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RESEARCH OF PERSPECTIVE METHODS OF ELECTROMAGNETIC WAVE GENERATION TO CREATE MULTIFREQUENCY MEANS OF ELECTROMAGNETIC DAMAGE OF RADIO TECHNICAL SYSTEMS ON THEIR BASIS
Fyk O.,
Doctor of Technical Sciences, Associate Professor Department of Military Communications and Informatization National Academy of the National Guard of Ukraine Defenders of Ukraine sq., 3, Kharkiv, Ukraine, 61001
Honchar R., Candidate of Military Sciences Research Center "Military Combat Activities of National Guard of Ukraine" National Academy of the National Guard of Ukraine Defenders of Ukraine sq., 3, Kharkiv, Ukraine, 61001
Vlasov K. senior lecturer
Department of Military Communications and Informatization National Academy of the National Guard of Ukraine Defenders of Ukraine sq., 3, Kharkiv, Ukraine, 61001
Abstract
The peculiarities of choosing the method of construction of the generator device, which is able to create a single or a series of short powerful electromagnetic pulses, which, after radiation from the antenna as a result of electromagnetic radiation, disable the sensitive semiconductor elements of the receiver (current destruction of the p-n junction) are established. Research allows to determine the features and conditions of application of classical technological methods of creation of modern powerful short-pulse generators and to determine the prospects of creation of new generator systems. The necessary properties of generator systems include power, frequency range, and their dimensions. In order to determine the degree of efficiency of the electromagnetic pulses of a powerful generator, an analysis of all existing methods of its construction is made on the basis of the interaction of the electron flow with the electrodynamic system or with the use of forming lines, and restrictions on their use by power, frequency, figure of merit and overall dimensions are determined. To reduce the size of the system and improve its controllability in power and frequency, it is suggested to use a circulator system. Such systems will allow the tuning of the frequency of the generator system and thereby provide the possibility of creating electromagnetic destructive radiation for a larger range of receiving systems. The paper outlines the basic conditions for electronic flow control using a virtual cathode and the creation of high frequency pulses of ultra-short duration. The results of the work allow us to choose, depending on the purpose of the electromagnetic radiation, the type of generator its control modes and to estimate the power level, the duration of the created pulses. Such results can be used not only in the synthesis of electromagnetic multi-frequency high-power damage devices designed to create electromagnetic radiation that causes current on the elements of radio-electronic devices and destroys their p-n junctions, but also to study the possibility of developing effective means of electromagnetic protection of radioelements
Keywords: microwave generator, Cherenkovsky generator, vircator, radio-electron beam of electrons, electromagnetic damage
1 Introduction
This research will present essential means of creating the generators of radiation in a wide range of frequency and the prospects of further development for electromagnetic damage to electronic equipment[1,21-22].
The work of modern SHF generators is based on the interaction between electrons with electric field of stagnant water in endovibrator or with field of travelling wave in decelerating system. In this case the main mechanism of radiation of electronic wave has been the
transition radiation and Cherenkov radiation that requires the use of special electrodynamic systems and determines the constructive form of generator. SHF generator consisted of electron guns, modulating element and electrodynamic system to select energy of high-quality. Such scheme of a generator, driven by the mechanism of generation, has the range of fundamental disadvantages the main of which are the limitation of radiation power and the difficulty of gaining the radiation in the spectrum of short-wave area.
2.Literature review and problem statement
The limitation of frequency of radiation in classic generators is connected with the following reasons:
a) the size of electrodynamic systems is proportional to the wave-length to the small wave-length X ~ I mm it is hard to produce it;
b)gaining high levels of radiation intensity is possible with the increase of electronic waves within the structure which is followed by electrical breakdown during small wave-length;
c) with the changes in size of structure the quality of the structure decreases significantly that leads to the increase of energy lose, the heating of the structure, etc.
The limitation of generating power in these systems is caused by the following factors:
a) in the process of increase of electrical current beam there sharply increases the upward buoyant force of spatial charges that leads to electrical current collapse;
b)spatial charges worsen the particles grouping into the bunches that breaks the process of radiation generation.
To some extant these reasons can be weaken with the usage of the high-voltage relativistic electronic beams. In this case high-power electron-beam accelerator of impulsive activity is used as electronic injector. That gives the possibility to receive high electronic-current (of about 10 kA) having energy of a MeV range without a significant increase of injector's gauges. This way gives the possibility to increase the radiation power of known generators in two-three orders. For example, in magnetron of 10 cm the usage of charged par-
ticles accelerator (CPA) as an electron gun of class "Tonus" (e = 500 KeV, I=10kA) has posed the possibility to get the power of radiation up to 2 GW [1]. In that regard perspective direction of electronic SHF machines development is the creation of relativistic systems of radiation generation. Especially big possibilities occurr due to the creation of high-power (I = 10 - 1000 kA) high-voltage (voltage is up to 10 MV) relativistic electronic beams of impulsive activity (the duration up to (10~3 - 10) ^s). Precisely, due to such CPAs there has occurred the possibility to generate fluctuation of high-power in scope of SHF radiation as well as in more short-wave area of a spectrum. The usage of relativistic electronic beams allows getting shorter wave-length generating by radiation in technologically realized constructions of electrodynamic structure than it is allowed by its non-relativistic equivalent (due to relativistic effect there occurs the change of wave-length). For example, in relativistic monotron having the same wave-length of generation as it is in usual monotron there is the distance between the walls is to be YnX, where Yn is the energy of electrons of relativistic beam. The 1st table presents the results of theoretical researches of relativistic SHF generators, the main mechanism of fluctuation arising in electrody-namic structures of which is transition radiation or the Vavilov-Cherenkov effect[1,2].
