Abstract: Disclosed are .[.a.]. processes and reactors for rapidly producing large diameter, high-purity polycrystalline silicon rods for semiconductor applications by the deposition of silicon from a gas containing a silane compound. The equipment includes a reactor vessel which encloses a powder catcher having a cooled surface. Also within the vessel is a cylindrical water jacket which defines multiple reaction chambers. The silicon powder generated in this process adheres to the coolest surfaces, which are those of the powder catcher, and is thereby collected. Little of the powder adheres to the walls of the reaction chambers. In some embodiments, a fan can be provided to increase gas circulation.