RU2538780C1 - Magnetron with starting auto electronic emitters on end shields of cathode units - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: magnetron contains the cylindrical anode and coaxially placed inside it cathode unit, consisting of the secondary electronic emitter and the starting cathode, located at least on one end shield, consisting of a combination of washers-activators contacting with one or from both sides with the auto electronic emitter, the working edge of which faces towards the anode. The field-emission cathodes are made as washers from tantalum or special alloys of high-melting metals with the thickness from several microns up to several tens of microns. The activators containing an emission active material, are the sources of active metals or compounds, which are adsorbed on the surface of auto electronic emitters and thus provide a necessary field emission current.

EFFECT: creation of powerful and super-power magnetrons of centimetre, millimetre and sub-millimetre wavelength ranges with instantaneous starting into generation mode for no more than 0,5 second, high reliability, stability and operating life.

4 cl, 6 dwg

Description

The invention relates to electronic equipment and can be used in microwave devices of the M-type, in particular in magnetrons of the centimeter, millimeter and submillimeter wavelength ranges.

The main problem that arises when creating magnetrons of this class is to ensure the stability and durability of the cathode nodes under conditions of intense electron and ion bombardments, the effect of which leads to a change in the emission properties of emitters and their overheating. These changes affect the stability of magnetrons, lead to a change in the frequency of the generated oscillations, to a drop in output power and electronic efficiency, to a decrease in durability.

The solution to these problems is especially important when developing high-power short-wavelength magnetrons. In a number of cases, it is also necessary to solve the problem of the quick launch of the magnetron into the generation mode. This is achieved by adding an autoelectronic emitter to the cathode assembly.

Known magnetron with a non-cathode cathode [1] (RF patent No. 2380784). A magnetron contains an anode and a non-cathode cathode coaxially placed inside it, including a core, screens, field and secondary electronic emitters. Auto-electron emitters in the form of washers made of tantalum foil with a thickness of ~ 4 μm are placed between secondary electron cathodes, in particular, pressed palladium-barium emitters. When a pulse voltage is applied to the anode, the field emission current initiates the operation of the magnetron. Palladium-barium emitters, being activators of auto-electronic emitters, are at the same time secondary-electronic emitters that support the generation of microwave oscillations during the life of the devices. The disadvantage of this design of the cathodes is the impossibility of their use in high-power and heavy-duty magnetrons due to the rapid destruction (burn-out) of field emitters under the influence of ion and reverse electron bombardments.

Known magnetron [2] (Pat. RF №2136076, 01/08/1998). This magnetron is selected as a prototype.

A magnetron contains a cylindrical anode and a cathode assembly coaxially located therein containing secondary electronic and field emitters, and side flanges (end shields), where at least one of the screens is electrically isolated from the secondary electronic emitter and contains at least one field emitter whose working end faces the surface of the secondary electron emitter.

In this magnetron, the excitation of the generation of high-frequency electromagnetic waves is provided by an electron beam from a secondary-electron emitter under the influence of electron bombardment of its surface by an electron-emitter. The main disadvantage of such a mechanism for generating excitation is its inefficiency due to an extra link in the initiating electron flow formation chain: field emission current from the field emitter → formation of the stream of secondary electrons from the secondary electron emitter → excitation of the generation of electromagnetic waves by secondary electrons from the secondary electron emitter.

In the present invention, the working edge of the field emitter is directed towards the magnetron anode (in the prototype, the working edge of the field emitter is directed to the secondary electron emitter).

The generation excitation mechanism in the present invention is provided directly by the field emission from the field emitter (in the prototype, field current from the field emitter knocks electrons from the secondary electron emitter that actually initiate the generation of electromagnetic waves).

In addition, in the prototype, to create a primary electron flow from an electron emitter, an additional electronic circuit is needed to supply electrical voltage between the electron emitter and the secondary electron emitter. This, on the one hand, complicates the design of the magnetron power source and thereby degrades the mass and size characteristics of the transceiver equipment and, on the other hand, complicates the design of the magnetron in view of the need to manufacture and place an additional vacuum input for supplying an electric potential to the field emitter.

