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
The emission scale switch on the 11-065 ion gun control is used to change the scale of the emission to three levels: 100% (X1), 10%(X.1) and 1%(X.01). The effect of changing the emission switch is to reduce the emission current, which in turn reduces the ionization (pressure reading) and ion (target) current proportionally.
Initially, the emission needs to be set to 25mA in the X 1
scale and the leak valve is adjusted to achieve 15 to 25 mpA of pressure.
25 mA of emission currentAdjust Argon to get 15 t0 25 mPa of gas pressure
The graph below shows the target current vs. time and the effect of changing the emission current from X 1 to the X.1 and X.01 scales.
Ion current in uA
When changing the emission scale switch, the emission reading on the 11-065 front panel meter will not change, but the actual emission current will be reduced by a factor of 10 (X.1 scale ) or 100 (X .01 scale). So for example if the emission is set to 25 and the emission scale switch is changed to X .1, the meter still indicates 25mA but the actual emission is 25mA X .1 = 2.5mA. The pressure display will be reduced by a factor of 10 as well since the number of ions being generated are reduced proportionally to the emission current. Ideally, the target current will also be reduced by to 10% of the X1 value when the emission scale switch is changed to X.1. In the graph above we see that the target current drops from about 4.25uA to .8uA as the emission drops from 25mA to 2.5mA. As expected, the target current drops a factor of 10ish to 70 nA as the emission scale switch is changed to the X .01 position.
The picture below shows that the pressure drops to about 2mPa as the emission scale is changed to X.1
Emission scale x .1
This picture shows the pressure dropping to .2mPa as the emission scale switch is changed to the X.01 position.
Emission scale x .01
The emission scale switch is an easy way to reduce the ion target current by a factor of 10 or 100 in order to achieve lower sputter rates.
Note that Balzers RVG 050 thermovalve controllers cannot be used on older 11-065s in the X .1 or X .01 emission scale positions since they depend on the pressure reading for feedback. Newer 11-065s have a circuit that compensates so that the pressure output is correct at each emission scale setting.
11-065 LAS1515 regulator note.
The +15V LAS1515 regulator that is on the heatsink (second from the front) can be marginal. The symptom is that the emission current is unstable, or it becomes stable after the 11-065 warms up.
The SCC brand of LAS1515 regulators has inconsistencies. When measuring the waveforms between the two pins using the Huntron Tracker, 50% of the LAS1515s presented like a diode, the other 50% presented like a Z. The Z is correct. In addition, even the Z pattern SSC brand LAS1515 regulators did not perform properly. Either the emission instability happened right away, or it would happen once the 11-065 warmed up.
The solution was to replace the SSC brand LAS1515s with the NTE equivalent NTE1916 regulator. That worked fine.
This procedure will explain how to replace the channel plates (technically, they are Chevron plates) in the MCD detector used on Physical Electronics (PHI) 5600, 5700 and 5800 X-ray Photoelectron spectrometers. You may also want to check out our blog post on checking the MCD pins continuity.
Set up a work area with some aluminum foil and lint free cloths.
Vent the system.
Mark the MCD feedthrough flange to confirm the orientation of the flange when you replace it later.
Mark flange
Remove most of the bolts and nuts that secure the MCD feedthrough flange to the analyzer. The MCD feedthrough flange has some springs on the inside so there will be some tension when you remove the flange. There are 3 studs that are used to guide the MCD feedthrough flange when it is removed or installed.
Remove the last few nuts or bolts and carefully lower the MCD feedthrough flange and place it on the aluminum foil. Incidentally, most food grade aluminum foil has oil on it. If possible, use UHV compatible foil when working with electron optics.
Remove MCD feedthrough flange
The MCD assembly is located inside the 6″ CF flange where you just removed the MCD feedthrough flange from. You can remove one of the analyzer braces in order to gain better access to the MCD assembly.
MCD assembly
At this point put on a pair of gloves as you will be working inside the analyzer and want to prevent oil contaminator from your hands. Use tools that have been cleaned with Isopropanol or Methanol.
