CN104573252A - Calculation method of transient output characteristics of photomultiplier - Google Patents
Calculation method of transient output characteristics of photomultiplier Download PDFInfo
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- CN104573252A CN104573252A CN201510025271.7A CN201510025271A CN104573252A CN 104573252 A CN104573252 A CN 104573252A CN 201510025271 A CN201510025271 A CN 201510025271A CN 104573252 A CN104573252 A CN 104573252A
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Abstract
The invention discloses a calculation method of transient output characteristics of a photomultiplier, and relates to accurate calculation of quantity of electric charge of an output signal and accurate expression of time distribution of the photomultiplier. The method has four characteristics as that 1, the quantity of electric charge of an incident light signal which is converted into the electric signal can be accurately described, and the characteristic of a transient signal output by the photomultiplier in the time domain can be accurately described; 2, the output results are continuous in the time domain, so that the characteristics of the transient signal of the photomultiplier can be accurately described in the frequency domain; 3, the characteristic parameters in a formula are provided by the technical manual of the photomultiplier and the characteristics parameters of the incident light signal, and the calculation is of obvious physical significance; 4, the calculation formula is simple in structure, the calculation is fast, and the electronics design, physical analysis and data reconstruction of a large instrument apply. With the adoption of the method, the transient output signal of the photomultiplier can be accurately calculated; the method has the characteristics of novelty, creativity and practicability.
Description
Technical field
The invention belongs to photoelectric sensor field, relate to a kind of sensor for Feebleness Light Signal Examining, be i.e. the computing method of the transient state output characteristics of photomultiplier.
Background technology
Faint light signal is converted to the photoelectric sensor of electric signal as a kind of photoelectric effect that utilizes by photomultiplier, is widely used at numerous areas such as nuclear physics, biomedicine, chemical analysis and measure monitors.When faint light incides photomultiplier, photon wherein (several to thousands of) is by the photocathode effect with sensor and photoelectron of overflowing, and the photoelectron of effusion will double step by step under the effect of multiple multiplier electrode, finally collected by anode and export, being formed and can be detected the electric signal obtained.By the electric signal that calibrating anode exports, the quantity inciding the photon in photomultiplier will be determined, reach the object of optical signal detecting.
But, due in photomultiplier, the physical process that photon relates to photoelectronic conversion, transmitting and output etc. is numerous, make the modeling of photomultiplier and computing method be a difficult problem in related detector system always, particularly the computing method of its transient response not only have influence on the order of accuarcy of whole system, also have influence on the success or not of front-end electronics system.
Modal computing method, such as, in list of references (Photonis, Photomultiplier tubes principles & application, 2002) described formula, the transient state output characteristics of photomultiplier can be expressed as:
Wherein the transient state output characteristics of the photomultiplier of expression and time correlation, is unit step function,
mwith the form for representing transient state output pulse.Its output characteristics can be represented by the figure shown in the phantom line segments in Fig. 2.
This formula can reflect the transient response that photomultiplier outputs signal to a certain extent, i.e. the corresponding relation of voltage and current and time.But it exists defect and the deficiency of the following aspects, affect its effect in actual applications.
First, this formula is a pure mathematics formula, has isolated the contact between mathematical computations and physical process, computation process indigestion.This makes designer cannot utilize this formula or computing method, directly obtains the corresponding relation between Output rusults and actual photomultiplier performance parameter.So choosing of the morphological parameters about output pulse, the value of parameter will depend on experience but not technical manual, need other mathematical computations and the auxiliary of conversion.And this formula can't be directly used in the relation between light signal and the electric signal of output representing input.
Secondly, in order to the output of the actual photomultiplier of equivalence, often characterisitic parameter
mvalue all larger, in some cases even up to 50.This makes formula have high exponent number, and the solution procedure that result in these computing method is quite complicated and consume the plenty of time.Particularly when the method is used in the equipment needing a large amount of photomultiplier, the design of such as modern larger medical imaging system or large-scale physical unit, emulation and data analysis time, this problem seems more outstanding.
Further, because these computing method introduce unit-step function, make Output rusults discontinuous in time, block, namely the Output rusults of this function when being less than particular point in time is zero.This truncation points can be observed in fig. 2 clearly.Perhaps impact is little in physical analysis for this problem, but but has a great impact the design of electronic system.
