The pinch effect in microwave resonant streamer discharge
The work is devoted to experimental and theoretic study of a streamer discharge in the focus of microwave radiation in the open resonator. The observations show that if a gas pressure more than 0.1 atmosphere the single streamer discharge appears in the focus. When the resonant length of the streame...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2000
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| Цитувати: | The pinch effect in microwave resonant streamer discharge / I.I. Esakov, L.P. Grachev and K. V. Khodataev // Вопросы атомной науки и техники. — 2000. — № 3. — С. 138-140. — Бібліогр.: 9 назв. — англ. |
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irk-123456789-824022015-05-30T03:01:56Z The pinch effect in microwave resonant streamer discharge Esakov, I.I. Grachev, L.P. Khodataev, K. V. Low Temperature Plasma and Plasma Technologies The work is devoted to experimental and theoretic study of a streamer discharge in the focus of microwave radiation in the open resonator. The observations show that if a gas pressure more than 0.1 atmosphere the single streamer discharge appears in the focus. When the resonant length of the streamer is achieved, the all energy storage of resonator is adsorbed by the streamer with very high efficiency. The simulations show that if gas pressure is quite enough the pinch force of the current inducted in the resonant streamer compresses the discharge plasma. One can hop that the forecasted high plasma parameters can be achieved and be applied not only for design of a gamma or neutron sources but for creation of a fusion reactor 2000 Article The pinch effect in microwave resonant streamer discharge / I.I. Esakov, L.P. Grachev and K. V. Khodataev // Вопросы атомной науки и техники. — 2000. — № 3. — С. 138-140. — Бібліогр.: 9 назв. — англ. 1562-6016 http://dspace.nbuv.gov.ua/handle/123456789/82402 533.9 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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English |
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Low Temperature Plasma and Plasma Technologies Low Temperature Plasma and Plasma Technologies |
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Low Temperature Plasma and Plasma Technologies Low Temperature Plasma and Plasma Technologies Esakov, I.I. Grachev, L.P. Khodataev, K. V. The pinch effect in microwave resonant streamer discharge Вопросы атомной науки и техники |
| description |
The work is devoted to experimental and theoretic study of a streamer discharge in the focus of microwave radiation in the open resonator. The observations show that if a gas pressure more than 0.1 atmosphere the single streamer discharge appears in the focus. When the resonant length of the streamer is achieved, the all energy storage of resonator is adsorbed by the streamer with very high efficiency. The simulations show that if gas pressure is quite enough the pinch force of the current inducted in the resonant streamer compresses the discharge plasma. One can hop that the forecasted high plasma parameters can be achieved and be applied not only for design of a gamma or neutron sources but for creation of a fusion reactor |
| format |
Article |
| author |
Esakov, I.I. Grachev, L.P. Khodataev, K. V. |
| author_facet |
Esakov, I.I. Grachev, L.P. Khodataev, K. V. |
| author_sort |
Esakov, I.I. |
| title |
The pinch effect in microwave resonant streamer discharge |
| title_short |
The pinch effect in microwave resonant streamer discharge |
| title_full |
The pinch effect in microwave resonant streamer discharge |
| title_fullStr |
The pinch effect in microwave resonant streamer discharge |
| title_full_unstemmed |
The pinch effect in microwave resonant streamer discharge |
| title_sort |
pinch effect in microwave resonant streamer discharge |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2000 |
| topic_facet |
Low Temperature Plasma and Plasma Technologies |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/82402 |
| citation_txt |
The pinch effect in microwave resonant streamer discharge / I.I. Esakov, L.P. Grachev and K. V. Khodataev // Вопросы атомной науки и техники. — 2000. — № 3. — С. 138-140. — Бібліогр.: 9 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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| first_indexed |
2025-07-06T08:54:21Z |
| last_indexed |
2025-07-06T08:54:21Z |
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1836887113276063744 |
| fulltext |
UDC 533.9
Problems of Atomic Science and Technology. 2000. N 3. Series: Plasma Physics (5). p. 138-140 138
THE PINCH EFFECT
IN MICROWAVE RESONANT STREAMER DISCHARGE
Igor I. Esakov, Lev P. Grachev and Kirill V. Khodataev
Moscow Radiotechnical Institute RAS, Russia
khodata@online.ru Fax: (095) 314-1053
The work is devoted to experimental and theoretic study of a streamer discharge in the focus of microwave
radiation in the open resonator. The observations show that if a gas pressure more than 0.1 atmosphere the single
streamer discharge appears in the focus. When the resonant length of the streamer is achieved, the all energy storage
of resonator is adsorbed by the streamer with very high efficiency. The simulations show that if gas pressure is quite
enough the pinch force of the current inducted in the resonant streamer compresses the discharge plasma. One can
hop that the forecasted high plasma parameters can be achieved and be applied not only for design of a gamma or
neutron sources but for creation of a fusion reactor
Introduction
The electrodeless microwave discharges in a gas of
high pressure demand appropriately high level of the
electromagnetic field. For example the normal pressure
air breakdown needs the microwave radiation specific
energy flow 1 MW/cm2.The high amplitude microwave
field can be achieved in a focus of a radiation beam.
