CN108168727B - Low-temperature thermometer based on scintillation crystal and temperature calibration and measurement method thereof - Google Patents

Abstract

The invention belongs to the technical field of radiation detection, and in particular relates to a scintillation crystal-based cryogenic thermometer and a temperature calibration and measurement method thereof. It includes a temperature measurement module, a power supply module, a signal collection and calculation module, and a data collection and display module; the temperature measurement module includes a light hood and coaxially coupled photoelectric devices and signal amplification modules located in the light hood from bottom to top, scintillation crystals, radioactive Isotope sources, metal sheets, scintillation crystals, photoelectric devices and signal amplification modules; the power supply module is connected to the upper and lower photoelectric devices and signal amplification modules; the input terminals of the signal collection and calculation module are respectively connected to the upper and lower photoelectric devices and signal amplification modules The output end of the signal collection and calculation module is connected with the output end of the data acquisition and display module. It provides a new solution for temperature detection in the extremely low temperature environment in the universe.

Description

Cryogenic thermometer based on scintillation crystal and its temperature calibration and measurement method

technical field

The invention belongs to the technical field of radiation detection, in particular to a low temperature thermometer based on scintillation crystals.

Background technique

Temperature is one of the most basic physical dimensions. It is an important attribute for evaluating substances and the environment. It is also an indispensable existence in production and life. Therefore, effective monitoring of temperature is extremely necessary. As a device capable of monitoring temperature, thermometers are widely used in production, life and scientific research. In recent years, with the continuous advancement of people's exploration of the universe, thermometers that can detect the extreme environment of the universe, especially the extremely low temperature environment, are needed.

For the temperature detection of the extreme environment of the universe, the robustness of working for a long time in an extremely low temperature and strong radiation environment, and the detection accuracy of low temperature are particularly important. This requires the thermometer to be resistant to radiation, low temperature, and high enough sensitivity at low temperature, that is to say, the signal should increase as the temperature decreases, not decrease.

Commonly used thermometers can be divided into gas thermometers, resistance thermometers, infrared thermometers, thermocouple thermometers, high temperature thermometers, pointer thermometers, glass tube thermometers, etc. Under the environment, it often cannot work well, and at the same time, the extreme radiation environment in the universe is easy to affect its working state. This is related to the principle of their temperature measurement: a thermometer based on the principle of thermal expansion and contraction of solids, liquids, and gases affected by temperature, after the medium is liquefied or solidified at extremely low temperatures, the volume change decreases, and the Sensitivity; thermometers based on the principle of pyroelectric effect have high requirements on the circuit connection between components, which limits its use in complex environments and thermal radiation is difficult to detect when the temperature is extremely low; therefore For temperature detection in extremely cold environments in the universe, new solutions are needed.

Contents of the invention

The technical problem solved by the present invention is to provide a scintillation crystal-based low-temperature thermometer capable of realizing good temperature detection in an extremely low-temperature environment, and at the same time provide a temperature calibration and temperature measurement method based on the thermometer.

Scintillation crystals, as objects capable of generating scintillation signals, have been used in many applications in the field of radiation detection. However, most of the applications of scintillation crystals in the field of radiation detection are carried out at room temperature, and rarely at extremely low temperatures. The application potential of scintillation crystals at low temperatures has rarely been explored.

For many scintillation crystals at low temperature, due to the decrease in temperature, the thermal motion of the crystal lattice is weakened, and the energy consumption caused by thermal motion is significantly reduced, so that more energy can be output in the form of scintillation light, and the lower the temperature, the light output signal stronger (see Figure 1). Scintillation crystals with such characteristics have natural advantages over other thermometers in the application of low temperature thermometers. At the same time, there is no report on the low-temperature thermometer made by using the principle that the luminescence of the scintillator changes with the temperature at low temperature.

The technical solution of the present invention is to provide a low-temperature thermometer based on scintillation crystals, which is special in that it includes a temperature measurement module, a power supply module, a signal collection and calculation module, and a data collection and display module;

The above-mentioned temperature measurement module includes a hood and a photoelectric device and a signal amplification module, a scintillation crystal, a radioactive isotope source, a metal sheet, a scintillation crystal, a photoelectric device and a signal amplification module that are coaxially coupled from bottom to top in the hood;

The above-mentioned power supply module is respectively connected with the upper and lower photoelectric devices and the signal amplification module;

The input terminals of the above-mentioned signal collection and calculation module are respectively connected with the output terminals of the upper and lower photoelectric devices and the signal amplification module;

The output terminal of the signal collection and calculation module is connected with the data collection and display module.