According to Circuit theory, although this kind blocks show the result similar with actual signal in time-domain analysis, then can cause there is a large amount of radio-frequency components in signal spectrum when frequency-domain analysis, the behavior of its output signal produced is completely different with actual signal.The figure shown in pecked line section in Fig. 3 shows the Output rusults characteristic in a frequency domain that the computing method in list of references produce, and obviously can observe this signal there is a large amount of radio-frequency components always in figure in amplitude spectrum.This high frequency spectrum becomes branch to have influence on the order of accuarcy of the design of the critical components such as front-end electronics circuit design median filter greatly, and then has influence on the performance of whole system.
Summary of the invention
The object of the invention is to the deficiency overcoming existing computing method, a kind of calculating is provided to be associated with physical process, parameter directly can be obtained by technical manual, and the computing method of the transient state output characteristics of the efficient simple photomultiplier of computation process, make in its design that can be used in large-scale multi channel imaging and detection system etc., emulation and late time data process.
The present invention realizes above-mentioned purpose by the following technical solutions:
The transient state output characteristics of photomultiplier and the relation of time can be represented by following formula (1) or formula (2):
(1)
（2）
What wherein represent is the transient state output current of photomultiplier at particular point in time.What represent is the quantity of the photon incided in photomultiplier, then change and the photoelectronic quantity of overflowing through photocathode after representing incidence.
qEwith
cEthe quantum efficiency of the photomultiplier represented respectively and collection efficiency.Then represent the gain of photomultiplier under specific voltage condition.
efor electron charge, be constant, approximate C.
Function in formula (1) and formula (2), for representing the distribution in time of transient state output characteristics, can be represented by formula (3):
（3）
Wherein represent the transit time of electronics in photomultiplier, represent the time response parameter of the distribution of the transient state output characteristics of photomultiplier, its value can be determined by formula (4):
（4）
Wherein represent the rise time of photomultiplier anode signal,
represent the disturbance of electron-transit time.Then represent the broadening of input optical signal distribution.
Because function has following characteristic:
So formula (1) can represent the quantity of electric charge had after incident optical signal is converted to electric signal accurately.Formula (2) then represent accurately overflow incident optical signal after opto-electronic conversion the photoelectron that obtains be converted to electric signal again after the quantity of electric charge that has.The size of the quantity of electric charge depends on incident photon number
, or change and the photoelectronic quantity of overflowing through photocathode after incidence
, quantum efficiency
qE, collection efficiency
cEand the gain of photomultiplier
.Photomultiplier output characteristics is then expressed as the distribution of approximate Landau by formula (3), meets the output characteristics of photomultiplier, and nothing is blocked and is continuous on Annual distribution.Real segment in Fig. 3 shows this function distribution character in a frequency domain, the feature of realistic signal distributions.
In addition, from Ohm law, the transient voltage output characteristics of photomultiplier can be derived by formula (1) and formula (2) easily and be drawn formula (5):
（5）
Here must it is to be noted that above-mentioned Parameters in Formula, quantum efficiency
qE, collection efficiency
cE, the gain of photomultiplier
, the rise time of the anode signal of the transit time of electronics and the disturbance of electron-transit time and photomultiplier in photomultiplier, all come from the technical manual of photomultiplier, all there is clear and definite physical significance.And incide the quantity of the photon in photomultiplier
broadening with input optical signal distribution, depends on the characteristic of input signal, also has clear and definite physical significance.Output rusults of the present invention can be represented by the real segment in Fig. 2.Real segment in comparison diagram 1 and phantom line segments known, while the approximate transient state Output rusults of generation, computing method of the present invention do not produce in the signal and block.So also show as the feature of actual signal in the amplitude versus frequency characte spectrum shown in real segment in figure 3.
Therefore, the present invention compares background technology tool and has the following advantages:
(1) computing method of the photomultiplier transient response of the present invention's proposition, while the quantity of electric charge that can have after accurate expression incident optical signal is converted to electric signal, describe the transient signal characteristic in the time domain that it exports accurately.
