The FRS Ion Catcher is a set up which slows down exotic nuclei produced at relativistic energies to perform high precision measurements almost at rest. The properties of the exotic isotopes help to study the structure of the nuclei or the origin of the elements in the universe. The setup is located at  the fragment separator (FRS) of the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany. The setup has been designed in collaboration with other members mainly at the Justus Liebig University of Giessen, Germany. With the time, the collaboration has grown and members from several research institutes from different countries are part of it (see Collaboration section).

A bit of history: the first version of the set up consisted in a gas-filled stopping cell at room temperature, a radio frequency (RFQ) beam distribution system and a time-of-flight spectrometer with orthogonal acceleration (Orto-TOF-MS) [1]. The current FRS Ion Catcher consist in a cryogenic version of the stopping cell for improved cleanliness, an RFQ based beamline with improved capabilities and a  superior Multiple-Reflection time-of-flight Mass Spectrometer (MR-TOF-MS) [2]. Both versions are prototypes of future Ion Catchers which are planed in future facilitites, such as the low energy branch (LEB) of the Supe-FRS at FAIR and other connected projects from the collaboration (see Connected Projects).