Isochronicity Correction in the CR Storage Ring

TL;DR

This paper discusses methods to correct isochronicity in the Collector Ring at FAIR, enabling high-resolution mass measurements of exotic nuclei by addressing time aberrations and chromaticity effects through simulations and correction schemes.

Contribution

It introduces a correction scheme for isochronicity in the CR storage ring, improving mass resolution for exotic nuclei measurements.

Findings

Achieved potential resolution of dm/m=1E-6 with correction methods.

Demonstrated correction of time aberrations considering magnet inhomogeneities.

Presented calibration scheme for ions with different mass-to-charge ratios.

Abstract

A challenge for nuclear physics is to measure masses of exotic nuclei up to the limits of nuclear existence which are characterized by low production cross sections and short half-lives. The large acceptance Collector Ring (CR) at FAIR tuned in the isochronous ion-optical mode offers unique possibilities for measuring short-lived and very exotic nuclides. However, in a ring designed for maximal acceptance, many factors limit the resolution. One point is a limit in time resolution inversely proportional to the transverse emittance. But most of the time aberrations can be corrected and others become small for large number of turns. We show the relations of the time correction to the corresponding transverse focusing and that the main correction for large emittance corresponds directly to the chromaticity correction for transverse focusing of the beam. With the help of Monte-Carlo simulations for the full acceptance we demonstrate how to correct the revolution times so that in principle resolutions of dm/m=1E-6 can be achieved. In these calculations the influence of magnet inhomogeneities and extended fringe fields are considered and a calibration scheme also for ions with different mass-to-charge ratio is presented.