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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
???
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BL#6 1-cell equator, t = 306 deg. Downstream : Outside weld area
BL#6 #9-BP, t = 241 deg. -1
BL#6 #9-BP, t = 241 deg. -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
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BL#6 9-cell equator, t = 034 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.
BL#6 9-cell equator, t = 184 deg. Upstream : Outside weld area
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OLD_MHI-#0 cavity EP test 2009/07/07
EP condition : 4th EP after acid renewal
removal : 20 um
cavity surface area : 9000 cm2
acid soaking area : 5400 cm2
target average current : 270 A
acid flow : 15 litter / min
cavity rotation : 1 rpm
cavity acid temp at start : 20.9℃
acid tank temp : 20.1℃
room temp : 31℃
Typical EP parameter
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2009/5/27, BL#6, 1st EP after acid renew
2009/6/10, BL#7, 2nd EP after acid renew
2009/7/01, BL#8, 3rd EP after acid renew
2009/4/08, BL#5, EP before acid renewal
4div
4div
4div
2div
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2009/3/25, ERL-2cell #1, EP before acid renew
2div
2008/12/10, BL#6, EP before acid renew
2div
2009/7/07, OLD_MHI-#0 4th EP after acid renew
4div
2009/7/07, OLD_MHI-#05th EP after acid renew
4div
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After EP-20um, 5min rotate, HPR#1 equator, t = 248 deg.
After EP-20um, 5min rotate, HPR#1 equator, t = 304 deg.
After EP-20um, 30min rotate, HPR#1 equator, t = 248 deg.
After EP-20um, 30min rotate, HPR#1 equator, t = 304 deg.
after 4th EP after 5th EP
after 4th EP after 5th EP
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After EP-20um, 5min rotate, HPR#1 equator, t = 349 deg.
After EP-20um, 30min rotate, HPR#1 equator, t = 349 deg.
stains went away by EP 20um.
after 4th EP after 5th EP
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After EP-20um, 30min rotate, HPR#1 equator, t = 342 deg.
After EP-20um, 30min rotate, HPR#1 equator, t = 328 deg.
After EP-20um, 30min rotate, HPR#1 equator, t = 000 deg.
new stains comes up
after 5th EP
after 5th EP
after 5th EP
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stain in beam pipe edge
scrape out
scraped sample
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.
MHI#0 cavity
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AES001 had also similar stains, observed as received.( Jlab EP )
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AES001 #2-3 iris 212°
1mm
iris
back side of EL
Other spots that have no wall gradientsOther spots that have no wall gradients
Appendixback side of EL
to Equatorof #3 cell
to Equatorof #2 cell
arc scar?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.
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AppendixAES001 #4-5 iris 233°
1mm
irisback side of EL back side of EL
bright belt
to Equatorof #5 cell
All the Iris regions are yellowish. This spot is locally bright. It may be caused by EP?
to Equatorof #4 cell
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AppendixAES001 #4-5 iris 136°
1mm
iris
to Equatorof #5 cellDropped
coffee smear?
back side of EL back side of EL
to Equatorof #4 cell
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AppendixAES001 #7-8 iris 279°
1mmiris
to Equatorof #8 cell
back side of EL back side of EL
to Equatorof #7 cell
Dropped coffee smear?
scar?