The electric field and current density in a low-pressure inductive discharge measured with different B-dot probes

The magnitude and relative phase af the time varying magnetic field in an inductively coupled discharge have bern measured with two dB/dt (B-dot) probes: Due B-dol probe was enclosed by a dielectric tube (as is commonly used in dB/dt measurements) while the other, a thin wire probe, was immersed directly into the plasma, Each probe was used to measure the radial and axial component of dB/dt. A comparison of rf electric fields and currents obtained by the two probes showed essentially different results. The disagreement is interpreted to be due to a large local disturbance of the plasma density and current caused by the dielectric tube. (C) 1997 American Institute of Physics.