Andrzej Andrejczuk

High numerical aperture multilayer Laue lenses

The ever-increasing brightness of synchrotron radiation sources demands improved X-ray optics to utilise their capability for imaging and probing biological cells, nanodevices, and functional matter on the nanometer scale with chemical sensitivity. Here we demonstrate focusing a hard X-ray beam to an 8 nm focus using a volume zone plate (also referred to as a wedged multilayer Laue lens). This lens was constructed using a new deposition technique that enabled the independent control of the angle and thickness of diffracting layers to microradian and nanometer precision, respectively. This ensured that the Bragg condition is satisfied at each point along the lens, leading to a high numerical aperture that is limited only by its extent. We developed a phase-shifting interferometric method based on ptychography to characterise the lens focus. The precision of the fabrication and characterisation demonstrated here provides the path to efficient X-ray optics for imaging at 1 nm resolution.

Conductors, semiconductors, and insulators irradiated with short-wavelength free-electron laser

The results of a study of irreversible changes induced at surfaces of metals, semiconductors, and insulators by extreme ultraviolet (λ<100nm) ultrashort pulses provided by TESLA Test Facility Free-Electron Laser, Phase 1 (TTF1 FEL) are reported and discussed. The laser was tuned at 86, 89, and 98nm during the experiments reported here. Energy spectra of ions ejected from the irradiated surfaces are also reported. Special attention is paid to the difference in the ablation behavior of (semi)conductors and insulators that we have observed. The difference is dramatic, while the absorption coefficients are similar for all materials at the TTF1 FEL wavelength.

Ablation of various materials with intense XUV radiation

Ablation behavior of organic polymer (polymethylmethacrylate) and elemental solid (silicon) irradiated by single pulses of XUV radiation emitted from Z-pinch, plasma-focus, and laser-produced plasmas was investigated. The ablation characteristics measured for these plasma-based sources will be compared with those obtained for irradiation of samples with XUV radiation generated by a free-electron laser.

Total reflection amorphous carbon mirrors for vacuum ultraviolet free electron lasers

Sputter-deposited amorphous carbon coatings of high optical quality and very high radiation stability will be used as reflecting optical elements for free electron laser (FEL) applications in the vacuum ultraviolet (VUV) and soft x-ray spectral regions. Their reflectivity at grazing angles of 2° is typically 94–96% for photon energies between 50 and 250 eV. Using the focused radiation (λ=98 nm) of the VUV FEL at Deutsches Elektronen-Synchrotron DESY the damage threshold of such coatings was determined to 0.07 J/cm2. Ripples with a spatial period of 76 nm were found on the surfaces damaged by the FEL radiation.

Experimental station to study the interaction of intense femtosecond vacuum ultraviolet pulses with matter at TTF1 free electron laser

An experimental station to study the interaction of intense femtosecond vacuum ultraviolet pulses generated by the TTF1 free electron laser (FEL) (DESY, Germany) with solids was developed. The vacuum chamber, the sample holder and the detectors had been designed to fulfill strong constraints caused both by the unique properties of the interacting radiation and by TTF1 FEL innovative design. The applied mounting system allowed one to move and rotate the samples precisely with 4degrees of freedom and to heat them up to the maximal temperature of 1000K. In order to accomplish the in situ growth of thin metallic layers on the sample surfaces, evaporation cells had been installed in the vacuum chamber. A time-of-flight apparatus capable of recording both electrons and ions excited on the solid surfaces by the laser pulses had been included in the chamber design. A pulse energy monitor had been placed in the laser beam outside the experimental chamber. A second energy detector had been mounted inside the chambe...

Fabrication of wedged multilayer Laue lenses

We present a new method to fabricate wedged multilayer Laue lenses, in which the angle of diffracting layers smoothly varies in the lens to achieve optimum diffracting efficiency across the entire pupil of the lens. This was achieved by depositing a multilayer onto a flat substrate placed in the penumbra of a straight-edge mask. The distance between the mask and the substrate was calibrated and the multilayer Laue lens was cut in a position where the varying layer thickness and the varying layer tilt simultaneously satisfy the Fresnel zone plate condition and Bragg’s law for all layers in the stack. This method can be used to extend the achievable numerical aperture of multilayer Laue lenses to reach considerably smaller focal spot sizes than achievable with lenses composed of parallel layers.

Electron Momentum Density of Hexagonal Magnesium Studied by Compton Scattering

Directional Compton profiles of single crystal of hcp magnesium have been measured with scattering vectors along the [10 10], [1120] and [0001] directions in reciprocal space (special directions ΓΜ, ΓΚ, ΓΑ) using high-energy (662 keV) gamma radiation from a 137Cs isotope source. The experimental data were compared with corresponding theoretical Korringa-Kohn-Rostoker (KKR) calculations. The directional difference profiles, both experimental (of medium resolution) and theoretical ones, show very small anisotropy of the electron momentum density in magnesium, 2-3 times lower than in zinc and cadmium single crystals, significantly lower than observed in cubic metals. This small directional effect is in good agreement with Compton 60-keV energy experiments and positron annihilation data presented by other authors.

Ablation of Organic Polymers and Elemental Solids Induced by Intense XUV Radiation

The ablation efficiency of organic polymers (polymethylmethacrylate ‐ PMMA, polytetrafluoroethylene ‐ PTFE, polyethyleneterephtalate ‐ PET, and polyimide ‐ PI) and elemental solids (aluminum and silicon) by single pulses of extreme ultraviolet (XUV) radiation emitted from Z‐pinch, plasma‐focus, and laser‐produced plasmas was investigated. The ablation characteristics measured for these plasma‐based sources will be compared with those obtained for irradiation of samples with XUV radiation generated by a free‐electron laser (FEL). The Z‐pinch was driven by the S‐300 pulsed‐power machine (Kurchatov Institute, Moscow) and the plasma focus was realized in the PF‐1000 machine (Institute of Plasma Physics and Laser Microfusion, Warsaw). Higher temperature plasma than with the discharge plasmas was obtained by focusing the near‐infrared (fundamental frequency) beam from the PALS high‐power iodine laser system (Czech Academy of Sciences, Prague) on the surface of a metallic slab target or into single‐ and double‐g...

Electron momentum density of hexagonal zinc studied by Compton scattering

We have measured the directional Compton profiles of a single crystal of hexagonal zinc along the [001], [100], [110] and [111] directions using high-energy (662 keV) gamma radiation from a 137Cs isotope source. The experimental data have been compared with the corresponding theoretical Korringa-Kohn-Rostoker semi-relativistic calculations. The theory slightly overestimates the electron momentum densities at low momenta regions for all measured profiles. The directional difference profiles, both experimental and theoretical, show very small anisotropy of the electron momentum density in hexagonal zinc, at most half of that presented in the literature for cubic systems.

Sructural changes at solid surfaces irradiated with femtosecond, intense XUV pulses generated by TTF-FEL

Abstract Interaction of ultrafast (∼ 50 fs), high intensity (up to 1013 W/cm2) XUV (λ ∼ 85 nm) FEL beam with solids has been studied at the TTF-FEL facility. Damaged surfaces have been investigated using light, electron, and atomic force microscopy. Influence of the FEL radiation intensity on the structural changes at the surfaces has been investigated. Results obtained for different materials, i. e. metals (Au), semiconductors (Si), inorganic insulators (Ce:YAG, BaF2, SiO2), and organic polymers (polymethylmethacrylate - PMMA), are compared. Laser-induced periodic surface structures (LIPSS) were observed at amorphous carbon (a-C) layers.