CIV fenomen in gas-metal plasma
The paper deals with limitation of the rotational velocity of multicomponent gas-metal plasma, and also, with the effect of this phenomenon on mass separation in the rotating plasma. The measured data on the rotational velocity of the gas-metal multicomponent plasma are presented and analyzed. Розгл...
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| Zitieren: | CIV fenomen in gas-metal plasma / Yu.V. Kovtun // Вопросы атомной науки и техники. — 2015. — № 4. — С. 43-48. — Бібліогр.: 37 назв. — англ. |
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| citation_txt | CIV fenomen in gas-metal plasma / Yu.V. Kovtun // Вопросы атомной науки и техники. — 2015. — № 4. — С. 43-48. — Бібліогр.: 37 назв. — англ. |
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| description | The paper deals with limitation of the rotational velocity of multicomponent gas-metal plasma, and also, with the effect of this phenomenon on mass separation in the rotating plasma. The measured data on the rotational velocity of the gas-metal multicomponent plasma are presented and analyzed.
Розглянуто обмеження швидкості обертання багатокомпонентної газо-металевої плазми і вплив цього ефекту на розділення за масами в плазмі, що обертається. Проведені і узагальнені результати експериментальних вимірювань швидкості обертання газометалевої багатокомпонентної плазми.
Рассмотрено ограничение скорости вращения многокомпонентной газо-металлической плазмы и влияние этого эффекта на разделение по массам во вращающейся плазме. Проведены и обобщены результаты экспериментальных измерений скорости вращения газометаллической многокомпонентной плазмы.
|
| first_indexed | 2025-12-07T16:40:37Z |
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ISSN 1562-6016. ВАНТ. 2015. №4(98) 43
CIV FENOMEN IN GAS-METAL PLASMA
Yu.V. Kovtun
National Science Center “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine
E-mail: Ykovtun@kipt.kharkov.ua
The paper deals with limitation of the rotational velocity of multicomponent gas-metal plasma, and also, with the
effect of this phenomenon on mass separation in the rotating plasma. The measured data on the rotational velocity of
the gas-metal multicomponent plasma are presented and analyzed.
PACS: 52.80.Sm; 52.35.-g
INTRODUCTION
Possible physico-technical approaches to the realiza-
tion of the magnetoplasma method of substance separa-
tion for spent nuclear fuel (SNF) reprocessing are wide-
ly discussed in the current literature [1 - 9] as an alterna-
tive to the radiochemical method of SNF reprocessing.
With this method, the plasma ions, and accordingly, the
SNF substance, are supposed to be separated into light
and heavy mass groups (so-called “partial separation”), or
be separated element by element (“complete separation”).
Consideration was given to the feasibility of creating
a magnetoplasma device based of the beam-plasma dis-
charge [1, 2], and also, with the use of the ion-cyclotron
resonance [3].
Much attention of the investigators has been given to
the possibility of separating the substance, including
SNF, into mass groups and elements using the devices
with plasma rotating in crossed E×B fields. Various
versions of rotating-plasma devices for SNF separation
have been proposed [2, 4 - 9], among them the ones
based on the reflective discharge [2, 8, 9].
The realization of the SNF-separating magnetoplas-
ma method implies the creation of facilities and com-
plexes of capacities comparable in the order of magni-
tude with the radiochemical reprocessors of the same
profile. For this purpose, consideration is given to a
well-ionized dense plasma with a particle concentration
of up to 1020 m-3 (1014 cm-3). For plasma rotation-based
magnetoplasma facilities, the separation coefficient is
dependent on the rate of rotation and the difference of
separated masses. In view of this and the separation de-
vice capacity requirements, the rate of plasma rotation
should be of about 104 m/s.
In spite of the intensive studies into magnetoplasma
separation techniques, no or little consideration has been
given to some problems still not clearly understood.
Among them, we may mention the limitation of the ro-
tational velocity of multicomponent gas-metal plasma
and the effect of this phenomenon on mass separation in
the rotating plasma. The present work is the continua-
tion of our previous studies (see refs. [10 - 12]).
