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13Table 2
Table 1
Biological potato yield by varieties (2011-2016)
Variety Tubers' weight g / bush Number of tubers, pcs. / bush The average weight of a tuber, g Biological yield, t / ha
Early varieties
Lider (st) 630 8,9 71 36,8
Red Scarlett 726 8,6 92 42,4
Rozara 921 14,2 137 55,8
Mid - early varieties
Nevsky (st) 804 12,4 73 45,9
Mid - maturing varieties
Chaika (st) 776 8,8 91 44,8
Particle size distribution of potato tubers by varieties (2011-2016)
Variety The size of tubers in a crop, %
small < 30 mm for seed production 30-60 mm big > 60 mm good presentation, total
Early varieties
Lider (st) 5 73 22 95
Red Scarlett 5 66 29 95
Rozara 2 51 47 98
Mid - early varieties
Nevsky (st) 7 68 25 93
Mid - maturing varieties
Chaika (st) 6 70 24 94
On the basis of the analysis of the climatic factors it is possible to choose the varieties that adapt to specific conditions and to offer the cultivation technology that would develop its full yielding potential under specific circumstances.
References
1. Adaptive technologies as a tool for yield forecasting and the size, weight and quality characteristics of root crops. / R.A. Hrameshin, A.V. Hrameshin / Science, education and society: Trends and Prospects, The
collection of scientific papers on the materials of the International scientific-practical conference: 7 parts. Ltd. "Ar-Consult". Moscow, 2014. pp 157-161.
2. The quality of potatoes can be improved. / A.V. Hrameshin, F.R. Arslanov, A.N. Vasiliev / Storage and processing of agricultural raw materials. 2012. № 11. pp. 41-44.
3. The technique of photosynthetically active radiation measurement./ H. G. Tooming, B.I. Gulyaev -Moscow, 2002;
4. A plant and the Sun./ Shulgin I.A. - L., 1993.
GENERATION OF POWER RECTANGULAR NANOSECOND PULSES BASED ON SUMMATOR OF QUASI-HARMONIC
OSCILLATIONS
Kladukhin S. V., Khramtsov S.P.
Institute of Electrophysics of the Ural Division of the Russian Academy of Sciences (IEP UD RAS), Russia,
Ekaterinburg
ABSTRACT
An approach to synthesize generators of power nanosecond high-voltage pulses with short front based on its Fourier representation is presented. The design of the experimental generator of subgigawatt power level built on
formers of a spectral currents implemented as distributed oscillating system made on a basis of coaxial lines is shown. Common switch made as a multigap gas switch. Charging device was designed as a tesla transformer built into one of the coaxial lines. The generator test results proof the generator abilities. Keywords: nanosecond pulses, high-voltage, high power, summator.
1. Introduction
Usually forming of high-voltage rectangular nanosecond pulses GW power level bases on generators build on coaxial forming lines [1]. Low output impedance and high dependency of mass and dimensions on duration of output pulses are the basic drawbacks of such type of generators. Also generating of power rectangular pulses with microsecond duration widely uses a method based on its spectral representation. Within this method pulse generation is implemented by summing spectral (partial) currents on the common load. High-Q oscillating circuits with preliminary charged capacitive energy storages are used for generating partial currents [2]. The compactness of designed generators and ability of generators creation for a wide range of matched loads are the significant advantages of this method.
This paper describes the usage of this approach to design of experimental high-voltage nanosecond gen-
with 100 Ohm load based on summator of harmonic oscillations. Such loads are typical in particular for rela-tivistic MW BWO generators with explosive emission cathodes [3]. Where forming of partial currents is made by means of quasi-concentrated high-Q oscillating systems in the form of coaxial line segments and switching is realized by high-pressure gas gap switch. A sharp edge and flat peak of forming pulses are implemented by usage of additional low-Q circuit. Capacitive storage with built-in charging transformer provides starting voltage.
2. Design of the generator
For synthesis of rectangular pulse its extended representation in the form of meander which is a periodical asymmetrical function (Fig.1). Its Fourier representation consists of a sum of odd sinusoidal harmonics, i.e. the current pulse to be synthesize can be represented as a sum of sinusoidal partial currents (1).
erator of subgigawatt level pulses oriented for work
i(t ) = 2 J i(z )sin 7kz dz sin — =È 4 (t ) , k = 1 , œ _ 2
T k=1 o T T k=1
7lkt
(1)
Partial sinusoidal currents (ik) generation can be performed by oscillating LC-circuits which initially opened and its capacitances are charged to a voltage uo. Synchronous closing of LC-circuits initiates currents
there and all circuit currents are summed on the common load. To form single rectangular pulse on the load R with the amplitude U and duration t, the relation (2) should be fulfilled,
2U } . 7kt -I sin-
TR j
0
7kt
dt = (uo - U
t
slLkCk
r
Uo J (uo - UX YL Sin
Ck 0 ^ V Lk
4lkck j
dt = 0
As follows from these relations inductions and capacitances of generating circuits should be defined by
T
:
t
the
following
C = 4z / k R
u0 = 2U.
