Diagnostics of a plasma jet using optical emission …...Diagnostics of a plasma jet using optical...
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0.25 0.20 0.15 0.10 0.05 0.00 intensity [a.u.] 312 311 310 309 308 307 wavelength [nm] measured simulated 280 K 380 K 480 K Diagnostics of a plasma jet using optical emission spectroscopy Hayato Kawanami 1 , Kohki Satoh 1,2 and Hidenori Itoh 1 1 Division of Information and Electronic Engineering, Graduate School of Engineering, Muroran Institute of Technology, Muroran, 050-8585, Japan 2 Center of Environmental Science and Disaster Mitigation for Advanced Research, Muroran Institute of Technology, Muroran, 050-8585, Japan Email : [email protected] 1. Introduction 2. Experimental apparatus and conditions 3. Derivation method of rotational temperature To diagnose with a plasma jet by optical emission spectroscopy (1) Gas temperature of plasma jet Objective In this work, the emission spectra of OH are measured and the gas temperatures of the plasma jet are deduced. The emission spectra of OH from H 2 O contained in Ar or in air in the vicinity of the plasma jet are measured. The maximum gas temperature is 380 K at 1.0 mm away from the exit of the reactor, and the gas temperature tends to fall with the increase of the distance from the reactor exit. We generated an atmospheric-pressure argon plasma jet and measured the emission spectra of OH (A 2 S + → X 2 P) [2] , and then deduced the gas temperature of the plasma jet. Dielectric barrier discharge (DBD) DBD is well known as a stably generated discharge at atmospheric pressure. This dose not require vacuum system, allowing simple structure of discharge equipment. DBD has attracted attention and used for gas reforming and sterilization [1] . However, the discharge area of DBD is limited between electrodes. Recently, plasma jet, a kind of DBD has attracted as a novel plasma source. Plasma is generated by applying AC voltage to a glass tube with a rare gas flowing in the tube. Generated plasma is pushed out of the tube by the rare gas. The plasma reaches to solid and liquid easily; therefore, the plasma jet is used for sterilization, stimulation of germination, etc. To control the plasma jet properly , and studying the plasma characteristics is important. Discharge reactor • Glass tube :A T-shaped glass tube of 3 mm in inner diameter and 90 mm length. • High voltage electrode: A copper tube of 2 mm in inner diameter and 3 mm in outer diameter is inserted into an inlet of the T-shaped glass tube. • Earth electrode : An aluminium sheet is bound round the outside of the T-shaped glass tube. • The gap length between copper tube and aluminium electrode is 10 mm. Applied voltage • AC voltage 12 kV p-p at a frequency of 17 kHz. Gas conditions • An argon gas, the purity of which is 99.99 % is fed into the glass tube through the copper tube at constant flow rate of 10 L/min. Measurement of optical emission spectra • Optical emission intensity of the plasma jet is measured using monochromator (JASCO, CT-25CS, 0.16 nm resolution). • The monochromator is placed normal to the direction of gas flow to measure the spatial distribution of the emission intensity. • The distance between the plasma jet and the entrance slit of the monochromator is fixed at 10 mm. copper tube aluminium sheet 10 mm The shape of rotational spectra is partially affected by temperature. The shape of rotational spectra changes with temperature. It is possible to deduce gas temperature by the shape of rotational spectra. In this work, the shape of measured spectra of OH is compared with theoretical spectra considering temperature, calculated by LIFBASE [3] with different gas temperature. The rotational temperatures of plasma jet are deduced by the correspondence between measured and theoretical spectra. [1] Nagatsu: J. Plasma Fusion Res. Vol.83, No.7, pp.601 - 606 (2007 ) [2] J. Luque and D. R. Crosley , "LIFBASE (version 1.5)", SRI International Report MP 99 - 009 (1999) [3] R. W. B. Pearse and A. G. Gaydon: “The identification of molecular spectra”, Chapman and hall (1976) 4. Results and discussion 5. Conclusions The theoretical rotational spectra are calculated by equation (1). = 0 ∙ 2+1 ∙ − rot ∙ rot In the