X-ray source arcing

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.

 

 

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