Ion flows from area of beam plasma discharge at low magnetic field – physics and application
For verification of conclusions of the numerical experiment the measurements of a velocity distribution function of electrons escaping area of discharge to its collector, together with energy distribution of ions which are running out from discharge on a normal from an axis are carried out. The ef...
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Isaev, N.V. Shustin, E.G. Tarakanov, V.P. 2015-05-11T19:41:07Z 2015-05-11T19:41:07Z 2006 Ion flows from area of beam plasma discharge at low magnetic field – physics and application / N.V. Isaev, E.G. Shustin, V.P. Tarakanov // Вопросы атомной науки и техники. — 2006. — № 5. — С. 100-104. — Бібліогр.: 12 назв. — англ. 1562-6016 PACS: 52.80.-s https://nasplib.isofts.kiev.ua/handle/123456789/81164 For verification of conclusions of the numerical experiment the measurements of a velocity distribution function of electrons escaping area of discharge to its collector, together with energy distribution of ions which are running out from discharge on a normal from an axis are carried out. The effect of essential heating of electrons of plasma in paraxial area is detected in those regimes, when the acceleration of ions is observed. The effect of accumulation of a field of regular oscillations in the region of injection of a beam as well as their stochastisation in process of propagation along the axis of system are detected. The results of physical experiments qualitatively correlate with the data of computer simulation. Для проверки выводов численного эксперимента были проведены измерения функции распределения по скоростям электронов, выходящих из области разряда на коллектор, совместно с распределением по энергии ионов, которые выходят из разряда по нормали к оси. В режимах, когда наблюдаются ускоренные ионы, детектирован эффект существенного нагрева электронов плазмы. Детектирован эффект аккумуляции поля регулярных осцилляций в области инжекции пучка и их стохастизации в процессе распространения вдоль оси системы. Результаты физических экспериментов качественно коррелируют с данными компьютерного моделирования. Для перевірки висновків чисельного експерименту були проведені вимірювання функції розподілу за швидкостями електронів, що виходять з області розряду на колектор, разом з розподілом за енергіями іонів, які виходять з розряду по нормалі до осі. В режимах, коли спостерігаються прискорені іони, детектовано ефект суттєвого нагріву електронів плазми. Детектовано ефект акумуляції поля регулярних осциляцій в області інжекції пучка та їх стохастизації у процесі поширення вздовж осі системи. Результати фізичних експериментів якісно корелюють з даними комп’ютерного моделювання. The authors express thanks to professor A.A. Rukhadze for useful discussions, to Yu.V. Fedorov for participation in approbation of technology of etching. This work was executed at financial support of Russian Fund for Basic Researches and Government of the Moscow region (grant "Naukograd-2004" №04-02-97257). en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Газовый разряд, плазменно-пучковый разряд Ion flows from area of beam plasma discharge at low magnetic field – physics and application Ионные потоки из области пучково-плазменного разряда в слабом магнитном поле – физика и приложения Іонні потоки з області пучково-плазмового розряду у слабкому магнітному полі – фізика і застосування Article published earlier |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| title |
Ion flows from area of beam plasma discharge at low magnetic field – physics and application |
| spellingShingle |
Ion flows from area of beam plasma discharge at low magnetic field – physics and application Isaev, N.V. Shustin, E.G. Tarakanov, V.P. Газовый разряд, плазменно-пучковый разряд |
| title_short |
Ion flows from area of beam plasma discharge at low magnetic field – physics and application |
| title_full |
Ion flows from area of beam plasma discharge at low magnetic field – physics and application |
| title_fullStr |
Ion flows from area of beam plasma discharge at low magnetic field – physics and application |
| title_full_unstemmed |
Ion flows from area of beam plasma discharge at low magnetic field – physics and application |
| title_sort |
ion flows from area of beam plasma discharge at low magnetic field – physics and application |
| author |
Isaev, N.V. Shustin, E.G. Tarakanov, V.P. |
| author_facet |
Isaev, N.V. Shustin, E.G. Tarakanov, V.P. |
| topic |
Газовый разряд, плазменно-пучковый разряд |
| topic_facet |
Газовый разряд, плазменно-пучковый разряд |
| publishDate |
2006 |
| language |
English |
| container_title |
Вопросы атомной науки и техники |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| format |
Article |
| title_alt |
Ионные потоки из области пучково-плазменного разряда в слабом магнитном поле – физика и приложения Іонні потоки з області пучково-плазмового розряду у слабкому магнітному полі – фізика і застосування |
| description |
For verification of conclusions of the numerical experiment the measurements of a velocity distribution function of electrons
escaping area of discharge to its collector, together with energy distribution of ions which are running out from discharge on a
normal from an axis are carried out. The effect of essential heating of electrons of plasma in paraxial area is detected in those
regimes, when the acceleration of ions is observed. The effect of accumulation of a field of regular oscillations in the region of
injection of a beam as well as their stochastisation in process of propagation along the axis of system are detected. The results of
physical experiments qualitatively correlate with the data of computer simulation.
