CN210982762U - Aviation gamma energy spectrum instrument - Google Patents
Aviation gamma energy spectrum instrument Download PDFInfo
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- CN210982762U CN210982762U CN201922405986.1U CN201922405986U CN210982762U CN 210982762 U CN210982762 U CN 210982762U CN 201922405986 U CN201922405986 U CN 201922405986U CN 210982762 U CN210982762 U CN 210982762U
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Abstract
The utility model discloses an aviation gamma energy spectrum instrument, include: the gamma energy spectrum detector, the pulse signal amplifying circuit, the A/D digital acquisition circuit and the FPGA circuit are sequentially arranged along the photoelectric signal transmission direction; the gamma energy spectrum detector is connected with the pulse signal amplifying circuit and is used for generating current signal pulses according to the received incident gamma; the input end of the A/D digital acquisition circuit is connected with the pulse signal amplification circuit, and the output end of the A/D digital acquisition circuit is connected with the FPGA circuit; the FPGA circuit comprises a digital signal processor, a CPU processor and a double-port memory; the double-port memory connected with the digital signal processor is connected with the input end of the CPU processor through a bus interface; and the output end of the CPU processor is connected with an external computer. By the scheme, the acquired full-spectrum data can be displayed and recorded in real time in the display of a computer interface, and the cosmic ray track counting can be accurately counted and identified.
Description
Technical Field
The utility model relates to an aviation radioactivity geophysical exploration technical field, concretely relates to aviation gamma energy spectrum instrument.
Background
In the technical field of aviation radioactive geophysical exploration, the aviation gamma ray energy spectrum measurement technology in China has been developed for decades, only 4 channels (potassium, uranium, thorium and main channel) of simulation energy spectrum window data measurement can be carried out at first, the advanced level of 256 channels of radioactive energy spectrum digital measurement technology is gradually developed, and the new height of 1024 channels of aviation radioactive energy spectrum analysis and measurement with the international advanced level is achieved at present. The aerial radioactivity gamma energy spectrum measurement mainly utilizes a crystal gamma energy spectrum detector to receive gamma ray particles emitted by radioactive elements, extracts and analyzes data of electric signals generated by gamma energy spectrum rays, and specifically comprises the following steps: gamma energy spectrum ray with 0-3MeV energy emitted by radioactive element in nature is used for data acquisition and fast digital analysis.
Some types of aviation gamma spectrometers, when measuring radioactive element anomaly points with relatively high gamma ray energy, for example: in the radioactive element thorium abnormal area, along with the increase of energy window counting data, the counting increase phenomenon of the cosmic ray channel can occur in different degrees, so that the counting of the cosmic ray channel has larger deviation.
SUMMERY OF THE UTILITY MODEL
In view of the above, an object of the present application is to provide an aviation gamma spectroscopy instrument, so as to solve the technical problem in the prior art that the cosmic ray trace count has a large deviation.
In accordance with the above objects, there is provided, in a first aspect of the present application, an airborne gamma spectroscopy apparatus comprising: the gamma energy spectrum detector, the pulse signal amplifying circuit, the A/D digital acquisition circuit and the FPGA circuit are sequentially arranged along the photoelectric signal transmission direction;
the gamma energy spectrum detector is connected with the pulse signal amplifying circuit and is used for generating current signal pulses according to the received incident gamma;
the input end of the A/D digital acquisition circuit is connected with the pulse signal amplification circuit, and the output end of the A/D digital acquisition circuit is connected with the FPGA circuit;
the FPGA circuit comprises a digital signal processor, a CPU processor and a double-port memory;
the double-port memory connected with the digital signal processor is connected with the input end of the CPU processor through a bus interface; and the output end of the CPU processor is connected with an external computer.
Preferably, the FPGA circuit further includes: a phase-lock controller; and the digital signal processor is respectively connected with the phase-locked controller and the A/D digital acquisition circuit and is used for processing the received voltage pulse signals alternately output by the A/D digital acquisition circuit in real time according to the clock signals provided by the phase-locked controller.
