Stain appeared after EP acid renewal

1
Stain appeared after EP acid renewal
07.17.2009
???

• 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.

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
BL6 1-cell equator, t 306 deg. Downstream
Outside weld area
BL6 9-BP, t 241 deg. -2
BL6 9-BP, t 241 deg. -1
3
BL6 9-cell equator, t 034 deg. Upstream
Outside weld area
BL6 9-cell equator, t 184 deg. Upstream
Outside weld area
BL6 3-cell equator, t 291 deg.
BL6 3-4 iris, t 055 deg.
BL6 8-9 iris, t 053 deg.
BL6 9 equator, t 037 deg.
4
Typical EP parameter
OLD_MHI-0 cavity EP test 2009/07/07 EP condition
4th EP after acid renewal removal20 um cavity
surface area 9000 cm2 acid soaking area5400
cm2 target average current270 A acid flow15
litter / min cavity rotation1 rpm cavity acid
temp at start 20.9? acid tank temp 20.1? room
temp 31?
5
2009/5/27, BL6, 1st EP after acid renew
2009/6/10, BL7, 2nd EP after acid renew
4div
4div
2009/7/01, BL8, 3rd EP after acid renew
2div
4div
2009/4/08, BL5, EP before acid renewal
6
2009/3/25, ERL-2cell 1, EP before acid renew
2008/12/10, BL6, 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
MHI0 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
Appendix
AES001 4-5 iris 233
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
Appendix
AES001 4-5 iris 136
iris
back side of EL
back side of EL
to Equator of 4 cell
to Equator of 5 cell
Dropped coffee smear?
1mm
15
Appendix
AES001 7-8 iris 279
to Equator of 8 cell
to Equator of 7 cell
Dropped coffee smear?
scar?
back side of EL
back side of EL
iris
1mm