Plasma Emission Intensity Research Articles

Dynamic properties of water microwave plasma

Experiments were performed to generate water vapor plasma in a microwave discharge using a household magnetron (frequency 2.45 GHz). Plasma was ignited in a discharge tube during evaporation from the vessel, and also at the liquid-gas interface. The input power ranged from 1 to 2 kW, and the vapor pressure ranged from 1 to 10 mbar. The time dependence of the emission intensity for the first three lines of the Balmer series of hydrogen was constructed. It was revealed that the time required to heat the plasma to a steady state was 2 ms. A change in the anode current by 15% did not lead to an appreciable change in plasma emission intensity. The plasma temperature estimated using the Boltzmann method was about 4000 K. The plasma was shown not to be in thermodynamic equilibrium.

Enhancement of long wavelength preheating in dual-beam laser induced breakdown spectroscopy

Dual-beam laser induced breakdown spectroscopy (LIBS) is more sensitive than conventional single-pulse LIBS. A combined configuration of Nd:YAG and CW- CO2 lasers is used to improve the emission intensity of LIBS. The plasma of Al sample was observed under CW-CO2 laser and Nd:YAG laser excitation. The enhancement radiation was obtained from dual-beam LIBS rather than single LIBS, which indicated that IR preheating can cause significant enhancement of plasma. The effects of CO2 laser spot size, laser irradiation time and laser power on plasma emission intensity were investigated. And on this basis, the variation of electron temperature and electron density of plasma with delay time is obtained.

Validating Continuum Lowering Models via Multi-Wavelength Measurements of Integrated X-ray Emission

X-ray emission spectroscopy is a well-established technique used to study continuum lowering in dense plasmas. It relies on accurate atomic physics models to robustly reproduce high-resolution emission spectra, and depends on our ability to identify spectroscopic signatures such as emission lines or ionization edges of individual charge states within the plasma. Here we describe a method that forgoes these requirements, enabling the validation of different continuum lowering models based solely on the total intensity of plasma emission in systems driven by narrow-bandwidth x-ray pulses across a range of wavelengths. The method is tested on published Al spectroscopy data and applied to the new case of solid-density partially-ionized Fe plasmas, where extracting ionization edges directly is precluded by the significant overlap of emission from a wide range of charge states.

Effect of laser wavelength and energy on the detecting of trace elements in steel alloy

In order to investigate the effect of laser wavelength and energy on the detection of the trace elements in alloy steel, pulsed laser at 1064 nm and 532 nm wavelength have been employed to generate plasma. The effects of the laser energy of these two laser wavelengths on plasma emission intensity, plasma temperature and electron density were studied. The trace elements of Ni, Al and Cr in the sample were quantitatively analyzed by internal standard method under these two different laser wavelengths with different laser energies. The results have shown that the intensities of the spectral intensities increased with the increasing of laser energy at different wavelengths, and then tended to change gently. The plasma temperature also increased with the increasing of laser energy, and the change of plasma temperature under 532 nm wavelength is slower. The plasma electron density firstly increased with laser energy, and then decreased when the laser energy exceeded the threshold. The quantitative analysis results show that the elements of Ni and Al have lower detection limits at 1064 nm wavelength, while the lower detection limit of Cr corresponding to the 532 nm wavelength. When the sample was ablated at 1064 nm wavelength, the detection limit of the three elements was gradually reduced with the increasing of laser energy.

Synthesis and characteristics of nc-WC/a-C:H thin films deposited via a reactive HIPIMS process using optical emission spectrometry feedback control

A high-power impulse magnetron sputter deposition system with feedback control using an optical emission spectrometer (OES) is used to deposit nc-WC/a-C:H thin films using a tungsten (W) target material reaction with C2H2 gas in a reactive mode. The plasma emission intensity of W+ ions at an emission wavelength of 429.6 nm is monitored, and the amount of reactive C2H2 gas is precisely controlled in order to maintain stable emission intensity during the deposition process. By controlling the input flow rate of C2H2 and using different W+ ion optical emission intensity set points, various nc-WC/a-C:H thin films are obtained at a fixed duty cycle of 2% and pulse frequency of 133 Hz between deposition temperatures of 70 °C and 75 °C. The characteristics and mechanical properties of the obtained thin films are investigated. The highest peak current and peak power density of 189 A and 706 W/cm2, respectively, are obtained at an OES set point of 10%, which corresponds to a high amount of C2H2 gas injection. When the OES set point is <80%, a phase change from α-W2C to WC1−xis clearly identified using the XRD data. Raman analysis also depicts that a W-doped diamond-like carbon structure (nc-WC/a-C:H) is obtained below an OES set point of 30%. Additionally, the concentration of carbon in the nc-WC/a-C:H thin films is observed to gradually increase from 16.9 to 93.8 at.%, whereas the concentration of tungsten decreases from 78.1 to 5.4 at.% as the OES set point decreases from 90% to 10%. The highest hardness of 32.6 GPa was obtained at an OES set point of 90% when the film was composed of an α-W2C phase. However, the hardness values are observed to decrease as the OES set points decrease.

