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Development of Chemical-Mechanical Polishing for Superconducting Cavities. Shekhar Mishra, Fermilab Mark J. Oreglia, Univ. of Chicago Cliff Spiro, Cabot Microelectronics. Project Summary. High Gradient (~35 MV/m) and high yield of the SRF cavities are needed for

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development of chemical mechanical polishing for superconducting cavities

Development of Chemical-Mechanical Polishing for Superconducting Cavities

Shekhar Mishra, Fermilab

Mark J. Oreglia, Univ. of Chicago

Cliff Spiro, Cabot Microelectronics

project summary
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

ANL-FNAL-UofC Collaboration Meeting

9 cell test results
9-cell Test Results

ILC

Goal

Average A6-8, AES2,4 = 32 MV/m

A9 reprocess at Jlab

ANL-FNAL-UofC Collaboration Meeting

why alternate technique
Why alternate technique ?
  • The electrolyte is a mixture of hydrofluoric and sulfuric acid. Details not fully understood.
  • Manufacturing or acid related defect:

~600µm beads

on Nb cavity

  • Acid related contamination
    • Sulfur Deposit
  • Surface Smoothness: RMS:
    • 1247 nm fine grain BCP
    • 27 nm single crystal BCP
    • 251 nm fine grain ep

z

θ

These two problems will require mechanical polishing that can make a smooth surface.

1mm

ANL-FNAL-UofC Collaboration Meeting

introduction to cabot microlectronics and chemical mechanical planarization cmp
Introduction to Cabot Microlectronics and Chemical Mechanical Planarization (CMP)
  • 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

Non-planarized IC product

PlanarizedIC product

cmp of nb 20x field of view approx 230um x 300um
CMP of Nb 20X Field of View (approx. 230um x 300um)

BEFORE

Rq = 603nm

Heavily cratered surface from machining

AFTER

Rq = 3.5nm

Small islands appear to be grains.

Highest point to lowest point around 18.6nm.

fermilab tumbling machine
Fermilab Tumbling Machine

Not installed.

Design and Engineering needed to hold the cavity in place and liquid flow etc.

ANL-FNAL-UofC Collaboration Meeting

new vertical test @ fnal
New Vertical Test @ FNAL

Nine-cell Tesla-style cavity

  • 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

Plan for 2 more

VTS pits

VTS Cryostat:IB1

New RF & Control Room

ANL-FNAL-UofC Collaboration Meeting

plans and possibilities
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

ANL-FNAL-UofC Collaboration Meeting

budget
Budget
  • Build on Surface science Research
  • Student training in Accelerator R&D (Fermilab Accelerator Ph.d Program)
  • Local Industry involvement
  • Leverage existing laboratory infrastructure

ANL-FNAL-UofC Collaboration Meeting