Controlled growth of CsI〈Tl〉 single crystals

Abstract

CsI〈Tl〉 crystals have been grown by the axial-heat-flux-close-to-the-phase-interface (AHP) method in a purpose-designed apparatus at an argon overpressure. The furnace and crystallizer of the apparatus have been designed to ensure considerable (5 to 100 K/cm) axial and low (within 1 K/cm) radial temperature gradients at the growth interface. The effects of the melt layer thickness, temperature gradient, and activator concentration in the melt on the crystal quality have been studied. The results demonstrate that reducing the AHP heater temperature for even a short time (by 2°C in 3 min) markedly raises the actual growth rate, from 2 to 15 mm/h, and leads to entrapment of bubbles of various diameters and TlI inclusions.