Temperature calibration device capable of tracing to second definition and temperature calibration method

Abstract

The invention discloses a temperature calibration device capable of tracing to second definition and a temperature calibration method, and belongs to the field of temperature measurement and quantum precision measurement. The inner walls of a blackbody radiation reference shielding cavity and a blackbody radiation measurement shielding cavity in the device are blackened and are independently arranged in a vacuum cavity; the pulse tube refrigerator is connected with the blackbody radiation reference shielding cavity, the fourth-order Peltier is connected with the blackbody radiation measurement shielding cavity, one end of the high-heat-resistance quartz tube is arranged in the blackbody radiation measurement shielding cavity, and the other end of the high-heat-resistance quartz tube is arranged outside the vacuum cavity. And a platinum resistance thermometer to be calibrated is arranged in the high-heat-resistance quartz tube and is in close contact with the blackbody radiation measurement shielding cavity. The problem that in the prior art, the absolute uncertainty of a temperature calibration result at the room temperature is too high, and the requirement for high-precision measurement is difficult to meet can be solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of temperature measurement and quantum precision measurement, and particularly relates to a temperature calibration device traceable to the definition of a second and a temperature calibration method. BACKGROUND

[0002] Temperature, as one of the seven basic physical quantities of the International System of Units (SI), is of great importance in scientific research, industrial production and metrology. Although the Kelvin was redefined based on the Boltzmann constant in 2019, the practical application still relies on the ITS-90 fixed-point system, which fails to fully exploit the potential of quantum metrology.

[0003] Currently, the International Temperature Scale (ITS-90) and traditional temperature calibration methods rely on the phase transition characteristics of materials (such as the phase transition points of water, hydrogen, silver, and the melting point of gallium) or the performance of radiation standards. The accuracy is limited by the physical state of the material, such as purity, pressure stability, chemical composition, and thermodynamic equilibrium conditions. For example, the reproduction of the triple point of water may introduce errors on the order of millikelvin due to trace impurities or pressure fluctuations, and the fixed-point method is only suitable for discrete temperature points, making it difficult to achieve continuous temperature calibration. In addition, traditional fixed-point calibration methods require bulky constant-temperature ovens and high-purity materials, and can only perform intermittent calibration at specific phase transition points (such as the triple point of water), introducing additional errors through interpolation for other temperatures.

[0004] With the development of quantum precision measurement technology, new temperature measurement methods based on atomic physics principles have shown unique advantages. Existing quantum temperature measurement techniques are mainly based on the blackbody radiation frequency shift effect of Rydberg atoms. The principle is to use the sensitive response of highly excited atoms to GHz-THz band radiation field to infer the environmental temperature. Although this method theoretically realizes direct measurement independent of the traditional temperature scale, there are significant limitations in practical application. First, the selective field ionization detection of Rydberg atoms is extremely sensitive to stray electric fields, and even small electric field fluctuations (as low as mV / cm) can cause significant distortion of the ionization signal, severely affecting the reliability of the measurement results, and it is difficult to shield the thermal radiation interference from the walls of the vacuum cavity and other experimental devices themselves. Second, the temperature measurement uncertainty of existing techniques can only reach about 2 K (Kelvin) near room temperature, which cannot meet the precision measurement requirements. SUMMARY

[0005] The purpose of the present application is to provide a temperature calibration device traceable to the definition of a second and a temperature calibration method to solve the problem of high absolute uncertainty of existing temperature calibration results at room temperature, which is difficult to meet the high-precision measurement requirements.

[0006] To achieve the above purpose, the present application adopts the following technical solutions: In a first aspect, a temperature calibration device traceable to a second definition comprises: a vacuum cavity, a pulse tube refrigerator, cold strontium atom groups, a blackbody radiation reference shield cavity, a probe laser, a movable optical lattice, a blackbody radiation measurement shield cavity, a high thermal resistance quartz tube, a fourth-order Peltier, and a platinum resistance thermometer to be calibrated. Inner walls of the blackbody radiation reference shield cavity and the blackbody radiation measurement shield cavity are blackened, and are independently arranged inside the vacuum cavity. The pulse tube refrigerator is connected to the blackbody radiation reference shield cavity, the fourth-order Peltier is connected to the blackbody radiation measurement shield cavity, one end of the high thermal resistance quartz tube is arranged inside the blackbody radiation measurement shield cavity, and the other end is arranged outside the vacuum cavity. The platinum resistance thermometer to be calibrated is installed inside the high thermal resistance quartz tube and closely contacts the blackbody radiation measurement shield cavity. In use, the cold strontium atom groups are transported from the vacuum cavity to the blackbody radiation reference shield cavity and the blackbody radiation measurement shield cavity through the movable optical lattice. The probe laser synchronously and differentially measures the atomic transition frequency of the cold strontium atom groups in the blackbody radiation reference shield cavity and the blackbody radiation measurement shield cavity, so as to calculate the absolute temperature of the blackbody radiation measurement shield cavity to calibrate the platinum resistance thermometer to be calibrated.

