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Comment by wohlergehen | Hacker News Reader

Does anyone know why these apparatuses are usually "inverted", i.e. hang from the ceiling. I've seen the same thing for quantum computers. Is it related to the way they are cooled? Or is it easier to work with somehow?

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The entire apparatus sits in a cryostat (a fancy Thermos bottle) which is filled with liquid helium. In general, one supports things in liquid baths from above.

Swinging wild-ass guess - it might because it makes it easier to damp the equipment against vibrations.

The STM in a surface chemistry lab I worked in for a while was inside a box, and hanging from the roof of the box. By choosing appropriate springs to hang the sensitive bits from and sound proofing the box, it could adequately isolate the scanning table from its environment.

I'm sharing this prior to reading it:

https://en.m.wikipedia.org/wiki/Dilution_refrigerator

The Germans working on the same problem are running at 100 mK aka 0.1 K, so pretty chilly yes

http://iopscience.iop.org/article/10.1088/1681-7575/54/1/S1/...

Thank you for sharing.

I've started searching for "dilution refrigerator" and found this video, explaining a little bit how ³He–⁴He mixture cooling works and what the applications are. I think the video also helps putting the Wikipedia article in a perspective and vice versa.

Quantum Cooling to (Near) Absolute Zero (2013): https://www.youtube.com/watch?v=7jT5rbE69ho

It's because in a dilution refrigerator, the bottom of the dilution unit gets cold. So its easier to put the coldest part at the bottom.

One thing that I know is that it is easier to dump vibrations by hanging your device with springs than by supporting it above springs.

But I don't think this is relevant here.

EDIT: Yeah, pohl answered it. Vibrations are not relevant.

If you read the article he posted the cooling mechanism is very susceptible to vibrations, which is why they suspend it.

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