Fig. 1. Images of the nitrogen-doped CVD diamonds. Snapshots in reflected light: as-received (a), after LPHT treatment at temperature 1800 “C (bl, after electron irradiation and LPHT treatment at 1800 "C (c). Fluorescence images with 360 nm excitation: as—received (d), after LPHT ll'&3lT‘|1€I‘|( at temperature 1800 “C (e), after electron irradiation and LPHT treatment at 1800 “C (f). DiamondVieW fluorescence images: a5—received (g), after LPHT treatment at temperature 1800 “C (h), after electron irradiation and LPHT treatment at 1800 °C (kl. Birefringence images ofone ofthe diamonds in as—received state: magnification >