The 2d table presents the results of experimental researches of SHS fluctuation at the heart of which there is a mechanism of Vavilov-Cherenkov generating
Table 1
Mechanism of induced radiation The mode of SHF radiation generator Resonance condition Efficiency of generator %
Monotron - 22
Transitional of Vavilov-Cheren-kov Orotron - 23.5
Twistron - 58
Klystron with the distribution of interaction - 58
From the carried researches it is seen that the characteristics of radiation in relativistic machines depend on the tension of magnetic field and pressure of tail gas in electrodynamic structure.
Table 2
The mode of electrodynamic The parameters of relativistic The parameters of radiation
structure electronic beam
Diaphragmatic waveguide in mag- q = 670 70 KeV P ~ 100 MW
netic field The tension of magnetic field r ~ 15%
H = 2 kgF
Diaphragmatic waveguide (vac- q = 500 -900 KeV X = 3 sm
uum type) I = 2 - 15 kA P = 500 MW
r| = 17 %
The same q = 1 MeV X = 3 sm
I = 50 kA P=200-300MW
Tu = 30 ns r= 3 %
Diaphragmatic waveguide (plasma q = 1 MeV X = 3 sm
type), p = 6 mm Hg I = 50 kA P = 600 MW
Ti = 30 ns 1= 6 - 7 %
Such influence is driven by the appearance of new regimes of energy transformation and by the conditions of structure's incitement (plasma regime, transmission of energy from the beam to the structure through the cyclotron regime). Moreover, as a result of theoretical and experimental researches there have been set new regimes of fluctuation incitement (collective effects inside the beam) and transformation of frequency with simultaneous strengthen of fluctuation power (induced Raman effect and Compton effect). Taking into consideration that the mentioned new schemes of radiation generators allow gaining the positive effect (to increase the power and efficiency of radiation, decrease the wave-length of generating radiation, etc.), let's discuss these machines in details(section 3)
3. The aim and objectives of the study.
This study objective is to elaborate recommendations on the use of modern methods, technologies, synthesis devices electromagnetic destruction receiver elements (of their p-n structures).
To achieve the objective, it is necessary to solve the following tasks:
- analysis of methods of generating powerful electromagnetic frequency radiation and the prospects of building them on the basis of fixed (mobile) devices electromagnetic destruction.
- study the possibility of constructing powerful devices of the generating sequence (30-40) short(duration of 10-30 NS) pulses, using current relativistic beams modulated spatially-periodic field (using the accelerating effect of electron trapping potential well of virtual cathode).
- study of the possibilities of using generators powerful electromagnetic pulse-based high-voltage forming lines for electromagnetic devices of destruction.
- research of supercritical oscillator beam current with a controlled amplitude and phase of the high frequency signal (wired) and the prospects for its use in systems of electromagnetic destruction receiver elements.
4. Materials and methods for creating a HTSC based prototype of a protective device
4.1 Cherenkov plasma generator
Cherenkov generators are based on the interaction between waves of spatial charges of electronic beam with slaw waves (or their harmonics) in electrodynamic structure. In Cherenkov vacuum generators on relativistic beam there is the size of maximal power of generation which is limited by the acceptable electrical current of beam in Ikr. This limitation is connected with the activity of space charge of beam and with the creation of vircator in injection area which leads to the reflection of a part of beam electrons backwards. To slow down the structure of a "corrugated waveguide" type with external radius R, beam radius r, and value Ikr that is
'kr
_ B.S(y3/2-l) /3 _
where
Ln — r
8.5 (y3/2-1)5/r ,(1)
y = 1 -ß2 =
n2\1/2 ' c2
is a relativistic factor,
5= R - r
Including the fact that there is R =3 sm, beam with Y = 3 and Ikr = 16 kA for corrugated waveguide. But the limitation of power in Cherenkov generator will happen when I < Ikr. Due to radial electrical fields in bunches there will occur the process of spreading the particles due to their speed. The process of filling the electrodynamic structures with plasma allows significantly reduce upward buoyant force in electronic beam and ensure the stative electrical current flow when electrical current is I > Ikr. It increases the power of radiation in Cherenkov plasma generator. Besides that the presence of plasma in the structure increases the increment of electromagnetic fluctuation development 5 during the incitement of resonance structure by impulsive flow of charges:
, y/3 Í 2 n r \„2 N o = — a 2 0
fW0
0 =
V3
2/
-vacuum resonator
- plasma resonator
(2)
where ro is classic radius of an electron, N is linear density of charges in beam
W0 = 2n J*Ez (r) dr (3)
that is a norm of field, rao is a frequency of own fluctuations of resonator without plasma, wb is a frequency of beam fluctuations in magnetic field. Longitudinal power flows of electromagnetic energy for these both cases has such form:
pvac = ^S(0.15 y2 +2.56) E2
p/1 = —(13.8 Y2 +2) 0.16 E2
(4)
From this information it is possible to see that in plasma generator the value Pz is by an order of magnitude exceeds the value of current of power of vacuum machine. Physically it is connected with the fact that the vacuum diaphragmatic waveguide sends a significant part of energy to fill the pieces of space among the discs, that means that radial flows of energy have significant size. For plasma waveguide the flow of energy is mainly concentrated in plasma capacity and radial components of the field turn out to be small. Efficiency of Cherenkov generator which is equal to the ratio of SHF electrical current of energy and its relation with current of kinetic energy of beam electrons, can be distinguished in the following way[2]:
n =
N m0c3 (y-l)
(5)
where m0 is mass of electrons and c is light speed Having equal kinetic energy of electric beam
n
pi~10
n
1
1
max
2
max
P
z
So, theoretical and experimental grades point out to undoubted advantages of plasma Cherenkov SHF generators in comparison with their vacuum equivalents. That is connected with the features of generating SHF fluctuations in plasma system. In the process of injection of electric beam into the slowing down structure which is filled with gas, plasma forms due to ionizing of tail gas. When density of plasma becomes relatively big, that means plasma frequency becomes relatively comparable with its own frequency of diaphragmatic waveguide, and plasma type and waveguide type of fluctuation start to compete. Incited voluminous waves have bigger amplitude then it is in vacuum regime.
