photocathode from 0.6 to 1.5mm.
  Smaller (than 0.6mm) beam size can be achieved by
  using smaller aperture after the beam shaper
• Design avoids small beam size on optics, which
  could cause damage

18
Transport Tubes Installation
19
Transport Tubes Installation
20
Transport Tubes in the Vault
21
Response to the April FAC Recommendations

• Strengthening of the laser team
• The LCLS Laser Group leader Bill White started
  in May
• Long term staffing plan for the group has been
  developed
• One engineer was hired

22
Response to the April FAC Recommendations

• Coordination of the laser RD activities
• Coordination of the efforts of LLNL and ANL is
  centralized in the LCLS Laser Group.
• As design elements are completed at LLNL and ANL,
  they are incorporated into the final design which
  is then reviewed by all interested parties.
• Purchase of the second laser
• The purchase of a second laser is not in the
  current baseline, but we hope to get it in the
  future
• Laser Bay has space and power for two lasers

23
Summary

• First LCLS injector item Laser transport tubes
  were installed
• Design of the gun has been changed to normal
  incidence. It significantly simplifies the
  optical set-up and the makes beam shaping less
  problematic
• Manufacturing of the Drive Laser and RD work
  according to the schedule