US3308331A - Electron discharge device wherein electromagnetic waves along the slow wave structure have components transverse to the electron beam and deflect out-of-phase electrons from the beam - Google Patents

Description

March 7, 1967 J. M OSEPCHUK ELECTRON DISCHARGE DEVICE WHEREIN ELECTROMAGNETIC WAVES ALONG THE SLOW WAVE STRUCTURE HAVE COMPONENTS TRANSVERSE TO THE ELECTRON BEAM AND DEFLECT OUT-OF-PHASE ELECTRONS FROM THE BEAM 2 Sheeiis-Sheet 1 Filed May 27, 19s;

POWER SUPPLY FIG?) FIG.6

INVENTOR. JOHN M OSEPCHUK March 7, 1967 J. M. OSEPCHUK 3,308,331

ELECTRON DISCHARGE DEVICE WHEREIN ELECTROMAGNETIC WAVES ALONG THE SLOW WAVE STRUCTURE HAVE COMPONENTS TRANSVERSE TO THE ELECTRON BEAM AND DEFLECT OUT-OF-PHASE ELECTRONS FROM THE BEAM Filed May 27, 1963 2 Sheets-Sheet 2 F X 4 Z 3; l I L 2x;

INVENTOR. JOHN M. OSEPCHUK AGE/VT 3,308,331 ELECTRON DISCHARGE DEVICE WHEREIN ELECTROMAGNETIC WAVES ALONG THE SLOW WAVE STRUCTURE HAVE COMPO- NENTS TRANSVERSE TO THE ELECTRON BEAM AND DEFLECT OUT-OF-PHASE ELEC- TRONS FROM THE BEAM John M. Osepchuk, Lexington, Mass, assignor to Raytheon Company, Lexington, Mass, a corporation of Delaware Filed May 27, 1963, Ser. No. 283,443 6 Claims. (Cl. 3153.6)

This invention relates to crossed-field type electron discharge devices wherein electrons are compelled by transverse electric and magnetic fields to move in energy exchanging relationship with electromagnetic waves, and more particularly to such a device wherein electrons in unfavorable phase relative to the wave are removed from the region wherein the interaction occurs.

Heretofore, electron sorting has been accomplished in crossed-field traveling wave tubes to remove electrons which are in an unfavorable phase relative to the fields of waves conducted adjacent the electrons so that these electrons in unfavorable phase do not exchange energy with the wave. Generally, the sorting of electrons takes place by accelerating the electrons parallel to the electron drift velocity which is in turn transverse to the crossed electric and magnetic fields which compel the drift velocity. One scheme for accomplishing this type of sorting is disclosed in my United States Patent 3,073,991 which issued January 15, 1963. The patent described structure in which waves are conducted by a slow wave conducting structure coextensive with an elongated interaction spa-ce. Electrons are injected into the interaction space at one end and compelled to drift to the other end of the space by transverse D.C. electric and magnetic fields. Electrons which are in favorable phase relative to the fields of the waves immediately adjacent the electrons will give up energy to the wave and decelerate and will move to higher and higher equipotential levels. If the DC. electric field runs toward the wave conducting structure, then these electrons will drift closer to the wave conducting structure and will couple more tightly with the fields of waves conducted by the structure. On the other hand, electrons in an unfavorable phase relative to the wave will accelerate and extract energy from the wave and, as a result, will move to lower equipotential levels and, thus, they will move away from the wave conducting structure and will eventually be collected by another electrode called the sole electrode which is coextensive with the wave conducting structure and combines with the structure to bound the DC. electric field. As the electrons gain or give up energy to the wave, depending upon whether they are in unfavorable or favorable phase relative to the wave, they will he accelerated or decelerated in a direction parallel to the drift velocity of the electrons and parallel to the flow of wave power. This causes the electrons to bunch and form favorable bunches or unfavorable bunches. The favorable bunches will continue to exchange energy with the waves, and the unfavorable bunches will be removed from the interaction region and collected by the sole electrode. Thus, it may be said that the sorting process takes place parallel to the electron drift velocity.

