The article reports the excitation of a helical argon atmospheric pressure plasma jet using a pulse-modulated 13.56 MHz radio frequency (RF) power source. This helical structure is observed in open ambient air, which is far different from the conventional conical shape. This helical structure originates due to the periodic pressure variation in the discharge region caused by pulse-modulated RF (2 kHz modulation frequency) and propagates downstream into the ambient air. The geometrical characteristics of the observed structure are explored using optical imaging. Moreover, the influence of various input parameters, viz., duty cycle, gas flow rate, and RF power, of the modulated pulse on the formation of a helical structure are studied. These helical structures have an implication on the plasma jet chemical features (enhancement of reactive oxygen and nitrogen species) as these are involved in an increase in air entrainment into the ionization region desired for various plasma applications.

中文翻译：

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使用射频脉冲调制激发螺旋形氩气大气压等离子体射流

该文章报告了使用脉冲调制的 13.56 MHz 射频 (RF) 电源激发螺旋式氩气大气压等离子体射流。这种螺旋结构是在开放的环境空气中观察到的，与传统的圆锥形状大不相同。这种螺旋结构源于脉冲调制射频（2 kHz 调制频率）引起的放电区域的周期性压力变化，并向下游传播到环境空气中。使用光学成像探索观察到的结构的几何特征。此外，研究了调制脉冲的各种输入参数，即占空比、气体流速和射频功率对螺旋结构形成的影响。