Negative-potential operation of TMX-Upgrade

Abstract

V eA •s> s?s iM> ^p-f UCID-19341 KOTOE "'• PORTIONS OF THIS REPORT ARE ULIESIBIE. It has been reproduced from the best available copy to permit the broadest possible availability.

Use of ICRH for startup and initial heating of the TMX-U central cell

“…This high central-cell beta makes MHD stability difficult to obtain unless the beta can be concentrated in regions of the central cell that have good curvature. 26 Low neutral-gas densities are required to allow the long charge-exchange lifetimes of greater than ~20 ms that are necessary to sustain such high hot-ion densities with ~200 A of incident neutral beam in the central cell. For these reasons, we conclude that neutral-beam heating is not optimum during startup; although some plausible sct-narios have been proposed.…”

“…18. The average energy of a charge exchanged ion is estimated from computations as follows 26 : A gas penetration code A1 computes the current and power lost from the central cell due to charge exchange on the amount of gas needed to sustain the plasma core by ionization. The average energy of a charge exchange neutral is then computed to be .…”

“…The first is the conversion of electrostatic potential energy to kinetic energy by radially diffusing ions, which could be included by increasing the coefficient on the average energy of radially diffusing ions to greater than 1.5 T j<: . The second effect is due to the pump beams, 26 as discussed in Appendix A. The power loss from the central cell is…”