When the ray power is solved for, the Deposited Ray Power subnode is available from the context menu (right-click the 
Wall, parent node) or from the 
Physics toolbar, 
Attributes menu. The 
Deposited Ray Power subnode computes the total incident energy flux on a surface based on the power of incident rays.
 
    Select the Compute smoothed accumulated variable check box to enter a 
Smoothing radius r (SI unit: m) The smoothing radius functions like the corresponding setting for the 
Accumulator (Boundary) node.