Laser Replacement Procedure – with Purge

Tools and Equipment Required

  • Anti-static wrist strap
  • Purge gas, regulator, flow controller, fittings (optional)
  • Quick-connect fitting for AERI purge port (optional)
  • Phillips screw driver
  • Hex balldriver set
  • Pliers (preferably with tips bent 90 deg) for tensioning the laser brackets (optional)
  • Small bags/cups for loose screws
  • Small zip ties
  • Tape / stand for stabilizing laser power supply
  • Lens tissue + 95% ethanol, for laser cleaning, if necessary


  1. If it is available, set up a purge gas source near the AERI.  This can be dry air, nitrogen, or equivalent.  Otherwise be sure the area is clear of debris, and that the instrument is not left open for extended periods of time.  (If not using purge, skip steps 2, 3, 5, 24.)
  2. Locate the AERI quick-release purge fitting, inside the AERI accessories case (black pelican case) (see Fig. 2).
  3. Connect the quick-release fitting to the purge gas source.  The quick release fitting has a Swagelok thread.  The flow should be regulated to about 10 scfh.
  4. Turn off the AERI instrument using the power bar in the back-end, and unplug the main AC power cable from the instrument.
  5. Connect the quick-release fitting to the AERI purge port.  Make sure the fitting ‘clicks’ into place.  Set the flow to about 10 scfh (see Fig. 5).
  6. Remove the laser access panel in the middle of the back of the instrument – it’s held on by 8 Philips head screws.  (see Fig. 5)
  7. Always wear an anti- static wrist strap when handling components inside the AERI.
  8. The laser inside the access panel may still have charge on it, and needs to be discharged.  Using a screw driver with an isolated handle, discharge the laser tube by making short-circuit between the laser output terminal and the metal case of the instrument.  Usually a small spark will be visible at the laser output terminal (see Figs. 7a, 7b).
  9. Cut the zip-tie around the laser power supply input power cord, and disconnect the connector (see Fig. 7a).
  10. Unscrew the laser power supply: it’s secured with two Philips head screws located above the power supply. (see Fig. 7a)
  11. Remove the laser power supply, being careful not to strain the wires going to the laser.  The power supply will need to be secured near the instrument.  One option is to hold the power supply against the AERI case using tape (see Fig. 10).
  12. Unscrew the two screws that hold the metal straps that keep the laser tube in place.  Gently remove the laser tube, along with the power supply.
  13. Note the serial numbers for the old laser and power supply (if also being replaced).
  14. Inspect the new laser.  The lasing surface should be clean – clean with 95% ethanol if necessary.
  15. Note the serial numbers for the new laser and power supply (if also being replaced).
  16. If needed, remove the metal plate from old laser power supply and attach it to the new one (3 hex screws)
  17. Install the new laser tube.  It’s best to first secure the power supply, as before (e.g. with tape against the case).  Make sure the guide pin on the ring on the right side slides into position in the alignment hole in the bracket.
  18. Secure the two metal straps around the tube and attach with the two screws.  Note that the bracket holding the ballast resistor will need to be attached with the right screw.  Note that the resistor should be oriented with the red wire going to laser coming out from the top (see Fig. 14a).  Snug the straps against the laser tube, either by gently pushing down from above, or by gripping the bottom with tweezers/pliers and pulling down gently (see Fig. 14b).  Tighten the two screws holding the straps.
  19. Ensure that the laser tube is secure.  Gently grip the glass laser tube, and test if it can be moved with respect to its bracket.  If the laser tube can be moved, then the strap holding it down needs to be re-tightened: loosen the hex-head screws and retighten the straps, as described in step 14 above.
  20. Take a photo of the configuration.
  21. Mount the laser power supply.  The two Philips head screws have limited access, so it is best to use a captive screwdriver, or simply use electrical tape to tape the head of the Philips screw and the shaft of the screwdriver, then remove once the screw has caught.  Be careful not to catch and squeeze the red and black laser wires behind the power supply.  It is best to get both screws of the laser power supply loosely into their thread, then route the laser wires so that they are loose, then fully tighten the laser power supply screws.  Take a photo of the configuration.
  22. Reconnect the laser power supply input power cord, and use a cable-tie to secure the loose wires.  Take a photo of the configuration.
  23. Re-install the laser access panel.
  24. Turn off the purge gas and remove the quick-release purge fitting.  Stow the quick-release purge fitting.
  25. Reconnect the instrument to AC power, and turn on using the power bar in the back-end.
  26. Verify the laser alignment:  Observe the startup sequence of LEDs (visible as a reflection on the back wall on the right side of the instrument) (see Fig. 22).  After the startup sequence (~1 minute), the top green light should be solid, and the bottom orange light should be blinking rapidly.
    1. If the orange is blinking then the laser is operating correctly and the replacement is complete.
    2. If the orange light is not blinking, then the laser detector may not aligned correctly.  Consult the mentor team on testing and aligning the laser detector.
      1. Note the amplitude of the laser on the laser detector:  Terminate AERI data collection by typing <CTRL> + c in the cygwin/terminal window; close all other windows.  Open a browser and type, to connect to the instrument.  Click “Service”.  Enter the password “@Bb”.  Click “Closed-loop Mode ON”.  Note the values of F, D and Phase.  If F>=5%, D>=5% and Phase >=45%, then the laser is installed correctly.
      2. Click “Closed-loop Mode OFF”. Close the browser.  Click “ingest.bat” on the desktop to resume data collection.


Figure 2.


Figure 5.


Figure 7a.


Figure 7b.


Figure 10.


Figure 14a.


Figure 14b.


Figure 22.