The solid particle receiver (SPR) is a direct absorption receiver in which solar energy heats a curtain of falling ceramic particle to a temperature in excess of 1000 degrees C. A small scale test platform was built to investigate particle flow properties. The curtain was comprised of approximately 697 mu m ceramic particles that were dropped within the receiver cavity of the test platform. Tests were conducted to experimentally determine the distribution of particles velocity, curtain thickness, and curtain opacity along a drop length of approximately 3 m. Velocity data were measured using a high speed digital camera to obtain images of the particle flow at 1000 frames per second with an exposure time of 100 mu s. Five mass flow rates ranging from 1 kg/s-m to 22 kg/s-m were examined, and it was found that all flows approached a terminal velocity of about 6-7 m/s in a vertical drop distance of 3 m. The experimental results were validated with computational results and were found in excellent agreement with the simulation results. In addition, a similar study was performed with various sizes of the particles to better understand how the particle flow characteristics were affected by the size of the particles. (C) 2009 Elsevier Ltd. All rights reserved.