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具有合适径向密度分布的等离子体通道可以用于超短超强激光导引, 这使得等离子体通道在激光尾波加速中有着重要的应用. 本文介绍了在上海交通大学激光等离子体实验室开展的毛细管放电和光导引实验. 通过光谱展宽法测量了充氦气的放电毛细管中的等离子体密度分布, 在长度为3 cm、内径为300 μm的毛细管中实现了轴向均匀, 径向呈抛物线型的等离子体密度分布. 通过改变放电延时和喷气时长, 确定和优化了产生等离子体通道的参数区间, 得到的最大通道深度为28 μm, 与实验中使用的激光焦斑半径匹配. 在此基础之上, 开展了不同能量的激光脉冲在放电等离子体通道中的导引研究, 结果发现当通道深度与焦斑半径匹配时, 激光可以不散焦地在通道中传输, 实现激光导引. 这项研究为未来的激光尾波级联加速和锁相加速等研究奠定了基础.
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关键词:
- 激光等离子体相互作用 /
- 激光等离子体尾波加速 /
- 等离子体波导
Preformed plasma channels play important roles in many applications, such as laser wakefield acceleration, plasma lens, and so on. Laser pulses can be well guided when the radial density distribution of the plasma channel has a parabolic profile and it is matched with the laser focus. Discharging a gas-filled capillary is a possible way to form such plasma channels. In this work, we report the capillary discharging and laser guiding experiments performed in the Laboratory for Laser Plasmas at Shanghai Jiao Tong University. The plasma density distributions in the Helium-filled discharged capillary are measured by using the spectral broadening method. In a capillary with a length of 3 cm and a diameter of 300 μm, the plasma density profile is observed to be uniformly distributed along the axial direction and have a parabolic profile along the radial direction. Parameters for plasma channel generation are scanned. The deepest channel depth obtained is 28 μm, which is close to the focal spot radius of the laser used in the experiment. Laser guidance in the plasma channel is also studied. The results show that the laser can maintain its focus and continuously propagate when the channel depth matches the focal spot, indicating that the well guiding of the laser pulse by the preformed plasma channel is obtained. These studies may serve as the ground work for the future studies, such as staged laser wakefield acceleration and phase-locked wakefield acceleration.[1] Tajima T, Dawson J M 1979 Phys. Rev. Lett. 43 267
Google Scholar
[2] Esarey E, Schroeder C B, Leemans W P 2009 Rev. Mod. Phys. 81 1229
Google Scholar
[3] Chen M, Liu F, Li B Y, Weng S M, Chen L M, Sheng Z M, Zhang J 2020 High Power Laser and Particle Beams 32 092001
Google Scholar
[4] Steinke S, van Tilborg J, Benedetti C, Geddes C G R, Schroeder C B, Daniels J, Swanson K K, Gonsalves A J, Nakamura K, Matlis N H, Shaw B H, Esarey E, Leemans W P 2016 Nature 530 190
Google Scholar
[5] Luo J, Chen M, Wu W Y, Weng S M, Sheng Z G, Schroeder C B, Jaroszynski D A, Esarey E, Leemans W P, Mori W B, Zhang J 2018 Phys. Rev. Lett. 120 154801
Google Scholar
[6] Rittershofer W, Schroeder C B, Esarey E, Gruner F J, Leemans W P 2010 Phys. Plasmas 17 063104
Google Scholar
[7] Li W T, Liu J S, Wang W T, Zhang Z J, Chen Q, Tian Y, Qi R, Yu C H, Wang C, Tajima T, Li R X, Xu Z Z 2014 Appl. Phys. Lett. 104 093510
Google Scholar
[8] Sadler J D, Arran C, Li H, Flippo K A 2020 Phys. Rev. Accel. Beams 23 021303
Google Scholar
[9] Palastro J P, Shaw J L, Franke P, Ramsey D, Simpson T T, Froula D H 2020 Phys. Rev. Lett. 124 134802
Google Scholar
[10] Palastro J P, Malaca B, Vieira J, Ramsey D, Simpson T T, Franke P, Shaw J L, Froula D H 2021 Phys. Plasmas 28 013109
Google Scholar
[11] Steinhauer L C, Ahlstrom H G 1971 Phys. Fluids 14 1109
Google Scholar
