Films and getters · Future bench (tested)
Nb3Sn films on copper cavities
Nb3Snvalues describe: Nb₃Sn on Cu
Big science (accelerators, light sources, public fusion)
What it enables
SRF at 4.2 K instead of 2 K: deletes a cryoplant stage.
Status and pusher
Single-cell records improving yearly; not yet a machine baseline. Pushed by Fermilab, Cornell, CERN.
Properties
The values below are candidate: compiled from the sources named, not yet individually validated. Provisional provenance: SRF cavity preparation literature (DESY, Fermilab, JLab); CERN Accelerator School, vacuum and materials proceedings.
Wet cleaning
| Recipe | the substrate gets the full SRF cleaning before coating |
|---|---|
| Forbidden | particles, as always in SRF |
| Limit | substrate surface quality propagates straight through the film |
Vacuum and outgassing
| Vapour pressure | tin evaporates during the diffusion process, by design |
|---|
Temperature
| Bake, assembled | 120 °C |
|---|---|
| Braze / H2 firing | 1100 diffusion °C |
| Metallurgical limit | Tc 18 K |
Mechanical
| Strength | coating |
|---|---|
| Elongation | nil |
| Density | 8.9 g/cm3 |
Electrical and magnetic
| Relative permeability | superconductor, Tc 18 K |
|---|---|
| Resistivity | zero below Tc |
Engineering
| Joining | grown on the cavity wall |
|---|---|
| Process notes | twice the Tc of niobium means 4 K operation instead of 2 K |
| Availability and cost | research, moving to pilot |