Negative ion beam plasma characterization by retarding field energy analyzer

NIO1 (Negative Ion Optimization 1) is a source of negative hydrogen beams, located at RFX facility in Padua. Its purpose is to analyze the optimal configurations for negative ion beam production and propagation. The propagation of ion beams in a low-density gas exploits space-charge compensation effects, that consists in the generation and confinement by the beam itself of charged particles that balance the beam charges. This thesis focuses on the characterization of the beam-generated plasma using a four-gridded probe called RFA (Retarding Field Analyzer) which provides information about compensation parameters. During this thesis work, the probe was installed and operated in NIO1. These data will be compared with those taken at NIFS, in Toki (Japan) in 2016, to study compensation plasma. These plasma parameters were then compared also with the expected ones, the probe used allowed to estimate compensation plasma parameters succesfully.