Orbit response measurements with oscillating trajectories

TL;DR

This paper presents a method for measuring orbit responses in a linac by exciting correctors with sine waves at different frequencies and analyzing BPM signals in the Fourier domain, enabling efficient multi-corrector response recording.

Contribution

It introduces an efficient technique for recording orbit response matrices using oscillating trajectories at multiple frequencies simultaneously.

Findings

Successful implementation at PIP2IT test linac

Effective measurement of transverse and longitudinal responses

Improved signal-to-noise ratio for multi-corrector excitation

Abstract

Optical properties of components in a linac can be reconstructed from analysis of the orbit response matrix, composed from responses of BPMs to changes in currents of dipole correctors. An efficient way to record such response, discussed in this note, is to excite the corrector current with a sine wave and record its Fourier component of the BPM spectrum. Because of a narrow band of the excitation signal, response to multiple correctors can be recorded at the same time without significantly affecting the signal-to-noise ratio. For that, the correctors are oscillated at different frequencies, and the corresponding BPM Fourier components are recorded. In an ion (non-relativistic) linac, similar measurements can be performed for the longitudinal plane as well. Examples of measurements at the PIP2IT test linac are shown.