RU2388101C1 - Relativistic magnetron with resonator waveguide channels - Google Patents

Abstract

FIELD: physics, radio.

SUBSTANCE: invention relates to relativistic high frequency electronics and can be used for generating powerful microwave radiation. The relativistic magnetron has a multi-resonator anode block (2), with an explosive emission cathode (3) and a cylindrical drift tube (1) both lying on an axis, an external magnetic system (6) from two coils which form a Helmholtz pair. The resonators, arranged next but one, are connected to waveguide channels (7, 8) numbering s=1, 2,…N/2 and having wavelength λm, where N is the number of resonators of the anode block, m is a positive whole number, λ is the wavelength in the waveguide. There are radiating slots (9) in the waveguide channels (7, 8). The central radiating slot lies on the axis of electrical symmetry of the waveguide channel. The radiating slots (9) are made in the wide wall of the waveguide channels (7, 8) such that lateral radiating slots are at a distance (2n+1) λ/4 from the central slot alternately on different sides of the centre line of the channel wall, where n is a whole number, or such that lateral radiating slots are at a distance nλ from the central radiating slot on one side of the centre line of the channel wall, or such that lateral radiating slots are at a distance nλ from the central radiating slot on the centre line of the channel wall.

EFFECT: increased intensity of the high frequency field on the axis of the radiating system, which is a multi-dimensional antenna array composed of separate waveguide channels with radiating slots.

4 cl, 2 dwg

Description

The invention relates to the field of relativistic high-frequency electronics and can be used to generate powerful microwave radiation. The practical use of microwave radiation imposes requirements on the stable operation of devices, on preservation of the amplitude, time, and frequency parameters of the microwave signal from pulse to pulse, and for some applications a high radiation directivity is required.

A device is known - a classic magnetron [Samsonov D.E. Basics of calculation and design of multi-resonator magnetrons. Owls Radio, 1966, 224 pp.], Consisting of a multi-cavity anode block with a waveguide power output, coaxially located thermionic cathode, connected through a cathode holder to a power source. Outside, a magnetic system is installed in the form of a permanent magnet, or in the form of an electromagnet of two coils forming a Helmholtz pair. In the gap between the poles of the magnet, a waveguide output of power passes through a coupling gap with one of the resonators of the anode block. The anode block is under ground potential, and a negative polarity pulse is supplied to the cathode from the power source. In a crossed radial electric field between the cathode and the anode and the magnetic field created by the magnetic system, the electrons, rotating azimuthally in the "spokes", give their energy to microwave radiation and radially drift to the anode. The energy of microwave radiation is removed through a coupling gap in one of the resonators and a smooth waveguide transition.

The disadvantage of this device is the low output power due to the low values of the output parameters of the power source - voltage and current. An increase in voltage is impeded by the development of breakdown between the cathode and anode, i.e. transition of the thermionic cathode to the explosive electron emission mode. This breakdown leads to the destruction of the cathode surface, the loss of its emissive ability, violation of the vacuum conditions in the device and the failure of the magnetron. The magnitude of the current is limited by the emissivity of the cathode material.

A device is also known - a relativistic magnetron containing a multi-cavity anode block with one or more waveguide power leads, a cylindrical drift tube with an inner diameter greater than the inner diameter of the anode block, coaxially connected to the anode block, a cathode connected by a cathode holder with a negative polarity of the power source, and a magnetic the system. The power terminals of two opposite resonators are connected by means of a rectangular waveguide through communication channels. Radiating slots are made in the communication channels. The central slot is made on the axis of electrical symmetry of the communication channel. [Vintizenko I.I .; Zarevich A.I .; Novikov S.S. Relativistic magnetron. Patent RU 2228560, published May 10, 2004]. We select this device as a prototype.

High-current electron accelerators are used as power sources for relativistic magnetrons. In relativistic magnetrons, the anode block and the drift tube are grounded, and a negative voltage pulse of 50–200 ns duration and an amplitude of up to 1000 kV is applied to the cathode. The cathode is made of metal or graphite and operates in explosive electron emission mode. In a crossed radial electric field between the cathode and the anode block and the magnetic field created by the magnetic system, the electrons emitted by the explosive electron emission move in two directions. As in the classical magnetron, the electrons, rotating azimuthally in the "spokes", give off the potential energy of the microwave energy and radially drift to the anode block. In the axial direction of the device, the electrons of the end current emitted by the end of the cathode move. This current arises under the influence of crossed electric edge and longitudinal magnetic fields. The use of a large diameter drift tube allows one to return some of the electrons back to the interaction space, increasing the efficiency of the device. The electrons of the end current that did not return to the region of the anode block are deposited on the surface of the drift tube in the region of the decreasing magnetic field. The power outputs from the opposite resonators of the anode block are connected through one or more (maximum N / 2, N is the number of resonators) communication channels designed to increase the output characteristics of the relativistic magnetron. Radiation slots are made in the external communication channels for outputting microwave radiation, and such a communication channel is a one-dimensional antenna array. As shown by experimental studies [Vintizenko II, Novikov S.S., Zarevich A.I. Relativistic magnetron with distributed microwave output. Letters to ZhTF, 2005, v.31, v.9, p.63-68], the use of external communication channels increases the efficiency of the relativistic magnetron and improves its spectral characteristics in comparison with the case of using one power output from the anode block.

