Optical radiation special features from plasma of low pressure discharge initiated by microwave radiation with stochastic jumping phase
We study the plasma discharge, initiated by microwave radiation with stochastically jumping phase (MWRSJP) in a coaxial waveguide at the optimal mode of the beam-plasma generator. Present results continue the line of the previous research. In this paper we experimentally examine the optical characte...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
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| Цитувати: | Optical radiation special features from plasma of low pressure discharge initiated by microwave radiation with stochastic jumping phase / V.I. Karas΄, А.F. Alisov, О.V. Bolotov, V.I. Golota, I.V. Karas΄, А.М. Yegorov, A.G. Zagorodny, I.А. Zagrebelny, I.F. Potapenko // Вопросы атомной науки и техники. — 2013. — № 4. — С. 183-188. — Бібліогр.: 8 назв. — англ. |
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irk-123456789-1121702017-01-23T22:34:59Z Optical radiation special features from plasma of low pressure discharge initiated by microwave radiation with stochastic jumping phase Karas, V.I. Alisov, А.F. Bolotov, О.V. Golota, V.I. Karas, I.V. Yegorov, А.М. Zagorodny, A.G. Zagrebelny, I.А. Potapenko, I.F. Плазменно-пучковый разряд, газовый разряд и плазмохимия We study the plasma discharge, initiated by microwave radiation with stochastically jumping phase (MWRSJP) in a coaxial waveguide at the optimal mode of the beam-plasma generator. Present results continue the line of the previous research. In this paper we experimentally examine the optical characteristics of the discharge plasma in a wide range of both an air pressure and microwave radiation power. In general the research aims to develop a new type of sources of optical radiation. Вивчаєтся плазма розряду, ініційованого мікрохвильовим випромінюванням, зі стохастично стрибковою фазою в коаксиальному хвилеводі в оптимальному режимі пучково-плазмового генератора. Наведені результати є продовженням раніше проведених досліджень. Експериментально досліджувались оптичні характеристики розрядної плазми в широкій області тисків повітря та потужності мікрохвильового випромінювання. Метою дослідження є розвиток нового типу джерела оптичного випромінювання. Изучается плазма разряда, инициируемого микроволновым излучением, со стохастически прыгающей фазой в коаксиальном волноводе в оптимальном режиме пучково-плазменного генератора. Представленные результаты являются продолжением ранее проведенных исследований. Экспериментально исследовались оптические характеристики разрядной плазмы в широкой области давлений воздуха и мощности микроволнового излучения. Цель исследования – развитие нового типа источника оптического излучения. 2013 Article Optical radiation special features from plasma of low pressure discharge initiated by microwave radiation with stochastic jumping phase / V.I. Karas΄, А.F. Alisov, О.V. Bolotov, V.I. Golota, I.V. Karas΄, А.М. Yegorov, A.G. Zagorodny, I.А. Zagrebelny, I.F. Potapenko // Вопросы атомной науки и техники. — 2013. — № 4. — С. 183-188. — Бібліогр.: 8 назв. — англ. 1562-6016 PACS: 52.80.Pi, 52.65.-y, 52.65.Ff, 52.70. Ds, 52.70.Kz, 84.40Fe http://dspace.nbuv.gov.ua/handle/123456789/112170 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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English |
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Плазменно-пучковый разряд, газовый разряд и плазмохимия Плазменно-пучковый разряд, газовый разряд и плазмохимия |
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Плазменно-пучковый разряд, газовый разряд и плазмохимия Плазменно-пучковый разряд, газовый разряд и плазмохимия Karas, V.I. Alisov, А.F. Bolotov, О.V. Golota, V.I. Karas, I.V. Yegorov, А.М. Zagorodny, A.G. Zagrebelny, I.А. Potapenko, I.F. Optical radiation special features from plasma of low pressure discharge initiated by microwave radiation with stochastic jumping phase Вопросы атомной науки и техники |
| description |
We study the plasma discharge, initiated by microwave radiation with stochastically jumping phase (MWRSJP) in a coaxial waveguide at the optimal mode of the beam-plasma generator. Present results continue the line of the previous research. In this paper we experimentally examine the optical characteristics of the discharge plasma in a wide range of both an air pressure and microwave radiation power. In general the research aims to develop a new type of sources of optical radiation. |
| format |
Article |
| author |
Karas, V.I. Alisov, А.F. Bolotov, О.V. Golota, V.I. Karas, I.V. Yegorov, А.М. Zagorodny, A.G. Zagrebelny, I.А. Potapenko, I.F. |
| author_facet |
Karas, V.I. Alisov, А.F. Bolotov, О.V. Golota, V.I. Karas, I.V. Yegorov, А.М. Zagorodny, A.G. Zagrebelny, I.А. Potapenko, I.F. |
