Line Profile Method Research Articles

The influence of patient positioning and immobilization equipment on MR image quality and image registration in radiation therapy.

MRI is preferred for brain tumor assessment, while CT is used for radiotherapy simulation. This study evaluated immobilization equipment's impact on CT-MRI registration accuracy and MR image quality in RT setup. We included CT and MR images from 11 patients with high-grade glioma, all of whom were immobilized with a thermoplastic mask and headrest. T1- and T2-weighted MR images were acquired using an MR head coil in a diagnostic setup (DS) and a body matrix coil in RT setup. To assess MR image quality, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were considered in some dedicated regions of interest. We also evaluated the impact of immobilization equipment on CT-MRI rigid registration using line profile and external contour methods. The CNR and SNR reduction was in the RT setup of imaging. This was more evident in T1-weighted images than in T2-weighted ones. The SNR decreased by 14.91% and 12.09%, while CNR decreased by 25.12% and 20.15% in T1- and T2-weighted images, respectively. The immobilization equipment in the RT setup decreased the mean error in rigid registration by 1.02mm. The external contour method yielded Dice similarity coefficients (DSC) of 0.84 and 0.92 for CT-DS MRI and CT-RT MRI registration, respectively. The image quality reduction in the RT setup was due to the imaged region's anatomy and its position relative to the applied coil. Furthermore, optimizing the pulse sequence is crucial for MR imaging in RT applications. Although the use of immobilization equipment may decrease the image quality in the RT setup, it does not affect organ delineation, and the image quality is still satisfactory for this purpose. Also, the use of immobilization equipment in the RT setup has increased registration accuracy.

Optical and thermal characterization of pure CuO and Zn/CuO using laser-induced breakdown spectroscopy (LIBS), x-ray fluorescence (XRF), and ultraviolet–visible (UV–Vis) spectroscopy techniques

We present elemental analysis and thermal characterization of pure and two different concentrations of zinc-doped copper oxide (CuO) samples using different analytical techniques. The quantitative as well as qualitative investigations, were performed by incorporating calibration-free laser-induced breakdown spectroscopy (CF-LIBS) technique. The plasma was generated on the samples surface by focusing a first harmonic of Nd: YAG laser of 1064 nm wavelength and the time-integrated emission spectra was achieved through a set of five spectrometers equipped with a charge-coupled-device. The acquired optical emission spectra from laser-generated plasma show different concentrations of zinc and copper in different samples which are consistent with their percentage composition measured during the sample synthesis. Using LIBS emission analytical lines, the Boltzmann technique was utilized for estimating the excitation temperature, while the number density was evaluated using the well-known Stark broadening line profile method. Besides, the CF-LIBS elemental analysis was validated by the x-ray fluorescence technique. For the optical study, ultraviolet–visible spectroscopical analysis was performed to find the bandgap of pure and zinc-doped copper oxide samples and consequently, variation in bandgap was studied with the growth of zinc doping. In addition, the thermal properties of the samples were analyzed using the beam deflection spectroscopy technique. The results shows that thermal diffusivity () and thermal conductivity (), increased with an increase in zinc concentration.

Chemometrics and Spectroscopic Analyses of Peganum harmala Plant’s Seeds by Laser-Induced Breakdown Spectroscopy

