Plasma physics and engineering models of tandem mirror devices operated with a high-field technology test-cell insert in the central cell, which have been incorporated recently in the TMRBAR tandem mirror reactor physics code, are described. The models include particle and energy balance in the test-cell region as well as the interactions between the test-cell particles and those flowing through the entire device. The code calculations yield consistent operating parameters for the test-cell, central cell, and end cell systems. A benchmark case for the MFTF-..cap alpha..+T configuration is presented which shows good agreement between the code results and previous calculations.

Models of the plasma particle and power balances in a tandem mirror with a high-field test-cell insert in the central cell have been used to calculate operating points for test-cell upgrades of the MFTF-B configuration. The code results have been benchmarked against the proposal plasma parameters for the MFTF-..cap alpha..+T configuration operating in the high neutron wall loading mode. Some parametric studies have been done. Using the results from these parametrics an optimized set of operating parameters for an MFTF-..cap alpha..+T-like configuration with a test-cell which will accommodate two 1.5 m long blanket test modules has been generated. This operating point has the same test-cell neutron wall loading as the original configuration and lower input powers to other systems in the device. The neutral beam power per unit blanket module length is also somewhat reduced in the optimized case.

Models of tandem mirror devices operated with a test-cell insert have been used to calculate operating parameters for FPD-II+T, an upgrade of the Fusion Power Demonstration-II device. Two test-cell configurations were considered, one accommodating two 1.5 m blanket test modules and the other having four. To minimize the cost of the upgrade, FPD-II+T utilizes the same coil arrangement and machine dimensions outside of the test cell as FPD-II, and the requirements on the end cell systems have been held near or below those for FPD-II. The maximum achievable test cell wall loading found for the short test-cell was 3.5 MW/m/sup 2/ while 6.0 MW/m/sup 2/ was obtainable in the long test-cell configuration. The most severe limitation on the achievable wall loading is the upper limit on test-cell beta set by MHD stability calculations. Modification of the shape of the magnetic field in the test-cell by improving the magnet design could raise this beta limit and lead to improved test-cell performance.

With the employment of a novel octopole end plug scheme, we examine the plasma engineering design of MINIMARS, a small compact fusion reactor based on the tandem mirror principle. With a net electric output of 600 MW/sub e/, MINIMARS is expressly designed for short construction times, factory built modules, and a passively safe blanket system. We show that the compact octopole/mantle provides several distinct improvements over the more conventional quadrupole (yin-yang) end plugs and enables ignition to be obtained with much shorter central cell length. In this way we can design economic small reactors which will minimize utility financial risk and provide attractive alternatives to the conventional larger fusion plants encountered to date.