A novel non-adiabatic approach to transition crossing in a circular hadron accelerator

TL;DR

This paper introduces a novel non-adiabatic method for transition crossing in circular hadron accelerators by creating stable phase space islands with sextupoles and octupoles, enabling controlled beam displacement.

Contribution

It combines concepts of stable resonances with transition crossing, proposing a new technique for rapid, controlled energy transition in particle accelerators.

Findings

Demonstrates generation of stable islands in phase space using sextupoles and octupoles.

Enables non-adiabatic transition energy change by shifting the beam between closed orbits.

Provides a potentially cleaner and more controlled transition crossing method.

Abstract

Crossing the transition energy is always a delicate process, representing a potential source of strong perturbations of the dynamics of charged particle beams in a hadron circular accelerator. Since the first generation of multi-GeV rings, intense studies have been devoted to understanding the possible harmful mechanisms involved in transition crossing and to devise mitigation measures. Nowadays, several circular particle accelerators are successfully operating across transition and this process is well mastered. In a completely different context, stable resonances of the traverse phase space have been proposed as new means of manipulating charged particle beams. While the original aim of such a proposal was multi-turn extraction from the CERN Proton Synchrotron to the Super Proton Synchrotron, many more applications have been proposed and studied in detail. In this paper, the two topics, i.e. transition crossing and stable resonances, have been brought together with the goal of providing a novel and non-adiabatic approach to perform a clean transition crossing. The idea presented here is that by judiciously using sextupoles and octupoles it is possible to generate stable islands of the horizontal phase space. These islands represent a second closed orbit whose properties can be selected independently of those of the standard, i.e. central, closed orbit. This provides a means of performing a non-adiabatic change of the transition energy experienced by the charged particles by displacing the beam between the two closed orbits.