Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Hayashi Nobuya Last modified date:2020.07.10

Professor / High Density Energy Science / Department of Advanced Energy Science and Engineering / Faculty of Engineering Sciences


Papers
1. Minoru Noda, Yoshinobu Sakai, Yoshiro Sakaguchi, Nobuya Hayashi, Evaluation of low-temperature sterilizer using peracetic acid-containing hydrogen peroxide gas, Biocontrol Science, 2020.10.
2. Sitti Subaedah Sahabuddin, Haruka Ueamatsu, Nobuya Hayashi, Activation of EL-4 T-cells by irradiation with atmospheric oxygen plasma, Japanese Journal of Applied Physics, https://doi.org/10.35848/1347-4065/ab83db, 59, SJ, SJJF03, 2020.04, The activation of EL-4 T-cells is investigated when the T-cells are sensitized with monoclonal antibodies against CD3/CD28 followed by irradiation with atmospheric oxygen plasma. The proliferation of anti-CD3/CD28-sensitized EL-4 T-cells was evaluated as a function of the oxygen plasma irradiation duration. The plasma irradiation promotes cell proliferation: when plasma irradiation was applied to sensitize T-cells for 40 s, the cell number increased by five times over 24 h compared with that in a cell population that was not exposed to irradiation. Also, the plasma irradiation increases the production of interferon gamma in T-cells by a factor of two. Gene expression analysis of T-cell supports results of the proliferation and the immune function enhancements..
3. N. Hayashi, Y. Inoue, Y. Kyumoto, T. Kukita, Characteristics of differentiation of osteoclast cells irradiated with active species in atmospheric oxygen plasma, Japanese Journal of Applied Physics, https://doi.org/10.35848/1347-4065/ab7ba9, 59, SJ, SJJF02, 2020.04, Variations in osteoclast cell number are observed when osteoclast precursor cells are irradiated with atmospheric dielectric barrier discharge plasma. Active species generated by the oxygen plasma control the differentiation function of the osteoclast precursor cells. Long-lifetime active species such as H 2 O 2 and NO x–dissolved in the culture medium decrease the osteoclast number due to the inactivation of the differentiation function of the osteoclast precursor cells. When short-lifetime active species such as O* and OH* make contact with the osteoclast precursor cells directly, the osteoclast number tends to increase. Short-lifetime active species induce the enhancement of the gene expression of NFATc1..
4. N. Hayashi, Y.C. Yao, Y. Matsunaga, Regulation of macrophage-like cell activity driven by atmospheric oxygen plasma, Japanese Journal of Applied Physics, https://doi.org/10.35848/1347-4065/ab72cf, 59, SH, SHHF03, 2020.03, Oxygen plasma that is a kind of external biological stimulus activates the macrophage-like cell. Active oxygen species in the oxygen plasma-irradiated macrophage-like cells in culture medium to investigate the effects of different treatment periods and applied voltages. Macrophage-like cells were activated and increased 10% after 48 h from the short period plasma irradiation of 30 s. The long period irradiation for 60 and 120 s decreased the cell number by almost 33%. The phagocytosis capability increased by 1.5 times during the shorter plasma irradiation period, which would be owing to the increase of active oxygen species inside the macrophage cells..
5. Norrawit Tonmitr, Akira Yonesu and Nobuya Hayashi, Effect of gas composition on surface sterilization by using LF-microwave hybrid plasma source, Japanese Journal of Applied Physics, https://doi.org/10.7567/1347-4065/ab4614, 59, SA, SAAB02-1-SAAB02-6, 2019.11.
6. Nobuya Hayashi, Yukie Miyamaru, Reona Aijima, Yoshio Yamashita, Activation of p53-Mediated Apoptosis Pathway in HSC3 Cancer Cell Irradiated by Atmospheric DBD Oxygen Plasma, IEEE Transactions on Plasma Science, 10.1109/TPS.2018.2867431, 47, 2, 1093-1099, 2019.02, Oral cancer cell HSC3 is inactivated by the direct irradiation of oxygen plasma generated by torch-type oxygen dielectric barrier discharge. Selective inactivation of the cancer cells is observed at the discharge voltage of 4.2 kV, where normal cells suffer no damages from the plasma. Inactivation mechanism of HSC3 cells irradiated by the plasma is considered as the apoptosis. Activation of mitogen-activated protein kinase and p53 proteins owing to the phosphorylation is one of the pathways to the cancer cell apoptosis..