1. MASS SEPARATION IN THE ROTATING
PLASMA
The possibility of using centrifugal effects for sub-
stance separation in the rotating multicomponent plasma
has been indicated in ref. [13]. As noted in [14], the cen-
trifugal effect of separation is not the only mechanism,
which may take place in the rotating plasma. The radial
separation coefficient for the two-component plasma is
determined as:
( ) ( )( )
( ) ( )( )000 NN
NN
B
i
A
i
B
i
A
i rr
=α , (1)
where Ni
A(0), Ni
B(0) and Ni
A(r), Ni
B(r) denote the density
of ions of species A and B on the axis and at a distance
of r from the axis, respectively. For the case of a fully
ionized isothermal plasma at Zi
A = Zi
B =1, vφ
A =
vφ
B =vφ = ωφr the separation coefficient α0 can be esti-
mated by the relation [15]:
∆
=
kT
mv
2
exp
2
0
ϕα , (2)
where vφ is the rate of plasma rotation, T is the plasma
temperature, k is the Boltzmann constant; Δm = mi
A-
mi
B, mi
A and mi
B denote the masses of ions of species A
and B. The estimation shows that at T = 2 eV, Δm = 25,
vφ = 103 m/s and vφ = 104 m/s the separation coefficient α0
is equal to 1.1 and 1.78·104, respectively. So, by increas-
ing the rate of rotation it is possible to increase the sepa-
ration coefficient. However, as is evident from the exper-
iments with plasma in the crossed BE × fields, the rate
of rotation vφ is limited by the critical velocity vс.
2. LIMITATION OF PLASMA ROTATIONAL
VELOCITY
The notion of the critical ionization velocity (CIV)
was first introduced by H. Alfven as a part of his theory
of solar system evolution [16]. Alfven has postulated a
strong interaction between the plasma in the magnetic
field and the neutral gas, which results in the ionization
of neutral atoms as the relative velocity between the
plasma and the neutral gas exceeds the critical ioniza-
tion velocity vс:
n
i
c m
ev φ2
= , (3)
where iφ is the ionization potential, mn is the mass of
the neutral atom or the molecule. The CIV hypothesis
was first tested with experiment in the device known as
a homopolar device [17], where the neutral gas and
plasma filled in the space between two cylinders. Fur-
ther experimental studies were carried out in space and
laboratory environments [18, 19]. In a laboratory envi-
ronment, a great number of experiments were performed
in electric discharges with crossed E×B fields for dif-
ferent conditions [18 - 21], including such as the dis-
charge gap geometry; the neutral gas pressure; the kind
of gas; magnetic field, discharge current, plasma density
values. The studies have shown that the experimentally
observed rotational velocity is limited within 50% of vс
given by formula (1). Fig. 1 shows the vс values calcu-
lated by eq. (1) versus the atomic number of the ele-
ments. Table 1 lists the calculated vс values for the UO2
mailto:Ykovtun@kipt.kharkov.ua
ISSN 1562-6016. ВАНТ. 2015. №4(98) 44
molecule and its dissociation products. The estimation
shows that at T = 2 eV, vφ = 2.2·103 m/s (equal to vс for
U), Δm=25 and Δm=50 the separation coefficient α0 is
equal to 1.6 and 2.58, respectively. As is obvious, the
limitation of the plasma rotational velocity may substan-
tially decrease the separating capacities of rotating-
plasma devices.
Fig. 1. Critical ionization velocities of the elements.
(Atomic weights and ionization potentials of elements
with atomic numbers 1 to 99 are taken from [22], with
100 to 104 – from [23], ionization potential At [24])
When postulating the CIV, Alfven has indicated two
necessary conditions: i) presence of plasma in the mag-
netic field, and ii) neutral gas presence. In his review
[18], Brenning has summed up the results of CIV phe-
nomenon studies over two empirical criteria, the fulfill-
ment of which leads to the CIV.
