Presentation on theme: "T. Saeki (KEK) 15 May 2014 AWLC2014 at FNAL"— Presentation transcript:
1T. Saeki (KEK) 15 May 2014 AWLC2014 at FNAL VEP studies at STF/KEKT. Saeki (KEK)15 May 2014AWLC2014 at FNAL
2Electro-polishing (EP) process EP is thought to be the best final surface-polishing process of ILC 9-cell cavity to achieve high-gradient specification of ILC.EP is also most complicated/costy surface-preparation process in the cavity mass-production of ILC.The current standard EP method is called “horizontal EP process”, where a cavity is set up in a horizontal posture and the cavity is rotated during the EP process.In order to achieve simpler and more cost-effective EP process, ”vertical EP process” is studied in many laboratories in the world, where a cavity is set up in a vertical and fixed posture.
3Horizontal EP (HEP) / Vertical EP (VEP) Rotation of cavity in HEP process.(HEP setup at KEK-STF)EP electrolyte is fully filled.EP electrolyte is half filled.Turning the EP-bed for drainingNo rotation of cavity in VEP process.(VEP setup at Saclay)
4Horizontal EP / Vertical EP Horizontal EP (HEP)Asia: KEK-STFEurope: DESY, Saclay, RI, ZanonUS: FNAL, ANL, Jlab, AESVertical EP (VEP)Asia: KEK / Marui Galvanizing Co. Ltd.Europe: SaclayUS: Cornell, JLabI will present these activities.Vertical electro-polishing (VEP)・No need of large space・No need of cavity rotation・No need of horizontal-verticalconversion systemMore suitable for mass production
5Development of retractable wing-shape cathode in collaboration with Marui Co. Ltd. The retractable-wing cathode to realize uniform flow of electrolyte and uniform distribution of electric current.EP electrolyte is circulated to remove hydrogen gas and for low temperature.Flow directionAcid bathPumpSide ViewTop ViewOpenedRetractedAlRotation of cathodeMarui Galvanizing Co. Ltd. named the cathode “Ninja”, which is registered as a trade name.
6VEP experiments with “Ninja” cathode 1, VEP experiments with two single-cell cavities for vertical tests・To optimize VEP condition and evaluate acceleration gradient2, VEP experiments with one coupon single-cell cavity・To investigate the relationship between VEP condition (temperature, current, etc.)and surface state after VEP (roughness, removal thickness etc.)・To achieve more uniform VEP3, VEP experiments with one 9-cell cavity for vertical tests・To optimize VEP condition and evaluate acceleration gradient・To develop the VEP mass production system
7VEP experiment with single-cell cavity VEP setupsingle-cell cavityVEP condition (an example)EP solution: H2SO4(98%):HF(55%)=9:1Voltage: 9VFlow rate: 5L/minCathode rotation speed: 5rpmEP duration: 90minFlow direction: Bottom to topSchematic view of VEP setup
8Development of retractable wing-shape cathode in collaboration with Marui Co. Ltd. The hydrogen gas generated during EP process is the most difficult problem.Lower side: smooth.Upper side: stripe by bubbles.Flaws observed after VEP with inadequate parameters (voltage, temp, flow rate, etc...):Stripe on surface (due to bubbles)Rough surfaceThese problems should be overcome.
9VEP experiment with single-cell cavity Logged data (Temperature-time)Logged data(Voltage, Current density-time)123456789101112131415161718192021222324UpperInner surface of cavityRemoval thicknessIn the next step, we would like to do vertical test and knowthe acceleration gradient of VEP’ed cavity.Lower
10Plan of VEP + VT with single-cell cavity in collaboration with CEA Saclay Vertical test (VT) result (37 MV/m) at CEA Saclay before transportation to KEK /Marui1AC3 cavity sent from CEA Saclay to KEK / Marui.VEP + VT plan with 1AC3 cavity・Inner surface inspection etc.at MaruiInner surfaceat Marui(Digital camera)Marui VEP with “Ninja”・Transportation back to CEA Saclay.・Vertical Test (VT) at CEA SaclayInner surfaceat Marui(Endoscope)1AC3 cavity will be VEP’ed at Marui and will be sent back to CEA Saclay for VT.
11VEP experiments with coupon single-cell cavity Nb coupons (6 points)・EP current・Temperature・Surface roughness・Removal thickness・Impuritiescan be investigated.Coupon cavity(with 6 Nb coupons andtransparent windows)Transparent window(4 points)・State of bubbles・State of cathodecan be seenduring VEP process.VEP condition (an example)EP solution: H2SO4(98%):HF(55%)=9:1Voltage: 9–11VFlow rate: 5L/minRotation speed: 1rpmEP time: 150minFlow direction: Bottom to topVEP setup
12Schematic for a coupon single-cell cavity with a VEP cathode “Ninja” wingUpper windowCouponWindowCouponLower windowCathode rod
13VEP experiment with coupon single-cell cavity Temperature(After 120min)Current density(After 120min)Removal thicknessSurface roughness Ra: Coupon positionUpperlower(Temperature near coupon)The influence of bubble hitting from wings?(Now under investigation)・TemperatureEquator is highestBubbles・Current density・Removal thickness・Surface roughness RaLargest at top irisTo achieve more uniform VEP,we need to develop how to control bubbles.EP solutionflow
14VEP experiment with 9-cell cavity VEP setup for 9-cell cavityDegassing tank9-cell cavityVEP condition (an example)EP solutiontankEP solution: H2SO4(98%):HF(55%)=9:1Voltage: 7-9VFlow rate: 10L/minRotation speed: 1rpmEP time: 90minFlow direction: Bottom to topWaterWasteliquidSchematic view of VEP setup
15VEP experiment with 9-cell cavity UpperUpperLogged data (Temperature-time)LowerLowerTotal average18.2μmTemperature in EP tankAverage temperatureof each cell (After 60min)Average removal thicknessof each cellLogged data(Voltage, Current density-time)
16VEP experiments with 9-cell cavity Inner surface inspectionFrom upper side5th cell upper iris5th cell equatorTemperature ofeach parts (after 60min)Removal thickness ofeach parts5th cell lower iris5th cell – 6th cellWe need more optimization (voltage, flow rate, temperature etc.)→After optimization, we would like to perform vertical test of 9-cell cavity
17COI: Center-of-Innovation Building at KEK 2012 supplementary-budget: model facility for ILC assembly & TestingSTF buildingCOI building construction areaCOI building
18COI: Center-of-Innovation Building As a model facility for ILC assembly & TestingClean-roomHe CryogenicsEP(vertical-EP)Cavity Testing(4-cavities-test)Cryomodule Assembly(cantilever)Cryomodule TestingCantileverVertical-EP
19New VEP setup delivered for COI building Cathode motorEP bed is used both for HEP and VEP (2 ways). This enables the direct comparison of HEP and VEP processes.Cathode insertion tool.EP bedManufacturer is MHI
20SummaryKEK started the R&D of Vertical EP (VEP) process in collaboration with Marui Galvanizing Co. Ltd.Special cathode “Ninja” is developed by Marui Galvanizing Co. Ltd. for VEP process. The “Ninja” cathode has retractable-wings which realize uniform flow of electrolyte and uniform distribution of electric current.VEP experiments are performed with single-cell cavities, single-cell coupon cavity, and 9-cell cavities to optimize the parameters.Single-cell cavity “1AC3” provided by CEA Saclay will be VEP’ed with “Ninja” cathode and the cavity will be VT’ed at CEA Saclay.New COI building will be equipped with VEP/HEP compatible setup by MHI, which was already delivered to KEK. The setup will be installed into the new COI building in 2015.