| author_sort |
Karas, V.I. |
| title |
Optical radiation special features from plasma of low pressure discharge initiated by microwave radiation with stochastic jumping phase |
| title_short |
Optical radiation special features from plasma of low pressure discharge initiated by microwave radiation with stochastic jumping phase |
| title_full |
Optical radiation special features from plasma of low pressure discharge initiated by microwave radiation with stochastic jumping phase |
| title_fullStr |
Optical radiation special features from plasma of low pressure discharge initiated by microwave radiation with stochastic jumping phase |
| title_full_unstemmed |
Optical radiation special features from plasma of low pressure discharge initiated by microwave radiation with stochastic jumping phase |
| title_sort |
optical radiation special features from plasma of low pressure discharge initiated by microwave radiation with stochastic jumping phase |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2013 |
| topic_facet |
Плазменно-пучковый разряд, газовый разряд и плазмохимия |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/112170 |
| citation_txt |
Optical radiation special features from plasma of low pressure discharge initiated by microwave radiation with stochastic jumping phase / V.I. Karas΄, А.F. Alisov, О.V. Bolotov, V.I. Golota, I.V. Karas΄, А.М. Yegorov, A.G. Zagorodny, I.А. Zagrebelny, I.F. Potapenko // Вопросы атомной науки и техники. — 2013. — № 4. — С. 183-188. — Бібліогр.: 8 назв. — англ. |
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Вопросы атомной науки и техники |
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ISSN 1562-6016. ВАНТ. 2013. №4(86) 183
OPTICAL RADIATION SPECIAL FEATURES FROM PLASMA OF LOW
PRESSURE DISCHARGE INITIATED BY MICROWAVE RADIATION
WITH STOCHASTIC JUMPING PHASE
V.I. Karas΄1,4, А.F. Alisov1, О.V. Bolotov1, V.I. Golota1, I.V. Karas΄1,
А.М. Yegorov1, A.G. Zagorodny2, I.А. Zagrebelny1, I.F. Potapenko3
1National Science Center “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine;
2Bogolyubov Institute for Theoretical Physics of NASU, Kiev, Ukraine;
3Keldysh Institute of Applied Mathematics of RAS, Moscow, Russia;
4V.N. Karazin Kharkov National University, Ukraine, E-mail: karas@kipt.kharkov.ua
We study the plasma discharge, initiated by microwave radiation with stochastically jumping phase (MWRSJP)
in a coaxial waveguide at the optimal mode of the beam-plasma generator. Present results continue the line of the
previous research. In this paper we experimentally examine the optical characteristics of the discharge plasma in a
wide range of both an air pressure and microwave radiation power. In general the research aims to develop a new
type of sources of optical radiation.
PACS: 52.80.Pi, 52.65.-y, 52.65.Ff, 52.70. Ds, 52.70.Kz, 84.40Fe
INTRODUCTION
High-frequency (HF) heating is very important field
in connection with fundamental questions of plasma
physics and applications. This area of physics is inten-
sively investigated as theoretically and experimentally
(for example, see [1 - 3] and references therein). The is-
sues widely discussed in literature are connected with
additional plasma heating in tokamaks [1], the nature of
accelerated particles in space plasmas, gas discharge
physics [2, 3]. Among the problems that attract attention
of scientific community is development of sources with
solar spectrum. This is utmost important problem from
the point of fundamental, as well as practical application,
and in this direction interesting achievements is obtained
(see, for example [3]). It is worth mentioning that one of
the difficulties associated with additional plasma heating
in tokamaks is a well-known dependence of the Ruther-
ford cross-section on velocity. As a consequence, the
probability of collisions decreases with plasma tempera-
ture rising, thus creating obstacles for further plasma
heating. Another important challenge in interaction of HF
radiation with plasma is a barrier of the radiation penetra-
tion into the overdense plasma. To our knowledge, the
most part of investigations in this direction are made with
help of HF generators of electromagnetic radiation with
regular phase. Thus the new opportunities that microwave
radiation with jumping phase provides in this area would
be very important.
In this paper, we describe results of the theoretical and
experimental investigation of the plasma interaction with
microwave radiation with jumping phase that obtained
with help of the unique beam-plasma generator (BPG)
made in KIPT [4]. This study continues research on be-
haviour of plasma discharge subjected to microwave ra-
diation with stochastically jumping phase (MWRSJP)
which started in [5, 6]. The paper is organized as follows.
