背景气体对激光等离子体和外磁场界面上槽纹不稳定性的影响

张振驰; 唐桧波; 王金灿; 佀化冲; 王志; 蓝翔; 胡广月

doi:10.7498/aps.72.20231108

摘要

等离子体在外磁场中膨胀产生的抗磁腔和不稳定性是空间物理和聚变物理中的重要现象. 本文实验研究了激光产生的等离子体在外磁场中膨胀时在抗磁腔表面产生的槽纹不稳定性, 数据分析显示实验中观察到的不稳定性属于大拉莫尔半径槽纹不稳定性. 实验发现充入稀薄背景气体能够显著抑制槽纹不稳定性的发展, 背景气体气压超过50 Pa时(约为抗磁腔表面等离子体密度的1%), 槽纹不稳定性几乎被完全抑制. 动理学分析表明离子-离子碰撞是抑制不稳定性发展的主要因素. 这些结果对磁场辅助激光聚变和爆炸空间物理现象等领域有重要参考价值.

关键词:

Abstract

Diamagnetic cavity and flute instability generated by plasma expansion in an external magnetic field are important phenomena in space and fusion physics. We use a nanosecond laser irradiated carbon planar target to generate plasma, and the plasma expands in a 7 T transverse pulsed magnetic field to produce diamagnetic cavity. The flute instabilities formed on the surface of the diamagnetic cavity are explored experimentally. Data analysis shows that, under our experimental parameters, the gyroradius of electron ($ {\rho }_{{\rm{e}}} $) is much smaller than the density gradient scale length of the diamagnetic cavity ($ {L}_{{\rm{n}}} $), while the ion’s gyroradius ($ {\rho }_{{\rm{i}}} $) is much larger than $ {L}_{{\rm{n}}} $, indicating that the electrons are magnetized while the ions are not. The relative drift between electrons and ions provides free energy for developing the flute instability, which is composed of gravity drift and diamagnetic drift. The calculation shows that the gravity drift velocity is much larger than the diamagnetic drift velocity in our experiment, so the instability belongs to the large Larmor radius instability. By filling the target chamber with rarefied helium ambient gas, we find that the flute instabilities are inhibited significantly. When the ambient gas pressure exceeds 50 Pa (about 1% of the interface plasma density of diamagnetic cavity), the flute instabilities are almost completely suppressed. Kinetic analyses show that ion-ion collision and electron-ion collision, especially the former, are the main effects that inhibit the development of instability. Our results are of benefit to laser fusion and address the fundamental question of explored space phenomena.

Keywords:

作者及机构信息

1.
中国科学技术大学核科学技术学院, 中国科学院近地空间环境重点实验室, 合肥　230026

2.
中国科学院上海光学精密机械研究所, 中国科学院超强激光科学卓越创新中心, 上海　201800

3.
哈尔滨工业大学物理学院, 哈尔滨　150001

通信作者: 唐桧波, tanghb@ustc.edu.cn ; 胡广月, gyhu@ustc.edu.cn

基金项目: 国家自然科学基金(批准号: 12175230, 11775223, 12205298)、中国科学院战略先导专项项目(批准号: XDB16)和中央高校基本科研业务费专项资金资助的课题.

Authors and contacts

1.
Key Laboratory of Near Earth Space Environment of Chinese Academy of Sciences, School of Nuclear Science and Technology, University of Science and Technology of China, Hefei 230026, China

2.
Ultra Intense Laser Science Excellence and Innovation Center of Chinese Academy of Sciences, Shanghai Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Shanghai 201800, China

3.
School of Physics, Harbin Institute of Technology, Harbin 150001, China

Corresponding author: Tang Hui-Bo, tanghb@ustc.edu.cn ; Hu Guang-Yue, gyhu@ustc.edu.cn

Funds: Project supported by the National Natural Science Foundation of China (Grant Nos. 12175230, 11775223, 12205298), the Strategic Priority Research Program of Chinese Academy of Sciences, China (Grant No. XDB16), and the Fundamental Research Funds for the Central Universities of China.

