DE1491446A1 - Magnetron with internal magnet - Google Patents

Description

Priority March 13, 1964 - V. St. v. America, Ser. No, 351,749

The invention relates generally to cold cathode magnetron oscillators and amplifiers, and in particular a magnetron with an improved magnet, due to the size and weight of the magnetron tube be reduced. Such improved magnetrons are particularly useful as transmitter tubes in radar systems, radar jammers, radio astronomy, Radio links and as a noise generator.

They are already cold cathode cross-field amplifier or oscillator tubes of circular structure, hereinafter referred to as magnetrons, have been built. In the following, a cathode is to be used under "cold cathode"

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will stand at a temperature below during operation the typical glow emission temperature for the cathode material works, so that when the cathode is also the emitter, the predominant emission mechanism is other than glow emission is, for example secondary emission or field strength emission, etc. The known cold cathode magnetrona contained permanent magnets to generate the magnetic field in the beam-field interaction. These permanent magnets have so far been outside of the tubular vessel were arranged and spanned the interaction gap. Some of these well-known magnets are cylindrical, others C-shaped and others were bowl-shaped and surrounded the entire gap. Because of the high flow dispersion are all these magnets were relatively heavy and bulky, they were mainly decisive for the size and weight of the whole tube.

According to the invention, the permanent magnet is used to generate the magnetic field in the interaction space of a cold cathode magnetron within the cold cathode arranged so that the size and weight of the Permanent magnets is significantly reduced, for example by a factor of 10.

The invention aims to provide an improved magnetron with a smaller one and lighter magnet can be created.

According to the invention, a permanent magnet is placed in a cavity in the cathode of a cold cathode magnetron oscillator or amplifier

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arranged to generate the static magnetic field in the jet field interaction space , so that the size and weight of the tube is significantly reduced.

Veiter, according to the invention, a noise generator is made available » in which the anode line for amplifying and decoupling noise « Signals in a wide frequency band, which in the space charge Spokes have been created inside the magnetron tube.

Further features and advantages of the invention emerge from the following description in conjunction with the drawing; show it 1 shows a longitudinal section through a magnetron with features of the invention

Fig. 2 is a cross-section along the line 2-2 in Fig. 1} FIG. 3 shows a development according to line 3-3 in FIG. 2j i'ig. 4 is an O-A diagram to illustrate the dispersion curve of FIG

Delay line of the tube according to FIGS. 1 and 2} and 5 shows the dependence of the magnetic field strength H as a function the distance along the axial center line of the Weohsel action gap with representation of the relative position and the shapes of the anode, cathode and the magnetic H-field lines for the tube according to FIGS. 1 and 2.

In * 'ign. 1 and 2 the amplifier tube according to the invention is shown. In particular, a hollow cylindrical main body 1, for example made of copper, with end walls, for example made of copper, shown; all parts together form the vacuum seal of the Tube.

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An arcuate, split double comb delay line 2 is arranged coaxially in the main body 1. The delay line 2 exists of two interlocking conductive combs, which in turn consist of axially spaced apart and opposite one another » lying conductive back parts A and B are made, which are a two-wire line form (see. Fig. 3) and a series of interlocking, interdigitated conductive plate-like prongs 3 · ^ ie prongs 3 bind at 4 forked to introduce a reactive inductive load in series with the two conductors A and B, while the space between the adjacent 3 prongs of opposing conductors a capacitive Tension developed across conductors A and B. The anode consists of cylinder 1 and anode lead 2.

The delay line 2 has a spatially harmonious fundamental forward wave mode of operation, as shown by curve 5 in the (^ - ^ - diagram Fig. 4 indicated.

A hollow cylindrical cold cathode 6, for example made of beryllium, Copper, or aluminum, is arranged coaxially in the delay line 2, so that an annular electronic interactions bereioh 7 in the space between the cathode 6 and the delay line 2 is limited

Two cathode pole shoes Θ, for example made of iron, close the open cathode emitters 6 and also serve as cathode end caps. A cylindrical cathode support pin 9, for example made of non-magnetic stainless steel, protrudes axially through the tube

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vessel through a high-voltage insulator 11 of conventional design, so that the cathode emitter is held coaxially with this * you Rod 9 is provided with silk bark at the end and the cold cathode with its end caps θ is held on the rod by means of a nut 12.

A low-pressure gas filling, for example H ₂ , Ar or Xe under a pressure of 10 "mm Hg, is used in the Weohsel action space to initiate the cold cathode discharge when the tube is operated as a smoke generator. Gas-filled cathode magnetronosailizers are described in" Crossed-Field Microwave Devices ", Volume 2, Okress, pages 30I-313 (196I). This operating mode will be described in more detail later. If the tube is operated as an amplifier, the HP drive power is sufficient to initiate the development of electrons for the cold cathode under high vacuum. The cathode closes the emitter 6 together with the end caps θ.

