The influence of magnetic field gradients and boundaries on double layer formation in capacitively coupled plasmas

The axial position of a magnetic field gradient has been varied for capacitive discharges in the linear plasma device VINETA. For low magnetic fields (B ≤ O(10 mT)), double layers have been observed to form predominantly at the interface between the source and the plasma chamber. In particular, double layer position is independent of the position of the magnetic field gradient. However, shifting the axial location of the magnetic field gradient leads to a global change of the plasma potential and the strength of the double layer. For higher magnetic fields the position of the double layer can be disentangled from the position of both the diameter interchange and the magnetic field gradient.