US2397822A - Electron multiplier - Google Patents

Description

April 1946. F. J. G. VAN DEN BOSCH 2,397,822

ELECTRON MULTIPLIER Filed Aug. 10, 1942 7 Own 191v nw/va 0520a [20 15a lie 53/ El,

INVENTOR OlgM/fi-Mfld; M im 501mb ATTORNEY 9, 1942, and an anode i2.

Patented Apr. 2, 1946 ELECTRON MULTIPLIER Francois Joseph Gerard van den Bosch, Surrey. England, assignor to Vacuum-Science Products Limited, London, England, a British company Application August 10, 1942, Serial No.'454,213 In Great Britain August 5, 1940 i Claims. 01. 179-1715) This invention relates to electron multipliers primarily for dealing with ultra-high frequencies but applicable also for use with lower frequencies.

According to the present invention there is provided an electron multiplier apparatus comprising one or more secondary cathodes disposed in the electron stream between a primary cathode and an anode, a pair of electron-grouping electrodes disposed in the electron stream of the multiplier, means for applying an alternating po-' tential across said pair of grouping electrodes so as to vary the velocities'of successive electrons to a diflerent extent whereby grouping or bunching of the electrons along the stream is effected, means for subjecting the stream to 'a' signal modulating potential before or during lating potential through a transformer l6 and is biased by one part ll of a potentiometer which potentiometer is connected at different potential points along its length to the other electrodes. Thus, the primary direct current electron stream is modulated. The electron grouping elements 13 and M of the first pair are connected respectively through adjustable impedances l8 and IS with the output of a carrier-wave generator 8. The grid I3 is also influenced by the signal by being connected to the first secondary cathode l i. This may be accomplished by connecting one or other of the output terminals of generator 8 to the first secondary cathode Ii. By spacing the electron grouping electrodes l3 and M of the first pair a suitable distance apart and by grouping or bunching of the electrons, and an electron energy collecting electrode or electrodes.

The alternating signal potentials are applied to the two electron-grouping electrodes in out-ob phase relationship, for example in opposed phase,

and the spacing of these electrodes is determined according to the frequency of the signals. Similarly, two electron energy collecting electrodes are disposed at an appropriate distance from the electron grouping electrodes and are spaced apart in the electron stream the same distance as the electron grouping electrodes.

The aforesaid one or more secondary cathodes of the electron multiplier may be disposed between the electron grouping electrodes and the electron energy collecting electrode or electrodes so as to produce a multiplication of the electrons in the process of grouping.

One specific arrangement according to the invention suitable for a transmitter is now described with reference to the accompanying drawing which shows diagrammatically an electron multiplier having a primary cathode Ill with heater 9,'a plurality of secondary cathodes ii', Ha, lib, iic, lid and lie, each having an equipotential grid 5, 5a, 5b, 5c, 5d and 5e, respectively, associated with it as set out in specification oi United States Patent No. 2,285,848, dated June A pair of spaced electron grouping electrodes in the form of grids i3 and M and its and Ma is provided between successive pairs of secondary cathodes. At least one of these grouping electrodes may be consti tuted by a secondary cathode. A pair of energy collecting electrodes and 2! is provided between the final secondary cathode and the anode 12. A control grid i5 is provided between the primary cathode and the first secondary cathode which con rol W4 is imparted to it a main adjusting the phase relationship of their alternating potentials the stream of electrons passing through the space between the electrodes is sub- Jected to an alternating field strength. The effeet 01 this on a succession of electrons passing through the field is to accelerate certain of them while de-accelerating others. Thus the density of the electrons along the stream is varied in a 2 non-sinusoidal manner and so to speak produces bunches of electrons separated from one another along the stream, the density of the bunches varying with the signal potential. Preferably, the electrodes [3- and M are separated a distance apart such that the transit time of the electrons is half the period of the carrier wave. The stream of bunched electrons is multiplied by impact upon and passage through the succeeding secondary cathodes llb and lie whereafter the bunching effect may be further accentuated by the passage of the stream through another alternating field formed between a second pair of electron grouping electrodes I3a and [4a which are preferably disposed in the locality of maximum bunching produced by the first pair of grouping electrodes, The second pair of electrodes are connected in parallel with the first pair by the conductors 6 and have their potentials additionally modulated by being connected back to the secondary cathode lib. In order that the modulating potentials may be brought into the appropriate phase relationship with the preceding electrodes i3 and I4 variable impedances I So and We are provided respectively between the second pair of electron grouping electrodes i3a and Ma and the last-mentioned secondary cathode llb.

