Next step spherical torus design studies

Studies are underway to identify and characterize a design point for a next step spherical torus (NSST) experiment. This would be a ‘proof of performance’ device which would follow and build upon the successes of the national spherical torus experiment (NSTX) ‘proof of principle’ device which has operated at PPPL since 1999. With the decontamination and decommissioning (D&D) of the tokamak fusion test reactor (TFTR) nearly completed, the TFTR test cell and facility will soon be available for a device such as NSST. By utilizing the TFTR test cell, NSST can be constructed for a relatively low cost on a short time scale. In addition, while furthering spherical torus (ST) research, this device could achieve modest fusion power gain for short pulse lengths, a significant step toward future large burning plasma devices now under discussion in the fusion community. The selected design point is Q=2 at HH=1.4, Pfusion=60 MW, 5-s pulse, with R0=1.5 m, A=1.6, Ip=10 MA, Bt=2.6 T, CS flux=16 weber. Most of the research would be conducted in DD, with a limited DT campaign during the last years of the program.