Using the data sheets dimensions I was able to calculate the lamps output in joules per mm^2 at its surface as:
(300 watt * 1 hour) / (30mm*400mm) = 90J/mm
Using the inverse square law, the energy will drop off as a function of 1/R^2
At 7 feet(2133mm)
1/2133^2 * (300 watt * 1 hour) / (30mm*400mm) = 1.978 mj / cm^2