[12] Sprangle P, Esarey E, Krall J, Joyce G 1992 Phys. Rev. Lett. 69 2200
Google Scholar
[13] Zigler A, Ehrlich Y, Cohen C, Krall J, Sprangle P 1996 J. Opt. Soc. Am. B 13 68
Google Scholar
[14] Hooker S M, Spence D J, Smith R A 2000 J. Opt. Soc. Am. B 17 90
Google Scholar
[15] Gonsalves A J, Rowlands-Rees T P, Broks B H P, van der Mullen J J A M, Hooker S M 2007 Phys. Rev. Lett. 98 025002
Google Scholar
[16] Esarey E, Sprangle P, Krall J, Ting A, Joyce G 1993 Phys. Fluids B:Plasma Physics 5 2690
Google Scholar
[17] Nakamurac K, Naglerd B, Tóth Cs, Geddes C G R, Schroeder C B, Gonsalvesf A J, Hooker S M, Esarey E, Leemanse W P 2007 Phys. Plasmas 14 056708
Google Scholar
[18] Gonsalves A J, Nakamura K, Daniels J, Benedetti C, Pieronek C, de Raadt T C H, Steinke S, Bin J H, Bulanov S S, van Tilborg J, Geddes C G R, Schroeder C B, Tóth Cs, Esarey E, Swanson K, Fan-Chiang L, Bagdasarov G, Bobrova N, Gasilov V, Korn G, Sasorov P, Leemans W P 2019 Phys. Rev. Lett. 122 084801
Google Scholar
[19] Miao B, Feder L, Shrock J E, Goffin A, Milchberg H M 2020 Phys. Rev. Lett. 125 074801
Google Scholar
[20] Ta Phuoc K, Corde S, Shah R, Albert F, Fitour R, Rousseau J P, Burgy F, Mercier B, Rousse A 2006 Phys. Rev. Lett. 97 225002
Google Scholar
[21] Katsouleas S W T, Su J D J 1987 Part. Accel 22 81
[22] Schroeder C B, Benedetti C, Esarey E, Leemans W P 2013 Phys. Plasmas 20 123115
Google Scholar
[23] Lu W, Tzoufras M, Joshi C, Tsung F S, Mori W B, Vieira J, Fonseca R A, Silva L O 2007 Phys. Rev. Spec. Top. -Ac 10 061301
[24] Esarey E, Krall J, Sprangle P 1994 Phys. Rev. Lett. 72 2887
Google Scholar
[25] Hosokai T, Kando M, Dewa H, Kotaki H, Kondo S 2000 Optics Lett. 25 10
Google Scholar
[26] Ehrlich Y, Cohen C, Kaganovich D, Zigler A, Hubbard R F, Sprangle P, Esarey E 1998 J. Opt. Soc. Am. B 15 2416
Google Scholar
[27] Mangles S P D, Murphy C D, Najmudin Z, Thomas A G R, Collier J L, Dangor A E, Divall E J, Foster P S, Gallacher J G, Hooker C J, Jaroszynski D A, Langley A J, Mori W B, Norreys P A, Tsung F S, Viskup R, Walton B R, Krushelnick K 2004 Nature 431 7008
[28] Gaul E W, Le Blanc S P, Rundquist A R, Zgadzaj R, Langhoff H, Downer M C 2000 Appl. Phys. Lett. 77 4112
Google Scholar
[29] Griem H R, Baranger M, Kolb A C, Oertel G 1962 Phys. Rev. 125 177
Google Scholar
[30] Nikiforov A Y, Leys C, Gonzalez M A, Walsh J L 2015 Plasma Sources Sci. Technol. 24 034001
Google Scholar
[31] Hiromitsu T, Nadezhda B, Pavel S, Takashi K, Toru S, Takeshi H, Noboru Y, Ryosuke K 2011 J. Appl. Phys. 109 053304
Google Scholar
[32] Guillaume E, Döpp A, Thaury C, Ta Phuoc K, Lifschitz A, Grittani G, Goddet J P, Tafzi A, Chou S W, Veisz L, Malka V 2015 Phys. Rev. Lett. 115 155002
Google Scholar
[33] Zhu X Z, Chen M, Li B Y, Liu F, Ge X L, Sheng Z M, Zhang J 2022 Phys. Plasmas 29 013101
Google Scholar
[34] Wang W T, Feng K, Ke L T, Yu C H, Xu Y, Qi R, Chen Y, Qin Z Y, Zhang Z J, Fang M, Liu J Q, Jiang K N, Wang H, Wang C, Yang X J, Wu F X, Leng Y X, Liu J S, Li R X, Xu Z Z 2021 Nature 595 516
Google Scholar
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图 1 上海交通大学激光等离子体实验室用于激光尾波加速的放电毛细管装置
Fig. 1. Discharged capillary for laser wakefield accelerator at the Laboratory for Laser Plasmas, SJTU.
图 2 毛细管的放电电路和电流 (a) 毛细管放电电路图; (b) 典型的放电电流
Fig. 2. Capillary discharge circuit and current: (a) Discharge circuit; (b) typical discharge current.
