High-intensity attosecond beamline for XUV pump–XUV probe measurements with photon energies up to 150 eV

Abstract

The field of attosecond physics has expanded significantly in recent years, yet experimental facilities supporting attosecond pump–attosecond probe spectroscopy remain rare. Here, we present a newly constructed beamline for the generation and application of energetic, isolated extreme ultraviolet (XUV) and soft x-ray attosecond pulses via upscaling of high-harmonic generation (HHG) in a gas medium. The fundamental properties of the HHG radiation—energy, beam profile, spectrum, and divergence—are characterized and optimized. The source delivers up to 55 nJ of pulse energy within the Zr window (65–150 eV) with high stability (∼5%–10%) and a divergence of 0.1 mrad. Numerical simulations identify optimal operating conditions consistent with experimental results. Temporal super-resolution of the driving laser is applied, resulting in a broadened spectral continuum. Furthermore, the beamline includes a split-and-delay stage before focusing the HHG radiation to a <6 μm spot for pump–probe experiments using two distinct focusing optics. Spatially resolved ion microscopy is employed to trace the generated ions at the focus. The presented beamline is designed for nonlinear XUV studies with isolated attosecond pulses.