Cooler Rings Research Articles

Facilities and Methods: Experiments with Stored Relativistic Exotic Nuclei at the FRS-ESR Complex

For almost three decades, storage and cooler rings have been indispensable tools for atomic, nuclear, and high-energy physics. While electrostatic storage rings (ELISA at Aarhus, Denmark; CSR at Heidelberg, Germany) are specialized for the lowest beam kinetic energies, electromagnetic rings cover the energy range from the Coulomb barrier (ASTRID at Aarhus, Denmark; TSR at Heidelberg, Germany; CRYRING at Stockholm, Sweden) up to the relativistic regime (CELSIUS at Uppsala, Sweden; COSY at Jülich, Germany; IUCF at Bloomington, USA). The past LEAR machine, the present AD (both located at CERN in Geneva, Switzerland), and the future FAIR-facilities HESR and FLAIR will provide antiproton beams at relativistic and low energies (from a few MeV down to rest).

Nuclear structure studies with RI beams and cooler rings

Selected topics in present days nuclear structure physics studied by reactions of RI beams are presented. They are change in nuclear radii, single particle orbitals, and shapes. Dynamical changes are shown for nuclei far from the stability line in particular in p-sd shell. Among the future reaction study, a thick target method for a storage ring is presented. A possibility to obtain the highest luminosity for an internal target experiment is proposed.

Hadronic threshold reactions

First investigations on meson production at threshold in the strong interaction began in the fifties when sufficient energies of accelerated protons were available. Early experiments performed with bubble chambers revealed already typical ingredients of threshold studies, which were superseded by more complete meson production investigations at the nucleon beam facilities TRIUMF, LAMPF, PSI, LEAR and SATURNE. Currently, at the cooler rings IUCF, CELSIUS and COSY the field is entering a new domain of precision and further progress. The analysis of this new data in the short-range limit permits a more fundamental consideration and a quantitative comparison of the production processes for different mesons in the few-body final states. The interpretation of the data takes advantage of the fact that production reactions close to threshold are characterized by only a few degrees of freedom between a well-defined combination of initial and exit channels Deviations from predictions of phase-space-controlled one-meson exchange models are indications of new physics. Precision data on differential cross-sections, isospin and spin observables —partly but by no means adequately available— are presently turning up.

Close-to-Threshold Meson Production at COSY-11

Meson production at threshold in the hadron-hadron interaction began in the fifties when sufficient energies of accelerated protons were available. A strong interdependence between developments in accelerator physics, detector performance and theoretical understanding led to a unique vivid field of physics. With the advent of the new cooler rings the field entered a new domain of precision.The analysis of these new data permits a more fundamental consideration and a quantitative comparison of the production processes for different mesons in the few-body final states. The interpretation of the data takes advantage of the fact that production reactions close to threshold are characterized by only a few degrees of freedom between a well defined combination of initial and exit channels. Deviations from predictions of one-meson-exchange models are indications of new physics. In future, precision data on differential cross sections, isospin and spin observables will test theoretical models.

Storage rings for radioactive, highly charged ions

After a condensed survey on the basics of ion storage–cooler rings, Schottky mass spectrometry on unstable nuclei at the ion cooler-ring ESR is discussed, emphasizing efficiency, resolving power, and sensitivity of this method. Then the extension of in-ring mass spectrometry to short-lived nuclei by a newly developed time-of-flight technique will be outlined. Cooler rings are the only tools to address beta decay of highly charged ions which has an obvious connection to nucleosynthesis in hot stellar plasmas. That is elucidated for the cases of electron capture and bound-state beta decay, whose astrophysical impact will be finally discussed at the example of the galactic chronometer 187Re/ 187Os.

Sunshine by cooling.

An overview of the development of cooler rings for fast ions with emphasis on electron cooling of heavy ion and radioactive beams is presented. Some of the most important discoveries made with the use of this new experimental tool include the first observation of string-like ordered ion beams, the development of Schottky mass spectrometry for precision mass measurements of radioactive nuclei, the discovery of bound-state beta-decay of highly ionized nuclei and the calibration of the Re/Os cosmochronometer including a determination of the age of our Galaxy. First results of 1 s-state hyperfine interaction, and Lambshift measurements in hydrogen-like heavy ions are presented, together with an outlook on ongoing developments.

