Towards Optimization and Adaptive Control: The Performance of Helium Guided Cold Atmospheric Plasma Jet Open Access
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Cold Atmospheric Plasma (CAP), including the Dielectric Barrier Discharge (DBD) and the Cold Atmospheric Plasma Jet (CAPJ), plasma needle, and plasma torch is currently under intensive studies of its biomedical applications, especially the cancer therapy. The advantage of plasma-based cancer treatment is the so-called “selectivity” that the plasma can lead to apoptosis differently from cell lines to cell lines. Based on such a difference, CAP may achieve a “selective kill” that statistically significant lower viability of cancer cells compared with the value of normal cells. In other words, CAP treatment could be a future cancer therapy without side effects when the plasma parameters are optimized correctly. However, the current understanding of CAP-cell interactions is still not complete to optimize the plasma. Therefore, this research work focuses on the behavior of CAPJ which can be altered by the local environment and target cells which are two major topics of the CAPJ control. The objective of this study is thus to discover some of the detail CAPJ behaviors and prepare for the future development of a self-adaptive CAPJ which can automatic optimize itself under a variety of conditions.To understand the CAPJ behaviors, the electron temperature is usually a critical variable to analysis. However, as the most common method of electron temperature measurement for cold plasmas, Laser Thomson Scattering (LTS) usually provides results with large error bars for the CAPJ due to the low ionization degree of such plasma. Therefore, a new electron temperature diagnostic technology is developed in this work. Also, to achieve the future adaptive control, real-time observations of target properties are also required. Combining these new diagnostic methods with other traditional technologies including the Rayleigh Microwave Scattering (RMS) and Optical Emission Spectroscopy (OES), how the permittivity of a dielectric target can feedback and change the CAPJ is revealed. On the other hand, for a conductive target, how an ionization wave in CAPJ can be reflected is discovered using an Intensified Charged-Coupling Device (ICCD) camera and a numerical simulation. Same diagnostic technologies are also used to observe how the CAPJ performs in the humid daily air. A shift of Electron Energy Probability Function (EEPF) is thus concluded as the humidity effect of the environment which alters multiple CAPJ parameters. Finally, the plasma bullet propagations and the optical emissions of chemical species from the CAPJ working under an external electric field is studied as an extra manipulation method. These works provide a path towards a future CAPJ self-adaptive control. To achieve such automatic optimization, the understanding and manipulation of CAPJ behaviors are prerequisites. Therefore, in this dissertation, how the CAPJ reacts with conductive and dielectric targets was revealed. Also, how it performs in a manipulated environment was analyzed. The next step in the future will be a control algorism and hardware development for the CAPJ, based on the discovery reported in this dissertation and real-time observations of CAPJ parameters.