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A Fresnel Zone Plate (ZP) is a circular diffraction grating, with radially varying line period such that the diffracted light forms a focal spot at some distance f from the ZP. In diffraction limited conditions, the size of the focal spot is equal to 1.22 * drn, where drn is the width of the outermost zone of the ZonePlate. f = ( D*drn ) / ( n*w ), is the focal length of the ZP, where D is the diameter, n is the diffraction order (1,2,3...), and w is the wavelength.
Use this simple Calculator to assess the effect of various parameters on probe formation
The diffraction efficiency of the Zone Plate is a function of the operating wavelength, the zone material and thickness, as well as the quality of nanostructuring of the zones.
I necessary, a Gold Central Stop up to 4 µm thick can be electroplated directly on the ZP, adequate for operation up to ~5 KeV! For higher energies we use 25 or 50 µm thick Pt Central Stop foils which are pre-