文章全文 : translate this paragraph

参考文献

[1]	Lühr H, Klöcker N, Acuña M H 1988 Adv. Space Res. 8 11
[2]	Bernhardt P A 1992 Phys. Fluids B 4 2249 Google Scholar
[3]	Valenzuela A, Haerendel G, Föppl H, Melzner F, Neuss H, Rieger E, Stöcker J, Bauer O, Höfner H, Loidl J 1986 Nature 320 700 Google Scholar
[4]	Bernhardt P A, Roussel-Dupre R A, Pongratz M B, Haerendel G, Valenzuela A, Gurnett D A, Anderson R R 1987 J. Geophys. Res. Space Phys. 92 5777 Google Scholar
[5]	Dimonte G, Wiley L G 1991 Phys. Rev. Lett. 67 1755 Google Scholar
[6]	Peyser T A, Manka C K, Ripin B H, Ganguli G 1992 Phys. Fluids B 4 2448 Google Scholar
[7]	Collette A, Gekelman W 2011 Phys. Plasmas 18 055705 Google Scholar
[8]	Zakharov Y P 2002 Adv. Space. Res. 29 1335 Google Scholar
[9]	Yao W P, Capitaine J, Khiar B, Vinci T, Burdonov K, Béard J, Fuchs J, Ciardi A 2022 Matter Radiat. Extremes 7 026903 Google Scholar
[10]	Plechaty C, Presura R, Esaulov A A 2013 Phys. Rev. Lett. 111 185002 Google Scholar
[11]	Ripin B H, McLean E A, Manka C K, Pawley C, Stamper J A, Peyser T A, Mostovych A N, Grun J, Hassam A B, Huba J D 1987 Phys. Rev. Lett. 59 2299 Google Scholar
[12]	Brecht S H, Gladd N T 1992 IEEE Trans. Plasma Sci. 20 678 Google Scholar
[13]	Tang H B, Hu G Y, Liang Y H, Wang Y L, Tao T, Hu P, Yuan P, Zhu P, Zuo Y, Zhao B, Zheng J 2020 Phys. Plasmas 27 022108 Google Scholar
[14]	Tang H B, Hu G Y, Liang Y H, Tao T, Wang Y L, Hu P, Zhao B, Zheng J 2018 Plasma Phys. Controlled Fusion 60 055005 Google Scholar
[15]	Hu P, Zhao J Y, Wang J C, Zhang Z C, Tang H B, Hu G Y 2022 J. Instrum. 17 P07036 Google Scholar
[16]	Wang Y L, Hu G Y, Hu P, Liang Y H, Yuan P, Zheng J 2019 Rev. Sci. Instrum. 90 075108 Google Scholar
[17]	Hu P, Hu G Y, Wang Y L, Tang H B, Zhang Z C, Zheng J 2020 Rev. Sci. Instrum. 91 014703 Google Scholar
[18]	Hassam A B, Huba J D 1987 Geophys. Res. Lett. 14 60 Google Scholar
[19]	Gisler G, Lemons D S 1989 J. Geophys. Res. Space Phys. 94 10145 Google Scholar
[20]	Winske D 1988 J. Geophys. Res. Space Phys. 93 2539 Google Scholar
[21]	Huba J D, Hassam A B, Winske D 1990 Phys. Fluids B 2 1676 Google Scholar
[22]	Ali A W, McLean E A 1985 J. Quant. Spectrosc. Radiat. Transfer 33 381 Google Scholar
[23]	Fiuza F, Swadling G F, Grassi A, et al. 2020 Nat. Phys. 16 916 Google Scholar

施引文献

图 1 实验设置

Fig. 1. Experimental setup.

下载: 全尺寸图片幻灯片

图 2 飞秒激光干涉测量的不同背景气压下碳等离子体在20 ns时刻形成的抗磁腔和槽纹不稳定性　(a) 真空背景(0.01 Pa); (b)—(l) 背景气体气压从10—800 Pa变化. 虚线位置为初始靶位, 其左侧是从干涉条纹图解相位时产生的无效数据

Fig. 2. Structures of diamagnetic cavity and flute instability at 20 ns after laser ablation measured by femtosecond laser optical interferometry: (a) Vacuum ambient at 0.01 Pa; (b)–(l) ambient helium gas with pressure from 10–800 Pa. The left side of dotted line (the target surface) is invalid data generated by the process of phase unwrapping from interferogram fringes.

