利用非线性汤姆逊散射产生太赫兹波与X射线的研究

Electromagnetic fields generated by nonlinear Thomson scattering of high energy electrons in monochromatic plane wave electromagnetic fields cover the frequency range from terahertz to X-ray. In this project we shall study the terahertz wave and X-ray generation by nonlinear Thomson scattering and the research on terahertz wave generation by nonlinear Thomson scattering will be a groundbreaking work. This mechanism is hopeful of providing novel cheap radiation source scheme, especially for those of great value to research and technology such as terahertz, “water window” and soft X-ray photoetching wave bands. Based on the analytical theory of electron rest frame, we shall develop general analytical theory of nonlinear Thomson scattering of arbitrary polarized electromagnetic field, arbitrary electron energy, arbitrary electromagnetic wave intensity and arbitrary scattering geometry. For this purpose we should solve the following problem: Since the scalar potential component of the new four-vector potential obtained by an arbitrary Lorentz transformation from a four-vector potential of Lorentz gauge is not zero in general where the Lorentz gauge could not be retained and the electromagnetic wave polarization could not be confirmed, the general analytical theory of nonlinear Thomson scattering which is described by the electromagnetic wave polarization and vector potential is unknown. Employing the obtained analytical nonlinear Thomson scattering theory in arbitrary frame of reference we shall calculate the terahertz wave and X-ray generation by nonlinear Thomson scattering and analyze the effects on the scattering results of the angle between the electron velocity and the direction of the electromagnetic wave propagation, the electromagnetic wave polarization, frequency, electron energy etc. and present reasonably proposals and optimal schemes considering the experiments conditions.

高能电子与单色平面电磁波的非线性汤姆逊散射产生的电磁波可覆盖从太赫兹波到X射线的所有频谱。本项目研究利用非线性汤姆逊散射产生太赫兹波与X射线，开创了以该物理机制产生太赫兹波的研究。该机制有望提供新型的辐射源方案，特别是服务于对研究与应用具有重要价值的太赫兹、“水窗”、软X射线光刻等波段的廉价辐射源。在电子静止参照系解析理论的基础上，本项目将发展任意能量电子同任意椭圆偏振、任意强度单色平面波的任意角度非线性汤姆逊散射的解析理论。洛伦兹规范下的四矢势在任意方向的洛伦兹变换下所得到的四矢势的标势分量一般不为0，不再保持洛伦兹规范，无法确定电磁波偏振态，故不能得到用矢势和偏振态等参量来表达的解析结果，本项目将研究并解决这些问题。根据解析理论计算太赫兹波与X射线的产生，从理论上分析电子运动方向与电磁波传播方向夹角、电磁波的偏振态、频率、电子能量等参数对散射结果的影响，结合实验给出优化的建议和方案。

高能电子与单色平面电磁波的非线性汤姆逊散射产生的电磁波可覆盖从太赫兹波到X射线的所有频谱。本项目研究利用非线性汤姆逊散射产生太赫兹波与X射线，开创了以该物理机制产生太赫兹波的研究。该机制有望提供新型的辐射源方案，特别是服务于对研究与应用具有重要价值的太赫兹、“水窗”、软X射线光刻等波段的廉价辐射源。在电子静止参照系解析理论的基础上，本项目得到了任意能量电子同任意椭圆偏振、任意强度单色平面波的任意角度非线性汤姆逊散射的解析理论。X射线产生的数值模拟结果显示，在激光脉冲与电子束相互作用时间和区域控制比较精确的实验条件下，电子束的束腰和脉宽与激光脉冲的束腰和脉宽存在定量的匹配关系，主要依赖于散射角；在对相互作用的区域的控制相对粗略的实验条件下，为了使X射线产量最大化，应采用束腰较大的电子束。X射线产量在圆偏振时取最大值，线偏振取最小值。随着激光强度的增加，辐射角功率、辐射能量、X射线光子数先增大后减小，存在极大值点，频率、频谱分布范围减小，激光强度越大，说明X射线的单色性越好。辐射角功率、辐射能量随着散射角的增加单调递减，频率、频谱分布范围随着散射角的增加而减小，频谱范围变窄，说明X射线的单色性变好；但是随着散射角的增加，相互作用时间也变短，从而X射线光子数也变少。X射线产量随着电子能量、入射激光能量的增加而增加，随着入射激光波长的增加而减小。入射激光能量越大，单色性越好。