The objective of the invention is the creation of powerful and super-powerful magnetrons of the centimeter, millimeter and submillimeter wavelength ranges with a cathode assembly that instantly starts the magnetron in the generation mode in no more than 0.5 seconds.

This is achieved by the fact that the cathode assembly is structurally divided into two functional parts, each of which has a very specific role: the field-emission emitter initiates generation, and the secondary-electron emitter ensures the operability of the magnetrons throughout the entire service life.

Subject of invention

The essence of the invention consists in the following: a magnetron containing a cylindrical anode and a cathode assembly coaxially placed therein, including a secondary-electronic emitter and placed at least on one of the end screens, an electron-emitter emitter, characterized in that on one or two end screens electrically connected to the secondary electronic emitter, trigger cathodes are placed that contain one or more combinations of washers - activators made of refractory metal containing rare earth granules or alkali metal and in contact with one or both sides with a field emitter, the working edge of which faces the anode, and projects above the surface of the activator.

The rare-earth or alkaline metal contained in the activator is adsorbed on the surface of the field emitter, thereby activating it and provides a stable field emission current, which is necessary for the continuous and stable initiation of magnetron generation.

Below are various structural and technological solutions according to the invention. In the drawings, the following notation is used: 1 - anode, 2 - screens, 3 - secondary electronic emitter; 4 - core; 5 - field emission emitter; 6 - activators; 7 - separating washers; 8 - a separating washer with rounding.

Figure 1 shows a schematic representation of a magnetron with triggering cathodes located on both end screens, which consists of an anode, screens, a secondary electron emitter, a core, an electron emitter, separating washers and activators having a conical surface. After switching on the high voltage, the electrons emitted from the field-emission cathode, rushing towards the anode along the electric field lines, form an electron stream that initiates the instantaneous launch of the magnetron into the generation mode. It should be noted that the number of field emitters and activators can vary depending on the thickness of the triggering cathode h and the magnitude of the nominal field emission current sufficient to initiate the generation of a particular type of magnetron.

Figure 2 shows a similar cathode assembly containing a trigger cathode on one of the end screens.

Figure 2 (a) shows a fragment A of figure 2, in which the starting cathode is enlarged and the following dimensions are indicated: d ₁ - diameter of the secondary-electronic emitter, the upper base of the activator and the separating washer; d ₂ is the diameter of the lower base of the activator; d ₃ - the diameter of the end screen; h is the thickness of the starting cathode.

The geometric dimensions of the starting cathode correspond to the conditions:

. $$d_{\mathrm{one}}<{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="00000020.png,00000021.png"\; state="\{\{state\}\}">d</figure-callout>}}_2<{\mathrm{<figure-callout\; id="3"\; label="d"\; filenames="00000018.png,00000019.png"\; state="\{\{state\}\}">d</figure-callout>}}_3$$

.

The angle of inclination φ between the generatrix of the conical surface and the axis is determined from the relation

; где $$\text{ 0}\le \phi \le {\text{arctg(d}}_{\text{2}}{\text{ - d}}_{\text{1}}\text{)/2h;}$$

$$\text{tg}\varphi ={\text{(d}}_{\text{2}}{\text{- d}}_{\text{one}}\text{) / 2h}$$

; Where $$\text{0}\le \phi \le {\text{arctg (d}}_{\text{2}}{\text{- d}}_{\text{one}}\text{) / 2h;}$$

то наряду с увеличением паразитного тока на анодно-резонаторную систему и полюсные наконечники произойдет перераспределение электронного потока, в результате которого уменьшится доля электронов инициирующих запуск магнетрона в режим генерации.If $$\varphi <0,$$

then, along with an increase in the parasitic current to the anode-resonator system and pole tips, the electron beam will be redistributed, as a result of which the fraction of electrons initiating the start of the magnetron to the generation mode will decrease.

- между активатором и вторично-электронным эмиттером образуется ступенька, которая может привести к ухудшению параметров магнетрона.If $$\phi >{\text{arctg (d}}_{\text{2}}{\text{- d}}_{\text{one}}\text{) / 2h}$$

- a step is formed between the activator and the secondary electronic emitter, which can lead to a deterioration of the magnetron parameters.

