Experimental study of the equilibrium of field-reversed configurations

Experimental data combining side-on interferometry and diamagnetic measurement on the FRX-C device are used to determine the gross features of field-reversed configurations during their equilibrium phase. These data give clear evidence for high beta, field-reversed structures. The separatrices are elongated, nearly elliptical cylinders in shape and are filled with fairly uniform plasma. The density on the separatrix is 0.5-0.6 of its maximum value at the field null and the width of the plasma layer outside the separatrix is 2-6 ion gyroradii.