[0007] In some embodiments, the movable optical lattice is composed of two 813 nm lasers propagating towards each other.

[0008] In some embodiments, the probe laser is a 698 nm ultra-stable clock laser, and the frequency is stabilized at the order of hertz.

[0009] In a second aspect, a temperature calibration method of a temperature calibration device traceable to a second definition is based on the temperature calibration device, and comprises the following steps: Starting the pulse tube refrigerator to reduce the temperature in the blackbody radiation reference shield cavity, and at the same time, applying electricity to the fourth-order Peltier to control the temperature of the blackbody radiation measurement shield cavity through the fourth-order Peltier; After preparing two groups of cold strontium atom groups in the vacuum cavity by using laser cooling technology, the groups are synchronously transported to the center of the blackbody radiation reference shield cavity and the blackbody radiation measurement shield cavity along different directions through the movable optical lattice; The platinum resistance thermometer to be calibrated is placed in the blackbody radiation measurement shield cavity through the high thermal resistance quartz tube and closely contacts the blackbody radiation measurement shield cavity; The atomic transition frequency of the cold strontium atom groups in the blackbody radiation reference shield cavity and the blackbody radiation measurement shield cavity is synchronously and differentially measured by the probe laser, and the blackbody radiation frequency shift of the atoms in the blackbody radiation measurement shield cavity is obtained; Based on the relationship between the blackbody radiation frequency shift and the temperature, the temperature of the blackbody radiation measurement shield cavity is inversely deduced according to the blackbody radiation frequency shift of the atoms in the blackbody radiation measurement shield cavity, and is compared and calibrated with the reading of the platinum resistance thermometer to be calibrated, so as to realize the temperature calibration traceable to the second definition.

[0010] In some embodiments, the pulse tube refrigerator is started to reduce the temperature in the blackbody radiation reference shielded cavity to 4.2K.

[0011] In some embodiments, the calibration range of the temperature of the blackbody radiation measurement shielded cavity controlled by the fourth-order Peltier is 200K~350K.

[0012] In some embodiments, the calibration accuracy of the temperature of the blackbody radiation measurement shielded cavity controlled by the fourth-order Peltier is greater than 0.01K.

[0013] In some embodiments, the temperature of the blackbody radiation measurement shielded cavity controlled by the fourth-order Peltier is stabilized within ±0.1K of the calibration range.

[0014] In some embodiments, the synchronous differential measurement adopts a synchronous data acquisition system to ensure that the atomic transition frequency measurement time of the blackbody radiation reference shielded cavity and the blackbody radiation measurement shielded cavity is synchronized, thereby reducing system error.

[0015] In some embodiments, the cold strontium atom group is synchronously transported to the center of the blackbody radiation reference shielded cavity and the blackbody radiation measurement shielded cavity in different directions respectively by the movable optical lattice, and is kept in an adiabatic trapping state to avoid atom heating or coherence destruction.

[0016] Compared with the prior art, the present application has the following beneficial effects: The present application provides a temperature calibration device traceable to the second definition, which first sets double cavities, i.e., a blackbody radiation reference shielded cavity and a blackbody radiation measurement shielded cavity, inside a vacuum cavity, and connects pulse tube refrigerators and fourth-order Peltiers respectively for temperature control, thereby realizing active isolation and precise control of environmental blackbody radiation and overcoming the problem of uncontrollable parasitic radiation introducing system error in traditional Rydberg temperature measurement. Secondly, one end of a high-thermal-resistance quartz tube is arranged inside the blackbody radiation measurement shielded cavity, and the other end is arranged outside the vacuum cavity. A platinum resistance thermometer to be calibrated is installed inside the high-thermal-resistance quartz tube and closely contacts the blackbody radiation measurement shielded cavity, which can insert the platinum resistance thermometer to be calibrated without damaging the vacuum. Finally, a cold strontium atom group is transported from inside the vacuum cavity to the blackbody radiation reference shielded cavity and the blackbody radiation measurement shielded cavity respectively by a movable optical lattice, which can realize precise transportation of the cold strontium atom group. In combination with the above device structure, the blackbody radiation reference shielded cavity and the blackbody radiation measurement shielded cavity are equivalent to two independent strontium atom optical lattice clocks. Through synchronous differential measurement technology, the absolute uncertainty of temperature calibration can be greatly reduced.

