Surface properties of metal-nitride and metal-carbide films deposited on Nb for RF superconductivity

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Various effects occur which can prevent attainment of the high Q's and/or the high gradient fields necessary for the operation of rf superconducting cavities. One of these effects, multipactor, both causes the cavity to detune during filling due to resonant secondary electron emission at the cavity walls, and lowers the Q by dissipative processes. TiN deposited onto the high field regions of room temperature Al cavities has been used at SLAC to successfully reduce multipactor in the past. We have therefore studied TiN and its companion materials, NbN, NbC, and TiC, all on Nb substrates under several realistic conditions: (1) ... continued below

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Pages: 29

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Garwin, E.L.; King, F.K.; Kirby, R.E. & Aita, O. September 1, 1983.

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Description

Various effects occur which can prevent attainment of the high Q's and/or the high gradient fields necessary for the operation of rf superconducting cavities. One of these effects, multipactor, both causes the cavity to detune during filling due to resonant secondary electron emission at the cavity walls, and lowers the Q by dissipative processes. TiN deposited onto the high field regions of room temperature Al cavities has been used at SLAC to successfully reduce multipactor in the past. We have therefore studied TiN and its companion materials, NbN, NbC, and TiC, all on Nb substrates under several realistic conditions: (1) as deposited, (2) exposed to air, and (3) 1 keV electron-bombarded. The studied films (up to 14 nm thickness) were sputter deposited onto sputter-cleaned Nb substrates. Results indicate that the materials tested gave substantially the same results. The maximum secondary electron yields for as-deposited films was about 1.0 to 1.2. These yields rose to greater than 1.5 upon air-exposure and were reduced to nearly the pre-oxidized values after electron bombardment (about 3 x 10/sup 17/ electrons-cm/sup -2/ in the case of NbN and NbC). XPS analysis showed that the oxides (e.g. TiO/sub 2/ in the case of TiN films) formed during air exposure were only slightly reduced (converted to lower oxides) by the electron beam exposure. AES showed a slight reduction in the surface O concentration following beam exposure. The results indicate that any of these films would be poor choices if simply deposited and exposed to air, but, in fact, the in-situ electron bombardment which occurs in cavities serves to reduce the effective secondary electron yield and thereby causes a substantial reduction in multipacting.

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Pages: 29

Notes

NTIS, PC A03/MF A01.

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  • 9. international vacuum congress and 5. international conference on solid surfaces, Madrid, Spain, 26 Sep 1983

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  • Other: DE84001491
  • Report No.: SLAC-PUB-3213
  • Report No.: CONF-8309103-10
  • Grant Number: AC03-76SF00515
  • DOI: 10.2172/5680937 | External Link
  • Office of Scientific & Technical Information Report Number: 5680937
  • Archival Resource Key: ark:/67531/metadc1093346

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  • September 1, 1983

Added to The UNT Digital Library

  • Feb. 10, 2018, 10:06 p.m.

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  • April 10, 2018, 2:02 p.m.

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Garwin, E.L.; King, F.K.; Kirby, R.E. & Aita, O. Surface properties of metal-nitride and metal-carbide films deposited on Nb for RF superconductivity, report, September 1, 1983; United States. (digital.library.unt.edu/ark:/67531/metadc1093346/: accessed October 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.