Observation of instability in presence of E×B flow in a direct current cylindrical magnetron discharge plasma

Abstract

An electrostatic instability with an intermediate frequency range (50–100 MHz) between the electron collision frequency and electron cyclotron frequency has been observed in presence of crossed electric and magnetic fields in a dc cylindrical magnetron plasma. The amplitude of the instability becomes maximum at particular values of the magnetic field and the discharge voltage. It is seen that when the magnetic field is increased the instability peaks at lower discharge voltages. The different modes of instability are prominent only when the neutral gas pressure is sufficiently low (∼4×10−3 mbar). The instability becomes suppressed when the magnetic field is high (>200 G). A constant amplitude test signal applied to the plasma through the cathode grows when its frequency matches with the frequency of the instability. The current-voltage characteristics form hysteresis loop in the instability excitation region.