Questions tagged [cryogenics]

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

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37 views

Do metallic meshes work in practice as thermal radiation shields?

The other day I was thinking about the wire mesh cover used in microwaves to keep the microwave radiation inside cooking your food. The idea is that the spacing of the mesh is much smaller than the ...
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1answer
35 views

How do we cool gases to the $mK$ range?

When we set new records for coldest temperature in the universe, we usually do it with gases (see: https://physicsworld.com/a/millikelvin-cooling-of-large-molecules-is-no-myth/) How do we pull this ...
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1answer
53 views

Greatest volumetric heat capacity at very low temperatures

There is a theoretical device that I want to keep at a temperature of 3 K using a liquid helium coolant loop, and a block of material as heat sink, initially at 0.1 K. The main limitation is the ...
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1answer
35 views

What are the differences between anything at just above absolute zero and something just above the event horizon?

I believe an item that has a half-life would decay at the same rate regardless of temperature (maybe I am wrong on this assumption) but it would definitely slow down due to time dilation above an ...
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38 views

How cold does Something need to be for String Theory to be relevant?

I’ve often read casually that in order for modern string theory and other competing quantum gravity theories to be tested absolutely enormous temperatures (or rather energy densities) are required. ...
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1answer
90 views

Is it possible to build a “DIY” quantum memory?

I am currently working on a home project which is a computer which will be capable of doing basic quantum computations (my first goal is a random-number generator) based on optical devices. Nowadays I ...
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2answers
138 views

How much energy needed to liquify H?

I want to know how much pounds (or the correct measure) would an air compressor need to liquify Hydrogen As its boiling point is somewhat close to -250°C i want to know how to calculate the pressure ...
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1answer
147 views

Does the uncertainty principle for energy and time prove it is impossible to reach absolute zero? [duplicate]

I have long wondered why nobody seems to think that this form of the uncertainty principle proves it impossible to reach absolute zero. I noticed that there is a proof suggesting it requires infinite ...
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97 views

How well do magnets work in zero kelvin?

I have read about zero-point energy, this means - alongside Heisenberg's uncertainty principle - that electrons can never be completely motionless. Therefore, since magnet strength is proportional to ...
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1answer
622 views

Gas at absolute zero

According to Charles's Law, the volume of gas is proportional to temperate at constant pressure. So, the volume of a gas decreases as temperature decreases. Then, in theory, as the temperature ...
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0answers
135 views

Would cooling matter and antimatter to as close to Absolute Zero as possible allow them to coexist?

I was reading about Bose-Einstein condensates and how they affect matter and energy, and I wondered if "draining" that amount of energy from an atom of hydrogen and positronium would potentially allow ...
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2answers
5k views

Did NIST fudge this news story about absolute zero?

This press release by NIST, titled "NIST Physicists ‘Squeeze’ Light to Cool Microscopic Drum Below Quantum Limit", makes the following claim: The new technique theoretically could be used to cool ...
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1answer
139 views

How did we know that everything had to stop at the absolute zero

The absolute zero is the temperature at which basically even atoms stop moving ( of course I know the enthalpy and entropy version of this but that is not what we are concerned with). Everyone would ...
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279 views

How to achieve temperature below absolute zero?

Firstly i am not a physicist, so kindly go easy on me. So i grew up believing that absolute zero is the bottom of temperature chart. Recently i read that scientist achieved the feat of going below ...
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4answers
208 views

Measuring very small temperature differences

Can one use a thermometer with $\pm$5 mK accuracy to measure a temperature difference of 2 mK (the measurement is near 100 mK temperature on a sample on an ADR)? Using the same thermometer, I am ...
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29 views

Should I continue pumping the bolometer overnight?

It's getting late in the lab and I want to head home as fast as I can. The only problem is, that there's a far-infrared bolometer operating at a temperature of 1.8K. This low temperature is attained ...
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1answer
106 views

How much helium will there eventualy be in the insulating vacuum space of a helium dewar

If we were to start with a good vacuum in a dewar that was used to hold helium and the helium diffused in slowly and out to the atmosphere from the outer container wall. What would the equilibrium '...
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1answer
3k views

Why doesn't Helium freeze at 0K?

I have read that Helium does not freeze at absolute zero under normal pressures. How could this be possible given that the absolute zero is the lowest attainable temperature and at that temperature, ...
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2answers
116 views

Could superconducting magnets be used to form a shield around a spacecraft?

If superconducting magnets could be used in space to form a field around a spacecraft of a similar field strength on the earth 25 to 65 microtesla's? Would the temperature in space at -246c be OK for ...
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555 views

How are LIGO mirrors cooled?

The recent LIGO announcement Observation of Gravitational Waves from a Binary Black Hole Merger has some technical details about LIGO. For example, LIGO is a modified Michelson interferometer. The ...
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1answer
178 views

Cryogenic (LN2) gas vs liquid for cooling

For cooling, would you recommend using gas over liquid or vice-versa? What is the temperature differential between gas and liquid? In other words, at standard volumes and pressures from a gas ...
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1answer
2k views

A “bump” in the cooling curve of naphthalene? [closed]

While doing an experiment, I noticed a slight bump in the cooling curve. I have searched for it on the internet and all of the articles say that it is something related to super-cooling. The graph's ...
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40 views

Is lossless storage of cryo liquids practically possible due to pressure?

All cryogenic liquid storage tanks I've seen in labs are equipped with pressure relief valves, which will eventually vent all of the liquid when the tank is stored at room temperature. I am wondering ...
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90 views

Question about Meissner Effect video

In this video, what material is on top of the superconductor disk that keeping it cold? Is it just a circular chunk of dry ice? http://www.youtube.com/watch?v=Ws6AAhTw7RA I'm planning on recreating ...
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1answer
44 views

How does a liquefied gas work as a coolant?

What makes liquefied Helium a better coolant than other liquefied gases (like Nitrogen, for example)? Is it because it has a lower boiling point (in which case, will it cool any substance it's in ...
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1answer
45 views

Cryogenic Conductivity of a Defective Semiconductor

If I have a semiconductor with a lot of defects what happens to its conductivity at at mK type temperatures? I'm expecting that defects would give rise to greater conductivity than for a perfect ...
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4answers
1k views

What happens when I place an object of certain temperature in space ? Does it loose its entire heat energy?

Can i obtain absolute zero temperature this way? And let's assume there is no cosmic microwave background and also assume that there is a way to shield the object from any heat source, such as the ...
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392 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. To make ...
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3answers
1k 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? ...
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5answers
594 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 ...
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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 ...
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1answer
226 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 ...
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1answer
310 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.
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629 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 ...
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2k 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. ...
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2answers
569 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 ...
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4answers
24k 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 ...
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1answer
915 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 ...
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243 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 ...