L-mode divertor heat flux profiles on COMPASS

Divertor heat flux was studied for a set of L-mode discharges performed in the COMPASS tokamak. The heat flux profiles were measured by divertor infrared thermography ( 0.6 mm/px, 8 kHz for this experiment) for both the inner and the outer divertor region and by divertor probes (two radial arrays of Langmuir probes and one array of Ball-pen probes, spatial step 4 mm, 4 MHz sampling rate) for the outer divertor region. Dependence of the heat flux decay length λ_q on main plasma parameters was studied by varying the toroidal magnetic field, the heating power, the line averaged electron density and the plasma current. Very good agreement of both diagnostics for the sheath heat transmission coefficient γ = 11 is presented. Observed heat flux decay lengths are compared to several existing multi tokamak scalings and modification of these scalings is proposed based on the measured data.