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We have developed a novel method for efficient structuring of the surface of materials by applying femtosecond near infrared laser pulses simultaneously with a weak extreme ultraviolet beam, which leads to a very strong radiation-matter interaction and brings a dramatic increase of the surface processing speed. We present our recent experimental results on surface nanostructuring of thin films of amorphous carbon and polymethyl methacrylate deposited on bulk substrates and discuss the underlying physical mechanisms. In the case of amorphous carbon, large areas of laser-induced periodic surface structures with a spatial period of 550 nm were created, having their origin in laser-induced convective currents. Our method provides a powerful tool for fast modification of tribological properties of the irradiated sample.

The recent development of intense sources in the XUV range (10-100 nm), such as X-ray laser, Free Electron Laser and High order Harmonics (HoH), allows the study of high flux processes and ultra-fast dynamics in various domains. At the SLIC facility of CEA-Saclay, we have built a gas-harmonic beamline to investigate the interaction of intense XUV pulse with solids. High Harmonics of an IR laser (Ti:Sa at 800 nm, 35 fs, 13 mJ/pulse, 1 kHz) are generated in a rare gas cell (Xe). The useful XUV range (40-60 nm) is selected with metallic filters. The harmonic beam is focused with a parabolic mirror to a 10 m focal spot on sample, leading to a fluence per shot of up to 1 mJ/cm2(within a typical 10 fs pulse duration). Studies aimed at understanding the damaging mechanisms caused by XUV irradiation on surface of various samples by systematically varying of fluence and exposure time. For PMMA irradiated in the desorption regime (fluence/shot ≤ 0.2 mJ/cm2), the surface presents craters whose profile depends on the dose (Grey [Gy] = 1 J/kg). The crater evolution proceeds from the competition between two main degradation processes, that is chain scission and cross linking. Namely, at low dose (≤ 1 GGy) polymer chain scission is followed by the blow up of the volatile, molecular fragments, forming the crater. At high dose (> 10 GGy) the broken chain-ends, in the near-surface layer of the remaining material, recombine by cross-linking, opposing desorption by surface hardening. In a recent experiment at LCLS FEL facility, PMMA was irradiated at high fluence; the cross-linking signature was identified from Raman spectroscopy. A kinetic model could be adapted for interpreting these original and very promising results.

Soft X-ray contact microscopy (SXCM) experiments have been performed using the Prague Asterix Iodine Laser System (PALS). Laser wavelength and pulse duration were λ = 1.314 μm and τ (FWHM) = 450 ps, respectively. Pulsed X rays were generated using teflon, gold, and molybdenum targets with laser intensities I ≥ 1014 W/cm2. Experiments have been performed on the nematodes Caenorhabditis elegans. Images were recorded on PMMA photo resists and analyzed using an atomic force microscope operating in contact mode. Our preliminary results indicate the suitability of the SXCM for multicellular specimens.

The diamond films, properties of which are presented in this contribution, were grown on a silicon substrate using the microwave plasma-enhanced chemical vapour deposition (MPECVD) technique. The films were characterised by means of Raman/photoluminescence/FTIR spectroscopy, XRD, RBS and elastic recoil detection analysis (ERDA). Thermoluminescent (TL) responses of this material to photons provided by radionuclide 60Co source (1.173/1.332 MeV) over a dose range from 1 to 50 Gy were measured. During the initial, i.e. first irradiation cycle, the dependencies of TL signals on the γ-ray doses seem to be quite linear up to 20 Gy. However, dramatic changes in the evolution of the TL signals occur during further irradiation, i. e. when the irradiation continues with another irradiation cycle. Then the sensitivity of the TL material to high-energy photons increases significantly with the dose. An explanation of this phenomenon lies very likely in the radiation driven formation of TL active defects.

In this paper we describe the efficient and substantial decomposition of C60 in toluene solution, induced by moderate intensity (I = 20 - 55 MW cm-2) near infrared (γ = 1064 nm) laser radiation. This behavior is surprising since both uncharged fullerene and toluene do not have any absorption bands at this wavelength. The decomposition efficiency and products are investigated with UV-Vis absorption spectrophotometry and high-performance liquid-chromatography (HPLC). Possible mechanisms of the fullerene decomposition are discussed.

