Service d'astrophysique
Laboratoire AIM

Presentation: 

• SPIRAL2 [SPIRAL: Système de Production d'Ions Radioactifs Accélérés en Ligne, production system of on-line accelerated radioactive ions] is the project of a facility intended for the production of new beams of stable and radioactive ions at GANIL (Large-scale national accelerator for heavy ions). 
• The present GANIL facility produces and accelerates stable beams, ranging from ¹²C to Uranium. GANIL produces also radioactive beams using two techniques, either the fragmentation of stable beams on thick targets, or the ISOL technique (Isotope Separation On-Line, to produce and select the nuclei) with the SPIRAL1 system. The SPIRAL2 project aims at extending the possibilities of the beam production at GANIL: the beams will be delivered with increased intensities and it will offer a wider domain of radioactive ions.  Under operation in 2012, it will open a new horizon for the research on the nuclear properties. The international community (more than 700 physicists of the field) will have new possibilities for the exploration of the nuclear structure, in these different topics: observation of nuclei far from the valley of stability, neutron-rich or neutron-deficient species, measurement of their shapes, determination of the new nuclear shell structure effects, formation of new super-heavy nuclei, studies of nuclei involved in the astrophysical processes.
• The construction of SPIRAL2 will require overcoming several technological challenges.  It will thus correspond to an important step between the existing ISOL facilities (SPIRAL, ISOLDE au CERN...) and the future projects like EURISOL (EURopean Isotope Separation On-Line) in Europe or RIA (Rare Isotope Accelerator) in the United States.
  SPIRAL2 was designed by the teams of GANIL, of CEA/DAPNIA and the institutes of CNRS/IN₂P₃.

Beams

SPIRAL2 will produce very intense, stable and radioactive beams and will provide an intense neutron flux.
New intense beams of radioactive nuclei will be produced in the regions of the nuclear chart located above the Krypton isotopic chain.
The radioactive beams will be post-accelerated by the existing CIME cyclotron, well-adapted for the separation and acceleration of ions in the energy range between 3 and 10 MeV/nucleon for masses A~100-150. The SPIRAL2 beams, both before and after acceleration, will be transmitted to the existing experimental area of GANIL.

Refer to the chapter "Experimental techniques" to see the access to the different regions of the nuclear chart:
- The variety of beams of the existing GANIL/SPIRAL facility;
- The fission fragments produced by SPIRAL2;
- The combination of the LINAG beams and of the radioactive beams from SPIRAL2.

 Goals 

The radioactive nuclei far from the valley of stability are produced only in laboratory or in the stars. They are qualified as "exotic" because they present unusual properties, not predicted by the usual nuclear models which were elaborated from the studies of stable nuclei. For instance, the shell model and its well-established sequence of magic numbers for the spherical nuclei close to the stability are put into question in the case of exotic nuclei: phenomena like the vanishing of the sphericity of the assumed magic nuclei and the appearance of new magic shells were found with the first generation of radioactive beams. These effects are also expected to occur in the new regions of the nuclear chart opened by SPIRAL2. The properties of exotic nuclei are explored with the radioactive beam facilities. The objective of the studies is to check the validity of the existing model and to improve the predictive power of the nuclear theories in the most extreme conditions, to the limits of the nuclear binding. For these studies, we need to produce and to study nuclei with large isospin (difference between neutron and proton numbers) compared to their stable isotopes, or nuclei with a large number of nucleons (super-heavy nuclei), or very-deformed nuclei.
 
In summary, the scientific goal of the SPIRAL2 facility is to provide a new domain for the experimental studies in nuclear physics by extending the variety of the beams of GANIL and of SPIRAL: it will produce and accelerate heavier (towards Uranium) neutron-rich radioactive ions. The exploitation of the SPIRAL2 beams will allow us to extend our knowledge on the nuclear phenomena in the field of the exotic radioactive nuclei.

Moreover, due to the large flux of neutrons created by SPIRAL2, the facility can be used as a tool to irradiate materials; these studies will be useful for the construction of the future machines for fusion research (ITER, DEMO ...).
The interdisciplinary researches in radiobiology, atomic physics, and solid state physics, carried out by the existing laboratories (CYCERON and CIRIL) will benefit from the very large fluxes of stable and radioactive heavy ion beams.

Localization

The SPIRAL2 facility will be located on the GANIL site at Caen in Normandy, to complete the existing devices of beam production for stable and radioactive heavy ions. These devices, together with the detection systems placed at GANIL, are the tools for the fundamental research on the nucleus structure.

Operation

The operation of the SPIRAL2 accelerator is scheduled for the end of 2011, the first experiments with stable ions will be done in 2012 and the production of radioactive beams will begin in 2013.

Context

Throughout the world, there are a few accelerators producing an extended variety of radioactive beams, with intensities sufficient for the studies of nuclear structure and reactions: in Europe, the GANIL accelerator (beams at energies of the order of a few 10 to 100 MeV/nucleon), GSI (a few 100 MeV/nucleon), in Japan, RIKEN (10-150 MeV/nucleon), in the United States, MSU, and for more limited ranges of energies and beams, ISAAC et Oak Ridge.

France is one of the few countries occupying a leading world position in the field of the exotic radioactive beams, thanks to the activities done with the beams delivered by GANIL, accelerator established and managed in collaboration by the CEA and the CNRS organisms. To maintain this leading-edge position, the first-generation facility SPIRAL was built; it started to deliver beams in 2001; it is particularly well adapted to the production and acceleration of light and medium-mass nuclei at energies from 2 to 25 MeV/nucleon.

