In the CIRCE experimental apparatus we have chosen as a medium undergoing adiabatic compression the plasma created by a pulsed reflex discharge, which is preheated by oscillating electromagnetic fields. We have been able to realize the following conditions necessary for an effective compression: a quasi-thermalized medium, for which the ionic and electronic temperatures, which can be measured and calculated, are of the order of a few electron volts low pressure of neutrals outside the discharge with ionization greater than 70% in the plasma column high initial charge density in order to have rapid thermalization; ne = 1014 electrons/cm3 purity of the initial plasma magnetic field trapped in the discharge uniform, reversable in direction and well determined before the compression finally, the possibility of varying at will the parameters electronic temperature, ionic temperature, density of neutrals, electronic density, level of ionization, compression magnetic field and mirror ratio. Thanks to a battery of 28 capacitors of 2.5 μF and 25 kV, the compression apparatus enables the production of a 70-kG magnetic field in a volume of 280 cm3. The rise time is some 1.5 μsec. Provision is made for a short circuit permitting one to prolong the duration of this field to 100 μsec.Magnetic compression is thus applied to the ionized medium under well defined, controlable and reproducible conditions, which can be made very close to the hypotheses used in the theory of the phenomenon. The comparison of this theory with experiment thus becomes particularly favorable.
Axial compression of a field reversed configuration plasma