Ion channeling in natural and synthetic beryl crystals

The transmission of ions by channeling through natural beryl and synthetic emerald has been studied extensively. The transmission ratios depend upon the angle of incidence with a full half width of less than 0.32°. While the maximum ratio obtained up to now is only 4×10⁻⁴ for 350 keV protons through a crystal of 21 μm thickness, the energy of the transmitted ions is high, the loss being in the order of a few keV/μm. About 60–80% of the particles emerging from the rear surface are ionized. By varying the ion species transmission could be observed up to atomic number 9. It is assumed that the transmission is facilitated by the existence of an electron free channel core. Higher transmission ratios can be expected for sufficiently perfect crystals.