The first section contains introduction and brief review of
previous research. In section 2, we consider experimental
parameters of MWRSJP obtained from the BPG. The
scheme of measurement of various parameters is given
and experimental studies of optical radiation from the
plasma discharge initiated by MWRSJP are presented.
The illustrative simulation re-sults are presented graphi-
cally. Concluding remarks fol-low at the end.
It was shown in [7], both theoretically and experi-
mentally, that the phenomenon of anomalous penetra-
tion of microwave radiation into plasma, conditions for
gas breakdown and maintenance of a microwave gas
discharge, and collisionless electron heating in a micro-
wave field are related to jumps of the phase of micro-
wave radiation. In this case, in spite of the absence of
pair collisions or synchronism between plasma particles
and the propagating electromagnetic field, stochastic
microwave fields exchange their energy with charged
particles. In such fields, random phase jumps of micro-
wave oscillations play the role of collisions and the av-
erage energy acquired by a particle over the field period
is proportional to the frequency of phase jumps.
Gas breakdown and maintenance of a discharge in a
rarefied gas by a pulsed MWRSJP were studied theo-
retically and experimentally in [8], as well as propaga-
tion of this radiation within the plasma produced in such
a way. The conditions for ignition and maintenance of a
microwave discharge in air by MWRSJP were found.
The pressure range in which the power required for dis-
charge ignition and its maintenance has its minimum
was determined [7, 8]. It was shown that, in the interval
of pressures that have a level less than optimal (about
50 Pa for argon), the minimum of MWRSJP breakdown
power depends weakly on the working gas pressure ow-
ing to several reasons. These reasons are efficient colli-
sionless electron heating, weakening of diffusion and,
finally, decrease of elastic and inelastic collisional
losses. This allows one to extend the domain of dis-
charge existence toward lower pressures. The intensity
of collisionless electron heating increases with increas-
ing rate of phase jumps in MWRSJP. There is an opti-
mal phase jump rate at which the rate of gas ionization
and, accordingly, the growth rate of the electron and ion
densities reach their maximum. The optimal phase jump
rate is equal to the ionization frequency at electron en-
ergies close to the ionization energy of the working gas.
In the present work, the effect of high power pulsed
decimeter MWRSJP action on a plasma, produced in a
coaxial waveguide filled with a rarefied gas, is investi-
gated with use of the above mentioned BPG [4], which
was upgraded for the given experimental conditions.
The goal of this work is to study the special features of
ISSN 1562-6016. ВАНТ. 2013. №4(86) 184
low pressure discharge initiated by MWRSJP und also
optical radiation spectra. For interpretation of the ex-
perimental results on the ignition and maintenance of a
microwave discharge in air obtained with MWRSJP
BPG, a numerical code has been developed. This code
allows simulating the process of gas ionization by elec-
trons heated in the MWRSJP field and studying the be-
haviour of plasma particles in such a field.
1. EXPERIMENTAL STUDIES
1.1. MWRSJP PARAMETERS OBTAINED FROM
THE BPG, AND THE SCHEME OF THEIR
MEASUREMENTS
We study MWRSJP parameters and optical radiation
characteristics from the plasma discharge of induced by
MWRSJP in a gas (air for the present case), taken at low
pressure. To conduct experiments, a coaxial waveguide
with axial vacuum pumping is connected to the BPG.
Coaxial waveguide filled with gas with impedance of
about 75 Ohms and a length of 1000 mm is made of
brass pipes with inner diameter of 45 mm and external
diameter of 50 mm (Fig. 1).
Fig. 1. Block diagram of measurement of BPG
and plasma principal parameters
The central conductor is a brass rod diameter of
12 mm. At the ends of the coaxial waveguide, tapered
flanges provide the joining of coaxial transitions. In the
middle of the coaxial waveguide a tube is installed to
pump gas or gas mixtures, which also mounted a ther-
mocouple tube to monitor the pressure of the gas. Ad-
mission process of gases or gas mixtures is carried out
with sufficient precision using the second inlet valve
through diametrically located holes 2 mm in diameter
that are situated at both ends of the coaxial waveguide.
