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Low-temperature plasma production is possible as a result of photoionization using high-intensity extreme ultraviolet (EUV) and soft X-ray (SXR) pulses. Plasma of this type is also present in outer space, e.g., aurora borealis. It also occurs when high-velocity objects enter the atmosphere, during which period high temperatures can be produced locally by friction. Low-temperature plasma is also formed in an ambient gas surrounding the hot laser-produced plasma (LPP). In this work, a special system has been prepared for investigation of this type of plasma. The LPP was created inside a chamber filled with a gas under a low pressure, of the order of 1–50 mbar, by a laser pulse (3–9 J, 1–8 ns) focused onto a gas puff target. In such a case, the SXR/EUV radiation emitted from the LPP was partially absorbed in the low-density gas. In this case, high- and low-temperature plasmas (T e ~100 eV and ~1 eV, respectively) were created locally in the chamber. Investigation of the EUV-induced plasmas was performed mainly using spectral methods in ultraviolet/visible (UV/VIS) light. The measurements were performed using an echelle spectrometer, and additionally, spatial–temporal measurements were performed using an optical streak camera. Spectral analysis was supported by the PGOPHER numerical code.

Optics express 30(26), 47867 (2022). doi:10.1364/OE.477726, Published by Optica, Washington, DC

A near 1-keV photons from the Xe/He plasma produced by the interaction of laser beam with a double stream gas puff target were employed for studies of L absorption edges of period 4 transitional metals with atomic number Z from 26 to 30. The dual-channel, compact NEXAFS system was employed for the acquisition of the absorption spectra. L1–3 absorption edges of the samples were identified in transmission mode using broadband emission from the Xe/He plasma to show the applicability of such source and measurement system to the NEXAFS studies of the transition metals, including magnetic materials.

Interaction of extreme ultraviolet (EUV) pulses of high intensity with gases results in the creation of non-thermalized plasmas. Energies of the driving photons and photoelectrons are sufficient for creation of excited states, followed by emission of the EUV photons. In most cases, decay times of these states are short comparing to the driving EUV pulse. It means that just after stopping of the driving pulse, the EUV emission corresponding to the excited states should also stop. From our earlier measurements in the optical range, however, it can be concluded that lifetimes of such plasmas exceed a time duration of the driving pulse even two orders of magnitude. Hence, it can be expected that the time duration of the EUV emission can be also significantly longer than the irradiation time. In this work, EUV-induced, low-temperature helium (He), krypton, and xenon plasmas were investigated. EUV emission from these plasmas was studied, using a specially prepared detection system, allowing for time-resolved measurements, in selected spectral ranges. The detection system was based on a paraboloidal collector and a semiconductor photodiode, sensitive for the EUV photons. For spectral selection, the corresponding filters or multilayer mirrors were employed. In most cases, the time duration of the EUV emission was significantly longer than the driving EUV pulse. In case of He plasmas, the emission corresponding to excited atoms was detected even hundreds of nanoseconds after the irradiation. It was also shown that the corresponding time profiles depended on densities of gases to be ionized.

In this work, the time development of plasmas produced by interaction of laser pulses, with a nitrogen gas, was investigated. The interaction took place inside a small portion of dense nitrogen gas injected temporarily into a chamber filled with the gas under low pressure. High-temperature plasmas produced directly by the laser pulse were a source of soft x rays and charged particles, ionizing and exciting the surrounding gas. In this way, low-temperature plasmas were produced. The formation of high-temperature plasmas was studied using soft x-ray spectroscopy and x-ray streak imaging. Low-temperature plasmas formed at various distances from the laser focus were investigated using an optical streak camera. Interpretation of the experimental data was supported by numerical modeling of the laser-produced plasma hydrodynamics. It was concluded that depending on the distance from the focal spot, the formation of the low-temperature plasmas was dominated by ion streams or by soft x-ray radiation.