Even in the case when the focusing system has a short
focus so that the area of the focus cross section equals
approximately wave length squared the needed
generator power for 10 cm wave length is 100 MW with
pulse duration more than few microseconds. It is
difficult to provide so high power during some
microsecond in a laboratory. But the field level needed
for breakdown of a gas with high pressure (more than
some atmosphere) can be achieved in a resonator
because the resonator quality can be very high.
The open resonator created by two spherical copper
mirrors was used in our experiments [1]. The resonator
allows us to create a discharge in air and other gases
with pressure which does exceed one atmosphere. A
high-pressure discharge in the focused traveling-wave
radiation beam represents a net of the thin hot strings
(connected among themselves), consistently appeared
one from another (of course if the radiation intensity in
the focus and pulse duration are enough). But the
discharge in the resonator represents the single hot
string. The string is a single because the stored energy
in resonator is finite. Usually the all stored energy is
adsorbed by one resonant streamer. The length of
developed streamer is close to half of wave length. It is
electrodynamic resonance. Appropriately the high
current is inducted in the streamer. The inducted current
heats the streamer plasma up to high temperature
because the streamer diameter is very small. The
heating up specific power related to the gas density is
proportional to gas pressure because the breakdown
electric field (and inducted current) is proportional to
one. If the gas density is quite enough the magnetic
pressure force of inducted current is able to compress
the plasma in streamer. The pinch instability in central
part of the resonant streamer can cause strong local
dissipation of energy in the pinch region. The attributes
of this phenomena are observed in our experiments as a
bright core. The courageous estimations clearly show
that very high temperature (up to thermonuclear
temperature) can be achieved in the resonant streamer if
the gas pressure is more than some decades of
atmosphere [2]. We will show the key experimental and
simulation results and discuss extrapolating estimations
based on simplified theory of a resonant streamer
discharge.
Experimental data
The scheme of experimental installation is shown on
Fig.1.
z
R
→
Ε
5
4
6
1 2 3
Fig.1 The scheme of the experimental installation. 1 –
magnetron generator, 2 – circulator, 3 – lens, 4 –
spherical mirrors of the open resonator, 5 -quarts retort,
6 – field prob.
The open resonator 4 consists from two spherical
copper mirrors displaced along common axis z. The
curve radius as, diameter 2am and distance between them
L equal 35 cm, 55 cm and 51.7 cm correspondingly.
The quarts retort 5 fulfilled by a gas is displaced in the
center of resonator. The retort represents the quarts long
tube with the inner diameter equaled to 8 cm and has the
optical windows on the ends. The gas pressure in the
retort can be varied from small value up to several
atmosphere. The magnetron generator feed the resonator
through wave guide with circulator 2 and reactive
attenuator 3 with the feeding coefficient ~10-3. The
output power of generator is 10 MW with pulse duration
40 µs. Wave length of radiation λ is 8.9 cm. The
repetition frequency is less than 1 Hz. The amplitude
envelop of field in resonator is monitored by the probe
6.
139
The application of the resonator allows to increase
the field in the focus in η times
L
ôc
ç
⋅
= , (c- light
velocity). The measurements show that the used
resonator has τ = 5 µs. It means that in our case η=52.
The most part of experiments was performed in air and
hydrogen.
The main results of experimental study of
microwave discharge in a gas of high pressure (p>0.2
atm) in the open resonator can be formulated by
following [3,4,5]. The electron avalanche starts from
one electron and represents the expanding the
immovable in average spherical electron cloud with
increasing electron number and radius. The streamer
evolution is shown by Fig, 2.
