Electra KrF Laser Hibachi Foil Cooling with Near-Wall Jets

摘要

Active cooling of the transmission foil separating the vacuum diodes from the laser cell in the Electra KrF Laser is necessaiy to prevent its failure under repetitively pulsed (5Hz) operating conditions. This paper investigates the effectiveness of forced convection cooling using near-wall jets as a means of protecting the foil. Two different near-wall jet configurations are examined. The first one uses a planar, lmm-thick, high-speed jet flowing parallel to the laser gas stream along the entire width of the hibachi foil structure. The second one uses small, 0.8mm-diameter circular jets positioned in staggered locations, 12.7mm apart, along the ～30cm height of each of the 24 hibachi rib spans with flow perpendicular to the laser gas stream. Bench-top experiments simulating a single 3.4cm×30cm foil span between two neighboring ribs have been conducted. For both jet configurations, experiments have been performed at different jet velocities and heat inputs. The goal of these experiments is to demonstrate quantitatively that near-wall jets can effectively cool the Electra hibachi foil under prototypical pulsed operating conditions without adverse impact on beam quality or laser efficiency. Preliminary tests with a full-size hibachi on Electra have shown this to be true.