04aE21P
窒素・酸素混合ガス表面波プラズマによる芽胞菌不活化における励起原子種の効果

Effect of Reactive Atomic Species in N2/O2 Surface-wave Plasma on Inactivationof Spore-forming Microorganisms
楊 小麗1，昌 錫江1，鄭 霊棟2, 佐々木 浩一3, 永津 雅章1,2
Xiaoli Yang1, Xijiang Chang1, Reitou Tei 2, Koichi Sasaki3, and Masaaki Nagatsu1,2
1

静大創造科技院，〒432-8011 浜松市中区城北3-5-1
2
静大院工，〒432-8011 浜松市中区城北3-5-1
3北大院工,〒060-8628, 北海道札幌市北区北13条西8丁目,
1
Graduate School of Science and Technology, Shizuoka University
2
Graduate School of Engineering, Shizuoka University
3
Graduate School of Engineering, Hokkaido University
1. Introduction
With the advantages of low-temperature,
non-toxic, and shorter time treatment, plasma
sterilization attracted much attention fromresearchers. To figure out the plasma inactivation
mechanism of spore-forming microorganisms isimportant to improve the sterilization property. But
so far, the mechanism of low temperature plasma
sterilization is still not fully understood. In ourprevious work, N2 and O2 gas mixture surface-wave
plasma (SWP) generated in a 30 cm diameter SUS
cylindrical chamber was used for thelow-temperature plasma sterilization of medicalinstrument. Different possible factors such as
oxygen etching, UV radiation and ion bombardment
were studied to figure of the sterilization
mechanisms. To a further study on the sterilization,
the information of neutral species generated byplasma discharge is inevitably important.
Spectroscopy measurement does little influence
to the processing plasma. Among different
spectroscopy diagnosis methods, only the resonant
absorption spectroscopy can directly determine theabsolute density of reactive species. In this study,
surface-wave plasma produced with N2/O2 mixturegas was used for investigating the mechanism of theinactivation of Geobacillus stearothermophilus
spores. The effect of N atomic species in N2/O2
surface-wave
plasmaoninactivationofspore-forming microorganisms was investigated byusing VUV absorption spectroscopy technique witha compact coaxial microwave plasma light source.
The transition lines used for N atom density
measurements were 2p23s 4P5/2–2p3 4S°3/2 at 119.995
nm, 2p23s 4P3/2–2p3 4S°3/2 at 120.022 nm and 2p23s4P1/2–2p3 4S°3/2 at 120.071 nm of N atom. First weneed to find the best operation of the light source,
such as finding the optical emitting intensity withdifferent mixing ratio of N2 and Ar, reducing theself-absorption of the N2 microwave plasma
discharge in the light source. Then thismeasurement system will be used to diagnosis theN atom density under different plasma sterilization
conditions to figure out the role of the N atom
density during the inactivation of spore-forming
microorganisms.
2. Experimental
The experimental setup consists of a stainlesssteel cylindrical vacuum chamber (300 mm indiameter and 300 mm in height) with a microwave
launcher and 2.45 GHz microwave generator, as
shown in Figure1. The light source was installed on
one side (10 cm away from the top) of the chamber
and the VUV monochromator (Acton ResearchCorp., VM–502) was fixed at the opposite port.
Two MgF2 glass windows were inserted to separate
it into three different pressure areas. Inside thechamber, the absorption length L is constricted toabout 30 cm. The pressures both in themonochromator and processing chamber could bekept on 10-5 Torr by separated two-stage differential
pumping systems.

Fig. 1. Schematic drawing of the experiment set-up.