Remove the screw that holds the capacitor in place.
Remove capacitor screw
Remove the capacitor by pulling on the pin that is connected to the MCD assembly. Do not pull on the capacitor. The pin wire is silver soldered to the capacitor and it can come off easily, so be very careful with the capacitor.
Remove capacitor by pulling on the pin connector
Remove the POS and NEG pins from the MCD assembly. Just pull up on the pins, keep the wires attached to the SHV feedthrough pins.
Remove POS and NEG pin connectors
The MCD assembly is held in place with 2 slotted screws. Remove one of the screws completely. Be careful as it is easy to drop.
Loosen the second screw and then reach up and hold the MCD assembly as you remove the screw. Ease the MCD assembly down and out of the 6″ CF flange.
Remove MCD assembly
Set the MCD assembly on a clean working surface.
Pull up on the pins and insert a small Allen wrench or rod to hold the pins in place. The pins are spring loaded and by inserting a small Allen wrench or rod into the holes in the pins, that will prevent the pins from contacting the plates or 16 channel ceramic when replacing the plates.
Insert Allen wrenches or rods
Remove the two inner slotted screws.
Remove inner two screws
Hold the MCD assembly as you rotate it 180 degrees so that the grid screen is facing up.
Hold together and rotate so that grid is facing up
Remove the grid screen. Set it to the side.
Remove the grid screen
Remove the ceramic. Set it next to the grid screen. As you remove parts, set them down next to each other in sequence. That will make it easier to reassembly the parts in the correct order.
Ceramic with grid screen removed
Remove the gold spacer. Sometimes that part will stick to the bottom of the ceramic.
Ceramic and gold spacer removed
Remove the Teflon tubes
Remove the Teflon tubes
Remove the top plate.
Remove the top plate
Remove the second plate. Note that the plates have a little dot on them. Those dots need to face each other. So, the bottom plate has the dot facing up, and the top plate has the dot facing down.
Dot on plate, near the holeRemove the bottom plate
Use some clean air or nitrogen to blow off the 16 channel ceramic. Feel free to dust off the MCD assembly and plates frequently. Dust is to be avoided as much as possible.
16 channel ceramic
Install the new bottom plate. It sits on the gold spacer which is on top of the 16-pin ceramic. The hole in the plate needs to line up with the pin. The pin is centered in the hole in the plate. The little dot on the plate needs to face up.
Install bottom plate. Dot up.
Install the new top plate. The dot needs to face down and the pin should be centered in the hole in the plate.
Install top plate, dot facing down
Install the gold spacer. The tab on the spacer should be above the pin.
Install gold spacer. Tab over pin.
Install the Teflon tubes.
Install Teflon tubes
Install the ceramic over the Teflon tubes. The top of the tubes should be flush with the ceramic.
Install ceramic
Set the grid screen on top of the ceramic.
Position grid screen
While holding the grid screen and ceramic in place, rotate the MCD assembly 180 degrees so that the pins face up. Since the screw are not get installed, the only thing holding the grin screen and ceramic in place is you.
Rotate MCD assembly so that pins face up
Install the two screws to secure the grid screen. You may need to rotate things just a little bit. Tighten the screws firmly but not too tightly or you may crack the ceramic.
Install screws
Remove the Allen wrench or rods from the pins. Rotate the pins a little bit to make sure that they are seated.
Remove Allen wrenches or rods from pins
Measure the resistance between the POS and NEG pins. You should have 15 to 24 meg ohms. From the other pin to POS or NEG should be about 1 Meg ohm.
Measure resistance between POS and NEG
The MCD assembly is now ready to install back into the analyzer.
Before you insert the MCD assembly, prepare one of the screws for mounting. A pronged grabber works well as does a starter screw driver. In a pinch you can use a regular screw driver with a little bit of tape to hold the screw on. The tape needs to stick to the screwdriver so that it all comes out when you remove the screwdriver.
Insert the MCD assembly (it can only go in one way or else the screw will not line up) and rotate it slightly to make sure that it is seated properly. Tighten the one screw to where it is just snug.
