Transportation of QSPA plasma streams in longitudinal magnetic field
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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: | Transportation of QSPA plasma streams in longitudinal magnetic field / V.A. Makhlaj, A.N. Bandura, V.V. Chebotarev, I.E. Garkusha, N.V. Kulik, D.G. Solyakov, V.I. Tereshin, S.A. Trubchaninov, A.V. Tsarenko, H. Wuerz // Вопросы атомной науки и техники. — 2002. — № 4. — С. 129-131. — Бібліогр.: 5 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859612588946489344 |
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| author | Makhlaj, V.A. Bandura, A.N. Chebotarev, V.V. Garkusha, I.E. Kulik, N.V. Solyakov, D.G. Tereshin, V.I. Trubchaninov, S.A. Tsarenko, A.V. Wuerz, H. |
| author_facet | Makhlaj, V.A. Bandura, A.N. Chebotarev, V.V. Garkusha, I.E. Kulik, N.V. Solyakov, D.G. Tereshin, V.I. Trubchaninov, S.A. Tsarenko, A.V. Wuerz, H. |
| citation_txt | Transportation of QSPA plasma streams in longitudinal magnetic field / V.A. Makhlaj, A.N. Bandura, V.V. Chebotarev, I.E. Garkusha, N.V. Kulik, D.G. Solyakov, V.I. Tereshin, S.A. Trubchaninov, A.V. Tsarenko, H. Wuerz // Вопросы атомной науки и техники. — 2002. — № 4. — С. 129-131. — Бібліогр.: 5 назв. — англ. |
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| container_title | Вопросы атомной науки и техники |
| first_indexed | 2025-11-28T15:29:44Z |
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TRANSPORTATION OF QSPA PLASMA STREAMS IN LONGITUDINAL
MAGNETIC FIELD
V.A.Makhlaj, A.N. Bandura, V.V.Chebotarev, I.E.Garkusha, N.V. Kulik, D.G.Solyakov,
V.I.Tereshin, S.A.Trubchaninov, A.V.Tsarenko, H.Wuerz*
Institute of Plasma Physics of the NSC KIPT, 61108 Kharkov, Ukraine
*Forschungszentrum Karlsruhe, IHM, 76021 Karlsruhe, Germany
PACS: 52.25.Xz; 52.30.-q; 52.50.Dg
INTRODUCTION
Plasma stream-magnetic field interaction is one of the
fundamental problems of plasma dynamics, which is of
importance for hot plasma injection into magnetic traps of
different kinds. At the same time powerful magnetized
plasma streams are widely used now for investigations of
hot plasma interaction with solid surfaces simulating
power load conditions in future fusion devices [1-4].
The main aim of this work is analysis of efficiency of
QSPA powerful plasma streams transportation in
longitudinal magnetic field in dependence on operational
mode of accelerator and plasma stream parameters.
EXPERIMENTAL DEVICE
Experiments were carried out in the QSPA Kh-50
device. The full-block powerful quasi-steady-state plasma
accelerator consists of two stages. The first one is used for
plasma production and pre-acceleration. The second stage
(main accelerating channel) is a coaxial system of shaped
active electrodes-transformers with magnetically screened
elements (those elements are current supplied either from
independent power sources or branching partly the
discharge current in self-consistent regime of operation).
The geometry of QSPA accelerating channel is formed
mainly by profile of the cathode. Two types of cathodes
were used in these experiments. The first one is semi-
active cathode of 62 cm in length and with maximum
diameter of 36 cm described in details in [1]. The second
one is new cathode transformer with the length of profiled
part 63 cm and maximum diameter of 40 cm. It profiled
surface is formed with 20 solid strips of 20 mm in width
and 5 mm in thickness. Thus the distance between
cathode and anode in critical section of main accelerating
channel is reduced (Fig.1). Also the distance between the
0,0
0,2
0,4
0,6
0,8
1,0
L 63 cm
Anode
D=36 cm;L=97cm
D=40 cm;L=57cm
R
/R
a
Fig.1. Scheme of QSPA main accelerating channel
with the cathodes of different diameters (D). L -distance
between the nozzles of the input ionization chambers and
profiled part of the cathode; Ra=27,5 см- radius of
anode collector.
nozzles of the input ionization chambers and profiled part
of the cathode transformer is essentially reduced in
experiments with new cathode transformer.
