Calculate sample to detector distance

Where 5.838 nm is the d₀₀₁ spacing of silver behenate;

S-D is sample to detector distance (unit: mm)

λ is the wavelength of the X-ray. At 12 Kev, the wavelength is 0.1033 nm

Pixel size will be detector-dependent. (unit: mm/pixel)

Radius is the radius of silver behenate ring in the unit of pixel.