US2190914A - Electronic device - Google Patents

Description

Feb. 20, 1940. Q Z 2,190,914

ELECTRONIC DEVICE v Filed May-27, 1957 2 Sheets-Sheet 1 INVENTOR 0770 KRENZ/EN ATTORNEY Feb. 20, 1940. o. KRENZIEN ELECTRONIC DEVICE 2 Sheets-Sheet 2 Filed May 27, 1957 INVENTOR 0770 lgsNzlEN 7 ATTORNEY 35 being a like amount above that of the. respective interms of volts as ascertained at the indicated Patented FetuZO, 1940 I v UNITED STATES PATENT OFFICE Otto Krenzien, Berlin-Siemensstadt, Germany,

assignor to Siemens & Halske Aktiengesellschaft, Berlin, Germany, a corporation of Germany ApplicationMay 2'2, 1937, Serial No. 144,984

, In Germany May'30,"193 6 5 Claims. (Cl. 250-166) This invention relatesto electronic devices and size. as here suggested makes it also possible to in particular to method and means for increasing use incident light raysof greater aperture with the efiiciency of photoelectric secondary electron a substantial increase in the initial energy.

emissive amplifier tubes. In describing the invention in detail, reference In a great number of practical applications of will be made to the drawings, in which Fig. 1 5

photo-tubes, the extremely small photo-electric shows a potential distribution between two eleccurrents released by impacting light are in need trodes and a secondary emissive amplifier for of large amplification before they are capable of purposes of explanation, while Figs. 2 and 3 show insuring the desired actuation of electric load the electrostatic contour potentials in electron 1o circuits. 1 l devices embodying applicants invention; and

Such an amplificationof photo-electric cur- Figs. 4, 4a 5, 5a, and 6 show the combination rents is accomplished in the so-called secondaryand modifications of applicants invention whereemission amplifiers or multipliers by that the pri-' in several stages of electron multiplication are mary electrons produced by virtue ofphoto-elecshown. 4 V

lo tric action upon a cathode are caused to impinge The actions of auxiliary electrodes upon the upon an electrode which presents as high as feaselectrical field in front of photo-cathodes accordible a positive potential in reference to the phoing to this invention may be seen in Figs. 1 to, 3, to-cathode with the result that secondary elec- Which illustrate the results of experimental trons are released therefrom. If the countermeasurements to ascertain the distribution .of the electrode or'plate at the-points where the primary potential with various electrode systems, these 20 photo-electrons are caused to strike is coated with measure being made in an electrolytic an electron-active substance in the form of a film ter vat as well known in the prior art. or layer, say of alkali or alkaline-earth metals, Fi 1 ShOWS e constructifln known from t then, in the presence .of appropriate conditions, ear r a t of a photo-Cathode K With a Cylindrisuch impacting primary electron will be able to cal hollow electrode Z1 being mounted'anteriorly 25 produce say, from 8 to 10 secondary electrohsjin thereo W the Provision of any l 'y 6160- other words, with the use of a single collecting trode, Z1 being the first input S a of a a electrode approximately 10 fold amplification by p fi multiplier being predicatedlfor soper means of secondary electron emission is obtaintion upon Seco d y electron emission, and workable. ing at a positive biasing voltage in reference to If the secondary electrons thus generated are, the cathode. Anumber of equi o ntm lines bein turn, caused, toimpinge upon other similar tween K and Z1 are indicated schematically. by plates, in which case each such additional gatherthe solid lines, the numerical values indicated at ing plate would be operated by a positive potential the ends thereof giving the potential increments preceding electrode or plate, then a correspondplaces in comparison to the photocathode. The ing boost of the electronic current or stream is broken linesindicate theelectric field lines along obtainable at each such plate as a result of secwhich ,the electrons which are released without ondary emission. Yet, the general aim will be any appreciable initial speed will travel in the to insure as high as feasible an initial current, electrical field, and which,as known, are at right 0 that is, the current entering or put into the mulangles to the equipotential lines. The figure will tiplier system. make it clear that substantiallyonly those elec- With this end inview, according to the inventrons released on the cathode will enterthe apertion, one or more auxiliary electrodes are mount ture O of the electrode Z1 which are emitted from r 45. ed anteriorly of the photo-cathode, which, by the the central portions of the cathode between an aid of a suitable electrical potential chosen there-.. and :12, whereas such electrons as are emitted for, are so made to act upon the electrons emafrom the cathode outside the said solid angle will nating from the photo-cathode that they will be fail to strike electrode Z1, d, Will travel past united or concentrated upon the smallest possible the same. i Y space. Such an arrangement makes it feasible Figs. 2 and. 3, on the contrary, illustrate ar- 50 to use photo-electrically active cathodes of esrangeme or n to t invention W ch sentially larger size than heretofore, while yet so comprise an auxiliary electrode G interposed becombining practically all of the photo-electricaltween the photo-cathode K and the multiplier 1y released electrons that they will enter the mul-, electrode Z1. From the position of the equipotentiplier system. The photo-cathode of increased tial lines, for instance, in Fig. 2, it will be seen 55 I pliers according to this invention being of the T type known in the prior art. The p that the utilizable (useful) solid angle over the cathode surface extends here as far as the boundary lines b1 and bz,-if the auxiliary electrode G is kept at cathode potential.

