Abstract: A highly efficient, open-ended solar energy receiver is disclosed having a porous element through which air passes and a conventional heat exchanger positioned above and immediately adjacent to the porous element such that when solar energy is focused onto the porous element, a constant controlled temperature hot air stream from the element is conveyed by the temperature controlled convectively rising hot air to the conventional heat exchanger to produce steam, thereby minimizing pumping requirements. The quantity of air flowing through the receiver is regulated, if desired, by a low-power exhaust fan operating at a relatively low temperature due to the removal of heat by the heat exchanger. Regulation may also be obtained by an opening at the top of the receiver, controlled in such a manner as to vary the air flow through the system to maintain a constant temperature output from the heat exchanger. Additionally, if desired, water flow control may be utilized to maintain the proper energy balance.

Abstract: Focus correction in a laser to compensate for thermal lensing effects in the laser rod is achieved by applying a system of loads to the H.R. mirror of the laser cavity to develop a deformation thereof that counteracts optical path distortion of the laser rod occasioned by the thermal lensing effects therein.