Continued Hot-Electron Plasma Production Studies in the Hanbit Plug

Continuing the experiments reported previously, additional microwave power has been applied to the plug region of Hanbit in order to increase the stored energy and beta of the hot-electron plasma created there. Two new 1.5-kW VA-806 klystrons at 7.67 GHz and 7.87 GHz have been used in conjunction with the existing 2-kW CPI klystron at 14 GHz. The plasma is created in order to provide a high-beta ring to stabilize the Hanbit central cell plasma against ballooning instabilities. An array of Hall probes mounted on the outside of the Hanbit plug cavity was installed to measure the axial profile of the Bz fields. The total stored energy was measured by diamagnetic loops and the radial location of the plasma was determined by a Si-PIN diode detector measuring the energetic electron end loss. All three measurements were to be used to determine the radial and axial location of the plasma, the plasma volume, the stored energy, and hence the plasma beta. However, the Bz signal was too small to measure and the diamagnetic signal was smaller than previously found. The ring was found to be very wide and not adequate to stabilize the central cell plasma.