The interactions between intense laser pulses and a solid target generate energetic and intense radiations such as electrons, ions, and x-rays. Since these radiations are driven at a time and space scale resembling the pulse width and focusing diameter of the laser, they have the characteristic of short pulse and high brightness. Researches have been achieved to apply these radiations as probe pulses, which have a short pulse and high brightness. The laser-driven charged particles, for example, are possible to measure electromagnetic fields varying with ultra-high-speed. In proton radiography, it is observed the spatial distribution of electromagnetic fields that change within a few picoseconds from moment to moment[1]. On the other hand, since the laser-accelerated electrons have a pulse width of less than picoseconds, they can observe an electric field varying at a higher speed[2-4]. Also, since electrons are much lighter than protons, they are sensitive to electromagnetic fields with small amplitudes that protons cannot measure. Therefore, this electron pulse has the potential for measuring the ultrafast fields such as laser-induced plasmas with high spatial and temporal resolutions.
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