The Service de Physique Nucléaire (SPhN) of Irfu conducts basic research on nucleons and nuclei, the fundamental building blocks of matter held together by the strong interaction. This research is mostly experimental, strengthened by theoretical activity. In extreme conditions of temperature and energy, these building blocks may lose their identity and give rise to a quark-gluon plasma, the evidence and nature of which are being studied. SPhN also applies its knowledge and expertise to fundamental studies of questions of public interest linked to the transmutation of nuclear waste, the dismantling of nuclear installations and the study of new fuel cycles for nuclear power generation. Within Irfu, SPhN contributes to the national effort in basic research, and through the whole of its actions is at the heart of the missions of the CEA.

Objectives

The strong interaction manifests itself at two successive scales; the first is that of assemblies of quarks and gluons, which may be deconfined in a plasma or bound in a nucleon, or more generally in hadrons; the second concerns assemblies of nucleons in the form of atomic nuclei. The objective of SPhN is to deepen our knowledge of these systems. These activities are grouped around four main areas of research:

- Quark-gluon plasma,

- Structure of the nucleon,

- Structure of the nucleus,

- Interface between fundamental research and applications

Resources

At present, SPhN gathers 45 researchers, about 12 doctoral students and 10 post-docs, to which are added 4 technicians and administrative staff.

The development of the instrumentation required for experiments conducted by the SPhN research groups is carried out in close collaboration with the technical divisions of Irfu.

Experiments are carried out within national or international collaborations, in partnership for most of them with IN2P3, or in some cases with other directions of CEA. The main laboratories where SPhN physicists perform their experiments are : in France, GANIL (Caen), ILL (Grenoble); in Europe, GSI (Germany), Geel and Double Chooz (Belgium), Jyväskylä (Finland), as well as CERN (Geneva); in the United States, Jefferson Lab (Virginia), BNL (New York) and MSU (Michigan); in Japan, RIKEN. Data analyses and theoretical activities are carried out at Saclay, thanks to the computing resources of SPhN and Irfu, of large computer centres and of the LHC-grid.

Perspectives

The different research groups nourish and complement each other. The proper balance between them is a source of dynamism which SPhN is bound to preserve.

In the mid-term, the most important effort in the search of a phase transition of nuclear matter toward a quark-gluon plasma will focus on the Alice experiment, with the ongoing preparation of the data taking phase with the first beams of Cern/LHC. At the same time physicists analyze data from the Phenix experiment at BNL/Rhic.

Experiments at Cern and Jefferson Lab aim at determining how quarks and gluons group together to form hadrons, and nucleons in particular. The measurement of generalized parton distributions in the nucleon is a new field of study which, after a first generation of dedicated experiments at Jefferson Lab, should lead to new developments and new orientations, at Jefferson Lab (experiments Clas, Clas12 and Hall A) and at Cern (COMPASS experiment). Other areas of hadronic physics are covered as well by these experiments. In parallel, SPhN contributes to theoretical large-scale calculations of lattice QCD.

The perspectives concerning nuclear structure are rich and very open, as ambitious projects, to which SPhN is associated at different levels, are foreseen in Europe in order to extend the range and intensity of available radioactive beams; in the mid-term Spiral2 at Ganil and Fair in Germany; then in the long-term, EURISOL. All these projects will considerably extend the range and intensity of available radioactive beams. In the mean time, our physicists use all existing heavy ion accelerators (Ganil, Cern/ISOLDE, , Legnaro, RIKEN, MSU), each according to specific needs. In parallel, a lonf-term theoretical effort has been launched to reach a complete understanding of nuclear structure, including of the most exotic nuclei.

Physics for nuclear power generation is also rich in new projects: nTOF at Cern just started a new phase of exploitation, with applications to the understanding of nucleosynthesis; the spallation program at GSI is entriched through applications to hadron therapy and space sciences; a new generation of fission experiment is being designed, in particular at the facility NFS at Spiral2. These studies are applied in the definition of new nuclear reactors, in all systems using spallation targets (production of neutron beams, of radioactive nuclei, accelerator-driven reactor or ADS, etc), and, among others, in the non-destructive characterization of nuclear waste and in non-proliferation.

Head of division: Michel Garçon