Questions
How is the flatness in the myQA Daily calculated?
Answer
Please see here a layout of the chambers in the myQA Daily:
There are 25 and 57 chambers for the flatness measurement for field size, 10 cm ×
10 cm and 20 cm × 20 cm (Fig. 4.3), respectively.
Calculation of the Beam Flatness
Beam flatness F is calculated from the uniformity- and kTP -corrected measurement signals Mi,j of the
chambers marked in image above for the two reference fields. Indices i and j denote the chamber position in
X and Y direction, with i = j = 0 at the center position.
F = 100.0% ▪ max{ Mi,j } / min{ Mi,j }
Note: Beam flatness is also calculated for FFF beams. In the case of FFF beams, it is normal to obtain
unusually large values for the flatness parameters that also may be very sensitive to variations in
beam center offsets. If this raises a problem, please increase the acceptance tolerance for the
flatness parameter in the test-setup.