(2) computing method of the photomultiplier transient response of the present invention's proposition, because its Output rusults is in the time domain continuously and without blocking, make it can describe the characteristic of its transient signal in a frequency domain accurately, and meet the feature of actual signal, be conducive to design and the emulation of the critical components such as the wave filter in front-end electronics.
(3) computing method of the photomultiplier transient response of the present invention's proposition, characterisitic parameter wherein all derives from the technical manual of photomultiplier and the characteristic parameter of incident light signal, so formula not only represents Mathematical Calculations, also reflects the physical process wherein contained.This makes computing be provided with obvious physical significance, is convenient to designer and understands.
(4) computing method of the photomultiplier transient response of the present invention's proposition, higher order term is not introduced in calculating, formula structure is simple, has higher arithmetic speed, in the design being convenient to make its physical analysis expanding to large-scale instrument and data reconstruction and electronic system and emulation.
Accompanying drawing explanation
Fig. 1 is the process flow diagram of computing method of the present invention in embodiment.
Fig. 2 is the Output rusults contrast in the time domain that the computing method in embodiment in computing method of the present invention and list of references obtain.
Fig. 3 is the Output rusults contrast in a frequency domain that the computing method in embodiment in computing method of the present invention and list of references obtain.
Fig. 4 is the Output rusults contrast in the time domain adopting computing method of the present invention to obtain when input optical signal broadening is different in embodiment.
Fig. 5 is the Output rusults contrast in a frequency domain adopting computing method of the present invention to obtain when input optical signal broadening is different in embodiment.
Embodiment
For making object of the present invention, technical scheme and effect clearly and clearly, referring to accompanying drawing examples, the present invention is further described.The invention provides the calculating of a kind of effective method for photomultiplier transient state output characteristics, the relation between its Output rusults and time can be determined by following formula (1) and formula (2):
（1）
（2）
Then being determined by following formula (3) in formula
（3）
And in formula can be by
obtain.
When needing the transient response of certain type photomultiplier is carried out to modeling and calculated, the use of the method and computation process, by shown in the process flow diagram in Fig. 1, specifically comprise the following steps:
Step 101: the time response parameter first choosing this type photomultiplier, comprises the transit time of electronics in photomultiplier, the disturbance of electron-transit time and the rise time of photomultiplier anode signal.These three characterisitic parameters come from the technical manual of the photomultiplier of specific model or the test result for practical devices usually.
Step 102: the condition of work of setting photomultiplier, i.e. gain
.
Step 103: select suitable incoming signal to be photon or photoelectron according to actual needs, namely select correct computing formula.
Step 104: if incoming signal is photoelectron, then selective light electronics computing formula.
Step 105: if incoming signal is photon, then select photon computing formula.
Step 106: if previous step selection is photon formula, then also need the quantum efficiency setting photomultiplier
qEand collection efficiency
cE.These two parameters are also obtained by technical manual or test.
Step 107: after formula to be calculated is selected, determines the characteristic parameter of input optical signal further, comprise the photon number of input
or the broadening of the distribution of photoelectron number and light signal.
Step 108: bring set parameter into transient response that formulae discovery obtains the photomultiplier of respective model.
It is 2.5 that Fig. 2 then shows a photoelectron number, light signal broadening be 0 light signal through certain photomultiplier amplify output obtain transient current response.The gain of this multiplier tube is 10
6, the transit time of electronics is 20 ns, and the disturbance of electron-transit time is 3.3 ns, and the rise time of anode signal is 3 ns.Its maximum anode current is about 33 μ A, and the quantity of electric charge exporting electric signal is 400 fC.In order to show contrast, the method recorded in list of references in Fig. 2, is also utilized to create an approximate Output rusults, now in formula
mvalue be set to 1, be set to 6 ns.Due to the effect of unit-step function, this Output rusults equals 15 ns places in the time to be blocked.Therefore, in the amplitude versus frequency characte figure shown in Fig. 3, the computing method in list of references all show output by a relatively large margin in full frequency band, do not meet the feature of actual signal.
