Tagged Questions

concerned with temperatures below 123 K (-150 deg C), widespread usage in gas liquefaction and storage, vacuum science and supercondcutivity

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5
votes
1answer
121 views

How can I make a dry dilution refrigerator quiet?

The pulse tubes are really loud. We've wrapped the helium lines in sound absorbing foam, and we have a cage around the top of the cryostat also lined with foam, but it's still pretty loud. Are there ...
1
vote
0answers
32 views

Cost vs. purity producing liquid oxygen [closed]

We are a group of rocket amatures who build rockets using LOX and ethanol as propellent. We normally buy the LOX from supplier. But lately we have been discussing if there is an easy way to produce it ...
4
votes
3answers
276 views

Can any gas be liquidified by lowering the temperature?

Can any gas be liquidified by lowering the temperature? What happens with gases at absolute zero? Are there gases that remain gases at absolute zero? Do their molecules move at these temperatures? ...
4
votes
5answers
298 views

Economical ways for Cooling liquid nitrogen

To have some fun with superconductors I am planning to buy them from here. But it requires me to cool liquid nitrogen to a temperature of 77 degrees Kelvin. Can some one tell me what kind of ...
1
vote
0answers
46 views

Help wanted achieving cryogenic temperatures [closed]

My son's science project involves liquifying air. I found the Linde process which is the way it was done first. We are trying and not getting very far so I am looking for advice. I have an air ...
4
votes
1answer
137 views

Why 1 Month LHC Magnet Cooling Times

An often quoted figure is that the LHC magnets take a month to completely cool and a month to warm. There is never an explanation as to why that is. I can conjure any number of reasons (slow changes ...
1
vote
1answer
79 views

Conductive glue

I would like to use some conductive glue to contact a silicon chip's back gate. Any suggestions on what to use? Can I use thermal silver paste? I would be operating at cryogenic temperatures below 4K. ...
5
votes
1answer
244 views

Why does the conductivity $\sigma$ decrease with the temperature $T$ in a semi-conductor?

We performed an undergrad experiment where we looked at the resistance $\rho$ and Hall constant $R_\text H$ of a doped InAs semiconductor with the van der Pauw method. Then we cooled it down to around ...
3
votes
2answers
278 views

Measuring Cryogenic Temperatures

I need an inexpensive instrument to measure cryogenic temperatures (down to -200C). I can build a thermistor-based thermometer using an Arduino that is accurate to under 1 degree for 0 to 100C. ...
4
votes
2answers
192 views

From which side should I solder electrical feedthroughs into a vacuum flange?

I work on an experiment that requires electrical connections to a vacuum vessel, which is submerged in liquid helium (LHe). For sending the signals into the vessel, we use a feedthrough flange. I am ...
11
votes
3answers
3k views

How to prolong life of liquid nitrogen in hosehold vacuum flask?

I need to do some work with liquid nitrogen at home. The main question is how to store it without buying huge vacuum flask specifically for liquid nitrogen. I've tried to use usual steel household ...
1
vote
0answers
64 views

1 Mohm Resistivity at cryogenic temperature for doped silicon

I would like to pick the correct doping of silicon to get 1 Mohm cm resistivity at liquid helium temperature of 4.2 K. The metal insulator transition implies that I need a very accurate doping. Are ...
1
vote
1answer
298 views

Does a Peltier Thermoelectric layer make a good regulator for LN2 heat-sink interfacing

I understand that when cooling water with LN2 directly (through pipes for example), that it can be too effective, freezing the water (and blocking the pipe). From what I read, regulation of the heat ...
4
votes
1answer
150 views

What is the smallest amount of He you can use to cool a superconducting magnet?

This is an engineering question, but it is adressed to physicists who build accelerators. This question: An electromagnetic space elevator? notices that a NbSn superconducting ring around the equator ...