Dynamic process during axial magnetic compression of field-reversed configuration for equilibrium shape control

Adiabatic magnetic compression experiments on a field-reversed configuratio n (FRC) plasma are reported. The compression is performed on a long FRC hel d in a straight mirror field. The separatrix length of the FRC is limited b y the distance between the magnetic mirrors. The mirror distance is compres sed in time to 35% of the original one by the compression coil installed in side the chamber, and the separatrix length is shortened to 38%. The separa trix radius of the compressed FRC increases by 56% and the aspect ratio (se paratrix length/separatrix diameter) changes from 12.6 to 4.1. Magnetic pro bes with the compensation circuit are utilized to investigate the dynamic t ransition phase during the compression. The transition process is found fro m these measurements to be divided into three stages, where a new equilibri um state is achieved in the final stage. (C) 2001 American Institute of Phy sics.