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Proyecto 2013

The R3B experiment

The R3B (Reactions with Relativistic Ion Beams) collaboration, at the international FAIR facility, has proposed to build a multi-purpose detection set-up to investigate reactions induced by radioactive beams at relativistic energies.

R3B wil be the only faciliy worldwide providing the capability for kinematically complete measurements of reactions with relativistic heavy-ion beams up to around 1 AGeV, which provides sufficiently high resolution to enable a comprehensive experimental investigation of fundamental questions using a wide variety of scattering experiments, such as heavy-ion induced electromagnetic excitations, knockout and breakup reactions, reactions of astrophysical interest, or light-ion (in)elastic and quasi-free scattering in inverse kinematics, and thus enabling a broad physics programme with rare-isotope beams to be performed.


Secondary beams from the Super-FRS will impinge on the reaction target. Surrounding this target one would find the R3B Si-tracker (light charged particle tracker) and the CALIFA detector (calorimeter for gammas and high energy light charged particles). The products of the nuclear reactions will be bend by the super conducting magnet GLAD and tracked by different detectors. Neutrons that will not experience the effect of the strong magnetic field will be detected by the new neutron detector NeuLAND.

More than 200 scientists from 50 different institutions contribute to this experiment, where our group is strongly involved in the design and construction of CALIFA, an outstanding calorimeter for both gamma and light charged particles, with high-efficiency and high-resolution, for nuclear structure investigations with exotic nuclei.

The scientific and technical program of the R3B experiment was reviewed very positively by the FAIR PAC.

In the case of CALIFA, an estimated cost of 3.2 M€  (prices 2005) was reviewed by the experts panel CORE Cost Review Committee. The period comprised between 2005-2012 was dedicated to the R&D of the key R3B detectors.  The USC team is strongly involved with the development of this detector. D. Cortina is responsible of  the coordination of CALIFA design and construction. H. Álvarez is responsible of the simulation workpackage and the full team has a strong implication in tasks related with the general design of CALIFA and had also a leading role in the characterization and choice of scintillating crystals and readout devices. The UVigo team, with J. Vilán and E. Casarejos, have been in charge of the innovative mechanical design of the detector.

The major outputs of this working group are summarized in the approved Technical Design Report for the CALIFA Barrel section (D.cortina acting as convener of the document) with a strong participation of our teams (USC and Uvigo).

CALIFA  a dedicated CALORIMETER for the R3B experiment

CALIFA is a calorimeter intended for the high-efficiency detection of gammas and light charged particles produced in secondary reactions at the R3B target. A large resolution both in the individual gamma energy as well as the total energy (up to tens of  MeV) is requested. Protons (up to 300 MeV) produced in the target region crossing the crystal bulk should also be detected with good energy resolution. 

The main properties of this device, high efficiency and good angular resolution, are imposed by the very particular kinematics of energetic gamma rays emitted by sources moving with relativistic velocities and by the typically low intensities of the secondary beams involved. They also suggest the division of the detector in two main parts: the CALIFA BARREL and the CALIFA Forward ENDCAP.

The design of the CALIFA BARREL is nowadays complete, being their main characteristics

Intrinsic photopeak efficiency


(at Eγ= 15MeV projectile frame)

γ-ray sum energy resolution Δ(Esum)/sum > < 10% for 5 γ rays of 3Mev
Calorimeter for high-energy light-charged particles up to 300 MeV p in Lab system
γ-energy resolution 5-6% ( ΔE/E at Eγ=1 MeV)
Light-charged particle resolution <1% ΔEp/Ep
proton-γ ray separation for 1 to 30 MeV

The detector is highly segmented (~3000 individual crystals for the full detector and 1952 for the BARREL part). The detectors have different shape and angular aperture for different polar angle regions. The high granularity and total absorption efficiency determine the shape of the crystals.

The size and form of the crystals are fitted to ensure acceptable energy resolution and efficiency and also to get a complete circle (ring).

To obtain high efficiency, an alveolar structure made of thin carbon fibre is devised. Groups of four crystals are inserted in the structure, minimizing the dead volume and the amount of material between detectors. The alveoli are glued together, obtaining a honeycomb-like structure with strong mechanical properties. The structure is fixed by thicker carbon fibre tabs to the external mechanical support, formed by aluminum tiles that also hold the very front electronics modules. An additional support structure fixes the calorimeter in the measurement place, allowing the displacement of the Barrel and EndCap halves for service.

View of the R3B target area. The beam is coming from the right






Detail of the R3B target area. The beam is coming from the right, The target is surrounded by the Si-Tracker and the CALIFA calorimeter.











Detailed view of the three layers of the CALIFA mechanical structure.



CALIFA Barrel Demonstrator

After approval of the CALIFA Barrel TDR in 2013, we have initiated the construction of the CALIFA BARREL Demonstrator.  The Demonstrator, with a dedicated mechanical structure, represents a significant part of the final CALIFA Detector. It has a modular structure comprised of up to 12 petals.


A Petal is a set of 9x2 carbon fiber alveoli ( each alveolus holds 4 crystals) and 72 individual detection channels. Covering the furthest forward angles of the CALIFA BARREL.

Last Updated (Tuesday, 14 January 2014 11:43)