          mass_frac, den = MATERIALS[material]
                if material == &#39;al&#39;:
                    thickness = thickness * 0.8
                parts.append(
                    self.create_material(name=material,
                                         fractional_masses=mass_frac,
                                         thickness=thickness,
                                         density=den))
            self.components[name] = Compound(parts)

    def get_transmission(self, energies, atten