RU2074448C1 - Magnetic focusing system of o-type microwave device - Google Patents

Abstract

FIELD: vacuum microwave devices. SUBSTANCE: device has magnetic periodic focusing system which is designed as sequence of opposite-polarity ring magnets with ring pole pieces. In addition device has magnetic screen which is located on side of electron gun and has central hole in its face side. In addition device has ring magnet, magnetic field rectifier, which is designed as sequence of alternating thin ring disks which are made from magnetically soft material and non-magnetic material. Rectifier is located in central hole of face side of magnetic screen, is coaxial to magnetic focusing system and conforms to given equations. EFFECT: increased functional capabilities. 2 cl, 4 dwg

Description

 The invention relates to microwave electric devices, in particular to elements of magnetic focusing of electron beams in such devices. The invention can be used in high-power microwave devices "0" type packaged with permanent magnets.

 Known designs of magnetic focusing systems (MPFS) (German patent N 1296276, MKI H 01 J 21 g 13/17), with which the formation of electron beams in electron guns and focusing of beams in the passage channels of microwave devices "0" type. These MPPS contain permanent magnets that create magnetic focusing fields in the passage channel and in the region of the electron gun, magnetic screens that allow you to modify the magnetic focusing field in the gun, as well as magnetic elements, for example, a washer made of soft magnetic material or a small movable plate (German patent N 1491437, MKI N 01 J 21 g 13/17)), with which it is possible to compensate for the azimuthal inhomogeneities of the magnetic field in the gun and at the entrance to the MPPS.

 The disadvantage of these MPPS is that these magnetic elements provide only local compensation of field inhomogeneities.

 It is also known that the compensation of field inhomogeneities over an extended section can be achieved using a series of rings of soft magnetic material (armco) located at intervals perpendicular to the axis of the electron beam (German patent N 1541059, MKI. H 01 J 23/06) and (German patent N 1491453; MKI. 21 g 13/17).

 The disadvantage of such systems is that the ring elements affect the nature of the distribution of the axial focusing fields in the gun.

 The closest in technical essence and the achieved result to the proposed device is a magnetic focusing system for the microwave device "0" type (Melnikov Yu.A. Permanent magnets of microwave electric devices. M. Sov. Radio, 1967. S. 94. fig. 5.12b ) containing a magnet covering the shell of the “0” type device and a magnetic rectifier located between the shell of the device and the magnet. The field rectifier is made in the form of a set of thin permalloy and aluminum ring disks and allows to shield transverse magnetic fields in the device.

 The disadvantage of this design is that in the area of the gun, the rectifier is located outside the shell and, therefore, has a large internal diameter. This leads to large dimensions and mass of the rectifier and low efficiency of reducing the level of transverse fields in the region of the electron gun.

 The purpose of the invention is to ensure the effectiveness of reducing the level of magnetic transverse fields in the gun region and the input part of the magnetic focusing system through the use of a rectifier of small weight and dimensions.

где: l осевая длина выпрямителя магнитного поля;
h₁ и D толщина и диаметр центрального отверстия торцевой стенки магнитного экрана пушки;
h₂ толщина кольцевого магнита, расположенного между МПФС и магнитным экраном;
d₁, d₂ соответственно внутренний и наружный диаметры кольцевых дисков выпрямителя,
d_н внутренний диаметр полюсного наконечника МПФС.The goal is achieved in that the magnetic focusing system of the microwave device "type 0" contains a magnetic periodic system (MPFS) in the form of a series of ring magnets with ring poles following each other with reverse polarity, a magnetic screen located on the side of the electron gun with a central hole in its end wall, an annular magnet located between them, a magnetic field rectifier in the form of alternating thin magnetic materials from non-magnetic ring disks, the rectifier is installed in the center the front hole of the end wall of the magnetic screen coaxially MPFS in compliance with the ratios:
l ≅ h ₁ + h ₂ ; d ₁ ≥ d _n ;

where: l is the axial length of the rectifier of the magnetic field;
h ₁ and D the thickness and diameter of the Central hole of the end wall of the magnetic shield of the gun;
h _{2 the} thickness of the annular magnet located between the MPFS and the magnetic screen;
d ₁ , d _2, respectively, the inner and outer diameters of the annular disks of the rectifier,
d _{n the} inner diameter of the pole tip MPFS.

 In addition, the rectifier has the shape of a truncated cone with a decrease in the outer diameter of the annular disks away from the MPFS.

In sources and patent technical literature there are no signs similar to those claimed. Installing a magnetic field rectifier in the central hole of the end wall of the magnetic shield of the electron gun so that there is a non-magnetic annular gap (vacuum, air, between the outer cylindrical surface with a diameter d ₂ equal to the outer diameter of its annular disks, the rectifier and the inner cylindrical surface with a diameter D of the central hole of the end wall or filled with a nonmagnetic material, for example, part of the copper anode) value of D d _2/2.