Temperature dependence of emission intensity in femtosecond laser-induced Ge plasma

The Ge(i) 422.66 nm line in femtosecond laser-induced germanium plasma at different initial sample temperatures is investigated.

The effect of nature and pressure of ambient environment on laser-induced breakdown spectroscopy and ablation mechanisms of Si

AbstractThe effect of nature and pressure of ambient environment on laser-induced breakdown spectroscopy (LIBS) and ablation mechanisms of silicon (Si) have been investigated. A Q-switched Nd-YAG laser with the wavelength of 1064 nm, pulse duration of 10 ns, and pulsed energy of 50 mJ was employed. Si targets were exposed under ambient environments of inert gases of argon, neon, and helium for different pressures ranging from 5 to 760 torr. The influence of nature and pressure of ambient gases on the emission intensity of Si plasma have been explored by using the LIBS spectrometer system. The plasma parameters such as electron temperature and number density were determined by applying Boltzmann plot and Stark broadening method, respectively. Our experimental results suggest that the nature and pressure of ambient environment play a significant role for generation, recombination, and expansion of plasma and consequently affect the excitation temperature as well as electron density of plasma. The surface morphological analysis of laser-irradiated Si was performed by using scanning electron microscope (SEM). Various kinds of structures, for example laser-induced periodic surface structures or ripples, cones, droplets, and craters have been generated and their density and size are found to be strongly dependent upon the ambient environment. A quantitative analysis of particulate size and crater depth measured from SEM images showed a strong correlation between plasma parameters and the growth of micro/nanostructures on the modified Si surface.

Spectroscopic study on the time evolution behaviors of the double laser-induced breakdown of Al plasma

To study the time evolution characteristics of plasma fluorescence, aluminum feature spectrum was measured and analyzed through dual-pulse laser-induced breakdown spectroscopy in the standard ambient temperature and pressure experimental conditions. Two Nd:YAG lasers were used to perform the experiment; one laser ablated the target, and the other reheated the plasma in air. The plasma emission intensity was enhanced at an optimal inter-pulse delay time of 200ns. The plasma fluorescence lifetime was measured in a dual-pulse laser excitation mode at different inter-pulse delays. The plasma fluorescence lifetime changed with the changing of inter-pulse delay under double pulse excitation. The results can further understand of the time evolution of the plasma under double-pulse laser excitation.

Optical emission spectroscopy of magnetically confined laser induced vanadium pentoxide (V2O5) plasma

Optical emission spectra of a laser induced plasma of vanadium pentoxide (V2O5) using a Nd:YAG laser (1064 nm, 10 ns) in the presence and absence of the magnetic field of 0.45 T have been investigated. The effect of the magnetic field (B) on the V2O5 plasma at various laser irradiances ranging from 0.64 GW cm−2 to 2.56 GW cm−2 is investigated while keeping the pressure of environmental gases of Ar and Ne constant at 100 Torr. The magnetic field effect on plasma parameters of V2O5 is also explored at different delay times ranging from 0 μs to 10 μs for both environmental gases of Ar and Ne at the laser irradiance of 1.28 GW cm−2. It is revealed that both the emission intensity and electron temperature of the vanadium pentoxide plasma initially increase with increasing irradiance due to the enhanced energy deposition and mass ablation rate. After achieving a certain maximum, both exhibit a decreasing trend or saturation which is attributable to the plasma shielding effect. However, the electron density shows a decreasing trend with increasing laser irradiance. This trend remains the same for both cases, i.e., in the presence and in the absence of magnetic field and for both background gases of Ar and Ne. However, it is revealed that both the electron temperature and electron density of the V2O5 plasma are significantly enhanced in the presence of the magnetic field for both environments at all laser irradiances and delay times, and more pronounced effects are observed at higher irradiances. The enhancement in plasma parameters is attributed to the confinement as well as Joule heating effects caused by magnetic field employment. The confinement of the plasma is also confirmed by the analytically calculated value of magnetic pressure β, which is smaller than plasma pressure at all irradiances and delay times, and therefore confirms the validity of magnetic confinement of the V2O5 plasma.

