A fresnel zone plate list of polynomial coefficients describing the focal length of the zone plate, in increasing powers of photon energy, that describes the focal length of the zone plate (in microns) at an X-ray photon energy (in electron volts). how the zone plate was manufactured Material of the zones themselves Material present between the zones. This is usually only present for the "zone doubled" fabrication process If no mask is present, set mask_thickness to 0 and omit the mask_material field "Engineering" position of the fresnel zone plate