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The recently discovered, chlorophyll-f-containing, far-red photosystem II (FR-PSII) supports far-red light photosynthesis. Participation and kinetics of spectrally shifted far-red pigments are directly observable and separated from that of bulk chlorophyll-a. We present an ultrafast transient absorption study of FR-PSII, investigating energy transfer and charge separation processes. Results show a rapid subpicosecond energy transfer from chlorophyll-a to the long-wavelength chlorophylls-f/d. The data demonstrate the decay of an ∼720-nm negative feature on the picosecond-to-nanosecond timescales, coinciding with charge separation, secondary electron transfer, and stimulated emission decay. An ∼675-nm bleach attributed to the loss of chl-a absorption due to the formation of a cation radical, PD1+•, is only fully developed in the nanosecond spectra, indicating an unusually delayed formation. A major spectral feature on the nanosecond timescale at 725 nm is attributed to an electrochromic blue shift of a FR-chlorophyll among the reaction center pigments. These time-resolved observations provide direct experimental support for the model of Nürnberg et al. [D. J. Nürnberg et al., Science 360, 1210–1213 (2018)], in which the primary electron donor is a FR-chlorophyll and the secondary donor is chlorophyll-a (PD1 of the central chlorophyll pair). Efficient charge separation also occurs using selective excitation of long-wavelength chlorophylls-f/d, and the localization of the excited state on P720* points to a smaller (entropic) energy loss compared to conventional PSII, where the excited state is shared over all of the chlorin pigments. This has important repercussions on understanding the overall energetics of excitation energy transfer and charge separation reactions in FR-PSII.

A method for probing the temporal evolution of ultra-fast carrier generation and recombination processes in wide-bandgap semiconductors, e.g. diamond, is described. Two extreme ultraviolet (pump) pulses produced by high-order harmonic generation in Argon gas (with a photon energy of 32 eV) are superimposed on a sample with a small angle between them, inducing periodic changes in the refractive index of the material causing it to act as a transient diffraction grating. A delayed synchronized infrared (probe) pulse gets diffracted on the induced phase grating and is detected in the first diffraction order. By varying the time-delay between pump and probe, the full temporal evolution of the free carrier generation and recombination processes can be resolved. Feasibility calculations and the first steps towards experimental implementation are presented.

We report on the fabrication and characterization of amplitude and phase samples consisting of well defined Au or Al features formed on ultrathin silicon nitride membranes. The samples were manufactured using electron beam lithography, metallization and a lift-off technique, which allow precise lateral control and thickness of the metal features. The fabricated specimens were evaluated by conventional microscopy, atomic force microscopy and with the digital in-line holography set-up at the Lund Laser Centre. The latter uses high-order harmonic generation as a light source, and is capable of recovering both the shape and phase shifting properties of the samples. We report on the details of the sample production and on the imaging tests with the holography set-up.

In this paper a new approach to a laser-produced plasma EUV source based on a tin target is presented. A thin layer of pure tin and composite layers consisting of Sn with Si, SiO and LiF are investigated. The target composed of several thin layers produces less debris than the other targets and provides a conversion efficiency (CE) in the 13.5-nm±1% band at least comparable to the CE for the pure tin slab target. The largest CE was observed for the target composed of a mixture of Sn and LiF, due to the fact that lithium, similarly to tin, is a strong emitter at 13.5 nm.

A compact, high-repetition table-top EUV source, based on a gas-puff target, is presented. This source was developed in our group and is capable of emitting quasi-monochromatic radiation at 13.8 nm wavelength with the inverse relative bandwidth of 140 and pulse energies up to ∼1.3 μJ/pulse at 10-Hz repetition rate. The source is debris-free, operates near the lithographic wavelengths and offers the energy density of ∼0.4 mJ/cm2 in each EUV pulse. These three features make the source attractive for lithographic experiments. The timing optimization of the source, its energy per pulse, spectral and spatial distributions are pointed out in detail as well as the enhancement in energy density achievable with a multi-layer collector mirror compared to a planar mirror of equal reflectivity.

