MICE 201-MHz Cavity Construction

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MICE 201-MHz Cavity Construction
MICE Collaboration Meeting 21 June 7, 2008

• Derun Li
• Lawrence Berkeley National Laboratory

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Outline

• MICE 201-MHz cavity
• Based on MuCool 201-MHz prototype cavity
• Review of MuCool prototype cavity
• Engineering design is complete
• RF cavity design review at CM21
• Fabrication scheme follows successful MuCool
  prototype with minor differences
• Cavity body
• RF coupler
• Be windows
• Tuners
• Recent progress
• Vendor identification
• Engineering CAD model
• Tuners
• Cavity support
• Schedule
• Summary

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Eight 201-MHz Cavities for MICE
Eight 201-MHz RF cavities
MICE Cooling Channel Courtesy of S. Q. Yang,
Oxford Univ.
RFCC modules
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Latest CAD Model of RFCC Module
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MuCool Prototype Cavity

• MICE 201-MHz cavity design is based on MuCool
  prototype cavity with minor differences
• Prototype cavity
• Physics Design
• Couplers and ceramic RF windows
• Engineering
• Fabrication cavity body, ports, tuners, etc.
• Large, pre-curved and thin 42-cm diameter Be
  windows
• Commissioning and operation
• RF Conditioning and background
• High gradients ( 16 MV/m)
• With the thin and curved Be windows
• With external magnetic fields

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The Cavity Body Profile
Spherical section at the equator to ease
addition of ports ( 6.5o) Elliptical-like (two
circles) nose to reduce peak surface field
Stiffener ring
2o tilt angle
42-cm
6-mm Cu sheet allows for uses of spinning
technique and mechanical tuners similar to SCRF
ones
121.7-cm
De-mountable Pre-curved Be windows to terminate
RF fields at the iris
Low peak surface E-field at iris
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Cavity Design Parameters

• The cavity design parameters
• Frequency 201.25 MHz
• ß 0.87
• Shunt impedance (VT2/P) 22 M?/m
• Quality factor (Q0) 53,500
• Be window diameter and thickness 42-cm and
  0.38-mm
• Nominal parameters for MICE and cooling channels
  in a neutrino factory
• 8 MV/m (16 MV/m) peak accelerating field
• Peak input RF power 1 MW (4.6 MW) per cavity
• Average power dissipation per cavity 1 kW (8.4
  kW)
• Average power dissipation per Be window 12 watts
  (100 watts)

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201 MHz Cavity Concept
Spinning of half shells using thin copper sheets
and e-beam welding to join the shells extruding
of four ports each cavity has two pre-curved
Beryllium windows, but also accommodates
different windows
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Fabrication of the MuCool Cavity

• Two 6-mm thick copper shells are formed from
  annealed, flat sheet using a spinning technique
• Two half shells are e-beam welded together at
  equator to form the cavity
• Separate copper nose piece rings are e-beam
  welded to cavity iris (aperture)
• RF and vacuum ports are formed by pulling a die
  through a hole cut across the equator weld
  (extruding)
• Externally brazed tubes provide cooling
• Cavity inside surfaces are finished by
  mechanically buffing and electro-polishing
• Two thin, pre-curved beryllium windows are
  mounted on cavity aperture
• Cavity is mounted between two thick aluminum
  vacuum support plates
• See Allan DeMellos talks for details for
  fabrication and QC

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Prototype RF Coupler

• Two loop couplers each cavity to give critical
  coupling
• Prototype coupling loop design uses standard
  off-the-shelf copper co-axial components
• Parts were joined by torch brazing at LBNL
• Coupling loop has integrated water cooling lines
• Two SNS style RF windows mfg. by Toshiba
• High power tested up to 2.5 MW per coupler, 10 kW
  (avg.)

