US2647219A - Catcher circuits for velocity modulation tubes - Google Patents

Description

July 28, 9 3 E. TOURATON EIAL CATCHER cmcuns FOR VELOCITY MODULATION TUBES Filed Nov. 9, 1948 nuns DUMOUSSF/I BY ATTORNEY Patented July 28, 1953 CATCHER CIRCUITS FOR VELOCITY MODULATION TUBES Emile Tcuraton, Paris, and Claude Dumousseau, Pierrefitte, France, assignors to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application November 9, 1948, Serial No. 59,154 In France November 15, 1947 12 Claims.

The present invention relates to catcher circuits used in wide frequency band vacuum tubes.

In very wid band width amplifier tubes the catcher space is considerably damped by the load connected in the output circuit of the tube. The impedance of the catcher space is low and the high frequency potential induced between the terminals of the catcher space is of relatively low amplitude.

The larger the desired band width, the smaller will be the useful power in the vacuum tube, while the energy available in the electron beam does not depend on the band width. In order to take advantage of all the energy available in the electron beam, it is therefore necessary to pick up energy several times at different points. One object of the present invention is to provide a catcher circuit for a vacuum tube having a very wide band width.

According to features of the invention a catcher circuit may comprise a cylinder inside which are provided a number of cylinders of a smaller diameter, arranged in succession one after the other, and connected one to the other by helically wound conductors.

According to another feature of the invention the catcher circuits may b constituted by a helically wound conductor arranged inside a cylinder. Along a line parallel to the axis of the helix, at each turn, a hole is provided in the conductor through which flows the electron beam.

The above mentioned and other features and objects of this invention will become more apparent, and the invention itself, though not necessarily defined by said features and objects will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawing in which:

Figure 1 shows in longitudinal cross-section a tube having a coaxial catcher circuit incorporating features of the invention,

Figure 2 shows a cross-sectional view taken along line 22 of Fig. 1.

Figure 3 shows in longitudinal cross-section another catcher circuit incorporating alternative features of the invention and Figure 4 is a cross-sectional view taken along line 4-4 of Fig. 3.

Referring to Figures 1 and 3, the catcher circuit shown comprises in an evacuated envelope a first cylinder I inside which are provided one after the other, a number of cylinders 2, 3, l, 5, 6. An electron beam from a cathode I flows through these small cylinders, along axis Ia. which is also the axis of cylinder I.

Helically wound conductors, such as 8 and 9, connect one cylinder to the other, as shown on the drawing. Each of these conductors makes an almost complete turn when it connects one cylinder to the other. In Fig. l, 3 represents the conductor connecting cylinder 4 to cylinder 5, and line 9 the conductor connecting cylinder 5 to cylinder 6. Cylinders 2 and 6, at both ends of tube 1, are shorter and the distance between two adjacent cylinders is chosen equal to one half wave length i. e. corresponding to one half period.

In this manner the electron bunches are slowed down as and when they travel in the elementary catcher spaces provided between the cylinder and give up their energy. If the electron bunches are thus slowed down a number of times it may be necessary that the pitch of the helixes conmeeting the cylinders be progressively reduced, as well known in the art, in order to compensate for the reduction in the speed of the electron.

In this manner it is possible to pick up almost the extire available energy of the electron beam, but the number of the catcher spaces sets a limit to the band Width.

The differences in the transit times of the electrons for the extreme frequencies of the band add themselves up and after a certain number of passages no more slowing down effect is obtained. If F, the mean frequency of the wave be 3000 megacycles, for instance, and :AF, 50 mega-cycles, for instance, and a band width of megacycles, the number of possible passages are i. e. in this case It is therefore possible to provide in the example given 15 successive passages.

