An apparatus and a method for etching of the inner surfaces of superconducting radio frequency (SRF) accelerator cavities are described. The apparatus is based on the reactive ion etching performed in an Ar/Cl2 cylindrical capacitive discharge with reversed asymmetry. To test the effect of the plasma etching on the cavity rf performance, a 1497 MHz single cell SRF cavity was used. The single cell cavity was mechanically polished and buffer chemically etched and then rf tested at cryogenic temperatures to provide a baseline characterization. The cavity's inner wall was then exposed to the capacitive discharge in a mixture of Argon and Chlorine. The inner wall acted as the grounded electrode, while kept at elevated temperature. The processing was accomplished by axially moving the dc-biased, corrugated inner electrode and the gas flow inlet in a step-wise manner to establish a sequence of longitudinally segmented discharges. The cavity was then tested in a standard vertical test stand at cryogenic temperatures. The rf tests and surface condition results, including the electron field emission elimination, are presented.
Original Publication Citation
Upadhyay, J., Palczewski, A., Popovic, S., Valente-Feliciano, A. M., Im, D., Phillips, H. L., & Vuskovic, L. (2017). Cryogenic rf test of the first SRF cavity etched in an rf Ar/Cl2 plasma. Aip Advances, 7(12), 5. doi:10.1063/1.4991888
0000-0003-1364-0579 (Janardan Upadhyay), 0000-0002-3668-4841 (Svetozar Popovic)
Upadhyay, J.; Palczewski, A.; Popovic, S.; Valente-Feliciano, A.-M.; Im, Do; Phillips, H. L.; and Vuskovic, L., "Cryogenic rf Test of the First SRF Cavity Etched in an rf Ar/Cl2 Plasma" (2017). Physics Faculty Publications. 115.