But mentioned generators have a range of significant disadvantages. The main of which is a limited value of generating power. That is connected with a limited area of interaction between plasma and beam. Maximal level of power of Cherenkov generator is to be distinguished with the help of penetrating tension
Epe and cross section of interaction zone S:
P = S
1 max ^
(6)
where t is the length of impulse of electronic beam.
For generators with wave-length by an order of centimeters magnitude with frequency by an order of magnitude of 100 ns, value Pmax = 109 + 1010 W. It is possible to increase significantly Pmax, if we turn to the constructions with big value of an area of interaction between the beam with the structure, which has a higher value Epe . The examples of such generators are the generators with cyclonic waves.
4.2 Generators with cyclonic resonance
Generators of this type are based on the interaction between electronic beams with spatial and periodic
magnetic field (or with magnetic field which has localized disturbance). In such machines the required configuration of magnetic field can be created in huge amounts in comparison with Cherenkov resonance generator. In generators with cyclonic resonance the electronic beam is injected into the spatial and periodic magnetic field with the period of modulation in L = 2n/k. During the interaction between electronic beam with external spatial and periodic field there has place resonant turning of energy of beam longitudinal movement into transverse one. This situation is followed by the beam modulation of speed as well as of electrical current with a period in = 2n/k0 . Under these circumstances due to parametric link between wave-density of electrical current with speedy electromagnetic waves there appears microwave radiation on the modulated due to its density beam. Thus, if there is no limitations for the size of a phase wave-speed than it is possible to use a flat cylindrical waveguide as an electrodynamic system. Generator with the mentioned structure is called ubitron. To figure out the frequency of generation in ubitron there is a need to solve collectively dispersal equation for waveguide (w2 = c2k2 ± ^2) and for beam Doppler (w2 = kvn + mh), where vn is longitudinal speed of particles' movement. For that the fixed value of generating power and efficiency equals [3]:
\r2 2 P = 8 x 104^ —.
C2 (2+^30)
W; n
_ v\\
V« 1
c *30 (i+^)1/2
TT (7)
where ^30 = 3.8 and is the root of Bessel function for a round waveguide (the main mode). When y = 7 (the energy of electrons is 3 MeV) and electrical current is I=8kA: P = 0.2 x 1010 V, ^ « 10%
Table 3 presents the results of experimental researches of ubitron which work in cyclotron regime [3,4].
Table 3
2
E
c
pe
1
Characteristics of distribution of magnetic field The parameters of electronic beam Radiation parameters
g=300-400KeV P = 10 MW
Spatial and periodic magnetic field I = 35 kA q = 1-2%
L = 3 cm = 60 ns p=5x 10-5mm Hg
The same L = 3.8 cm g= 700 KeV
I = 20 kA T = 50 ns q ~ 2%
The same H = 10 kgF g = 3.3 MeV P = 1 GW
I = 60 kA ti = 70 ns f = 9 HHz
Longitudinal magnetic field H = 3 kgF g = 0.9 MeV I = 30 kA n = 80 ns P=1.5x 109 W q = 3% f = (3±1) HHz
g = 3 MeV P = 5 x 108 W
Spatial and periodic field I = 100 kA q = 0.4%;
li = 70 ns k = 3sm
The frequency of radiation ra can run the path of changes of tension of magnetic field, spatial period of
its changes or the value of speed of beam particles. Particularly, when the beam energy is big - y »1 the frequency of generation ra is connected with the frequency of changes of spatial period corrugation rao with ratio:
ra=Woy2
The calculations give us the following value:
when y = 40; X corrugations = 3 sm- Xisi = 2 mm ;
^ = 20%.
But in the mentioned structure except the cyclotronic resonance under definite circumstances there may appear a new mechanism of generation - radiation generation due to joint processes of fluctuation inciting in a beam and due to their interaction with electromagnetic waves under the following conditions:
— —— » 1
- 1-ß2 » 1
(8)
mainly, there is a range of theoretical material [3-7,912].
