US2897393A

US2897393A - Strophotron

Info

Publication number: US2897393A
Application number: US684590A
Authority: US
Inventors: Stanley A Iorio
Original assignee: Sylvania Electric Products Inc
Current assignee: GTE Sylvania Inc
Priority date: 1957-09-17
Filing date: 1957-09-17
Publication date: 1959-07-28
Anticipated expiration: 1976-07-28
Also published as: GB845495A; DE1132665B; FR1216305A

Description

July 28, 1959 INVENTOR.

STANLEY A. lOR/O STROPHOTRON Stanley A. Iorio, Long Island City, N.Y., assignor, by mesne assignments, to Sylvania Electric Products inc, Wilmington, Del a corporation of Delaware Application September 17, 1957, Serial No. 684,590

3 Claims. (Cl. 313-156) My invention is directed toward strophotron oscillators.

A strophotron is a multitransit electron tube adaptable for use in the VHF and UHF frequency ranges and is described, for example, in an article entitled A New Electron Tube: The strophotron by Hannes Alfeven and Dag Romell, published in the Proceedings of the IRE; page 1239, vol. 42, No. 8, August 1954.

In the copending patent applications of Ralph H. Bartram, Serial No. 680,761 filed August 28, 1957, Serial No. 682,457 filed September 6, 1957, and Serial No. 682,458 filed September 6, 1957, there are described various improved types of strophotrons.

In general, however, a strophotron comprises at least one elongated accelerator extending in a given direction and first and second separate, elongated reflectors separate from the accelerator and extending in said direction, the reflectors being so arranged with respect to the accelerator that a plane defined as a play of symmetry extends through the accelerator and equidistantly between the two reflectors, the plane also extending in the given direction.

The accelerator is maintained at a high positive potential relative to the reflectors and the geometry of the accelerator and the electrodes is so arranged that a hyperbolic electric field distribution is established in the electron interaction region bounded by the accelerator and the reflectors.

A uniform magnetic field is established within the electron interaction region, the magnetic field vector pointing in a direction perpendicular to the plane of symmetry.

A cathode is mounted in one of the reflectors adjacent one end of the accelerator and a planar anode or collector maintained at a high positive potential relative to the reflectors is positioned adjacent the other end of the accelerator. The surface of the collector is perpendicular to the plane of symmetry. A load is coupled between the two reflectors.

Under these conditions, electrons emitted from the cathode will migrate toward the collector along a curved path and will exhibit the characteristic strophotron behavior; i.e. the projection of this path onto the plane of symmetry resembles a trochoid, while the projection of the path onto a second plane perpendicular to the plane of symmetry and extending in the direction of the accelerator and the reflectors resembles a damped sinusoid having an axis defined by the intersection of the two planes.

The frequency of the sinusoid is the oscillation frequency and an output voltage of this frequency appears across the load.

All of the above described strophotrons, however, have a common disadvantage. As indicated previously, in all these strophotrons the planar collector has its electron receiving surface perpendicular to the plane of symmetry. Since the magnetic field vector points in a direction par allel to the surface of the collector, the resultant magnetic force on electrons in the vicinity of the surface tends to urge these electrons .in directions perpendicular 2,897,393 Patented July as, 1959 to the magnetic field vector but parallel to the surface. Further, the electric field vector also points in a direction parallel to the collector surface and the sinusoidal component of electron motion in the vicinity of the collector surface is so directed that the electrons tend to vibrate in a plane also paralell to this surface; i.e. the electrons tend to approach this surface tangentially. As a consequence, certain electrons are not collected by the collector and the strophotron functions ineificiently.

Accordingly, it is an object of the present invention to improve the electron collection efiiciency of a strophotron.

Another object is to provide a new and improved strophotron characterized by an increased electron collection efliciency. I

Still another object is to increase the electron collection elficiency of a strophotron by altering the position of the planar collector.

These and other objects of the present invention will either be explained or will become apparent hereinafter.

In accordance with the principles of my invention, the collector is rotated through an angle of as compared to the conventional collector position, and both surfaces of the collector are parallel to the aforesaid plane of symmetry and perpendicular both to the magnetic field vector and to the electric field vector. Under these conditions, the electrons in the vicinity of the collector are urged in directions perpendicular to the collector surfaces with consequent increased electron collection efiiciency. Moreover, electron collection occurs at both surfaces of the collector instead of the single surface hitherto used.

An illustrated embodiment of my invention will now be described in detail with reference to the accompanying drawings wherein:

Fig. 1 shows a strophotron in accordance with the invention; and

Figs. 2 and 3 graphically illustrate the electric field pattern in the electron interaction region of the device of Fig. 1.

Referring now to Fig. 1, enclosed in an evacuated tube envelope (not shown), is a pair of first and second, Vertically displaced, elongated accelerators 1i and 12. Each accelerator has a uniform cross section defining a branch of a hyperbola. Thefirst accelerator 10 forms an upper hyperbola branch having a central point 14, while the second accelerator 12 forms a lower hyperbola branch having a central point 16. Thus, the two accelerators are disposed upon a first plane of symmetry which extend in the same direction as the accelerators and which passes through

central points

14 and 16.

