Secondary streamers in the primary streamer channel

The propagation of the process with ionization and attachment in the remainder of the streamer channel is studied. From the simplified model consideration it is shown that in the conditions of the attachment instability development the spatially inhomogeneous perturbations move to anode. The conditi...

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Published in:Вопросы атомной науки и техники
Date:2019
Main Authors: Bolotov, O., Kadolin, B., Mankovskyi, S., Ostroushko, V., Pashchenko, I., Pugach, S., Taran, G., Zavada, L.
Format: Article
Language:English
Published: Національний науковий центр «Харківський фізико-технічний інститут» НАН України 2019
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Online Access:https://nasplib.isofts.kiev.ua/handle/123456789/194715
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Cite this:Secondary streamers in the primary streamer channel / O. Bolotov, B. Kadolin, S. Mankovskyi, V. Ostroushko, I. Pashchenko, S. Pugach, G. Taran, L. Zavada // Problems of atomic science and technology. — 2019. — № 1. — С. 184-186. — Бібліогр.: 6 назв. — англ.

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Digital Library of Periodicals of National Academy of Sciences of Ukraine
id nasplib_isofts_kiev_ua-123456789-194715
record_format dspace
spelling Bolotov, O.
Kadolin, B.
Mankovskyi, S.
Ostroushko, V.
Pashchenko, I.
Pugach, S.
Taran, G.
Zavada, L.
2023-11-29T09:18:45Z
2023-11-29T09:18:45Z
2019
Secondary streamers in the primary streamer channel / O. Bolotov, B. Kadolin, S. Mankovskyi, V. Ostroushko, I. Pashchenko, S. Pugach, G. Taran, L. Zavada // Problems of atomic science and technology. — 2019. — № 1. — С. 184-186. — Бібліогр.: 6 назв. — англ.
1562-6016
PACS: 52.80.Hc
https://nasplib.isofts.kiev.ua/handle/123456789/194715
The propagation of the process with ionization and attachment in the remainder of the streamer channel is studied. From the simplified model consideration it is shown that in the conditions of the attachment instability development the spatially inhomogeneous perturbations move to anode. The conditions, in which the perturbations move to cathode, as it is usually observed for the secondary streamers, are discussed.
Вивчається поширення процесу з іонізацією та налипанням у залишку каналу стримера. З розгляду спрощеної моделі видно, що в умовах розвитку налипальної нестійкості просторово неоднорідні збурення рухаються до анода. Обговорюються умови, за яких ті збурення рухаються до катода, як це зазвичай спостерігається для вторинних стримерів.
Изучается распространение процесса с ионизацией и прилипанием в остатке канала стримера. Из рассмотрения упрощенной модели видно, что в условиях развития прилипательной неустойчивости пространственно неоднородные возмущения движутся к аноду. Обсуждаются условия, при которых эти возмущения движутся к катоду, как это обычно наблюдается для вторичных стримеров.
en
Національний науковий центр «Харківський фізико-технічний інститут» НАН України
Вопросы атомной науки и техники
Low temperature plasma and plasma technologies
Secondary streamers in the primary streamer channel
Вторинні стримери в каналі первинного стримера
Вторичные стримеры в канале первичного стримера
Article
published earlier
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
title Secondary streamers in the primary streamer channel
spellingShingle Secondary streamers in the primary streamer channel
Bolotov, O.
Kadolin, B.
Mankovskyi, S.
Ostroushko, V.
Pashchenko, I.
Pugach, S.
Taran, G.
Zavada, L.
Low temperature plasma and plasma technologies
title_short Secondary streamers in the primary streamer channel
title_full Secondary streamers in the primary streamer channel
title_fullStr Secondary streamers in the primary streamer channel
title_full_unstemmed Secondary streamers in the primary streamer channel
title_sort secondary streamers in the primary streamer channel
author Bolotov, O.
Kadolin, B.
Mankovskyi, S.
Ostroushko, V.
Pashchenko, I.
Pugach, S.
Taran, G.
Zavada, L.
author_facet Bolotov, O.
Kadolin, B.
Mankovskyi, S.
Ostroushko, V.
Pashchenko, I.
