Abstract: There is provided a cylindrical valve 20 for placement in the flow path of a singlet-delta oxygen generator 12 that feeds O.sub.2.sup.* to a chemical laser gain medium 14. The feed path 22 includes a sharp 90.degree. bend 24 that causes fluid velocity variations in O.sub.2.sup.* entering the gain medium 14. Integral with the valve 20 is a tubular structure 12 having a partial circumferential radially extending surface 44 fitted with "O" ring for sealing and opening the feed path between the "O.sub.2.sup.* " generator 12 and gain generator 14. A series of vanes 32, 34, 36 disposed in velocity control zones 50, 52, 54 and 56 are integral with the valve 20 for leveling out the velocity variations and controlling the wake formation 58, 59 and 60 in the O.sub.2.sup.* entering the gain generator 14.