Measurements of evaporated aluminium concentration on self-absorbed spectral lines
In the paper we discuss the experimental results of powerful plasma-stream interaction with aluminum target at the presence of the magnetic field. The plasma streams are generated by a quasi-stationary plasma accelerator (QSPA Kh- 50). Such experiments performed with QSPA facility during last years...
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| Published in: | Вопросы атомной науки и техники |
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| Date: | 2002 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2002
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| Cite this: | Measurements of evaporated aluminium concentration on self-absorbed spectral lines / A.K. Lobko, S.A. Trubchaninov, A.V. Tsarenko // Вопросы атомной науки и техники. — 2002. — № 5. — С. 151-153. — Бібліогр.: 5 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1860129439870877696 |
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| author | Lobko, A.K. Trubchaninov, S.A. Tsarenko, A.V. |
| author_facet | Lobko, A.K. Trubchaninov, S.A. Tsarenko, A.V. |
| citation_txt | Measurements of evaporated aluminium concentration on self-absorbed spectral lines / A.K. Lobko, S.A. Trubchaninov, A.V. Tsarenko // Вопросы атомной науки и техники. — 2002. — № 5. — С. 151-153. — Бібліогр.: 5 назв. — англ. |
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| container_title | Вопросы атомной науки и техники |
| description | In the paper we discuss the experimental results of powerful plasma-stream interaction with aluminum target at the presence of the magnetic field. The plasma streams are generated by a quasi-stationary plasma accelerator (QSPA Kh- 50). Such experiments performed with QSPA facility during last years [1-3] are of great interest for current disruption simulation in ITER tokamak and testing divertor materials. Some experimental series in our activity were devoted to the problem of mass losses of target under the high power plasma stream irradiation. This work presents the spectral method of determination of the evaporated material quantities in plasma-target interaction experiments. The distinctive feature of the offered work is follows – all spectral measurements were carried out using aluminum spectral lines only. There are two mechanisms of mass losses – evaporation and splashing melt layer. We succeeded in the evaluation of the evaporation mechanism contribution to the mass defect for aluminum target.
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| first_indexed | 2025-12-07T17:43:45Z |
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MEASUREMENTS OF EVAPORATED ALUMINIUM CONCENTRATION
ON SELF-ABSORBED SPECTRAL LINES
A.K. Lobko, S.A.Trubchaninov, A.V.Tsarenko
Institute of Plasma Physics of the National Science Center “Kharkov Institute of Physics and
Technology”, 61108, Kharkov, Akademicheskaya Str., 1, Ukraine
In the paper we discuss the experimental results of powerful plasma-stream interaction with aluminum target at the
presence of the magnetic field. The plasma streams are generated by a quasi-stationary plasma accelerator (QSPA Kh-
50). Such experiments performed with QSPA facility during last years [1-3] are of great interest for current disruption
simulation in ITER tokamak and testing divertor materials. Some experimental series in our activity were devoted to the
problem of mass losses of target under the high power plasma stream irradiation. This work presents the spectral
method of determination of the evaporated material quantities in plasma-target interaction experiments. The distinctive
feature of the offered work is follows – all spectral measurements were carried out using aluminum spectral lines only.
There are two mechanisms of mass losses – evaporation and splashing melt layer. We succeeded in the evaluation of the
evaporation mechanism contribution to the mass defect for aluminum target.
PACS: 52.40.Hf; 52.70.Kz
INTRODUCTION
The problem of the interaction of powerful plasma
streams with materials presents a large interest for many
physical and technical areas. Especially, it concerns the
materials of the candidates on manufacturing ITER
divertor plates. Erosion of the divertor plates material
during a tokamak disruption event restricts the divertor
plates lifetime and presents an important problem of
ITER fusion technology. So the present work was done in
the frame of ITER tasks and it was aimed at
investigations of plasma-target interaction under
conditions simulating disruption in ITER.
The dense shielding layer that consists of ionized
vapors of target material is formed during interaction of
high power plasma stream with the target. The main part
of the energy of the stream is absorbed and radiated in the
shielding layer that comes to the screening effect. The
screening effect is amplified in the presence of the
magnetic field [2]. The main aim of the present work is
determination of the evaporated material quantities using
spectral technique.
EXPERIMENTAL SETUP AND
DIAGNOSTIC FACILITIES
Experiments were carried out on installation QSPA
Kh-50. Detail descriptions of the installation,
experimental conditions, diagnostic facility (including
spectroscopy) are adduced in series of publications [1-3].
It is necessary to point basic characteristics of plasma
stream – power density ~ 10 MW/cm2 (it is so called
“soft” regime of QSPA), plasma stream duration ~ 150 μs
and diameter of the stream ~ 10 cm.
