MPD
SFERA
Microwave
discharges at the surfaces of dielectrics
To treat the products made
of metals and alloys by plasma in order to harden their
surfaces and increase their strength several fold.
To produce a low-temperature plasma with various densities of
the charged particles
To study fundamental processes in various plasmas and the properties
of these plasmas.
To test and adjust the diagnostic plasma system.
To train the personal in operation with the plasma and experimental
device as well as with the diagnostic equipment for measuring
plasma parameters.
Construction
of the device.
MPD SFERA is a spherical
chamber. Diameter of the chamber is 30 cm. In the chamber there
are 5 ports with a passage diameter of 16 cm and 8 ports
with a diameter of 3 cm. The ports are used for the installation
of the plasma sources, for multipurpose vacuum introductions and
for connection of the diagnostic equipment.
Microplasma
treatment samples Photos.
Click photo to enlarge.
Microwave
discharges at the surfaces of dielectrics
Abstract
Electrodeless
pulsed microwave discharges occurring at the surface of insulating
crystals in the vacuum are being studied both experimentally and theoretically.
Investigations of nonlinear physical phenomena developing in the near-surface
layer of insulating crystals (excited by pulsed microwave discharges)
are in progress. A classification of different types of electrodeless
pulsed microwave discharges is under development.
Of
special interest are those physical processes in the near-surface
layer of insulating crystals which bring about the accumulation of
high concentrations of radiation-induced point defects, the arising
of luminescence of induced color centers, the appearance of induced
electrical conductivity, the stimulation of strong absorbtion of microwave
power, the occurring of both a contracted discharge and an electrodeless
breakdown of crystals in a field of microwaves.
Characteristics
of planar optical waveguides created at the surface of insulating
crystals (previously colored by microwave discharges) will be under
investigation both experimentally and theoretically. On the basis
of the created waveguides a number of new devices important for integrated
optics and fiber optics will be developed. The most important devices
are miniature lasers and optical amplifiers which will be frequency-tuned
in the near infrared spectral range.
Basic
and applied scientific problems at a solution which the project is
aimed. Urgency and priority of studies.
- Study of correlations between the secondary-electron
emission and electrical, energetic, and optical processes developing
in the near-surface layer of insulating crystals excited by electrodeless
pulsed microwave discharges.
- Study of mechanisms of physical processes
initiating pulsed microwave breakdown of insulating crystals.
- Classification of different types of electrodeless
pulsed microwave discharges developing at the surface of insulating
crystals.
- Creation of integrated-optics and fiber-optics
miniature lasers and optical amplifiers (frequency-tuned in the
near infrared spectral range) at the surface of insulating crystals
containing color centers induced by pulsed microwave discharges.
- The problems 1, 2 and 3 are very important
not only for plasma physics of gas discharges but also for plasma
physics of solids, for secondary-electron-emission electronics
of dielectrics, for optics and spectroscopy of crystals, for physics
of interaction of radiation with solids and etc. The results obtained
by us are beyond the scope of above-mentioned traditional areas
of physics. New relationships between the areas are discovered,
these relationships appear only under high-intensive excitation
of crystals by microwave discharges.
The obtained results conform to
world scientific standards and have a priority nature. These results
are published in prestige scientific journals (Sov. Phys.- J. Tech.
Phys. Letters, Sov. Phys. - J. Exp. Teor. Phys. (JETP) Letters, Physica
Status Solidi) as well as in proceedings of large international conferences
(ICPIG XXI; ICPIG XXII; Strong Microwaves in Plasmas 1990, 1996).
Main
scientific topics within the framework of formulated problems.
