Magnetic Cusp Contours and Measured ECRH Surfaces

In experiments with a microwave heated magnetic cusp, we have observed the formation and collapse of a strongly-magnetized, steady- state plasma. The formation and behavior of the plasma structure were examined in a variety of conditions. Holding microwave power constant and varying magnetic field strength, the plasma structure volume was observed to shrink, and the hole eventually collapsed as field strength was increased. Holding magnetic field strength constant and varying microwave power, the plasma structure's volume decreased as power was increased. However, we did not have sufficient microwave power to cause the hole structure to collapse. The magnetic confinement and the stability of the plasma in the cusp were also observed.