Laser plasma with temperature of the order of tens eV can be an efficient source of extreme ultraviolet (EUV). The radiation can be focused using different kind of optics, giving sufficient fluence for some applications. In this work we present results of investigations concerning applications of a laser plasma EUV source based on a double stream gas puff target. The source was equipped with two different grazing incidence collectors. One of them was a multifoil collector, the second one was an axisymmetrical ellipsoidal collector. The multifoil mirror was used mainly in experiments concerning micromachining of organic polymers by direct photo-etching. The experiments were performed for different polymers that were irradiated through a fine metal grid as a contact mask. The smallest element of a pattern structure obtained in this way was 5 μm, while the structure height was 50 μm giving an aspect ratio about 10. The laser-plasma EUV source equipped with the axisymmetrical ellipsoidal collector was used for surface modification of organic polymers and inorganic solids. The surface morphology after irradiation was investigated. Different forms of microand nanostructures were obtained depending on material and irradiation conditions.

In this paper a possibility of performing fluorescence experiments in extreme ultraviolet (EUV) using a laboratory EUV source was demonstrated. Usually such measurements are performed using third-generation synchrotrons because of extremely low probability of fluorescence in this wavelength range. In this work a 10 Hz laser-plasma EUV source based on a gas puff target was used. Fluorescent radiation from Al and Si was registered. Despite relatively low spectral resolution, some differences in Si spectra coming from different kind of samples were revealed.

Extreme ultraviolet (EUV) radiation is absorbed in a thin surface layer of any material. Irradiation of material samples with intense EUV pulses may cause different surface changes. Some of them, especially connected with material desorption, can be clearly visible using an optical or electron microscope. Other changes concerning crystal structure or chemical composition may not be visible under the microscope. They can however be detected using the EUV radiation itself. In this paper a new method of measurement of surface changes by irradiation with a laser-plasma EUV source is presented. The radiation was collected and focused on a material surface using a specially designed multifoil collector. Radiation scattered or excited in the material was detected with the use of a Wolter-type mirror coupled to a back-illuminated CCD camera. Depending on material samples, images with different intensity distributions were registered. For some samples, the intensity distributions of the images obtained before and after irradiation were slightly different. The intensity differences in such cases allowed us to obtain differential images. The appearance of such images was assumed to be evidence of surface changes.

Design and development of the multi-foil optic (MFO) condenser for a gas puff laser plasma source for EUV lithography is presented. The MFO in general is a soft x-ray optic which consists of two perpendicular sets of very thin reflecting surfaces, where photons are reflected at grazing angles. The aim of the work was to design the condenser working for ~100 eV photons focusing from point to point ~40 cm distant. Initial design and simulations are described and compared to early experiments performed in visible light. The performance of the optic over the initial requirements is discussed. We also briefly discuss several other MFO modifications, including condensers and collimators for laboratory purposes or the wide field x-ray scanning modules for satellite astronomy.

The first results of experiments on direct photo-etching of heated PTFE using a 10 Hz X-ray source based on a laser-irradiated gas puff target are presented. X-ray radiation in the wavelength range from 6 to 20 nm was produced as a result of irradiation of a double-stream gas puff target with Nd:YAG laser pulses of energy 0.8 J and time duration 3 ns. The resulting X-ray pulses with energy of about 100–200 mJ were used to irradiate samples of PTFE to create microstructures by direct photo-etching. Strong enhancement of the photo-etching process was observed for samples heated up to 300 °C.

The first results of experiments on direct photo-etching of organic polymers using a 10Hz X-ray source based on a laser-irradiated gas puff target are presented. X-ray radiation in the wavelength range from 2 to 15nm was produced as a result of irradiation of a double-stream gas puff target with Nd:YAG laser pulses of energy 0.8J and time duration 3ns. The resulting X-ray pulses with energy of about 100-200mJ were used to irradiate samples of organic polymers to create microstructures by direct photo-etching. The obtained results show that direct photo-etching using the laser-plasma X-ray source could be useful for micromachining of organic polymers.