Depending on the number of resonators of the anode block of the relativistic magnetron, the length of the communication channels and the arrangement of the emitting slots are different. When the number of magnetron resonators satisfying the condition N / 2 is an even number, the channel length is (2 m + 1) λ / 2. The central slot is located on the axis of electrical symmetry of the system, and the remaining (side) slots are located relative to the central one at a distance of (2n + 1) λ / 4, where k is an odd number, N is the number of resonators of the anode block, m, n is a positive integer, λ is the working wavelength. When the number of magnetron resonators satisfying the condition N / 2 is an odd number, the waveguide length is λm, the central gap is shifted relative to the axis of electrical symmetry of the system by λ / 2, and the remaining slots are located relative to the central one at a distance of (2n + 1) λ / 4.

The disadvantage of the prototype device is that when using several external communication channels connecting the opposite resonators of the anode block, it is impossible to create a two-dimensional (or multidimensional) antenna array and the formation of directional radiation. This is due to the fact that the waveguide communication channels intersect in space.

The objective of the invention is to increase the directivity of the output microwave radiation while stabilizing the amplitude, time and frequency parameters of the microwave pulses of the relativistic magnetron.

The expected technical result is an increase in the intensity of the high-frequency field on the axis of the radiating system, which is a multidimensional antenna array composed of individual waveguide channels with radiating slots.

To solve this problem, a relativistic magnetron with waveguide communication channels of resonators is proposed, which contains, like the prototype, a multi-cavity anode block with an explosion-emission cathode and a cylindrical drift tube located on the axis, an external magnetic system of two coils forming a Helmholtz pair, radiating slots are made in the communication channels moreover, the central radiating gap is located on the axis of electrical symmetry of the communication channel. In contrast to the prototype, waveguide communication channels with the number s = 1,2, ... N / 2 are connected by resonators located through one and the communication channel length is λm for anode blocks with any even number of resonators, where N is the number of resonators of the anode block, m - positive integer, λ is the wavelength of oscillations in the waveguide.

It is advisable that the radiating slots were made in a wide wall of the communication channel so that the lateral radiating slots are located relative to the central one at a distance of (2n + 1) λ / 4 alternately on different sides from the midline of the channel wall, where n is an integer.

It is also advisable that the radiating slots were made in a wide wall of the communication channel so that the lateral radiating slots are located relatively central at a distance nλ on one side of the midline of the channel wall.

In addition, the radiating slots can be made in the narrow wall of the communication channel so that the lateral radiating slots can be located relative to the central one at a distance nλ on the midline of the channel wall.

The device is shown in Fig. 1, Fig. 2 is a view of a magnetron in a plane perpendicular to the axis of symmetry in Fig. 1, where 1 is a cylindrical drift tube, 2 is a multi-cavity anode block, 3 is a cathode, 4 is a cathode holder, 5 is a power source , 6 - magnetic system, 7.8 - waveguide communication channels, 9 - radiating slots. The figures show an eight-cavity relativistic magnetron with two waveguide communication channels, in which eight emitting slots 9 are made (one central, seven side) in a wide waveguide wall alternately on different sides of the midline of the channel wall. The waveguide communication channels 7.8 form a two-dimensional slotted waveguide antenna array with high focusing properties and radiating along the axis of the relativistic magnetron.

The device operates as follows. Pre-included magnetic system 6, operating in continuous or pulsed modes. When the maximum magnetic field is reached, the power source 5 forms a pulse of negative polarity (voltage amplitude of 100-1000 kV and current 1-40 kA, depending on the type of source). In the gap between the cathode 3 - multi-cavity anode block 2 creates a high electric field strength, causing the development of explosive electron emission [E. Litvinov and other field-emission and explosive-emission processes in vacuum discharges. Success physical. sciences. 1983, t.139, s.265-302]. In crossed radial electric and axial magnetic fields, the formation of electron "spokes" of space charge occurs and the process of transfer of electron energy to microwave energy is carried out in the same way as in a classical magnetron.

