Formation and Steady State Maintenance of FRCs Using Rotating Magnetic Field Current Drive

Rotating Magnetic Fields (RMF) have been used to both form and sustain FRCs in cylindrical flux conservers. Penetration of the RMF into a conducting plasma cylinder is made possible by accelerating the electrons to rotate near synchronously with the RMF. When there are more than sufficient electrons, if rotating synchronously, to reverse the external confinement field, and when the force exerted by the RMF exceeds the electron-ion frictional force (resistivity), the electron slip will automatically adjust to provide just the degree of RMF penetration and current drive needed to maintain the FRC reversal current. The FRC flux will increase and the FRC will expand radially (and contract axially), increasing the plasma density until the RMF and resistive frictional forces are balanced. The plasma temperature will be determined by heating and loss rates, with the RMF penetration increasing automatically as the temperature rises to accommodate an increasing external field. This process can proceed until the total FRC toroidal current just equals the maximum possible synchronous electron current, at which time the RMF frequency would have to be increased to allow further temperature and confinement field increases. In the present experiments, with quartz first walls, our temperature appears to be limited by impurity radiation barriers, but we have still observed the above phenomena. Plans are underway to apply standard vacuum conditioning techniques on metal first walls to allow studies of non-radiation dominated power balance to be conducted.