Basic studies:
- Study of the processes of excitation and
maintenance of different types of electrodeless microwave discharges
at the surface of insulating crystals in a field of pulsed microwave
radiation;
- Study of mechanisms and kinetics of formation
and decay processes of short-lived electronic excitations (generated
by pulsed microwave discharges in the near-surface layer of insulating
crystals), which bring about the accumulation of high concentrations
of induced defects, the arising of luminescence of induced color
centers, the appearance of induced electrical conductivity, the
stimulation of strong absorbtion of microwave power, the occurring
of both a contracted discharge and an electrodeless breakdown
of crystals in a field of microwave radiation;
- Study of the secondary-electron-emission,
electrical, absorptional and optical processes developing in the
near-surface layer of insulating crystals excited by pulsed microwave
discharges;
- Formulation of qualitative and quantitative
criteria for the characterization of different types of electrodeless
pulsed microwave discharges developing at the surface of insulating
crystals;
- Determination of conditions for transformation
of one type of electrodeless pulsed microwave discharges to other;
- Classification of different types of electrodeless
pulsed microwave discharges (developing on the surface of insulating
crystals) on the basis of formulated criteria and studied properties
of microwave discharges.
Applied studies:
- Study of microwave discharges at the surface
of insulating crystals and other materials from the point of view
of raising an electric strength of output windows of microwave
devices and waveguides during powerful microwave radiation propagates
through the windows;
- Creation and study of planar optical waveguides
on the surface of insulating crystals (previously colored by microwave
discharges);
- Creation of miniature integrated-optics
and fiber-optics lasers and optical amplifiers (frequency-tuned
in the near infrared spectral range) at the surface of insulating
crystals containing color centers induced by pulsed microwave
discharges;
- It is possible also to perform the investigations
on the interaction of microwaves with solids for solving the urgent
problems of processing and modification of insulators and semiconductors:
- creation of sensitive optical storage media
at the surface of insulating crystals previously colored by
microwave discharges,
- coloration of jewels by use of microwave discharges,
- sputtering of different insulating targets by use of microwave
discharges,
- deposition of insulating films on the surface of different materials
by use of microwave discharges,
- sintering of different powdered mixtures for making the new types
of ceramics with use a microwave radiation,
- amorphization and modification of near-surface layer of semiconductors
and metals with use microwave discharges.
Main
scientific results obtained by the authors of the project.
-
Investigations of the
following phenomena taking place in plasma-flare microwave discharges
(developing at the surface of insulators) were performed:
- excitation of langmuir waves in a plasma resonance region,
- acceleration of electrons due to a self-breaking of strong
langmuir waves,
- acceleration of ions due to a potential jump in a plasma resonance
region,
- transformation of microwave power to the power of quasistationary
electric current in the plasma.
-
A new type of breakdown
was observed at the surface of solids - microwave breakdown
of insulating crystals initiated by a secondary-electron-emission
microwave discharge. The conditions of excitation of the secondary-electron-emission
discharge and the mechanisms for transformation of the one to
the plasma-flare microwave discharge were determined
- It was established that microwave breakdown
of insulating crystals is characterized by threshold values of both
power and duration of single pulses of microwave radiation.
- It was found that microwave breakdown of
insulating crystals is accompanied by a pronounced absorbtion of
microwave energy, an intense flash of light, and a formation of
contracted discharge and breakdown channel at the surface of crystals.
- The velocity of formation of the contracted
discharge was determined. Evaluations of values of both an electrical
conductivity and an electron density in the breakdown channel at
the surface of crystals were performed.
- It is shown that the further evolution of
the contracted discharge is accompanied by evaporation, dissociation,
ionization, and explosive fly to bits of the material in the breakdown
channel. In such a way the plasma-flare microwave discharge is formed.
- It was found that the characteristic duration
of luminescence growth/decay (for LiF, NaCl, KCl, CsI crystals excited
by pulsed microwave discharges at room temperature) is about 1-2
microseconds.
- Optical-absorption spectra of LiF crystals
previously colored by microwave discharges were measured. The induced
F, F2, F3-,
F3, F3+, N centers stable at room temperature
were observed.
- It is shown that a density of induced aggregate
F2 and F3+ color centers is about a density
of induced F centers. This fact testifies a high-intensive excitation
of LiF crystals by microwave discharges.
