Determination of plasma parameters by spectral line broadening in an electrosurgical argon plasma

TY - JOUR

T1 - Determination of plasma parameters by spectral line broadening in an electrosurgical argon plasma

AU - Hillebrand, Bastian

AU - Iglesias, Enrique

AU - Gibson, Andrew R.

AU - Bibinov, Nikita

AU - Neugebauer, Alexander

AU - Enderle, Markus

AU - Awakowicz, Peter

N1 - Publisher Copyright: © 2020 IOP Publishing Ltd.

PY - 2020/12/16

Y1 - 2020/12/16

N2 - An electrosurgical argon plasma with a 5% admixture of molecular hydrogen is studied in order to investigate time averaged plasma parameters by optical emission spectroscopy (OES). Electron densities in the range of 1015-1016 cm-3 are determined from the Stark broadening of the time averaged line profiles of the Balmer-α and -β emission lines of hydrogen. A two-profile fit corresponding to regions of different electron densities is found to provide a better representation of the line broadening than a single profile fit. This is consistent with time resolved ICCD imaging, acquired with 150 ns time resolution, that shows strong radial gradients in the plasma emission and the asymmetry produced by the discharge arrangement. Gas temperatures are determined using two different methods. Firstly, simulated spectra for different rotational temperatures are fitted to the measured N2(C-B, 0-1) emission band originating from ambient air diffusion into the argon/hydrogen gas flow. From the best fit, rotational temperatures between 1500 K and 1800 K are inferred. These measurements are in good agreement with those inferred by the second method, which is based on the collisional broadening of the emission lines of neutral argon at 750 nm and 751 nm. This latter method may be useful for the measurement of gas temperatures when the device is used inside hollow organs during endoscopic or laparoscopic interventions, where air mixing will be limited. Therefore, the results of this study are highly relevant to applications of these devices, e.g. for controlling tissue effects and the avoidance of excessive heating.

AB - An electrosurgical argon plasma with a 5% admixture of molecular hydrogen is studied in order to investigate time averaged plasma parameters by optical emission spectroscopy (OES). Electron densities in the range of 1015-1016 cm-3 are determined from the Stark broadening of the time averaged line profiles of the Balmer-α and -β emission lines of hydrogen. A two-profile fit corresponding to regions of different electron densities is found to provide a better representation of the line broadening than a single profile fit. This is consistent with time resolved ICCD imaging, acquired with 150 ns time resolution, that shows strong radial gradients in the plasma emission and the asymmetry produced by the discharge arrangement. Gas temperatures are determined using two different methods. Firstly, simulated spectra for different rotational temperatures are fitted to the measured N2(C-B, 0-1) emission band originating from ambient air diffusion into the argon/hydrogen gas flow. From the best fit, rotational temperatures between 1500 K and 1800 K are inferred. These measurements are in good agreement with those inferred by the second method, which is based on the collisional broadening of the emission lines of neutral argon at 750 nm and 751 nm. This latter method may be useful for the measurement of gas temperatures when the device is used inside hollow organs during endoscopic or laparoscopic interventions, where air mixing will be limited. Therefore, the results of this study are highly relevant to applications of these devices, e.g. for controlling tissue effects and the avoidance of excessive heating.

KW - atmospheric pressure

KW - electron density

KW - electrosurgical plasma

KW - gas temperature

KW - plasma spectroscopy

KW - spectral line broadening

U2 - 10.1088/1361-6595/abc411

DO - 10.1088/1361-6595/abc411

M3 - Article

AN - SCOPUS:85098530175

SN - 0963-0252

VL - 29

JO - Plasma Sources Science and Technology

JF - Plasma Sources Science and Technology

IS - 12

M1 - 125011

ER -