Install the second screw and tighten it to where it is just snug.
Slightly rotate the MCD assembly to make sure that it is seated properly and then tighten both screws firmly.
Reconnect the POS and NEG pins. Refer to the drawing to make sure that you do not insert the pins backwards. Also make sure that the POS and NEG wires are centered as the MCD feedthrough flange will need to clear the POS and NEG pins.
POS and NEG pin to SHV connectors
Insert the capacitor pin. Be careful not to stress the capacitor.
Reattach the capacitor wire screw and tighten the screw. The capacitor should be perpendicular (not tilted) as the MCD feedthrough flange will need to clear it.
POS, NEG and capacitor reconnected
Remove the used 6″ copper gasket.
Install a new 6″ copper gasket on the MCD feedthrough flange.
Carefully line up the MCD feedthrough flange and slide it onto the 3 guide studs. Install the 3 nuts to hold the MCD feedthrough flange in place and then slightly rotate the flange to make sure it is seated. The springs on the MCD feedthrough flange fit into the 16 holes in the MCD ceramic and press against the metal discs which in turn make contact with small capacitors inside the MCD assembly.
Install the bolts and lightly tighten the MCD feedthrough flange.
Measure the capacitance of all of the pins on the MCD feedthrough with respect to the vacuum chamber. The four center pins should read approximately 100 pf (open). All of the other pins should read 250 to 300 pf. If not, you need to drop the MCD feedthrough flange down and inspect to see where it is hanging up. Sometimes the spring pins do make contact with the MCD assembly and need to be adjusted slightly.
Once you have the correct capacitance on all of the pins, tighten all of the nuts and bolts.
The vacuum chamber is ready to pump down and baked.
Installation complete.
Note: Set the MCD multiplier voltage to 1800V in the software so that after the bake out you start outgassing the new plates at a lower operating voltage.
After you replace the filament in the 04-085 or 04-090 neutralizer you may need to readjust the current limit on the 72-030 neutralizer board. The 72-030 provides the filament current and bias voltage to the neutralizer. This procedure shows you how to set the current limit on the 72-030 so that you generate enough electrons to neutralize the sample and also maximize the filament lifetime.
Tools Needed:
HV card rack extender board
Voltmeter with 2 clip leads
Potentiometer adjustment tool
72-030 Calibration procedure
Turn off the card rack power
Extend the 72-030 neutralizer card (located in the card rack)
Connect the DVM across R59 / E6
Make sure that the filament cable is connected to the neutralizer on the system
Turn on the card rack power
Turn on the 147 PC Interface unit
Open AugerScan software
Turn on the neutralizer in AugerScan
Monitor the target current with a picoammeter and a +90V bias
Turn up the Emission in the Augerscan Neutralizer dialog box to 20 to 23 mA while monitoring the DC voltage in millivolts across R59 / E6.
There should be approximately 34 mV across R59 / E6 and you should also be able to see the end of the neutralizer glowing orange to white in the vacuum chamber.
Set the Emission to 25 mA and if necessary adjust R48 / B6 so that you have 2 to 3 uA of target current. Do not adjust R48 / B6 to exceed 36mV across R59 / E6. 36mV corresponds to 3.6 amps of filament current. The lower the filament current, the longer the filament lifetime.
Turn off the card rack power and reinstall the 72-030 neutralizer card in the card rack.
Ideally, adjusting R48 for a value that provides a few uA of target current and with less than 36mV across R59 / E6 will result in the longest filament lifetime.
72-030 board extendedR59 current sense resistorMeasure voltage across R59 34mV corresponds to 3.4 amps of filament current
72-030 Neutralizer bias voltage notes
There are two revisions of 72-030 neutralizer boards. The older original 72-030 has a bias voltage range of 0 to -12V. The newer 72-030s have a bias voltage range of 0 to -24V.
You can tell the difference by two things. First of all, U6 is a OP07 op amp on the older 72-030s, and it is a LM344H high voltage op amp on the newer 72-030s. Secondly, there is a 5V to 15V power convertor on the newer boards, the older 72-030s do not have that power converter.
