ISOLDE Seminar

Electron Beam Ion Source developments for ISOLDE

by Robert Mertzig (CERN)

Europe/Zurich
Isolde Visitor's room (CERN)

Isolde Visitor's room

CERN

Description
For more than a decennium REX-ISOLDE has been a key element at the ISOLDE radioactive beam facility. The post-accelerator consists of a Penning trap for bunching and cooling of the 1+ ions delivered from ISOLDE, an EBIS for charge breeding and a LINAC for the actual acceleration. While successful, the high beam demand has not allowed for intrusive machine studies to be carried out at the REX facility. In the case of the EBIS, several issues could not be investigated with the required thoroughness, for instance cathode poisoning and electron current limitations. The REXEBIS is designed to provide a stable 500 mA electron beam at an electron energy of approximately 4.5 keV. During long term operation the REXEBIS is typically run only at 200 mA or lower for reliability purposes. The full design value operation was never used in practice. Therefore, during the last three years a dedicated offline EBIS test bench, the TwinEBIS, has been setup at CERN. The TwinEBIS is a copy of the REXEBIS, although with minor modifications in the drift-tube structure, a more versatile control system and with no ion injection presently available. The setup has been commissioned and several investigations have begun. The 500 mA electron beam was achieved at TWINEBIS as the result of long term optimization progress under quasi-stable operation conditions for the first time. Furthermore the current density will increase linearly with the current, which means reduced breeding time by a factor of 2.5. In this contribution an overview of the setup and results will be given. In addition the planned new electron gun generations, the Medgun and the HEC2-gun, will be presented. The planned new electron gun generations open by providing higher current densities the opportunity to perform experiments covering very neutron and proton rich isotopes with short life times and increase the efficiency of the accelerators by producing higher ion charge states by higher electron beam energies. The Medgun is designed for providing a 1A electron beam at an energy of 10keV shortening the breeding time by at least a factor of 5, while the HEC2-gun as the second upgrade will be capable in providing a 5A electron beam at 49keV.