Stain appeared after EP acid renewal Field emission at low gradient happened on MHI-06, MHI-07, in...

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?