Effective sorting of the above type takes place along a considerable length of the slow wave structure, and as a result, the electrons in unfavorable phase interact along a considerable length of the structure and, thus, interfere with efficient operation of the device. One object of the present invention is toaccomplish phase sorting in a shorter length of the slow wave structure than in the United States Office 3,38 ,331 fiatented Mar. 7, 1967 past so that the electrons in unfavorable phase are removed from the interaction region after travel through only a relatively short portion of the interaction space.

It is a feature of the present invention to accomplish phase sorting in a crossed-field traveling wave tube in more than one direction at a time, and more particularly in at least two orthogonal directions so that electrons in unfavorable phase are more quickly removed from the interaction region and travel in energy exchanging relationship with waves conducted by the slow wave structure along only a relatively small portion of the interaction space. Specific embodiments of the invention include interdigital type slow wave structure formed so that the fringing fields of waves conducted by the structure along portions of the interaction space have components transverse to the general direction of electron drift through the interaction space and, thus, transverse to the length of the interaction space. More particularly, the interdigital slow wave structure is constructed so that the transverse component exists along opposite edges of the interaction space but is substantially nonexistent along the center of the interaction space. Thus, electrons moving along the edge of the interaction space which are in unfavorable phase are caused to move further from the center of the interaction space and are eventualiy collected by suitable electron collecting structure, whereas electrons along the edge in favorable phase are caused to move toward the center and form a tighter beam of electrons along the center of the space.

Other features and objects of the invention will be apparent from the following specific description taken in conjunction with the drawings in which:

FIG. 1 illustrates a plan-sectional view of a crossedfield traveling wave tube showing a section of an interdigital delay line along which the transverse sorting occurs;

FIG. 2 is a side-sectional view of the same tube shown in FIG. 1 to illustrate components of the tube;

FIG. 3 is a front-sectional view illustrating the flow of unfavorable electrons transverse to the drift direction of the beam to electron collecting structure;

FIG. 4 illustrates the high frequncy wave field structure and electron flow to illustrate conventional sorting along the drift path of the electron beam, as determined by favorable and unfavorable relative phase areas;

FIG. 5 is a plan view showing favorable and unfavorable phase areas of an interdigital delay line incorporating features of the present invention to illustrate transverse soiging and removal of electrons in unfavorable phase; an

FIG. 6 is a front-sectional view similar to the view in FIG. 3 showing another embodiment of the invention including another structure for collecting the unfavorable electrons sorted in the transverse direction.

Turning first to FIG. 1 there is shown a plan-sectional view of a crossed-field traveling wave tube incorporating features of the invention. The view illustrates the interdigital delay line structure whereby sorting is accomplished not only in a direction parallel to the electron beam but in a direction transverse to the beam. The tube includes an envelope 1 enclosing an interdigital delay line 2, a sole electrode 2 coextensive with the delay line defining an interaction space 4 therebetween and a cathode structure at one end of the interaction space. The cathode structure includes an electron emitting surface 5 at the end of a support 6 which encloses a heating element. Opposite the cathode structure 5 is an accelerating electrode 7 for accelerating electrons emitted from the cathode to an initial total velocity at which the electrons are injected into the interaction space. A transverse magnetic field B between the poles 8 and 9 of a magnet compel electrons issuing from the cathode to follow arcuate paths and thus enter the interaction space. Thereafter, the electrons proceed through the interaction space as a beam 11 and generally follow cycloidal or epicycloidal paths under the influence of transverse electric and magnetic fields E and B. The transverse electric field runs from the slow wave structure 2 to the sole electrode 3. The structure 2 preferably is at the same potential as the envelope which is ground potential, and so the electric field E is created by applying a negative potential from a power supply 12 to the sole electrode 3.