The spectral diagnostic technique elements and its
assignment:
− diffractive spectrograph DFS-452 (resolution – 0.3 Ǻ,
dispersion – 8 Ǻ/mm) - integral spectra registration of
plasma radiation;
− monochromator MDR-23 (resolution – 0.5 Ǻ,
dispersion – 13 Ǻ/mm). Monochromator with the
electron-optical converter (EOC) serves for receiving
optical spectra with the temporary and spatial
resolution. The monochromator was coupled with the
photomultiplier for the registration of separate
spectral lines. Signals from the photo multiplier were
recorded with the help of oscillograph C8-17;
− photo diodes - monitoring of the integral plasma
radiation, plasma velocity measurements;
− micro photometer IFO-451 – spectral data processing
The optical technique in details is described in [4].
The scheme of experiment is presented in Fig.1.
Aluminum target (diameter – 12 cm) was located
perpendicularly to the plasma stream. Spectral
measurements were performed in two sections (horizontal
and vertical) as shown in Fig.1.
DIAGNOSTIC PROCEDURE
Some intensive spectral lines of aluminum were
registered by the help of photomultiplier for the definition
of luminescence time of spectral lines. The examples of
oscillograms are represented in Fig.2. They were received
as follows: the upper line is a radiation of a spectral line
Al III (5696 Ǻ), and lower one – integral radiation of
plasma on the photodiode. It is visible, that the
luminescence time of aluminum in a shielding layer
makes 50 μs, and in the ambient plasma stream this time
is almost twice less (20 μs).
Problems of Atomic Science and Technology. 2002. № 5. Series: Plasma Physics (8). P. 151-153 151
H=0.57T
Streamline
plasma Plasma
stream
Vacuum chamber
Diagnostic
Cross sections
Al target
∅ 12cm
Target
plasma
Fig.1 Scheme of experiment
0 10 20 30 40 50 60 70
0,1
1
10
Al II (559.3nm)
Al II (358.7nm)
N
e,
10
17
c
m
-3
L, mm
Fig. 3. Plasma electron density
a) b)
Fig.2. Upper line - radiation of
Al III (λ=569.6nm) 50μs/cell;
Lower line - integral radiation:
a) in front of the target(1-2 cm)
b) behind the target (1-2cm)
The determination of plasma electron density was
carried out on the base of Stark broadening measurements
of spectral lines Al II after exception of a measured
contour Doppler and instrumental broadening with using
the Foigts contour method. Such lines of Al II: 5593Ǻ,
3900Ǻ, 3587Ǻ, 2816Ǻ and 2631Ǻ were used.
The Fig.3 presents radial distribution of plasma
electron density depending on the distance from the
target.
Differences in the density values may be explained
by self-absorption of multiplet – λ=3587 Ǻ and
considerable error under reconstruction the Stark
broadening. In the consequent evaluations of Te and
aluminum concentration we used data, obtained from Al
II 5593 Ǻ.
The electron temperature was determined from the
ratio of intensities of spectral lines of Al II (5593 Ǻ, 3900
Ǻ, 3587 Ǻ, 2816 Ǻ, 2631 Ǻ) and Al III (5722 Ǻ, 5696 Ǻ,
4512 Ǻ, 3612 Ǻ, 3601 Ǻ). The average value of the
electron temperature in a plasma shield is equal 1.9-2.1
eV.
The analysis of experimental data – intensities and
profiles lines - shows that some spectral lines of Al II
(3587Ǻ, 2816Ǻ) and Al III (3601Ǻ, 3612 Ǻ) are self-
absorbed. It is possible to calculate optical thickness using
proportion of the true width of spectral line to
experimentally measured one. Particularly, the measured
half width (Δλ=1.1Ǻ) of Al II spectral line 3p 1P0 – 4s 1S
(λ=2816Å) significantly exceed its calculated value for
the optically thin plasma - Δλ≈0.15÷0.2Ǻ. Calculations of
contour parameters for λ=2816Ǻ Al II, namely Doppler
and Stark contributions, were executed by Foigt function
technique using Ne data from Stark broadening of
λ=5593Ǻ as standard. All necessary data are available for
these procedures in [4]. Thus, we may obtain the value of
optical thickness – τ, using the well-known formula for
the Lorenz contour, counting the Stark broadening
mechanism as a dominant:
( )
1
-exp1
2ln
−
+
=
∆
∆
τ
τ
λ
λ
L (1)
Here ∆λ - observed half width, ∆λL - half width for the
optically thin plasma. For example, optical thickness
(λ=2816Å) for the near target region amounts to τ ~ 20÷
30.