[0017] The present application provides a temperature calibration method of a temperature calibration device traceable to the second definition, first, the atomic transition frequency of the cold strontium atom group in the blackbody radiation reference shielded cavity and the blackbody radiation measurement shielded cavity is measured by synchronous differential measurement of the probe laser, which successfully suppresses the system common mode noise and improves the stability and accuracy of the frequency shift measurement; second, the blackbody radiation frequency shift of the atom in the blackbody radiation measurement shielded cavity is obtained by synchronous differential measurement, and based on the relationship between the blackbody radiation frequency shift and the temperature, the temperature of the blackbody radiation measurement shielded cavity is inversely deduced according to the blackbody radiation frequency shift, and compared and calibrated with the reading of the platinum resistance thermometer to be calibrated, realizing the temperature calibration traceable to the second definition. Since the temperature inference is based on the quantitative response of the strontium atomic transition frequency to the blackbody radiation frequency shift, and the frequency can be directly traced to the second definition, the present application can realize absolute temperature measurement without relying on any intermediate temperature scale, which theoretically ensures the accuracy and reliability of temperature traceability, completely gets rid of the dependence on material properties, and directly realizes absolute temperature measurement traceable to the second definition of the international system of units through the physical correlation between atomic transition frequency and temperature, solving the calibration error problem caused by material instability in the traditional method. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 A structure diagram of a temperature calibration device traceable to the second definition is provided for the embodiments of the present application. Figure 2 A flowchart of a temperature calibration method of a temperature calibration device traceable to the second definition is provided for the embodiments of the present application.

[0019] In the figure, 1 is a vacuum cavity, 2 is a pulse tube refrigerator, 3 is a first cold strontium atom group, 4 is a blackbody radiation reference shielded cavity, 5 is a first probe laser, 6 is a first movable optical lattice, 7 is a blackbody radiation measurement shielded cavity, 8 is a second probe laser, 9 is a second movable optical lattice, 10 is a second cold strontium atom group, 11 is a platinum resistance thermometer to be calibrated, 12 is a high thermal resistance quartz tube, and 13 is a four-stage Peltier. DETAILED DESCRIPTION

[0020] In the following, only certain exemplary embodiments are simply described, and the described embodiments can be modified in various different ways without departing from the spirit or scope of the present application. Therefore, the drawings and the description are considered to be exemplary in nature rather than limiting.

[0021] In the description of the present application, it needs to be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed or operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0022] In addition, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited.

[0023] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral; it can be mechanical connection, or electrical connection, or communication; it can be direct connection, or indirect connection through intermediate medium, it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0024] The embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0025] Embodiment one As Figure 1 shown, the present embodiment provides a temperature calibration device traceable to the second definition, which comprises a vacuum cavity 1, a pulse tube refrigerator 2, a first cold strontium atom group 3, a second cold strontium atom group 10, a blackbody radiation reference shield cavity 4, a blackbody radiation measurement shield cavity 7, a high thermal resistance quartz tube 12 and a four-stage Peltier 13 arranged in the vacuum cavity 1, Figure 1In the embodiment, the vacuum cavity 1 constitutes the device main frame, the pulse tube refrigerator 2 is connected with the blackbody radiation reference shielded cavity 4, and the fourth-order Peltier 13 is connected with the blackbody radiation measurement shielded cavity 7. Two sets of independent optical systems are respectively used for atomic manipulation and detection of the blackbody radiation reference shielded cavity 4 and the blackbody radiation measurement shielded cavity 7, including the first movable optical lattice 6 and the second movable optical lattice 9, the first detection laser 5 and the second detection laser 8. The platinum resistance thermometer 11 is inserted into the blackbody radiation measurement shielded cavity 7 through the high-thermal-resistance quartz tube 12.

[0026] The inner walls of the blackbody radiation reference shielded cavity 4 and the blackbody radiation measurement shielded cavity 7 are blackened, the blackbody radiation measurement shielded cavity 7 is provided with a movable platinum resistance thermometer 11, the first detection laser 5 and the second detection laser 8 share the same reference laser source, and the first movable optical lattice 6 and the second movable optical lattice 9 respectively transport the first cold strontium atom group 3 and the second cold strontium atom group 10 to the blackbody radiation reference shielded cavity 4 and the blackbody radiation measurement shielded cavity 7.

