# What is Low temperature: Definition and 27 Discussions

In physics, cryogenics is the production and behaviour of materials at very low temperatures.
The 13th IIR International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of “cryogenics” and “cryogenic” by accepting a threshold of 120 K (or –153 °C) to distinguish these terms from the conventional refrigeration. This is a logical dividing line, since the normal boiling points of the so-called permanent gases (such as helium, hydrogen, neon, nitrogen, oxygen, and normal air) lie below −120 °C while the Freon refrigerants, hydrocarbons, and other common refrigerants have boiling points above −120 °C. The U.S. National Institute of Standards and Technology considers the field of cryogenics as that involving temperatures below −180 °C (93 K; −292 °F).
Discovery of superconducting materials with critical temperatures significantly above the boiling point of liquid nitrogen has provided new interest in reliable, low cost methods of producing high temperature cryogenic refrigeration. The term "high temperature cryogenic" describes temperatures ranging from above the boiling point of liquid nitrogen, −195.79 °C (77.36 K; −320.42 °F), up to −50 °C (223 K; −58 °F).Cryogenicists use the Kelvin or Rankine temperature scale, both of which measure from absolute zero, rather than more usual scales such as Celsius which measures from the freezing point of water at sea level or Fahrenheit with its zero at an arbitrary temperature.

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1. ### A Why low temperature is better in many precision experiments?

Hello! In many precision experiment, especially those overlapping with quantum computing techniques, such as trapping a few ions in a Paul trap, they use cryogenic systems (around 1K). I am not totally sure I fully understand the advantage of that, compared to room temperature. For example, a...
2. ### Heat Capacity of a Fermi Gas at Low Temperature

I find that $$U=\int Z \epsilon D(\epsilon) e^{-\epsilon β}d\epsilon=\frac{gV}{(2\pi)^3}\int Z \frac{(\hbar)^2k^2}{2m}k^2 (4\pi)e^{-β\frac{(\hbar)^2k^2}{2m}}dk$$ where g=2s+1=2, $$Z=e^{βµ}$$ and $$D(\epsilon)=\frac{gV}{(2\pi)^3}k^2 4\pi$$ for the density of states From here, I can use c_v...
3. ### How to calculate the thickness of a wall of a dewar?

Hello, i am trying to design a dewar for experiments at very low temperature. Unfortunately i do not know how to calculate the wall thickness. I can calculate the heat flow through the wall, but i do not know what to do further. Do someone know how to calcualte the thickness of the wall for a...
4. ### A What is best way to start learning DMRG for Fermions?

I want to learn the density matrix renormalization group (DMRG) method in traditional formalism (not MPS). While there are many good introductory level articles available for bosonic (and spin) systems, I have not encountered any introductory level article which deals with fermionic systems i.e...
5. ### I Can We Cool a Macroscopic Crystal to 1 nK?

Is it theoretically possible to cool a macroscopic crystal (for example NaCl 1×1×1 cm) to an extremely low temperature, like 1 nK? Will it retain its microscopic structure? Why? Does it have anything to do with zero point energy (I mean something like the lowest energy level of a quantum...
6. ### Low temperature production with compressed air

Suppose, there are two cylinders of compressed gas, say air. Both are at same temperature and pressure and the amount too is same. Now, contents of both are released but in a different way. One has been released directly and the other has been released through compressed air turbine having a...
7. ### Specific heat capacity of a metal at low temperature

Homework Statement The specific heat capacity of a metal at low temperature (T) is given as ##C_p = 32\left({\dfrac{T}{400}}\right)^3## (kJK-1kg-1). A 100g vessel of this metal is to be cooled from 20 K to 4 K by a special refrigerator operating at room temperature (27°C). The amount of work...
8. ### Insights High Temperature Low Temperature Duality for the Ising Model on an Infinite Regular Tree - Comments

domainwhale submitted a new PF Insights post High Temperature Low Temperature Duality for the Ising Model on an Infinite Regular Tree Continue reading the Original PF Insights Post.
9. ### What are the conditions to excite an atom by collision?

I know that an atom can become excited in one of two ways: by absorbing some energy from a source of electromagnetic radiation or by colliding with some other particle—another atom, for example, but my question is about the second part. So I want to know how and in what conditions (pressure...
10. ### Does alkali metals burned at very low temperature in air?

And does rubidium ignite spontaneity in air...in powder phase or small piece of metal.
11. ### Low temperature physics dangerous?

