Fusion-evaporation reactions induced by high intensity neutron-rich beams from SPIRAL2 will allow us to populate exotic compound nuclei, transferring more initial angular momentum to them (up to 100 h) than currently achievable with stable beams. This will be of great benefit for the study of vibrational and rotational collective phenomena at finite temperature, such as the Giant Dipole Resonance or exotic shape changes induced by fast rotation. Heavy-ion radiative capture and reaction dynamics studies will also benefit considerably from the availability of high intensity neutron-rich beams.

There are also interests related to study weak isomeric decays produced after fission or fragmentation of relativistic beams from FAIR, within the HISPEC/DESPEC experiments within NUSTAR@FAIR. Studying very weak gamma branches are also of astrophysical importance.

Gamma ray detection constitutes an important experimental probe common to all these physics topics. Therefore the main aim of the PARIS collaboration is develop and to construct a dedicated gamma-calorimeter with dynamical range from 100 keV to 50 MeV. Such a device might partly consist of existing European detectors. To complement the exciting challenges and opportunities afforded by SPIRAL2, it is also the intention to investigate designs for a novel gamma-calorimeter benefiting from recent advances in scintillator technology.

A clear plan for such a new gamma-calorimeter can only arise from an intensive R&D program, with GEANT4 simulations being a key component of this work. A number of scenarios are presently under consideration:

a) Develop and construct a completely new calorimeter, which can measure both high energy and low energy gammas. This can be done either simultaneously (using signal pulse processing), or by selecting one range or another (inserting/removing absorbers in front and changing the dynamical range).

b) Develop a 2-shell calorimeter, with inner (hemi-)sphere, highly granular, made of new short crystals (LaBr3(Ce), LaCl3, CeZnTe). The readout might be performed with APDs or with digital electronics which would offer the possibility of pulse shape analysis. The outer (hemi-)sphere, with lower granularity but with high volume detectors, could be made from conventional crystals (preferably of BaF2), or using existing detectors (Chateau de Crystal or HECTOR). The inner-sphere will be used as a multiplicity filter, sum-energy detector and will also serve as an absorber for the large detectors behind. The outer-sphere will measure high-energy photons.

c) Use existing high-energy gamma detectors (e.g. Chateau de Crystal or HECTOR) and fill the remaining solid angle with a new calorimeter.

The R&D phase and experimental investigations will be performed in synergy with the EXL-R3B and HISPEC/DESPEC collaborations within NUSTAR@FAIR community, as well as in cooperation with other SPIRAL2 projects.