Heterodyne wave number measurement using a double B-dot probe

An in situ method of wave number measurement inside a helicon plasma has been developed using a double B-dot probe with a heterodyne detection scheme. Each probe in the double B-dot probe measures the wave magnetic field. The signals from the two separately located probes inside the plasma are mixed with a local oscillator signal transforming the signals into transistor–transistor logic signals with intermediate frequency. The phase difference is obtained by a phase comparator yielding wave number information of a plasma wave.