Modification of the SPIDER PG current bus-bar routing for the optimization of the Filter Field topology

During 2019, severalexperimentshave evidenced anadverseeffect of the magnetic Filter Field (FF) on the plasma behaviour in the SPIDER negative ion source. This effect has been ascribedto a particular feature of the FF topologyin the plasma volume inside the radio frequency (RF) driver coils. Thisdocumentdescribesthe design and optimization ofa newlayout of the Plasma Grid (PG) current bus-barswhich implements a different FF topology insidethe RF driverregion (and behind), while keeping almost unchanged in the plasma expansion and accelerator regions.