Spectral Panoptic Analysers of Gamma rays in Hydrothermal Environments for Transport Time Inference – SPAGHETTI

We propose to develop a new approach for continuous, high-frequency monitoring of radon gas in all manifestations of volcanic hydrothermal systems (fumaroles, hot water springs, acidic lakes, soil diffuse degassing). The analysis of these fluids is fundamental to understand and monitor heat and chemical transfers between the hydrothermal cell, the magma at depth and the hydrosphere, that control the evolution of such systems and their ability to erupt. For this purpose, radon is a unique tracer that allows determining the fluids transport time but its use in operational volcano monitoring is currently limited by conventional detection techniques which are not adapted to the harsh conditions found on volcanoes. The proposed approach is based on in-situ detection of gamma rays emitted by short-lived radon daughters. Because gamma rays are highly penetrating radiations, the analysed volume can be large (1 cubic meter) and there is no need for direct contact between the sensitive detector and agressive fluids, resulting in a major gain of robustness, sensitivity and time resolution. We will first design and construct spectral panoptic gamma probes adapted to hydrothermal extreme conditions (WP1). The probes will initially be tested in Auvergne (France) and then deployed for one year on La Soufrière volcano in Guadeloupe (France) (WP2). We will couple Monte-Carlo simulations of radiation transport in matter to numerical models of porous and aquatic media in order to analyse data and extract the radon information from the gamma signal (WP3). We will finally produce an embedded intelligence connected to a Satellite IoT link so as to internally process the data within the probe (on a chip) and only transmit the main information (WP4).