ISSN 00204412, Instruments and Experimental Techniques, 2013, Vol. 56, No. 3, pp. 299–301. © Pleiades Publishing, Ltd., 2013. Original Russian Text © V.V. Andreev, Yu.P. Pichugin, V.G. Telegin, G.G. Telegin, 2013, published in Pribory i Tekhnika Eksperimenta, 2013, No. 3, pp. 58–60.
ELECTRONICS AND RADIO ENGINEERING
A HighVoltage Nanosecond Pulse Generator Based on a Barrier Discharge V. V. Andreev, Yu. P. Pichugin, V. G. Telegin, and G. G. Telegin Chuvash State University, Moskovskii pr. 15, Cheboksary, 428015 Russia email:
[email protected] Received May 21, 2012
Abstract—One of the specific features of the barrier electric discharge is the short duration of microdischarge processes that last about tens of nanoseconds. A highvoltage nanosecond pulse generator based on a barrier electric discharge is presented. A voltage of tens of kilovolts is usually applied to electrodes of the discharge cell. The peak values of the current pulse may be very high (from a few amperes to several tens of amperes). The presented highvoltage nanosecond pulse generator, having a sufficiently simple design, ensures quite good pulse repetition stability, and, when necessary, allows one to easily tune characteristics of pulses and their repetition rates by changing the geometrical, electrical, and physical–chemical parameters of the setup. DOI: 10.1134/S0020441213030160
A great interest has been lately expressed in studies of barrier electric discharges [1–3]. The characteristic feature of the barrier discharge is the short duration of separate microdischarge processes, sequences of which constitute this discharge [4]. In addition, each microdischarge lasts about tens of nanoseconds. A voltage of tens of kilovolts is often applied to elec trodes of discharge cells. The peak current pulse values can be as high as tens of amperes. All these properties of the barrier electric discharge allow one to pose a problem of creating a highvoltage nanosecond pulse generator on its basis. The barrier electric discharge between immobile and rotating electrodes was studied in air at atmo spheric pressure [5]. In the experimental setup, the rotating electrode is covered by a dielectric layer. The feature of the barrier discharge produced in a spark gap between rotating electrodes is that it is maintained with a constant voltage applied to the electrodes [5–8]. In addition, due to the barrier rotation, the stable structure of the barrier electric discharge is attained, although each separate microdischarge lasts from a few nanoseconds to several tens of nanoseconds. In this work, we investigated the barrier electric dis charge produced in air at atmospheric pressure in the setup (Fig. 1), which is similar to the setup described in [5]. The setup contains dielectric barrier–disk 1 rotated by electric motor 5, three electrodes (electrode 2 for visualization of the barrier discharge structure, electrode 3 having a sliding contact with barrier 1, and solid metallic electrode 8), and dc highvoltage source 4 to which these three electrodes are connected. Electrodes 2 and 3 are located on one side of the barrier, and the movable solid electrode 8 is directly adjacent to the rotating barrier on the other side.
In this case, electrodes 3 and 8 have the same poten tial. In the setup shown in Fig. 1, a 1mmdimeter cylindrical conductor is used as electrode 2, in con trast to the electric gasdischarge unit described in [5]. As a result, only one discharge channel is formed under electrode 2, which helps to obtain stable results. Each separate microdischarge in the discharge chan nel consists of microdischarge channel 6 and near barrier spot 7, which is the enlarged part of the micro discharge channel (see Fig. 1). Owing to rotation of the barrier–disk 1, the barrier discharge that arises in the discharge gap between elec
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ω R 8
View from above
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Fig. 1. Schematic drawing of the electric gasdynamic unit with the movable solid electrode, which is directly adjacent to the rotating barrier: (1) barrier–disk (dielectric), (2) metal electrode, (3) sliding metal electrode, (4) dc high voltage source, (5) electric motor, (6) microdischarge channel, (7) nearbarrier spot (lengthy part of the micro discharge channel), and (8) solid metal electrode.
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(a)
75 μs
(b)
0.25 A
Fig. 2. Oscilloscope traces of (a) current through load R (the scale division in the vertical direction is 0.25 A and in the horizontal direction is 75 µs), and (b) trains of pulses at load R.
trodes 2 and 8 is maintained at a constant voltage applied to these electrodes. In the experiments, a 10kV dc voltage was applied to the electrodes, and electrode 2 was under the negative potential. The dis tance from immovable electrode 2 to barrier 1 was 3.5 mm. Rotating barrier 1 was made of a 2mmthick glasscloth laminate. Let us consider operation of this unit. A barrier electric discharge, consisting of microdischarge 6 and nearbarrier spot 7, arises between rotating barrier 1 and electrode 2 at a sufficient electric field intensity in the gap. This discharge consists of separate microdis charges having a characteristic duration from a few nanoseconds to tens of nanoseconds. Electrode 3, having a sliding contact with rotating dielectric barrier 1, promotes stable repetitions of microdischarge patterns in this unit. As a result, due to the practical absence of gasdischarge processes at the boundary of sliding electrode 3 and barrier 1, the influ ence of the breakdown voltage and extinction voltage of the gasdischarge gap and their statistical character istics on the recharging processes of dielectric 1 is absent. Moreover, from the opposite side of barrier 1, where movable solid electrode 8 is located, the recharging current is determined only by the capaci tive component. In this case, the electric circuit [5] consists of dc highvoltage source 4, electrode 2, a discharge gap under investigation, first barrier capacitance, current conducting solid electrode 8, and second barrier capacitance. The first barrier capacitance is deter mined by the touch area of the nearbarrier spot 7 and dielectric 1 and by the barrier characteristics (such as the thickness and permittivity), and the second barrier capacitance is determined by the touch area of sliding contact 3 and dielectric 1. One of the additional elements in the experimental setup (see Fig. 1), as compared to the setup studied in [5], is the load resistor R, which can be further con nected to the matching transformer. The transformer is intended to change the amplitude of pulses and eliminate the dc component. The signal is applied to the oscilloscope from resistor R. In the experimental setup, the load resistor R = 10 kΩ.
