Abstract
The evolution of the separatrix and excluded flux radius was investigated in a mirror-less theta pinch with external magnetic and loop probes and by numerical simulation. In the numerical hybrid code the anomalous effect was taken as evolution of lower hybrid drift instability. At mid-plane of the coil the experimental and theoretical values of lift-off time, implosion time and equilibrium plasma radius were very close. The implosion time is 5 ± 1 cm/ps and the separatrix radius at mid-plane is around one half of the discharge tube radius. Within the experimental uncertainty the excluded flux radius has the same value along the coil, suggesting an elongated configuration with closed magnetic field lines.
Highlights
The field reversed configuration (FRC) is a toroid compact with high β plasma
With the reconnection process driven by mirror coils at the ends of main coil these opposite fields reconnect forming the closed magnetic field line configuration
In the present work we investigate the formation of a field reversed configuration measuring the excluded flux radius using loop and magnetic probes
Summary
The field reversed configuration (FRC) is a toroid compact with high β plasma. It is technologically simpler than the traditional toroidal system. The perturbations are notably high in high density and high temperature plasmas, as those produced in FRC's In this case the usual technique is the excluded flux probe, a combination of the flux measurement by a single loop around the discharge tube and a local magnetic field to measure the magnetic field intensity. In the present work we investigate the formation of a field reversed configuration measuring the excluded flux radius using loop and magnetic probes. The actual plasma dynamics observed by the diagnostic was very close to the behavior predicted by this theoretical approach It was observed almost the same value of the excluded flux radius along the discharge tube suggesting a plasma column longer than the coil length.
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