Ion pump: diode vs. triode

[Julien]

Hi everybody,

We still have issues with (small) beam instability that matches some spiking on the ion pump – probably related to some build-up of Ar from the P-10 that causes discharges. To further test, JEOL wants to “innovate” with old material on my new probe. Installing a (refurbish) triode ion pump. They say this kind of triode ion pump are more efficient to handle pollution by Ar, but this sounds a little experimental (never done on an 8230)… Any thoughts on that? Pros & cons?

Julien

[Probeman]

We still have issues with (small) beam instability that matches some spiking on the ion pump – probably related to some build-up of Ar from the P-10 that causes discharges. To further test, JEOL wants to “innovate” with old material on my new probe. Installing a (refurbish) triode ion pump. They say this kind of triode ion pump are more efficient to handle pollution by Ar, but this sounds a little experimental (never done on an 8230)… Any thoughts on that? Pros & cons?

I think this makes sense, if by diode/triode you mean one versus two sputter elements.

The early Cameca ion pumps had only Ti elements for ion pumping, but if I remember correctly, later models had both Ti and Ta elements.  And I believe the goal of these dual element ion pumps was to better pump Ar by sputter "burial", as opposed to chemical absorption.

http://nau.edu/cefns/labs/electron-microprobe/glg-510-class-notes/instrumentation/#SputPump

john