CN104573252B - A kind of computational methods of photomultiplier transient state output characteristics - Google Patents
A kind of computational methods of photomultiplier transient state output characteristics Download PDFInfo
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- CN104573252B CN104573252B CN201510025271.7A CN201510025271A CN104573252B CN 104573252 B CN104573252 B CN 104573252B CN 201510025271 A CN201510025271 A CN 201510025271A CN 104573252 B CN104573252 B CN 104573252B
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Abstract
The invention discloses a kind of computational methods for photomultiplier transient state output characteristics, it is related to accurate calculating and the precise expression of Annual distribution of the quantity of electric charge of photomultiplier output signal.This method has the feature of four aspects：First, it can accurately represent that incident optical signal is converted to the quantity of electric charge having after electric signal and accurately describes the characteristic of the transient signal of multiplier tube output in the time domain.2nd, because its output result is continuous in the time domain, it is made accurately to describe the characteristic of multiplier tube transient signal in a frequency domain.3rd, the characterisitic parameter in formula derives from the technical manual of photomultiplier and the characteristic parameter of incident optical signal, and calculating has obvious physical significance.4th, calculation formula is simple in construction, and calculating speed is fast, the electronics design of large-scale instrument can be applied to, in physical analysis and data reconstruction.The transient state output signal of photomultiplier can accurately be calculated by the present invention, the characteristics of it has novelty, creative and practicality.
Description
Technical field
The invention belongs to photoelectric sensor field, it is related to a kind of sensor for Feebleness Light Signal Examining, i.e. photoelectricity
The computational methods of the transient state output characteristics of multiplier tube.
Background technology
Photomultiplier is converted to faint optical signal as a kind of utilization photoelectric effect the photoelectric sensor of electric signal,
It is widely used in numerous areas such as nuclear physics, biomedicine, chemical analysis and measure monitors.When faint light incides light
During electric multiplier tube, the photocathode with sensor is acted on and escapes photoelectron by photon (several to thousands of) therein, and is escaped
Photoelectron will step by step double in the presence of multiple dynodes, finally collected and exported by anode, formation can be detected
The electric signal arrived.By examining and determine the electric signal that anode is exported, inciding the quantity of the photon in photomultiplier will be determined,
Reach the purpose of optical signal detecting.
But, due in photomultiplier, the physics mistake that photon to photoelectronic conversion, transmitting and output etc. is related to
Journey is numerous so that the modeling of photomultiplier and computational methods are always the problem in related detector system design, particularly
The computational methods of its transient response not only have influence on the order of accuarcy of whole system, also affect front-end electronics system design
Success or not.
Most common computational methods, such as bibliography (Photonis, Photomultiplier tubes
Principles＆application, 2002) in described formula, the transient state output characteristics of photomultiplier is represented by：
Wherein Rδ(t) the transient state output characteristics with the photomultiplier of association in time is represented, ε (t) is unit jump function,
M and σRFor representing that transient state exports the form of pulse.Its output characteristics can carry out table as the figure shown in the phantom line segments in Fig. 2
Show.
The formula can reflect to a certain extent the transient response of photomultiplier output signal, i.e. voltage and current and when
Between corresponding relation.But it has the defect and deficiency of the following aspects, its effect in actual applications is influenceed.
First, the formula is a pure mathematics formula, has isolated the contact between mathematical computations and physical process, had calculated
Journey indigestion.This causes designer can not utilize the formula or computational methods, directly obtains output result and actual photoelectricity
Corresponding relation between multiplier tube performance parameter.So, in the selection of the morphological parameters on exporting pulse, the value of parameter will
Depending on experience rather than technical manual, it is necessary to other mathematical computations and the auxiliary of conversion.And the formula can't be used directly
Relation between the optical signal and the electric signal of output for representing input.
Secondly, for the output of equivalent actual photomultiplier, often characterisitic parameter m value is all than larger, some feelings
50 are even as high as under condition.This causes formula to have high exponent number, result in the computational methods solution procedure it is considerably complicated and
Consume the plenty of time.Particularly a large amount of photomultipliers, modern larger medical imaging system are needed when this method is used in
Or large-scale physical unit design, emulation and data analysis when, this problem seems more prominent.