In the present work, the rapid identification of elements and their relative chemical composition in various Peganum harmala seed samples were investigated using a calibration-free laser-induced breakdown spectroscopy technique (CF-LIBS). A pulsed Nd:YAG laser-source with a 5 ns pulse-duration, and 10 Hz pulse repetition rates providing 400 and 200 mJ energy at 1064 and 532 nm wavelength, respectively, was focused on the Peganum harmala seed samples for ablation. A LIBS 2000+ spectrometer within the wavelength range (200 to 720 nm), emission-spectra were recorded. The measured spectra of the Peganum harmala sample gives spectral lines of Carbon (C), Magnesium (Mg), Lithium (Li), Sodium (Na), Calcium (Ca), Silicon (Si), Iron (Fe), Strontium (Sr), Copper (Cu), Potassium (K), and Lead (Pb). A CF-LIBS technique has been employed for the compositional study of the elements exist in the Peganum harmala seed samples. The measured results demonstrate that C, Mg, and Ca are found to be major elements in the Peganum harmala seed samples with compositions of ~36.64%, ~24.09%, and ~19.03%, respectively. Along with the major elements, the elements including Li, Na, Si, K, Fe, and Sr were identified as minor elements with compositions of ~2.87%, ~2.33%, ~3.72%, ~7.17%, ~2.83%, and ~1.14%, respectively. Besides Cu (~8.07 μg/g), and Pb (~1.10 μg/g) elements were observed as trace elements exist in the Peganum harmala seed samples. Furthermore, the electron number density including the plasma excitation-temperature were calculated using the stark-broadening line profile method and the Saha–Boltzmann plot method, respectively. The plasma parameters versus laser-irradiance and the distance from the sample were further investigated. Moreover, a principal component analysis (PCA) method was also utilized to the spectral data obtained by using LIBS to discriminate various seed samples with four classes, namely, α, β, γ, and Δ. Three principal-components (PCs) calculated from eigenvalues of score matrix described 87.6%, 4.6%, and 2.5% of total variance for PC1, PC2, and PC3, respectively. The LIBS spectral data variance covered by the initial 3 PCS was found as ~94.7% of total variance. The PCA results have successfully demonstrated the different classes of the Peganum harmala seed samples based on the different doping compositional ratios of the Zn element. This study confirmed the feasibility and ability of LIBS and PCA for the rapid analysis of Peganum harmala seed samples. Finally, the results achieved using CF-LIBS were incorporated with those obtained from the XRF and EDX analytical techniques.

Quantification of Aluminum Gallium Arsenide (AlGaAs) Wafer Plasma Using Calibration-Free Laser-Induced Breakdown Spectroscopy (CF-LIBS).

In this work, we report the results of the compositional analysis of an aluminum gallium arsenide (AlGaAs) sample using the calibration-free laser-induced breakdown spectroscopy (CF-LIBS) technique. The AlGaAs sample was doped with three various concentrations of gallium (Ga), arsenic (As), and aluminum (Al), as reported by the manufacturer, and the CF-LIBS technique was employed to identify the doping concentration. A pulsed Q-switched Nd: YAG laser capable of delivering 200 and 400 mJ energy at 532 and 1064 nm, respectively, was focused on the target sample for ablation, and the resulting emission spectra were captured using a LIBS 2000+ spectrometer covering the spectral range from 200 to 720 nm. The emission spectra of the AlGaAs sample yielded spectral lines of Ga, As, and Al. These lines were further used to calculate the plasma parameters, including electron temperature and electron number density. The Boltzmann plot method was used to calculate the electron temperature, and the average electron temperature was found to be 5744 ± 500 K. Furthermore, the electron number density was calculated from the Stark-broadened line profile method, and the average number density was calculated to be 6.5 × 1017 cm−3. It is further observed that the plasma parameters including electron temperature and electron number density have an increasing trend with laser irradiance and a decreasing trend along the plume length up to 2 mm. Finally, the elemental concentrations in terms of weight percentage using the CF-LIBS method were calculated to be Ga: 94%, Al: 4.77% and As: 1.23% for sample-1; Ga: 95.63%, Al: 1.15% and As: 3.22% for sample-2; and Ga: 97.32%, Al: 0.69% and As: 1.99% for sample-3. The certified concentrations were Ga: 95%, Al: 3% and As: 2% for sample-1; Ga: 96.05%, Al: 1% and As: 2.95% for sample-2; and Ga: 97.32%, Al: 0.69% and As: 1.99% for sample-3. The concentrations measured by CF-LIBS showed good agreement with the certified values reported by the manufacturer. These findings suggest that the CF-LIBS technique opens up an avenue for the industrial application of LIBS, where quantitative/qualitative analysis of the material is highly desirable.

