A mirror with a larger effective critical angle can be made by exploiting diffraction (with non-zero losses) that occurs from stacked multilayers. The critical angle of total reflection, in degrees, becomes approximately 0.1 ⋅ ⋅ λ λ ⋅ ⋅ m , where m is the "m-value" relative to natural nickel. m values in the range of 1–3 are common, in specific areas for high-divergence (e.g. using focussing optics near the source, choppers, or experimental areas) m=6 is readily available.