Further provided are first and second, horizontally displaced

elongated reflectors

18 and 20 extending in the same direction as accelerators 10 and 12. Each reflector has a uniform cross section defining a branch of a hyperbola. The two reflectors are symmetrically disposed about opposite sides of the first plane of symmetry so as to define left and right hand hyperbola branches; the left hand branch having a central point 22, the right hand branch having a central point 24-. Hence, the two reflec tors are disposed about a second plane of symmetry perpendicular to the first plane of symmetry and extending through the

central points

22 and 24.

A uniform magnetic field is established within the region bounded by the accelerators and reflectors, the magnetic field vector pointing in a direction perpendicular to the first plane of symmetry. (Means for establishing this field are conventional and are not shown here.)

A cathode 34 is mounted in reflector 18 at a point intermediate to the central point 22 of this reflector and accelerator 10, the cathode being adjacent one end of both electrodes. An anode or collector 30, maintained for convenience at the same potential as the accelerators 10 and 12, is positioned adjacent the other end of both accelerators. A load 38 is coupled between

reflectors

18 and 20. a

Collector 36 is so positioned that it is substantially coincident with plane A and its surfaces are perpendicular to themagnetic field vector.

Electrons are emitted from the cathode at an extremely low velocity and enter the interaction region. Many of these electrons then drift toward the collector along a curved path and exhibit the characteristic strophotron behavior previously described.

However, as indicated above, the collector surfaces are perpendicular to the magnetic field vector. 7

Further, it will be seen from a study of Fig. 2 (which is a plot of the electric field lines in the electric interaction region remote from the collector) and Fig. 3 (which is a plot of the electric field lines in the interaction region adjacent the collector) that the electric field vector (which is represented by the electric field lines) is perpendicular to the plane of collector 36.

Since the electric and magnetic field vectors are substantially parallel in regions adjacent the collector surfaces, the magnetic field has no effect on the electron trajectory in these regions, and the electric field guides or compels the electrons to these surfaces.

The accelerator-reflector configuration of Fig. l is essentially that shown in the above identified Bartram patent application Serial No. 682,458 filed September 6, 1957. However, it is to be emphasized that the collector arrangement taught herein is applicable to all of the 'strophotrons disclosed in the Bartram patent applications as well as to the strophotron described in the IRE article previously cited.

While I have shown and pointed out my invention as applied above, it will be apparent to those skilled in the art that many modifications can be made within the scope and sphere of my invention as defined in the claims which follow.

What is claimed is:

1. A strophotron comprising at least one elongated, electrically conductive accelerator extending in a given direction; first and second separate, electrically conductive reflectors extending in said direction and disposed about said accelerator to define a plane of symmetry extending through said accelerator and equidistantly between said reflectors, said plane extending in said given direction; an electrically conductive planar collector positioned adjacent one end of said accelerator, said collector being substantially coincident with said plane of symmetry; and means to establish a time invariant magnetic field about said reflectors, said accelerator and said collector, the magnetic field vector pointing in a direction perpendicular to said plane of symmetry.

r a,s97,393 e 2. In combination, first, second, third and fourth separate, elongated, electrically conductive members extending in a selected direction, each member, in cross section, defining a branch of a hyperbola, said first and second members being designated as accelerators and having positions at which said first and second members respectively define, in cross section, upper and lower hyperbola branches, said third and fourth members being designated as reflectors and having positions at which said third and fourth members respectively define, in cross section, left hand and right hand hyperbola branches, said members defining a plane of symmetry which extends between said accelerators equidistantly between said reflectors, said plane extending in said direction; and a planar collector positioned adjacent one end of each of said members, the surfaces of said collector being parallel to said plane.

3. In combination, first, second, third and fourth separate, elongated, electrically conductive members extending in a selected direction, each member, in cross section, defining a branch of a hyperbola, said first and second members being designated as accelerators and having positions at which said first and second members respectively define, in cross section, upper and lower hyperbola branches, said third .and fourth members being designated as reflectors and having positions at which said third and fourth members respectively define, in cross section, left hand and right hand hyperbola branches, said members defining a plane .of symmetry which extends between said accelerators equidistantly between said reflectors, said plane extending :in said direction; a planar collector positioned adjacent one end of each of said members, the surface of said collector being parallel to said plane; and means to maintain said first and second members and said collector at high positive potentials with respect to said third and fourth members; and means to establish a time invariant magnetic field about said first, second, third and fourth members and said collector, the magnetic field vector pointing in a direction perpendicular to said plane of symmetry.

References Cited in the file of this patent UNITED STATES PATENTS 2,284,733 Haeif June 2, 1942 2,414,121 Pierce Jan. 14, 1947 2,806,177 Haefi Sept. 10, 1957 2,834,908 Kompfner May 13, 1958 2,844,753 Quate July 22, 1958 FOREIGN PATENTS 729,930 Great Britain May 11, 1955