Tower System - Influence of Circum Solar Ratio

We have 2 questions regarding the heliostat field efficiency calculation wihtin the Tower model :
- Do you take into account the effect of the half angle of the sun (circumsolar)?
- how the shapes (slight focalization) of the heliostat mirrors have been taken into account?

Thanking you in advance,

Regards

The sun shape model used in DELSOL3 is a limb-darkened sun with the following equation:



Where r is the radial distance from the centroid of the sun, and R is the maximum angle subtended, equal to 4.65*10^-3 in DELSOL.

Each heliostat is assumed to be focused and canted at a focal length equal to the distance from the heliostat to the receiver.

Best regards,
Paul.

Thanks for your very clear answer
Best regards