High Performance Charge Breeder for HIE-ISOLDE and TSR@ISOLDE Applications

TL;DR

This paper presents the development of the HEC2 charge breeder, a high-performance device designed to produce highly charged ions for advanced nuclear physics experiments at ISOLDE, capable of matching the upgraded linac and storage ring requirements.

Contribution

The paper introduces the HEC2 charge breeder with high electron beam current and energy, demonstrating prototype operation and advancements towards CW operation for high charge state ion production.

Findings

Prototype electron gun achieved 1.5 A pulsed beam at 30 keV.

Electron beam current density of 10-20 kA/cm2 suitable for high charge states.

Progress towards CW operation with matching ion acceptance and beam quality.

Abstract

We report on the development of the HEC2 (High Energy Compression and Current) charge breeder, a possible high performance successor to REXEBIS at ISOLDE. The new breeder would match the performance of the HIE-ISOLDE linac upgrade and make full use of the possible installation of a storage ring at ISOLDE (the TSR@ISOLDE initiative [1]). Dictated by ion beam acceptance and capacity requirements, the breeder features a 2-3.5 A electron beam. In many cases very high charge states, including bare ions up to Z=70 and Li/Na-like up to Z=92 could be requested for experiments in the storage ring, therefore, electron beam energies up to 150 keV are required. The electron-beam current density needed for producing ions with such high charge states at an injection rate into TSR of 0.5-1 Hz is between 10 and 20 kA/cm2, which agrees with the current density needed to produce A/q<4.5 ions for the HIE-ISOLDE linac with a maximum repetition rate of 100 Hz. The first operation of a prototype electron gun with a pulsed electron beam of 1.5 A and 30 keV was demonstrated in a joint experiment with BNL [2]. In addition, we report on further development aiming to achieve CW operation of an electron beam having a geometrical transverse ion-acceptance matching the injection of 1+ ions (11.5 {\mu}m), and an emittance/energy spread of the extracted ion beam matching the downstream mass separator and RFQ (0.08 {\mu}m normalized / +/- 1% ).