Table 1.

Definition of model variables.

Symbol	Definition
(x,y,z)	X ray interaction location (z=depth in crystal)(0,0,0)=x-ray crystal entrance
l	Position along x ray travel direction(=0 at x-ray crystal entrance) $=\sqrt{x^2+y^2+z^2}$
θ	90° minus the angle between the l and x axes(sin θ=x∕l)
ϕ	90° minus the angle between the l and y axes(sin ϕ=y∕l)
zmax	Thickness of crystal
μpe(E)	Photoelectric attenuation coefficient of CsI (cm−1)
μtot(E)	Total attenuation coefficient of CsI (cm−1)
E	Energy of incident x rays (keV)
No	No. of incident x ray photons
γ	X ray to optical-photon gain factor (keV−1)