Qualitative and quantitative analysis of steatite using calibration-free laser-induced breakdown spectroscopy in conjunction with x-ray fluorescence spectroscopy and Fourier-transform infrared spectroscopy.

The qualitative and quantitative study of raw steatite was carried out using a pulsed nanosecond Nd:YAG laser set to fundamental harmonic (1064 nm) at atmospheric pressure. To cross-validate the data, x-ray diffraction (XRD), x-ray fluorescence (XRF) spectroscopy, and Fourier-transform infrared spectroscopy (FTIR) were used. The analysis of optical emission spectra in the wavelength range 200-720 nm showed the existence of silica (Si), magnesium (Mg), and calcium (Ca). The plasma temperature and electron number density were estimated using the Boltzmann plot and Stark-broadening line profile methods, with results at 4906 K and ${1.47}\times{{10}^{17}}\;{{\rm cm}^{- 3}}$, respectively. The quantitative study was carried out using the calibration-free laser-induced breakdown spectroscopy (CF-LIBS) process, assuming local thermodynamic equilibrium and an optically thin plasma, and the following results were obtained: Si = 63.37%, Mg = 35.95%, and Ca = 0.671%. The quantitative findings obtained using the CF-LIBS approach were consistent with those obtained using XRD, XRF, and FTIR, demonstrating the applied methods' potential to be effective and complementary for the qualitative and quantitative study of multiphase raw steatite.

Elemental analysis of sage (herb) using calibration-free laser-induced breakdown spectroscopy.

In this work, laser-induced breakdown spectroscopy (LIBS) has been used for the quantitative and qualitative analysis of the sage sample using the calibration-free LIBS (CF-LIBS) technique. The sage plasma is generated by focusing the second harmonics (532 nm) of a Q-switched Nd:YAG laser with a repetition rate of 10 Hz and pulse duration of 5 ns. The emission spectra are recorded using a LIBS 2000 detection system spectrometer consisting of five high-resolution spectrometers covering a wavelength range from 200 to 720 nm. The optical emission spectra of the sage sample reveal the spectral lines of Fe, Ca, Ti, Co, Mn, Ni, and Cr. The plasma temperature and electron number density of the neutral spectral lines of the pertinent elements have been deduced using the Boltzmann plot and Stark-broadening line profile method, with average values 8855±885K and 3.89×1016cm-3, respectively. The average values of the plasma parameters were used for the quantification of the detected elements in the sample. Based on the calibration-free method, the measured results demonstrate that Fe is the major constituent in the sample, having a percentage concentration of 48.1%, while the remaining elements are Ca, Ti, Co, Mn, Ni, and Cr, with percentage concentrations 0.7%, 5.3%, 8%, 11%, 12.3%, and 14.6%, respectively. This study demonstrates the feasibility of LIBS for the compositional analysis of major and trace elements present in the plant samples and its further applications in medicine.

Plasma Diagnostic by Optical Emission Spectroscopy on Dolomite and Cross-Validation Using Scanning Electron Microscopy Coupled with Energy Dispersive X-ray Spectroscopy and Electron Probe Micro-Analysis

Dolomite [CaMg(CO3)2] is an important carbonate mineral mainly composed of calcium magnesium carbonate. The correct determination of magnesium content in carbonate rocks is important for accessing its suitability for different applications; however, presence of different phases with varying magnesium contents makes their analysis difficult. In the present work, a natural carbonate mineral dolomite is analyzed qualitatively and quantitatively using laser-induced breakdown spectroscopy along with X-ray diffraction, scanning electron microscopy coupled with energy dispersive spectroscopy and electron-probe microanalysis. The optical emission spectra recorded in 200–720 nm wavelength region revealed presence of emission lines for Ca, Mg, Al, Sr, and Na with varying intensities. We used two different techniques, that is, Boltzmann plot and Saha–Boltzmann plot methods to calculate the plasma temperature, and an average value of 4500 ± 450 K was deduced.The Stark broadening line profile method was exploited to calculate the electron number density using calcium and magnesium lines which resulted in 2.39 × 1017 cm–3. The quantitative compositional analysis was carried out using calibration-free laser-induced breakdown spectroscopy method for which the local thermodynamic equilibrium and optically thin plasma conditions were satisfied.The composition for dolomite major constituents calcium and magnesium were estimated as 68.58 and 31.41%, respectively.The results demonstrated the LIBS, EDS, and EPMA ability as an effective, powerful and complementary analytical techniques for the elemental composition analysis of carbonate minerals.

