Heat balance evaluation linked with a direct approach model using ray trace simulation (DARTS) was able to provide quantitative heat information which was applicable to the reflector design for a rapid thermal processing system. The absorbed ray intensity obtained by the DARTS model showed that the array of very small half-cylindrical hills built on the reflector surface had the function of flattening the sharp heat peaks formed beneath the infrared lamps. The temperature profile, obtained by the entire heat balance calculation using mainly the thermal conduction and the radiation heat to and from the susceptor, quantitatively agreed with the measurements. The power value for one ray defined in the DARTS model was consistent with that estimated from the division of power loaded into the lamp by the emitted ray number. (c) 2005 The Electrochemical Society. All rights reserved.