- Luminescence spectra of LiF crystals (previously
colored by microwave discharges) excited by laser were obtained.
Optical characteristics of F2 and F3+ centers
in LiF crystals were measured. Similarity of investigated here color
centers with those produced in gamma-irradiated LiF crystals was
obtained.
- It was measured (at room temperature) a
luminescence spectrum of short-lived F2 and F3+
color centers temporaly induced in uncolored LiF crystals by pulsed
microwave discharges at the pre-breakdown stage of evolution. The
spectrum is very close to the one that was measured for LiF crystals
(previously colored by microwave discharges and containing F2
è F3+ centers) excited by laser.
- The explanations of origin and further evolution
of pulsed microwave discharges were done on the basis of the idea
of high-intensive excitation of electronic subsystem of solids.
A relaxation of the excitation in the near-surface layer of insulating
crystals leads to a creation of short-lived color centers with high
density. A recombination of induced color centers brings about the
microwave breakdown of the crystals.
- The following original techniques for investigation
of processes developing in the crystals and in the plasma-flare
microwave discharges have been proposed and applied in experiments:
- the photoelasticity technique for studying of strong acoustic
waves in the bulk of crystals excited by pulsed microwave discharges;
- the techniques for resonance-laser-absorbtion and resonance-laser-fluorescence
measurements of probe laser beams for studying of movement of Na
(or Cs) atoms emitted from the surface of NaCl (or CsJ) crystals
as a result of microwave breakdown.
These techniques as applied to study of pulsed microwave discharges
developing at the surface of insulating crystals are unique.
- Methods for selective formation of induced
color centers (stable at room temperature) in the near-surface layer
of insulating crystals, excited by microwave discharges, were developed.
- Methods for creation of an optically-dense
layer on the surface of insulating crystals during coloring by microwave
discharges were developed.
- Processes of excitation and maintenance
of electrodeless microwave discharges on a surface of dielectric
crystals were studied. In the process, radiation defects (color
centers) are created in the near surface layers of the crystals.
Kinetics of accumulation and relaxation of metastable and stable
defects in the crystals, excited by microwave discharges, was studied.
It was shown, that a high density of defects in the crystals considerably
changes the characteristics of microwave discharges, developing
on the surface of dielectric crystals. For example, when compared
to uncolored crystals, the excitation of microwave discharges on
the surface of colored lithium fluoride (LiF) crystals (containing
induced stable F2 è F3+ color centers
with high density ~1x(1020-1021) ñì-3)
is accompanied by considerable decrease of electron current from
the discharge and luminescence intensity of induced F2
è F3+ color centers. It was found that under this
conditions the luminescence kinetics of LiF crystals (excited by
microwave discharges) changes substantially: in the bands of light
emission of induced F2 è F3+ color
centers (in the wavelength regions 670±30 nm and 540±30
NM) there appear, together with slow components of luminescence
~ 1 microsecond (typical for uncolored crystals), fast components
(typical for colored crystals) with characteristic intensity rise
and fall times ~ 0.1 microsecond.
- The physical mechanisms and dynamics of
formation of induced electrical conductivity in the near-surface
layer of dielectric crystals, excited by electrodeless microwave
discharges, were studied. It was shown that microsecond microwave
discharge at the pre-breakdown stage of development gives rise to
a high-intensive excitation of the surface layer of the crystals.
It was found that excitation of the surface layer of LiF crystals
by low-energy electrons from a microwave discharge with a characteristic
electron energy of 1 keV, electron density 1x1010 cm-3,
and microwave discharge pulse duration 1 microsecond is characterized
by a specific input energy density ~ 500 J/cm3. In the
process, the excitation is accompanied by creation of short-lived
aggregate F2 è F3+ color centers with
high density ~1x(1020-1021) ñì-3
in the surface layer of LiF crystals. These values are several orders
of magnitude higher than the corresponding ones when LiF crystals
are excited with high-current pulsed electron beams, x rays or gamma
rays. It is proposed the physical model of transformation of secondary-electron-emission
microwave discharge to plasma-flare microwave discharge as a result
of formation of contracted discharge and arising electrodeless microwave
breakdown of dielectric crystals.
