近日，西安交通大学的赵永涛&任洁茹及其研究团队取得一项新进展。经过不懈努力，他们实现多孔结构泡沫靶中激光加速碳离子的电荷平衡。相关研究成果已于2024年4月9日在国际知名学术期刊《物理评论A》上发表。

该研究团队通过实验测量了激光加速的碳离子，穿过三纤维素-乙酸酯（TCA, C₉H₁₆O₈）泡沫靶的平衡电荷态分布。离子是通过靶正常鞘加速机制产生的，这种方法使研究人员能够在接近单次激光射击的最大能量损失的大能量范围内，精确地获得平衡电荷状态。值得一提的是，该泡沫具有独特的多孔结构，其体积密度为2 mg/cm³，介于典型的气体和固态物质密度之间。

研究人员发现，实际测量到的平均平衡电荷态数值远低于气体目标理论模型的预测，但却与半经验公式和基于离子-固体相互作用的速率方程预测结果高度一致。他们进一步对泡沫结构中的固密度纤维长丝进行了细致的分类和深入论证。研究发现，靶密度效应在泡沫靶中扮演着至关重要的角色，它通过增加离子与物质之间的碰撞频率，进而提升了电离概率，同时降低了电子捕获概率。鉴于泡沫靶在激光等离子体相互作用实验中的广泛应用，这一研究成果具有重要的实用价值。

附：英文原文

Title: Charge equilibration of laser-accelerated carbon ions in a porous-structure foam target

Author: Bubo Ma et al.

Issue&Volume: 2024/04/09

Abstract: The equilibrium charge state distribution of laser-accelerated carbon ions traversing a tri-cellulose-acetate (TCA, C₉H₁₆O₈) foam target was measured experimentally. The ions were generated through the target normal sheath acceleration mechanism. This allowed us to obtain the equilibrium charge state for a wide energy range near the maximum energy loss within a single laser shot. The foam had a porous structure with 2 mg/cm³ volume density, which is between the typical density of gas- and solid-state matter. We found that the measured average equilibrium charge states were significantly underestimated by theoretical models applicable for gas targets, while were in close agreement with both semiempirical formulas and rate equation predictions based on ion-solid interactions. The solid-density fiber filaments in the current foam structure were attributed and demonstrated. The target density effects, which increase the ionization probability through frequent collisions and decrease the electron capture probability, were proven to play an important role in the foam target. Since the foam targets are widely used in laser plasma interaction experiments, our findings are relevant for a broad range of applications.

DOI: 10.1103/PhysRevA.109.042810

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.109.042810