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Energy dependence of detector response (photon
interactions within the detector)
Energy absorption coefficient (
μ
en
/
ρ
) ratios, norm. at 1 MeV
0.1
1
10
100
0.01
0.10
1.00
10.00
Photon energy (MeV)
Medium / Water
Film (Ag based)
Silicon (Diode)
Air (Ion chamber)
Film (Nylon based)
Carbon (Diamond)
Isooctane (LIC)
Max ratio ~115 at 40 keV
Z
Ag
=47
Max ratio ~8 at 30 keV
Z
Si
=14
Min ratio ~0.33 at 15 keV
Z
eff
(Isooctane)
5.4
Z
eff
(water)
7.4
Max ratio ~1.1 at 30 keV
Z
eff
(Air)
7.6
What is meant by “Energy dependence”?
A varying relation between the detector signal and the investigated dose
(water), caused by spectral changes of the beam.