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Investigation of the characteristics and mechanism of subnanosecond switching of a new type of plasma switches.I. Devices with counter-propagating electron beams - kivotrons

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Plasma Sources Science and Technology
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P A Bokhan
P A Bokhan
P A Bokhan
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P. P. Gugin at Russian Academy of Sciences
P. P. Gugin
Maxim A. Lavrukhin at Russian Academy of Sciences
Maxim A. Lavrukhin
D. E. Zakrevsky at Russian Academy of Sciences
D. E. Zakrevsky
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Novel opportunities of waveform tailoring for controlling plasma parameters based on the development of a high-voltage gas-discharge switch with a subnanosecond breakdown time and high pulse repetition frequency are discussed. The studies of characteristics and breakdown development mechanisms of the switch based on an ‘open’ discharge—kivotron are summarized. The discharge in the switch is carried out in conditions when counter-propagating electron beams in high electric field are generated. In this case, when using helium as an operating medium, firstly, atoms are effectively excited into the resonance state by fast particles. Secondly, due to the Doppler effect, resonant photons without reabsorption reach the cathode surface, maintaining the discharge current due to photoemission. Thirdly, fast heavy particles modify the cathode surface, thereby significantly (up to an order of magnitude) increasing the photoemission coefficient. The combination of these processes leads to an increase in the switching rate with an increase in the operating voltage U and helium pressure pHe. At U > 20 kV and pHe > 10 Torr, the switching time becomes less than 100 ps both in the experiment and according to the simulation. It is preferable to use planar geometry without a drift space as a switching device, in which, on the one hand, the most complete use of EB energy is realized in creating a plasma with a high charge density, on the other hand, a small wave impedance of the switch is realized. As a result, currents of tens of kiloamperes are achieved at voltages up to 100 kV. In an interpulse period plasma in the discharge gaps recombinates fast. As a result, switches can operate up to pulse repetition frequency 100 kHz. Together these achievements open new opportunities to control plasma parameters.
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Plasma Sources Science and Technology
Plasma Sources Sci. Technol. 29 (2020) 084002 (12pp) https://doi.org/10.1088/1361-6595/ab9d90
Investigation of the characteristics and
mechanism of subnanosecond switching of
a new type of plasma switches. I. Devices
with counter-propagating electron
beams—kivotrons
P A Bokhan1,PPGugin
1,MALavrukhin
1, D E Zakrevsky1,
IVSchweigert
2andALAlexandrov
2
1A V Rzhanov Institute of Semiconductor Physics, Siberian Branch of Russian Academy of Sciences,
Novosibirsk, Russia
2Khristianovich Institute of Theoretical and Applied Mechanics, Siberian Branch of Russian Academy of
Sciences, Novosibirsk, Russia
E-mail: bokhan@isp.nsc.ru
Received 31 March 2020, revised 28 May 2020
Accepted for publication 17 June 2020
Published 4 August 2020
Abstract
Novel opportunities of waveform tailoring for controlling plasma parameters based on the
development of a high-voltage gas-discharge switch with a subnanosecond breakdown time
and high pulse repetition frequency are discussed. The studies of characteristics and
breakdown development mechanisms of the switch based on an ‘open’ discharge—kivotron
are summarized. The discharge in the switch is carried out in conditions when
counter-propagating electron beams in high electric eld are generated. In this case, when
using helium as an operating medium, rstly, atoms are effectively excited into the resonance
state by fast particles. Secondly, due to the Doppler effect, resonant photons without
reabsorption reach the cathode surface, maintaining the discharge current due to
photoemission. Thirdly, fast heavy particles modify the cathode surface, thereby signicantly
(up to an order of magnitude) increasing the photoemission coefcient. The combination of
these processes leads to an increase in the switching rate with an increase in the operating
voltage Uand helium pressure pHe.AtU>20 kV and pHe >10 Torr, the switching time
becomes less than 100 ps both in the experiment and according to the simulation. It is
preferable to use planar geometry without a drift space as a switching device, in which, on the
one hand, the most complete use of EB energy is realized in creating a plasma with a high
charge density, on the other hand, a small wave impedance of the switch is realized. As a
result, currents of tens of kiloamperes are achieved at voltages up to 100 kV. In an interpulse
period plasma in the discharge gaps recombinates fast. As a result, switches can operate up to
pulse repetition frequency 100 kHz. Together these achievements open new opportunities to
control plasma parameters.
