Predicting PDF tails of flux in plasma sheath region

This letter provides the first prediction of the probability density function (PDF) of flux R in plasma sheath region in magnetic fusion devices which is characterized by dynamical equations with exponential non-linearities. By using a non-perturbative statistical theory (instantons), the PDF tails of first moment are shown to be a modified Gumbel distribution which represents a frequency distribution of the extreme values of the ensemble. The non-Gaussian PDF tails that may be enhanced over Gaussian predictions are the result of intermittency caused by short lived coherent structures (instantons).