强流离子束在等离子体中的传输研究

The interaction of high-intensity ion beam pulses with plasma has been an interesting topic during the past decades due to the fact that the background plasmas can neutralize the effect of space-charge within ion beam pulses and provide the guarantee for stable transmission or effective compression of high intensity beams. Understanding the interaction of high intensity beams with plasmas is of crucial importance to several applications, including the high-intensity ion beam accelerator (HIAF), inertial confinement fusion (ICF) driven by ion beams and the high energy and density matters (HEDM). However, as the intensity of the ion beam pulses increases, the dynamics of the ion beam pulses will be dominated by the collective effect, which is caused by the repulsive force between ion particles. And these results from linear theory become unreliable to describe the interaction between the ion beam pulses and plasmas. In this project, we develop a massively parallel particle-in-cell (PIC) algorithm to simulate the transport of high-intensity ion beam pulses in plasmas. With the guarantee of large scale simulations, motions of all ion beam particles, electrons and ions in plasmas, as well as the evolution of space electromagnetic field are included in our calculations. By using this self-consistent PIC method, the energy loss effects , self-pinch effects, wakefield effects and the self-modulation effects are combined together to study the complex processes when ion beam pulses passing through plasmas. By performing large amounts of simulations, we are trying to answer the question that on what condition can high-intensity ion beam pulses efficiently transport or focus in plasmas. At last, by comparing simulation results with the analytical models, we try to find the influence of collective effects when high-intensity ion beam pulses passing through plasmas. The results of this research will improve the understanding of the interaction of ion beams with plasmas and provide theoretical guild lines for the extensive experimental studies in the ICF, HIAF and HEDM.

在离子束流传输领域，随着束流流强的不断增加，强流离子束的传输和聚焦变得越发困难。作为一种传输介质和聚焦手段，等离子体能有效的抵消强流离子束中离子间的库伦排斥力，保证束流的稳定传输以及在一定条件下实现束流的聚焦。本课题拟自行开发大规模并行particle-in-cell（PIC）算法研究强流离子束在等离子体中的传输。通过研究强流束的集体效应对束流在等离子体传输过程中的能损、电流电荷中和效应、等离子尾场激发、尾场自调制效应以及束流动力学演化等过程的影响,寻找强流离子束在等离子体中稳定传输和有效聚焦的条件和关键参数；并将模拟结果跟已有的等离子体能损理论、束流箍缩模型、等离子体尾场激发模型、束流动力学模型等理论模型对比，探索强集体效应下，强流离子束在等离子中传输的规律。本课题对涉及到离子束传输相关的领域，如强流离子加速器、重离子驱动惯性聚变、重离子产生高能量密度物质等领域都具有积极意义。

作为一种传输介质和聚焦手段，等离子体能有效的抵消强流离子束中离子间的库伦排斥力，保证束流的稳定传输以及在一定条件下实现束流的聚焦。本课题以中科院先导专项CIADS项目中强流质子直线加速器为依托，系统研究了能量200——300MeV，流强从1mA到20mA的强流质子束在等离子体中的传输。利用Vorpal软件和自行开发的并行particle-in-cell（PIC）算法研究强流质子束在等离子体中传输时： 1长束团传输时尾场自调制效应以及等离子尾场激发或者抑制；2脉冲束团的关联效应对离子束能损的影响；3磁化等离子体对束流能损的增强或者削弱效应；4高能质子束诱发的等离子不稳定性以及等离子体波等过程。本课题试图通过以上研究，寻找强流离子束高效、稳定的通过等离子的方案。本课题的研究结果对涉及到离子束传输相关的领域，如强流离子加速器、重离子驱动惯性聚变、重离子产生高能量密度物质等领域都具有积极意义。