Jitter-free 40-fs 375-keV electron pulses directly accelerated by an intense laser beam and their application to direct observation of laser pulse propagation in a vacuum

Shunsuke Inoue,Yoshihide Nakamiya,Masaki Hashida,Shuji Sakabe

doi:10.1038/s41598-020-77236-2

Abstract

We report the generation of ultrashort bright electron pulses directly driven by irradiating a solid target with intense femtosecond laser pulses. The duration of electron pulses after compression by a phase rotator composed of permanent magnets was measured as 89 fs via the ponderomotive scattering of electron and laser pulses, which were almost at the compression limit due to the dispersion of the electron optics. The electron pulse compression system consisting of permanent magnets enabled extremely high timing stability between the laser pulse and electron pulse. The long-term RMS arrival time drift was below 14 fs in 4 h, which was limited by the resolution of the current setup. Because there was no time-varying field to generate jitter, the timing jitter was essentially reduced to zero. To demonstrate the capability of the ultrafast electron pulses, we used them to directly visualize laser pulse propagation in a vacuum and perform 2D mapping of the electric fields generated by low-density plasma in real time.

Highlights

We report the generation of ultrashort bright electron pulses directly driven by irradiating a solid target with intense femtosecond laser pulses
In the development of ultrashort electron pulses, which began with the generation of short pulses of electrons using a DC electron g un[18], a major challenge is preventing the space charge effect, which increases the pulse width owing to self-generated electric fields[19,20]
Ultrashort electron pulses with extremely low timing jitter and a short pulse width were achieved by using electrons that were directly accelerated by irradiating a thin aluminium foil with an intense femtosecond laser in conjunction with a pulse compression method involving a phase rotator based on permanent magnets

Summary

Introduction

We report the generation of ultrashort bright electron pulses directly driven by irradiating a solid target with intense femtosecond laser pulses. Advanced phase and amplitude control of the RF cavity by active synchronization feedback and passive microwave generation without an optical microwave mixer has successfully enabled stable control with timing jitter of approximately 50 fs in 6 h30 These methods use high-frequency electric fields for pulse compression, and jitter cannot be completely eliminated. Ultrashort electron pulses with extremely low timing jitter and a short pulse width were achieved by using electrons that were directly accelerated by irradiating a thin aluminium foil with an intense femtosecond laser in conjunction with a pulse compression method involving a phase rotator based on permanent magnets.

Methods

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Conclusion