·参加衍射的晶粒 Ewald's Diffraction sphere cone Dcbyc ring Incident beam Detector Fig.8.1 The origin of the powder diffraction cone as the result of the infinite number of the com- pletely randomly oriented identical reciprocal lattice vectors,dk forming a circle with their ends placed on the surface of the Ewald's sphere,thus producing the powder diffraction cone and the corresponding Debye ring on the flat screen(film or area detector).3 The detector is perpendicular to both the direction of the incident beam and cone axis,and the radius of the Debye ring inghis geometry is proportional to tan 20.5 • 参加衍射的晶粒