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 www.rbdinstruments.com
The 9103 USB picoammeter is often equipped with a +90 V bias option which improves the accuracy of electron and ion current measurements (by reducing the number of low energy secondary electrons that are generated by the beam from leaving the target).
The +90 V bias comprises two 45V batteries in series which are located inside the 9103 chassis. This blog post will explain how to test and replace the batteries in a 9103 picoammeter.
1. Connect a DVM (digital volt meter) to the 9103 Input BNC connector. A BNC to double banana cable works well. Set the DVM to DC volts.
2. In Actuel (the 9103 software), select the input Grounded and bias On.
3. Sample the current.
4. When the bias ON is checked there will be about +90V DC on the input of the 9103.
5 .The input impedance of most DVMs when measuring DC voltage is 10 meg ohms. The two 45 volt batteries should total 90 to 95V DC. The bias voltage divided by the input impedance of the DVM will equal the current. In this case the voltage of the two 45 volt batteries totaled 94V and the current was 9.414 uA.
9.4 uA in Actuel
94 V DC on DVM
6. It is recommended that the bias batteries be tested every 6 months and replaced when the voltage drops below 80 volts. It is normal for the batteries to wear out over time and with use. Once the bias voltage drops to less than 50 V the effectiveness of preventing secondary electron emission is greatly reduced, which in turn reduces the accuracy of electron and ion beam current measurements.
The RBD part number for the 45 V battery is BAT-45-213.
Whether you have an RBD 9103 USB picoammeter or an older Keithley with a PHI model 78 bias box, you should test the batteries as part of your preventive maintenance procedure and replace them as needed.
To replace the batteries in a 9103:
Unplug the 9103 USB power and input cables.
Using the Torx wrench that was included with the 9103, remove the screws from the front and rear 9103 chassis covers.
Slide the board out from the front of the 9103. You will need to rotate the back cover to feed it in. The back cover has a ground wire that is attached to the 9103 board. Also note which groove the 9103 board is in as you will need to put it back in the same groove.
Remove the battery support bracket (white plastic).
Carefully remove the old batteries.
Install the new batteries.You may need to adjust the contacts on the batteries to get them to fit onto the board snaps more easily.
Reattach the battery support bracket.
Carefully slide the back cover and board back into the chassis. Make sure that you put the board back in the same groove that it came out of. If the front cover does not line up with the chassis then you are not in the correct groove.
Reattach the screws to the front and back covers. Do not over tighten the screws!
Once you have installed the new batteries, test the voltage. You should have 90 to 95 Volts.
This post will show how to replace the 10-610 monochromator X-ray source anode and filaments. The 10-610 monochromator X-ray source is used in conjunction with the 10-410 or 10-420 monochromator. When replacing the anode you should also replace both filaments and the deionizer cartridge (located in the 16-0XX heat exchanger).
Once the anode and filaments have been replaced the vacuum chamber needs to be baked out and the new filament and anode need to be out gassed and conditioned. The monochromator may also need to be adjusted slightly to optimize the counts with the new anode and filaments.
Please read the entire procedure first, then watch the picture slideshow at the bottom of the post.
Anode replacement procedure
Vent the chamber.
Remove the water lines from the source.
Remove the safety cover from the source (3 screws).
Remove the high voltage cable
Remove the sixteen 5/16” bolts on the 6” flange and remove 10-610 mono source from the monochromator.
Next, remove the screw that connects the ground wire to the manifold.
Remove the Teflon block from the source base (2 spline cap head screws).
Remove the Teflon block from the source base. Twist it as you slide it off the anode.
Loosen the nut on the high voltage connector (3/4” open end wrench) and remove the high voltage connector.
Remove the silicone rubber insulator and spring. The spring makes electrical contact between the high voltage connector and the anode flange.
Remove the three spline cap head screws that hold the base to the flange and remove base from the flange. Note, this is optional as the base can stay on for bake out.
Remove the two screws that hold the filament cover on and remove the filament cover.
Remove the two screws that hold the filament cover support on and remove the filament cover support. Note the position of the covers as you take them out as they need to go back the same way.
Remove the 6 cap head screws that hold the anode to the base and lift the old anode out of the source housing.
