Category Archives: General Optics and Vacuum

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

How to test an ion gauge filament

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This post will explain how to test and replace the nude ion gauge filament assembly on a Physical Electronic (PHI) X-ray photoelectron, Auger electron or SIMS system. Look at the pictures at the bottom of the post before you read the procedures.

Background – On most PHI surface analysis systems the ion gauge filament is located either above the table tops in back of the vacuum chamber, or just under the tabletops.  The newer (as in less than 30 years old) systems have a cover that protects the user from the exposed electrical connections to the ion gauge pins. On the oldest PHI systems the ion gauge pins are exposed, but located under the table tops and difficult to access (and so relatively safe).

Here are links to some videos that explain how an  ion gauge works –

https://www.youtube.com/watch?v=IKKuWeEShM4

https://www.youtube.com/watch?v=6zv_Y0_vwsg

How to measure the resistance on the ion gauge:

  1. Turn off the DGCIII (or other brand of) ion gauge control.  This is not only the first step; it is the most important step! Ion gauge controls such as the DGCIII used on older PHI systems have about 200 volts of DC on the grid. If you do not turn off the DGCIII (or other) ion gauge control before removing the wires to the ion gauge you will likely receive a potentially lethal electrical shock. If you are not familiar with working safely with electricity then refer this procedure to qualified personnel.  Or, turn off the DGCIII and also and also unplug the 120 VAC power cord on the back of the DGCIII and then there is no danger of electrical shock.
  2. Loosen the set screws on the shield retaining collar. Do not loosen or remove the bolts that connect the ion gauge to the system! See the pictures at the bottom of this post for clarification.
  3. Loosen the strain relief screws and slide the shield out and away from the ion gauge, being careful to support the wires.
  4. Using an 048-4 spline wrench, loosen the ion gauge coupler set screws by turning the set screws closest to the flange CCW 1 to 2 turns and then gently pulling the coupler and wires off of the ion gauge pins. TIP: As you remove the couplers turn the set screws CW 1 turn so that they do not fall out of the couplers. RBD provides the 048-4 spline wrench and the setscrews.
  5. Use an ohmmeter and measure the resistance between the center filament pin (common) to the outside two filament pins. See the picture below. The pins resemble a smiley face and the filaments are the smile. The grid is the eyes (some ion gauges have 2 grid pins, some only one), and the collector is the center pin (nose). The filament resistances should be 1 ohm or less when measured from the center filament post to the outside two filament post. If a filament is burnt out (open) then the resistance will be infinite or some high value if there is a tungsten coating on the filament base.
  6. If one filament is burnt out but the other one is good, then you can switch filaments.  If you have 3 wires connected to the filaments then swap the outside two filament connectors. If you have just two filament wires, then move the outside filament wire to the other side.
  7. If both filaments are open, then the filaments need to be replaced. See the replacement procedure in the following section.

ion-gauge-wire-connection-types

ion-gauge-wire-connectionsHow to replace the ion gauge filaments:

  1. Vent the chamber.
  2. If not already done, remove the connectors from the ion gauge as per the previous procedure.
  3. Remove the bolts from the ion gauge flange.
  4. Remove the shield retaining collar.
  5. Carefully remove the ion gauge.
  6. Loosen the top set screws on the 3 filament base connectors. These are typically .050 hex screws.
  7. Remove the old filament assembly.
  8. Install the new filament assembly and tighten the set screws. Make sure that the filaments are parallel with the grid.
  9. Use a new copper gasket and place the ion gauge up to the flange. Make sure that the filaments are facing down. They will not line up perfectly parallel, so just choose the best position where the bolt holes line up. By facing the filaments down you will prevent any debris from falling onto the grid which may short out and damage the ion gauge control.
  10. Place the shield retaining ring up next to the ion gauge flange and rotate it so that the set screws in the shield retaining ring are accessible.
  11. Insert the bolts and tighten the flange.
  12. Reattach the ion gauge couplers. Make sure that the pins are bent slightly in towards the center collector wire so that none of the pins will short to the shield when it is installed.
  13. Carefully slide the shield over the wires and press the shield firmly into the shield retaining collar.
  14. Tighten the shield retaining set screws.
  15. Slightly tighten the strain relief screws.