What Fig. 4 represented is utilize the method recorded in the present invention, to 1 inch of photomultiplier R1924A of Japanese Bin Song company (Hamamatsu), is all 1 photoelectron at input optical signal, but the result of calculation of transient response when signal duration is different.According to technical manual, the gain of this type photomultiplier is set as 10
6, the transit time of electronics is 17 ns, and the disturbance of electron-transit time is 0.9 ns, and the output signal rise time is 1.5 ns.The transient state that the figure that in Fig. 4, phantom line segments represents is the broadening of the distribution of input optical signal when being 1 ns exports response, and when the broadening of the distribution of input optical signal that what real segment wherein represented is then is 5 ns, transient state exports response.When broadening is 1 ns, the maximum current of this photomultiplier transit tube anode is about 32 μ A; And broadening is when being 5 ns, be then 22 μ A.But two quantities of electric charge exporting electric signal are equal to 160 fC, meet the calculated results of photomultiplier.The broadening that Fig. 5 then shows the distribution of input optical signal is respectively the signal contrast in a frequency domain of 1 ns and 5 ns, the feature of all realistic signal of its result.
In addition to the implementation, all employings are equal to the technical scheme of replacement or equivalent transformation form, all belong to the protection domain of application claims.
Claims (3)
1. computing method for photomultiplier transient state output characteristics, can calculate photomultiplier transient state output current and the accurate corresponding relation between voltage and time, it is characterized in that these computing method comprise following content:
Be photon or photoelectron according to input optical signal, the transient state output current of photomultiplier and the relation of time can be represented by following formula (1) or formula (2):
（1）
（2）
What wherein represent is the transient state output current of photomultiplier at particular point in time, expression be the quantity of the photon incided in photomultiplier, then change and the photoelectronic quantity of overflowing through photocathode after representing incidence,
qEwith
cEthe quantum efficiency of the photomultiplier represented respectively and collection efficiency, and
then represent the gain of photomultiplier under specific voltage condition,
efor electron charge, be constant, approximate C.
2. the computing method of a kind of photomultiplier transient state output characteristics according to claim 1, is characterized in that: the function in formula (1) and formula (2), for representing the distribution in time of transient state output characteristics, can be represented by formula (3):
（3）
Wherein represent the transit time of electronics in photomultiplier, represent the time response parameter of the distribution of the transient state output characteristics of photomultiplier, its value can be determined by formula (4):
(4)
Wherein represent the rise time of photomultiplier anode signal, represent the disturbance of electron-transit time, then represent the broadening of input optical signal distribution, photomultiplier output characteristics is expressed as the distribution of approximate Landau by formula (3), meet the output characteristics of photomultiplier, nothing is blocked and is continuous on Annual distribution;
Because function has following characteristic:
So, formula (1) can represent the quantity of electric charge had after incident optical signal is converted to electric signal accurately, formula (2) then represent accurately overflow incident optical signal after opto-electronic conversion the photoelectron that obtains be converted to electric signal again after the quantity of electric charge that has, the size of the quantity of electric charge depends on incident photon number
, or change and the photoelectronic quantity of overflowing through photocathode after incidence
, quantum efficiency
qE, collection efficiency
cEand the gain of photomultiplier
.
3. the computing method of a kind of photomultiplier transient state output characteristics according to claim 1, is characterized in that: the transient output voltage characteristic of photomultiplier can be derived by formula (1) and formula (2) and be drawn formula (5):
（5）。
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1066648A1 (en) * | 1998-03-25 | 2001-01-10 | Elgems Ltd. | Adjustment of propagation time and gain in photomultiplier tubes |
| CN201689861U (en) * | 2010-01-14 | 2010-12-29 | 北京滨松光子技术股份有限公司 | Fast photomultiplier |
-
2015
- 2015-01-19 CN CN201510025271.7A patent/CN104573252B/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1066648A1 (en) * | 1998-03-25 | 2001-01-10 | Elgems Ltd. | Adjustment of propagation time and gain in photomultiplier tubes |
| CN201689861U (en) * | 2010-01-14 | 2010-12-29 | 北京滨松光子技术股份有限公司 | Fast photomultiplier |
Non-Patent Citations (3)
| Title |
|---|
| （德）格鲁彭等: "《粒子探测器》", 1 January 2015, 中国科学技术大学出版社 * |
| 张利光等: "光电倍增管构造参数对性能的影响", 《舰船防化》 * |
| 王绍明: "光电倍增管时间分辨特性的探讨", 《物理学报》 * |
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