Plasma control by modification of helicon wave propagation in low magnetic fields

T. Lafleur, C. Charles, R. W. Boswell
2010 Physics of Plasmas  
By making use of nonuniform magnetic fields, it is shown experimentally that control of helicon wave propagation can be achieved in a low pressure ͑0.08 Pa͒ expanding plasma. The m = 1 helicon waves are formed during a direct capacitive to wave mode transition that occurs in a low diverging magnetic field ͑B 0 Ͻ 3 mT͒. In this initial configuration, waves are prevented from reaching the downstream region, but slight modifications to the magnetic field allows the axial distance over which waves
more » ... e over which waves can propagate to be controlled. By changing the effective propagation distance in this way, significant modification of the density and plasma potential profiles can be achieved, showing that the rf power deposition can be spatially controlled as well. Critical to the modification of the wave propagation behavior is the magnetic field strength ͑and geometry͒ near the exit of the plasma source region, which gives electron cyclotron frequencies close to the wave frequency of 13.56 MHz.
doi:10.1063/1.3460351 fatcat:qm4uohhg7zhpplpzxrosyylmyq