1. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_051 A RD 05: SURFACE PREPARATION STUDIES FOR SUPERCONDUCTIVE CAVITIES F. Eozénou, T. Saeki

2. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_052 OUTLINE CONTEXT INVOLVED SURFACE TREATMENTS RESULTS ACHIEVED DURING THE PREVIOUS PROGRAM PROPOSALS FOR THE NEW PROGRAM

3. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_053 CONTEXT

4. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_054 TWO MAIN PROJECTS RELATED TO THE “COLD” TECHNOLOGY International Linear Collider –~17000 Superconductive Nb cavities > 31.5 MV/m –1 Tev XFEL (X-Ray Free-Electron Laser) –17.5 GeV λ=0.1nm –808 cavities E=23.5 MV/m assembled in 101 cryomodules Building of Clean Room at Saclay in Progress.

5. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_055 MAIN ISSUE FOR ILC ILC is in the Technical Design Phase. The goal of GDE S0 task is to achieve high gradient >35MV/m with yield >90% by the end of 2012 Main reasons for gradient limitation: Field emission Early quench (thermal transition) → More R&D is necessary to overcome these issues = IMPROVEMENT OF THE SURFACE TREATMENT

6. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_056 INVOLVED SURFACE TREATMENTS

7. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_057 SMOOTHENING: ELECTRO – POLISHING (EP) ∆V = 17V AND KEK’s LOCAL GRINDING: SEE “PROPOSAL” PART Parameters: Electrolyte’s Composition, Applied Potentiel, Flowrate, Cavity rotation speed, Temperature.

8. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_058 EP FACILITIES AT KEK (STF) AND SACLAY + PROGRAM FOR VERTICAL EP FACILITY AT SACLAY 9Cell EP set-up at KEK 1Cell EP set-up at Saclay

9. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_059 Rinsing Cavity Filling for tank Water for cooling Rinsing Tank Tank Acid1 Nitrogen for Cavity Nitrogen for tank Liquid Exhausts Gas Scrubber filtersfilters filtersfilters Tank Acid2 20V, 2kA cathode QaQa QgQg QgQg QgQg TT T Tair Hydrogen Sensor T: Temperature Sensor Qg/Qa: flow meter acid/gas

10. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_0510 CLEANING OF THE CAVITY AFTER EP Cleaning of Cavity at STFHigh Pressure Rinsing at STF + additional rinsing with solvant (ethanol, H 2 O 2, etc.)

11. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_0511 Ultra High Vacuum Baking at KEKFast Baking at Saclay BAKING OF CAVITIES

12. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_0512 LAST ACHIEVEMENTS AT KEK AND SACLAY

13. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_0513 Al 3+ SO 4 2- S Nb 5+ H+H+ H2H2 CHEMICAL REACTIONS DURING EP: SULFUR IS GENERATED + -

14. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_0514 Reduction Reactions at the Cathode Reduction of H + : 2 H + + 2 e - → H 2 (Predominant) Reduction of SO 4 2- : SO 4 2- + 8H + + 6e - → S + 4H 2 O Does a cathodic overpotential lead to an increased sulfur generation? → Two Niobium samples electro-polished at 5V and 20V for a similar heavy removal with 1-9-1 (HF-H 2 SO 4 -H 2 O) Mixture Sample A, 20 Volts: 9.18g removed 51 hours EP Sample B, 5 Volts: 9.11g removed 115 hours EP = Theoritical way to reduce Sulfur Contamination (experience on going) TEST OF LOW VOLTAGE EP (5V) AT SACLAY TO REDUCE SULFUR CONTAMINATION Presented at TTC Meeting 2008

15. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_0515 TEST OF LOW VOLTAGE EP (5V) TO REDUCE SULFUR CONTAMINATION SULFUR FOUND IN THE EP MIXTURE (200mL) AFTER TREATMENTS OF SAMPLES A AND B. SULFUR EXTRACTED WITH CHLOROFORM: SampleA (20 V)B (5V) 1 st Rinse 4.5mg2.6-2.7mg 2 d Rinse 1.2-1.3mg0.9-1.2mg

16. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_0516 EXCELLENT GRADIENTS WITH LOW VOLTAGE EP: C1-21 Cavity (Tesla Shape) Quench located at the equator.

17. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_0517 POLLUTION OF CATHODE BAG AT STF/KEK (Presented by T.Saeki at TILC09) Commissioning run of STF EP facility 30 June – 1 July 2008 Location: Iris Cell#4-cell#5, Iris cell#5-cell#6 Cavity X-section Beam Pipe Cathode Cathode bag (Teflon mesh-sheet) EP acid level

18. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_0518 RINSING STUDIES AT KEK (PRESENTED BY T.SAEKI AT TILC09) U.P.W. ultrasoni c rinse Ethanol rinse (vibration) Ethanol ultrasonic rinse Detergent FM-550 2 % Detergent FM-550 5 % Detergent FM-550 10 % Detergent FM-550 20 % Cleanin g Result × △○△△○○ Before rinse After rinse Many white dots are sulfur contaminatio n Ethanol ultrasonic rinseFM-550 (>10%) rinse Sulfur removed U.P.W. ultrasonic rinse Teflon texture

19. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_0519 Test on 1C03 (Tesla Shape Cavity) + 30’ Chloroform Rinsing + HPR: Suppression of emitters + Excellent Gradient: Eacc ~ 45MV/m at 1.5K Seems efficient for Rinsing of Cavity! (Sulfur highly soluble in chloroform) USE OF CHLOROFORM RINSING TO REMOVE PARTICULATE CONTAMINATION (Saclay) Presented at TTC Meeting 2008

20. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_0520 SYSTEMATIC USE OF CHLOROFORM AS RINSING STEP AT CEA SACLAY Use as a rinsing step after each EP on single-cell R&D cavities → No problem of field emission → Tested on Ichiro Single-Cell cavity

21. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_0521 Cavity Limited by early quench… TESTS OF LOW VOLTAGE EP + CHLOROFORM RINSING WITH IS15 ISHIRO CAVITY

22. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_0522 PROPOSALS FOR THE NEW PROGRAM

23. CEA DSM Irfu Lab-EP study with Nb-plate samples at Nomura/KEK Lab-EP of Nb-plate sample Nb sample + Teflon fixture on Nb base-plate (10cm x 10cm) Repetition of EP (2 min) + Rotation of sample w/o EP (2 min) Sponge cleaning with U.P.W. Wipe 10 times for each arrow = 40-times wipes in total After EP(70 um)

24. CEA DSM Irfu Sample#1: many field emitters Low FE onset ~ 10 MV/m Sample#2: much less field emitters Higher FE onset Area inside circle is scanned by SFEM at JLab. Nb-sample-1 w/o sponge-cleaning Nb-sample-2 w/ sponge-cleaning Sponge-cleaning test with Nb sample disks (w/ and w/o sponge-cleaning) at JLab

25. CEA DSM Irfu Poly-Ethylene (PE) sponge wipe handle Sponge mechanics Insertion Sponge Expansion and Wipe by rotation UPW + detergent inlet UPW + detergent outlet PE sponge First wiping/fitting test of proto-type sponge-cleaner for single-cell cavity at KEK

26. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_0526 Latest VT result of C121 (TESLA single-cell cavity) at Saclay Cavity exchange program is planned : C1-21 will be shipped to KEK for sponge-cleaning and will be shipped back to Saclay for VT. C1-21 (TESLA-shape) suffered from field emission in latest VT at Saclay.

27. CEA DSM Irfu

28. 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_0528 HOW DO THE SURFACE IMPERFECTIONS (PITS, BUMP, etc.) CONTRIBUTE TO QUENCHES. It is possible to determine thanks to thermometry, location of the quench. The cavity might be inspected thanks to camera systems to check if the quench location do correspond to a surface deffect. Presented at TILC09 K.Watanabe

29. CEA DSM Irfu Partial mechanical grinding tool to remove the defects (KEK) CCD camera ＋ LED Head : Diamond seat Motor (3000 rpm) Grinding machine Scratches on irisAfter grinding Cavity exchange program 2 Saclay cavity with quench at low gradient will be grinded at KEK and sent back for VT.

30. CEA DSM Irfu Surface Analyses (XPS) elemental analysis （ >He), chemical analysis Surface Analyses (Auger/AES) elemental analysis （ >He) Surface Analyses (SIMS) elemental analysis （ all) Surface Conditioning (Electron Irradiation, Sputtering, Heating) ElectronArgon Various analysis tools at KEK (XPS, Auger/AES, SIMS, Sputtering, etc..) Sample exchange program Saclay samples EP’ed with normal and low V can be analyzed by various analysis tools at KEK.

31. CEA DSM Irfu Pit-shape development on Nb sample in EP (KEK + JLab) BCP (30um) EP (30um) EP (60um)EP (90um) As received Pit3 EP (120um) After BCP(30um)+EP(120um), still the edge of pit is sharp! Large steps at grain-boundaries after BCP. 40 um

32. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_0532 Some proposal for COMSOL + sample EP test DiffusionMigrationConvection Moving Mesh: The border moves as a function of N i In previous LIA Program, COMSOL used to model fluids in 9Cell Ichiro cavities → non uniform Outlook: Use the software at the microscopic scale to study theoritical evolution of pits/bumps under EP treatment. + Comparison with experiments on samples Bump ~20 µm

33. CEA DSM Irfu BAKING EXPERIMENTS ON ICHIRO CAVITIES (B. Visentin) Additional EP and Baking are planned to reach the quench After additional baking, the cavity did not reach the quench.

34. CEA DSM Irfu Draft Plan for new program June 2009JulyAugSeptOctNovDecJan 2010FebMar COMSOL + EP experiment EP experiment of sample with pits at KEK Cavity exchange program C1-21 to KEK Sponge at KEK VT at Saclay C1-21 to KEK Grinding at KEK VT at Saclay Sample exchange program Design + fabrication of sample EP of samples at Saclay Analysis of samples at KEK COMSOL simulation of EP at Saclay Fast baking with argon EP + Fast baking / VT at Saclay

35. CEA DSM Irfu 16/05/2008- F. Eozénou, T. Saeki - FJPPL 2009 A_RD_0535 SUMMARY The goal of ILC GDE S0 task is to achieve high gradient >35MV/m with yield >90% by the end of 2012. For this goal, we need more R&D of surface treatments. Saclay and KEK are both contributing to the ILC S0 activities. EP facilities at Saclay & KEK. Innovative surface treatments in both laboratories. Cavity / Nb-plate sample exchange program is planned to test these innovative surface treatment techniques as new program. Sponge-cleaning for field emission, Local grinding for quench, Low voltage EP’ed sample to reduce sulfur generation, Fast baking with argon, EP simulation (COMSOL) and EP experiment (EP samples with pits). Thank you for your attention.