US2204999A

US2204999A - Electric discharge device

Info

Publication number: US2204999A
Application number: US178650A
Authority: US
Inventors: Siebertz Karl
Original assignee: Siemens AG
Current assignee: Siemens and Halske AG; Siemens AG
Priority date: 1936-11-30
Filing date: 1937-12-08
Publication date: 1940-06-18
Anticipated expiration: 1957-06-18
Also published as: FR830154A

Description

June 18, 1940. Kq $|EBERTZ f 2,204,999

ELECTRIC DISCHARGE DEVICE Filed Dec. 8, 1937 //V VEN TR KARL S/EBERTZ A TTORNE Y lPatented June 18, 1940 UNITED STATES PATENT OFFICE ELECTRIC DISCHARGE kDEVICE poration of Germany Application December 8,

1937, Serial No. 178,650

In Germany November 30, 1936 7 Claims.

This invention relates to electric discharge devices in which electric currents according to the principle of the electron multiplication are amplied in various steps by the secondary electrons. In this case it is immaterial whether the currents to be amplified are released as photo currents by the exposure of a photo-electric surface or whether the electrons supplied by an electron emitting source, for instance, a hot cathode are influencedv by any control means, for instance, by the electrostatic or electromagnetic control. The electron multipliers hitherto known present a relatively elongated construction which gives rise to a number of diliculties in the manufacture of such devices.

These diiculties may be removed if the electrodes of the electron multiplier are arranged in the form of a circular arc. In this manner it is possible to place on the one hand a large number of steps in a relatively narrow space and on the other hand the substances for preparing the active surfaces of the electrodes of the multiplier may be centrally'arranged so that for the preparation of these layers all electrodes are under the same conditions and, therefore, there is no great diiculty in giving the same emissive power to the electrodes of the individual steps that emit secondary electrons. It is also possible to provide for a uniform heating of the electrodes when degassing and activating. The arrangement of the electrodes in the form of a circular arc may be employed for purely electrostatically operating apparatus; however, particularly also' for apparatus in which the released secondary electrons are deflected by means of magnetic fields towards the next following electrode. Sucharrangements have the further advantage that the necessary magnetic field may be produced with the aid of a relatively small and simply constructed coil.

An embodiment of the invention is shown in the accompanying drawing for an electron multiplier operating with magnetic deflection.

Fig. 1 shows the plan view, Fig. 2 the elevational view of the electron multiplierin diagrammatic form, Fig. 3 shows in detail one of the secondary emissive surfaces, while Fig. l shows in somewhat more detail a portion of the sensitizing apparatus.

I denotes the vacuum vessel in which are sen cured the layers 2, for instance, or mica serving to secure the individual electrodes. The electrodes which emit secondary electrons (main electrodes) are denoted by the numeral 3. They are supported by the rods 4 secured to the mica layers. The effective surface of the electrode itself projects towards the center of the discharge device as will be seen from Fig. 3 in which an electrode is shown on an enlarged scale. This construction has the purpose to prevent asv far as possible non-uniform iields which may be created by holding wires 4. Within the circle on which the electrodes 3 are arranged are disposed the acceleration electrodes 5 which are kept in a known manner at a suitable voltage. In the central portion of the discharge device are arranged the substances for the preparation of an active surface of the electrodes 3. In most cases it is sufficient to place only the metal serving to directly activate the surface, such as, for instance, an alkali metal, for instance, caesium or an alkaline earth metal such as barium, in the central portion of the electric discharge device in the form of known getter pills which are denoted by the numeral I5 supported from the central support member 2 I. In order to produce a uniform deposit on all electrodes various of such pills are provided facing the single sections of the electrodes. A uniform impinging of the vapor on the electrode surfaces may be attained in a still more certain manner if the vapor of the active metal is caused to issue from a circular gap or a portion of a circular gap. Such a gap may be, for instance, obtained if the getter is placed in a pot 6 as shown in Fig. 4, a covering plate l being arranged in spaced relation thereto. The circular gap may be covered opposite to the portions of the pot walls which are not to be provided with a deposit in order to leave, for instance, an aperture free for the passage of the light. Such a cover is denoted in Fig. 4 by the numeral 8. The material evaporated inside the pot li leaves the same substantially in the direction as indicated by the arrows. A similar construction may be employed in order, for instance, to provide the electrodes 3 with a silver coating previous to the impinging of the active material thereon, which silver coating may be subsequently oxidized in a well known manner.` In this case the silver to be evaporated is preferebly heated with the aid of a tungsten spiral, whereas the evaporation of the active material may be effected by heating the container with the aid of high-frequency currents. To provide the electrodes with a silver coating also a tungsten wire provided with a silver coating may be preferably arranged inside the space enclosed by the acceleration electrodes 5 and opposite to the electrodes 3.