Soft x-ray emission from a new double-stream gas puff target irradiated with a nanosecond, high-power Nd:YAG laser pulse has been studied. The target was formed by pulsed injection of gas into a hollow gas stream made from helium by using a double-nozzle setup. Strong x-ray emissions near 10 nm from the double-stream krypton/helium, near 11 nm from the xenon/helium, and at 13 nm from the oxygen/helium targets were observed. The emission from the double-stream gas puff target was several times higher as compared to the ordinary gas puff targets, and comparable to the emission from the solid targets irradiated in the same conditions.

X-ray emission from a double-stream gas puff target irradiated with a nanosecond Nd:glass laser pulse was studied for the first time. The target was formed by pulsed injection of a high-density gas into a gas cloud by using the double-nozzle setup. This new concept allows a high-density gaseous target to be formed at a relatively large distance from the nozzle output. Enhanced X-ray emission in the 1-keV energy range and a smaller source size were observed as compared to the ordinary gas puff target created by pulsed injection of gas into vacuum. This new approach should be useful in the development of a laser-produced X-ray source for various applications.

We study high-order harmonic generation in argon driven by an intense 800 nm laser field and a small fraction of its second harmonic. The intensity and divergence of the emitted even and odd harmonics are strongly modulated as a function of the relative delay between the two fields. We provide a detailed analysis of the underlying interference effects. The interference changes drastically when approaching the cutoff region due to a switch of the dominant trajectory responsible for harmonic generation.

We characterize and control the harmonic emission in the spectral and spatial domains in order to define in which conditions the harmonic radiation can be a high-quality seed for soft x-ray and x-ray free-electron lasers. The length of the gas cell, where harmonics are generated, was optimized and the energy per pulse was determined in absolute value with a calibrated x-ray photodiode. The beam spatial profile was measured and, in some conditions, a very collimated beam with a half-angle divergence below 1 mrad could be obtained. We also show that increasing the intensity of the fundamental laser field leads to a considerable broadening of the bandwidth of the harmonic radiation, allowing us to cover a large spectral range. This effect is due to fundamental reshaping leading to an efficient phase matching of both short- and long-trajectory contributions.

Extreme ultraviolet (EUV) is strongly absorbed in any materi al and can be transmitted only through very thin foils. The material surface after irradiation can remain unchanged or becomes modified in some way depending on radiation fluence and material properties. In so me materials the surface changes may aris e due to fast melting or boiling followed by solidification. In other cases photochemical or photothermal ablation can occur. It requires relatively high radiation fluence of the order of tens mJ/cm 2 . A laser-plasma EUV source based on a gas pu ff target equipped with a proper optic can deliver such conditions. In this work EUV radiation coming from xenon or krypton plasma was focused using an ellipsoidal grazing incidence collector. Different kind of material samples were irradiated in the focal plane or at some distance behind the focal plane. This way different intensitie s were applied for irradiation of the samples. Irradiation was performed with 10 Hz repetition rate and different time duration varying from 1s to 2 min. Surface morphology after irradiation was investigated using a scanni ng electron microscope. In a case of so me materials EUV intensity in the focal plane was sufficient for ablation. In other cases material ablation was not possible but surface structure was modified. Forms of the structures for a certain material depend both on EUV fluence in a single shot and the number of shots. Keywords: laser-plasma, EUV, gas puff target , photo-etching, surface modification

For the detection of the energy radiation a detection system is necessary. The sysytem usually consists of optical filters detectors and electronics units It should provide to measure energy radiation with defined uncertainty in the specific wavelength range. The wavelength range is determined by features of optical filters. As the filters, the multilayer mirrors, Fresnel lens or absorption layers could be used. It is worth to notice, that it is very difficult to separate water widow spectrum using single optical element. The efficient filtration can be achieved by using a system of filters. For example the determination of the band-pass filter could be accomplished by two filters operated in the shorter wavelength range and in the longer one. Analysis of the literature and databases from some research centers show that for the detection system some multilayer mirrors or absorption filters can be appropriate. The simulation procedure was proposed for designing of the mirrors with high reflectivity in the water window spectrum. The three models of mirrors (Cr/Sc, Cr/V, Cr/Ti ) were taken into consideration in mentioned above analysis. The results of the simulations are presented in Fig. 1. Fig. 1. Reflectance of the simulated multilayer mirrors. The curves were determined theoretically. Basis on the results the two types of multilayer mirrors were selected for further considerations. The calculations were made together with scientists from Fraunhoffer Institute (Jena, Germany). The conclusions from the results were implemented practically during technological process. The results showed that better parameters of fabricated mirrors achieved for Cr/Ti structures. For optimal features of the structure (layer period of 4.235 nm, layers number of 150, incidence angle of 70 °), the reflectivity characteristics were determined. The analyzed mirrors show both high reflectivity and spectral selectivity. It is worth to note, that the energy measurements for the whole water window region are not provided because of shortcomings of mirror selectivity. During the next