expressions: Lk = zR /4 , where k = 1,3,5,..., a
Since the generator is directed to form nanosecond pulses at subgigawatt power level its construction arrangement should minimize oscillating circuit's magnetic fields interaction also a high electric strength of components of the circuits should be ensured. A generator design based on four loops with coaxial oscillating circuits was chosen to meet the mentioned conditions. The inductances of coaxial oscillating circuits are made as short segments of spiral lines and capacitances are made as segments of uniform transmission line. An axes of lines are mutually orthogonal oriented that minimize its magnetic fluxes interaction. Also the fifth low-Q oscillating circuit with inductance which made in a form of a segment of cylindrical conductor in order to get a short front and flat peak of pulses the fifth oscillating circuit with low quality factor. All forming loops are joined with the gas gap switch which provides its simultaneous nanosecond connection onto load [4]. The charging transformer built into coaxial capacitive storage (a segment of coaxial line) of first quasi-harmonic loop provides initial voltage for capacitances of
other loops. Charging transformer is built as a Tesla transformer (two inductively coupled circuits) with coupling coefficient about 0.9 provided by disrupted magnetic conductor combined with conductors of coaxial line [5]. An inductance of first (low voltage) circuit implemented as a singleturn broad coil and its capacitance is made by means of standard cooled capacitors. An inductance of the second (high voltage) circuit realized by multiturn conical coil connecting inner and outer conductors of coaxial line. This connection provides accordance of its turn's potential with potential distribution in a radial gap of coaxial line during a charging process. The sum of coaxial line segments combines a capacitance of a secondary circuit.
Charging process is initiated by closing of thyristor switch in primary circuit. The duration of half-wave charging process is about 30 us that eliminates the influence of inductance of oscillation circuits on a charging process.
Results of numerical simulation of 30 ns pulse generation by mean of summing partial currents on a load is shown on Fig. 2., where numbers specify partial currents of according systems and S means sum current on the load. Vertical axis means current normalized in relation to Uo/R, and the horizontal one is a time.
s 1
1 5 /
2
4
0.75
0.5
0.25
-0.25
10
20
30
40
50
60
70
80
Fig.2. The process of pulse forming on a load
The implementation of experimental generator is oriented on generation of rectangular pulses with 300 kV amplitude and pulse duration 25 ns on 100 Ohm resistive load. A SF6 gas under 10 bar pressure was used as an insulating medium in forming loops. The same gas was used in the gas gap switch. The design of generator is shown on Fig.3, where 1 - partial oscllaing loops, 2 - low-Q loop, 3 - joining electrode, 4 - multi-gap gas switch, 5 - built-in transformer, 6 - the outer magnetic conductor of a charging transformer, 7 - the
inner magnetic conductor of a charging transformer, 8 - primary coil, 9 - secondary coil of a charging transformer, 10 - incoming connection slots of a primary coil of charging transformer. The appearance of generator is presented on Fig.4.
The dimensions of generator are: height -1200mm, width - 800mm, length - 800mm and are determined, to a considerable extent, by the dimensions of summator and built-in charging transformer.
Fig.4. Generator's appearance
3. Experimental results
The purpose of generator's tests was to determine the generation abilities and its workability in different pulse generation modes. Six meters 100 Ohm measuring coaxial line filled in with oil and with resistive energy absorber on its end was used as load for generator. Measuring of formed pulses were taken by means of capacitive divider built into beginning of this line and were registered by Tektronix 3052B oscilloscope with 500 MHz bandwidth. The voltage on capacitors were
measured by built-in capacitive dividers. The experimental results have shown good generation ability. The generator have performed generation of pulses with amplitude up to 300 kV with repetition rates up to 100 Hz. Pulses had a quasi-rectangular shape. The half-height pulse duration was 25 ns with 3 ns front. An oscillogram on Fig.5 shows the pulse shape on the inlet of measuring line. Some distortions after 60 ns are caused by reflections from the resistive load on the end of the measuring line.
4. Conclusion
The described approach is appropriate to be used to design compact generators to form pulses with 20200 ns duration and short front 3-5ns on the load 50300 Ohm. High dielectric strength of generators components enables the creation of generators to form pulses with up to 1 MV amplitude. High average power of generator is supported by charging transformer and gas gap switch which enable the pulse-periodic regime (up to 500Hz) of pulse forming. Short fronts and rectangular shape of pulses make it appropriate for generation of high-current electron beams in relativistic MW generators with explosive emission cathodes.
References
1. El'chaninov A.S., Zagulov F.Ya., Korovin S.D., et al. Relyativistskaya vysokochastotnaya elektronika (Relativistic High-Frequency Electronics) // Gor'kii: Inst. Prikl. Fiz. Akad. Nauk SSSR. 1981. P. 5.
2. G.N. Glasoe, J.V. Lebacqz. Pulse Generators. Vol. 5 of MIT Radiation Laboratory Series. McGraw-Hill. New York. 1948. P. 742.
3. Goykhman M.B., Kladukhin V.V., Kladukhin S.V., Kovalev N.F., Kolganov N.G., Khramtsov S.P. A high-power relativistic backward wave oscillator with a longitudinal slot slow-wave system // Technical Physics Letters. 2014. V. 40. № 1. P. 84.
4. Kladukhin V.V., Kladukhin S.V., Khramtsov S.P., Kovalev N.F. Sequential Nanosecond Switch // Proc. of 2007 IEEE Pulse Power Conference (PPPS-2007): Digests of Technical Papers 1976-2007. Albuquerque. NM. USA. 2007. P. 423.
5. Zagulov F.Ya., Borisov I.Ya., Vlasov G.Ya., et al. Pulsed high-current nanosecond electron accelerator with pulsing frequency of up 100 Hz // Instruments and Experimental Techniques. 1976. V. 19. № 5. P. 1267.
