Electromagnetic lens for an SEM

[reduction]

Does anyone know how the machining tolerance in the construction of an electromagnetic lens affects resolution in a scanning electron microscope?

 

[euni1968]

Can you be a bit more specific with respect to what tolerances you are referring to?

In general, as long as it wasn't made by Joe Bloggs out of bits from his garden shed, SEM lens construction tolerances don't have much affect on resolution. Good practice in an EM unit would be to align the microscope on a weekly basis. Proper alignment can overcome small manufacturing defects in the lenses. In a properly aligned machine, of greater importance is the machining of the apertures in the final condensing lens. Tolerances here are very small, and can effect resolution greatly.

If you are having problems with image resolution, I would look in 100 other places before I started worrying about machining tolerances in the lenses.

[Source: BSc(Hons) Physics, MMedSc Electron Microscopy]

 

[reduction]

Can you be a bit more specific with respect to what tolerances you are referring to?

In general, as long as it wasn't made by Joe Bloggs out of bits from his garden shed, SEM lens construction tolerances don't have much affect on resolution. Good practice in an EM unit would be to align the microscope on a weekly basis. Proper alignment can overcome small manufacturing defects in the lenses. In a properly aligned machine, of greater importance is the machining of the apertures in the final condensing lens. Tolerances here are very small, and can effect resolution greatly.

If you are having problems with image resolution, I would look in 100 other places before I started worrying about machining tolerances in the lenses.

[Source: BSc(Hons) Physics, MMedSc Electron Microscopy]

Many thanks for your reply. I'm not actually troubleshooting an SEM but merely curious about their construction and operation. I'd be very appreciative if you could point me towards any literature on those topics.