Laser Synchronization

Find the DOOCS control screen

• First open the JDDD interface to the laser synchronization
  • Either type ./jddd into a console at the ~erpopr home directory
  • Or, press the jddd button on the main EDM window

• Eventually... a window like this will pop up

• Press the "50 MHz Synchron." button and a new window will pop up

• The default is unfortunately to point at the wrong hardware, so please select "UTCA02_DAMC1" from the upper-right dropdown menu.
• Now, there should be visible data as below

Determine current state of synchronization

Example "Turned on and working" state

• All of the upper-left buttons are green
• The timing jitter is something around 300-400 fs (not >600 fs, not <100 fs, and not jumping around by factors of 2)
• If the timing jitter looks suspicious, the laser oscillator probably needs adjustment (requires laser training)

Example "Turned off, but still working" state

• Things to check
  • Upper left buttons are grey, and the state is red and says "RF lock is open"
  • The error frequency is ~0-50 KHz, and drifting only slowly, no jumps on the 100-1000s of KHz scale
  • If there are big jumps, the laser oscillator probably needs adjustment (requires laser training)
• To begin synchronization
  1. Click "close RF lock"
  2. Click "FPGA FB loop enable"
  3. Watch as the error frequency (eventually) goes to zero, though it may briefly increase at first
  4. When it goes to zero, things should turn green, and the piezo voltage will slowly increase to the happy range (currently ~60-90V)

Example "Turned off, and laser is not working" state

• If the data looks like it is just very low amplitude noise, then the laser oscillator is probably turned off
  • The timing jitter will usually report a very good number in this state, ~10s of fs, and this is an erroneous reading
  • Turning on the oscillator requires laser training
• If the data has a large amplitude, but the "error frequency" is jumping around, then the settings of the laser oscillator probably need adjusting, and this also requires laser training.