本研究計畫著重於利用解析理論與數值模擬方法來探討雷射電漿交互作用之非線性動態行為，包含四個主要研究子題：1.次兆瓦雷射尾場電子加速器之研究：將次兆瓦雷射脈衝導入高密度氣體靶材中，可以產生高重覆率輸出、飛秒時寬且百萬電子伏特能量的電子束。透過電漿粒子模擬系統，我們能解析次兆瓦雷射與高電漿密度電漿交互作用的物理現象。隨後，我們將透過模擬研究建立高原子序的氣體游離模型及設計兩階段的氣囊，以提高電子注入的穩定度與加速效益。2.雷射直接加速電子之研究: 透過徑向極化雷射脈衝導入密度週期耦合的電漿波導管，可以有效的直接加速電子束。當其加入前導電子束，加速電子束的品質可以被有效的改善。我們將透過模擬最佳化的電漿波導管，使其達到更優化的加速電子束輸出。3.強場雷射產生高能質子束之研究：透過高功率雷射脈衝與薄靶材作用，能夠產生高能質子束。然而，雷射脈衝與超薄靶材(<10 nm)的作用機制轉換細節尚未被釐清。此外，藉由結合接近臨界密度靶材與超薄靶材的設計，以得到更有效益的質子加速機制。我們預計發展模擬程式，來探討強場雷射與超薄靶材/雙層靶材作用之物理機制。4.螺旋子電漿之研究: 透過激發螺旋電漿波方式，可以提供穩定的高密度且低電子溫度的電漿源。目前相關的理論研究都是透過假定電漿密度溫度分部都不隨時變去推導的，以至於跟實驗結果會有落差。因此，我們透過流體模擬來探導螺旋子電漿的動態行為，以了解其電漿產生及演化機制。 ;The purpose of the project is to apply the theoretical analysis and numerical simulation on the study of the dynamical behaviors of interactions between the intense electromagnetic wave and plasma in the relativistic regime. Four major research topics are included:1.Sub-terawatt laser wake-field acceleration: The femtosecond, MeV electrons can be generated in a high repetition rate by introducing sub-terawatt laser pulses into highly dense plasmas. Interactions between the sub-terawatt laser pulse and dense plasma can be simulated and analyzed using the particle-in-cell simulations. Furthermore, we will establish the gas ionization model of high Z gas and/or design the two-stage gas cell in our simulations to stabilize the electron self-injection and enhance the acceleration efficiency.2.Direct laser acceleration of electron beams: Direct laser acceleration of electron beams can be achieved by utilizing the axial field of a well-guided, radially polarized laser pulse in a density-modulated plasma waveguide. Since a favorable ion-focusing force is provided by the precursor, the transverse properties of witness bunch can be maintained. Moreover, we will modify the design of density-modulated plasma waveguides to achieve an improved the quality of the accelerated electron beam.3.Laser plasma proton/ion acceleration: The energetic protons can be generated by the interaction between intense laser with a ultrathin solid target. However, the transition of dominant regimes has not been studied yet. Moreover, we will combine the near critical density target with the ultrathin (< 10 nm) graphene target to seek for a more efficient acceleration mechanism. In this topic, the simulation model will be developed to investigate the laser plasma proton/ion acceleration. 4.The study of helicon plasma: By employing the helicon wave, the high-density and low electron temperature plasma under a wide range of parameters can be stably generated. Theoretical calculations often assume that various physical variables, e.g. the plasma density and temperature, are given a priori and are constant in time. Our project intends to investigate a temporal behavior of the helicon plasma system by computing the helicon discharge self-consistently and bridge the gap between theory and the experiment.