图 3 使用Stark展宽标定He放电等离子体的密度 (a) 氦等离子体的谱线; (b) 谱线在587.6 nm附近的展宽; (c) 在放电电压10 kV, 背压15 psi (1 psi = 6.89476 × 103 Pa)时测量到的等离子体密度
Fig. 3. Measuring the density of Helium plasma with Stark broadening: (a) Spectra of Helium plasma; (b) spectra broadening at 587.6 nm; (c) plasma density at 10 kV and 15 psi backpressure.
图 4 在放电电压10 kV, 充气背压5 psi 下毛细管的轴向放电光谱和密度 (a)探测器示意图; (b)轴向放电光谱; (c)轴向等离子体密度
Fig. 4. On-axis discharge spectrum and density distribution of the capillary at 10 kV and 5 psi: (a) Schematic of the detector; (b) the axial spectra along the capillary; (c) the axial plasma density.
图 5 在15 kV下毛细管放电时的端面光谱和径向等离子体密度分布 (a) 500 μm 毛细管的径向光谱; (b) 300 μm 毛细管的径向光谱; (c) 500 μm毛细管的径向密度分布; (d) 300 μm毛细管的径向密度分布
Fig. 5. End-face spectra detected during the discharge and the radial plasma density distribution at 15 kV: (a) Spectra of 500 μm capillary; (b) spectra of 300 μm capillary; (c) radial density distribution of 500 μm capillary; (d) radial density distribution of 300 μm capillary.
图 6 300 μm口径毛细管的通道半径和中轴线密度随放电时间和背压的演化 (a)
$ {r}_{0} $ 和$ {n}_{0} $ 随时间的演化; (b)$ {r}_{0} $ 和$ {n}_{0} $ 随背压的演化Fig. 6. Evolutions of the channel radius and the on-axis density in the capillary with 300 μm inner diameter: (a)
$ {r}_{0} $ and$ {n}_{0} $ evolution with time; (b)$ {r}_{0} $ and$ {n}_{0} $ evolution with backpressure.
图 7 毛细管的光导引实验装置示意图
Fig. 7. Schematic of laser guiding by discharged capillary experiment.
图 8 放电毛细管导引小能量激光 (a) 毛细管前的激光焦斑; (b) 正中心入射穿过通道的激光光斑; (c) 偏轴10 μm 入射穿过通道的激光光斑; (d) 偏轴20 μm 入射穿过通道的激光光斑
Fig. 8. Small energy laser guiding by discharged capillary: (a) Laser spot before capillary; (b) laser spot after capillary for on-axis incidence; (c) laser spot after capillary for 10 μm off-axis incidence; (d) laser spot after capillary for 20 μm off-axis incidence.
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[1] Tajima T, Dawson J M 1979 Phys. Rev. Lett. 43 267
Google Scholar
[2] Esarey E, Schroeder C B, Leemans W P 2009 Rev. Mod. Phys. 81 1229
Google Scholar
[3] Chen M, Liu F, Li B Y, Weng S M, Chen L M, Sheng Z M, Zhang J 2020 High Power Laser and Particle Beams 32 092001
Google Scholar
[4] Steinke S, van Tilborg J, Benedetti C, Geddes C G R, Schroeder C B, Daniels J, Swanson K K, Gonsalves A J, Nakamura K, Matlis N H, Shaw B H, Esarey E, Leemans W P 2016 Nature 530 190
Google Scholar
[5] Luo J, Chen M, Wu W Y, Weng S M, Sheng Z G, Schroeder C B, Jaroszynski D A, Esarey E, Leemans W P, Mori W B, Zhang J 2018 Phys. Rev. Lett. 120 154801
Google Scholar
[6] Rittershofer W, Schroeder C B, Esarey E, Gruner F J, Leemans W P 2010 Phys. Plasmas 17 063104
Google Scholar
[7] Li W T, Liu J S, Wang W T, Zhang Z J, Chen Q, Tian Y, Qi R, Yu C H, Wang C, Tajima T, Li R X, Xu Z Z 2014 Appl. Phys. Lett. 104 093510
Google Scholar
[8] Sadler J D, Arran C, Li H, Flippo K A 2020 Phys. Rev. Accel. Beams 23 021303
Google Scholar
[9] Palastro J P, Shaw J L, Franke P, Ramsey D, Simpson T T, Froula D H 2020 Phys. Rev. Lett. 124 134802
Google Scholar
[10] Palastro J P, Malaca B, Vieira J, Ramsey D, Simpson T T, Franke P, Shaw J L, Froula D H 2021 Phys. Plasmas 28 013109
Google Scholar
