GNGTS 2022 - Atti del 40° Convegno Nazionale

232 GNGTS 2022 Sessione 2.1 AN UPDATE OF THE CENTRAL ITALY ELECTROMAGNETIC NETWORK WITH RADON DETECTORS C. Fidani 1,2,3 , G. De Antoni 2 , T. Milan 2 , M. Siciliani 3 , S. Tadioli 3 1 Central Italy Electromagnetic Network, Fermo, Italy 2 Osservatorio Geofisico di Novara, Novara, Italy 3 Osservatorio Sismico “A. Bina”, Perugia, Italy The Central Italy Electromagnetic Network (CIEN) has measured various electric and magnetic phenomena on different frequency bands in association with Italian seismic activity (Fidani, 2011, 2015, 2017, 2020). Tocomplete thedescriptions of thesephenomenaandpropose a physical model, capable of quantitatively describing these measurements, the monitoring of the network was extended to one of the hypothesized sources in the atmosphere, namely Radon gas decay (Pulinets et al. , 2015). The updating of CIEN with detectors for this radioactive gas, able to ionize the atmosphere, and therefore producing electric charges, began in 2020. Since then, CIEN has utilized a project of the Novara Geophysical Observatory, at http://www. osservatorionovara.it/. Fig. 1 - The block diagram of the detectors proposed by the Novara Geophysical Observatory team. The surprising aspect of both the camera and the signal analyser is that they are powered at low voltage. The instrument is enclosed in a metal box divided into two sections (Fig. 1). The first measures 5x2x2.5 cm collection chamber. One of the walls is perforated to allow the Radon, carried by the air to enter. The second section measuring 5x8x2.5 cm is the housing of the electronic circuit. The collection chamber is basically a condenser in air. The walls themselves constitute one of the armatures and this is at mass potential. There is second armor (detector) and it is a small copper plate measuring 2x1 cm positioned at centre. This plate is at a potential of -6 Volts versus mass. The circuit is powered by a dual voltage of ± 12 Volts that comes reduced to ± 8 Volts to prevent voltage drops on the long power cable, which can on average be 10 meters and longer, disturbing the functioning of the circuit. When a 222Rn atom decays inside the chamber it emits a high α particle energy (about 5.6 MeV) which, along its path in the air, produces a trail of ions (about 25000 pairs / cm) capable of perturbing the surrounding electric field. Such a disturbance results in a very weak variation of the detector potential, estimated to be about 0.4 mV. After the start, in 2017, of the experimental phase, a verification of the instrument functioning was carried out utilizing Torbernite samples and afterword quantitative comparisons were made to professional instruments. Moreover, the Novara Observatory has undertaken the monitoring at various sites around Novara and in Central Italy. Towards the end of 2019 one of the detectors was made available to CIEN and in the first months of 2020 it was installed at the Fermo station. A year later, CIEN built 4 other instruments, following the directives of the Novara observatory, and therein installed 3 of these in the municipality of Gubbio; see the installation setting of the historical centre of Gubbio in Fig. 2, and the fourth was installed in Perugia at the Bina Seismic Observatory.