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This procedure describes how to document and turn on the laser after long down times (i.e. Winter Closure) and power outages. Note that this procedure is not sufficient for turning on the laser. You must have explicit approval to turn on the laser from the SLSO.

Power just came back on, now what?

On 3/4/24 after the power went out on 3/2/24 the S10 laser room was found in the following state:

  1. The LSS was in LASER OFF. This is the correct response. This is safe.
  2. The Vitara chiller was on and at 20C. This is safe.
  3. The Lytron chiller (beige box) for the regen was on and at 20C. This is good or bad.
  4. The Polyscience chillers (2x) for the Revolution MPA pump lasers were off. This is not desirable.
  5. The Vitara, Regen and Revolution 1 laptops were off. This is safe.
  6. The Revolution 2 laptop was on. This is also safe.
  7. The amplifier for the RF lock was on. This is not desirable.


Item #3 is good or bad because Brendan is getting mixed messages from the experts on what happens if the Lytron is on, but the facility cooling water is off.

Item #4 is undesirable because chillers that are not running tend to grow algae, which is bad for performance and requires several days of effort to clean out. Brendan needs to look into if there is an autorestart feature like on the Lytrons. It is desirable to get these chillers running as soon as possible.

Item #7 is undesirable because the RF locking system is going to be in an unknown state, and groups will be restarting devices that could send it funny signals and break the piezo that does the fast cavity length control. Shut off the piezo amp (red box near the SDG.

Starting the Laser

  1. Turn on the Revolution chiller (instructions here: S10 laser chillers)
  2. Turn on the Evolutions (2x) and Revolution (Legend)
    1. Switch on the control box
    2. Confirm the LBO temperature set point on the control computer matches the value written on the control computer
    3. On the control computer turn OFF, "ramp down the LBO" switch. 
      The "ramp down the LBO" switch is the switch labeled "SHUTDOWN:
       Set LBO Temp to 75 deg" in the factory panel of the Regen control computer software.
       When the switch is down it means it is NOT ramping down the LBO temp.
      The temperature will rise.
    4. Wait at least one hour until temperature stabilizes at the set point.
    5. Turn the key on the control unit to "on" (this allows the laser to be turned on, it does not turn on the laser)
    6. Confirm the settings on the control computer "system" panel match the settings recorded at shutdown (you'll need to access the facet elog)
      1. Confirm: Q-Switch Mode, Q-Switch Pulse Width, Current Setting
      2. If you need to change Q-switch Mode it will pop up a warning about making sure you don't try to run the laser out of specifications. Acknowledge this warning.
    7. Turn on the pump lasers using the computer control panel (green RUN button). You will need to hold down the button until the control unit begins to beep.
      1. If there's a Q-switch VSWR error, cycle keys
  3. Turn on the Vitara
    1. Turn the key on the control unit to "on".
    2. The slit and prism values should match the preset noted next to the touch pad on the Vitara computer. If they do not match, call the SLSO.
    3. Turn on the pump laser using the computer control panel. Turn on "Remote", then turn on "Diode".
      1. Confirm control panel diode pump level is +/- 0.1W compared to shutdown value in ELOG
    4. Confirm modelocking at 760 nm via computer control panel and using spectrometer (spectrum will be > 20 nm FWHM)
      1. If laser does not modelock, call the SLSO
    5. Allow laser to run at 760 nm while modelocked
      1. Wait at least one hour until the laser stabilizes
      2. If laser does not modelock, call the SLSO
    6. Enable the RF lock
      1. Power on the piezo amp (make sure the RF lock is DISABLED and stays disabled)
      2. Enable the RF lock
  4. Run through the shutdown images in the logbook and check shutdown values to current settings.
    1. "Document the Laser State" has a list of things to check: S10 Laser Shutdown Procedure
    2. Pay close attention to the SDG. A power dip somehow reset a heap of settings on the SDG.
    3. SDG settings can also be found in Andy's service document: https://drive.google.com/drive/folders/1I846GetQfdcpEfJKtCN45D34aNHP6DYV?usp=share_link
    4. Check and adjust (if necessary) the motor positions for all six motion controllers in S10: MOC-LR10-LS03, MOC-LR10-LS04, MOC-LR10-LS05, MOC-LR10-LS06, MOC-IN10-LS01, MOC-IN10-LS02
    5. Check the SLAC timing system
  5. Measure the laser energy and update S10 energy document: https://docs.google.com/spreadsheets/d/1OkifFC2Dw0UpbIavq1T5kBR-vykIuglx/edit#gid=698192852


Possible Issues

  1. Vitara doesn't mode lock
    1. The vitara does not come back perfectly on wavelength and bandwidth every time. However, it should modelock. If it does not modelock at 800 nm, or doesn't stay modelocked when moving to 760 nm: call the SLSO
  2. Build up in regen doesn't match shutdown image
    1. Either Vitara pointing has changed (unlikely)
    2. Vitara power output is low (compare Vitara power now to shutdown)
    3. Regen triggers are bad. Check the SLAC triggers
  3. MPA output is low
    1. Pointing through the MPA has shifted (this can happen if temp/humidity control is lost due to a power outage)
    2. Check regen and MPA images against shutdown images, has the pointing shifted?




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