4.3 Generators of short-length radiation on the basis of relativistic radiation
Nowadays there are created generators which work in IR and UV diapasons with intensity in 100 MW[5]. Such short-wave radiation is received due to relativistic effect of transforming frequency and power. It is known that under the reflection of electromagnetic waves from the conductive mirror, there happens the reflection of wave with the changes of frequency œ — œ'
, 1+2ß)cos &+ß)2 = M -^-
(10)
It is natural that the usage of corrugated waveguide leads to the appearance of radiation generation due to the interaction between Cherenkov waves of spatial charge with returning electromagnetic waves. For such mentioned cases there is the increment of radiation increase
3 l 4 I
Y = < © Y* ^m 3 ko. I4* q2 (X-8)- (9)
Besides the machines with magnetic cyclotronic resonance nowadays there are researches of generators with spatial and periodic electrical field. Nowadays,
where 8 is the angle of electromagnetic wave fall onto the flatness of a moving mirror with speed in v. If the fall happens in a normal way (8=0°) the equitation has the following form [5] :
œ' = œr
when v — c the coefficient of frequency transfor-
2 ii
-1- 9
(11)
It is possible to use relativistic electronic beam as a moving mirror. For such beam there are given in the 4th table the values of coefficient rn depending on the accelerating tension.
Table 4
V
1-
c
mation rn is:
-1
r
t
V, MeV 0.1 1 2 5 10 100
rn 3.44 33 94 463 1690 154800
From the mentioned information it is possible to see that small-sized accelerators (7~5 + 10 MeV) when the wave-length by an order of magnitude in 10 sm allow getting the radiation which in IR and UV zone diapason. An essential feature of this way of short-waves radiation generation is power increase of a reflected signal (through the energy of a moving electrical current). During the first approach this power increase happens in rt . To receive a short-wave super-powerful radiation there can be used generators which have been mentioned above. In this case the generating radiation of big intensity with the wave-length by an order of centimeter magnitude is not radiated into the open space, but returns to the moving electronic item which has been created by it and it is transformed by the frequency and only then the process of radiation takes place.
Despite the fact that the possibility of generation of very short waves based on the radiation overabundance, has been shown as early as 50s, the possibility of using the effects of induced scattering by moving relativistic beams has come into research just in 1968. Let's remember that the first possibility of induced scattering of photons on electrons has been presented by Kapitsa and Dirac as early as 30s. The researches of a possibility of using the scattering on moving plasma
and electronic beams with rather big but mono energetic current has been theoretically and experimentally researched Kharkiv Institute of Physics and Technology in 1959-1960s. New possibilities have been opened due to the appearance of high-power audio power am-plifier[10]. They have given a new impulse for the development of methods of frequency (multiplying) transformation based on the usage of induced Comp-ton- and Raman effects on the relativistic electronic beams.
Nowadays the most successful are the researches carried out in two directions:
- the usage of Raman effect in high-power beams. On the ubitron of Cornell University (q = 2 MeV, I = 60 kA,X = 2 sm) due to the transformation of frequency of received radiation: X = 400 [im, P = 1 mw,tl = 30 ns;
- the usage of Compton effect on the relativistic electronic beams which are receive from audio power amplifier of a simple type. On the linear amplifier (Stanford) with parametres: I = 70 mA, q=43 MeV radiation: P = 10KW, Ti~ 10 [is.
Radiation generation in infrared spectrum zone (50MW) is experimentally measured in [5]. Nowadays in the USA there are intensively work over the creation of short-waves radiation generators. Due to that it is
considered that the mentioned systems are more desirable then laser machines due to their efficiency as well as due to energy of radiation [3-5,8]. In laser systems there is a limitation of impulse energy (for today Qt < 5 KJ [5] and has a principal way of behaving that is connected with the limitation of size of inciting area. Such limitations are absent in high-power electronic beams and in applied structures.
4.4 Radiation generation by plasma fluctuations
where N is full number and d is the distance between the flatnesses.
In the papers [9] there are calculated the parameters of a beam and plasma which allow getting the maximal level of radiation when the energy spending is the least. It is shown that with the help of this way there can be created the radiation with the wave-length in 1.0 -0.1 mm. The absence of electrodynamic structure (resonators, deaccelerating systems, etc.) ensures the possibility of plasma inciting in huge amounts and allows getting bigger levels of radiating power.
Plasma fluctuations which are incited by the external source (for example by the flow of charged particles) can create intensive radio wave in zone of millimeter and submillimeter length of waves. The possibility of radiation generation in this frequency range is connected with resonance characteristics of plasma itself and does not depend on the parameters of the external radio waves' elements and contours. Own (resonance) frequency of plasma fluctuations with electronic concentration n is:
5. Discussion of the results of a study of technologies for creating devices of electromagnetic damage
One of possible regimes of effective damage to electronic equipment and its components in the process of impact of microwave radiation on the radiation of ultrashort-length impulse is the regime with the sequence of short impulses (10-100 impulses in the raw) which move with small pulse ratio.
f0=fp = 9 • 106 Jn,sm-3,Hz,
(12)
During the formation of this equation there has taken place the process of neglecting of the value of thermal speed of electrons, if one takes them into account the equation gets the following form:
W„
w2 — k2v2
=1
As a phase speed of wave v = w/k, than the equation is equitable, when the wave speed is significantly bigger of thermal speed of particles (v > vT). To use such fluctuations of plasma as a source of electromagnetic fluctuations there is a need to incite these fluctuations with the help of a flow of charged particles [5,10-14]. In this case the presence of a directed electronic flow in plasma can change the form of disper-sional dependence:
w;.
w
2
k2vï
+
(w — k voy
=1
If the speed of particles will be higher than thermal speed of plasma electrons and will be equal to phase speed then the particles of a flow will be intensively giving their energy to the longitudinal wave (Langmuir wave) and will swing out and support plasma fluctuations [9].
