UPDATE LEAD ATTENUATORS AND LENSES Dorothea Pfeiffer GIF++ Project Meeting Lead attenuators Asked Calder Industrial Materials Ltd for quote for two of the field uniformity lenses Bart simulated: Spherical lense: Euros Double cylindrical lense: Euros Will be mounted onto metal sheet (free issue plate) Lead type used will be to BS3909/2 4%Sb alloy Lead time will be 8-10 weeks from time of order and receipt of the free issue plates Tolerances will be as per drawings, the flatness tolerance on the free issue plate will have an effect so will need to be good Expensive ! Dorothea Pfeiffer Lead attenuators Received technical drawings of lead attenuators and movement system from Hans Reithler (RWTH Aachen) THANKS! Also received CNC programming files Aachen might be willing to help with the attenuators and mechanical system Dorothea Pfeiffer Field uniformity lense Attempt to find the ideal shape For 82Pb and E kin = 662 keV, linear attenuation coefficient =1.17 cm -1 I = I 0 exp(- d) I(x) = cos( ) 2 I max Opening angle : 37 horizontally, 28 vertically => in upper corners: 43 Ratio corner/center = cos(43) 2 = 0.53 d(x) = - ln(cos( ) 2 )/mu Dorothea Pfeiffer 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) Dorothea Pfeiffer Field uniformity lense Drawing in AutoCAD Export as *.stl file Conversion into Geant4 geometry format GDML with STL2GDML (tesselated volume) Geant4 simulations very slow due to tesselated volume with 6000 vertices Not enough statistics yet ! Use Geant4 polycone approximation instead ? Simulate in FLUKA with polycone approximation ? Dorothea Pfeiffer Field uniformity lense Dorothea Pfeiffer Field uniformity lense Dorothea Pfeiffer Field uniformity lense Dorothea Pfeiffer Field uniformity lense Dorothea Pfeiffer