US3320425A - Photomultiplier tube circuit with substantially linear output - Google Patents

Photomultiplier tube circuit with substantially linear output Download PDF

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US3320425A
US3320425A US323632A US32363263A US3320425A US 3320425 A US3320425 A US 3320425A US 323632 A US323632 A US 323632A US 32363263 A US32363263 A US 32363263A US 3320425 A US3320425 A US 3320425A
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anode
circuit
cathode
dynode
source
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Moatti Paul Joseph
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Centre National de la Recherche Scientifique CNRS
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Centre National de la Recherche Scientifique CNRS
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J43/00—Secondary-emission tubes; Electron-multiplier tubes
    • H01J43/04—Electron multipliers
    • H01J43/30—Circuit arrangements not adapted to a particular application of the tube and not otherwise provided for

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  • the present invention relates to a photomultiplier tube circuit enabling a photomultiplier tube to supply a substantially linear output current, both as a function of the amplitude and the frequency of the input signal in D.C. and in AC. operation.
  • Photomultiplier tubes also known as electronmultiplier phototubes
  • dynodes secondary emissive electrodes
  • Such apparatus comprise an anode and a cathode between which are arranged a plurality of secondary emissive electrodes called dynodes, as will be more specifically detailed hereinafter, and are conventionally energized by means of a single high-voltage stabilized power source and a potentiometer bridge consisting of resistors having equal or unequal resistance values, the terminals of said bridge being respectively connected to the terminals of said source, and to the cathode and the anode, while the dynodes are respectively connected to the connecting points of the successive resistors of said bridge.
  • the currents carried by the electrodes are hereinafter referred to as i for the anode, I ⁇ ; for the cathode, and i i i i for the respective dynodes, and the load currents carried by the resistors in the bridge are hereinafter referred to as 1 I I I respectively. See FIGURE 1.
  • Such a conventional photomultiplier tube circuit has however the serious drawback of not providing a linear amplification of the anodic pulse amplitude, as shown for the first time by J. F. Rafile, E. J. Robbins (Proo Phys. Soc. 1952, B65, No. 5, 320-4).
  • the cause of this objectionable non-linearity phenomenon was ascribed to small space charges produced by the pulses in the vicinity of the dynodes, or to the effects of the dynode currents which give rise to dynode potential variations.
  • a pulse amplification if achieved non-linearily by a conventional photomultiplier tube, results, in particular, in a distortion of the pulse height and in a broadening of the radiation lines, when the intensity of the incident radiations increases.
  • the gain distortion is a function of the radiation energy and of the activity of the source, even if the high-voltage source is perfectly stabilized.
  • the bridge therefore does not operate any more as a simple potentiometer. It follows that the gains of the stages are in operation different from the gains at rest, resulting in an amplitude distortion of the anode current, i.e., of the overall gain of the photomultiplier tube. It has also been shown experimentally that in the conventional circuit arrangement, the photomultiplier tube does not constitute a linear current amplifier, even for Weak currents, due to the sole effect of the dynode currents. The overall distortion as a function of the amplitude of the anode current may reach 40% of the total gain when the anodic current intensity i is close to the rest current l The near perfect stabilization of the high-voltage D.C.
  • the first stage of the photomultiplier circuit displayed substantial overvoltages resulting in a return bombardment from the ions and, consequently, in an increase of the background noise of the photomultiplier tube and even in possible breakdowns. Finally, it is in the anodic stage that the highest voltage drop takes place in operation, the said stage also indirectly contributing to the increase of the photomultiplier gain.
  • the gain variations change as a function of the amplitude and of the count rate and result in an absence of linearity (shift and broadening of radiation lines), even if the high-voltage source is perfectly stabilized.
  • the main object of the present invention is to provide a circuit adapted to achieve a substantial linearity of the cathode current amplification independently from the cathode current or pulse amplitude, from the counting rate thereof and from the frequencies composing the cathode signal.
  • the circuit of a photomultiplier tube comprises two stabilized high-voltage sources, and, connected in series, the first of said sources feeding the cathode and a first group of N-q dynodes as counted from the cathode, q being an integer smaller than N, and the second source feeding the last dynode of the said first group, the groups of the remaining q dynodes and the anode, the output being at the dynode common to both high voltages and including a RC-circuit comprising a resistor and a capacitor, both of which are adjustable.
  • the photomultiplier tube circuit should also include, as above-mentioned, by-pass capacitors connected in parallel across the feed resistors in the bridge. At the dynode output and for the AC. amplification, the time constants of the RC circuits of the general supply circuit and at the output of the common dynode should be identical.
  • the potential of the high-voltage sources is constant under load.
  • the RC circuit of the common dynode functions both as a regulating circuit and as a load circuit.
  • the resistance value of the load resistor at the output of the common dynode provides the DC regulation, while the associated capacitor intervenes in the case of AC. or pulse operation.
  • the value of the said load resistance may be determined, as will be seen below, by
  • the capacitance value of the capacitor cooperating with said resistance is determined by the time-constant equation, after calculating the load resistance and once the capacitance C of each stage of the supply bridge has been measured.
  • the cathode and all the dynodes of the photomultiplier tube are fed by the first high-voltage I source, while the second high-voltage source feeds only the last dynode before the anode and the anode itself at which the output is taken.