Scintillation crystals exist on both the upper and lower sides, and the scintillation crystals that are directly coupled with the radioisotope source are used to receive the radiation from the environment and the radioisotope source and convert it into an optical signal; the scintillation crystals that are in direct contact with the metal sheet are used to accept the environment The radiation in the radioactive isotope can be obtained by processing the signals of the two scintillation crystals and converting the radiation signal into an optical signal.

Preferably, for long-term application in a strong radiation environment, the scintillation crystal material is a semiconductor whose forbidden band width should be larger than 2.2eV.

Preferably, the radioactive isotope source is film-shaped, and its lateral dimension is smaller than that of scintillation crystals, photoelectric devices, signal amplification modules, and metal sheets.

Preferably, the lateral dimensions of the scintillation crystal, the photoelectric device, the signal amplification module and the metal sheet are the same.

Preferably, the radioactive isotope source is a heavy ion isotope source, and the generated particles can fully deposit energy in the scintillation crystal and make the scintillation crystal emit light, while being unable to penetrate the metal sheet; the activity of the radioactive isotope source is greater than 1000Bq.

Preferably, the thickness of the radioactive isotope source is less than 100 μm; the thickness of the scintillation crystal is 1-5 mm; and the thickness of the metal sheet is 0.2-2 mm.

The present invention also provides a method for calibrating the above-mentioned low temperature thermometer based on scintillation crystals, comprising the following steps:

Step 1: Place the temperature measurement module in the cryogenic chamber;

Step 2: Vacuum the low-temperature chamber until the air pressure in the low-temperature chamber is lower than 1×10 ^-4 Pa, turn on the power module, and apply voltage to the photoelectric device and signal amplification module to enter the working mode;

Step 3: Record the signal data displayed on the signal collection and calculation module and the temperature displayed in the cryogenic chamber;

Step 4: Operate the low temperature room, control the temperature in the low temperature room, make the system work in different temperature environments, record the corresponding signal data on the signal collection and calculation module at different temperatures, and determine the monotonous increase of the signal strength with the decrease of temperature. The signal data corresponds to the temperature;

Step 5: Keep the air pressure constant, return to normal temperature, and repeat steps 3 and 4 to ensure that the relationship between the obtained signal data and temperature is credible;

Step 6: Input the relationship between the signal data and temperature in step 5 to the data acquisition and display module, and set it in the program so that it can be corrected according to the use time and the attenuation of the radioisotope source, so that the data acquisition and display module The temperature data can be output correctly.

Preferably, the signal collection mode of the signal collection and calculation module in step 3 depends on the activity of the radioisotope source, when the activity of the radioisotope source is less than the set value, the signal collection and calculation module is in pulse mode; when the radioisotope When the activity of the source is greater than the set value, the signal collection and calculation module is adjusted to the current working mode.

The present invention also provides a temperature measurement method using the above scintillation crystal-based low temperature thermometer, comprising the following steps:

Step 1: The scintillation crystal coupled with the radioisotope source directly receives the radiation from the environment and the radioisotope source, and converts it into an optical signal; the scintillation crystal directly in contact with the metal sheet receives the radiation in the environment, and converts the radiation signal into an optical signal ;

Step 2: The signal collection and calculation module collects the two optical signals in step 1, and subtracts them to obtain a net signal;

Step 3: The data collection and display module counts the net signals output by the signal collection and calculation module, and converts them into temperature data for display or output.

Preferably, the signal collection mode of the signal collection and calculation module in step 2 depends on the activity of the radioisotope source, when the activity of the radioisotope source is less than the set value, the signal collection and calculation module is in pulse mode; when the radioisotope When the activity of the source is greater than the set value, the signal collection and calculation module is adjusted to the current working mode.

Principle of the present invention is:

Under low temperature conditions, the luminescence of many scintillation crystals can be greatly enhanced, and the lower the temperature, the greater the enhancement range. This kind of luminescence is sensitive to temperature, which makes it have considerable light output at extremely low temperatures, and is suitable for applications as low temperature detectors. .

Wide bandgap semiconductors are resistant to radiation and are suitable for applications in the complex environment of the universe.

Radioactive isotopes emit radioactive particles all the time. The present invention uses a medium-long (or long) half-life radioactive isotope source, which is a stable excitation source and has a long service life. It does not require additional manual maintenance and only needs to be set The program can modify the result by considering its attenuation.

