CN110133710B - Signal correction method and device - Google Patents
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- CN110133710B CN110133710B CN201910333375.2A CN201910333375A CN110133710B CN 110133710 B CN110133710 B CN 110133710B CN 201910333375 A CN201910333375 A CN 201910333375A CN 110133710 B CN110133710 B CN 110133710B
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Abstract
The invention provides a method and a device for correcting signals, wherein the method comprises the following steps: selecting two radiation sources with different characteristic energies; respectively measuring energy spectrums corresponding to the two radiation sources under a fixed voltage by using the same scintillation detector, and respectively obtaining corresponding peak values from the energy spectrums; determining an actual relationship between the electrical signal received by the signal processor and the number of avalanche diodes activated in the silicon photomultiplier of the scintillation detector; and respectively substituting the characteristic energy and the peak-to-peak value parameters into a formula to solve the unknown number. The device comprises an energy comparator, a peak value collector and a parameter calculator. The invention can realize the linear calibration of the silicon photomultiplier, solves the problem of nonlinear deviation of the silicon photomultiplier in response to energy, and has simple operation and ideal correction effect.
Description
Technical Field
The present invention relates to the field of signal processing, and more particularly, to a method and an apparatus for signal correction.
Background
The photoelectric effect refers to that under the irradiation of electromagnetic waves with a frequency higher than a certain frequency, electrons in certain substances are excited by photons to form current, i.e. photogeneration. The photoelectric conversion device mainly converts an optical signal into an electrical signal by using a photoelectric effect. From the discovery of photoelectric effect, photoelectric conversion devices have been developed rapidly, and various photoelectric conversion devices have been widely used in various industries. Commonly used photoelectric conversion devices include a photoresistor, a photomultiplier tube (PMT), a photocell, a PIN diode, a CCD (charge coupled device), and the like.
A photomultiplier tube (PMT) is a vacuum device, which is composed of a photoemission cathode (also called photocathode), a focusing electrode, an electron multiplier, an electron collector (also called anode), and the like, and its main working process is as follows: when light irradiates the photocathode, the photocathode excites photoelectrons into vacuum, the photoelectrons enter an electron multiplier under the action of an electric field of a focusing electrode, multiplication amplification is obtained through further secondary emission, and the amplified electrons are collected by an anode to be output as signals. The secondary emission multiplication system is adopted, so that the photomultiplier has extremely high sensitivity and extremely low noise in the photoelectric detector for detecting the radiation energy in ultraviolet, visible and near infrared regions, and has the advantages of quick response, low cost, large cathode area and the like.
However, the photomultiplier is not suitable for application environments such as a strong magnetic field, which greatly restricts the application. Therefore, a silicon photomultiplier (referred to as SiPM for short) is produced. It should be noted that the photomultiplier and the silicon photomultiplier are two photoelectric conversion devices with great performance difference, the silicon photomultiplier is a novel photoelectric conversion device, and is composed of Avalanche Photo Diode (APD) arrays working in a geiger mode, and has the characteristics of high gain, high sensitivity, low bias voltage, insensitivity to magnetic field, compact structure and the like, and is widely applied to the fields of high-energy physics and nuclear medicine (such as PET), and the like, and the development in the nuclear medicine field is rapid in recent years, and the silicon photomultiplier is widely considered as the development direction of future infinitesimal photodetectors.
Each silicon photomultiplier consists of a large number (hundreds to thousands) of units, each unit is formed by connecting an Avalanche Photodiode (APD) and a quenching resistor in series, and the units (also called pixels) are connected in parallel to form a planar array. After a reverse bias voltage (generally tens of volts) is applied to a silicon photomultiplier, a depletion layer of an avalanche diode in each unit has a high electric field, when photons are emitted from the outside, Compton scattering occurs between the photons and electron-hole pairs in a semiconductor to release electrons or holes, and the high-energy electrons and holes are accelerated in the electric field to release a large amount of secondary electrons and holes, namely avalanche. At this time, the current in each unit circuit suddenly increases, the voltage shared by the quenching resistor also suddenly increases, the voltage shared by the avalanche diode decreases, that is, the electric field instantaneously decreases, the avalanche stops after the avalanche diode outputs a transient electric signal (or referred to as a pulse signal), and the quenching resistors of different units have the same resistance value, so that theoretically, each unit can output an equal-magnitude electric signal. Therefore, in the dynamic range of a silicon photomultiplier, the magnitude of its output electrical signal is proportional to the number of avalanche cells. When one pixel in the silicon photomultiplier receives an incident photon, an electric signal with a certain amplitude is output, if a plurality of pixels receive the incident photon, each pixel outputs an electric signal, and the electric signals are finally superposed and output by a common output end.
