Abstract
Precision experiments with relativistic fragments separated in-flight require special ex- perimental methods to overcome the inherent large emittance from the creation in nuclear reactions and atomic interactions in matter. At GSI relativistic exotic nuclei have been produced via uranium projectile fragmentation and fission and investigated with the in- flight separator FRS directly, or in combination with either the storage-cooler ring ESR or the FRS Ion Catcher. 1000 AMeV 238 U ions were used to create 60 new neutron-rich isotopes separated and identified with the FRS to measure their production cross sections. In another experimental campaign the fragments were separated in flight and injected into the storage-cooler ring ESR for accurate mass and lifetime measurements. In these exper- iments we have obtained accurate new mass values analyzed via a novel method which has reduced the systematic errors for both Schottky Mass Spectrometry (SMS) and for Isochronous Mass Spectrometry (IMS). Pioneering experiments have been carried out with the FRS Ion Catcher consisting of three experimental components, the dispersive magnetic system of the FRS with a monoenergetic and a homogeneous degrader, a cryo- genic stopping cell filled with pure helium and a multiple-reflection time-of flight mass separator. The FRS Ion Catcher enables high precision spectroscopy experiments with eV to keV exotic nuclides. Results from these different FRS experiments are presented in this overview together with prospects for the next-generation facility Super-FRS. The novel features of the Super-FRS compared with the present FRS will be discussed in addition.
Highlights
Precision experiments with relativistic fragments separated in-flight require special experimental methods to overcome the inherent large emittance from the creation in nuclear reactions and atomic interactions in matter
The corresponding in-flight facilities aim at high kinetic energies to reach preferably the velocities where all fragments up to uranium emerge fully ionized from the production target
The energy determines the absolute value of the resulting range straggling and has to be selected as low as possible but such that the in-flight separation is not hampered by the appearance of ionic charge states
Summary
Heavy neutron-rich nuclei in the neighborhood of and at the N=126 shell closure are of great interest for nuclear spectroscopy and astrophysics [1]. The corresponding in-flight facilities aim at high kinetic energies to reach preferably the velocities where all fragments up to uranium emerge fully ionized from the production target Another way to reach experimental conditions for precision experiments with exotic nuclides is to reduce the phase space via cooling. The energy determines the absolute value of the resulting range straggling and has to be selected as low as possible but such that the in-flight separation is not hampered by the appearance of ionic charge states Besides these primary conditions it must be the aim to have a large areal density and an excellent extraction efficiency and time of the gas-filled stopping cell. The prospects of such research at the international facility for antiprotons and ions FAIR will be briefly outlined in the last chapter of this review
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