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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•Presentation on ‘High Power RF couplers’ by James Rogers in ASTeC

•Investigate on coax structure to match 50ohm impedance @ 324MHz

•investigate waveguide-to-coax transition

•RF energy transferred from klystron to RFQ via waveguide, waveguide-coax transition, RF window and RF input coupler.

•@ waveguide-coax transition structure, coupling @ 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)

RF coupler preliminary design approach

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RF coupler preliminary design approach

•Coax matching.

•Outer diameter of insulation fixed @ 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

•Studying klystron o/p T-struc wg-coax

•Coupler varied in distance from waveguide end-plate and in height

S11 = -3.32dB S21 = -2.589dB

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RF coupler preliminary design approach

•Studying doorknob wg-coax

•Increased wg length

•Coupler varied in distance from waveguide end-plate and in height

S11 = -22.59dB S21 = -0.717dB

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Summary

1. Bead pull measurement almost ready to go. Other issues are finding suitable bead

2. 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.

3. Other tasks:

• Microwave signal generator and amplifier in the process of purchasing:

• Delivers 20W-50W to drive klystron and RF control purposes