However, for avalanche diodes in silicon photomultipliers, there is a recovery period after avalanche occurs, during which a single avalanche diode can only receive one photon. Because the number of avalanche diodes in the monolithic silicon photomultiplier is limited, the number of photons that the silicon photomultiplier can receive is also limited, when a large number of photons are reached in a short time (or in the recovery period of the silicon photomultiplier), many of the photons strike the activated avalanche diodes, and no reaction is generated on the corresponding avalanche diodes, so that the photons cannot be detected by a detector, and further, nonlinear deviation is generated between the output charge amount and the input photon number of the silicon photomultiplier, and the dynamic range of the silicon photomultiplier is limited. For a wide photon range usage scenario, such as high-energy physical applications like energy spectrometers, radiation detectors, etc., the errors generated by the measurement equipment are increased.
Disclosure of Invention
The invention aims to provide a method and a device for correcting signals, thereby solving the problem of nonlinear deviation between the output charge quantity and the input photon quantity of a silicon photomultiplier in the prior art.
In order to solve the above technical problem, the signal correction method provided by the present invention comprises the following steps:
step S1: selecting two radiation sources with different characteristic energies, and respectively recording the two characteristic energies as E1And E2；
Step S2: respectively measuring energy spectrums corresponding to the two radiation sources at fixed voltage by using the same scintillation detector, and respectively obtaining corresponding peak values, recorded as V, from the energy spectrums1、V2；
Step S3: determining an actual relationship between the electrical signal received by the signal processor and the number of avalanche diodes activated in the silicon photomultiplier tube of the scintillation detector as described in equation (1):
V＝[m(1-e-Ek)]q (equation 1);
wherein V is the peak-to-peak value of the electrical signal, m is the number of avalanche diodes in the silicon photomultiplier, E is the characteristic energy, and q and k are unknown constants;
step S4: will be parameter E1、V1And E2、V2And respectively substituting the k and the q into the formula (1) to be solved immediately.
In step S1, the difference between the characteristic energies corresponding to the two radiation sources is preferably not less than the product of the energy resolution of the scintillation crystal in the scintillation detector and the corresponding characteristic energy.
In the above step S2, the peak-to-peak values V1 and V2 may be obtained by: respectively measuring a first energy spectrum corresponding to a first type of the radiation source under a fixed voltage by using the same scintillation detector, and acquiring a corresponding first peak-to-peak value from the first energy spectrum, wherein the first peak-to-peak value is marked as V1, and the first peak-to-peak value is a peak-to-peak value of a characteristic peak in the first energy spectrum; respectively measuring second energy spectrums corresponding to the second radiation source at fixed voltage by using the same scintillation detector, and acquiring corresponding second peak-to-peak values, recorded as V, from the second energy spectrums2And the second peak-to-peak value is the peak-to-peak value of the characteristic peak in the second energy spectrum.
In the above step S2, the first peak-to-peak value may be repeatedly measured at least three times, and the average value of the first peak-to-peak values is taken as V1(ii) a The second peak-to-peak value can be repeatedly measured at least three times, and the average value of the second peak-to-peak values is recorded as V2。
The fixed voltage preferably does not exceed the reverse breakdown voltage of the SiPM.
