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.
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.
That’s a pretty neat idea. I have been fortunate enough not to break one of those feedthroughs yet, but with how much I’ve had to take the SED on/off I may utilize this mod the next time I remove it.