The LNS radioactive beam facility
|Rosa Alba and Marcello Lattuada (2011), Scholarpedia, 6(3):10859.||doi:10.4249/scholarpedia.10859||revision #91869 [link to/cite this article]|
Dr. Rosa Alba accepted the invitation on 17 May 2010
Prof. Marcello Lattuada accepted the invitation on 14 May 2010
The Laboratori Nazionali del Sud (LNS) is one of the four National Laboratories of Istituto Nazionale di Fisica Nucleare (INFN), the Italian public research Institution whose mission is research in basic and applied nuclear physics. The LNS main building (Fig.1) is located in the campus area of the Catania University. Born thanks to an agreement between INFN, Catania University and Centro Siciliano di Fisica Nucleare signed in 1976, LNS was equipped with a 15 MV Tandem accelerator and started to deliver beams in 1983. At the beginning of the nineties a K=800 Superconductive Cyclotron (CS), designed by the Milano INFN accelerator team, was also installed and came into operation in 1994. Now, a large variety of ions, from protons to Uranium, with energies ranging from a few MeV to 80A MeV, is available. Such a wide beam offer attracts many users from Italy and from abroad. Typically, LNS hosts 300 users per year, about one third of them from abroad. Around the accelerators an intense experimental activity, spanning from nuclear physics to applications and interdisciplinary research, is performed. In recent years, the LNS research field has been extended to astroparticle physics and, in particular, to the project of an underwater cosmic neutrino observatory. Dedicated to this activity, two shore stations, located, respectively, in the Catania harbour and at Portopalo di Capo Passero (South-east Sicily coast), have been realized and connected to their respective submarine sites through electro-optical cables.
Exotic beams at LNS
EXCYT is the ISOL facility for the production of exotic beams at LNS. It is based on the use of the two accelerators of LNS: the cyclotron as driver and the Tandem as post-accelerator. The layout of the facility is shown in fig.2. The main feature of the beams produced are those of a Tandem accelerator, i.e. easily variable energy, good emittance and very low energy spread. Beams with energies from a few MeV till about 200 MeV can be produced. For special requirements, beams of some hundreds of keV, extracted before the injection into the Tandem, can also be used. According to the requests of the potential users, the first beam produced was 8Li. In July 2006 the 8Li beam, produced via the reaction 13C+12C at 45A MeV using a 150 Watt primary beam, was successfully extracted from the Tandem with an intensity of some 104 ions/s. Now, an intensity of 7\(\cdot\)104 ions/s has been achieved. An intense R&D activity is still in progress to improve the intensity. At the same time, the production of new beams is under study. The next ones will be 9Li, already partially tested, and 15O.
Born as an experiment on specific interests of a group of researchers, FRIB’s is going to become a laboratory facility for in-flight production of exotic beams at intermediate energy. It is based on the fragmentation of projectiles accelerated by the CS. The production target is located close to the exit of the cyclotron and the exotic fragments produced are selected and transported by the same optical elements of the line normally used to transport the beams to the experimental areas, acting as a fragment separator. Since all the species produced with the same rigidity are transported along the beam line, it is necessary to identify event by event the ions impinging on the experimental target. This is done with a tagging detector located before the experimental point. In this way, it is also possible to perform simultaneously experiments with different projectiles, just selecting off line the beam required. An example of ion identification is shown in fig.3. Several tests have been done not only to study the production of the exotic species for different projectile-target combination, but also to improve the transmission along the beam lines to the experimental points that host the large detection devices (see below). Rates of the order of some 105 ions/s have been obtained and already used in experiments aimed at studying the fragmentation of exotic species and at investigating the diproton decay of neutron deficient nuclei. An upgrade of the facility, consisting in the use of new, more performant, transport elements is under way. An increase of the intensity by a factor of 10 to 30 is expected.
The LNS experimental devices
To fully exploit the potentialities offered by such a richness of beams, LNS has been equipped with high quality detection systems. Some examples are:
The CHIMERA multidetector array
About 1200 telescope detectors, providing almost full solid angle coverage and the capability of discriminating in charge and mass a large variety of reaction products (Fig. 4).
The MEDEA-SOLE-MACISTE complex
A ball made of 180 barium fluoride detectors, providing very large solid angle coverage for high energy photon and light charged particle detection, completed by a superconducting solenoid collecting the forward reaction products on a focal plane detector 15 meters away from the target.
The MAGNEX magnetic spectrometer
A large acceptance device, based on a vertically focusing quadrupole and a bending dipole, with excellent energy and angle resolution.
Other modular detection arrays can be occasionally mounted in two large multi-purpose scattering chambers:
The CICLOPE scattering chamber
A general purpose, large volume (about 70 m3) scattering chamber specially suited for intermediate energy experiments.
The 2000 scattering chamber
Thanks to its very sophisticated positioning control systems, it is particularly suited for precision measurements at Tandem energies. It represents a perfect device for resonant scattering experiments using a given gas as target and degrader at the same time.
In addition, an experimental line has been equipped to perform hadrontherapy treatments and it is particularly suited to perform radiobiology and dosimetry experiments using the proton and carbon beams from the CS.
