Characteristics of atmospheric pressure
microplasma light emission
Marius Blajan and Kazuo Shimizu
Organization for Innovation and Social Collaboration, Shizuoka University,
3-5-1 Jyouhoku, Hamamatsu, 432-8561, JAPAN; E-mail：blajanmarius@yahoo.com
Introduction

Stark Broadening

Microplasma
canbefoundin
manyapplications. In the last years, the technology
was used in applications such as NOx removal,
surfacetreatmentandsterilization
orinactivation of bacteria [1],[2]. In order tofurthermore improve the technology thefundamental phenomena should be analyzed.
Emission spectroscopy, imaging and Stark
broadening techniques were used to clarify
the characteristics of microplasma. Due to thesmall discharge gaps our microplasma could
be analyzed only using these non invasivemethods.

A pseudo Voigt function was used todetermine Lorentzian FWHM of the Ar I peakat 696.5 nm.
LW2V( )  V0  S(mu
22 4(   0 )  L W

Experimental Setup(1)Microplasma Electrodes
The electrodes consist in perforated metallic
plates covered with a dielectric layer.

(1  mu )Discharge voltage andcorresponding discharge current

4 ln 24 ln 2exp( 2 (   0 )2 )
G W
GW

Gw is Gaussian FWHM, Lw is Lorentzian
FWHM, λ is the wavelength, λ0 is the centroidwavelength. Calculated Lw=0.0042564 nm
and considering van der Waals broadening
Ww=0.003
nm→Starkwidth
Sw=0.0012564 nm.

1) Streamer reaches cathode up to 1 ns

0 ns

1 ns

2 ns

S W  2(1  1.75* 104 * 4 Ne *  *(1  0.0068* 6 Ne1)) * 1016 * w * Ne
TeFor electron temperature Te=10000
electron density Ne=1.338*1015 /cm3 [2].

→AnodeCathode100 µm2) Cathode layer formation up to 30 ns3) Cathode layer enhancement up to 70 ns

10 ns

30 ns

60 ns

Fig. 1 Microplasma electrodes.
Electrode size was 20 mm versus 40 mm foremission spectroscopy analysis. Discharge gap
was set at 100 μm in this study.
A Marx Generator with MOSFET switches aspulse power supply:•Output Voltage: -2 kV negative•Rise time: 40 ns•Pulse width: 1 µs(2) Experimental setup
Emission spectrum was measured by aspectrometer, and an ICCD camera. Photos ofmicrodischarges
weretakenusingamicroscope and a digital camera.
Gas flow rate: Ar and N2/Ar at 10 L/min.

Fig. 2 An experimental setup.

Fig. 5 Measured and fitted spectra of Ar I peak at
696.5 nm .
Spatial and temporal distribution of Ar I peakat 696.5 nm and N2 SPS peak at 337.1 nm
shows higher intensity towards anode up to20 ns and after that shifted to cathode.

CathodeFig. 6 Spatial and temporal evolution of therelative intensity of Ar I peak at 696.5 nm
for microplasma discharge in Ar at 1 kV。
AnodeMeasured area

Fig. 3 Measured area of emission spectra.
(3) Microdischarges

Diameter
Ø~10 µm

Grounded Positive Faraday dark
spaceelectrode column
Fig. 4 Images of microdischarges phenomena.

270 nsFig. 8 Spatial and temporal evolution ofmicroplasma discharge in 3% N2 in Ar at 1 kV .
ICCD camera shutter was opened for 2 ns.

Conclusions•Stark broadening was used for calculating
electron density and estimated to be
Ne=1.338*1015 /cm3.

•ICCD camera images showed the evolutionof microdischarges from the phase whenstreamer reaches anode to cathode layer
formation, cathode layer enhancement andfinally cathode layer decay.

Very small discharge gaps and relatively low
discharge voltages (about 1 kV). A highintensity electric field (107-108 V/m) assures
the formation of microplasma.

60 µm

100 ns•Spatial and temporal evolution of therelative intensities of ArI peak at 696.5 nm
and N2 SPS peak at 337.1 nm showed higher
intensity towards anode up to 20 ns andafter it shifted towards cathode.

Gas flow

Negative
electrode Negative glow
(high voltage)4) Cathode layer decay up to 270 ns

70 ns

CathodeLeftelectrodeactiveAnode

Acknowledgment
Fig. 7 Spatial and temporal evolution of the relative
intensity of N2 SPS peak at 337.1 nm for
microplasma discharge in 1% N2 in Ar at 1 kV。

Spatial and Temporal Evolution ofMicroplasma
The observation of microdischarge by fast
ICCD camera shows the streamer formationand the correlation of the microdischarge
evolution with the discharge current.

The authors would like to thank Prof. M.
Nagatsu from Shizuoka University for thefruitful discussions.

References[1] K. Shimizu, M. Yamada, M. Kanamori,and M. Blajan, IEEE Trans. Ind. Appl. 46,
641 (2010).
[2] M. Blajan, A. Umeda, S. Muramatsu,and K. Shimizu, IEEE Trans. Ind. Appl. 47,
1100 (2011).