US2940003A - Counting tube arrangement - Google Patents

Description

June 7, 1960 Y E. F. DE HAAN COUNTING TUBE ARRANGEMENT Filed Aug. 5, 1957 INVENTOR EDWARD FOKKO E HAAN United States Patent COUNTING TUBE ARRANGEMENT Edward Fokko de Haan, Eindhoven, Netherlands, as-

signor to North American Philips Company Inc., New York, N.Y., a corporation of Delaware Filed Aug. 5, 1957, Ser. No. 676,216 Claims priority, application Netherlands Aug. 14, 1956 1 Claim. (Cl. 3158.6)

The invention relates to an arrangement comprising a counting tube producing an electron beam which can be deflected and held in difierent positions, and to a counting tube intended for use in such a device. The invention relates particularly to the collecting electrode for the electron beam.

In a known device of this kind, the beam is held in given positions in that the beam current in these positions is distributed among two electrodes. One of these electrodes is shaped in the form of a slotted screen, behind which is arranged a second collecting electrode to collect the electrons passing through the slots. This second collecting electrode is also provided with windows or apertures, so that part of the electrons pass through them to the tube wall. At the areas concerned the tube wall is coated with a phosphor to permit a visual indication of the beam position.

This system of collecting electrodes, however, is comparatively complicated. In accordance with the invention, a simple construction is possible by collecting, in such a device, the electrons of the beam on a collecting electrode which is preferably applied to the tube wall and which consists of two strips of good conductivity extending parallel to the deflection direction of the beam and connected to one another by a series of straps of a material of which the electrical conductivity varies strongly upon electron impact, to which straps the beam can be directed, while between the strips of good conductivity a voltage ditference is applied, while 'one of the strips may be connected to one of the deflection plates and via a resistor to a terminal of the voltage source. The straps are preferably made of a substance which does not only exhibit the aforesaid property of electron bombardment induced conductively, but also luminescence upon electron impact. The strips and straps may be applied directly to the bulb of the tube, for example by vaporization or by brushing. The strips may be made of silver, whereas the straps may be made of metal sulphides, for example, cadmium sulphide, zinc sulphide and the like. Such substances and the fact that their electrical conductivity increases materially upon electron impact are known per se. The invention provides a very simple arrangement. It is advisable to coat the tube wall previously with a slightly conductive layer in order to permit collection of the electrons of the beam not striking the said straps. This layer may be connected to one of the silver strips. However, as an alternative, these-strips may be applied without using further means to the said wall, in which case the resistance of the Wall layer must be so high that the current remains low with respect to the current passing through the straps, when the latter are struck by electrons.

The conductive strips may be arranged in one plane, but as analternative, they may be arranged one behind the other, these conductive strips being separated by the substance of which the conductivity varies upon elec tron impact. The electrons must then pass the first conductive layer in order to reach this substance. One

2,940,003 Patented June 7, 1960 conductive ship may then be made of tin oxide and be cathode.

applied directly to the tube wall; it may be coated with the straps of cadmium sulphide, which may, in turn, be covered with straps of aluminum. The aluminum layer must be so thin that the electrons can penetrate it.

The invention will now be described more fully with reference to the accompanying drawing in which Figs. 1 and 2 show different embodiments of a tube for use in a device according to the invention, in a diagrammatical view.

Referring to Fig. 1, reference numeral 1 designates the bulb or transparent envelope of the tube, in which a cathode 2 and deflection plates 3 and 4 are housed,

which electrodes produce a ribbon-shaped electron beam 5. The beam 5 strikes a collecting electrode consisting of strips 6 and 7 of good conductivity, which are connected to one another by straps 8 of a substance, for example zinc sulphide, of which the conductivity increases strongly upon electron impact. A current which is to lOOO-times the incident electron current can be readily obtained. The strips and straps may be arranged on a slightly conductive Wall layer 9, which serves to conduct away electrons falling at the side of the straps 8. The strip 6 is connected via a resistor 10 to a positive voltage of a few 100 'v.; the strip 7 is connected to the In the position shown the beam 5 indicates the number 7, if there are ten straps 8. The deflection plate 3 is connected to the strip 6. The beam partly bypasses the left-hand side of the said strap and lands partly on this strap. Consequently, this strap exhibits a low resistance, so that the current from the strip 6 to the strip 7 increases strongly, and the voltage of the strip 6 drops owing to the voltage drop across the resistor 10. The beam is held in this position, since, if the beam moves slightly to the right, the voltage of the strip 6 and hence that of the deflection plate 3 drops, as the beam strikes a larger part of the strap, so that it is again deflected to the left-hand side, whereas the reverse takes place when the beam moves further to the left, i.e. away from the strap. Only by supplying a positive pulse to the plate 4 can the beam be moved to the next following strap.