[0027] The temperature of the blackbody radiation reference shielded cavity 4 of the embodiment is cooled to 4.2K by the pulse tube refrigerator 2, and the temperature of the blackbody radiation measurement shielded cavity 7 is controlled by the fourth-order Peltier 13 to be in the range of 200K-350K. The platinum resistance thermometer 11 is inserted into the blackbody radiation measurement shielded cavity 7 from the outside of the vacuum cavity 1 through the high-thermal-resistance quartz tube 12, and is in direct contact with the inner wall of the blackbody radiation measurement shielded cavity 7 to achieve thermal equilibrium.

[0028] The first detection laser 5 and the second detection laser 8 use the same reference laser source, and detect the first cold strontium atom group 3 in the blackbody radiation reference shielded cavity 4 and the second cold strontium atom group 10 in the blackbody radiation measurement shielded cavity 7 through a beam splitting device, respectively. The first movable optical lattice 6 and the second movable optical lattice 9 are generated by the same laser system, and the frequencies of the two light lattice lasers are controlled by an acousto-optic modulator, respectively.

[0029] The blackbody radiation reference shielded cavity 4 and the blackbody radiation measurement shielded cavity 7 are both made of high-thermal-conductivity copper material, and the emissivity of the inner surface after blackening treatment is greater than 0.97.

[0030] The device provided by the embodiment works as follows: first, two groups of identical cold strontium atoms are prepared in the center of the vacuum cavity 1 by laser cooling, and then the two groups of atoms are transported to the blackbody radiation reference shielding cavity 4 and the blackbody radiation measurement shielding cavity 7 by the first movable optical lattice 6 and the second movable optical lattice 9 respectively. Since the embodiment adopts a double-cavity differential measurement design, the blackbody radiation reference shielding cavity 4 maintains a 4.2K ultra-low temperature environment, and the influence of the blackbody radiation of the blackbody radiation reference shielding cavity 4 on the atomic clock transition frequency can be ignored; the temperature change of the blackbody radiation measurement shielding cavity 7 affects the atomic clock transition frequency through blackbody radiation, and by measuring the difference between the atomic clock transition frequencies in the blackbody radiation reference shielding cavity 4 and the blackbody radiation measurement shielding cavity 7 and combining the theoretical relationship between the blackbody radiation frequency shift and the temperature, the absolute temperature of the measurement shielding cavity 7 can be directly deduced. The temperature measurement method is completely based on the Boltzmann constant and the atomic clock transition frequency, and realizes the direct traceability of the basic unit (second) in the International System of Units (SI).

[0031] The main body of the device is constructed in an ultra-high vacuum system maintained by the vacuum cavity 1, and the two groups of identical atoms prepared in the center of the vacuum cavity 1 are transported to the blackbody radiation reference shielding cavity 4 and the blackbody radiation measurement shielding cavity 7 respectively under the driving of the one-dimensional movable optical lattice to measure the transition frequency, which is equivalent to two independent strontium atomic clocks. The blackbody radiation reference shielding cavity 4 and the blackbody radiation measurement shielding cavity 7 are both made of copper with high thermal conductivity, and the inner walls of the two cavities are blackened to improve the emissivity and make them approach ideal blackbodies. The pulse tube refrigerator 2 reduces the temperature of the blackbody radiation reference shielding cavity to 4.2K, and after the first group of cold strontium atoms 3 is moved into the blackbody radiation reference shielding cavity by the movable optical lattice, the first group of cold strontium atoms 3 mainly receives the blackbody radiation from the 4.2K inner wall. The influence of the blackbody radiation at this temperature on the atomic transition frequency is very small and can be ignored, so the measurement result can be regarded as a reference frequency independent of the blackbody radiation of the shielding cavity, which is used for subsequent differential frequency analysis.