Could temperatures at a fraction of a kelvin be dangerous? We have only naturally observed temperatures of 1k But in a lab they did 100pk
12. ### Chip carriers and sockets for low temperature

I'm looking for chip carriers and sockets that will work well down to 4 K. Most aren't rated below -70 C, but I know in the past I've seen sets used down to 1.6 K. (Wish I could remember what they were!) Does anyone have specific recommendations? Or general advice, plastic vs ceramic, etc...
13. ### Velocity Distribution function of molecule at low temperature

Dear all, In classical molecular dynamics simulation initial velocities are generated using the so called Maxwell distribution. At low temperature it's no longer effective, so I'm wandering whether there is a similar way to generate velocities at low temperature taking into account quantum...
14. ### Low Temperature Plasma: Limits & Possibilities

What is the lowest temperature plasma we can make? What substance is it.. what is the temperature it becomes a plasma (ions brake loose (?)) ? And what is the theoretical minimum - or even is there a limit? From what I know it depends on how strong the bounds are and how well the electrons are...
15. ### Band diagram of pn-junction diode at low temperature

Hi What could be the band diagram of pn-junction diode at very low temperature where dopant ionzation is completely frozen out? Would it still be like the band diagram at room temperature?
16. ### Low temperature around body's extremities

Hi Please remember that I'm not asking you for a diagnosis. My hands and feet are generally at low temperature than the overall temperature even when I'm wearing gloves or socks, or when in bed. Otherwise, I'm a healthy person. What could be the reason for this? Does genetics have anything...
17. ### How to prevent diesel fuel from gelling at low temperatures?

Low Temperature Diesel Fuel (urgent) I'm having a problem with diesel fuel at the moment and would greatly appreciate insight into the subject. I'm currently stranded in Colorado where it's somewhere like -10 degrees (F) and our diesel truck isn't starting. I've narrowed down the problem to...
18. ### Does low temperature effect bonding?

Are elements able to form a wider variety of molecules at lower temperatures vs say 20oC?
19. ### Low temperature LCC chip carrier

I need a LCC for low temperature measurement down to 10K or at least 77K. but I couldn't find any LCC capable of operating at that low temp. most commercially available LLC can only operate -70C. how you guys find a LCC operating below 77K? is it custom made?
20. ### Multiplicity of a Einstein Solid, Low Temperature Limit

Homework Statement (a) The formula for the multiplicity of an Einstein solid in the “high-temperature” limit, q >> N, was derived in one of the lectures. Use the same methods to show that the multiplicity of an Einstein solid in the “low-temperature” limit, q << N, is Ω(N,q)=(eN/q)^q...
21. ### Heat up water with low temperature steam

Homework Statement - Is it possible to heat up water from 50 °C to 100 °C with saturated steam of 30 °C? - If my hand is at 37 °C, is this 30 °C steam hot or cold when I touch it? Homework Equations Steam tables. The Attempt at a Solution I'm a bit confused here because there...
22. ### What is considered low temperature in Debye/Einstein theories?

Hi, This may seem basic bit but it is causing me a little confusion, any help would be appreseated. In theories such as Debye / Einstein it is stated that it this is true for low temperatures, coudl someone tell me what sort of temerautres they acutally mean by this? do they mean low as in...
23. ### Low Temperature Expansion of Chemical Potential

I'm trying to derive a low temperature series expansion for the chemical potential of a weakly interacting Fermi gas. The starting point is, of course, the Fermi-Dirac distribution function (p is the particle momentum): f(p) = \frac{1}{e^{\beta(\epsilon(p) - \mu)}+1} , where, in the...
24. ### Diesel Fuel Viscosity at Low Temperature

I need to do some head loss calculations for pumping diesel fuel or No. 2 fuel oil from a storage tank to an emergency generator. I see in many places that diesel fuel is specified to have kinematic viscosities of 1.3 to 4.1 cSt at 40C. However, under worst case scenarios, this fuel is likely...
25. ### A low temperature flame that melts carbon?

A low temperature flame that melts carbon?? I saw this on television the other day. I have no idea how it works. It sound promising but so have a lot of other things in the past. There is a clickable news video in the link. http://freeenergynews.com/Directory/RhodesGas/index.html
26. ### How Can Low Temperature Systems Be Used to Measure Thermal Properties?

This is my solid state physics report questions but I think it's related to thermodynamics or something. I have never taken a course in that respect and I have no clue:frown: . Please tell me what books or websites I can look for the answer. THX! 1. Lattice heat capacity Debye T3 law is valid...
27. ### Einstein Cycle: Analysis of Low Temperature Refrigeration Performance

I'm sure most of you have heard of the Einstein Referigeration Cycle . For those who have not I've listed the references for further reading.. http://www.me.gatech.edu/energy/pubs/SLA_2.pdf ok 342 K is about 156 F ,for anyone with an attic , it seems to me that this is the perfect solution to...