Tubes for the introduction of diagnostic probes are lo-
cated along the length of the coaxial waveguide. The
first tube is located at 60 mm from the input microwave
power of stochastic electromagnetic waves; the second
one is placed at a distance of 260 mm and a third – at
840 mm. During the working process, such arrangement
of instruments allows us to have controlled diagnostic
probes of a spatial distribution, as well as to monitor
parameters of the microwave discharge along
throughout the waveguide length. This provides more
detailed information about processes that take place
inside the waveguide. The block diagram shown in
Fig. 1 schematically represents measurements of the
main parameters of the BPG and of the plasma, which is
produced in the coaxial waveguide. Stochastic micro-
wave oscillations generated by the BPG (1) were sup-
plied from the output of the slow-wave structure
through a broadband directional coupler (2) and 75-Ω
conical coaxial junction (3) to the input of the coaxial
waveguide (4) and then, through a conical coaxial junc-
tion (5) and coupler (6), were fed to an IBM-2 high
power gauge (7).
For operating in the regime of narrow-band signal
generation the input of the BPG slow-wave structure
was attached to a shorting plug (8). The oscilloscopes
(11, 12) and the submodulator (9) and modulator (10) of
the high voltage supplied to the cathode of the BPG
electron gun were triggered synchronously by using a
timing unit (13). A time-delay circuit (14) was used to
vary the instant of triggering the oscilloscopes with re-
spect to the beginning of the high voltage pulse. This
allowed us to observe the shape of the generated signal
at different instants after the beginning of the electron
beam pulse. A detector head (15) and D2-13 variable
resistive-capacitive attenuator (16) connected to the
secondary line of the coupler (2) were used to measure
the envelope of microwave oscillations and the wave-
forms of the electron beam pulse. The temporal realiza-
tions and spectral characteristics of MWRSJP at the
input and output of the coaxial waveguide were studied
using an HP Agilent Infinium four-channel broadband
(2.25 GHz) oscilloscope (12). A PEM-29 photomultip-
lier (17) powered from a VSV-2 high-voltage stabilized
rectifier (18) was used to measure the integral intensity
of optical radiation from the plasma. An ISP-51 three-
prism glass spectrograph (19) and PEM-106 photomul-
tiplier (20) were used for optical spectroscopy of the
discharge in the coaxial waveguide.
Ignition of the discharge does not affect the penetra-
tion into dense plasma of MWRSJP what is evidenced by
nearly constant amplitude at the entrance to the
waveguide (curves 1 in Fig. 2). Because of expenditures
of radiation energy on air ionization for the discharge
maintenance the MWRSJP amplitude at the output of the
coaxial waveguide (see curves 2 in Fig. 2) is essential
diminished. It is also important that the MWRSJP local
spectrum on the output waveguide significantly changed
(see curves 2΄ in Fig. 2), a peak associated with the main
spectral component of MWRSJP is absent. It should be
noted that in the pressure range from P = 30 to P = 2 Pa at
a MWRSJP power that conforming to the optimal operat-
ing mode of BPG a similar situation is observed.
The optimal operating mode of BPG corresponds to
the following parameters: magnetic induction in the
interaction range of the beam with slow-wave structure
in BPG is B =0.096 T, a high voltage is Uopt = 13.2 kV,
the current electron gun is Ib= 3…5 A, high-voltage
pulse is 160 μs, MWRSJP power is W = 36 kW, the
pulse repetition frequency is 5 Hz.
The results presented in Fig. 2 shows that, as the
spectrum of the micro-wave signal used to initiate and
maintain a steady-state discharge is narrowed, the am-
plitude of the MWRSJP electric field can be decreased
by nearly a factor of 2.
ISSN 1562-6016. ВАНТ. 2013. №4(86) 185
a b
Fig. 2. Waveforms of MWRSJP at the (1) input and (2) output of the coaxial waveguide, respectively, and local
microwave spectra on a logarithmic scale (10 dB/div) at the (1') input and (2') output of the coaxial waveguide,
respectively. The gas pressure in the waveguide is P = (a) 2.0 and (b) 30 Pa, respectively.
The time scale is 5 ns/div, and the voltage scale is 100 (V·cm⎯¹)/div
However, in order for the pressure range in which
breakdown occurs and a steady-state discharge exists to
be sufficiently broad, it is necessary that the phase jump
frequency be suffi-ciently high (as will be seen below, it
should be about one-third of the microwave frequency).
Let us now analyze the measured characteristics of
MWRSJP at the input and output of the coaxial wave-
guide in the optimal BPG mode. The oscillograms
shown in Fig. 2 were processed by the method of corre-
lation analysis, and the frequency spectra, the time de-
pendence of the phase of microwave oscillations, and
self-correlation functions were determined. It was
shown that gas breakdown takes place only after the
electric field amplitude of MWRSJP reaches a certain
critical value, which depends on the gas pressure. The
instant of discharge ignition can be easily determined
from the abrupt decrease in the amplitude of the micro-
wave signal at the output of the coaxial waveguide to
almost zero. It can also be seen that the electric field
amplitude required to maintain a steady-state discharge
is one order of magnitude lower than that required for
breakdown. From Fig. 2 it can be seen that, MWRSJP
amplitude at the waveguide outlet is reduced substan-
tially (more than an order of magnitude) due to the de-
velopment of the discharge and also the discharge igni-
tion and maintenance lead at the waveguide outlet to a
strong damping of the spectral components, which are
corresponded to the maximum range of input signal into
the waveguide.
