Vallar, Matteo (2015) Operational limits and disruptions in RFX-mod. [Laurea specialistica biennale]
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This work can be framed in the purview of hot plasma magnetically confined in the configuration called Reversed Field Pinch. This configuration shares some physical aspects with astrophysical plasma phenomena, such as the solar flares. The common element that lies behind these two systems is the magnetic relaxation, which allows the plasma to reach a more favourable state in terms of energy minimisation. In the tokamak magnetic configuration for plasma confinement a phenomenon called disruption has been interpreted as a critical relaxation event that tends to reorganise the magnetic configuration in order to reach the minimum energy state but instead leads the plasma to a sudden loss of confinement and current. In the Reversed Field Pinch, phenomena similar to disruptions, called fast terminations, have been recently recorded but never systematically analysed. In this thesis, the phenomenology of fast terminations in the Reversed Field Pinch configuration is systematically studied for the first time in the RFX-mod device. Some particular disruptive discharges are presented and typical quench times, magnetic instability behaviour and some statistical analysis are shown. The main operational parameters bounded by disruptions are investigated. Finally, an analysis of the halo currents in a RFX-mod Reversed Field Pinch disruption is presented.
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