US2941111A

US2941111A - Focused electron flow electron tubes for very high frequencies

Info

Publication number: US2941111A
Application number: US522702A
Authority: US
Inventors: Veith Werner; Meyerer Paul
Original assignee: Siemens AG
Current assignee: Siemens and Halske AG; Siemens AG
Priority date: 1954-09-21
Filing date: 1955-07-18
Publication date: 1960-06-14
Anticipated expiration: 1977-06-14
Also published as: NL200487A

Description

June 14, 1960 w. VElTH ETAL 2,941,111

FOCUSED ELECTRON FLOW ELECTRbN TUBES FOR VERY HIGH FREQUENCIES Filed July 18, 1955 3 Sheets-Sheet 1 Fig. 1

Fig. 2 +8 (2) we zjor5. Werner 765 5 June 14, 1960 w, vElTH ETAL 2,941,111

FOCUSED ELECTRON FLOW ELECTRON TUBES FOR VERY HIGH FREQUENCIES Filed July 18, 1955 3 Sheets-Sheet 3 Fig. La

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hired rates fiice aocusnn utncrnon snow: ELECTRON TUBES non VERY men FREQUENCIES Werner Veith and Paul Meyerer, Munich, Germany, assignors to Siemens & Halske Aktiengesellschaft, Munieh and Berlin, Germany, a corporation of Germany This invention is concerned with focused electron flow electron tubes for very high frequencies.

Focused electron flow is used in numerous tubes for very high frequencies, particularly in tubes operating in the nature of travelling wave tubes, special means being in suchv cases required for guiding the electron fiow along extended paths. Magnet coils traversed by current are usually employed for thi Purpose. It is, however, in many cases suitable to use a magnet system containing permanent magnets.

Magnet systems having permanent magnets have been proposed for such tubes, comprising a tubular interior wave guide provided at its ends with annular extensions connected at their outer margins with magnet rods. It is in numerous cases of tubes of this kind, for example, traveling wave tubes necessary, for the coupling of the high-frequency energy, to provide. the interior wave guide tube with a suitable hollow conductor; forming apertures corresponding to its cross-section. The distrubance of the rotation symmetry of the magnetic field, caused by such apertures may be held small if the tubular wave guide is stepped following the apertured parts, that is, if such wave guide comprises a relatively wide portion fiom which extends a relatively narrow portion having a diameter which is considerably smaller than the length thereof.

It has now been discovered that the above noted construction brings about a deterioration of the field strength characteristics in longitudinal direction of the magnet system, by causing an increase in the field strength in the vicinity of the transition of the wave guide tube from the wide to the narrow portion thereof while causing decrease in the field strength at the other end of the magnet system. The decrease at the other end may be traced to the fact that the lines of force are due to the potential drop prevailing at such other end deflected in the direction of the axis. Auxiliary lines of force resulting from the increased field strength enter after the transition again into the narrow guide tube because the condition, according to which the tangential component of the excitation must be constant, is not fulfilled for these lines of force.

The object of the invention is to correct the field characteristics of the magnetic field strength within the magnet system and to avoid above all a decrease of the field strength at the end thereof. In a variable field tube, such decrease would cause splitting of the electron flow and therewith an impermissible increase of the electron current flowing to the delay line.

In order to effect such a correction of the field characteristics, the invention proposes to provide for a narrow guide tube portion extending from the relatively wide portion and exhibiting gradually decreasing magnetically effective cross-sectional area. The decrease may be steady or in small increments, from the point of transition from the wide portion to the other end of the narrow guide tube. In accordance with another feature of the invent o th e ay e pro ed. mag ic. s unts for; he

g et y t m or. for other ae shbor nay em; c rt connected therewith, The. decrease, of; the magnetically effective cross-section may be; such that there, r It along the narrow inner space? dfi lfid' by the narrow guide tube asubstantially homogeneous distribution of the magnetic' field strength.

The various; objects and. features of the invention will appear from the description which will be rendered below withreference to the accompanying diagrammatic; drawings showing in simplified manner parts of a proposed atrangement and contrasted therewith embodiments ac,- cording to, the invention, with their parts. which are essent-ial for the understanding thereof likewise, simplified and known parts omitted for convenience. of represents: tion. In these drawings:

Fig. 1 shows the proposed arrangement;

Fig. 2 illustrates the axially directed field characteristic present in the structure according to Fig. 1;

Fig. 3 indicates an embodiment according to the in vention;

Fig. 4a shows. a diagrammatic longitudinal section through a further embodiment; and

Fig. 4b is a transverse section taken along line 4b.?4b of Fig. 4a. t

The proposed arrangement of 'Fig. 1 is provided with a magnet system including an inner flux guide tube comprising the relatively narrow portion 1 and the relatively wide portion 8 which is interconnected with the narrow portion by means of a transverse wall 7. At the outer ends of the magnet system, there are provided

annular end plates

2 and 3 and on the outside is disposed a tubular permanent magnet or a number of'rodeshaped permanent magnets as indicated at 4 and 5. A high frequency input Wave guide enters the system at 6', requiring the enlargement of the inner space provided by the wide guide tube portion 8. The magnetic lines of force are symbolically indicated by the arrows 9.

