Forced Convective Cooling of Foils in a Repetitively Pulsed Electron-Beam Diode
Forced Convective Cooling of Foils in a Repetitively Pulsed Electron-Beam Diode
复制标题
DOI：
10.1109/tps.2008.922919
复制
发表时间：
2008-06
影响因子：
1.5
通讯作者：
F. Hegeler;J. Giuliani;J. Sethian;M. Myers;M. Wolford;P. Burns;M. Friedman
中科院分区：
文献类型：
--
作者：
F. Hegeler;J. Giuliani;J. Sethian;M. Myers;M. Wolford;P. Burns;M. Friedman
电子束 (e-beam) 泵浦高功率气体激光器需要使用传输窗/箔将真空二极管与激光单元分开。在重复操作下，箔片会受到电子束热负荷的影响，如果不冷却，最终会失效。本文研究了通过使激光气体绕闭环流动来对 Electra KrF 激光器主放大器中的箔片进行强制对流冷却。实验数据是使用工作电压为 500 kV、110 kA、半峰全宽为 140 ns、外部轴向磁场为 0.14 T 的两个二极管之一获取的。T 型热电偶用于测量各种条件下的箔片温度，包括由于百叶窗插入而导致的流速增强、重复率、阴极配置、气体成分和沿箔片的高度。考虑湍流导致的冷却以及内部箔片热传导和辐射的一阶模型再现了数据中观察到的总体趋势。目标是在 5 Hz 频率下运行时，将 25 微米厚的不锈钢箔的温度保持在拉伸强度和长期热疲劳极限以下。数据与模型相结合，预测可以通过使激光气体沿箔表面高速流动来实现这一目标。
Electron-beam (e-beam)-pumped high-power gas lasers require the use of a transmission window/foil to separate the vacuum diode from the laser cell. Under repetitive operation, the foil is subject to an e-beam heat load and would eventually fail without cooling. This paper investigates forced convective cooling of a foil in the main amplifier of the Electra KrF laser by flowing the laser gas around a closed loop. The experimental data were taken with one of the two diodes operating at 500 kV, 110 kA, a full-width at half-maximum of 140 ns, and with an external axial magnetic field of 0.14 T. Type-T thermocouples are used to measure the temperature of the foil under a variety of conditions including flow-velocity enhancement due to louver inserts, repetition rate, cathode configuration, gas composition, and height along the foil. A first-order model that considers cooling due to turbulent flow, as well as internal foil thermal conduction and radiation, reproduces the general trends observed in the data. The goal is to keep the temperature of a 25-mum-thick stainless steel foil below the tensile strength and long-term thermal fatigue limits when operating at 5 Hz. The data, in combination with the model, predict that this goal can be achieved by diverting the laser gas to flow at high velocity along the foil surface.