a geant4 based engineering tool for fresnel lenses...a geant4 based engineering tool for fresnel...
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A Geant4 based engineering tool for Fresnel lensesJoão Costa1, Mário Pimenta2, Bernardo Tomé2
1-Laboratoire de l’Accélérateur Linéaire, IN2P3-CNRS et Université Paris-Sud 11, Centre Scientifique d’Orsay, B. P. 34, 91898 Orsay, Cedex, France.2-Laboratório de Instrumentação e Física Experimental de Partículas, Av. Elias Garcia, 14–1, 1000-149 Lisboa, Portugal.
Geant4 is a simulation toolkit including optical-photon tracking in complex 3D geometries. This ca-pability was explored to develop a simulation tool for Fresnel lenses. This tool can be used on stand-alone design and optimization studies or integrated in a full Geant4-based detector simulation.
R
∆Z
R
FRESNEL LENS GEOMETRY IMPLEMENTATIONVRML visualization of a simulated Fresnel lens consisting of a cen
tral mo
no
lithic len
s and
two
layers of p
etals
Possibility of simulating monolithic or segmented lenses
X (mm)
-30-20
-100
1020
30Y (mm)
-30-20
-100
1020
300
50
100
150
200
250
300
Lens-Detector distance (mm)1950 2000 2050 2100 2150 2200 2250
PSF
radi
us (m
m)
0
2
4
6
8
10
12
14 320 nm
400 nm
500 nm
600 nm
Radius (cm)0 10 20 30 40 50 60 70 80 90 100
Det
ectio
n e�
cien
cy
0.5
0.6
0.7
0.8
0.9
1
No bulk absorption
With bulk absorption
Realistic incident ligth spectrum;
Effects of finite groove size ;
VRML visualization of a simulated Fresnel lens illustrating the focusing of on-axis light
Each facet of the Fresnel lens is built from a piece of the original lens surface translated to the flat side of the lens
The lens geometry is described in Geant4 through a para- meterized replication of conical shaped facets (G4Cons vo-lumes)
SIMULATIONS TAKE INTO ACCOUNT:
Study of light detection efficiency and assessment of the effect of grooved lens structure onto light throughput (bottom left)
Study of point spread function (PSF) for varying focal distance and wavelength (bottom right);
PERFORMANCE STUDIESINCLUDE:
Example of simulated point spread function