ANL Proposal to Perform Electropolishing for the ILC

ANL Proposal to Perform Electropolishing for the ILC Speaker: Mike Kelly December 5-7, 2005 Argonne National Laboratory A U.S. Department of Energy Office of Science Laboratory Operated by The University of Chicago Office of Science U.S. Departm ent of Energy Joint ANL/FNAL Cavity Processing Facility 2 Pioneering Science and Technology December 5-7, 2005 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy Electropolishing at Argonne Argonne has electropolished ~150 SC niobium cavities Cavity performance at ANL using EP is directly relevant to ILC Experience with various geometries is directly applicable to ILC Major infrastructure for EP of large SC cavities is in place 3 Pioneering Science and Technology December 5-7, 2005 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy Outline I. Cavity Processing at ANL II. Cavity Performance III. An ANL Proposal for the ILC IV. Technical Issues with 9-cell EP 4 Pioneering Science and Technology December 5-7, 2005 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy I. Cavity Processing: High Performance SC Structures for RIA 57.5 MHz QWRbased structures 0.03<  <0.14 115 MHz =0.15 SteeringCorrected QWR 345 MHz =0.40 Double-spoke 172.5 MHz =0.26 HWR 345 MHz =0.62 Triple-spoke 345 MHz =0.5 Triplespoke Pioneering Science and Technology 1m 5 December 5-7, 2005 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy I. Cavity Processing: High-Pressure Water Rinsing Horizontal HPR Development Manual HPR Automated HPR: RIA Triple-Spoke Pioneering Science and Technology Automated HPR: RIA Half-wave 6 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy December 5-7, 2005 I. Cavity Processing: Clean Room Assembly Goal: Minimize or eliminate field emission from particulates using a simple, practical and effective curtained clean area Coupler & pumping lines mounted in class 100 (or better) area Simplicity is crucial; cavity connections ideally made in seconds Work performed below & downstream from open cavity Hardware must be compatible with clean conditions Half-wave for RIA 7 Pioneering Science and Technology Office of Science U.S. Department of Energy December 5-7, 2005 Michael Kelly, ANL Physics Division Cavity Processing: Clean room assembly 8 Pioneering Science and Technology December 5-7, 2005 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy I. Cavity Processing: ANL Recipe for EP with TEM Cavities Electropolishing has been a mainstay at ANL Based on the Siemens process Cavity (anode) - observed no polishing rate sensitivity to electrical connection point even for large cavities High purity Al cathode (3003 series) tailored to the cavity Acid composition 85:10 mixture of 96% H2SO4, 40% HF, reagent grade Temperature 28-32o C (chilled water through the cathode) Average anode current density ~40 mA/cm2, acid replaced when value drops below 30 mA/cm2 9 Pioneering Science and Technology December 5-7, 2005 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy I. Cavity Processing: Niobium Geometries Electropolished at ANL Quarter-wave Co-axial half-wave Important EP Technical Issues:   Temperature gradients and stability Acid flow patterns Pioneering Science and Technology Double spoke 10 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy December 5-7, 2005 I.Cavity Processing: ANL  =0.63 Triple-Spoke Cavity, Area ~1.5 m2 11 Pioneering Science and Technology December 5-7, 2005 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy I. Cavity Processing: High RRR & Hydrogen Q-disease Test #2 after 48 h @ 110-140 K Issue: Hydrogen is introduced during fabrication Has been shown that in high RRR cavities hydrides form preferentially at surface, grain boundaries, lattice imperfections Data clearly indicate the presence of hydrogen Q-disease Pioneering Science and Technology 12 December 5-7, 2005 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy I. Cavity Processing: Hydrogen Degassing FY06 program to bake out all high RRR cavities for RIA 600 oC bake for 10 hours to degas hydrogen has been performed 10 mm chemical polish, highpressure rinse, clean assembly (Furnace is also suitable for 9-cell cavities) 13 Pioneering Science and Technology December 5-7, 2005 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy II. Cavity Performance: Beta=0.63 Multi-Spoke Cavities Q-disease was observed; hydrogen degassing at 600 oC was performed at ANL 2 K surface resistance decreased substantially after 600 0C bake. T = 4.2 K (unchanged after bake) No X-rays 14 Pioneering Science and Technology December 5-7, 2005 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy II. Cavity Performance: Residual Surface Resistance vs. BPEAK Residual RF Surface Resistance (Ohms) (Best =0.61 Cavity) Lower is better Peak Surface Magnetic Field (Gauss) Pioneering Science and Technology 15 Office of Science U.S. Department of Energy December 5-7, 2005 Michael Kelly, ANL Physics Division III. An ANL Proposal for the ILC: Electropolishing Motivation It has been generally agreed that a U.S.-based technical capability to build, process and operate high-performance 9-cell elliptical cavities is required for the proposed International Linear Collider Proposal To leverage the existing infrastructure and expertise at Argonne to build a complete electropolish apparatus for ILC-type 9-cell elliptical cavities and perform electropolishing on 9-cell cavities Deliverables FY06: An operational electropolishing facility for ILC 9-cell cavities Resources Required FY06: Pioneering Science and Technology 1.5 FTE (0.75 Scientist, 0.75 Designer/Technician); $135K M&S 16 December 5-7, 2005 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy III. An ANL Proposal for the ILC: Electropolishing FY07 Activities 1. 