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Laser driven fusion requires a high-degree uniformity in laser energy deposition in order to achieve the high-density compression required for sustaining a thermonuclear burn. Nowadays, uniform irradiation of capsule is still a key issue in direct drive inertial confinement fusion. The direct drive approach is to drive the target with laser light, by irradiating it with a large number of overlapping laser beams. In the direct drive scheme, the laser deposition pattern on the target can be decomposed into a series of Legendre spherical harmonic modes. The high mode (shorter wavelength) nonuniformity can lead to Rayleigh-Taylor instability, which may result in the failure of target compression. This nonuniformity can be suppressed by thermal conduction and beam conditioning technologies, such as continuous phase plate, smoothing by spectral dispersion and polarization smoothing. The low mode (longer wavelength) nonuniformity is related to the number, orientation and power balance of laser beams, which is hard to suppress by thermal conduction and beam conditioning technologies. Generally, the nonuniformity of laser irradiation on a directly driven target should be less than 1% (root mean square, RMS), to meet the requirement for symmetric compression. Several methods have been proposed to optimize the irradiation configuration in direct drive laser fusion, such as truncated icosahedron with beams at the 20 faces and 12 vertices of an icosaherdron, dodecahedron-based irradiation configurations, self-organizing electrodynamic method, etc. However, limited by the different parameters of incident beams, the irradiation uniformity is often not satisfactory. Therefore, it is necessary to find new way to improve the irradiation uniformity and make it more robust. According to the analytical result, the irradiation nonuniformity can be decomposed into the single beam factor and the geometric factor. Simulation results show that the single beam factor is mainly determined by the parameters of the incident beams, including beam pattern, beam width and beam wavelength. By analyzing and simulating the single beam factor with different incident beam parameters, and comparing the single beam factor with the geometric factor, a matching relationship between them is found by using the optimized parameters. Based on the simulation results, a method to optimize the incident beam parameters is proposed, which is applied to the 32-beam and 48-beam irradiation configurations. The results show that there is a set of optimal incident beam parameters which can attain the highest irradiation uniformity for a given configuration. The feasibility to achieve more uniform irradiation by optimizing the incident beam parameters is proved. When the single beam factor is optimized in a directly driven inertial confinement fusion system, the restrictions on the beam pointing error and power imbalance between incident beams can be relaxed. The results provide an effective method of designing and optimizing the uniform irradiation system of direct drive laser facility.
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Keywords:
- inertial confinement fusion /
- direct drive /
- irradiation uniformity /
- incident beam parameters
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[2] Miller G H, Moses E I, Wuest C R 2004 Opt. Eng. 43 2841
[3] Fleurot N, Cavailler C, Bourgade J L 2005 Fusion Eng. Des. 74 147
[4] Zheng W, Zhang X, Wei X, Jing F, Sui Z, Zheng K, Yuan X, Jiang X, Su J, Zhou H, Li M 2008 J. Phys. Conf. Ser. 112 032009
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[6] Hallo L, Olazabal-Loumé M, Ribeyre X, Dréan V, Schurtz G, Feugeas J L, Breil J, Nicolaï P, Maire P H 2008 Plasma Phys. Control. Fusion 51 014001
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[8] Bodner S E 1981 J. Fusion Energy 1 221
[9] Skupsky S, Lee K 1983 J. Appl. Phys. 54 3662
