Search

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 (Te ~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.

The article presents comparative studies of low-temperature plasmas produced by two different experimental methods. In the first method [laser-produced plasma (LPP)-induced], low-temperature plasmas were created as a result of the interaction of laser-produced plasma (LPP) with ambient gas in the form of a gas mixture at low pressure surrounding the LPP. The LPP was produced by irradiating a gas puff target, formed from the same gas mixture, with an Nd:YAG laser pulse. In the second method [extreme ultraviolet (EUV)-induced], low-temperature plasmas were created by irradiating a small amount of a gas mixture, injected into a vacuum chamber, with a nanosecond pulse of extreme ultraviolet (EUV) radiation. The EUV pulses were generated using a laser plasma EUV source. Plasmas, created employing both methods, were investigated using time-resolved optical spectrometry. The results of measurements showed different time dependencies regarding emission lines and molecular bands, indicating differences in the processes leading to the formation of low-temperature plasmas. It has been shown that both methods produce CN molecular species; however, the emission times of the corresponding spectral bands differ significantly. It was found that these differences result from different mechanisms of atomic and molecular processes dominant in both methods of generating low-temperature plasma. [ABSTRACT FROM AUTHOR]

An Nd:YAG pulsed laser was employed to irradiate a nitrogen gas-puff target. The interaction gives rise to the emission of soft X-ray (SXR) radiation in the ‘water window’ spectral range (λ= 2.3÷4.4 nm). This source was already successfully employed to perform the SXR microscopy. In this work, a Silicon Carbide (SiC) detector was used to characterize the nitrogen plasma emission in terms of gas-puff target parameters. The measurements show applicability of SiC detectors for SXR plasma characterization.

In this work we present three experimental, compact desk-top imaging systems: SXR and EUV full field microscopes and the SXR contact microscope. The systems are based on laser-plasma EUV and SXR sources based on a double stream gas puff target. The EUV and SXR full field microscopes, operating at 13.8 nm and 2.88 nm wavelengths are capable of imaging nanostructures with a sub-50 nm spatial resolution and short (seconds) exposure times. The SXR contact microscope operates in the “water-window” spectral range and produces an imprint of the internal structure of the imaged sample in a thin layer of SXR sensitive photoresist. Applications of such desk-top EUV and SXR microscopes, mostly for biological samples (CT26 fibroblast cells and Keratinocytes) are also presented. Details about the sources, the microscopes as well as the imaging results for various objects will be presented and discussed. The development of such compact imaging systems may be important to the new research related to biological, material science and nanotechnology applications.

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.

Spectral lines of low-temperature nitrogen photoionized plasma were investigated. The photoionized plasma was created in the result of irradiation N2 gas using laser plasma EUV radiation pulses. The source was based on a 10J/10ns Nd:YAG (λ = 1064 nm) laser system and a gas puff target. The EUV radiation pulses were collected and focused using a grazing incidence multifoil EUV collector. The emission spectra were measured in the ultraviolet and visible (UV/Vis) range. It was found that the plasma emission lines in the lower region of the UV range are relativley weak. Nonetheless, a part of the spectra contains strong molecular band in the 300 - 430 nm originated from second positive and first negative systems band transitions of nitrogen. These molecular band transitions were identified using a code for study the diatomic molecules, LIFBASE. The vibrational band of Δv = 0 and ±1 transitions were significantly populated than of that with Δv = ±2 and 3 transitions. A comparison of the calculated and measured spectrum is presented. With an assumption of a local thermodynamic equilibrium (LTE), the vibrational temperature was determined from the integrated band intensities with the help of the Boltzmann plot method and compared to the temperature predicted by SPECAIR and LIFBASE simulations. A summary of the results and the variations in the vibrational temperatures was discussed.