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ECR plasma: a possible in-situ cavit y processing technique

ECR plasma: a possible in-situ cavit y processing technique. G. Wu, W-D. Moeller, C. Antoine T. Khabiboulline, E. Harms, Y. Terechkine, H. Edwards, D. Mitchell, A. Rowe, C. Boffo, C. Cooper, T. Koeth, W. Muranyi, Fermilab. Contents. Introduction – Field emission problem

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ECR plasma: a possible in-situ cavit y processing technique

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  1. ECR plasma: a possible in-situ cavity processing technique G. Wu, W-D. Moeller, C. Antoine T. Khabiboulline, E. Harms, Y. Terechkine, H. Edwards, D. Mitchell, A. Rowe, C. Boffo, C. Cooper, T. Koeth, W. Muranyi, Fermilab SRF materials workshop

  2. Contents • Introduction – Field emission problem • Introduction to plasma cleaning • General application • SRF field activity • ECR plasma and RF cavity • Experimental plan and the issues to be addressed • Potential benefit and other applications SRF materials workshop

  3. Field emission is a continuing problem Red represents the FE limitation DESY cavity experience L. Lijie’s summary of DESY cavity databank, DESY, 2006 SRF materials workshop

  4. Field emission is a continuing problem JLAB SNS cavity experience J. Ozelis, SRF 2005 SRF materials workshop

  5. Field emission sources Inclusions from weld-prep machining, forming Residues from chemical processing (EP,BCP) Water impurity (HPWR) Clean room particles Assembly particulates Particulates includes: (Ni, Mn, In, Cu, C, F, Cl, Ca, Al, Si), Nb, Fe, Cr, S, etc… Particle counter recording has not been very indicative Particle free is not guaranteed FE is a localized statistical problem: • Success else where does not guarantee the local success • Past success does not guarantee the future success experienced in all Lab’s SRF materials workshop

  6. Introducing plasma Plasma induces chemical reactions in reduced temperatures, converts some surface materials, contaminants to gaseous phase Plasma generates accelerated ions to bombard the surface (including loose particles) Glow discharge, RF discharge and ECR plasma are common methods Noble gas, N2, O2, H2, mixtures, … SRF materials workshop

  7. Applications [3,4] • Semiconductor industry [1,6,9] • Micro-electronics – Josephson junctions [8] • Automobile industry – painting [2,10] • Aircraft industry – painting [11] • Medical applications – pre-cleaning for coating and sterilization • Optical industry • Antique preservation – surface protection • Particle accelerator – beam line components [14] • Microwave power - multiMW, large-orbit, coaxial gyrotron [7] • SRF Field • Plasma etching for Nb cavity – JLAB [13] • Plasma cleaning – INFN/Lagnero, JLAB [12] • Coupler processing – DESY (W-D. Moeller, Dennis?) SRF materials workshop

  8. ECR plasma and RF cavity Figure 3: Electron being accelerated clockwise by periodic electric field. External magnetic is pointing out of the paper (not shown). Color reflects energy ECR = electron cyclotron resonance SRF materials workshop

  9. ECR plasma and RF cavity n0= 3.21017 /m3 =2.610-6 s Minimum field 130 V/m for 90eV r< 0.3 mm P=110-5 torr 9-cell Cavity Eacc for 15 kilo-watt RF input under different input coupling for cavity Q0 Eacc for 150 watt RF input under different input coupling for cavity Q0 SRF materials workshop

  10. x-wave L R 3.9GHz Microwave traveling inside magnetized plasma SRF materials workshop

  11. Experimental plan and the issues to be addressed Usual cleaning Cold RF test to find FE limit Plasma processing at room temperature Cold RF test to verify improvement Gas mixtures: Ar, H2, O2, He, Kr. Surface contamination removal? Ar implantation? Ar ion creates surface defects? Dry-oxidation afterwards? If Hydrogen, how about Q-disease? If Oxygen, oxidation compound? He also effective? Gas pressure Plasma density Temperature distribution Ion energy distribution Ion flux rate Chemical reaction SRF materials workshop

