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The RFX-mod2 device, the upgraded version of the previous RFX-mod with a modified magnetic boundary, is presently under realization and will start to be operated in 2025. Significant upgrades of the diagnostic capabilities have been proposed and are under development. These include a largely increased number of in-vessel magnetic and electrostatic sensors, a new fast reciprocating manipulator for the exploration of the edge plasma in a wide range of experimental conditions, the improved Thomson scattering and soft x-ray diagnostics system for a detailed determination of the behavior of the electron temperature profile, new dedicated systems for the space and time resolved analysis of x-ray spectra and neutron rate, a reflectometric diagnostic for real-time determination of plasma position, two diagnostics devoted to the imaging of light impurities and influxes behavior along with arrays of halo current sensors. These diagnostic upgrades will be accompanied by a significant effort to improve the control of the electron density and of the impurity influxes by means of proper treatment of plasma facing components with in-vessel fixed electrodes distributed over the first wall. The described advancements will allow a deeper understanding of physics phenomena in the wide variety of magnetic configurations, including the tokamak, the reversed-field pinch and the Ultra-low q, which can be produced in RFX-mod2 thanks to its flexibility and unique MHD control capabilities.

The presented work shows a systematic study of the temporal characteristics of ELM events on the COMPASS divertor obtained with high temporal resolution probe measurements (∼1 μ s). The resulting temporal evolution of the total ELM power on the outer target provides the values of rise ( τ _rise ) and decay ( τ _decay ) times for each single ELM event. It has been found that τ _rise values are in the range of about 50 μ s–100 μ s. These values are comparable to the time of the ELM parallel propagation ( τ _|| ) given by the sound speed and the connection length between the outer midplane and the outboard divertor. This comparison indicates that the magnetic field lines in the SOL region are not significantly ergodized during the pedestal crash on COMPASS. It also implies that the peak ELM energy fluence on the outboard divertor is dominated by the ELM parallel transport, which is confirmed by a good agreement with model prediction. In addition, the values of the ratio of τ _decay and τ _rise for each ELM event fit very well to the boundaries 1.5 < τ _decay / τ _rise < 4, as already shown on JET as well as on the HL-2A tokamak, using IR measurements. The ratio does not show any clear dependence on the relative ELM energy or line averaged electron density. It was also found that the ELM energy fluence decay length ( λ _ϵ ^mid ) is clearly linked to this ratio.