(частный случай), конструкция катода принимает вид, показанный на фиг.3 с активаторами, имеющими цилиндрическую поверхность, где может быть добавлена разделяющая шайба 8, имеющая радиус скругления, соответствующий условию $$0<r\le 0,1$$

, и диаметр, равный диаметру активаторов. Следует отметить, что и для этой конструкции запускающего эмиттера количество автоэлектронных эмиттеров с активаторами может меняться в зависимости от толщины запускающего катода h и величины номинального тока автоэлектронной эмиссии, достаточной для инициирования генерации конкретного типа магнетрона.If $$\varphi =0$$

(special case), the cathode design takes the form shown in Fig. 3 with activators having a cylindrical surface, where a separating washer 8 can be added, having a radius of rounding corresponding to the condition $$0<r\le 0,\mathrm{one}$$

, and a diameter equal to the diameter of the activators. It should be noted that for this design of the triggering emitter, the number of field emitters with activators can vary depending on the thickness of the field cathode h and the magnitude of the nominal field emission current sufficient to initiate the generation of a particular type of magnetron.

Figure 3 (a) shows a fragment A of figure 3, in which an enlarged view shows the starting cathode with activators in the form of cylinders and the following dimensions are indicated: d ₁ - diameter of the secondary electronic emitter; d ₂ is the diameter of the activators; d ₃ - the diameter of the end screen; d ₄ is the diameter of the field emitter; h is the thickness of the starting cathode.

The geometric dimensions of this cathode correspond to the conditions:

; $$0<(d_4-d_2)<0,4мм$$

. $$d_{\mathrm{one}}<{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="00000020.png,00000021.png"\; state="\{\{state\}\}">d</figure-callout>}}_2<d_{\mathrm{four}}<{\mathrm{<figure-callout\; id="3"\; label="d"\; filenames="00000018.png,00000019.png"\; state="\{\{state\}\}">d</figure-callout>}}_3$$

; $$0<(d_{\mathrm{four}}-d_2)<0,\mathrm{four}mm$$

.

- автоэлектронные эмиттеры экранируются активаторами.If $$(d_{\mathrm{four}}-d_2)<0$$

- field emitters are shielded by activators.

- высока вероятность разрушения кромки автоэлектронного эмиттера вследствие перегрева, обусловленного ионной бомбардировкой и протеканием через него тока автоэлектронной эмиссии.If $$0,\mathrm{four}mm<(d_{\mathrm{four}}-d_2)$$

- high probability of destruction of the edge of the field emitter due to overheating due to ion bombardment and the flow of field emission current through it.

Figure 3 (b) schematically shows a fragment A of figure 3, which shows one embodiment of the trigger cathode. In this example, in order to increase the activation efficiency of field emitters, a cylindrical groove is made on the activator, on one or both sides of the field emitter. The geometric dimensions of this cathode correspond to the conditions:

; $$0<(d_4-d_2)<0,4мм$$

. $$d_{\mathrm{one}}<{\mathrm{<figure-callout\; id="5"\; label="d"\; filenames="00000018.png,00000021.png"\; state="\{\{state\}\}">d</figure-callout>}}_5<{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="00000020.png,00000021.png"\; state="\{\{state\}\}">d</figure-callout>}}_2<{\mathrm{<figure-callout\; id="3"\; label="d"\; filenames="00000018.png,00000019.png"\; state="\{\{state\}\}">d</figure-callout>}}_3$$

; $$0<(d_{\mathrm{four}}-d_2)<0,\mathrm{four}mm$$

.

In the present invention, autoelectronic emitters with a thickness of several microns to several tens of microns are made in the form of washers from tantalum or special alloys of refractory metals, for example tantalum with tungsten, tantalum with zirconium, tungsten with rhenium, tantalum with rhenium, etc. The working edge of the autoelectronic emitter is turned to anode and protrudes above the surface of the activator.

As activators, various chemical compounds or alloys containing a rare earth or alkali metal can be used.

