04-202 SED detector flange

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The model 97 SED preamp which is used on PHI scanning auger surface analysis systems converts secondary electron current into a video signal. It is designed so that it can be mounted onto a vacuum flange which houses a Channeltron electron multiplier.    The 97 SED preamp housing is made of aluminum and if extreme care is not taken when mounting or removing the preamp from the detector flange it is possible to crack one of the three electrical feedthroughs. The picture below shows a broken connector on a 04-202 SED detector flange.

broken-ceramic-feedthrough

broken-ceramic-feedthrough

 

 

 

 

 

 

 

One of the difficulties of mounting the 97 SED preamp to the detector flange is that you can’t really see what you are doing as you slide the preamp over the flange.   There are three larger holes inside the 97 SED preamp mount which go over the electrical feedthroughs on the flange.   It is important that the electrical feedthroughs clear the holes on the 97 SED preamp mount and that the preamp is flush on the flange before the mounting screws are tightened. The mouthing screws should be tightened finger tight while holding the 97 SED preamp firmly against the flange, and then a little bit tighter which a screwdriver.

One way to make sure that the feedthroughs are not touching the holes in the preamp mount is to take the cover off the 97 SED before you mount it, and then put the cover back on after the preamp has been mounted.

Or, you can replace the cover with a piece of Plexiglas.   In the pictures below I have modified a 97 SED preamp by removing the cover and using the cover as a template to mark a piece of Plexiglas so that it is the same size as the original cover. I drilled holes in the Plexiglas and then mounted it on the 97 SED preamp.

With a clear Plexiglas cover on the 97 SED preamp it is very easy to install the preamp onto the 04-202 SED detector flange with less chance of breaking one of the feedthroughs. And the Plexiglas still provides user protection from the high voltage which is present during normal operation of the preamp.

So whether you remove the cover when mounting the 97 SED preamp and then re-install the cover, or replace the metal cover with a Plexiglas one, by being able to see the feedthroughs as you install the 97 SED preamp you can safely mount the preamp with less risk of damage to the 04-202 detector flange.

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Filament Housing Cleaning Procedure

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25-120A Filament Housing Cleaning Procedure

Overview

The filament housing contains two micrometers which are used to position the filament for maximum beam current. The filament is mounted in a ceramic that is attached to a bellows which is supported by an aluminum ring that slides against a plate. The ring and the plate are lubricated and when the lubrication dries out from baking, the ring becomes scored and the filament housing “sticks”. This procedure explains how to disassemble the filament housing and repair this problem.

  1. Vent the system. This removes all tension from the filament bellows.
  2. Remove the two filament micrometers.
  3. Removed the two spring housings. CAUTION! The springs are very strong, remove the top and bottom screws first and then “walk” out the spring with the two side screws.
  4. Remove the top screws from the filament housing.
  5. Remove the top of the filament housing.
  6. Remove the micrometer levers. Note the positions for re-assembly.
  7. Remove the screws that connect the aluminum ring to the ceramic.
  8. Remove the lower filament housing Bristol screws.
  9. Carefully lift up the lower filament housing.
  10. Sand down the surfaces of the aluminum ring and plate.
  11. Lubricate the aluminum ring and plate with C5A (copper based anti-seize lubricant).
  12. Reassemble in reverse order.

If you have questions about this procedure, please contact us or post a comment.

660 System up to air procedure

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Overview

This procedure will allow you to safely bring the 660 scanning auger system up to air for maintenance.

 

  1. Shut down AugerMap and turn off the 20-610 electron gun control (filament down slowly) Also turn off the 20-622 gun control.
  2. Turn off the card rack power
  3. If V4 is open, close it by pressing the Diff Pump Ion Gun button on the AVC remote.
  4. Pump the intro.
  5. Turn off the DIGIII ion gauge.
  6. Turn off the Ion pump control and Boostivac control.
  7. Allow the system to cool for at least 30 minutes. (Or just a few minutes if the electron gun was not on.)
  8. Make sure that the turbo pump is on. If you have more than one turbo pump, they both need to be on.
  9. With the turbo pump on and the intro still being pumped, depress the Backfill Chamber button on the Auto Valve control located behind the vacuum console.
  10. You will hear a hissing sound as air is back-filled into the chamber.
  11. Slightly loosen the intro hatch cover so that when the system is pressurized it will open.
  12. Once the system is vented, turn OFF the turbo pump(s).

 

 

660 System Pump Down procedure

Overview

This procedure will allow you to safely pump down the system after being up to air for maintenance.

 

  1. Make sure that all flanges are secured (use new copper gaskets whenever removing and replacing optics on the vacuum chamber).
  2. With the turbo pump(s) off, depress the Rough Chamber button on the Auto Valve control located behind the vacuum console.
  3. Make sure that the intro hatch is closed.
  4. Turn on the turbo pump(s) by depressing the pumping unit button. You will hear the V2 valve close and the V3 and V4 valves open and the turbo(s) will begin to pump the system out.
  5. After about 20 minutes you should have 5 bars on the Auto Valve control remote. Once you have 5 bars, cycle each of the 4 titanium sublimation filaments for about 2 minutes each at 50 amps on the Boostivac control.
  6. Cycle each filament 2 times, with a few minutes of cool down time between filaments.
  7. After all 4 filaments have been out-gassed, make sure that you still have 5 bars on the Auto valve control remote and then turn on the DIGIII by turning the power switch to UHV and depressing the I/T 3 button.
  8. The DIGIII should indicate in the low 10-3 to mid 10-4 range. Allow the turbo to pump until the system pressure is in the low 10-4 to high 10-5 range, about 30 additional minutes.
  9. Cycle the #1 titanium sublimation filament for about 2 minutes at 50 amps. (Note: If a TSP filament can no longer get at least 45 amps, use the next filament).
  10. When the vacuum is in the low 10-5 range, start the ion pump control by turning the Mode switch to Start. Monitor the 10KV scale. The voltage should be increasing (maximum is about 5.5 kV), and the DIGIII should indicate that the vacuum is dropping into the 10-6 range.  (Note that the meter on the Boostivac does not always read, if not then just make sure that you are in the 10-6 range and dropping on the ion gauge).
  11. Once the DIGIII indicates the high 10-6 range, close the V1 valve by depressing the Rough Chamber button on the Auto Valve control located behind the vacuum console one more time. You will hear the V1, V3 and V4 valves close.
  12. On the Auto valve control remote, depress the Diff Pump Ion Gun button to differentially pump the ion gun.
  13. The system vacuum will continue to improve over the next few hours. Cycle the #1 titanium sublimation filament every 30 to 45 minutes to help the ion pumps pull the vacuum down.
  14. Once the base pressure is in the low 10-7 to mid 10-8 range, the system can be baked out to obtain the best possible base pressure.