Interlaced bilateral filtering and wavelet thresholding for flaw detection in the radiography of weldments

The recognition of damages and defects is very important in welded joints radiographic images. The experts’ evaluations of the weld images are dependent on both image quality and interpreter’s experience. This evaluation will become difficult if the radiography images have low quality and have been corrupted with noise and other quality decreasing factors. Therefore, some image processing methods are required to improve the radiography images’ quality. Here, an interlaced multistage bilateral filtering and wavelet thresholding have been implemented to radiography images of welded objects for better detection of weld flaws, which can effectively obviate the defect regions in real noisy radiography images. The line profile method has been implemented for the evaluation of the results, i.e., the quality of the radiographs before and after applying the image processing algorithm. The line profiles were compared in the image quality indicator region. The comparison of the line profiles shows that the quality of the reconstructed radiographs, which is measured here by the contrast to background level, enhances almost by a factor of two for the subtracted images in comparison with the original radiographs.

Quantitative elemental analysis of high silica bauxite using calibration-free laser-induced breakdown spectroscopy.

Bauxite is a primary ore of aluminum. Precise information about bauxite mineralogical composition is challenging and crucial for efficient aluminum extraction and for the determination of its appropriateness for different industrial applications. For the qualitative and quantitative analysis of bauxite ore, we performed laser-induced breakdown spectroscopy (LIBS) in conjunction with x-ray diffraction (XRD), x-ray fluorescence spectroscopy (XRF), scanning electron microscopy coupled with energy dispersive x-ray spectroscopy (SEM-EDS), and Fourier transform infrared spectroscopy (FTIR). Analysis of the acquired optical emission spectrum revealed the presence of Si, Al, Fe, K, Ti, Ca, Mg, Na, Cr, and Sr. The plasma temperature and electron number density values estimated using Boltzmann plot and Stark-broadening line profile methods were 5600K and 7.65×1017 cm-3, respectively. In the present study we show that a calibration-free LIBS method presents a powerful solution, enabling quantitative analysis of multi-element bauxite ore better than traditional analytical techniques. The bauxite quantification obtained using CF-LIBS under the assumption of local thermodynamic equilibrium and optically thin plasma was Si=47.31%, Al=31.90%, Fe=16.54%, K=2.45%, Ti=1.64%, and Ca=0.16%, and its comparison with the outcome from XRD, XRF, SEM-EDS, and FTIR not only assisted but potentially enhanced the mineralogical composition understanding of bauxite ore in the present study.

Plasma diagnostics by optical emission spectroscopy on manganese ore in conjunction with XRD, XRF and SEM-EDS

Manganese (Mn) is an important industrial mineral. Information about the chemical and phase constitution along with the concentration of impurities presented in Mn ore is compulsory in assessing its suitability for different applications. We performed the qualitative and quantitative analysis of low-grade Mn ore (LGMO) using laser-induced breakdown spectroscopy (LIBS) in conjunction with x-ray diffraction (XRD), x-ray fluorescence (XRF) and scanning electron microscopy (SEM) coupled with energy dispersive x-ray electron spectroscopy (EDS). The optical emission spectra of the LGMO sample displayed the presence of Mn, Si, Ca, Fe, Al, Mg, V, Ti, Sr, Ni, Na, Ba and Li. The plasma parameters, electron temperature and number density were estimated using the Boltzmann plot and Stark broadening line profile methods and were found to be 7500 K ± 750 K and 8.18 ± 0.8 × 1017 cm−3, respectively. Quantitative analysis was performed using the calibration-free LIBS (CF-LIBS) method and its outcome along with XRD, XRF and SEM-EDS data showed almost analogous elemental composition, while the LIBS method gave acceptably precise elemental analysis by detecting the low atomic number element Li besides V and Sr. The results obtained using LIBS for the LGMO exhibited its ability as a powerful analytical tool and XRF, XRD and SEM-EDS as complementary methods for the compositional analysis of complex low-grade mineral ore.