Irradiation of gases with intense pulses of extreme ultraviolet (EUV) can result in the formation of low-temperature plasmas. During the time of irradiation, various non-thermal processes driven by the EUV photons and photoelectrons take place, leading to the creation of excited states of atoms and ions. Fast relaxation of these states should result in EUV emission within a time comparable to the driving EUV pulse. On the other hand, from our earlier works, a time duration of the emission in an optical range is over an order of magnitude longer. It can be thus expected that the time of EUV emission can be also relatively long. In this work, time-resolved measurements of the EUV emission from low-temperature plasmas induced in He, Ne, and Ar gases were performed. Due to a low intensity of the emitted radiation, a specially prepared detection system, based on an EUV collector and an EUV sensitive photodiode, was employed. In all cases, a time duration of the EUV emission was much longer compared with the driving EUV pulse. Time profiles of the corresponding signals were specific for particular gases. In case of He and Ne plasmas, these time profiles varied with initial densities of gases to be ionized. The corresponding dependence was especially visible in case of plasmas induced in helium. In case of Ar plasmas, such dependence was not revealed.

In this work, extreme ultraviolet (EUV) emission, from EUV induced, low-temperature microplasmas, were investigated. To perform temporal measurements of the EUV pulses of low intensity, in a medium vacuum, under the pressure of the order of 0.1–0.01 mbar a special detection system was prepared. The system was based on an EUV collector and a semiconductor detector, sensitive for the EUV photons. The collector consisted of two identical grazing incidence, paraboloidal mirrors, and allowed to focus a part of the radiation emitted from the microplasma onto the detector surface. An absorption filter, mounted between the collector and the detector, allowed for selection of an interesting wavelength range. Plasmas were created by irradiation of small portions of gases, injected into the vacuum chamber, using a laser produced plasma EUV source. Three gases were used for the EUV induced plasma formation: neon, krypton, and xenon. Low-temperature plasmas, created in these gases, contained multiply charged ions, emitting radiation in similar wavelength ranges. Two detectors, AXUV20HS1 and AXUVHS5, were used for the measurements. It was shown that differences between the corresponding signal profiles, obtained using both detectors, were not very significant. Moreover, it was demonstrated that the duration of the EUV emission from plasmas, created in different gases, were comparable with the duration of the driving EUV pulse. The longest EUV emission was observed for Kr plasmas, approximately 1.5 times the full width half maximum of the driving EUV pulse.

In this work, a comparative study of low-temperature plasmas, induced in a gaseous nitrogen by photoionization of the gas using two different irradiation systems, was performed. Both systems were based on laser-produced Xe plasmas, emitting intense extreme ultraviolet (EUV) radiation pulses in a wide wavelength range. The essential difference between the systems concerned formation of the EUV beam. The first one utilized a dedicated ellipsoidal mirror for collecting and focusing of the EUV radiation. This way a high radiation fluence could be obtained for ionization of the N2 gas injected into the vacuum chamber. The second system did not contain any EUV collector. In this case, the nitrogen to be ionized was injected into the vicinity of the Xe plasma. In both cases, energies of emitted photons were sufficient for dissociative ionization, ionization of atoms or even ions. The resulting photoelectrons had also sufficiently high energy for further ionizations or excitations. Low-temperature plasmas, created this way, were investigated by spectral measurements in the EUV, ultraviolet (UV) and visible (VIS) spectral ranges. Time-resolved UV/VIS spectra, corresponding to single-charged ions, molecules, and molecular ions, were recorded. Numerical simulations of the molecular spectra were performed allowing one to estimate vibrational and rotational temperatures of plasmas created using both irradiation systems.

In this work, low-temperature plasmas, induced in a gaseous CO2 by intense extreme ultraviolet (EUV) pulses were investigated with a purpose to determine their ionic/molecular composition and the resulting, potentially reactive species. Two laser-produced plasma EUV sources based on a xenon gas puff target were used to irradiate and ionize of the CO2 gas. The sources, driven by Nd:YAG lasers of different parameters, delivered EUV beams created using reflective, focusing collectors. The CO2-based, low-temperature plasmas induced using both systems, emitted radiation in a wide wavelength range, from vacuum ultraviolet (VUV) to visible light (VIS). The radiation was measured using spectrometers and a streak camera operating in these spectral ranges. In the VUV range, multiple emission lines corresponding to ionic and atomic species together with the CO molecular bands were acquired. Spectra from the UV–VIS range were mainly composed of the CO2 + molecular bands. Numerical simulations of the molecular spectra allowed us to estimate rotational and vibrational temperatures of the EUV induced plasmas. As could be expected, plasmas created in both experimental systems were characterized by different temperatures and intensity ratios of the ionic–atomic spectral lines. The spatio-temporal measurements performed using the streak camera indicated a few times longer lifetime of the EUV induced plasmas, compared to the driving, EUV pulses.