Keywords: subnanosecond switching, plasma switch, counter-propagating electron beams,
high voltage, elctron beams applications
(Some gures may appear in colour only in the online journal)
0963-0252/20/084002+12$33.00 1 ©2020 IOP Publishing Ltd Printed in the UK
... To explain such a large value of γ ph in [27,28], the phenomenon of adsorption and implantation of the working species into the surface of a pure cathode [29] was introduced. This allowed to explain the obtaining of the decreasing CVCs in various kinds of discharges [30][31][32][33][34], high (close to 100%) efficiency of EB generation in gas discharge [30][31][32] and creation of fast subnanosecond and picosecond switches [34]. ...
... To explain such a large value of γ ph in [27,28], the phenomenon of adsorption and implantation of the working species into the surface of a pure cathode [29] was introduced. This allowed to explain the obtaining of the decreasing CVCs in various kinds of discharges [30][31][32][33][34], high (close to 100%) efficiency of EB generation in gas discharge [30][31][32] and creation of fast subnanosecond and picosecond switches [34]. ...
... From this consideration we can conclude, that the uncertainty in the value of <γ> has not been yet overcome. Bearing this in mind, the authors of the present work have continued the studies begun in [30][31][32][33][34] in order to obtain and verify new data on the physical processes in the gas discharge and, in particular, in the cathode layer and on the cathode surface. The specificity of author's research consists, firstly, in realization of especially pure conditions in the discharge and, secondly, in operation at elevated voltages. ...
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... They are used for fast switching of high voltage pulses, generation of vacuum ultraviolet (VUV) and x-ray radiation, forming of high intensity electron beams, pumping of gas and solid-state lasers and other applications [1][2][3][4][5][6]. This class of devices also includes recently developed open discharge switching devices [7][8][9][10][11][12]. Their use makes it possible to improve the output characteristics of a number of devices and facility, in particular, copper vapor lasers [13], to generate high-frequency oscillations with a frequency of several GHz and the duration of a few pulses [8], etc. ...
... extended drift space. A structure with two oppositely spaced discharge gaps and consequently counter propagating electron beams being generated in the discharge can function as a voltage sharper-a kivotron [7][8][9]11] with the number of commutated pulses up to at least 10 11 [6,9,14,15]. Fast switching, up to a switching time of ∼80-100 ps, is provided mainly by photoemission under the influence of resonant VUV radiation from fast helium atoms, having a large Doppler shift relative to the line center, and at the final stage of current development, due to secondary electron emission [16], which determine the long lifetime of the devices. ...
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... SRIM is a Monte-Carlo based code for calculating the interaction of ions with material using electronic and nuclear stopping for the energy loss mechanisms [32]. The exponential function in equation (6) and its normalization N describe that only a fraction of 1/e of electrons generated at depth λ escape contribute to γ, as explained in detail in [10]. The kinetic emission model (equation (6)) has only one fitting parameter, the factor C metal . ...
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... The physics of discharges of this type attracts great attention due to the ability of discharges with high efficiency, close to the geometrical transparency of the mesh anode, to generate electron beams of keV energies and leads to nanosecond and sub-nanosecond current development times. [24][25][26][27][28][29][30][31][32][33] The listed properties allow creating effective frequency functioning plasma switching devices of nanosecond range (pulse repetition rate up to 200 kHz, voltage up to 50 kV, and switching efficiency higher than 90%) on the basis of such discharges. 24,26 Earlier in Ref. 34, the preliminary results of the breakdown time-time of voltage drop on the discharge gap in noble gases in the open discharge initiated by voltage pulses with nanosecond frontswere presented. ...
... [24][25][26][27][28][29][30][31][32][33] The listed properties allow creating effective frequency functioning plasma switching devices of nanosecond range (pulse repetition rate up to 200 kHz, voltage up to 50 kV, and switching efficiency higher than 90%) on the basis of such discharges. 24,26 Earlier in Ref. 34, the preliminary results of the breakdown time-time of voltage drop on the discharge gap in noble gases in the open discharge initiated by voltage pulses with nanosecond frontswere presented. The results 34 showed that the open discharge, due to the conditions in the discharge gap, differs from discharges with the Townsend and streamer mechanisms of current development. ...
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