SDN0013-01

SDN013.01 – Density of GNIRS Materials
Revision A

1. Introduction

Densities are tabulated for room temperature. Because all the materials listed contract at lower temperatures, typically by 0.2-0.4% in linear dimension at 60K, densities at operating temperatures will be ~1% higher – but of course the mass of a given part or element will be unchanged.

2. Tabulation

Material	Density (g/cm³)
6061 T651 Al	2.70
OFHC Cu	8.94
G-10CR (glass fiber/epoxy, cryo grade)	1.75-1.90
302 stainless steel	7.92
304 stainless steel	7.93
440 stainless steel	7.67
Vespel SP3	1.60
tungsten carbide	15.0 (varies w/ Co)
BaF₂	4.89
CaF₂	3.18
MgF₂	3.18
Schott SF6 glass	5.18
Schott SF57 glass	5.51
Schott BK7 glass	2.51

3. Sources and Discussion

The temperature at which the density was measured is usually not specified, and so could plausibly be anywhere from 273K to 298K. Over this range volumes will vary by 0.15% for a CTE of 20 ppm/K, so one should not have a lot of faith in any third decimals.

Most of the structural material densities were originally given as lb/in³, which convert to cgs units by multiplying by 27.68 . Such values were usually tabulated to the nearest 0.001 lb/in³, which translates into the nearest 0.03 g/cm³.

Densities for optical materials were taken from manufacturers (Schott for glasses, various for the fluorides). Densities for structural materials were taken from a tabulation by Earl Pearson, which was checked (partially) against data from manufacturers.

It should be noted that the density of 6061 aluminum was only quoted to 0.01 g/cm³, so the uncertainty is presumably as large as 0.005 g/cm³ – which is equivalent to an uncertainty in the instrument weight of almost 4 kg.

4. Revisions

Revision A, 10/07/99 – Added materials, added density r