Ultra high precision refractive index measurement of Si at $\gamma$-ray energies up to 2 MeV

摘要

The refractive index of silicon at $\gamma$-ray energies from 181 - 1959 keVwas investigated using the GAMS6 double crystal spectrometer and found tofollow the predictions of the classical scattering model. This is in contrastto earlier measurements on the GAMS5 spectrometer, which suggested asign-change in the refractive index for photon energies above 500 keV. Wepresent a re-evaluation of the original data from 2011 as well as data from a2013 campaign in which we show that systematic errors due to diffractioneffects of the prism can explain the earlier data.