Heat exchanger preventive maintenance

Posted on July 29, 2013 by Randy

The 16-020 and 16-050 heat exchangers that are used with many Physical Electronics X-ray sources require a minimal amount of preventive maintenance to ensure that they provide sufficient cooling power.

Typically, the only maintenance that is performed is that the water filter and deionizer cartridge are replaced when the leakage current starts to creep up above 3-to-5mA. The deionizer cartridge helps to maintain the high resistivity of the distilled water that is circulated out to the x-ray source and back to the water tank via the radiator heat exchanger.

Note that the old 12″ Millipore housings that worked with the blue DI cartridges have a centering tab and that will push up on the new White deionizers. If you are replacing an original blue deionizer with the new white one, then you need to cut out the bottom of the original housing as otherwise the new deionizer can break and cause leakage of the mixed bed material into the water. Or, you can replace the 12″ original housing with new 12″ housing that is the correct size for the new deionizers. Contact RBD Instruments for more information about the 12″ deionizer and housing.

As shown in the pictures at the bottom of this post, one thing that is not obvious but should be checked once a year is the space between the cooling fan (in the 16-020) or fan blade (in the 16-050) and the radiator heat exchanger. Dust can collect on the fins of the heat exchanger radiator, which in turn can significantly reduce the cooling capacity of the heat exchanger.

Heat exchanger radiator cleaning procedure:

Turn off the 32-095, 32-096, or 50-096 X-ray source control. This will ensure that the pump motor or air fan does not turn on.
For the 16-050, trace the power cord back to the system and unplug it.
Take the top cover off and remove the 4 screws that hold the cooling fan to the heat exchanger radiator. Unplug the fan power connector and set the fan aside.
For the 16-020, turn the circuit breaker in the back of the unit to OFF.
Remove the side panel to get better access to the heat exchanger radiator.
Use a soft brush and a vacuum cleaner to remove any built-up dust from the heat exchanger radiator fins. If the fins have been bent from lack of care when removing the filter or deionizer cartridges, straighten the fins out with a small needle-nosed pliers or flat tweezers.
For the 16-050, reinstall the fan. If the fan does not spin freely or makes a grinding noise when operated, it should be replaced as a preventive measure. Here is a link to a replacement fan: http://www.alliedelec.com/search/productdetail.aspx?SKU=70103674

Replacement parts for the heat exchanger (such as the deionizer and filter cartridges, flow switch and pump) are available from RBD Instruments at this link: Heat exchanger deionizer parts

Flow rate adjustment procedure:

If the pump has been replaced it needs to be adjusted to the proper flow rate. For the original Procon pumps you need to remove the acorn nut to get access to the adjustment screw. The new RBD replacement pumps do not have an acorn nut. Turn the screw CW to raise the flow rate and CCW to lower the flow rate.

There are 2 possible flow rates depending on which model of X-ray source(s) you have on your system.

If you have only the standard 04-500 or 04-548 15kV dual anode X-ray source, the flow rate should be set to 1.8 GPM.

If you have just the 10-550/560/610 mono source, the flow rate should be set to .9 GPM.

If you have both the standard 04-500/548 and a 10-550/560/610 mono source then the pressure should be set to .9 GPM.

Note that the flow rate is measured with the source(s) connected. The 16-050 has a built-in flow meter which makes this adjustment easy. In the case of the 16-020 (which does not have a flow meter), you need to either

1. Insert a flow meter in series for this adjustment
or
2. Simply disconnect the outlet of the last source in the string and drain the water into a clean bucket for 1 minute and then measure the amount of water that you collect. It is important to use a clean bucket so that you can reuse the water.