Cooled beam diagnostics

The specific diagnostics systems used in cooler rings will be reviewed. The hardware used and the ways in which the physical characteristics of the beam are accessed will be described. It will also be shown how to evaluate the forces that are exerted on the beam during cooling.

STORAGE RING : AN ADVANCED TOOL IN MODERN RESEARCH

These introductory notes give a personal flavoured view on the developments, opportunities and perspectives of ion storage rings with cooling devices including some highlights of applications in various fields of research. First some historical remarks are made on the development of cooler rings and cooling techniques, highlighted by the observation of “orderliness” in cooled heavy ion beams. In the main part recent experimental highlights from storage rings in the fields of particle-, nuclear and atomic physics are reviewed. The lecture will end with a look at future projects and a dream.

Nuclear structure studies at GSI — present status and perspectives

The first experiments with exotic nuclei in the ESR heavy ion storage ring already indicated the new possibilities for nuclear structure research in storage and cooler rings [1–6]. The present status and future possibilities for nuclear reaction studies in storage rings will be addressed in this paper.

Precision laser spectroscopy of highly charged ions

Recently, intense beams of highly charged ions have become available at heavy ion cooler rings. The obstacle for producing these highly interesting candidates is the large binding energy of K-shell electrons in heavy systems in excess of 100 keV. One way to remove these electrons is to strip them off by passing the ion through material. In the cooler ring, the ions are cooled to a well defined velocity. At the SIS/ESR complex it is possible to produce, store, and cool highly charged ions up to bare uranium with intensities exceeding 108 atoms in the ring. This opens the door for precision laser spectroscopy of hydrogenlike-heavy ions, e.g.209Bi82+, and allows to examine the interaction of the single electron with the large fields of the heavy nucleus, exceeding any artificially produced electric and magnetic fields by orders of magnitude. In the electron cooler the interaction of electrons and highly charged ions otherwise only present in the hottest plasmas can be studied.

Storage rings for low-energy experiments

In this article an introduction and overview of heavy ion storage rings is given. The different cooling schemes for ion beams, i.e. electron, laser, and stochastic cooling as well as beam heating mechanisms are described. Connected to this are collective effects in cold stored ion beams which lead to a form of crystallization. The potential of cooler rings in atomic and molecular physics experiments with stored and cooled ion beams is discussed. This will be exemplified with results from atomic lifetime measurements and the interaction of atomic and molecular ions with electrons and photons utilizing the electron cooler.

Atomic physics experiments at ion storage rings

Within the last several years a number of heavy ion storage rings has been completed and the related experimental programs were started with striking success. Unique new results could be obtained — particularly in the field of atomic physics — by employing the outstanding possibilities of cooler rings for preparation and manipulation of high-quality beams of ions. Some of the new experimental possibilities provided by heavy ion storage rings are reviewed. Several groups of experiments involving inner-shell excitation in ion-atom and in electron-ion collisions are discussed. In addition, results are presented on work extending the classical scope of X-ray and inner-shell studies to a new class of atomic inner-shell physics experiments which have become feasible only by the construction and use of heavy ion storage rings.

Atomic physics with cooled heavy ions

The high brightness ion beams of the new cooler rings allow for many new experiments in atomic physics. In some experiments the electron cooler is also used as an electron target, in others cw or pulsed lasers are employed to study the interaction with photons. For molecular ions also the internal degrees of freedom can be cooled.

Exotic atoms ? a new scope

Heavy ion cooler rings have been installed in a number of laboratories around the world. They allow for a new generation of experiments using the products of high energy heavy ion collisions, i.e. highly charged andpossibly radioactive ions. The first series of investigations at the SIS-ESR facility at the GSI, reviewed here, includes the observation of beta decay into a bound state of a highly charged ion andprecision spectroscopy of inner-shell levels by means of X-ray spectroscopy, laser spectroscopy andresonant di-electronic recombination.

New physics with cooled ion beams

We review new possibilities for heavy ion cooler rings in different fields of physics and describe present experiments at the Heidelberg Test Storage Ring TSR.

Few body physics at new proton cooler rings

With the new accelerator techniques of phase space cooling it became possible to do experiments with high quality beams on internal targets and on external targets after superslow extraction. Three cooler rings are working or under construction in Bloomington, Uppsala and Jülich which will make possible a new generation of few body experiments in the medium energy range.