Spherical Vacuum - Interface Window With Axial - Flow Impingement Cooling

Glenda S. Holderbaum; Richard J Phillips

doi:10.1117/12.951355

11 July 1989 Spherical Vacuum - Interface Window With Axial - Flow Impingement Cooling

Glenda S. Holderbaum, Richard J Phillips

Proceedings Volume 1047, Mirrors and Windows for High Power/High Energy Laser Systems; (1989) https://doi.org/10.1117/12.951355
Event: OE/LASE '89, 1989, Los Angeles, CA, United States

Abstract

A spherical vacuum - interface window and an axial - flow impingement cooling system for high - energy laser applications are described. The vacuum - interface window is a 65 - cm diameter, 0.5 - cm thick, fused silica dome with a 10° edge angle. Both window optical surfaces are coated with anti - reflective coatings. Finite element analysis techniques were used to determine window thermal, structural, and optical performance characteristics for both uniform and Gaussian, 50 - cm diameter laser beam profiles. The axial - flow impingement cooling system provides convective cooling on a window surface. Helium gas is drawn into a throat duct, flows axially towards the window, impinges the window, and then flows radially outwards through a diffuser. Thermal, fluid, and optical performance testing was performed on a sub - scale apparatus to optimize convective cooling, minimize pumping power, and determine optical path distortion. A 40% scale factor was selected based on similitude. For the configurations tested, a diffuser angle of 30 degrees and a diffuser gap width to duct radius ratio of 0.3 maximized heat transfer with a Nusselt number of 610 at a flow Reynolds number of 740,000. This Nusselt number corresponds to a 30 - second thermal response time constant for the window. A gap width ratio of 0.4 minimized pumping power but at a 20% reduction in heat transfer. Use of turbulence promoters in the throat duct can increase convective cooling by 50%.

Citation Download Citation

Glenda S. Holderbaum and Richard J Phillips "Spherical Vacuum - Interface Window With Axial - Flow Impingement Cooling", Proc. SPIE 1047, Mirrors and Windows for High Power/High Energy Laser Systems, (11 July 1989); https://doi.org/10.1117/12.951355

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