Category Archives: General Optics and Vacuum

General information on repair, maintenance, and operation of both PHI (Physical Electronics) and other manufacturers’ systems and components

10-155 Filament replacement procedure

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This blog post is an updated version of the 10-155 filament replacement procedure first published on the RBD Instruments website as a Technical Tip a number of years ago. This version has been updated with some close up pictures of the electron gun assembly shown at the bottom of this post.

Use gloves, de-magnetize all tools and clean all tools with Isopropanol.

  1. Set analyzer on stand or use manuals and support analyzer on handles, facing up.
  2. Remove outer magnetic shield (4 screws)
  3. Remove inner magnetic shield (4 screws)
  4. Carefully remove conical ceramic
  5. Loosen VM (outer cylinder) wire and lift inner cylinder off of base ceramic.
  6. Remove 3 screws inside inner cylinder.
  7. Carefully lift inner cylinder up and off of the electron gun assembly. Note: If the inner cylinder does not move freely, use a heat gun to expand the inner cylinder so that it will slide off. Do not force it!
  8. Look at the 10-155 electron gun detail PDF file to familiarize yourself with the electron gun assembly.
  9. Remove the three long screws that hold the electron gun assembly together.
  10. Remove the V1 emission screw
  11. Remove the 2 filament couplers from the filament posts. You will need a .048 4 spline wrench.
  12. Remove the 3 filament ceramics.
  13. Remove the filament assembly. Note the orientation of the emission tab and filament posts.
  14. Remove the 3 screws that hold the filament base on and remove the filament.
  15. Install the new filament in the same orientation as the old filament into the emission cap.
  16. Install the 3 screws and the filament base and tighten slightly.
  17. Position the filament so that it is centered in the hole and tighten the 3 screws. This is best done using a microscope.
  18. Install the filament assembly on top of the 3 filament ceramics and use the 3 long screws to hold the assembly together. The three long screws need to be tightened so that they all have the same distance with respect to the base.
  19. Reconnect the V1 wire
  20. Reconnect the filament couplers.
  21. Ohm out the connections to the filament and V1.
  22. Degauss the gun assembly.
  23. Install the inner cylinder over the electron gun assembly.
  24. Reinsert and tighten the three screws inside the inner cylinder.
  25. Reinstall the outer cylinder and attach the VM wire.
  26. Carefully install the conical ceramic. The resistor part should be 180 degrees out from the bottom flat ceramic. Ohm out VM to ground and make sure it has the correct resistance – typically that is about 3 Meg ohms from VM (the outer cylinder) to ground. You may need to shim the inner or outer cylinder with some silver or platinum foil, see the 10-155 shim document for more information. Both the flat and conical termination ceramics need to make a good electrical connection in order for the CMA to properly focus the electrons into the analyzer aperture.
  27. Install the inner magnetic shield
  28. Degauss the analyzer.
  29. Install the outer magnetic shield.
  30. Degauss the analyzer. Installation complete!

RBD Instruments provides the C75-010 filament and electron multiplier used in the 10-155 CMA. Contact us for more information.

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Removing oil from a turbo pump

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This post will explain the procedure for removing oil from a turbo pump if the vent valve failed and oil was sucked up into the blades.

Under normal conditions, when an oil rotary vane mechanical backed turbo pump is turned off it should be vented (preferably with dry nitrogen) to prevent the back streaming of oil or oil vapors onto the turbo pump blades. Sometimes the vent valve will fail, or some other mishap can lead to oil being sucked up the roughing line from the mechanical pump into the turbo pump. When this happens, the symptoms are that the pump will not come up to full speed – usually only 50% to 75%. Or, sometimes the pump will come up to full speed (barely) but the pumping efficiency has been greatly reduced.

For Balzers turbo pumps, the procedure is to pull the turbo pump and place it in a beaker of isopropanol up to the bottom of the inlet as shown in the picture below. For other turbo pumps the procedure is probably similar, but you should check the turbo pump manual to be sure. NOTE: This procedure is only for turbo pumps that have a magnetic bearing on the front end.

turbo pump oil

Turbo pump shown upside down in container – motor is on top.

 

 

 

 

 

 

 

 

 

If you fill the container higher than the inlet shown in the picture above then you will get isopropanol into the motor (not good).  Let the turbo sit in the isopropanol for a few minutes and then move the turbo up and down a little bit to help remove more oil from the blades. Remove the turbo and if the isopropanol is yellow from the oil, discard the isopropanol (in the appropriate container so that it can be disposed of properly) and repeat.

Once the turbo is clean, remove it and place it on some Kim wipes or paper towels and let it dry thoroughly. Note that in the original Balzers procedure that Freon TF was used. Isopropanol has similar degreasing properties and is not nearly as bad for the environment.

As long as you have the turbo pump out, you should check the condition the bottom bearing. Remove the plug and inspect the felt washer or washer assembly. Clean or replace as needed.

Once the turbo pump is dry, it should be good to go.

You can also use isopropanol to clean the rough lines that go from the mechanical pump to the turbo pump.

Electron multipliers used in PHI AES and XPS analyzers

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The Physical Electronics AES cylindrical mirror (CMA), double-pass ESCA (XPS) and single channel SCA hemisphere analyzers use variations of the Channeltron® (registered trade mark of Photonis – Burle – Galileo) type of electron multiplier. The function of the electron multiplier is to increase the number of electrons that the analyzer detects by a gain of up to 2 X 108.

All of these electron multipliers have the same connection scheme – the front of the multiplier is where the electrons enter and it is biased by the negative (NEG) lead of the electron multiplier supply. With respect to ground, the multiplier NEG is actually biased positive by 50 to 300 VDC, depending on the specific analyzer. The center connector of the electron multiplier is connected to the positive (POS) lead of the electron multiplier supply. The POS is biased with a positive voltage of up to 3000 VDC depending on the specific analyzer.  Typically though, once the multiplier voltage needs to be set above 2500 VDC in order to obtain reasonable signal to noise, it is time to replace the electron multiplier. Finally, the back end of the multiplier (furthest away from the opening at the front) is connected to the collector connector on the analyzer. For most CMAs the collector wire on the electron multiplier is connected to the PC (pulse count) connector via a 50pf capacitor, and to the COL or ANA connector via a 100k ohm resistor.electron multiplier

 

 

 

 

 

There are only two things that you need to know about these multipliers:

  1. They have a limited shelf life. If you are not planning on using an electron multiplier shortly after you buy it then you need to store it under vacuum. Storing it in a desiccator will not prevent degradation. A few weeks are OK, but after a few months the gain will start to drop off noticeably.
  2. When installing the multiplier, remember that the front with the hole in it is the NEG, the middle is the POS and the back end is the COL.

Below is a table that shows the RBD Instruments Inc. part numbers for the electron multipliers used in the various Physical Electronics analyzers that we service and provide replacement parts for.

System Type Analyzer Electron Multiplier
5100 XPS 10-360 SCA 4821GRE
540 AES 10-150, 10-155 4839RE
545 AES, 15-110 4731GRE
590 AES 25-110 4731GRE
548 ESCA 15-255G 4831GRE
560 ESCA, 570  ESCA 25-260, 25-270 4831GRE
600 AES 660 AES 25-120A 4831GRE

 

RBD Instruments Inc. also provides channel plates for the 5300 and 5400 XPS analyzers, and the Chevron plates for the 5500 to 5800 series of XPS analyzers.