case of OH : Z elec = 4, Z rot = rot ℎ 0 = 0 ∙ 2+1 ∙ − () rot 4∙ rot ℎ 0 (1) k B : Boltzmann Constant, h : Planks Constant, c : Speed of Light, B 0 : OH Spec. Constant It is found that the shape of rotational spectra is determined by the rotational temperature. (2) Variation of the gas temperature with different distance from the exit of the reactor 0 mm 1 mm 2 mm 0.30 0.25 0.20 0.15 0.10 0.05 0.00 intensity [a.u.] 310.0 307.5 wavelength [nm] measured simulated 360 K 0.25 0.20 0.15 0.10 0.05 0.00 intensity [a.u.] 310.0 307.5 wavelength [nm] measured simulated 380 K 0.20 0.15 0.10 0.05 0.00 intensity [a.u.] 310.0 307.5 wavelength [nm] measured simulated 360 K 0.20 0.15 0.10 0.05 0.00 intensity [a.u.] 310.0 307.5 wavelength [nm] measured simulated 340 K 0.15 0.10 0.05 0.00 intensity [a.u.] 310.0 307.5 wavelength [nm] measured simulated 330 K 0.16 0.12 0.08 0.04 0.00 intensity [a.u.] 310.0 307.5 wavelength [nm] measured simulated 310 K 3 mm 4 mm 5 mm The band head of OH is 309 nm, and rotational spectra lie at 306.8 – 308.8 and 309.5 – 311.5 nm. The emission spectra of OH are due to H 2 O contained in Ar or in air in the vicinity of the plasma jet. The theoretical rotational spectra at 380 K agree well with the measured rotational spectra, therefore; the gas temperature of the plasma jet is determined to be 380 K. 120 100 80 60 40 20 0 intensity [a.u.] 312 311 310 309 308 307 wavelength [nm] simulated 280 K 380 K 480 K OH (rotational) OH (rotational) OH ( A 2 S + → X 2 P, 309 nm ) The maximum gas temperature is 380 K at 1.0 mm away from the exit of the plasma jet reactor. The gas temperature tends to fall above 1.0 mm away from the exit of the reactor. Background OH (rotational) OH (rotational) OH (A 2 S + → X 2 P, 309 nm) 380 360 340 320 300 gas temperature [K] 5.0 4.0 3.0 2.0 1.0 0.0 distance [mm] The exit of the reactor 1 2 3 4 0 5 mm
Transcript of Diagnostics of a plasma jet using optical emission …...Diagnostics of a plasma jet using optical...
0.25
0.20
0.15
0.10
0.05
0.00
inte
nsi
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a.u
.]
312311310309308307wavelength [nm]
measuredsimulated 280 K 380 K 480 K
Diagnostics of a plasma jet using optical emission spectroscopy
Hayato Kawanami1, Kohki Satoh1,2 and Hidenori Itoh1
1Division of Information and Electronic Engineering, Graduate School of Engineering, Muroran Institute of Technology, Muroran, 050-8585, Japan2Center of Environmental Science and Disaster Mitigation for Advanced Research, Muroran Institute of Technology, Muroran, 050-8585, Japan
Email : [email protected]
1. Introduction 2. Experimental apparatus and conditions
3. Derivation method of rotational temperature
To diagnose with a plasma jet by optical emission spectroscopy
(1) Gas temperature of plasma jet
Objective
In this work, the emission spectra of OH are measured and the gas temperatures of the plasma jet are deduced.
The emission spectra of OH from H2O contained in Ar or in air in the vicinity of the plasma jet are measured.
The maximum gas temperature is 380 K at 1.0 mm away from the exit of the reactor, and the gas temperature tends to fall with the increase of the distance from the reactor exit.
We generated an atmospheric-pressure argon plasma jet and measured the emission
spectra of OH (A2S+ → X2P)[2], and then deduced the gas temperature of the plasma jet.
Dielectric barrier discharge (DBD)
DBD is well known as a stably generated discharge at atmospheric pressure.
This dose not require vacuum system, allowing simple structure of discharge equipment.
DBD has attracted attention and used for gas reforming and sterilization[1].
However, the discharge area of DBD is limited between electrodes.
Recently, plasma jet, a kind of DBD has attracted as a novel plasma source.
Plasma is generated by applying AC voltage to a glass tube with a rare gas flowing in the
tube.
Generated plasma is pushed out of the tube by the rare gas.
The plasma reaches to solid and liquid easily; therefore, the plasma jet is used for
sterilization, stimulation of germination, etc.
To control the plasma jet properly, and studying the plasma characteristics is important.
Discharge reactor
• Glass tube : A T-shaped glass tube of
3 mm in inner diameter and 90 mm
length.