References.
[1] G.M.Batanov, V.A.Ivanov, I.A.Kossyi,
K.F.Sergeichev. Large-Amplitude Plasma Waves and Particle Acceleration
in the Plasma Corona of a Microwave Discharge. Sov. Phys. - J. Plasma
Physics, 1986. Vol. 12. No. 5. Pp. 317-325.
[2] G.M.Batanov, V.A.Ivanov. Plasma-Flare
Conversion of the Energy of Microwaves in the Decimeter Band into
the Energy of Quasi-Stationary Electric Current . /In: "Generation
of Nonlinear Waves and Quasistationary Currents in Plasma", Ed.
by L.M.Kovrizhnykh. New-York: Nova Science Publishers, Inc., 1992.
227 p.(Proc. of the Institute of General Physics, Academy of Sciences
of the USSR. Moscow: Nauka, 1988. Vol. 16. Pp. 46-79 [in Russian]).
[3] G.M.Batanov, V.A.Ivanov, M.E.Konyzhev
et al. Generation of High Potentials in the Plasma by the Interaction
with Intense Microwave Radiation. /Proc. Of the International Workshop
on Strong Microwaves in Plasmas. Suzdal (USSR), September 17-22, 1990.
[4] V.A.Ivanov, M.E.Konyzhev et
al. Generation of High Potentials and Fast Electron Diagnostic in
Microwave Produced Plasma Flare. /Proc. Of the XX-th International
Conference on Phenomena in Ionized Gases. Contributed
Papers. Vol. 5. Pp. 1091-1092. Pisa (Italy), July 8-12, 1991.
[5] G.M.Batanov, V.A.Ivanov, M.E.Konyzhev,
V.A.Konyushkin, and S.B.Mirov. Coloration of LiF Single-Crystals by
Surface Microwave Discharges. /Proc. Of the International School of
Plasma Physics (ISPP-13 "Piero Caldirola").
Industrial Application of Plasma Physics, Ed. By G.Bonizzoni, W.Hooke
and E.Sindoni. SIF, Bologna 1993. Pp. 521-525.
[6] G.M.Batanov, V.A.Ivanov, M.E.Konyzhev,
V.A.Konyushkin, and S.B.Mirov. Microwave Discharge Method for Formation
of Optically-Dense Submicron- Thickness Layers with High Concentrations
of Color Centers on the Surfaces of Alkali-Halide Crystals /Proceedings
I. XXI International Conference on Phenomena in Ionised Gases. Pp.
37-38. Sept. 19-24, 1993. Rurh-University, Bochum, Germany.
[7] G.M.Batanov, V.A.Ivanov, M.E.Konyzhev,
V.A.Konyushkin, and S.B.Mirov. Creation of an Optically Dense Layer
on the Surface of a Lithium Fluoride Crystal During Coloring in a
Microwave Discharge. Sov. Phys. - J. Tech. Phys. Lett., 1993. Vol.
19. No. 11. Pp. 653-654.
[8] G.M.Batanov, V.A.Ivanov, M.E.Konyzhev.
Microwave Breakdown of Ionic Crystals Initiated by a Secondary-Emission
Discharge. Sov. Phys. - J. Exper. Theor. Phys. Lett. (JETP Lett.),
1994. Vol. 59. No. 10. Pp.
690-694.
[9] G.M.Batanov, V.A.Ivanov, M.E.Konyzhev.
Microwave Breakdown on the Surface of Ionic Crystals in Vacuum.
XXII Conference on Phenomena in Ionized Gases. Vol.IV. /Editors: K.H.Becker,
W.E.Carr, E.E.Kunhardt. Hoboken, New Jersey, USA, 1995. Pp. 143-144.
