We experimentally studied electron beams and synchrotron x-ray radiation generated from the interaction of high-intensity picosecond laser pulses of 1–3 × 10¹⁹ W/cm² with underdense plasmas of 1–8 × 10¹⁹ cm⁻³. Electron beams with maximum energy over 120 MeV, hundreds mrad divergence and tens of nC charge were generated in the experiments. The measured x-ray spectra were fit well with a synchrotron radiation spectrum combination with a bremsstrahlung spectrum. When laser pulses with intensity of 2.38 × 10¹⁹ W/cm² interacting with pure Nitrogen gas with density of 2.35 × 10¹⁸ cm⁻³, we obtained betatron x-ray radiation with critical energy 3–4 keV and photon number up to 10¹³ photons/Sr per shot, the energy conversion efficiency is about 3 × 10⁻⁵. The high photon yield and large energy conversion efficiency are due to large amounts of electrons trapped by self-modulated laser wakefield and mainly accelerated by direct-laser-acceleration mechanism. Such high yield betatron x-ray sources have widely application prospect as backlight or probe in large scale of laser facilities used for high energy density or fusion sciences.

我们通过实验研究了1–3×10 ¹⁹  W / cm ²的高强度皮秒激光脉冲与1–8×10 ¹⁹ cm ^-3的低密度等离子体相互作用产生的电子束和同步加速器X射线辐射。实验中产生的电子束具有超过120 MeV的最大能量，数百mrad的发散度和数十nC的电荷。所测量的X射线光谱与同步辐射光谱与bre致辐射光谱的组合非常吻合。当强度为2.38×10 ¹⁹  W / cm ^2的激光脉冲与密度为2.35×10 ¹⁸ cm ^-3的纯氮气相互作用时，我们获得了临界能量为3–4 keV且每次发射的光子数高达10 ^13个光子/ Sr的Betatron X射线辐射，能量转换效率约为3×10 ^-5。高光子产量和高能量转换效率是由于大量的电子被自调制激光尾场捕获，并且主要由直接激光加速机制加速。这种高产的电子感应加速器X射线源作为背光源或探针在用于高能量密度或聚变科学的大规模激光设备中具有广泛的应用前景。