Stark shift measurement as a temperature diagnostic of Cu-dominated thermal plasmas

Abstract

We investigate the temperature-dependence of the light emission properties of Cu-dominated plasmas with pressures in the order of 1 bar and for currents between 0 and 2 kA. While the wavelength of Cu I 3d 9 4s5s transitions for currents above 1 kA is essentially constant, a 0.1 nm Stark blueshift is observed with decreasing current from 1 kA to zero. Using a lineshape analysis of the light emission spectra, which is based on solving a one-dimensional radiative transfer equation along the line-of-sight across the arc, we show that the transition wavelength increases linearly with temperatures in the 5000-10 000 K range. Based on this observation, we propose a simple method for the temperature diagnostic of plasmas that neither requires an absolute calibration of the intensity of the detected signal, nor complex simulation tools.

Impact of Stark Shifts on the Radiation Cooling of Cu-Dominated Plasmas

“…1(c). Note that we plot I 1/4 rather than I as the former quantity can be used to estimate the shape of the arc temperature profile [3]. A decrease in current leads both to a slight decrease in the arc peak emission intensity and to a reduction in the width of the intensity profile along the y-axis.…”

“…We described in Ref. [3] a method to extract the time-dependence of the arc peak temperature and pressure from the analysis of high-speed camera images combined with a lineshape fit of the spectra. This method requires several assumptions, that we list in the following: (i) the arc exhibits a radial symmetry, (ii) the width of the fourth-root of the intensity profiles along the y-axis in Fig.…”

“…This method requires several assumptions, that we list in the following: (i) the arc exhibits a radial symmetry, (ii) the width of the fourth-root of the intensity profiles along the y-axis in Fig. 1(a) is equal to 0.72 w, with w the width of the arc temperature profile [3], and (iii) the ratio between w and the width of the arc pressure profiles is equal to 3 [4]. In Ref.…”

“…In that purpose, knowledge of the oscillator strengths and Stark broadening parameters of the optical transitions of the atoms and ions constituting the plasma is necessary. While Stark line shifts are usually neglected when computing the absorption of Cu plasmas [2], we have recently reported that Cu I 3d 9 4s5s transitions exhibit a Stark shift of about 0.1 nm with increasing temperatures from 5000 to 10000 K [3].…”

On the semiclassical perturbation Stark shifts of Ar II spectral lines

“…Stark broadening data are also useful for laboratory plasmas diagnostic. Corfdir et al (2019) used Stark shift as a temperature diagnostic of Cu dominated plasma.…”