DETECTIVE (Development of a novEl Tube-bundlE-CaviTy lInear receiVEr for CSP applications) is a project that aims at enhancing the overall performance of the current solar parabolic trough collectors. The proposed design focuses on improving such performance by substituting the traditional single metal absorber tube with a tubular bundle whose outer contour largely matches the outer circumference of the replaced tube. To assess the optical performance of the proposed receiver, a Monte Carlo ray tracing technique was employed by utilizing the SolTrace software. The effects of the two design parameters, such as cavity opening angle and cavity radius, on the overall optical behavior have been explored and the optimum design is determined with the maximum optical performance. The ray tracing data proved that the cavity-like space formed within the multi-tube arrangement results in a multi-reflection process between bundle tubes and could result in a higher ray absorption compared to the conventional design, leading to lower optical losses. The obtained numerical results indicated that an aperture angle of 60 degrees could provide the highest optical performance among the studied options. Considering the second parameter, the rise in the cavity radius is shown to increase the ray intersection inside the cavity, while the optical efficiency decreases. Finally, the most efficient design reaches an enhancement of 10% in optical efficiency if compared to the conventional PTC design.