The beneficial effects of the present invention are:

1. The present invention provides a low-temperature thermometer based on scintillation crystals. The lower the temperature, the stronger the signal. Compared with other thermometers, it is more suitable for extremely low-temperature ambient temperature measurement;

2. A low temperature thermometer based on scintillation crystals provided by the present invention, its key part is scintillation crystals that are often used as radiation detection materials, and its materials are wide bandgap semiconductors, which are resistant to radiation and are more suitable for use in the universe Temperature measurement in harsh environments;

3. The present invention adopts a medium-long (or long) half-life radioactive isotope source, which is a stable excitation source and has a long service life. It does not require additional manual maintenance. It only needs to set the program to consider its attenuation and correct the result. Can.

Description of drawings

Figure 1 shows the variation of the luminous intensity of a typical scintillation crystal with temperature;

Fig. 2 is the structure schematic diagram of the low temperature thermometer based on scintillation crystal of the present invention;

Fig. 3 is the calibration schematic diagram of the thermometer in Fig. 2;

The reference signs in the figure are: 1-radioactive isotope source, 2-scintillation crystal, 3-photoelectric device and signal amplification module, 4-signal collection and calculation module, 5-power supply module, 6-light hood, 7-metal sheet, 8-data acquisition and display module, 9-low temperature room.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

As can be seen from Figure 2, the low temperature thermometer based on scintillation crystals in this embodiment mainly includes a radioactive isotope source 1, a scintillation crystal 2, a photoelectric device and a signal amplification module 3, a signal collection and calculation module 4, a power supply module 5, and a light shield 6, Metal sheet 7, data acquisition and display module 8.

The radioactive isotope source 1 is a thin film with a thickness of less than 100 μm, and there is no limit to the lateral size (that is, the size of the sheet), which is smaller than the lateral size of the scintillation crystal 2, the photoelectric device and the signal amplification module 3, and the metal sheet 7; The lateral dimensions of the scintillation crystal 2, the photoelectric device and the signal amplification module 3, and the metal sheet 7 should be exactly the same. The thicknesses of the upper and lower scintillation crystals 2 should be exactly the same, and the thickness is 1-5 mm; the thickness of the metal sheet 7 is 0.2-2 mm.

Wherein the radioactive isotope source 1 is a heavy ion isotope source (including but not limited to ²⁴¹ Am, ²⁴³ Am, ²⁴² Cm, ²⁴⁴ Cm, ²²⁶ Ra, etc.), the material depends on the particle type and half-life it produces, and the particles produced should be penetrating Weak heavy ions make it possible to fully deposit energy in the scintillation crystal 2 and make it luminous, and at the same time, due to the weak penetrating power, it cannot penetrate the metal sheet 7; the half-life of the material depends on the expected use time of the thermometer, and the general half-life should be within For more than 20 years, if the expected life of the thermometer is longer, a nuclide with a longer half-life should be used.

The activity of the radioisotope source 1 should be at least 1000Bq. When the activity of the radioisotope source 1 is low (such as the activity is less than 1 Curie), the photoelectric device and the signal amplification module 3, the signal collection and calculation module 4 and the data acquisition and The display module 8 works in pulse mode; when the activity of the radioactive isotope source 1 is high (such as the activity is greater than 1 Curie), the photoelectric device and signal amplification module 3, the signal collection and calculation module 4, and the data acquisition and display module 8 Working in current mode, there are different data acquisition schemes according to different modes, which will be explained in the specific working process.

There are scintillation crystals 2 on the upper and lower sides, and the function of the scintillation crystal 2 coupled with the radioisotope source 1 is to receive the radiation from the environment and the radioisotope source 1 and convert it into an optical signal; the scintillation crystal directly in contact with the metal sheet 7 The role of 2 is to accept the radiation in the environment and convert the radiation signal into an optical signal, so that the signals of the two scintillation crystals 2 can be processed to obtain the signal size of the radiation of the radioactive isotope 1; therefore, the upper and lower scintillation crystals 2 The materials should be exactly the same, as should the blinking properties. The material of the scintillation crystal 2 should be a wide bandgap (bandgap greater than 2.2eV) semiconductor, such as silicon carbide (SiC), gallium nitride (GaN), zinc oxide (ZnO), diamond, aluminum nitride (AlN) and oxide Gallium (Ga ₂ O ₃ ) and other materials, because of the wide band gap, high thermal conductivity and radiation resistance of the above materials, are more suitable for long-term applications in strong radiation environments; at the same time, the luminous intensity of this material varies with temperature decreases and monotonically increases. The photoelectric device and the signal amplification module 3 collect the scintillation signal of the scintillation crystal 2, convert it into an electrical signal, and amplify it. The magnification factor is adjusted according to the actual situation.