Для проверки выводов численного эксперимента были проведены измерения функции распределения по скоростям электронов, выходящих из области разряда на коллектор, совместно с распределением по энергии ионов, которые выходят из разряда по нормали к оси. В режимах, когда наблюдаются ускоренные ионы, детектирован эффект существенного нагрева электронов плазмы. Детектирован эффект аккумуляции поля регулярных осцилляций в области инжекции пучка и их стохастизации в процессе распространения вдоль оси системы. Результаты физических экспериментов качественно коррелируют с данными компьютерного моделирования.
Для перевірки висновків чисельного експерименту були проведені вимірювання функції розподілу за швидкостями
електронів, що виходять з області розряду на колектор, разом з розподілом за енергіями іонів, які виходять з розряду по
нормалі до осі. В режимах, коли спостерігаються прискорені іони, детектовано ефект суттєвого нагріву електронів
плазми. Детектовано ефект акумуляції поля регулярних осциляцій в області інжекції пучка та їх стохастизації у процесі
поширення вздовж осі системи. Результати фізичних експериментів якісно корелюють з даними комп’ютерного
моделювання.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/81164 |
| citation_txt |
Ion flows from area of beam plasma discharge at low magnetic field – physics and application / N.V. Isaev, E.G. Shustin, V.P. Tarakanov // Вопросы атомной науки и техники. — 2006. — № 5. — С. 100-104. — Бібліогр.: 12 назв. — англ. |
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2025-11-26T16:16:37Z |
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2025-11-26T16:16:37Z |
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1850627625180987392 |
| fulltext |
ION FLOWS FROM AREA OF BEAM PLASMA DISCHARGE
AT LOW MAGNETIC FIELD – PHYSICS AND APPLICATION
N.V. Isaev, E.G. Shustin, V.P. Tarakanov*
Institute of Radio Engineering a. Electronics of RAS, Fryazino, Russia
E-mail: shustin@ms.ire.rssi.ru
*Institute of Thermal Physics of Extreme States of UIHT of RAS, Moscow
For verification of conclusions of the numerical experiment the measurements of a velocity distribution function of electrons
escaping area of discharge to its collector, together with energy distribution of ions which are running out from discharge on a
normal from an axis are carried out. The effect of essential heating of electrons of plasma in paraxial area is detected in those
regimes, when the acceleration of ions is observed. The effect of accumulation of a field of regular oscillations in the region of
injection of a beam as well as their stochastisation in process of propagation along the axis of system are detected. The results of
physical experiments qualitatively correlate with the data of computer simulation.
PACS: 52.80.-s
1. INTRODUCTION
In our researches [1] the effect of formation of ion
flow in beam plasma discharge (BPD) at low magnetic
field was detected. The flow propagates from a dis-
charge axis on normal to periphery. BPD is generated
by an electron beam with energy ~2 keV and current
density 0,1…1 A/cm2 in gas medium of low pressure
(0,01…0,1 Pa) at low magnetic field (0.2…0.5 mTl). At
these conditions electrons of both beam and plasma are
magnetized (their Larmour radius is much less than the
transversal size of the interaction chamber), while for
plasma ions magnetic field is practically imperceptible.
The attempts to determine a mechanism of genera-
tion of the ion flow were performed in [2,3], where pos-
sibility has been estimated of ion acceleration due to
their trapping by low frequency waves excited at beam
plasma interaction: helicon [2] or azimuth wave in radi-
ally inhomogeneous plasma [3].
The realizability in principle of such mechanisms in
conditions, close to conditions of experiments [1], was
shown. In these estimations that was supposed, howev-
er, that at stage of excitation of low frequency waves the
beam saved a narrow enough velocity distribution func-
tion (approximation of monokinetic beam).
