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Measurements under non-reference conditions:
Output factors
Large fields:
Changes in photon fluence in the beam axis.
More low energy photons.
Air vented ion chamber:
Diode:
f
Q
(A
ref
)= f
Q
(A) = S
w,air
Burlin cavity theory:
f = d·S +(1-d) · [μ /ρ] ,
H
2
0
output factors
Q w,med
en w silicon
[μ
en
/ρ]
w
,
silicon
for A and A ref differ