Design of Routing of In-Vessel Diagnostic Signals for RFXmod2

Reversed Field eXperiment modified 2 (RFXmod2) is the upgraded version of the experiment RFXmod, a toroidal fusion device that can be operated both as a Reversed Field Pinch and as a Tokamak. This experiment is hosted by Consorzio RFX, Padua, Italy, and has a major radius R=2 m and a minor radius a=0.5 m. The upgrade of the previous machine consists mainly on a larger vacuum vessel and a more efficient active and passive plasma control system. Another important improvement involves the already wide set of in-vessel diagnostics, which includes now a large variety of sensors: electrostatic (single-pin, five-pin, 12-pin, ball pen), magnetic (flux loops, pick-up coils, saddle probes, halo shunts), mechanical (strain gauges), and thermal (thermocouples), for a total of about 5000 signals. The technological relevance of RFXmod2 is related indeed to the development of advanced plasma diagnostics and control systems. This work is focused on the integration of all the in-vessel diagnostics, especially from the point of view of electromagnetic compatibility and wire routing. In fact, the presence of several different families of sensors, having considerable differences in voltage and current output, together with the limited space in which those signal have to be routed, poses a challenging problem of electromagnetic compatibility. To solve this problem, the non-compatibilities between different types of signals were identified, and a series of criteria were drawn to design the cable routing of the whole machine. A preliminary and schematic routing map was developed, then a specific cable tray was designed and tested on a mock-up. This article describes all the activities related to the design of the wiring harness for the in-vessel diagnostics for RFXmod2: the signal classification, the electromagnetic compatibility problem, and the design of wire routing and cable trays.