超冷等离子体演化早期的离子温度与库仑耦合强度

doi:10.19596/j.cnki.1001-246x.8554

计算物理 ›› 2023, Vol. 40 ›› Issue (3): 275-281.DOI: 10.19596/j.cnki.1001-246x.8554

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超冷等离子体演化早期的离子温度与库仑耦合强度

方锋¹^,², 周文长¹^,⁵, 罗长杰¹^,², 李煜璠⁶, 杨杰¹^,³^,⁴^,*()

1. 中国科学院近代物理研究所, 甘肃兰州 730000
2. 中国科学院大学, 北京 100049
3. 先进能源科学与技术广东省实验室, 广东惠州 516003
4. 中国科学院高精度核谱学重点实验室, 甘肃兰州 730000
5. 中山大学中法核工程与技术学院, 广东珠海 519082
6. 安阳师范学院物理与电气工程学院, 河南安阳 455000

收稿日期:2022-05-05 出版日期:2023-05-25 发布日期:2023-07-22
通讯作者: 杨杰
作者简介:
方锋，男，博士研究生，研究方向为超冷等离子体
基金资助:
国家重点研发计划(2017YFA0402300); 国家自然科学基金(U1832175); 中国科学院先导B专项(XDB21030900)

Ion Temperature and Coulomb Coupling Parameter of Ultracold Neutral Plasma in Ion Equilibration Stage

Feng FANG¹^,², Wenchang ZHOU¹^,⁵, Changjie LUO¹^,², Yufan LI⁶, Jie YANG¹^,³^,⁴^,*()

1. Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, Gansu 730000, China
2. University of Chinese Academy of Sciences, Beijing 100049, China
3. Advanced Energy Science and Technology Guangdong Laboratory, Huizhou, Guangdong 516003, China
4. CAS Key Laboratory of High Precision Nuclear Spectroscopy, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, Gansu 730000, China
5. Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-sen University, Zhuhai, Guangdong 519082, China
6. School of Physics and Electrical Engineering, Anyang Normal University, Anyang, Henan 455000, China

Received:2022-05-05 Online:2023-05-25 Published:2023-07-22
Contact: Jie YANG

摘要/Abstract

摘要：

利用开发的磁光阱-离子速度成像装置, 实验测量超冷等离子体的离子温度与库仑耦合参数。同时利用带电粒子追踪数值方法模拟超冷等离子体的早期演化过程。实验和模拟结果表明: 在超冷等离子体演化早期, 无序诱导加热机制导致离子温度快速上升, 而库仑耦合强度下降至2.5。进一步研究还发现: 在离子非平衡演化阶段, 等离子体膨胀速度会快速接近并超过离子热速度, 因此离子达到局域热平衡之后的库仑耦合参数会高于测量值。

关键词: 超冷等离子体, 无序诱导加热, 库仑耦合参数

Abstract:

Using a newly developed velocity map imaging apparatus coupled with a magneto-optical trap, we measured ion temperature and Coulomb coupling parameter of ultracold neutral plasma (UNP). We carried out numerical simulation in early evolution of UNP. The experimental and simulation results showed that the disorder-induced heating mechanism led to a rapid rise in ion temperature during the ion equilibration, and the Coulomb coupling parameter dropped to 2.5. Furthermore, we found that the plasma expansion velocity would quickly approach the thermal velocity of ions in the ion equilibration, which results in a higher Coulomb coupling parameter than experimental values.

Key words: ultracold neutral plasma, disorder-induced heating, Coulomb coupling parameter

方锋, 周文长, 罗长杰, 李煜璠, 杨杰. 超冷等离子体演化早期的离子温度与库仑耦合强度[J]. 计算物理, 2023, 40(3): 275-281.

Feng FANG, Wenchang ZHOU, Changjie LUO, Yufan LI, Jie YANG. Ion Temperature and Coulomb Coupling Parameter of Ultracold Neutral Plasma in Ion Equilibration Stage[J]. Chinese Journal of Computational Physics, 2023, 40(3): 275-281.

图/表 5

图1 实验装置示意图

Fig.1 A schematic of experimental setup

图2 (a) td=0 ns时，探测器获得的离子成像; (b) 图(a)经反阿贝尔变换算法MEVIR处理后得到的速度三维分布剖面; (c) 将三维分布对立体角积分后得到的速度分布

Fig.2 (a) A detected imaging result at delay time td= 0 ns; (b) A slice cut of three-dimensional velocity distribution of ions obtained through Abel inversion; (c) Velocity distribution obtained from three-dimensional distribution shown in panel of (b)

图3 不同延时下，速度成像结果得到的离子速率分布(实点)以及相应的拟合结果(实线)

Fig.3 Measured velocity distributions (solid dots) and corresponding fitting results (solid lines) at different delay time

图4 (a) 离子温度随时间的演化(黑色实线是CPT模拟结果，蓝色虚线是由式(2)计算的无序诱导加热的离子温度，红色实点是实验测量结果。) (b)库仑耦合参数Γ随时间的演化(黑色实线是CPT模拟结果，红色实点是实验测量结果。)

Fig.4 (a) Evolution of ion temperature (The black solid line, the blue dashed line and the red solid dots represent the results of CPT simulation, calculation by Eq. (2) and experimental measurement, respectively.) (b) Evolution of Coulomb coupling parameter Γ (The black solid line and the red solid dots are the results of CPT simulation and experimental measurement, respectively.)

图5 由CPT模拟得到的离子均方根速度(黑色实线)和自相似模型计算得到的等离子体平均膨胀速度(红色虚线)

Fig.5 Evolution of rms velocity of ions from CPT simulation and expansion velocity calculated with self-similar expansion model

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超冷等离子体演化早期的离子温度与库仑耦合强度

Ion Temperature and Coulomb Coupling Parameter of Ultracold Neutral Plasma in Ion Equilibration Stage

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