Abstract: A heating system has a substantially cylindrical hollow muffle formed of a alumina ceramic with a plurality of heat-generating windings therearound. A light-actuated power control is operatively connected to the windings. A computer is operatively connected to a temperature monitor associated with an article being heated in the muffle. The computer is also operatively connected to a light-signal generator and provides commands to the generator in the form of a train of equidistantly spaced electrical pulses in response to temperature measurements provided by the monitor such that an article can be heated to an elevated steady state temperature and controlled at that steady state temperature within precise predetermined limits. The precise temperature control makes the system particularly valuable in the fabrication of crystals with uniform properties or having special growth requirements.