Results and conclusions of the IEA-SSPS High Experiment are presented together with the thermodynamic theory of the Advanced Sodium Receiver. During the experiment, flux distributions, surface temperature distributions, efficiencies and losses, were measured and calculated in a power range of 0.8-3.5 MW at different sodium inlet/outlet temperatures. The design heat flux of 1.4 MW/m2 was increased to 2.5 MW/m2 resulting in a slightly increased total receiver efficiency of over 90%.