Laser-induced plasma electron number density:Stark broadening method versus the Saha-Boltzmann equation

We report spectroscopic studies on plasma electron number density of laser-induced plasma produced by ns-Nd：YAG laser light pulses on an aluminum sample in air at atmospheric pressure. The effect of different laser energy and the effect of different laser wavelengths were compared. The experimentally observed line profiles of neutral aluminum have been used to extract the excitation temperature using the Boltzmann plot method, whereas the electron number density has been determined from the Stark broadened as well as using the Saha-Boltzmann equation （SBE）. Each approach was also carried out by using the AI emission line and Mg emission lines. It was observed that the,SBE method generated a little higher electron number density value than the Stark broadening, method, but within the experimental uncertainty range. Comparisons of Ne determined by the two methods show the presence of a linear relation which is independent of laser energy or laser wavelength. These results show the applicability of the SBE method for Are determination, especially when the system does not have any pure emission lines whose electron impact factor is known, Also use of Mg lines gives superior results than Al lines.

Electron Density and Temperature Measurement by Stark Broadening in a Cold Argon Arc-Plasma Jet at Atmospheric Pressure

Determination of both the electron density and temperature simultaneously in a cold argon arc-plasma jet by analyzing the Stark broadening of two different emission lines is presented. This method is based on the fact that the Stark broadening of different lines has a different dependence on the electron density and temperature. Therefore, a comparison of two or more line broadenings allows us to diagnose the electron density and temperature simultaneously. In this study we used the first two Balmer series hydrogen lines Ha and Ha for their large broadening width. For this purpose, a small amount of hydrogen was introduced into the discharge gas. The results of the Gigosos-Cardenoso computational model, considering more relevant processes for the hydrogen Balmer lines, is used to process the experimental data. With this method, we obtained reliable electron density and temperature, 1.88 × 1015 cm^-3 and 13000 K, respectively. Possible sources of error were also analyzed.

Electron density calculation based on Stark broadening of D Balmer line from detached plasma in EAST tungsten divertor

The electron density within the volume of the tungsten divertor of the Experimental Advanced Superconducting Tokamak （EAST） is calculated based on Dε line （396.9 nm） Stark broadening （SB） measurements. The quasistatic approximation is employed in the SB calculation of the Dε line. The influences of other broadening mechanisms on the calculation error of electron density have been evaluated. The SB method is applied to the study of spatial distribution and time evolution of the electron density in the W divertor. Two electron density bands are observed in the detached divertor plasma during an L-mode discharge sustained by low hybrid wave （LHW） heating, which could be related to the striated particle flux distribution induced by LHW. After the onset of detachment, the upper electron density band corresponding to outer strike point firstly increases then decreases, while the lower density band corresponding to striated particle flux increases continually although the electron densities from Langmuir Probes at the divertor plate keep a descending trend. This could indicate a downward movement of the radiation region that approximately moves along the magnetic field lines after the onset of detachment.

Atomic Emission Spectra Diagnosis and Electron Density Measurement of Semiconductor Bridge (SCB) Plasma

Emission spectra of a semiconductor bridge （SCB） plasma in a visible range was studied in air. The electron density was measured in a conventional way from the broadening of the Al Ⅰ 394.4 nm Stark width. Based on the Saha equation, a system for recording the intensity of Si Ⅰ 390.5 nm and Si Ⅱ 413.1 nm was designed. With this technique, the SCB plasma electron density was measured well and accurately. Moreover, the electron density distribution Vs time was acquired from one SCB discharge. The individual result from the broadening of the Al Ⅰ 394.4 nm Stark width and Saha equation was all in the range of 1015 cm^-3 to 1016 cm^-3. Finally the presumption of the local thermodynamic equilibrium （LTE） condition was validated.

Research of welding hyperbaric arc electron density in TIG welding

The arc spectrum of TIG welding in high pressure was analyzed by Stark broadening. Using the characteristic line of Arl in welding arc, a study of electron density in high pressure revealed that the electron density of the welding arc had an upward trend with the pressure increase. According to data analysis, a curve of relationship between electron density alwl environmental pressure was established. It has a universal significance for change of electron density in high pressure. Through the analysis of electron density changing in time-domain in different pressure, a theoretical basis was provided for the problem of poor arc stability in high pressure.

Spatial confinement effects of laser-induced breakdown spectroscopy at reduced air pressures

Spatial confinement is a simple and cost-effective method for enhancing signal intensity and improving the detection sensitivity of laser-induced breakdown spectroscopy(LIBS).However,the spatial confinement effects of LIBS under different pressures remains a question to be studied,because the pressure of the ambient gas has a significant influence on the temporal and spatial evolution of plasma.In this study,spatial confinement effects of LIBS under a series of reduced air pressures were investigated experimentally,and the plasma characteristics under different air pressures were studied.The results show that the reduced air pressure can lead to both earlier onset and weakening of the enhancement effect of the spatial confinement on the LIBS line intensity.When the air pressure drops to 0.1 kPa,the enhancement effect of the emission intensity no longer comes from the compression of the reflected shock wave on the plasma,but from the cavity’s restriction of the plasma expansion space.In conclusion,the enhancement effect of spatial confinement technology on the LIBS is still effective when the pressure is reduced,which further expands the research and application field of spatial confinement technology.