Influence of target self-absorption on the energy spectrum and angular distribution of X-ray source
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摘要: 靶材自吸收效应是影响激光驱动X射线源性能的关键因素之一，明确其对X射线能谱和角分布的作用机制对优化光源设计具有重要意义。利用蒙特卡罗模拟方法，系统研究了电子源与丝靶端面距离、丝靶直径及靶材原子序数三个参数在自吸收效应下对X射线源特性的影响。研究结果表明：电子源在50～150 μm范围内轴向移动对能谱形态及角分布影响不显著；丝靶直径增大导致低能光子吸收增强，能谱明显硬化，同时光子角分布展宽，准直性下降；高原子序数靶材可显著提升高能光子产额，但伴随角分布发散加剧。揭示了靶材自吸收对不同能段光子的选择性衰减与多次散射对光束定向性的影响规律。Abstract:
Background The self-absorption effect of target materials plays a crucial role in shaping the performance of laser-driven X-ray sources, directly impacting their energy spectrum and angular distribution, which are critical parameters for applications such as high-resolution backlighting and radiographic diagnostics.Purpose This study aims to systematically investigate how key parameters, including the electron source position relative to the wire target end-face, the diameter of the wire target, and the atomic number of the target material, affect the energy spectrum and angular distribution of emitted X rays.Methods A series of Geant4-based Monte Carlo simulations were performed using a validated wire target model. Key parameters were varied: electron source offset (50–150 μm), wire diameter, and target material (Cu, Mo, W, Au). The simulation model was benchmarked against experimental data obtained from the Xingguang-III laser facility.Results The results indicate that varying the electron source position within the studied range has a negligible influence on both the photon energy spectrum and angular distribution. In contrast, increasing the wire diameter leads to enhanced absorption of low-energy photons, resulting in noticeable spectral hardening and a broadening of the angular distribution due to increased multiple scattering. Furthermore, higher-Z target materials (W, Au) significantly enhance the high-energy photon yield but concurrently induce greater angular divergence.Conclusions The findings provide quantitative insights into the self-absorption mechanism and its differential impact across parameters. This study offers concrete guidance for optimizing target design: selecting appropriate wire diameter and high-Z materials can tailor the spectral hardness and brightness, while mindful management of angular broadening is necessary for applications requiring high directivity. -
图 2 归一化背光源强度的实验与模拟数据对比
Figure 2. Comparison of normalized backlighter intensity between experimental and simulation data
图 3 不同电子源-丝靶距离下的光子能谱
Figure 3. Photon energy spectra for different electron source-to-wire target distances
图 4 不同电子源-丝靶距离下的光子极角分布与高斯拟合图
Figure 4. Polar angular distribution of photons with Gaussian fits for different electron source-to-target distances
图 5 不同电子源-丝靶距离下的光子角分布图
Figure 5. Angular distribution of photons for different electron source-to-target distances
图 6 不同丝靶直径下光子能谱图
Figure 6. Photon energy spectra for different wire targets with diameters
图 7 不同丝靶直径下光子极角分布与高斯拟合图
Figure 7. Polar angular distribution of photons with Gaussian fits for different wire targets with diameters
图 8 不同丝靶直径下光子角分布图
Figure 8. Angular distribution of photons for different wire targets with diameters
图 9 不同丝靶直径下光子平均自由程
Figure 9. Photon mean free path for different wire targets with diameters
图 11 Cu、Mo、W、Au的光子极角分布与高斯拟合图
Figure 11. Polar angular distribution of photons with Gaussian fits for Cu, Mo, W, and Au targets