In this paper, we present the application of partially spatially coherent extreme ultraviolet (EUV) radiation from xenon plasma from a laser-plasma source, based on a double stream gas puff target, in coherent imaging. The radiation at the wavelength of 13.5 ± 0.5 nm was employed to record Gabor-type holograms. An iterative algorithm, based on a phase retrieval technique, was developed and used to remove the twin image from the reconstructed EUV image of test objects. Using partially coherent radiation from a compact, laser-plasma source based on a double stream gas puff target, which is intrinsically incoherent, a Gabor EUV holography was successfully demonstrated.

Short wavelength radiation with a wavelength from 10 nm to 120 nm is called Extreme ultraviolet (EUV) radiation. Radiation with an even shorter wavelength, i.e. 0.1-10 nm, is called soft X-ray (SXR). EUV and SXR radiation is very strongly absorbed in matter, which allows obtaining high natural optical contrast in nanoimaging experiments with solid density, or in direct observation of the spatial distribution of gas density. In addition, it is absorbed in the surface, in a layer of about 100-500 nm, which allows the material to be modified in a very thin surface layer, without changing its properties in the entire volume, in experiments related to micro- and nano-machining of materials, or to study the properties of these materials in near-edge X-ray absorption fine structure, e.g. for determining chemical composition using NEXAFS spectroscopy or atomic structure using EXAFS. In addition, it allows the generation of large doses of absorbed radiation in radiobiological experiments, or allow for multilayer structure determination with nm accuracy. A very brief overview of such experiments will be presented.

Over the last decades, remarkable efforts have been made to improve the resolution in photon-based microscopes. The employment of compact sources based on table-top laser-produced soft X-ray (SXR) in the “water window” spectral range (λ = 2.3–4.4 nm) and extreme ultraviolet (EUV) plasma allowed to overcome the limitations imposed by large facilities, such as synchrotrons and X-ray free electron lasers (XFEL), because of their high complexity, costs, and limited user access. A laser-plasma double stream gas-puff target source represents a powerful tool for microscopy operating in transmission mode, significantly improving the spatial resolution into the nanometric scale, comparing to the traditional visible light (optical) microscopes. Such an approach allows generating the plasma efficiently, without debris, providing a high flux of EUV and SXR photons. In this review, we present the development and optimization of desktop imaging systems: a EUV and an SXR full field microscope, allowing to achieve a sub-50 nm spatial resolution with short exposure time and an SXR contact microscope, capable to resolve internal structures in a thin layer of sensitive photoresist. Details about the source, as well as imaging results for biological applications, will be presented and discussed.

We present results of applying a compact laboratory system based on a laser-plasma soft X-ray (SXR) source to the extended X-ray absorption fine structure (EXAFS) spectroscopy of titanium in the vicinity of the LIII absorption edge. The source, operating with a plasma produced as a result of irradiation a krypton/helium double-stream gas-puff target, was optimized for an intense emission in the spectral range between 200 and 700 eV. A broad SXR spectrum and high photon flux are indispensable in the EXAFS studies. The experimental setup assured the simultaneous acquisition of both the reference and the absorption spectra. A grazing-incidence flat-field spectrometer was used to record the spectra. The absorption spectra of a thin (200-nm thick) titanium sample revealed the features in the EXAFS region allowing for quite accurate determination of the radial distances between the atoms. Results are in good agreement with the output of numerical modeling based on photoelectron wave function scattering and with the data reported for using a synchrotron source. This confirms the suitability of the source for using it in the standard EXAFS method.

