Spectroscopy of heterophase plasma of electric ARC discharge between W and Mo electrodes
This paper deals with spectroscopy of plasma of electric arc discharge between tungsten and molybdenum
 electrodes. Spectrum of electric arc discharge between metal electrodes usually contains atomic lines of metals,
 which can be used for plasma diagnostics. In case of high-melting...
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| author | Lebid, A.V. Veklich, A.N. |
| author_facet | Lebid, A.V. Veklich, A.N. |
| citation_txt | Spectroscopy of heterophase plasma of electric ARC discharge between W and Mo electrodes / A.V. Lebid, A.N. Veklich // Вопросы атомной науки и техники. — 2018. — № 6. — С. 255-258. — Бібліогр.: 7 назв. — англ. |
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| description | This paper deals with spectroscopy of plasma of electric arc discharge between tungsten and molybdenum
electrodes. Spectrum of electric arc discharge between metal electrodes usually contains atomic lines of metals,
which can be used for plasma diagnostics. In case of high-melting metals such as tungsten and molybdenum, not
only line spectrum, but also continuous emission are observed. The attempts of simulation of such continuous
emission and comparison with experimentallyobtained spectrum were performed.
Розглядаються особливості спектроскопії плазми електродугового розряду між вольфрамовими або
молібденовими електродами. Спектр електричної дуги між металевими електродами, як правило, містить
лінії атомів металу. У випадку тугоплавких металів вольфраму та молібдену спостерігається не лише
лінійчатий, але і неперервний спектри. Пропонуються результати моделювання такого неперервного спектра
та його порівняння з експериментально зареєстрованим спектром.
Рассматриваются особенности спектроскопии плазмы электродугового разряда между вольфрамовыми
или молибденовыми электродами. Спектр электрической дуги между металлическими электродами, как
правило, содержит линии атомов металла. В случае тугоплавких металлов вольфрама и молибдена
наблюдается не только линейчатый, но и непрерывный спектры. Предлагаются результаты моделирования
такого непрерывного спектра и сравнение его с экспериментально зарегистрированным спектром.
|
| first_indexed | 2025-12-07T18:00:17Z |
| format | Article |
| fulltext |
ISSN 1562-6016. ВАНТ. 2018. №6(118)
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2018, № 6. Series: Plasma Physics (118), p. 255-258. 255
SPECTROSCOPY OF HETEROPHASE PLASMA OF ELECTRIC ARC
DISCHARGE BETWEEN W AND Mo ELECTRODES
A.V. Lebid, A.N. Veklich
Taras Shevchenko National University of Kyiv, Kyiv, Ukraine;
E-mail: tgctg@yandex.ru, van@univ.kiev.ua
This paper deals with spectroscopy of plasma of electric arc discharge between tungsten and molybdenum
electrodes. Spectrum of electric arc discharge between metal electrodes usually contains atomic lines of metals,
which can be used for plasma diagnostics. In case of high-melting metals such as tungsten and molybdenum, not
only line spectrum, but also continuous emission are observed. The attempts of simulation of such continuous
emission and comparison with experimentallyobtained spectrum were performed.
PACS: 52.70.-m, 52.80.Mg
INTRODUCTION
Electric arc discharge between high melting
materials as tungsten and molybdenum attracts scientific
and practical interests. For example, tungsten cathodes
are applicable in high-power thermal plasma torches
(plasmatrons) [1], but usually only for non-oxidizing
working gases or with special inert gas cathode
protection. This circumstance explained by fast
oxidation of hot tungsten and molybdenum with
formation of relatively low-melting and even volatile
oxides [2]. In the same time oxidation of tungsten and
molybdenum can be used as advantage for fabrication of
structured materials (oxides)and such oxidation can be
performed in electric arc plasma source [3].
The aim of this work is investigation of spectra of
plasma of electric arc discharge between tungsten and
molybdenum electrodes, which contain strong
continuous emission.