[10] Emery M H, Gardner J H, Boris J P 1982 Phys. Rev. Lett. 48 677
[11] Gardner J H, Bodner S E 1981 Phys. Rev. Lett. 47 1137
[12] Zhang R, Li P, Su J Q, Wang J J, Li H, Geng Y C, Liang Y, Zhao R C, Dong J, Lu Z G, Zhou L D, Liu L Q, Lin H H, Xu D P, Deng Y, Zhu N, Jing F, Sui Z, Zhang X M 2012 Acta Phys. Sin. 61 054204 (in Chinese) [张锐, 李平, 粟敬钦, 王建军, 李海, 耿远超, 梁樾, 赵润昌, 董军, 卢宗贵, 周丽丹, 刘兰琴, 林宏奂, 许党朋, 邓颖, 朱娜, 景峰, 隋展, 张小民 2012 物理学报 61 054204]
[13] Liu L Q, Zhang Y, Geng Y C, Wang W Y, Zhu Q H, Jing F, Wei X F, Huang W Q 2014 Acta Phys. Sin. 63 164201 (in Chinese) [刘兰琴, 张颖, 耿远超, 王文义, 朱启华, 景峰, 魏晓峰, 黄晚晴 2014 物理学报 63 164201]
[14] Li P, Wang W, Zhao R C, Geng Y C, Jia H T, Su J Q 2014 Acta Phys. Sin. 63 215202 (in Chinese) [李平, 王伟, 赵润昌, 耿远超, 贾怀庭, 粟敬钦 2014 物理学报 63 215202]
[15] Garanin S G, Derkach V N, Shnyagin R A 2004 Quantum Electron. 34 427
[16] Schmitt A J 1984 Appl. Phys. Lett. 44 399
[17] Murakami M 1995 Appl. Phys. Lett. 66 1587
[18] Seidel J J 2001 J. Stat. Plan. Infer. 95 307
[19] Murakami M, Sarukura N, Azechi H, Temporal M, Schmitt A J 2010 Phys. Plasmas 17 082702
[20] Xu T, Xu L, Wang A, Gu C, Wang S, Liu J, Wei A 2013 Phys. Plasmas 20 122702
[21] Temporal M, Canaud B, Garbett W J, Ramis R 2015 Phys. Plasmas 22 102709
[22] Kruer W L 2003 The Physics of Laser Plasma Interactions (Oxford: Westview Press) p45
[23] Xu T 2014 Ph. D. Dissertation (Hefei: University of Science and Technology of China) (in Chinese) [徐腾 2014 博士学位论文 (合肥: 中国科学技术大学)]
[24] Li L, Gu C, Xu L, Zhou S 2016 Phys. Plasmas 23 043103
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[1] Lindl J 1995 Phys. Plasmas 2 3933
[2] Miller G H, Moses E I, Wuest C R 2004 Opt. Eng. 43 2841
[3] Fleurot N, Cavailler C, Bourgade J L 2005 Fusion Eng. Des. 74 147
[4] Zheng W, Zhang X, Wei X, Jing F, Sui Z, Zheng K, Yuan X, Jiang X, Su J, Zhou H, Li M 2008 J. Phys. Conf. Ser. 112 032009
[5] Bodner S E, Colombant D G, Gardner J H, Lehmberg R H, Obenschain S P, Phillips L, Schmitt A J, Sethian J D, McCrory R L, Seka W, Verdon C P 1998 Phys. Plasmas 5 1901
[6] Hallo L, Olazabal-Loumé M, Ribeyre X, Dréan V, Schurtz G, Feugeas J L, Breil J, Nicolaï P, Maire P H 2008 Plasma Phys. Control. Fusion 51 014001
[7] Boehly T R, Brown D L, Craxton R S, Keck R L, Knauer J P, Kelly J H, Kessler T J, Kumpan S A, Loucks S J, Letzring S A, Marshall F J 1997 Opt. Commun. 133 495
[8] Bodner S E 1981 J. Fusion Energy 1 221
[9] Skupsky S, Lee K 1983 J. Appl. Phys. 54 3662
[10] Emery M H, Gardner J H, Boris J P 1982 Phys. Rev. Lett. 48 677
[11] Gardner J H, Bodner S E 1981 Phys. Rev. Lett. 47 1137
[12] Zhang R, Li P, Su J Q, Wang J J, Li H, Geng Y C, Liang Y, Zhao R C, Dong J, Lu Z G, Zhou L D, Liu L Q, Lin H H, Xu D P, Deng Y, Zhu N, Jing F, Sui Z, Zhang X M 2012 Acta Phys. Sin. 61 054204 (in Chinese) [张锐, 李平, 粟敬钦, 王建军, 李海, 耿远超, 梁樾, 赵润昌, 董军, 卢宗贵, 周丽丹, 刘兰琴, 林宏奂, 许党朋, 邓颖, 朱娜, 景峰, 隋展, 张小民 2012 物理学报 61 054204]
[13] Liu L Q, Zhang Y, Geng Y C, Wang W Y, Zhu Q H, Jing F, Wei X F, Huang W Q 2014 Acta Phys. Sin. 63 164201 (in Chinese) [刘兰琴, 张颖, 耿远超, 王文义, 朱启华, 景峰, 魏晓峰, 黄晚晴 2014 物理学报 63 164201]
[14] Li P, Wang W, Zhao R C, Geng Y C, Jia H T, Su J Q 2014 Acta Phys. Sin. 63 215202 (in Chinese) [李平, 王伟, 赵润昌, 耿远超, 贾怀庭, 粟敬钦 2014 物理学报 63 215202]
[15] Garanin S G, Derkach V N, Shnyagin R A 2004 Quantum Electron. 34 427
[16] Schmitt A J 1984 Appl. Phys. Lett. 44 399
[17] Murakami M 1995 Appl. Phys. Lett. 66 1587
[18] Seidel J J 2001 J. Stat. Plan. Infer. 95 307
[19] Murakami M, Sarukura N, Azechi H, Temporal M, Schmitt A J 2010 Phys. Plasmas 17 082702
[20] Xu T, Xu L, Wang A, Gu C, Wang S, Liu J, Wei A 2013 Phys. Plasmas 20 122702
[21] Temporal M, Canaud B, Garbett W J, Ramis R 2015 Phys. Plasmas 22 102709
[22] Kruer W L 2003 The Physics of Laser Plasma Interactions (Oxford: Westview Press) p45
[23] Xu T 2014 Ph. D. Dissertation (Hefei: University of Science and Technology of China) (in Chinese) [徐腾 2014 博士学位论文 (合肥: 中国科学技术大学)]
[24] Li L, Gu C, Xu L, Zhou S 2016 Phys. Plasmas 23 043103
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