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A next generation experimental setup for studies of

Reactions with Relativistic Radioactive Beams

During the past decade it has been demonstrated that reactions with high-energy secondary beams are an important tool to explore static and dynamic properties of nuclei far off stability. Relativistic beam energies allow a quantitative description of the reaction mechanisms, while also having experimental merits, such as the possibility of using relatively thick targets (in the order of 1 g/cm2). Moreover, due to the kinematical forward focusing full-acceptance measurements are feasible with moderately sized detectors. This makes it possible to gain nuclear-structure information from reaction studies even with very low beam intensities, as low as about 1 ion/s. An excellent place to perform such type of studies will be a next generation experimental setup for studies of Reactions with Relativistic Radioactive Beams (R³B).

Enlarge pic
Phase 1 R³B experimental setup. In phase 2 also the high-resolution magnetic spectrometer will be included.

The R³B experimental setup is versatile reaction setup with unprecedented efficiency, acceptance, and resolution for kinematically complete measurements of reactions with high-energy radioactive beams. The experimental configuration (initial setup, see Figure), is based on a concept similar to the existing R³B/LAND reaction setup at GSI introducing substantial improvement with respect to resolution and an extended detection scheme, which comprises the additional detection of light (target-like) recoil particles and a high-resolution fragment spectrometer.


The setup will be located at the focal plane of the high-energy branch of the Super-FRS and is adapted to the highest beam energies (corresponding to 20 Tm magnetic rigidity) provided by the Super-FRS, capitalizing on the highest possible transmission of secondary beams. The sophisticated R³B experimental setup will enable a broad physics programme with rare-isotope beams with emphasis on nuclear structure and dynamics as well as on different astrophysical aspects and technical applications. A survey of reaction types and associated physics goals that can be achieved is given in the table. In order to cover such a large physics programme several state-of-art detection subsystems and sophisticated DAQ system are planned and being built. This work is done inside the R³B collaboration which includes more than 50 different institutes from all over the world.

Reaction types with high-energy beams measurable with R3B and corresponding achievable information

Reaction type Physics goals
Total-absorption measurements Nuclear matter radii, halo and skin structures
Elastic p scattering Nuclear matter densities, halo and skin structures
Knockout Shell structure, valence-nucleon wave function, many-particle decay channels unbound states, nuclear resonances beyond the drip lines
Quasi-free scattering Single-particle spectral functions, shell-occupation probabilities, nucleon-nucleon correlations, cluster structures
Heavy-ion induced electromagnetic excitation Low-lying transition strength, single-particle structure, astrophysical S factor, soft coherent modes, low-lying resonances in the continuum, giant dipole (quadrupole) strength
Charge-exchange reactions Gamow-Teller strength, astrophysics, soft excitation modes, spin-dipole resonance, neutron skin thickness
Fission Shell structure, dynamical properties
Spallation Reaction mechanism, astrophysics, applications: nuclear-waste transmutation, neutron spallation sources
Projectile fragmentation and multifragmentation Equation-of-state, thermal instabilities, astrophysics, structural phenomena in excited nuclei, γ-spectroscopy of exotic nuclei

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