Here is a neat video I took of the Objective Aperture mechanism for the AMRAY SEM I have been taken apart. The aperture sits right below the objective lens. It has a dial in the back for adjusting the apertures in and out (Z axis). Another dial makes the copper rod pivot towards the back, enabling sideways adjustment (X axis). I am not 100% the rod is made of copper, could be coated brass, or a non magnetic stainless. I may disassemble it further for the rest of this series, weigh it, and measure its displacement in water, and calculate its density. However, much higher resolution scopes made by Philips/FEI Aperture holders are made of a non magnetic stainless steel. So, copper is not really necessary.
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