Index of refraction of neutron irradiated diamond
Large changes in density of neutron irradiated diamond have been reported by Primak, Fuchs and Day 1) (about 1%o for a dose of 7.1018 n/cm2). For this reason measurable changes in index of refraction could be expected for irradiated diamond, even at much lower doses.
Because of the high index of refraction of diamond only the minimum deviation method could be applied. A diamond prism of about 200 mg and with an angle of about 43 ยฐ was used. The index was measured for different neutron doses up to 1,2.1017 n/cm ~. We could not apply higher doses because the diamond turned green and its transparency became insufficient to continue the measurements.
The index was measured for a wavelength of 5893 A, with an accuracy of -}-0.0001. No changes of the index could be detected. Two subsequent anneals of 30 minutes, one at 400ยฐC and one at 750ยฐC, which turned the green into a light brown colour, did not change the index of refraction.
We thank the Soci~t6 Beige d'Optique et d'Instruments de Precision (Gent) for the loan of a precision goniometer.