Table 1
Gas Spe-
cies
Atomic (molecular)
weight, amu
vс, m/s
O 16 12.8·103
O2 32 8.5·103
U 238 2.2·103
UO 254 2.06·103
UO2 270 1.96·103
The first criterion that characterizes the desired
magnetic field value is the Alfven Mach number [18]:
2/1
0
2
2
00
2
2
==
µB
VNm
V
VM ii
A
A
, (4)
where ( ) 2/1
0 iiA NmBV µ= is the Alfven velocity,
Ni – ion density; mi – ion mass; μ0 – magnetic constant;
B – magnetic induction; V0 – velocity. The analysis of
the experimental results, carried out in [18], has shown
that the CIV is observed in strong magnetic fields
(VA > 10 V0), while in the range from VA=V0 up to
VA =10 V0 the CIV be observed, but not always. In weak
magnetic fields at VA < V0 the CIV is virtually never ob-
served. As indicated in [18], in terms of the magnetic
field, the value of VA > 3 V0 (VA > 3 vс) may be consid-
ered to be a sufficient condition for the CIV. From the
above it follows that 1 ≥ MA. For example, for the ura-
nium plasma of density Ni = 1018…1020 m-3 at the mag-
netic field inductions B > 5·10-3 T (for 1018 m-3) and
B > 0.05 T (for 1020 m-3), the condition VA > 3 vс will be
fulfilled. In the magnetoplasma devices with crossed
E×B fields under development, the expected magnetic
field value generally exceeds the above-estimated mag-
netic field induction values. So, the magnetic field crite-
rion for the CIV in the magnetoplasma devices will be in
many cases fulfilled.
The second criterion characterizing the required neu-
tral gas density is the Townsend criterion [18]:
maxee
c
n V
dzN
σ
ν
∫ > , (5)
where Nn is the density of neutral atoms (molecules);
Ve – electron velocity; σe – electron-impact ionization
cross section; <σeVe>max = Ke,max – maximum rate con-
stant of electron-impact ionization. In accordance with
the data of ref. [25], taking the Ke,max values to be
3.3·10-13 m3/s for U, 3.6·10-13 m3/s for UO,
3.8·10-13 m3/s for UO2, we obtain, respectively,
vс/Ke,max ≈ 6.7·1015 m-2 (U), 5.7·1015 m-2 (UO),
5.2·1015 m-2 (UO2). For the O2 molecule, we have
vс/Ke,max ≈ 5.7·1016 m-2 at Ke,max ≈ 1.5·10-13 m3/s [26],
this being an order of magnitude higher than the esti-
mated values for uranium and its oxides. Correspond-
ingly, for the monatomic O at Ke,max ≈ 7.9·10-14 m3/s
[27] we have vс/Ke,max ≈ 1.6·1017 m-2. Naturally, the
Ke,max values taken for the estimations may differ by or-
der of magnitude from the Ke,max value under real exper-
iment conditions. Thus, the vс/Ke,max value may vary in a
rather wide range.
In completely ionized plasma, the CIV effect will not
be observed. However, in laboratory conditions the
plasma is always bounded, and its interaction with the
surface will result in the production of neutral atoms,
e.g., in the surfaces of the vacuum chamber. As a result,
the rotational velocity will be limited to vс. In the mag-
netoplasma devices, the mass separation of substance
calls for a constant supply of the feed stock to the plas-
ma volume; that will eventually lead to the CIV and to
the velocity vc limitation. In refs. [28 - 30], Lehnert has
put forward several ideas as to the possibility of increas-
ing the rate limit of plasma rotation. One of his pro-
posals was confirmed experimentally. In the magnetic
field of mirror configuration with limitation of plasma
rotation velocity in the chamber ends vφ = vс, giving due
consideration to isorotation [28], the maximum rotational
velocity in the center body section (middle part) will be
described by the expression (see [21]):
2/1
max Rvv c= , (6)
where R is the mirror ratio. As is seen from eq. (6), the
maximum rotational velocity can be increased by a fac-
tor of R1/2. So, the introduction of the substance to be
separated to the magnetoplasma device in the region be-
hind the mirrors, where vφ will be limited to vc, will make
it possible to increase the rate limit of plasma rotation in
the middle part. However, as estimations show [12], a
substantial increase is possible at high mirror ratios.
