Correcting Diamagnetic-Loop Measurements for Beam Corkscrew Motion

Abstract

Diamagnetic loops (DML) are used as a non-invasive method for measurements of beam size in electron beam accelerators that use solenoidal magnetic transport. The loop fundamentally measures the magnetic flux excluded by a diamagnetic object. One of the sources of background in these measurements is the flux produced by a straight filamentary current that is offset from the axis and tilted in the plane orthogonal to the offset. This was only a small effect in our experiments, because the beam was steered to be centered on average at the DML. However, we devoted some time to understanding and quantifying the effect, and we recount that effort in this report.