Quantitative analysis of Fuller's earth using laser-induced breakdown spectroscopy and inductively coupled plasma/optical emission spectroscopy.

Fuller's earth, most commonly known as Multani Matti (clay) in Urdu, among its various utilizations is traditionally used in skin care cosmetics, particularly for removing blackheads and to treat oily skin. It is also used for improving skin complexion. In this paper, laser-induced breakdown spectroscopy (LIBS) was effectively employed for the quantitative investigation of various clay samples for their special uses. To get the LIBS spectra with an optimal signal-to-noise as well as for a more robust and accurate analytical investigation, different experimental parameters (laser energy, gate delay time, and the distance between target and focusing lens) were optimized before the experiments on actual samples. The analysis of emission spectra revealed the presence of many different elements, including Al, Ca, Fe, Mg, Mn, Na, K, Li, S, Si, and Zn. The electron number density and plasma temperatures were determined using the Stark broadened line profile and Boltzmann plot method, respectively. To determine the relative concentration of observed elements, we used an integrated intensity ratio method, integrated intensity of every line from all elements, and calibration free (CF)-LIBS. The prevailing condition of local thermodynamic equilibrium during the experimental executions was verified with multiple criteria. The spectral lines used in CF-LIBS were characterized for the influence from the self-absorption phenomenon, but the same was found insignificant. The findings of our LIBS system were found to agree excellently with the outcomes of the inductively coupled plasma/optical emission spectroscopy, thereby yielding a high statistical correlation factor and hence enlighten the significance of LIBS as a safe and reliable tool for elemental analysis of clay samples.

Experimental evaluation of reconstruction algorithms for scintillation crystal array based on charge projection readout

Abstract Although the technological advances in hardware of gamma camera lead to an obvious increase of detector performance, the final reconstructed image is still strongly restricted by reconstruction algorithms. In this work, an experiment evaluation of four popular algorithms, i.e., truncated Center-of-Gravity (TCOG), Raise-to-Power (RTP), Least Squares Estimator based on Particle Swarm Optimization (PSO-LSE) and Gaussian fitting (GF), for estimating the position of scintillation events detected by scintillation crystal array based on charge projection readout is performed. The detector of the gamma camera consists of a 22 × 22 array of CsI(Tl) scintillation crystals and an 8 × 8 matrix of SiPM pixels. The readout circuit, known as symmetric charge division (SCD) circuit, reduces an 8 × 8 array of signal channels into 8+8 signal channels coming from rows and columns projections. The imaging performances, in terms of flood image, average peak-to-valley ratio of line profile, useful field-of-view (UFOV) and position linearity response are measured. The result indicates that the four presented algorithms show good applicability for charge projection readout. RTP and PSO-LSE algorithms perform better in pixel identification of flood image and peak-to-valley of line profile, and PSO-LSE and GF methods are helpful to increase the UFOV. Among the four implemented reconstruction algorithms, PSO-LSE is a potential and promising algorithm that allows achieving excellent pixel identification of flood image, peak-to-valley ratio of line profile, spatial resolution, UFOV and position linearity response at the same time. The application of the PSO-LSE algorithm may offer the possibility to obtain high-quality reconstructed image in scintillation crystal array based on charge projection readout.

