Cold atmospheric plasma (CAP) is a simple and inexpensive method to produce plasma in ambient air. In this study, CAP was generated by flowing helium gas through a glass tube with a copper electrode rounded externally around it to provide an electric field for gas excitation. The plasma extended for up to a few centimeters from the opening of the tube forming a plume. Optical emission spectroscopy (OES) was used to identify the composition of the plasma along the length of the plume. Four positions along the plume were investigated at flow rates of 1, 1.5, and 2.5 L min⁻¹. Results revealed that the plume consisted of a varying composition of excited state species dependent on the location in the plume and gas flow rate. Identified in the emission spectra were the nitrogen second positive and first negative system along with OH^* emissions at 282 and 308nm. The OH^* emissions, found at the opening of the tube, had a higher intensity as the flow rate increased and were attributed to impurities from the ambient air in the source tubing, while the N₂ and N₂ ⁺ emissions came from the nitrogen of the ambient air and dominated the rest of the measured spectra. Identifying the species and their intensities at different locations of the plume with different flow rates helped in determining the appropriate location and flow rate needed for a specific application of the surface treatment of ultra-high-molecular-weight-polyethylene (UHMWPE) to change its roughness. Additional spectra were taken in situ with an UHMWPE sample present to compare the reactive species of a free jet with those when a target was present. Finally, preliminary roughness tests showed increases of as low as three and as much as over ten times the pristine value depending on the position of the polymer in the plume and the source flow rate.

冷大气等离子体 (CAP) 是一种在环境空气中产生等离子体的简单且廉价的方法。在这项研究中，CAP 是通过使氦气流过玻璃管产生的，该玻璃管带有一个外部环绕的铜电极，以提供用于气体激发的电场。等离子体从管子的开口处延伸了几厘米，形成了一股羽流。使用光学发射光谱 (OES) 来确定沿羽流长度的等离子体的组成。^{在 1、1.5 和 2.5 L min -1}的流速下研究了沿羽流的四个位置. 结果表明，羽流由不同组成的激发态物质组成，这取决于羽流中的位置和气体流速。在发射光谱中确定了氮的第二正和第一负系统以及 282 和 308nm 处的 OH ^*发射。在管开口处发现的 OH ^*排放随着流速的增加而具有更高的强度，这归因于源管中环境空气中的杂质，而 N ₂和 N ₂ ⁺排放来自环境空气中的氮，并主导了其余的测量光谱。识别具有不同流速的羽流不同位置的物种及其强度有助于确定超高分子量聚乙烯 (UHMWPE) 表面处理的特定应用所需的适当位置和流速，以改变其粗糙度。在存在 UHMWPE 样品的情况下原位获取额外的光谱，以比较自由射流的反应性物质与存在目标时的反应性物质。最后，初步粗糙度测试表明，根据聚合物在羽流中的位置和源流速，原始值的增加低至原始值的 3 倍至 10 倍以上。