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2,594,703 424-21%-4 April 29, 1952 L. F. WOUTERs 2,594,703 PHOTOMULTIPLIER TUBE CIRCUIT Filed March 7, 195l. 62 222 34 A2 SQUARE WAVE VOLTAGE GENERATOR INVENTOR, LOUIS F WOUTERS BY 424-21%-4---- ATTORNEY. Patented Apr. 29, 1952 2,594,703 UNITED STATES PATENT OFFICE 2,594,703 PHOTOMULTIPLERTUBE CIRCUIT Louis F. Wouters, Oakland, Calif., assignor to the United States of America as represented by the United States Atomic Energy Commission Application April 17, 1951, serial No. 221,396 4 Claims. (CL 250-207) 2 This invention relates to a photomultiplier prising a plurality of similar resistors and tube circuit and more particularly to a method similar capacitors 8, is connected between the and apparatus for increasing the output of a cathode and penultimate dynode with intermedi photomultiplier tube. ate connections thereof connected to the first In many circuits utilizing photomultiplier tubes s seven dynodes, so that a resistor and a capacitor it is necessary to amplify the output of such are parallel-connected between each of such elec tubes so that they may be applied to auxiliary trodes. In the present embodiment of the inven circuits. Thus, if the source of light is faint, tion the penultimate dynode is connected directly the electron multiplication of the photomulti to ground by a lead 2 while the cathode is con plier tube may be insufficient to raise the output () nected to one side of a storage capacitor 22 by to a readily useful level requiring expensive, as a lead 23. The other side of the capacitor 22 is well as, extensive amplifier circuits. In some connected to the anode of a triode type tube 26, instances the desire to maintain the pulse shape the Cathode of which is grounded. and resolution time of the output requires addi As a means for supplying unidirectional volt tionally complex pulse forming and shaping am 5 age to the photomultiplier tube 3 there is pro plifiers. vided a conventional power supply 3. having. a The present invention provides a photomulti plurality of output voltages. For purposes of plier tube circuit which overcomes the above illustration the values of such output voltages outlined difficulties by operating the photomulti will hereinafter be numerically identified by the plier tube at voltages many times the normal op 20 voltage existing with respect to a grounded ter erating voltages for such tube. The foregoing minal 32, but should not be understood as limit is made practical by pulsed operation which pre ing the circuit to the exact voltages set forth. vents deleterious overloading of the photomulti A negative terminal 33 having a value of -100 plier tube. - volts is connected to the control grid of the tube It is therefore an object of the present inven 25 26 through a biasing resistor 36. A positive 'ter tion to provide a new and improved photomulti minal 35 having a value of -2000 voltS. is con plier tube circuit. nected through a dropping resistor 36 to the Another object of the invention is to provide anode of the tube 26 to supply operating voltage a photomultiplier tube circuit which may di thereto and also a charging voltage to the rectly drive an auxiliary circuit. 30 capacitor 22. A second positive terminal 37 Still another object of the invention is to having a value of -250 volts is connected to provide a photomultiplier tube circuit having a the final dynode of the tube 3 to Supply a Suit pulsed power supply therefor to provide greater able operating potential thereto through a drop amplification through such tube. ping resistor 38. A third positive terminal 39 A further object of the invention is to provide 35 having a value of --500 volts is connected to a photomultiplier tube circuit which is simple in the anode of the tube 13 through a dropping construction and which eliminates the necessity resistor 40 to supply a suitable operating poten of amplifiers in the output circuit. - tial thereto. ... Still further objects and advantages of the It will be seen that with the power supply 3 invention will be apparent from the following 40 suitably energized that the capacitor 22 will be description and claims considered together with come charged to the value of the power Supply the accompanying drawing which is a schematic terminal 35, that is --2000 volts, but that the side wiring diagram. - of the capacitor connected to the cathode of the Referring to the drawing in detail there is tube 3 is at ground potential. Now, if the posi provided a source of light, Such as a Scintilla 45 tively charged side of the capacitor 22 is Sud tion crystal f, placed in the path of a beam of denly connected to ground, the voltage of the charged