Separate the old anode from the anode flange.
Install a new O-ring on the new anode bottom and slide the anode flange into the new anode. There are 4 O-rings in the anode kit. The anode flange forces the cooling water to the tip of the anode.
Use a new copper gasket and mount the new anode onto the anode flange. Use care as you slide the anode in not to touch the sides of the anode housing (like the old game Operation). The anode surface is coated with a thin layer of aluminum on a copper substrate. Any contact with the top of the anode surface can cause little dents in the anode surface that can cause arc points. Tighten the 6 cap head screws very lightly as the anode will need to be adjusted.
Using plastic tweezers or needle nose pliers, carefully rotate the anode until it is parallel to the filament housing. The idea is that the anode should be parallel to the anode housing and also centered so that there is a maximum and equal distance between the anode and the housing in order to prevent arcing.
Once the anode is parallel, tighten the six cap head screws on the base all the way down.
center the anode
Next, if necessary loosen the 4 screws on the copper pedestal and move it to center the anode for maximum distance between the anode and the filament housing. If available, you can use the anode alignment tool to help center the anode and then tighten the 4 screws on the base of the copper pedestal.
anode alignment tool
The anode surface should be the same level as the fence that is between the filaments and the anode. If not loosen the spline head cap screw that secures the filament housing to the copper pedestal. You can use the anode alignment tool, a straight edge or just eye ball it.
Filament replacement procedure
The filaments are coated with Yttrium so that they can provide sufficient electrons for emission at a lower filament operating current. Be careful when handling the filaments so that you do not knock off any of the coating on the filaments.
Loosen the filament clamp screws on the large 7mm (diffused) area filament and remove the old filament. Note that the large 7mm filament is closest to the filament connector and wires.
Carefully insert the new filament into the filament clamps and lightly tighten them. The filament should be centered with respect to the anode and the top of the filament should be even with the top of the filament cavity (level with the anode guard). It should also be parallel to the anode guard and centered in the filament cavity. If not, remove the filament and carefully bend the legs as needed. Once the filament height and centering is correct, firmly tighten the filament clamp screws.
Repeat this procedure for the small 2mm (focused) filament.
Install the filament cover base and cover. Note that the little cut out goes over the 2mm filament.
Condition the anode and filaments procedure
Once the new anode and filaments have been installed onto the 10-610 monochromator X-ray source, the source needs to be baked out and then outgassed and conditioned.
First, bake out the system.
Next, outgas the filaments
Finally, condition the anode
Bake out the system
Follow the bake out procedure in the PHI manual or search for the RBD Techspot blog- Bake-out procedure to improve base vacuum.
The O-rings on the mono source, HV connector and silicone rubber insulator and Teflon block are all removed from the 10-610 mono source before bake out. After bake out, use a little bit of vacuum grease on the O-rings to help provide a tight water seal when the Teflon block is replaced.
Replace the deionizer cartridge in the 16-0XX heat exchanger. PHI recommends that the deionizer cartridge be replaced each time the anode is replaced to help make sure that the water does not react with the anode.
Outgas the filaments
Prior to outgassing the filaments the system should have been baked out and the mono source housing and water lines reassembled. The deionizer cartridge should also have been replaced. The system should be cool and the base pressure in the low 10-9 to low 10-10 Torr range.
The filaments need to be initially outgassed slowly in order to prevent warping and also to set them.
Select the Outgas/ACT mode on the X-ray source controller.
Select the 2mm focused filament and ramp the current up to 5 amps in increments of .5 amps over a period of 2 to 5 minutes. Wait for the outgassing to subside somewhat as indicated by the ion gauge.
Set the 2mm focused filament current to zero amps and then repeat the procedure with the 7mm diffused filament. Once up to 5 amps, let the 7mm diffused filament sit there for 4 to 8 hours or until the base vacuum returns to the low 10-9 Torr range. Then set the filament current to zero and turn off the Outgas/ACT mode on the X-ray source controller.
Degas the Anode
Set the beam voltage to 500V and turn it on.
On the X-ray source controller, select the Outgas/ACT mode
Select the 2mm focused filament (Mg filament on a 32-095/6)
Slowly increase the amps to 3.5 and then monitor the anode current (emission current) meter.
