The contribution of electrode spacing and operating voltage on the time-resolved optical emission spectra of atmospheric-pressure air and Ar DBD plasma

Abstract

This paper reports the optical characterization of a controlled atmospheric-pressure dielectric barrier discharge (DBD) plasma source in air and Ar environments. In this study, Ar flow rate is held constant at 1 L/min while the operating voltages varied from 6.5 kV to 12.7 kV. Under these conditions, a calibrated commercial compact spectrometer covering the range from 200 to 850 nm was used to record the emission spectra of DBD plasma operating at different voltages, gap distances, and gas types. Using the Boltzmann distribution, we calculated the electron density ($n_e$) and excitation temperatures in the plasma of air and Ar DBD at 2 mm gap distance . The emission spectra lines of the hydroxyl radicals (OH), $N_2$, and Ar ions are acquired at different operating conditions. According to the findings, the light intensity of Ar DBD is significantly higher than that of air DBD under the same conditions of operation. The intensity of the generated plasma spectrum is also shown to rise with both an increase in the input voltage and a decrease in the gap distance. The measurements also showed that the average temperature of the excited electrons is around 1.1 eV for air DBD and 0.11 eV for Ar DBD, while $n_e$ for both is on the order of ${10}^{16}{\mathrm{cm}}^{-3}$. These results show that as the working voltage increases, the plasma changes from a filamentary state to a homogeneous mode. Knowing the DBD parameters increases its chance to compete with traditional methods in many fields, such as water, polymers, and biomedical treatments.

Keywords:

• DBD
• optical emission spectroscopy (OES)
• cold plasma
• excitation temperature
• electron density
• Boltzmann plot

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Mohamed Mokhtar Hefny

Mohamed Mokhtar Hefny was born in Cairo, Egypt, in 1984. He received the B.Sc. degree in physics from Ain Shams University, Cairo, in 2006, the pre-master's degree in physics from Ain Shams University, Cairo, Egypt, in 2008, the M.Sc. degree from Ain Shams University, Cairo, Egypt, in 2012, and the Ph.D. degree from Ruhr University Bochum, Faculty of physics, plasmas with complex interactions in 2014. He is also working as assistant professor of physics at Future University in Egypt since 2014, where he taught physics for many students with different interests such as engineering, oral medicine, computer science. He has many research articles related to plasma applications and anomalous diffusion, where he collaborated with different groups around the world. His main goal is to introduce plasma to more life applications in industrial scale.

S.T. Abd El-latif

S.T. Abd El-Latif currently works as a Lecturer at the Plasma and Nuclear Fusion Dept., Nuclear Research Center, Egyptian Atomic Energy Authority. She received her PhD from Ain Shams University, Faculty of Girls in 2014. She does research in Plasma Physics and its applications. Her most recent publication is Experimental studies on DC axial virtual cathode electric discharge, coaxial plasma, microwave plasma, DBD, and polymer treatments.

F.B. Diab

F.B. Diab was born on March 10, 1977, in Sohag, Egypt. He received the B.Sc. degree (Special Physics) from Al-Azhar University (Assiut branch), in 2001.The M.Sc degree from European Master in Nuclear Fusion and Engineering Sciences from Gent University (Gent, Belgium) & Université Henri Poinçaire (UHP, Nancy, France) & University of Carlos III (Madrid, Spain) in 2009 in( Plasma wall Interaction , Hydrogen and Helium Recycling , Plasma physics).The Ph.D. degree (Electrothermal plasma Gun) from Al-Azhar University (Cairo branch), in 2013. He joined the plasma & Nuclear Fusion department, Nuclear Research Center (NRC), Egyptian Atomic Energy Authority (EAEA), Anshass, Egypt from 2004 up to now. His current interests include plasma diagnostics, electrothermal plasma Accelerators, the physics of dense plasmas, plasma focus, plasma torch and magnetron plasma and its applications. He is an experimental research in the Plasma & Nuclear Fusion department deals with the ablation of surfaces exposed to dense plasmas produced in capillary discharges.

Kamal M. Ahmed

Kamal M. Ahmed was born in Minya, Egypt, in 1979. He received the B.Sc. degree in electrical engineering from Minya University, Minya, in 2001, the pre-master's degree in electrical engineering from Cairo University, Giza, Egypt, in 2006, the M.Sc. degree from the European Master of Science in Nuclear Fusion and Engineering Physics, Gent University- Ghent, Belgium, Henri Poinçaire University (UHP)- Nancy, France, and the Complutense University of Madrid-Madrid, Spain, in 2009, and the Ph.D. degree from Benha University- Benha, Egypt, in 2014. He has been with the Plasma and Nuclear Fusion Department, Nuclear Research Center, Egyptian Atomic Energy Authority (EAEA), Cairo, Egypt, since 2005. He holds an STDF-IFE Post-Doctoral Fellowship at CEA-Cadarache, Saint-Paul-lez-Durance, France. He is now an Associate Professor on Experimental plasma and its applications in EAEA. His current research interests include high-voltage engineering related to plasma and fusion reactors, R&D in continuous and pulsed plasma sources' design, characterization and their applications in the fields of material science and biomedical applications.