Further, because the computational methods introduce unit-step function so that output result is discontinuous in time, have and cut
Disconnected, i.e. output result of function when less than particular point in time is zero.The point of cut-off in fig. 2 can be visible in detail.
This problem perhaps influences little in physical analysis, but has a great impact to the design of electronic system.
According to Circuit theory, although such a block shows the result similar with actual signal in time-domain analysis,
It can then cause the presence of substantial amounts of radio-frequency component in signal spectrum in frequency-domain analysis, the behavior of its output signal produced and actual letter
It is number entirely different.The output result that the computational methods in the figure shows bibliography shown in pecked line section in Fig. 3 are produced
It can substantially observe that the signal has substantial amounts of radio-frequency component always in amplitude spectrum in characteristic in a frequency domain, figure.This height
Spectrum component meeting strong influence is entered to the order of accuarcy of the design of the critical components such as front-end electronics circuit design median filter
And have influence on the performance of whole system.
The content of the invention
It is an object of the invention to overcome the shortcomings of existing computational methods, there is provided one kind calculating is associated with physical process
, what parameter can directly be obtained by technical manual, and calculate the calculating of the transient state output characteristics of efficiently simple photomultiplier
Method, makes it to be used in the design, emulation and later data of large-scale multi channel imaging and detection system etc. processing.
The present invention realizes above-mentioned purpose using following technical scheme：
The transient state output characteristics and the relation of time of photomultiplier can be represented by following equation (1) or formula (2)：
iPMT(t)=nphoton·QE·CE·GPMT·e·h(t) (1)
iPMT(t)=nphotoelectron·GPMT·e·h(t) (2)
Wherein iPMT(t) what is represented is transient state output current of the photomultiplier in particular point in time.nphotonRepresent be
Incide the quantity of the photon in photomultiplier, and nphotoelectronThen represent the light changed and escaped through photocathode after incidence
The quantity of electronics.The quantum efficiency and collection efficiency for the photomultiplier that QE and CE are represented respectively.And GPMTThen represent photoelectricity times
Increase gain of the pipe under the conditions of specific voltage.E is electron charge, is constant, is approximately equal to -1.6022 × 10-19C。
Function h (t) in formula (1) and formula (2) is used to represent the distribution of transient state output characteristics in time, can be by public affairs
Formula (3) is represented：
Wherein ttRepresent the transition time of electronics in photomultiplier, tpRepresent the transient state output characteristics of photomultiplier
The time response parameter of distribution, its value can be determined by formula (4)：
Wherein trRepresent the rise time of photomultiplier anode signal, tjRepresent the disturbance of electron transit time.tlThen generation
The broadening of table input optical signal distribution.
So, formula (1) can accurately represent that incident optical signal is converted to the quantity of electric charge having after electric signal.Formula
(2) it is then accurate to represent that incident optical signal escapes obtained photoelectron after opto-electronic conversion and is reconverted into after electric signal and had
The quantity of electric charge.The size of the quantity of electric charge depends on the number of photons n of incidencephoton, or the photoelectron changed and escaped through photocathode after incidence
Quantity nphotoelectron, quantum efficiency QE, the gain G of collection efficiency CE and photomultiplierPMT.And formula (3) is then by light
Electric multiplier tube output characteristics is expressed as approximate Landau distribution, meets the output characteristics of photomultiplier, and nothing was blocked and in the time point
It is continuous on cloth.Real segment in Fig. 3 shows the distribution character of the function in a frequency domain, meets the spy of actual signal distribution
Point.
In addition, from Ohm's law, the transient voltage output characteristics of photomultiplier can be easily by formula (1) and formula
(2) it is derived from formula (5)：
vPMT(t)=iPMT(t)·R (5)
Here must be it is to be noted that parameter in above-mentioned formula, quantum efficiency QE, collection efficiency CE, photomultiplier
Gain GPMT, the transition time t of electronics in photomultipliertAnd the disturbance t of electron transit timejWith the anode of photomultiplier
The rise time t of signalr, both from the technical manual of photomultiplier, all with clear and definite physical significance.And incide
The quantity n of photon in photomultiplierphotonThe broadening t being distributed with input optical signall, depending on the characteristic of input signal,
With clear and definite physical significance.The output result of the present invention can be represented by the real segment in Fig. 2.Real segment in comparison diagram 1 and
Phantom line segments understand that while approximate transient state output result is produced, computational methods of the invention are not produced in the signal blocks.Therefore
And in the amplitude versus frequency characte spectrum shown in real segment in figure 3 the characteristics of also show as actual signal.
