Table-top Soft X-ray Source Research Articles

A THz streak camera based on a highly efficient velocity map imaging spectrometer in collinear geometry

In this paper we report on a velocity map imaging spectrometer with the implementation of an on-axis geometry where the electrons travel parallel to the ionizing beam towards the detector. Owing to a usually low photon flux from table-top soft x-ray sources, the instrument is optimized for high detector efficiency and high target density. The collinear design offers the possibility to freely choose the state and orientation of the polarization of light fields in streaking experiments. First results of an experiment using THz pulses for streaking using a Xe gas target are presented and compared to the simulated performance of the spectrometer.

Direct Determination of Absolute Absorption Cross Sections at the L-Edge of Dilute Mn Complexes in Solution Using a Transmission Flatjet.

The 3d transition metals play a pivotal role in many charge transfer processes in catalysis and biology. X-ray absorption spectroscopy at the L-edge of metal sites probes metal 2p-3d excitations, providing key access to their valence electronic structure, which is crucial for understanding these processes. We report L-edge absorption spectra of MnII(acac)2 and MnIII(acac)3 complexes in solution, utilizing a liquid flatjet for X-ray absorption spectroscopy in transmission mode. With this, we derive absolute absorption cross-sections for the L-edge transitions with peak magnitudes as large as 12 and 9 Mb for MnII(acac)2 and MnIII(acac)3, respectively. We provide insight into the electronic structure with ab initio restricted active space calculations of these L-edge transitions, reproducing the experimental spectra with excellent agreement in terms of shapes, relative energies, and relative intensities for the two complexes. Crystal field multiplet theory is used to assign spectral features in terms of the electronic structure. Comparison to charge transfer multiplet calculations reveals the importance of charge transfer in the core-excited final states. On the basis of our experimental observations, we extrapolate the feasibility of 3d transition metal L-edge absorption spectroscopy using the liquid flatjet approach in probing highly dilute biological solution samples and possible extensions to table-top soft X-ray sources.

High-flux table-top soft x-ray source driven by sub-2-cycle, CEP stable, 1.85-μm 1-kHz pulses for carbon K-edge spectroscopy.

We report on the first table-top high-flux source of coherent soft x-ray radiation up to 400 eV, operating at 1 kHz. This source covers the carbon K-edge with a beam brilliance of (4.3±1.2)×10(15) photons/s/mm(2)/strad/10% bandwidth and a photon flux of (1.85±0.12)×10(7) photons/s/1% bandwidth. We use this source to demonstrate table-top x-ray near-edge fine-structure spectroscopy at the carbon K-edge of a polyimide foil and retrieve the specific absorption features corresponding to the binding orbitals of the carbon atoms in the foil.

Near diffraction limited coherent diffractive imaging with tabletop soft x-ray sources

Tabletop coherent x-ray sources hold great promise for practical nanoscale imaging, in particular when coupled with diffractive imaging techniques. In initial work, we demonstrated lensless diffraction imaging using a tabletop high harmonic generation (HHG) source at 29 nm, achieving resolutions ∼ 200 nm. In recent work, we significantly enhanced our diffractive imaging resolution by implementing a new high numerical aperture (up to NA=0.6) scheme and field curvature correction where we achieved sub-100 nm resolution. Here we report the first demonstration of Fourier transform holography (FTH) with a tabletop SXR source, to acquire images with a resolution ≈ 90 nm. The resolution can be refined by applying phase retrieval. Additionally, we show initial results from FTH with 13.5 nm HHG radiation and demonstrate ∼ 180 nm resolution.

Soft X-ray Microscope Constructed with 130-nm Spatial Resolution Using a High Harmonic X-ray Source

Using high harmonic radiation as an X-ray light source, a soft X-ray microscope with nanometer-scale spatial resolution was investigated. A transmission soft X-ray microscope was constructed using a Mo/Si multilayer concave mirror as a condenser and a Fresnel zone plate as a microscope objective. The high-order harmonic source at 13 nm, emitted from neon atoms driven by intense femtosecond laser pulses, was optimized by controlling laser chirp. Objects, patterned on 160-nm-thick hydrogen silsesquioxane coated on a 100-nm-thick Si3N4 membrane, were used for imaging. The analysis of object images, captured on an X-ray charge-coupled device, showed that the spatial resolution of the microscope was about 130 nm, verifying the usefulness of the tabletop soft X-ray source.

A pulse-train laser driven XUV source for picosecond pump–probe experiments in the water window

We describe the development of a table top soft X-ray source based on a laser produced plasma. The plasma is produced by a Nd:YLF pulse-train laser which delivers pulse trains of up to 400 pulses each of about 25 ps duration. Number and energy of the micropulses are fully computer controlled adjustable for an optimum interaction with a rotating solid target. Spectral, spatial and temporal characteristics of the X-ray emission from Mylar and copper targets have been studied. A calibrated back-illuminated CCD camera together with a slit grating spectrograph were utilized for the measurement of the absolute soft X-ray photon fluxes. The temporal measurements were performed using a streak camera while the plasma size was measured with a zone plate. An application of the system in a X-ray absorption experiment is shown. The advantages of the system in view of possible optical pump and soft X-ray probe experiments will be discussed.