  • FIGURE 1 illustrates a conventional photomultiplier circuit
  • FIGURE 2 is a diagrammatic circuit arrangement of a photomultiplier tube according to the present invention, incorporating two high-voltage sources and the output being at the dynode common to both sources.
  • FIGURE 3 is a graph showing the variation of the load resistance R on the dynode output in the circuit illustrated in FIGURE 2.
  • FIGURE 4 is a graph showing the output distortion AG /G as a function of the ratio a of the amplitude of the anodic current to the rest current I and of the number q of independently fed dynodes.
  • FIGURE 5 illustrates an alternative embodiment of the circuit according to the invention.
  • a conventional photomultiplier tube circuit comprises a photomultiplier tube having an anode A, N dynodes D D D and a cathode K, cathode K, anode A and the dynodes are energized by voltage produced by a high-voltage source HT, which 4 is uniformly or non-uniformly distributed between the various stages of the tube through resistors R R R forming a bridge.
  • By-pass capacitors C C C C may be connected in parallel with resistors R R R R respectively to form R-C circuits, as shown in solid lines in the last circuit stages and in dotted lines in the first stages, and a capacitor C cooperates similarly with a resistance R connected on the feeding line of anode A. All the mentioned above capacitors are such that their capacitance values are not smaller than those of the residual capacitances in the circuit arrangement.
  • the anode current is indicated by i and the currents carried by the dynodes D D D D by i i i respectively, the cathode current being designated by i;;.
  • the load currents carried by resistances R R are indicated, respectively, by I I and the load current produced by the high-voltage source HT, by I.
  • the photomultiplier circuit illustrated in FIGURE 2 also comprises a photomultiplier having an anode A, a cathode K and N dynodes designated by D D respectively, a feeding resistor bridge network comprising resistors R R R which may have equal or different resistance values, as well as capacitors C C C shunted across said resistors, whilst the anode may also comprise a R C -circuit.
  • a first source (not shown) of stabilized high voltage HT feeds cathode K and the N-q first dynodes as counted from the cathode, q being an integer lower than N, and one terminal thereof is therefore connected to cathode K while the other is connected to the connection point of the feeding lead of dynode D with the said resistor bridge, said connection point possibly may be grounded, and a second source (also not shown) of stabilized high voltage HT feeds dynode D the remaining q dynodes and anode A, one of the terminals thereof being therefore connected to said connecting point while the other is connected to anode A, the said two sources being in series.
  • the outlet is taken on the dynode D common to both said sources and includes an R-C circuit comprising an adjustable resistor R and an adjustable capacitor C It has been established that the necessary condition for achieving a substantially linear regulation of the output of the tube in the case of a DC. feed is given by relation 1) hereafter between the values of resistance R the supply resistance R of stage (Nq), the number q (or the number N-q, which the order of the selected dynode common to both feeding sources) and 6, which is the average stage gain at rest, of the photomultiplier tube:
  • FIGURE 3 there is shown the network of curves Showing in ordinates the values of ratio Rd/R plotted against the values of n-q in abscissae, according to various values of 6. Use may be made of the nomogram in FIGURE 3 to determine with a good approximation the value of resistance R In the case of detection of scintillations from a radioactive source, requiring a very sharp adjustment, the intensity of the radioactive source may be varied, for instance by removing the same at a distance. In order for the adjustment to be satisfactory, it is necessary that the amplitudes of the photoelectric peaks do not vary during the movement of the source.
  • the regulation may be readily extended to the case of an AC. or variable signal by defining the equality of the,
  • the value of capacitor C may be obtained, after measurement of the capacitances of the successive stages of the supply bridge by means of above relation (2).
  • the fine adjustment of C may be effected by varying the pulse amplitude in a broad range by means of radioactive sources having widely different radiating energies. For the adjustment to be satisfactory, it is necessary that the photoelectric peak amplitudes be proportional to the energies transmitted by said sources.
  • the instantaneous current regulation achieved by the circuit according to the invention holds true for each frequency component and may be effected for the nonperiodic current and for pulse operation, this feature being a highly desirable fundamental property of the photomultiplier circuit according to the invention.
  • the graph of FIGURE 4 may be used to calculate the regulation provided by the photomultiplier as shown in FIGURE 2, in said graph, the number N q has been plotted on the abscissae (order of the dynode selected for the output) and on the ordinates the following expression:
  • AG /G is the distortion 6 is the average gain at rest a is the approximate ratio of the amplitude of the anodic current to that of the rest current 1 i.e., more exactly:
  • z' cathode current intensity G gain of the photomultiplier at rest.
  • time constant R C may not have any desired value, since it is limited by the known condition:
  • the RC time constant must be matched to the maximum frequency of the input signal.
  • the rapidity of response of the photomultiplier is thus essentially connected to its method of supply.
  • the resistances R may be reduced, thus increasing the rest current I and consequently the amplitude of the output current.
  • the drawback lies in that the amplitude of the dynode output current is very much lower than that of the anodic current. In fast operating electronics, it is necessary to have a high current, without amplification subsequent to the photomultiplier, which therefore commands the provision of the anode output.
  • FIGURE 5 of the drawings shows an alternative embodiment of the circuit according to the invention, incorporating such an anodic output.
  • q is zero
  • there is no dynodic circuit R -C which would introduce a strong distortion in the dynode and in the anode
