Session GP1 - Poster Session IV.
POSTER session, Tuesday afternoon, October 30
Exhibit Hall B,
Disruptions in FTU are usually accompanied by the generation of a strong pulse of photoneutrons (Y_N 10^12n/s), resulting from photonuclear reactions induced by the bremsstrahlung radiation emitted when runaway electrons (REs) strike the plasma facing components. Measurements of Y_N during major disruptions on TS [1] showed variations of three orders of magnitude when the toroidal field B_t increases from 1.8T to 3.9T. Similar results were found on JT-60 [2], where no REs are produced for low B_t (<2.2T) and a large Y_N was measured for higher fields (up to 4T). The range of B_t available in FTU (4T-8T) allows to extend such analysis so that useful predictions can be obtained for operation in next-step high field tokamaks (IGNITOR, ITER). The dependence of Y_N on B_t is investigated in several FTU disruptions. Y_N increases with B_t for B_t=4T-6T, while no variation is found for B_t=6T-8T: the role played by n_e and I_p on such trend is discussed. [1]P.Joyer,G.Martin,Contr.Fusion and Plasma Heating,Proc.17^thEPS Conf.Amsterdam(1990) [2]R.Yoshino et al.,Nucl.Fus.39 151 (1999)