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

TL;DR

This paper introduces a compact, efficient setup for femtosecond laser-induced generation of broadband hard X-ray pulses, with detailed characterization of the laser and X-ray properties for various samples.

Contribution

The work presents a simplified apparatus design for femtosecond laser X-ray generation, including novel beam focusing and characterization techniques, advancing the practical implementation of broadband X-ray sources.

Findings

X-ray spectra match literature for titanium, iron-chromium, and copper.

Laser pulse duration characterized by frequency-resolved optical gating.

Upper bound established for X-ray pulse duration.

Abstract

We present a simple apparatus for femtosecond laser induced generation of X-rays. The apparatus consists of a vacuum chamber containing an off-axis parabolic focusing mirror, a reel system, a debris protection setup, a quartz window for the incoming laser beam, and an X-ray window. Before entering the vacuum chamber, the femtosecond laser is expanded with an all reflective telescope design to minimize laser intensity losses and pulse broadening while allowing for focusing as well as peak intensity optimization. The laser pulse duration was characterized by second-harmonic generation frequency resolved optical gating. A high spatial resolution knife-edge technique was implemented to 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 femtosecond laser generated X-rays give spectral lines consistent with literature reports. We present a rms amplitude analysis of the generated X-ray pulses, and provide an upper bound for the duration of the X-ray pulses.