Research at LNS
Main research lines with accelerators
- Experimental nuclear physics:
- Nuclear Structure and Reaction Dynamics
- Study of special structures, like exotic clustering and halo in nuclei far from the stability valley
- Study of structure effects on reaction mechanisms
- Study of the evolution of the Giant Dipole Resonance (GDR) properties in hot nuclei
- Timescale of reaction mechanisms around Fermi energy
- \(\alpha\) - transfer reactions onto light nuclei
- Coulomb breakup of radioactive nuclei
- Study of the isospin and mass dependence of reaction mechanisms at Fermi energies
- Study of population and decay of nuclei and resonances at the border of drip lines, searching for exotic decays
- Study of the symmetry term of nuclear Equation Of State
- Spectroscopy of neutron rich nuclei populated via charge exchange and multineutron transfer reactions
- Nuclear Astrophysics
- Big bang nucleosynthesis
- Stellar nucleosynthesis
- Depletion of light elements in stellar environment
- Electron screening
- Nuclear Structure and Reaction Dynamics
- Interdisciplinary research
- Analysis of cultural heritage samples with proton beams (DPPA)
- Study of new superconductive materials at high critical temperature
- Radiation damage and radiation hardening
- Radiation dosimetry
As an example of the beam time sharing among the different activities, the situation of the two accelerator operation is shown in Fig.5. It can be seen that a large fraction of the total beam time is used for nuclear physics, but also interdisciplinary research, mainly concerning the interaction of ion beams with the biological matter and the radiation-induced damage on materials, plays a relevant role. Moreover, a not negligible fraction of the CS operation time is devoted to proton therapy.
Main research lines without accelerators
- Theoretical nuclear physics (essential support to the experimental activities)
- High energy neutrino astrophysics (NEMO and Km3Net projects)
- Ion source development
- Non-destructive analysis of cultural heritage samples (LANDIS laboratory)
- Acoustic and geophysical monitoring of deep sea environment (LIDO-ESONET project)
Some recent scientific highlights
- First observation of di-proton decay of excited 18Ne
The branching ratio between 2He diproton resonance and sequential decay was measured for the first time
- Evidence of structure effects on reaction mechanisms at near Coulomb barrier
Combining data from LNS and ISOLDE experiments, the influence of halo structure on total reaction cross section has been evidenced
- Evidence of isospin effects on the competition between different reaction channels
The competition between fusion-like and binary reactions has been shown to be able to constrain the parametrization of the symmetry energy in the nuclear Equation of State
- Precise determination of the 8Li(\(\alpha\ ,\)n)11B cross section at energies of astrophysical interest
The accurate knowledge of the rate of this reaction is particularly relevant in determining the big bang nucleosynthesis scenario
- Precise determination of the 18O(p,\(\alpha\))15N reaction rate at high temperatures
The reliable measurement of the low energy resonance parameters is very important to infer the production of some key isotopes in several astrophysical scenarios
- Analysis of the interaction microwaves-plasma for the development of top level ion sources
A step forward in the LNS R&D activity related to ion sources that already led to the design and construction of sophisticated sources. Examples: Serse at LNS, TRIPS at LNL)
- Location of sperm whales in the Mediterranean sea
During the survey of the acoustic background at the Nemo test site, the characteristic sperm whale clicks were recorded with a frequency indicating a stable presence of these big creatures, before considered very rare in this area
- Characterization of the Misurata treasure Roman coins
In collaboration with IBAM and ITABC of Italian CNR the coins were studied using different in situ (PIXE-ALFA for the surface and XRF for the substrate and trace element characterization) and accelerator based (DPPA for the core) techniques. Relevant information about the economy of late Roman Empire were deduced
The societal impact of LNS activities: some examples
LNS is involved in local Consortia whose aim is to promote the transfer of knowledge, the technological innovation, the applied research, the advanced training and, more in general, the development of the territory. Its researchers are very active in disseminating the scientific culture and guided tours are organized for high school students, attracting several thousands visitors per year. The CATANA facility is used since 2002 to treat patients affected by uveal melanoma with the 62 MeV protons delivered by the Superconductive Cyclotron thanks to an official agreement with Catania University Hospital. Moreover, LNS is involved in the study of a Treatment Plan System, mainly for hadrontherapy with carbon beams, to be commercialized thanks to an agreement with an industrial partner. A similar agreement exists to commercialize a cyclotron for hadrontherapy designed at LNS. The LANDIS laboratory, devoted to the application of nuclear techniques to the study, conservation and safeguard of Cultural Heritage masterpieces, has many collaboration agreements with public Institutions and Italian and foreign museums. LNS has also an irradiation facility, certified by ESA (European Space Agency), used by industries to measure the radiation hardness of electronic components to be used in space missions. To conclude, it is important to mention the collaboration of LNS with other research institutions and, in particular, its interdisciplinary aspects. As an example, the Catania harbour NEMO test site hosts the first European cabled seafloor multiparameter observatory whose seismological data are integrated in the Italian Istituto Nazionale di Geofisica e Vulcanologia land-based national seismic network.