In this work investigations concerning interaction of intense, nanosecond EUV pulses with matter were performed. Various laser-produced plasma radiation sources were employed for creation of the driving EUV pulses. The sources were based on two different laser systems with pulse energies ranging from 0.8 J to 10J and pulse duration 4 ÷ 10 ns. They were equipped with the EUV collectors for focusing of the radiation. This way radiation fluence up to 0.5 J/cm2 in the interaction region was obtained. In our experiments solid material samples or gases injected into the vacuum chamber synchronously with the EUV pulses were irradiated. Irradiation of the gases resulted in ionization and excitation of atoms and molecules forming low temperature plasmas with a relatively high electron density. Emission spectra obtained from these plasmas, contained spectral lines corresponding to radiative transitions in atoms, molecules, atomic or molecular ions. For analysis of the EUV spectra numerical simulations were performed, using a collisional-radiative PrismSPECT code. For computer simulations of the molecular spectra measured in the UV/VIS range a LIFBASE and Specair codes were employed. This way ionization states together with various thermodynamic parameters were deduced. Irradiation of solid samples resulted in melting of a thin near-surface layer or, in some cases its ablation or even conversion to a low temperature plasma. It depended on physico-chemical properties of the material and its thickness. In case of organic polymers, usually ablation connected with fragmentation of the polymer molecules, took place. In case of thick samples of inorganic solids, a thin near surface layer was heated up to a high temperature exceeding melting or even boiling point. In most cases different kinds of micro- or nanostructures were created, modifying the surface morphology. Except the EUV interaction with solid materials, simultaneous EUV and the EUV induced plasma treatment was investigated. Plasmas were created in gases injected close to the exposed surface. Part of the EUV radiation was absorbed in the injected gas forming the low temperature plasma near the surface, while the other part of radiation, that was not absorbed, interacted with the surface material. This way additional atoms could be incorporated into the molecular structure of the exposed material, or reactive etching took place. Especially interesting results were obtained using molecular gases for creation the reactive plasmas.

In this work two kinds of reflective optical systems were used for creation and investigation of low temperature, photoionized plasmas. The plasmas were created in gases, irradiated with a focused beam of extreme ultraviolet (EUV) radiation. In experiments a laser-produced plasma source based on a 10 J/ 10 ns Nd:YAG laser system, and a double stream gas puff target, working with a 10 Hz repetition rate was used. The EUV radiation was focused using a ruthenium-plated, grazing incidence, ellipsoidal mirror with a high reflective coefficient in the wavelength range λ>10 nm. Different gases were injected into the vacuum chamber, perpendicularly to an optical axis of the irradiation system at the focal region, using an auxillary gas puff valve. Irradiation of the gases resulted in various excited states in atoms and ions. Spectra in EUV range were measured using a spectrometer (McPherson Model 251), equipped with a flat-field, 450 lines/mm toroidal grating. In all cases the most intense emission lines were assigned to singly or doubly charged ions, however, lines corresponding to ions with higher charge were also recorded. Apart from the time integrated spectral measurements also spectrally integrated but time-resolved measurements were performed, using a specially prepared detection system. The system was based on a paraboloidal collector and an EUV sensitive photodiode. In all cases the EUV emission time from the EUV-induced, low temperature plasmas was significantly longer comparing to the driving EUV pulse.

We present a brief review of radiography technique (shadowgraphy) and its extension to tomography. We used both techniques to characterize i.e. multi-jet gas puff target for different gases with a variable number of jets for various applications. The characterization measurements have been performed with the use of EUV shadowgraphy at 13.5 nm wavelength. Pulses of the EUV radiation were produced with a laser plasma EUV source based on a double-stream gas puff target. The shadowgrams of the characterized gas puff targets were registered using a back-illuminated CCD camera, sensitive to the EUV radiation. The gas density maps were calculated based on 2D transmission map and an atomic photoabsorption cross-section. To obtain 3D tomography reconstruction of multi-jet gas puff target we acquired projections at different viewing angles and performed the reconstruction numerically. This unique technique based on a compact laser-produced plasma source allows imaging 2D and 3D objects having a density 3 orders of magnitude smaller than the density of water.

Acquiring spectral information about the samples using near edge X-ray absorption fine structure (NEXAFS), which is a well-known and established method employed for compositional analysis of the samples, yields information about its elemental composition through the observation of the spectral features in the vicinity of the high energy side of the X-ray absorption edge. In particular, NEXAFS is often used to study the structure of intermolecular bonds of polymers by probing the electronic transitions from the core level to the unoccupied states. The NEXAFS spectra contain information which is element specific, indicating additionally the structure of the molecular bonds. This requires short wavelength sources, capable of delivering sufficient flux to achieve high signal-to-noise and of high quality spectral data in the time frame from fs to ns. These sources are synchrotrons, and FEL, but also compact sources, such as the laser-plasma source based on a double stream gas puff target. The applications of this source to recently developed compact NEXAFS spectroscopy system and an overview of some recent applications will be the main topic of this overview paper. Acquisition of static NEXAFS data for composition analysis of various materials and organic compounds, a raster scanning of the sample and acquiring spatially localized spectral data in so-called spectromicroscopy, as well as a single shot NEXAFS, allowing future timeresolved studies, will be presented with references to the original works.