The formula (1) can be obtained specifically by the following steps:
step S31: the number of avalanche diodes activated in the silicon photomultiplier was calculated:
wherein the photons detected by the silicon photomultiplier tube conform to a two-dimensional poisson distribution P (μ, n), μ being the expectation, n being the number of samples, which is here equal to the number of photons detected by the silicon photomultiplier tube; h is the number of activated avalanche diodes in the silicon photomultiplier; m is the number of avalanche diodes in the silicon photomultiplier; n is a radical ofdNumber of photons detected for a silicon photomultiplier, NdN is the number of photons incident on the light sensitive surface of the silicon photomultiplier, D is the photon detection of the silicon photomultiplierEfficiency;
step S32: substituting the parameters of formula (2) with NdN and E P0Substituting into equation (2) can result in:
wherein, P0Is the light output of the scintillation crystal, P0D and m are constants, performing parameter substitution, and adding P0D/m is denoted as k, yielding:
H＝m[1-e-(Ek)](equation 4);
step S33: determining an actual relationship between a peak-to-peak value V of the electrical signal received by the signal processor and a number of activated APDs in the SiPM:
V＝H/q＝[m(1-e-Ek)]and/q (equation 1).
The method for correcting the signal further includes step S5: and correcting the difference value according to the delivery parameters of the silicon photomultiplier.
The signal correction device provided by the invention comprises an energy comparator, a peak value collector and a parameter calculator, wherein the energy comparator is used for comparing the characteristic energies of two selected radiation sources, and the two characteristic energies are respectively marked as E1And E2(ii) a The peak value collector respectively obtains corresponding peak value from the energy spectrums of two kinds of radiation sources under fixed voltage, and the peak value is respectively marked as V1、V2(ii) a The parameter calculator receives the characteristic energy data sent by the energy comparator and the peak-to-peak data sent by the peak value collector respectively, the parameter calculator further solves unknown parameters according to a formula (1) and the characteristic energy data and the peak-to-peak data and determines the actual relation between the electric signals received by the signal processor and the number of activated avalanche diodes in the silicon photomultiplier, wherein the formula (1) is as follows:
V＝[m(1-e-Ek)]q (equation 1);
wherein V is the peak-to-peak value of the electrical signal, m is the number of avalanche diodes in the silicon photomultiplier, E is the characteristic energy, and q and k are unknown constants.
The energy comparator preferably compares the characteristic energies corresponding to the two sources when comparing the characteristic energies corresponding to the two sources, such that the difference between the characteristic energies corresponding to the two sources is not less than the product of the energy resolution of the scintillation crystal and the corresponding characteristic energy.
The fixed voltage preferably does not exceed the reverse breakdown voltage of the SiPM.
The signal correction method and the signal correction device provided by the invention can realize the linear calibration of the silicon photomultiplier and solve the problem of nonlinear deviation of the silicon photomultiplier in response to energy; the method provided by the invention can realize calibration only by using two radiation sources, does not need a standard light source, is simple and convenient to operate and has stable output; the equation calibrated by the method can be directly used for energy linear calibration of the scintillation detector, and the correction effect is very ideal.
Drawings
FIG. 1 is a schematic diagram of a connection of a scintillation crystal and a silicon photomultiplier in the art;
FIG. 2 is a schematic diagram of the steps of a method of signal correction according to one embodiment of the present invention;
FIG. 3 is a schematic diagram of error correction of a signal correction method according to an embodiment of the present invention;
FIG. 4 is an energy spectrum before correction according to a method of signal correction according to one embodiment of the present invention, wherein the source employs Cs-137 and Na-22, respectively;
fig. 5 is a power spectrum after correction according to the signal correction method of the embodiment of the invention.
Detailed Description
The present invention will be further described with reference to the following specific examples. It should be understood that the following examples are illustrative only and are not intended to limit the scope of the present invention.
It will be understood that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected/coupled" to another element, it can be directly connected/coupled to the other element or intervening elements may also be present. The term "connected/coupled" as used herein may include electrical and/or mechanical physical connections/couplings. The term "comprises/comprising" as used herein refers to the presence of features, steps or elements, but does not preclude the presence or addition of one or more other features, steps or elements. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
In addition, in the description of the present application, the terms "first", "second", "third", and the like are used for descriptive purposes only and to distinguish similar objects, and there is no order of precedence between the two, and no indication or implication of relative importance is to be inferred. In addition, in the description of the present application, "a plurality" means two or more unless otherwise specified.