Laser plasma source in WAT, Poland, is used as the source of EUV radiation for lithography and illumination of biological samples. The source has to be equipped with a complementary condensor with the goal of having a higher peak intensity than using current systems and moreover with the ability to illuminate larger areas homogeneously. The work concentrates on the analysis and design process of the optics based on the known source parameters, namely typical spectra, angular and intensity distributions and other constraints. Further, the question of illuminating the samples via multi shot approach by shifting the sample is discussed and estimates on the optimal sample shift in between two shots are explained.

In this paper some results of investigations concerning interaction of EUV radiation with inorganic and organic materials were presented. Samples of different materials were irradiated with a 10 Hz laser - plasma EUV source based on a gas puff target. The source was equipped with grazing incidence and multilayer collecting mirrors. The grazing incidence collector was used in experiments concerning surface modification and micromachining of different materials. The micromachining experiments were performed for different polymers that were irradiated through a fine metal grid as a contact mask. For fluoropolymers, EUV radiation with fluence of 10 mJ/cm 2 was enough for efficient photo-etching. The photo-etching speed was maximal for polytetrafluoroethylene (PTFE) reaching 30nm per shot. It was shown that using such a method microstructures with high aspect ratio could be produced. Experiments connected with surface modification were performed either with organic or inorganic materials. Different kinds of surface structures were obtained depending on irradiated materials and irradiation parameters. The Mo/Si collector together with argon plasma was used for obtaining a quasi-monochromatic radiation for EUV microscopy and some metrological applications.

Elongated plasma columns can be formed by irradiation a gas puff target with a laser beam focused in line using an axicon. The plasma columns created from high-density gas puff targets based on a double-stream approach have been studied. The results of investigations with the use of optical and X-ray imaging and X-ray spectroscopy are presented.

Results on micro- and nanoprocessing of organic polymers with extreme ultraviolet (EUV) radiation from a compact laser plasma EUV source based on a gas puff target are presented in the paper. Processing of polymers is connected with non-thermal ablation under the influence of energetic EUV photons. The process can be useful for practical applications as it makes possible to produce structures with sub-micron spatial resolution that is not possible using the thermal ablation. The new technology will be used for production of photonic microstructures and for modification of polymer surfaces for biomedical applications.

The paper presents a measuring system of extreme ultraviolet radiation pulses (13.5 nm). The system is used for monitoring a gas-puff laser-plasma source constructed at the Institute of Optoelectronics. The radiation source and the system are used in metrology of EUV optics. The system consists of a detection head and a system of optical filters, which are housing in a special construction. Additional element of the measuring system is a special processing unit. The measuring system was used during investigations of the plasma-laser optimization. The results were comparable with the ones from a spectrograph and an Emon energy meter.

The results of the spectral and spatial measurements of a laser-produced (LPP) plasma source of extreme ultraviolet (EUV) for 13.5 nm are presented. The double stream Xe/He gas puff target in the source was utilizing. The source was equipped with a Nd: YAG laser system (E = 0.55 J, t = 3.9 ns, f = 10 Hz, M2 = 2.5) and was dedicated to EUV metrology purposes. An advantage of this approach of the laser-plasma source is a debris free EUV emission. For the spectral research a transmission grating spectrograph (TGS) and a grazing incidence spectrograph (GIS) were utilized. For spatial measurements a pinhole camera was employed. The influence on EUV emission of the laser focal spot position in relation to the gas puff target and the time delays between opening valves and the laser pulse were investigated.

