Finding beam loss locations in a linac with oscillating dipole correctors

TL;DR

This paper introduces a method to locate beam loss points in a linear accelerator by analyzing phase signals from oscillating dipole correctors and beam position monitors, enabling non-invasive optics measurements.

Contribution

The paper presents a novel phase-based technique using oscillating dipole correctors and BPM signals to identify beam loss locations and measure optics parameters in a linac.

Findings

Accurately locates beam loss points using phase analysis.

Provides a method for parasitic optics measurements with negligible emittance impact.

Enables determination of the ta}-function and phase advance at BPMs.

Abstract

The paper proposes a method of finding the beam loss locations in a linac. If the beam is scraped at an aperture limitation, moving its centroid with two dipole correctors located upstream and oscillating in sync produces a line at the corresponding frequency in spectra of current-sensitive devices downstream of the loss point. The phase of this signal contains information about the location of the beam loss. Similar lines appear also in the position signals of Beam Position Monitors (BPMs). The phases of the BPM position lines change monotonically (within each 2{\pi}) along the linac and can be used a reference system. The phase of the loss signal compared with this reference system pinpoints the beam loss location, assuming that longitudinal coordinates of the BPMs are known. If the correctors deflection amplitudes and the phase offset between their waveforms are chosen optimally and well calibrated, the same measurement provides values of the \b{eta}-function and the betatron phase advance at the BPM locations. Optics measurements of this type can be made parasitically, with negligible effect on the emittance, if a long measurement time is acceptable.