Joints and magnetics · Banned
Zinc, and therefore brass
Znvalues describe: brass C36000
Why it's out
Vapor pressure reaches the 1e-7 mbar range near bake temperatures: it metallizes the system and poisons cathodes and optics.
Where it hides
Brass fittings smuggled in from plumbing suppliers; galvanized fasteners.
Properties
The values below are candidate: compiled from the sources named, not yet individually validated. Provisional provenance: Honig vapour pressure tables, RCA 1969; O'Hanlon, A User's Guide to Vacuum Technology.
Wet cleaning
| Recipe | not applicable |
|---|---|
| Forbidden | the material itself |
| Limit | vapour pressure |
Vacuum and outgassing
| Vapour pressure | THE CONDEMNING NUMBER: Zn reaches 1e-6 Torr vapour pressure near 250 °C, so it evaporates during a routine bakeout and plates itself onto everything colder |
|---|
Thermal
| CTE | 20.5 ppm/K |
|---|---|
| Thermal conductivity | 120 W/m·K |
| Specific heat | 380 J/kg·K |
| Melting / softening | 900–940 °C |
Mechanical
| Young's modulus | 100 GPa |
|---|---|
| Density | 8.5 g/cm3 |
Electrical and magnetic
| Relative permeability | ~1.0 |
|---|---|
| Resistivity | 6.4 µΩ·cm |
Engineering
| Availability and cost | everywhere, which is the danger |
|---|
Outgassing
2 sourced measurements for this card. A rate means nothing without the pumping time it was read at, so each one states it or declares it missing. The whole base, filters included, is at /tools/outgassing/.
Signature: 1e-6 unbaked to no baked reading baked.
| Material as published | Species | State | Pumping time | Rate |
|---|---|---|---|---|
| Brass (wave-guide) | total | unbaked | the abscissa of the curve below | 5.33e-7 at 1 h to 1.33e-8 at 10 h |
| Zinc | total | unbaked | the abscissa of the curve below | 2.95e-7 at 1 h to 4.29e-8 at 10 h |
Sources: S-ELSEY-1975-II. Full citations and conditions at the base and in /data/outgassing.json.
Sources · 2
- Honig vapor pressure tables, RCA 1969
- O Hanlon, A Users Guide to Vacuum Technology