Current pulse waveforms were obtained, and the typical example is shown in Fig. 2a. In this oscillo gram, the current amplitude is about 0.5 A, the rise time is no more than 5 ns, and the pulse duration is about 50 ns. For this case, the oscillogram from a unidi rectional pulse train is shown in Fig. 2b for a slower scan. The time interval between separate pulses is about several microseconds and determined as follows: Tpls = d/ωr, where r is the radius from the rotation axis of disk 1 to the center of the nearbarrier spot 7 (see Fig. 1), d is the diameter of the nearbarrier spot 7, and ω is the angular speed of disk 1. In the experimental setup, these param eters had the following values: ω ≈ 300 rad/s, r = 9 cm, and d = 4 mm. Therefore, we have Tpls ≅ 150 μs. Figure 3a shows pulse waveforms obtained from the secondary winding of the matching transformer under the same conditions as the oscillograms shown in Fig. 2. In this case, its primary winding is connected in paral lel to the load resistor R (Fig. 1). In addition, bidirec tional pulses are observed at the output of the match ing transformer. Similar experiments were also performed, when a lengthy electrode was used, as was the case in [5], instead of cylindrical electrode 2 (see Fig. 1). A 5cm long extensive electrode was placed along the radius of disk 1. As it is seen from the pulse waveform in Fig. 3b, the pulse repetition rate becomes higher, as compared with the case when thinwire cylindrical electrode 2 is used (see Fig. 2b). Note that the time interval between pulses in the oscillogram in Fig. 2b is virtually the same, but in the oscillogram in Fig. 3b the pulses go with different time intervals. The latter results from the fact that, when lengthy electrode 2 (see Fig. 1), placed along the radius of the disk 1 is used, several channels of micro discharge sequences are simultaneously excited [5]. Thus, the use of movable electrodes allows one to convert the dc voltage and obtain a pulse train without long pauses. Note that the immovable electrode system powered from the industrialfrequency voltage source will
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(b) Fig. 3. Oscilloscope traces of pulse trains (a) from the secondary winding of the matching transformer and (b) when a 5cmlong extended electrode is used instead of electrode 2 (Fig. 1). The scale division in the vertical direction is 0.25 A and in the horizontal direction is 75 µs.
operate as the considered highvoltage nanosecond pulse generator. In this case, we obtain an inverter converting the sinusoidal industrialfrequency voltage to nanosecondduration pulses. In addition, the pulses should go as trains with pauses. Then, the pause rate is determined by the industrial frequency of the voltage source that powers the setup. The presented highvoltage nanosecond pulse gen erator, having a sufficiently simple design, ensures quite good pulse repetition stability. In this generator, when necessary, one can easily tune the characteristics of pulses and their repetition rate by changing the geometry (e.g., by changing the distance between elec trode 2 and dielectric 1), as well as the electrical and physical–chemical parameters of the setup. REFERENCES 1. Gibalov, V.I., Tkachenko, I.S., and Lunin, V.V., Russ. J. Phys. Chem. A, 2008, vol. 82, p. 1020.
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2. Solov’ev, V.R., Konchakov, A.M., Krivtsov, V.M., and Aleksandrov, N.L., Plasma Phys. Rep., 2008, vol. 34, p. 594. 3. Shibkov, B.M., Aleksandrov, A.F., Ershov, A.P., Timo feev, I.B., Chernikov, V.A., and Shibkova, L.V., Plasma Phys. Rep., 2005, vol. 31, p. 795. 4. Lunin, V.V., Popovich, M.P., and Tkachenko, S.N., Ozone Physical Chemistry, Moscow: MGU, 1998. 5. Andreev, V.V., Pichugin, Yu.P., Telegin, V.G., and Tele gin, G.G., Plasma Phys. Rep., 2011, vol. 37, p. 1053. 6. Andreev, V.V., Vasil’eva, L.A., Kravchenko, G.A., Pichugin, Yu.P., and Filippov, V.G., Nelineinyi Mir, 2009, vol. 7, p. 811. 7. Andreev, V.V., Vasil’eva, L.A., Matyunin, A.N., and Pichugin, Yu.P., Appl. Phys., 2011, no. 1, p. 52. 8. Andreev, V.V., Vasilyeva, L.A., Matyunin, A.N., and Pichugin, Yu.P., Plasma Phys. Rep., 2011, vol. 37, p. 1190. Translated by N. Pakhomova
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