1. Quality control study with single-cell cavities1
Quality control study with single-cell cavities
TTC KEK
26 Sept. 2006
T.Saeki

2. Horizontally Rotated Electro-Polishing (EP)2
Horizontally Rotated Electro-Polishing (EP)
Circulating EP acid
H2SO4(95%) : HF(46%)
= 10 : 1 in volume
Cavity X-section
Temperature
sensor
Beam Pipe
Acid
Level
EP acid
circulates
Cathode
bag
Electric
Current
Back to EP-acid
reservoir
tank (100L)
Cathode
Voltage ~ 20 V, Current ~ 40A

3. Online monitor parameters of EP system3
Online monitor parameters of EP system
Current
Voltage
Removal
EP acid Temp. in cavity
EP acid Temp. in tank
Room Temperature

4. Online monitor parameters of EP system4
Online monitor parameters of EP system
Charge
Average current
Average
Current density
Removal
Resolved Nb
Resolved Nb / L
< ~ 9 g/L
[KEK criteria]

5. Single-cell study (Run1)5
Single-cell study (Run1)
KEK recipe : CBP, Light CP(10 um),
Annealing(3 750C),
EP(80 um, EP tank),
HPR(1 h, UPW),
Baking( C)
IS#2
IS#6
IS#3
IS#4
IS#5
IS#7
Light EP (20 um, EP tank)
EP(3 um, fresh EP acid)
+ HF rinse + HPR + Baking
EP(80 um)
Light EP(20 um)
EP acid in 100L
reservoir tank
EP(20 um, tank) + EP(3 um, fresh)
All 6 cavities, Eacc > ~44 MV/m
EP(3 um)
Fresh EP acid

6. Single-cell study (Run2)6
Single-cell study (Run2)
Reset = applying KEK recipe again:
CBP, Light CP(10 um), Annealing(3 750 C),
EP(80 um, tank) + EP(3 um, fresh EP acid) + HF rinse,
HPR(UPW), Bake( C).
 Vertical tests
IS#2
IS#3
IS#4
IS#5
IS#6
IS#7
KEK Recipe
Eacc
16.4
42.0
46.1
44.7
39.3 Qo
2.04e9
9.72e9
9.47e9
1.08e10
 See the presentation of Furuta for Eacc distributions (run1&run2).

7. What were plotted / checked7
What were plotted / checked
【Nb】(g/L) vs.
Voltage, Current, Room-Temperature,
EP acid Temp. in cavity, Current density,
EP acid Temp. in Reservoir tank were plotted.
Cavity performance (Eacc max) was plotted.
Correlation of active 【F-】(g/L) and cavity performance was checked. (only run1).
 CE analysis (Method is presented by Taguchi).
Correlation of cloudy surface and cavity performance was checked.

8. EP acid in 100L tank (single-cell cavities) run1 & run28
EP acid in 100L tank (single-cell cavities) run1 & run2
Run2 (summer)
Difference
btw R1&R2
Run1 (winter)
Operator tried to keep constant-current and constant-temperature.

9. EP acid in 100L tank (single-cell cavities) run1 & run29
EP acid in 100L tank (single-cell cavities) run1 & run2

10. EP acid (T~26 C0 is constatnt)10
Room temperature
Room Temperature
T~18 C0 in winter, T~28 C0 in summer
Heat (winter > summer)
EP acid (T~26 C0 is constatnt)
from 100 L tank
Temperature sensor
EP acid (T~30 C0 is constant)
Incoming heat = V*I, (I~40A is constant, V changes)
equal
Outgoing heat = Heat taken by EP acid flow (~3.7 L/min) is constant,
Heat flow from cavity surface to the air changes
We need room-temperature control for more reliable EP quality-assurance.
EP facility in STF should be equipped with air conditioner.

11. 【Nb】, active 【F】 vs. cavity performance (Run1, Nov05~Apr06)11
【Nb】, active 【F】 vs. cavity performance (Run1, Nov05~Apr06)
Surface
a bit cloudy FE
EP(30 um, tank) +
EP(fresh acid, 3 um) 10:3
Visit later  P13
EP(20 um, tank) +
EP(3 um, fresh acid)
EP(80 um) + EP(3 um)
CE analysis
Total 【F-】
Active 【F-】
100 L tank
【Nb】~9(g/L) seems OK.
Active 【F-】 ~ 14 (g/L) seems OK.

12. 【Nb】 vs. cavity performance (Run2, Jun06~Sept20)12
【Nb】 vs. cavity performance (Run2, Jun06~Sept20)
All EP(80 um, tank) + EP(3 um, fresh acid)
Starting point is
different from run1. FE
Surface a bit cloudy
【Nb】~9(g/L) seems OK.
IS2 (cavity problem?)
Sampling of EP acid for all points were already done.
CE (F- concentration) analysis is ongoing for all points.
 We will check the correlation between 【 F- 】 and cavity performance.