[11] Steinhauer L C, Ahlstrom H G 1971 Phys. Fluids 14 1109
Google Scholar
[12] Sprangle P, Esarey E, Krall J, Joyce G 1992 Phys. Rev. Lett. 69 2200
Google Scholar
[13] Zigler A, Ehrlich Y, Cohen C, Krall J, Sprangle P 1996 J. Opt. Soc. Am. B 13 68
Google Scholar
[14] Hooker S M, Spence D J, Smith R A 2000 J. Opt. Soc. Am. B 17 90
Google Scholar
[15] Gonsalves A J, Rowlands-Rees T P, Broks B H P, van der Mullen J J A M, Hooker S M 2007 Phys. Rev. Lett. 98 025002
Google Scholar
[16] Esarey E, Sprangle P, Krall J, Ting A, Joyce G 1993 Phys. Fluids B:Plasma Physics 5 2690
Google Scholar
[17] Nakamurac K, Naglerd B, Tóth Cs, Geddes C G R, Schroeder C B, Gonsalvesf A J, Hooker S M, Esarey E, Leemanse W P 2007 Phys. Plasmas 14 056708
Google Scholar
[18] Gonsalves A J, Nakamura K, Daniels J, Benedetti C, Pieronek C, de Raadt T C H, Steinke S, Bin J H, Bulanov S S, van Tilborg J, Geddes C G R, Schroeder C B, Tóth Cs, Esarey E, Swanson K, Fan-Chiang L, Bagdasarov G, Bobrova N, Gasilov V, Korn G, Sasorov P, Leemans W P 2019 Phys. Rev. Lett. 122 084801
Google Scholar
[19] Miao B, Feder L, Shrock J E, Goffin A, Milchberg H M 2020 Phys. Rev. Lett. 125 074801
Google Scholar
[20] Ta Phuoc K, Corde S, Shah R, Albert F, Fitour R, Rousseau J P, Burgy F, Mercier B, Rousse A 2006 Phys. Rev. Lett. 97 225002
Google Scholar
[21] Katsouleas S W T, Su J D J 1987 Part. Accel 22 81
[22] Schroeder C B, Benedetti C, Esarey E, Leemans W P 2013 Phys. Plasmas 20 123115
Google Scholar
[23] Lu W, Tzoufras M, Joshi C, Tsung F S, Mori W B, Vieira J, Fonseca R A, Silva L O 2007 Phys. Rev. Spec. Top. -Ac 10 061301
[24] Esarey E, Krall J, Sprangle P 1994 Phys. Rev. Lett. 72 2887
Google Scholar
[25] Hosokai T, Kando M, Dewa H, Kotaki H, Kondo S 2000 Optics Lett. 25 10
Google Scholar
[26] Ehrlich Y, Cohen C, Kaganovich D, Zigler A, Hubbard R F, Sprangle P, Esarey E 1998 J. Opt. Soc. Am. B 15 2416
Google Scholar
[27] Mangles S P D, Murphy C D, Najmudin Z, Thomas A G R, Collier J L, Dangor A E, Divall E J, Foster P S, Gallacher J G, Hooker C J, Jaroszynski D A, Langley A J, Mori W B, Norreys P A, Tsung F S, Viskup R, Walton B R, Krushelnick K 2004 Nature 431 7008
[28] Gaul E W, Le Blanc S P, Rundquist A R, Zgadzaj R, Langhoff H, Downer M C 2000 Appl. Phys. Lett. 77 4112
Google Scholar
[29] Griem H R, Baranger M, Kolb A C, Oertel G 1962 Phys. Rev. 125 177
Google Scholar
[30] Nikiforov A Y, Leys C, Gonzalez M A, Walsh J L 2015 Plasma Sources Sci. Technol. 24 034001
Google Scholar
[31] Hiromitsu T, Nadezhda B, Pavel S, Takashi K, Toru S, Takeshi H, Noboru Y, Ryosuke K 2011 J. Appl. Phys. 109 053304
Google Scholar
[32] Guillaume E, Döpp A, Thaury C, Ta Phuoc K, Lifschitz A, Grittani G, Goddet J P, Tafzi A, Chou S W, Veisz L, Malka V 2015 Phys. Rev. Lett. 115 155002
Google Scholar
[33] Zhu X Z, Chen M, Li B Y, Liu F, Ge X L, Sheng Z M, Zhang J 2022 Phys. Plasmas 29 013101
Google Scholar
[34] Wang W T, Feng K, Ke L T, Yu C H, Xu Y, Qi R, Chen Y, Qin Z Y, Zhang Z J, Fang M, Liu J Q, Jiang K N, Wang H, Wang C, Yang X J, Wu F X, Leng Y X, Liu J S, Li R X, Xu Z Z 2021 Nature 595 516
Google Scholar
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