22P064-P
UV Emitter by Using a Molecular Gas Discharge/Plasma Confined in Multi-Pole
Magnetic Fields and Its Applications
分子性ガス多極磁場中多相交流放電プラズマを用いた新規紫外線源の開発とその応用
Kazunori Matsumoto, Seiji Oda, Hidefumi Uchiyama*1, Hirofumi Ninomiya*2, Jyunji Saito*1, Nobuyuki Nojima*1

松本和憲，織田誠二，内山英史*1，二宮弘文*2，斉藤潤二*1，能島信行*1
Department of Intelligent Systems Design Engineering, Toyama Prefectural University,
5180 Imizu-city, Toyama 939-0398, Japan
富山県立大学工学部知能デザイン工学科，〒939-0398 富山県射水市黒河5180*1Tateyama Machine Co., LTD., 30 Shimoban, Toyama, Japan2

立山マシン㈱，〒930-1305 富山市下番30* MRC Polysaccharide Co., LTD., 3 Kaigan-tori, Toyama, Japan
MRCポリサッカライド㈱，〒931-8601 富山市海岸通3番地
We have investigated and developed a ultra-violet (UV) emitter by using nitric oxide gas mixed with nitrogen molecular one, where gases are excited by a poly-phase ac discharge/plasma confined into
multi-pole magnetic fields. An intense UV irradiation ranging from 200nm to 300nm was emitted, which issuitable for sterilization. We have applied this UV emitter to sterilizing powdered polysaccharides. Sterilization equipment has designed and manufactured, where powders are carried by an air flow and irradiatedby the UV emitter. A conventional low-pressure mercury UV lamp was employed as a reference.

1. Introduction
As environmental issues have become serious, theneed for mercury-free lamp has become an important subject. Molecular radiators are one of the candidates for mercury-free lamps [1,2]. An UV-emitterby using nitric oxide molecular gas NO mixed withnitrogen molecular one N2 has been proposed by us,
where plasma is produced by a poly-phase ac discharge and it is confined by an advanced multi-polemagnetic field [3].
The propose of present study is to develop a UV
lamp by using NO/N2 molecular gas and to apply
the lamp for sterilizing foods, medicines and perfumes, especially powdered ones extracted fromnatural materials. It is not suitable to sterilize theseby conventional high temperature wet steam or a
toxic gas [4] such like an ethylene oxide gas. Because, powders become firm or include residues.
Sterilization by irradiation from radioactive elements [4] is also one of promising candidates. But
its use is prohibited legally in Japan.
2. A model of UV lamp and its features
Figure 1 shows a model of our UV emitter driven
by a poly-phase ac discharge/plasma, where thecross section is drawn schematically. Discharges/
plasmas are produced among divided electrodes
whose surfaces are covered with a dielectric, which
are confined by multi-pole magnetic fields generated
by permanent magnets. Intense light emissions areirradiated from excited gases in confined regions.
This UV lamp is expected to have the following

Fig. 1 Cross section of UV emission device, where asymmetric poly-phase ac power source is connected todivided electrodes.
Table Comparison with conventional UV lamps fromthe view point of industrial usefulness

characteristics: (a) high Intensity & efficient emission by magnetic confinement, (b) uniform emission
from divided electrodes with flexible shape, (c)emission with no temperature dependence, (d) filament-less & rapid emission, (e) no electrical noiseby canceling out symmetrical poly-phase ac discharges.
A comparison between our UV lamp and conventional ones is summarized in a table, where shapeflexibility, operating temperature and eco-friendlyIntensity (arb. unit)

Sterilizing Efficiency Curve

1NO(10%)+N2(90%)

0Wavelength [nm]Fig. 2 Spectra observed in NO/N2 mixture gas excited
twelve-phase ac discharge/plasma; blue solid curveshows sterilizing efficiency versus wavelength.

Optical Reflectivity [%]100(a)

80

Polysaccharide of the kind A
Ploysaccharide of the kind B
Polysaccharide of the kind C
Polysaccharide of the kind D
Polysaccharide of the kind E604020030
Optical Transmissivity [%]3. Results and discussions
Figure 2 shows a typical spectrum emitted from aNO/N2 mixture gas-plasma, where a normalized
curve of sterilizing efficiency versus wavelength isinserted. The ratio of NO to N2 is 10% to 90%, thetotal gas pressure is 0.3 Torr and a twelve-phase ac
power source is supplied. An intense UV spectrum
from 180nm to 300nm is emitted from NO molecule,
excited by discharge/plasma. Each line emitted fromNO is identifiedγspectrum [5,6].
We have applied this NO/N2 UV emitter to sterilize several kinds of polysaccharide-powder, whose
optical reflectivity and transmissivity are shown inFig. 3(a) and 3(b), respectively. Here, a spectrophotometer with an integrating sphere is used and optical length is 1mm and powder density is ~0.5g/cm3.
Experimental results indicate that UV components
with wavelength less than 300nm have small reflectivity and transmissivity. It is found that UV components successfully penetrate into powers at thesurface and dissipate their energy due to scattering
among powers. Then, bacteria adhering to powders
can be sterilized effectively by UV irradiation.
Figure 4 shows a photograph of sterilizationequipment originally designed and manufactured,
where powders are carried by an air flow through aquart tube installed along the central axis. Andpowders are irradiated from the circumference,
where poly-phase NO/N2 ac discharges are generated. The equipment is ~1500mm in length and~100mm in inner diameter. The wall is cooled bywater. The quartz tube is ~50mm in inner diameter.
Photograph of visible light emission from theabove UV device is shown in Fig. 5, where electrodeis divided into 12 pieces and twelve-phase ac powersource is supplied. Pressure of NO/N2 gas is 0.3Torr
and ac discharge power is ~100W. The radiant flux
density is ~ 1mW/cm2.

Sterilizing Efficiency

Japanese, Tokyo Denki University press, 1982, Tokyo.
[6] H. Okabe, “Photochemistry of small molecules”, A
Wiley-Interscience publication, 1978, New York.

aspect are superior points of our lamp.

200300400500(b)600700

Polysaccharide of the kind B
Polysaccharide of the kind A
Polysaccharide of the kind C
Polysaccharide of the kind E
Polysaccharide of the kind D20100200300

400500600700Wavelength [nm]Fig. 3 Optical characteristics of five kinds of polysaccharide powder whose average sizes are ~80μm. Reflectivity is for (a) and transmissivity for (b), where
optical length is 1mm, power density is ~0.5g/cm3.

This research is granted aid from Japan Scienceand Technology of Agency.
References[1] D. Uhrlandt, R. Bussiahn, S. Gortchakov, H. Lange
and D. Loffhagen, Proceedings of the 10th International Symposium on the Science and Technology ofLight Sources, Toulouse, 15(2004).
[2] M. Jinno, S. Takubo, Y. Hazata, S. Kitsinelis and H.
Motomura, J. Physics D 38, 3312 (2005).
[3] K. Matsumoto, Plasma Sources Science and Technology 5, 245 (1996).
[4] H. Kobayashi, “Infection Control “, Health Publisher,
Tokyo, 2000.
[5] J. S. Chang, R.M. Hobson, S. Itikawa and T. Kaneda,“Atomic and molecular processes of ionized gases”, in800

Fig. 4 Photograph of sterilization equipment originallydesigned and manufactured, where powders are carriedby an air flow through a quart tube and irradiated fromthe circumference.

Fig. 5 Photograph of visible lightemission from the above UV device,where electrode is divided into 12
pieces and twelve-phase ac powersource is supplied. Pressure ofNO/N2 gas is 0.3Torr and ac discharge power is ~100W.

800