Characterization of Xe emission in the spectral range between 1 and 1.5 keV is presented in the case when the laser-plasma is generated by nanosecond laser pulse irradiation of a double stream Xe/He gas-puff target. Gas target density was estimated using extreme ultraviolet (EUV) radiography. Emission spectral characteristics in the wavelength range from 0.8 to 5.2 nm were determined by using a flat field SXR spectrometer. Significant emission was recorded in two high-energy bands, the first one at wavelengths 0.8–1.6 nm (photon energy range 0.78–1.5 keV) and the second one at 1.6–2.5 nm (0.5–0.78 keV). Both plasma size and photon yield in each band were measured separately to individually assess radiation and source characteristics. Moreover, a proof-of-principle experiment for near-edge X-ray absorption fine structure spectroscopy of metallic sample near the L2,3 absorption edge was performed to show one of the applicability areas of such a compact source.

We report on a very compact desk-top transmission extreme ultraviolet (EUV) microscope based on a laser-plasma source with a double stream gas-puff target, capable of acquiring magnified images of objects with a spatial (half-pitch) resolution of sub-50 nm. A multilayer ellipsoidal condenser is used to focus and spectrally narrow the radiation from the plasma, producing a quasi-monochromatic EUV radiation (λ = 13.8 nm) illuminating the object, whereas a Fresnel zone plate objective forms the image. Design details, development, characterization and optimization of the EUV source and the microscope are described and discussed. Test object and other samples were imaged to demonstrate superior resolution compared to visible light microscopy.

The near edge X-ray absorption fine structure (NEXAFS) is an established method employed for a compositional analysis of the samples. The information about sample's elemental composition is obtained through the observation of the soft X-ray (SXR) spectra in the proximity of the high energy side of the X-ray absorption edge of a particular element of interest. This technique allows one to characterize the matter, obtaining useful and important information, such as the structure of intermolecular and atomic bonds in SXR spectral range. The NEXAFS requires, however, short wavelength sources, capable of delivering sufficiently high flux to obtain high quality spectral data. Typical sources for NEXAFS are synchrotrons, free electron lasers, but, more recently, also compact laser produced plasma (LPP) sources; among them, the laser-plasma source based on a double stream gas puff target. In this short review, the application of this source to the recently developed NEXAFS spectroscopy and spectromicroscopy systems will be presented and discussed in more details with the references to the original works.

We present a 2-D mapping of a sample thickness with nanometer accuracy employing a compact arrangement of near-edge X-ray absorption fine structure (NEXAFS) technique. A NEXAFS spectrum coupled with a scanning system was used to generate a 2-D thickness map of the TiO2 sample (anatase form) deposited on the top of a SiN membrane. The thickness values were retrieved from the experimental data by applying different methods of data processing. In the paper, the detailed analysis of the data processing methods and the identified sources of the errors show that the proposed procedure based on averaging two imperfect estimates reduces the error caused by the uncontrolled bias of the measured signals. This procedure was termed as the average one. The estimates from the proposed average approach and the standard absorption-jump ratio in the absorption edge vicinity were compared with the direct results obtained by applying scanning electron microscopy (SEM). The experimental arrangement of the NEXAFS spectroscopy system, the data acquisition method, as well as the possible error sources, are presented and discussed in detail.

Laser-plasma short-wavelength source based on double-stream gas-puff target and emitting soft X-rays (SXR) is demonstrated as a compact tool suitable for X-ray absorption spectroscopy (XAS) of metal oxides. The source, optimized for emission in the spectral range between 1.5 and 5 nm from a krypton/helium target appears to be useful for the near edge X-ray absorption spectroscopy (NEXAFS) close to the Ti L-edge and Mo M-edge, as well as the K-edge of oxygen. High photon flux from the source enabled the simultaneous acquisition of the reference and transmission spectra using a flat-field grating spectrometer. The measurements conducted in the transmission mode revealed the spectral features near the absorption edges (Ti-L2,3 and Mo-M5) in metal oxides.

