User routine rfrndx.f

Dear FLUKA expert,
The attachment shows in the file"CERN-2005-10.pdf" at page 348,it use the user routine to define refraction index and only return this value,but “what(1)” at the card of OPT-PROP can input the value,so why exist this user routine?

Dear Xiong,

  • The OPT-PROP card allows to set the refraction index at the central wavelength (or central angular frequency) as a constant.
  • The rfrndx.f user routine allows to specify the refraction index as a function of wavelength, energy or frequency.

I hope this helps

Dear Vojtěch,
I understand it,thank you for your help