21 July 2000 Thermal blooming of HEL in the nonflowing beam tube with various wall temperatures
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Abstract
The flowing gas system was almost always used for beam path conditioning in the past to reduce thermal blooming in the high energy laser (HEL) system. For an airborne system, however, system weight is important. The non-flowing medium was considered in order to keep the system weight down. This paper shows that the combination of high thermal diffusivity and low index of reflection of helium enables it to be used as the beam path medium at the non-flowing mode of operation. Wall temperatures have a significant effect on optical path difference (OPD) in the non-flowing beam tube, because there is no thermal boundary layer and the temperature gradient occupies the entire beam tube. The effect of wall temperatures on the OPD in the non-flowing helium system was evaluated analytically. Results show that the OPD in the non-flowing helium compares favorably to that in the flowing system with moderate flow velocity under the same wall conditions. In summary, results presented confirm that the non-flowing helium is indeed a viable alternative to the flowing systems used in the HEL systems in the past.
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Peter I. Shen, Peter I. Shen, Marya Andrepont, Marya Andrepont, } "Thermal blooming of HEL in the nonflowing beam tube with various wall temperatures", Proc. SPIE 4034, Laser Weapons Technology, (21 July 2000); doi: 10.1117/12.391861; https://doi.org/10.1117/12.391861
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