Spectral analysis of mint (pudina) using laser-induced breakdown spectroscopy and inductively coupled plasma/atomic emission spectroscopy

In the current study, pulsed Nd:YAG laser-induced breakdown spectroscopy (LIBS) was successfully applied, at 532 nm with a suitable detector, for the spectral analysis of mint (domestic mint and wild mint) available in Pakistan. From the spectral emissions of the mint plasmas recorded with the spectrometer (LIBS2000+, Ocean Optics, Inc.), 17 elements were identified in the domestic mint whereas the wild mint was observed to have 18 different elements, comprising both nutritional elements and toxic metals. Prior to recording the spectral emissions, the sensitivity of our LIBS detection was enhanced by optimizing various LIBS parameters. Under ambient environments, a laser pulse irradiance of about 2.0 × 1011 W cm−2 was employed for the generation of the plasmas on the surfaces of the target samples. The quantitative analyses were performed via calibration curves drawn for all the elements through standard samples prepared in a known concentration in the mint matrix, as well as by a weight percentage method under the assumptions of local thermodynamic equilibrium and optically thin plasma. The electron temperature and number density were determined through the Boltzmann plot method and stark broadened line profile method, respectively, using Ca-I spectral lines. Furthermore, to verify the precision of our LIBS findings, the abundance of each element in the mint samples was also estimated by means of a standard analytical tool, such as inductively coupled plasma/atomic emission spectroscopy (ICP/AES). The outcomes of the LIBS system were found to be in good agreement with the results of ICP/AES statistically, which guarantees that the method is reliable in the illustration and detection of both nutritional and toxic chemical differences in the mint samples, and is hence a step forward in securing human health through environmental and agricultural development.

X-ray diffraction analysis of KY3F10 nanoparticles doped with Nd and preliminary studies for its use in high-dose radiation dosimetry

In this work, the structure and microstructure of Nd:KY3F10 nanoparticles was probed using X-ray synchrotron diffraction analysis. Rietveld refinement was applied to obtain cell parameters, atomic positions and atomic displacement factors to be compared with the ones found in literature. X-ray line profile methods were applied to determine mean crystallite size and crystallite size distribution. Thermoluminescent (TL) emission curves were measured for different radiation doses, from 0.10 kGy up to 10.0 kGy. Dose-response curves were obtained by area integration beneath the peaks from TL. The reproducibility of the results in this work has shown that this material can be considered a good dosimetric material.

An improved gray line profile method to inspect the warp–weft density of fabrics

Image processing has become a tremendous tool for various fields of applications as well as for textile manufacturing industry in recent years. Inspection of fabric density is one of the major issues for fabric manufacturers in textile industries. In this study, an image processing method comprising of linear and nonlinear techniques for automatic inspection of warp and weft yarn density of fabrics has been proposed. By avoiding common problems of linear filtering such as blurring and localization, anisotropic diffusion filtering has been applied as preprocessing operation to enhance the edge region/boundaries between adjacent yarns of the fabric images. We conjecture that given a skewed gray level image, the number of peaks in the gray line profile of the image is minimized if the image is rotated in such a way that the inter-spaces between yarns are aligned with the vertical axis. Gabor filter, an orientation-sensitive filter, is applied to the skewed image at that angle to boost the edges between inter-spaces. The number of warp and weft yarn density has been inspected by applying gray line profile method. Simulations have been done on a wide range of fabric image data set. The results have shown that nonlinear and steered filters made a contribution to the performance of the method. The number warp and weft yarn densities are determined with an accuracy rates above 90%.

Evidence for a core–shell configuration in Tb-doped KY3F10 nanoparticles using synchrotron x-ray line profile and pair distribution function analyses

The microstructure of Tb-doped KY3F10 nanoparticles synthesized by coprecipitation was analysed using x-ray synchrotron diffraction data. Size-strain analysis was performed by means of x-ray line profile (XLPA) methods such as Warren–Averbach and whole powder pattern modelling. Additionally, the structural coherence of the sample was accessed using pair distribution function analysis, supporting the XLPA results. The combination of all methods revealed that the nanoparticles exhibit a more ordered core and a less ordered surface comprising a core–shell configuration.

