Secondary Particles in the Acceleration Stage of High Current, High Voltage Neutral Beam Injectors:the Case of the Injectors of the Thermonuclear Fusion Experiment ITER

The thermonuclear fusion experiment ITER requires a 33 MW auxiliary heating power from two Neutral Beam Injectors (HNB), each of them providing 40 A of negative deuterium ions. The EU activities oriented to the realisation of a negative ion electrostatic accelerator for the HNB comprise the construction in Padova of SPIDER, a test bed devoted to the optimisation of the beam source. The secondary particles which are generated inside the SPIDER accelerator are the subject of the present contribution.