Update of beam coupling impedance evaluation by the stretched-wire method

TL;DR

This paper discusses an improved method for evaluating beam coupling impedance using the stretched-wire technique, emphasizing calibration improvements and practical application to RF cavity and kicker measurements.

Contribution

It introduces a calibration method using 2-X THRU de-embedding to enhance the accuracy of the stretched-wire impedance evaluation.

Findings

Successful application to RF cavity measurement

Effective calibration method developed

Improved accuracy in impedance evaluation

Abstract

In many cases beam coupling impedances or wake fields are calculated with computer simulator such as CST Studio Suite, GdfidL Electromagnetic Field Simulator and so on. But evaluation with the stretched-wire method is still very useful by its flexibility to the change of the device-under-test configuration, speed to get results and, more than anything, its accessibility on the real devices. One of the drawbacks in the practical procedure, difficulty of Thru-Reflect-Line calibration, is overcome using the calibration method recently introduced in high frequency vector network analyzers, "2-X THRU de-embedding". Here the procedure is explained in detail. The method has been successfully applied to RF cavity and FX kicker measurement in the J-PARC MR.