  • voltage HT from the first source feeds cathode K and all the dynodes D D
  • voltage HT from the second source feeds only dynode D and the anode.
  • Such a circuit provides, in DC. operation, a satisfactory linearity with a conventional photomultiplier. This holds also true in AC. operation if the time constants of the bridge network are all equal, a high common time constant being desirably selected (for instance about microseconds). For fast measurements, the higher amplitude components are those of higher frequency: they are therefore limited by the capacitances of the bridge (for instance 1000 pf.).
  • modern photomultipliers may provide an anodic current which is substantially higher than the bridge current I
  • high-voltage pulses will advantageously be used, which, in this case, are current pulses, the supply voltages being conventional.
  • the time constants of the bridge should obviously be all equal, but in order to maintain the steep leading edge of the supply pulses, very short time constants should be selected (for instance 10" seconds).
  • a photomultiplier tube has been tested, connected in a dynode-output circuit according to the invention, having the following particulars:
  • the scaling ratio of the 'y rays emitted by a sample of cobalt-60 was caused to vary from 250 to 11,000 HZ., and a good agreement of the corresponding energy spectra was obtained.
  • the invention therefore provides a solution to the problem of linearity of the photomultiplier tubes, both in amplitude and in frequency, over the whole passband of the presently known apparatus, even the speediest.
  • a photomultiplier tube circuit comprising a photomultiplier tube having an anode, a cathode, and a number N of dynodes arranged in succession between said cathode and said anode, first and second stabilized high-voltage sources each having two terminals, one terminal of said first source being connected to one terminal of said second source for series grouping of said sources, said reciprocally connected terminals of said sources being further connected through a parallel resistor and capacitor which comprise a regulation and output circuit to the dynode of order (N-q) as counted from said cathode, q being an integer smaller than -N which may be zero, the other terminal of said first source being connected to said cathode and the other terminal of said second source being connected to said anode, and a resistor bridge comprising one resistor connected between said cathode and the dynode adjacent to said cathode, a plurality of further resistors, each two successive dynodes being connected by one of
  • a photomultiplier tube circuit comprising a photomultiplier tube having an anode, a cathode, and a number N of dynodes arranged in succession between said cathode and said anode, a first and a second stabilized high-voltage source each having two terminals, one terminal of said first source being connected to one terminal of said second source for series grouping of said sources, said reciprocally connected terminals of said sources being further connected to the dynode of order (N q) as counted from said cathode, q being an integer smaller than N which may be zero, the other terminal of said first source being connected to said cathode and the other terminal of said second source being connected to said anode, a chain of (N+1) fixed resistances forming a bridge network of said cathode, each of said N dynodes and said anode, respectively, an anode resistance connected between said anode and said bridge to form a non-linear anode circuit, and an output
  • a photomultiplier tube circuit comprising a photomultiplier tube having an anode, a cathode, and a number N of dynodes arranged in succession between said cathode and said anode, a first and a second stabilized high-voltage source each having two terminals, one terminal of said first source being connected to one terminal of said second source for series grouping of said sources, said reciprocally connected terminals of said sources being further connected to the dynode of order (Nq) as counted from said cathode, q being an integer smaller than N which may be zero, the other terminal of said first source being connected to said cathode and the other terminal of said second source being connected to said anode, a chain of (N +1) fixed resistances forming a bridge network with said cathode, each of said N dynodes and said anode, respectively, each resistor in said chain having a capacitor connected in parallel therewith, each pair of said resistors and capacitors thereby forming
  • a photomultiplier tube circuit comprising a photomultiplier tube having an anode, a cathode, and a number N of dynodes arranged in succession between said cathode and said anode, a first and a second stabilized high-voltage source each having two terminals, one terminal of said first source being connected to one terminal Of said second source for series grouping of said sources, said reciprocally connected terminals of said sources being further connected to the dynode adjacent to said anode, the other terminal of said first source being connected to said cathode and the other terminal of said second source being connected to said anode, and a resistor bridge comprising one resistor connected between said cathode and the dynode adjacent to said cathode, a plurality of further resistors, each two successive dynodes being connected by one of the resistors in said plurality of further resistors, and an output circuit connected to said anode and including a resistor.
  • a photomultiplier tube circuit comprising a photomultiplier tube having an anode, a cathode, and a number N of dynodes arranged in succession between said cathode and said anode, a first and a second stabilized high-voltage source each having two terminals, one terminal of said first source being connected to one terminal of said second source for series grouping of said sources, said reciprocally connected terminals of said sources being further connected to the dynode adjacent to said anode, the other terminal of said first source being connected to said cathode and the other terminal of said second source being connected to said anode, and a resistor bridge comprising one resistor connected between said cathode and the dynode adjacent to said cathode, a plurality of further resistors, each two successive dynodes being connected by one of the resistors in said plurality of further resistors; each resistor in said bridge having a capacitor connected in parallel therewith, each pair of said resistors and