We report oxygen K-shell photoabsorption measurements in CO2 plasmas, using a table-top laser produced plasma soft X-ray and extreme ultraviolet (EUV) source. Significant differences are observed between the photoabsorption spectra of the neutral CO2 molecule and photoionized CO2 plasmas, as new spectral features emerge in the case of the latter. These features are attributed to 1s → 2p photoexcitation in O, O+ , O 2+ species identified with the aid of calculations performed with the Cowan suite of atomic structure codes. Such signatures of atomic ions in the photoionized plasma point to the fragmentation of the parent molecule upon absorption of a soft X-ray photon.

High energy attosecond electron bunches from the laser-plasma wakefield accelerator (LWFA) are potentially useful sources of ultra-short duration X-rays pulses, which can be used for ultrafast imaging of electron motion in biological and physical systems. Electron injection in the LWFA depends on the plasma density and gradient, and the laser intensity. Recent research has shown that injection of attosecond electron bunches is possible using a short plasma density ramp. For controlled injection it is necessary to keep both the laser intensity and background plasma density constant, but set to just below the threshold for injection. This ensures that injection is only triggered by an imposed density perturbation; the peak density should also not exceed the threshold for injection. A density gradient that only persists over a short range can lead to the injection of femtosecond duration bunches, which are then Lorentz contracted to attoseconds on injection. We consider an example of a sin^2 shaped modulation where the gradient varies until the downward slope exceeds the threshold for injection and then reduces subsequently to prevent any further injection. The persistence above the threshold determines the injected bunch length, which can be varied. We consider several designs of plasma media including density perturbations formed by shaped Laval nozzles and present an experimental and theoretical study of the modulated media suitable for producing attosecond-duration electron bunches.

Laser-produced plasmas (LPP) are efficient sources of soft X-ray (SXR) and extreme ultraviolet (EUV) radiation. The emitted radiation can be collected and focused using grazing incidence or multilayer mirrors. This way radiation beams of high fluence can be formed. Their interaction with gases results in formation of photoionized plasmas of different parameters, depending on the fluence and properties of the gas. In this work LPP SXR and EUV sources, based on nanosecond Nd:YAG lasers and a double stream gas puff target are described. Parameters of the radiation pulses focused using the corresponding collectors, were measured. The sources were used for creation of the EUV induced, low temperature plasmas. For measurements of the weak EUV emission signals from these plasmas, a special detection system, containing a paraboloidal collector, was prepared. Time integrated, EUV intensity distribution in a focal spot of the collector, was measured using a back-illuminated CCD detector. Temporal measurements of the EUV signals were performed employing an AXUV photodiode mounted in the focal plane.

Low temperature plasmas induced by irradiation of molecular gases with extreme ultraviolet (EUV) pulses were studied. The EUV pulsed beams of high intensity, were formed using laser-produced plasma (LPP) sources, based on Nd:YAG laser systems and a double-stream Xe/He gas-puff target. The EUV beams were used for irradiation of small portions of gases, injected into a vacuum chamber synchronously with the radiation pulses. Low temperature plasmas produced this way in oxygen, nitrogen or sulfur hexafluoride gas emitted radiation in a wide spectral range. The corresponding EUV spectra were dominated by emission lines originating from singly charged, atomic ions. In case of spectra recorded in an optical range, emission lines, corresponding to radiative transitions in atomic or molecular species, were detected. Taking into account a Stark broadening of F I emission lines an electron density was estimated. Its value exceeded 1017cm-3, which is a few orders of magnitude higher comparing to plasmas produced in standard generators. Employing the SF6 – based plasmas an experiment concerning plasma treatment of a silicon surface was performed. A possibility to create different kinds of nanostructures was demonstrated.

