CRYRING is a heavy ion storage ring, formerly located at the Manne Siegbahn Laboratory at Stockholm University. During close to two decades of operation in Sweden, many significant scientific contributions to atomic and molecular physics were achieved using CRYRING. To further leverage its capabilities into the realm of intense beams of highly charged ions, of exotic  isotopes, and antiprotons, it has for long been proposed to relocate CRYRING from Sweden to GSI/FAIR. In cooperation with our Swedish partners and further international contributors, we are presently working on the CRYRING@ESR project.

In Darmstadt, the ring is being modernized and adapted to the GSI/FAIR standards and set up downstream of ESR (Report). There, it is to become both, a test bed for new FAIR technologies, as well as a new home for research with slow exotic ion beams for several collaborations of FAIR: SPARC, BioMat, FLAIR, and NuSTAR for pursuing precision measurements on forefront of atomic and nuclear physics and beyond. Details of our planned experiments are laid out in the Physics book.


CRYRING@ESR can store, cool and decelerate heavy, highly charged ions down to a few 100 keV/nucleon. It features excellent vacuum conditions to achieve ion beam lifetimes of several seconds to minutes for even the highest charge states of ions. It is equipped with a high performance electron cooler, as well as with a gas-jet target. Moreover, an independent injector beamline will allow for standalone operation during commissioning and prototyping while the FAIR accelerators are unavailable.

The ions are kept in orbit by twelve 30° magnetic dipoles and a number of magnetic quadrupoles and sextupoles (not shown in the figure) in six of the twelve straight sections. The other six sections house an injection and an extraction system, an rf-gap for deceleration and acceleration , and the electron cooler. Finally, one section is available for experimental installations as for instance a gas target. 



54.17 m (ESR/2)


0.054 – 1.44 Tm (– 0.8 Tm for protons/antiprotons)

Maximum energy for p, pbar

30 MeV

   - for 12C6+

24.7 MeV/u

   - for 238U92+ (238U89+)

14.8 MeV/u (13.9 MeV/u)

Lowest energy

Charge exchange limited

Magnet ramping (de- and acceleration)

1 T/s (4 T/s, 7 T/s)

Vacuum pressure

N2 equiv. 10-12 – 10-11 mbar

Beam injection

Multiturn and fast

Beam extraction

slow and fast

Ion source for stand alone operation

Yes (300 keV/u, A/q < 2.85)

A new FAIR-type control system is being implemented and operated for the first time in a machine providing real beam conditions and hence will be the perfect occasion to test not only the interplay of the newly implemented tools and concepts but also to scrutinize on the stability of the system. Moreover, with the local ion source the ring can also be operated independently. This makes it a perfect training environment for the operators crew to get accommodated with the new control system. Both allow for valuable feedback on the operational concept well in advance before the commissioning of FAIRs key machines.


Presently, CRYRING@ESR is in commissioning with beam from the local injector. The local ion source with 300 keV/u RFQ accelerator as well as the injector beamline from ESR to CRYRING are operating and have both successfully demonstrated ion beam transport towards CRYRING. Ion storage has been achieved Sep. 2017. H2+ and other singly charged ions were injected from the local injector into CRYRING and observed in all beam diagonistic elements of the ring for many seconds, the beam lifetime was only limited by the prevailing vacuum conditions. The first experimental systems (particle detectors, fluorescence setups) have recorded signals induced by the stored ion beams.

Our next steps are to bring the electron cooler into service, to set up the extraction beamline, and to perform first experiments.

Simulated ion beam in the yet empty cave ready for installation of CRYRING@ESR (2014).
CRYRING@ESR construction site (2015-12-03).
Cut through a 3D model of CRYRING@ESR with Cave.
First beam of H<sub>2</sub><sup>+</sup>transported from the local ion source fully around CRYRING onto the last beam viewer
M. Lestinsky (GSI)
W. Geithner (GSI)
CRYRING project team


The CRYRING@ESR project is realized with the support of international collaboration partners. Their efforts are kindly acknowledged:

Documents and publications