Electric Field Analysis in a Cold-Ion Source Using Stark Spectroscopy of Rydberg Atoms
Electric Field Analysis in a Cold-Ion Source Using Stark Spectroscopy of Rydberg Atoms
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DOI：
10.1103/physrevapplied.19.044051
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发表时间：
2023-03
影响因子：
4.6
通讯作者：
A. Duspayev;G. Raithel
中科院分区：
文献类型：
--
作者：
A. Duspayev;G. Raithel
我们分析了在1064 nm激光作用下，囚禁在近同心真空腔焦斑中的冷Rb原子准连续光致电离离子源中产生的电场。离子流是用外加电场提取的。利用Rb 57$F和附近高角动量里德堡能级的斯塔克效应，研究了离子源区在0.35$V/cm引出电场范围内的净电场概率分布。对于$F=0$，我们还研究了60$P{1/2}$态的电离场感生斯塔克谱，它表现出(较小的)二次电场响应，提供了简化的电场分析。实验Rydberg谱与理论Stark谱进行了比较，理论Stark谱与经典离子轨迹模拟得到的包含库仑相互作用的净电场分布进行了加权。实验和模型吻合得很好。在小的$F和高的离子源率下，电场近似服从霍尔茨马克分布，离子流被库仑微场退化。随着$F$的增加和较低的离子源率，磁场在${\bf{F}}$附近的分布变得狭窄，导致定向离子流较少被微场退化。我们的结果对于监测聚焦离子束应用中的冷离子源和研究冷等离子体中的电场是有意义的，其中库仑相互作用是值得关注的。
We analyze electric fields in ion sources generated by quasi-continuous photo-ionization of cold Rb atoms trapped in the focal spot of a near-concentric, in-vacuum cavity for 1064-nm laser light. Ion streams are extracted with an external electric field, ${\bf{F}}$. Stark effects of Rb 57$F$ and of nearby high-angular-momentum Rydberg levels, which exhibit large, linear Stark shifts, are employed to study the net electric-field probability distribution within the ion-source region over an extraction-field range of $0<F<0.35$ V/cm. For $F=0$, we also investigate ion-field-induced Stark spectra of the 60$P_{1/2}$-state, which exhibits a (lesser) quadratic electric-field response that affords a simplified electric-field analysis. Experimental Rydberg spectra are compared with theoretical Stark spectra, which are weighed with net electric-field distributions obtained from classical ion-trajectory simulations that include Coulomb interactions. Experiments and models agree well. At small $F$ and high ion source rates, the field approximately follows a Holtsmark distribution, and the ion streams are degraded by the Coulomb micro-fields. With increasing $F$ and at lower ion source rates, the fields become narrowly distributed around ${\bf{F}}$, resulting in directional ion streams that are less degraded by micro-fields. Our results are of interest for monitoring cold-ion sources for focused-ion-beam applications, where Coulomb interactions are of concern, and for studies of electric fields in cold plasmas.