[0032] The fourth-order Peltier 13 can accurately control the temperature of the blackbody radiation measurement shielded cavity 7 in the range of 200K-350K. The high thermal resistance quartz tube 12 extends into the blackbody radiation measurement shielded cavity 7 at one end and extends out of the vacuum cavity at the other end, connecting the blackbody radiation measurement shielded cavity to the environment outside the vacuum cavity. The platinum resistance thermometer to be calibrated 11 can be placed into the blackbody radiation measurement shielded cavity from outside the vacuum cavity through the quartz tube 12 without breaking the ultra-high vacuum environment in the vacuum cavity, and the high thermal resistance of the high thermal resistance quartz tube 12 can also avoid the influence of external environment fluctuations on the calibration results. The platinum resistance thermometer to be calibrated 11 is in direct contact with the blackbody radiation measurement shielded cavity 7, and after quickly reaching thermal equilibrium, it can be considered that its temperature is the same as the temperature of the cavity. By synchronously measuring the atomic transition frequency in the two cavities, the temperature of the blackbody radiation measurement shielded cavity 7 is obtained, and the temperature calibration of the platinum resistance thermometer to be calibrated 11 is realized. In order to improve the measurement accuracy, the first probe laser 5 and the second probe laser 8 share a reference laser for synchronous differential measurement of the two atomic samples.

[0033] The key of the whole device is its independent double-cavity design and synchronous measurement function. After laser cooling and trapping, the atomic samples form two equivalent atomic groups. These two atomic groups are then transported to the blackbody radiation reference shielded cavity 4 and the blackbody radiation measurement shielded cavity 7 by the moving optical lattice. Both of them are measured for clock transition frequency under the irradiation of the same reference laser. Since the blackbody radiation frequency shift of the atomic clock transition frequency in the blackbody radiation reference shielded cavity 4 can be ignored, the measured transition frequency can be regarded as the system reference zero point; at this time, the frequency shift of the atomic clock transition frequency in the blackbody radiation measurement shielded cavity 7 is completely contributed by the blackbody radiation frequency shift caused by the wall temperature of the blackbody radiation measurement shielded cavity 7. The difference between the two is the net blackbody radiation frequency shift caused by the temperature of the blackbody radiation measurement shielded cavity 7, so that the absolute temperature of the blackbody radiation measurement shielded cavity 7 is inversely deduced through the known relationship between the blackbody radiation frequency shift and the temperature, which is used to calibrate the platinum resistance thermometer. Since the blackbody radiation frequency shift inversely deduces the temperature without depending on any material or experimental conditions, but only related to the Boltzmann constant, the device realizes the temperature calibration traceable to the definition of second.

[0034] Embodiment two Based on the temperature calibration device provided in embodiment one, as shown in Figure 2 The temperature calibration method of the temperature calibration device traceable to the definition of second includes the following steps: First, start the pulse tube refrigerator 2 to reduce the temperature of the blackbody radiation reference shielded cavity 4 to 4.2K, and at the same time, power on the fourth-order Peltier 13 and accurately control the temperature of the blackbody radiation measurement shielded cavity 7 in the target temperature range of 200K-350K through feedback adjustment. Under the ultra-high vacuum environment of the vacuum cavity 1, two groups of strontium atomic samples, i.e. the first cold strontium atomic group 3 and the second cold strontium atomic group 10, are prepared by using laser cooling technology.

[0035] The first and second cold strontium atom groups 3 and 10 are then loaded into the first and second movable optical lattices 6 and 9, respectively. Both movable optical lattices are composed of two counter-propagating 813 nm laser beams with tunable frequencies. By precisely controlling the frequency difference between the two laser beams, the overall translation of the lattice potential is achieved, thus the cold strontium atom groups are synchronously transported from the main experimental zone to the center of the blackbody radiation reference shielded cavity 4 and the blackbody radiation measurement shielded cavity 7 without breaking the confinement. Specifically, two cold atom groups with consistent conditions, comparable atom numbers and close temperatures are prepared in one experimental cycle, and are synchronously transported to the center of the blackbody radiation reference shielded cavity 4 and the blackbody radiation measurement shielded cavity 7 along different directions by the two movable optical lattices, respectively. The dynamic control of the lattices ensures that the atoms are always in the adiabatic trapping state during the transfer process, avoiding heating and coherence destruction caused by lattice acceleration or asymmetric potential.

[0036] During the measurement, the first and second cold strontium atom groups 3 and 10 are confined in the blackbody radiation reference shielded cavity 4 and the blackbody radiation measurement shielded cavity 7, respectively. The blackbody radiation reference shielded cavity 4 is maintained at 4.2 K, and its inner wall is treated with a special coating, which has high emissivity and good radiation uniformity. According to the blackbody radiation frequency shift theoretical model (i.e., the relationship between the blackbody radiation frequency shift and the temperature): The calculation shows that the contribution of the blackbody radiation frequency shift to the atomic transition frequency at 4.2 K can be ignored, so the measurement result of the atomic transition frequency in the blackbody radiation reference shielded cavity 4 is taken as the system reference frequency zero point.

