Breakdown and discharge in low pressure gas created by a microwave radiation undergoing stochastic phase jumps (II)
The objective of the paper is to discuss the results of theoretical and experimental studies and numerical simulations of following phenomena: the anomalous character of the breakdown conditions, the anomalous behavior of microwave gas discharges, and the anomalous nature of collisionless electron...
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| Date: | 2006 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2006
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| Cite this: | Breakdown and discharge in low pressure gas created by a microwave radiation undergoing stochastic phase jumps (II) / V.I. Karas`, A.F. Alisov, A.M. Artamoshkin, R. Bingham, I.V. Gavrilenko, A.G. Zagorodny, I.A. Zagrebel`ny, M. Lontano, V.I. Mirny, I.F. Potapenko, V.S. Us // Вопросы атомной науки и техники. — 2006. — № 6. — С. 163-165. — Бібліогр.: 6 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859675551251300352 |
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| author | Karas`, V.I. Alisov, A.F. Artamoshkin, A.M. Bingham, R. Gavrilenko, I.V. Zagorodny, A.G. Zagrebel`ny, I.A. Lontano, M. Mirny, V.I. Potapenko, I.F. Us, V.S. |
| author_facet | Karas`, V.I. Alisov, A.F. Artamoshkin, A.M. Bingham, R. Gavrilenko, I.V. Zagorodny, A.G. Zagrebel`ny, I.A. Lontano, M. Mirny, V.I. Potapenko, I.F. Us, V.S. |
| citation_txt | Breakdown and discharge in low pressure gas created by a microwave radiation undergoing stochastic phase jumps (II) / V.I. Karas`, A.F. Alisov, A.M. Artamoshkin, R. Bingham, I.V. Gavrilenko, A.G. Zagorodny, I.A. Zagrebel`ny, M. Lontano, V.I. Mirny, I.F. Potapenko, V.S. Us // Вопросы атомной науки и техники. — 2006. — № 6. — С. 163-165. — Бібліогр.: 6 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | The objective of the paper is to discuss the results of theoretical and experimental studies and numerical simulations
of following phenomena: the anomalous character of the breakdown conditions, the anomalous behavior of microwave
gas discharges, and the anomalous nature of collisionless electron heating that are attributed to stochastic jumps in the
phase of microwave radiation.
|
| first_indexed | 2025-11-30T15:56:46Z |
| format | Article |
| fulltext |
Problems of Atomic Science and Technology. 2006, 6. Series: Plasma Physics (12), p. 163-165 163
BREAKDOWN AND DISCHARGE IN LOW PRESSURE GAS CREATED BY A
MICROWAVE RADIATION UNDERGOING STOCHASTIC PHASE JUMPS (II)
V.I. Karas`, A.F. Alisov, A.M. Artamoshkin, R. Bingham1, I.V. Gavrilenko, A.G. Zagorodny2,
I.A. Zagrebel`ny, M. Lontano3, V.I. Mirny, I.F. Potapenko4, V.S. Us
NSC “Kharkov Institute of Physics and Technology”, Akademicheskaya Str.1, 61108 Kharkov, Ukraine;
1Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, UK;
2Bogolyubov Institute of Theoretical Physics of NAS of Ukraine, Metrologichna Str. 14b, 03143, Kiyv;
3 Istituto di Fisica del Plasma, Associazione Euroatom-ENEA, Italy, 20125, Milan, 53 Roberto Cozzi Str.;
4Keldysh Institute of Applied Mathematics of RAS, 125047, Moscow, Miusskaya sq.4
The objective of the paper is to discuss the results of theoretical and experimental studies and numerical simulations
of following phenomena: the anomalous character of the breakdown conditions, the anomalous behavior of microwave
gas discharges, and the anomalous nature of collisionless electron heating that are attributed to stochastic jumps in the
phase of microwave radiation.
