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Beam Profiles: Penumbra measurements
using detectors of different sizes
The volume effect
Krauss [20]
6 MV,
d
max
(1.4 cm depth)
6 MV, 30 cm depth
Penumbra widening due to
overestimated beam tails
(scattered radiation outside
beam – energy dependence)
31002 is a 125 mm
3
air ion chamber (PTW)
80/20%
31002 is a 125 mm
3
air ion chamber (PTW)
80/20%
Pin point 2.9mm