CRYRING@ESR - Facility for Antiproton and Ion Research

10 Chapter 2. Scientific Motivation
or unwanted spectator electrons. The interpretation of the experiments is thus straightforward
and without ambiguity. In addition, the inverse processes of many fundamental atomic and
nuclear reaction and decay mechanisms only become experimentally accessible if corresponding
vacancies in the atomic shell are available. Examples of these inverse effects include radiative
recombination (inverse of photoeffect), dielectronic capture (inverse of autoionization), bound
state beta decay (inverse of nuclear electron capture, EC) or nuclear excitation by electron
capture (inverse of internal conversion).
Low-energy phase space of cooled ions provide extremely well-defined experimental conditions
for precision spectroscopy experiments (electrons, ions, and photons). At the same time,
compared to ions at rest, orders of magnitude higher luminosity in collision experiments using
low-energy ions in a storage ring is achieved due to the repeated interaction of the stored ion
beam with a target (gas, free electrons, laser). These luminosities may be comparable to or even
exceed those obtainable in single-pass fixed-target experiments while the dilute targets induce
only a minimum amount of angular and energy straggling which can be compensated by beam
cooling and guarantee for single collision conditions.
For atomic collision studies, another appealing aspect is the very strong perturbation to
the target atoms due to the impact of the slow highly charged ions with conditions far from
equilibrium. CRYRING operates in a particular interesting energy range for nuclear reactions,
that is at the Coulomb barrier and in the astrophysically relevant Gamow window of p- and rpprocesses
of nucleosynthesis. The swift low-energy beam also makes the detection and monitoring
of primary and secondary ions either in a destructive manner with particle detectors or in a
non-destructive manner down to the level of single particles by means of Schottky techniques
experimentally much easier. Hereby, the storage ring itself serves as a high-resolution magnetic
heavy ion spectrometer. The dynamic range that is covered with the various experimental
techniques covers the span from single stored ions, detected by means of Schottky noise analysis
up to beams at the space charge limit.
As stated in a previous section, the capabilities for future research on atomic, nuclear,
and astrophysics with a combined CRYRING and ESR facility will be outlined in a dedicated
“Physics book: CRYRING@ESR” which is in preparation. The current draft of the physics
book is appended to this document. Moreover, since by the installation of CRYRING@ESR
a substantial part of the heavy ion program as foreseen at FAIR for NESR and FLAIR can
already be addressed, we also like to refer to the already positively evaluated physics programs
as described in the FAIR documents of the contributing collaborations (SPARC [18], FLAIR
[19], EXL [20], ILIMA [21], and ELISe [22]).