stain appeared after ep acid renewal field emission at low gradient happened on mhi-06, mhi-07, in...
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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
???
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
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
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
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
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
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
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
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
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
AES001 had also similar stains, observed as received.( Jlab EP )
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.
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
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
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?