Preferably, the gamma spectrum detector comprises a NaI (Tl) crystal and a photomultiplier tube;
the gamma ray irradiated into the NaI (Tl) crystal generates photoelectrons through the cathode of the photomultiplier tube, and after multiple multiplication and amplification, charge current signal pulses are generated at the anode.
Further, the device also comprises a high-voltage power supply module connected with the photomultiplier tube and used for providing a high-voltage power supply for the photomultiplier tube.
Preferably, the pulse signal amplifying circuit is a high-frequency operational amplifier AD8065 chip.
Furthermore, the pulse signal amplifying circuit is connected with the anode of the photomultiplier and is used for receiving the current pulse signal output by the anode of the photomultiplier.
Further, the digital signal processor adopts an EP4CE15F23 chip.
Further, the a/D digital acquisition circuit includes: and the A/D converter is used for collecting current signal pulses generated by the pulse signal amplifying circuit and converting the current signal pulses into voltage pulse signals.
Further, the a/D converter includes an AD9226 chip;
and the output pin of the AD9226 chip is connected with the interface pin of the digital signal processor.
The aviation gamma energy spectrum instrument can display and record the collected full-spectrum data in real time in the display of a computer interface, and can accurately count and identify the cosmic ray channel count.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the technical solutions in the prior art will be briefly described below. Throughout the drawings, like elements or portions are generally identified by like reference numerals. In the drawings, elements or portions are not necessarily drawn to scale.
FIG. 1 is a schematic structural diagram of an airborne gamma spectroscopy instrument according to an embodiment of the present application;
fig. 2 is a schematic structural diagram of a pulse signal amplifying circuit according to an embodiment of the present application;
fig. 3 is a schematic structural diagram of an FPGA hardware circuit according to an embodiment of the present application.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and therefore are only examples, and the protection scope of the present invention is not limited thereby.
It is to be noted that unless otherwise specified, technical or scientific terms used herein shall have the ordinary meaning as understood by those skilled in the art to which the present invention belongs.
Fig. 1 is a schematic structural diagram of an airborne gamma spectroscopy instrument according to an embodiment of the present application, shown in fig. 1.
The method specifically comprises the following steps:
as can be seen from fig. 1, the aviation gamma energy spectrum instrument of the present embodiment includes a gamma energy spectrum detector, a pulse signal amplifying circuit, an a/D digital acquisition circuit, and an FPGA circuit, which are sequentially arranged along the photoelectric signal transmission direction; the gamma spectrum detector comprises: a gamma spectrum detector, which comprises a NaI (Tl) crystal and a photomultiplier;
the aviation gamma energy spectrum instrument also comprises a high-voltage power supply module connected with the photomultiplier and used for providing a high-voltage power supply for the photomultiplier.
The gamma ray irradiated into the NaI (Tl) crystal generates photoelectrons through the cathode of the photomultiplier tube, and after multiple multiplication and amplification, charge current signal pulses are generated at the anode.
The gamma energy spectrum detector is used for receiving incident gamma rays, generating excited electrons, further generating photoelectrons, and generating current signal pulses through multiple multiplication and amplification; the pulse signal amplifying circuit is used for converting the generated current signal pulse into a voltage pulse signal; the A/D digital acquisition circuit is used for acquiring and alternately outputting the converted voltage pulse signals and detecting cosmic rays according to electric signal pulse overflow; the FPGA circuit is used for providing a clock signal;
the FPGA circuit comprises a digital signal processor, a CPU processor and a double-port memory;
the double-port memory connected with the digital signal processor is connected with the input end of the CPU processor through a bus interface; and the output end of the CPU processor is connected with an external computer. And then displaying and recording the acquired full-spectrum data through a full-spectrum data display module of an external computer.
In addition, the pulse signal amplifying circuit shown in fig. 2 is a high-frequency operational amplifier AD8065 chip.
The pulse signal amplifying circuit is connected with the anode of the photomultiplier and used for receiving a current pulse signal output by the anode of the photomultiplier.
