X-ray source arcing

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X-ray source arcing results in unstable XPS data and can also damage the x-ray source power supply or high voltage control.

Typically X-ray source arcing is caused by contamination on the anode, a coated anode support ceramic (the football ceramic) or a loose filament.

However one unseen cause of x-ray source arcing is when the high voltage cable to the x-ray source is not tightened all the way down until it snaps in. The procedure is simple – line up the slot on the cable with the two little tabs on the source connector. Then press down all the way and turn the cable collar clockwise until it snaps in.

On the newer 04-548 15kV dual anode sources this is easy to do as the connector is exposed. But the connector is recessed on the older dual anode sources and all of the mono sources.

To properly connect the high voltage cable on the older dual X-ray sources or a mono source you need to remove the cover on the source so that you can see the connector and make sure that the cable slots line up and that the cable locks down when the collar is turned fully clockwise.

high-voltage-connector-slots

high-voltage-connector-slots

high-voltage-connector-snapped-in

high-voltage-connector-snapped-in

If the high voltage cable is not snapped all the way down then it can arc at higher voltages and damage the cable connector, the source connector, or more typically both connectors.

The pictures below show damaged cable and source high voltage connectors.

melted x-ray source connector

melted x-ray source connector

 

 

burnt x-ray source connector

burnt x-ray source connector

 

Once arcing damage occurs the cable end and or source connector need to be replaced.

RBD Instruments provides the source connector and we can also repair or exchange your cable. Visit our website and look under Parts – Optics – X-ray Photoelectron Spectroscopy Model 04-500 and04-548 X-ray source parts or call us at 541 550 5016

Revised outgas procedure for PHI dual anode x-ray sources and single anode mono sources.

Out-gassing the filaments and conditioning the anode are essential steps needed to remove adsorbed gases from the filament area of any PHI X-ray source.

Recently I have seen a couple of instances where a 10-610 monochromator source was not properly out-gassed and the result was a contaminated anode and very low counts. So degassing the anode is essential for proper operation.

To prevent anode contamination, the anode needs to be degassed per the PHI manual. However I have found that by changing the order of the out-gas procedure steps that the amount of time it takes to out gas the source to full power can be significantly reduced.

The manual states that the out-gas procedure sequence is as follows:

  1. Outgas the filaments
  2. Condition the high voltage
  3. Degas the anode

But from a practical standpoint it makes more sense to degas the anode before conditioning the high voltage. The reason is that a degassed anode is less likely to arc.

So the faster way to out-gas an X-ray source is:

  1. Outgas the filaments
  2. Degas the anode
  3. Condition the high voltage

 

Step 1. Outgas the filaments.

You need to out-gas the filaments after new filaments have been installed or anytime the system has been brought up to air and baked out. For this procedure it is assumed that the system has been baked out. (The only bake out exception is if you have just replaced the 04-303 ion gun ionizer and back-filled the chamber with dry nitrogen).

  1. Turn on the 32-095/096 power.
  2. On the 32-095/6, press the Blue Out/Act out-gas activate button.
  3. Select both filaments
  4. Select the Mg filament (or filament 1)
  5. Slowly increase the amps to 3.5
  6. Select the Al filament (or filament 2)
  7. Slowly increase the amps to 3.5
  8. Let the filaments sit there for a few minutes and then slowly increase each filament to 4.5 amps.
  9. Let the filaments sit at 4.5 amps for a minimum of 4 hours (overnight is best).
  10. After out-gassing for at least 4 hours set the filament current to zero on both filaments and turn off the Out/Act out-gas button by pressing it one more time.

Step 2 Degas the Anode

  1. Set the beam voltage to 500V and turn it on.
  2. On the 32-095/6, press the Blue Out/Act out-gas activate button
  3. Select the Mg filament (or filament 1)
  4. Slowly increase the amps to 3.5 and then monitor the anode current (emission current) meter.
  5. VERY SLOWLY 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.
  6. Monitor the ion gauge vacuum reading and wait until the out-gassing comes back down then slowly increase the beam voltage to 1 kV. If necessary reduce the filament current to keep the emission below 2mA.
  7. In steps of 1kV 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 10 minutes to several hours, depending on how much the anode out-gasses. For best results keep the vacuum in the chamber in the low 10-9 Torr range. The higher the pressure from out-gassing, the more likely an arc will occur.
  8. Once the anode has been out-gassed 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.

Step 3 Condition the high voltage

  1. Make sure that the Out/Act button is OFF and that the filament current is set to zero on both filaments.
  2. SLOWLY bring the high voltage up to 10kV while monitoring the vacuum chamber ion gauge.
  3. Step the high voltage up increments of 500V until you get to 16.5kV. When you see some signs of out-gassing (the pressure in the vacuum chamber will come up) then back down the high voltage a little bit and wait until the vacuum recovers.
  4. 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 out-gassing 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.

 

 

32-095 X-ray source control

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When the 32-095 X-ray source control is not working properly there are some easy  possible solutions that you can check before sending the unit to RBD Instruments Inc. for repair.