3. LIMITATION OF MULTICOMPONENT
PLASMA ROTATIONAL VELOCITY
The CIV phenomenon was investigated by experi-
ment not only in molecular and atomic gases, but in
their mixtures, too [18, 19, 31]. Besides, the CIV was
observed in the gas-metal plasma produced in the pulsed
magnetron discharge, where the metal component en-
tered the discharge due to sputtering of the cathode ma-
terial [32, 33].
ISSN 1562-6016. ВАНТ. 2015. №4(98) 45
Based on eq. (3), the authors of ref. [31] have de-
rived a semiempirical relation for a two-component gas
mixture:
( )( )
( ) B
ni
A
ni
B
ii
A
ii
c mm
eev
αα
φαφα
−+
−+
=
1
12* , (7)
where B
n
A
n mm , and B
i
A
i φφ , denote, respectively, the
mass of a neutral atom or a molecule of species A and B,
and their ionization potentials; αi is the fractional ion
production rate of component A equal to αi = (vi
A/ vi
A+
vi
B); vi
A and vi
B – ionization frequency of particles of
species A and B, respectively. Since vi
A = Nn
A Ke
A (vi
B =
Nn
B Ke
B), then at Ke
A = Ke
B the fractional ion production
rate αi will take on the form αi = (Nn
A / Nn
A + Nn
B). The
comparison in [31] between the calculated and experi-
mentally measured vc
* values for a number of gas mix-
tures has shown in some cases a satisfactory agreement
between the experimental data and the values calculated
by formula (7). In refs. [12, 32], evaluations of vc
* were
made for a number of gas-metal mixtures. We give here
the vc* estimates for the case of UO2 dissociation into
atoms and molecules. For complete dissociation of the
UO2 molecule into 2O and U, we obtain αi = 0.667
(Ke
O= Ke
U) and αi = 0.324 (Ke
O ≈ 7.9·10-14 m3/s, Ke
U ≈
3.3·10-13 m3/s), respectively, vс
* = 4.87·103 m/s and
3.15·103 m/s. For the case of O2 and U, we obtain αi =
0.5 ( 2O
eK = Ke
U) and αi = 0.313 ( 2O
eK ≈ 1.5·10-13 m3/s,
Ke
U ≈ 3.3·10-13 m3/s), respectively, and hence vс
* =
3.6·103 and 2.98·103 m/s. For O and UO we obtain αi =
0.5 (Ke
O= Ke
UO) and αi = 0.18 (Ke
O ≈ 7.9·10-14 m3/s, Ke
UO
≈ 3.6·10-13 m3/s), respectively, and hence vс
* = 3.7·103
and 2.54·103 m/s.
A somewhat different approach to the CIV problem
in the multicomponent mixture has been considered in
[34], according to which the CIV may be observed on
condition that the following energy equilibrium equa-
tion is fulfilled:
( )[ ]
0
21
,
,
2
0,, ≥
−
=∆
∑
∑
ji
jijnji eVm
E
ν
φν , (8)
where
ji,φ , mn,j, vi,j are, respectively, the ionization po-
tential, the neutral atom (molecule) mass, and the ioni-
zation frequency of the j-th component in the mixture.
At the electron-impact ionization cross-section σe,max for
all the mixture components, eq. (8) is asymptotically
reduced to the form [34]:
jn
j
j
ji
j
j
mx
ex
v
,
,2
∑
∑
=∞
φ
, (9)
where xj is the mole fraction of the component j. For the
two-component mixture eq. (9) is similar to eq. (7) at
Ke
A = Ke
B. To estimate v∞ for the multicomponent mix-
ture, we put the temperature of UO2 to be 3500 K, and
in this case, according to the data of ref. [35], the vapor
composition would be: x = 0.59782 (UO2);
x = 8.30306·10-4 (O2); x = 0.36284 (UO3); x = 0.00922 (UO);
x = 2.10898·10-5 (U); x = 0.02927 (O). The estimation
gives v∞ = 2.32·103 m/s, this being close to the vс value
for U (see Table 1).