2. 3. Electropolish cavities obtained through the ILC collaboration Study technical issues and optimize operating parameters Document procedures and train personnel Near term plan 1. 2. 3. 4. Generate at ANL together with Tajima (LANL) a technical plan and drawings (2 months) Take this plan out for design review by technical experts at Fermilab, JLab, KEK and DESY Fabricate and test the apparatus using a test cavity obtained though ILC collaboration Pre-rinse possibly at ANL, seal cavities in the joint clean room facility. Final HPR at Fermilab 17 Pioneering Science and Technology December 5-7, 2005 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy III. An ANL Proposal for the ILC: Capability at Argonne  Comprehensive chemical processing capability suitable for several cavities per week  Primary infrastructure: 1. A pair of large chemistry rooms 2. A large air scrubber 3. Three clean room areas for post-processing (highpressure rinsing) 4. A large volume de-ionized water system 5. Procedures for procurement, storage, handling, disposal 6. Hardware: power supplies, acid pumps, water chiller 18 Pioneering Science and Technology December 5-7, 2005 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy III. An ANL Proposal for the ILC: Resources for ILC EP 60 feet EP Power Supplies Pioneering Science and Technology 10 kW Chiller 32 l/m DI Water 19 Office of Science U.S. Department of Energy December 5-7, 2005 Michael Kelly, ANL Physics Division III. An ANL Proposal for the ILC: A “Closed Loop” EP Flow Diagram AIR/ N2 INTAKE 20 Pioneering Science and Technology December 5-7, 2005 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy III. An ANL Proposal for the ILC: A 9-cell Cavity in the ANL Chemistry Room Floor Plan Side View 16 feet Pioneering Science and Technology 16 feet 21 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy December 5-7, 2005 IV. Technical Issues: Horizontal and Vertical Polishing Direct ANL experience indicates the following issues are important: 1. Orientation of the niobium surface: Horizontal downward facing Nb surfaces polish faster than horizontal upward facing surfaces. 2. Hydrogen bubbles: Streaming from the cathode can cause grooves, streaks in the cavity. Increasing bubble density raises resistivity of the electrolyte bath 3. Uneven polishing: Differential polishing in elliptical cavities is not a cathode proximity effect; however is likely due to flow rate/temperature effects 22 Pioneering Science and Technology December 5-7, 2005 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy IV. Technical Issues: Orientation of the Niobium Surface Horizontal-downward facing surfaces polish faster than horizontal upward surfaces Uneven polishing will be difficult to avoid in with a 9-cell cavity oriented vertically Polishing Rate at 3 Different Points on a Cavity Cavity flipped after every 50 cycles Surface facing down Surface facing up 23 Pioneering Science and Technology December 5-7, 2005 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy IV. Technical Issues: Differential Iris/Equator Polishing Relevant niobium EP information contained in the literature Cathode Distance vs. Bath Potential Hydrogen bubbles shown to lead to an increase in the electrolyte resistivity Reference: Diepers et al, Research Laboratories of Siemens (1971) Data implies that the cathode distance is not critical Horizontal elliptical cavities should polish uniformly, however not so in practice Pioneering Science and Technology 24 December 5-7, 2005 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy IV. Technical Issues: Differential Iris/Equator Polishing Test: Cathode distance vs. polishing rate Impeller Anode Cathode Anode – 12”x7/8”x1/8” RRR=250 Nb (Wah Chang) Cathode – 3 Turns 3/8” 3003 Series Aluminum Anode/Cathode voltage = 16 V Temperature = 28-30 oC Time = 1 hour, continuous Acid flow rate ~ 1 cm/s at the cathode 13 inches Pioneering Science and Technology 25 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy December 5-7, 2005 IV. Technical Issues: Differential Iris/Equator Polishing Cathode Distance vs. Polishing Rate EP removal rate mm/minute Sample 1 Sample 2 Distance to Cathode (cm) NO RATE DEPENDENCE ON CATHODE PROXIMITY NO MASKING OR COMPLITCATED SHAPES NEEDED FOR 1.3 GHz CAVITIES Pioneering Science and Technology 26 December 5-7, 2005 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy IV. Technical Issues: The ANL Proposal Would Address… Uneven polishing 4 flow rate effect? 4 separate flow rate from temp. stability by direct (water) cooling of cavity The perceived need to polish without a He vessel Temperature stability 4 use high-purity Al heat exchanger coil rather than Teflon 27 Pioneering Science and Technology December 5-7, 2005 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy Concluding Statement  ANL is eager to contribute to the ILC collaboration in an area of strong technical expertise and capability at this laboratory, namely, electropolishing 28 Pioneering Science and Technology December 5-7, 2005 Michael Kelly, ANL Physics Division Office of Science U.S. Department of Energy