The function of the signal collection and calculation module 4 is to collect the two signals and subtract them to obtain a net signal. The function of the power supply module 5 is to supply power to the photoelectric device and the signal amplification module 3 . The shading cover 6 is used to shield the ambient light and heavy ion radiation in the environment, and uniformly transmit the external temperature to the scintillation crystal 2, and the material is a substance with good thermal conductivity and stable physical and chemical properties. The metal sheet 7 is used to separate the radioactive isotope source 1 and the scintillation crystal 2 above, to prevent the heavy ion radiation emitted by the radioisotope source 1 from affecting the scintillation crystal 2 above, and to shield the light of the two scintillation crystals to make them glow They do not affect each other, but also play a role in heat conduction. The function of the data collection and display module 8 is to make statistics on the net signals output by the signal collection and calculation module 4, and convert them into temperature data for display or output.

The process of calibrating the thermometer is as follows (taking Figure 3 as an example):

1: Contact and couple the radioactive isotope source 1, scintillation crystal 2, photoelectric device and signal amplification module 3, and metal sheet 7 in the order shown in Figure 2, and ensure that the geometric centers of the above modules are on the same central axis, and cover with a light shield 6 , to encapsulate it.

2: Place the light shield 6 equipped with the radioactive isotope source 1, scintillation crystal 2, photoelectric device and signal amplification module 3, and metal sheet 7 in the low temperature chamber 9, and connect the cables as shown in Figure 3.

3: Vacuum the low-temperature chamber 9 until the air pressure in the low-temperature chamber 9 is lower than 1×10 ^-4 Pa, turn on the power module 5 , and apply voltage to the photoelectric device and the signal amplification module 3 to enter the working mode.

The low temperature chamber 9 should be vacuumed to at least 1×10 ^-4 Pa level, the higher the vacuum degree, the easier it is to realize the low temperature, and the easier it is to maintain the low temperature on the system.

4: Record the signal data displayed on the signal collection and calculation module 4 and the temperature displayed in the low temperature chamber 9;

The signal collection method is explained here:

The signal collection method depends on the activity of the source. When the activity of the source is low, the system is in the pulse working mode. At this time, the signal collection and calculation module 4 plays the role of a multi-channel analyzer, and the statistics are the total of each pulse. Charge, and by accumulating multiple (>10 ⁵ ) pulses, output the amplitude spectrum of the signal, and determine the peak address P(T0) at the temperature T0 from it; when the source activity is high (>1 Curie), it can be considered to adjust the system to the current working mode. At this time, the signal collection and calculation module 4 counts the output currents of the two photoelectric devices and the signal amplification module 3, and subtracts them to eliminate the environmental background, and obtains The net signal current I(T0) at the temperature T0 is input to the data acquisition and display module.

5: Operate the low temperature room 9, control the temperature in the low temperature room, make the system work in different temperature environments, record the peak value or net signal current at different temperatures, and determine the relationship between the signal strength and the monotonous increase of the temperature decrease, so that the peak position The address (or signal current) corresponds to the temperature.

The system should be measured after the temperature in the cryochamber 9 has stabilized.

6: Keep the air pressure constant, return to normal temperature, and repeat steps 4-5 to ensure that the relationship between the obtained peak address (or signal current) and temperature is credible.

7: Input the relationship between the peak value (or signal current) and temperature in step 6 to the data acquisition and display module 8, and set it in the program so that it can be corrected according to the use time and the attenuation of the radioisotope source 1 , so that the data acquisition and display module 8 can correctly output temperature data.

8: After returning to room temperature, return to atmospheric pressure.

Claims (10)

1. A scintillation crystal based cryostat, characterised in that: comprises a temperature measuring module, a power supply module (5), a signal collecting and calculating module (4) and a data collecting and displaying module (8);

the temperature measurement module comprises a light shield (6), and a photoelectric device and signal amplification module (3), a scintillation crystal (2), a radioactive isotope source (1), a metal sheet (7), the scintillation crystal (2), the photoelectric device and signal amplification module (3) which are sequentially and coaxially coupled from bottom to top and are positioned in the light shield (6);

the power supply module (5) is respectively connected with the upper photoelectric device, the lower photoelectric device and the signal amplification module (3);

the input end of the signal collecting and calculating module (4) is respectively connected with the output ends of the upper photoelectric device, the lower photoelectric device and the signal amplifying module (3);

the output end of the signal collection and calculation module (4) is connected with the data acquisition and display module (8).