Figures 3 and 4 show another preferred embodiment of the invention. The cavity resonator comprises a hollow cylinder II) at one end of which is provided an opening II the purpose of which will appear later. Inside this cylinder is provided helically wound solid conductor [2. This conductor may have any appropriate cross section, for instance a square cross section as shown on the drawing. Along line l4, parallel to the axis I5 of cylinder l0, each turn of the helix is provided with a hole I3 in order to allow the flow of the electron beam, as shown by arrow Hi. The axis of the helix coincides with axis l of cylinder Hi. The high frequency energy may be picked up, just after the last catcher space through which the electron beam has flown. The opening H is provided for the end of the helix 1 6. In order to avoid a loss of energy at the other end of the tube it is convenient to separate the catcher spaces by a distance corresponding to a transit time equal to A of the period of the wave travelling along the helix, so that any reflected waves generated at each passage be in phase opposition one to the other, in order to minimise their influence. In the embodiment shown in Figs. 3 and 4 the line is homogeneous, i. e. at each point of the lin the series impedance, the shunt impedances and the coupling impedances with respect to the adjacent elements, are identical.

The present invention has been described in relation with preferred embodiments. The embodiments shown in Fig. 1 may be used with standing waves.

The arrangement of Fig. 3 is advantageous when operating as a very wide band amplifier.

While we have described a particular embodiment of our invention for purposes of illustration it should be understood that various modifications and adaptations thereof may be made within the spirit of the invention as set forth in the appended claims.

What we claim is:

1. In a wide band amplifier tube having means for producing an electron beam and means for bunching the electrons of said beam, a coaxial catcher circuit positioned to receive the electron bunches and absorb energy therefrom, comprising in combination a cylindrical member constituting the outside conductor, a plurality of cylinders mounted coaxially inside the first said cylinder at substantially equal distances one from the other and helically wound conductors of substantially one turn each connecting the said cylinders one to the other.

2. An amplifier tube as in claim 1 in which the small cylinders are mounted at a distance of one half Wavelength one from the other.

3. An amplifier tube as in claim 2 in which the helical connection to helices joining the said cylinder to the preceding and following ones are diametrically in opposition.

4. In a high frequency tube having means defining an electron beam path and means for launching the electrons in said path, a catcher circuit positioned along said path at a point to receive the electron bunches and to absorb energ therefrom, comprising conductor means adapted to be disposed along said beam path, said conductor means including a plurality of spaced apart conductor portions each having an opening therethrough, the openings of said conductor portions being disposed in alignment coaxially of said beam path and helical conductor portions of substantially one turn each interconnecting the first mentioned conductor portions.

5. A high frequency tube according to claim 4, wherein the first mentioned conductor portions comprise hollow cylinders.

6. A high frequency tube according to claim 4, wherein the first mentioned conductor portions comprise parts of a continuous helix.

7. A high frequency tube according to claim 4, wherein the first and second mentioned conductor portions comprise a continuous helix each turn of which contains one of said openings.

8. A high frequency tube according to claim 4, wherein the conductor means includes a cylindrical conductor disposed for the major length thereof in spaced relation about the first and second mentioned conductor portions.

9. A high frequency tube according to claim 8, wherein at least one of the conductor portions is connected to said cylindrical conductor.

10. A high frequency tube according to claim 8 wherein said cylindrical member constitutes the outside conductor and said first and second conductor portions comprise a concentric helically wound solid conductor provided with said openings in the form of holes at each turn along a direction parallel to the axis of said cylinder.

11. A high frequency tube as in claim 10 in which the distance between each consecutive turn of the helix is equal to one half wavelength of the operating frequency.

12. A high frequency tube as in claim 10 in which the distance between each consecutive turn of the helix is equal to A; of a wave-length of the operating frequency.

EMILE TOURATON. CLAUDE DUMOUSSEAU.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,064,469 Haeii Dec. 15, 1936 2,233,779 Fritz Mar. 4, 1941 2,289,756 Clavier et a1 July 14, 1942 2,300,052 Lindenblad Oct. 27, 1942 2,367,295 Llewellyn Jan. 16, 1945 2,489,082 DeForest Nov. 22, 1949

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