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Hiromasa Yamada1 2 Tetsuji Shimizu1 3 Masanori Fujiwara1 Susumu Kato1 Jaeho Kim1 Sanae Ikehara4 Yuzuru Ikehara1 4 3 Hajime Sakakita1 3

1, Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, , Japan
2, Nagano College, National Institute of Technology, Nagano, , Japan
3, Graduate School of Medicine, Chiba University, Chiba, , Japan
4, Biotechnology Research Institute for Drug Discovery, National Institute of Advanced Industrial Science and Technology, Tsukuba, , Japan

Abstract
Atmospheric pressure plasma jet (APPJ) is attracting attention in many research fields such as biology and medicine. Low energy atmospheric pressure plasma (LEAPP) equipment specially designed by Sakakita et al. [1] is one of the APPJ. Stop bleeding accompanied with blood coagulation without thermal damage using the LEAPP has been confirmed as an attractive surgical procedure necessary for minimally invasive surgery [2]. To control the interactions between the plasma and treated targets such as blood, it is necessary to understand the plasma’s behavior. We have already reported several characteristics of the LEAPP, such as dynamic gas-flow behavior [3], gas temperature [4], spatial distribution of reactive species [5], electrical characterization [6], and emission propagation phenomena [7, 8]. In the emission propagation phenomena, a bullet-like emission [9] and a spatially continuous emission [10] were observed depending on the treated target conditions [8]. Moreover, striations have been also observed in the LEAPP [7, 8].
In this study, the characteristics of the emission propagation in the LEAPP under several experimental conditions were analyzed using a high-speed camera. All the observations were synchronized with the measurement of electrical characteristics such as the applied voltage, current and power consumption. As working gases, helium, argon, and neon gases were used. For the target, a copper plate was used and the emission propagation was measured with and without the target. In case with the target, the distance between the nozzle exit of the LEAPP equipment and target surface were changed. Furthermore, an optical emission spectroscopy (OES) was applied in order to identify the reactive species in the plasma. The experimental results are summarized and at the symposium, we discuss the mechanism of emission propagation associated with the characteristics of plasma such as electrical property and optical emission.

Acknowledgments
This study was financially supported by Grants-in-Aid for Scientific Research on Priority Area (24108006) from the Ministry of Education, Culture, Sports, Science and Technology of Japan.

References
[1] H. Sakakita, et al. WO2012/005132 (2012). [2] Y. Ikehara, et al. J. Photopolymer Sci. Tech. 26 (2013) 555. [3] H. Yamada, et al. Jpn. J. Appl. Phys. 55 (2016) 01AB08. [4] J. Kim, et al., Plasma Med. 5 (2015) 99. [5] H. Yamada, et al., J. Phys. D. Appl. Phys. 49 (2016) 394001. [6] H. Sakakita, et al. Plasma medicine 5 (2015) 189. [7] Y. Fujiwara, et al. Jpn. J. Appl. Phys. 55 (2016) 010301. [8] H. Yamada, et al. Plasma Sources Sci. Technol. 27 (2018) 05LT02. [9] M. Teschke, et al., IEEE Trans. Plasma Sci. 33 (2005) 310. [10] J. L. Walsh., J. Phys. D. Appl. Phys. 43 (2010) 75201.

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