To provide the regenerated feedback, the process of receiving the radiation level which is higher than the radiation of thermal noises in inciting plasma there is created stagnant water (for example in the way of setting in it two parallel reflecting surfaces). Then the electronic flow interacts with one of running waves and another component of stagnant water which is directed to the opposite direction of beam movement, ensures the required feedback connection. The condition of regenerating connection creation is the following:
5.1 Radiation generation of ultra-short length of impulse in frequency and periodic regime with a small pulse ratio
There is presented below the possibility of such radiation regimes creation on the basis of effects which arise in ECM with supercritical electrical current and, as well, in the process of their interaction with some electrodynamic structures (EDS).
Injection of radioactive machines with Iinj > Ivac into the vacuum drift areas leads to incitement of intensive SHF fluctuations in zone of frequency œ ^ œb and simultaneously stimulates the development of different compensative processes. They show themselves in massive ionization of tail gas and in appearance of radial and axes ions' flow which is taken of electrode plasma. In this case the time of neutralization is distinguished by the condition of the process of plasma creation, its ion composition and geometry:
tn = œp-1 + ar-v.
(14)
where «i is a coefficient of massive ionization of gas (auxiliary ions and electronic processes are included), Vi is the speed of acceleration of plasma ions, a is a form-factor. Magnetization of electronic beam, direction along the beam and ion movement form a "running away" virtual cathode with a changing size of potentiality (p (z,t). There are created low-frequency relaxation fluctuations of potentiality and flowing electrical current of ECM and, as well, intensive flows of accelerated ions .
The condition of forming such relaxation regimes and spectrums of low-frequency modulations of ECM have been researching experimentally with the help of high-power electronic beam with parameters qb = 250 + 300 KeV, Ib = 1 + 3 kA,Ti = 1.2 p.s which is form in diode with magnetic isolation .
It was possible to have influence on the presence of massive of surface situations in the dynamic of relaxations of ECM by the process of choosing the gas pressure or by the condition of surface ionization on the DMI electrodes (mainly on anodes). It is found out that for the realization of frequency and periodic regimes of work (in limits of tu), the main role is played by the processes in plasma of electrodes which is the source of accelerated ions which ensure the fast reconstruction of a virtual cathode. The potentiality of a beam in injection area z = Lk — a*rk, where a* = 0.3 + 5 is a form-factor, under the condition hnj/Ikrvac > 1 and ^t — 10 + 50 ns has been reaching (1.3+1.5) cp0 and for bigger distances its value sharply falls down up to (0.2+0.3) . The formation of movable electronic fields with Ef= 105V/cm which has been followed by the partial locking of ECM and by the appearance of accelerated ions with electrical current up to 150+200 A. If hnj/Ikrvac < 0.8 + 0.9 there are no relaxation situations and accelerated ions. Specific time of relaxation in a beam with Iinj > Ivac has been figured out by the time of accelerated ions leaving and by the reconstruction of virtual cathode in injection zone.
Trel — arkv"1 — 10 + 50 ns.
Arising pulses of electrical current ECM with amplitude up to 40% has been registered by a collector machine, sounds and X-ray sensors. Parametrical research of conditions of formation of low-frequency spectrums of a passing ECM has shown that their frequency is fif — t-1 = 18 ±6 MHz.
The possibility of change vt = vt (z, t) by the time of capturing of ions by movable potential well of a virtual cathode has been used for a collective ions' acceleration by the density-waves of a charge of ECM which is formed during injection by the modulated in DMI beam into the zone of drift which has been placed into the spatial and periodic magnetic field. During this time there has been observed the effect of accelerating frequency of low-frequency relaxations of ECM which, depending on the selection of the conditions of spatial modulation, has reached 50+ 70 MHz. Under the conditions of experiments the impulse of a microsecond ECM, which has been modulated as a result of processes in DMI and in drifting canal, has been containing the sequence of 30+ 40 impulses with the length in 10+ 30 ns.
The way of getting the frequency and periodic regimes of SHF generation can be realized in the apparatus^]. The specificity of this apparatus is its possibility of effective managing of deep modulation and pulse ratio of sequence of impulse of ultra-short length due to the changes of DMI regimes work which have been created by the source of plasma. Despite that it is registered that the regime of formation of impulses' sequence can be optimized from the point of view of reaching 100% of ECM electrical current modulation through the usage of low-frequency electrodynamic structure (EDS) which is configured on the main frequency of bunch sequence. During numerous experiments as a representative of such structure there has been used coaxial vacuum resonator or their sequence , which are well adjusted with high-power ECM. Due to quiet low resonance frequency of EDS its size has occurred to be too big. Thus, the apparatus which consists
of sequence of three coaxial resonators which are adjusted to 60+150 mHz, has had longitudinal size up to 3 m. There has been analyzed the possibility of using the waveguide of artificial and anisotropic dielectric as the more compact low-frequency ECM. The possibility of using the material with e >> 1 ensures the presence of deceleration of longitudinal size of a working apparatus and ensures the reach of more qualified parameters of a forming sequence of impulses through the use of more effective length of EDC.