The stream of bunched electrons leaving this second pair of electrodes l3a, Ha is multiplied by a furth r pair 98 se ondary catheter Ha I I a the , rect' current component and a non-usoidal component. A considerable fraction of the power can be collected by ca :"1 the str to pass between two energy collecting electrodes at and 2i which are disposed at a locality where maximum bunching occurs and are spaced apart at a corresponding distance to the energy collecting electrodes, which energy collecting electrodes are arranged to be at a less potential than the anode I2 and may have their individual potentials adjustedby the resistances 22 and 2s. The effect of the grouped electron stream on these collecting electrodes is to produce an alternating field between them. The energy collected by the electrodes 2d and 2| is conducted to a dual antennae aerial i. In the case where the apparatus is used for measuring frequencies the two collecting electrodes may be replaced by a single electrode in which a pulsating D. 0. current suitable for measurement is induced. I

In this manner there is obtained a high degree of amplification oi the applied signals for transmission or reception purposes by which the disadvantages arising from transit time are avoided.

Instead of modulating the primary electron stream, the carrier-wave produced by the generator 8 may be directly modulated. The electron multiplying apparatus provides both voltage and current amplification.

I- claim:

1. An electron multiplier apparatus comprising a primary cathode and anode between which are disposed, a signal input electrode, at least one secondary cathode and a pair of electron grouping electrodes, means for applying direct current potentials of ascending order to. the pri- 4 mary cathode, secondary cathode and anode,

means for applying an alternating current po-' tential across the'pair o1 electron-grouping elec- 7 trodes so as to vary the velocities of successive electrons in the stream flowing between the prithe primary cathode and anode, whereby grouping or launching of the electrons along the stream is efiected, means for applying a signal potential to said input electrode, and an output assemblage in said electron stream adapted to collect the energy from the bunched stream.

3. An electron multiplier apparatus comprising a primary cathode and anode between which are disposed, a signal input electrode, successive pairs of non-emissive electron grouping electrodes and at least one secondary cathode between successive pairs of the grouping electrodes, means for applying direct current potentials of ascending order to the primary cathode, secondary cathode and anode, means for applyin alternating current potential across the pair of electron-grouping electrodes so as to vary the velocities of successive electrons in the stream flowing between the primary cathode and anode, whereby grouping or bunching of the electrons along the stream is eifected, means for applying a signal potential to said input electrode, and an output assemblage in said electron stream adapted to collect the energy from the bunched stream.

4. An -electron multiplier apparatus comprising a primary cathode and anode between which are disposed a signal input electrode, a number of pairs of non-emissive electron grouping electrodes, at least one secondary cathode between two adjacent pairs of grouping electrodes, means for applying a direct current potential of ascending order to the primary cathode, secondary cathode and anode, means for applying an alternatmary cathode and anode, wherebygrouping or bunchin of the electrons along the stream is offected, means for'applying a signal potential to said in ut electrode and two electron energy collecting electrodes arranged adjacent the anode and spaced apart an equivalent distance to the grouping electrodes.

2. An electron multiplier apparatus comprising a primary cathode and anode between which are disposed, a signalinput electrode, at least one secondary cathode and a pair of non-emissive electron grouping electrodes, means for applying direct current potentials of ascending order to the primary cathode, secondary cathode and anode, means for applying an alternating current potential across the pair of electron-grouping electrodes so as to vary the velocities of successive electrons in the stream flowing between ing current potential across each pair of electron grou in electrodes, means for applying a signal potential to said input electrode and an output assemblage in said electron stream adapted to collect the energy from the bunched stream.

5.'An electron multiplier apparatus comprising, a primary cathod and anode between which are disposed a. signal input electrode, a number of pairs of non-emissive electron grouping electrodes, a pair of collector electrodes and a number of secondary cathodes, at least one between the input electrode and first pair of grouping electrodes, at least One between adjacent pairs of grouping electrodes and at least one between the last pair ofgrouping electrodes an the collector electrodes, means for applying a direct current potential of ascending order to the primary cathode, secondary cathode and collector electrodes and anodes, and means for applying an alternating current potential across the grouping bunching of the electrons.

FRANCOIS JOSEPH vale DEN BOSCH.

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