SOURCE SHAPE AND COLLIMATOR OF GIF++ IRRADIATOR Dorothea Pfeiffer GIF++ Project Meeting

Algorithm field uniformity lense  Attempt to find the ideal shape using point source  For stainless steel and E kin = 662 keV, linear attenuation coefficient μ = cm -1 I = I 0 ·exp(- μ ·d)  I(x) = cos( α ) 2 · I max  Opening angle α : 37° horizontally, 37° vertically => α in upper corners: 47°  Ratio corner/center = cos(47°) 2 =  d(x) = - ln(cos( α ) 2 )/mu Dorothea Pfeiffer

Fit field uniformity lense  Calculation in MATLAB  Fit function to calculated profile  Good fit with function of type: a 1 ·cos(b 1 ·x) + a 2 ·cos(b 2 ·x) 3 Dorothea Pfeiffer

Real scale field uniformity lense  In Geant4 implemented as polycone with 20 sections 4 Dorothea Pfeiffer

137 Cs Source in RSL6040 capsule 5 Dorothea Pfeiffer

Collimation window and source  Collimation window pyramid shape (converges in center of source in one point)  Collimation window trapezoid shape (schematic drawing, angles should be +/-37 ° horizontally and vertically ) 6 Dorothea Pfeiffer Side view Top view LeadSteel 137 Cs Air Trapezoid shaped Pyramid shaped

Pyramid shaped collimator yz 7 Dorothea Pfeiffer Point source Cylindrical source Large difference between point and cylindrical source

Trapezoid shaped collimator yz 8 Dorothea Pfeiffer Point source Cylindrical source No difference between point and cylindrical source

Energy distribution point source 9 Dorothea Pfeiffer 600 – 662 keV 300 – 600 keV0 – 300 keV

Reserve slides 10 Dorothea Pfeiffer

Pyramid shaped collimator xz 11 Dorothea Pfeiffer Point source Cylindrical source

Trapezoid shaped collimator xz 12 Dorothea Pfeiffer Point source Cylindrical source