A low-power magnetic-field-assisted plasma jet generated by direct-current glow discharge at atmospheric pressure

Summary form only given. Atmospheric-pressure plasma jets (APPJs) can be easily produced with high voltage applied between two naked electrodes in the DC circuit, but considerable Joule heat is generated in the ballast resistor that is used to prevent glow-to-arc transition, resulting in waste of a large amount of energy. From point of view of energy saving and cost reduction, a magnetic field (B = 0.42T) is introduced to the dielectric-barrier discharge enhanced direct-current glow discharge for efficient plasma generation. The introduction of magnetic field allows the discharge power to decrease to 2.7 from 4.9 W reported in our previous work and the Joule heat to drop to 10 from 32.4 W, with the total energy consumption reduced to 34% of the original. This greatly improves the energy utilization efficiency in the plasma generation. Comparison of the plasma physical appearance with and without magnetic field shows that the application of magnetic field makes the plasma jet not only more stable and more uniform in vision, but also lengthened along the gas flow. Spatially examining the emission spectra and plasma temperature indicates that their peaks shift from edges to the center and the negative and anode glows merge into the positive column and disappear. For the magnetized electrons, the E x B drift in the same direction as gas flow is examined to be 4.3×10⁶ cm/s which is 55.4 times more than the electron drift of 0.8×10⁵ cm/s in the direction from cathode to anode, indicating the significant enhancement of plasma drift along the gas flow. The electron-neutral ionization frequency is increased up to 1.2×10¹⁰ s^-1 from 2.2×10⁸ s^-1 in the case without magnetic field. Moreover, due to the Lorentz force, electrons would travel and meet more gas molecules in the curved and lengthened path in the downstream regions, rather than concentrate in a straight line, leading to - he increment of α-reaction and the dispersion of discharge domains. These effects not only promote the generation of plasma with a larger scale, but also improve the uniformity, stability, and chemical activity of plasma. Thus, this plasma jet can be used as an efficient cost effective source for biomedical and materials processing applications. This work was financially supported by the CAS/SAFEA International Partnership Program for Creative Research Teams and the China Postdoctoral Science Foundation under Grant No. 2012M512041.