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7

Try a styrofoam cooler: They're about $5 at Walmart. Your homemade dewars should fit easily inside and should be reasonably sealed from atmosphere. We used to use this in my Senior Lab in undergrad to freeze samples overnight, there was always plenty left in the morning, so I imagine that the combination should get you near that 3 day mark.


6

As an "infrared survey technician" part of my job was keeping our infrared camera topped off with liquid nitrogen. We had a large dewar (about the size of a barrel) at the shop that was filled bi-weekly. For daily excursions we used a smaller dewar (about the size of a pony keg). Both of these dewars were specifically designed to contain cryogenic liquids, ...


5

This should be a comment as I'm not knowledgeable about the LHC refrigeration, but it's too long for a comment and I can hazard a pretty good guess. Sheer heat capacity likely accounts for a great deal of this time. Assuming the total amount of kit that needs to be cooled is, say $2\times10^4$ tonnes, and if it has roughly a $1{\rm kJ K^{-1} kg^{-1}}$ heat ...


3

Just spit-balling as I have never tried this. Use the best dewar(s) you can find. Silvered glass walls and a vacuum gap. Assuming you can take as much LN2 as you want, use the biggest dewar(s) you can find. Not only is there more there, but the surface area to volume ratio works in your favor. Keep the dewar(s) in a cool, enclosed place. You'd like them to ...


2

This answer is only an order of magnitude estimation. The main uncertainty comes from the fact that for a constant current the cooling power is not determined by the superconducting wire but from the quality of the isolation against radiation, convection and conduction of warmer parts of the structure to the cold wire at 4.2K We can use the LHC ring as an ...


2

If this case is still open, here are a couple of options. Both PRT-100 and thermocouples are feasible solutions. If using a thermocouple, E type has the highest sensitivity at cryogenic temperatures (even down till 40 K, LN2 is 77 K as you know). However as pointed out above, thermocouples generate very low voltage and this output signal is prone to EM ...


2

You ether can take usual K-type thermocouple (like in multimeters), and calibrate it - it supposed to work fine in LN2. I personally tried that with DMM and it worked (though showed large error). Multimeters use simplified conversion formulas and could give huge errors at cryogenic temperatures - so remember that you ether need table-based conversion, or ...


1

Your chamber's thermal cycling environment is indeed "very demanding". You have my sympathy... From O'Hanlon's A User's Guide to Vacuum Technology, Chapter 17, Joints, Seals and Components: Welds: It is important to make the weld on the surface which will be exposed to vacuum. If the weld is made on the atmospheric surface, a gap may be created which ...



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