Fig. 1 is a schematic diagram of a connection between a scintillation crystal and a silicon photomultiplier in the art, and as can be seen from fig. 1, a scintillation detector includes a scintillation crystal 10 and a silicon photomultiplier 20 coupled to each other, and the scintillation detector can convert ionizing radiation rays such as X-rays and gamma-rays into electrical signals, specifically, the scintillation crystal 10 receives the ionizing radiation rays and converts the ionizing radiation rays into visible light photons, and the output number of the visible light photons is proportional to the energy of the ionizing radiation rays incident on the scintillation crystal 10; the silicon photomultiplier tube 20 receives the visible light photons converted by the scintillation crystal 10 and converts them into electrical signals. Further, the power supply 30 is electrically connected to the silicon photomultiplier 20 and supplies power to the silicon photomultiplier 20, the signal processor 40 is communicatively connected to the silicon photomultiplier 20 to process the electrical signals converted by the silicon photomultiplier 20, and the signal processor 40 can classify the electrical signals according to the magnitude of the amplitude and record the number of each type of signal to generate a corresponding energy spectrum.
It should be noted that, in the art, a scintillation detector refers to a type of detector that can convert ionizing radiation rays into an electrical signal, and may also be referred to as a photon detector, a high-energy detector, or the like; the scintillator crystal 10 is a generic term for a type of material that can convert ionizing radiation rays into visible light, and may also be referred to as a crystal, a phototransistor, or the like; the electrical signal output by the silicon photomultiplier tube includes various forms, and a typical one is a pulse signal.
Further, in the embodiment of fig. 1, the power supply 30 is preferably a dc power supply, and since the gain of the silicon photomultiplier (the amount of charge output by the silicon photomultiplier per input of a photon) is affected by temperature and voltage, keeping the temperature and voltage constant during use will positively affect the result. The signal processor 40 preferably employs a Multi-channel pulse height analysis (MCA), and the MCA may acquire a distribution histogram of an electrical signal output by the silicon photomultiplier, normalize a voltage height (abscissa) to a corresponding ray energy, and acquire spectral data, and further may display the spectral data in the form of a digital code or a spectral curve on a display, or may output the spectral data from a flash printer or a plotter.
Fig. 2 is a schematic diagram illustrating steps of a signal correction method according to an embodiment of the present invention, and as can be seen from fig. 2, the signal correction method provided by the present invention at least includes the following steps:
step S1: selecting two kinds of radiation sources with different characteristic energies, wherein the two characteristic energies are respectively marked as E1And E2；
Step S2: respectively measuring energy spectrums corresponding to two kinds of radiation sources under fixed voltage by using the same scintillation detector, and acquiring peak-to-peak values corresponding to two kinds of electric signals from the energy spectrums, and recording the peak-to-peak values as V1、V2；
Step S3: determining an actual relationship between the electrical signal received by the signal processor and the number of avalanche diodes activated in the silicon photomultiplier tube, as described in equation (1):
V＝[m(1-e-Ek)]q (equation 1);
wherein V is the peak-to-peak value of the electrical signal, m is the number of avalanche diodes in the silicon photomultiplier, E is the characteristic energy, and q and k are unknown constants;
step S4: will be parameter E1、V1And E2、V2And respectively substituting the k and the q into the formula (1) to be solved immediately.
In step S1, the source is a radiation source, and the characteristic energy refers to the energy of the high-energy radiation generated by different sources, for example, in the case of cesium 137(Cs-137) source, the energy of the high-energy radiation emitted by the source is 662keV, so the characteristic energy of cesium 137 is 662 keV. It should be noted by those skilled in the art that when two sources with different characteristic energies are selected, the difference or difference between the characteristic energies corresponding to the two sources is preferably not less than the product of the energy resolution of the scintillation crystal 10, which is an inherent property of the scintillation crystal 10, and the corresponding characteristic energy, and the size of the scintillation crystal 10 is related to the material and shape of the scintillation crystal 10, and the energy resolution is a known value for a particular specification and material of the scintillation crystal 10.
