Films and getters · Future bench (lab)
Scandate cathodes
Sc2O3values describe: Sc₂O₃-doped W
Vacuum electronics & X-ray sources
What it enables
Scandia-doped tungsten dispensers emit at lower temperature and higher density than B and M types: longer tubes, denser beams, the next rung of the cathode ladder.
Status and pusher
Reproducibility and life data still maturing; pushed by the vacuum electronics community (IVEC circuit) and mm-wave TWT programs.
Watch out
Emission uniformity is the historic failure mode.
Properties
The values below are candidate: compiled from the sources named, not yet individually validated. Provisional provenance: Electron tube and ceramic-to-metal sealing practice.
Wet cleaning
| Recipe | never: the impregnant is water reactive |
|---|---|
| Forbidden | moisture and air exposure after activation |
| Limit | poisoning by oxygen and water, measured in ppm |
Vacuum and outgassing
| Vapour pressure | barium and scandium evaporate by design |
|---|
Temperature
| Vacuum degas | 1200 °C |
|---|---|
| Metallurgical limit | activation 1100–1200 °C |
Mechanical
| Elongation | nil |
|---|
Electrical and magnetic
| Relative permeability | ~1.0 |
|---|
Engineering
| Process notes | 10 A/cm² at lower temperature than any current cathode |
|---|---|
| Availability and cost | research and specialist tube makers |
Grades
| Scandia-doped W dispenser | lab and pilot tubes |
|---|
Sources · 1
- IVEC proceedings, scandate cathode sessions