In forward wave operatoin, where wave power flows in the same direction as the electron beam, radio frequency waves are conducted to the slow wave structure 2 by the coaxial transmission line 13, and these waves after interacting with the electrons in the beam 11 are conducted from the slow wave structure 2 by another coaxial transmission line 14. The fields of the waves extend into the interaction space 4 in the manner shown in FIG. 4 so that the electrons in the beam 11 interact with these fields and exchange energy with the fields. In backward wave interaction, the wave power flows in a direction opposite the beam direction; however, the phenomenon involved in the exchange of energy between the waves and the electrons is substantially the same as in forward wave interaction.

FIG. 4 illustrates the fringing fields of the waves in the interaction space 4 between the delay line 2 and sole electrode 3. The electron beam 11 in FIG. 4 is shown directed from left to right, and the direction of the fringing fields is shown for one instantaneous condition. The vertical broken lines represent the areas along the beam where the electrons are instantaneously in favorable or unfavorable phase relative to the instantaneous wave fields. Favorable phase areas denoted F exists where the instantaneous fields are directed substantially in the same direction as the electron beam, and unfavorable regions denoted U exist where the fields are directed opposite to the direction of the beam. As a result, the electrons located at areas of instantaneous favorable phase give up energy to the fields and move to higher equipotential lines as illustrated by the broken arrows 15. Thus, these electrons move toward the wave structure 2. In areas of unfavorable phase, on the other hand, the electrons gain energy from the fields and move to lower equipotential lines as illustrated by the broken arrows 18. This action causes the electrons to bunch and to form an undulating charge concentration of electrons moving adjacent the delay line. This phase focusing action brings the undulations into favorable phase with respect to the wave fields so that there is an efiicient exchange of energy between the electrons and the waves.

Electron storing is a similar but different phenomenon and serves to remove from the beam electrons which are not properly phase focused. Electron sorting as accomplished in my above-mentioned patent is due to electron motion transverse to the beam in the XY plane as shown in FIG. 4. It is one object of the present invention to also accomplish this type of electron sorting in at least one other plane such as the YZ plane, for example, with electron motion in the Z direction so that sorting occurs in more than one plane and is substantially completed along a relatively short section of the wave conducting structure 2.

The transverse sorting in the Z direction is accomplished by forming the tortuous path provided by the interdigital delay line or any other type of delay line with portions that conduct the RF waves so that the electric fields of the waves have a component in the Z direction. This is shown by the section of the wave structure 21 in FIG. 1 wherein the base 22 and end 23 of a number of the fingers which form this section of the structure are at an angle other than 90 to the direction of the beam, whereas the center portions of the fingers are disposed at a 90 angle to the beam. It is preferred that the structure be formed so that the fringing wave fields 4 have a component transverse to the beam along the edges of the interaction space rather than along the center of the interaction space so that the transverse sorting will be accomplished along the edges where it is most effective.

The interdigital delay line construction 21 as shown in FIG. 1 is merely one example of a suitable structure whereby the wave fields have a component transverse to the direction of the beam so that transverse sorting is accomplished. Other structures whereby this transverse component is produced are apparent to those skilled inthe art and will also accomplish the transverse sorting.

FIG. 5 is a plan view showing the areas of instantaneous favorable and unfavorable phase (F and U) for the section of delay line 21 as viewed in the YZ plane. The phase areas are shown by broken lines similar to the lines in FIG. 4 and represent an edge view in the YZ plane of phase areas similar to those designated F and U in FIG. 4. As shown in FIG. 5, the phase areas have substantially the same shape as the fingers in the section 21 of delay line 2. The solid-line arrows 32 extending from unfavorable phase area, denoted U, represent the instantaneous direction of wave fields in the ZY plane, just as the solid vectors in FIG. 4 represent the instantaneous direction of RF fields in the XY plane. Along opposite edges of the interaction space, the fields in the vicinity of an unfavorable phase area, denoted U, obviously have components such as 34 and 35 directed toward the beam 11, while the fields 3a in the vicinity of favorable phase area, denoted F, have a component such as 37 and 38 directed away from the center of the beam. The components 34 and 35 will cause electrons to disperse from the beam as indicated by broken arrows 41 and move transverse to the direction of the beam. No such action will occur in the vicinity of a favorable phase area, and, in fact, the beam will become tighter and dispersed electrons will be driven back into the center of the beam in this plane. Thus, electron sorting is accomplished in the Z direction as well as in the Y direction, and unfavorable electrons are removed quite rapidly from the beam, and the undulations of the beam become quickly synchronized and in phase with the fields of the waves so that efficient operation results.