In the above step S2, the peak-to-peak value V1And V2Can be obtained by the following method: respectively measuring a first energy spectrum corresponding to a first radiation source at a fixed voltage by using the same scintillation detector, and acquiring a corresponding first peak-to-peak value from the first energy spectrum, and marking as V1(ii) a Respectively measuring a second energy spectrum corresponding to a second radiation source at a fixed voltage by using the same scintillation detector, and acquiring a corresponding second peak-to-peak value from the second energy spectrum, and marking as V2。
In the above step S2, the peak-to-peak value V1And V2Can also be obtained by the following method: respectively measuring the energy spectrum corresponding to the first radiation source at a fixed voltage by using the same scintillation detector, obtaining a first peak-to-peak value corresponding to the first electric signal from the energy spectrum, repeating the measurement for at least three times, and taking the average value of the first peak-to-peak value as V1(ii) a Respectively measuring the energy spectrum corresponding to the second source at fixed voltage by using the same scintillation detector, obtaining the second peak-to-peak value corresponding to the second electric signal from the energy spectrum, repeating the measurement at least three times, and taking the average value of the second peak-to-peak value as V2。
In the above step S2, the fixed voltage preferably does not exceed the reverse breakdown voltage of the SiPM. The reverse breakdown voltage of the SiPM refers to a voltage value when the electric field intensity generated in the depletion layer region by the voltage applied to the SiPM is just enough to cause geiger discharge to occur. When the SiPM production is completed, the reverse breakdown voltage value can be obtained through related technical data. In the art, the reverse breakdown voltage is also referred to as reverse voltage, breakdown voltage, reverse bias voltage, and the like. When the fixed voltage adopts any value within the range, the silicon photomultiplier can be kept in a good working state, so that the measurement result is more accurate, and the accuracy of the correction result is facilitated.
In the above step S3, determining the actual relationship between the electrical signal received by the signal processor and the number of avalanche diodes activated in the silicon photomultiplier tube may be obtained by:
step S31: the number of avalanche diodes activated in the silicon photomultiplier was calculated:
wherein the photons detected by the silicon photomultiplier tube conform to a two-dimensional poisson distribution P (μ, n), μ being the desired, n sample number, here being equal to the number of photons detected by the silicon photomultiplier tube; h is the number of activated avalanche diodes in the silicon photomultiplier; m is the number of avalanche diodes in the silicon photomultiplier; n is a radical ofdNumber of photons detected for a silicon photomultiplier, NdN is the number of photons incident on the light sensitive surface of the silicon photomultiplier, and D is the photon detection efficiency of the silicon photomultiplier;
step S32: substituting the parameters of formula (2), specifically, substituting NdN and E P0Substituting into equation (2) can result in:
wherein, P0Is the light output (also known as light yield), P, of the scintillation crystal0D and m are constants, performing parameter substitution, and adding P0D/m is denoted as k, we can get:
H＝m[1-e-(Ek)](equation 4);
step S33: determining an actual relationship between the peak-to-peak value V of the electrical signal received by the signal processor and the number H of avalanche diodes activated in the silicon photomultiplier:
V＝H/q＝[m(1-e-Ek)]q (equation 1);
because the electric signals output by the silicon photomultiplier are the superposition of pulse signals in all the avalanche diodes, the number H of the activated avalanche diodes is in direct proportion to the peak value V of the electric signals; further, the relation between the actual energy E of the high-energy ray and the peak-to-peak value V of the electric signal can be obtained by transforming the formula (1):
e ═ 1/k × ln [1- (Vq/m) ] (formula 5).
In the above step S4, E1、V1And E2、V2Two equations about unknown numbers k and q can be obtained by respectively substituting the unknown numbers into the formula (1), and the formula (1) can be determined by simultaneously solving the unknown numbers k and q.
