Pinhole closure in spatial filters of large-scale ICF laser systems

R. G. Bikmatov; Charles D. Boley; I. N. Burdonsky; V. M. Chernyak; A. V. Fedorov; A. Yu. Goltsov; V. N. Kondrashov; S. N. Koptyaev; N. G. Kovalsky; V. N. Kuznetsov; David Milam; James E. Murray; Michael I. Pergament; V. M. Petryakov; Ruslan V. Smirnov; Victor I. Sokolov; E. V. Zhuzhukalo

doi:10.1117/12.354165

23 July 1999 Pinhole closure in spatial filters of large-scale ICF laser systems

R. G. Bikmatov, Charles D. Boley, I. N. Burdonsky, V. M. Chernyak, A. V. Fedorov, A. Yu. Goltsov, V. N. Kondrashov, S. N. Koptyaev, N. G. Kovalsky, V. N. Kuznetsov, David Milam, James E. Murray, Michael I. Pergament, V. M. Petryakov, Ruslan V. Smirnov, Victor I. Sokolov, E. V. Zhuzhukalo

Author Affiliations +

Proceedings Volume 3492, Third International Conference on Solid State Lasers for Application to Inertial Confinement Fusion; (1999) https://doi.org/10.1117/12.354165
Event: Third International Conference on Solid State Lasers for Application to Inertial Confinement Fusion, 1998, Monterey, CA, United States

Abstract

Pinhole plasma effects on parameters of the laser beam passing through the spatial filter in conditions of interest for large scale ICF laser facilities were investigated. The experiments on pinhole irradiation were conducted at power density range 10¹⁰-10¹¹ W/cm² with approximately 15 ns laser pulses. Al, Fe, and Ta pinholes were used. The diagnostic approach was chosen based on probing the pinhole region with frequency doubled 3-ns-long laser pulse. Ablative-plasma dynamics was studied with shadowgraphy and interferometry. Also measured were the parameters of transmitted probing beam in the near- and far-fields. The rate of pinhole 'closure' is found to decrease with the increase in the atomic number of pinhole material. The rate o pinhole closure ranges from approximately 5*10⁶ cm/s for aluminum pinhole down to approximately 2*10⁶ cm/s for tantalum pinhole in experiments with power density at the pinhole edge of approximately 50 GW/cm². For aluminum and steel pinholes the parameters of the transmitted probing beam deteriorate to unacceptable level for approximately 15-20 ns after the irradiation start. In the same experimental conditions the pinholes of tantalum exhibits acceptable performance till the end of the irradiation process. Fast plasma jets converging to the pinhole axis with velocities up to approximately 10⁷ cm/s and significantly deteriorating transmitted probing beam quality are observed. Reasonable agreement was found between the data obtained in experiments with circular pinholes and linear edge experiments.

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R. G. Bikmatov, Charles D. Boley, I. N. Burdonsky, V. M. Chernyak, A. V. Fedorov, A. Yu. Goltsov, V. N. Kondrashov, S. N. Koptyaev, N. G. Kovalsky, V. N. Kuznetsov, David Milam, James E. Murray, Michael I. Pergament, V. M. Petryakov, Ruslan V. Smirnov, Victor I. Sokolov, and E. V. Zhuzhukalo "Pinhole closure in spatial filters of large-scale ICF laser systems", Proc. SPIE 3492, Third International Conference on Solid State Lasers for Application to Inertial Confinement Fusion, (23 July 1999); https://doi.org/10.1117/12.354165

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