Characteristics of a low-frequency-driven ferroinductor-coupled discharge

We present characteristics of a low-frequency (LF) inductively coupled discharge where, instead of using an inductorlike rf antenna, we used a ferromagnetic core with a primary winding ("ferroinductor"). A dense (> 10(12) cm(-3)), highly ionized (30%-40%) plasma was obtained in this ferroinductor at gas pressures as low as 10(-4) Torr. In a wide range of comparatively low frequencies the core and winding losses were found to be small compared with the LF driving power delivered to the plasma. The driving frequency could be very low compared with typical inductively coupled discharges. The input impedance was found to be almost purely active (cos phi approximate to 0.9), and it was possible to achieve various input resistances (e.g., 50 Omega) in the whole investigated range of frequencies, powers, and pressures, which made unnecessary any matching box between the LF driver and the ferroinductor-coupled plasma device. Such a combination of properties makes this kind of discharge attractive for many applications. (c) 2005 American Institute of Physics.