Use of cover members when preparing a melt of silicon in a crucible assembly

A method for preparing a melt of silicon in a crucible of a crystal pulling system, the crystal pulling system comprising a housing defining a growth chamber, a crucible assembly disposed within the growth chamber for containing the silicon melt and a heat shield that defines a central passage through which an ingot passes during ingot growth, the method comprising:

• adding a charge of solid polycrystalline silicon to the crucible assembly;
• lowering a cover member through the central passage defined by the heat shield to cover at least a portion of the charge;
• heating the silicon charge to produce a silicon melt in the crucible assembly while the cover member covers a portion of the charge;
• and
• raising the cover member after the melt has been formed.