A clinical study of failure in microchannel cooled diodes used in large laser systems |
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| Authors: | Steven Jackel Avi Meir Zvi Horvitz Inon Moshe Yehoshua Shimoni Yaakov Lumer Revital Feldman Izhak Hershko Yotam Pekin |
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| Institution: | 1. Nonlinear Optics Group, Laser Department, Soreq NRC, 81800 Yavne, Israel;2. Nondestructive Testing Department, Soreq NRC, 81800 Yavne, Israel;1. Young Researchers and Elite Club, Mashhad Branch, Islamic Azad University, Mashhad, Iran;2. Department of Mechanical Engineering, Mashhad Branch, Islamic Azad University, Mashhad, Iran;1. PV Technology Laboratory, FOSS Research Centre for Sustainable Energy, Department of Electrical and Computer Engineering, University of Cyprus, Nicosia 1678, Cyprus;2. Centro de Estudios Avanzados en Energía y Medio Ambiente, Universidad de Jaén, Campus las Lagunillas, Jaén 23071, Spain;3. Suncore Photovoltaics, Inc., Albuquerque, NM 87109, USA;4. Institute of Mechanical, Process and Energy Engineering, Heriot-Watt University, Edinburgh EH14 4AS, UK;1. Department of applied Chemistry, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China;2. Engineering Laboratory for the Next Generation Power and Energy Storage Batteries, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China;3. McNair Technology Company, Limited, Dongguan City, Guangdong 523700, China;1. School of Chemistry and Environmental Engineering, Key Laboratory for Green Chemical Process of Ministry of Education, Hubei Novel Reactor & Green Chemical Technology Key Laboratory, Wuhan Institute of Technology, Wuhan 430073, PR China;2. School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Hubei Key Laboratory of Materials Chemistry and Service Failure, Wuhan 430074, PR China |
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| Abstract: | In this paper we investigate the source of failure in commercial, microchannel cooled CW diode bars placed in 12 bar horizontal arrays. The arrays were used to pump Nd:YAG rods in our 10 kW developmental laser. The laser was operated at low duty factor over a period of over 2 years. Experimental evidence indicated that the sudden, catastrophic failure was because of degraded cooling. We used optical microscopes, an X-ray microfocus imager, and a thermal neutron scattering camera to look inside the microcoolers. Our investigations revealed only one possible failure mechanism: cooling flow reduction because of delamination of the Au coating the walls of the microcoolers and the entrapment of Au flakes within the microchannel structures. We observed blisters in the microcoolers under working bars, and flake-like structures in the microcoolers under burnt-out bars (all taken from the laser). We observed no evidence of either massive blockages because of electrochemical deposits, or of corrosion/erosion in the microchannel walls. Integral operation times of the high flow-rate cooling system and of the diodes themselves were too short by one and two orders of magnitude, respectively, to explain the observed failures. Microchannel immersion times in the deionized water were, however, long enough to allow for corrosion of metals that may have been exposed through defects in the Au coatings. Three-dimensional heat flow simulations showed that blockage of multiple microchannels towards the edge of a bar can easily lead to catastrophic temperature increases. |
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