Let us now consider the conditions for breakdown in
air by microwave radiation from the BPG described in
[4]. In optimal regime at narrowband signal of this gen-
erator the working frequency is 500 MHz, the mean rate
of the phase jumps being jpν = 2×108 s-1. It is impor-
tant to keep in mind that, when the electron energy in-
creases from zero to the ionization energy airI , the
cross section for elastic collisions of electrons with air
atoms and molecules varies greatly (by a factor of about
30), being at its maximum several times larger than the
ionization cross section corresponding to electron ener-
gies of 15…20 eV. This makes it possible to initiate
discharges in air 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 elec-
tron 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 effi-
ciently transferred to electrons.
Fig. 3. The general view of the coupler (6) internal
structure
To determine the dependence of the threshold
power, required for ignition of the discharge in a coaxial
waveguide, on the pressure of working gas, BPG has
worked in the mode of generating the maximum output
power level of narrow-band signal in which the genera-
tion of microwave radiation with a maximum frequency
of phase jumps occurs. In this case part of the power
with the help of a broadband directional coupler with
variable coupling (Fig. 3) was supplied to analyezed
gas-filled coaxial waveguide. The rest of the power as-
signed to the matched load. Such a method of regulating
the power delivered to the coaxial waveguide for igni-
tion of the discharge allows conserving the permanent
parameters of microwave radiation. In particular, this
concerns the mean rate of the phase jumps and the en-
ergy spectrum density of MWRSJP, because in this
situation BPG works in the same mode.
In Fig. 3 the general view of the coupler (6) internal
structure is shown.
ISSN 1562-6016. ВАНТ. 2013. №4(86) 186
While conducting experiments, to determine the de-
pendence of the threshold power on the gas pressure, the
left center coax transition coupler was connected to BPG,
the lower left coax transition joined the coaxial wave-
guide, the right central and the lower coaxial transitions
were connected to the load. By changing the bond be-
tween the central and the lower shoulders of the coupler
through the use of different linked curved shoulders, we
adjusted the peak power coming into the coaxial wave-
guide from 6 to 28 kW. Fig. 6 shows the dependence of
peak power required for the discharge ignition in the air
that filled coaxial waveguide on its pressure.
From Fig. 4 (curves 1, 2) it can be seen that, the
peak power levels from 6 to 28 kW MWRSJP discharge
is ignited stably at a pressure of gas (air) ranging from
1.5 to 3990 Pa. This result clearly demonstrates the ad-
vantages of the discharge, supported by microwave with
stochastic jumps in the phase compared with the micro-
wave discharge in the fields of regular waves.
Fig. 4. Dependences for breakdown electric field
strength of a microwave narrowband signals with a
stochastically jumping phase versus a pressure for air
in the optimal BPG mode (curves 1 – ■; 2 – *), in the
non-optimal BPG mode: for air (curve 3 – •), argon
(curve 4 – ▲), helium (curve 5 – ▼), respectively
Thus we have the opportunity to create a discharge
at a pressure of almost two orders of magnitude lower
than the pressure that is necessary for the fulfillment of
the condition of minimum capacity of the discharge
ignition by regular microwave radiation. Namely, (see
[20]) for ω≈νcol (where colν is the frequency of bi-
nary collisions, as well ω is the frequency of micro-
wave radiation), effectiveness of such a discharge is
much higher because of the small contribution of energy
loss on unnecessary elastic and inelastic collisions when
working at low pressures. For comparison, dependence
of microwave radiation power required for the discharge
ignition in air (curve 3), argon (curve 4) and helium
(curve 5), which are filled the coaxial waveguide, on its
pressure, obtained while working in the non-optimal
BPG mode is given. It is seen that the pressure range in
which it is possible the ignition of the discharge is much
narrower than under the optimal BPG mode functioning.
This is due to a significant difference in mean rates of
the phase jumps in these modes of BPG.
