Gas cluster ion beam surface treatments for reducing field emission and breakdown of electrodes and SRF cavities.
Sub-micron-scale surface roughness and contamination cause field emission that can lead to high-voltage breakdown of electrodes, and these are limiting factors in the development of high gradient RF technology. We are studying various Gas Cluster Ion Beam (GCIB) treatments to smooth, clean, etch and/or chemically alter electrode surfaces to allow higher fields and accelerating gradients, and to reduce the time and cost of conditioning high-voltage electrodes. For this paper, we have processed Nb, stainless steel and Ti electrode materials using beams of Ar, O{sub 2}, or NF{sub 3} + O{sub 2} clusters with accelerating potentials up to 35 kV. Using a scanning field emission microscope (SFEM), we have repeatedly seen a dramatic reduction in the number of field emission sites on Nb coupons treated with GCIB. Smoothing effects on stainless steel and Ti substrates, evaluated using SEM and AFM imaging, show that 200-nm-wide polishing scratch marks are greatly attenuated. A 150-mm diameter GCIB-treated stainless steel electrode has shown virtually no DC field emission current at gradients over 20 MV/m.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- SC
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 941497
- Report Number(s):
- ANL/MCS/JA-62990
- Journal Information:
- Nucl. Instrum. Methods Phys. Res. B, Journal Name: Nucl. Instrum. Methods Phys. Res. B Journal Issue: 2007 Vol. 261; ISSN 0168-583X; ISSN NIMBEU
- Country of Publication:
- United States
- Language:
- ENGLISH
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