HP output power is supplied via coaxial line 18 from the tube accepted and forwarded to a suitable consumer not shown. The coaxial line 18 enters the tube body at 19 and is formed in the side wall of the main body by means of an axially directed bore 21, and the body serves as the outer conductor for the coaxial line 18 within the tube body 1. The center conductor 22 of the coaxial line 18 engages axially through the bore 21 and is electrically connected to the outer conductor Bottom of the bore 21 connected, eo that a short circuit is formed will.

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A conductive finger 23 protrudes radially from the central conductor 22 into the body of the ear. The finger 23 is arranged a quarter wavelength away from the short-circuit end of the coaxial line 18} so that a KOaX ¹¹ T ¹¹ section is formed with which a high impedance is reflected from wave energy that wanders past the pinger 23 to the short-circuit end of the coaxial line. An opening 24 is arranged in the side wall of the outer conductor of the coaxial line so that the finger 23 can protrude. The finger 23 is connected to the delay line 2 via an in-fitting quarter-wave section according to FIG.

The coaxial line 18 has a certain inherent impedance, for example 50 ohms. The double comb line 2 has a certain inherent impedance of, for example, 85 ohms. The adjustment is in the direction of the path 1 an electrical quarter of a wavelength, including the effect of the reactive load of section 26. The characteristic

The conductor impedance Z of the quarter-wave section 25 is equal to the om

The square root of the product of _{the inherent impedance Z_ 2 of} the delay line and the impedance Z _{Q1 of} the coaxial line, ie

Z -V Z _n * χ Z _nri . If this condition is met for section 25- Om I Ui Od

and the quarter-wave choke carrier is provided on the ^H T "section of the coaxial line 18, a practically reflection-free flow of energy from the delay line 2 to the coaxial line 18 is achieved»

A line separator 27 is at the bottom end of the delay line and the adaptation 25 is provided. The separator 27 extends

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over an arc of about 45 · delay line 2 begins At the other end of the partition 27 · Sin damping element 28, for example made of alumina soaked in carbon, is in the WUn of the first half-apprenticeship. the delay line between the line 2 and the inner wall of the vessel 1 arranged to To absorb wave energy moving in reverse direction on the delay line 2 moves in order to prevent a reflection that could otherwise cause undesired vibrations in the tube

A hollow cylindrical permanent magnet 29 is coaxial in the cathode emitter 6 arranged between the cathode carrier 9 and the emitter 6. A permanent magnet 29 », for example made of Alnico VIII axially magnetized so that a Hordpol N is formed at one end and a South Pole 3 at the other end of the magnetic cylinder. Of the Magnet 29 is preferably removed in the radial direction from the inner wall of the emitter 6 in order to dissipate heat from the cathode Magnet 29 reduce. On the inside, however, the magnet 29 is preferably seated on the cathode carrier 9 with good heat conductivity around the Heat dissipation from the magnet to one outside the Röhrengei'ässee 1 arranged to facilitate heat dissipation via the cathode carrier 9.

The cylindrical inner magnet 29 with the Ilagnetpolschuhe B is generated an axial magnetic field of strength H in the electroaieo & en interaction area 7 »*? As shown in FIG. The field strength is for example 900 Gauss in the middle plane of the gap and grows to about 1000 Gauss at the ends of the gap 7 in the

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Proximity of the end caps 8. The depression in the fillet of the field helps to do this, the space charge on the mean area of action of the Delay line 2 to restrict where the electronic 'J Wechselwifkungsspannungen of delay line 2 are strongest.

The end cap pole pieces 8 hang radially considerably over the outer circumference of the magnet 29 and the cathode 6 to the magnetic To lead plus lines H and thus reduce the stray field, and at the same time to shape the field in the interaction area 7 « The end cap pole shoes 8 essentially straighten the field lines running through the interaction area 7, so that a strong interception of the jet on the line 2 is prevented.