1. EXPERIMENT
The vertically oriented free-burning arc was ignited
in air between the end surfaces of metallic tungsten or
molybdenum non-cooled electrodes. The diameter of
the rod electrodes was 6 mm, the discharge gap was
8 mm and DC current was 3.5 A.
The middle cross-section of electric arc discharge
plasma was studied by optical emission spectroscopy
technique [4]. The realized configuration of
experimental setup with optical scheme on base of
diffraction grating 600 g/mm permits simultaneous
registration of spatial intensity distribution in spectral
range 400…660 nm.
Spectrum of electric arc discharge between metal
electrodes usually contains atomic lines of metals,
which can be used for plasma diagnostics. But in case of
high-melting metals as tungsten and molybdenum, not
only linear spectrum, but continuous emission in
background was also observed (Figs. 1, 2 ).
2. MODELING
Further diagnostics of plasma are complicated due to
superposition of the continuous emission and line
spectrum. For example, application of Boltzmann plots
method for temperature measurement without
considerationof this overlapping tends to unacceptable
results. So, it is reasonable to study this continuous
emission.
Continuous emission can be caused by different
factors – thermal emission of heated bodies,
recombination and bremsstrahlung continuum.
The bremsstrahlung emissioncaused by losing of
kinetic energy of electrons due to Coulomb interaction
with other charged particles, i.e. braking in electrostatic
field. The bremsstrahlung,also known as free-free
transactions, because particles don’t change their free
state during interaction and only change their energy by
photon emission. The spectrum of bremsstrahlung
continuum has flat form with exponential cut-off in
short-wave range [5]. The emission coefficient of such
continuum proportional to degree of ionization (≤10-3
for arcs) and this type of spectra seems not typical for
non-extremalelectric arcs.
Recombination continuum (free-bound transactions)
differ from bremsstrahlung due to particles became
bonded after interaction. As rule bremsstrahlung
intensity dominate and only in short-wave part of
spectrum recombination emission became important [5].
Therefore, recombination emission intensity is
negligible in the arc spectrum, because it’s intensity is
lower than for bremsstrahlung.
In the same time injection of hot particles from
electrodes into the arc volume is expected. Therefore,
plasma can be considerate as hetero phase medium. For
example, hot particles observed in plasma volume of
electric arc discharge between composite Cu-W
electrodes [6].
Thermal emission can be explained by radiationof
hot matter injected in plasma volume by upward
convective flows [3] or directly from electrodes’
surface. In this assumption spectral brightness can be
calculated according to Planck’s law:
,1exp
2
),(
1
5
2
Tk
hchc
Tb
B
Planck
where λ – wavelength; h and kB – Planck and Boltzmann
constants; c – speed of light; T – heated bodies
temperature.
mailto:van@univ.kiev.ua
256 ISSN 1562-6016. ВАНТ. 2018. №6(118)
Fig. 1. Spectrum of electric arc between tungsten electrodes
Fig. 2. Spectrum of electric arc between molybdenum electrodes
Sensitivity of spectral device can be obtained from
registration of heated body with known temperature, for
example tungsten ribbon lamp. So, spectral sensitivity
S(λ) was obtained previously. The observed brightness
bobs can be calculated with respect to spectral sensitivity:
,, fTbSb Planckobs
where f – some adjusting factor from absolute scale to
arbitrary units. It must be noted, that f is not strictly
defined and must be selected carefully. In general, the
task of superposition of calculated end experimental
spectrum has solution in some f andTparameter space.
Intensity of simulated spectrum significantly rises
whiletemperature T increasing, so appropriate
decreasing of f is needed.
Simultaneous variation of T and f shows best
coincidence of experimental and simulated spectrum at
4500…5500 K (Figs. 3, 4). If T < 4500 K simulated
spectrum situated below experimental in short-wave
range, while if T > 5500 K is situated above
experimental spectrum.
Calculated in such way spectrum was compared with
experimental spectrum (see Figs. 3, 4). So, continuous
spectra can be treated by Planck formula and subtract
for following study of spectra.
