Lab6 filament replacement procedure

Posted on by
Reply
Print Friendly, PDF & Email

This procedure shows the steps to replace the Lab6 filament in the 25-120A CMA used in the Physical Electronics 600 and 660 scanning auger systems.

First, vent the system. Here is a link to a procedure on how to do that: 600_System_Up-to-air_Procedure

  1. Remove the filament cap on the top of the analyzer. Do not unscrew the cable! Remove the 3 screws as shown in the picture below and then lift the cap up and off of the analyzer filament ceramic.
  2. Remove the twenty 5/16″ bolts that hold the filament flange to the CMA. Those may be 1/2 ” hex head or 12 point cap head bolts.
  3. Tilt the filament flange back on the hinge.
  4. Use gloves and a clean straight blade screwdriver to loosen the 4 filament screws as shown in the picture below.
  5. Remove the 4 filament screws and carefully lift up and remove the whenelt cap. The filament is mounted inside the whenelt cap.
  6. Install the new filament making sure that the filament legs line up with the filament contact tabs.
  7. Hold the filament down while you install and tighten the 4 filament screws.
  8. Install a new 8″ copper gasket and gently tilt the filament housing back onto the analyzer.
  9. Tighten the bolts (use anti seize compound if the bolts are dry) and then
  10. Pump the system down.

Although it is recommended that the system is baked out where ever it is up to air, baking may not be necessary if the system is back filled with dry nitrogen and given a few days for the vacuum to recover. If you install the new filament on a Friday and let the system pump over the weekend, then the vacuum will likely recover into the low 10-9 Torr range without a bake out.

To condition the new filament, slowly (over a period of an hour or more)  bring up the filament current to a starting value of 1.3 amps at 3 kV beam voltage and see if you can get sufficient emission current and target current. If so, then you can operate the filament with 1.3 amps of filament current. You may need to use oxygen to rejuvenate the filament if the emission does not come right up. Here is a link to a tech tip on how to thoroughly characterize the new filament if you want to really dial it in: imaging procedure for 600 and 660

RBD Instruments provides the Lab6 filaments used in the Physical Electronics 600 and 660 scanning auger analyzers.

Removing oil from a turbo pump

Posted on by
8
Print Friendly, PDF & Email

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

Posted on by
Reply
Print Friendly, PDF & Email

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.