Check out the scanning electron microscope Ben Krasnow made. It’s a fine example of some of the higher-end DIY lab equipment starting to show up in garages and hackerspaces around the world. Ben says he’ll be exhibiting the SEM at Maker Faire Bay Area May 21st-22nd and that people are encouraged to stop by to check it out in person. [via Neatorama]
10 thoughts on “DIY Scanning Electron Microscope”
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This is a totally awesome hack. I’m a little concerned though – I tried to get an SEM working when I was in college, and never did because the vacuum was never hard enough to allow me to turn on the beam. The physics professor I was working with told me that it would generate pretty hard x-rays if the electron beam struck stray gas molecules. I hope he as a dosimeter or geiger tube setup when he fires that thing up…
I’m a material science and engineering grad student and work with electron microscopes often, so I feel like I can speak to this topic. First of all…kudos! It can be difficult for beginners, as it was for me, to get a handle on the beam in a commercial unit, let alone one made in your home workshop. I’m impressed, even though I suspect you are far from a beginner! Two quick things.
1. Mr. Anderson is right in that there are definitely x-rays being generated. They can come from the gas molecules, the sample, the aluminum plate, or anything else the beam contacts. That being said you can only generate x-rays with energies, measured in electron volts, below the accelerating voltage. I would look into getting a leaded glass bell jar to prevent the x-rays from exiting the chamber. Not sure where you would find them commercially, but they are still high strength and optically transparent, but they have high x-ray absorption.
2. You didn’t mention the use of any sort of aperture. An aperture, placed directly after the accelerating plates, is an ideal way to limit the cross-sectional size of the beam and exclude off-axis electrons. You will lose beam brightness, but gain resolution with decreasing aperture size. Alignment is fairly simple and may take your images to the next step without the need for complicated stigmator coils or other electronics.
Here’s what Ben Krasnow has to say about x-rays (from his blog): “AdShea, you are right, decelerating electrons will cause X-rays to be generated. However, my accelerating voltage is 6KV, so the resulting X-ray wavelength is very long and will not penetrate matter very far (like a couple micrometers). Even the aluminum and glass of the chamber will contain all traces of the X-rays. This is why older black-and-white TV sets (and oscilloscopes) did not need thick leaded glass — their acceleration voltage was under 10KV, and only produced soft X-rays. Color TVs needed higher acceleration voltages 25-35KV, and would produce penetrating X-rays, thus necessitating the thick leaded glass shield.”
That man is true mad scientist!
Hi
Excellent and really ambitious project. Are thos spark plug insulators on the base of the contraption?
Nick