Effect of magnetic field on laser induced breakdown spectroscopy of zirconium dioxide (ZrO2) plasma

Laser induced breakdown spectroscopy of ZrO2 plasma in the presence and absence of magnetic field has been investigated. The plasma was generated by employing Nd: YAG laser (1064nm, 10ns) at various fluences ranging from 6.4Jcm−2 to 25.6Jcm−2 under argon environment of pressure of 100Torr. Both emission intensity and electron temperature show increasing trend with increasing the fluence, whereas, electron number density of ZrO2 plasma decreases with increasing the laser fluence. It is revealed that values of emission intensity, electron temperature and electron number density of ZrO2 plasma are slightly higher in the presence of magnetic field as compared to field free case at all fluences. This increase in plasma parameters is attributed to magnetic confinement and Joule heating effect. With the variation of fluence the electron temperature of ZrO2 plasma varies slightly from 5345K to 5475K in the absence of magnetic field, whereas in case of magnetic field this value enhances from 5435K to 5600K. Similarly the electron number density of ZrO2 plasma varies from 1.80×1018cm−3 to 3.50×1018cm−3 in the absence of magnetic field, whereas in case of magnetic field, the variation in electron number density varies from 1.75×1018cm−3 to 4.25×1018cm−3. The existence of magnetic confinement effects is confirmed by the analytical evaluation of plasma parameter β, which is smaller than 1 under all experimental conditions. It is also revealed that both the laser fluence as well as magnetic field significantly influence the ZrO2 plasma parameters.

Magnetic field effect on laser-induced breakdown spectroscopy and surface modifications of germanium at various fluences

AbstractThe effect of the transverse magnetic field on laser-induced breakdown spectroscopy and surface modifications of germanium (Ge) has been investigated at various fluences. Ge targets were exposed to Nd: YAG laser pulses (1064 nm, 10 ns, 1 Hz) at different fluences ranging from 3 to 25.6 J/cm2 to generate Ge plasma under argon environment at a pressure of 50 Torr. The magnetic field of strength 0.45 Tesla perpendicular to the direction of plasma expansion was employed by using two permanent magnets. The emission spectra of laser-induced Ge plasma was detected by the laser-induced breakdown spectroscopy system. The electron temperature and number density of Ge plasma are evaluated by using the Boltzmann plot and stark broadening methods, respectively. The variations in emission intensity, electron temperature (Te), and number density (ne) of Germanium plasma are explored at various fluences, with and without employment of the magnetic field. It is observed that the magnetic field is responsible for significant enhancement of both excitation temperature and number density at all fluences. It is revealed that an excitation temperature increases from Te,max,without B = 16,190 to Te,max,with B = 20,123 K. Similarly, the two times enhancement in the electron density is observed from ne,max,without B = 2 × 1018 to ne,max,with B = 4 × 1018 cm−3. The overall enhancement in Ge plasma parameters in the presence of the magnetic field is attributed to the Joule heating effect and adiabatic compression. With increasing fluence both plasma parameters increase and achieve their maxima at a fluence of 12.8 J/cm2 and then decrease. In order to correlate the plasma parameters with surface modification, scanning electron microscope analysis of irradiated Ge was performed. Droplets and cones are formed for both cases. However, the growth of ridges and distinctness of features is more pronounced in case of the absence of the magnetic field; whereas surface structures become more diffusive in the presence of the magnetic field.

RETRACTED: Semi-emprical techniques for the specification of Shafranov shift in the large aspect ratio tokamaks

Equilibrium reconstruction consists in identifying, from experimental measurements, a distribution of the plasma current density that satisfies the pressure balance constraint. Numerous methods exist to solve the Grad–Shafranov equation, describing the equilibrium of plasma confined by an axisymmetric magnetic field. In this research, we have reviewed six techniques for determination of the plasma position in IR-T1 tokamak and the effects of superconducting coils and chamber: an optical, flux loops, magnetic probes, multipole moments techniques, and two methods based on the vertical field coil characteristics and analytical solution of Grad–Shafranov equation. In the first method an image processing technique used for the output signal of CCD camera and plasma emission intensity profile and then plasma position obtained. To compare the plasma position obtained using this method, flux loop method, magnetic probe method, multipole moments method, analytical solution of Grad–Shafranov equation, and a sensor-less method based on vertical field coil characteristics are also experimented on the IR-T1 tokamak. Results were compared and discussed.

