Chopper wheel Rotates at 100 Hz and contains a timing photodiode to signal position on each turn. A slot cut in the disc passes a 130  s laser pulse train every turn. Stanford DG535 (Repetition Rate) This unit sets the macropulse repetition rate by inhibiting the 100 Hz timing signal from the chopper wheel Quantum Composer 8-Channel timing unit This unit is triggered by the Repetition Rate DG535, and takes a clock input from the MHz RF reference. On triggering, it waits for the next RF clock cycle, then cascades trigger signals to the Mechanical Shutter (selecting a specific macropulse), and to the Macropulse Length DG535 to set the macropulse length. Additional trigger signals are provided to the rack room and the TW laser. Mechanical Shutter The mechanical shutter selects specific macropulses from the 100 Hz macropulse train to define the 1, 2, 5, 10 or 20 Hz repetition rate Stanford DG535 (Macropulse Length) This unit provides trigger to the Pockels cell driver to define the macropulse length AΠBAΠB

Quantum Composers Timing Unit Settings ChannelDelayWidthDriving 'A'0 ms140 usMain RF trigger (goes out via #1 channel on roof feed-thru box) 'B'24.8 ms4 msMechanical chopper 'C'Not used (suspected faulty) 'D' ms15 usTrigger to DG535 'E'20 ms100 usFeed to rack room (goes out via #7 channel on roof feed-thru box) 'F' 'G'Streak Camera trigger 'H'Trigger to QC timing unit for the TW laser

DG535 Unit Settings: Macro Pulse Repetition Rate ChannelDelayDriving ‘EXT’ 'A'A = T + 0 'B'B = T Quantum Composers Master Timing Unit 'C'C = T ms delay, specify 10 Hz repetition rate 'D'D = C + 0Trigger to DG535 ‘A-B'14 usA-B Signal triggers Quantum Composers unit at macropulse repetition rate

DG535 Unit Settings: Macro Pulse Length (Pockels Cell) ChannelDelayDriving 'A'A = T Trigger onset delay 'B'B = A Macro Pulse length (example shows 10 ns) 'C'C = T + 0 'D'D = T Trigger to rack room feedthrough #3 for the BPM system T0T0 Trigger to rack room feedthrough #4