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Desorption from Hot Scandate Cathodes: Effects on Vacuum Device Interior Surfaces after Long-Term Operation
Mujan N Seif1, T John Balk1, Matthew J Beck1
1Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506-0046, USA.
Materials (Basel, Switzerland)
|November 19, 2020
Summary
Scandate cathodes show material desorption over time, with calcium desorbing unevenly and minimal scandium loss. This study provides crucial insights into scandate cathode lifespan for vacuum devices.
Area of Science:
- Materials Science
- Vacuum Electronics
- Surface Science
Background:
- Scandate cathodes offer superior electron emission compared to M-type cathodes.
- Limited understanding of scandate cathode operational lifespan hinders vacuum device integration.
Purpose of the Study:
- Investigate thermal desorption from scandate cathodes after prolonged operation.
- Analyze material deposition on internal surfaces of a sealed vacuum device.
Main Methods:
- X-ray Photoelectron Spectroscopy (XPS)
- Energy-Dispersive X-ray Spectroscopy (EDS)
- Transmission Electron Microscopy (TEM)
- Analysis of a vacuum device after ~26,000 hours of operation.
Main Results:
- Approximately 1 wt.% of the cathode impregnate desorbed over its lifetime.
- Calcium (Ca) desorption was non-uniform over time.
- Scandium (Sc) desorption was negligible or undetectable.
Conclusions:
- Scandate cathodes exhibit a low rate of material desorption, suggesting potential for long-term use in vacuum devices.
- Understanding desorption products is key to predicting and mitigating effects on device performance.
- This study provides the first long-term operational data for scandate cathodes.