During operation, a cold cathode-anode voltage of, for example, 3 kV is applied via a voltage supply 31 and supply lines 32. The applied DC voltage is strong enough to cause a breakdown in the gas filling and thereby generate space charge, which initiates the operation of the tube. The continuous operating state results from secondary emission from the cathode, space charge noise voltages in the interaction gap excite a wave on delay line 2. The noise energy on the line with frequencies in the band from to * to λλ, cf. 4, the cumulative electronic interaction with the barely charged charge is intensified, so that rotating spokes of a space charge are formed which rotate at a synchronous speed corresponding to an electron energy of 500 V. The amplified noise energy in a wide frequency band, for example an octave,

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is via the output matching section 25 and the coaxial line 18 removed from the line 2 and forwarded to a suitable consumer, not shown. The electronic interaction causes an electronic Rüokbombardierung of the cold cathode 6, so that a secondary emission is caused with which is replenished with the space charge collected on the anode. The space charge is in equipotentials in the presence of the axial The magnetic field is captured and continues to recirculate around the cathode 6 until it is captured. The separator 27 extends over a sufficiently lance arc to cause the space charge to unbundle through the drift space in the area of the separator 27 runs so that electronic feedback oscillations are prevented.

A typical noise generator of this type generates a noise in an octave frequency with the center frequency of 1.5 GHz. The tube can also be used as a standard forward or reverse wave amplifier can be operated with two openings. In this case the tube is essentially constructed similarly to the tube just described, only that no gas filling needs to be used and instead a high vacuum is used, and that one not shown JInput coaxial line is used, which is identical to line 18 is constructed. In this case, the input line is connected to the beginning of the delay line 2, via a quarter-wave en truncated section as described above and a quarter-wave impodance adjustment 25ι «as described above ·

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The RF signal to be amplified calls for adequate cathode backbombing and secondary emission to maintain gain and output power. In such a In the L-band, the tube has a gain of 20 dB over one frequency octave achieved at an output power of 1 kW. A common external magnet for such a tube would weigh about 5 kg, while in the case of an L-band tube of the type described above, the Iiagnet weighs about 0.5 kg, so magnet size and weight around an order of magnitude are reduced.

The invention has been described in connection with a special type of magnetron in which the cold cathode is also the cathode emitter was. However, this is not necessary to carry out the invention. The cold cathode, i.e. the electrode working at cathode potential, need not be emissive and the electron emission can come entirely from a separate incandescent emitter, the Electrons in the ring-shaped electron stream in the usual way injected. The tube can also be operated as an oscillator, if the waveguide is selected accordingly, for example in the usual way consists of interconnected flags, and that Separating piece 27 is omitted.

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Claims (7)

PATENT ANWA-. DIPL-ING. H. KLAUS BERNHARDT 14c? IhAd 8000 MÖNCHEN 23 · MAINZERSTR. 5 S2 P3 D patent claims 1. A microwave magnetron tube with a generally cylindrical cold cathode, a device for generating an arc-shaped current of electrons in the vicinity of the cold cathode, an anode which is arranged coaxially with the cathode at a distance therefrom and with this delimits an electronic interaction region, and the has a curved waveguide, which is opposite the cylindrical cathode and provides for an electronic interaction between waves on the line and the electron flow, and a device for removing microwave energy from the line, characterized in that a permanent magnet is arranged in the cathode, with the axially directed magnetic field is generated in the interaction area, by means of which the electron flow is caused to move tangentially to the waveguide in order to produce a cumulative electronic interaction between the electron flow and waves on the anode lead. 2. Tubes according to claim 1, characterized in that the cathode has an arcuate cold cathode emitter which consists of a material with a secondary emission ratio noticeably greater than one, and which at the same time serves as a device for generating -.-, ¹ UH ₁ -; which serves electrons in the arcuate stream. ../A2 909824/0524 BATH H91U6 49. 3. Tube according to claim 2, characterized! that the permanent magnet is arranged radially away from the cold cathode emitter in order to ensure the heat transfer from the emitter to the magnet during operation to belittle. 4. Tube according to claim 1, 2 or 3 »characterized in that the cathode has two end caps at the two axial ends of the magnet, which over the jacket of the cylindrical cathode protrude towards the anode, and that the end caps are made of a magnetically permeable material, so that they serve as pole pieces for the magnet. 5 · Tube according to one of claims 1 to 4 »characterized in that that the tube is a noise generator and the waveguide is a delay line which is dimensioned so that Space charge noise signals generated internally in the tube are magnified. 6. Tube according to claim 5, characterized in that the delay line consists of two conductive combs, the prongs of which interlock, and that the prongs are forked so that a double-comb delay line with a space harmonic Fundamental forward wave is formed to have a cumulative electronic interaction with the electron flow across a to get a wide frequency band. ... / A3 909824/0524 H91U6 -β 7. tube naoh claim 5 or 6, characterized in that it contains a cross-field interaction region, which with a Gas is filled because when the tube is in operation it is ionized to produce free electrons and ions that cause a start the electronic discharge in the tube is improved. 909824/0524 ι Le e rs eι te