2. The scintillation crystal-based cryostat of claim 1, wherein: the scintillation crystal (2) is made of a semiconductor with a forbidden band width larger than 2.2 eV.

3. The scintillation crystal-based cryostat of claim 2, wherein: the radioactive isotope source (1) is in the shape of a film, and the transverse dimension of the radioactive isotope source is smaller than that of the scintillation crystal (2), the photoelectric device, the signal amplification module (3) and the metal sheet (7).

4. The scintillation crystal-based cryostat of claim 3, wherein: the transverse sizes of the scintillation crystal (2), the photoelectric device, the signal amplification module (3) and the metal sheet (7) are the same.

5. The scintillation crystal-based cryostat of claim 4, wherein: the radioactive isotope source (1) is a heavy ion isotope source, and the generated particles can completely deposit energy in the scintillation crystal (2) and enable the scintillation crystal (2) to emit light and cannot penetrate through the metal sheet (7); the activity of the radioisotope source (1) is greater than 1000 Bq.

6. The scintillation crystal-based cryostat of claim 5, wherein: the thickness of the radioisotope source (1) is less than 100 μm; the thickness of the scintillation crystal (2) is 1-5 mm; the thickness of the metal sheet (7) is 0.2-2 mm.

7. Method for calibrating a scintillation crystal based cryostat according to any of claims 1 to 6, comprising the steps of:

the method comprises the following steps: placing the temperature measuring module in a low-temperature chamber (9);

step two: the interior of the low-temperature chamber (9) is vacuumized until the air pressure in the low-temperature chamber (9) is lower than 1 x 10^-4After Pa, the power supply module (5) is started, and voltage is applied to the optoelectronic device and the signal amplification module (3) to enable the optoelectronic device and the signal amplification module to enter a working mode;

step three: recording the signal data displayed on the signal collection and calculation module (4) and the temperature displayed by the low-temperature chamber (9);

step four: operating the low-temperature chamber (9), controlling the temperature in the low-temperature chamber (9), enabling the system to work in different temperature environments, recording corresponding signal data on the signal collecting and calculating module (4) at different temperatures, and determining the relationship that the signal intensity monotonically increases along with the decrease of the temperature, so that the signal data correspond to the temperature;

step five: keeping the air pressure unchanged, recovering the normal temperature, and repeating the third step and the fourth step to ensure that the relation between the obtained signal data and the temperature is credible;

step six: and inputting the relationship between the signal data and the temperature in the step five into the data acquisition and display module (8), and setting in a program to correct the relationship according to the use time and the attenuation condition of the radioisotope source (1), so that the data acquisition and display module (8) can correctly output the temperature data.

8. The method of calibrating a scintillation crystal based thermometer according to claim 7, wherein the method further comprises the steps of:

in the third step, the signal collection mode of the signal collection and calculation module (4) depends on the activity of the radioisotope source (1), and when the activity of the radioisotope source (1) is less than a set value, the signal collection and calculation module (4) is in a pulse working mode; and when the activity of the radioisotope source (1) is greater than a set value, adjusting the signal collection and calculation module (4) to be in a current working mode.

9. Method for measuring the temperature using a scintillation crystal based cryostat according to any of the claims 1-6, characterised in that it comprises the following steps:

the method comprises the following steps: the scintillation crystal (2) which is directly contacted and coupled with the radioactive isotope source (1) receives the radiation of the environment and the radioactive isotope source (1) and converts the radiation into an optical signal; the scintillation crystal (2) which is in direct contact with the metal sheet (7) receives radiation in the environment and converts a radiation signal into an optical signal;

step two: the signal collection and calculation module (4) collects the two optical signals in the step one and subtracts the two optical signals to obtain a net signal;

step three: and the data acquisition and display module (8) counts the net signals output by the signal collection and calculation module (4) and converts the net signals into temperature data to display or output.

10. The method of claim 9 for measuring temperature using the scintillation crystal based thermometer of any one of claims 1 to 6, wherein: in the second step, the signal collection mode of the signal collection and calculation module (4) depends on the activity of the radioisotope source (1), and when the activity of the radioisotope source (1) is smaller than a set value, the signal collection and calculation module (4) is in a pulse working mode; and when the activity of the radioisotope source (1) is greater than a set value, adjusting the signal collection and calculation module (4) to be in a current working mode.