It is preferable to arrange that the vapors serving to activate the electrode Yare directed by guide surfaces towards those electrodes. To this end, the disks 9 and l0 are employed between which lies the active material. These disks may consist of metal and may serve at the same time in the case of high-frequency heating to supply to the active metal the heat necessary for its evaporation. It is advisable to provide still further surfaces l l consisting preferably of insulating material for instance, mica which surfaces may be, for instance, secured to the acceleration electrodes 5. A portion of the circular gap formed by the disks il and l0 is covered preferably by the strip l2 as will be seen from Fig. l in order to maintain an aperture free for the passage of the light when employing the device for the amplification of photo-currents. If the individual electrodes are impressed in a known manner with a suitable voltage in the clockwise direction so that the electrode denoted by 3a represents, for instance, the input electrode, care must be taken that this electrode be struck by the luminous rays which are to release the photoelectrons. If the device is to be employed to amplify the currents supplied by a hot cathode and influenced by a control grid or the like, the input system consisting of the hot cathode and the control electrode must be so arranged that the electrons emitted therefrom impinge upon the input electrode. In the majority of cases this is made possible by arranging the system consisting of the hot cathode and the control electrode in the same manner as the electrodes 3. Such a cathode 3| and control electrode 33 are shown in Fig. l. in this system one of the rods 5 or the electrode 3a may serve as an anode. The supply leads to the individual electrodes are shown only in part for clearness of illustration. The coil 23 serves to produce the magnetic deflecting iield and surrounds the envelope.

The above-described construction of the electron multiplier is particularly employed in such cases where substances which evaporate in a relatively diilcult manner, such as barium, are utilized to activate the individual electrode surfaces. Such substances are chiefly employed in apparatus in which the electron multiplier is utilized to control the currents produced by a hot cathode and influenced by grids or the like and in which the active layer of the hot cathode contains alkaline earth metals, such as barium or strontium. In this case the use of caesium or other alkali metals is under circumstances disadvantageous, since, for instance, evaporating alkaline earth metal deteriorates the layers active as secondary electron emitting sources or it deposits on the electrodes of the incandescent electron arrangement.

What is claimed is:

l.. A discharge device comprising an elongated symmetrical tubular envelope, an elongated cylindrical support member having its axis coincident with the axis of the envelope, a plurality of equi-spaced cylindrical accelerating electrodes disposed concentrically about the support member and a plurality of individual secondary emissive electrodes concentric with said accelerating electrodes, a plurality of support rods supporting each one of the plurality of secondary emissive electrodes, and spacing means maintaining the supported secondary emissive electrodes in spaced relationship to each other and to both the support member and accelerating electrodes.

2. A discharge device comprising an elongated symmetrical tubular envelope, an elongated cylindrical support member having its axis coincident with the axis of the envelope, a plurality of equi-spaced cylindrical accelerating electrodes disposed concentrically about the support member, a plurality of individual secondary emissive electrodes concentric with said accelerating electrodes, a cathode, a plurality of support rods supporting each one of the plurality of secondary emissive electrodes, spacing means maintaining the supported secondary emissive electrodes in spaced relationship to each other and to both the support member and accelera-ting electrodes and maintaining the secondary emissive electrodes equi-distantly spaced from each other, said cathode being positioned at a radial distance substantially equal to that of said concentric secondary emissive electrodes.

3. A discharge device comprising an elongated symmetrical tubular envelope, an elongated cylindrical support member having its axis coincident with the axis of the envelope, a plurality of equi-spaced cylindrical accelerating electrodes disposed concentrically about the support member, a plurality of individual secondary emissive electrodes concentric With said accelerating electrodes, a plurality of support rods supporting each one of the plurality of secondary emissive electrodes, spacing means maintaining the supported secondary emissive electrodes in spaced relationship to each other and to both the support member and accelerating electrodes, and

means supported from the support member for sensitizing the secondary emissive electrodes.

4. An electron discharge device comprising an elongated cylindrical support member, a plurality of parallel cylindrical accelerating electrodes equi-spaced from each other and concentric with said support member, a plurality of secondary emissive electrodes equi-spaced from each other and concentric with said support member, and lying beyond the accelerating electrodes, said secondary emissive electrodes having an arcuate surface facing the support member, and means supported from the support member for sensitizing the arcuate surface of the secondary emissive electrodes.

5. An electron discharge device comprising an elongated cylindrical support member, a plurality of parallel cylindrical accelerating electrodes equi-spaced from each other and concentric with said support member, a plurality of secondary emissive electrodes equi-spaced from each other and concentric with said support member, and lying beyond the accelerating electrodes, each of said secondary emissive electrodes having an arcuate surface facing the support member, said arcuate surface subtending an angle substantially not greater than the angle subtended by two adjacent accelerating electrodes, and means supported from the support member for sensitizing the arcuate surface of the secondary emissive electrodes.

6. An electron discharge device comprising an elongated cylindrical cathode, an elongated cylindrical support member, a plurality of parallel cylindrical accelerating electrodes equi-spaced from each other and concentric with said support member, a plurality of secondary emissive electrodes equi-spaced from each other and concentric with said support member, said secondary emissive electrodes being at the same radial distance as said cathode and lying beyond the accelerating electrodes, each of said secondary emissive electrodes having an arcuate surface facing the support member, said arcuate surface subtending an angle substantially not greater than the angle subtended by two adjacent accelerating electrodes, and means supported from the support member for sensitizing the arcuate surface of the secondary einissive electrodes.

7. An electron discharge device comprising an elongated cylindrical support member, a plu ralty of parallel cylindrical accelerating elec trodes mounted concentrically about said support member, a plurality of equi-spaced secondary emissive electrodes mounted concentrically about the accelerating electrodes, each of said plurality of secondary emissve electrodes having the shape of a non-planar base prism, said non-planar base prism being sensitized to provide highly secondary electron emission and each of said secondary emissive electrodes being supported from the apex of the prism, and an envelope concentric withl and enclosing said support member, said accelerating electrodes, and said secondary @missive electrodes.

KARL SIEBERTZ.