高功率飞秒激光脉冲诱导^(181)Ta核激发  

Nuclear Excitation of^(181)Ta Induced by High Power Femtosecond Laser Pulses

作　　者：徐永生[1] 贺创业[1] 兰小飞 赵保真 XU Yongsheng;HE Chuangye;LAN Xiaofei;ZHAO Baozhen(China Institute of Atomic Energy,Beijing 102413,China;China West Normal University,Nanchong 637000,China)

机构地区：[1]中国原子能科学研究院,北京102413 [2]西华师范大学,四川南充637000

出　　处：《原子能科学技术》2025年第3期524-531,共8页Atomic Energy Science and Technology

基　　金：国家重点研发计划(2022YFA1602403);国家自然科学基金(12205378)。

摘　　要：诱导核激发技术在同位素分离、新型γ激光器研发等方面有着广泛的应用前景,本文利用掺钛蓝宝石激光器产生的飞秒激光脉冲轰击固体Ta靶,对^(181)Ta的核激发现象进行研究。实验采用NaI探测器探测^(181)Ta退激发射的γ射线信号。结果显示,当激光功率密度超过1016 W/cm^(2)的核激发阈值时,每个激光脉冲能诱导产生(7.51±1.07)×10^(4)个激发核,其退激的γ射线能量为(6.40±2.37)keV,与^(181)Ta的第一激发态退激能量基本一致。然而,从衰变时间看,这些γ射线发射的时间与^(181)Ta第一激发态的衰变规律并不相同,它是否来自^(181)Ta某个特定物理过程或未知亚稳态衰变,还需进一步的理论与实验研究。The study focuses on investigating the nuclear excitation of^(181)Ta induced by femtosecond laser pulses.The objective is to explore the excitation mechanisms and yield of nuclear states under high-intensity laser conditions.Utilizing a commercial Ti:Sapphire laser system,femtosecond laser pulses with power densities exceeding 1016 W/cm²were directed at solid^(181)Ta targets.The laser pulses,characterized by a wavelength of 800 nm and pulse width of 33 fs,interact with the target to create dense plasma,inducing nuclear excitation.The experimental setup included precise control of laser parameters and the detection of de-excitationγ-rays using NaI scintillation detectors.These detectors were calibrated with a 55Fe standard source,ensuring high detection efficiency and accuracy.The experimental conditions were optimized by adjusting the lens-to-target distance,monitored via a CCD camera,to maintain stable power density on the target surface.Results show that upon reaching the threshold laser intensity of 1016 W/cm²,characteristicγ-ray signals with an energy of(6.40±2.37)keV are observed.Each laser pulse induces(7.51±1.07)×10^(4)nuclear excitations,resulting in(1.05±0.15)×10^(3)γ-ray signals.Comparative experiments with 184W targets,which have similar plasma characteristics but different nuclear energy levels,confirm that the observedγ-ray signals are specific to^(181)Ta.The study also includes theoretical calculations to estimate the number of excited nuclei and the expectedγ-ray yield.These calculations consider the plasma conditions and the interaction dynamics between superheated electrons,ions,and^(181)Ta nuclei.The theoretical estimates of theγ-ray yield,ranging from 0.4×10^(3)to 1.2×10^(3)γ-rays per pulse,are in good agreement with the experimental data.The investigation highlights the significance of direct photoexcitation as primary mechanism for nuclear excitation in high-temperature laser plasmas.The results emphasize the role of laser intensity and plasma conditions in achieving efficient

关 键 词：飞秒激光 181Ta 同核异能态 核激发 Γ射线 

分 类 号：TL11[核科学技术—核能科学] O571.1[理学—粒子物理与原子核物理]