Therefore, the present invention has the following advantages that compared to background technology：
(1) computational methods of photomultiplier transient response proposed by the present invention, can accurately represent incident light letter
While number being converted to the quantity of electric charge having after electric signal, the spy of the transient signal of its output in the time domain is accurately described
Property.
(2) computational methods of photomultiplier transient response proposed by the present invention, because its output result is continuous in the time domain
And without blocking, the characteristics of making it accurately to describe the characteristic of its transient signal in a frequency domain, and meet actual signal, be conducive to
The design and emulation of the critical components such as the wave filter in front-end electronics.
(3) computational methods of photomultiplier transient response proposed by the present invention, characterisitic parameter therein derives from light
The characteristic parameter of the technical manual of electric multiplier tube and incident optical signal, so formula not only represents Mathematical Calculations,
Reflect the physical process wherein contained.This makes computing be provided with obvious physical significance, is easy to designer to understand.
(4) computational methods of photomultiplier transient response proposed by the present invention, because not introducing higher order term, formula in calculating
It is simple in construction, with higher arithmetic speed, it is easy to physical analysis and data reconstruction and the electricity for it is expanded to large-scale instrument
In the design and emulation of sub- system.
Brief description of the drawings
Fig. 1 is the flow chart of computational methods of the invention in embodiment.
Fig. 2 is that the output result obtained by the computational methods in computational methods and bibliography of the invention in embodiment exists
Contrast in time domain.
Fig. 3 is that the output result obtained by the computational methods in computational methods and bibliography of the invention in embodiment exists
Contrast in frequency domain.
Fig. 4 is the output result obtained using the computational methods of the present invention when input optical signal broadening is different in embodiment
Contrast in the time domain.
Fig. 5 is the output result obtained using the computational methods of the present invention when input optical signal broadening is different in embodiment
Contrast in a frequency domain.
Embodiment
To make the purpose of the present invention, technical scheme and effect more clear and clearly, referring to the drawings and give an actual example pair
The present invention is further illustrated.The invention provides a kind of effective method based on photomultiplier transient state output characteristics
Calculate, its output result and the relation between the time can be determined by following equation (1) and formula (2)：
iPMT(t)=nphoto·QE·CE·GPMT·e·h(t) (1)
iPMT(t)=nphotoelectron·GPMT·e·h(t) (2)
H (t) in formula is then determined by following formula (3)
And the t in h (t) formulaspCan be byObtain.
When needing that the transient response of certain type photomultiplier is modeled and calculated, this method using and calculating
Journey specifically includes following steps as shown in the flow chart in Fig. 1：
Step 101：Choose the time response parameter of the type photomultiplier first, including electronics is crossed in photomultiplier
More time tt, the disturbance t of electron transit timejWith the rise time tr of photomultiplier anode signal.These three characterisitic parameters lead to
Technical manual often from the photomultiplier in specific model or the test result for practical devices.
Step 102：Set the condition of work of photomultiplier, i.e. gain GPMT。
Step 103：It is photon or photoelectron to select suitable incoming signal according to actual needs, that is, selects correct meter
Calculate formula.
Step 104：If incoming signal is photoelectron, photoelectron calculation formula is selected.
Step 105：If incoming signal is photon, photon calculation formula is selected.
Step 106：If previous step selection be photon formula, also need set photomultiplier quantum efficiency QE and
Collection efficiency CE.The two parameters are also obtained by technical manual or test.
Step 107：After formula to be calculated is selected, the characteristic parameter of input optical signal is further determined that, includes the light of input
Subnumber nphotonOr photoelectron number nphotoelectronAnd the broadening t of the distribution of optical signall。
Step 108：Bring set parameter into transient response that formula calculates the photomultiplier for obtaining respective model.