The working gas is hydrogen. The power supply of all
accelerator units comes from the capacitor banks. The
main results were obtained with capacitor voltage of the
main discharge up to 12 kV (total energy about 0.5 MJ).
Plasma streams, generated by QSPA Kh-50 were
injected into magnetic system of 1.6 m in length and 0.44
m in inner diameter consisting of 4 separate magnetic
coils. The first magnetic coil was placed at the distance of
ZS = 1.2 m from accelerator output. The currents in each
coil were specially selected to provide plasma streams
propagation in slowly increasing magnetic field (Fig. 2).
The maximum value of magnetic field B0=0.54 T was
achieved in diagnostic chamber (in the region between 3
and 4 magnetic coils) [4,5].
0 40 80 120 160 200 240 280 320
0,0
0,2
0,4
0,6
0,8
1,0
1,2 4321
Diagnostic vacuum chamber
Plasma stream
B0=0.54 T
B
/B
0
L, cm
Fig. 2. Dependence of normalized vacuum magnetic field,
on the distance from the accelerator output.
EXPERIMENTAL RESULTS
The main parameters of plasma streams (density,
velocity, electron temperature) were measured in the
vicinity of maximum value of a magnetic field for
different operation regimes of plasma accelerator. The
plasma stream velocity was measured by the time-of-
flight of the plasma stream between two magnetic probes,
the electron density in the plasma stream was evaluated
on the basis of Stark broadening of the Hβ spectral line,
radial distributions of the plasma stream energy density
were measured with a movable copper calorimeter, the
power density was calculated on the basis of
measurements of the time dependencies of the plasma
stream density and its velocity. Plasma pressure was
measured by piezoelectric detectors. Electron temperature
Problems of Atomic Science and Technology. 2002. № 4. Series: Plasma Physics (7). P. 129-131 129
was evaluated on the base of measurements of the ratio of
CIII and CII spectral lines intensities.
Time behaviour of some plasma parameters in
diagnostic chamber, obtained with magnetic field B0 =
0.54 T, for both profiles of accelerating channel are
shown in Figs. 3 and 4. The plasma stream parameters for
regime with cathode of 36 cm in diameter were as
follows: the electron density (2-3)×1016 cm-3, maximum
proton energy 200 eV, maximum power density up to 20
MW/cm2, the duration of plasma generation (half-height
width of power density curve) achieved (0.15-0.17) ms.
0 50 100 150 200 250 300 350
0
5
10
15
20
25
P, MW/cm2
V
ne
P
n e,1
016
cm
-3
;V
, 1
06 cm
/s
τ , µ s
Fig.3. Time dependencies of plasma stream parameters:
velocity (v), electron density (n) and power density (P);
regime of QSPA operation with 36 cm cathode.
0 50 100 150 200 250 300 350 400
0
2
4
6
8
P
V
n
P, MW/cm2
n e,
10
16
cm
-3
V
, 1
07 cm
/s
τ , µ s
80
60
40
20
0
Fig.4. Time dependencies of plasma stream parameters:
velocity (v), electron density (n) and power density (P);
regime of QSPA operation with new geometry of
accelerating channel
Variation of the accelerating channel profile and
distance between accelerator stages results to difference
in temporal evolution of plasma density. Average density
((2-4)×1016cm-3) is not changed, but maximum value is
increased up to 7×1016 cm-3. While the maximum value
(about 2×107 cm/s) and time dependence of plasma
stream velocity remains unchanged.
The peak power density of plasma stream increased up
to 45 MW/cm2. The total energy content in the plasma
stream passing through the magnetic field increased from
56 kJ to 100 kJ.
The plasma stream pressure in magnetic field
increased also. Typical signal of the plasma stream
pressure for new geometry of accelerating channel is
shown in Fig.5. The plasma pressure in near axis region
in achieves P≈16 Bar and has peaked character. The
plasma pressure time behavior correlates with temporal
evolution of plasma density. It is necessary to note that
the maximal pressure of the plasma stream, generated by
QSPA with cathode of 36 cm in diameter, was not more
than 3 Bar.
0 50 100 150 200 250 300 350 400
0
4
8
12
16
20
P
∆ B
0
0,2
0,4
0,6
0,8
1
P,
B
ar
τ , µ s
∆ B/B0
Fig.5. Time dependencies of plasma pressure (P) and
displaced magnetic field (∆B), normalized by the value of
vacuum magnetic field (B0=0.54 T), in diagnostic vacuum
chamber.
