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

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

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

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

Single-cell study (Run1) 5 Single-cell study (Run1) KEK recipe : CBP, Light CP(10 um), Annealing(3 h @ 750C), EP(80 um, EP tank), HPR(1 h, UPW), Baking(48 h @ 120 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

Single-cell study (Run2) 6 Single-cell study (Run2) Reset = applying KEK recipe again: CBP, Light CP(10 um), Annealing(3 h @ 750 C), EP(80 um, tank) + EP(3 um, fresh EP acid) + HF rinse, HPR(UPW), Bake(48 h @ 120 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).

What were plotted / checked 7 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.

EP acid in 100L tank (single-cell cavities) run1 & run2 8 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.

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

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.

【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.

【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.

(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 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.

Typical EBW seam after EP 15 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 Pit @ overlap region No pit

CBP removal thickness depends on surface roughness at EBW seam 16 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

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.

ICHIRO (LL) 9-cell cavities 18 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.

Multi-Pacting simulations by L. Ge at SLAC 19 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

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)

Inner surface of EBW-seam 21 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.

Schedule for 9-cell cavities 22 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.