It should be noted that in the case of multicompo-
nent mixtures, the criteria required for the CIV occur-
rence should also take into account the multicomponent
composition. For the two-component plasma, the crite-
rion VA > 3 vс may have the form VA > 3 vс
*, and, corre-
spondingly, for the multicomponent mixture we have
VA > 3 v∞. However, in this case there is some uncertain-
ty in the choice of the VA value. For example,
at Ni = 1018 m-3 and B = 5·10-3 T the Alfven velocity is
equal to 7.07·103 m/s and 2.7·104 m/s for U and O, re-
spectively. As a result, at vс
* = 4.87·103 m/s (2O and U)
and Ni = 1018 m-3, the condition VA > 3 vс
* is fulfilled at
B > 1·10-2 T (Alfven velocity for U) and B > 2.7·10-3 T
(Alfven velocity for O). According to ref. [36], in case
of several ion species in the plasma, the Alfven wave
has two modes: R – the right-hand circularly polarized
mode, and L – left-hand circularly polarized mode. At
frequencies ω << Ω2, where Ω2 is the cyclotron frequen-
cy of the large-mass ion, the dispersion relationship is
written as zAT kV≈ω . Correspondingly, the Alfven ve-
locity is equal to ( )12
1 1 ρρ+= AAT VV , where VA
1 is the
Alfven velocity of the smaller-mass component, ρ1 and
ρ2 are the respective densities of the components of
lower and higher masses, m1<m2. In view of the above,
the criterion VA > 3 vс
* can be represented as VAT > 3 vс
*.
Taking vс
* = 4.87·103 m/s (2O and U) and Ni = 1018 m-3,
the condition VAT > 3 vс
* will be fulfilled at the magnetic
induction B > 6.4·10-3 T, this being somewhat higher
than for U (B > 5·10-3 T). In the case of the two-
component (multicomponent) plasma, the Townsend
criterion will be written as eff
ec K max,
*ν ( eff
eK max,∞ν ), where
eff
eK max, is the maximum effective electron-impact ioniza-
tion rate constant of the mixture. The estimation of this
criterion gives eff
ec K max,
*ν ≈ 1.9·1016 m-2 (vс
* = 3.15·103 m/s)
for the two-component mixture (2O, U), and
eff
eK max,∞ν ≈ 6.8·1015 m-2 (v∞ = 2.32·103 m/s) for the mul-
ticomponent mixture, which is close in value to vс/Ke,max
≈ 6.7·1015 m-2 for U.
4. EXPERIMENTAL SETUP
The rotational velocity of the gas-metal plasma in
crossed E×B fields was investigated by experiment at
the MAKET setup [10]. The setup provides a high-
current pulsed reflective discharge in the magnetic field
of mirror configuration, R=1.25. The detailed descrip-
tion of electrophysical parameters of both the setup and
the discharge can be found in refs. [10 - 12]. The gas-
metal plasma was produced in the working environ-
ments of gases (H2, Ar, 88.9% Kr-7% Xe-4% N2-0.1% O2)
and the sputtered cathode material (Ti). The discharge
resulted in the production of a dense
(Ne ≤ 2·1014 cm-3), highly ionized (≤ 100%) gas-metal
plasma with Ti amounting to 40…50% [12]. The results
of the investigations on the gas-metal plasma parame-
ters have been summarized in [12].
The rotation of multicomponent gas-metal plasma
was investigated by the method of microwave correla-
tion reflectometry (MCR) [11, 37]. The MCR technique
rests on the definition of the autocorrelation function
(ACF) and cross-correlation function (CCF) of two po-
loidally spaced microwave signals reflected from the
layer of same-density plasma. The microwaves are re-
flected from the plasma layer of critical density Ncr, i.e.,
at the plasma electron density Ne≥Ncr. So, unlike the op-
ISSN 1562-6016. ВАНТ. 2015. №4(98) 46
tical Doppler spectrometry, the MCR method can be
used to determine the rotational velocity vφ of the re-
flecting layer having Ne≥Ncr. To a first approximation,
its value is found to be ≈ Er/Bz [11]. The plasma rota-
tional velocity for the case of circular symmetry profile
is given by the relation vφ = ωφ rcr = ∆φ r/∆t, where ∆φ
is the angular distance between the reflected-wave re-
ceiving points; rcr is the reflecting layer position deter-
mined from the phase shift of the reflected wave; ∆t is
either the time shift of the CCF maximum, or the ACF
period, ωφ is the angular rate of rotation. Some possible
errors of rotational velocity measurements by the MCR
technique were analyzed in ref. [37]. According to the
estimations in [37], the measurement errors may vary
from several percent’s up to 30% and more.
