Development of Chemical-Mechanical Polishing for Superconducting Cavities Shekhar Mishra, Fermilab...
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Transcript of Development of Chemical-Mechanical Polishing for Superconducting Cavities Shekhar Mishra, Fermilab...
Development of Chemical-Mechanical Polishing for
Superconducting Cavities
Shekhar Mishra, Fermilab
Mark J. Oreglia, Univ. of Chicago
Cliff Spiro, Cabot Microelectronics
04/21/23ANL-FNAL-UofC Collaboration Meeting
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Project Summary
• High Gradient (~35 MV/m) and high yield of the SRF cavities are needed for
– International Linear Collider (ILC) and High Intensity Proton Accelerator (Project-X).
• State of the art cavity manufacturing and processing :– Electo-polishing and High Pressure Rinse
• Remove the damaged Niobium layer
– Average Gradient is 20% lower – Yield is less than 25%
• Limitation: – Complicated procedure, dangerous chemical, expensive– Niobium surface contamination and/or surface imperfection caused
by either manufacturing or processing (Sulfur contamination)
• Proposal: – Chemical-Mechanical Planarization technology to remove the
damaged Niobium layer
04/21/23ANL-FNAL-UofC Collaboration Meeting
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9-cell Test Results
Average A6-8, AES2,4 = 32 MV/m A9 reprocess at Jlab
ILCGoal
Why alternate technique ?
• The electrolyte is a mixture of hydrofluoric and sulfuric acid. Details not fully understood.
• Manufacturing or acid related defect:
04/21/23ANL-FNAL-UofC Collaboration Meeting
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1mm
θ
z
~600µm beadson Nb cavity
These two problems will require mechanical polishing that can make a smooth surface.
• Acid related contamination• Sulfur Deposit
• Surface Smoothness: RMS:
•1247 nm fine grain BCP
• 27 nm single crystal BCP
• 251 nm fine grain ep
Confidential
5
© 2005 Cabot Microelectronics Corporation
Introduction to Cabot Microlectronics and Chemical Mechanical Planarization (CMP)
Non-planarized IC product Planarized IC product
• Leader in CMP slurries– Pioneer in CMP technology– Copper, Tungsten, Dielectric, Data Storage– CMP pad offering in early stage commercialization– ESF consumable and service offering in non-semiconductor applications
• Unparalleled track record– Deliver tens of millions of gallons to customers globally
• Outstanding technology and manufacturing infrastructure– Robust ramp of new products to high volume production– Provide global support and service
• World-class team of scientists and technologists
Confidential
6
© 2005 Cabot Microelectronics Corporation
CMP of Nb 20X Field of View (approx. 230um x 300um)
AFTERRq = 3.5nm
Small islands appear to be grains.Highest point to lowest point around 18.6nm.
BEFORERq = 603nm
Heavily cratered surface from machining
Fermilab Tumbling Machine
04/21/23ANL-FNAL-UofC Collaboration Meeting
7
Design and Engineering needed to hold the cavity in place and liquid flow etc.
Not installed.
04/21/23ANL-FNAL-UofC Collaboration Meeting
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New Vertical Test @ FNAL
• Recently commissioned (IB1)– Existing 125W@ 1.8 K Cryogenic plant– RF system in collaboration with Jlab– Capable of testing ~50 Cavities/yr– Evolutionary upgrades:
• Thermometry for 9-cells, 2 cavities at a time, 2 top plates, Cryo upgrades
• Plan for two additional VTS cryostats
– Ultimate capacity ~ 264 cavity tests/yr
VTS Cryostat:IB1
New RF & Control Room
Plan for 2 more VTS pits
Nine-cell Tesla-style cavity
04/21/23ANL-FNAL-UofC Collaboration Meeting
9
Plans and Possibilities
• Development of the chemical that would be used in the Chemical Mechanical Polishing (CMP) of Niobium
– Small sample test
• Accelerating Gradient Test:– Polish 1-cell (1.3 GHz) Nb cavity using the Fermilab Tumbling machine – Rinse with high purity water – RF test in the Fermilab Vertical Test Facility
• Possible Advantage• No dangerous chemical• A much simplified procedure that could lead to considerable cost saving• Could potentially reduce acid related defects and contamination• Could eliminate surface defects produced during manufacturing
• Small size R&D project with great potential• Excellent training opportunities for students in Accelerator R&D
Budget
04/21/23ANL-FNAL-UofC Collaboration Meeting
10
%FTE UofC Fermilab CabotSalary and Fringe Benefits
- Post-doctoral
-Graduate Student Assistant
-Undergraduate Student Assistant
-Engineers
-Technician
100%
5%
20%
$12,500
$6,500
$26,000Graduate Student Tution
Material and Supplies $1,000 $17,500 $35,000
Publication Cost (Conference) $1,500
Total Direct Cost $15,000 $50,000 $35,000
• Build on Surface science Research• Student training in Accelerator R&D (Fermilab Accelerator Ph.d Program)• Local Industry involvement• Leverage existing laboratory infrastructure