US3553457A - Image intensifier including matrix of elongated electrodes for locating output signals geometrically - Google Patents

Abstract

A particle detector system comprising a channel image intensifier having a planar output electrode subdivided into an array of parallel electrode conductors with each conductor connected to a separate terminal, an array of parallel target conductors lying in a plane parallel to the electrode conductors on the output side of the device and orientated perpendicular to the electrode conductors, and a second set of terminals each of which is associated with one of the target conductors. The target conductors may be associated with luminescent elements to generate a two-dimensional visual display.

Description

United States Patent lnventor Brian William Manley Burgess Hill, Sussex, England Appl. No. 743,764 I Filed July 10, 1968 Patented Jan. 5, 1971 Assignee U.S. Philips Corporation New York,N.Y. a corporation of Delaware. by mesne assignments Priority July 12, 1967 Great Britain No. 32016/67 IMAGE INTENSIFIER INCLUDING MATRIX OF ELONGATED ELECTRODES FOR LOCATING OUTPUT SIGNALS GEOMETRICALLY 5 Claims, 5 Drawing Figs.

U.S. Cl 250/209, 178/76; 250/213, 250/220; 313/96 Int. Cl H01j 39/12 Field of Search 250/83.3, 213, 209, 220; 178/76, 7.1; 340/173; 313/96, 97,

[56] References Cited UNITED STATES PATENTS 2,892,968 6/1959 Kallmann et a1 178/7.6X 3,121,861 2/1964 Alexander 250/213X 3,449,582 6/1969 Sackinger 250/213V.T.

Primary Examiner-James W. Lawrence Assistant Examiner- C. M. Leedom Attorney-Frank R. Trifari ABSTRACT: A particle detector system comprising a channel image intensifier having a planar output electrode subdivided into an array of parallel electrode conductors with each conductor connected to a separate terminal, an array of parallel target conductors lying in a plane parallel to the electrode conductors on the output side of the device and orientated perpendicular to the electrode conductors, and a second set of terminals each of which is associated with one of the target conductors. The target conductors may be associated with luminescent elements to generate a two-dimensional visual display.

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INVENTOR. BRIAN w. MANLEY AGENT PATENTEU m SHEET 3 0F 3 INVENTOR, BRIAN w. MANLEY AGEN IMAGE INTENSIFIER INCLUDING MATRIX F ELONGATED ELECTRODES FOR LOCATING OUTPUT SIGNALS GEOMETRICALLY This invention relates to electronic image intensifier devices. More particularly the invention relates to channel intensifier devices and to electronic imaging tubes employing such devices. Such devices are secondary-emissive electronrnultiplier devices comprising a matrix in the form of a plate having a large number of elongated channels passing through in the direction of, its thickness, and both sides of the matrix separated by its thickness are covered by conductive layers which act respectively as input and output electrodes Such intensifier devices are well known and when incorporated in electronic imaging tubes, a potential difference is applied between the two electrode layers of the matrix so as to set up an electric field which establishes a potential gradient along the channels created by current flowing through the bulk material of the matrix or if such material has a very high resistance through resistive surfaces fonned inside the channels. Secondary-emissive multiplication takes place in the channels and the output electrons may be acted upon by a further accelerating field which may be set up between the output electrode and a suitable target, for example a luminescent display screen. a v

It is an object of the present invention to employ a channel intensifier device for detecting particles or radiation quanta and determining the distribution thereof over a given area. Such distribution may, in some cases, be sufficiently complex to represent a crude form of imaging in which the definition and the number of picture elements are very low as compared with imaging applications of the broadcast television type. The invention is also applicable in cases where, from a low particle rate (defined below) a picture of fairly high definition can be built up gradually with the aid of additional storage means, for example gamma radiography for medical purposes.

The invention provides a particle or radiation quantum detector system comprising a channel intensifier device as defined above wherein the output electrode is substantially planar and is subdivided into an array of parallel electrode conductors with each conductor connected to a separate terminal, an array of target conductors lying substantially in a plane parallel to the plane of said electrode conductors on the output side of said device which target conductors are parallel to each other and orientated at, or approximately at right angles to the direction of the electrode conductors, and a second set of terminals each of which appertains to one of said target conductors.

In such an arrangement the array of electrode conductors replaces the more normal form of output electrode which is usually (but not always) described as a single electrically continuous layer. Similarly, the present array of target conductors replaces the continuous conductive target layer which is more usually provided on a phosphor screen on the output side of a channel intensifier device.

p A particle or radiation quantum detector system according to the invention can be combined with an output circuit arrangement comprising a separate charge detector for each electrode conductor and a separate charge detector for each target conductor, and means whereby each event causes a simultaneous response in one of the electrode detectors and in one of the target detectors so as to provide, together a coordinate position for the event. This mode of operation is suitable for applications in which there is a low particle or quantum rate, i.e., there are so few events that the chance of two simultaneous events can be ignored. If the rate is higher, means can be provided (as will be described) to inhibit the system when ambiguities arise as to the number and position of events for example, two simultaneous events which are spaced apart in both the X and the Y directions will identify four (instead of two) electrode intersections between two electrode conductors and two target conductors (it is convenient to use the term intersection" even though the two arrays of conductors are spaced apart.)

