Study on laser beam breakup effects in atomic laser isotope separations of uranium

铀原子激光同位素分离中激光束破碎效应的研究

• 批准号: 06452431
• 负责人: IZAWA Yasukazu
• 金额: $ 4.16万
• 依托单位: Osaka University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (B)
• 财政年份: 1994
• 资助国家: 日本
• 起止时间: 1994 至 1995
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06452431/
• 关键词: AVLIS; near-resonant effects; laser beam propagation; spatial nonuniformity; self-focusing; nonlinear refractive index; beam breakup; 非線形伝搬特性; 自己位相変調

In atomic vapor laser isotope separations of uranium, the laser beams propagate through the uranium atomic vapor for a long distance in interacting with U-235 on resonance and U-238 in near-resonance. The nonuniformity in spatial intensity distribution of incident laser pulse will be amplified by nonlinear effects of near-resonant interaction (nonlinear refractive index) during the propagation, which leads the laser beam breakup. In this study, the growth of nonuniformity and the effects of such growth on uranium enrichment have been investigated by the experiments and the numerical calculations.1) The 2-D simulation code named CEALIS-P-2P has been developed to study the spatial effects in laser beam propagation and atomic excitation simultaneously in multilevel photoionization system.2) In the simulations, the effects of diffraction and the growth of nonuniformity on the ionization rates of target atoms have been successfully analyzed. When the incident laser beam is highly nonuniform, it was found that the ionization rate suddenly decrease after a critical distance of propagation. The nonuniformity should be less than <plus-minus>5% for atomic laser isotope separation of uraniu3) The growth of nonuniformity was observed experimentally in the dye laser pulse propagating in the Na vapor in near-resonant conditions. By increasing nonlinear refractive index, the growth moves from linear region to nonlinear region which induced the higher harmonics components and finally the beam breakup. These features are in good agreements with the simulation results.

在铀原子蒸气激光同位素分离中，激光束在铀原子蒸气中长距离传播，与共振态的U-235和近共振态的U-238相互作用。近共振相互作用的非线性效应（非线性折射率）会放大入射激光脉冲空间光强分布的不均匀性，导致激光束分裂。本文通过实验和数值计算研究了非均匀性的增长及其对铀浓缩的影响。1）开发了二维模拟程序CEALIS-P-2 P，研究了多能级光电离系统中激光束传输和原子激发的空间效应。成功地分析了衍射和非均匀性增长对靶原子电离率的影响。当入射激光束高度非均匀时，电离率在传输到临界距离后突然下降。3<plus-minus>）在近共振条件下，实验观察到染料激光脉冲在钠蒸气中传输时非均匀性的增长。随着非线性折射率的增加，光束从线性区向非线性区移动，产生高次谐波分量，最终导致光束分裂。这些特征与仿真结果吻合较好。

项目成果

K. Nomaru and Y. Izawa and Y.-W. Chen: "Growth of Spatial Nonuniformity of Laser Pulse Propagating in Near-Resonant Atomic Vapor" Journal of Nuclear Science and Technology. (投稿予定).

K. Nomaru、Y. Izawa 和 Y.-W. Chen：“近共振原子蒸气中传播的激光脉冲的空间不均匀性的增长”核科学与技术杂志（待提交）。

Y.W.Chen, Y.Izawa et al.: "Numerical study on propagation of laser pulse in multilevel photoionization system" Journal of Optical Society of America B. 11. 1585-1594 (1994)

Y.W.Chen、Y.Izawa 等人：“多级光电离系统中激光脉冲传播的数值研究”美国光学学会杂志 B.11.1585-1594 (1994)

K.Nomaru, Y.Izawa et al.: "Near-resonant effects on propagation of frequency swept laser pulse in atomic vapor laser isotope separation" Journal of Nuclear Science and Technology. 31. 914-920 (1994)

K.Nomaru、Y.Izawa 等人：“原子蒸气激光同位素分离中频率扫描激光脉冲传播的近共振效应”核科学与技术杂志。

K.Nomaru,Y.Izawa et al.: "“Near-resonant effects on propagation of frequency swept laser pulse in atomic vapor laser isotope separation"" Journal of Nuclear Science and Technology. 31. 914-920 (1994)

K. Nomaru、Y. Izawa 等人：“原子蒸气激光同位素分离中扫频激光脉冲传播的近共振效应”《核科学与技术杂志》31. 914-920 (1994)。

K. Nomaru, Y. Izawa, et al.: "Near-resonant effects on propagation of frequency swept laser pulse in atomic vapor laser isotope separation" Journal of Nuclear Science and Technology. 31. 914-920 (1994)

K. Nomaru、Y. Izawa 等人：“原子蒸气激光同位素分离中扫频激光脉冲传播的近共振效应”核科学与技术杂志。