A Multi-length Bunches Design for Electron Storage Rings with Odd Buckets

TL;DR

This paper proposes a novel scheme using two superconducting RF cavities to generate multi-length electron bunches in storage rings with odd buckets, demonstrated on HLS II, enhancing bunch length flexibility without low-alpha optics.

Contribution

It introduces a new multi-length bunches design for odd bucket storage rings using two superconducting RF cavities, enabling simultaneous generation of long, medium, and short bunches.

Findings

Successfully generated three different bunch lengths in HLS II.

Achieved short bunch current limit of 6.6 mA, over 60 times higher than low-alpha mode.

Validated beam dynamics and stability through particle tracking and calculations.

Abstract

A scheme with two superconducting RF cavities (sc-cavities) is designed to upgrade electron storage rings with odd buckets into multi-length bunches. In this paper, Hefei Light Source II (HLS II) is given as an example for odd buckets. In accordance with 45 buckets, which is multiples of 3, three different length of bunches generated simultaneously is proposed in the presently applied user optics. The final result is to, without low-alpha optics, fill HLS II with long bunches of 50 ps length, medium bunches of 23 ps and short bunches of 6 ps. Each third buckets can be filled with short bunches, of which the current limit is up to 6.6 mA, more than 60 times the value of low-alpha mode. Moreover, particles tracking about beam dynamics performed by ELEGANT and calculations about beam instabilities are presented in this paper.