In addition to the individual charge detectors it may in some cases be desirable to provide one general discriminator either in a common supply circuit of the target detectors or in that of the electrode detectors for purposes such as determining whether the magnitude of an event :is greater or smaller than a given datum.

The target conductors may or may not be associated with luminescent elements to provide a two-dimensional visual display of the positions of detected particles in addition to the counting and/or recording action of the circuit actuated by the output signals. If this is done, the luminescent elements may or may not form a continuous phosphor screen and they may be provided on the side of the target array remote from the channel plate (if so, the array can be in the form of aluminum backing strips).

Embodiments of the invention will now be described by way of example with reference to the drawing in which:

FIG. 1 shows schematically a system according to the present invention arranged within an evacuated envelope;

FIG. 2 shows a detail of the output surface of the matrix;

FIG. 3 shows schematically part of a more complete arrangement;

FIG. 4 shows the arrangement completed with a cathode ray tube; and

FIG. 5 shows a schematic representation of the electric circuit.

The envelope comprises a channel intensifier device I together with a target system TaTn. The channel intensifier device 1 includes an input electrode El covering its input face and an output electrode composed of an array of parallel electrode conductors in the form of strips E2a, E2b-E2n. Each of the latter is connected through a separate charge detector or amplifier to a common supply source Bl. For simplicity all these electrode detectors are shown as a combined electrode detector system ED.

In some applications input radiation can be imaged on to the device I by an optical system and the system may require a photocathode on the input side of the channel plate I either in contact therewith or spaced therefrom as described in prior specifications.

By contrast, in diagnostic X-ray radiography or gamma-ray autoradiography it may not be necessary to use a photocathode since gamma or X-ray photons can cause electron emission from the material of the matrix which is usually made of a suitable glass or combination of glasses. Moreover, optical systems are not used in these applications and for this reason the body to be examined is usually placed as close to the channel intensifier device as is practicable, and this is indicated schematically at B. As an example of this, in the case of gamma-ray radiography, the body B which is to be examined can be placed as close as possible to the device I and I emits a pattern of gamma'radiation via a lead matrix collimator (not shown) on to the input face of the device I. Whenever a gamma particle enters the material of the channel plate, one or more electrons may be produced and may escape into a channel. Then electron multiplication can take place in the manner well known. A pulse of secondary electrons will emerge from the output end of the said channel and in so doing will provide an output signal in the detector corresponding to the particular electrode strip.

FIG. 1 can also be taken as illustrating the case in which the input radiation is constituted by X-rays irradiating the body B from a point source (not shown). In conclusion, FIG. 1 can be taken as illustrating both this case and also the use of gamma rays directed from the body B to the channel plate via a lead collimator.

The target is constituted by a set of parallel target conductors Ta, Tb --Tnwhich lie in a direction which is at, or approximately at, right angles to the direction of the electrode strips, for example in a vertical direction if the electrode strips E2a, E2b,E2n are horizontal. These target conductors are also each connected to a separate charge detector or amplifier, but said detectors are all shown for simplicity as a combined target detector system TD connected to a common source of accelerating potential B2.

Although it is not essential to have an extremely regular disposition of the channels in the channel plate nor to have an extremely accurate registration between individual output electrode conductors and the individual channels, it is possible to have one row of channels corresponding to each one of the electrode strips-as shown in FIG. 2. Alternatively it is possible to have more than one row of channels corresponding to one electrode strip, or just a statistically uniform band of channels covered by each electrode strip if the channel structure is materially finer than the desired resolution.

The arrangement of FIGS. 1 and 2 is shown more clearly in FIG. 3 where, for the sake of clarity, only a very small number of electrode conductors and target conductors is shown, namely four of each. As will be seen, each of the electrode conductors is a strip E2a-E2d connected through a separate charge detector EDa-EDd. Similarly each of the target conductors Ta-Tdis a strip connected through a separate charge detector TDa-TDd. If a particle enters a particular channel Cx it will cause an output of secondary electrons as shown and it will also cause an output signal in the electrode detector EDa and also an output signal in the target detector TDc. These two signals, if collated will give the position of the event in channel Cx as a pair of coordinates.

This collation can be carried out e.g. with the aid of a ferrite core store which can be used as the source of information from which a C.R.T. display can be generated.

Alternatively the collated coordinate information can be directly fed to a cathode-ray storage tube in order to build up therein and display the information.

Both these arrangements are illustrated schematically in FIG. 4 where the unit M may be a ferrite core store with readout means connected to a conventional C.R.T. display tube. For the alternative arrangement, the unit M can be a ferrite core matrix used only for collation while the CRT is a display tube of the storage type.

A circuit arrangement shown in greater detail, in FIG. 5 includes inhibiting means of the kind referred to previously.