Organic polymers (PMMA, PTFE, PET, and PI) are considered as the important materials in microengineering, especially for biological and medical applications. Micromachining of such materials is possible with the use of different techniques that involve electromagnetic radiation or charged particle beams. Another possibility of high aspect ratio micromachining of PTFE is direct photo-etching using synchrotron radiation. X-ray and ultraviolet radiation from other sources, for micromachining of materials by direct photo-etching can be also applied. In this paper we present the results of investigation of a wide band soft X-ray source and its application for direct photo-etching of organic polymers. X-ray radiation in the wavelength range from about 3 nm to 20 nm was produced as a result of irradiation of a double-stream gas puff target with laser pulses of energy 0.8 J and time duration of about 3 ns. The spectra, plasma size and absolute energies of soft X-ray pulses for different gas puff targets were measured. Photo-etching process of polymers irradiated with the use of the soft X-ray radiation was analyzed and investigated. Samples of organic polymers were placed inside a vacuum chamber of the x-ray source, close to the gas puff target at the distance of about 2 cm from plasmas created by focused laser pulses. A fine metal grid placed in front of the samples was used as a mask to form structures by x-ray ablation. The results of photo-etching process for several minutes exposition with l0Hz repetition rate were presented. High ablation efficiency was obtained with the use of the gas puff target containing xenon surrounded by helium.

In the paper a newly developed compact and debris-free laser plasma soft X-ray source is presented. The source is based on the double-stream gas puff target approach. The targets are formed by pulsed injection of high-Z gas (xenon, krypton or argon) into a hollow stream of low-Z gas (helium or hydrogen) using the valve system composed of two electromagnetic valves and equipped with the double-nozzle setup. The outer stream of gas confines the inner stream improving the gas puff target characteristics (higher density of high-Z gas at longer distance from the nozzle output). It causes efficient absorption of laser energy in a plasma and strong soft X-ray production. Additionally, the use of the double-stream gas puff target approach makes possible to avoid degradation of the nozzle by the laser plasma. Spectral characteristics of soft X-ray emission from the source are presented. Applications in X-ray pulsed radiography, microprocessing of polymers by direct soft X-ray photo-etching, and EUV technologies are discussed.

The results of experiments on micromachining of organic polymers by direct photo-etching using a compact laser plasma soft X-ray source based on a gas puff target are presented. Soft X-ray radiation in the wavelength range from 2 to 15 nm was produced as a result of irradiation of a double-stream gas puff target with 0.8 J/3 ns laser pulses from a Nd:YAG laser. The soft X-ray pulses with energy of about 100-200 mJ in a single pulse were used to irradiate samples from organic polymers to form microstructures. The obtained results show that direct photo-etching using the laser plasma soft X-ray source could be useful for micromachining of organic polymers. Strong enhancement of the photo-etching process was observed for the samples heated up to 140° C.

A new high-density gas puff target for experiments on laser-driven X-ray lasers is presented. The target is based on a double-stream gas puff target approach, which makes possible to form an elongated gas sheet with steep density gradient and high density of gas in the interaction region. In the paper the valve system to produce the gas puff targets and the results of the target characterization measurements performed using X-ray backlighting technique are presented.

A pulse-train Nd:YAG laser system consisting of repetitively Q-switched Nd:YAG oscillator with Cr 4+ :YAG saturable absorber, double pass Nd:YAG amplifier and stimulated Brillouin scattering (SBS) pulse compressor has been demonstrated. Number and energy of the laser pulses were controlled by adjusting width and amplitude of the flash lamp pumping pulses. Efficient SBS compression of Nd:YAG laser pulses was obtained using single-cell compressor.