To test the assumptions on mechanism of accelera-
tion of ions we have conducted computer simulation of
interaction in a beam plasma system at parameters of
model qualitatively appropriate to conditions of experi-
ments [1]. In this formulation of the task we aimed to
reveal main features of interaction in a longitudinally
bounded system and their corollary, important for the
main problem: definition of a current balance and ener-
gy relations for components of plasma in the system.
2. NUMERICAL EXPERIMENT
The simulation was conducted with usage of the
"Karat" code [4]. Mathematical model underlying the
code is the Maxwell equations with different matter
equations, including one in the form of kinetic equation
solved by a method of particles (PIC-method), and also
ones in the form of different phenomenological models.
The Maxwell equations are solved by a plain finite-dif-
ference method on shifted grids having the second order
of accuracy.
In this work the two-dimensional version was used,
in which all components of speed of particles were tak-
en into account.
The axisymmetrical problem is considered. Count-
able area is a tube of 20 cm in length and 5 cm in radius.
Its surface is under a zero potential. From the left end
face in a circle of 1 cm radius a beam with energy 2 keV
and current 0.5 A is injected. Initially the cylinder is
filled with plasma with density np=1010 cm-3. All count-
able area is immersed in an external permanent magnet-
ic field 50 Gs.
Numerical and the physical parameters were select-
ed so that the Debye screening distance was more than
step of a grid, and the number of macroscopic particles
in a Debye orb was much more than unity.
On a surface of the cylinder and end faces limiting
plasma the condition of a total absorption of particles
was set.
The main results of computer experiment are re-
duced to following.
The fastest process developing in the system, as well
as follows from a theory of interaction in a beam plasma
system, is the excitation of oscillations of electrons of a
beam and plasma with frequency ω≈ωpe and longitudi-
nal wave number kz≈ω/V0, and appropriate generation of
an electrical field. However already in time about 2…
5 ttrans (ttrans is a transit time of an unperturbed beam) ob-
viously appears essential feature of model: the system
under research represents a plasma resonator, the accu-
mulation of energy in which results in constant change
of conditions, in which the injected beam falls. It is ob-
vious from phase portraits of electrons in different in-
stants after the injection begins (Fig.1).
Until moment t≈ttrans=7,6 ns the typical bunching of
a beam appropriate to development of instability on
fixed frequency is observed. It is important, that the
wave is localized in the region of a beam: though the
electrons gain considerable transversal oscillation veloc-
ity, beam, being dilated, does not fall outside the limits
~2rb0. In the same limits energy of an electrical field of a
wave is concentrated also.
At the subsequent stages of injection the new por-
tions of a beam fall in a field generated at the previous
stage, therefore already after 10 ns the bunching occurs
much faster, and at the end of an interaction region the
phase bunches practically get mixed up. In time
~100 periods of a principal frequency this is not only
full chaotization of motion of the beam that is observed,
but also deceleration and even return of a part of the
________________________________________________________________
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2006. № 5.
Серия: Плазменная электроника и новые методы ускорения (5), с.100-104.
100
mailto:shustin@ms.ire.rssi.ru
electrons: the electrons of the beam become physically
indistinguishable from electrons of plasma.
A temporal structure of a HF field of the excited
wave is shown in Fig.2. One can see, that while near to
a point of injection the field on the initial stage has reg-
ular character appropriate to conception of the theory of
hydrodynamic beam instability (an amplitude-modulat-
ed wave at Langmuir frequency), further the wave gets
stochastic. Amplitude of the field at stage, where it is
regular, reaches 1000 V/cm, and then it is reduced up to
200…300 V/cm.
Fig.1. Phase portraits of beam electrons at moments
t=8 ns (a); 120 ns (b)
0 20 40 60 80
-1000
-500
0
500
1000
t, ns
U, V
U,
V
Z=5 cm
0 20 40 60 80
t, ns
Z=15 cm
Fig.2. Electric potential at the system axis in time
It is possible to observe energy exchange of the
beam with the field and with electrons of plasma in
Fig.3. The curves indicate, that up to 15 ns the shape of
a distribution function of electrons on velocities (EDF)
qualitatively meets to conception of the non-linear theo-
ry of hydrodynamic instability. 2 bunches are formed in
the beam, in-phase (delayed) and counter-phase (accel-
erated), more and more dispersing and extending in
space of velocities in process of the wave amplitude
growth. Thus the distribution function of electrons of
plasma practically does not vary. Further chaotization of
oscillations results in intermixing bunches and forma-
tion of EDF, almost monotonically falling up to speeds
~ 1,5V0. Since t~30…40 ns there is also heating of elec-
trons of plasma by an intensive HF wave. As a result a
group of accelerated electrons of plasma (“a superther-
mal tail”) is created in the beginning, and then heating
of all bulk of plasma electrons occurs.
