CEA DSM Irfu May 28th A RD 05: SURFACE PREPARATION STUDIES FOR SUPERCONDUCTIVE CAVITIES F. Eozénou, T. Saeki - F. Eozenou / T. Saeki - A_RD_05

CEA DSM Irfu May 28th F. Eozenou / T. Saeki - A_RD_052 CONTEXT

CEA DSM Irfu May 28th F. Eozenou / T. Saeki - A_RD_053 Members IrfuKEK Leader: Eozénou Fabien Leader: Takayuki Saeki Visentin BernardHitoshi Hayano Berry StéphaneKen Watanabe Antoine ClaireShigeki Kato Masashi Yamanaka Motoaki Sawabe PARTICIPANTS Visit Saeki San & Yamanaka Saclay in March 2012

CEA DSM Irfu May 28th F. Eozenou / T. Saeki - A_RD_054 SURFACE TREATMENTS FOR LARGE SCALE CAVITY PRODUCTION International Linear Collider ~16000 Superconductive Niobium cavities > 31.5 MV/m Improvement of the preparation of the SC Nb cavities  Cleaning of the surface  Reparation of defects  Increase in the reprocubility of the process  Cost reduction  Industrialization  Cavity tratment/exchange program  Sample treatments/analysis

CEA DSM Irfu May 28th F. Eozenou / T. Saeki - A_RD_055 EXAMPLES OF CONTRIBUTION WITHIN TYL

CEA DSM Irfu May 28th F. Eozenou / T. Saeki - A_RD_056 LOCAL GRINDING AT KEK CCD camera ＋ LED Head : Diamond seat Motor (3000 rpm) Grinding machine Scratches on irisAfter grinding

CEA DSM Irfu May 28th F. Eozenou / T. Saeki - A_RD_057 Recovery of the cavity after local grinding of the defects at iris. grinding IMPROVEMENT AFTER GRINDING OF DAMAGED CAVITY RF test of damaged 1Cell Test after grinding and EP

CEA DSM Irfu May 28th F. Eozenou / T. Saeki - A_RD_058 Poly-Ethylene (PE) sponge wipe handle Sponge mechanics Insertion Sponge Expansion and Wipe by rotation UPW + detergent inlet UPW + detergent outlet PE sponge SET-UP FOR SPONGE WIPING ON SINGLE-CELL

CEA DSM Irfu May 28th F. Eozenou / T. Saeki - A_RD_059 RESULTS ACHIEVED WITH SINGLE-CELL Test with a good cavity (Eacc>35 MV/m, no FE) Sponge wipe at KEK VT at Saclay The performance of the cavity is maintained The process do not deteriorate performance Tests in challenging conditions (FE limited cavity) No improvement achieved But suspicious cleaning sequence Experiment will be repeated

CEA DSM Irfu May 28th F. Eozenou / T. Saeki - A_RD_0510 Field flatness degradation experimentally observed at KEK after electropolishing, How can modelling help us understand (and solve) the problem? Fluid velocity [HF] at s [HF] at s Good electropolishing of central cell #5 Electro-polishing will depend on the cell location for others →Electropolishing needs to be improved in the other cells HF mol/m3 Velocity m/s TESLA Cavities MODELLING OF ELECTRO-POLISHING (Saclay)

CEA DSM Irfu May 28th F. Eozenou / T. Saeki - A_RD_0511 SURFACE CONTAMINATION ANALYSIS OF SAMPLES Samples EP’ed at KEK & Saclay Analysis at KEK Same contaminants found (S, F, C) More KEK Influence of anode-cathode distance? → Experiments to be continued Surface Analyses (XPS) Surface Analyses (Auger/AES) Surface Analyses (SIMS)

CEA DSM Irfu May 28th F. Eozenou / T. Saeki - A_RD_0512 NEW EQUIPMENTS, NEW CHALLENGES

CEA DSM Irfu May 28th F. Eozenou / T. Saeki - A_RD_0513 VERTICAL EP (VEP) AT CEA SACLAY

CEA DSM Irfu May 28th F. Eozenou / T. Saeki - A_RD_ cm EVOLUTION OF CEA SACLAY 2004: Experiments on flat samples: 2006: Operation of 1Cell Horizontal EP set-up 2011: Operation of Vertical EP Set-up

CEA DSM Irfu May 28th F. Eozenou / T. Saeki - A_RD_0515 September 2011: Commissioning, Tests with water October 2011: Connections to exhausts, tests with acid in november January 2012: Area closed. Final configuration. EVOLUTION OF THE VEP SET-UP