 The non-magnetic annular gap makes it possible to effectively act on the transverse components of the magnetic field and practically do not change the distribution of the longitudinal magnetic field in the cathode to anode region of the input part of the MPPS.

The choice of the internal diameter d _{1 of the} rectifier equal to the internal diameter d _{n of the} pole pieces of the MPFS allows the rectifier to be brought as close as possible to the axis of the device and thereby enhance its effect on azimuthal inhomogeneities of the magnetic field. The choice of d ₁ > d _n . However, for given diameters of the central hole D in the end wall and the outer diameter of the rectifier d ₂ , with an increase in diameter d ₁ , the width of the annular disk d ₂ d _1/2 of soft magnetic material decreases and, therefore, the efficiency of the rectifier decreases.

The axial length of the rectifier l can be taken equal to both the thickness h _{1 of the} end wall of the gun’s magnetic screen and the total length equal to the thickness of the end wall n ₁ and the thickness h _{2 of the} additional ring magnet located between the MPFS and the gun’s magnetic screen. In the latter case (lh ₁ + h ₂ ), the impact on the transverse magnetic field is carried out not only in the region of the anode of the gun and the end wall of the screen, but also in the area between the gun and the input part of the MPPS. A case is possible when the axial length of the rectifier is l <h ₁ + h ₂ . A specific choice of length l is made according to the results of experimental measurements at which the lowest level of transverse magnetic fields is achieved. The inner diameter of the additional annular magnet is equal to or greater than the inner diameter D of the central hole in the end wall of the gun’s magnetic screen.

The use of a magnetic field rectifier is also possible in a variant of the device when there is no additional ring magnet of thickness h ₂ between the MPFS and the magnetic screen of the gun. At this point there is a non-magnetic gap with an axial length of h ₂ . In this embodiment, the axial length of the field rectifier is also selected based on the relation l ≅ h ₁ + h ₂ according to the results of experimental measurements of transverse magnetic fields. Since the rectifier is structurally fit into the Central hole of the end wall of the screen and the additional ring magnet, it is significantly smaller in radial size and weight compared to the rectifier in the prototype.

 The invention is illustrated by drawings, where figure 1 shows a longitudinal section of a magnetic focusing system for microwave device "0" type of the proposed device; figure 2 created by this device, the distribution of the axial magnetic focusing field in the field of the gun and the MPS device.

 The positions indicated: in figure 1. 1 ring magnets MPFS, 2 pole tips MPFS, 3 magnetic screen of the electron gun, 4 cylindrical wall of the magnetic screen of the gun, 5 end wall of the magnetic screen of the gun, 6 additional ring magnet MPFS, 7 electron gun, 8 anode of the electron gun, 9 cathode of the electron gun, 10 magnetic field rectifier.

 In FIG. 2. 11 distribution of the longitudinal components of the magnetic focusing field, 12 electron beam circuit. The collector part of the device is made in the usual form and in FIG. not shown.

) в области анода, торцевой стенки магнитного экрана пушки и дополнительного магнита МПФС прибора, где: 13 распределение

для случая МПФС с выпрямителем магнитного поля, 14 распределение

для случая без выпрямителя магнитного поля.In FIG. 3 shows the results of measurements of the axial distribution of the transverse component B _{⊥ of the} magnetic field (in relation to the longitudinal field

) in the region of the anode, the end wall of the magnetic screen of the gun and the additional magnet of the MPFS device, where: 13 distribution

for the case of MPPS with a magnetic field rectifier, 14 distribution

for the case without a magnetic field rectifier.

In FIG. Figure 4 shows the design of the magnetic field rectifier, where l is the total axial length of the rectifier, h _{3 is the} thickness of the annular disk of soft magnetic material (permalloy), h _{4 is the} thickness of the nonmagnetic ring disk, d _{1 is the} inner diameter of the ring disks of the rectifier, d _{2 is the} outer diameter of the ring disks of the rectifier.

As can be seen in figure 1, the magnetic focusing system for the microwave device "type 0" contains MPFS, made in the form of a series of ring magnets 1 following the opposite polarity one after another and separated by ring pole tips 2 of soft magnetic material, the magnetic shield of the gun 3 with a cylindrical 4 and end 5 walls of soft magnetic material, an additional ring magnet 6 MPFS, together with a magnetic screen 3, creates a magnetic field that grows from a value of B _to at the cathode of the gun to a value of B ₁ in the middle of magnet 6 (curve 11 in figure 2). In the area occupied by the end wall 5, in its central hole and inside the additional magnet 6 along the axis of the device, a magnetic field rectifier 10 is installed in the form of a series of thin-walled ring disks made of soft magnetic material (e.g. permalloy) separated by non-magnetic ring disks. it is seen that in the case of installing a magnetic rectifier in the device, the level of the transverse magnetic field 13 is two times lower than that in the absence of a rectifier 14. The geometric dimensions of the magnetic field rectifier (Fig. 4) are chosen in each ohm case, based on the requirements to achieve the minimum level of the transverse magnetic field.

