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Proposed Button Design for a Series of High Power Button Tests Arash Zarrebini-Esfahani 22 nd August 2007

Proposed Button Design for a Series of High Power Button Tests

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Proposed Button Design for a Series of High Power Button Tests. Arash Zarrebini-Esfahani 22 nd August 2007. 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 - PowerPoint PPT Presentation

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Page 1: Proposed Button Design for a Series of High Power Button Tests

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

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

Page 3: Proposed Button Design for a Series of High Power Button Tests

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

Page 4: Proposed Button Design for a Series of High Power Button Tests

201 MHz Cavity Fabrication

1 - Half shell spinning

2 - Fabrication of stiffener ring

Page 5: Proposed Button Design for a Series of High Power Button Tests

201 MHZ Cavity Fabrication

3 – Nose hole and half shell lip machining

4 – Half shell electro polishing

Page 6: Proposed Button Design for a Series of High Power Button Tests

201 MHz Cavity Fabrication

5 – Equator electron beam welding

6 – Fabrication of nose ring

Page 7: Proposed Button Design for a Series of High Power Button Tests

201 MHz Cavity Fabrication

7 – Cavity port pulling

8 – Cooling pipes TIG welding

Page 8: Proposed Button Design for a Series of High Power Button Tests

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

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

Page 10: Proposed Button Design for a Series of High Power Button Tests

Who Are We?

U.K Cavity Development Consortium:

• Imperial College

• Cockcroft Institute

• Brunel University

• Liverpool University

Page 11: Proposed Button Design for a Series of High Power Button Tests

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

Page 12: Proposed Button Design for a Series of High Power Button Tests

Button Design

MuCool

• Single part

New Design

• 2 Individual Parts

Page 13: Proposed Button Design for a Series of High Power Button Tests

Button Design

The new design would allow testing of:

• Wider range of material

• Wider range of manufacturing and surface treatment process

Cap Holder

Page 14: Proposed Button Design for a Series of High Power Button Tests

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

Page 15: Proposed Button Design for a Series of High Power Button Tests

Surface Preparation

Ultrasonic Cleaning

Surface Characterisation

Deoxidation/etchSurface characterisation

Electro-Polish Surface Characterisation

Deionised Water high-pressure rinse Surface Characterisation

Page 16: Proposed Button Design for a Series of High Power Button Tests

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

Page 17: Proposed Button Design for a Series of High Power Button Tests

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

Page 18: Proposed Button Design for a Series of High Power Button Tests

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

Page 19: Proposed Button Design for a Series of High Power Button Tests

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

Page 20: Proposed Button Design for a Series of High Power Button Tests

Overall Outcome

• Understanding the effect of limiting factors

• Understanding the effect of various techniques on performance

• Development of better manufacturing and processing techniques

Page 21: Proposed Button Design for a Series of High Power Button Tests

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