Thecharge detectors are constituted by the stages of two shift registers. When a pulse of charge is registered on both horizontal and vertical arrays, a digit is stored in each shift register in the stages corresponding to the row position and column position of the event. The readout process then entails the shifting of the contents of the registers to the right in such manner as to simulate line and frame scanning. Thus in each register position of the column register, it is necessary to cycle completely the row register. Therefore the shift pulses to the column register occur with a frequency a factor n lower than the row shift pulses (i n is equal to the number of rows) and the cycling continues until the stored digits appear at the right hand end of the registers at the same instant. A bright-up pulse is then produced on the writing beam control of an integrating storage display tube which is being scanned in synchronism with the register shifts. In detail, the operation is as follows.

Charge emerging from a channel and striking a target (or column) strip will produce a pulse of charge in that strip and also in the electrode (or row) strip containing the channel. These pulses will be similar in magnitude but opposite in sign since one is due to electrons leaving and the other is due to electrons arriving. The purpose of exclusive OR 1 and exclusive OR 2 is to ensure that there is only one pulse of charge from the rows and one from the columns. In the event of there being either no pulse from one of the sets of strips, or more than one from one or both sets, AND gate 3 produces no output and AND gate 4 does not produce a start pulse. Thus the unwanted signal is ignored. This is to guard against spurious events and to inhibit the system against two simultaneous events which the system cannot analyze unambiguously.

In the event that there is only one row pulse and one column pulse, the analysis proceeds as follows. The column pulse produces a pulse from exclusive ORgate 5 which results in a start ulse from AND gate 4. This pulse acts via unit 6 (a J-K fhpop) to open the switch 7 so preventing further pulses (arriving during the analysis of the present pulse) from producing disturbing signals. The start pulse is also'fed into AND gate 8 and thereby results in a sequence of clock pulses to the shift registers, so cycling them until each produces an output pulse into AND gate 9, when a bright-up gating pulse is producedon the writing gun of the storage c.r.t. In addition, a stop pulse goes to the unit 6, so stopping the register cycling process and clearing the registers, and closing the switch 7 to await the next signal pulse (flip-flop 6 is of the known bistable J-K type having always 0 at one output and 1" at its other output, these outputs being reversed when the unit changes state).

The synchronized operation of the scan generator is ensured by a frame-trigger and line sync (FL) unit 11 which is controlled by clock pulses which have been divided by-n in the divider unit 10.

In space applications it may not be desirable to have an evacuated envelope for the channel plate and target system as shown in FIG. 1, and therefore the electrode and target conductor terminals, referred to throughout this Specification, may be circuit connections or connectors rather than terminals formed in the wall ofa tube.

Iclaim: t

l. A particle or radiation quantum detector system comprising a channel intensifier device comprising input and output electrodes separated by an insulating matrix having elongated channels therein extending between said input and output electrodes, the walls of said channels being secondary emissive, said output electrode being substantially planar and being subdivided into an array of parallel electrode conductors with each conductor connected to a separate terminal, an array of target conductors lying substantially in a plane parallel to the plane of said electrode conductors on the output side of said device which target conductors are parallel to each other and orientated at, or approximately at, right angles to the direction of the electrode conductors, and a second set of terminals each of which appertains to one of said target conductors.

2. A detector system as claimed in claim 1 contained in an evacuated envelope and wherein the electrode conductor terminals and the target conductor terminals are secured on said envelope.

3. A detector system as claimed in claim 2 wherein the target conductors are associated with luminescent elements to provide a two-dimensional visual display of the positions of detected particles.

4. A detector system as claimed in claim 1 wherein an output circuit arrangement comprises a separate charge detector for each electrode conductor and a separate detector for each target conductor, and means whereby each event causes a simultaneous response in one of the electrode detectors and in one of the target detectors so as to provide, together, a coordinate position for the event.

5. A combination as claimed in claim 4 including means for..

Claims (5)

1. A particle or radiation quantum detector system comprising a channel intensifier device comprising input and output electrodes separated by an insulating matrix having elongated channels therein extending between said input and output electrodes, the walls of said channels being secondary emissive, said output electrode being substantially planar and being subdivided into an array of parallel electrode conductors with each conductor connected to a separate terminal, an array of target conductors lying substantially in a plane parallel to the plane Of said electrode conductors on the output side of said device which target conductors are parallel to each other and orientated at, or approximately at, right angles to the direction of the electrode conductors, and a second set of terminals each of which appertains to one of said target conductors.

2. A detector system as claimed in claim 1 contained in an evacuated envelope and wherein the electrode conductor terminals and the target conductor terminals are secured on said envelope.

3. A detector system as claimed in claim 2 wherein the target conductors are associated with luminescent elements to provide a two-dimensional visual display of the positions of detected particles.

4. A detector system as claimed in claim 1 wherein an output circuit arrangement comprises a separate charge detector for each electrode conductor and a separate detector for each target conductor, and means whereby each event causes a simultaneous response in one of the electrode detectors and in one of the target detectors so as to provide, together, a coordinate position for the event.

5. A combination as claimed in claim 4 including means for inhibiting the system whenever two or more events occur simultaneously at different coordinate positions.

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