Light ion driver research for inertial fusion

The generation of low emittance beam (or low divergence beam) at the diode is most important issues to use the light ion beam as an energy driver of inertial fusion energy. We have been investigated a two-stage ion diode which suits to an induction adder accelerator Reiden-SHVS (4-MV, 100-ns). In two-stage diode, the output beam of first stage is optionally stripped charge and is accelerated at the second (main) diode efficiently with improving the beam emittance. Beam trajectories and emittances in the two-stage diode were observed in time integrated manner. The measured beam trajectories were compared with a numerical calculation. Even in the large virtual anode limit, in which condition partial ions are reflected back by the virtual anode, no significant growth of local beam divergence of non-reflected parts of beam was observed. An emittance of injected beam was improved about factor 1.6 by acceleration at second with the first and second diode voltage of 0.6 and 1.2-MV, respectively. This improvements factor is in agreement with a predicted value.