If the problem is that one filament works but the other one does not, then you should check the fuses located on the filament power supply board inside the 32-095 X-ray source control in the back left hand corner of the unit. (The other possibility is that the x-ray source filament is open.)     With the 32-095 power off, slide the unit out and remove the cover, then measure the resistance on the fuses.  Usually it is easiest to just completely unplug the 32-095 and remove it from the electronics rack.

The fuses are 5 amp slow blow and are shown in the board layout figure below.

filament_board_fuses

Filament power supply board fuses

The next most common problem is instability in the controller or flashing digits on the digital panel meter. These can be caused by high AC ripple on the +/-15V or +5 V supplies on the local power supply board which is located in the front left hand side of the 32-095.

The figure below shows the layout of the local power supply board and the location of the +/-15V and +5V supplies.

local power supply board layout

local power supply board layout

The picture below shows the points where you measure the +5v supply.   To measure the +5V supply, connect your test clips to the pins as shown in the picture below. Turn on the 32-095 power and then measure both the DC and AC voltage using a DVM. The correct value is +5.0 V DC (+/- 100 mV) and the AC ripple should be less than 10mV.   If the +5V supply has a problem the DC will be more like 4V and the AC will be 1 to 2V.  Power supply board problems are usually caused by bad capacitors.

 

32-095 local power supply board +5V

32-095 local power supply board +5V

The pictures below show the test points for the + and – 15V supplies.   The correct voltage values are + and – 15.0V (+/- 200 mV) and the AC ripple should be less than 20mV. If the DC voltage is low and the AC ripple is high then the supply has a problem.

32-095 local power supply board -15V

32-095 local power supply board -15V

32-095 local power supply board +15V

32-095 local power supply board +15V

The figures below show the +5 and +/- 15V local power supply board schematics.

5V schematic

5V schematic

15 V schematic

15 V schematic

 

Below is a table that lists common problems and possible solutions.   Sometimes the problems are easy to fix, but often the problem may be a hard to find bad capacitor, diode or integrated circuit.

Problem Possible solution
No current on one filament Bad power supply board fuse, open filament on source
No filament current but fuse is OK Bad PIC 645 regulator
Unstable operation Bad capacitor on local power supply board

If the problem is not an easy fix then RBD Instruments can repair your 32-095/96 x-ray source control and also provide you with a loaner unit to use while we are repairing yours.

Additional test info:

04-500/548 X-Ray Source Filament Test

The following information is helpful in testing the condition of the filaments in 04-500 or 04-548 15 kV dual anode X-ray sources and in troubleshooting the 32-095 X-ray source control.

 X-Ray Sources

On the big filament connector on the source, pins A and B (filament 1) and C and D (filament 2) should have less than 1 ohm of resistance. All pins should be open to ground.

The HV connector (anode) should be open to ground. Check that with the X-ray high voltage supply OFF and the HV cable to the source disconnected.

32-095 Test

Follow the 32-095 Outgas/Activate procedure in the 32-095 manual.

To bench check the 32-095, short pins A and B on the Pressure Interlock connector, and pins A and E on the Pump Control connector.

You can use two large paper clips as dummy loads when testing the filament current.  Put the clips on the end of the cable or on the filament connector on the back of the 32-095.

32-095 outgas activate  test load

Endoscopic ion pump inspection

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An easy way to determine whether or not an ion pump needs to be rebuilt is to perform an endoscopic ion pump inspection. The hard way is to drop the ion pumps.

In the last few years the prices have really come down on USB and android/iPhone endoscopes. If you do a search on EBay for USB endoscope you will see a lot of choices for under $20.00. The one used in this blog post is 7mm in diameter, which is small enough to fit into a 1.33” CF flange hole.

endoscope

endoscope

endoscope_for_phone

endoscope_for_phone

 

 

 

 

 

 

For this example we inspected a PHI 660 scanning auger system equipped with a 220 l/s ion pump. This system has been in use for about 10 years primarily for depth profiling using Argon gas.

Since there is a shield below the TSP filaments the only way into the ion pumps was thru the un-used 1.33 CF flange that is opposite the ion pump high voltage connector.

This video link shows what it looks like as you move the endoscope around inside the ion pump – https://www.youtube.com/watch?v=5DQVW3DCG9A&feature=youtu.be  Note that the video has a blue tint to if from the built in LED camera lighting.

The color corrected pictures below show that the ion pump elements are pitted, the insulating ceramics are coated and there are some flakes in the bottom of the pump well.   The conclusion was that the pump elements have another year or so left on them and so we will plan on replacing them in 12 to 18 months.

ion_pump_cf_flange

ion_pump_cf_flange

endoscope_inserted

endoscope_inserted

High_voltage_feedthru

High_voltage_feedthru

flakes_in_pump_well

flakes_in_pump_well

Pits_on_titanium_plate

Pits_on_titanium_plate

coating_on_ceramic

coating_on_ceramic