[10] G.M.Batanov, V.A.Ivanov,
M.E.Konyzhev. Luminescence of short-lived color centers in LiF crystals
excited by secondary-electron emission microwave discharge. /In book:
Strong Microwaves in Plasmas. Vol.1. Ed. By A.G.Litvak. Nizhny Novgorod:
Institute of Applied Physics, 1997. Pp. 401-406.
[11] V.V.Ter-Mikirtychev, T.Tsuboi,
M.E.Konyzhev, V.P.Danilov. Spectroscopic characteristics of color
centers produced in a LiF crystal surface layer by microwave
discharge. Phys. Stat. Solidi (b), 1996. Vol. 196. No. 1. Pp.
269-274.
[12] G.M.Batanov, V.A.Ivanov,
M.E.Konyzhev, A.A.Letunov. Luminescence of short-lived color centers
induced in LiF crystals by a pulsed microwave discharge. Sov. Phys.
- J. Exper. Theor. Phys. Lett. (JETP Lett.), 1997. Vol. 66. No 3.
Pp. 170-174.
Available
installation and scientific equipment.
1. The experimental installation
consists of the following main components:
- pulsed magnetron (microwave power is up
to 5 ÌW, oscillation frequency of microwaves is 2 GHz,
pulse duration ranges from 1 to 50 microseconds),
- waveguide for delivery of microwave power
from the magnetron to the vacuum chamber,
- titanium pumps for pumping down the chamber
to a high vacuum,
- high-voltage rectifier unit,
- pulsed modulator unit,
- power sources.
2. Scientific equipment consists
of the following main components:
- directional waveguide couplers for measurements
of power of the incident to the discharge and reflected from the
discharge pulsed microwave radiation,
- optical techniques for measurements of
spectral and kinetic characteristics of luminescence and optical-absorbtion
of insulating crystals excited by pulsed microwave discharges,
- optical techniques for measurements of
both luminescence and optical-absorbtion spectra of insulating
crystals previously colored by pulsed microwave discharges,
- multigrid electrostatic analyzers of energy
of charge particles for measurements of currents of electrons
and ions from the region of microwave discharges, photoelasticity
technique for studying of strong acoustic waves in the bulk of
transparent insulating crystals excited by pulsed microwave discharges;
- optical techniques for resonance-laser-absorbtion
and resonance-laser-fluorescence measurements of probe laser beams
for studying of movement of NA (or Cs) atoms emitted from the
surface of NaCl (or CsJ) crystals as a result of microwave breakdown.
- integrated-optics technique for study
of characteristics of planar optical waveguides created at the
surface of insulating crystals previously colored by microwave
discharges.
Scientific
studies planned for 2000-2002 yrs.
- Study of electron current ejected from
the region of microwave discharges (developing at the surface
of LiF crystals) at the different stages of discharge evolution.
- Study of dynamical and spectral characteristics
of luminescence of LiF crystals excited by pulsed microwave discharges
at different stages of evolution.
- Study of dynamical and spectral characteristics
of optical absorbtion of LiF crystals excited by pulsed microwave
discharges at different stages of evolution.
- Determination of characteristic values
of life time and density of short-lived color centers generated
in the near-surface layer of LiF crystals excited by pulsed microwave
discharges at different stages of evolution.
- Study of a relationship between the density
of indused color centers, stable at room temperature, and the
evolution of microwave discharges at the surface of LiF crystals.
- Study of an evolution of a density of
Cs atoms emitted from the surface of CsJ crystals exited by microwave
discharges.
- Study with use an electron microscope
technique of erosion areas produced at the surface of LiF crystals
as a result of interaction of pulsed microwave discharges with
the crystals.
- Study of characteristics of planar optical
waveguides created at the surface of LiF crystals (previously
colored by microwave discharges) with use of integrated-optics
and fiber-optics techniques.
- Creation of integrated-optics and fiber-optics
miniature lasers and optical amplifiers (frequency-tuned in the
near infrared spectral range) at the surface of LiF crystals containing
color centers induced by pulsed microwave discharges.
If required, not only LiF crystals
but also another insulating crystals will be used for studies.
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