engleski

STUDY OF ATMOSPHERIC PRESSURE PLASMA JET FROM OPEN AIR TO VACUUM

Atmospheric pressure plasma jets (APPJ) attract interest due to many technological applications in biomedicine, materials treatments, food industry etc. Comparing to lowpressure plasmas they offer new possibilities due to simpler setup and ability to operate in atmospheric environment. This work is focused on studying APPJs at controlled underpressure conditions, contrary to the open air conditions. The APPJ electrode was a copper wire with a diameter of 0.1 mm inserted in a 50 mm long and 1.5 mm outer diameter borosilicate glass capillary tube [2]. Power source was the same as in ref. [3], AC at 25 kHz at about 2.5 kV. This capillary plasma source was inserted into a glass tube of 11.5 cm diameter and 150 cm length. In order to maintain under-pressure conditions, the tube was connected to a rotary vacuum pump and vacuum gauge while the gas (for example helium, purity 99.996%) input flow was controlled with mass flow controller in the range of several L/min. The experimental setup allows various diagnostics to be applied: imaging, spatially resolved optical emission spectroscopy, determination of voltage-current curves and E-M probe measurements, versus total pressure and mass flow in the tube. We describe different regimes of the APPJ behaviour depending on the total pressure and mass flow, in terms of the jet lengths, and discuss jet operating mode transitions form atmospheric pressure conditions towards vacuum conditions. This work has been supported by Croatian Science Foundation under project #2753. [1] A. Režek Jambrak, T. Vukušić, V. Stulić, J. Mrvčić, S. Milošević, M. Šimunek, Z. Herceg, Food and Bioprocess Technology: An International Journal, 8(4), 791-800 (2015). [2] R. Zaplotnik, Z. Kregar, M. Bišćan, A.Vesel, U. Cvelbar, M. Mozetič, S. Milošević, EPL, 106 2500 (2014). [3] R. Zaplotnik, M. Bišćan, Z. Kregar, U. Cvelbar, M. Mozetič, S. Milošević, Spectrochemica Acta B, 103, 124-130 (2015).

Atmospheric pressure plasma jet ; Optical emission spectroscopy ; pressure effect

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