Somewhat different technique was used for the
determination of optical thickness for the Al III spectral
multiplet 3d2D – 4p2P0 – λ=3601.6 Ǻ and λ=3612 Ǻ. It is
common knowledge that intensities proportion for
components of spectral multiplets is defined by gf
proportion only, and is independent of Ne, Te in the case
of neglible optical thickness (usually values of Te
considerably larger than fine structure of corresponding
terms). Generally differences of λ for multiplets are
neglible also. Equally it is concerned to τ, because of the
same broadening parameters. Distortion of the “atomic”
line intensities ratio indicates on a large optical thickness.
We have possibility to evaluate τ in such a way:
( )
( )α
τ
τ
-exp1
-exp1
−
−=R (2)
Where R – observed ratio intensities; α – “atomic” ratio
between gf; τ – optical thickness for center of strongest
line. When τ → ∞ (Plank limit), R →1; given τ → 0,
R → α – optically transparent plasma. In the Eq. 2) the
matter concerns brightness in a center of line, the whole
intensity distort too, but slightly complex. For the
mentioned above Al III multiplet, R is equal to 1.3 (region
behind target), under α ~ 2. We have the value τ ~2 for
the spectral line λ=3601.6 Ǻ. There is necessary to mark
that the ratio intensities is more “sensitive“ to optical
thickness in comparison with line shapes. Namely,
distortions of contour are observable under the significant
values of optical thickness - τ »1.
152
0 5 10 15 20 25 30 35 40 45
1,2
1,6
2,0
2,4
2,8
Al III(559.6nm)/II(559.3nm)
Al III(361.2nm)/II(358.7nm)
T e,
eV
L - distance from the target, mm
Fig.4. The electron temperature distribution
The information about τ permits us to determine the
quantity of evaporated Al in the shielding layer and in the
ambient plasma stream. We may use the following
relation:
−⋅⋅⋅
∆
⋅⋅⋅= ∗−
eT
LNfk ε
λ
λτ -exp110
2
20 (3)
Where ∆λ[nm] – half width for optically transparent
plasma; λ[nm] – wavelength; f – absorption oscillator
force; L[cm] – geometrical thickness of luminescence
layer; N*[cm-3] (for Al in our case) – population on lower
exciting level of corresponding transition; ε[eV] – photon
energy; Te[eV] – the electron temperature; k – coefficient
depending on contour type k=5.6 for Lorenz type and
k=8.2 for Gauss type. Under the commensurable
contributions of both broadening mechanisms one may
take k=7. For the determination N* from Eq.(3) we used
values Te presented on Fig.4. There are some differences
in finding ∆λ – half width for optically transparent
plasma. For the λ=2816 Ǻ (the near target region) we
have taken theoretically calculated half width by setting
ion temperature of Al – Ti=Te≈2eV. In the case of
λ=3601.6 Ǻ the measured and corrected ∆λ according to
Eq.(1) have been used. For L in front of target we used
geometric size – 12cm. Value L behind of target was
determined from the spectra in vertical cross section
(Fig.1), as the doubled thickness of ambient stream.
Further the concentrations of Al I – Al IV and the
whole (sum on ionization states) density of Al have been
calculated using well-known Saha-Boltzmann
correlations, taking into account statistical sums.
Application of these correlations is wholly justified
because of large values of Ne at that significant
magnitudes of τ for resonance lines just promote the LTE
conditions. All atomic data, constants, parameters of ions
(ionization and excitation potentials, statistical weights,
oscillator forces, Stark broadening parameters, etc.) that
are necessary in this case are present at [4,5]. Fig.5
demonstrates results of the calculation of whole density of
aluminum along with Ne and Ne
Al= ΣzAlz (Alz – partial
concentration of corresponding ion) – part of the electron
density, caused by the evaporated aluminum.
These data have been used for the evaluation of mass
losses taking into account velocity of the ambient flow
and geometry of the experiment. All main results of
measurements and calculations are submitted in the Table.
NAl is regarded as a full quantity of evaporated Al atoms
in the shielding layer or in the ambient stream, M – mass
loss, t – lifetime of Al in front of or behind of target. One
can see that the most part of the evaporated material is
pressed out from the shielding layer and passed away with
the ambient flow.
The values of mass loss obtained in such a way are in
a good agreement with direct measurements of mass
defect by weighing.
Table.
