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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.