Communication channels 7, 8 connect located through one of the resonators of the anode block 2, which leads to the interaction of microwave fields in the resonators. As is known [Centimetric magnetrons. T1, 2. Trans. from English under the editorship of S.A. Zusmanovskogo. - M .: Owls. Radio, 1950], for the main working π-type of oscillations, resonators located through one are in phase. For all other types of oscillations, the phase distribution of the high-frequency field is different from the phase distribution for the π-type, therefore, these types will be suppressed by an external communication channel. In order to stabilize the π-type of oscillations, the waveguide length is λm. In this case, the phase of the incoming microwave wave is in phase with the oscillations of this resonator. To output and distribute microwave radiation and stabilize the working type of magnetron oscillations in the walls of the communication channel (rectangular waveguide), k (k≥1) radiating slots 9 are made. Positioning the radiating slots 9 in each group at a distance multiple of λ / 2 from each other alternately in different sides of the midline of the waveguide wall, we get in-phase excitation of all the slots [Automated design of antennas and microwave devices: a tutorial / D.I. Voskresensky, S.D. Kremenetsky, A.Yu. Grinev, Yu.V. Kotov. - M .: Radio and communications, 1988. - 239 p.]. The location of the slots on opposite sides of the midline of the wide wall of the waveguide allows to double their number per unit length of the communication channel.

Another embodiment of waveguide communication channels, when the radiating slots 9 are cut in a wide wall of the communication channel. The central radiating slit is located on the axis of electrical symmetry of the communication channel, and the side slots are located relative to the central one at a distance λ from each other on one side of the midline of the channel wall. The radiating slots 9 can be cut in a narrow wall of the waveguide communication channel. The central radiating slit is located on the axis of electrical symmetry of the communication channel, and the side slots are located relative to the central one at a distance nλ on the midline of the wall of the communication channel. In both cases described, we also obtain in-phase excitation of all the gaps.

If the wave impedances of the radiating slots are equal, a uniform distribution of the magnetron output energy is realized.

A diagram of a specific implementation of the proposed device is shown in FIGS. 1, 2. Four resonators of the anode block 2 of an eight-cavity relativistic magnetron fed by a section of a linear induction accelerator 5 are connected through two waveguide channels 7 and 8, in which eight emitting slots are made 9. Magnetic system 6 made of two magnetic coils forming a Helmholtz pair, is powered by an adjustable constant current source, has water cooling and provides a magnetic field with induction up to 0.54 T. Relativis The magnetron has a water jacket for cooling the anode block 2 and drift tubes 1, a graphite cathode 3 with a diameter of 22 mm, mounted on the cathode holder 4. The inner diameter of the anode block is 43 mm, the diameter of the resonators is 86 mm, and the length of the anode block is 72 mm. The diameter and length of the drift pipe are 1,200 and 700 mm, respectively. The experimental setup provides the generation of microwave pulses with a repetition rate of up to 320 Hz and is characterized by high repeatability of performance.

The waveguide communication channels 7.8 are made of segments of a standard copper rectangular waveguide with an internal cross section of 72x34 mm ² . The length of each communication channel is 1385 mm, which corresponds to ~ 9λ (where λ is the wavelength in the waveguide) at a frequency of 2840 MHz for the working π-type oscillations of the magnetron. To rotate the communication channels through 90 ° in order to create a two-dimensional antenna array, smooth waveguide bends in the E- and H-planes are used (standard waveguide elements are not highlighted in the drawings). The output of microwave energy was carried out through the emitting slots 9 in a wide wall of communication channels.

In the used relativistic magnetron, the main competing modes of vibration are the π-type and 2π / 3-type (and its (-1) harmonic), which have close excitation voltages. The latter, in contrast to the π-type, is characterized by the antiphase oscillations in opposite cavities, which at the indicated sizes of the waveguide communication channels leads to its suppression.

Thus, the proposed relativistic magnetron with external waveguide communication channels allows the formation of highly directional radiation while maintaining high amplitude, time and frequency parameters of the microwave pulses of the relativistic magnetron.

Claims (4)

1. A relativistic magnetron with waveguide communication channels of resonators, containing a multi-cavity anode block, with an explosive emission cathode and a cylindrical drift tube located on the axis, an external magnetic system of two coils forming a Helmholtz pair, radiating slots are made in the communication channels, and the central radiating slit is located on axis of electrical symmetry of the communication channel, characterized in that the waveguide communication channels of number s = 1, 2, ... N / 2 are connected resonators located through one and the length of the communication channel is and λm for anode blocks with any even number of resonators, where N - number of cavities of the anode block, m - a positive integer, λ - wavelength of the oscillations in the waveguide. 2. A relativistic magnetron with waveguide communication channels of resonators according to claim 1, characterized in that the radiating slots are made in a wide wall of the communication channel so that the lateral radiating slots are located relative to the central one at a distance of (2n + 1) λ / 4 alternately on different sides from the midline of the channel wall, where n is an integer. 3. The relativistic magnetron with waveguide communication channels of the resonators according to claim 1, characterized in that the radiating slots are made in a wide wall of the communication channel so that the lateral radiating slots are located relatively central at a distance nλ on one side of the midline of the channel wall. 4. A relativistic magnetron with waveguide communication channels of resonators according to claim 1, characterized in that the radiating slots are made in a narrow wall of the communication channel so that the lateral radiating slots are located relatively central at a distance nλ on the midline of the channel wall.

Images