The basic tandem mirror concept entails the improved axial confinement of a long cylindrical fusion plasma within a solenoid by means of strong elec trostatic potentials at the ends. In the original tandem mirror concept, the confining electrostatic potential was produced by mirror-confined, end-plug plasmas of considerably higher density than the fusion plasma in the solenoidal center cell. As shown in a conceptual reactor design study completed in 1977, the requirement for a high plasma density plug led to advanced techno logical requirements for plug magnets and neutral-beam injectors. Based on preliminary calculations, we set as the goal for the new re actor design a 500-MWe output from a high Q (±10) fusion plasma confined in a central cell about 60 m in length. Although our progress toward this goal has been significant, additional work must be done to achieve a self-consistent reactor design which satisifes all of the known physics constraints. The pre sent magnet design has proved inadequate against the criterion for MHD bal looning stability at our assumed value for central cell 8. Ongoing work em phasizes the redesign of the magnet system to increase the 8 limit for sta bility.
Abstract-A critical problem for melt-processed silversheathed Bi-2212 tapes is gas release during heat treatment which deforms the sheath ("bubbling") and forms voids in the superconducting core. An overpressure furnace is used to study how the extent of bubbling changes with the total pressure (Plot). By processing in PI,,, up to 9 atmospheres with constant oxygen partial pressure (pOz = 1 atm), bubbling in coils is eliminated. The critical current density increases with increasing PI,. Also, the phase assemblage in overpressure-processed tapes is unchanged compared to conventionally processed tapes.
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