450 500 550 600
0
20
40
60
80
100
120
140
Wavelength, nm
W I 551.47
W I 505.33
W
I
5
0
1
.5
3
W I 522.466
W
I
5
0
0
.6
1
5
W
I
4
9
8
.2
6
W
I
4
8
8
.6
9
W
I
4
6
8
.0
5
W spectrum
T3000F0.9
T3250F0.55
T3500F0.35
T3750F0.2
T4000F0.12
T4500F0.06
T5000F0.03
T5500F0.022
Intensity, a.u.
W
I
4
8
4
.3
8
Fig. 3. Spectrum of electric arc discharge between tungsten electrodes and continuum simulation
450 500 550 600
0
20
40
60
80
100
120
140
Intensity, a.u.
M
o
I
4
7
6
.0
M
o
I
4
7
3
.1 Mo spectrum
T3000F0.3
T3250F0.2
T3500F0.1
T3750F0.08
T4000F0.05
T4500F0.03
T5000F0.018
T5500F0.012
M
o
I
4
4
1
.1 Mo I 553.3
Mo I550.6
M
o
I
6
0
3
.0
Mo I 557.0
Wavelength, nm
Fig. 4. Spectrum of electric arc discharge between molybdenum electrodes and continuum simulation
ISSN 1562-6016. ВАНТ. 2018. №6(118) 257
2.4 2.6 2.8 3.0 3.2
34.5
35.0
35.5
36.0
36.5
468.05
484.38
488.69
498.26
500.615
501.531
505.33 522.466
551.47
E, eV
W I lines
Linear fitting
Ln(I
gf)
3.5 4.0 4.5 5.0
30.5
31.0
31.5
32.0
32.5
33.0
33.5
34.0
34.5
4411.69
4731.44
4760.16
5506.49
5533.03
5570.44
6030.66
E, eV
Mo I
Linear fitting
Ln(I
3
/gf)
a b
Fig. 5. Boltzmann plots for arc plasma of electric arc discharge between tungsten (a) and molybdenum (b)
electrodes
For further plasma diagnostics is necessary to
subtract continuous emission from whole observed
spectrum It can be performed in following way.
Intensity of a spectral line I at certain spatial pointxcan
be evaluated from spectral brightness distribution b(λ)
as:
,
,
dbI
x
where – Δλ and +Δλ some spectral range within spectral
line profile. In case of digital image of spectra it is
possible to substitute integration by summation:
,
,
n
x
nbI
where n is pixel’s numbers belong to appropriate range
from – Δλ to +Δλ.
Thereby, real line intensity without continuous
spectra can be expressed
.
))((
,
n
continuous
n
obs
continuous
n
obsxreal
nbnb
nbnbI
3. TEMPERATURE CALCULATION
This technique of continuum subtraction was
performed for further plasma diagnostics, particularly
for estimation of temperature by Boltzmann plots
method. Applicable for diagnostics atomic spectral lines
of W and Mo were selected previously [7]. Nine
spectral lines for W (Fig. 5,a) and six spectrallines for
Mo (Fig. 5,b) were used. The best satisfied simulated
continuous spectra were subtracted.
The emission intensities along central axis of
spectrum were used (see Figs.1, 2). The Abel inversion
was not performed, so obtained results can be used only
as temperature estimation. In the same time Abel
inversion is not contradict with proposed method and
will be performed in future studies.
The Boltzmann plot method is applicable when
plasma is in local thermodynamic equilibrium (LTE),
then the slopes of line, whichdrawn through the points
corresponding to spectral lines, depends on plasma
excitation temperature as:
skTTks BB /1/1
wheres – slope, kB – Boltzmann constant.
Thereby, Boltzmann plots for plasma of electric arc
discharges between tungsten (see Fig. 5,a) and
molybdenum (see Fig. 5,b) electrodes with subtraction
of continuous emission intensity allow us to estimate
plasma excitation temperature. For tungsten the
temperature is estimated as 5600 and about 6600 K for
molybdenum.