Fig. 2 shows a curve indicating the field progressing in the structure according to Fig. 1 in axial direction. From the curve will be seen the field strength increase in the vicinity of the transition from the wide to the narrow flux guide tube and the decrease thereof at the end of the magnet system which is due to the deflection of the lines of force toward the axis, caused by the potential drop obtaining at such end. The auxiliary lines of force again enter the narrow flux guide tube after the transition point because the condition, according to which the tangential component of the excitation must be constant, is not fulfilled therefor.

If the magnetically effective cross-section of the flux guide tube or the wall thickness thereof is now diminished or decreased, from the transition point to the end of the narrow guide tube, continually or in small steps or increments, there will result along such guide tube or portion a more or less steady increase of the excitation. The field progression may be made homogeneous by suitable dimensioning of the decrease of the magnetically effective cross-section of the narrow guide tube and consequent increase of excitation; moreover, if desired, the field strength at the output of the tube may be increased. Means by which this may be done will now be explained with reference to Fig. 3 showing an embodiment according to the invention.

In Fig. 3 are shown parts, simplified for convenience, of a traveling wave tube in which an electron stream coming from the cathode 11 afiects a helical delay conductor 12 contained in a glass tube 10.

Following the cathode 11 are a Wehnelt cylinder 13 and further electrodes 14 and 15 forming with the cath ode an electron radiation source or system. At the end of the electron path is disposed a target electrode 16.

The parts of the magnetic system serving for the focused guiding of the electron stream are indicated by like reference numerals as in Fig. 1. In the embodiment illustrated in Fig. 3, the narrow innerflux guide tube 1 isformed interiorly flaring; in accordance with the 'desired field strength increase, the flare of the-conical bore may be at an angle up to about 10. The inner flux guide tube thus has a wall thickness which diminishes gradually longitudinally thereof.

i In the embodiment shown in Figs. 4a and 4b, there is provided an inner narrow flux guide tube 17 which has not been altered as to the wall thickness thereof. A second tube 18 is, however, provided which is connected magnetically in parallel with the tube 17 and exhibits the reduction of wall thickness throughout its length. As is clearly apparent from Fig. 4b, this arrangement has the advantage that the interiorly flaring tube 18 may be repeatedly'slotted, thus permitting localization,'at the rev sulting' air gaps, of the rotation unsymmetries inwardly scattered by the positions of the magnet rods 19 to 26.

Changes may be made withinthe scope and spirit of theappended claims. a We claim: a 1. A travelling wave tube device having a travelling wave tube including a vessel having a relatively wide por- I travelling wave tube closely adjacent thereto, the magnetically operatively effective cross-sectional area of said narrow flux guide portion eflfectively continuously decreasing throughout its length from adjacent said transverse wall toward the opposite end thereof to avoid respectively occurrence of a field strength increase in the vicinity of the juncture thereof with said transverse wall and field strength diminution at the end thereof remote from said juncture.

2. A structure and cooperation of parts according to claim 1, comprising a tubular member surrounding said narrow guidetube portion, and means for connecting said tion constructed to receive a portion of a high frequency waveguide and a relatively narrow elongatedportion extending therefrom, and having for the guidance of the electron flow within the extended path of said vessel a magnet system including permanent magnet means extending'radially spaced from a tubular flux guide surrounding said vessel and forming with parts of said tubular flux guide at least one closed unidirectional magnetic circuit, said tubular flux guide comprising'a rela- ;tively wide portion terminating in a transverse wall and 'a' relatively narrow elongated portion extending from said transverse wall for respectively embracing said wide and 'narrow portions of the vessel of said travelling wave tube,

said relatively wide portion of said tubular flux guide containing high frequency input wave guide means, said relatively narrow elongated flux guide portion surrounding the narrow elongated portion of the vessel of said tubular member magnetically in parallel with such guide tube portion.

3. A structure and cooperationof partsaccording to claim 1, comprising a tubular member surrounding said narrow guide tube portion, and means for connecting said tubular member magnetically in parallel with such guide tube portion, said tubular member having longitudinally extending slots fo'rmedtherein.

4. A structure and cooperation of parts according to claim 1, comprising a tubular member surroundingsaid narrow guide tube portion, and means for connecting said tubular member magnetically in parallel with such guide tube portion, said tubular member having longitudinally extending slots formed therein and producing along the inner space formed by said narrow guide tube portion a substantially homogeneous field strength.

References Cited in the tile of this patent UNITED STATES PATENTS