Experiments on direct photo-etching of organic polymers induced by high-intensity nanosecond pulses of soft X-ray radiation from a laser plasma X-ray source based on a gas puff target are presented. X-rays in the wavelength range from about 1 nm to 8 nm were produced by irradiation of the xenon/helium double-stream gas puff target with laser pulses from the Prague Asterix Laser System (PALS). The resulting X-ray pulses were used to irradiate samples from organic polymers and form microstructures. The results show relatively high efficiency of X-ray direct photo-etching that could be useful for micromachining of organic polymers.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

For conventional wavelength (UV-Vis-IR) lasers delivering radiation energy to the surface of materials, ablation thresholds, ablation (etch) rates, and the quality of ablated structures often differ dramatically between short (typically nanosecond) and ultrashort (typically femtosecond) pulses. Various short-wavelength (l < 100 nm) lasers emitting pulses with durations ranging from ~ 10 fs to ~ 1 ns have recently been put into a routine operation. This makes it possible to investigate how the ablation characteristics depend on the pulse duration in the XUV spectral region. 1.2-ns pulses of 46.9-nm radiation delivered from a capillary-discharge Ne-like Ar laser (Colorado State University, Fort Collins), focused by a spherical Sc/Si multilayer-coated mirror were used for an ablation of organic polymers and silicon. Various materials were irradiated with ellipsoidal-mirror-focused XUV radiation (λ = 86 nm, τ = 30-100 fs) generated by the free-electron laser (FEL) operated at the TESLA Test Facility (TTF1 FEL) in Hamburg. The beam of the Ne-like Zn XUV laser (λ = 21.2 nm, τ < 100 ps) driven by the Prague Asterix Laser System (PALS) was also successfully focused by a spherical Si/Mo multilayer-coated mirror to ablate various materials. Based on the results of the experiments, the etch rates for three different pulse durations are compared using the XUV-ABLATOR code to compensate for the wavelength difference. Comparing the values of etch rates calculated for short pulses with those measured for ultrashort pulses, we can study the influence of pulse duration on XUV ablation efficiency. Ablation efficiencies measured with short pulses at various wavelengths (i.e. 86/46.9/21.2 nm from the above-mentioned lasers and ~ 1 nm from the double stream gas-puff Xe plasma source driven by PALS) show that the wavelength influences the etch rate mainly through the different attenuation lengths.

Summary form only given. In this paper, we present the first experiments on direct photo-etching of organic polymers using a laser plasma x-ray source based on a laser-irradiated gas puff target.

Summary form only given. In this paper a newly developed compact EUV source is presented. The source is based on the double-stream gas puff target. Using the double-stream gas puff target approach a compact low-power laser plasma light source for metrology of optics, masks and resists for EUV lithography technologies has been developed.

In the paper a newly developed compact laser plasma EUV source is presented. The source is based on the double-stream gas puff target approach. The targets are formed by pulsed injection of high-Z gas (xenon) into a hollow stream of low-Z gas (helium) using the valve system composed of two electromagnetic valves and equipped with the double-nozzle setup. The outer stream of gas confines the inner stream improving the gas puff target characteristics (higher density of high-Z gas at longer distance from the nozzle output). It causes efficient absorption of laser energy in a plasma and strong EUV production. The source has been developed in the frame of the EUV sources development project under the MEDEA+ program.

Spectral measurements of a laser-produced soft x-ray and EUV source based on a double-stream gas puff target are described. The target was irradiated with a Nd:glass laser producing 1 ns pulses with energy up to 10 J. Production in the wavelength range up to 20 nm (x-ray and EUV emissions) have been measured from xenon, krypton, argon, and nitrogen targets using the transmission grating spectrometer with the back-illuminated CCD. Spectral characteristics of x-ray and EUV emissions are presented.

In this work we demonstrate a soft x-ray laser with neon-like argon ions using a gas puff target irradiated with acombination of long 600 ps and short 6 ps high-power laser pulses with a total of 10 J energy. The gas puff target was formed by pulsed injection of gas from a high-pressure solenoid valve through a nozzle in the form of a narrow slit. Thetarget was irradiated in a travelling-wave excitation geometry. Lasing was observed on the 3p 'So —f 3s 1P1 transition at 46.9 nm and the 3d 1P1 — 3p 1P transition at 45. 1 nm. Gain of 1 1 cm' was measured on these transitions for targets upto 0.9 cm long.Keywords: x-ray lasers, laser-produced plasmas, x-ray optics, gas puff target 1. INTRODUCTION Significant progress towards the realization of a laser-driven tabletop x-ray laser has been achieved during the last few years using different variants of the prepulse technique.15 In this technique a solid target is irradiated with several laserpulses. The first pulse is used to create a large-scale length plasma, which has the appropriate density range for gain andsufficiently small density gradients for laser propagation. The subsequent pulses can be absorbed more efficiently and heatthe preformed plasma to lasing conditions. Efficient, high-brightness soft x-ray lasers with neon-like and nickel-like ions

