A blog on the repair, operation and calibration of surface analysis systems and components including electron spectrometers, sputter ion guns and vacuum related hardware. Click on the Index tab below to see a list of all posts. Visit our website at http://www.rbdinstruments.com
Category Archives: General Optics and Vacuum
General information on repair, maintenance, and operation of both PHI (Physical Electronics) and other manufacturers’ systems and components
Located in Barcelona, ALBA is a Synchrotron Light Source producing radiation for experiments in many fields of science, www.cells.es. The quality of the radiation delivered to users depends on the quality of the electron beam and it is therefore necessary to continuously monitor the beam status in a non-invasive way. At ALBA, the visible part of the synchrotron radiation itself is used to measure distribution of electrons in the machine. The used synchrotron radiation is guided far from the machine tunnel up to an “extraction mirror”. In order to maintain the vacuum in the tunnel, the radiation routed up to the mirror is in-vacuum too. A Torr Scientific viewport is used for extracting the light. The goal this year is to measure the transverse beam size by using the interference pattern produced by the synchrotron radiation passing through a double slits aperture. The performance of this kind of experiment requires the preservation of the quality of the light. Torr Scientific therefore provided a special viewport with a flatness better than lambda/10 and a curvature better than 1 arc sec. Accelerator Division Researcher Laura Torino
said ‘the special viewport we ordered fulfills all the requirements outstandingly; even better than what we were asking. Thank you for the great job you did’. This ALBA project is sponsored by oPAC.
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 –
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.
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.
Loosen the strain relief screws and slide the shield out and away from the ion gauge, being careful to support the wires.
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.
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.
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.
If both filaments are open, then the filaments need to be replaced. See the replacement procedure in the following section.
ion-gauge-wire-connectionsHow to replace the ion gauge filaments:
Vent the chamber.
If not already done, remove the connectors from the ion gauge as per the previous procedure.
Remove the bolts from the ion gauge flange.
Remove the shield retaining collar.
Carefully remove the ion gauge.
Loosen the top set screws on the 3 filament base connectors. These are typically .050 hex screws.
Remove the old filament assembly.
Install the new filament assembly and tighten the set screws. Make sure that the filaments are parallel with the grid.
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.
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.
Insert the bolts and tighten the flange.
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.
Carefully slide the shield over the wires and press the shield firmly into the shield retaining collar.
Tighten the shield retaining set screws.
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.
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.
Remove the 4 screws that hold down the exit aperture.
Remove the exit aperture.
Remove the 4 shoulder washer ceramics from the deflection plates.
Lift up the 4 deflection plates and position the wires so that you can remember where they go back to later.
Remove the deflection ceramic. If it is not in broken into pieces you can reuse it.
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.
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.
Remove the filament housing. Note that the anode ceramic will still be inside the filament housing.
Remove the wehnelt cap.
Hold the filament in place and slide the filament connectors down and off of the filament posts.
Remove the filament.
Install the new filament. While holding the filament in place slide the filament connectors on.
Install the wehnelt cap (carefully) over the filament.
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.
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.
Install the anode aperture ceramic.
Install the deflection ceramic.
Move the deflection plates into position and install the shoulder washer ceramics into the deflection plates.
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.
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.
