# (Specific) Heat capacity of brass at milliKelvin temperatures

• A

## Main Question or Discussion Point

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.

Xavier

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Bystander
Homework Helper
Gold Member
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).

Bystander
Homework Helper
Gold Member
A clue
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.

Perhaps anyone else?

Lord Jestocost
Gold Member
There are some papers by "J. A. Rayne" on the "heat capacity" of "brasses" (GoogleScholar).

• xavier_Ghz