Further, when the formula (1) is determined, the method may further include step S5: and correcting the difference value according to the delivery parameters of the silicon photomultiplier. After the relationship between the peak-to-peak value V of the electrical signal and the characteristic energy E is obtained, as shown in fig. 3, theoretically, the relationship between the peak-to-peak value V of the electrical signal and the characteristic energy is a linear corresponding relationship, and in practice, the relationship between the peak-to-peak value V of the electrical signal and the characteristic energy is a curve as shown in formula (5), so that after the actual relationship between the peak-to-peak value V of the electrical signal and the characteristic energy (i.e., formula 5) is obtained, the error can be corrected by referring to the known linear relationship, and the characteristic energy E of any one of the radiation sources can be obtainednCorresponding actual peak-to-peak value Va。
The invention also provides a device based on the signal correction method, which comprises an energy comparator, a peak value collector and a parameter calculatorWherein the energy comparator is used for comparing the characteristic energies of two selected radiation sources, and the two characteristic energies are respectively marked as E1And E2The compared characteristic energy data are sent to a parameter calculator; the peak value collector respectively obtains corresponding peak value from the energy spectrums of two kinds of radiation sources under fixed voltage, and the peak value is respectively marked as V1、V2After the collection is finished, sending the peak-to-peak data to a parameter calculator; the parameter calculator solves unknown parameters and determines an actual relationship between the electrical signal received by the signal processor and the number of activated avalanche diodes in the silicon photomultiplier according to formula (1) and the characteristic energy data and the peak-to-peak data, wherein formula (1) is as follows:
V＝[m(1-e-Ek)]q (equation 1);
wherein V is the peak-to-peak value of the electrical signal, m is the number of avalanche diodes in the silicon photomultiplier, E is the characteristic energy, and q and k are unknown constants.
After the formula (1) is determined, the difference can be corrected according to the factory parameters of the silicon photomultiplier, which is not described herein again.
It is noted that the energy comparator, when comparing the characteristic energies corresponding to the two sources, is based on the difference, or difference, between the characteristic energies corresponding to the two sources being no less than the product of the energy resolution of the scintillation crystal and the corresponding characteristic energy.
Fig. 4 is an energy spectrum before correction according to an embodiment of the present invention, fig. 5 is an energy spectrum after correction according to a method for signal correction according to an embodiment of the present invention, wherein the two sources selected in the embodiments of fig. 4 and 5 are Cs-137 and Na-22, respectively, the characteristic energy corresponding to Cs-137 is 662keV, and the characteristic energy corresponding to Na-22 is 511keV, as can be seen from fig. 4, there are two distinct characteristic peaks a and B in the measured energy spectrum, wherein the characteristic energy corresponding to characteristic peak a is about 510keV, the characteristic energy corresponding to characteristic peak B is about 608keV, which is 8% error from the characteristic energy of Cs-137, and the error is very large and is not enough for a person skilled in the art to clearly distinguish the corresponding source type. Further, as can be seen from the comparison in fig. 5, after the correction is performed by the method of the present invention, the characteristic energy corresponding to the characteristic peak a 'in the energy spectrum is about 511keV, and the characteristic energy corresponding to the characteristic peak B' is about 660keV, which is substantially 0 error compared with the characteristic energy 662keV of Cs-137.
In summary, the signal correction method and device provided by the invention can realize the linear calibration of the silicon photomultiplier, solve the problem of nonlinear deviation of the response of the silicon photomultiplier to energy, improve the photon response dynamic range of the silicon photomultiplier, and are particularly suitable for the application scenario that the silicon photomultiplier directly measures photons or couples with a scintillation crystal to measure ionizing radiation. The method provided by the invention can realize calibration only by using two radiation sources, does not need a standard light source, is simple and convenient to operate and has stable output; the equation calibrated by the method can be directly used for energy linear calibration of the scintillation detector, and the correction effect is very ideal.
The above embodiments are merely preferred embodiments of the present invention, which are not intended to limit the scope of the present invention, and various changes may be made in the above embodiments of the present invention. All simple and equivalent changes and modifications made according to the claims and the content of the specification of the present application fall within the scope of the claims of the present patent application. The invention has not been described in detail in order to avoid obscuring the invention.
Claims (8)
1. A method of signal correction, the method comprising the steps of:
step S1: selecting two radiation sources with different characteristic energies, wherein the two characteristic energies are respectively marked as E1And E2；
Step S2: respectively measuring energy spectrums corresponding to the two radiation sources under fixed voltage by using the same scintillation detector, and respectively obtaining corresponding peak-to-peak values from the energy spectrums, and marking the peak-to-peak values as V1、V2The fixed voltage does not exceed the reverse breakdown voltage of the silicon photomultiplier;
step S3: determining an actual relationship between the electrical signal received by the signal processor and the number of avalanche diodes activated in the silicon photomultiplier tube of the scintillation detector as described in equation (1):
V＝[m(1-e-Ek)]q (equation 1);
wherein V is a peak-to-peak value of the electrical signal, m is the number of avalanche diodes in the silicon photomultiplier, E is characteristic energy, and q and k are unknown constants;
step S4: will be parameter E1、V1And E2、V2And respectively substituting the k and the q into the formula (1) to be solved immediately.
