...

If it reads 0.5V or -0.1V or something else odd check to make sure the Vitara is on and modelocked. You can check that the Vitara is modelocked using the laptop, if the spectrum is >25 nm fwh or the light on the control software has a green dot next to "modelocked" then the Vitara is modelocked.

Right below "Diode Power" is "Piezo Amp Mon". If Piezo Amp Mon is something like <=0.3V and red it means the piezo amplifier is off. That is the red box next to the SDG, above the regen.

4) "Meas. Freq" should be 68 MHz +/- 50 kHz

...

6) Adjust oscillator cavity motor to get to 68 MHz +/- 50 Hz. Yes 50 hertz.

Roughly the cavity Measured Frequency/Counter/Vitara Repetition Rate should change at a rate of -30.8 MHzHz/mum. So a 1 um step will change the cavity by 30 Hz, 10 um by 308 Hz and 100 um by 3080 Hz. There is pretty annoying backlash when trying to move the motor by less than 10 um, so be patient.

7) Enable the RF lock

Image Added

In this example the lock is already on. When the lock isn't on it will say "Disabled". In the previous steps (Meas - Target) should have been +/- 50 Hz, this should drop to +/- 10 Hz. No matter what the value, it should be stable at the 0.5 Hz level.

8) Enable "Automatic" PID control

Image Added

This enables the PID loop for the coarse oscillator cavity frequency control. It will say either "Automatic" or "Manual". When set to "Automatic" software will enable and disable "PID Mode" below it to keep the Piezo Amp Monitor at ~2V.

Troubleshooting

The "Target Time" doesn't work or energy jitter is higher than expected.

Increased energy jitter is a symptom of the timing system not working correctly. Please see the troubleshooting section for the timing system in S20 for how to troubleshoot.

https://confluence.slac.stanford.edu/display/FACET/Adjusting+Laser-Electron+Beam+Timing