Pugach, S.
Taran, G.
Zavada, L.
topic Low temperature plasma and plasma technologies
topic_facet Low temperature plasma and plasma technologies
publishDate 2019
language English
container_title Вопросы атомной науки и техники
publisher Національний науковий центр «Харківський фізико-технічний інститут» НАН України
format Article
title_alt Вторинні стримери в каналі первинного стримера
Вторичные стримеры в канале первичного стримера
description The propagation of the process with ionization and attachment in the remainder of the streamer channel is studied. From the simplified model consideration it is shown that in the conditions of the attachment instability development the spatially inhomogeneous perturbations move to anode. The conditions, in which the perturbations move to cathode, as it is usually observed for the secondary streamers, are discussed. Вивчається поширення процесу з іонізацією та налипанням у залишку каналу стримера. З розгляду спрощеної моделі видно, що в умовах розвитку налипальної нестійкості просторово неоднорідні збурення рухаються до анода. Обговорюються умови, за яких ті збурення рухаються до катода, як це зазвичай спостерігається для вторинних стримерів. Изучается распространение процесса с ионизацией и прилипанием в остатке канала стримера. Из рассмотрения упрощенной модели видно, что в условиях развития прилипательной неустойчивости пространственно неоднородные возмущения движутся к аноду. Обсуждаются условия, при которых эти возмущения движутся к катоду, как это обычно наблюдается для вторичных стримеров.
issn 1562-6016
url https://nasplib.isofts.kiev.ua/handle/123456789/194715
citation_txt Secondary streamers in the primary streamer channel / O. Bolotov, B. Kadolin, S. Mankovskyi, V. Ostroushko, I. Pashchenko, S. Pugach, G. Taran, L. Zavada // Problems of atomic science and technology. — 2019. — № 1. — С. 184-186. — Бібліогр.: 6 назв. — англ.
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fulltext ISSN 1562-6016. ВАНТ. 2019. №1(119) 184 PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2019, № 1. Series: Plasma Physics (25), p. 184-186. SECONDARY STREAMERS IN THE PRIMARY STREAMER CHANNEL O. Bolotov, B. Kadolin, S. Mankovskyi, V. Ostroushko, I. Pashchenko, S. Pugach, G. Taran, L. Zavada National Science Center “Kharkov Institute of Physics and Technology”, Kharkiv, Ukraine E-mail: ostroushko-v@kipt.kharkov.ua The propagation of the process with ionization and attachment in the remainder of the streamer channel is studied. From the simplified model consideration it is shown that in the conditions of the attachment instability development the spatially inhomogeneous perturbations move to anode. The conditions, in which the perturbations move to cathode, as it is usually observed for the secondary streamers, are discussed. PACS: 52.80.Hc INTRODUCTION The discharge between the needle anode and the plane cathode is used in plasma chemistry for a long time. In the form of cathode directed streamers [1] the discharge is effective for the non-equilibrium plasma production. The study of the processes, which accompany the streamer propagation, is continued up to now [2, 3]. In the paper [4], the numerical simulations of the cathode directed streamer propagation in the electronegative gases with strong attachment are carried out for the quasi-stationary stage, far from electrodes, and for the stage of going out to cathode. In the present paper, the phenomenon of the secondary streamer is studied. It is observed at the final stage of streamer propagation in some electronegative gases, when the streamer goes out to cathode. The secondary streamer is the domain with intensive glow in the channel of the primary streamer. Sufficiently convinced explanation of the secondary streamers nature is presented in the paper [5]. It is shown that the attachment instability leads to monotonous increase of electron and ion density perturbations and to appearing of the channel domains with strong and weak field. But in the approximation considered in [5], the boundaries of the domains are motionless. In the present paper, it is carried out the study of the model near to one studied in [5], with estimation of the displacement velocity for the charge density perturbations. It is shown that in the conditions of the attachment instability the perturbations move to anode, whereas