  This paper demonstrates a detailed characterization of argon plasma in a
variable multi-pole line cusp magnetic field (VMMF). The VMMF has been produced
by placing six electromagnets (with embedded profiled vacoflux-50 core) over a
large cylindrical volume (1 m axial length and 40 cm diameter). The magnetic
field have been measured by hall probe method and compared with simulated
magnetic field by performing simulation using FEMM tools. Results from magnetic
field simulation indicate that the rate of change of pole magnetic field
(maximum magnetic field) with respect to magnet current for vacoflux-50 core is
high (7.53 G/A) as compared to the simple air core electromagnet (2.15 G/A).
The area of the nearly field free region (null region) in the chamber volume
can be controlled without changing a number of pole magnets. From the
experimental results, it has been observed that in this field configuration the
confinement of the primary electrons increases and leak width of plasma
decreases with increasing the magnetic field. Thus the mean density, particle
confinement time and the stability of the plasma increase with increasing
magnetic field. In addition to this, it has been found that the radial
uniformity of the plasma density explicitly depends on the VMMF. It is also
shown that the VMMF controls the scavenging of confined primary electrons and
confinement of primary electron increased with magnetic field which helps to
boost up the plasma density.

Plasma Physics