INFN-LNS facility upgrade for the Nuclear Physics Renaissance

A broad range of Nuclear Physics research activities have been carried out at INFN-LNS until the summer 2020, when the accelerators were stopped for the upgrade. The upgrade of LNS is a project mainly funded by a PON-FESR (National Program for Research and Innovation) strategic line for boosting the research infrastructures, having its own goals, time-schedule and deadlines. In addition to such an action promoted by the Italian Ministry of Research, further funds have been made available from INFN budget. The end of the phase supported by the PON for procurement and tenders is currently set for the end of 2023. A series of actions will therefore be implemented to improve scientific opportunities for users. In particular, the focus is on the commissioning of the Tandem and Superconducting Cyclotron with the new set-up, completed by the renewal of the experimental areas and the commissioning of the new fragment separator FRAISE, also financed under the PON. The high-intensity program, including the determination of the nuclear matrix elements (NME) for the double beta decay and the study of EOS for nuclear matter with large neutron content, will be made feasible by these improvements to accelerators, beamlines and detectors. Some highlights of the whole activity as well as of the Applied Physics perspectives and the Astroparticle Physics multi-messenger program, strictly connected to the Nuclear Physics program, are given.


The accelerators upgrade
The Laboratori Nazionali del Sud (LNS) of the Istituto Nazionale di Fisica Nucleare (INFN) are one of the four national laboratories of INFN, the major national institute that deals with managing nuclear physics in Italy.The LNS operate in the fields of nuclear physics and nuclear and particle astrophysics, also distinguishing themselves in different fields of applied research, such as medicine and cultural heritage, R&D in the field of new acceleration techniques, design of high intensity ion beam injectors, applications in the fields of energy and environmental physics.LNS operates two accelerator facilities: a 15 MV Tandem and a K-800 Superconducting Cyclotron (SC) delivering beams from H to Pb, including long-lived radioactive species produced in batch-mode [1].The SC has been in operation for more than 25 years with a maximum beam intensity limited to ~ 10 11 -10 12 pps [2].
Since June 2020 the accelerators have been shut down to start the project to upgrade the entire infrastructure.The project has been financed by the PON Research and Innovation 2014-2020 dedicated to the Strengthening of Research Infrastructures.The main aim is to produce high intensity light ion beams intensity up to 10 13 -10 14 pps (for ions with A<40) accelerated with the SC using the extraction by stripping, to be able to perform studies of rare processes in nuclear physics.The extraction via electrostatic deflection (ED) will continue to be available through the ED extraction channel with a beam intensity up to 10 12 pps.The construction of a new In-Flight facility for Radioactive Ion Beams (RIBs) production, named FRAgment Ion SEparator (FRAISE) will exploit the high intensity beams of the SC [3,4].Fragmentation of light and medium mass primary beams delivered by the SC, with beam intensity up to 10 13 pps and energies in the range 20-70 MeV/A, impinging on light Be or C targets, will be used to produce RIBs.Production of neutron rich and neutron poor light (A £ 40) RIBs in the Fermi energy domain will be possible, with intensities going from about 10 3 to 10 7 pps for radioactive isotopes, near and far from the stability valley.A novel tagging system for cocktail RIBs based on radiation-hard and fast SiC array is under development.The feasibility of production of heavier RIBs will be also investigated.The LNS has a wide expertise in ion source development for accelerators [5].Several types of ion sources have been used at the LNS accelerator complex.Recently, a new ion source called AISHa (Advanced Ion Source for Hadrontherapy) has been operated with the aim to obtain highly charged ion beams with low ripple, high stability, and high reproducibility [6].
A copy has been installed in Pavia, for the CNAO hadron therapy facility and a third one may be built in about two years to provide hundreds of eµA beams for the SC.In order to optimize the acceleration of the intense beams of multiply charged ions so produced, a parallel program to improve the accelerators' ancillary equipment has also been established, including the modifications to the axial injection beamline between the ECR ion sources and the Cyclotron, the upgrade of diagnostics and controls and a dedicated study for the beam dynamics optimization.The construction of the SC coils has been completed and preliminary tests confirmed the capabilities to reach the goal, provided that some mechanical constraints are fulfilled.These modifications are under way, so that the new assembly of magnets and cryostat will be delivered on site in 2024.
As for the Tandem, the production of high intensity monocharged light ions may also permit a different approach in the production of negative ion beams (implemented in the so-called NESTOR source for noble elements [7]).In addition to the well-established activity for the design and construction of accelerators, LNS participate in the R&D for future accelerators with particular attention to new schemes for high gradient devices that may extend the opportunities for nuclear physics, as well as to ions and plasma sources based on high power lasers.