CEA DSM Irfu - F. Eozenou / T. Saeki - A_RD_0516 HORIZONTAL VS VERTICAL Pros: -Good evacuation of gases (cavity half filled) -Demonstrated efficiency -Large range of parameters Cons: -Complicated process -Rotary seals -Switching of the cavity -Low removal rate Pros: -Simple process -Low floor surface -Improved safety -Higher removal rate Cons: -Sensitive to fluid dynamics -Proper parameters to be determined… …Voltage and fluid velocity May 28th 2012

CEA DSM Irfu r Z VERTICAL CONFIGURATION AND MODELLING Cathode Fz Configuration simpler in VEP case: Symmetry according to z-axis → 2D axisymmetry model Fluid velocity [HF] at s [HF] at s Modelling of horizontal EP: Difficult: no symmetry Hints for non uniform polishing - F. Eozenou / T. Saeki - A_RD_05May 28th 2012

CEA DSM Irfu 18 EXAMPLE OF MODELLING Modelling (COMSOL) with rod cathode Area close to the cell poorly swept with SPL cavities Needs improvement Electrolyte velocity: m/s Flow profile from the cathode to the cavity: Fluid velocity m/s Vs x Fluid velocity m/s - F. Eozenou / T. Saeki - A_RD_05May 28th 2012

CEA DSM Irfu 19 Modified Cathode Shape (SPL cavity) VEP WITH CIRCULATING ACID SHOULD NOT BE CELL DEPENDENT SHAPED CATHODE MAKE IT POSSIBLE TO IMPROVE THE FLOW Example of fluid modelling with alternative shape Fluid velocity m/s Fluid velocity m/s Vs x Fluid velocity m/s - F. Eozenou / T. Saeki - A_RD_05May 28th 2012

CEA DSM Irfu 20 Parameters for 1st VEP sequence: - 3 hours VEP - Shaped and masked cathode - 8 L/min acid flowrate, Nitrogen blowing - 20 V - Temperature < 26°C FIRST VEP WITH 1Cell Benefits from VEP: operator friendly! -No flaw observed during the first VEP sequence -Easy preparation of the cavity (time saved + security) -More efficient rinsing procedures -Very stable process → Adapted to industry - F. Eozenou / T. Saeki - A_RD_05May 28th 2012

CEA DSM Irfu Bright Surface Brighter on top half-cell … but bubble traces → 20 V = Oxygen generation RESULTS AFTER EPV A 20V Acid flow (8L/min) not sufficient to stir the gas - F. Eozenou / T. Saeki - A_RD_05 +Ar Baking 3hx145°C May 28th 2012

CEA DSM Irfu 22 EPV WITH LOWER VOLTAGE (12V) No obvious bubble trace at the upper cell Brightening of the surface Promising Voltage → Waiting for the RF Test of the cavity - F. Eozenou / T. Saeki - A_RD_05May 28th Cell Vertically EP’ed at 12V. Improvement of the surface.

CEA DSM Irfu - F. Eozenou / T. Saeki - A_RD_0523 NEW CAVITY FABRICATION FACILITY AT KEK May 28th 2012

Introduction of KEK activities The fabrication-cost reduction of superconducting cavity is not enough for future project like ILC. We have constructed a new superconducting Cavity Fabrication Facility (CFF) at KEK for the study of cost-effective mass-production of cavity. All the necessary equipment for the cavity fabrication were installed in the CFF at KEK. We have fabricated 9-cell cavity KEK-00 (without HOM) in CFF. The fabrication process of KEK-00 and the vertical test result of KEK-00 will be shown. Future plan of CFF will shown as well as the plan of FJPPL collaboration between Saclay and KEK. 24

25 Main Equipments of Cavity Fabrication Facility Inspection equipment for Nb surface EBW room Installation of EBW machine started from April Vertical lathe Press machine (servo control) Measuring system for half cell shape (Under developing) Chemical Polishing room

30 June – Dumbbell, 8 – Dumbbell EBW at Job-shop (June 2011 – July 2011) Beam 8 July July

Fabrication of KEK-00 Cavity (w/o HOM) Center cells (Nb) / EBW at job shop Dumb-bell (Nb) Beam-pipe (Nb) End-cells (Nb) Input-port pipe (Nb) End-Plates (Ti) + Nb ring Beam-pipe (Nb) End-Plates (Ti) + Nb ring Flanges (Nb-Ti alloy) 27

Final EBW at Equator of End-Cell at Job Shop 1 Dec Failure in the EBW at the equator of end-cell (cell#1)/ 120 kV, 30 – 29 mA. Voltage Beam Current Position of hole Cell#1 28