  12. Coupler Qext 3x104 – 2x109 SRF materials workshop

  13. Potential benefit and other applications Reduce field emission, increase cavity production yield through in-situ processing, improve cryomodule performance Potential new design for cryomodule recovery (Build-in magnetic coil) Processing opportunity in between Or built-in capability CF4+O2, Cl2 in plasma – etching of niobium [15, 16] NbCl5– coating of niobium Sn/SnClx vapor – Nb3Sn formation B2H6+Mg – similar to Penn State HPCVD [17] SRF materials workshop

  14. 1.Kim, H.-w. and R. Reif, In-situ low-temperature (600[deg]C) wafer surface cleaning by electron cyclotron resonance hydrogen plasma for silicon homoepitaxial growth. Thin Solid Films, 1996. 289(1-2): p. 192-198. 2.Steffen, H., et al., Process control of RF plasma assisted surface cleaning. Thin Solid Films, 1996. 283(1-2): p. 158-164. 3.Kruger, P., R. Knes, and J. Friedrich, Surface cleaning by plasma-enhanced desorption of contaminants (PEDC). Surface and Coatings Technology, 1999. 112(1-3): p. 240-244. 4.Kegel, B. and H. Schmid, Low-pressure plasma cleaning of metallic surfaces on industrial scale. Surface and Coatings Technology, 1999. 112(1-3): p. 63-66. 5.Li, H., et al., An in situ XPS study of oxygen plasma cleaning of aluminum surfaces. Surface and Coatings Technology, 1997. 92(3): p. 171-177. 6.Choi, K., et al., Removal efficiency of organic contaminants on Si wafer by dry cleaning using UV/O3 and ECR plasma. Applied Surface Science, 2003. 206(1-4): p. 355-364. 7.William E. Cohen, R.M.G., Reginald L. Jaynes, Christopher W. Peters, and Y.Y.L. Mike R. Lopez, Scott A. Anderson, and Mary L. Brake, Thomas A. Spencer, Radio-frequency plasma cleaning for mitigation of high-power microwave-pulse shortening in a coaxial gyrotron. APPLIED PHYSICS LETTERS, 2000. 77(23): p. 3. 8.T. S. Kuan, S.I.R., and R. E. Drake Journal of Applied Physics, 1982. 53(11): p. 7. 9.Th. Schäpers, R.P.M., G. Crecelius, H. Hardtdegen, and H. Lüth Preparation of transparent Nb/two-dimensional electron gas contacts by using electron cyclotron resonance plasma cleaning. Journal of Applied Physics, 2000. 88(7): p. 3. 10 D.F. O'Kane, K. L. Mittal, Plasma cleaning of metal surfaces. Journal of Vacuum Science and Technology, 1974. 11(3): p. 3. 11.Petasch, W., et al., Low-pressure plasma cleaning: a process for precision cleaning applications. Surface and Coatings Technology, 1997. 97(1-3): p. 176-181. 12.N. Patron, R.B., L. Phillips, M. Rea, C. Roncolato, D. Tonini, and V. Palmieri. Plasma cleaning of cavities. in Thin Films and new ideas for pushing the limits of RF superconductivity. 2006. Padua, Italy. 13. H. L. Phillips, private communications 14. H.F. Dylla, J. Vac. Sci. Technol.. A6 (1988) 1276. 15. M. Chen and R. H. Wang, J.Vac.Sci. Technol. A, Vol. 1, No. 2, Apr/June 1983 16. Jay N. Sasserath and John Vivalda, J.Vac.Sci. Technol. A, Vol. 8, No. 6, Nov/Dec 1990 17. Xi, X.X., In Situ Growth of MgB2 Thin Films by Hybrid Physical-Chemical Vapor Deposition. IEEE Transactions on Applied Supconductivity, 2003. 13(2): p. 5 SRF materials workshop

  15. Acknowledgement H. Padamsee, Cornell P. Kneisel, L. Phillips, G. Bialas, R. Rimmer, H. Wang, B. Manus, G. Slack, JLAB SRF materials workshop

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