A system for growing a crystal ingot from a melt is provided. The system includes a crucible assembly, a first heater, a second heater, and a passive heater. The crucible assembly includes a crucible and a weir separating an outer melt zone of the melt from an inner melt zone of the melt. The first heater is configured to supply thermal energy to the melt by conduction through the crucible. The second heater is configured to generate thermal radiation. The passive heater is configured to supply thermal energy to the outer melt zone by transferring thermal radiation generated by the second heater to the outer melt zone.