Scientific Mission and Main Research Programs
The scientific mission of the LNS mainly concerns with the study of nuclear reactions at low and intermediate energies, of key relevance for nuclear physics and nuclear astrophysics.Research activity in multidisciplinary fields also plays a pivotal role.There are several ongoing research programs, some of them already well established such as the nuclear physics and nuclear astrophysics activity, covering topics related to the equation of state of nuclear matter and the role of symmetry energy [8], the influence and role of isospin and clustering [9], the spectroscopy of light nuclei around the neutron dripline [10], the single and double charge-exchange reactions [11], the stellar and primordial nucleosynthesis and energetics with indirect methods, such as the Trojan Horse Method [12] and the Asymptotic Normalization Coefficient.New activities are ongoing: to determine the NUclear Matrix Element of the Neutrinoless (NUMEN) double beta decay by measuring heavy ion double charge exchange reactions; this driving physics case is one of the most challenging experiments over the world scientific community for the determination of the nuclear matrix elements (NME) for the double beta decay.Only the combination of the CS plus the magnetic spectrometer MAGNEX upgrades can allow to access the NME from the double charge exchange reactions including those with 76 Ge, of interest for the GERDA experiment.An intense activity is currently in progress for the upgrade of the MAGNEX spectrometer focal plane detector [13,14]; -in the field of astroparticle physics, foreseeing the completion of the KM3NeT/ARCA telescope to detect high-energy cosmic neutrinos from point-like sources as well as in a diffuse flux.In the actual configuration the detector is constituted by 21 detection units in full data acquisition since September 2022.This corresponds to about a 10% of the total configuration, but already enough to start the physics program in the framework of multimessenger astronomy [15].The project is directed by LNS researchers and supported by actions of the Piano Nazionale di Ripresa e Resilienza (PNRR) also through the recruitment of new staff at LNS.
-PANDORA (Plasma for Astrophysics, Nuclear Decay Observation and Radiation for Archaeometry), which aims to carry out measurement of β decays in plasmas of astrophysical relevance, and to measure the opacities of such plasmas (Kilonovae' ejecta).PANDORA is an innovative plasma trap [16,17], under construction at LNS, emulating some stellar-like conditions in terms of in-plasma charge states distribution.The setup, expected to be completed at the end of 2024, is based on three pillars, namely the compact superconducting plasma trap, the gamma-detection array and a plasma multi-diagnostics system operating in synergy in order to measure the in-plasma half-lives for different plasma thermodynamical properties.
-BCT (Breast Cancer Therapy), which involves the installation and commissioning of an ultrashort pulse power laser (45 TW, 25 fs, 5 Hz) for the generation of ion and electron beams aimed at radiobiological and preclinical radiation studies.
-I_LUCE (INFN Laser IndUCEd particle acceleration, 200-500 TW), which will provide the community with a new laser-driven electron, gamma and ion beams for nuclear and multidisciplinary applications.