Using the delay device (14), the time for start of the
oscilloscope can be modified within the length of high-
voltage pulse. This circumstance allows us to observe
the shape of the generated signal at a different time
moments starting from the very begin of the electron
beam current pulse. Features MWRSJP at the inlet and
outlet of the coaxial waveguide are studied using the
four-channel broadband (2.25 GHz) oscilloscope (12)
HP Agilent Infinium Oscilloscope. In the next part we
present the results of experimental studies of optical
characteristics of plasma discharge. Preliminary results
of an optical characteristic studies presented in [8].
1.2. EXPERIMENTAL STUDIES OF OPTICAL
RADIATION FROM THE PLASMA DISCHARGE
INITIATED BY MWRSJP
Optical characteristics of plasma discharge initiated
by MWRSJP in coaxial waveguide are examined in the
conditions of BPG operation in the optimal mode in air
for a wide pressure range, in which the discharge is ig-
nited and maintained stably. For spectroscopic studies
of the discharge in the visible spectrum a monochroma-
tor (19) MDR-1 is used. With help of the lens, the radia-
tion from the discharge is focused onto the entrance slit
(slit width is 0.01 mm) of the spectrograph. By the out-
put gap with width of 0.015 mm the spectrograph is
attached to the photoelectron multiplier (20) of type
PEM-106. The photomultiplier PEM-106 has high spec-
tral sensitivity in the wavelength range from 350 to
550 nm. Within zone from 550 nm to 1000 nm the sen-
sitivity is less that will lead to distortion of the discharge
optical spectra which are observed on oscilloscope (11).
This fact should be taken into account when the wave
forms of the emission spectra are analyzed. The signal
from the photomultiplier PEM-106 was fed to the digital
(2 GB/s) oscilloscope (11) Le Croy Wave Jet 324 with a
frequency band of 200 MHz. The ISP-51 spectrograph
was calibrated using the spectral lines of a PRK-2M mer-
cury lamp (21) and the Balmer hydrogen lines emitted by
a Geissler tube (22). The mercury lamp and the Geissler
tube were powered from an OU-1 lighting unit (23).
The MWRSJP power was input via the conical coax-
ial junction in the waveguide pumped out to a pressure
of 1.33 Pa. In certain ranges of the gas pressure, gas
composition, and microwave power, a discharge was
ignited in the coaxial waveguide.
Remark, that in the consequent Figs. 5-8, which pre-
sents radiation spectra from the low-pressure discharge,
the real dependence of the spectral sensitivity of the
photomultiplier is taken into account, and for the sim-
plicity of comparison the same arbitrary units are used.
For the necessary observations, apertures were drilled
with a diameter 2.5 mm on the lateral surface of the
coaxial waveguide in the area of the curved quartz opti-
cal window. On the one hand, these apertures provide
properly output of the light radiation from a coaxial
waveguide and, on the other hand, they prevent output
of the microwave radiation from the discharge region. It
is seen that the discharge radiation intensity decreases
along the waveguide.
In Figs. 5-8 the dependence of optical radiation from
the discharge on air pressure is compared at the condi-
tions when a stable regime of the gas discharge is held
at the MWRSJP power that correspond the optimal BPG
mode. It should be noted that the discharge color de-
pends on the working gas pressure and the microwave
power input in the waveguide.
ISSN 1562-6016. ВАНТ. 2013. №4(86) 187
a b
c d
Fig. 5. The emission spectra of discharges in air for
a wavelength of 337 nm (a), for a wavelength of 357 nm
(b), for a wavelength of 486 nm (c), for a wavelength of
656.3 nm (d) at a pressure P = 28 Pa and the MWRSJP
power 18 kW
a b
c d
Fig. 6. The emission spectra of discharges in air for
a wavelength of 337 nm (a), for a wavelength of 357 nm (b),
for a wavelength of 486 nm (c) for a wavelength of 656.3 nm
(d) at a pressure P = 4.8 Pa and the MWRSJP power 18 kW
a b
Fig. 7. The dependence of the optical radiation intensity
in air vs power for a wavelength of 337,2 nm at P = 4 Pa
at the MWRSJP power 5 kW (a) and 16 kW (b)
Figs. 5-7 show that the spectrum of optical radiation
intensities of optical radiation for four specific wave
lengths) from the discharge depends strongly on the
pressure of the working gas (air) and MWRSJP power
in a coaxial waveguide. In particular, within the lower
range of air pressure, the optical radiation from the dis-
charge is pronouncedly enriched with shorter wave-
lengths. In this way, if value of pressure is P1 = 28 Pa
then spectrum is depleted at the wavelengths shorter
than 600 nm, i.e. red radiation prevails, see Fig. 5. At
the same time, when the pressure is reduced nearly an
order of magnitude, see Fig. 6 a spectrum becomes sig-
nificantly enriched with short wavelengths, i.e. blue
light prevails. Further Fig. 7 represent the experimental
studies of the dependence of the optical radiation inten-
sity in air versus a power for a wavelength of 337,2 nm
at P=4 Pa and the MWRSJP power 5 kW (a) and 16 kW
(b). It can see that the optical radiation intensity increase
at magnify of MWRSJP peak power.