The work of the proposed magnetic focusing system (MFS) for the microwave device "0" type, containing a magnetic periodic focusing system (MPFS) with ring magnets and pole tips and a magnetic shield of the electron gun, in the central hole of the end wall of which there is a magnetic field rectifier, is as follows . Electrons simulated by cathode 9 are formed into a converging beam 12 by the electric field of the compression gun and monotonically increasing from the cathode B _to the first maximum B _{1 by the} magnetic field 11, and then it is focused by the periodic field of the MPPS and passes through the passage channel to the collector of the device.

), приведенные на кривой 13 (фиг.3), получены с использованием магнитного выпрямителя с геометрическими размерами:
l 6 мм
h₃ 0,3 мм
h₄ 0,7 мм
d₁ 5,3 мм
d₂ 13 мм
При этом выбраны следующие геометрические размеры магнитного экрана пушки и МПФС: h₁ 3 мм, h₂ 3,2 мм, D 15 мм, d_н 5,3 мм, что соответствовало соотношениям

h₁ + h₂ 6,2, d₁ d_н приведенным в формуле изобретения.Example. Transverse field distribution measurement results

), shown on curve 13 (figure 3), obtained using a magnetic rectifier with geometric dimensions:
l 6 mm
h ₃ 0.3 mm
h ₄ 0.7 mm
d ₁ 5,3 mm
d ₂ 13 mm
In this case, the following geometric dimensions of the magnetic shield of the gun and MPPS were selected: h ₁ 3 mm, h ₂ 3.2 mm, D 15 mm, d _n 5.3 mm, which corresponded to the ratios

h ₁ + h ₂ 6,2, d ₁ d _n given in the claims.

 Thus, by placing the rectifier in the gun region according to the prototype, it would be necessary to increase its radial dimensions and, consequently, its weight by at least 6 times. The effectiveness of the compensation of the level of transverse magnetic fields decreases.

From curve 13 (Fig. 3) it can be seen that the rectifier acts more efficiently on the value of B _⊥ in the middle part and is somewhat worse in the area closest to the gun’s cathode.

 In the proposed device, the magnetic rectifier can significantly reduce the level of the transverse component of the magnetic field in the gun region and the input part of the MPPS, decrease the defocusing effect on the electron beam, and therefore reduce the current loss of the electron beam on the walls of the passage channel. The latter leads to a decrease in the thermal load on the electrodynamic system of the microwave device type "0".

The use of a rectifier with an outer surface made in the form of a cone (Fig. 5), tapering from a diameter of d ₂ 13 mm to d ₂ 10 mm in the direction of the gun (in the opposite direction from MPFS), can improve the efficiency of the rectifier also at the end section of the rectifier ( curve 15 in FIG. 3).

 Another advantage of the device compared with the prototype is to reduce the size and weight of the applied magnetic field rectifier.

 Thus, the device allows to reduce the size and weight of the MFS, as well as improve the operational characteristics of the device.

Claims (2)

1. The magnetic focusing system of an O-type microwave device, containing a magnetic periodic system in the form of a series of ring magnets with circular poles following each other with reverse polarity, a magnetic screen located on the side of the electron gun with a central hole in its end wall, an annular magnet located between them, a magnetic field rectifier in the form of alternating thin magnetic-soft material and non-magnetic ring disks, characterized in that the rectifier is installed in the central th hole of the end wall of the magnetic screen coaxially with the magnetic periodic focusing system in compliance with the ratios
l ≅ h ₁ + h ₂ ; d ₁ ≥ d _n ;
d ₂ / D 0.7 0.9,
where l is the axial length of the rectifier of the magnetic field;
h ₁ and D the thickness and diameter of the Central hole of the end wall of the magnetic shield of the gun;
h _{2 the} thickness of the annular magnet located between the magnetic periodic focusing system and the magnetic screen;
d ₁ , d _2, respectively, the inner and outer diameters of the annular disks of the rectifier;
d _{n the} inner diameter of the pole piece of the magnetic periodic focusing system.  2. The system according to claim 1, characterized in that the rectifier has the shape of a truncated cone with a decrease in the outer diameter of the annular disks away from the system.

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