Injection of powerful plasma streams into magnetic
field is accompanied by magnetic field displacement out
of plasma. The magnetic field displaced by plasma ∆B
was measured by magnetic probes located in different
cross- sections along the magnetic system. The value of a
magnetic field in plasma Bpl was found as a difference B0
- ∆B, where B0 is vacuum a magnetic field
The Bpl value in incoming plasma stream depends on
the distance from input of magnetic system. For example,
in the region between first and second magnetic coils
(Z=1.55 m from a accelerator output) the full
displacement of magnetic field by incoming plasma
stream was observed for plasma stream with the power
density of 45 MW/cm2. While the value of displaced
magnetic field in diagnostic cross-section is of order ∆
B/B0∼ 0.7 (for time moment corresponding to maximum
of power density). The signal of magnetic probe which is
located at the region of homogeneous magnetic field
(Z=2.3 m from a accelerator output) was shown in the
Fig.(5). The temporal behavior of the signal of displaced
magnetic field is not differs from the temporal
dependence of the plasma pressure.
For a detailed investigation of plasma stream
magnetization the radial distributions of magnetic field in
plasma stream were measured at the different distances
from accelerator. The radial profiles of relative values of
magnetic field in plasma (Bpl/B0=(B0 - ∆B)/ B0)) for both
regimes of QSPA operation are shown in Figs.6 and 7.
130
0 2 4 6 8 10 12 14 16
0,0
0,2
0,4
0,6
0,8
1,0
(B
0-∆
B)
/B
z0
R, cm
Z=1.55 m; B0z=0.315 T
Z=1.95 m; B0z=0.46 T
Z=2.3 m; B0z=0.54 T
Fig.6. Radial distributions of magnetic field in plasma
stream normalized by vacuum magnetic field value (B0) at
the different distances (Z) from accelerator output, in
moment of time corresponding to maximum of power
density; regime of QSPA operation with 36 cm cathode
0 2 4 6 8 10 12 14 16 18 20
0,0
0,2
0,4
0,6
0,8
1,0
1,2
(B
0-∆
B)
/B
0
R, cm
Z=1.95m; B0z=0.46 T
Z=2.3m; B0z=0.54 T
Fig.7. Radial distributions of magnetic field in plasma
stream normalized by vacuum magnetic field value (B0) at
the different distances (Z) from accelerator output.
Regime of QSPA operation with new cathode.
As follows from these pictures, propagation of plasma
stream along the magnetic system is accompanied by
magnetization of plasma. The efficiency of magnetic field
penetration into plasma is in dependence on incident
plasma parameters. For instance, for plasma stream with
power density equal to 20 MW/cm2 about 90 % of
external magnetic field penetrates into the plasma stream.
Meanwhile, with increase of a power density of incoming
plasma stream up to 45 MW/cm2 about 30% of external
magnetic field penetrates into plasma stream.
At the same time a decrease of plasma stream
diameter with the distance along magnetic system was
observed. Plasma stream radius was defined as the radius
of plasma boundary where ∆Bz = 0. Despite of
sufficiently different plasma parameters for two regimes
of operation, one can see from Figs.6 and 7 that plasma
stream radii are more or less comparable and equal to 8-
10 cm at the position of diagnostic chamber.
An ordinary pressure balance equation on the plasma
boundary was used for estimation of the transversal
plasma pressure. It was found that in the case of high
level of plasma magnetization the average plasma
pressure >+×> = << )TT(nP ie was equal (1.4-1,6)х1017
eV/см-3 while for low magnetization ‹P›=(2-5)×1017
eV/см3. Average β value, calculated on the basis of
plasma pressure and vacuum magnetic field β = 8πP/B0
2
is about 0.4-0.6 for plasma stream with higher peak
density, and 0.1-0.2 for the regime with lower plasma
density. This indicates more effective plasma
magnetisation in the latter case.
Electron temperature was calculated from the ratio of
intensities of impurity lines (СII and С III) and from time
of magnetic field diffusion into plasma τD=4πR2σ0/c2(1+(
ωBeτei)2). Here R-radius of plasma, σ0- Spitzer
conductivity of plasma, с- velocity of light, ωBeτei- the
Hall parameter. Obtained values of Te= (2-4) eV by both
methods are in satisfactory agreement with each other.
Temperature of ions Тi was determined from the Doppler
broadening of lines СII and NII. The ion temperature
value was at the level of Тi= (10-20) eV. This result is in
good agreement with plasma temperature estimation from
the pressure balance equation.