The secondary electronic emitter can be made of emission-active compounds or metals with stable secondary electronic properties and resistant to ion and reverse electron bombardments, for example iridium, platinum, osmium, rhenium, or various intermetallic alloys: iridium with lanthanum, iridium with cerium, osmium with lanthanum, rhodium with barium, etc., provides high reliability and durability of the magnetron.

End screens can be made of molybdenum, hafnium, zirconium or other refractory metal or alloy with high work function, provides shielding of the electron beam in the space of interaction of electromagnetic fields in the magnetron.

To prevent processes of interaction of materials of the secondary electronic emitter and the activator, as well as materials of the activator and the field emitter, it is allowed to place separating washers 7 or 8 between them, which can be made of refractory metal, for example tungsten or molybdenum.

Results Achieved

In the magnetron, which is the subject of the invention, the cathode assembly is structurally divided into two functional parts, each of which has a very specific role: the field emitter initiates generation, and the secondary-electron emitter ensures the operability of the magnetrons throughout the entire service life.

Thanks to this separation, an instantaneous start of the magnetron in the generation mode, high reliability and stability, operational parameters of high-power and super-powerful magnetrons of the short-wavelength range of wavelengths are achieved.

Practical implementation of the invention

The service life of various magnetrons, including powerful and super-powerful magnetrons of the centimeter, millimeter and submillimeter wavelength ranges with the proposed cathode assembly design, which is the subject of the invention, is significantly longer than that of magnetrons with the standard cathode assembly design.

Also, the proposed cathode design provides instant start-up of powerful and super-powerful magnetrons of the specified wavelength range into the generation mode in no more than 0.5 seconds.

Example

To study the process of instantly starting a magnetron into the generation mode, magnetrons of the 3 mm wavelength range with a power of P ~ 6 kW were fabricated and investigated. The cathode assemblies corresponded to the design shown in FIG. 2 and consisted of field emitters made of tantalum foil ~ 4 μm thick and pressed palladium-barium activators. A metal-alloyed iridium-lanthanum cathode was used as the main secondary electron emitter.

The generation of this magnetron was initiated at the cathode temperature T _cat. ~ 300K for 0.5 s after applying the anode voltage.

Information sources.

1. Li I.P., Dubois B.Ch., Kashirina N.V., Komissarchik S.V., Lifanov N.D., Zybin M.N. Magnetron with a non-cathode cathode. RF patent No. 2380784, priority of 10.24.2008

2. Patent RU 2136076 C1, 08.27.1999. Makhov V.I.

3. The magnetron of the centimeter range, trans. from English under the editorship of S.A. Zusmanovsky, ed. "Soviet Radio", M., 1951, pp. 134-138.

Claims (4)

1. A magnetron containing a cylindrical anode and a cathode assembly coaxially placed therein, including a secondary-electronic emitter and located at least on one of the end screens, an electron-emitter emitter, characterized in that on one or two end screens electrically connected to the secondary -electronic emitter, placed the trigger cathodes, which contain one or more combinations of washer activators made of refractory metal containing rare earth or alkali metal and in contact with one and and on both sides with a field emitter, the working edge of which faces the anode, and projects above the surface of the activator. 2. The magnetron according to claim 1, characterized in that the activators are made in the form of a cone, and the angle φ - the inclination of the generatrix - is selected from the condition
$$0<\varphi \le arctg\frac{(d_2-d_{\mathrm{one}})}{2h};$$

$$d_{\mathrm{one}}<d_2<d_3,gde$$

d ₁ is the diameter of the secondary electronic emitter, equal to the diameter of the upper base of the activator, d ₂ is the diameter of the lower base of the activator, d ₃ is the diameter of the end screen, h is the thickness of the starting cathode. 3. The magnetron according to claim 1, characterized in that the activators are made in the form of cylinders, and the geometric dimensions correspond to the conditions
$$d_{\mathrm{one}}<d_2<d_{\mathrm{four}}<d_3,gde$$

d ₁ is the diameter of the secondary electronic emitter, d ₂ is the diameter of the activators, d ₃ is the diameter of the end screen, d ₄ is the diameter of the field emitter. 4. The magnetron according to any one of claims 1 to 3, characterized in that a cylindrical groove is made on the activator from one or both sides of the field-emitter.

Images