In this work, a near edge X-ray fine structure spectroscopy (NEXAFS) based on a laser-plasma compact soft X-ray (SXR) source is presented. The NEXAFS spectrum was acquired simultaneously for all energies near the absorption edge, using a broadband emission from krypton plasma, in contrary to the existing, synchrotron-based spectroscopic systems. In such SXR source, a plasma is produced by an interaction of a laser beam with a double stream gas puff target. The plasma efficiently emits SXR radiation from 2-5 nm wavelength (250-620 eV photon energy). Such broadband emission allows acquiring simultaneously a sample and a reference spectra, to obtain optical density spectrum of the sample near C-Kα absorption edge, due to a special construction of the SXR spectrometer. The NEXAFS spectra were obtained using PET polymer test sample, from both, the large area and spatially localized to ~30×30 μm2 area. The spatially localized spectra were used to construct 2-D spectromicroscopic maps of sample constituents. Single-shot spectra were also acquired with laser pulse energies of ~10 times larger than in the case of multiple exposures. A short overview of those NEXAFS experiments will be presented.

We present a proof of principle experiment on single-shot near edge soft X-ray fine structure (NEXAFS) spectroscopy with the use of a laboratory laser-plasma light source. The source is based on a plasma created as a result of the interaction of a nanosecond laser pulse with a double stream gas puff target. The laser-plasma source was optimized for efficient soft X-ray (SXR) emission from the krypton/helium target in the wavelength range from 2 nm to 5 nm. This emission was used to acquire simultaneously emission and absorption spectra of soft X-ray light from the source and from the investigated sample using a grazing incidence grating spectrometer. NEXAFS measurements in a transmission mode revealed the spectral features near the carbon K-&alpha, absorption edge of thin polyethylene terephthalate (PET) film and L-ascorbic acid in a single-shot. From these features, the composition of the PET sample was successfully obtained. The NEXAFS spectrum of the L-ascorbic acid obtained in a single-shot exposure was also compared to the spectrum obtained a multi-shot exposure and to numerical simulations showing good agreement. In the paper, the detailed information about the source, the spectroscopy system, the absorption spectra measurements and the results of the studies are presented and discussed.

We present a few examples of imaging experiments, which were possible using a compact laser-plasma extreme ultraviolet (EUV) and soft X-ray (SXR) source, based on a double stream gas puff target. This debris-free source was used in full-field EUV imaging to obtain magnified images of test samples, ZnO nanofibers and images of the membranes coated with salt crystals. The source was also employed for SXR microscopy in the “water-window” spectral range using grazing incidence Wolter type-I objective to image test samples and to perform the initial studies of biological objects. Gas puff target EUV source, spectrally tuned for 13.5 nm wavelength with multilayer mirror and thin film filters, was also used in variety of shadowgraphy experiments to study the density of newly developed modulated density gas puff targets. Finally, the source was also employed in EUV tomography experiments of low density objects with the goal to measure and optimize the density of the targets dedicated to high harmonic generation.

The results of formation of elongated krypton/helium plasma channels are presented. Two laser pulses were used: one to produce plasma channels and the second one for conversion to soft X rays. The soft X-ray radiation was in turn used for backlighting the channels and their visualization. The study of their formation and uniformity was performed using a combination of soft X-ray shadowgraphy and pinhole camera imaging. The plasma channels, with various lengths and various densities, were visualized and the results of their characterization are presented. Using moderate laser pulse energy quite uniform channels, up to 9 mm in length, were demonstrated.

In this work a laser-produced plasma (LPP) source was used to create low temperature plasmas. An extreme ultraviolet and soft X-ray (EUV/SXR) radiation pulse was used for ionization of molecular gases, injected into a vacuum chamber synchronously with the EUV/SXR pulse. Energies of photons exceeding 100 eV were sufficient for dissociative ionization, ionization of atoms or even ions. The resulting photoelectrons had also enough energy for further ionizations or excitations. Time resolved UV/VIS spectra, corresponding to single charged ions, molecules and molecular ions, were recorded. For spectral lines, corresponding to radiative transitions in F II and S II ions, electron temperature was calculated based on a Boltzmann plot method. Numerical simulations of the molecular spectra were fitted to the experimental spectra allowing for determination of vibrational and rotational temperatures.

A laser-plasma double stream gas-puff target source coupled with Fresnel zone plate (FZP) optics, operating at He-like nitrogen spectral line λ=2.88nm, is capable of acquire complementary information in respect to optical and electron microscopy, allowing to obtain high resolution imaging, compared to the traditional visible light microscopes, with an exposition time of a few seconds. The compact size and versatility of the microscope offers the possibility to perform imaging experiments in the university laboratories, previously restricted to large-scale photon facilities. Source and microscope optimization, and examples of applications will be presented and discussed.