[0037] The blackbody radiation measurement shielded cavity 7 is the main temperature calibration area. Its temperature can be accurately controlled between 200 K and 350 K by the fourth-order Peltier 3 and the temperature control module. The blackbody radiation measurement shielded cavity 7 has the same structure as the blackbody radiation reference shielded cavity 4, and the inner wall is also blackened to have a high equivalent emissivity. When calibrating the platinum resistance thermometer 11 to be calibrated, the platinum resistance thermometer 11 to be calibrated is first placed in the blackbody radiation measurement shielded cavity 7 through a high-thermal-resistance quartz tube 12 and is in close contact with the cavity of the blackbody radiation measurement shielded cavity 7. After thermal equilibrium, it is considered that the temperature of the platinum resistance thermometer 11 to be calibrated is the same as that of the blackbody radiation measurement shielded cavity 7. Two beams of 698 nm ultra-stable clock lasers from the same narrow line width and with frequency stability in the order of hertz, i.e., the first probe laser 5 and the second probe laser 8, are used to synchronously and differentially measure the atomic transition frequencies in the blackbody radiation reference shielded cavity 4 and the blackbody radiation measurement shielded cavity 7. Since there is only a temperature difference between the two cavities, and the blackbody radiation frequency shift of the blackbody radiation reference shielded cavity 4 can be ignored, the differential measurement result is the blackbody radiation frequency shift of the blackbody radiation measurement shielded cavity 7. The temperature of the blackbody radiation measurement shielded cavity 7 can be inferred by using the relationship between the blackbody radiation frequency shift and the temperature. Since the frequency stability of the ultra-stable clock laser used in the measurement is in the order of millihertz and can be directly traced to the international second definition, the temperature of the blackbody radiation measurement shielded cavity 7 inferred based on the change of the atomic transition frequency is essentially an absolute temperature measurement. Specifically, the blackbody radiation frequency shift is caused by the perturbation of the atomic energy level by the electromagnetic radiation field, and the frequency shift amount can be strictly calculated by quantum electrodynamics theory, and the relationship with the temperature has been verified in many high-precision experiments.

[0038] Therefore, the temperature of the blackbody radiation measurement shielded cavity 7 is inferred by combining the frequency shift amount obtained by synchronous differential measurement with the above theoretical model, and the calibration of the platinum resistance thermometer 11 to be calibrated is realized. It does not rely on any intermediate temperature standard or empirical calibration, but is directly based on the basic physical constants and the second definition, and has absolute traceability. Based on this, the temperature of the blackbody radiation measurement shielded cavity 7 inferred by this method can be used as a high-accuracy temperature reference for the calibration and calibration of platinum resistance thermometers, significantly improving the reliability and accuracy of the temperature measurement system.

[0039] In another embodiment, different kinds of alkaline earth metal atoms (such as ytterbium, calcium, magnesium, etc.) can be used instead of strontium atoms, and only the laser cooling system and the probe laser wavelength need to be adjusted accordingly. The temperature of the blackbody radiation reference shielded cavity 4 can also be selected as other extremely low temperatures (such as 10 K), as long as the blackbody radiation frequency shift at this temperature can be ignored. The temperature range of the blackbody radiation measurement shielded cavity 7 can be extended to 77 K-500 K according to actual needs, and only the temperature control system needs to be adjusted accordingly. These variants are within the scope of the present application.

[0040] The above embodiment addresses the key defects of Rydberg atomic temperature measurement technology and establishes a new quantum temperature standard with millikelvin-level accuracy. The existing Rydberg method is limited by the uncertainty of ionization detection and environmental interference, and can only achieve a measurement uncertainty of about 2 K in the room temperature region. The above embodiment uses a strontium atomic optical lattice clock as a quantum sensor and utilizes its The ultra-narrow linewidth and precisely controllable blackbody radiation frequency shift response of the optical lattice clock reduce the absolute uncertainty of temperature measurement to below 15 mK. This breakthrough is primarily due to three technological innovations: first, the optical lattice clock's atomic transition frequency response to blackbody radiation has a higher signal-to-noise ratio; second, the dual-temperature reference cavity design (blackbody radiation reference shielded cavity 4 and blackbody radiation measurement shielded cavity 7) effectively suppresses ambient thermal radiation interference; and finally, a synchronous differential measurement protocol eliminates system common-mode noise. These improvements enable the temperature calibration device provided in this embodiment to meet the stringent national metrology standards for temperature standards.

