Proposed Button Design for a Series of High Power Button Tests Arash Zarrebini-Esfahani 22 nd August...
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![Page 1: Proposed Button Design for a Series of High Power Button Tests Arash Zarrebini-Esfahani 22 nd August 2007.](https://reader030.fdocuments.in/reader030/viewer/2022032800/56649d4b5503460f94a28e21/html5/thumbnails/1.jpg)
Proposed Button Design for a Series
of High Power Button Tests
Arash Zarrebini-Esfahani22nd August 2007
![Page 2: Proposed Button Design for a Series of High Power Button Tests Arash Zarrebini-Esfahani 22 nd August 2007.](https://reader030.fdocuments.in/reader030/viewer/2022032800/56649d4b5503460f94a28e21/html5/thumbnails/2.jpg)
MICE
• 2 RFCC module each containing 4 cavities
• High gradients up 16 MV/m at 201 MHz
• Normal conducting Rounded Pillbox cavities
– Lower peak surface field
– High accelerating efficiency
– Lower RF power
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201 MHz Cavity Design
• Cavity body + water cooling lines
• Four ports and flanges
• RF loop couplers
• Cavity support structure
• Cavity tuners
• Ceramic RF windows
• Curved Be windows
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201 MHz Cavity Fabrication
1 - Half shell spinning
2 - Fabrication of stiffener ring
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201 MHZ Cavity Fabrication
3 – Nose hole and half shell lip machining
4 – Half shell electro polishing
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201 MHz Cavity Fabrication
5 – Equator electron beam welding
6 – Fabrication of nose ring
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201 MHz Cavity Fabrication
7 – Cavity port pulling
8 – Cooling pipes TIG welding
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What are the Problems?
1) Production techniques offer poor reproducibility
2) Achievable gradients are poor
• Surface features are one of main limiting factors
− Field emission not an issue when average surface roughness, RA < 2 µm
− Current Electro polishing techniques offers RA < 1 µm , But it is a `Black Art ‘
Surface Impurities or Defects are dominant cause of limited accelerating gradient ? (Must be verified)
![Page 9: Proposed Button Design for a Series of High Power Button Tests Arash Zarrebini-Esfahani 22 nd August 2007.](https://reader030.fdocuments.in/reader030/viewer/2022032800/56649d4b5503460f94a28e21/html5/thumbnails/9.jpg)
What is the solution?
To introduce New manufacturing processes
This can improve:
• Reproducibility of cavity half shells
• Surface quality before and after cleaning process
• Welding quality
• Final assembly
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Who Are We?
U.K Cavity Development Consortium:
• Imperial College
• Cockcroft Institute
• Brunel University
• Liverpool University
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Proposed research program
A series of Button Tests to investigate the effect of manufacturing and surface treatment processes
This aims to study and understand the factors limiting: • Achievable accelerating gradients
• Reproducibility
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Button Design
MuCool
• Single part
New Design
• 2 Individual Parts
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Button Design
The new design would allow testing of:
• Wider range of material
• Wider range of manufacturing and surface treatment process
Cap Holder
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Manufacturing Procedure
Cap Forming
Surface Characterisation Holder Forming
Cap Material Selection
Surface Characterisation
Final Cap Surface Characterisation High Power Testing
Cap Surface Treatment Surface Characterisation
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Surface Preparation
Ultrasonic Cleaning
Surface Characterisation
Deoxidation/etchSurface characterisation
Electro-Polish Surface Characterisation
Deionised Water high-pressure rinse Surface Characterisation
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Surface Preparation
Initially we investigate two chemistries for Electro-polishing
• Standard Phosphoric/butanol (J-Lab recipe)
• Phosphoric, butanol, PEG, Citric acid
PEG, known to prevent etch pitting Citric acid, known to increase surface
planarisation
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Surface Characterisation
• Atomic Force Microscope (AFM) / Scanning Electron Microscope (SEM)
– Surface topology– Average roughness– Stress– Planarisation
• X-ray photoelectron Spectrometer (XPS)
– Chemical make up of the surface layers of the RF surface
– Identifying Orbitals involved in bonding impurities, etc
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What Do We Get?
From processes:
• surface topology (roughness, planarisation, stresses, defects)
• surface chemical composition• identify how the fabrication processes alters
Topology and Chemistry
From characterisation techniques:
• statistical models to predict the expected surface topology of a cavity produced, using each of the evaluated manufacturing techniques
Hence, being able to extrapolate the manufacturing
reliability and performance of high gradient cavities
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Future plans
• Expanding the button test by introducing:
– Other manufacturing techniques– Different EP chemical compositions
– Other Surface preparation techniques
• Design and Manufacture a high frequency pillbox cavity
– Smaller in size – Lower in cost– Closer to MICE cavity, hence better results
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Overall Outcome
• Understanding the effect of limiting factors
• Understanding the effect of various techniques on performance
• Development of better manufacturing and processing techniques
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References
• 201 MHz NC RF Cavity R&D, Derun Li, April 26, 2005 and July 28, 2004
• RFCC Module Design Update, Steve Virostek, June 13, 2007
• MICE RF Cavity Design and Fabrication Update, Steve Virostek, October 27, 2004
• Neutrino Factory and Muon Collider R&D in the US “Two Mints in One?, Alan Bross, June 14, 2007
• Proposed Investigation of High Gradient RF Cavity Limitations, Dr. Matthew Stables, Dr. Rebecca Seviour, 5th June 2007