5.2 The creation of intensive EMP fields' creation on the basis of high-voltage forming lines and ECM
As a result of researches of resilience, reliability of elemental basis of ECM[1,6-7,22], armament and military machines under the conditions of impact of electromagnetic fluctuations intensive fields there has arisen the big interest in the possibility of the creation of sources of generating the powerful ultra-short electromagnetic pulses (PEMP) with parameters[10]: Ef =
103 - 105 V/sm,
10"
S, T^Y
= 10"
H
10"
- m2
102 + 104 ,Ti = 10-9 +
s.
Such impulsive fields can be created on the basis of the use of traditional elements of high-power ECM accelerators and of some effects which follow their movement through the vacuum and plasma structures.
5.2.1 Generating of PEMP fields with the help of forming lines
The easiest way of forming PEMP is the use of traditional methods of receiving identical high-voltage (HV) impulses which are used in technologies of highpower accelerators [10]. At the same time, tough demands, which are turned to time parameters of such apparatus, bring them closer to powerful apparatus of SHF diapason with the line in 108 + 1010 Hz because of their constructive features. Relatively small loses and wideband of coaxial long lines give the possibility to use them as the main forming and transmitting elements of PEMP generators. The most responsible elements of such apparatus is HV commutator of a forming line (FL) and HV testing chamber (TC) which is agreed with FL.
Relatively bid wave resistance of FL and TC Zt = 100 + 300 Q gives the possibility to use gas or fluid with low e as HV dielectrics of FL. Paying attention to the mentioned above the demands turned to HV commutator are not very tough:
Lk <
ZlTfr
5 • 10-9 H,Zk — 10 ft «Zt (15)
TC is to ensure relatively high homogeneity of electromagnetic fields in the area of an analyzed subject and simultaneously is agreed with HV load of FL. The specificity of apparatus is the use of two forming coaxial lines which give the possibility to change the duration of PEMP in the limits of (1+4) • 10"8 s, but, as well, to use the regime of idling of the second forming line to ensure overexertion in the area of outbound commutator-exacerbate which allow reaching the sub-nanosecond fronts of line. TC is formed in the way of an area of long coaxial line which has at the end agreed load which is designed for the amplitude of a falling wave in 300+500 KW. Water is used as an absorber of
1
2.2
wideband alignment. The wideband of coaxial construction and of features of load resistance in interested frequency diapason ensures the possibility of using apparatus in given interval in Tfr and ii.
5.2.2 The process of creation of PEMP fields during ECM injection into the vacuum structure and neutral gas
Injection of impulsive ECM into the vacuum chamber or neutral gas is followed by the incitement in area of drift of intensive movable electronic and magnetic fields. Their size can not extend some limit values which are distinguished by geometry, energy and by current of particles and the degree of neutralization of charges and electrical current [11]. For a typical case of injection of homogeneous, due to the radius, magnetic ECM with I < Ivac into the vacuum cylindrical chamber with the length in L relative components of quasipermanent E and H fields which have the following form when r « rk:
E = 2nerl{\ - fe)n(t )xr -Hv=27ie/3/o(l-fr)xn(t)xr-1
(16)
Aœ-1
■n\1/3 \nb)
10-9 + 10-8c <
are complicated, the dynamic of ECM field is to be distinguished by relaxation processes which arise as a result of slower changes of potentiality. The situations at ECM front, which spreads in vacuum chamber in strong magnetic field and, as well, which come through gas of big-density are experimentally analyzed in the works [13-16]. Low-frequency spectrums of fluctuations of potentiality with f <70 MHz have been analyzed in experiments at microsecond DMI which is described above. More high-power relaxation spectrums MHz and regimes of vircator radiation of sHf fields have been registered during the experiments with injections with supercritical electrical current of nanosecond ECM in cylindrical vacuum chamber.
The size of tension of movable magnetic field of ECM electrical current in the process of its moving through neutral gas mainly depends on the gas-density, on the plasma creation and on the speed of development of gas penetration. Till the moment of charging neutralization t < T; magnetic field of ECM which is formed by a passing by electrical current the value of which is:
<p
7
E = — E <<Er
z L r
When there is gas through the processes of impact and avalanche ionizations there are created the fields of compensated ion backstage and return electrical current of plasma electrons [12,13].
Throughout the growth of plasma conductivity = u>2/4nv , where v is the frequency of collisions of these compensative mechanisms during the time t~ ti which are turned out to be essential if the requirement is ensured:
Ti c2
S > IT "T
4n rf-
for such neutralization and:
1 L2 5 > - —
Ti r2
for the charge neutralization. The condition of plasma formation in different gases, charging and electrical current neutralization of beam fields and their spatial features have been analyzed with the help of experiments and with the help of numerous modellings which have taken into account not only elemental but also collective effects (plasma and beam probes). It turned out that the fields of longitudinal plasma fluctuations, which are incited by ECM through the development of beam instability, can significantly influence the dynamics and speed of plasma creation. Their accounting in numerous cases gives the possibility to provide more detailed description of the dynamic of plasma-creation which happens on ECM front within:
h <
L
(1-fe)
and if fe « 1 it turns out to be not big. In case of quiet full charging neutralization fe = 1 and fm « 1 the beam electrical current does not exceed IA = 17 • p • y kA. Maximal magnetic field can be received under the conditions of partial neutralization of charge fe ~1/y2 [15]. when:
V2
I = ¡I = ¡A
P2 +fe~1
»¡l.
