U. Ratzinger

Accelerated radioactive beams from REX-ISOLDE

In 2001 the linear accelerator of the Radioactive beam EXperiment (REX-ISOLDE) delivered for the first time accelerated radioactive ion beams, at a beam energy of 2 MeV/u. REX-ISOLDE uses the method of charge-state breeding, in order to enhance the charge state of the ions before injection into the LINAC. Radioactive singly-charged ions from the on-line mass separator ISOLDE are first accumulated in a Penning trap, then charge bred to an A/q < 4.5 in an electron beam ion source (EBIS) and finally accelerated in a LINAC from 5 keV/u to energies between 0.8 and 2.2 MeV/u. Dedicated measurements with REXTRAP, the transfer line and the EBIS have been carried out in conjunction with the first commissioning of the accelerator. Thus the properties of the different elements could be determined for further optimization of the system. In two test beam times in 2001 stable and radioactive Na isotopes (Na-23-Na-26) have been accelerated and transmitted to a preliminary target station. There Ni-58- and Be-9- and H-2-targets have been used to study exited states via Coulomb excitation and neutron transfer reactions. One MINIBALL triple cluster detector was used together with a double sided silicon strip detector to detect scattered particles in coincidence with gamma-rays. The aim was to study the operation of the detector under realistic conditions with gamma-background from the beta-decay of the radioactive ions and from the cavities. Recently for efficient detection eight tripple Ge-detectors of MINIBALL and a double sided silicon strip detector have been installed. We will present the first results obtained in the commissioning experiments and will give an overview of realistic beam parameters for future experiments to be started in the spring 2002.

Fission fragment accelerators for the Grenoble and Munich high flux reactors

Abstract Accelerators for the Munich and Grenoble high flux reactors are under design 1 , 2 . These accelerators will be able to deliver intense beams of very neutron rich fission fragments out of a target ion source inside the reactor tube for the production of super heavy elements [3] . In order to obtain an efficient acceleration in a LINAC, charge breeding of the 1+ ion beam from the reactor to a q/A⩾0.16 is required. Depending on the scheme of charge breeding the LINAC can work with 10% duty cycle with a final energy between 3.7 and 5.9 MeV/u. Two sources which can deliver highly charged ions are to be considered as possible charge breeders: the Electron Beam Ion Source (EBIS) and the Electron Cyclotron Resonance Ion Source (ECRIS). The LINAC will consist of an Radio Frequency Quadrupole (RFQ) accelerator, three interdigital H-type (IH) structures and two seven-gap resonators to vary the final energy of the ions. The whole concept, the charge breeding and the LINAC parameters will be discussed carefully in this paper.

Status of the REX-ISOLDE project

The radioactive beam experiment REX-ISOLDE, a pilot experiment testing a new concept of post acceleration of radioactive ions at ISOLDE/CERN is in progress. Singly charged radioactive ions delivered by the online mass separator ISOLDE are accumulated in a Penning trap (REX trap), charge bred in an electron beam ion source (EBIS), separated from the residual gas in a mass separator and then accelerated in a linac with output energies between 0.8 and 2.2 MeV/u. The REX trap is in operation, a first test beam was already injected. The design phase of the EBIS is finished and the construction has been started. The superconducting magnet is delivered. The linac consists of a radiofrequency quadrupole (RFQ) accelerator, an interdigital IH-structure and 3 seven gap resonators to vary the final energy.

RES-ISOLDE - Post-accelerated radioactive beams at CERN-ISOLDE

The ISOLDE RIB-facility at CERN has today been producing a vast range of radioactive beams since more than 30 years. The low-energy beams of ISOLDE will be complemented by a post-accelerator, REX-ISOLDE, currently being assembled. In order to convert the pseudo-DC, singly-charged beam from the ISOLDE mass separators into a cooled and bunched beam at higher charge states, a novel scheme of trapping, cooling, and charge-state breeding has been devised, using a linear Penning trap and an Electron Beam Ion Source (EBIS). This allows for subsequent acceleration by a short, cost-effective LINAC consisting of an RFQ, an IH-structure and three seven-gap resonators, reaching 0.8–2.2 MeV/u. The installation of REX-ISOLDE is well underway and the first post-accelerated radioactive beams are expected to be obtained during late 2000.