But as indicated by the equi-potential lines in Fig. 3, the conditions may be still further improved by, that the whole cathode area is fully utilized, if electrode G is imparted a negative potential in reference to the cathode. The values of the potentials indicated in Fig. 3 are referredtz to the auxiliary electrode G as zero potential, with the cathode K, for instance, tial of 100, whereas the multiplier electrode Z being the point of the field being at the highest positive potential is identical with equipotential line 200. 1

A number of practical embodiments of mu1ti-. v are schemati cally illustrated in Figs. 4 to 6.

Fig. 4 shows a cathode K in the form of a con-. cave mirror or reflector and positioned obliquely in reference to thetube wall W, aphoto-electrically active coat P covering the inner surface of the said cathode K, consisting, for instance, of a surface film of caesium brought upon a metallic silverfilm acting as a substratum, andcaesium oxide for the intermediary layer. An auxiliary grid G connected with the cathode is formed of threeuprights which surmount the cathode surface to such a point that the parts thereof extending parallel to the mirror aperture are roughly at the same distance from the glass wall of the tube; In this embodiment the secondaryemission multiplier is of the double-stage type, with growing potential inthe direction of the anode. .Each stage consists of a cylindrical concave electrode Z1 and Z2 respectively, of the well known L form. The primary electrons experience an accelerative effect towards Z1, they enter at O'into'the concave electrode, and generate secondary electrons in the main axis at the specially activated kneeor elbow part B1. The secondary electrons thus ensuing, in turn, are accelerated by'Zaand whenthey strike a'similarly activated knee'or elbow piece at Bz they cause again the emission of secondary electrons. The stream of electrons amplified or multiplied in the said manner finally reaches the anode A which is kept at the highest potential level. Potential is applied to the various stagesby way of leads brought through the'press Q. The exciting light enters from the right-hand side and, thus strikes the cathodejas can be seen from another elevation view of the cathode it is hardly impeded at all by the narrow auxiliary grid strips. Inasmuch'as the auxiliary grid G is at cathode potential, a; large portion also of the photo-electric current emitted at points closer to the cathode edge or rim will still be directed into the multiplier system, and these portions, as will be understood, would fly past the aperture of the system in the absence of the auxiliary grid of this invention.

In the exemplified embodiment shown in Fig. 5, auxiliary electrode G is united by stays S with the photo-cathode K, and'it'consists of a thin metal ring G which is raised above the median part ofthe concave cathode. The secondary-emission system in this instance comprises three multiplier stages Z1, Z2, Z3, the various concave cylinders being at a poten-'- to said multiplier.

highly activated places in each case are located directly opposite the inlet openings for the electrons, that is to say, at the inner portions of the cylindrical electrodes as indicated at B1, B2, B3. Also in this case the shadow thrown by the auxiliary grid upon the active photoelectric film will be immaterial. odejis sufiiciently great so that the cylinder electrode Z1, in the case of light falling in from the left approximately on a horizontal level will throw a shadow only upon a comparatively small portion of the cathode surface so that this loss may be readily accepted.

The arrangement shown in Fig. 6 differs from the embodiment Fig. 5 in that the auxiliary grid G is no longer united directly with the photocathode K, but is brought into the tube by way of 'a distinct lead-in L and is insulated (separated) therefrom. In this manner, the auxiliary grid may be impressed with a markedly negative potential ii relation to the cathode so that the concentration" (focusing) of photo-electrically released electrons is essentially improved.

' Having described the invention, what is claimed is:

1. An electron device comprising a concave photoelectric cathode, a T-shaped secondary electron emissive'electrode positioned in register with the cathode, a ring electrode positioned intermediate the cathode and the electrode and symmetrical with the cathode and an anode for collecting electrons from the secondary electron emissive electrode.

2. An electronic device comprising a photoemissive concave cathode, a ring electrode positioned closely adjacent to and in register with the cathode and symmetrical therewith, anda secondary electron multiplier having a plurality of stages positioned to receive electrons from the photoelectriocathode said multiplier including an anode for collecting the multiplied electrons.

'3."An electronic device comprising a photo emis'siveconc'ave cathode, a ring electrode supported'fromf and conductively connected to the cathode; and a secondary electron multiplier having a plurality of stages positioned toreceive electrons from the photoelectric cathode said muItiplierincIuding an anode 'for collecting the multiplied" "electrons.

"4.'An. electronic device comprising a photo-' emissive concave cathode, a ring electrode positioned closely ad acent to and in register with the cathode and symmetrical therewith, and

adapted to bemaintained at a negative potential with respect tothecathode, and a secondary elec-" tronmultiplier having a plurality of stages positioned to receive'electrons from the photoelectric cathodesaid multiplier including an anode for collecting the multiplied electrons.

- 5. An electronic device comprising a photo emissive. concave cathode, a secondary electron multiplier having a pluralityof stages spaced from said cathode, said multiplier including an anode and'ajocusing electrode closely adjacent to, in" register'with, and symmetrical with said cathode and positioned intermediate said oath Moreover, the size of the cathode and saidmultiplier, and said electrode circum scribing the electro OTTO KRENZIEN.

paths from said'cathode'

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