Further increase of plasma size there is created the compensative return electrical current Ipi and value Hv is to be distinguished by the difference of electrical current's beam and plasma
H<p (r > r0 ) =
2 (¡b- 'pi)
(17)
In the case of injection of supercritical ECM electrical current into the drifting area there appears the process of creation of the virtual cathode with a particular falling distribution of potentiality along the direction of ECM spreading. In strong magnetic field with quiet small gas-density, when the conditions of impact and avalanche ionizations as well as penetration of tail gas
The process of electrical current compensation has specific stages which depend on gas tension. During ECM injection with sharp front into the neutral gas the value of magnetic field changes (17) during the whole duration of electrical current impulse. The speed of changing Hv depends on the tension and the type of gas. The condition of movable magnetic field creation has been analyzed experimental during the movement of ECM in a drifting chamber which has been fulfilled with gases with different tension. It has been noticed that if the tension is small the time of gas penetration t pn and, relatively, the time of forming reflected electrical current t m can be turned out to be comparable with t í. Meanwhile t fr (PEMP) equals t fr (ECM). With the increase of gas tension t m > t fr. Maximal values t m and t fr (PEMP) has been corresponded to gases which have had lower level of ration and, as well, equality to atom ionization. The experiments have shown out that as a result of selection of the conditions of penetration in the drifting chamber there appears the process of generating the magnetic field which is close to maximal and which are relative to the value of injecting ECM electrical current and reach up to 103 ^ 104 Oe. Meanwhile t fr impulsive magnetic fields are to be distinguished by t fr of ECM. Thus, the parameters of E and H are the fields incited by relativistic high-power
rc
T
beams in drifting areas and they can destructively influence different physical items including radioactive apparatus.
5.3 Creation of microwave radiation sources of high-potentiality and their usage as effective EW means of affection
Recently, due to the problem of the increase of microwave radiation power of beams' systems it turned out to be possible to realize the energy of own quasi-statistical ECM fields with supercritical electrical current [16].
The result of these researches has been the appearance of new class machines - EBM-vircator with rather high impulsive power. The easiness of the construction, the possibility to adjust the frequency, the easiness of its alignment with ECM and the system of radiation output - all those factors distinguish the interest in such generators. However, their radiation is instable in frequency and mode structure because of the difficulties of the processes in diode with high-accuracy [14-16]. The use of resonators gives the possibility to run greatly the parameters of radiation and effectiveness of interaction between SHF fields with ECM particles in the area of virtual cathode formation. However, the use of resonators as accumulative elements of SHF path increases the possibility of penetrations of SHF and, as well, prevents the process of getting radiation of impulse of ultra-short length.
In analyzed auto-generator at the super-critical ECM electrical current with a running amplitude and phase of high-frequency signal-virtod [15-17] has been used to create positive feedback in the area of beam acceleration up to 15% of power of own radiatio. Intensive radiation (P = 600 MW) has been incited in rectangular waveguide in frequency diapason in 3.8+5.8 hHz when the ECM injection of energy into it has been 400+500KeV and electrical current up to 14kA. Transformation due to the frequency takes place through the changes of the happening situation and oscillation of ECM current in the way of moving the grounded collector. The use of the external magnetic field with the tension up to 5+6 kEC gives the possibility to record the beam's geometry and to produce additional setting of frequency and sHf radiation power. Introduction of feedback significantly influence the effectiveness of generation without changing its frequency. The level of radiation power with optimal settings of connection has increased in comparison with the level of free fluctuations in 8+10 times[17]. The change of signal phase of feedback in limits of ft = 0 + 3n has created a particular dependence P/Po (ft) with several maximal values which are relevant to the conditions of feedback creation with the wave on oscillating beam. Meanwhile there has place the increase of intensity of electrical current oscillations and, relatively, of vircator radiation. Efficiency of apparatus has been changing in limits of 3+17%. Distance between extremum of depend-
ence P/Po (ft) recorded for different conditions of generator's settings shows that the beam has spatial modulation on density, which is equal to:
Yp =Yo[1 + (Yo/Ykr)2] -1/2 where ykr is a critical length of wave in waveguide. Thus, in virtod the frequency of fluctuations is strictly set by resonant characteristics of oscillating beam itself and it does not depend on the phase of external signal. At the same time, unlike vircators with resonant flatness this system gives the possibility to increase the effectiveness of interaction between the beam with SHF field without the accumulation of energy and without the increase SHF fluctuations amplitude in the area of interaction. It fundamentally removes the process of delaying the impulse of radiation of impulse of ultra-short length and decreases the probability of penetration of EMF.
Due to the need of qualified description of the main processes in vircator on the passing by beam and of the spectrums of radiation there has been carried out the research of its simplified model.
Let's look closer at the set processes of fluctuation in monoenergetic homogeneous in ECM ratio which fills in the cylindrical waveguide (rp = R) and final length L « R cycled at the end.