In the mean time, the nuclear community, in the  laboratories of Germany, Belgium, Finland, France, United Kingdom, Italy, Sweden and at CERN) has begun to examine the future plans for the field, at the European level.  The NuPECC committee (Nuclear Physics European Collaboration Committee) in the report of April 2000 gave recommendations for the study and development of second-generation facilities to produce rare radioactive isotopes. NuPECC recommended that the new facilities should be under operation in the years 2010-2012.

A Research & Development program has been undertaken at the European scale, and financed by the European Community in the 5th and 6th PCRD. This is the EURopean Isotope Separation On-Line (EURISOL) program. Along these lines, and founded on the study report «LINAG Phase 1», the SPIRAL2 project has turned out to be the necessary intermediate step   between SPIRAL (in operation since September 2001) and EURISOL. It should place the GANIL and France in a privileged position regarding the future choice of the EURISOL location.

For all these reasons, the two organisms, the Direction of Material Sciences [Direction des Sciences de la Matière, DSM] of CEA and the Institut for Nuclear Physics and Particles [Institut National de Physique Nucléaire et des Particules, IN2P3] of CNRS decided to launch a detailed study for the preparation of the project [avant-projet détaillé (APD) de SPIRAL2] on Nov. 1st 2002, during two years. The region of Basse-Normandie has placed the research as one of its main priorities and has brought support for the development project of GANIL in an European perspective. This region gave its agreement for a co-funding of the APD phase, together with the CEA and the CNRS.

The APD phase ended in 2005, and the DSM, IN2P3 and the region Basse-Normandie, with the agreement of the Ministry (May, 23rd 2005) decided to start the realization of the SPIRAL2 project. The representatives of the State, of the region Basse-Normandie and of the conurbation in the neighborhood firmed the agreement on September the 4th, 2006 with the CEA and the CNRS.

International competition at the starting of the machine in 2012 - Specificities

World widely, the production of radioactive ions will be mainly carried out at RIKEN with the RIBF factory, in the United States with the RIA project and the future beams at Oak Ridge, in Europe with GSI/FAIR (2013) and SPIRAL2.
But SPIRAL2 will offer a large variety of radioactive beams with a unique combination of beam intensities and energies (<10 MeV/nucleon).
In the long-term scale, the European project EURISOL will complete the range of the beams delivered SPIRAL2 and then higher energies (50 MeV/nucleon) should be available.

Contributions of DAPNIA 

Scientific responsibilities:

The support and the contributions of the SPhN physicists for the project SPIRAL2 are strong, both on the elaboration of the scientific program founded on the assets of the future beams and on the preparation of the future detection. The SPhN teams were deeply involved in the working groups which contributed to the writing of the White Book "PHYSICS CASE" for SPIRAL2. This document presents the motivations and the future experiments planned with the beams of SPIRAL2.

In the field of the nuclear structure of radioactive beams, the DAPNIA teams carry on with their work at SPIRAL2 on three main research subjects. They will explore:
i) The evolution of the excitations and of the structure of very neutron-rich nuclei, towards the drip-lines,
ii) The extremely deformed nuclei, 
iii) The conditions of the formation of very-heavy nuclei at the limits of the nuclear binding.

DAPNIA teams participate in defining several future experiments.  These SPIRAL2 experiments will be realized either at the end of the line of the primary accelerator for stable ions (this is the case for the project with the S3 spectrometer, and also for the program with the neutron beams, called NFS-Neutrons For Science), or, when the production of the new radioactive ions will be operational,  in one of the existing experimental area of GANIL ( experiments are foreseen with the photon detector AGATA, or with GASPARD, the project of a light-charged particle and photon detector).

In the list of the presentations for the future experiments (Letters of Intent: LOI) examined by the SAC committee in November 2006 (see chapters: Science, and Links and documents), amongst 19 LOI  (+ 6 related to the program with the AGATA detector), 12 LOI involve strongly the SPhN groups; amongst these LOIs,  5 have a co-spokesperson from SPhN. One LOI is devoted to the NFS program- which also involves SPhN physicists.
These LOI will require the Research & Development of new equipments and the formation of collaborations. The AGATA project is underway but S3 and GASPARD are still under discussion (conception, collaboration to organize, R&D in the different European laboratories).
The DAPNIA teams will use their know-how acquired when working with the SPIRAL beams (during experiments with the MUST2, EXOGAM, VAMOS detections that the DAPNIA has contributed to build) to design and develop the new detectors which will be employed for the SPIRAL2 experiments.

Look at the chapter SCIENCE

Contact for the pages "experiment SPIRAL2": V. Lapoux, SPhN

Look at the projects : AGATA, MUST2, S³ ( web address in the chapter LINKS AND DOCUMENTS)

AGATA =  Advanced GAmma Tracking Array
GASPARD = Gamma Spectroscopy and PARticle Detection
NFS = Neutron For Science
S3= Super Separator Spectrometer

Technical responsibilities:

The DAPNIA teams contribute strongly in the study and in the realization of the accelerator.

They are responsible for:

• The mounting of the injector and the study, the realization and the tests of the sub-systems (deuteron source, RFQ, vacuum chambers,...)
• The study, the realization and the tests of the cryomodules A of the LINAG
• The study, the realization of the RF controls (Low Level RF).

The DAPNIA also brings an important expertise in the field of the beam dynamics, and should also bring an expertise in the studies of the nuclear material wastes and of the radioprotection of the whole project.