DE1098626B - Electron beam tube for very short electrical waves with a coupling gap in front of a reflection electrode, in particular in the manner of a reflex klystron - Google Patents

Description

GERMAN

The invention relates to a cathode ray tube for very short electrical waves with a reflection electrode in front of it lying coupling gap, in particular like a reflex klystron, in the space between the coupling gap and the concavely curved reflection electrode, whose reflector surface effective for reflection is significantly larger than the (effective) area of the coupling gap penetrated by the electron beam, which Electron reversal is effected without the use of further electrodes, in such a way that as many of the reflected ones as possible Electrons of a velocity group pass through the coupling gap at the same time.

The invention is of particular importance for reflex klystrons, but also for other tubes of this or similar type in which electron inversion is used. If you have powerful reflex klystrons want to build, one is usually careful that the current strength is as high as possible and the acceleration voltage is kept as low as possible. The increase in performance in this way is due to two circumstances A limit is set, namely on the one hand by the productivity of the cathode and on the other hand by the Effect of the space charge in the reflector space. As a result of the space charge effect, the electrons, in particular on the reverse surface in front of the reflector electrode, instead of trying to fly apart laterally to return to the coupling gap in the direction of the bullet path. They tried to spread this open in front of the reflector electrode by appropriately shaping the reflector electrode and its surroundings.

Cathode ray tubes are in the manner of a reflex klystron with a concavely curved reflection electrode known several times. Some of these tubes are located in the space between the reflection electrode and the Coupling gap another electrode, which forms a virtual cathode in front of the reflection electrode should influence favorably. Apart from the fact that the tube is structurally more complex due to this auxiliary electrode designed, a strong space charge arises in the reversal space. With other reflex klystrons with Concavely curved reflection electrode, the reflector is designed so that a concentration of the electron beam is favored. There are even special means for focusing the reflected electrons. Inevitably, the electrons approaching the reflector are thereby also bundled, so that again one strong space charge is created.

The invention is based on the endeavor to significantly reduce the space charge in the reversal space. this is in a cathode ray tube for very short electrical waves with a front of a reflection electrode lying coupling gap, in particular in the manner of a reflex klystron, in which in the space between the Coupling gap and the concave curved reflection

Cathode ray tube

for very short electric waves

with one in front of a reflection electrode

lying coupling gap,

especially in the manner of a

Reflex klystrons

Applicant:

Siemens & Halske Aktiengesellschaft,

Berlin and Munich,
Munich 2, Witteisbacherplatz 2

Dr. rer. nat. Werner Veith, Munich,
has been named as the inventor

electrode whose reflective surface is much larger than that of the electron beam interspersed (effective) area of the coupling gap, the electron reversal without the use of further electrodes is effected in such a way that as many of the reflected electrons of a speed group as possible pass the coupling gap run through simultaneously, achieved according to the invention in that the electrodes involved in the beam guidance so designed and arranged at such distances from one another and with such DC potentials are acted upon that the incoming from the cathode at the coupling gap and almost the expansion of the Coupling gap exhibiting electron beam already more divergent enters the coupling gap and after diverging passage through the coupling gap in the reversal space spreads widely.

A reflex klystron with a concave curved reflection electrode, in which the reflector surface effective for the reflection much larger than the (effective) area of the coupling gap penetrated by the electron beam is and in which the electron beam spreads more strongly in the reversal space, is known per se. However, there is the reflection electrode is preceded by a grid electrode that connects the coupling gap to the reversal space limiting electrode is galvanically connected. There is thus between the coupling gap and the grid electrode

109 508/321

a static, field-free space is formed, which results in that the electron beam spreads more widely than at a cathode ray tube according to the invention. In addition, the use of the grid electrode is essential Disadvantage that this electrode will intercept electrons and thereby next. Ejnejn loss of performance a causes additional heating of the electrode system.

The invention is to be explained in more detail with reference to the drawing. .

The figures show two exemplary embodiments in their for the invention essential parts in a greatly simplified schematic representation.

In Fig. 1, a cathode ray tube is illustrated, in which a large, concavely curved cathode 1 with a relatively low current density "in known Art is used in such a way that the electron beam initially converges and after passing through an acceleration electrode, it diverges to a greater or lesser extent. Those with 2 and 3 designated inner and outer walls of a cavity resonator are with the grid electrodes 4 and 5 connected, which limit the coupling gap. A concavely curved plate 6 is provided as a reflector. the Electron movement takes place within the area delimited laterally by the dashed lines 7 and 8. 10 is the accelerating electrode, also known as the electron collector serves.