Experiments designed to clarify the role of molecular oxygen in the photolysis of fullerene are described. The formation of oxygen-fullerene adducts, both in fullerene solutions in various solvents and in micro-crystallites formed by evaporating these solutions, and their photolysis was studied under various experimental conditions. The results confirm that the role of oxygen in the photolysis process in these systems is ambivalent and highly dependent on the conditions under which the irradiation of the fullerenes occurs (wavelength and intensity of the photolyzing radiation, character of the solvent molecules, presence of additional molecules in the solvent-fullerene-oxygen system, etc.).

Thermoluminescent dosemeters of LiF:Mg,Ti, LiF:Mg,Cu,P and CaF2:Dy were used as secondary standards in calibration measurements of X-ray emission from a laser-produced aluminium plasma. Relative sensitivities of the thermoluminescent dosemeters were found to be independent of dose rate over a wide dose rate region. The photon detection efficiency of thermoluminescent dosemeters is compared to that of semiconductor Si photodiodes. The thermoluminescent dosemeters are presented as a powerful tool for testing of capability of a semiconductor photodiode detector of X-ray pulse energy emitted from the laser-produced plasma.

Applying a deconvolution of the thermoluminescence glow curves, parameters of single glow peaks of CaF2: Dy TLD 200 dosemeters irradiated by soft X-rays were determined. A dependence of the height ratio of low temperature (T?393, 413 and 473 K) single peaks on energy of absorbed photons was measured in a region of 1–22.2 keV. Standard radionuclides109Cd,238Pu,55Fe and iodine laser produced aluminium plasma (Te~500 eV) were used as soft X-ray sources. The ratios of the heights of different single peaks are discussed with respect to high local doses. The decreasing ratio of the heights of the first and third and/or second and third peak with increasing photon energy allows to determine reversely a mean photon energy of absorbed soft X-ray radiation.

We report on a single-shot micropatterning of an organic polymer achieved by ablation with demagnifying projection using a Ne-like Zn 21.2 nm soft x-ray laser. A nickel mesh with a period of 100 μm was ~10× demagnified and imprinted on poly(methyl methacrylate) via direct ablation. The quality of the ablated microstructure was found to be mainly dependent on the quality of the projected mask. This first demonstration (to our knowledge) of single-shot projection, single-step lithography illustrates the potential of soft x-ray lasers for the direct patterning of materials with a resolution scalable down to submicrometer domain.

Preparation of macroscopic amount of C60 clusters (fullerenes) by the iodine laser is reported.

Laser–plasma interaction (LPI) at intensities $10^{15}{-}10^{16}~\text{W}\cdot \text{cm}^{-2}$is dominated by parametric instabilities which can be responsible for a significant amount of non-collisional absorption and generate large fluxes of high-energy nonthermal electrons. Such a regime is of paramount importance for inertial confinement fusion (ICF) and in particular for the shock ignition scheme. In this paper we report on an experiment carried out at the Prague Asterix Laser System (PALS) facility to investigate the extent and time history of stimulated Raman scattering (SRS) and two-plasmon decay (TPD) instabilities, driven by the interaction of an infrared laser pulse at an intensity ${\sim}1.2\times 10^{16}~\text{W}\cdot \text{cm}^{-2}$with a ${\sim}100~\unicode[STIX]{x03BC}\text{m}$scalelength plasma produced from irradiation of a flat plastic target. The laser pulse duration (300 ps) and the high value of plasma temperature (${\sim}4~\text{keV}$) expected from hydrodynamic simulations make these results interesting for a deeper understanding of LPI in shock ignition conditions. Experimental results show that absolute TPD/SRS, driven at a quarter of the critical density, and convective SRS, driven at lower plasma densities, are well separated in time, with absolute instabilities driven at early times of interaction and convective backward SRS emerging at the laser peak and persisting all over the tail of the pulse. Side-scattering SRS, driven at low plasma densities, is also clearly observed. Experimental results are compared to fully kinetic large-scale, two-dimensional simulations. Particle-in-cell results, beyond reproducing the framework delineated by the experimental measurements, reveal the importance of filamentation instability in ruling the onset of SRS and stimulated Brillouin scattering instabilities and confirm the crucial role of collisionless absorption in the LPI energy balance.

