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 working on the CRYRING@ESR project.

In Darmstadt, the ring was modernized and adapted to the GSI/FAIR standards and set up downstream of ESR (Report). There, it is 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.


CRYRING@ESR commissioning is almost complete and ready for first beamtimes with user experiments. G-PAC approved beamtimes are scheduled and first shifts have already been completed. The local ion source provides a range of singly charged ions from gaseous and solid sample materials. The source transmits beams through a 300 keV/u RFQ accelerator to the ring. Also, beam transfer from ESR to CRYRING is operating. Ion storage with beam from the local source has been achieved Sep. 2017, transfer and storage of ions from ESR was established in Dec. 2019. Ion energy can be ramped up to maximum rigidity and ramped down. Beam lifetime was only limited by the prevailing vacuum conditions.

Our next steps completing the commissioning of the extraction beamline and all preparations for the approved experiments.


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

Documents and publications