particles 2. Disposed adjacent the cathode of the tube 3 will be effectively lowered crystal it is a photomultiplier tube f3 in Such to a value of -2000 volts which will be evenly position that light from the crystal falls upon distributed across the resistors f to ground, the light-sensitive cathode of the tube. The 50 Thus the photomultiplier tube 3 will be opera photomultiplier tube 3, as illustrated in the tive to pass electrons between the cathode and drawing, has nine dynodes disposed between the. anode by way of the dynodes upon activation of cathode and anode and it will be readily ap the cathode by light striking thereon. To ac parent that other types of photomultiplier tubes complish Such mode of operation a Square Wave may be substituted. A voltage divider 6, com 55 voltage generator 46 of conventional design and 2,594,708 3 4 having an output sufficient to overcome the the other side of the resistor 52 by the capacitor negative grid bias of the tube 26 is connected 57 the unidirectional voltages at such electrodes between the control grid and cathode thereof. are blocked and only the varying voltage caused The duration of the square wave output of the by the electron flow is passed. Such varying generator 46 should be short as compared to the voltage establishes a push-pull voltage across the time constant of the capacitor 22 and the re resistor 52 and thereby causes deflection of the sistance of the resistors so that the high Volt electron beam of the oscilloscope 59. Thus a age across the elements of the photomultiplier pattern of the magnitude and duration of the tube will not be damaged by prolonged over light scintillation at the crystal is formed on voltage. The repetition rate of the generator 46 O the Screen of the Oscilloscope 59. is not critical, but should be sufficiently rapid to From the foregoing it will be readily apparent energize the circuit for each Scintillation of the that any desired light source may be utilized in crystal in the present embodiment of the in the position of the crystal . It will also be vention and still have an average value which readily understood that numerous types of loads is not in excess of the voltage rating of the may be connected to the output of the photo tube f3. multiplier tube to be driven thereby, in the place The output of the photomultiplier tube 3 may of the OScilloscope 59. be taken from between the final dynode and While the salient features of this invention anode thereof and will be of sufficient magnitude have been described in detail with respect to one to directly drive an auxiliary circuit. As illus 20 embodiment it will, of course, be understood that trated in the drawing a lead 5 is connected to numerous modifications may be made within the the final dynode of the tube 3 and coupled to Spirit and Scope of the invention and it is there one end of a center-grounded resistor 52 by a ca fore not desired to limit the invention to the exact pacitor 53. A lead 56 is similarly connected to details shown except insofar as they may be de the anode of the tube 3 and coupled to the other ; fined in the following claims. end of the resistor 52 by a capacitor 57. Thus a What is claimed is: push-pull voltage is developed across the re 1. In a photomultiplier tube circuit, the comi sistor 52 which may then be impressed between bination comprising a source of light, a photo the vertical deflecting plates of an oscilloscope multiplier tube having an anode, a plurality of 59. The oscilloscope 59 is equipped with a power dynodes, and a cathode with substantially low Supply 6 to energize the electron gun and to values of operating voltages, said tube being dis energize the Sweep generator 62 which is in turn posed adjacent Said source to receive light there connected to the horizontal deflecting plates. from, a voltage divider having a plurality of Now consider the operation of the present in equally Spaced taps connected between the penul wention, as described above, with the power Sup timate dynode and said cathode with the taps plies 3 and 6 and the square wave generator respectively connected to the dynodes, said penul 46 suitably energized. Under such condition a timate dynode being connected to ground, said Square Wave of voltage at the output of the gen cathode being connected to a storage capacitor, erator 46 renders the triode tube 26 conductive power supply means having a grounded terminal, to ground the positively charged side of the a positive terminal connected to said capacitor capacitor 22. Thus the cathode of the photo for charging the capacitor to a high value of multiplier tube f3 is biased to -2000 volts.
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