The FPGA circuit shown in fig. 3 further comprises: a phase-lock controller; and the digital signal processor is respectively connected with the phase-locked controller and the A/D digital acquisition circuit and is used for processing the received voltage pulse signals alternately output by the A/D digital acquisition circuit in real time according to the clock signals provided by the phase-locked controller.
The digital signal processor adopts an EP4CE15F23 chip.
The A/D digital acquisition circuit comprises: and the A/D converter is used for collecting current signal pulses generated by the pulse signal amplifying circuit and converting the current signal pulses into voltage pulse signals.
The A/D converter comprises an AD9226 chip;
and the output pin of the AD9226 chip is connected with the interface pin of the digital signal processor.
In this embodiment, the airborne radioactive gamma spectrum measurement mainly uses a crystal gamma spectrum detector to receive gamma ray particles emitted by radioactive elements, and extracts and analyzes data of an electrical signal generated by gamma spectrum rays. The design of the 1024-channel gamma spectrometry instrument for the aviation radioactivity mainly comprises the following steps: gamma ray data acquisition, energy spectrum pulse signal digital analysis processing, radioactive full-spectrum data graphic display and data storage, specifically: gamma energy spectrum rays with 0-3MeV energy emitted by radioactive elements in the nature are subjected to data acquisition and rapid digital analysis processing, the gamma energy spectrum data are respectively and correspondingly accumulated and recorded to data storage positions of 0-1023 channels, and the gamma ray energy spectrum of the main radioactive elements which is monitored and displayed is as follows: setting a potassium channel: 457-523 channel (1370-1570keV), uranium channel setup: 553, 620 (1660, 1860keV), the thorium channel is disposed: 803-937 channels (2410-2810 keV). The gamma rays emitted by the atomic nuclei of natural radioactive substances in the nature have energy below 3MeV, and the gamma rays with energy exceeding 3MeV are high-energy particles from the outer space. Therefore, the gamma ray energy corresponding to 1024 traces of spectral data is 0-3.07MeV, 3 KeV/trace, and the gamma ray particles with energy exceeding 3.07MeV are counted as cosmic rays.
The aviation gamma energy spectrum instrument of the embodiment can adopt a scintillator gamma energy spectrum detector consisting of 16-inch NaI (Tl) crystals and a photomultiplier, and the photomultiplier is supplied with power at high voltage by an adjustable positive high-voltage power supply module with the maximum voltage of 1400V.
When gamma rays are irradiated into the NaI (Tl) crystal, a large number of excited electrons are generated in the crystal, photons generated by the excited electrons capable of emitting fluorescence are emitted to the cathode of the photomultiplier to generate photoelectrons, and after multiple multiplication and amplification, charge current signal pulses are generated at the anode, wherein the charge amplification relation can be expressed as: a ═n(the dynode multiplication coefficient of the photomultiplier tube, and n is the number of dynodes), the charges are collected by an anode capacitor to generate signal pulses, and the amplitude of the pulse signals has a linear relation with the energy of incident gamma rays. Photoelectric multiplierThe tube-added anode output signal is expressed by the following formula:
in the formula, τflThe luminous time constant of NaI (Tl) crystal is about 0.25 uS; tau isαIs a charging time constant; u shape0Is the maximum voltage amplitude after the charge is fully collected.
The A/D digital acquisition circuit selects an AD9226 chip, is 12-bit high-speed A/D conversion and parallel output, the highest conversion rate can reach 65MSPS, a 50MHz sampling frequency is selected, a clock of the A/D converter is provided by an FPGA phase-locked loop module, the sampling period is 20ns, the VREF of the AD9226 chip is set to be 2V, and the corresponding input pulse signal ranges are 1-3V and 2V p-p values. The pulse signal amplifying circuit amplifies and converts the current pulse signal output by the anode of the photomultiplier tube into a voltage pulse signal which accords with the input characteristic of the AD9226 chip; the design requirements are as follows: the output pulse signal generated by gamma ray with 0-3.07MeV energy at the anode of the photomultiplier tube is amplified into a voltage pulse signal of 1-3V. The amplifier circuit is designed by using a high-frequency operational amplifier AD8065 chip, and the power supply design of the amplifier circuit adopts a low ripple coefficient, linearity and +5V single power supply for power supply.
