@AlphaPhoenixChannel

1 year ago

Hey everybody! comments, corrections, and FAQs here: 1) Go check out reddit.com/r/trytryagain, there are a bunch of posts now and it's great! 2) Thanks to Kunal and Aidan for previewing this video and making sure I wasn't too egregiously wrong in my explanations! Kunal wanted to add that for TEM and STEM imaging, the vast majority of the time the sample isn't pointed "at the beam" - normally it's at a wonky angle to produce very specific diffraction effects. This lets us do some cool things, like look at strain fields from dislocations, but I didn't do that in this video. Also because of diffraction effects, by the time you've zoomed all the way into atoms, the "shadow" analogy is actually pretty terrible, and image formation is complicated (hence switching to STEM). Aidan had some comments on STEM-vs-TEM, notably that despite the beam paths being completely different, they actually DO interact with the sample in largely the same way and produce similar contrast when you aren't at atomic resolution. When I said they were mechanistically completely different, that was accurate from the perspective of the mechanics of the microscope being different, but the beam-sample interaction physics is EXTREMELY similar. 2 (TLDR) I swept a lot under the rug in order to focus exclusively on atomic-resolution microscopy - Diffraction and strain contrast microscopy is arguably a lot more important, certainly more common, but also a LOT more complicated. 3) I've got t-shirts for sale! If you ever wanted to have a t-shirt with a giant red flaming alpha on the front - NOW YOU CAN… alphaphoenix.creator-spring.com/ 4) If anybody's super-curious, here's the paper we published: doi: pubs.acs.org/doi/10.1021/acs.cgd.2c00188 unfortunately it's not on SciHub yet, but if you check back in a couple days I should have a link to the manuscript available! 5) I’ve had a lot of people ask about the drift - yes the sample is rigidly mounted, and yes the beam keeps pointing in the same direction, but when was the last time you tried to hold something so still that it didn’t move by an atom? Thermal expansion and contraction is actually a huge problem - if the sample stage is warmer than the microscope, when you load it in, the arm that holds the sample is going to cool down and contract - super slowly - for a couple hours minimum, and that’s enough to ruin long exposure pictures with crazy rolling shutter artifacts. 6) a few people have mentioned the mask and while I think most of these commenters are just being irritants because they can, it actually brings up a very interesting point about these scopes. To reduce noise, vibration, and changes in temperature, the room that houses this microscope is designed to have almost zero air changeover. This is fantastic for consistent microscope operation, but real bad to leave an airborne virus in a room and have somebody else walk into the same air a few minutes later. 7) I did some math and changed the title from 10000000x magnification to 50000000x magnification (eh - same order of magnitude). magnification is very poorly-defined because it technically depends on the viewing screen. There IS a "standard" display size from when all TEM images were published on paper in the same journal format, but I don't remember the size, so I took one of the shots where I was focusing with a field of view of a little over 4 nanometers and assumed it was 8-10 inches tall on the monitor, then rounded nicely. according to the manufacturer's site, the magnification goes up to 230M - again, not sure what the intended display size is. I wonder if they ship computer monitors with the microscope??? 8) I'm sure there are more things wrong or fuzzy so complain away and I'll add notes here!

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