Investigation of temporal long-range correlation and anti-correlation of the fluctuations in a radiofrequency produced plasma in a diverging magnetic field configuration

Abstract

Long range temporal correlation of the fluctuations in both the floating potential (ϕ f ) and the ion-saturation current (I s ) have been investigated in a radio frequency produced magnetized plasma, in which the magnetic field diverges from a narrower quartz tube into a bigger stainless steel expansion chamber. Both argon and helium have been used as the filling gases. The Hurst exponents estimated from the rescaled range statistics indicate that the fluctuations in the ion-saturation current in argon plasma are anti-correlated inside a conical surface. The same fluctuations exhibit a transition to long range correlated behaviour over a narrow radial region of the conical surface. For helium plasma, the fluctuations in I s are mostly long range anti-correlated. The log-log plot of the power spectra of the fluctuations in I s and ϕ f have been observed to follow power laws and the same happens in the power spectrum of the particle flux also, indicating that the self-organized-criticality may exist in the present system.