Fig. 2 is a schematic structural diagram of a pulse signal amplifying circuit according to an embodiment of the present application. The voltage amplitude of the signal at the point u1 output by the AD8065 in the amplifying circuit can be represented by the following formula:
in the formula, EYIs the energy of the gamma ray;
Nphotfor gamma rays to enter the scintillator, the number of photons/MeV produced,
efficiency of photon collection for the cathode of a photomultiplier, GPMTIs the photomultiplier gain.
As shown in fig. 3, which is a schematic structural diagram of an FPGA circuit according to an embodiment of the present invention, the FPGA selects a cyclic series EP4CE15F23 chip from a L TERA corporation, the selected external crystal oscillator is 50MHz, a crystal oscillator frequency signal provides a stable clock signal for each functional component through P LL, a 12-bit digital output pin output by a parallel port of an AD9226 chip is connected to an FPGA interface pin, 50M clock frequency required by the AD9226 chip is provided by the FPGA, the data output chip selects a USB to UART chip CP2102, and transmits data to an external computer through the CP2102 in real time through analysis processing of the FPGA, and displays and records the acquired full spectrum data in real time in computer interface display.
Some types of aviation gamma spectrometers, when measuring radioactive element anomaly points with relatively high gamma ray energy, for example: in the radioactive element thorium abnormal area, along with the increase of energy window counting data, the counting increase phenomenon of the cosmic ray channel can occur in different degrees, so that the counting of the cosmic ray channel has larger deviation.
Cosmic gamma rays are high-energy gamma ray particles that enter the earth in the space outside the earth, with energies in excess of 3 MeV. In the design, the input voltage range of the A/D converter is 1-3V, and the corresponding received gamma ray energy is 0-3.07MeV to generate an electric pulse amplitude signal. Gamma rays with energies greater than 3MeV produce pulse signals that can spill out of the a/D converter. The A/D converter causes overflowing signal pulses, namely, pulse signals generated by cosmic gamma rays and non-cosmic gamma rays generate larger signal pulses exceeding 2Vp-p caused by that two or more particles almost simultaneously enter a gamma spectrum detector in a very close time to generate signal superposition at the same time, and the signal pulses also cause A/D overflow; therefore, the pulse signal overflowing from the a/D converter cannot be judged as the count of cosmic rays with energy greater than 3MeV, otherwise, this may cause the phenomenon that the cosmic ray trace count is significantly higher and the cosmic ray recording deviation is larger when the gamma ray spectrum detector measures at the natural radioactive element anomaly point with higher gamma ray energy.
In order to reduce the counting deviation of cosmic rays, a GR-820 aviation gamma ray spectrum instrument developed by Explooranium corporation sets a cosmic ray counting threshold value to be 4MeV, and electric pulse signals generated by gamma rays with energy exceeding 4MeV are counted as cosmic rays.
The technical scheme of the application adopts the following method: and detecting an electric pulse signal corresponding to the gamma ray, starting to detect the overflow time of the electric pulse signal when the amplitude of the electric pulse signal is greater than the 2Vp-p value, and recording the overflow time as cosmic ray count when the overflow time exceeds 1.8 us. The method greatly reduces the probability of gamma rays emitted by radioactive elements with higher energy to enter cosmic ray channel counts.
Designing FPGA program function, namely respectively establishing a P LL phase-locked loop and a double-port memory in engineering, namely establishing 2 modules of the double-port memory with 16-bit data width and 1024 memory units, a CPU, a UART serial port and the like;
the FPGA program design adopts Verilog HD L programming language, 1024-channel gamma ray energy spectrum analysis hardware program design mainly comprises that a 50 MHz/second high-speed receiving ADC circuit collects data, a digital signal processor adopts register number to track and record the data, fast filtering, signal starting point baseline judgment, a pulse shape analysis method is adopted to extract pulse signal amplitude and pulse accumulation identification, a abandoning or correcting processing method is adopted to process pulse accumulation data according to the overlapping size of pulses, judgment and identification processing are carried out on cosmic gamma rays, and the collected energy spectrum data are recorded into a double-port memory through an A port of the double-port memory in real time and are subjected to full spectrum data counting accumulation in the memory.
