(Specific) Heat capacity of brass at milliKelvin temperatures

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Hi all,

I do an calorimeter experiment at temperatures around 40 mK. To get more grip on the time constants that are associated with the heat flows, I calculate the thermal resistance as well as the heat capitance of the materials in the set-up.

We assume that Newton's law of cooling is the only relevant process, as the compartiments of the cryostat are all in a vacuum (no convection) and the nearest plate from the dilution refrigerator (14 mK) has a temperature of 50 mK (so the importance of radiative heat transfer is negligible).

My question is: what is Cbrass @ mK temperatures? I can't find it anywhere.

Let's assume that I use the common 70/30 brass. I found somewhere (lost the link) that

Cbrass = 3*10^-2 J / (Kg*K) at T = 1 K.

This is somewhat comparable to that of copper, as

CCu = 1.3*10^-2 J / (Kg*K) at T = 1 K.

However, the experiments for copper are done for the submillikelvin temperatures, which yield

CCu = 6*10^-4 J / (Kg*K) at T = 40 mK, (Fig. 3.12 from 'Matter and Methods at Low Temperatures by Pobel).

There, on a log(C)-log(T) scale, almost all curves decrease in a linear way. Should I assume that this is also the case for Cbrass to extrapolate to T = 40 mK? With a slope that is comparable to that of the heat capacity of copper? I probably make a lot of mistakes then, but it would give me

Cbrass = 1.4*10^-3 J / (Kg*K) at T = 40 mK.

Your help is much appreciated!

Xavier
 
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  • #2
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A clue about the heat capacity of any type of brass is good, although I assumed the most common type of brass (Cu with 30 or 37% Zinc).
 
  • #4
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Having absolutely zero experience at anything less than 20 K, my input doesn't count for a whole lot. I'm not aware of any pathological behavior of any of the brasses, but there're no guarantees that niobium-tin type phenomena don't occur. i.e., for estimating properties/behavior of your calorimeter, what you've proposed sounds good.
 
  • #5
Perhaps anyone else?
 
  • #6
Lord Jestocost
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There are some papers by "J. A. Rayne" on the "heat capacity" of "brasses" (GoogleScholar).
 

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