324MHz FETS RFQ RF measurement and components

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324MHz FETS RFQ RF measurement and components

• By
• Aaron Cheng
• 18 December 2006

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Overview

• 1. Bead-pull measurement
• 2. RF coupler preliminary design approach

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Bead pull measurements
ISIS copper cold model in Imperial College
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Bead pull measurements
Bead pull results on ISIS copper cold model
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Bead pull measurements
Bead pull results on ISIS copper cold model
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Bead pull measurements
LabVIEW beadpull measurement control program
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RF coupler preliminary design approach

• Presentation on High Power RF couplers by James
  Rogers in ASTeC
• Investigate on coax structure to match 50ohm
  impedance _at_ 324MHz
• investigate waveguide-to-coax transition
• RF energy transferred from klystron to RFQ via
  waveguide, waveguide-coax transition, RF window
  and RF input coupler.
• _at_ waveguide-coax transition structure, coupling _at_
  lowest mode TE101
• Study klystron output waveguide-coax transition
  structure (magnetic field coupling) Current
  waveguide size is WR2300
• Implementing a doorknob structure (electric field
  coupling)

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RF coupler preliminary design approach

• Coax matching.
• Outer diameter of insulation fixed _at_ 40mm (KF
  flange size on RFQ), modelled as vacuum
• Optimized conductor to obtain 50ohm match ? inner
  diameter 17.4mm

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RF coupler preliminary design approach
S11 -3.32dB S21 -2.589dB

• Studying klystron o/p T-struc wg-coax
• Coupler varied in distance from waveguide
  end-plate and in height

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RF coupler preliminary design approach
S11 -22.59dB S21 -0.717dB

• Studying doorknob wg-coax
• Increased wg length
• Coupler varied in distance from waveguide
  end-plate and in height

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Summary

• Bead pull measurement almost ready to go. Other
  issues are finding suitable bead
• Waveguide-Coax transition design started and
  on-going. Current status
• Electric field probing show promising results
• Investigate into half-height wg, different
  T-shape geometry, conductor with cooling pipes
  etc.
• Other tasks
• Microwave signal generator and amplifier in the
  process of purchasing
• Delivers 20W-50W to drive klystron and RF control
  purposes