PACS: 52.80. Pi
1. Fainberg et al.[1] showed that stochastic electric
fields with a finite phase correlation time can efficiently
heat particles in a collisionless plasma, so physically the
inverse correlation time in the interaction between a
particle and an electromagnetic wave has in fact the
meaning of an effective collision frequency [1]. Earlier
we shown with help of the theoretical and experimental
investigations and numerical simulation that: (1) a
monochromatic wave is reflected from the dense plasma
almost totally (except for its front); (2) the microwave
with stochastic jumping phase (MWSJP) is reflected to a
lesser extent due mainly to the penetration of the wave
pulses associated with stochastic jumps in the wave
phase; (3) the transmission coefficient for a broad band
regular wave with the such spectral enegy density
(BBWSSED) as that of MWSJP is one order of
magnitude less because, in this case, the plasma slab
simply acts as a filter that transmits waves with the
frequencies pωω > ( pω is electron longmuir frequency)
and reflects others. In particular, the electromagnetic
wave incident on the plasma has a strong impact on the
electron dynamics, especially at large angles of incidence.
The longitudinal electric fields in the plasma are close in
strength to the transverse fields. The longitudinal energy
of the electrons and their temperature increase
severalfold. The electron distribution function becomes
non-Maxwellian: it has a tail of accelerated electrons. The
energy of the incident transverse MWSJP is partially
converted into the energy of the longitudinal wave and
partially into the electron energy [2].
In order to illustrate the practical importance of the
situation under examination, we present characteristic
waveforms of stochastic signals in new types of beam–
plasma devices generating intense stochastic microwave
radiation in the interaction of electron beams with hybrid
plasma waveguides that were developed and put into
operation at the National Science Center Kharkov
Institute of Physics and Technology (Ukraine) (see [2]).
Our experimental investigations of the excitation of
regular and stochastic electromagnetic waves in plasmas
of different densities and their passage through a cavity
allow us to draw the following conclusions:
- A regular wave excites a cavity less efficiently than
does a wave with a stochastically jumping phase (in
order for the transmitted signals from an incident
regular wave and from an incident wave with a
stochastically jumping phase to have the same
amplitude, the amplitude of the former should be one to
two orders of magnitude larger than that of the latter).
- As a regular monochromatic signal excites a cavity and
passes through it, selectivity between eigenmodes and
unnatural waves is lacking.
The results of our experimental investigations are in
satisfactory qualitative agreement with the theoretical
predictions.
2. In 1992 specialists from the Fusion System
Corporation (Maryland) designed a highly efficient light
source operating in the quasi-solar spectral region and
based on an electrodeless microwave gas discharge in a
sulfur-containing tube [3]. The continuous (molecular)
spectrum of high-power optical radiation from a sulfur-
containing lamp resembles that of the Sun, but with
depressed levels of IR and UV radiation.
The main problems associated with microwave
pumping are as follows (see, e.g., [4]):
- To choose the power of a microwave signal and its
shape (continuous or amplitude-modulated).
- To design a microwave transmission line from a
microwave source (generator) to a load (electrodeless
lamp), to construct a transmitter (whose operating
regime should depend on the mode of microwave
radiation), and to provide an appropriate topography of
the microwave field in the region where it interacts with
the working substance of the lamp (just after the
generator is switched on and in the plasma operating
mode).
- To maintain the stable operation of the microwave
generator loaded by the lamp, whose parameters change
substantially during the development of a microwave
discharge (from the switching on of the generator up to
the beginning of the steady-state plasma operating
mode).
The underlying problem is that of choosing the
microwave field frequency so as to satisfy the
requirement that the input microwave power be minimum.
164
In order to determine the working microwave frequency,
it is necessary to compare three parameters: the diameter
of the shell ( 1…2 cm), the electron mean free path l,
and the electron oscillation amplitude A. Discharges in
argon that evaporate sulfur (which is an electronegative
element) can be initiated only when the electrons oscillate
within a quartz shell, i.e., when A < /2. The capture of
electrons by sulfur molecules can only be balanced by
intense ionization. It is known (see, e.g., [5]) that, for all
gases, the dependence of the threshold field for gas
breakdown on the pressure has a minimum that separates
two branches.
