Joints and magnetics · Workhorse
Indium
Invalues describe: 99.99 % wire
Why it wins
Stays soft and seals at 4 K where every elastomer is glass; also the stress-relief interlayer between metal clamps and fragile optics through bake cycles.
Why not the alternative
Viton is dead below about minus 20 C; copper knife edges need force that windows cannot take.
Watch out
Melts at 157 C: no bake; creeps; alloys with gold on contact.
Properties
The values below are candidate: compiled from the sources named, not yet individually validated. Provisional provenance: O'Hanlon, A User's Guide to Vacuum Technology; NIST cryogenic material properties database.
Wet cleaning
| Recipe | wipe the sealing faces with IPA; use the wire straight from its packet |
|---|---|
| Forbidden | touching the wire: skin oils and oxide are what ruin the seal |
| Limit | the fresh cut surface is the seal, so handling is the cleaning |
Vacuum and outgassing
| Outgassing, unbaked (10 h) | 1e-8 mbar·L/s/cm² |
|---|---|
| Outgassing, baked | not bakeable |
| Vapour pressure | negligible cold |
Temperature
| Bake, assembled | 120 °C |
|---|---|
| Vacuum degas | 120 °C |
| Braze / H2 firing | 157 melt °C |
| Metallurgical limit | melts 157 °C |
Thermal
| CTE | 32.1 ppm/K |
|---|---|
| Thermal conductivity | 82 W/m·K |
| Specific heat | 233 J/kg·K |
| Emissivity | 0.1 |
| Melting / softening | 157 °C |
Mechanical
| Strength | 2–4 tens MPa |
|---|---|
| Tensile | 2–4 MPa |
| Elongation | high |
| Young's modulus | 11 GPa |
| Hardness | very soft |
| Density | 7.31 g/cm3 |
Electrical and magnetic
| Relative permeability | ~1.0 |
|---|---|
| Resistivity | 8.4 µΩ·cm |
Engineering
| Corrosion | oxidises; the fresh surface is what seals |
|---|---|
| Joining | cold-flowed wire seal |
| Process notes | single use, and it will not survive a bakeout |
| Availability and cost | commodity wire |
Outgassing
0 sourced measurements for this card, 1 prescribed condition or published threshold. 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/.
Prescribed, not measured
- procedure, Indium, pure. Bake 120 C, 48 h, vacuum.
Sources: S-LIGO-E960022-V24. Full citations and conditions at the base and in /data/outgassing.json.
Grades
| In 99.99 plus wire | cryo seals and optic interlayers |
|---|---|
| In52Sn48 | 118 C eutectic: gentle soldering near sensitive parts |