the secondary streamers usually move to cathode. So, the attachment instability may be considered as the cause of appearing of the channel domains with strong and weak field, but movement of these domains to cathode may take place in the conditions of the attachment instability absence, when spatially inhomogeneous perturbations fade away. 1. SIMPLIFIED MODEL In the model considered in [5], the ratio of attachment and relaxation frequency is small parameter, the relationships are deduced in the assumption about such degree of plasma quasi-neutrality, which does not prohibit the electric field strength distribution to be inhomogeneous, and the displacement current is neglected. Also, in fact, the assumption is made that the emission current from cathode, eI , is near to the ratio 0I of the applied voltage and the discharge gap resistance. In reality, the emission current is determined by a lot of factors, and the difference between the entrance current and the exit current leads to change of the total charge value inside the gap. If e 0I I then it is formed the comparatively thin near-cathode layer with large non-compensated positive charge density and not very small part of the total potential drop, and the ratio of the other parts of the potential drop and the discharge gap resistance should be near to eI . To consider the next approximations in the expansion with respect to the mentioned small parameter, it is necessary to impose the clear condition on the entrance current. To keep the main results of [5], it is necessary to keep quasi- neutrality. To ensure the absence of the non- compensated charge in the whole discharge gap, the entrance and exit currents should be equal. The results obtained in consideration of such model may be applied for more real situation of non-equal entrance and exit currents with aid of decrease of the potential drop over the gap on the value of the potential drop over the mentioned near-cathode layer. So, it is considered the plasma in the gap between cathode ( 0x  ) and anode ( 0x b  ). Ion motion is neglected. The plasma is described by the equations e e e a e i( )t x tn n E n n       , (1) 0 0 e i( )xE e n n    , (2) where  with index means derivative with respect to the variable indicated in index, e and en are mobility and density of electrons, in is the difference of the densities of positive and negative ions, E is the quantity opposite to the x -component of the electric field strength ( xE E  , 0E  ), 0 is electric constant, 0e is elementary charge ( 0 0e  ), a is difference between the attachment and ionization frequencies. It is assumed that a a ( )E  and e const  . It is imposed the condition 0 b dxE U , where U is voltage applied to the gap, and the condition i e 0 ( ) 0 b dx n n  . (3) Integration of the equation (2) and the equality i e e e( ) ( )t xn n n E    (following from (1)) with use of (3) gives the equalities 0| |x x bE E  and e 0 e( ) ( )x x bn E n E  , (4) ISSN 1562-6016. ВАНТ. 2019. №1(119) 185 and then the quantities en , etn , itn , and e( )x n E at the different boundaries ( 0x  and x b ) also should have equal values. The condition (4) may be imposed instead of (3). 2. APPROXIMATE SOLUTION For the homogeneous distribution, indicating the quantities with the index 0 , one gets e0 a0 e0tn n   , e0 e0 a0( ) (0)exp( )n t n t  , i0 e0n n , and 0E U b . To ensure (4), the linear perturbations of the homogeneous distribution are searched in the form of the real parts of the products of the amplitudes (dependent on time and indicated with the index 1 ) and the factor exp( )ikx with 2k n b and nonzero integer n . For the amplitudes one gets the equations e1 e e1 0 e0 1 a0 e1 a 0 1 e0 i1 ( ) [ ( ) ( ) ( )] ( ) ( ) ( ) ( ) t E t n t ik n t E n t E t n t E t n t n t             , (5) 0 1 0 e1 i1( ) [ ( ) ( )]ik E t e n t n t   , (6) where a 0E is the value of the derivative a ( )E E at 0E E . Denoting i1 e1( ) ( ) ( )Q t n t n t  , e0 e 0v E , 1 r0 0 0 e e0(0)e n   , and r r0 a0( ) exp( )t t    , with use of the equations (5) and (6) one gets the equations 1 1 0 0( ) ( ) ( )E t ik e Q t   , e1 i1( ) ( ) ( )n t n t Q t  , e0 i1 e0 r( ) ( ) [ ( )] ( )tikv n t Q t ikv t Q t    , 2 e0 a0 r a 0 0 r ( ) [ ( )] ( ) ( ) ( ) t t E Q t ikv t Q t E t Q t            . The function -1 r0( ) ln ( )P t Q t obeys to the equation -1 2 2 r0 -1 e0 a0 