For regular microwave radiation, the threshold field
just obtained is directly proportional to the frequency and
is inversely proportional to the gas density (pressure) and
the size of the discharge region, in complete agreement
with the known experimental data (see, e.g., [5]). An
important task is to determine the power of a microwave
generator that is required to initiate a discharge in a buffer
gas and then to maintain it in a plasma after the
evaporation and ionization of sulfur. Recall that, for
microwave discharges in regular electromagnetic fields,
the threshold field is minimum when the collision
frequency is equal to the electromagnetic field frequency
(see, e.g., [5]). Thus, at a frequency of f 3.0 GHz, the
minimum threshold field for breakdown of Ar at a
pressure of about 650 Pa is 500 V/cm. Such field
strengths can be achieved in a cavity in which one of the
walls is transparent to light.
In the present paper, we propose to initiate microwave
discharges in argon containing sulfur vapor by MWSJP.
The advantages of this method are as follows: (1) such
microwaves are capable of initiating discharges at lower
gas pressures because the jumping phase slows electron
diffusion; (2) the jumps in the phase ensure that the
collisionless electron heating is not accompanied by
energy losses in elastic and inelastic collisions; (3) a
uniform microwave discharge is easy to initiate because
microwaves with a stochastically jumping phase can
deeper penetrate into an overcritical plasma.
Let us now consider the conditions for breakdown in
argon by microwave radiation from the generator
described in [6]. The working frequency of this generator
is 450 MHz, the mean rate of the phase jumps being
8102 ⋅=jpν s-1. It is important to keep in mind that, when
the electron energy increases from zero to the ionization
energy ArI , the cross section for elastic collisions of
electrons with argon atoms varies greatly (by a factor of
about 30), being at its maximum several times larger than
the ionization cross section corresponding to electron
energies of 15…20 eV. This makes it possible to initiate
discharges in argon by microwaves with a stochastically
jumping phase at pressures as low as 4 Pa. In this case,
the mean rate of phase jumps is equal to the maximum
inelastic collision frequency, which corresponds to
electron energies close to the ionization energy. Operation
under such conditions is advantageous in that, first, no
energy is lost in elastic collisions, and, second, due to the
jumps in the phase, the electron diffusion remains
insignificant and the electromagnetic energy is efficiently
transferred to electrons.
Our numerical simulations and preliminary
experiments show (see Figure) that, in order to initiate a
microwave discharge at a frequency of 450 MHz in argon
at a pressure of 4 Pa, the microwave electric field strength
should be about 50 V/cm, whereas sulfur vapor can be
excited by an electric field of 25 V/cm, which can easily
be microwave cavities.
10-2 10-1 100
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
4,0
4,5
5,0
5,5
N
, k
W
P, torr
Air
Ar
He
a
1E-2 1E-1 1
0
1
2
3
4
5
6
7
8
9
10
N
, k
W
P, torr
Air
Ar
He
b
Dependences for breakdown power of a micro-wave
signals with a stochastically jumping phase vs a pressure
for air (curves!), argon (curves,), helium (curves7)
a) at broadband signal, b) at narrowband signal
With the use of such chambers, it is possible to
substantially reduce the generator power. The working
microwave frequency of this system, 450 ± 50 MHz, is
consistent with standards adopted for industrial, scientific,
and medical applications. With the version of the light
system proposed by the company, it becomes possible to
design compact low-power SLSs, in addition to the
already existing traditional SLSs with output powers in
the kilowatts range [3,4,6], which are usually based on
2450 ±50 MHz magnetrons.
165
CONCLUSIONS
The main results of our investigations are the
necessary conditions for gas breakdown and for the
maintenance of a microwave discharge in stochastic fields
in a light source have been determined. The anomalously
large transmission coefficient for microwaves, the
anomalous character of the breakdown conditions, the
anomalous behavior of microwave gas discharges, and the
anomalous nature of collisionless electron heating have
been attributed to stochastic jumps in the phase of
microwave radiation.
REFERENCES
1. Ya. B. Fainberg, F.G. Bass, and V.D. Shapiro // Zh.
Eksp. Teor. Fiz. 1965, v. 49, p. 329-337. [Sov. Phys.