The first observation of fullerene C60ultraviolet photolysis in hexane solution was published two years ago [1]. Similar further experiments realized with an ultraviolet lamp and solar light gave inconsistent results with ambiguous interpretations. We report the unexpectedly fast and efficient degradation of the fullerenes in n-hexane solutions, induced by an XeCl-excimer laser. Well-defined experimental conditions and good reproducibility in these experiments allow us to estimate the minimal value of the quantum yield of fullerene photolysis.The first observation of fullerene C60ultraviolet photolysis in hexane solution was published two years ago [1]. Similar further experiments realized with an ultraviolet lamp and solar light gave inconsistent results with ambiguous interpretations. We report the unexpectedly fast and efficient degradation of the fullerenes in n-hexane solutions, induced by an XeCl-excimer laser. Well-defined experimental conditions and good reproducibility in these experiments allow us to estimate the minimal value of the quantum yield of fullerene photolysis.

The recent commissioning of a X-ray free-electron laser triggered an extensive research in the area of X-ray ablation of high-Z, high-density materials. Such compounds should be used to shorten an effective attenuation length for obtaining clean ablation imprints required for the focused beam analysis. Compounds of lead (Z=82) represent the materials of first choice. In this contribution, single-shot ablation thresholds are reported for PbWO4and PbI2exposed to ultra-short pulses of extreme ultraviolet radiation and X-rays at FLASH and LCLS facilities, respectively. Interestingly, the threshold reaches only 0.11 mJ/cm2 at 1.55 nm in lead tungstate although a value of 0.4 J/cm2is expected according to the wavelength dependence of an attenuation length and the threshold value determined in the XUV spectral region, i.e., 79 mJ/cm2at a FEL wavelength of 13.5 nm. Mechanisms of ablation processes are discussed to explain this discrepancy. Lead iodide shows at 1.55 nm significantly lower ablation threshold than tungstate although an attenuation length of the radiation is in both materials quite the same. Lower thermal and radiation stability of PbI2is responsible for this finding.

The irradiation effects of multiple ultrafast shots of laser beams with estimated fluences of some tens of mJ/cm2on a EUV Mo/Si multilayer have been studied. Irradiation damage has been induced by multiple shots of two different lasers (100 fs 400 nm the first, 1.5 ns 46.9 nm the second). The study has been motivated by the need of multilayer Mo/Si optics for the delay lines of the FEL source FERMI@Elettra, where these mirrors will be used to reflect 100 fs pulses at 13 nm with a fluence of some mJ/cm2. The analysis has been performed by means of different techniques as EUV and soft X-ray reflectivity, XPS, and Standing wave enhanced XPS. Simulations have been carried on by means of an indigenously developed software OPAL (Optical Properties of Anisotropic Layers) for the calculation of the absorbed energy by the stratified medium. AFM and SEM surface images have been also acquired. In the irradiation at 400 nm, we observed a significant change in the multilayer performance at fluences of 100 mJ/cm2and above with a significant reduction of reflectivity. Spectroscopic analysis allowed to correlate the decrease of reflectivity with the degradation of the multilayer stacking, ascribed to Mo-Si intermixing at the Mo/Si interfaces of the first few layers, close to the surface of the mirror. Preliminary tests have been also performed on the sample irradiated at 46.9 nm.

ELI-Beamlines will be a high-energy, repetition-rate laser pillar of the ELI (Extreme Light Infrastructure) project. It will be an international facility for both academic and applied research, slated to provide user capability since the beginning of 2016. The main objective of the ELI-Beamlines Project is delivery of ultra-short high-energy pulses for the generation and applications of high-brightness X-ray sources and accelerated particles. The laser system will be delivering pulses with length ranging between 10 and 150 fs and will provide high-energy petawatt and 10-PW peak powers. For high-field physics experiments it will be able to provide focused intensities attaining 1024Wcm-2, while this value can be upgraded in a later phase without the need to upgrade the building infrastructure. In this paper we describe the overall conception and layout of the designed ELI-Beamlines facility, and review some essential elements of the design.

A multichannel detection system having a dynamic range of "1 x 10-9 Gy - 20 Gy was developed with the use of commercially produced Si-photodiodes and TLDs for accurate measurement of X ray energy emitted from plasma-focus facility and from laser-produced plasmas. The proof of linearity of the employed detectors accomplished by a comparison of their responses to a broad band spectrum of X rays emitted from plasmas, is reported. It is demonstrated that TLDs irradiated with no protective filter show an incorrect response due to overloading in the sub-keV range and repopulation of dosimetric peaks induced by the UV radiation. The measurement of the power of undesirable secondary X ray sources driven by the primary plasma inside the interaction chamber was performed on the basis of analysis of space dependence of X ray intensity with respect to the assumed r-2 decrease in the intensity far away from the plasma.