Inter-ELM power decay length for ASDEX Upgrade, JET and ITER

Experimental measurements of the SOL power decay length ($\lambda_q$) estimated from analysis of fully attached divertor heat load profiles from two tokamaks, JET and ASDEX Upgrade, are presented. Data was measured by means of infrared thermography. An empirical scaling reveals parametric dependency $\lambda_q/{\rm mm} = 0.73 \cdot B_{T}^{-0.78}q_{cyl}^{1.2}P_{SOL}^{0.1}R_{geo}^{0}$. A comparison of these measurements to a heuristic particle drift-based model(R.J.GOLDSTON, www.pppl.gov/pub\_report//2011/PPPL-4604.pdf) shows satisfactory agreement in both absolute magnitude and scaling. Extrapolation to ITER gives $\lambda_q\simeq$1 mm decay length and $\lambda_{int}\simeq$2.4 mm integral width.