In this work, two laser-produced plasma (LPP) sources – extreme ultraviolet (EUV) and a LPP soft X-ray (SXR) source were used to create Ne photoionized plasmas. A radiation beam was focused onto a gas stream, injected into a vacuum chamber synchronously with the radiation pulse. EUV radiation spanned a wide spectral range with pronounced maximum centered at λ≈11 nm, while in case of the SXR source spectral maximum was at λ≈1.4 nm. Emission spectra of photoionized plasmas created this way were measured in a wide spectral range λ = 10–100 nm. The dominating spectral lines originated from singly charged ions (Ne II) and neutral atoms (Ne I). For the highest radiation fluence, spectral lines originating from Ne III and even Ne IV species were detected. Differences between the experimental spectra, obtained for all irradiation conditions, were analyzed. They were attributed either to different fluence or spectral distribution of driving photons.

Characterization measurements of a pulsed capillary channel gas puff target, developed for applications in laser-matter interaction experiments, are presented. The target is produced by pulsed injection of gas through a slit-shaped nozzle into a capillary channel and has been characterized by EUV radiography at 13.5 nm wavelength. Time dependent gas flow effects and flow shaping by capillary walls were visualized. Density measurements for argon were performed on axis for variable timing conditions and variable backing pressures. This target, due to its advantages, might be an interesting alternative for lower repetition rate and higher energy laser-matter interaction experiments.

In this paper, we present the first measurements of the partial spatial coherence of the EUV emission from xenon plasma in laser-plasma source, based on a double stream gas puff target. The Young double slit approach was employed to measure complex coherence factor of the EUV Xe emission at 13.5-nm wavelength in two orthogonal directions. The radius of coherence of ~60 μm was estimated at the distance of 2.1 m from the source. The number of coherently emitted photons was sufficient to demonstrate coherent imaging. Using partially coherent radiation from such source Gabor EUV holography was successfully demonstrated.

In this work different kinds of reflective optical systems were used for creation and investigation of low temperature, photoionized plasmas. The plasmas were created in gases, irradiated with a focused beam of extreme ultraviolet (EUV) or soft X-ray (SXR) radiation, from laser-plasma sources employing 10 Hz Nd:YAG laser systems (0.8 J/ 4 ns and 10 J/ 1-10 ns). In both cases, the EUV radiation was focused using a gold-plated grazing incidence ellipsoidal collector in the wavelength range λ = 9÷70 nm or a gold-plated grazing incidence multifoil collector in the wavelength range λ = 5 ÷ 70 nm. Additionally, in case of the 10 J Nd:YAG laser with the pulse duration 1 ns, a paraboloidal collector optimized for the wavelength range λ ≥ 1 nm was employed. Different gases were injected into the vacuum chamber, perpendicularly to an optical axis of the irradiation system at the focal region, using an auxillary gas puff valve. Irradiation of the gases resulted in ionization and excitation of atoms/molecules. Spectra in SXR/EUV range were measured using a grazing incidence, flat-field spectrometer (McPherson Model 251), equipped with a 450 lines/mm toroidal grating or a home-made spectrograph based on the 5000 l/mm transmission grating. Optical spectra were recorded using the Echelle Spectra Analyzer ESA 4000. In all cases the most intense emission lines were assigned to singly charged ions, however, lines corresponding to ions with higher charge were also recorded. Based on spectral lines originating from ions electron temperature was estimated.

We report for the first time on a compact, desk-top size, laboratory-type microscopy setup, based on nitrogen gas puff target soft X-ray source, which emits radiation in “water-window” spectral range. The microscope employs Wolter type-I objective and allows capturing magnified images of objects with 850 nm spatial resolution and exposure time as low as a few seconds. Details about the source and the microscope as well as imaging results for test and biological objects are presented and discussed.

Characterization measurements and modes of operation of a novel, dual-gas multi-jet target, developed for experiments on high-order harmonic generation, are presented. The target has been formed by pulsed injection of argon through a nozzle in a form of linearly oriented small orifices. The argon jets were separated with the helium jets formed by injection of helium through alternate orifices in the nozzle. The targets have been characterized by extreme ultraviolet backlighting at 13.5 nm wavelength. Density profiles for this type of targets have been obtained, to our knowledge, for the first time.