Characterization measurements of a laser-produced x-ray source based on a double-stream ga puff target are presented. The target was irradiated with a Nd:glass laser producing 1 ns pulses with energy up to 10 J. Production in the wavelength range up to 200 nm have been measured form xenon, krypton, argon, and nitrogen targets using the transmission grating spectrometer with the back-illuminated CCD and the absolutely calibrated silicon photodiodes. Spectral characteristics of x-ray and EUV emissions are presented.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Generation of x-ray and extreme ultraviolet (EUV) radiation from laser-produced source with a new double-stream gas puff target has been investigated. The target was formed by pulsed injection of heavy gas (argon, or xenon) into a hollow gas stream from helium by using a double-nozzle setup. This new approach allows to form a high-density gaseous target at a relatively large distance from the nozzle output. X-ray emission was produced by irradiation of the argon/helium target with pulses of 1 ns time duration with energy up to 20 J from a Nd:glass laser. Strong x-ray emission at the wavelength near 0.4 nm from the argon target, similar to the emission from the solid sulphur target irradiated in the same conditions, have been observed. These new results may be useful to develop a laser-produced radiation source for x-ray lithography. To generate EUV radiation the xenon/helium target was irradiated using a Nd:YAG laser producing pulses of 10 ns and 0.7 J or energy. Efficient production near 11 nm from the xenon target exceeding emissions from solid targets was observed that should be useful for EUV lithography.

In this work a double stream ga puff target was applied in experiments connected with a laser plasma soft x-ray source. The results of the gas puff target density measurements was presented. The experimental results of x-ray measurements concern two experiments. The first one was performed in the Institute of Optoelectronics using 1 ns Nd:glass laser. In this experiment soft x-ray radiation around 1 keV and 3 keV was investigated. The measurements were performed using an x-ray pinhole camera, a flat crystal spectrograph and a soft x-ray photodiode. The second experiment was performed in the Institute for Plasma Physics using a 27 ns KrF laser. In this experiment EUV radiation of the wavelength around 13 nm from the gas puff plasma was measured using a multilayer mirror combined with an x-ray detector. In both experiments it was shown that the emission from the plasma created in the double stream gas puff target was even an order of magnitude higher than in a case of using the ordinary gas puff target.

Soft x-ray emission from plasmas produced using a laser- irradiated gas puff target have been investigated. The use of the gas puff targets, created by pulsed injection of high- density gas from a solenoid valve through a nozzle, eliminates the production of debris associated with solid targets. To improve the gas puff target two approaches have been used: (1) cooling of the valve with liquid nitrogen to increase condensation of gas and (2) formation of the target by injection of gas in gas surrounding the nozzle output using the double nozzle setup. The gas puff targets created with these two approaches were characterized with x-ray backlighting method using laser-produced x-ray source. Laser pulses of 1 ns time duration with energy up to 10 J from a Nd:glass laser and of either 0.9 ns or 10 ns time duration with energies up to 0.7 J from a Nd:YAG laser were used to produce plasmas. Emissions in the soft x-ray range from laser- produced gas puff plasmas were studied for various gases. Significant improvement of x-ray production from the double stream gas puff target has been observed.

We develop and implement an experimental strategy for the generation of high-energy high-order harmonics (HHG) in gases for studies of nonlinear processes in the soft x-ray region. We generate high-order harmonics by focusing a high energy Ti:Sapphire laser into a gas cell filled with argon or neon. The energy per pulse is optimized by an automated control of the multiple parameters that influence the generation process. This optimization procedure allows us to obtain energies per pulse and harmonic order as high as 200 nJ in argon and 20 nJ in neon, with good spatial properties, using a loose focusing geometry (f#≈400) and a 20 mm long medium. We also theoretically examine the macroscopic conditions for absorption-limited conversion efficiency and optimization of the HHG pulse energy for high-energy laser systems.

