1. First results Plasma etching
Ari D. Palczewski, SRF Scientists
Jefferson Lab, USA
11/12/2015
Plasma etch performed by Janardan Upadhyay – ODU
Chemistry performed by staff w/ help from Anne-Marie Valente-Feliciano

2. Plasma etching – Ar/Cl2 Plasma
Single cell cavity with electrode and conical gas flow inlet
J.Upadhyay et al., Phys. Rev. ST Accel. Beams.17,122001(2014). – system setup and sample results

3. First results – residual very high

4. First results 120C bake – no change

5. SEM results residual powder
Chromium and iron found – suspect stainless steel contamination
From etched cone contaminating surface

6. HF free Chemical etch Aqua Regia and Phosphoric rinse
Aqua Regia (3 part HCl, 1 part HNO3) – ambient 60 minute plus flip 60 minutes
85% Phosphoric rinse - 100C 60 minutes
Rough surface, but was there before etch – inherent in plasma from parameters used

7. RF after chem w/ 120C
Possible small change from 120C but not dominant

8. Surface resistance fitting
R=RS+A/T+e^(U/T) U=17.02
Rough surface cause slope, not hydrogen – possible contamination left

9. Compare to BCP
Next step HF rinse