324MHz FETS RFQ RF measurement and components By Aaron Cheng 18 December 2006

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

3 Bead pull measurements ISIS copper cold model in Imperial College

4 Bead pull measurements Bead pull results on ISIS copper cold model

5 Bead pull measurements Bead pull results on ISIS copper cold model

6 Bead pull measurements LabVIEW beadpull measurement control program

7 Presentation on ‘High Power RF couplers’ by James Rogers in ASTeC Investigate on coax structure to match 50ohm 324MHz investigate waveguide-to-coax transition RF energy transferred from klystron to RFQ via waveguide, waveguide-coax transition, RF window and RF input waveguide-coax transition structure, 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

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

9 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 = -3.32dBS21 = dB

10 RF coupler preliminary design approach Studying doorknob wg-coax Increased wg length Coupler varied in distance from waveguide end-plate and in height S11 = dBS21 = dB

11 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