7. Reoto Ono, Shohei Uchida, Nobuya Hayashi, Rina Kosaka and Yasutaka Soeda, Inactivation of bacteria on plant seed surface by low-pressure RF plasma using a vibrating stirring device, Vacuum, 10.1016/j.vacuum.2016.07.017, 136, 214-220, 2017.07.
8. Keisuke Mine, Yukie Miyamaru, Nobuya Hayashi, Reona Aijima, Yoshio Yamashita, Mechanism of inactivation of oral cancer cells irradiated by active oxygen species from DBD plasma, Plasma Medicine Journal, 10.1615/PlasmaMed.2017019246, 7, 201-213, 2017.07.
9. Akira Yonesu, Kazunori Koga, Masaharu Shiratani, Nobuya Hayashi, Influence of plasma irradiation on silkworm, Plasma Medicine, 7, 4, 313-320, 2017.01, Silkworms have recently been proposed as an animal model for safety testing in basic research. We propose using silkworms for in vivo trials of direct plasma treatment. In this study, the influence of plasma irradiation on silkworms was investigated using a non-thermal atmospheric pressure plasma. Silkworm survival rate decreased with increasing low-frequency voltage and plasma irradiation period. Further investigation of the plasma-generated agents (oxygen related radicals, UV light, and charged particles), revealed that the contribution of charged particles significantly increases silkworm mortality..
10. Nobuya Hayashi, Reoto Ono, Riku Nakano, Masaharu Shiratani, Kosuke Tashiro, Satoru Kuhara, Kaori Yasuda, and Hiroko Hagiwara, DNA microarray analysis of plant seeds irradiated by active oxygen species in oxygen plasma, Plasma Medicine Journal, DOI: 10.1615/PlasmaMed.2016018933, 6, 459-471, 2016.12.
11. Riku Nakano, Kosuke Tashiro, Reona Aijima, and Nobuya Hayashi, Effect of oxygen plasma irradiation on gene expression in plant seeds induced by active oxygen species, Plasma Medicine Journal, DOI: 10.1615/PlasmaMed.2016019093, 6, 303-313, 2016.10.
12. Yagyu Yoshihito, Hatayama Yuuta, Hayashi Nobuya, Mishima Tomoko, Nishioka Terumi, Sakudo Akikazu, Ihara Takeshi, Ohshima Tamiko, Kawasaki Hiroharu, Suda Yoshiaki, Direct Plasma Disinfection of Green Mold Spore on Citrus by Atmospheric Pressure Dielectric Barrier Discharge for Agricultural Applications, Trans. Mat. Res. Soc. Japan, 10.14723/tmrsj.41.127, 41, 127-130, 2016.07.
13. Tomomasa Itarashiki, Nobuya Hayashi, Akira Yonesu, Decomposition of Proteins Using a Microwave Air Plasma Sterilizer, Trans. Mat. Res. Soc. Japan, 10.14723/tmrsj.41.179, 41, 179-182, 2016.01.
14. Reoto Ono, Nobuya Hayashi, Variation of antioxidative activity and growth enhancement of Brassicaceae induced by low-pressure oxygen plasma, Japanese Journal of Applied Physics , 10.7567/JJAP.54.06GD03, 54, 6, 06GD03-1- 06GD03-4, 2015.06.
15. Hayashi Nobuya, Ono Reoto, Yonesu Akira, Antioxidative activity of plant and regulation of Brassicaceae induced by oxygen radical irradiation, Japanese Journal of Applied Physics, 10.7567/JJAP.54.06GD01, 54, 06GD01-1-06GD01-6, 2015.05.
16. Itarashiki Tomomasa, Hayashi Nobuya, Yonesu Akira, Sterilization effect of nitrogen oxide radicals generated by microwave plasma using air, VACUUM, 10.1016/j.vacuum.2014.06.018, 110, 217-220, 2014.12.
17. Kitazaki Satoshi, Tanaka Akimasa, Hayashi Nobuya, Sterilization of narrow tube inner surface using discharge plasma, ozone, and UV light irradiation, VACUUM, 10.1016/j.vacuum.2014.06.014, 110, 217-220, 2014.12.