Facilities for Nuclear Physics Experiments
The LNS host several facilities and several more are about to come.They have traditionally provided the users with the so-called CT-2000 scattering chamber, available for experiments with Tandem beams.The chamber, with a diameter of 2 meters, is equipped with 2 independently rotating arms to host the detectors and a collimation system with a goniometer that allows to measure precise angular distributions.Another chamber, called CICLOPE, devoted to experiments with cyclotron beams, will be soon replaced with a smaller cylindrical chamber, called GIRA, with a diameter of 1.5 meters and a length of 2 meters, still reliable for complex detection systems with hundreds of detectors.This chamber will be used with both CS and fragmentation beams.
The CHIMERA 4π charged particle detector [18] has been operating at LNS since 2000.It consists of 1192 (Si + CsI) telescopes able to detect both charged particles and gamma-rays.The ancillary FARCOS array is underway with 20 triple telescopes made of cluster of DSSSDs and CsI(Tl) detection stages.A novel neutron detector based on EJ276G scintillating cells read by SiPM and including digital acquisition is under development.Coupling of all these devices will allow to perform very accurate and complete measurements with both stable and radioactive beams.
MAGNEX is a large solid angle and large momentum acceptance spectrometer.It is going to be significantly upgraded in view of its application with the very intense SC beams foreseen by the NUMEN project.The target and the detection systems will be completely rebuilt to make them compliant with the required radiation hardness.The target will be cooled by liquid He using Highly Oriented Pyrolityc Graphite backings and remotely handled by a robotic arm.The scattering chamber will be replaced with a thinner and smaller one to host a new calorimeter for gamma ray detection (G-NUMEN [13]), based on about 100 LaBr3(Ce) scintillators.The focal plane detector (FPD) will be replaced with a new one, based on a gas filled tracker and a wall of SiC-CsI telescopes, optimized to sustain the very intense flux of heavy ions reaching it.In addition, an array of LaBr3(Ce) will be installed around the FPD to detect e + e -pairs from the de-excitation of 0 + excited states, relevant for the search of double GT giant resonance.
ASTRHO is an array of double-sided silicon strip detectors (DSSSD), each of 48 × 48 mm 2 active area.It is a compact and versatile device that couples the high angular and energy resolution with the large detection efficiency.[19] POLYFEMO is 4π thermalization neutron counter with 12 cylindrical proportional counters filled with 3 He, embedded into a polyethylene moderator.It can be used to investigate the beta-delayed neutron emission processes, of relevance in the nucleosynthesis of elements heavier than iron [20].
The LNS have also inhouse a BaF2 crystal ball of 180 elements for gamma and light particle detection.In Figs. 2 and 3, past and future layouts of the LNS facilities: the SC and the axial injection setup will change as for the performance whilst its extraction beamline and the other beamlines will change significantly to provide more scientific opportunities.Additionally, the ESS setup, CICLOPE detector and MEDEA-SOLE-MACISTE will be removed after years of remarkable activity to host in those areas the laser with two multipurpose interaction rooms, the PANDORA setup and a versatile experimental area ("punto misura 2" in figure 3).

Nuclear Physics applied research
As mentioned before, the LNS host several activities related to applied research.The LANDIS laboratory develops advanced technologies for cultural heritage based on X-rays [21].New mobile analytical techniques for the chemical speciation (RIS/EXAFS/XES) and elemental imaging by using the MA-XRF scanning technique is being conceived.In the latter field, new three-dimensional arrays of SDD detectors will allow the MA-XRF investigation with sensitivity and limit of detections comparable to those obtained in synchrotron beam lines with a single detector setup.The LNS centre for proton therapy of ocular tumours (CATANA) has treated more than 400 patients so far with a success rate of 97% [22].For clinical applications, besides using ion beams, a X-ray tube and high-voltage X-Ray tube (up to 320 kVp), able to deliver a homogeneous and shaped photon beam, have been installed.This will also represent an irradiation facility, fully available for internal and external users, with potential applications in the field of irradiation of in-vitro and in-vivo samples for radiobiological purposes.A second irradiation beamline is also present for sample in-air irradiation with ion beams (Z>1), for medical and space application and detector characterisation.A large number of activities related to Life Sciences involves the collaboration of INFN-LNS researchers and the use of the know-how accumulated for years.
A similar case regards the Plasma Physics and Accelerator Physics research with applications to fusion devices studies (DTT project), to the study of new techniques of acceleration, to high power accelerator facilities [23].
The LARA laboratory (LAboratorio di Radioattività Ambientale) is engaged in several activities.Recently, a gamma spectroscopy has been performed to measure the activity in the ashes emitted by the Etna volcano in the last paroxysms starting from May 2021.

Figure 1 .
Figure 1.An ariel view of LNS

Figure 2 .
Figure 2. The layout of accelerators and experimental areas until 2020.

Figure 3 .
Figure 3.The layout of accelerators and experimental areas in 2024-25.