0,0 0,1 0,2
0
10
20
30
40
50
0,0 0,1 0,2
8
7
6
5
4
3
2
1
f(Vz), rel. units.
Vz/C
16
15
14
13
12
11
10
9 Vz/C
Fig.3. Velocity distribution function of electrons close
to back wall of the volume at different time moments:
since 10 to 50 ns in 5 ns (curves 1-9) and since 50
to120 ns in 10 ns (curves 9-16). Dotted line is undis-
turbed beam velocity
0,0
0,5
1,0
0,0
0,5
1,0
1,5
2,0
2,5
20 40 60 80 100 120
0
20
40
60
80
100
120
20 40 60 80 100 120
0
500
1000
Iel,
A
3
2
1
Iion,
A
3
21
〈W〉,
eV
t,
ns t,
ns
b
2
2
1
a
〈W〉,
eV
3
3
1
Fig.4. Currents and mean energies of electrons (a) and
ions (b) to different parts of plasma volume walls: 1 –
to paraxial part of back plate (R<2.5 cm); 2 – to pe-
ripheral part of back plate (R>2.5 cm); 3 – to side wall
(15 cm<Z<20 cm)
Returning to the analysis of an electrical field, gen-
erated in a system, it is necessary to note, that HF oscil-
lations exist on a background of increasing quasi-steady
potential: mean value of a potential on a time interval
>>1/ωpe reaches value ~150 V to the moment 120 ns.
The growth of a potential is caused by increase of ener-
gy of electrons of plasma and appropriate increase of a
difference of flows of electrons and ions to interaction
region boundaries (Fig.4). As is already pointed above,
the generated fields are localized in area occupied by
the beam. So the potential gradient on radial boundary
of the area accelerating ions to a lateral wall of a vol-
ume is created that is obviously seen from a Fig.4.
Thus, it is possible to select two regions in a volume
of plasma with different parameters. Inside a beam re-
________________________________________________________________
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2006. № 5.
Серия: Плазменная электроника и новые методы ускорения (5), с.100-104.
101
Z, cm
b
a
gion the intensive stochastic oscillations in frequency
band near to Langmuir frequency are localized. In this
area strongly non-equilibrium plasma is formed that is
characterized by rather energetic and non-isotropic elec-
tron component (the mean energy reaches hundreds eV)
and different directions of a drift of electrons and ions.
On periphery much more feeble oscillations are excited
which don’t influence parameters of plasma in this area
essentially. The intensive escape of electrons from
paraxial area to end plates of the system boosts increase
of a potential of this area of plasma and, as a corollary,
drift of unmagnetized ions to periphery of this area. En-
ergy of thus accelerated ions can reach several tens eV.
3. PHYSICAL EXPERIMENT
Results of computer experiments boosted measure-
ments of a spatial distribution of high frequency fields
excited in the system and analysis of distribution func-
tion of electrons (EDF) at an exit from the interaction
region. The installation diagram is shown in a Fig.5.
2
1
4 4
2
6
8 5
4 4
3
1
7
Pump out
Pump out
Fig.5. Diagram of experiment. 1 – Pierce type electron
gun; 2 – beam focusing coils; 3 – plasma chamber;
4 – Helmholtz coils; 5 – ion energy analyzer; 6 – HF
dipole probe; 7 – HF spectrum analyzer; 8 – collector
At an opposite wall of the plasma chamber the col-
lector of electrons combined with an energy analyzer of
electrons (an electrostatic grid analyzer with decelerat-
ing field) is placed. For diagnostics of oscillations in
plasma the symmetrical dipole probe loaded with an in-
put of a spectrum analyzer through a resistance trans-
former is used. The probe is movable along an axis and
on radius of the chamber.