r0 a0 -1 a 0 0 r0 a0 ( ) [ ( )] [( ) exp( )] ( ) exp( ) t t t E P t P t ikv t P t E t                    . (7) function ( )P t may be given with the asymptotic expansion r00 ( ) [ ( )]m mm P t p t    . Its substitution into (7) gives the equation r 00 [ ( )] 0m mm Z t    , with 0 0 0 a0( ) ( )[ ( ) exp( )]t tZ t p t p t t     , 2 1 0 a0 1 a 0 0 1 e0 a0 0 ( ) ( ) exp( )[ ( ) ] [2 ( ) ] ( ) t t E t t Z t p t t p t E p t ikv p t                , 2 2 1 e0 a0 1 1 0 a0 2 ( ) ( ) [ ( )] ( ) [2 ( ) exp( )] ( ) t t t t t Z t p t ikv p t p t p t t p t               . It is imposed the requirement ( ) 0mZ t  , for each m . For 0m  one gets two different solutions: 1 0 0 a0 a0( ) (0) [1 exp( )]p t p t       , 0 0( ) (0)p t p  . The next terms for these two solutions are the following: 1 1 e0 a 0 0( ) (0) ( )Ep t p ikv E t    , 1 1 a 0 0( ) (0) Ep t p E t   , 2 2 e0 a0 a 0 0( ) (0) ( )( )Ep t p f t ikv E       , with 1 a0 a0 a 0 0( ) [exp( ) 1] Ef t t E     . It is worthy to note that r0exp( ) ( ) exp[ ( )]ikx Q t ikx P t  , the sum r0 ( )ikx P t  contains the parameter k in the term 0[ ( )]ik x x t , with 1 0 r0 e0( ) ( )x t v f t   , 0 e0( )x t v t  , and for a 0 0E  one gets the relationship a 0 0 ( ) 0E t x t   , which connects the direction of the perturbation movement with the sign of a 0E . The solution ( )P t is characterized by the fast decay, and the perturbations move to anode with the electron velocity. The time evolution of the spatial perturbations determined by the solution ( )P t is described by the factor a 0 0exp( )E E t . So, the stability of the solution ( )P t depends on the sign of a 0E . For a 0 0E  , the solution ( )P t is unstable, the perturbations move to anode with the velocities much less than electron velocity. Such motion direction is typical for the attachment instability [6]. For a 0 0E  , the solution ( )P t is stable, and the perturbations move to cathode. The evolution of the homogeneous electron density is described by the factor a0exp( )t . The cases a0 0  and a0 0  correspond to attachment decay and ionization growth, respectively. 3. DISCUSSION So, in the conditions of attachment instability, the perturbations move to anode, whereas the secondary streamers usually move to cathode. In the paper [5], the motion of the leading edge of the glow domain to cathode is obtained in assumption of gas density decrease with time (due to streamer channel heating) and relevant increase of the ratio of electric field strength and the gas density, which determines the rates of electron processes. The same effect may be obtained with relevant increase of the potential drop on the gap. As it is mentioned above, the electric field strength distribution in the gap essentially depends on the entrance current. In particular, in the limit case when the entrance current becomes zero, the channel soon gets the additional positive charge through the electron going out to anode, and then the quasi-stationary field distribution is set (if the ion motion is neglected), in which almost all potential drop is related to the comparatively thin near-cathode layer, and in the plasma channel the field is very weak. When the streamer goes out to cathode the situation is near to the opposite one. Namely, before the streamer approach to cathode the considerable part of the potential drop falls on the small domain in front of streamer. During the streamer going out to cathode, the domain dimension decreases, and also, the electron emission from cathode considerably increases, leading to the field strength decrease near the cathode. As a result, the field strength in the other part of channel increases, leading to propagation of glow in the channel in both directions. The velocity of the intensive glow domain boundary propagation is very small for the boundary, near which the spatial variation of the field strength is very sharp. So, such field strength increase can give the secondary streamer with propagating forward boundary and practically motionless backward boundary situated near the space with the comparatively large difference 186 ISSN 1562-6016. ВАНТ. 2019. №1(119) between the positive and negative ion densities in the channel remainder. The propagation of the secondary streamer backward boundary to cathode (Fig. 2 in [5]) may be the ionization wave propagation, which starts near the mentioned