RF-loss measurements in an open coaxial resonator for characterization of copper plating

Frank L. Krawczyk, Gerald O. Bolme, William L. Clark, J. Patrick Kelley, Felix A. Martinez, Dinh C. Nguyen, Karen A. Young, John Rathke, Dale L. Schrage, Thomas Schultheiss, Lloyd M. Young
2007 2007 IEEE Particle Accelerator Conference (PAC)  
An experiment has been conducted to measure differences in cavity Q caused by various cavity surface treatments. A requirement of the experiment was that it show little sensitivity to the reassembly of the apparatus with various test pieces. We chose a coaxial half-wave resonator, with an outer conductor extending significantly beyond the length of the inner conductor. At 700 MHz the outer conductor acts as a cut-off tube, eliminating the need for electric termination and thus any RF-contacts
more » ... at can influence the accuracy of the Q-measurements. The experiment is aimed at qualifying the performance of cyanide-copper plated GlidCop Al-15 LO-OX in comparison with that of a machined GlidCop Al-15 LO-OX surface. To maximize the sensitivity of the measurement we use a fixed outer conductor made of Oxygen Free Electronic (OFE) copper and only replaced the inner conductor, which is mounted on a low-loss Teflon pedestal located in the low electric field region of the half-wave TEM mode. The Q-values of machined GlidCop Al-15 and cyanide-copper plated GlidCop Al-15 inner conductors are measured against the reference Q of the annealed OFE co-axial cavity. This extremely simple configuration allows a statistically significant number of repetitions of measurements and should provide accurate comparative measurements. The results will be useful for the community in deciding the surface treatments for high-Q copper accelerators. While outside of the scope of the qualification of the cyanide copper plating, two UBAC plated OFE copper pieces have been added to the comparison.
doi:10.1109/pac.2007.4441255 fatcat:mj4l7scd4zblvhbz76tdnbfk7e