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Stain appeared after EP acid renewal

Stain appeared after EP acid renewal. Field emission at low gradient happened on MHI-06, MHI-07, in VT. Kyoto-camera found brown stain trace in beam pipes, irises and equators. Now we are investigating STF EP process using old MHI-#0 cavity (with simple beam pipe).

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Stain appeared after EP acid renewal

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  1. Stain appeared after EP acid renewal Field emission at low gradient happened on MHI-06, MHI-07, in VT. Kyoto-camera found brown stain trace in beam pipes, irises and equators. Now we are investigating STF EP process using old MHI-#0 cavity (with simple beam pipe). They seems to be Niobium-Oxide. However, the problem is not yet solved, not yet fixed. 07.17.2009 ??? H. Hayano, KEK

  2. Brown spot and traces; MHI-06： spot or traces on BP-#1、#1、#2、#3、#4、#8、#9、#9-BP (red indicate bad) MHI-07：BP-#1、#1、#2、#3、#4、#5、#6、#7、#8、#9、#9-BP Kyoto-camera picture examples using new LED illumination BL#6 1-cell equator, t = 306 deg. Downstream : Outside weld area BL#6 #9-BP, t = 241 deg. -2 BL#6 #9-BP, t = 241 deg. -1

  3. BL#6 9-cell equator, t = 034 deg. Upstream : Outside weld area BL#6 9-cell equator, t = 184 deg. Upstream : Outside weld area BL#6 3-cell equator, t = 291 deg. BL#6 3-4 iris, t = 055 deg. BL#6 8-9 iris, t = 053 deg. BL#6 9 equator, t = 037 deg.

  4. Typical EP parameter OLD_MHI-#0 cavity EP test2009/07/07 EP condition ：4th EP after acid renewal removal：20 um cavity surface area： 9000 cm2 acid soaking area：5400 cm2 target average current：270A acid flow：15 litter / min cavity rotation：1 rpm cavity acid temp at start：　20.9℃ acid tank temp：　20.1℃ room temp ：　31℃

  5. 2009/5/27, BL#6, 1st EP after acid renew 2009/6/10, BL#7, 2nd EP after acid renew 4div 4div 2009/7/01, BL#8, 3rd EP after acid renew 2div 4div 2009/4/08, BL#5, EP before acid renewal

  6. 2009/3/25, ERL-2cell #1, EP before acid renew 2008/12/10, BL#6, EP before acid renew 2div 2div 4div 4div 2009/7/07, OLD_MHI-#0 5th EP after acid renew 2009/7/07, OLD_MHI-#0 4th EP after acid renew

  7. After EP-20um, 5min rotate, HPR #1 equator, t = 248 deg. After EP-20um, 30min rotate, HPR #1 equator, t = 248 deg. after 4th EP after 5th EP After EP-20um, 5min rotate, HPR #1 equator, t = 304 deg. After EP-20um, 30min rotate, HPR #1 equator, t = 304 deg. after 4th EP after 5th EP

  8. After EP-20um, 5min rotate, HPR #1 equator, t = 349 deg. After EP-20um, 30min rotate, HPR #1 equator, t = 349 deg. after 4th EP after 5th EP stains went away by EP 20um.

  9. after 5th EP After EP-20um, 30min rotate, HPR #1 equator, t = 342 deg. After EP-20um, 30min rotate, HPR #1 equator, t = 328 deg. after 5th EP after 5th EP new stains comes up After EP-20um, 30min rotate, HPR #1 equator, t = 000 deg.

  10. MHI#0 cavity scrape out stain in beam pipe edge sample was glued by silver paste on Si substrate. Then, apply XPS analysis. results; Nb 11 at% O 48 at% C 27 at% Si 14 at% (substrate) No special material, just Niobium-oxide, maybe. scraped sample

  11. AES001 had also similar stains, observed as received. ( Jlab EP )

  12. Other spots that have no wall gradients Other spots that have no wall gradients Appendix back side of EL AES001 #2-3 iris 212° to Equator of #3 cell iris to Equator of #2 cell arc scar? back side of EL The result of SI measurements shows that this spot is flat. This spots looks like a sign of Field Emission or Arcing. Many spots like this were observed. 1mm

  13. AES001 #4-5 iris 233° Appendix iris back side of EL back side of EL bright belt to Equator of #4 cell to Equator of #5 cell All the Iris regions are yellowish. This spot is locally bright. It may be caused by EP? 1mm

  14. AES001 #4-5 iris 136° Appendix iris back side of EL back side of EL to Equator of #4 cell to Equator of #5 cell Dropped coffee smear? 1mm

  15. AES001 #7-8 iris 279° Appendix to Equator of #7 cell to Equator of #8 cell Dropped coffee smear? scar? back side of EL back side of EL iris 1mm

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