As a receiver of an ion flow the electrostatic analyzer
with a flat deflecting mirror movable along a side of thep-
lasma chamber is used. A collimator of ions is oriented
on normal to axis of the chamber. Parameters of an ana-
lyzer are: range of energies 0…100 eV, sensitivity
~0,5·10-9 A/cm2, resolution on energy ∆W/W0=0.12.
400 600 800
0
2
4
6 S, rel. units
Frequency, Mc/s
L=5 cm
7
9
400 600 800
0
2
4
6
Frequency, Mc/s
S, rel. units
L=25 cm
30
36
Fig.6.The power spectra of Ez component
In a Fig.6 the power spectra of Ez component in band
ω≈ωpe, registered by the probe on different distances L
from a collector are shown.
One can see that in the beginning of an interaction
region a spectrum is rather narrow-band, then the spec-
trum widens to more high frequencies. In Fig.7 the lon-
gitudinal distributions of the oscillation intensity in fre-
quency band appropriate to peak of the spectrum in the
beginning of area (an integral of a spectral curve on a
band 610±10 Mc/s – curve 1), and in the whole of band
of generated oscillations (curve 2) are shown. Effect of
accumulation of regular (near monochromatic) oscilla-
tions near to a point of beam injection is evident here,
after which goes more or less smooth growth of intensi-
ty of stochastic oscillations. The analysis of transversal
distribution of a field strength displays, that the oscilla-
tions in range of Langmuir frequencies are obviously lo-
calized on radius in limits Rbeam.
0 5 10 15 20 25 30 35 40 45
0,0
0,5
1,0
1,5
2,0
2,5
3,0
Ez
2, rel. units
Z, cm
1
2
Fig.7. The longitudinal distributions of the oscillation
intensity
In Fig.8 the curves of distribution function of elec-
trons on longitudinal velocities (EDF) of electrons
reaching a collector are represented at different chamber
pressures (so, at different relations nb/np). (For visualiza-
tion curves in Figs.3,8 and 9 sequentially are biased on a
vertical). The EDF on a collector in pre-discharge
regime (p=0,05 mTorr) represents peak of electrons of
the beam, spreading to smaller velocities due to twist of
the beam in a non-uniform magnetic field at input to the
plasma chamber. At a pressure buildup there is an
avalanche ignition of beam plasma discharge. The EDF
of beam is jump-like spread to smaller velocities, run-
ning up to a shape of a plateau at this interaction length.
In process of gas pressure growth plasma density in-
________________________________________________________________
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2006. № 5.
Серия: Плазменная электроника и новые методы ускорения (5), с.100-105.
102
creases (accordingly, the relation nb/np decreases), and
the diffusion of EDF of the beam decreases. Simultane-
ously with diffusion of the beam on velocities the part
of EDF appropriate to electrons of plasma is obviously
dilated also: the mean energy of a longitudinal motion
of plasma electrons in the area occupied by the beam
reaches 100…120 eV.
The measurements with an energy analyzer moving
on radius have shown, that both heating of main bulk of
electrons of plasma and group of electrons with interme-
diate energies are observed only in a central part of a
plasma column, where the beam is present.
At approach of the collector with the energy analyz-
er to a gun, both parameters of the beam and pressure of
gas being constant, there is a discontinuation of dis-
charge on length of an interaction area L≈15 cm: density
of plasma diminishes by order, both the intensity and
shape of glow, intensity and spectrum of UHF of radia-
tion from plasma vary essentially. At increase of length,
followed by ignition of the discharge, EEDF sequential-
ly is dilated, reaching a plateau, and then becomes
monotonically falling curve.
0,00 0,02 0,04 0,06 0,08 0,10
v/c
p=0.05 mTorr
0.2 mTorr
0.3 mTorr
0.5 mTorr
0.8 mTorr
V0
f(V), arb. units
Fig.8. A distribution function of electrons on longitudi-
nal velocities of electrons
The distribution function on energies (IEDF) of ions
which escape from area of discharge on a normal to an
axis, in different points on length of the chamber togeth-
er with power distribution of electrons on a collector are
shown in a Fig.9. The flow of ions varies on intensity
and on value of mean energy along length of area of dis-
charge, reaching a maximum of both these values in an
region, where the maximum value of intensity of excit-
ed HF oscillations is registered. This is characteristic,
that the flow of accelerated ions is detected only when
the obvious heating of electrons of plasma is observed.