channel non-uniformity in consequence of the field strength increase up to the level, at which the tendency to decrease of the difference between the positive and negative ion densities is replaced with the tendency to its increase and the following space charge field strengthening. And the field strength increase, which gives the start to the ionization wave propagation, may be the result of the increase of the potential drop on the relevant part of streamer channel during the streamer going out to cathode. On the other hand, the ionization wave propagation is accompanied with recovery of high conductivity behind the wave front, and so, with the potential redistribution and the field strength increase between the front and cathode, leading to the additional propagation of the secondary streamer forward boundary to cathode. CONCLUSIONS The secondary streamer is the moving glowing domain with comparatively large field strength, in the streamer channel. In the paper [5], it is substantiated that the contrast in glow increases due to the attachment instability. In the present paper, from the simplified model consideration, it is estimated the velocity of the spatially inhomogeneous perturbation movement in the conditions of the attachment instability and it is attracted the attention to the movement direction, which is opposite to one usually observed for the secondary streamers. Besides the gas density decrease through the channel heating, the propagation of the forward boundary of the large field strength domain to cathode may be resulted from the potential redistribution during going out of the ionization waves to cathode, which leads to the field strength increase in the considerable part of the discharge gap not very near to cathode. When field strength increases near the domain with the enlarged difference between the positive and negative ion densities in the channel remainder, the ionization wave may start from there, so that the wave front becomes the backward boundary of the secondary streamer, and the wave front propagation to cathode leads to further field strength increase between the front and cathode, that is, to further propagation of the forward boundary of the large field strength domain to cathode. REFERENCES 1. Yu.P. Raizer. Gas discharge physics. Springer: “Verlag”, 1991. 2. O.V. Bolotov, V.I. Golota, B.B. Kadolin, et al. Similarity laws for cathode-directed streamers in gaps with an inhomogeneous field at elevated air pressure // Plasma Physics Reports. 2010, v. 36, № 11, p. 1000- 1011. 3. O.V. Manuilenko. Computer simulation of positive streamer dynamics in uniform and non-uniform electric fields in air. // Problems of Atomic Science and Technology. Series “Plasma Electronics and New Methods of Acceleration” (8). 2013, № 4, p. 194-199. 4. O. Bolotov, B. Kadolin, S. Mankovskyi, et al. Numerical simulations of cathode directed streamer propagation in electronegative gases // Problems of Atomic Science and Technology. Series ”Plasma Electronics and New Methods of Acceleration” (10). 2018, № 4, p. 172-175. 5. R.S. Sigmond. The residual streamer channel: Return strokes and secondary streamers // Journal of Applied Physics. 1984, v. 56, № 5, p. 1355-1370. 6. R.A. Haas. Plasma stability of electric discharges in molecular gases // Physical Review A. 1973, v. 8, № 2, p. 1017-1043. Article received 23.09.2018 ВТОРИЧНЫЕ СТРИМЕРЫ В КАНАЛЕ ПЕРВИЧНОГО СТРИМЕРА О. Болотов, Б. Кадолин, С. Маньковский, В. Остроушко, И. Пащенко, С. Пугач, Г. Таран, Л. Завада Изучается распространение процесса с ионизацией и прилипанием в остатке канала стримера. Из рассмотрения упрощенной модели видно, что в условиях развития прилипательной неустойчивости пространственно неоднородные возмущения движутся к аноду. Обсуждаются условия, при которых эти возмущения движутся к катоду, как это обычно наблюдается для вторичных стримеров. ВТОРИННІ СТРИМЕРИ В КАНАЛІ ПЕРВИННОГО СТРИМЕРА О. Болотов, Б. Кадолін, С. Маньковський, В. Остроушко, І. Пащенко, С. Пугач, Г. Таран, Л. Завада Вивчається поширення процесу з іонізацією та налипанням у залишку каналу стримера. З розгляду спрощеної моделі видно, що в умовах розвитку налипальної нестійкості просторово неоднорідні збурення рухаються до анода. Обговорюються умови, за яких ті збурення рухаються до катода, як це зазвичай спостерігається для вторинних стримерів.