In this paper, we present a systematic procedure to design a solar simulator for high-temperature concentrated solar thermal and thermochemical research. The $45\u2002kWe$ simulator consists of seven identical radiation units of common focus, each comprised of a $6.5\u2002kWe$ xenon arc lamp close-coupled to a precision reflector in the shape of a truncated ellipsoid. The size and shape of each reflector is optimized by a Monte Carlo ray tracing analysis to achieve multiple design objectives, including high transfer efficiency of radiation from the lamps to the common focal plane and desired flux distribution. Based on the numerical results, the final optimized design will deliver 7.5 kW over a 6 cm diameter circular disk located in the focal plane, with a peak flux approaching $3.7\u2002MW/m2$.