18. Kitazaki Satoshi, Sarinont Thapanut, Kazunori Koga, Hayashi Nobuya, Masaharu Shiratani, Plasma induced long-term growth enhancement of Raphanus sativus L. using combinatorial atmospheric air dielectric barrier discharge plasmas, CURRENT APPLIED PHYSICS, 10.1016/j.cap.2013.11.056, 14, S149-S153, 2014.07.
19. Hayashi Nobuya, Yagyu, Yoshihito, Yonesu Akira, Masaharu Shiratani, Sterilization characteristics of the surfaces of agricultural products using active oxygen species generated by atmospheric plasma and UV light, JAPANESE JOURNAL OF APPLIED PHYSICS, 10.7567/JJAP.53.05FR03, 53, 5, 05FR03-1-05FR03-5, 2014.05.
20. T. Sarinont, T. Amano, Hayashi Nobuya, Kazunori Koga, Masaharu Shiratani, Growth enhancement effects of radish sprouts: atmospheric pressure plasma irradiation vs. heat shock, Journal of Physics, 10.1088/1742-6596/518/1/012017, 518, 012017-1-012017-6, 2014.03.
21. T. Sarinont, Hayashi Nobuya, Kazunori Koga, Masaharu Shiratani, Effects of Atmospheric Air Plasma Irradiation on pH of Water, Journal of Physics Society, 10.7566/JPSCP.1.015078, 1, 015078-1-015078-4, 2014.03.
22. Reoto Ono, Akimasa Tanaka, Shohei Uchida, Tomomasa Itarashiki, Hayashi Nobuya, Effect of Active Oxygen Species in Low Pressure Oxygen Plasma on Antioxidative Substances, Institute of Applied Plasma Sciences, 7, 45-46, 2014.01.
23. S. Kitazaki, Kazunori Koga, Masaharu Shiratani, Hayashi Nobuya, Growth Control of Dry Yeast Using Scalable Atmospheric Pressure Dielectric Barrier Discharge Plasma Irradiation, Jpn. J. Appl. Phys., 51, 11PJ02, 2013.01.
24. Hayashi Nobuya, Yusuke Akiyoshi, Yasuyo Kobayashi, Kohzo Kanda, Kazusato Ohshima, Masaaki Goto, Inactivation Characteristics of Bacillus Thuringiensis Spore in Liquid Using Atmospheric Torch Plasma Using Oxygen, Vacuum, 88, 173-176, 2013.01.
25. Sakudo A, Hayashi Nobuya, Shimizu N, Shintani H, Degradation of Influenza Virus Nucleoprotein by N2 Gas Plasma, MRS Proc., 1469, mrss12-1469-ww06­08, 2012.10.
26. S Kitazaki, Kazunori Koga, Masaharu Shiratani, Hayashi Nobuya, Rapid Growth of Radish Sprouts Using Low Pressure O2 Radio Frequency Plasma Irradiation, MRS Proc., mrss12­1469­ww02­08, 2012.10.
27. S Kitazaki, Kazunori Koga, Masaharu Shiratani, Hayashi Nobuya, Effects of Atmospheric Pressure Dielectric Barrier Discharge Plasma Irradiation on Yeast Growth, MRS Proc., mrss12­1469­ww0608, 2012.10.
28. Y. Akiyoshi, Hayashi Nobuya, S. Kitazaki, Kazunori Koga, Masaharu Shiratani, Influence of Atmospheric Pressure Torch Plasma Irradiation on Plant Growth, MRS Proc., 1469, mrss12-1469-ww06-10, 2012.10.
29. Satoshi Kitazaki, Kazunori Koga, Masaharu Shiratani, Hayashi Nobuya, Growth Enhancement of Radish Sprouts Induced by Low Pressure O2 RF Discharge Plasma Irradiation, Jpn. J. Appl. Phys., 10.1143/JJAP.51.01AE01, 51, 01AE01-1 - 01AE01-4, 2012.01.
30. Nobuya Hayashi, Takaomi Nakashima, Akira Yonesu, Sterilization of Medical Equipments Using Air Torch Plasma Produced by Microwave Discharge, IEEE Trans. on Plasma Science, 39, 2976-2977, 2011.12, Sterilization of non-heat-proof equipments was
performed by irradiation from air torch plasma produced by
microwave discharge. The downstream region of the torch
plasma exhibits a yellowish color. Light emission spectra and chemical indicators show that nitrogen oxide radicals are the origin of this color. Inactivation of spore-type Geobacilius stearothermophilus with the population of 105 was successful for a treatment period of 10 minutes..