Near the
target
0.1 cm
Distance
from the
target
3.6 cm
Behind the
target 2cm
Ne, cm-3 1*1017 0.45*1017 0.5*1017
Te, eV 2 2 2
NAl, cm-3 2.8*1016 1.1*1016 6.6*1015
Ne
Al cm-3 5*1016 2*1016 1.3*1016
L, cm 12 12 6
S, cm2
d~4cm
~110 V~500cm3
V=Sd
V=1.5*104
NAl ~1019Al ½1019Al
Whole loss
~1020Al
t, μs 100 100 20
M,
10-3g
~0.5
per
pulse
~0.2
per
pulse
~4.6
per
pulse
SUMMARY
The described method of determination of the plasma
optical thickness starting from the distorted multiplet
intensities is of great interest not only for the plasma-wall
interaction problems, but also for the dense plasma
spectroscopy, generally. Evidently our work is a first
attempt of practical work with such effect.
REFERENCES
1. V.I.Tereshin, V.V. Chebotarev, et al., Disruption
modeling experiments with utilizing the powerful
quasistationary plasma streams, Proc. of 18th
Symposium on plasma physics. Prague, 17-20 June
1997.
2. V.V.Chebotarev, V.A.Makhlaj, et al., Optical
measurements of the parameters of high power
plasma streams generated by quasi-steady-state
plasma accelerator and propagated in a longitudinal
magnetic field, Problems of Atomic Science and
Technology. Series “Plasma physics” 3(3), 4(4),
1999, pp 298-300.
3. V.I.Tereshin, V.V. Chebotarev, et al., Powerful
Quasi-Steady-State Plasma Accelerator for Fusion
Experiments, Brazilian Journal of Physics, vol.32,
N1, March, 2002.
4. Griem G. Spektroskopia plasmy, Atomizdat, Moskva
1969 (in Russian).
Problems of Atomic Science and Technology. 2002. № 5. Series: Plasma Physics (8). P. 151-153 153
0 10 20 30 40 50
0,1
1
10
Ne
Whole density of Al
NeAl
N
, 1
016
c
m
-3
L, mm
Fig. 5. Density distributions, depends on
distance from the target
5. Striganov A.R., Sventicki N.S. Tablicy spektralnyh
liniy, Atomizdat, Moskva 1966 (in Russian).
154
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| id | nasplib_isofts_kiev_ua-123456789-79289 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T17:43:45Z |
| publishDate | 2002 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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| spelling | Lobko, A.K. Trubchaninov, S.A. Tsarenko, A.V. 2015-03-30T09:44:19Z 2015-03-30T09:44:19Z 2002 Measurements of evaporated aluminium concentration on self-absorbed spectral lines / A.K. Lobko, S.A. Trubchaninov, A.V. Tsarenko // Вопросы атомной науки и техники. — 2002. — № 5. — С. 151-153. — Бібліогр.: 5 назв. — англ. 1562-6016 PACS: 52.40.Hf; 52.70.Kz https://nasplib.isofts.kiev.ua/handle/123456789/79289 In the paper we discuss the experimental results of powerful plasma-stream interaction with aluminum target at the presence of the magnetic field. The plasma streams are generated by a quasi-stationary plasma accelerator (QSPA Kh- 50). Such experiments performed with QSPA facility during last years [1-3] are of great interest for current disruption simulation in ITER tokamak and testing divertor materials. Some experimental series in our activity were devoted to the problem of mass losses of target under the high power plasma stream irradiation. This work presents the spectral method of determination of the evaporated material quantities in plasma-target interaction experiments. The distinctive feature of the offered work is follows – all spectral measurements were carried out using aluminum spectral lines only. There are two mechanisms of mass losses – evaporation and splashing melt layer. We succeeded in the evaluation of the evaporation mechanism contribution to the mass defect for aluminum target. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Plasma diagnostics Measurements of evaporated aluminium concentration on self-absorbed spectral lines Article published earlier |
| spellingShingle | Measurements of evaporated aluminium concentration on self-absorbed spectral lines Lobko, A.K. Trubchaninov, S.A. Tsarenko, A.V. Plasma diagnostics |
| title | Measurements of evaporated aluminium concentration on self-absorbed spectral lines |
| title_full | Measurements of evaporated aluminium concentration on self-absorbed spectral lines |
| title_fullStr | Measurements of evaporated aluminium concentration on self-absorbed spectral lines |
| title_full_unstemmed | Measurements of evaporated aluminium concentration on self-absorbed spectral lines |
| title_short | Measurements of evaporated aluminium concentration on self-absorbed spectral lines |
| title_sort | measurements of evaporated aluminium concentration on self-absorbed spectral lines |
| topic | Plasma diagnostics |
| topic_facet | Plasma diagnostics |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/79289 |
| work_keys_str_mv | AT lobkoak measurementsofevaporatedaluminiumconcentrationonselfabsorbedspectrallines AT trubchaninovsa measurementsofevaporatedaluminiumconcentrationonselfabsorbedspectrallines AT tsarenkoav measurementsofevaporatedaluminiumconcentrationonselfabsorbedspectrallines |