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[1] Li Huan, Tang Xiaobin, Hang Shuang, et al. High-directional laser-plasma-induced X-ray source assisted by collimated electron beams in targets with a self-generated magnetic field[J]. Fusion Engineering and Design, 2019, 144: 193-201. doi: 10.1016/j.fusengdes.2019.05.001 [2] 盛政明. 强场激光物理研究前沿[M]. 上海: 上海交通大学出版社, 2014Sheng Zhengming. Advances in high field laser physics[M]. Shanghai: Shanghai Jiaotong University Press, 2014) [3] 李孟婷. 康普顿成像硬X射线源辐射特征研究[D]. 合肥: 中国科学技术大学, 2021Li Mengting. Study of radiation characteristic of hard X-ray source for compton radiography[D]. Hefei: University of Science and Technology of China, 2021) [4] Kostenko O F. Simulations of hard X-ray generation by hot electrons in a silver target[J]. Quantum Electronics, 2019, 49(3): 216-219. doi: 10.1070/QEL16828 [5] Compant La Fontaine A. Photon dose produced by a high-intensity laser on a solid target[J]. Journal of Physics D: Applied Physics, 2014, 47: 325201. doi: 10.1088/0022-3727/47/32/325201 [6] Tommasini R, Bailey C, Bradley D K, et al. Short pulse, high resolution, backlighters for point projection high-energy radiography at the National Ignition Facility[J]. Physics of Plasmas, 2017, 24: 053104. doi: 10.1063/1.4983137 [7] Tommasini R, Hatchett S P, Hey D S, et al. Development of Compton radiography of inertial confinement fusion implosions[J]. Physics of Plasmas, 2011, 18: 056309. doi: 10.1063/1.3567499 [8] Armstrong C D, Brenner C M, Jones C, et al. Bremsstrahlung emission from high power laser interactions with constrained targets for industrial radiography[J]. High Power Laser Science and Engineering, 2019, 7: e24. doi: 10.1017/hpl.2019.8 [9] Tommasini R, Macphee A, Hey D, et al. Development of backlighting sources for a Compton radiography diagnostic of inertial confinement fusion targets (invited)[J]. Review of Scientific Instruments, 2008, 79: 10E901. doi: 10.1063/1.2953593 [10] Debayle A, Gremillet L, Honrubia J J, et al. Reduction of the fast electron angular dispersion by means of varying-resistivity structured targets[J]. Physics of Plasmas, 2013, 20: 013109. doi: 10.1063/1.4789451 [11] Nagel S R, Chen H, Park J, et al. Two-dimensional time-resolved ultra-high speed imaging of K-alpha emission from short-pulse-laser interactions to observe electron recirculation[J]. Applied Physics Letters, 2017, 110: 144102. doi: 10.1063/1.4979802 [12] Huang L G, Molodtsova M, Ferrari A, et al. Dynamics of hot refluxing electrons in ultra-short relativistic laser foil interactions[J]. Physics of Plasmas, 2022, 29: 023102. doi: 10.1063/5.0077222 [13] Yin L, Luedtke S V, Stark D J, et al. Advances in laser-based bremsstrahlung x-ray sources. I. Optimizing laser-accelerated electrons[J]. Physics of Plasmas, 2024, 31: 123101. doi: 10.1063/5.0228834 [14] Tian Chao, Yu Minghai, Shan Lianqiang, et al. Radiography of direct drive double shell targets with hard x-rays generated by a short pulse laser[J]. Nuclear Fusion, 2019, 59: 046012. doi: 10.1088/1741-4326/aafe30 [15] Eder D C, Pretzler G, Fill E, et al. Spatial characteristics of Kα radiation from weakly relativistic laser plasmas[J]. Applied Physics B, 2000, 70(2): 211-217. [16] 徐妙华. 超短超强激光脉冲与薄膜靶相互作用中的高能离子加速和超热电子输运的研究[D]. 北京: 中国科学院物理研究所, 2008Xu Miaohua. Study of high-energy ion acceleration and hot electron transport in the interaction of ultra-intense, ultra-short laser pulses with thin foil targets[D]. Beijing: Institute of Physics, Chinese Academy of Sciences, 2008 [17] Khan S F, Martinez D A, Kalantar D H, et al. A dual high-energy radiography platform with 15 μm resolution at the National Ignition Facility[J]. Review of Scientific Instruments, 2021, 92: 043712. doi: 10.1063/5.0044043 [18] Wilks S C, Kruer W L, Tabak M, et al. Absorption of ultra-intense laser pulses[J]. Physical Review Letters, 1992, 69(9): 1383-1386. doi: 10.1103/PhysRevLett.69.1383 -
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