The code to calculate the coded mask modulation effect is implemented in the batdrmgen tool. It utilizes attenuation coefficients of the mask lead (Pb) tiles and other passive materials in formulas and can calculates the attenuation efficiency through the materials at each energy. The modulation effect is derived from a difference between the attenuation at a tile and the attenuation where there is no tile.
Because we have been ranging the energy region below 150 keV so far, the current formula for the Pb attenuation is valid only below 200 keV. Here I would like to propose an update of the attenuation code to cover the energy region up to 1000 keV. This is quite important for the energy region even below 200 keV because the low energy tail of higher energy photons are coming down to below 200 keV.Therefore, it is necessary to extend the calculattion of the mask modulation effect to such high energy region.
// formulation of the absorption coefficient for Pb
Double_t pb_rho = 11.35; // Pb density [g/cm^3]
if (energy < 88.0) { A=199826.0; B=2.58574; } // valid for 15.86-88.0 keV
else { A = 575578.1; B=2.50726; } // valid for 88.0-200.0 keV
Double_t pb_mu = A*pow(energy,-B);// absorption coefficienct [cm^2/g]
// formulation of the absorption coefficient for Pb (modified 02Nov2004)
Double_t pb_rho = 11.35; // Pb density [g/cm^3]
Double_t pb_mu; // Pb absorption coefficienct [cm^2/g]
if (energy < 88.0) {
A=199826.0; B=2.585738; // valid for 15.86-88.0 keV
pb_mu = A*pow(energy,-B);
} else {
A = 749996.1; // valid for 88.0-1000.0 keV
B = 2.568129;
C = 15.26810;
D = 0.7868281;
n = 1.513170;
pb_mu = pow(pow(A*pow(energy,-B),n) + pow(C*pow(energy,-D),n),1.0/n);
}