One can observe that the optical emission starts with
a delay relatively to the beginning of current pulse how-
ever, duration of the optical emission exceeds the dura-
tion of the high voltage pulse. From Fig. 8 it is seen that
the discharge plasma optical emission is sufficiently
stable in time.
Thus, relying on the quantitative indicators of the
electric field intensity, frequency MWRSJP and fre-
quency of phase jumps, etc., the prospect of creating a
source of light radiation of low power (100 W) is im-
plemented. It is based on the consideration of a stochas-
tic microwave discharge with high efficience at low
pressure of working gas.
a b
Fig. 8. The dependence of the optical radiation intensity
versus time for a wavelength of 336 nm (a)
and a wavelength of 337,2 nm (b) at air pressure
P = 4.8 Pa and the MWRSJP power W = 18 kW
CONCLUSIONS
At the stage of discharge in the coaxial waveguide,
the discharge becomes nonuniform along its length due
to the strong absorption of MWRSJP. The electric field
amplitude decreases by more than one order when ap-
proaching to the waveguide exit.
During the maintenance of MWRSJP discharge in
the waveguide, gas ionization leads to almost complete
decay in the spectrum of the output signal from the co-
axial waveguide of the main spectral components of the
input microwave signal.
With the distance increasing from the input of
MWRSJP into the coaxial waveguide, the discharge
optical radiation intensity decreases significantly, be-
coming inhomogeneous.
With air pressure decreasing, the optical radiation
from the discharge becomes more reach with shorter-
wavelength. Thus, if at the pressure of 20 Pa, the radia-
tion has red colour, then at pressure of 2 Pa the radiation
becomes blue.
MWRSJP and discharge optical radiation are obser-
ved in time almost throughout the pulse duration of
electron beam current in BPG.
ISSN 1562-6016. ВАНТ. 2013. №4(86) 188
When the frequency of MWRSJP signal and the fre-
quency of phase jumps are those as observed in the con-
ducted investigations, there is enough to have the mag-
nitude of electric field equals to 50 V/cm, for the crea-
tion and maintainence of the discharge in air.
Thus, based on the quantitative indicators, such as
the electric field intensity, frequencies of MWRSJP and
phase jumps it can be expected the following. The pro-
spective creation of an efficient light radiation source of
low power (100 W) in a wide range of air pressure, in
which the discharge is ignited and maintained stably,
becomes a reality. The main task of future experimental
and theoretical research is to optimize the gas mixture
for the discharge of quasi-solar optical spectrum.
The results might also be of some use in connection
with additional plasma heating in nuclear fusion devices
due the fact that, the electron heating by microwave
radiation with jumping phase is collisionless. Thus the
heating efficiency by MWRSJP does not decreas when
the temperature increases, whereas the usual heating by
the regular radiation is to be collisional and becomes
less and less efficient at increasing temperature. More-
over, instead of pulse working regime of BPG, the con-
stant working regime which is important for tokamak
plasma, in principle may be elaborated.
The developing of a new type of the high efficiency
sources of optical radiation with quasi solar spectrum
would make a fundamental breakthrough in lighting
technology.
REFERENCES
1. S. Shiraiwa, J. Ko, O. Meneghini, R. Parker,
A.E. Schmidt, S. Scott, M. Greenwald, A.E. Hubbard,
J. Hughes, Y. Ma, Y. Podpaly, J.E. Rice, G. Wallace,
J.R. Wilson, S.M. Wolfe, and Alcator C-Mod Group.
Full wave effects on the lower hybrid wave spectrum
and driven current profile in tokamak plasmas //
Phys. Plasma. 2011, v. 18, p. 080705.
2. S.I. Gritsinin, A.M. Davydov, I.A. Kossyi,
K.A. Arapov and A.A. Chapkevich. A Biresonant
Plasma Source Based on a Gapped Linear Microwave
Vibrator // Plasma Phys. Rep. 2011, v. 37, p. 263-272.
3. J.T. Dolan, M.G. Ury and D.A. MacLeean. Micro-
wave Powered Electrodeless Light Source // Proc.
VI Int. Symp. on Science and Technology of Light
Sources (Budapest, Hungary). 1992, p. 301-311.
