Electromagnetic Simulations and Measurements of the K-800 Superconducting Cyclotron RF Cavity at INFN-LNS

In this paper, a complete three-dimensional (3D) RF model of the cyclotron coaxial resonator—including the coaxial sliding shorts, the “Liner” vacuum chamber, the coupler, the trimmer, and the high RF voltage “Dee” structures—has been developed. An eigenmode analysis was used to simulate the tuning of the resonator in the operating frequency range of 15–48 MHz obtained by two movable sliding shorts and a trimmer. A driven analysis has been performed in order to compute the |S11| parameter (or impedance matching) of the cavity excited by a movable coaxial power coupler. The numerical simulations have been performed using the different peculiarities of two commercial tools, COMSOL Multiphysics and CST microwave studio. Experimental validation of the developed model is presented. The evidence of an unwanted electric field component, orthogonal to the accelerating field, was discovered and a mitigation is also proposed. The impact of the proposed modification was evaluated by using a 3D beam dynamics code under development in the framework of the Superconducting Cyclotron upgrade ongoing at INFN-LNS.

The NUMEN Project: An Update of the Facility Toward the Future Experimental Campaigns

The goal of NUMEN project is to access experimentally driven information on Nuclear Matrix Elements (NME) involved in the neutrinoless double beta decay (0νββ) by accurate measurements of the cross sections of heavy-ion induced double charge-exchange reactions. In particular, the (18O, 18Ne) and (20Ne, 20O) reactions are adopted as tools for β+β+ and β−β− decays, respectively. The experiments are performed at INFN–Laboratory Nazionali del Sud (LNS) in Catania using the Superconducting Cyclotron to accelerate the beams and the MAGNEX magnetic spectrometer to detect the reaction products. The measured cross sections are very low, limiting the present exploration to few selected isotopes of interest in the context of typically low-yield experimental runs. In order to make feasible a systematic study of all the candidate nuclei, a major upgrade of the LNS facility is foreseen to increase the experimental yield by more than two orders of magnitude. To this purpose, frontier technologies are being developed for both the accelerator and the detection systems. An update description of the NUMEN project is presented here, focusing on recent achievements from the R&D activity.

The NUMEN Project: Toward New Experiments with High-Intensity Beams

The search for neutrinoless double-beta (0νββ) decay is currently a key topic in physics, due to its possible wide implications for nuclear physics, particle physics, and cosmology. The NUMEN project aims to provide experimental information on the nuclear matrix elements (NMEs) that are involved in the expression of 0νββ decay half-life by measuring the cross section of nuclear double-charge exchange (DCE) reactions. NUMEN has already demonstrated the feasibility of measuring these tiny cross sections for some nuclei of interest for the 0νββ using the superconducting cyclotron (CS) and the MAGNEX spectrometer at the Laboratori Nazionali del Sud (LNS.) Catania, Italy. However, since the DCE cross sections are very small and need to be measured with high sensitivity, the systematic exploration of all nuclei of interest requires major upgrade of the facility. R&D for technological tools has been completed. The realization of new radiation-tolerant detectors capable of sustaining high rates while preserving the requested resolution and sensitivity is underway, as well as the upgrade of the CS to deliver beams of higher intensity. Strategies to carry out DCE cross-section measurements with high-intensity beams were developed in order to achieve the challenging sensitivity requested to provide experimental constraints to 0νββ NMEs.

Upgrade of the MAGNEX spectrometer toward the high-intensity phase of NUMEN

The NUMEN experimental activity with accelerated beams is performed at INFN–Laboratori Nazionali del Sud (LNS) in Catania using the Superconducting Cyclotron and the MAGNEX magnetic spectrometer. The scientific motivation of NUMEN is to extract experiment-driven information on the nuclear matrix elements entering in the expression of the 0νββ decay half-life. The reaction cross sections involved, especially for the double charge exchange process, are very low, thus limiting the present exploration to a few selected isotopes of interest in the context of typically low-yield experimental runs. In order to make feasible a systematic study of all the candidate nuclei, a major upgrade of the LNS facility is foreseen to increase the experimental yield by more than two orders of magnitude. To this purpose, frontier technologies are being developed for the accelerator and the detection systems. An updated description of the choices derived from the recent R&D activity on the target system and MAGNEX focal plane detector is given.