Our previous blog post https://www.rbdinstruments.com/blog/ion-pump-element-rebuild-procedure/ we explained how to flip the ion pump Tantalum and Titanium plates in order to provide fresh surface area for the sputtering process that occurs as part of the ionization / pumping process.
But what happens if you flip the plates and then years later the ion pumps are worn out again? That is, what if both sides of the plates have been sputtered?
This blog post will explain how you can modify the plates to expose a fresh surface area which functionally is the same thing as replacing the plates.
Like most things, ion pump elements have gone up in price post COVID. A set of 8 elements (there are 8 elements in a 220 l/s ion pump) can cost $5,000 or more. Rather than replacing the elements, you can replace just the ceramics for a lot less and flip the plates. If the plates have already been flipped once, then both sides of the plates will have sputtered craters.
By elongating the mounting holes in the plates by 1.5 mm the sputter area on the plates would also shift by 1.5 mm onto a fresh area that has not been sputtered, at least not sputtered very much.
The photos below show the sputtered craters and the location of where the new sputtering will occur.
In this case I was lucky enough to be at a university with a machine shop and the machinist was able to punch the holes without using any oil. If you do not have a machine shop, you could use a Dremel cutting bit to elongate the holes.
When you reassemble the elements, you want to make sure that you offset both the Tantalum and the Titanium plates in the same direction. You will be able to tell that the Tantalum plate is offset by the 1.5mm gap with respect to the stainless-steel backing plate. Then make sure that the Titanium plate lines up with the location of the Tantalum plate. You can confirm that the Titanium plate is offset correctly by looking at the distance on the mounting tabs on the back of the Titanium plate.
After performing this procedure on the plates shown in this blog post the ion pump elements performed as well as new elements. The increase in pumping capacity was noticeable.
If you suspect that your ion pumps may need to be inspected (slow pumping, arcing, or shorted) I recommend that you buy the ion pump ceramics before you vent so that you have them on hand if needed. RBD Instruments provides ion pump ceramics. Contact us for more information here – https://support.rbdinstruments.com/portal/en/signin