Plasma diagnostics update and consequences on the upgrade of existing sources

The development and upgrade of ion sources for accelerators depends more and more on the optimization of the microwave-to-plasma coupling. Proton sources require to optimize the Electron Energy Distribution Function (EEDF) in the range of a few tens of eV. Multicharged ions sources require the optimization of EEDF in the keV scale depending on the needed charge state. The energy tail of EEDF must be damped since hot electrons are detrimental for the source performances. Last but not the least, also the spatial distribution of the EEDF within the plasma chamber should be known since RF power have to be deposited mainly in the regions of the plasma core near to the extraction hole and around the axis. In a few words, plasma parameters diag-nostics will play a fundamental role for next developments and upgrade of existing sources, as well as for the design of new ones. This work presents the set of plasma diagnostics (including interferometer, polarimeter, optical emission spectroscopy, Langmuir probe, pin-hole camera and X rays detectors) already installed at the INFN-LNS testbenchs, the characterization of the EEDF as a function on the source parameters (magnetic field profile, microwave power and frequency and neutral pressure) and the expected consequences on the future design of ion sources.