The aerial gamma energy spectrum instrument can display and record the collected full-spectrum data in real time in the display of a computer interface, and can accurately count and identify the cosmic ray channel count.
Furthermore, through the utility model provides an aviation gamma energy spectrum instrument surveys the gamma ray in. The method also comprises the process of debugging the aviation gamma energy spectrum instrument before detection, and specifically comprises the following steps:
placing a Cs source and a Th source of radioactive elements near a NaI (Tl) crystal, observing 1024 received gamma-ray full-spectrum graphic data, checking the display position of a characteristic peak of an energy spectrum of each element, adjusting a static working point of an amplifier and the amplification factor of the amplifier, recording the display corresponding to the peak position of the gamma-ray energy spectrum generated by the radioactive element cesium to 220 data storage positions, and displaying the peak position of the gamma-ray energy spectrum generated by the radioactive element thorium to 872 data recording positions.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the scope of the embodiments of the present invention, and are intended to be covered by the claims and the specification.
Claims (9)
1. An airborne gamma spectroscopy instrument, comprising: the gamma energy spectrum detector, the pulse signal amplifying circuit, the A/D digital acquisition circuit and the FPGA circuit are sequentially arranged along the photoelectric signal transmission direction;
the gamma energy spectrum detector is connected with the pulse signal amplifying circuit and is used for generating current signal pulses according to the received incident gamma;
the input end of the A/D digital acquisition circuit is connected with the pulse signal amplification circuit, and the output end of the A/D digital acquisition circuit is connected with the FPGA circuit;
the FPGA circuit comprises a digital signal processor, a CPU processor and a double-port memory;
the double-port memory connected with the digital signal processor is connected with the input end of the CPU processor through a bus interface; and the output end of the CPU processor is connected with an external computer.
2. The airborne gamma spectrometry apparatus of claim 1, wherein the FPGA circuit further comprises: a phase-lock controller; and the digital signal processor is respectively connected with the phase-locked controller and the A/D digital acquisition circuit and is used for processing the received voltage pulse signals alternately output by the A/D digital acquisition circuit in real time according to the clock signals provided by the phase-locked controller.
3. The airborne gamma spectrometry apparatus of claim 1, wherein the gamma spectrometry detector comprises a nai (tl) crystal and a photomultiplier tube;
the gamma ray irradiated into the NaI (Tl) crystal generates photoelectrons through the cathode of the photomultiplier tube, and after multiple multiplication and amplification, charge current signal pulses are generated at the anode.
4. The airborne gamma spectrometry apparatus of claim 3, further comprising a high voltage power supply module connected to the photomultiplier tube for providing high voltage power to the photomultiplier tube.
5. The airborne gamma spectrometry instrument according to claim 1, wherein the pulse signal amplification circuit is a high-frequency operational amplifier (AD 8065) chip.
6. The airborne gamma spectrometry apparatus according to claim 3, wherein the pulse signal amplification circuit is connected to the photomultiplier anode for receiving the current pulse signal output from the photomultiplier anode.
7. The airborne gamma spectrometry apparatus of claim 2, wherein the digital signal processor is implemented using an EP4CE15F23 chip.
8. The airborne gamma spectrometry apparatus of claim 4, wherein the A/D digital acquisition circuit comprises: and the A/D converter is used for collecting current signal pulses generated by the pulse signal amplifying circuit and converting the current signal pulses into voltage pulse signals.
9. The airborne gamma spectrometry instrument of claim 8, wherein the a/D converter comprises an AD9226 chip;
and the output pin of the AD9226 chip is connected with the interface pin of the digital signal processor.
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| CN112505745A (en) * | 2020-11-30 | 2021-03-16 | 核工业航测遥感中心 | Automatic music score stabilizing system |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112505745A (en) * | 2020-11-30 | 2021-03-16 | 核工业航测遥感中心 | Automatic music score stabilizing system |
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