Scaling of L-mode heat flux for ITER and COMPASS-U divertors, based on five tokamaks

Based on {\em Nuclear Fusion} paper, we improve scalings of divertor L-mode power decay length. We employ data from tokamaks JET, EAST, MAST, Alcator C-mod and COMPASS and validate it against 2D turbulence simulation HESEL. The analysis covers 500 divertor heat flux profiles with 11 varying global plasma parameters. We see that two previously published scalings describe well only part of the database. We therefore derive 20 new scalings describing 86-93~\% of the measured decay length variability. We so-predict for attached highest current L-mode in ITER: 10-20~MW/m$^2$ surface perpendicular heat flux and twice that for COMPASS-Upgrade.