CONCLUSIONS
Spectrum of electric arc between tungsten and
molybdenum electrodes contains strong continuum in
background, whichmust be taken into account during
plasma diagnostics. Continuous emission can be caused
by injection of electrodes material in arc volume, i.e.
heterophase plasma has place. The mechanism of such
injection must be defined by further investigation.
Probably droplet transfer from electrode working
surface has place. In the same time, some part of
electrodes material can be transported into arc volume
by upward convection flows.
Thesimulated according Planck’s law continuum
shows reasonable agreement with real obtained spectra
in 4500…5500 K temperature range. Thereby, it is
possible to subtract continuum emission and properly
define plasma temperature by spectral lines intensity.
Plasma temperature was estimated after subtraction
of continuum emission by Boltzmann plot method. The
temperature of plasma of electric arc discharge at 3.5 A
between tungsten electrodes for central cross-section
was estimated as 5600 K. In case of molybdenum
electrodes, the temperature was estimated as 6600 K in
the same conditions.
258 ISSN 1562-6016. ВАНТ. 2018. №6(118)
REFERENCES
1. M.F. Zhukov, I.M. Zasypkin. Thermal plasma
torches. Cambridge, UK: “Cambridge International
Science Publishing Ltd”, 2007.
2. S.G. Orlovskaya, M.S. Shkoropado, F.F. Karimova.
Growth kinetics of oxides structures on refractory metal
surface during heating in air // Physics and Chemistry of
Solid State. 2012, v. 13, № 3, p. 733-737.
3. A. Lebid, A. Veklich, V. Boretskij, S. Savenok,
O. Andreev. Thermal plasma source for processing of
MoO3 crystals // Journal of Physics: Conference Series.
2014, v. 550, p. 012027.
4. A. Veklich, A. Lebid Technique of electric arc
discharge plasma diagnostic: peculiarities of registration
and treatment of spectra // Bulletin of Taras Shevchenko
National University of Kyiv. Radiophysics and
Electronics. 2012, v. 18, p. 6-9.
5. F.C. van den Bosch. Physical Processes in
Astronomy.A treatment of fluid dynamics and radiative
processes. New Haven: “Yale University”, 2017.
6. I.L. Babich, V.F. Boretskij, R.V. Minakova,
A.N. Veklich. Plasma of electric arc between electrodes
from composite materials // Problems of Atomic Science
and Technology. Series “PlasmaPhysics” (14). 2008,
№ 6, p. 159-161.
7. A.V. Lebid, A.N. Veklich, T.A. Tmenova. Spectroscopy
of electric arc discharge plasma with admixtures of W, Mo,
Cr // Problems of Atomic Science and Technology. Series
“Plasma Physics” (32). 2016, № 6, p. 219-222.
Article received 18.10.2018
СПЕКТРОСКОПИЯ ГЕТЕРОФАЗНОЙ ПЛАЗМЫ ЭЛЕКТРОДУГОВОГО РАЗРЯДА
МЕЖДУ W- И Mo-ЭЛЕКТРОДАМИ
А.В. Лебедь, А.Н. Веклич
Рассматриваются особенности спектроскопии плазмы электродугового разряда между вольфрамовыми
или молибденовыми электродами. Спектр электрической дуги между металлическими электродами, как
правило, содержит линии атомов металла. В случае тугоплавких металлов вольфрама и молибдена
наблюдается не только линейчатый, но и непрерывный спектры. Предлагаются результаты моделирования
такого непрерывного спектра и сравнение его с экспериментально зарегистрированным спектром.
