output to accelerator area drive laser: MHz, sync’d to master RF = 1064 nm ~7 ps pulses ~10 watts average (~120 nJ/pulse) chopper wheel: ~100Hz, ~120  s opening solenoid shutter: 1, 2, 5, 10, 20 Hz Pockels cell: 5ns – 120  s opening frequency doubler: output = 532 nm ~ 40 nJ/pulse pulse train monitor photodiode variable attenuator pulse stacker: output ~28 ps pulses variable beam size optics shutter for release to accelerator Photo-injector laser: functional overview

drive laser: MHz, sync’d to master RF = 1064 nm ~7 ps pulses ~10 watts average (~120 nJ/pulse) chopper wheel: ~100Hz, ~120  s opening solenoid shutter: 1, 2, 5, 10, 20 Hz Pockels cell: 5ns – 120  s opening frequency doubler: output = 532 nm ~ 40 nJ/pulse pulse stacker: output ~28 ps pulses variable beam size optics output to accelerator area pulse train monitor photodiode variable attenuator shutter for release to accelerator monitored/changed in normal operation changed occasionally

Laser room light box virtual cathode laser source exit from laser room cathode [mm] beam on virtual cathode photo-injector lasers transport mirrors on translation stages cathode

photo-injector lasers transport Movable mirrors for changing beam position on cathode “VTM” vertical “HTM” horizontal

CW “unchopped”pulse train chopped, 532nm, train (macrobunch, before attentuator) master 81.25MHz delivered to laser room

Laser timing signals signal used for RF triggering (also with ~23 ms advance) general trigger signal (for BPM’s, cameras, etc) max pretrigger ~270  s Chopper detect chopper open shutter open pockels cell open/close

drive laser shutter open/closed (laser operators key required) shutter to accelerator open/closed (general control panel operation) laser macro-bunch length & external trigger signals Laser system controls...

Chan A: Pockels cell open (~270  s) Chan B: macro-pulse width (~5ns- 100  s) Chans C, D used by BPMs control can be released for manual “local” operation in laser room “internal” triggering used for equip testing when laser not operational

opens laser position control.. left-right defined from electron frame NOT looking back at cathode KNOWN “bug”: if power lost to motor control, the control-system zero position will change. (restarts at zero on control system, but motors actually at position as before power cycle)

ERLPcon2 desktop “Pylon viewer” Viewing the (real) cathode New (more reliable) camera, BUT, not yet tested with laser beam on cathode.... Sensitivity to be determined on startup camera synchronised to laser macro bunch train

Viewing the (real) cathode... as viewed with old camera.... new colour camera to be used this commissioning period Looking at scattered light from cathode, though side port on light-box not enough light with short macro bunch trains observed profile dependent on scattering flatness of cathode position is reliable (not dependent on survey, etc)

Viewing the virtual cathode “virtual cathode” icon on ERLPcon1 desktop no camera control screen shots for now....(will add later) from underneath light-box cross-hair for alignment reference variable attenuator (for camera sensitivity/protection) sensitive enough for monitoring laser with “few-bunch” train lengths beam position accuracy depenent on survey (can cross-check with real cathode at long bunch trains) camera synchronised to laser macro bunch train

Laser-RF synchronisation spacing set by round trip