A Ti:sapphire femtosecond laser with a relativistic intensity is focused onto a four-loop solenoid target to produce an ultrafast pulsed magnetic field. The magnetic field is generated due to a cold electron bunch which flows toward the laser focal spot to neutralize the remaining positive charge from the escaping hot electrons. The temporal evolution of the magnetic fields is evaluated by an improved Faraday rotation measurement [Baojun Zhu et al., Applied Physics Letters 113.7(2018)]. Effects of pulse duration on laser-driven magnetic fields have been studied. A peak field strength is obtained when the laser pulse duration is extended to be 50 fs.

中文翻译：

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脉冲持续时间对激光驱动线圈产生的磁场的影响

具有相对论强度的Ti：蓝宝石飞秒激光聚焦到四环螺线管靶上，以产生超快脉冲磁场。磁场是由于冷电子束流向激光焦点而产生的，以中和来自逸出的热电子的剩余正电荷。通过改进的法拉第旋转测量来评估磁场的时间演化[Baojun Zhu等人。，应用物理快报113.7（2018）]。研究了脉冲持续时间对激光驱动磁场的影响。当激光脉冲持续时间延长到50 fs时，将获得峰值场强。