FIG. 6 is a front-sectional view of the tube already described with reference to FIGS. 13 and shows an alternate structure including two additional electrodes within the envelope disposed coextensive with and adjacent the edges of the sole electrode for collecting the electrons sorted in the transverse or Z direction. These additional electrodes 51 and 52 are mounted on insulating bases 54 and 55, respectively, and leads 56 are provided coupling these electrodes to the power supply 12. The sole electrode 57 in the embodiment shown in FIG. 6 is preferably a fiat plate without the end shields 3a and 3b shown in the embodiment of FIG. 3. Furthermore, it is generally preferred that the electrodes 51 and 52 be at the same DC. potential which is preferably somewhat greater than cathode potential so that the transverse sorting action will result in a more rapid removal of unfavorable electrons. The end shields will act as retaining boundaries on the properly focused and phased beam electrons. The potentials on the additional electrodes 51 and 52 are preferably adjusted for an optimum combination of transverse electron sorting and beam containment.

The above descriptions with reference to structure in FIGS. 16 relate to what is sometimes called a positiveline crossed-field tube because the delay line or wave conducting structure 2 is positive with respect to the coextensive sole electrode 3. Principles of the invention are readily applicable to the negative line tube where the Wave conducting structure is negative relative to the sole electrode. Electron sorting of the type described in my Patent 3,073,991 employed in a negative line tube would result in the flow of unfavorably phased electrons along paths similar to paths 18 in FIG. 4 but toward the delay line. However, transverse sorting illustrated in FIG. 5 would occur substantially as described herein.

This concludes descriptions of specific embodiments of the present invention wherein electrons are sorted and removed from a beam depending upon whether the electrons are in favorable or unfavorable phase relative to the fields of high frequency waves conducted by structure adjacent the beam, this sorting being accomplished in a direction transverse to the direction of the beam by the action of field components of the waves directed transverse to the beam. The specific embodiments include an interdigital delay line for conducting the wave adjacent the beam, the serpentine passage formed by the delay line including portions which conduct the wave along paths at an acute angle to the direction of the beam. However, these embodiments are described by way of example and do not limit the spirit and scope of the invention as set forth in the accompanying claims.

What is claimed is: 1. An electron discharge device comprising: a source of electrons; means producing mutually perpendicular D.C. electric and magnetic fields for compelling said electrons to move as a beam through an interaction space; and a slow wave structure for conducting electromagnetic waves adjacent said interaction space so that I the electric fields of said waves along opposing edges of said interaction space form oblique angles with and have a component transverse to the direction of said beam and parallel to said magnetic field; whereby favorably phased electrons along the edges of the interaction space are caused to move toward the center of the beam and unfavorably phased electrons are caused to move away from the center of said beam. 2. An electron discharge device comprising: a source of electrons; an interaction space; means producing mutually perpendicular D.C. electric and magnetic fields for compelling said electrons to move through said interaction space as a beam; and a wave conducting structure adjacent said interaction space, at least a portion of which conducts radio frequency waves along paths adjacent to opposing edges of said interaction space defining oblique angles with respect to the direction of movement of said beam and along a path parallel to said magnetic field adjacent to the center of said beam. 3. An electron discharge device comprising: a source of electrons; an elongated interaction space adjacent said source of electrons; means for injecting said electrons into said interaction space; means for producing transverse D.C. electric and magnetic fields in said interaction space for compelling said electrons to move through said space as a beam; and a wave conducting structure adjacent said interaction space for conducting waves in synchronism with said electrons whereby there is an exchange of energy between said electrons and said waves, and the radio frequency fields of said Waves in said space along opposing edges of said interaction space defining oblique angles with respect to said beam and having a component parallel to said magnetic field. 4. An electron discharge device comprising:

a source of electrons; an elongated interaction space adjacent said source of electrons; means for injecting said electrons into said interaction space; means for producing transverse D.C. electric and magnetic fields in said interaction space for compelling said electrons to move through said space as a beam;

action space for conducting waves in synchronism with said electrons whereby there is an exchange of energy between said electrons and said waves, said structure including portions having a single surface parallel to the magnetic field and perpendicular to the DC. electric field together with two additional surfaces extending therefrom and forming oblique angles with respect to said magnetic field so that the radio frequency fields of said waves have a substantial component transverse to said beam.

5. An electron discharge device comprising:

a source of electrons;

an elongated interaction space adjacent said source of electrons;

means for injecting said electrons into said interaction space;

means for producing transverse D.C. electric and magnetic fields in said interaction space for compelling said electrons to move through said space as a beam;

and a wave conducting structure adjacent said interaction space for conducting waves in synchronism with said electrons whereby there is an exchange of energy between said electrons and said waves, said structure including portions adjacent to the electron injection means having a single surface parallel to the magnetic field and perpendicular to the DC. electric field together with two additional surfaces extending therefrom and forming oblique angles with respect to said magnetic field so that the radio frequency fields of said waves along opposing edges of said interaction space have a substantial component transverse to said beam for compelling electrons which are in an unfavorable phase relative to said wave fields to move away from the center of said beam and electrons which are in a favorable phase relative to said wave fields to move toward the center of said beam.

6. A crossed-field electron discharge device comprising:

an envelope enclosing a slow wave conducting structure;

an electrode coextensive with said structure defining an interaction space therebetween;

a source of electrons at one end of said interaction space;

means for producing transverse D.C. electric and magnetic fields in said interaction space for compelling electrons from said source to move as a beam through said space in a direction substantially transverse to both said fields;

said wave conducting structure including portions adjacent to the electron source having a single surface parallel to the magnetic field and perpendicular to the DC. electric field together with two additional surfaces extending from the ends of said single surface and forming oblique angles with respect to said magnetic field whereby the radio frequency fields of said waves along opposing edges of said interaction space have a substantial component transverse to said beam so that electrons in an unfavorable phase relative to the fields of said waves are caused to move away from the center of said beam and electrons in favorable phase are caused to move toward the center of said beam;

and means adjacent to opposing edges of said interaction space for collecting said unfavorably phased electrons.

References Cited by the Examiner UNITED STATES PATENTS HERMAN KARL SAALBACH, Primary Examiner.

and a wave conducting structure adjacent said inter- R. D. COHN, Assistant Examiner.

Claims (1)

1. AN ELECTRON DISCHARGE DEVICE COMPRISING: A SOURCE OF ELECTRONS; MEANS PRODUCING MUTUALLY PERPENDICULAR D.C. ELECTRIC AND MAGNETIC FIELDS FOR COMPELLING SAID ELECTRONS TO MOVE AS A BEAM THROUGH AN INTERACTION SPACE; AND A SLOW WAVE STRUCTURE FOR CONDUCTING ELECTROMAGNETIC WAVES ADJACENT SAID INTERACTION SPACE SO THAT THE ELECTRIC FIELDS OF SAID WAVES ALONG OPPOSING EDGES OF SAID INTERACTION SPACE FORM OBLIQUE ANDLES WITH AND HAVE A COMPONENT TRANSVERSE TO THE DIRECTION OF SAID BEAM AND PARALLEL TO SAID MAGNETIC FIELD; WHEREBY FAVORABLY PHASED ELECTRONS ALONG THE EDGES OF THE INTERACTION SPACE ARE CAUSED TO MOVE TOWARD THE CENTER OF THE BEAM AND UNFAVORABLY PHASED ELECTRONS ARE CAUSED TO MOVE AWAY FROM THE CENTER OF SAID BEAM.

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