If you have leakage current problems with your source, we have found that draining all the water out of the heat exchanger and X-ray sources and replacing the water with distilled water from a grocery store will restore the water to the correct resistance. The deionizer cartridge (if it is still in good condition) will then maintain the water quality. To test for leakage current, increase the voltage on the X-ray source high voltage supply to 15kV with no power to the filaments and see what the leakage current is. Typically the leakage current should be less than 2mA if the deionizer is working properly. If the leakage current starts to get up to 3-to-5 mA then it is time to replace the deionizer cartridge. For mono sources it is recommended that the deionizer cartridge be replaced whenever the anode is replaced even if the leakage current is fine.

Keeping the heat exchanger radiator clean will help the X-ray source to run cooler, and that will extend the anode lifetime.

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10-155 Filament replacement procedure

Posted on July 22, 2013 by Randy

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.

Set analyzer on stand or use manuals and support analyzer on handles, facing up.
Remove outer magnetic shield (4 screws)
Remove inner magnetic shield (4 screws)
Carefully remove conical ceramic
Loosen VM (outer cylinder) wire and lift inner cylinder off of base ceramic.
Remove 3 screws inside inner cylinder.
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!
Look at the 10-155 electron gun detail PDF file to familiarize yourself with the electron gun assembly.
Remove the three long screws that hold the electron gun assembly together.
Remove the V1 emission screw
Remove the 2 filament couplers from the filament posts. You will need a .048 4 spline wrench.
Remove the 3 filament ceramics.
Remove the filament assembly. Note the orientation of the emission tab and filament posts.
Remove the 3 screws that hold the filament base on and remove the filament.
Install the new filament in the same orientation as the old filament into the emission cap.
Install the 3 screws and the filament base and tighten slightly.
Position the filament so that it is centered in the hole and tighten the 3 screws. This is best done using a microscope.
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.
Reconnect the V1 wire
Reconnect the filament couplers.
Ohm out the connections to the filament and V1.
Degauss the gun assembly.
Install the inner cylinder over the electron gun assembly.
Reinsert and tighten the three screws inside the inner cylinder.
Reinstall the outer cylinder and attach the VM wire.
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.
Install the inner magnetic shield
Degauss the analyzer.
Install the outer magnetic shield.
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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XPS analyzer focal point

Posted on July 16, 2013 by Randy

This post will explain how to find the analyzer focal point on a PHI 5000 series XPS system and then align the system microscope to that point.

The general idea is that the lens on the SCA (spherical capacitive analyzer) has a very specific focal point where the highest counts, smallest analysis area, and best energy resolution can be obtained. By using a special slotted silver specimen that specific SCA focal point can be located and the system microscope and ion gun are then aligned to that same point. Once this procedure is performed then each time the sample is brought into focus on the microscope TV image the sample will be aligned to the analyzer focal point.

This procedure is written for the Physical Electronics 5000 series XPS instruments, but can be applied to other XPS instruments as well. In addition to this written procedure, there is also a video at this link: Finding the focal point of an XPS system.

slotted-silver-specimen

Concept: The X-ray source illuminates the slotted silver sample and generates an XPS silver spectrum. The lens on the analyzer is set and the sample is moved while looking at the silver peak during a refresh alignment acquisition. By selecting progressively smaller lens areas and moving the sample, you can determine exactly where the focal point of the SCA is for the smallest analysis area.

If your system is equipped with a standard dual anode 15kV X-ray source, use it for the alignment and select it in the software hardware properties dialog box. If your system only has a mono source then you will need to use that as the source. It is more difficult to find the focal point with the mono source as the excitation area produced on the specimen is much smaller than the standard source.

