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Abstract:
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In recent years experimental advances at the GAMMA -10 facility in Tsukuba , Japan have shown that tandem mirrors should remain an important subject for theoretical study . The absence of toroidal curvature and relatively weak internal plasma parallel currents in a tandem mirror gives the mirror system strongly favorable stability and transport properties compared with toroidal systems . GAMMA -10 experiments (T . Cho et al . PRL (97 ) , 2006 ) demonstrate that sheared plasma rotation suppresses turbulent radial losses by controlling radial potential profiles . Achievements of the GAMMA -10 include 2 .5 keV ion confining potentials and electron temperatures approaching 1 keV (T . Cho , Private correspondence , Dec 24th , 2006 ) . Total energy confinement times for the GAMMA -10 experiment are significantly larger than corresponding empirical confinement times in toroidal devices . At the temperatures currently achieved in the GAMMA -10 , the end loss rate [mathematical symbols] 100 ms so that radial losses determine the energy confinement time [mathematical symbol] , as intended in tandem mirror reactor designs (R . F . Post , T .K . Fowler , et al . , Fusion Science and Technology , (47 ) , 2005 ) . The most current measurements of [mathematical symbol] are on the order of 72 ms . Tandem mirrors exhibit a qualitatively different type of drift wave transport than do toroidal devices , as we have shown by developing confinement time scaling predictions (J . Pratt and W . Horton , Phys . Plasmas (13 ) , 2006 . W . Horton , J . Pratt , H .L . Berk , M . Hirata . Proceedings of the Open Magnetic Systems For Plasma Confinement Conference . Tsukuba , Japan , July 17 -21 , 2006 ) . These predictions use a variety of standard transport models , e .g . , Bohm , gyro -Bohm , and electron -temperature gradient models . We analyze electrostatic drift wave eigenmodes for the electrostatic potential and the magnetic perturbation in the GAMMA -10 . We use teraFLOPS speed , large scale parallel computers to integrate the orbits in models of the drift wave losses in the GAMMA -10 . We extrapolate these results to reactor designs for the kinetically stabilized tandem mirror reactor proposed by Post et al . , and discuss implications for its stability , transport , and performance . |