[0041] Furthermore, to address the environmental interference challenge in temperature measurement, the blackbody radiation measurement shielding cavity 7 and the blackbody radiation reference shielding cavity 4 are precision-machined from high-thermal-conductivity, oxygen-free copper, and their inner surfaces are specially treated to achieve an emissivity very close to that of a blackbody. The blackbody radiation reference shielding cavity 4 is stabilized at an ultra-low temperature of 4.2K via a closed-loop controlled pulse tube refrigerator; the blackbody radiation measurement shielding cavity 7 utilizes a four-stage Peltier temperature control system, whose temperature can be precisely adjusted within a range of 200-350K. This dual-cavity design allows the trapped atoms to perceive only the controllable blackbody radiation field within the shielding cavity, virtually isolating them from external thermal radiation interference. Through synchronous differential measurement technology, the above embodiment achieves systematic suppression of four key interference factors: residual ambient blackbody radiation, second-order Zeeman frequency shift, background gas collision frequency shift, and lattice light frequency shift. The core of this approach is the real-time, synchronous measurement of the transition frequency offset of the strontium atomic optical lattice clock in the blackbody radiation reference shielding cavity 4 and the blackbody radiation measurement shielding cavity 7, eliminating common-mode noise by constructing a differential signal.

[0042] Therefore, the present invention adopts strontium atomic optical lattice clock as quantum sensor, and utilizes its 10 -19The ultra-narrow linewidth and high signal-to-noise ratio transition characteristics of the order of magnitude reduce the absolute temperature measurement uncertainty to below 15 mK, which is significantly better than the traditional Rydberg technology. The performance improvement benefits from the innovation of the specific technical solution: first, the double-cavity (blackbody radiation reference shield cavity and blackbody radiation measurement shield cavity) design combines pulse tube refrigeration and four-stage Peltier temperature control, realizes active isolation and accurate control of the environmental blackbody radiation, and overcomes the problem of uncontrollable parasitic radiation in the traditional Rydberg temperature measurement. Second, through synchronous differential measurement, the relative frequency shift measurement of the two groups of strontium atomic optical lattice clocks is carried out under the same beam of ultra-stable laser, which successfully suppresses the system common-mode noise and improves the stability and accuracy of the frequency shift measurement. Since the temperature inference is based on the quantitative response of the strontium atomic transition frequency to the blackbody radiation frequency shift, and the frequency can be directly traced to the second definition, the present application can realize absolute temperature measurement without relying on any intermediate temperature scale, which ensures the accuracy and reliability of temperature traceability in principle. In addition, the present application completely eliminates the dependence on material properties through blackbody radiation (BBR) frequency shift measurement based on strontium atomic optical lattice clocks, and directly realizes absolute temperature measurement traceable to the second definition of the International System of Units through the physical correlation between atomic transition frequency and temperature, solving the calibration error problem caused by material instability in traditional methods. Through modular design (such as a movable optical lattice clock), the system has comparable portability to traditional platinum resistance thermometers and is suitable for various scenarios such as laboratories and industrial sites. Therefore, the present application has fundamentally surpassed the existing Rydberg temperature measurement technology in terms of precision, environmental control and traceability.

[0043] From the technical common sense, the present application can be realized by other embodiments without departing from the spirit or essential characteristics thereof. Therefore, the above disclosed embodiments, in terms of various aspects, are only illustrative and not the only ones, and all changes within the scope of the present application or within the scope equivalent to the present application are included in the present application.