下载: 全尺寸图片幻灯片

图 3 不稳定性结构图2(a)—(e)的局部放大图

Fig. 3. Enlarged views of the flute instability of Fig. 2(a)-(e).

下载: 全尺寸图片幻灯片

图 4 不稳定性结构的振幅和波长随气压的变化

Fig. 4. Amplitude and wavelength of instability structure vs. ambient gas pressure.

下载: 全尺寸图片幻灯片

图 5 抗磁腔尺寸和射流长度随气压的变化

Fig. 5. Diamagnetic cavity size and jet length vs. ambient gas pressure.

下载: 全尺寸图片幻灯片

图 6 抗磁腔两侧电子密度随气压的变化

Fig. 6. Lined integrated electron density at the surface of the diamagnetic cavity vs. ambient gas pressure.

下载: 全尺寸图片幻灯片

图 7 密度梯度标长随气压的变化. 认为等离子体为球形膨胀, 选取打靶点为球心, 从 θ = 40°, 50°, 60°, 70°四个角度测量梯度标长

Fig. 7. Density gradient scale length at the surface of diamagnetic cavity vs. ambient gas pressure. Considering that the plasma expands spherically around the laser irradiated target, the gradient scale lengths are measured at four angles of θ = 40°, 50°, 60°, 70°.

下载: 全尺寸图片幻灯片

图 8 不同气压时的不稳定性色散曲线, 实线同时包含离子-离子碰撞项和电子-离子碰撞项　(a) 虚线仅包含离子-离子碰撞; (b) 虚线仅包含电子-离子碰撞

Fig. 8. Instability dispersion curves at different gas pressures, the solid lines include both ion-ion and electron-ion collision effect: (a) Dashed lines include only the ion-ion collision; (b) dashed lines include only the electron-ion collision.

下载: 全尺寸图片幻灯片

图 9 计算的不同气压时的不稳定性增长, 实线同时包含了离子-离子碰撞项和电子-离子碰撞项　(a) 虚线仅包含离子-离子碰撞项; (b) 虚线仅包含电子-离子碰撞

Fig. 9. Growth rates calculated at various gas pressure, the solid lines include both ion-ion and electron-ion collision effect: (a) Dashed lines include only the ion-ion collision; (b) dashed lines include only the electron-ion collision.

下载: 全尺寸图片幻灯片

图 10 不稳定性增长率随气压的变化

Fig. 10. Instability growth rate vs. ambient gas pressure.

下载: 全尺寸图片幻灯片

表 1 真空背景(0.01 Pa)时典型的等离子体参数

Table 1. Characteristic plasma parameters at vacuum (0.01 Pa) ambient conditions.

参数	符号	真空条件下的值
靶材料	—	C
有效电荷数	Z	4.5
磁场强度/T	B	7
界面电子密度/(10¹⁸ cm^–3)	n_e	3
离子初始速度/(μm·ns^–1)	V_i0	150
电子温度/eV	T_e	20—50
离子温度/eV	T_i	20—50
电子热速度/(μm·ns^–1)	V_e	2300
离子热速度/(μm·ns^–1)	V_i	15.5
不稳定性增长率/ns^–1	γ	0.3
不稳定性波长(μm)	λ	120
等效加速度/(μm·ns^–2)	g	5.8
密度梯度标长/μm	L_n	300
等效“重力”漂移速度(μm·ns^–1)	V_g	23.1
抗磁漂移速度/(μm·ns^–1)	V_di	2.5
总漂移速度/(μm·ns^–1)	V_E	25.6
离子回旋半径/μm	ρ_i	604
电子回旋半径/μm	ρ_e	1.9
电子回旋频率/(10¹² rad·s^–1)	ω_ce	1.2
离子回旋频率/(10⁸ rad·s^–1)	ω_ci	2.5
低杂化频率/(10⁶ rad·s^–1)	ω_lh	3.6
电子等离子体频率/(10¹³ rad·s^–1)	ω_pe	6.5
离子等离子体频率/(10¹¹ rad·s^–1)	ω_pi	9.3
磁约束半径/mm	R_B	1
背景气体密度/(10¹² cm^–3)	n_b	2.4
离子-离子碰撞频率/(10⁵ s^–1)	$ {\nu }_{{\rm{i}}{\rm{i}}\text{'}} $	5.1
电子-离子碰撞频率/(10⁵ s^–1)	$ {\nu }_{{\rm{e}}{\rm{i}}\text{'}} $	2.3
电子扩散系数/(10⁵ μm²·s^–1)	D_e	4.1