Load the slotted silver sample into the system. It should be mounted on a recessed sample mount. If you do not have a slotted sample mount then use washers to raise the slotted silver specimen up from the sample mount. The slits in the silver specimen should line up with the Y axis of the chamber (parallel with the analyzer lens).
Position the silver sample so that it is about 0.65 inches from the end of the analyzer lens. This is approximately the correct Z height and is a good starting point.
Lightly sputter clean the slotted silver sample with the largest possible raster size (10 mm X 10 mm on most systems).
Set up an alignment acquisition on the silver peak: 375eV upper limit, 365eV lower limit, a high pass energy such as 187.75, eV per step of 1 and a time per step of 30 to 50mS. The pass energy for your system may be different, just use a large one that is about 150 to 200 eV.
Select aperture 3 minimum area in the XPS hardware properties dialog box and also set the analyzer lens knob to 3. That will set the analysis area to 400 µM. Note: This part of the procedure is written for a 5500, 5600 or 5700 XPS system. If you have a 5400 then set the analyzer lens to 2 and select aperture 2 small area. For more information on the lenses for the different PHI analyzers refer to this link: phi-xps-lens-area-information
If using the standard –x-ray source, turn the screw CCW on the X Y Z aligner until the nose of the X-ray source is as close as you can get without blocking the microscope TV image. If using a mono source do not move the source. If necessary, refer to the PHI user manual or contact RBD Instruments for information on how to align the monochromator if you are not sure it is properly aligned.
Start the alignment acquisition and adjust the X and Y on the x-ray source for maximum counts on the 367.8 eV silver peak (standard dual anode source only, do not change any settings on the mono source).
Move the silver specimen until you can determine that you are in the largest slit. When the analyzer lens is looking in the slit the silver peak counts will drop. Move to where you are in the corner of the slit. Since the analysis area on the lens is set to 400 µm and the largest slit is 1000 µm, the counts will drop to essentially zero when you are in the slit, and will come up to some maximum when out of the slit.
Once you are certain that you have determined where the analysis area is on the largest slit, place an erasable mark on the TV monitor at that spot. This is your initial alignment location. You may need to adjust the microscope X and Y to get the image to match where you think you are looking at on the specimen.
Next, move over to the 800 µm slit and confirm that the analysis area is where you think it is. Adjust the spot on the TV monitor if needed.
Move into the 400 µm slit and adjust the Z height for the lowest counts when in the slit. For the 400 µm analysis area setting, the counts will drop by two thirds when in the slit – they will not go to zero. Once you have found the minimum count rate in the 400 µm slit Z height, then move over to the 400 µm hole and fine tune the X, Y and Z positions on the specimen stage for the lowest count rate when inside the hole. That should be about 30% of the maximum signal.
Using the highest zoom on the microscope, adjust the camera focus ring and X Y positions so that the 400 µm hole is centered and in focus on the TV monitor.
Now, we will repeat the procedure using the smallest aperture. In the XPS hardware properties dialog box select lens 1 minimum area. On the analyzer set the lens knob to position 1.
For the 5500, 5600 and 5700 XPS systems, repeat this procedure using the 150 µm slit and hole. For the 5400 XPS systems, repeat this procedure using the 200 µm slit and hole.
Once the focal point as been determined using the 150 µm hole, adjust the microscope focus ring (at the highest zoom), X and Y position so that the hole is centered and in focus. Only the center of the image will be in focus, the edges will be slightly blurred. TIP: Once the camera is in focus and tightened down, gently whack it a few times and see if the image comes back to the exact same place. If not, readjust and re-tighten until it stays in the same place when whacked. If it is not really tight then it may move when the system gets bumped and you will no longer be at the correct focal point. Also, by having it really tight then if you need to remove the microscope for a bake out the X and Y should stay pretty close, this will make the post bake-out alignment check easier.

The key to this alignment is to have a known good silver slotted specimen. Over time the silver coating on the specimen will wear away (from sputter cleaning) and although still coated, the silver may be very thin in some areas. That can give you a false minimum when adjusting the position of the slotted silver sample. RBD Instruments now provides these slotted silver samples for a fraction of what they cost elsewhere. At our low price, you can replace your old slotted silver sample with a known good one. You can get more information on our slotted silver sample at our website or by phoning us at 541 330 0723 X 310. For a limited time, mention this blog post and receive a 25% discount off the purchase price of any slotted silver specimen alignment standard.