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  • Measurement Of Radiation (AREA)
US323632A 1962-11-15 1963-11-14 Photomultiplier tube circuit with substantially linear output Expired - Lifetime US3320425A (en)

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FR915433A FR1354838A (fr) 1962-11-15 1962-11-15 Photomultiplicateur à amplification linéaire

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CH (1) CH441516A (en:Method)
FR (1) FR1354838A (en:Method)
GB (1) GB1009537A (en:Method)
NL (1) NL300596A (en:Method)

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FR3069925B1 (fr) 2017-08-01 2023-12-08 Bertin Technologies Sa Dispositif de collecte et de detection d'aerosols

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2434405A (en) * 1944-06-29 1948-01-13 Farnsworth Res Corp Television background control system
US2571838A (en) * 1949-12-03 1951-10-16 Westinghouse Electric Corp Control means for radiation detectors
US2583143A (en) * 1948-12-17 1952-01-22 Westinghouse Electric Corp Sensitivity regulator for photomultiplier tubes
US2758217A (en) * 1951-05-17 1956-08-07 Perforating Guns Atlas Corp Automatic scintillation counter
US2822479A (en) * 1954-02-25 1958-02-04 William W Goldsworthy Radiation counter
US3004167A (en) * 1958-09-12 1961-10-10 Atomic Energy Authority Uk Nuclear particle discriminators
US3076896A (en) * 1961-05-01 1963-02-05 Lockheed Aireraft Corp Voltage supply and control system
US3089959A (en) * 1960-05-02 1963-05-14 Philco Corp Self-limiting photomultiplier amplifier circuit
US3243588A (en) * 1962-08-17 1966-03-29 Serge A Scherbatskoy Scintillation detector system using a white light as a standard to stabilize the system

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2434405A (en) * 1944-06-29 1948-01-13 Farnsworth Res Corp Television background control system
US2583143A (en) * 1948-12-17 1952-01-22 Westinghouse Electric Corp Sensitivity regulator for photomultiplier tubes
US2571838A (en) * 1949-12-03 1951-10-16 Westinghouse Electric Corp Control means for radiation detectors
US2758217A (en) * 1951-05-17 1956-08-07 Perforating Guns Atlas Corp Automatic scintillation counter
US2822479A (en) * 1954-02-25 1958-02-04 William W Goldsworthy Radiation counter
US3004167A (en) * 1958-09-12 1961-10-10 Atomic Energy Authority Uk Nuclear particle discriminators
US3089959A (en) * 1960-05-02 1963-05-14 Philco Corp Self-limiting photomultiplier amplifier circuit
US3076896A (en) * 1961-05-01 1963-02-05 Lockheed Aireraft Corp Voltage supply and control system
US3243588A (en) * 1962-08-17 1966-03-29 Serge A Scherbatskoy Scintillation detector system using a white light as a standard to stabilize the system

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NL300596A (en:Method)
GB1009537A (en) 1965-11-10
CH441516A (fr) 1967-08-15
FR1354838A (fr) 1964-03-13

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