(a) (b) (c)
Fig.2 The streamer development.
(a) – the photo of the streamer by the exposed lens, (b) –
the scanned image of the streamer (the total time
durance is 70 ns), (c) – the shadow of the shock wave,
generated by the exploded streamer. The vertical size of
the plot is 5 cm
When the electron number in avalanche is quite
enough the electron cloud starts to transform to a string
which is oriented along vector of electric field. It is
streamer (Fig.2a and Fig.2b). The speed of the streamer
arising can exceed 108 cm/s if the pressure is quit
enough [6].
When the streamer length achieve the resonant value
(near half wave length) the field in resonator breaks
down and farther exists on a small level. The streamer
development is stopped.
After breakdown the shock wave runs out from the
streamer (see Fig.2c) [7]. The measured shock wave
parameters show that the streamer adsorbs almost all
energy stored by resonator and explodes.
If gas pressure equals or more than 0.5 atm the
bright core is observed in central part of the resonant
streamer (see Fig2a and Fig.3). In hydrogen some times
two bright cores can arise near center of the streamer.
One can suppose that the most part of stored energy is
adsorbed in the core. It is important to note that the hard
boundary on gas pressure exists between state with the
core and without one.
The theoretical model of the discharge
The streamer development is the very complicated
nonlinear process. The simulation model must to
describe many complicated factors of the real process:
the electrodynamic interaction the system generator-
resonator-discharge with the developing streamer taking
into account the main physical-chemical processes in
the streamer. The MW generator provides the energy to
the resonator but refraction and heat losses caused by
the streamer decrease the stored energy. Both factors is
took into account in differential equation for electric
field at the resonator focus. It is supposed that resonator
is tuned in resonance with generator frequency. The
evolution of the streamer is defined by the ionization
front velocity [8], that defined by the local values of
electric field on the ends of the streamer and
unperturbed gas density and temperature.
1 2 3 4 5
0
50
100
150
200
250
Light intensity, arb. units
Distance along streamer , cm
Fig.3 The measured light intensity distribution along the
streamer axis
The estimations show that at high unperturbed gas
pressure the pinch force of the inducted current can be
more than the discharge plasma pressure gradient thus
the pinch force is included in the movement equation
The calculated state equation, thermal capacity in
and electric conductivity for diatomic molecular gas for
wide diapason of a temperature and the electron
continuity equation for the not equilibrium ionization
pretend to be near to realty:
The task parameters are the microwave length,
power of generator, the resonator parameters, the gas
pressure and the moment of appearance of initial free
electron.
The simulation results and its comparison with
experimental data
The task parameters was the same that in the
experiment: maximum field in resonator in stationary
regime Em = 35 kV/cm, time constant of resonator τ =
5µs, the initial free electron appears in the focus of
resonator when electric field in the focus achieves the
critical value depending on gas pressure. The gas
pressure was varied from 50 Torr up to 760 Torr.
The simulation shows that independently on the gas
pressure if electric field exceeds the critical value the
electron avalanche starts to develop and transforms into
the streamer. The streamer length, electric conductivity
and inducted current rise up to maximum value limited
by finite energy stored by resonator. Electric field in the
resonator decreased quickly, it is breakdown. The
streamer radius rises initially up to value limited by
ambipolar process and after heating rises quickly
because of the explosion. The electron temperature Te
and gas temperature T is the same and achieve the value
30,000 K at the gas pressure 760 Torr.
The maximum inducted current and maximum
velocity of streamer ends are near the theoretic limit if
the pressure is quit high. The current is limited by the
140
radiation resistance of an ideal resonant vibrator in the
critical external field Ecr. The ends velocity is limited by
the product of the free electron diffusion and maximum
ionization frequency. The product almost do not
depends on the gas pressure.
The streamer has the maximum temperature at the
its middle only. It means that the light intensity of the
middle of the streamer must be strongly higher than one
of the streamer branches. The observing bright corn at
the middle of the streamer can be explained by the high
gas temperature at the middle. It is clear why the corn
arises if the pressure is more than 500 Torr.
The calculated and measured values of the streamer
radius are in a quite good agreement. It gives us some
assurance that designed model has relation to the realty.
This assurance gives us a good possibility to forecast
the discharge parameters by means of designed model if
the pressure is much more 1 atm.
