Radial characteristics of magnetized plasma behind an insulating obstacle

Interplay between external objects and plasma has enormous significance on global plasma properties. It has a relevance ranging from wake creation behind a satellite to the scrape of layer plasma region created in the shadow of a limiter in the edge of tokamak, or a low density region created behind a macroscopic object inserted in a flowing plasma column. The equilibrium properties of plasma inside the wake region depends on several factors like, the external magnetic field, charge-neutral collisions and flow of plasma. But the most important factor is the nature of the obstacle that is immersed inside a magnetized plasma column. Many fundamental research on conducting macroscopic object have been carried out to unravel its effect on charged particle transport in magnetized plasma column, but the role of insulating object has not been well understood.

In regard to the above investigation, an experiment has been designed to study the radial plasma characteristics behind an insulating object placed inside a non-flowing partially magnetized plasma column, created by hot cathode filament and gridded anode. It is found that the hotter electrons are able to reach the central region behind the insulating obstacle more efficiently and give rise to higher electron temperature. Besides, the higher transport of charged particles behind the obstructed region with increasing the axial magnetic field strength also reflects in reduction of radial plasma density and potential gradients. A phenomenological model based on particle balance and energy conservation has been used to explain the above observed trends.