This is a continuation of last time’s discussion on Electron Microscopy. In that one, we covered the question of why you’d want one of these and gave a summary of how you’d work one. Take some electrons, throw it at your sample, and watch what bounces off for information. Sounds so simple when we put it that way, right? This week we’re talking about what happens when you actually buckle down to do it in practice.

Okay, just looking at the thing isn’t doing me much good. What’s going on there, and why? Start from the top. That bottle on the left? That’s for liquid nitrogen, used in the x-ray detector. (Neat! Why do we want to detect x-rays? That’s a subject for a future column.) The cylinder on top marked “GEMINI” is your column; the electron gun is in the top, and the rest of it contains the magnets for focusing and directing the electron beam. The cube-ish box it’s sitting on is your sample chamber; the front pulls out to reveal the stage where you’d put your puck holding the samples. The dark grey table surface is granite, used to lend stability to the whole apparatus. The cabinet it’s sitting on contains electronics and the vacuum pumps. Now let’s get to how all that works together.