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VEP studies at STF/KEK T. Saeki (KEK) 15 May 2014 AWLC2014 at FNAL.

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Presentation on theme: "VEP studies at STF/KEK T. Saeki (KEK) 15 May 2014 AWLC2014 at FNAL."— Presentation transcript:

1 VEP studies at STF/KEK T. Saeki (KEK) 15 May 2014 AWLC2014 at FNAL

2 Electro-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.

3 Horizontal EP (HEP) / Vertical EP (VEP) Rotation of cavity in HEP process. (HEP setup at KEK-STF) Turning the EP-bed for draining No rotation of cavity in VEP process. (VEP setup at Saclay) EP electrolyte is half filled. EP electrolyte is fully filled.

4 Horizontal EP / Vertical EP Horizontal EP (HEP) Asia: KEK-STF Europe: DESY, Saclay, RI, Zanon US: FNAL, ANL, Jlab, AES Vertical EP (VEP) Asia: KEK / Marui Galvanizing Co. Ltd. Europe: Saclay US: Cornell, JLab I will present these activities. Vertical electro-polishing (VEP) ・ No need of large space ・ No need of cavity rotation ・ No need of horizontal-vertical conversion system More suitable for mass production

5 The retractable-wing cathode to realize uniform flow of electrolyte and uniform distribution of electric current. Development of retractable wing-shape cathode in collaboration with Marui Co. Ltd. Flow direction Acid bath Pump Side View Top View OpenedRetracted Al EP electrolyte is circulated to remove hydrogen gas and for low temperature. Rotation of cathode Marui Galvanizing Co. Ltd. named the cathode “Ninja”, which is registered as a trade name.

6 VEP experiments with “Ninja” cathode 1, VEP experiments with two single-cell cavities for vertical tests ・ To optimize VEP condition and evaluate acceleration gradient 2, 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 VEP 3, 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

7 VEP experiment with single-cell cavity VEP condition (an example) EP solution: H 2 SO 4 (98%):HF(55%)=9:1 Voltage: 9V Flow rate: 5L/min Cathode rotation speed: 5rpm EP duration: 90min Flow direction: Bottom to top single-cell cavity VEP setup Schematic view of VEP setup

8 The hydrogen gas generated during EP process is the most difficult problem. Flaws observed after VEP with inadequate parameters (voltage, temp, flow rate, etc...): -Stripe on surface (due to bubbles) -Rough surface These problems should be overcome. Development of retractable wing-shape cathode in collaboration with Marui Co. Ltd. Lower side: smooth. Upper side: stripe by bubbles.

9 VEP experiment with single-cell cavity Logged data (Temperature-time)Logged data (Voltage, Current density-time) Upper Lower Inner surface of cavityRemoval thickness In the next step, we would like to do vertical test and know the acceleration gradient of VEP’ed cavity.

10 Plan 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 /Marui ・ Inner surface inspection etc. at Marui Marui VEP with “Ninja” ・ Transportation back to CEA Saclay. ・ Vertical Test (VT) at CEA Saclay VEP + VT plan with 1AC3 cavity Inner surface at Marui (Digital camera) Inner surface at Marui (Endoscope) 1AC3 cavity sent from CEA Saclay to KEK / Marui. 1AC3 cavity will be VEP’ed at Marui and will be sent back to CEA Saclay for VT.

11 VEP experiments with coupon single-cell cavity Coupon cavity (with 6 Nb coupons and transparent windows) VEP setup Nb coupons (6 points) ・ EP current ・ Temperature ・ Surface roughness ・ Removal thickness ・ Impurities can be investigated. Transparent window (4 points) ・ State of bubbles ・ State of cathode can be seen during VEP process. VEP condition (an example) EP solution: H 2 SO 4 (98%):HF(55%)=9:1 Voltage: 9–11V Flow rate: 5L/min Rotation speed: 1rpm EP time: 150min Flow direction: Bottom to top

12 Cathode rod Cathode wing Schematic for a coupon single-cell cavity with a VEP cathode “Ninja” Window Upper window Lower window Coupon

13 VEP experiment with coupon single-cell cavity Temperature (After 120min) Current density (After 120min) Removal thickness (Temperature near coupon) Upper lower Surface roughness Ra ・ Temperature Equator is highest ・ Current density ・ Removal thickness ・ Surface roughness Ra Largest at top iris The influence of bubble hitting from wings? (Now under investigation) Bubbles EP solution flow To achieve more uniform VEP, we need to develop how to control bubbles. : Coupon position

14 EP solution tank Water Waste liquid Degassing tank VEP experiment with 9-cell cavity 9-cell cavity VEP setup for 9-cell cavity Schematic view of VEP setup VEP condition (an example) EP solution: H 2 SO 4 (98%):HF(55%)=9:1 Voltage: 7-9V Flow rate: 10L/min Rotation speed: 1rpm EP time: 90min Flow direction: Bottom to top

15 VEP experiment with 9-cell cavity Logged data (Temperature-time) Logged data (Voltage, Current density-time) Average temperature of each cell (After 60min) Average removal thickness of each cell Upper Lower Total average 18.2μm Temperature in EP tank

16 VEP experiments with 9-cell cavity Inner surface inspection 5 th cell upper iris 5 th cell equator 5 th cell lower iris 5 th cell – 6 th cell From upper side Removal thickness of each parts Temperature of each parts (after 60min) We need more optimization (voltage, flow rate, temperature etc.) →After optimization, we would like to perform vertical test of 9-cell cavity

17 STF building COI: Center-of-Innovation Building at KEK COI building COI building construction area 2012 supplementary-budget: model facility for ILC assembly & Testing 17

18 COI: Center-of-Innovation Building Cantilever Vertical-EP As a model facility for ILC assembly & Testing Clean-room He Cryogenics EP(vertical-EP) Cavity Testing(4-cavities-test) Cryomodule Assembly(cantilever) Cryomodule Testing 18

19 New VEP setup delivered for COI building EP bed is used both for HEP and VEP (2 ways). This enables the direct comparison of HEP and VEP processes. EP bed Manufacturer is MHI Cathode insertion tool. Cathode motor

20 Summary KEK 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.


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