US2495289A

US2495289A - Electron discharge device

Info

Publication number: US2495289A
Application number: US509962A
Authority: US
Inventors: William W Rigrod; Pawlishen John
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1943-11-12
Filing date: 1943-11-12
Publication date: 1950-01-24
Anticipated expiration: 1967-01-24
Also published as: GB618364A; BE469363A; CH253826A

Description

Jan. 24, 1950 w. w. RIGROD ET AL ELECTRON DISCHARGE DEVICE Filed Nov. 12} 1943 em w m5 E NGHE N E/GH M W T mmww N W B 7 Mb Patented Jan. 24, 1950 UNlTED STATES NT OFFICE ELECTRON DISCHARGE DEVICE Pennsylvania Application November 12, 1943, Serial No. 509,962

Claims.

The invention relates to electron discharge devices and particularly to such which utilize a beam of electrons.

One species of electron discharge devices of the general characterization given above, is known as a reflex klystron and provides a resonant cavity through which electrons are passed from a cathode and bunched in transit and then approach a negative reflector and caused thereby to return to the resonant cavity where they give up energy for useful purpose. It should be emphasized at the outset that in such a reflex device, if a positive potential were applied to the reflector it would cause the electrons to be collected by the reflector instead of being reflected and that, as reflex devices are now constituted, such collector at positive potential would keep the electrons from returning to the resonant cavity and therefore no energy would be delivered to the said cavity and no output would be obtained there-from. Thus, in reflex devices the use of negative potential on the reflector has been a fundamental requirement of the prior art.

Certain limiting factors have been present in heretofore known structures of reflex klystrons of which may be mentioned that the power which can be delivered to the resonating cavity depends upon thenumber of electrons that can be returned to the cavity to deliver energy. It would be very diflicult, even if at all possible, to design a reflector which would return all electrons coming thereto back to the resonant cavity. A portion of the electrons are lost to the adjacent wall during their return trip without entering the cavity and hence that part of the energy is merely converted to heat with the result of impaired efiiciency. Another limitation of power output of the prior art structure exists for the reason that the resonator grid diameter is limited by the wavelength desired and the attendant necessary cavity dimensions, and hence the size of the electron beam and cathode producing the same are necessarily limited. This limitation prevents high operating current through the tube since the prior art production of electron emission has set a definite limit to the density of electron emission, that is to say, to the electrons produced per unit time per unit area, as the cathode cannot be effectively larger than the grid area.

Generally considered, therefore, an object of the invention is to increase the number of electrons that can be usefully employed to produce power output with relatively less expenditure of energy in the production thereof.

Also broadly, a desideratum of the invention is to increase the efliciency of a beam-type electron discharge device of the general character indicated.

More in detail, the invention proposes employment of an electrode, having similarity to a reflector, which is copiously emissive of secondary electrons, and to utilize a positive potential instead of a negative potential on said reflector-like electrode in conjunction with means to render secondary emission effective in the resonator.

A further object of the invention. is to obtain an augmented supply of bunched electrons back in the resonator from which output energy is derived.

Another object of the invention is to provide maximum quantity of electrons returning to the resonant cavity from a less quantity moving forward and bunched in the cavity while passing therethrough.

A further object of the invention is to overcome limitations of cathode and resonator grid sizes and obtain increase of electron density of the electron flow back into the resonator above those electron densities possible in reflex klystrons of the prior art by reason of equally eificient focusing action and greater total electron current.

Yet another object of the invention is to utilize secondary emission material with yield greater than unity for increasing the number of electrons available to produce power.

Specifically, an object of the invention is to introduce a field close to the secondary emitting surface for preventing secondary electrons from falling back to that surface.

Still further objects of the invention will appear to those skilled in the art as the description progresses, both by direct recitation thereof and by implication from the context.

Referring to the accompanying drawing, the figure thereof is an elevational sectional view, showing a beam-type electron discharge device embodying the invention.

Considering initially the basic. disclosure of the invention illustrated in said drawing, there is shown a beam-type electron discharge device having near resemblance to a reflex klystron, the general construction of which is to a considerable extent in accord with prior art practice, in that it is fabricated as a body of revolution about an axis and provides a coaxial hollow resonant chamber H3 therein with a cathode H on the axis adjacent the chamber and an opposed electrode 12 also on the axis at the other 3 side of said chamber. In terms of the prior art, said electrode l2 has constituted a reflector, and because of similarity of appearance and construction to a reflector, that term is adopted in this description, but must be understood with the qualification that it is constituted herein as an electrode for secondary emission and that it is secondary emission which goes back toward the cathode and not reflected primary electrons. To accomplish this purpose, the reflector-like electrode I2 is appropriately positioned in the direct path of the beam of primary electrons and constructed to be copiously emissive of secondary electrons and has a positive potential applied thereto, as from a battery or other source IS. The constructiton accordingly provides an axial passageway from the cathode to the reflectorlike electrode.

To draw the secondary electrons in the direction of reflection and to prevent the secondary electrons from falling back to the reflector-like electrode, .a grid I4 is provided closely in front of said electrode, said grid having a more positive potential applied thereto than is applied to said reflector-like electrode, as by a battery or other source of voltage l5. By virtu of this construction and polarities, primary electrons are attracted to the reflector-like electrode and produce a greater emission therefrom of secondary electrons which are impelled in a reflex direction back to the resonator. Since the primary electrons arrive at the reflector in bunched condition, the reflex secondary electrons are correspondingly bunched and travel in that condition to the resonator where they give up their energy. The energy thus produced is taken from the resonator by a suitable output connection I6 such as the loop shown.

