Numerical modeling of Czochralski growth of Li2MoO4 crystals for heat-scintillation cryogenic bolometers

Carmen Stelian, Matias Velázquez, Philippe Veber, Abdelmounaim Ahmine, Jean-Baptiste Sand, Gabriel Buşe, Hugues Cabane, Thierry Duffar

Index: 10.1016/j.jcrysgro.2018.04.003

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Abstract

Lithium molybdate Li2MoO4 (LMO) crystals of mass ranging between 350-500 g are excellent candidates to build heat-scintillation cryogenic bolometers likely to be used for the detection of rare events in astroparticle physics. In this work, numerical modeling is applied in order to investigate the Czochralski growth of Li2MoO4 crystals in an inductive furnace. The numerical model was validated by comparing the numerical predictions of the crystal-melt interface shape to experimental visualization of the growth interface. Modeling was performed for two different Czochralski furnaces that use inductive heating. The simulation of the first furnace, which was used to grow Li2MoO4 crystals of 3-4 cm in diameter, reveals non-optimal heat transfer conditions for obtaining good quality crystals. The second furnace, which will be used to grow crystals of 5 cm in diameter, was numerically optimized in order to reduce the temperature gradients in the crystal and to avoid fast crystallization of the bath at the later stages of the growth process.