Removing oil from a turbo pump

Posted on June 24, 2013 by Randy

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 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.

: oil contaminated turbo pump

: place turbo pump into container

: pour isopropanol into container

: oil contaminated isopropanol

Electron multipliers used in PHI AES and XPS analyzers

Posted on May 17, 2013 by Randy

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.

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

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.
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.

X-ray Photoelectron Spectroscopy Tutorial

Posted on May 8, 2013 by Randy

X-ray photoelectron spectroscopy (also known as XPS and originally as ESCA), has become one of the most prevalent and useful techniques for surface analysis since the introduction of commercially available instrumentation beginning in the 1960s. XPS is a UHV surface analysis technique that provides quantifiable elemental and chemical state information from the top 20 to 100 angstroms of surfaces.

Today’s modern XPS systems use monochromatic aluminum X-rays and include the ability to produce real time XPS elemental images with spatial resolution in the range of a few microns. If you need an XPS system for your research or production testing and can’t afford the $500K to over $1M for a new XPS system, RBD Instruments is your headquarters for refurbished Physical Electronics XPS systems and components. Contact us for more information.

Below I have listed a number of links to X-ray photoelectron spectroscopy tutorials. They are in no particular order. Collectively, these tutorials provide an in-depth overview of the history, theory and applications for X-ray photoelectron spectroscopy.

Here is new link to an XPS data knowledge base (and a wealth of information on XPS) from Vincent Crist at The XPS library – https://xpslibrary.com/free-library-membership/ Please support The XPS Library with your donation!

http://www.physics.ucdavis.edu/fadleygroup/BasicConceptsofXPS.pdf

http://mmrc.caltech.edu/SS_XPS/XPS_PPT/XPS_Slides.pdf

http://www.jhu.edu/~chem/fairbr/surfacelab/xps.html