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基于CTMC与ETACHA4的重离子在径迹上碰撞电离的研究

Impact Ionization Investigation of Heavy Ion-Atom Along Penetration Tracks Based on CTMC and ETACHA4

  • 摘要: 离子束驱动是产生高能量密度物质的重要途径,研究在穿透径迹上离子电荷态的变化以及产生电离电子的情况,对认识离子束在靶中的能量沉积过程有重要意义。本工作提出了一种计算径迹上重离子碰撞电离的方法,首先采用ETACHA4程序计算了重离子(如 \textHe^\text2+\text,\textU^\text92+)穿透固体靶(如D,Pb)过程中能量与电荷态随入射深度的变化,再利用CTMC程序计算在径迹上碰撞电离产生的电离电子平均能量。结果表明, \textHe^\text2+\text、\textU^\text92+ 与Pb靶碰撞时,电离电子能量集中在0~100 keV范围内,平均电离电子能量随入射深度增加而增加;当入射粒子能量较低时(~几十MeV/u),平均电离电子能量变化不显著。 \textU^\text92+ 穿透D靶时,电离电子能量集中在100 eV以内,平均电子能量几乎保持不变,维持在16~18 eV。该结果对于推动离子束驱动高能量密度物质的数值模拟有一定的意义,也可以为靶设计提供参考。

     

    Abstract: Ion beam driving is a critical method for producing high energy density materials. It is of great significance to study the change of ion charge state and the generation of ionized electrons on the penetration track for understanding the energy deposition process of ion beam in the target. A method for calculating impact ionization of heavy ions along the tracks is proposed in this paper. Firstly, the ETACHA4 code is used to calculate the energy and charge state with penetration depth in collisions of heavy ions (He2+, U92+) with solid targets (D, Pb). Then the CTMC code is used to obtain detailed results of impact ionization along the track. The results of He2+ and U92+ ions colliding with Pb target reveal that the energy of ionized electrons is concentrated in the 0~100 keV range, and the average ionized electron energy increases with the penetration depth. The average electron energy does not change considerably when the incident energy is modest (~ tens of MeV/u). For U92+ ions colliding with D target, the average energy of ionized electrons is distributed below 100 eV, and it remains almost constant, maintaining at 16~18 eV. The results of this study can help to further the numerical simulation of high energy density materials driven by heavy ion beams, as well as serve as a reference for target design.

     

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