Development and Application of Combined Schottky+Isochronous Storage Ring Mass Spectrometry

Yury A. Litvinov

GSI Helmholtzzentrum für Schwerionenforschung, 64291 Darmstadt, Germany

Storage of freshly produced secondary particles in a storage ring is a straightforward way to achieve the most efficient use of the rare species as it allows for using the same secondary ion multiple times. Employing storage rings for precision physics experiments with highly-charged ions (HCI) at the intersection of atomic, nuclear, plasma and astrophysics is a rapidly developing field of research. The number of physics cases is enormous. The focus in this presentation will be on the most recent results obtained at the Experimental Storage Ring ESR of GSI in Darmstadt.

The ESR is presently the only instrument dedicatedly utilized for precision studies of decays of HCIs. Radioactive decays of HCIs can be very different as known in neutral atoms. Some decay channels can be blocked while new ones can become open. Such decays reflect atom-nucleus interactions and are relevant for atomic physics and nuclear structure as well as for nucleosynthesis in stellar objects.

Up to now, all investigations of the decays of HCIs were done by employing the time-resolved Schottky mass spectrometry (SMS). The latter relies on the electron cooling and non-destructive monitoring of intensities of the mass-resolved nuclear species of interest. The electron cooling requires at least several seconds and the conventional SMS can be applied to relatively long-lived ions. In the course of the last decade highly-sensitive Schottky detectors were developed enabling us entering the regime of half-lives in several ten milliseconds. Furthermore, the Isochronous Mass Spectrometry (IMS) is employed, which allows avoiding the lengthy cooling processes. In this way the combined Schottky+Isochronous Mass Spectrometry (S+IMS) has been established.

The power of the technique has been verified by measuring the de-excitation of the first excited 0+ state in 72Ge, which is a pure two-photon decay in the absence of bound electrons.

The reported developments will be put in the context of the present research programs in a worldwide context, where, thanks to fascinating results obtained at the presently operating storage rings, a number of projects is planned.