Quantitative description and correction of longitudinal drifts in the Fermilab linac

TL;DR

This paper presents a quantitative method to describe and correct longitudinal beam drifts in Fermilab's Linac, improving beam stability and reducing losses through phase shift adjustments.

Contribution

It introduces a scheme to express beam drifts as phase shifts in the low-energy Linac, enabling simplified visualization and an effective compensation algorithm.

Findings

Drifts can be accurately modeled as phase shifts.

The proposed correction scheme improves beam stability.

The method estimates compensation efficiency effectively.

Abstract

The Fermi National Accelerator Laboratory (Fermilab) Linac accepts 750 keV H- ions from the front end and accelerates them to 400 MeV for injection into the Booster rapid cycling synchrotron. Day-to-day drifts in the beam longitudinal trajectory during regular operation are of the order of several degrees. They are believed to cause additional losses in both the Linac and the Booster and are addressed by empirically adjusting cavity phases of front end and Linac RF cavities. This work explores a scheme for expressing these drifts in terms of phase shifts in the low-energy part of the Linac. Such a description allows for a simplified visual representation of the drifts, suggests a clear algorithm for their compensation, and provides a tool for estimating efficiency of such compensation.