The strips 6 and 7 may be made of silver and be provided by vaporization of metal, or by brushing on of a paste, similarly for the'straps 8. For the strips use may then be made of a known silver paste; for the straps use may be made of a paste of cadmium sulphide or zinc sulphide. The latter substance has the advantage that it luminesces so that it may serve as an indicator for the beam position. The slightly conductive substratum 9, whose resistance may be approximately equal to that of the unbombarded straps, may be constituted by a very thin metal layer or a tin oxide layer, by which the inner side of the bulb 1 may be covered. Between the deflection plates 3 and 4 and the collecting electrode provision may be made of one or more grid or screen electrodes in order to obtain a sharp definition of the beam and to withhold secondary electrons from the collecting electrode.

With the tube modification shown in Fig. 2, the strips and straps are arranged one behind the other, viewed in the direction of travel of the electrons.

To the glass wall 11, of which only part is shown in the drawing, is applied a layer 12 of tin oxide. On this layer are arranged straps 13, for example, of cadmium sulphide, which are covered by a thin aluminum layer 14. The layers 13 and 14 may be applied for example by means of a mask, for example by vaporization. The aluminum straps are connected to the strip 15, which may be connected via a resistor to a positive voltage. The layer 12 may be connected to a higher positive voltage. However, the reverse is also possible. In this case'a beam 16 of circular partly on the strap 14 and partly on the layer 12, where a it is held since the strap 15 is also connected to a defiec tion plate The electrons penetrate thethin aluminum layer 14 and producefan increase in conductivityof the "straps 13,.so, that th Current from the layer 12 to the strap 14 increases. 7 V a 'The advantage of this embodiment of, the lnvention consists in the possibility of a simple arrangement of the electrodes, while a high amplification can be obtained,

since a comparativelygreat current variation can be obtained in the straps by means of a slight beam current. Therefore, use may be made of a rod shaped beam.

obvious that further embodiments we possible within ection is used, which falls 7 collecting electrode comprising plural, spaced, electronreceiving portions constituted of amaterial whose elec 5 Although two embodimentsare described, it Will be I:

the scope of the invention. For example, as a rule means 7 will be provided to move the beam from the last strap counting tubes.

What is claimed is:

arrangement including an electron-beam counting 5 tube comprising beam-producing means and deflection means for directing the beam along plural paths, a collect} ing electrode for receiving said beam and controlling the position of said beam along said plural paths, said back to the first, but thesetrneans are known to those skilled in the art in View of the means usedtin known tncal conducti vity is a function of the extent of electron bombardment and each mounted to receive electrons when the beam occupies one of its'plural paths, terminal connections to spaced jointsot each of said spaced electron-receiving portions, means for applying a difference 'of potential'across said terminal coilnection, a directelectrical connection between the deflection means and one of the terminal connections, and an: impedance connecting said direct electrical connection to a-fsource ofpotential,

- Referencesbited in the file of this patent, Y

52,776,371 'Clogston et a1. Jan.l.;1957 OTHER REFERENCES" i A Decade Counter Tube for Counting Rates,"

" Philips Industries, May 1953; vol. 14, No. ll pa ges' UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2340,0055 June 7 1960 Edward Fokko de Haan It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1 9 line 48, for "conductively" read conductivity Signed and sealed this 4th day of April 19610 (SEAL) Attest: ERNEST W. SW IDER XQQQX XXXKK ARTHUR W. CROCKER Attesting Oflicer Acting Commissioner of Patents

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