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Questions tagged [cryogenics]

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

The word 'cryogenics' means generation of extremely cold temperatures. In technical terms it is the branch of refrigeration that deals with temperatures below 123 K or -150 degree C. The subject focuses on various methods of generating and sustaining low temperatures, their usage in gas liquefaction and storage, vacuum science and technology, superconductivity, low temperature material science, space simulation chambers, low temperature measurement techniques, etc. More can be learnt about cryogenics by visiting

1) http://eng.fsu.edu/cryolab

2) http://nptel.iitm.ac.in/courses/112101004/

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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 objects to absolute zero, the temperature at which…
Sasha
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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 vacuum bottles, added ~1 cm of extra insulation…
BarsMonster
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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, all random movements of the atom stop? Shouldn't…
AmeyaS
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Minimal temperature achievable by vanilla Peltier element?

I wonder, are there any fundamental issues leading to reduced performance of Peltier elements at cryogenic temperatures (-100C and lower)? What is theoretical/practical minimum temperature achievable by a cascade of Peltier elements, provided that…
BarsMonster
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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 test masses are 40 kg fused silica mirrors that…
mmesser314
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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 this an interesting physics question I ask: how is…
DanielSank
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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 40 K and did temperature-dependent measurements…
Martin Ueding
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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. First of all, can ordinary NTC thermistors be used at…
Dov
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Is the zero-point energy of helium stronger than other liquids to disfavour freezing?

Under normal atmospheric pressures, liquid helium does not freeze even when cooled very close to absolute zero. This is attributed to the uncertainty principle or due to zero-point energy. But the quantum uncertainty or zero-point energy is not an…
Solidification
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High pressure cryonics

In this link, it is suggested to use high-pressure cryonics to freeze living cells, tissues or small organism as opposed to various and potentially toxic anti-freeze agent. The core idea is that over a certain pressure, ice is anamorphic and will…
Anon21
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What is the absorption spectrum of liquid nitrogen?

I know that even pure water absorbs some visible light enough to be noticeable over short distances. According to the file File:Absorption spectrum of liquid water.png, the the wavelength of visible light with the lowest absorptivity is 500 nm at…
Timothy
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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 refrigerators (most economical) do I need to purchase…
gpuguy
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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 to prevent stress, very low temperature deltas,…
electroCutie
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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 currently redesigning this flange, but there is…
Martin J.H.
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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 will launch itself into orbit. The question is…
Ron Maimon
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