Diagnostics of Pulsed Powered Microplasma Discharge in N 2by Emission Spectroscopy
Marius Blajan, and Kazuo Shimizu
Innovation and Joint Research Center, Shizuoka University,
3-5-1 Jyouhoku, Hamamatsu, 432-8561, JAPAN; E-mail：blajanmarius@yahoo.com

Introduction

Intensity of the N2 SPS peaks at 367.2 nm,
371.1 nm, 375.5 nm and 380.5 nm were used
to calculate vibrational temperature:
Tv = 3400 KTheratiooftheintensity
peaks
corresponding to N2+ FNS at 391.4 nm and N2SPS at
394.3 nm was used to calculate
electron temperature. Thus at -1.5 kV:
Te = 3.1 eV

Microplasma
canbefoundinmany
applications. In the last years, the technology
was used in applications such as NOx removal,
surfacetreatment
andsterilizationorinactivationofbacteria.
Emission
spectroscopy is one of the methods to analyze
plasma process .
Microplasmaisatmosphericpressure
nonthermalplasma.
The
microplasma
processes in nitrogen were analyzed using
emission spectroscopy method since nitrogengas is a component in environmental
applications.

Experimental Setup

N2 SPS
Experimental setup
Gas flow rate: N2 at 2.5 L/min.

(4) Electrical Characteristics(1)Microplasma Electrodes
The electrodes consist in perforated metallic
plates covered with a dielectric layer.

N2+ FNS

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

N2 SPS

Emission spectrum in UV region.
N2 second positive band system 337.1 nm:
Excitation of nitrogen molecules in theground state by direct electron impact:
e + N2(X1Σg+)v=0 → N2(C3πu)v’=0 + e(ΔE=11eV)
Spontaneous radiation of formed excitedstate of nitrogen:N2(C3πu)v’=0 → N2(B3πg)v’’=0 + hν(τoC=40ns)

Microplasma electrodes

Waveforms of the discharge voltage, corresponding
discharge current and gate signal for ICCD camera.

Electrode size was 20 mm versus 40 mm.
Discharge gap was set at 50 μm in this study.
Emission spectra of microplasma discharge
was observed from the side part of electrodes.

Emission Spectroscopy(2) Marx Generator
Capacitors are charged in parallel connection
at voltage V.
⇨ When the MOSFET are turned on thecapacitors are discharge in series connection
with an output voltage V multiplied with thenumber of capacitors.

Emission spectrum of microplasma discharge
in pure N2 shown N2 second positive system,
N2 first positive band peaks and N2+ firstnegative system band peaks.
Camera shutter was open for 1 µs.

N2 SPS
Waveform of the discharge voltage, discharge
current and emission signal of microplasma
discharge (337.1 nm) in N2.
Lifetime emission signal of N2 SPS peak at
337.1 nm was 60 ns.
LIFBASEsoftware
wasusedforthecalculation of the rotational temperature.

(a)Tgas = Trot = 400 K⇨Microplasma=Nonthermal plasma

N2 FPS+VSimulated(b)Experimental

TriggerVout

380.5 nm

Negative pulse Marx Generator (a) circuit of MarxGenerator, (b) photo of Marx Generator.
Marx Generator with MOSFET switches:•Negative pulses•2 stages•Charge voltage up to 1 kV
 Output Voltage: -2 kV•Rise time: 80 ns•Pulse width: 1 µs
•Frequency: 1-24 kHz(3) Experimental setup
Emission spectrum was measured by aspectrometer, an ICCD camera and aphotomultiplier tube. The ICCD camera wastriggered by a pulse generator.
Spectrometer was set at narrow and widegratings.

0-2375.5 nm
1-3367.2 nm

371.1 nm

3-5

2-4Experimental
andsimulated
spectrumcorresponding to N2+ first negative system peakof 391.4 nm emitted by microplasma discharge in
N2.

Conclusions
Emission spectrum of N2 at -1.5 kVEmission spectrum in N2 shows:•N2 second positive band system peaks at
315 nm, 337.1 nm, 357.7 nm, 380.4 nm, 400nm and 405 nm.
•N2 first positive band system peaks at 632.2
nm, 670.5 nm, 676.4 nm, 678.6 nm, 705.9
nm, 716.5 nm and 762.7 nm.
•N2+ first negative band system peak at391.4 nm.

•Emission spectrum of microplasma in N2
shown intensity peaks of N2 SPS, N2 FPS andN2+ FNS.
•Lifetime emission signal peak of the 337.1
nm N2 SPS peak for microplasma in N2 wasafter 60 ns.
•Temperature
calculation
showedmicroplasma is nonthermal plasma: Te>Tvib>Trotthat