Characterization of the Goubau line for testing beam diagnostic instruments

Abstract

A: One of the main characteristics of the Goubau line is that it supports a low-loss, nonradiated surface wave guided by a dielectric-coated metal wire. The dominant mode of the surface wave along the Goubau line is a TM 01 mode, which resembles the pattern of the electromagnetic fields induced in the metallic beam pipe when the charged particle beam passes through it. Therefore, the Goubau line can be used for the preliminary bench test and performance optimization of the beam diagnostic instruments without requiring charged particle beams from the accelerators. In this paper, we discuss the basic properties of the Goubau line for testing beam diagnostic instruments and present the initial test results for button-type beam position monitors (BPMs). The experimental results are consistent with the theoretical estimations, which indicates that Goubau line allows effective testing of beam diagnostic equipment. K: Beam-line instrumentation (beam position and profile monitors; beam-intensity monitors; bunch length monitors); Instrumentation for particle accelerators and storage rings -high energy (linear accelerators, synchrotrons); Instrumentation for particle accelerators and storage rings -low energy (linear accelerators, cyclotrons, electrostatic accelerators)

Measuring vacuum component impedance for the Argonne Advanced Photon Source upgrade

“…These findings are consistent with the simulation results of Ref. [19], who found that the wire needs to be sufficiently long to insure good launching and receiving efficiency. This is because the G-line needs sufficient space between the cones and the DUT for the surface waves to fully develop.…”

“…The G-line has been used by several groups to characterize beam position monitors (BPMs) and current transformers [15,17,19,26]. Simulations showing the G-line's potential to assess vacuum component impedance were described in Refs.…”

“…The mathematical theory describing surface waves on a dielectric-coated wire can be found in many places (see, e.g., [15,16,19,22]). In this section we will review that part of the theory that is relevant to understanding the design of our experimental apparatus, paying particular attention to the extent to which the fields mimic a relativistic electron beam and fall off ∼1=r, where r is the radial distance from beam axis.…”

“…II we describe the novel G-line method, starting with a brief mathematical description based on that found in Ref. [15,19], and proceeding to a detailed description of the experimental design and our measurement procedures. Section III describes how we benchmarked the G-line setup using a relatively simple and well-known pillbox-type cavity, and compares impedance results between measurement and simulation.…”