Particle detectors for beam diagnosis and for experiments with stable and radioactive ions in the storage-cooler ring ESR O. Klepper * , C. Kozhuharov Gesellschaft fuer Schwerionenforschung mbH (GSI), Planckstrasse 1, D-64291 Darmstadt, Germany Abstract A survey of the 12 available detector positions and of their applications is given. Emphasis is on the new pneumatic linear drives with accelerator controlled positioning and on new detectors for the positions dedicated to experiments. Ó 2003 Elsevier Science B.V. All rights reserved. PACS: 29.20.Dh; 29.40.Cs; 29.40.Gx; 23.40.)s Keywords: Storage ring; Highly ionised atoms; Radioactive ion beams; Multiwire detectors 1. Introduction and concept In the experimental storage ring (ESR) at GSI the ions are stored at relativistic energies. This allows us to apply the concept of movable pockets with thin windows to detect ions that have chan- ged their magnetic rigidity in experiments, e.g. in the electron cooler or in the gas-jet target on the straight sections of the ESR and then leave the primary beam in the next bending magnet. This means detectors of various kinds (multiwire chambers, scintillator counters, etc.) are separated from the ultra-high vacuum of the storage ring by a thin foil. They can, therefore, easily be ex- changed or temporarily be removed during the baking of the vacuum chamber. The first five po- sitions, as described in [1], turned out to be ap- plicable and even indispensable for the injection and the storage procedure of low-intensity radio- active ion beams. For this reason, additional de- tector pockets for beam diagnosis were installed in the ESR, in the injection part, and in the extrac- tion beam-line to the experimental caves. This is described in [2], where Fig. 1 presents an overview of the present 12 detector positions. Here we mainly report on the recent progress concerning those detectors assigned for experiments. 2. Detector positions for beam diagnosis For the beam diagnosis of low-intensity radio- active ion beams and for the operation control of the storage ring, four pockets have been installed in the ring chamber and in the injection beam-line. They (and the corresponding detectors [2]), are identical except for their length and for the thick- ness of their entrance windows (Fig. 1). In order to handle beams decelerated in the ESR down to 10 A MeV, the thickness of the stainless-steel windows * Corresponding author. Tel.: +49-6159-71-24-39; fax: +49- 6159-71-29-02. E-mail address: o.klepper@gsi.de (O. Klepper). 0168-583X/03/$ - see front matter Ó 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0168-583X(02)02131-6 Nuclear Instruments and Methods in Physics Research B 204 (2003) 553–556 www.elsevier.com/locate/nimb