Experimental evidence for self-organized criticality in tokamak plasma turbulence

Abstract

Measurements of plasma turbulence spectra and particle flux from the DIII-D tokamak exhibit significant agreement with predictions of self-organized criticality (SOC) modeling. Power spectra of density n ̃ , potential g̃f, and particle flux Γ, are observed to have three regions of frequency dependence: f 0, f −1 and f −4. In addition, the particle flux probability distribution displays a Γ −1 scaling over two decades in Γ. These results provide the first evidence that the plasma is in a state consistent with SOC models and place a constraint on plasma transport models.