4. А.К. Berezin, Ya.B. Fainberg, A.M. Artamoshkin,
I.A. Bez`yazychny, V.I. Kurilko, Yu.M. Lyapkalo
and V.S. Us. Beam-Plasma Generator of Stochastic
Oscillations of Decimeter Wavelength Band // Plas-
ma Phys. Rep. 1994, v. 20, p. 703-709.
5. V.I. Karas' and V.D. Levchenko. Penetration of a
Microwave with a Stochastic Jumping Phase (MSJP)
into Overdense Plasmas and Electron Collisionless
Heating by It // Problems of Atomic Sci. and Tech-
nol. Ser. «Plasma Electronics and New Acceleration
Methods». 2003, № 4(3), р. 133-136.
6. V.I. Karas`, Ya.B. Fainberg, A.F. Alisov, R. Bingham,
A.M. Artamoshkin, I.V. Gavrilenko, V.D. Levchenko,
M. Lontano, V.I. Mirny, I.F. Potapenko,
A.N. Starostin. Interaction of Microwave Radiation
Undergoing Stochastic Phase Jumps with Plasmas or
Gases // Plasma Phys. Rep. 2005, v. 31, p. 748-760.
7. V.I. Karas`, A.F. Alisov, A.M. Artamoshkin,
S.A. Berdin, V.I. Golota, A.M. Yegorov,
A.G. Zagorodny, I.A. Zagrebelny, V.I. Zasenko,
V.I. Karas’, I.V. Karas’, I.F. Potapenko,
A.N. Starostin. Low Pressure Discharge Induced by
Microwave Radiation with a Stochastically Jumping
Phase // Plasma Phys. Rep. 2010, v. 36, p. 736-749.
8. А.М. Artamoshkin, А.F. Alisov, О.V. Bolotov,
V.I. Golota, V.I. Karas`, I.V. Karas`, I.F. Potapenko,
А.М. Yegorov, I.А. Zagrebelny. Low pressure dis-
charge induced by microwave with stochastically
jumping phase // Proc. Int. Conf. on Plasma Physics
EPC ICPP (Stockholm, Sweden, 2012). Problems of
Atomic Sci. and Technol. Ser. «Plasma Physics» (19).
2012, № 6, p. 133-136.
Article received 17.04.2013.
OCОБЕННОСТИ ОПТИЧЕСКОГО ИЗЛУЧЕНИЯ ИЗ ПЛАЗМЫ РАЗРЯДА НИЗКОГО ДАВЛЕНИЯ,
ИНИЦИИРОВАНОГО МИКРОВОЛНОВЫМ ИЗЛУЧЕНИЕМ СО СТОХАСТИЧЕСКИ
ПРЫГАЮЩЕЙ ФАЗОЙ
В.И. Карась, А.Ф. Aлисов, О.В. Болотов, В.И. Голота, И.В. Карась, А.М. Егоров, А.Г. Загородний,
И.А. Зaгребельный, И.Ф. Потапенко
Изучается плазма разряда, инициируемого микроволновым излучением, со стохастически прыгающей
фазой в коаксиальном волноводе в оптимальном режиме пучково-плазменного генератора. Представленные
результаты являются продолжением ранее проведенных исследований. Экспериментально исследовались
оптические характеристики разрядной плазмы в широкой области давлений воздуха и мощности микровол-
нового излучения. Цель исследования – развитие нового типа источника оптического излучения.
OCОБЛИВОСТІ ОПТИЧНОГО ВИПРОМІНЮВАННЯ З ПЛАЗМИ РОЗРЯДУ НИЗЬКОГО ТИСКУ,
ІНІЦІЙОВАНОГО МІКРОХВИЛЬОВИМ ВИПРОМІНЕННЯМ ЗІ СТОХАСТИЧНО СТРИБКОВОЮ
ФАЗОЮ
В.I. Карась, А.Ф. Aлісов, О.В. Болотов, В.I. Голота, І.В. Карась, О.М. Єгоров, А.Г. Загородній, I.А. Зaгребельний,
I.Ф. Потапенко
Вивчаєтся плазма розряду, ініційованого мікрохвильовим випромінюванням, зі стохастично стрибковою
фазою в коаксиальному хвилеводі в оптимальному режимі пучково-плазмового генератора. Наведені ре-
зультати є продовженням раніше проведених досліджень. Експериментально досліджувались оптичні харак-
теристики розрядної плазми в широкій області тисків повітря та потужності мікрохвильового випроміню-
вання. Метою дослідження є розвиток нового типу джерела оптичного випромінювання.
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