Simultaneously with the reflectometry measure-
ments, the maximum Nc = Ncr and the average density
were also measured by means of a microwave interfer-
ometer that permitted the determination of the time in-
terval of the existence of the critical density layer.
5. EXPERIMENTAL RESULTS
AND DISCUSSION
The use of the MCR technique has made it possible
to measure the plasma rotational velocity in the reflec-
tive discharge in time. The plasma dynamics in time can
be arbitrarily divided into several stages [11]. At the first
stage, plasma layers with Ne=Ncr, of radius equal to the
sensing wavelength r = λ, are formed; at the second stage
the radial dimensions of the plasma layers with Ne=Ncr
increase up to a certain value, r = rmax, upon reaching
which the radius of the layers remains practically the
same for the time Δt (~ hundreds of μs); at the third stage
the radial dimensions of plasma layers start decreasing,
the density falls off and the plasma decays. It has been
demonstrated experimentally in [11] that the increase in B
caused the increase in rmax, ωφ, and, correspondingly, the
plasma rotational velocity vφ in the reflective discharge.
The measured data on the rotational velocity vφ of
the gas-metal plasma produced in the reflective dis-
charge are generalized in Fig. 2. The data spread is indi-
cated for sampling from n>5 measurements of the max-
imum rate of rotation; for the n<5 sampling the mean
values of ϕv are indicated. The solid and dotted lines in
Fig. 2 also show the vc values for the elements entering
into the composition of the gas-metal plasma. From the
data given in Fig. 2 it follows: first, the rotational veloc-
ity vφ is dependent on the magnetic induction value, at
least, up to B≈0.15 T (see Figs. 2,b,c); secondly, vφ is
dependent on the atomic weight of ions present in the
plasma (see Figs. 2,b,c). As mentioned earlier in [10,
11], the dependence of vφ on B and mi is qualitatively
described by the one-fluid MHD plasma model. For ex-
ample, the estimation in [10] for pure H2 gives
vφ > 105 m/s, which is not observed in the experiment
(see Fig. 2,a), whereas for the 50%H2+50%Ti mixture
the estimate vφ = (2.8…5.6)·104 m/s is close to the ex-
perimental value (see Fig. 2,a).
We now consider the limitation of the plasma rota-
tional velocity. As is seen from Fig. 2, at the magnetic
induction B less than ≈ 0.1 T the rotational velocity is
vφ< vс(Ti), but with the B increase up to B > 0.1 T, the
rotational velocity becomes vφ> vс (Ti).
Fig. 2. Maximum rotational velocity of the plasma layer
with Ne ≥ 1.7∙1019 m-3 versus magnetic induction:
a – H2+Ti, ● – p = 0,267 Pa, Udis. = 3.6 kV
(Imax ≈ 1.66 kA); b – Ar + Ti : ● – p = 0,8 Pa,
Udis. = 3.8 kV (Imax ≈ 1,7 kA); ▲ – p = 0.133 Pa,
Udis. = 3,2 kV (Imax ≈ 1.53 kA);
c – (Kr - Xe - N2 - O2)+ Ti: ● – p = 0.8 Pa,
Udis. = 3.8 kV (Imax ≈ 1.7 kA); ▲ – p = 0.133 Pa,
Udis. = 3.4 kV (Imax ≈ 1,56 kA)
Actually, an excess of the critical velocity takes
place, but since in the given case the multicomponent
gas-metal plasma is investigated, a more detailed con-
sideration will be given here to the rotational velocity
limitation. Table 2 lists the vc values calculated for the
elements entering into the plasma composition, and also
the vс
* (v∞) values for their mixtures. As is seen from
Table 2, the condition VA > 3 vс (VAT > 3 vс
*) is fulfilled
at B > 0.02…0.03 T (1.7·1019 m-3), and hence, in the
given experiments, too (see Fig. 2). At given experi-
mental conditions, the neutral atoms come to the plasma
in longitudinal and radial directions relative to the plas-
ma column. In the process, Ti atoms come to the plasma
in the longitudinal direction. The calculations carried
out in [12] have shown the content of neutral titanium
atoms in the basic plasma column to be insignificant.