Fig. 2 then shows that a photoelectron number is 2.5, and optical signal broadening is put for 0 optical signal by certain photomultiplier
Big output obtains transient current response.The gain of the multiplier tube is 106, the transition time of electronics is 20ns, electron transit time
Disturbance be 3.3ns, rise time of anode signal is 3ns.Its maximum anode current is about 33 μ A, exports the electric charge of electric signal
Measure as 400fC.In order to also generate an approximate output knot using the method described in bibliography to show in contrast, Fig. 2
Really, now m value is set to 1, σ in formulaRIt is set to 6ns.Due to the effect of unit-step function, the output result is in time etc.
Blocked at 15ns.Therefore, in the amplitude versus frequency characte figure shown in Fig. 3, the computational methods in bibliography are equal in full frequency band
Show output by a relatively large margin, the characteristics of not meeting actual signal.
What Fig. 4 was represented is using the method described in the present invention, to 1 inch of light of Japanese Bin Song companies (Hamamatsu)
Transient response in the case that electric multiplier tube R1924A, is all 1 photoelectron in input optical signal, but signal duration is different
Result of calculation.According to technical manual, the gain of the type photomultiplier is set as 106, the transition time of electronics is 17ns,
The disturbance of electron transit time is 0.9ns, and the output signal rise time is 1.5ns.The figure that phantom line segments are represented in Fig. 4 is input
Transient state output response when the broadening of the distribution of optical signal is 1ns, and it is then input optical signal that real segment therein, which is represented,
Transient state output response when the broadening of distribution is 5ns.When broadening is 1ns, the maximum current of the photomultiplier transit tube anode is about 32 μ
A；And broadening be 5ns when, then be 22 μ A.But, the quantity of electric charge of two output electric signals is equal to 160fC, meets photomultiplier transit
The calculated results of pipe.Fig. 5 then shows that the broadening of the distribution of input optical signal is respectively 1ns and 5ns signal in frequency domain
In contrast, the characteristics of its result meets actual signal.
In addition to the implementation, the technical scheme of all use equivalent substitution or equivalent transformation form, belonging to the present invention will
The protection domain asked.
Claims (1)
1. a kind of computational methods of photomultiplier transient state output characteristics, can calculate photomultiplier transient state output current and
Accurate corresponding relation between voltage and time, it is characterised in that the computational methods include herein below：
It is photon or photoelectron according to input optical signal, the transient state output current and the relation of time of photomultiplier can be by following
Formula (1) or formula (2) are represented：
iPMT(t)=nphoto·QE·CE·GPMT·e·h(t) (1)
iPMT(t)=nphotoelectron·GPMT·e·h(t) (2)
Wherein iPMT(t) what is represented is transient state output current of the photomultiplier in particular point in time, nphotoWhat is represented is to incide
The quantity of photon in photomultiplier, and nphotoelectronThat changes and escape through photocathode after then expression is incident is photoelectronic
The quantum efficiency and collection efficiency for the photomultiplier that quantity, QE and CE are represented respectively, and GPMTPhotomultiplier is then represented to exist
Gain under the conditions of specific voltage, e is electron charge, is constant, is approximately equal to -1.6022 × 10-19C；
Function h (t) in formula (1) and formula (2) can be used for representing the distribution of transient state output characteristics in time, can be by formula
(3) represent：
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Wherein ttRepresent the transition time of electronics in photomultiplier, tpRepresent the distribution of the transient state output characteristics of photomultiplier
Time response parameter, its value can determine by formula (4)：
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Wherein trRepresent the rise time of photomultiplier anode signal, tjRepresent the disturbance of electron transit time, tlThen represent defeated
Photomultiplier output characteristics is expressed as approximate Landau and is distributed by the broadening of optical signal distribution, function h (t), meets photoelectricity times
Increase the output characteristics of pipe, nothing is blocked and is continuous on Annual distribution；
So, incident optical signal escapes obtained photoelectron and is reconverted into the electricity having after electric signal after opto-electronic conversion
The size of lotus amount, depends on the number of photons n of incidencephotoOr the photoelectronic quantity changed and escaped through photocathode after incidence
nphotoelectron, quantum efficiency QE, the gain G of collection efficiency CE and photomultiplierPMT。
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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 (2)
| Title |
|---|
| 光电倍增管时间分辨特性的探讨;王绍明;《物理学报》;19621127(第11期);全文 * |
| 光电倍增管构造参数对性能的影响;张利光等;《舰船防化》;20030815(第4期);第43-45、29页 * |
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