Dispersal equation for the waves of such beam if it is considered that there is endlessly big external magnetic field has the following form [17-19]:
Kb + Kb -
(a - W
= 0; K' =
Ml Rb
It takes into account the existence of independent decisions for four plasma waves one of which is return. Existence of return wave in a beam appears because of the transition to the regime of vircator when the beam-density exceeds the equilibrium value of Pkr . On the basis of results received from the equation of macroscopic hydrodynamics and from the Poisson's equation it is possible to see that wave-vector and frequency of inciting fluctuations can be expressed through the beam's parameters and their frequency detuning Sm relatively to the frequency of merging of the roots of slow waves Me = m (k). The formation of the field of a set oscillating process happens as a result of interference of waves' fields which arise in the process of numerous reflections in the frames of specific spatial scale l . Under the conditions of merging of roots the coefficient of reflection from the border lines takes maximal value. Physically it means that any disturbance leads to the appearance of reflected wave in the system with amplitude which depends on the detuning Sk. This process can be interpreted as the mass in the resonator's beam the quality of which is the function of Sk as well. The line of personal frequencies of such resonator is distinguished by the area of existence of collective decisions only of the line and return slow wave of a mentioned process: 0 < m < we.
Resultant field in oscillating beam can be highlighted through the amplitude of field of the first signal E0 and its parameters of beam-waves and of waveguide:
E (I)
En
J-ia (1-u/ue) /2(1-x/l)\ _
1 — b (1 — w/we) e
/2(1-x/l)\
J-ia (1-u/ue) 1/2] —[1
where a = • ke • I; b — is the parameter which is equal to detuning (Sk,)2.
-2b(1- u/ue)] eia(1-M/Me)1/2
Received results have shown that ECM in regime of supercritical electrical current is incited at the frequency in 0 < m < Me . It is correspondent to well-known way of setting of vircators due to frequency by simple changes of injection electrical current or of energy particles. Meanwhile the spectrum of own wave numbers has threshold specificity < Kkr. The specificity of frequency spectrum is the presence of a number of non-equidistant narrow resonances = Mr (nv), the quantity of which is distinguished by choosing definite length . Thus, there is one more possibility to run the spectrum of changes of a specific longitudinal scale. In the realized virtod machine such mode selection is reached with the help of transmission of electrical current ECM collector. Optimal conditions of waveguide incitement require having uneven quantity of half-waves on the specific size of waveguide with Kn = Ke(n). Such situation occurs in the system on oscillating beam and thus their effectivity is higher than in transient vircator where the field's spectrum has not been recorded. Despite the other vircators in this vircator there is selection due to K^ which in broad limits allows running the parameters of radiation without using the machine with energy accumulation of SHF fluctuations (that is selection due to K±) launching the regime of running wave as well as the high efficiency of the whole machine n — Vosc.
Running the parameters of the generator of microwave radiation of transient vircator type can be reached not just because of the use of mode selection of beam's fluctuations when their frequency is strictly set by the geometry of drift area and by the beam's parameters. Another possibility is connected with modulating ECM effect which occurs during the impact of external changeable potentiality U on the beam which is in subthreshold regime U = U0 [18]. In this case the value of modulated ECM electrical current is distinguished with the help of acting accelerating potentiality = U0+ U : 1= I0(U/ Uo)1/2 6. Conclusions
This way of beam's modulation by relatively weak external signal is taken to the basis pf microwave autogeneration on the transient beam. There has been used resonator in it, which is incited by modulated ECM of high-accuracy, part of energy of which has been brought through the chain of external feedback to the area of beam formation creating the regime of automodulation. Preparatory beam's modulation increases the effectiveness of its interaction with resonator's fluctuations at its own frequency through the increase of increment of an absolute instability of the transient beam which has been injected into the vacuum resonant EMF.
Interaction of a modulated beam with the resonator's field has been analyzed in the approach of a given field (). The value of feedback coefficient which is required for the incitement of ECM on the chosen frequency of resonator has the following form [19]: ,= E30\\n 3^c (y-1)
q I^IAQ3/2Rcb1/1Ay2 where \\^\\ is form-factor, Q is the quality of resonator, Rcb is the resistance of feedback.
Dependency of value of beam's energy lose in resonator which comes to radiation A y can be optimized throughout the field E0 = Eopt and it is connected with
the parameters % = ek0 Eopt /тш^ , which reflect the connection with amplitude of a field's structure in resonator. Resulting electronic efficiency of the mentioned system in the following form:
Ay(Eopt)
Летах ,, л Уо-1
for typical conditions of experiment (y0 = 2,10 = 20 kA) it can reach up to 86%. In the proposed scheme of auto-generator the line of resonator's frequency 2Af - f0/Qnagr due to its quiet high quality (Q = 10 + 30) it turned out to be significantly smaller than the spectrum of vircator system's frequency. It gives the possibility to use selective features of resonator to narrow the spectrum of auto-generator in general. To complete the work of such apparatus with external feedback in regime of generating impulse of ultra-short lengths it is required to have the duration of electrical current impulse xu less than the time required to set the generating regime xset , that is the time spent by the frequency spectrum of vircator to narrow itself up to width which is figured out by the flat features of resonator, Ti > xset. Depending on the time spent for signal passing through the chain of feedback Tfb the time for setting fluctuations in the system is equal to [19-20]:
\Qh! f° fb ^Qh' fo
[(т^хЛfxN,Tfi>QH/fo
The calculations of parameters of auto-generator which are carried out for a definite type of fluctuations of rectangular resonator Hiin , which is incited by ECM with electrical current in 20 kA on frequency in 3 x 109 Hz when Tfb - 0.5 • 10-9 s that show out that the value Tset does not exceed 10-8 s, that gives the possibility to such system to generate radiation with impulse of ultra-short length.
Thus, the vertical systems of different types which use the tough feedback in the field to run the process, may have quiet high effectivity, and can be used to create high-power sources of radiation with adjustment of frequency and with the changes of output power in broad limits.
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