下载: 导出CSV

[1]	Lühr H, Klöcker N, Acuña M H 1988 Adv. Space Res. 8 11
[2]	Bernhardt P A 1992 Phys. Fluids B 4 2249 Google Scholar
[3]	Valenzuela A, Haerendel G, Föppl H, Melzner F, Neuss H, Rieger E, Stöcker J, Bauer O, Höfner H, Loidl J 1986 Nature 320 700 Google Scholar
[4]	Bernhardt P A, Roussel-Dupre R A, Pongratz M B, Haerendel G, Valenzuela A, Gurnett D A, Anderson R R 1987 J. Geophys. Res. Space Phys. 92 5777 Google Scholar
[5]	Dimonte G, Wiley L G 1991 Phys. Rev. Lett. 67 1755 Google Scholar
[6]	Peyser T A, Manka C K, Ripin B H, Ganguli G 1992 Phys. Fluids B 4 2448 Google Scholar
[7]	Collette A, Gekelman W 2011 Phys. Plasmas 18 055705 Google Scholar
[8]	Zakharov Y P 2002 Adv. Space. Res. 29 1335 Google Scholar
[9]	Yao W P, Capitaine J, Khiar B, Vinci T, Burdonov K, Béard J, Fuchs J, Ciardi A 2022 Matter Radiat. Extremes 7 026903 Google Scholar
[10]	Plechaty C, Presura R, Esaulov A A 2013 Phys. Rev. Lett. 111 185002 Google Scholar
[11]	Ripin B H, McLean E A, Manka C K, Pawley C, Stamper J A, Peyser T A, Mostovych A N, Grun J, Hassam A B, Huba J D 1987 Phys. Rev. Lett. 59 2299 Google Scholar
[12]	Brecht S H, Gladd N T 1992 IEEE Trans. Plasma Sci. 20 678 Google Scholar
[13]	Tang H B, Hu G Y, Liang Y H, Wang Y L, Tao T, Hu P, Yuan P, Zhu P, Zuo Y, Zhao B, Zheng J 2020 Phys. Plasmas 27 022108 Google Scholar
[14]	Tang H B, Hu G Y, Liang Y H, Tao T, Wang Y L, Hu P, Zhao B, Zheng J 2018 Plasma Phys. Controlled Fusion 60 055005 Google Scholar
[15]	Hu P, Zhao J Y, Wang J C, Zhang Z C, Tang H B, Hu G Y 2022 J. Instrum. 17 P07036 Google Scholar
[16]	Wang Y L, Hu G Y, Hu P, Liang Y H, Yuan P, Zheng J 2019 Rev. Sci. Instrum. 90 075108 Google Scholar
[17]	Hu P, Hu G Y, Wang Y L, Tang H B, Zhang Z C, Zheng J 2020 Rev. Sci. Instrum. 91 014703 Google Scholar
[18]	Hassam A B, Huba J D 1987 Geophys. Res. Lett. 14 60 Google Scholar
[19]	Gisler G, Lemons D S 1989 J. Geophys. Res. Space Phys. 94 10145 Google Scholar
[20]	Winske D 1988 J. Geophys. Res. Space Phys. 93 2539 Google Scholar
[21]	Huba J D, Hassam A B, Winske D 1990 Phys. Fluids B 2 1676 Google Scholar
[22]	Ali A W, McLean E A 1985 J. Quant. Spectrosc. Radiat. Transfer 33 381 Google Scholar
[23]	Fiuza F, Swadling G F, Grassi A, et al. 2020 Nat. Phys. 16 916 Google Scholar

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