JETP. 1965, v. 22, p. 230-238].
2. V.I. Karas`, Ya.B. Fainberg, A.F. Alisov, et al. // Fiz.
Plazmy. 2005, v. 31, p. 810-822. [Plasma Phys. Rep.
2005, vol. 31, p. 748-760].
3. J.T. Dolan, M.G. Ury and D.A. MacLeean //Proc. of VI
International Symposium on Science and Technology of
Light Sources, Budapest, 1992. p. 301.
4. A. Kozlov, V. Perevodchikov, R. Umarhodzhaev and
E. Shlifer //Proc. of IV International Workshop on
Microwave Discharges: Fundamentals and Applications,
Zvenigorod, 2000. /Ed. by Yu. A. Lebedev. Moscow:
Yanus-K, 2001, p. 235-244.
5. Yu.P. Raiser. Fundamentals of Modern Gas-Dis-
charge Physics. Moscow: Nauka, 1980 (in Russian).
6. A. Didenko, B. Zverev, A. Koljashkin, and
A. Prokopenko //Proc. of IV International Workshop on
Microwave Discharges: Fundamentals and Applications,
Zvenigorod, 2000. /Ed. by Yu. A. Lebedev. Moscow:
Yanus-K, 2001, p. 205-214.
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| id | nasplib_isofts_kiev_ua-123456789-82308 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-11-30T15:56:46Z |
| publishDate | 2006 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Karas`, V.I. Alisov, A.F. Artamoshkin, A.M. Bingham, R. Gavrilenko, I.V. Zagorodny, A.G. Zagrebel`ny, I.A. Lontano, M. Mirny, V.I. Potapenko, I.F. Us, V.S. 2015-05-27T15:28:49Z 2015-05-27T15:28:49Z 2006 Breakdown and discharge in low pressure gas created by a microwave radiation undergoing stochastic phase jumps (II) / V.I. Karas`, A.F. Alisov, A.M. Artamoshkin, R. Bingham, I.V. Gavrilenko, A.G. Zagorodny, I.A. Zagrebel`ny, M. Lontano, V.I. Mirny, I.F. Potapenko, V.S. Us // Вопросы атомной науки и техники. — 2006. — № 6. — С. 163-165. — Бібліогр.: 6 назв. — англ. 1562-6016 PACS: 52.80. Pi https://nasplib.isofts.kiev.ua/handle/123456789/82308 The objective of the paper is to discuss the results of theoretical and experimental studies and numerical simulations of following phenomena: the anomalous character of the breakdown conditions, the anomalous behavior of microwave gas discharges, and the anomalous nature of collisionless electron heating that are attributed to stochastic jumps in the phase of microwave radiation. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Plasma electronics Breakdown and discharge in low pressure gas created by a microwave radiation undergoing stochastic phase jumps (II) Article published earlier |
| spellingShingle | Breakdown and discharge in low pressure gas created by a microwave radiation undergoing stochastic phase jumps (II) Karas`, V.I. Alisov, A.F. Artamoshkin, A.M. Bingham, R. Gavrilenko, I.V. Zagorodny, A.G. Zagrebel`ny, I.A. Lontano, M. Mirny, V.I. Potapenko, I.F. Us, V.S. Plasma electronics |
| title | Breakdown and discharge in low pressure gas created by a microwave radiation undergoing stochastic phase jumps (II) |
| title_full | Breakdown and discharge in low pressure gas created by a microwave radiation undergoing stochastic phase jumps (II) |
| title_fullStr | Breakdown and discharge in low pressure gas created by a microwave radiation undergoing stochastic phase jumps (II) |
| title_full_unstemmed | Breakdown and discharge in low pressure gas created by a microwave radiation undergoing stochastic phase jumps (II) |
| title_short | Breakdown and discharge in low pressure gas created by a microwave radiation undergoing stochastic phase jumps (II) |
| title_sort | breakdown and discharge in low pressure gas created by a microwave radiation undergoing stochastic phase jumps (ii) |
| topic | Plasma electronics |
| topic_facet | Plasma electronics |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/82308 |
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