  We investigate the discharge characteristics of a low-pressure geometrically
asymmetric cylindrical capacitively coupled plasma discharge with an
axisymmetric magnetic field generating an EXB drift in the azimuthal direction.
Vital discharge parameters, including electron density, electron temperature,
DC self-bias, and Electron Energy distribution function (EEDF), are studied
experimentally for varying magnetic field strength (B). A transition in the
discharge asymmetry is observed along with a range of magnetic fields where the
discharge is highly efficient with lower electron temperature. Outside this
range of magnetic field, the plasma density drops, followed by an increase in
the electron temperature. The observed behavior is attributed to the transition
from geometrical asymmetry to magnetic field-associated symmetry due to reduced
radial losses and plasma confinement in the peripheral region. In this region,
the DC self-bias increases almost linearly from a large negative value to
nearly zero, i.e., the discharge becomes symmetric. The EEDF undergoes a
transition from bi-Maxwellian for unmagnetized to Maxwellian at intermediate B
and finally becomes a weakly bi-Maxwellian at higher values of B. The above
transitions present a novel way to independently control the ion energy and ion
flux in a cylindrical CCP system using an axisymmetric magnetic field with an
enhanced plasma density and lower electron temperature operation that is
beneficial for plasma processing applications.