The setup of EBW of KEK-00 to repair the hole of cell#1. Repair of 9-cell cavity KEK-00 by EBW 30 Jan (Mon.) Small Nb piece was made and it was set into the hole. EBW 29 EBW with 120kV, 20mA, and 5 mm/s. EBW bead

Observation of repaired part and local grinding A picture of repaired part: inner surface of cell#1-equator, theta=237 deg. (1 st Feb. 2012) EBW bead Area of EBW for repairing the hole of cell#1 Observation by Kyoto camera Local grinding was done for the inner surface of the repaired part of cell#1 by hand in order to make a smooth surface. (3 Feb. 2012). 30

31 Surface treatment of 9-cell cavity (KEK-00) Bulk EP (100 um), Degreasing (50 0 C, 30 min), HPR (1.5 h), Annealing(4 h, C), and final EP (20 um). HPR (7 hours) Brushing of beam-pipe and HOM antenna. Degreasing with detergent (FM-20 2%) in hot bath (50 0 C, 30 min). Brushing

Vertical Test Result of 9-cell cavity w/o HOM (KEK-00) 32 Cell#1 (repaired cell) reached to 42.7 MV/m in the 6pi/9 mode. Limitation in the pi mode might be quench at cell#8, because the T-mapping sensor detected higher temperature in cell#8 in coincidence with the quench at 29 MV/m. Eacc = 29 MV/m Q0 = 9 x 10^9

33 Future Plan of Cavity Fabrication Facility (CFF) Activities FY 2011FY cell cavity: KEK-00 without HOM April 9-cell cavity: KEK-01 with HOM Machining of all parts by KEK EBW of all seams at CFF(KEK) April Fabrication 9-cell cavities: KEK- 02 with HOM Single-cell cavity for FJPPL collaboration Surface preparation and VT Study for the high- pressure code application This cavity will be used for the vertical EP test at Saclay. Fabrication

Summary of KEK activities All equipment (press machine, CP room, EBW machine, etc) were installed in Cavity Fabrication Facility (CFF). 9-cell cavity KEK-00 (w/o HOM) was fabricated. Center cells were EBW’ed at job shop and end-groups were EBW’ed in CFF(KEK). Final EBW of KEK-00 cavity at the equator of end-cell was failed, but it was repaired. After surface preparation at KEK, KEK-00 reached to Eacc = 29 MVm in vertical test. 9-cell cavity KEK-01 and -02 (w/ HOM) will be fabricated where all seams will be EBW’ed at CFF(KEK) in FY2012. We will fabricate a single-cell cavity in CFF at KEK. This cavity will be used for the study of vertical EP at Saclay in the frame-work of FJPPL collaboration. 34

CEA DSM Irfu - F. Eozenou / T. Saeki - A_RD_0535 OBJECTIVE FOR FY 2012 May 28th 2012

Plan of Collaboration with Single-Cell Cavity 36 Fabrication of a single-cell cavity at CFF(KEK). This cavity will be used for the study of vertical EP at Saclay in the frame-work of FJPPL collaboration. Fabrication of single-cell cavity at CFF(KEK). Vertical EP of the cavity and vertical test at Saclay.

CEA DSM Irfu May 28th F. Eozenou / T. Saeki - A_RD_0537 ON-GOING SAMPLES EXPERIMENTS  Same contaminants observed  Quantities differ (Sulfur)  More sulfur found at iris at KEK  Electrodes’ configuration incriminated KEK. Rotating Nb samples. Saclay. static Nb samples. Samples measurements on KEK.  4 samples will be EP’ed, 4 different anode-cathode distance (Saclay)  Packing in Cleanroom in dedicated box  Analysis of samples (KEK)

CEA DSM Irfu May 28th F. Eozenou / T. Saeki - A_RD_0538 COMPARISON HEP/VEP KEK Saclay  2 advanced equipments  Efficiency of HEP demonstrated  Experience necessary for VEP  Unique opportunity for fruitful comparison  KEK HEP’ed cavity shipped to Saclay  Saclay  Saclay  Comparison

CEA DSM Irfu May 28th F. Eozenou / T. Saeki - A_RD_0539 ON-GOING GRIDING/WIPING EXPERIMENTS  KEK Grinder makes it possible to treat equator and iris  New head under development to reach any part of a cell  Saclay Cavity with pits sent to KEK  Local grinding of the defects  Cavity shipped back to Saclay for VT  Additional sponge-wiping of contaminated cavity Saclay cavity with pits Saclay cavity with FE KEK grinding system KEK wiping system

CEA DSM Irfu 40 THANK YOU FOR YOUR ATTENTION - F. Eozenou / T. Saeki - A_RD_05May 28th 2012