Fluctuations in electron cyclotron resonance plasma in a divergent magnetic field
ForfatterBhattacharjee, Sudeep; Fredriksen, Åshild; Chandra, Sayan
The dependence of fluctuations on electron-neutral collision frequency (Ven) and the radial location is investigated in an electron cyclotron resonance plasma in a divergent magnetic field region for a set of magnetic fields. Results indicate that the fluctuations depend strongly on the collision frequency. At lower magnetic fields and Ven, the fluctuation levels are small and are observed to peak around 3–5 cm from the central plasma region. Coherent wave modes are found to contribute up to about 30% of the total fluctuation power, and two to three harmonics are present in the power spectra. There are two principal modes present in the discharge: one appears to be a dissipative mode associated with a collisional drift wave instability initiated at a lower pressure (collision frequencies) (∼0.5mTorr) and is stabilized at a higher pressure (≳3mTorr). The other mode appears at intermediate pressure (≳1.75mTorr) and possesses the signature of a flute instability. The fluctuation levels indicate that flute modes are predominant in the discharge at higher pressures (>1.75mTorr) and at higher values of the magnetic field (∼540 Gauss).
Source at http://dx.doi.org/10.1063/1.4941595.