Compact arrangement for femtosecond laser induced generation of broadband hard x-ray pulses

摘要

We present a simple apparatus for femtosecond laser induced generation ofX-rays. The apparatus consists of a vacuum chamber containing an off-axisparabolic focusing mirror, a reel system, a debris protection setup, a quartzwindow for the incoming laser beam, and an X-ray window. Before entering thevacuum chamber, the femtosecond laser is expanded with an all reflectivetelescope design to minimize laser intensity losses and pulse broadening whileallowing for focusing as well as peak intensity optimization. The laser pulseduration was characterized by second-harmonic generation frequency resolvedoptical gating. A high spatial resolution knife-edge technique was implementedto characterize the beam size at the focus of the X-ray generation apparatus.We have characterized x-ray spectra obtained with three different samples:titanium, iron:chromium alloy, and copper. In all three cases, the femtosecondlaser generated X-rays give spectral lines consistent with literature reports.We present a rms amplitude analysis of the generated X-ray pulses, and providean upper bound for the duration of the X-ray pulses.