Sigma LBA-708, LBA-710, LBA-714PC, LBA-300, LBA-712, LBA-500PC, LBA-700 manual = ∑f i ⋅ NPix = Pk Total

parameter to describe quality of a Top Hat’s energy distribution. A perfect Top Hat has a single fluence value that makes up 100 percent of energy and plots curve A. The area under this curve yields the Top Hat Factor value of 1.0. A Gaussian beam plots the curve labeled C. The area, and thus the Factor, for beam C is 0.5.

Real-world Top Hat beams will plot curves somewhere between A and C, such as curve B. Thus, as the area under the curve approaches unity, the quality of the Top Hat is seen to improve.

Figure 56

The equation below describes how the curve of a particular beam profile would be derived from the pixel intensity data. The plot of such a curve is formed by the sum of the product of the number of pixels and the corresponding fluence for each fluence value, in a range starting from the maximum fluence value to the current value.

() = ∑f i ⋅ NPix

E f

i= Pk Total

Where:

E= The fraction of energy contained between the fluence value and the peak value.

f= The fluence value.

Pk	=	The peak fluence value.
Total =		The total energy in the beam.
Npix	=	The number of pixels that have the value of I.

To find the Top Hat Factor, sum the area under the curve formed from the above equation, as shown below:

Pk−1 E f + E f +1

∑

F = f =1 2

Pk

Operator’s Manual 140 LBA-PC