Experimental Validation of Beam Particle Self Interaction in JT-60U by Use of N-NB

In a toroidal system, circulating fast ions generated by neutral beam injection affect the beam stopping cross-section of the neutral beam itself. This effect is called “beam particle self-interaction (BPSI)”. In a recent experiment in JT-60U with a 350 keV H0 beam, an indication of this BPSI effect was seen for the first time. In a low density discharge at about 1 × 1019 m-3, the beam shine-through decreased by about 35% within several hundred msec after beam injection. This result is consistent with a prediction by the BPSI theory.