At large pressure of gas (small nb/np) the energy of a
longitudinal electron motion does not exceed 10 eV; si-
multaneously flow of ions to periphery decreases by the
order and has mean energy no more than 10…15 eV.
The results represented here qualitatively meet to con-
clusions of section 2. The accumulation of energy of co-
herent oscillations in the beginning of an interaction re-
gion with the subsequent development of stochastic oscil-
lations is observed. The diffusion of EDF of beam elec-
trons at stage of excitation of stochastic oscillations is ac-
companied by essential heating of electrons of plasma.
0 25 50 75 100
27 cm
23 cm
f(W)
W, eV
Z=32 cm
21 cm
Fig.9. A distribution function on energies of ions
The power characteristics of a flow of accelerated
ions on periphery of discharge are obviously related to
intensity of excited oscillations and with heating of plas-
ma electrons. Thus, it is possible to approve, that of-
fered above explanation of the mechanism of ions accel-
eration in BPD in a low magnetic field has experimental
confirmation.
4. DISCUSSION
In [5, 6] attention have been drawn first to the fact of
a relaxation distance reduction for a monochromatic
beam in semi-bounded plasma. This is owing to effect of
accumulation of oscillations in plasma near to a plane of
injection of a beam because of a smallness of their group
velocity in comparison with speed of the beam. Value of
a maximum field is rated there: for conditions of our ex-
periment (np=1010 cm-3, nb=108 cm-3, Wb=2*103 eV,
Te=10 eV) in absence of collisions of electrons with
heavy particles E2/4π≈4nbWb~3…5 kV/cm, that meets
well enough to the data of a Fig.2.
It is necessary to remind, that at stochastic oscilla-
tions one should account inverse of correlation interval
as an effective collision frequency [7]. Both in numeri-
cal and in physical experiments the effect of stochastiza-
tion of excited oscillations is obviously observed, thus
width of a spectrum (i.e. the reciprocal interval of a cor-
relation) reaches or even exceeds 0,1ω0. According to
[6], the accumulation of energy in this case is essentially
reduced (compare to a Fig.2,а,б).
Stochastization of excited oscillations is rather essen-
tial feature detected in numerical experiment. Let's re-
mind, that in physical experiments the generation noise-
like oscillations was observed regularly, including [1],
and the attempts were done to explain this effect by inter-
action of excited high-frequency waves with other types
of oscillations. From results shown above it is evident,
that stochastization comes already then, when any other
instabilities in the system are not manifested yet.
As is shown in [8], longitudinal limitation of the re-
alistic plasma beam system results in feedback obvious-
ly influential in dynamics of development of instability
and time-space structure of generated fields. In that pa-
per the analogy of the system to the generator of
stochastic microwave oscillations executed as a travel-
ing-wave tube with the delayed feedback was offered.
It is necessary to note, that the stochastic character of ex-
cited oscillations appears for the broad class of the determi-
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103
nate dynamic systems [9,10]. The particular mechanism of
stochastization in our case still should be researched.
Although our numerical experiment describes devel-
opment of process on the initial stage, the corollaries of
observed processes have become apparent at studies of a
stationary system as well, including at beam plasma dis-
charge, as is shown at section 2. Let's also remind of
measurements of dissipation of a beam on angles and en-
ergies in BPD without a magnetic field [11], where were
detected both superthermal electrons and monotonically
falling EDF of a beam simultaneously with generation of
a broadband spectrum of RF radiation from plasma. Pa-
per [8] was already mentioned above as well, containing
the proofs of a chaotization of generated oscillations due
to feedback in a beam - plasma system. In [12] the forma-
tion of a peak in distribution of HF fields in the beginning
of a system with amplitude, sufficient for essential
strengthening of ionization in this area is shown.
5. APPLICATION
In order to optimize the treatment of materials in plas-
ma processing reactors operating at low gas pressures, it
is very important to control the parameters of ions bom-
barding the processed material. Thus, in devices for the
ion etching of semiconductor materials in RF discharge
plasma, the ion energy distribution function (IEDF) and
the angular distribution of the ions bombarding the mate-
rial’s surface critically affect the rate of etching and the
degree of its anisotropy. It has been shown that the shape
of the IEDF can be controlled, e.g., by applying an RF
bias voltage directly to the substrate or by using an auxil-
iary electron source (either an additional discharge or a
thermal-cathode gun) to inject electrons into the dis-
charge. It was shown in [1] that a beam plasma discharge
(BPD) in a low-pressure gas can be used as a source of an
ion flow escaping the discharge region on normal to its
axis. We have shown that, by changing the external pa-
rameters of a beam plasma discharge in the equipotential
interaction chamber and by using electron beams pre-
modulated in velocity, the energy of the ions bombarding
the surface of a sample placed near the side wall of the
chamber can be varied within a range of 10…100 eV.