31. Nobuya Hayashi, Akari Nakahigashi, Masaaki Goto, Satoshi Kitazaki, Kazunori Koga, Masaharu Shiratani, Redox Characteristics of Thiol Compounds Using Radicals Produced by Water Vapor RF Discharge, Jpn. J. Appl. Phys., 50, 08JF04-1 - 08JF04-5, 2011.08.
32. Nobuya Hayashi, Akari Nakahigashi, Hao LIU, Masaaki Goto, Treatment of second order structures of protein using oxygen RF plasma, Jpn. J. Appl. Phys., 49, 08JH02-1 - 08JH02-4, 2010.08.
33. Yoshihito Yagyu, Akira Hikida, Nobuya Hayashi, Hiroharu Kawasaki, Tamiko Ohshima and Yoshiaki Suda, Studies on Allergic Substance Elimination by RF Plasma Treatment, J. Materials Research, 35, 119-122, 2010.06.
34. Nobuya HAYASHI, Ryutaro KAWAGUCHI and Hao LIU, Treatment of Protein Using Oxygen Plasma Produced by RF Discharge, J. Plasma and Fusion Research, 8, 552-555, 2009.04.
35. Weimin GUAN, Hiroharu KAWASAKI, Tamiko OHSHIMA, Yoshihito YAGYU, Toshinobu SHIGEMATSU Yoshiaki SUDA and Nobuya HAYASHI, Influence of Calcium Hydroxide Solution in RF Plasma on Sterilization of Bacterial Spores, J. Plasma and Fusion Research, 8, 573-577, 2009.04.
36. Yoshihito YAGYU, Nobuya HAYASHI, Weimin GUAN, Hiroharu KAWASAKI, Influence of Atomic and Singlet Molecular Oxygen Generated by RF Plasma on Reduction of Protein, J. Plasma and Fusion Research, 8, 578-581, 2009.04.
37. Nobuya Hayashi and Yoshihito Yagyu, Treatment of protein using oxygen plasma produced by RF discharge, Trans. of the Material Research Society of Japan, 33, 791-794, 2008.10.
38. Satoshi Kitazaki and Nobuya Hayashi, Sterilization characteristics of tube inner surface using oxygen plasma produced by AC HV discharge, IEEE Trans. on Plasma Science, 36, 1304-1305, 2008.10.
39. Nobuya Hayashi, Shinsuke Tsutsui, Tetsushi Tomari, Weimin Guan, Sterilization of Medical Equipments Using Oxygen Radicals Produced by Water Vapor RF Plasma, IEEE Trans. on Plasma Science, 36, 1302-1303, 2008.10.
40. Nobuya Hayashi, Shohei Sougumo, Suppression of by-product generation in the treatment of aromatic perfumery substances using a surface discharge, Vacuum, 83, 138-141, 2008.09.
41. Y. Yagyu, N. Hayashi, H. Kawasaki, T. Ohshima, Y. Suda and S. Baba, Fundamental Studies on Effect of Ozone Injection to the Internal-Combustion Engine – FTIR spectrum of Hydrocarbon Compound Reformulated by Ozone –, Journal of Physics: Conf. Ser., 100, 1-4, 2008.04.
42. Nobuya Hayashi, Weimin Guan, Shinsuke Tsutsui, Tetsushi Tomari, Yasushi Hanada, Sterilization characteristics for medical equipments using radicals produced by oxygen/water vapor RF plasma, Jpn. J. Appl. Phys., 45, 8358-8363, 2006.12.
43. Nobuya Hayashi, Tsutomu Yamakawa, Seiji Baba, Effect of additive gases on synthesis of organic compounds from carbon dioxide using non-thermal plasma produced by atmospheric surface discharges, Vacuum, 80, 1299-1304, 2006.06.
44. S. K. Hong, N. Hayashi, S. Ihara, S. Satoh, Formation properties of the main-discharge in pure Ar gas using the automatically pre-ionized plasma electrode, IEEE Trans. on Plasma Science, 33, 324-325, 2005.08.
45. Nobuya Hayashi, Saburoh Satoh, Treatment of Perfluorocarbon Using Nonthermal Plasma Produced by Atmospheric Streamer Corona Discharge, IEEE Trans. on Plasma Science, 33, 274-275, 2005.08.
