Double crystal monochromator for synchrotron radiation with decreased radiation power density

It is suggested to use the double crystal monochromator (spectrometer) having finite angle between diffracting planes and the surface of the crystals to increase the irradiated area on the first crystal. In both crystals the plane determined by the impinging beam and the normal to the diffracting planes is perpendicular to the plane determined by the normals to the diffracting planes and to the surface of the crystal, so that the diffraction remains symmetrical. The advantage of this system is that the range of Bragg angles is limited only by the dimensions of the crystals