If the gas pressure is more than 10 atm, the magnetic
pressure is able to exceed the plasma pressure so the
pinch effect can be observed [9]. The simulation at gas
pressure 10 atm confirms this conclusion. The Fig.4
demonstrates the simulation result. One can see the
pinch effect.
Possible applications
The experimental results simulation and theory data
specify the possible ways of the MW discharge streamer
discharge in an opened resonator. This type of discharge
has the important peculiarities.
At the moment of resonance the plasma density is
rising instead of usual decreasing at lower gas pressure.
It is consequence of the pinch effect. Also one can see
that at resonance the ion temperature is near to the
electron one. Estimations show that the temperature
increases proportionally to gas pressure. If the gas
pressure will be increased up to some tens of
atmosphere the temperature some keV can be achieved.
The pinch influence is important both for density
increasing and for ion heating. If plasma temperature is
high the electron-ion relaxation time is comparable with
time of the process so as electrons do not able to heat
ions through Coulomb collisions. But MW pinch effect
generates the strong shock wave every half period of
MW oscillations. The shock waves are dissipated by ion
component and ions are being heated directly during the
pinch time. Of course the discharge at the pressure
about several atm needs the significantly deeper
experimental and theoretic study than it is performed
here.
The simulations show that if gas pressure is quite
enough the average pinch force of the current inducted
in the resonant streamer strongly compress the
discharge plasma. The dense very hot plasma can be
created for a short time about seve ral nanoseconds. The
pinched plasma can have the parameters up to needed
for fusion in DT mix if the mix pressure is more than 40
atmosphere. At the compress stage the gas dynamic
time of plasma is compared with period of microwave
field. In this condition the pinching force generates the
periodical shock waves which are cumulated at the axis
of the filament. Thus the work of the pinch force is
transformed into ions temperature directly. This
discharge need not electrodes and arises far from the
walls of device chamber. It means that only work gas
takes part in the process without any impurities.
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
1 10
3
0.01
0.1
1
10
100
1 10
3
Te [eV], Ta [eV], N/No, fdis, fion
Time, ns
2
3
1
1
45
Fig.4. The simulation result achieved by means of
complete model for discharge at 10 atm. 1 – electron
temperature Te, 2 – gas temperature T, 3 – plasma
density ρ/ρ0, 4 – dissociation coefficient, 5 – ionization
coefficient
The small scale of phenomena and the device size,
very high efficiency of the energy utilization, absence of
electrodes and surfaces contacting with the hot plasma,
direct pumping of energy to the ion heating allows us to
hop that forecasted high plasma parameters really can
be achieved and applied not only for design of a gamma
or neutron sources but for creation of a fusion reactor. It
is the nearest possibilities. We also dream that the
Lowson criteria will exceeded at a high pressure of DT
mix and may be the resonant streamer discharge is one
from possible realistic ways to create the nuclear fusion
reactor.
References
1. L.P.Grachev, I.I.Esakov, G.I.Mishin, K.V.Khodataev.
Tech. Phys. 39(2), February 1994, pp.130-136.
2. L.P.Grachev, I.I.Esakov, G.I.Mishin, K.V.Khodataev.
Preprint of LFTI im. A.F.Joffe, 1992, ¹1577
3. L.P.Grachev, I.I.Esakov, G.I.Mishin, K.V.Khodataev,
V.V.Tsyplenkov. Pis'ma v JTF, 26 November 1992,
v.18, No. 22, pp. 34-38.
4. L.P.Grachev, I.I.Esakov, K.V.Khodataev. JTF, 1998,
ò.68, No4, pp. 33-36.
5. L.P.Grachev, I.I.Esakov, G.I.Mishin, K.V.Khodataev.
JTF, 1996, v.66, No. 7, pp. 32-45.
6. K.V.Khodataev. Proc. XXIII ICPIG, Contributed
papers, IV-24.
7. K.V.Khodataev. Proc. of the ICPIG-XX (Piza, 1991),
Invited papers 1991, pp. 207-217.
8. A.L.Vikharev, V.B.Gildenburg, A.V.Kim,
A.G.Litvak, V.E.Semionov. Proc. Of scientific works
«High frequency discharge in the wave fields», Gor'kiy,
1988, pp. 41-135.
9. K.V.Khodataev. Abstracts of the XXVI Zvenigorod
conference on plasma physics and control
thermonuclear fusion (5-9 April 1999, Zvenigorod), Ï-
Ñ2-26.
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