I've made some improvements to the microscope that have increased image quality somewhat. Here is a quick list of the changes:
-Made a new acrylic light guide that allows the scintillator to face the sample directly. The pipe is curved so that the light is directed upwards into the photomultiplier tube. The size of my bell jar necessitated that the PMT be mounted vertically, which is not good since a straight light pipe would cause the scintillator to be aimed directly at the bottom of the chamber.
-Added coaxial cabling and a fully-shielded box to the PMT amplifier circuitry.
-Adjusted PMT load resistor, and eventually installed a potentiometer so that I can change the load resistance to best match the raster scan rate
-Changed PMT amplifier circuitry so that the images are not inverted with respect to normal secondary electron micrographs
This is a MEMs gyroscope. I pried off the cover to expose the die.
This micrograph shows some structure on the die. Hopefully with better magnification and resolution, I'll be able to see the MEMs gyro itself.
It appears to me that the blurriness in these images is somewhat constant across all magnifications. This leads me to believe that focus is not the main issue, and that the problem is with PMT signal recovery. Scanning at a slower rate should help this, but the PMT amplifier is AC-coupled, so the scan rate cannot get too low, and I also cannot see the image on the oscilloscope at low scan rates -- making focus and various other adjustments difficult. I also haven't found a good way to synchronize my camera shutter to the raster scan.