46. Fumiaki Takeshita, Tomoaki Miichi, Nobuya Hayashi, Water treatment using discharge on the surface of a bubble in water, Plasma Processes and Polymers, 2, 246-251, 2005.04.
47. S. K. Hong, N. Hayashi, S. Ihara, S. Satoh, Main-discharge formation and light emission in pure Ar gas at multi-atmospheric pressure using the automatically pre-ionized plasma electrode, Vacuum, 79, 25-36, 2005.01.
48. M. Yamaura, N. Hayashi, S. Ihara, S. Satoh, Lifetime evaluation of weakly ionized plasma channel by accumulation effect of charged particles by means of laser absorption, J. Appl. Phys., 95, 6007-6010, 2004.12.
49. Mitsuaki Shimosaki, Nobuya Hayashi, Satoshi Ihara, Saburoh Satoh, Effect of trigger electrode configuration of a double discharge ozonizer on ozone generation characteristics, Vacuum, 73, 573-578, 2004.09.
50. Shunichi Kaneda, Nobuya Hayashi, Satoshi Ihara, Saburoh Satoh, Application of dielectric material to double-discharge-type ozonizer, Vacuum, 73, 567-571, 2004.09.
51. Joanna Pawlat, Nobuya Hayashi, Satoshi Ihara, Foaming Column with a Dielectric Covered Plate-to-Metal Plate Electrode as an Oxidants Generator, Advances in Environmental Research, 8, 351-358, 2004.06.
52. Hee-Sung Ahn, Nobuya Hayashi, Satoshi Ihara, Ozone Generation Characteristics by Superimposed Discharge in Oxygen- Fed Ozonizer, Jpn. J. Appl. Phys., 42, 6578-6583, 2003.11.
53. Joanna Pawlat, Nobuya Hayashi, Satoshi Ihara and Iwo Pollo, Studies on Oxidants, Generation in a Foaming Column with a Needle to Dielectric Covered Plate Electrode, 23, 569-583, 2003.09.
54. Joanna Pawlat, Nobuya Hayashi, Satoshi Ihara, Generation of Discharge in Dynamic Foam for Oxidants Formation Using Various Type of Electrode, Colloids and Surfaces A: Physicochem. Eng. Aspects, 220, 1-12, 2003.06.
55. Joanna Pawlat, Nobuya Hayashi, Satoshi Ihara, Studies on Oxidants’ Generation in a Forming Column with a Needle to Dielectric Cover Plate Electrode, Plasma Chemistry and Plasma Processing, 3, 567-581, 2003.05.
56. Michiteru Yamaura, Nobuya Hayashi, Satoshi Ihara, Saburoh Satoh, Evaluation of Weakly Ionized Plasma Channel by Accumulation Effect of Charged Particles Using High-Repettion-Rate KrF Excimer Laser, Jpn. J. Appl. Phys., 41, 6394-6397, 2002.11.
57. N. Hayashi, K. Yamamoto, S. Ihara, S. Satoh and C. Yamabe, Treatment of Fluorocarbon Using Nonthermal Plasma Produced by Atmospheric Discharge, Jpn. J. Appl. Phys., 41, 5399-5403, 2002.08.
58. Tomoaki Miichi, Nobuya Hayashi, Satoshi Ihara, Saburoh Satoh and Chobei Yamabe, Generation of Radicals using Discharge inside Bubbles in Water for Water Treatment, Ozone Science and Engineering, 24, 471-477, 2002.06.
59. Penghui Guan, Nobuya Hayashi, Saburoh Satoh, NOx Treatment by DC Streamer Corona Discharge with Series Gap, Vacuum, 65, 469-474, 2002.05.
60. Joanna Pawlat, Nobuya Hayashi, Chobei Yamabe and Iwo Pollo, Generation of oxidants with a foaming system and it’s electrical properties, Ozone Science and Engineering, 24, 181-191, 2002.03.
61. Karol Hensel, Nobuya Hayashi, Chobei Yamabe and Marcela Morvová, Positive DC Corona Discharge in N2–NO–CO2–O2 Mixtures, Jpn. J. Appl. Phys., 41, 336-345, 2002.01.