Claims

1. A temperature calibration device traceable to the definition of seconds, characterized in that include: Vacuum cavity (1), pulse tube refrigerator (2), cold strontium atomic group, blackbody radiation reference shielding cavity (4), detection laser, movable optical lattice, blackbody radiation measurement shielding cavity (7), high thermal resistance quartz tube (12), fourth-order Peltier (13) and platinum resistance thermometer to be calibrated (11); The inner walls of the blackbody radiation reference shielding cavity (4) and the blackbody radiation measurement shielding cavity (7) are both blackened and independently arranged inside the vacuum cavity (1). The pulse tube refrigerator (2) is connected to the blackbody radiation reference shielding cavity (4), and the fourth-order Peltier (13) is connected to the blackbody radiation measurement shielding cavity (7). One end of the high thermal resistance quartz tube (12) is arranged inside the blackbody radiation measurement shielding cavity (7), and the other end is arranged outside the vacuum cavity (1). The platinum resistance thermometer (11) to be calibrated is installed in the high thermal resistance quartz tube (12). The blackbody radiation measurement shielding cavity (7) is located inside the vacuum cavity (1) and is in close contact with the blackbody radiation measurement shielding cavity (7). When in use, the cold strontium atomic group is transported from the vacuum cavity (1) to the blackbody radiation reference shielding cavity (4) and the blackbody radiation measurement shielding cavity (7) respectively through the movable optical lattice. The detection laser synchronously and differentially measures the atomic transition frequency of the cold strontium atomic group in the blackbody radiation reference shielding cavity (4) and the blackbody radiation measurement shielding cavity (7), thereby calculating the absolute temperature of the blackbody radiation measurement shielding cavity (7) to calibrate the platinum resistance thermometer (11) to be calibrated.

2. A temperature calibration device traceable to the definition of seconds according to claim 1, characterized in that: The movable optical lattice is composed of two 813 nm laser beams propagating in opposite directions.

3. A temperature calibration device traceable to the definition of seconds according to claim 1, characterized in that: The detection laser is a 698nm ultra-stable clock laser, and the frequency is stable at the Hertz level.

4. A method for temperature calibration of a temperature calibration device traceable to the definition of seconds, characterized in that: The temperature calibration device according to any one of claims 1 to 3 comprises the following steps: Starting the pulse tube refrigerator (2) to reduce the temperature in the blackbody radiation reference shielding cavity (4), and simultaneously energizing the fourth-order Peltier (13) to control the temperature of the blackbody radiation measurement shielding cavity (7) through the fourth-order Peltier (13); After two cold strontium atomic clusters are prepared in a vacuum cavity (1) using laser cooling technology, they are synchronously transported in different directions to the centers of a blackbody radiation reference shielding cavity (4) and a blackbody radiation measurement shielding cavity (7) through the movable optical lattice; The platinum resistance thermometer (11) to be calibrated is placed into the blackbody radiation measurement shielding cavity (7) through the high thermal resistance quartz tube (12) and is in close contact with the blackbody radiation measurement shielding cavity (7); Performing synchronous differential measurement of the atomic transition frequencies of the cold strontium atomic clusters in the blackbody radiation reference shielding cavity (4) and the blackbody radiation measurement shielding cavity (7) by using the detection laser to obtain the blackbody radiation frequency shift of the atoms in the blackbody radiation measurement shielding cavity (7); Based on the relationship between the blackbody radiation frequency shift and temperature, the temperature of the blackbody radiation measurement shielding cavity (7) is inversely deduced according to the blackbody radiation frequency shift of the atoms in the blackbody radiation measurement shielding cavity (7), and is compared and calibrated with the reading of the platinum resistance thermometer (11) to be calibrated, thereby achieving temperature calibration traceable to the definition of seconds.

5. The temperature calibration method of a temperature calibration device traceable to the definition of seconds according to claim 4, characterized in that: The pulse tube refrigerator (2) is started to reduce the temperature in the blackbody radiation reference shielding cavity (4) to 4.2K.

6. The temperature calibration method of a temperature calibration device traceable to the definition of seconds according to claim 4, characterized in that: The temperature of the shielding cavity (7) is calibrated in the range of 200K to 350K by controlling the blackbody radiation through the fourth-order Peltier (13).

7. The temperature calibration method of a temperature calibration device traceable to the definition of seconds according to claim 6, characterized in that: The temperature of the shielding cavity (7) is measured by controlling the blackbody radiation through a fourth-order Peltier (13) with a calibration accuracy greater than 0.01K.

8. The temperature calibration method of a temperature calibration device traceable to the definition of seconds according to claim 6, characterized in that: The temperature of the blackbody radiation measurement shielding cavity (7) is controlled by a fourth-order Peltier (13) and stabilized within the calibration range of ±0.1 K.

9. The temperature calibration method of a temperature calibration device traceable to the definition of seconds according to claim 4, characterized in that: The synchronous differential measurement uses a synchronous data acquisition system.

10. The temperature calibration method of a temperature calibration device traceable to the definition of seconds according to claim 4, characterized in that: The cold strontium atomic group maintains an adiabatic capture state during the process of being synchronously transported to the center of the blackbody radiation reference shielding cavity (4) and the blackbody radiation measurement shielding cavity (7) in different directions through the movable optical lattice.

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