SPES: a second-generation ISOL facility dedicated to the forefront research in nuclear physics
SPES (Selective Production of Exotic Species) is a multi-user project aimed to develop a Radioactive Ion Beam (RIB) facility dedicated to the nuclear physics research of unstable nuclei, which are not commonly present on Earth, but are instead produced in the advanced stages of stellar evolution. Most of our present knowledge of nuclear properties has been in fact gained by studying nuclei near the so called “valley of beta stability” or on the neutron- deficient side. Very asymmetric combinations of protons and neutrons are however expected to reveal new aspects of nuclear structure.
The most severe constraint on our ability to advance the understanding of nuclear physics over the past several decades has been the fact that in any nuclear reaction both the beam and target species had to be stable. This imposes limiting restrictions on the regions of the nuclear chart which can be accessed as well as on the type of information which can be obtained. The most critical ingredients in determining the properties of a nucleus are the overall number of nucleons and the ratio N/Z of neutrons to protons. It is the extremes in these quantities, which define the limits of nuclear existence that will be opened up for study with radioactive beam accelerators.
The knowledge of the properties of nuclei far from stability both on the neutron and on the proton rich side is essential for addressing several open questions in Nuclear Astrophysics. In particular, measurements with radioactive beams are currently being pursued around the world since they can provide fundamental data needed for a better comprehension of the stellar evolution and of the elemental abundance in the Universe. New evidences, made possible by recent advances in astronomical observation or with a more refined geochemical analysis of meteorites, are providing fresh new data on the abundance distribution inside and outside the solar system. All these recent findings are posing new challenges in theoretical modeling of the chemical evolution of the Universe. At present, the calculation models fail in reproducing some aspects of the observed abundance pattern.
While more theoretical work is needed to clarify these issues, experimental constraints are requested to both guide the theory and provide data that represent fundamental inputs in the model calculations. This requires a more complete understanding of the nuclear physics underlying Stellar Nucleosinthesis.
In this respect, the SPES project will provide an important contribution to the large experimental and theoretical efforts currently devoted worldwide to the field of Nuclear Astrophysics. The intense radioactive beams, which will be produced at SPES, will open up new possibilities for measuring basic nuclear physics quantities related to the still unresolved issues of the chemical evolution of the Universe and shedding more light on processes like Supernovae explosions or X-ray bursts.
The main goal of the proposed facility is therefore to provide an accelerator system to perform forefront research in nuclear physics by studying nuclei far from stability. The SPES facility is mainly concentrating on the production of neutron-rich radioactive nuclei having mass in the range 80-160 based on the ISOL technique. Moreover the SPES facility will also cover interdisciplinary applied physics in the fields of material science and medical applications. A simplified layout sketch of SPES facility is shown in the picture below. SPES is a project of the INFN Road Map for the Nuclear Physics development.
Main SPES milestones
The whole SPES project has been divided into four basic development steps:
SPES phase alpha: construction of main infrastructure for an ISOL facility able to produce neutron rich nuclei by U fission. The fission rate expected is 1013 f/s;
SPES phase beta: extraction system, mass separation and charge breeder installation in order to start high purity exotic beams injection to PIAVE-ALPI linac accelerator complex;
SPES phase gamma: Research activities on new radiopharmaceuticals (67,64Cu, 188Re) of interest for nuclear medicine. Developments of new target technology and possible regional-scale production of radionuclides already used in diagnostic nuclear medicine (99Mo/99mTc).
SPES phase delta: Proton and neutron facilities for applied physics experiments aimed at radiation damage testing on new electronic devices for SEE (Single Event Effects) studies as well as nuclear data needs for next generation Gen-IV/ADS-like nuclear reactors.
For further details on SPES project see the dedicated SPES pages.