Both, the working gas atoms and the atoms (molecules)
desorbed from the discharge chamber wall come to the
plasma radially; their quantity can amount to several
percent’s [10].
The mass separation of the neutral component takes
place in the weakly ionized rotating plasma in the same
manner as in gas centrifuges [14, 29]. In this case, ac-
cording to [29], the radial concentration of the neutral
particles can be calculated from the relation:
=
kT
rm
NrN n
nn 2
exp)0()(
22
ϕω . (10)
In view of this, the concentration of neutral particles
and the percentage of the particles coming radially into
the plasma may substantially differ from the initial val-
ISSN 1562-6016. ВАНТ. 2015. №4(98) 47
ue. For illustration, Fig. 3 shows the radial distribution
of neutral particles calculated by formula (10) as the
Σ
0/ n
p
n NN ratio, where p
nN and Σ
0nN are, respectively, the
partial and total concentrations of the particles. The cal-
culation was performed for the mixture of
88.9% Kr-7% Xe-4% N2-0.1% O2 at the conditions close
to the ones of gas centrifuges [14]: ωφ = 7·103 rad/s
(vφ = 700 m/s at r=rmax) T = 600 K. So, in this case
for r/rmax = 0.5 the concentration will be
87.35% Kr-2.02% Xe-10.38% N2-0.25% O2, and hence,
v∞ = 5.9·103 m/s will be somewhat higher than at the
initial concentration (see Table 2). At ωφ = 1·104 rad/s
(vφ = 103 m/s at r=rmax) T = 600 K, and with
r/rmax = 0.5, the estimation gives the concentra-
tion 52.54% Kr-0.19% Xe-46.28% N2-0.99% O2, and
accordingly, v∞ ≈ 7·103 m/s. Therefore, this effect
should apparently be taken into account when consider-
ing the limitation of plasma rotational velocity. A more
detailed consideration calls for construction of the mul-
tifluid MHD model with due regard for a variety of
atomic processes occurring in the plasma.
Table 2
Gas Species vс, m/s vс
* (v∞),
m/s
B, T
(V > 3 v)
H 51·103 – 0.029
H2 38·103 – 0.031
Ti 5.2·103 – 0.021
50%H+50%Ti – 8.9·103 0.025
50%H2+50%Ti – 9.2·103 0.026
Ar 8.7·103 – 0.031
50%Ar+50%Ti - 7·103 0.026
Kr 5.7·103 – 0.029
50%Kr+50%Ti – 5.5·103 0.025
Xe 4.2·103 – 0.027
88,9% Kr-7% Xe -
4% N2-0,1% O2
– (5.6·103)
Fig. 3. Radial distribution of neutral particle
concentrations. The dotted lines show the initial
concentration; solid lines are for the concentration
at ωφ = 7·103 rad/s
Summarizing the results, it can be stated the follow-
ing: i) at B>0.1 T the plasma rotational velocity in the
mixtures under consideration is vφ> vс(Ti), this being
evidently due to an insignificant content of neutral Ti in
the plasma column; ii) the rotational velocity in the
H2+Ti plasma does not exceed vc of the H, H2 gas com-
ponents; for the (Kr - Xe - N2 - O2)+ Ti mixture the rota-
tional velocity is no more than 50% of vс(Kr); iii) the
same is the case for Ar + Ti at B ≤ 0.15 T, i.e., we have
vφ < 1.5 vс (Ar), and the excess of this value is apparent-
ly due to the entry of lighter impurities. Thus, the cho-
sen method of metal component delivery to the plasma
permits one to extend the limiting range of plasma rota-
tional velocity.
