It is proposed to conduct on the Cadarache neutral beam test bed an experiment with the following characteristics: 1 MeV, 0.1 A, D−, long pulses (several seconds). This experiment will deal with several ITER neutral beam relevant subjects, which are critical and still not (or poorly) explored: (i) development of scalable high‐energy (up to 1 MeV) D−accelerator concepts, with current densities in the 10 mA/cm2range, adequate optical quality and suppression of stray particles (electrons, etc.); a simplified concept of accelerator, SINGAP, will be compared to a multi‐hole multi‐gap accelerator; (ii) study of breakdowns in the presence of the beam with a vacuum insulated beamline and effects of a large stored electrostatic energy released during breakdowns (100 Joules range); (iii) development of critical HV devices (large insulator for bushing; decoupling devices for the external stray capacitances; fast protection systems in case of breakdowns). If this proposal is accepted by the European Community beginning of 1993, the experiments could start by mid‐1994.