A 42-kWe high-flux solar simulator with hexagonal reflector symmetry has been designed, built and optically characterized at IMDEA Energy Institute, Spain. This facility makes possible the lab-scale generation of a quasi-uniform high radiation flux density and high stagnation temperatures and it will be used as a platform for analyzing processes under concentrating solar energy conditions; for instance, central receivers in concentrating solar power plants and solar fuel production process in thermochemical reactors. The high-flux solar simulator consists of seven reflector-lamp pairs arranged in the center and vertices of a regular hexagon. The 6-kWe Xe short arc lamps are allocated in the primary focus of the corresponding truncated ellipsoidal reflector. This hexagonal symmetry provides compactness and quasi-uniform spatial distribution of the radiation at the system common focal plane.This work presents the experimental characterization of the solar simulator optical performance. Preliminary measurements indicate an average flux density at the focal plane of 3.5 MW/m2 that means 3,500 suns (1 sun = 1kW/m2) and stagnation temperature of approximately 2,800K