13. (H2SO4:HF=10:3) for EP(3 um, fresh acid)13
(H2SO4:HF=10:3) for EP(3 um, fresh acid)
Tried fresh EP acid (H2SO4:HF=10:3) for final 3 um removal in Run1.
 This caused Q-slope (no X-ray).
We tried 0, 24, 48 hours baking at 120 C0,
But Q- slope did not disappear for all tests.
 H2SO4:HF=10:3 : too much HF?
Under investigation.
No baking
24 h baking
48 h baking +

14. 14
EBW / CBP is important
If we would like to study EP quality-assurance, we must prepare perfectly defect-free surface before EP.
 EBW / CBP, CP, annealing/degassing before EP process is very importatnt.

15. Typical EBW seam after EP15
Best results
Typical EBW seam after EP #2 #3
Last cavity to reach
Eacc = 45MV/m.
CBP is important. #4
Worst EBW seam after EP
(If found)
No pit
overlap region
No pit

16. CBP removal thickness depends on surface roughness at EBW seam16
CBP removal thickness depends on surface roughness at EBW seam
Before CBP
Equator EBW seam
(inner surface)
EBW quality-assurance is also important
1st CBP(30um)
2nd CBP
Removal thickness
= 60 um.
Good
EBW
3rd CBP (90um)
12th CBP
Removal thickness
> 200 um.
Bad
EBW
2nd CBP (60um)
13th CBP
Removal thickness
> 200 um.
Bad EBW
with a pit

17. Summary Yield tests with single-cell cavities (run1/run2):17
Summary
Yield tests with single-cell cavities (run1/run2):
KEK recipe : EP(80 um, tank)
EP(20-30 um, tank) + EP(3um, fresh EP acid)
【Nb】vs Various EP parameters were plotted (run1/run2).
EP voltage increases with increasing 【Nb】: re-confirmed.
EP voltage is affected by room temperature.
 Air conditioner is necessary for better EP QA.
【Nb】, active 【F】 vs. cavity performance
 【Nb】 ~ 9 (g/L) seems OK.
 Active 【F】 ~ 14 (g/L) seems OK.
No correlation between cloudy surface and cavity performance.
EP(3 um, fresh EP acid) with (H2SO4:HF=10:3)
caused Q-slope.  H2SO4:HF=10:3 : too much HF ?
EBW and CBP quality-assurance before EP is important.

18. ICHIRO (LL) 9-cell cavities18
ICHIRO (LL) 9-cell cavities
Preparation : KEK recipe
9-cell #0 w/o HOM coupler.
Hard barrier around 29 MV/m.
This might be caused by MP at enlarged beam-pipe
9-cell #1 and #2 w/ HOM coupler.
Low Q-factor is related to HOM coupler?
No Q-disease was found.

19. Multi-Pacting simulations by L. Ge at SLAC19
Multi-Pacting simulations by L. Ge at SLAC
Multi-pacting points
were found at the taper part
of enlarged beam-pipe
from simulation.
MP Particles Distribution (surviving 50 impacts)
MP in end-group of ICHIRO Cavity with enlarged beam-pipe

20. Re-EBW of HOM antenna (#1 and #3)20
Re-EBW of HOM antenna (#1 and #3)
Low Q-factor problem
We suspected if EBW of HOM antenna is OK.
 Re-EBW of antenna
re-EBW
After re-EBW
(Fully-penetrated)
Before re-EBW
(Not fully-penetrated)

21. Inner surface of EBW-seam21
Inner surface of EBW-seam
Checked the inner-surface of cells at EBW-seam by CCD camera.
I9-#1
I9 #0 (Eacc max = 29 MV/m)
Bad EBW-seam for only 1 cell.
I9 #2 (Eacc max = 12 MV/m)
EBW-seam is OK.
Pit at EBW-seam
I9 #3 (VT not yet)
Bad EBW for all 9 cells.
I9 #1 (Eacc max = 17 MV/m)
Bad EBW-seam for half of 9 cells.
Re-CBP was already done.
CP, annealing, EP are scheduled.

22. Schedule for 9-cell cavities22
Schedule for 9-cell cavities
I9-#0
We already cut beam-pipes (w/o HOM)
EBW beam-pipes w/ HOM.
Do not care for MP. If Eacc ~ 29 MV/m  Install into STF.
I9-#1
Re-CBP was already done.
CP, Annealing, EP are scheduled.
Eacc ~ 29 MV/m.
Install into STF
Re-EBW of HOM antenna?
Re-EP and VT?
Or replace with straight B.P.s (MP-free).
I9-#2
I9-#3
Use for the study of tuner for a while.
First priority is :
to get one 9-cell cavity with Eacc ~ 29 MV/m w/ HOM couplers for STF.