2. The method for signal correction according to claim 1, wherein in step S1, the difference between the characteristic energies corresponding to two of the radiation sources is not less than the product of the energy resolution of the scintillation crystal in the scintillation detector and the corresponding characteristic energy.
3. The method of signal correction according to claim 2, wherein in the step S2, the peak-to-peak value V1And V2Obtained by the following method: respectively measuring a first energy spectrum corresponding to a first radiation source at a fixed voltage by using the same scintillation detector, and acquiring a corresponding first peak-to-peak value recorded as V from the first energy spectrum1(ii) a Respectively measuring second energy spectrums corresponding to the second radiation source at fixed voltage by using the same scintillation detector, and acquiring corresponding second peak-to-peak values, recorded as V, from the second energy spectrums2。
4. The method according to claim 3, wherein in step S2, the first peak-to-peak value is repeatedly measured at least three times, and the average value of the first peak-to-peak value is recorded as V1(ii) a Repeatedly measuring the second peak value for at least three times respectively, and taking the average value of the second peak values as V2。
5. The method of signal correction according to claim 1, characterized in that the formula (1) is obtained by:
step S31: calculating the number of avalanche diodes activated in the silicon photomultiplier:
wherein photons detected by the silicon photomultiplier tube conform to a two-dimensional Poisson distribution P (μ, n), μ being an expectation and n being a sample number; h is the number of the avalanche diodes activated in the silicon photomultiplier; m is the number of the avalanche diodes in the silicon photomultiplier; nd is the number of photons detected by the silicon photomultiplier, NdN is the number of photons incident on the light sensitive surface of the silicon photomultiplier, and D is the photon detection efficiency of the silicon photomultiplier;
step S32: substituting the parameters of formula (2) with NdN and E P0Substituting into equation (2) can result in:
wherein, P0Is the light output of the scintillation crystal, P0D and m are constants, performing parameter substitution, and adding P0D/m is denoted as k, yielding:
H＝m[1-e-(Ek)](equation 4);
step S33: determining an actual relationship between a peak-to-peak value V of the electrical signal received by the signal processor and a number of activated APDs in the SiPM:
V＝H/q＝[m(1-e-Ek)]and/q (equation 1).
6. The method of signal correction according to claim 1, characterized in that the method further comprises step S5: and correcting the difference value according to the delivery parameters of the silicon photomultiplier.
7. An apparatus for signal correction, the apparatus comprising:
an energy comparator for comparing the characteristic energies of two selected radiation sources, wherein the two characteristic energies are respectively marked as E1And E2；
The peak value collector respectively obtains corresponding peak value from the energy spectrums of the two radiation sources under fixed voltage and respectively records the peak value as V1、V2The fixed voltage does not exceed the reverse breakdown voltage of the silicon photomultiplier; and
a parameter calculator, which receives the characteristic energy data sent by the energy comparator and the peak-to-peak data sent by the peak collector, respectively, and further solves unknown parameters and determines the actual relationship between the electrical signal received by the signal processor and the number of activated avalanche diodes in the silicon photomultiplier according to formula (1), and the characteristic energy data and the peak-to-peak data, wherein formula (1) is as follows:
V＝[m(1-e-Ek)]q (equation 1);
wherein V is the peak-to-peak value of the electrical signal, m is the number of avalanche diodes in the silicon photomultiplier, E is the characteristic energy, and q and k are unknown constants.
8. The apparatus according to claim 7, wherein the energy comparator compares the characteristic energies corresponding to the two radiation sources, and the difference between the characteristic energies corresponding to the two radiation sources is not less than the product of the energy resolution of the scintillation crystal and the corresponding characteristic energy.
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