More in detail, the construction shown situates the cathode emissive surface and the emissive surface of the reflector-like electrode transverse to the common axis on which they are situated so as to be directly opposed and constituting the ends of the passageway therebetween. It furthermore appears that secondary electrons have a' tendency either not to leave the surface of the electrode or to return thereto in the absence of a more positive field penetrating the emitting surface, or to leave the electrode surface with a wide range of initial speeds and directions. However the random variation in initial speeds does not affect the bunching of the secondary beam because these speeds are so small relative to the maximum divergence in velocities of the bunched electrons. With regard to variation in initial directions, on the other hand, in order to prevent secondaries from assuming random trajectories and, with proper electrode configuration, to confine the electrons to an optimum channel passing into the resonator, it becomes necessary to apply an accelerating electric field close to the electrode surface. Accordingly grid l4 aforementioned is placed immediately in front of or proximate to said reflector-like electrode that the field of the grid includes the emitting surface in whole or in part therein. Said grid is likewise perpendicular to the common axis and interposed in the passageway between the reflectorlike electrode and the resonator. For distinguishing identification this grid will be referred to as the reflector grid.

The resonant cavity has a portion thereof intervening between the cathode and reflector grid, and to admit electron flow the walls of the cavity at the region around the axis provide openings,

thereby constituting a part of the passageway from the cathode to said reflector grid and reflector-like electrode. The openings through the resonator walls have perforate metal members across the same, and for distinguishing purposes these members will be referred to herein as resonator grids l1. Next the cathode is provided a focusing collar It, the region within which is likewise part of the passageway, and beyond the collar but in advance of the first resonator grid and within said passageway is a focusing grid l9. An evacuated envelope or enclosure, which includes the resonator as part thereof, is provided for the cathode, reflector-like electrode, grids, collar and passageway.

A positive potential from a suitable source, such as battery 20, is applied to the resonator and its grid. This positive potential is of higher order and preferably considerably higher than the positive potential on either the reflector-like electrode or reflector grid. Technically expressed, the reflector grid is more positive than the refiector-like electrode and the resonator and its grids are more positive than the reflector grid. By way of example, the resonator may be, say 1,000 volts positive, whereas the reflector-like electrode may be 200 volts positive and the reflector grid 250 volts positive, all with respect to the cathode. Adjustment of these voltages is made in use for obtaining maximum output. As the secondary emission is greater than unity (compared to primary emission) the output is proportionately increased. The primary electrons traverse the passageway as a beam from cathode H to the reflector-like electrode l2, and in transit through the resonator are bunched as usual. On reaching the reflector-like electrode the bunched primary electrons cause a greater number of secondary electrons to be emitted, and by virtue of the grid field the secondary electrons bunched in correspondence with the bunching of the primary electrons, move rearwardly into the resonator and give up their energy to the resonator and supply the desired output energy to the output connection 16 for utilization.

We claim:

1. An electron discharge device comprising in combination, a resonator, a cathode at one side of said resonator for producing primary electrons, means at the other side of said resonator for producing secondary electrons, means between said cathode and resonator for causing the primary electrons to move as a beam in a direction from the cathode through the resonator and to the secondary electron producing means, and means in the path of said secondary electrons between the secondary electron producing means and the resonator for causing the sec-' ondary electrons to enter into and move in the opposite direction in the resonator to the primary electrons.

2. An electron discharge device comprising in combination, a cathode for establishing a beam of primary electrons, means for bunching said electrons, means in the path of and activatable by the said beam for producing a secondary for causing the secondary electrons to enter said resonator.

3. An electron discharge device comprising a hollow body resonator having an axial passageway for electrons, a cathode having an emitting surface transverse to the axis of said passageway for producing primary electrons axially of the passageway, said cathode being located at one end portion of said passageway for projecting a beam of electrons therein, an electrode opposed to said cathode and beyond said resonator, said electrode being emissive of secondary electrons and at an end portion of and transverse to the axis of the passageway and comprising a source of secondary electrons, and a grid between said source of secondary electrons and resonator for obtaining entry of the secondary electrons into said hollow body resonator.

4. An electron discharge device comprising a cathode and a reflector-like electrode opposed to each other transversely of and on a common axis, a hollow-body resonator interposed between said cathode and electrode and having openings toward both thereof, said reflector-like electrode being emissive of secondary electrons and said hollow body resonator being receptive to entry of primary electrons from the cathode and secondary electrons from said electrode through said openings and means opposite each of said openings and outside of the resonator for directing electrons into said openings and resonator.

5. An electron discharge device comprising a resonator having an axis, a cathode transverse to and coaxial with said axis for producing pri- WILLIAM W. RIGROD. JOHN PAWLISHEN, Administrator for the Estate of Edward Paw- Zishen, Deceased.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,170,219 Seiler Aug. 22, 1939 2,216,169 George et a1. Oct. 1, 1940 2,259,690 Hansen et al Oct. 21, 1941 2,287,845 Varian et a1 June 30, 1942 2,410,822 Kenyon Nov. 12, 1946 2,414,785 Harrison et a1 Jan. 21, 1947 2,416,303 Parker Feb. 25, 1947 2,417,551 Hill Mar. 18, 1947 2,425,748 Llewellyn Aug. 19, 1947