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324MHz FETS RFQ RF measurement and components. By Aaron Cheng 18 December 2006. Overview. 1. Bead-pull measurement 2. RF coupler preliminary design approach. Bead pull measurements. ISIS copper cold model in Imperial College. Bead pull measurements.
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324MHz FETS RFQ RF measurement and components By Aaron Cheng 18 December 2006
Overview • 1. Bead-pull measurement • 2. RF coupler preliminary design approach
Bead pull measurements ISIS copper cold model in Imperial College
Bead pull measurements Bead pull results on ISIS copper cold model
Bead pull measurements Bead pull results on ISIS copper cold model
Bead pull measurements LabVIEW beadpull measurement control program
RF coupler preliminary design approach • 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 • 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
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
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
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