In this study, an in situ catalytic radical probe system together with a software platform is developed to measure concentrations of reactive species in low-temperature plasmas with high spatial resolutions. The radical probes can be used to determine radical densities of hydrogen, nitrogen, and oxygen independently, in pairs and often simultaneously in any continuous plasma source in a vacuum environment. The basic principle and advantage of a probe array is the capability to distinguish between different gas species due to several sensitive elements acting as recombination catalysts. Radical densities of hydrogen, nitrogen, and oxygen were measured in a helicon plasma source. Generally, it is observed that radical densities increase with respect to pressure and power. Additionally, the electron density and electron temperature were measured by Langmuir probes. The electron density increased with increasing power and pressure. Electron temperature increased with power but decreased with increasing pressure. The key to getting absolute numbers of radical densities is based on knowing the recombination coefficient of the given gas on the catalytic surface. The probe system measures densities in a broad range of reactive species’ concentrations varying from about 10¹³ to 10¹⁵ cm⁻³.

中文翻译：

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自由基探针系统，用于原位测量氢，氧和氮的自由基密度

在这项研究中，原位开发了催化自由基探针系统和软件平台，以高空间分辨率测量低温等离子体中反应性物质的浓度。自由基探针可用于独立，成对并且经常在真空环境中的任何连续等离子体源中同时测定氢，氮和氧的自由基密度。探针阵列的基本原理和优点是能够区分由于几种敏感元素充当重组催化剂的不同气体种类的能力。在螺旋等离子体源中测量了氢，氮和氧的自由基密度。通常，观察到自由基密度相对于压力和功率增加。另外，通过Langmuir探针测量电子密度和电子温度。电子密度随着功率和压力的增加而增加。电子温度随功率的升高而升高，但随压力的升高而降低。获得自由基密度绝对数的关键是基于已知催化表面上给定气体的复合系数。探针系统可测量各种反应物浓度范围内的密度，范围从大约10¹³至10 ¹⁵  cm ^-3。