Effect of an optical emission spectrometer feedback-controlled method on the characterizations of nc-TiC/a-C:H coated by high power impulse magnetron sputtering

An optical emission spectrometer (OES) feedback-controlled high power impulse magnetron sputter deposition system was used to deposit nc-TiC/a-C:H thin films in a reactive mode. The plasma emission intensity of Ti2+ ions at the emission wavelength of 365nm was monitored and the amount of reactive C2H2 gas was precisely controlled to maintain stable emission intensity during the deposition process. By controlling the C2H2 input flow rate and different Ti2+ ion optical emission intensities, various nc-TiC/a-C:H thin films were obtained at a fixed duty cycle of 2% and repetition frequency of 500Hz at 75°C. The characteristics and mechanical properties of the obtained films were also investigated. As the OES set point was 40%, the phase changing from TiC to nc-TiC/a-C:H films was clearly identified. The highest hardness of 26GPa was obtained at the OES set point of 40%, where the film was composed of TiC. In addition, the lowest friction coefficient of 0.08 was obtained at the OES set point of 7%, which represented the nanocomposite structure of nc-TiC/a-C:H films.

Abnormal oscillation modes in a waning light bridge

A sunspot acts as a waveguide in response to the dynamics of the solar interior; the trapped waves and oscillations could reveal its thermal and magnetic structures. We study the oscillations in a sunspot intruded by a light bridge, the details of the oscillations could reveal the fine structure of the magnetic topology. We use the Solar Dynamics Observatory/Atmospheric Imaging Assembly data to analyse the oscillations in the emission intensity of light bridge plasma at different temperatures and investigate their spatial distributions. The extreme ultraviolet emission intensity exhibits two persistent oscillations at five-minute and sub-minute ranges. The spatial distribution of the five-minute oscillation follows the spine of the bridge; whereas the sub-minute oscillations overlap with two flanks of the bridge. Moreover, the sub-minute oscillations are highly correlated in spatial domain, however, the oscillations at the eastern and western flanks are asymmetric with regard to the lag time. In the meanwhile, jet-like activities are only found at the eastern flank. Asymmetries in forms of oscillatory pattern and jet-like activities \textbf{are} found between two flanks of a granular light bridge. Based on our study and recent findings, we propose a new model of twisted magnetic field for a light bridge and its dynamic interactions with the magnetic field of a sunspot.

Computational simulation of laser plasma emission with shock-wave-affected density distribution in the gas-jet target

Based on the results of numerical fluid dynamics simulation, an imitation parameter has been constructed which simulates the observed intensity of the laser plasma emission in a short-wave range. Within the computational model frame, a high-temperature perturbation is created in the jet that generates a strong shock wave. The resultant complicated target structure and its evolution lead to nonmonotonic time variations of the simulation parameter. This result agrees well with the experimentally measured behavior of emission from the laser plasma formed on the target perturbed by an additional laser prepulse.

RETRACTED: A new perspective on hydrogen plasma equilibrium calculation along with the MHD potential energy

In this contribution we have presented two techniques for determination of plasma equilibrium position in IR-T1 tokamak: Relaxation and optical techniques. An analysis method of tokamak plasma equilibrium by a relaxation method with specified magnetic axis was presented. The degrees of freedom due to designated positions of the magnetic axis are possible by using poloidal field coil currents. Stable steady state tokamak plasma equilibria are calculated along with the Magnetohydrodynamic (MHD) potential energy. The plasma generates a plasma current which partially or fully cancels the magnetic field from the poloidal field coils. For low-temperature plasmas, the plasma current distribution is centrally peaked; for high-temperature plasmas, the plasma current has a hole. A centrally peaked current distribution in a low-temperature plasma is evolved into a current distribution with a hole by increasing the plasma pressure by Ohmic heating, RF heating, or by neutral beam injection heating. In the second technique, an image processing technique is used for the output signal of CCD camera. Then, plasma emission intensity profile and plasma position were obtained. Results were compared and discussed.

