Negative ion density in the ion source SPIDER in Cs free conditions

The SPIDER experiment, operated at the Neutral Beam Test Facility of Consorzio RFX, Padua, hosts prototype H-/D- ion source for ITER neutral beam injectors. maximization current extracted from and minimization amount co-extracted electrons are among most relevant targets to accomplish. Cavity Ring-Down Spectroscopy diagnostic measures negative density in close acceleration system, so as have feedback information optimize parameters maximize ions that can be optimal divergence. This work shows how magnetic filter field bias currents, present limit electron-ion stripping reactions, affect available extraction. Moreover, influence extraction process on is also presented. In this study was hydrogen deuterium Cs-free conditions, therefore were mostly produced by reactions plasma volume.