The GSI magnetic spectrometer

Abstract

I have presented a view on an instrument which takes advantage of the recent detector developments for very heavy ions. The features of these detectors were considered already in the design phase of the ion optical and geometrical layout of the spectrograph. The result is a modular setup with separated function magnets, with variable dispersion and a flexibility to adapt to the various requirements of the experments. The instrument was designed to be used exclusively for very heavy ions (A > 40). The combination of a time of flight measurement and magnetic analysis, together with a determination of δE, E and some geometrical quantities gives good particle identification properties. I have shown some examples of excellent mass- and Z-resolutions for the mass range 100 and above. The energy resolution of about 0.1 % is moderate, in fact, in most cases of appliance the limitation is not introduced by the performance of the spectrometer and detector system but by effects in the target and by the divergence of the incoming beam.

The instrument is used for the investigation of elastic and inelastic scattering in the heavy mass range (JiaC81) where the separation of the transfer channels seems to be absolutely necessary for the detailed understanding of the nuclear potentials. But I should mention, that the domain of application is the study of quasielastic transfer reactions (SchS81,BraS82,BreC82) to investigate the reaction mechanism for short interaction times. The excellent particle identification together- with a good energy resolution allows to see structures in the nuclide distributions due to shell effects in the nuclear potential as well as structures in the spectra of the different transfer channels. These experiments are still under way.

The project of the magnetic spectrograph was suggested by F. Pühlhofer and set up by a joint effort of groups from the University of Marburg, Max- Planck- Institut für Kernphysik Heidelberg and GSI. The ion optical design is due to Th. Walcher. I should like to thank F. Pühlhofer, W. Pfeffer, F. Busch, Th. Walcher, B. Langenbeck, K. Blasche, W.C. Shen and R. Bock for many fruitful discussions during the setup 1178 1474 V 3 time of the project and while preparing the manuscript. The project 1178 1474 V 3 was supported by the Bundesminister far- Forschung and Technologie.