Ceramic RF window
RF Window Conditioning
Loop coupler made at LBNL
SNS RF window
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Thin and Curved Be Windows

• Each cavity has two Be windows
• 42-cm diameter and 0.38-mm thick
• Window is formed at high temperature and later
  brazed to copper frames
• Thin TiN coatings on both sides of the window
• One window curves into the cavity and one curves
  out
• Already high power tested up to 5 MW in 201-MHz
  cavity at MTA, FNAL

42-cm
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Recent Progress

• RFCC engineering CAD model
• RF and Engineering design of 201-MHz RF cavity
• Integration and interface
• Vendor identifications

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Recent Progress RF Cavity Design

• See A. DeMellos talks on details
• Vendor Identification
• Engineering CAD model
• Integration and interface
• Improved Be window design
• Tuners and support
• Cavity post processing
• Cavity RF design
• 3-D CST MWS RF parameterized model with ports and
  curved Be windows
• Hard to reach the design frequency by spinning
• Frequencies between cavities should be able to
  achieve within ? 100 kHz
• Approaches
• Modification the spinning form
• Targeting for higher frequency
• Fixed tuner to tune cavity close to design
  frequency (deformation of cavity body)
• Tuners are in push-in mode ? lower frequency

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Cavity Tuner Concept
Tuner actuator (likely air)
Pivot point
Dual bellows feedthrough
Fixed (bolted) connection
Ball contact only
MICE RF Cavity Mechanical Design and Analysis
Page 14
Allan DeMello - Lawrence Berkeley National Lab -
June 4, 2008
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Hexapod Strut Arrangement

• Analysis of a hexapod strut system is ongoing
• Each cavity would contain a dedicated set of 6
  suspension struts arranged if a hexapod type
  formation
• This system spreads the gravity load of the
  cavity across several struts

MICE RF Cavity Mechanical Design and Analysis
Page 15
Allan DeMello - Lawrence Berkeley National Lab -
June 4, 2008
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Hexapod Strut Arrangement
Copper strut mounts e-beam welded to the
outside of the cavity
Stainless steel strut mounts welded to the inside
of the vacuum vessel
MICE RF Cavity Mechanical Design and Analysis
Page 16
Allan DeMello - Lawrence Berkeley National Lab -
June 4, 2008
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RFCC Review at CM21

• Review Charge
• Evaluate engineering design of MICE 201-MHz RF
  cavity
• Is LBNL ready to purchase long lead cavity
  materials and components?
• Copper sheets for cavity bodies
• Thin, curved beryllium windows
• Ceramic RF windows
• Evaluate engineering design and fabrication
  scheme of the 201-MHz cavity to determine
  readiness to initiate cavity body fabrication
• Spinning of cavity shells
• e-beam welding
• Port extruding
• Tuners
• Cavity support
• Review conclusion
• The purchase of long-lead items and materials
  should begin
• Discussion with potential manufacturers should
  intensify
• The design is very sound and should continue to
  completion of manufacturing drawings
• Final Design Review (at CM22) of
  production-readiness could be assumed

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Schedule Overview

• RFCC design and fabrication project originally
  expected to be a 3year project (10/06 to 10/09)
• Coupling coil design effort began in 2006 at ICST
  (Harbin)
• Design and fabrication of other RFCC module
  components was scheduled to begin 10/07
• Start was delayed due to lack of availability of
  qualified manpower
• Earlier this year, mechanical engineer A. DeMello
  joined MICE to work on RFCC module design (FTE)
• Additional manpower required to make up schedule

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Schedule Summary
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Summary

• MICE cavity design is heavily based on successful
  MuCool 201-MHz prototype RF cavity and lessons
  learned
• Fabrication, post processing, commissioning and
  operation
• Engineering design of the cavity is essentially
  complete
• CAD model of the cavity
• Tuners and support concepts developed and will be
  further analyzed
• Fabrication schemes
• Design review at CM21
• Significant progress on engineering designs of
  RFCC module
• WBS schedule is developed