- E143 tech note about the NH3/ND3 density measurement at LN2 temperature. I added at the end two E143 collaboration meetings slides showing the extrapolation to 1K and a sketch of the apparatus.
- spreadsheet for calculating the target radiation length listing the four densities for {14}^NH_3, {15}^NH_3, {14}^ND_3 and {15}^ND_3 at 1K. Related quantities for all other materials in the targets are also listed. It's an old eXcel version, but opens fine in new versions, or in open source software (LibreOffice, openOffice).
To save users the trouble of having to open the file to just find the numbers here they are [g/cm^3}:
15NH3 0.918
15ND3 1.057
14NH3 0.867
14ND3 1.007
The density of ammonia is ~0.817 g/cm3 at 193 K, from X-ray diffraction measurements. [1] There have been lower temperature measurements of the density although these measurements were on thin films μm’s thick. I’ve plotted a few, see graph. One thing to note is that Ammonia when deposited at low temperatures, >50 K, is amorphous and the density is decreased with temperature. It has also been shown that when these cold deposited films of ammonia are annealed above 57 K they restructure into FCC crystalline solids. Our ammonia should be polycrystalline due to the freezing process, handling, and storage. When deposited above this phase transition temperature the density is relatively constant. Additionally the thermal contraction of solids tend to level off at temperatures below 100K. Using a linear fit for the densities measured at 60 K and above suggests the density at 1 K would be ~ 0.9125 g/cm3, assuming linear contraction, OR averaging 0.864 g/cm3. I didn’t find much on deuterated ammonia, but I would assume the same chemical behavior with the density adjusted for the mass of the isotopes, but then the question is how much deuterium is actually there? This is what I’ve found and my thoughts on estimating the density. I would be curious if you see any change in the density over time while on the same ammonia cell or after an anneal and repacking (the martini shaker).
[1] Blum, A. (1975). On crystalline character of transparent solid ammonia. Radiation Effects, 24(4), 277–279. https://doi.org/10.1080/00337577508240819
