Screen Nozzles for Gasdynamic Lasers

Fine-hole o r i f i c e p l a t e s (screen nozzles) a r e considered a s a replacement f o r two-dimensional g r id nozz les i n gasdynamic l a s e r s . Analyses a r e made of t he downstream f u l l y mixed s t a t e , t he flow per turba t ion decay t o t h a t s t a t e , and the o p t i c a l gain d i s t r i b u t i o n f o r t yp i ca l N2-CO2 l a s e r condit ions . Experiments were conducted with a sc reen ! nozzle mounted on a shock tube. Density nonuniformi t ies were found to be below 1% a t 100 o r i f i c e spacings downstream (30 cm), with gains of 0.6-0.8 %/cm. These r e s u l t s agree with pred ic t ions and lead t o the conclusion t ha t screen nozzles o f f e r extreme s imp l i c i t y with only small performance pena l t y .