• High voltage electrode: A copper tube of
2 mm in inner diameter and 3 mm in
outer diameter is inserted into an inlet of
the T-shaped glass tube.
• Earth electrode : An aluminium sheet is
bound round the outside of the T-shaped
glass tube.
• The gap length between copper tube and
aluminium electrode is 10 mm.
Applied voltage
• AC voltage 12 kVp-p at a frequency of 17
kHz.
Gas conditions
• An argon gas, the purity of which is
99.99 % is fed into the glass tube through
the copper tube at constant flow rate of
10 L/min.
Measurement of optical emission spectra
• Optical emission intensity of the plasma
jet is measured using monochromator
(JASCO, CT-25CS, 0.16 nm resolution).
• The monochromator is placed normal to
the direction of gas flow to measure the
spatial distribution of the emission
intensity.
• The distance between the plasma jet and
the entrance slit of the monochromator is
fixed at 10 mm.
copper tube
aluminium
sheet
10 mm
The shape of rotational spectra is partially affected by temperature.
The shape of rotational spectra changes with temperature.
It is possible to deduce gas temperature by the shape of rotational spectra.
In this work, the shape of measured spectra of OH is compared with theoretical
spectra considering temperature, calculated by LIFBASE[3] with different gas
temperature. The rotational temperatures of plasma jet are deduced by the
correspondence between measured and theoretical spectra.
[1] Nagatsu: J. Plasma Fusion Res. Vol.83, No.7, pp.601-606 (2007)
[2] J. Luque and D. R. Crosley, "LIFBASE (version 1.5)", SRI International Report MP 99-009 (1999)
[3] R. W. B. Pearse and A. G. Gaydon: “The identification of molecular spectra”, Chapman and hall (1976)
4. Results and discussion
5. Conclusions
The theoretical rotational spectra are calculated by equation (1).
𝑁𝐽 = 𝑁0 ∙2𝐽+1 ∙ 𝑒
−𝐸 𝐽
𝑘𝐵𝑇rot
𝑍𝑒𝑙𝑒𝑐 ∙ 𝑍rot
In the case of OH : Zelec= 4, Zrot=𝑘𝐵𝑇rot
ℎ𝑐𝐵0
𝑁𝐽 = 𝑁0 ∙2𝐽+1 ∙ 𝑒
−𝐸(𝐽)
𝑘𝐵𝑇rot
4 ∙𝑘𝐵𝑇rotℎ𝑐𝐵0
(1)
kB : Boltzmann Constant, h : Planks Constant, c : Speed of Light, B0 : OH Spec. Constant
It is found that the shape of rotational spectra is determined by the
rotational temperature.
(2) Variation of the gas temperature with different distance from the exit of the reactor
0 mm 1 mm 2 mm0.30
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310.0307.5
wavelength [nm]
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simulated
360 K
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310.0307.5
wavelength [nm]
measured simulated
380 K
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310.0307.5
wavelength [nm]
measured
simulated
360 K
0.20
0.15
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0.05
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inte
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ty [
a.u
.]
310.0307.5
wavelength [nm]
measured
simulated
340 K
0.15
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inte
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.]
310.0307.5
wavelength [nm]
measured
simulated330 K
0.16
0.12
0.08
0.04
0.00
inte
nsi
ty [
a.u
.]
310.0307.5
wavelength [nm]
measured simulated
310 K
3 mm 4 mm 5 mm
The band head of OH is 309 nm, and rotational spectra lie at 306.8 – 308.8
and 309.5 – 311.5 nm.
The emission spectra of OH are due to H2O contained in Ar or in air in the
vicinity of the plasma jet.
The theoretical rotational spectra at 380 K agree well with the measured
rotational spectra, therefore; the gas temperature of the plasma jet is
determined to be 380 K.
120
100
80
60
40
20
0
inte
nsi
ty [
a.u
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312311310309308307wavelength [nm]
simulated 280 K 380 K 480 K
OH (rotational)
OH (rotational)
OH (A2S+ → X2P, 309 nm)
The maximum gas temperature is 380 K at 1.0 mm away from the
exit of the plasma jet reactor.
The gas temperature tends to fall above 1.0 mm away from the exit
of the reactor.
Background
OH (rotational)
OH (rotational)
OH (A2S+ → X 2P,
309 nm)
380
360
340
320
300
gas
tem
per
atu
re [
K]
5.04.03.02.01.00.0
distance [mm]
The exit of the reactor
1 2 3 40 5 mm