That’s it!  Pump the system down and the ion gauge is ready to turn on once you get into the 10-4 Torr or better vacuum.

RBD Instruments provides replacement filament assemblies, complete ion gauge assemblies and the required spline and Allen wrenches. Contact us for more information.

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Neutralizer filament replacement procedure

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This post will detail the neutralizer filament replacement procedure for the Physical Electronics (PHI) 04-085 and 04-090 neutralizers that are commonly found on many PHI X-ray photoelectron spectrometers and Static SIMS systems.

Before you can replace the filament you need a new filament. We also recommend having the deflection ceramic on hand, as well, since the deflection ceramic is usually cracked when you remove it as part of the neutralizer filament replacement procedure. The neutralizer ceramic and neutralizer filament are readily available from RBD Instruments dot com.

The part number for the filament (exchange) is 04090RF and the part number for the ceramic is 615838PR

Procedure

This procedure assumes that the system has been vented and the neutralizer is on a clean work area. Use clean tools and wear gloves while working on the neutralizer to prevent any oil contamination on the neutralizer parts. Tip: Use UHV aluminum foil to keep the work area clean, and fold up the ends of the aluminum foil to make a tray that will trap any small parts that you may drop during the procedure.  The pictures at the bottom of the post are helpful.

  1. Remove the 4 screws that hold down the exit aperture.
  2. Remove the exit aperture.
  3. Remove the 4 shoulder washer ceramics from the deflection plates.
  4. Lift up the 4 deflection plates and position the wires so that you can remember where they go back to later.
  5. Remove the deflection ceramic. If it is not in broken into pieces you can reuse it.
  6. Lift up the anode aperture and position the wire to the side. There is a groove in the filament housing so it can only go back one way.
  7. Remove the three screws at the bottom of the filament housing. Tip: Scribe the side of the filament housing to help you remember the orientation later.
  8. Remove the filament housing. Note that the anode ceramic will still be inside the filament housing.
  9. Remove the wehnelt cap.
  10. Hold the filament in place and slide the filament connectors down and off of the filament posts.
  11. Remove the filament.
  12. Install the new filament. While holding the filament in place slide the filament connectors on.
  13. Install the wehnelt cap (carefully) over the filament.
  14. Install the filament housing over the wehnelt cap and install then tighten the three screws that hold the filament housing to the neutralizer support base.   Make sure that the tip of the filament is centered in the wehnelt cap.
  15. Install the wehnelt ceramic over the wehnelt cap and center the wehnelt cap within the ceramic. If necessary, loosen the three filament housing screws to adjust the housing position a little bit, and then re-tighten them.
  16. Install the anode aperture ceramic.
  17. Install the deflection ceramic.
  18. Move the deflection plates into position and install the shoulder washer ceramics into the deflection plates.
  19. Place the exit aperture on top and install the screws to hold the exit aperture on top of the shoulder washer ceramics. This can be a little tricky.
  20. With the top screws tightened only slightly, adjust the space between all four deflection plates so that they are even, and tighten the four screws.

Installation is complete! When you burn in the new filament, start out with a low emission value and increase it until the filament is just starting to glow orange. Let the neutralizer outgas in that mode for an hour or so, then slowly bring the filament up to the normal emission setting as needed.

Heat exchanger preventive maintenance

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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.

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:

  1. 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.
  2. For the 16-050, trace the power cord back to the system and unplug it.
  3. 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.
  4. For the 16-020, turn the circuit breaker in the back of the unit to OFF.
  5. Remove the side panel to get better access to the heat exchanger radiator.
  6. 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.
  7. 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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