Note that it is precisely this ion energy range that is re-
quired for surface treatment (such as deposition of thin
films and etching) of materials for semiconductor elec-
tronics and acoustoelectronics.
The approbation of the technology of soft etching by
ion flows of Ar+ with mean energy 60…70 eV of pseu-
domorphic semiconducting heterostructures AlGaAs/In-
GaAs/GaAs (P-HEMT), brought up on substrates of
GaAs and applied for manufacturing of microwave field
effect transistors has been carried out. The influence of
such processing to concentration and mobility of elec-
trons of 2DEG, sensing to radiation defects imported
during etching was researched.
The researches that have been carried out on test
samples of p-HEMT structures with Hall contacts have
shown, that at conditions mentioned above there is no
accumulation of radiation defects aggravating parame-
ters of two-dimensional electron gas.
The version of technological process of manufacturing
gate grooves of p-HEMT devices through a slot in dielec-
tric is tested also. With the help of an electron beam lithog-
raphy narrow (0.1…0.5 microns) slots in resist were made,
through which the selective etching of dielectric coating
Si3N4 by width 80 nm up to a layer of the semiconductor
GaAs, where the process of etching is stopped, was made.
After resist removal the sizes of etched grooves were mea-
sured with the help of an atomic microscope. The depth of
etching at the designated above time of exposure has made
35 nm. There are no detected signs of a non-uniformity of
etching on a plate of 60 mm diameter. The presence of ef-
fect of etching without an essential degradation of parame-
ters of heterostructures (mobility of electrons) testifies to
small density of radiation disturbance and possibility of us-
ing BPD in the technology of manufacturing of het-
erostructure microwave НЕМТ devices.
The authors express thanks to professor A.A.
Rukhadze for useful discussions, to Yu.V. Fedorov for
participation in approbation of technology of etching.
This work was executed at financial support of Russian
Fund for Basic Researches and Government of the
Moscow region (grant "Naukograd-2004" №04-02-97257).
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ИОННЫЕ ПОТОКИ ИЗ ОБЛАСТИ ПУЧКОВО-ПЛАЗМЕННОГО РАЗРЯДА
В СЛАБОМ МАГНИТНОМ ПОЛЕ – ФИЗИКА И ПРИЛОЖЕНИЯ
Н.В. Исаев, Е.Г. Шустин, В.П. Тараканов
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ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2006. № 5.
Серия: Плазменная электроника и новые методы ускорения (5), с.100-105.
104
Для проверки выводов численного эксперимента были проведены измерения функции распределения по скоростям
электронов, выходящих из области разряда на коллектор, совместно с распределением по энергии ионов, которые выхо-
дят из разряда по нормали к оси. В режимах, когда наблюдаются ускоренные ионы, детектирован эффект существенного
нагрева электронов плазмы. Детектирован эффект аккумуляции поля регулярных осцилляций в области инжекции пучка
и их стохастизации в процессе распространения вдоль оси системы. Результаты физических экспериментов качественно
коррелируют с данными компьютерного моделирования.
ІОННІ ПОТОКИ З ОБЛАСТІ ПУЧКОВО-ПЛАЗМОВОГО РОЗРЯДУ
У СЛАБКОМУ МАГНІТНОМУ ПОЛІ – ФІЗИКА І ЗАСТОСУВАННЯ
Н.В. Ісаєв, Е.Г. Шустін, В.П. Тараканов
Для перевірки висновків чисельного експерименту були проведені вимірювання функції розподілу за швидкостями
електронів, що виходять з області розряду на колектор, разом з розподілом за енергіями іонів, які виходять з розряду по
нормалі до осі. В режимах, коли спостерігаються прискорені іони, детектовано ефект суттєвого нагріву електронів
плазми. Детектовано ефект акумуляції поля регулярних осциляцій в області інжекції пучка та їх стохастизації у процесі
поширення вздовж осі системи. Результати фізичних експериментів якісно корелюють з даними комп’ютерного
моделювання.
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