We examine the characteristics of high-order harmonics generated with 800 nm, 25 mJ, 160 fs laser pulses in an Ar gas cell with the objective of seeding a free electron laser. We measure the energy per pulse and per harmonic, the energy jitter, the divergence and the position stability of the harmonic beam. We perform ab initio numerical simulations based on integration of the time-dependent Schrodinger equation and of the wave equation within the slowly varying envelope approximation. The results reproduce the experimental measurements to better than a factor of two. The interaction of a frequency comb of harmonic fields with an electron bunch in an undulator is examined with a simple model consisting of calculating the energy modulation owing to the seed-electron interaction. The model indicates that the undulator acts as a spectral filter selecting a given harmonic. (Less)

As liver fibrosis is the result of persistent necroinflammation in the liver, pro-inflammatory cytokines secreted in response to cell injury have a central role in the pathogenesis of liver fibrosis. We aimed to investigate the association of cytokine gene polymorphism and liver fibrosis among Chinese patients with chronic hepatitis B.Polymorphisms at interleukin-10 (IL-10-627, -1117), interleukin-1-beta (IL-1beta-511, -31, -3964), interleukin-1 receptor antagonist (IL-1RN), and tumor necrosis factor-alpha (TNF-alpha-308, -238) among Chinese chronic hepatitis B patients were determined. Severe liver fibrosis was defined as Ishak fibrosis score = 4 (of 6).Fifty-nine of 273 (22%) patients had severe fibrosis. The distribution of genotypes for IL-10-627 was CC (11%), CA (41%), and AA (48%). The CC genotype at IL-10-627 was protective against severe fibrosis (odds ratio (OR) 0.11; 95% CI 0.014-0.82; P = 0.032). After adjusted for baseline variables, the adjusted OR of CC genotypes at IL-10-627 for severe fibrosis was 0.063 (95% CI 0.06-0.64; P = 0.063). Other gene polymorphisms at IL-1beta, IL-1RN, TNF-alpha, and IL-10 had no significant association with severe fibrosis. Weak linkage disequilibrium was observed between IL-10-627 and IL-10-1117 with linkage disequilibrium coefficient of 0.12 (P < 0.001). The distribution of haplotypes of IL-10-1117 and IL-10-627 was A-A (69%), A-C (26%), and G-C (5%). High and intermediate IL-10 production (A-C and G-C) haplotypes were protective against severe fibrosis (OR 0.62; 95% CI 0.39-0.99; P = 0.046).High production genotype and haplotypes of IL-10 were associated with less severe liver fibrosis in chronic hepatitis B in Chinese.

The paper describes a debris-free, efficient laser-produced plasma source emitting EUV radiation. The source is based on a double-stream Xe/He gas-puff. Its properties and spectroscopic signatures are characterized and discussed. The spatio-spectral features of the EUV emission are investigated. We show a large body of results related to the intensity and brightness of the EUV emission, its spatial, temporal, and angular behavior and the effect of the repetition rate as well. A conversion efficiency of laser energy into EUV in-band energy at 13.5 nm of 0.42% has been gained. The electron temperature and electron density of the source were estimated by means of a novel method using the FLY code. The experimental data and the Hullac code calculations are compared and discussed. The source is well suited for EUV metrology purposes. The potential of the source for application in EUV lithography was earlier demonstrated in the optical characterization of Mo/Si multi-layer mirrors and photo-etching of polymers.

The paper presents a laser plasma source with a gas pufi target as a metrology tool for EUV technology. The investigations of the source are described. The spectrum emitted from the source and the conversion e-ciency (CE) was measured. The results give an opportunity to design a procedure for a calibration of detectors for extreme ultraviolet. The special laboratory setup was developed based on the procedure. The setup is characterized by very low outlay and good metrology features as well. Compared to currently used systems, this setup can be applied in small factories and laboratories producing for instance EUV detectors.