Neutral beam shine-through power and its dependence on the line density of the DIII-D plasma

Neutral beams are the primary source of auxiliary plasma heating in the DIII-D Tokamak. Part of the beam power passes through the plasma and is deposited on the wall of the tokamak (shine-through power) and does not contribute to plasma heating. It is therefore crucial to know the shine-through power in order to give an accurate account of the total power deposited in the plasma. We have recently remeasured the shine-through power using data taken from thermocouples embedded in the beam target the of the tokamak vessel. The tile temperature rise was correlated to the injected beam power. A dependence of the tile temperature rise on the initial tile temperature has been empirically measured and accounted for in order to obtain a more accurate determination of the shine-through beam power. Measurements of the shine-through beam power as a function of plasma density and beam energy confirm that shine-through power decreases exponentially with plasma density, and increases linearly with beam energy.