СПЕКТРОСКОПІЯ ГЕТЕРОФАЗНОЇ ПЛАЗМИ ЕЛЕКТРОДУГОВОГО РОЗРЯДУ
МІЖ W- ТА Mо- ЕЛЕКТРОДАМИ
А.В. Лебідь, А.М. Веклич
Розглядаються особливості спектроскопії плазми електродугового розряду між вольфрамовими або
молібденовими електродами. Спектр електричної дуги між металевими електродами, як правило, містить
лінії атомів металу. У випадку тугоплавких металів вольфраму та молібдену спостерігається не лише
лінійчатий, але і неперервний спектри. Пропонуються результати моделювання такого неперервного спектра
та його порівняння з експериментально зареєстрованим спектром.
|
| id | nasplib_isofts_kiev_ua-123456789-149055 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T18:00:17Z |
| publishDate | 2018 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Lebid, A.V. Veklich, A.N. 2019-02-19T14:59:08Z 2019-02-19T14:59:08Z 2018 Spectroscopy of heterophase plasma of electric ARC discharge between W and Mo electrodes / A.V. Lebid, A.N. Veklich // Вопросы атомной науки и техники. — 2018. — № 6. — С. 255-258. — Бібліогр.: 7 назв. — англ. 1562-6016 PACS: 52.70.-m, 52.80.Mg https://nasplib.isofts.kiev.ua/handle/123456789/149055 This paper deals with spectroscopy of plasma of electric arc discharge between tungsten and molybdenum
 electrodes. Spectrum of electric arc discharge between metal electrodes usually contains atomic lines of metals,
 which can be used for plasma diagnostics. In case of high-melting metals such as tungsten and molybdenum, not
 only line spectrum, but also continuous emission are observed. The attempts of simulation of such continuous
 emission and comparison with experimentallyobtained spectrum were performed. Розглядаються особливості спектроскопії плазми електродугового розряду між вольфрамовими або
 молібденовими електродами. Спектр електричної дуги між металевими електродами, як правило, містить
 лінії атомів металу. У випадку тугоплавких металів вольфраму та молібдену спостерігається не лише
 лінійчатий, але і неперервний спектри. Пропонуються результати моделювання такого неперервного спектра
 та його порівняння з експериментально зареєстрованим спектром. Рассматриваются особенности спектроскопии плазмы электродугового разряда между вольфрамовыми
 или молибденовыми электродами. Спектр электрической дуги между металлическими электродами, как
 правило, содержит линии атомов металла. В случае тугоплавких металлов вольфрама и молибдена
 наблюдается не только линейчатый, но и непрерывный спектры. Предлагаются результаты моделирования
 такого непрерывного спектра и сравнение его с экспериментально зарегистрированным спектром. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Низкотемпературная плазма и плазменные технологии Spectroscopy of heterophase plasma of electric ARC discharge between W and Mo electrodes Спектроскопія гетерофазної плазми електродугового розряду між W- та Mo- електродами Спектроскопия гетерофазной плазмы электродугового разряда между W- и Mo-электродами Article published earlier |
| spellingShingle | Spectroscopy of heterophase plasma of electric ARC discharge between W and Mo electrodes Lebid, A.V. Veklich, A.N. Низкотемпературная плазма и плазменные технологии |
| title | Spectroscopy of heterophase plasma of electric ARC discharge between W and Mo electrodes |
| title_alt | Спектроскопія гетерофазної плазми електродугового розряду між W- та Mo- електродами Спектроскопия гетерофазной плазмы электродугового разряда между W- и Mo-электродами |
| title_full | Spectroscopy of heterophase plasma of electric ARC discharge between W and Mo electrodes |
| title_fullStr | Spectroscopy of heterophase plasma of electric ARC discharge between W and Mo electrodes |
| title_full_unstemmed | Spectroscopy of heterophase plasma of electric ARC discharge between W and Mo electrodes |
| title_short | Spectroscopy of heterophase plasma of electric ARC discharge between W and Mo electrodes |
| title_sort | spectroscopy of heterophase plasma of electric arc discharge between w and mo electrodes |
| topic | Низкотемпературная плазма и плазменные технологии |
| topic_facet | Низкотемпературная плазма и плазменные технологии |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/149055 |
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