Stacking fault density and bond orientational order of fcc ruthenium nanoparticles

We investigated crystal structure deviations of catalytic nanoparticles (NPs) using synchrotron powder X-ray diffraction. The samples were fcc ruthenium (Ru) NPs with diameters of 2.4, 3.5, 3.9, and 5.4 nm. We analyzed average crystal structures by applying the line profile method to a stacking fault model and local crystal structures using bond orientational order (BOO) parameters. The reflection peaks shifted depending on rules that apply to each stacking fault. We evaluated the quantitative stacking faults densities for fcc Ru NPs, and the stacking fault per number of layers was 2–4, which is quite large. Our analysis shows that the fcc Ru 2.4 nm-diameter NPs have a considerably high stacking fault density. The B factor tends to increase with the increasing stacking fault density. A structural parameter that we define from the BOO parameters exhibits a significant difference from the ideal value of the fcc structure. This indicates that the fcc Ru NPs are highly disordered.

Spatial characterization of red and white skin potatoes using nano-second laser induced breakdown in air

We presents spectroscopic study of the plasma generated by a Q-switched Nd:YAG (1064 nm) laser irradiation of the flesh of red and white skin potatoes. From the spectra recorded with spectrometer (LIBS2500+, Ocean Optics, USA) 11 elements were identified in red skin potato, whereas, the white skin potato was found to have nine elements. Their relative concentrations were estimated using CF-LIBS method for the plasma in local thermodynamic equilibrium. The target was placed in ambient air at atmospheric pressure. The electron temperature and number density were calculated from Boltzmann plot and stark broadened line profile methods, respectively using Fe I spectral lines. The spatial distribution of plasma parameters were also studied which show a decreasing trend of 6770 K–4266 K and (3–2.0) × 1016 cm-3. Concentrations of the detected elements were monitored as a function of depth of the potatoes. Our study reveals a decreasing tendency in concentration of iron from top to the centre of potato’s flesh, whereas, the concentrations of other elements vary randomly.

Formation mechanism of dot-line square superlattice pattern in dielectric barrier discharge

We investigate the formation mechanism of the dot-line square superlattice pattern (DLSSP) in dielectric barrier discharge. The spatio-temporal structure studied by using the intensified-charge coupled device camera shows that the DLSSP is an interleaving of three different subpatterns in one half voltage cycle. The dot square lattice discharges first and, then, the two kinds of line square lattices, which form square grid structures discharge twice. When the gas pressure is varied, DLSSP can transform from square superlattice pattern (SSP). The spectral line profile method is used to compare the electron densities, which represent the amounts of surface charges qualitatively. It is found that the amount of surface charges accumulated by the first discharge of DLSSP is less than that of SSP, leading to a bigger discharge area of the following discharge (lines of DLSSP instead of halos of SSP). The spatial distribution of the electric field of the surface charges is simulated to explain the formation of DLSSP. This paper may provide a deeper understanding for the formation mechanism of complex superlattice patterns in DBD.

Infrared laser induced plasma diagnostics of silver target

In the present work, the optical emission spectra of silver (Ag) plasma have been recorded and analyzed using the laser induced breakdown spectroscopy technique. The emission line intensities and plasma parameters were investigated as a function of lens to sample distance, laser irradiance, and distance from the target surface. The electron number density (ne) and electron temperature (Te) were determined using the Stark broadened line profile and Boltzmann plot method, respectively. A gradual increase in the spectral line intensities and the plasma parameters, ne from 2.89 × 1017 to 3.92 × 1017 cm−3 and Te from 4662 to 8967 K, was observed as the laser irradiance was increased 2.29 × 1010–1.06 × 1011 W cm−2. The spatial variations in ne and Te were investigated from 0 to 5.25 mm from the target surface, yielding the electron number density from 4.78 × 1017 to 1.72 × 1017 cm−3 and electron temperature as 9869–3789 K. In addition, the emission intensities and the plasma parameters of silver were investigated by varying the ambient pressure from 0.36 to 1000 mbars.