In Fig. 2, a further embodiment is illustrated in which instead of a large-area cathode a high-performance cathode with a small cross section is used, which is designated by 9. This cathode can, for example, be a metal capillary cathode with a high electron yield and is so close to the acceleration electrode 10 brought that very high currents with a relatively low acceleration voltage can be generated. A strongly diverging beam is formed again. Furthermore the same reference numerals as in FIG. 1 are used in this figure for the same parts.

As essential for the mode of action of a reflex klystron According to the invention it should be pointed out that it must be prevented that a can train virtual cathode. Experimentally and theoretically it has been shown that in the case of training a virtual cathode the returning electrons are only very vaguely defined in terms of their speed, which results in a slight slope of the current-voltage characteristic at the electron collector. These Steepness is a measure of the quality of the phase focusing of a reflex klystron. If the slope is low only a few electrons of a certain speed group come back into the coupling gap, so that the amplification of vibrations of a certain frequency is only possible with a low degree of efficiency. Conversely, steepness means the amplification of vibrations of a certain frequency with a high frequency "Efficiency.

The two grids of the cavity resonator delimiting the coupling gap are opposite in the two figures Ίεη electron beam coming from the cathode concave and are expediently not attached to the narrowest point of the electron beam, so that the arrangement can have a relatively large grid capacity. This in itself is a deterioration the circuit quality causing the arrangement is through the increased current strength and according to the Invention improved conditions in the reflector space more than compensated.

Reflex klystrons are also particularly suitable for modulation purposes, since they have a relatively large bandwidth own.

Theoretically, the strict condition for the non-appearance of a virtual cathode is precisely known. she causes a restriction for the length of the running space in the reflector space and can mathematically so S- "can be formulated that this length l /] / T of the distance between cathode and acceleration electrode - everything converted to a level arrangement - is. For the The arrangement according to FIG. 1 results accordingly in a favorable dimensioning if one follows the following ίο simplified formula aimed at:

2K ^ k * '

"T> ä at F means the effective reflector area, K the effective cathode area,« ■ the distance of the reflector area from the coupling gap (length of the possible braking distance) and k the distance of the cathode from the acceleration electrode (length of the acceleration distance).

Claims (5)

Patent claims: 1. Cathode ray tube for very short electrical waves with one in front of a reflection electrode lying coupling gap, in particular in the manner of a reflex klystron, in which in the space between the Coupling gap and the concave curved reflection electrode, whose reflector surface effective for reflection much larger than the (effective) area of the coupling gap penetrated by the electron beam is, the electron reversal is effected without the use of further electrodes, such that as many of the reflected electrons of a velocity group enter the coupling gap at the same time run through, characterized in that the electrodes involved in the beam guidance are formed in this way and are arranged at such distances from one another and have such direct potentials applied to them, that the incoming from the cathode at the coupling gap and having almost the extension of the coupling gap Electron beam already more divergent enters the coupling gap and after the divergent one Passing through the coupling gap in the reversal space spreads widely. 2. Cathode ray tube according to claim 1, characterized in that the electron beam is already in the coupling gap enters in a strongly divergent manner and the electrodes delimiting the coupling gap are shaped in this way are that despite the strong divergence of the electron beam, the electron trajectories in the coupling gap approximately run parallel to the high-frequency electric field lines of the coupling gap. 3. Cathode ray tube according to claim 1 or 2, characterized in that a high-performance cathode with a relatively small cross-section in is arranged a small distance in front of an acceleration electrode lying in front of the coupling gap (Fig. 2). 4. Cathode ray tube according to claim 3, characterized in that the electron-emitting part the cathode and the acceleration electrode in the space between the inner wall of one with the Coupling gap connected cavity resonator are arranged (Fig. 2). 5. cathode ray tube according to claim 1 or 2, characterized in that when using a concave. Cathode with an initially converging Electron beam the ratio of effective The total reflector area (F) to the effective cathode area (K) is greater than twice the ratio of the squares of the braking distance (α) between the reflector and the coupling gap to the acceleration distance (k) between the cathode and the coupling gap (Fig. 1). Considered publications: French Patent Nos. 942 609, 946 926; British Patent Nos. 654 237, 665 505; U.S. Patent No. 2,659,024. 1 sheet of drawings