Direct steam generation (DSG) for concentrating solar power (CSP) is an emerging technology that can unlock new avenues for efficient and affordable energy utilisation and expand the current capabilities of CSP. However, the direct evaporation of steam in parabolic trough solar collectors presents control and operational challenges due to the inherently complex two-phase nature and inherent unsteadiness of the boiling flow inside the tubes. Thus, a fundamental understanding of the hydrodynamic and heat transfer characteristics of this two-phase flow is required. A bespoke flow boiling facility has been constructed for the investigation of boiling flows using laser diagnostic techniques to gain accurate spatio-temporally resolved information on the flow characteristics. The facility has been validated and a proof of concept of the application of particle image velocimetry to boiling flows performed.