opened bottom crucible and ingot heater controller 24 that provides a temperature controlled thermal environment for the ingot as it passes through the ingot heater the temperature controlled thermal environment is provided to allow controlled conductive heating into the interior of the ingot sometimes referred to as heat u201c soaking u201d and controlled thermal radiation from the exterior surfaces of the ingot as the ingot cools so that cracking can be avoided the gas tight cevar furnace chamber 11 is diagrammatically illustrated in fig1 with dashed lines and includes a gas tight seal for drive actuator 34 which is further described below an ingot withdrawal drive system can be provided to withdraw the solidified ingot at a rate substantially equal to its vertical growth rate during steady state cevar process operation such that the arc zone and the top of the solidified ingot remain within the crucible or alternatively a drive system can be provided that lifts the crucible electrode and ingot heater while the solidified ingot remains stationary at the beginning and end of the cevar purification process the ingot withdrawal rate will vary due to transient startup and end process parameters as shown in fig1 the ingot withdrawal drive system can include base 32 upon which the bottom of the solidified ingot sits and drive actuator 34 that controls the rate of withdrawal drop of the ingot from the crucible in the downward direction base 32 can be configured with a contour that enhances interlocking contact with the bottom of the solidified ingot for example as.