VERY SLOWY increase the filament current until you get 1mA of emission current. Do not exceed 5 amps of filament current. Do not exceed 2mA of emission current.
Monitor the ion gauge vacuum reading and wait until the outgassing comes back down then slowly increase the beam voltage to 1 kV. If necessary reduce the filament current to keep the emission below 2mA.
In steps of 500V bring the high voltage up to 10kV while adjusting the filament current as needed to keep the emission current below 2mA. Do this over a period of 30 minutes to several hours, depending on how much the anode outgasses. For best results keep the vacuum in the chamber in the low 10-9 Torr range. The higher the pressure from outgassing, the more likely an arc will occur.
Once the anode has been outgassed to 10kV, turn the filament current to zero and set the high voltage to zero. Then switch to the other filament and repeat the procedure.
Condition the high voltage
Make sure that the Out/Act button is OFF and that the filament current is set to zero on both filaments.
SLOWLY bring the high voltage up to 10kV while monitoring the vacuum chamber ion gauge.
Step the high voltage up increments of 500V until you get to 16.5kV. When you see some signs of outgassing (the pressure in the vacuum chamber will come up) then back down the high voltage a little bit and wait until the vacuum recovers.
Once you are able to get to 16.5 kV with no arcing, let the anode sit there for at least 20 minutes.
The X-ray source is now ready for normal operation. For best results, start at a low power and kV such as 100 watts and 10kV. You can step up both the power and the kV over a period of a few hours based on how much outgassing you see when operating in this mode. Once you are up to full power of 300 watts and 15kv the X-ray source can be brought up to full power quickly.
Note that the maximum power that should be applied to the 2mm focused filament is 350 watts and the maximum power that should be applied to the 7mm diffused filament is 600 watts. Personally I do not recommend more than 300 watts on either anode. If you can get by with a lower wattage (such as 250) then both the filaments and anode will last longer.
It is also recommended that you inspect the 10-610 mono anode any time you vent your chamber for maintenance, or at least once a year. If you see indications of melting in the center of the anode you should replace the anode. Otherwise it will eventually develop a water leak and cause potentially catastrophic damage to system components and substantial downtime.
The heat exchanger cooling fan used on the Physical electronics 16-025 and 16-050 heat exchangers which are used to cool the x-ray sources on an XPS system can run slowly as the fan motor ages once the bearing lubricant begins to dry up. The result of a slow fan is that the anode will run warmer than normal and possibly melt. At a minimum reduced cooling will shorten the anode lifetime. The 16-020 heat exchanger has a fan that is attached to the pump motor, so it will not have this problem unless the pump motor fails.
The symptom for a slow heat exchanger fan is that with the source at full power after 20 minutes of operation the water lines to the x-ray source will be very warm or even hot rather than slightly warm.
To test the fan you can feel how much air is coming out the back side of the radiator when the 16-025 or 16-050 heat exchanger is on. The radiator will slow down the airflow, but it should still be a reasonable amount of air that escapes out the back side of the radiator. If the fan looks like it is spinning slowly and there is minimal airflow then the fan should be replaced.
If you want to test the actual RPMs of the fan you can use a non-contact laser tachometer (available for as little as $15.00). Or you can use an audio method as shown in this video on YouTube that uses Audacity:
It is held in place with some radiator mounting rods that are available at most auto parts stores. Look for Hayden Nylon mounting rods with vibration pads.
Nylon mounting rods
In addition to the cooling fan, if the pressure indicator on your 16-050 heat exchanger bounces during operation you should consider replacing the water pump as well. RBD Instruments provides the water pumps. The 16-020 and most 16-025 heat exchangers do not have a pressure gauge.
And of course, make sure that the radiator is free from dust as being covered with dust will also reduce the cooling efficiency of the 16-020, 16-025 or 16-050 heat exchangers. Refer to the RBD TechSpot post Heat Exchanger Preventive Maintenance for more information on dust and the radiator.
Heat exchanger preventive maintenance will prolong the anode lifetime on your 10-610 mono chromator anode and prevent a costly and time consuming anode meltdown.