Scope: This document is intended for use by persons already familiar with SLAC vacuum policy, the XCS control and vacuum systems, and standard CRL lens handling practices.
Setup: The following items are required before beginning the beryllium lens-change procedure.
- The beryllium lens storage boxes.
- The toolbox with the torque wrench, 5/64 hex key and non-metallic tweezers.
- The hemispherical light diffuser to capture clear, non-reflective pictures.
- The Panna-Vise lens cassette holder, UHV aluminum foil, and the localized HEPA filter.
- The HEPA hood is ON and the work surface is clean and uncluttered.
Note 1: All tools and components in contact with beryllium lenses and/or cassette must be clean and handled according to UHV practices. Double glove and change gloves immediately when contaminated.
Note 2: When accessing the beamline around the laser table near the rollup door, be extremely careful to not touch or bump the laser table. If it does get bumped or touched, notify the AM or Laser PI.
Note 3: When accessing the back side of the beamline, be careful not to bump any components around the experiment setup area. If it does get bumped or touched, notify the AM or Exp POC.
Note 4: Be aware of trip and bump hazards in the hutch.
Note 5: Do not try wipe down the lenses. Only clean if needed with the ionized air gun.
Checklist: (All steps must be done in this order, do not skip ahead, check off as you go)
At the XFLS chamber on the beamline:
- Unplug the power cable to the XFLS chamber turbo pump controller. (Note the time)
- Ensure the 4.5CF right angle isolation valve is CLOSED, fully CW.
- Isolate the XFLS chamber by closing both upstream and downstream manual gate valves.
- Close the manual valve on the turbo pump foreline vacuum hose.
In the FEH hallway outside XCS:
- Connect ionized air gun to a clean filtered compressed air supply or UHP nitrogen
- Verify LN Dewar has pressure 10psi and the valves are open to supply N2 to hutch systems.
In the XCS control room:
- Have the XCS AM, Controls PI, or Scientist, adjust the height of the lens to the lower limit.
- Open the XCS vacuum hutch 4 Screen and note the pressures at XCS-SB2-03 and 02
At the XFLS chamber on the beamline:
- Open the 5CF right-angle valve located above the XFLS chamber.
- Open the down-beam N2 valve at the turbo, ensure the PRV is venting.
- Once the turbo has been OFF for more than 30 minutes, slowly open the up-beam N2 valve.
- On the XCS vacuum screen, ensure XCS-SB2-02 and -03 pressures do not rise.
- Remove the viewport retaining screws so the doors are free to open when vented.
- The chamber is vented when the doors can open. Leave the N2 flowing.
- Via the viewport on back side, have a second person hold and support the lens cassette.
- Via the window port on the rollup door side, fully loosen the capture screw.
- Via the viewport on back side, have the second person carefully remove the lens cassette.
- Carefully take the lens cassette to the HEPA hood outside XCS in the FEH hallway.
- Loosely close both viewports to prevent atmospheric moisture from
In the FEH hallway outside XCS:
- Remove the lens hold-down springs and take a picture of current lens stacks, save as “BEFORE”.
- Loosen the screws on only one side of the side clamps for each lens stack. Ensure the opposite side screws are tight.
- Carefully remove the current lenses and place them in the appropriate storage tubes.
- One stack at a time, select the new lenses according to the recipe.
- If needed, blow off any particles from each lens and empty cassette with ionized air
- With cassette held and tilted upright, insert lenses in decreasing radii as viewed from left to right and ruffly centered in the tray with appropriate spacers on each end.
- Rotate lenses so that their radius inscription is visible and oriented the
- Snug the side clamp screws, ensure the lenses are secure.
- Ensure each lens is firmly seated and perfectly flush with each other.
- Place cassette under diffuser and take a picture clearly showing the R values, save as “AFTER”.
- Replace the hold-down springs.
- One stack at time and on only one side, loosen the side clamp screws.
- Lightly press on the springs to ensure each lens is firmly seated.
- Tighten the side clamp screws.
- Visually inspect the lenses to ensure they are fully seated and perfectly flush.
- Repeat the above hold down spring steps for each stack.
At the XFLS chamber on the beamline:
- Via the viewport on the back side, have a second person install the lens holder into the XFLS and carefully position it on the 3 kinematic mounts.
- Via the window port on the rollup door side torque down capture screw with driver in the kit.
- Close both N2 vent valves above the XFLS chamber.
- Close both XFLS viewport doors and lightly secure with retaining Do not over tighten, it may pull the hinge side open, and it will not pump down.
- Start pump down by slowly opening the turbo pump foreline vacuum
- After a few seconds, the scroll pump should quiet down, if not, firmly press on the center of both viewports to ensure they are seated and vacuum tight.
- After about 5 minutes, plug in the power cord to the turbo pump controller on the
- When XFLS gauge is < 1E-06 torr open upstream and downstream gate valves. (if a beamline gate valve trips, open it via the vacuum control screen)
- Close the 5CF angle valve on top of XFLS, fully CW.
- Leave the XFLS turbo ON with the 4.5CF right angle valve closed.
Out of the hutch:
- Ensure the beamline pressures and ion pumps are stable.
- Email the before and after lens pictures to the AM and attach to the ServiceNow ticket.
- Update Beryllium Lens Tracker on Google-Drive with the new lens
Note 6: If you haven not completed all steps then the lens change is incomplete. If the vacuum system is left in a non-standard configuration, you must inform the experimental POC and/or AM before leaving the hutch.