Vacuum ultraviolet spectral emission properties of Ga, In and Sn droplet-based laser produced plasmas

The Emission Spectra of gallium, indium and tin droplet-based laser produced plasmas are presented in the Vacuum Ultraviolet (VUV) emission range from 30nm to 160nm. The Ga ion transitions are investigated in detail as a function of background pressure level and laser irradiance. Different wavelength emission regions were detected according to the level of background gas. At short wavelengths (i.e. 30–50nm) the line emission from the higher charge states is reduced with increasing pressure, while at longer wavelengths (i.e. 100–160nm) the trend is inverted, as the plasma emission intensity of the lower charge states increases with higher background gas pressure level. The emitted lines are fitted with Voigt profiles to determine the electron density. The electron temperature is obtained from a fit based on the Planck distribution. These estimations are then used to identify the relevant processes that lead to the different charge state emissions as a function of background gas. Langmuir Probe measurements are also reported for evaluating the ion kinetic energy as a function of background gas. The gallium spectra are calibrated in units of spectral radiance, together with spectra from indium and tin. This calibration allows absolute power estimations from the light source in the VUV region. The presented experimental results are relevant as fundamental plasma emission spectroscopic measurements in an almost unexplored wavelength region as well as for applications such as Extreme Ultraviolet Lithography to determine the so-called Out-of-Band (OoB) radiation emission and for metrology applications for future inspection tools.

Characterization of titanium nitride–hydroxyapatite on PEEK for dental implants by co-axis target magnetron sputtering

Abstract In this work, the bioactive TiN-HA layer has been prepared by reactive DC magnetron sputtering system with co-axis target configuration on the polyetheretherketone (PEEK) bio-inert material. The proper plasma conditions used to deposit TiN-HA film on PEEK were carried out by the optical emission spectroscopy (OES). The relationship between the chemical composition of plasma to sputtering pressure, discharge voltage, duty cycle and the content of nitrogen gas were considered. The plasma emission intensity raised to the maximum level when the N 2 content was 0.6 sccm. The voltage was ranged about 500–700 V for the sputtering pressure at 3–7 mTorr and reduced to below 500 V when the pressure increased to more than 7 mTorr. The clear as-deposited films with high refractive index were observed and found to reduce surface contact angle as much lower as 10°. X-ray photoelectron spectroscopy (XPS) result revealed TiOH was also formed in the deposited film besides TiO 2 .

Effect of magnetic field on laser-induced breakdown spectroscopy of graphite plasma

The effect of transverse magnetic field on laser-induced breakdown spectroscopy of graphite plasma as a function of fluence has been investigated. Graphite targets were exposed to Nd:YAG (1064 nm, 10 ns) laser pulses at various laser fluences ranging from 0.4 to 2.9 J cm−2 under two different environment of air and Ar at a pressure of 150 and 760 torr. A transverse magnetic field of strength 0.5 tesla was employed by using permanent magnets. It is revealed that due to the presence of the magnetic field the emission intensity, electron temperature and number density of graphite plasma have been increased at all fluences and for all environmental conditions. The enhancement in plasma parameters is attributed to magnetic confinement effect and Joule heating effect. Initially by increasing the fluence from 0.4 to 1.5 J cm−2 (in air) and 0.4 to 1.8 J cm−2 (in Ar), the emission intensity, electron temperature and number density have been increased and have attained their maximum values. Further increase in fluence was responsible for the decreasing trend in all plasma parameters. More increase in fluence (beyond 1.8 J cm−2 in case of air and 2.2 J cm−2 in case of Ar) up to a maximum value of 2.9 J cm−2, the saturation or self-sustained regime was achieved, which is responsible for insignificant changes in plasma parameters. The value of plasma parameter “β” was also evaluated analytically, and it was less than one for all conditions (fluences as well as environments), which confirmed the existence of confinement effect.

Spectra of secondary emission during generation of optical harmonics in globular photonic crystals

Secondary emission spectra of globular silica photonic crystals when their surfaces were exposed to laser pulses 250 fs long at a power density to 1 TW/cm2 have been studied. Optical harmonics and plasma emission were detected in this case. For the opal matrix containing pores filled with air, in the reflection mode, the third optical harmonic with a conversion efficiency of ∼10% arises. The highest conversion efficiency for exciting radiation with wavelengths of 1026 or 513 nm is implemented when the frequencies of the exciting radiation or the second harmonic are near the stop band edge. In globular photonic crystals filled with sodium nitrite or barium titanate ferroelectrics, the second optical harmonic is observed. The exciting radiation conversion efficiency to the second optical harmonic was a few percent and depended on the frequency of exciting radiation and photonic crystal globule diameters. It is found that the plasma emission intensity increases with the exciting radiation power density. The dependences of the intensity of the second and third optical harmonics on the pump intensity are constructed for various photonic crystal globule diameters.