62. Saburoh Satoh, Nobuya Hayashi, Satoshi Ihara, Chobei Yamabe and Takio Tomimasu, Outlines of Saga FEL project, Jpn. J. Appl. Phys., 41, 41-43, 2002.01.
63. Joanna Pawlat, Nobuya Hayashi, Chobei Yamabe, Studies on Electrical Discharge Effects in a Foaming Environment, Jpn. J. Appl. Phys., 40, 12, 7061-7066, 2001.12.
64. Nobuya Hayashi, Hideo Suganuma, Masaki Kamatani, Saburoh Satoh, Treatment of Volaile Organic Compound by Positive Streamer Corona using a Series Gap, Jpn. J. Appl. Phys., 40, 10, 6104-6108, 2001.10.
65. N. Hayashi, Observation of Submicron Dust Particles Trapped in a Diffused Region of a Low Pressure Radio Frequency Plasma, Physics of Plasmas, 8, 6, 3051-3057, 2001.06, Submicron dust particles (Cu, ϕ 50 nm) were observed to be trapped in an rf plasma at relatively low pressure. The laser light scattering by particles shows the time evolution of the dust particles for several hours after pulsed injection of the particles. The dust particles were localized in the diffused region as a large volume cloud. The suspension mechanism of the dust particles in the diffused plasma was explained by an electrostatic force due to the potential structure. The spatial distribution of the charge of the dust particles was determined by this potential structure. The dispersion relations of the self-excited dust acoustic waves were adopted to confirm the spatial distribution and the time evolution of the charge of the dust particles. .
66. N. Hayashi, T. Nakashima and H. Fujita, Reduction of Electron Temperature in rf Plasma Using Magnetic Filter, Jpn. J. Appl. Phys., 38, 4301-4304, 1999.07.
67. K. Taniguchi, H. Kuwae, N. Hayashi, Y. Kawai, Observation of type-1 intermittency caused by current-driven ion acoustic instability, Physics of Plasmas, 10.1063/1.872724, 5, 2, 401-405, 1998.05, Intermittent chaotic phenomena caused by the current-driven ion acoustic instability are experimentally observed using a Double Plasma device, in which two mesh grids are installed to excite the instability. When a dc potential is applied to one of the two mesh grids and exceeds a certain threshold, the system suddenly transits from a periodic state to a chaotic state. At the same time, the signals picked up as perturbation components of a current exhibit intermittent turbulent bursts. The calculations of the correlation dimension and the Lyapunov exponent indicate that the system reaches a chaotic state. Furthermore, it is found that the results of mathematical and statistical analysis of observed signals agree with the theoretical properties of the type-1 intermittency: the occurrence of 1/f-type low-frequency noise and the probability distribution of the duration between two bursts. Therefore, it is concluded that the present system reaches a chaotic state via the type-1 intermittency. .
68. N. Hayashi and Y. Kawai, Observation of bifurcation phenomena in an electron beam plasma system, Physics of Plasmas, 10.1063/1.872062, 3, 12, 4440-4445, 1996.12, Bifurcation phenomena are experimentally observed in an electron beam plasma system using a double plasma device. When an electron beam is injected into the target plasma, an unstable wave and the subharmonics of period 2, period 3, and period 4 are observed. The fundamental unstable wave is specified to be a beam mode wave excited by an electron beam plasma instability. It is confirmed that these bifurcation phenomena originate from nonlinearity of the unstable wave. The correlation dimensions and Lyapunov exponents indicate that the system becomes chaotic when the subharmonics of period 3 or period 4 appear. .
69. N. Hayashi, M. Tanaka, S. Shinohara, and Y. Kawai, Excitation mechanism of standing waves produced by electron beam plasma instability, Physics of Plasmas, 10.1063/1.871057, 2, 10, 3582-3587, 1995.10, The excitation mechanism of standing waves produced by the electron beam plasma instability is experimentally studied using a Double Plasma device. When an electron beam is injected into the target plasma, standing waves around the electron plasma frequency are excited. A test wave is propagated in an electron beam plasma system and is identified as the beam mode from the dispersion relation. The propagation direction of the beam mode is determined from the wave pattern utilizing a phase shifter. It is found that a reflected beam mode exists as well as a forward beam mode, and is generated by the reflection of the forward beam mode from a potential well produced by the injection of the electron beam. The observed standing waves are formed by superposing the beam modes propagating in opposite directions from each other. .