CONCLUSIONS
We note finally:
1. Consideration has been given to the rotational ve-
locity limitation, including the case of multicomponent
gas-metal plasma, which is related to the critical ioniza-
tion velocity effect. It has been shown that the plasma
rotation velocity limitation can substantially reduce the
separative power of the rotating-plasma devices.
2. Measurements have been made and experimental
findings have been generalized for the rotational velocity
of the gas-metal multicomponent plasma produced in the
reflective discharge. It has been shown that the rotational
velocity of the gas-metal multicomponent plasma corre-
lates with the critical rate of gas component ionization.
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Article received 30.04.2015
КРИТИЧЕСКАЯ СКОРОСТЬ ИОНИЗАЦИИ В ГАЗОМЕТАЛЛИЧЕСКОЙ ПЛАЗМЕ
Ю.В. Ковтун
Рассмотрено ограничение скорости вращения многокомпонентной газо-металлической плазмы и влияние
этого эффекта на разделение по массам во вращающейся плазме. Проведены и обобщены результаты экспе-
риментальных измерений скорости вращения газометаллической многокомпонентной плазмы.
КРИТИЧНА ШВИДКІСТЬ ІОНІЗАЦІЇ B ГАЗОМЕТАЛЕВІЙ ПЛАЗМІ
Ю.В. Ковтун
Розглянуто обмеження швидкості обертання багатокомпонентної газо-металевої плазми і вплив цього
ефекту на розділення за масами в плазмі, що обертається. Проведені і узагальнені результати експеримента-
льних вимірювань швидкості обертання газометалевої багатокомпонентної плазми.
http://vant.kipt.kharkov.ua/CONTENTS/CONTENTS_2014_1.html
http://vant.kipt.kharkov.ua/CONTENTS/CONTENTS_2014_1.html
|
| id | nasplib_isofts_kiev_ua-123456789-112237 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T16:40:37Z |
| publishDate | 2015 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Kovtun, Yu.V. 2017-01-18T20:00:23Z 2017-01-18T20:00:23Z 2015 CIV fenomen in gas-metal plasma / Yu.V. Kovtun // Вопросы атомной науки и техники. — 2015. — № 4. — С. 43-48. — Бібліогр.: 37 назв. — англ. 1562-6016 PACS: 52.80.Sm; 52.35.-g https://nasplib.isofts.kiev.ua/handle/123456789/112237 The paper deals with limitation of the rotational velocity of multicomponent gas-metal plasma, and also, with the effect of this phenomenon on mass separation in the rotating plasma. The measured data on the rotational velocity of the gas-metal multicomponent plasma are presented and analyzed. Розглянуто обмеження швидкості обертання багатокомпонентної газо-металевої плазми і вплив цього ефекту на розділення за масами в плазмі, що обертається. Проведені і узагальнені результати експериментальних вимірювань швидкості обертання газометалевої багатокомпонентної плазми. Рассмотрено ограничение скорости вращения многокомпонентной газо-металлической плазмы и влияние этого эффекта на разделение по массам во вращающейся плазме. Проведены и обобщены результаты экспериментальных измерений скорости вращения газометаллической многокомпонентной плазмы. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Нерелятивистская электроника CIV fenomen in gas-metal plasma Критична швидкість іонізації в газометалевій плазмі Критическая скорость ионизации в газометаллической плазме Article published earlier |
| spellingShingle | CIV fenomen in gas-metal plasma Kovtun, Yu.V. Нерелятивистская электроника |
| title | CIV fenomen in gas-metal plasma |
| title_alt | Критична швидкість іонізації в газометалевій плазмі Критическая скорость ионизации в газометаллической плазме |
| title_full | CIV fenomen in gas-metal plasma |
| title_fullStr | CIV fenomen in gas-metal plasma |
| title_full_unstemmed | CIV fenomen in gas-metal plasma |
| title_short | CIV fenomen in gas-metal plasma |
| title_sort | civ fenomen in gas-metal plasma |
| topic | Нерелятивистская электроника |
| topic_facet | Нерелятивистская электроника |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/112237 |
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