CONCLUSIONS
Variation of the accelerating channel profile leads to
difference in temporal evolution of plasma stream density.
Maximum value of plasma density is increased up to 7×
1016 cm-3. The peak power density of plasma stream
achieved 45 MW/cm2. The efficiency of transportation of
plasma streams in magnetic field is also essentially
improved. The pressure of plasma stream propagating in
magnetic field is increased up to 16-18 Bar. Average β is
at the level of (0.4-0.6).
It is important to note that for providing comparison
of accelerator operation for both profiles of accelerating
channel the working regime parameters of first stage of
accelerator remain unchanged. Since accelerating rate for
new geometry of main accelerating channel is higher,
some mismatch of accelerator stages is occurred. As
result half-height width of power density curve is
decreased. Nevertheless total energy content in the plasma
stream passing through the magnetic field exceeded 100
kJ even in these nonoptimal conditions.
Thus modernization of a plasma accelerator allowed
to increase at least in twice the plasma stream power
density as well as the total energy content in the plasma
stream being magnetized in longitudinal magnetic field.
Further optimization of first stage of accelerator is
necessary to achieve compatible plasma inflow to the
main accelerating channel.
REFERENCES:
[1] V.I.Tereshin, Plasma Phys. Control. Fusion 37, 1995
p.177
[2] N. Arkhipov, V. Bakhtin et al. // Fusion technology,
vol. 32, 1997, p. 45-74.
[3] S.I. Ananin, V.M. Astashynski et al. Proc. of 29th EPS
Conf. On Plasma Physics and Controlled Fusion. ECA
Vol. 26 B, P-5.049 (2002)
[4] V.I.Tereshin, V.V.Chebotarev et al, Transactions of
fusion technology, v.35 No 1T, 1999, p.248-252.
[5] V.I.Tereshin, V.V.Chebotarev et al., Brazilian Journal
of Physics, v.32, No1, 2002. p165-171.
131
*Forschungszentrum Karlsruhe, IHM, 76021 Karlsruhe, Germany
Conclusions
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| id | nasplib_isofts_kiev_ua-123456789-80295 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-11-28T15:29:44Z |
| publishDate | 2002 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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| spelling | Makhlaj, V.A. Bandura, A.N. Chebotarev, V.V. Garkusha, I.E. Kulik, N.V. Solyakov, D.G. Tereshin, V.I. Trubchaninov, S.A. Tsarenko, A.V. Wuerz, H. 2015-04-14T17:13:20Z 2015-04-14T17:13:20Z 2002 Transportation of QSPA plasma streams in longitudinal magnetic field / V.A. Makhlaj, A.N. Bandura, V.V. Chebotarev, I.E. Garkusha, N.V. Kulik, D.G. Solyakov, V.I. Tereshin, S.A. Trubchaninov, A.V. Tsarenko, H. Wuerz // Вопросы атомной науки и техники. — 2002. — № 4. — С. 129-131. — Бібліогр.: 5 назв. — англ. 1562-6016 PACS: 52.25.Xz; 52.30.-q; 52.50.Dg https://nasplib.isofts.kiev.ua/handle/123456789/80295 en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Plasma dynamics and plasma-wall interaction Transportation of QSPA plasma streams in longitudinal magnetic field Article published earlier |
| spellingShingle | Transportation of QSPA plasma streams in longitudinal magnetic field Makhlaj, V.A. Bandura, A.N. Chebotarev, V.V. Garkusha, I.E. Kulik, N.V. Solyakov, D.G. Tereshin, V.I. Trubchaninov, S.A. Tsarenko, A.V. Wuerz, H. Plasma dynamics and plasma-wall interaction |
| title | Transportation of QSPA plasma streams in longitudinal magnetic field |
| title_full | Transportation of QSPA plasma streams in longitudinal magnetic field |
| title_fullStr | Transportation of QSPA plasma streams in longitudinal magnetic field |
| title_full_unstemmed | Transportation of QSPA plasma streams in longitudinal magnetic field |
| title_short | Transportation of QSPA plasma streams in longitudinal magnetic field |
| title_sort | transportation of qspa plasma streams in longitudinal magnetic field |
| topic | Plasma dynamics and plasma-wall interaction |
| topic_facet | Plasma dynamics and plasma-wall interaction |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/80295 |
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