Low-temperature blackbody source radiation power calibration method

Abstract

The invention discloses a low-temperature blackbody source radiation power calibration method, which comprises the following steps of: establishing a low-temperature test system, and calibrating the radiation power of a low-temperature blackbody source; changing the bath temperature of the superconducting dynamic inductance detector, testing response curves of the superconducting dynamic inductance detector at different bath temperatures, and extracting response amplitudes; calculating the number of quasi-particles under the bath temperature of the corresponding superconductive dynamic inductance detector; fitting the response amplitude and the quasi-particle number to obtain a function of the quasi-particle number of the superconducting dynamic inductance detector with respect to the response amplitude; the bath temperature of the detector is reduced to be lower than 100 mK, the temperature of the low-temperature blackbody source is reduced to be lower than 4 K, the temperature of the low-temperature blackbody source is changed, curves of the superconducting dynamic inductance detector at different blackbody source temperatures are tested, and amplitudes are extracted; calculating to obtain a corresponding quasi-particle number; calculating the radiation power of the low-temperature blackbody source according to the quasi-particle quantity; and calculating the radiation efficiency of the low-temperature blackbody source. The problem that the terahertz radiation power of the blackbody source cannot be calibrated at extremely low temperature can be solved.

Description

Technical Field

[0001] The present invention relates to the field of terahertz detection technology, and in particular to a method for calibrating the radiation power of a low-temperature blackbody source. Background Art

[0002] In the electromagnetic spectrum, the terahertz band (frequency range of 0.1THz to 10THz) is located between the microwave and infrared bands. Due to its unique physical properties, it has broad application prospects in the fields of national defense security, astronomical detection, etc. However, ultra-high-sensitivity terahertz detectors usually need to work in extremely low temperature environments, which places strict requirements on their calibration technology.

[0003] In the prior art, blackbody sources, as common terahertz radiation sources, can be used as calibration references for terahertz detectors at low temperatures. Blackbody radiation sources can emit broadband radiation at a specific temperature, thereby providing a calibration signal for the detector. However, when the operating temperature drops below 77K, there is still a lack of effective experimental means to directly measure and calibrate the power of blackbody radiation sources under low temperature conditions. Existing calibration methods mainly rely on theoretical calculations, which have significant limitations because the deviation between theoretical calculations and actual radiation power is difficult to accurately estimate. In addition, uncalibrated low-temperature blackbody radiation sources cannot be used to accurately characterize terahertz detectors, and uncalibrated terahertz detectors cannot be used to calibrate low-temperature blackbody radiation sources. This interdependent relationship makes the development of ultra-high sensitivity low-temperature terahertz detectors face difficulties. There is an urgent need for a simple and easy-to-use experimental method to measure and calibrate the radiation power of blackbody radiation sources under low temperature conditions. Summary of the invention

[0004] Purpose of the invention: The present invention provides a method for calibrating the radiation power of a low-temperature blackbody source, which can solve the problem that the terahertz radiation power of a blackbody source at extremely low temperatures cannot be calibrated.

[0005] Technical solution: A method for calibrating the radiation power of a low-temperature blackbody source described in the present invention comprises the following steps:

[0006] Step 1: Build a low temperature test system;

[0007] Step 2: Lower the blackbody source temperature to below 4K, change the detector bath temperature, and test the superconducting dynamic inductance detector S at different detector bath temperatures. 21 curve and extract the response amplitude;

[0008] Step 3, calculate the number of quasiparticles at the corresponding detector bath temperature;

[0009] Step 4, fitting the response amplitude obtained in step 2 and the number of quasiparticles obtained in step 3 to obtain a function of the number of quasiparticles of the superconducting dynamic inductance detector with respect to the response amplitude;

[0010] Step 5: Lower the detector bath temperature to below 100 mK, change the blackbody source temperature, and test the S of the superconducting dynamic inductance detector at different blackbody source temperatures. 21 curve and extract the amplitude;

[0011] Step 6, substituting the amplitude obtained in step 5 into step 4 to calculate the corresponding number of quasiparticles;

[0012] Step 7, calculating the radiation power radiated from the low-temperature blackbody source to the detector based on the number of quasiparticles in step 6;

[0013] Step 8: Calculate the radiation efficiency of the low-temperature blackbody source.

[0014] Furthermore, in step 1, the constructed test system includes: a low-temperature blackbody source, a terahertz filter and a superconducting dynamic inductance detector; the low-temperature blackbody source is fixedly installed on the 4K cold plate of the refrigerator, and the detector is fixed on the cold plate of the mixing chamber of the refrigerator; the low-temperature blackbody source is a radiation source and is also an object to be calibrated, and the terahertz filter is used to filter the electromagnetic waves radiated by the low-temperature blackbody source to obtain electromagnetic waves in a narrower frequency band for easy calculation; the superconducting dynamic inductance detector is used to detect the radiation of the low-temperature blackbody source.

[0015] Furthermore, in step 2, the temperature of the blackbody source should not exceed 4K, and the detector bath temperature is gradually increased from the lowest temperature until the detector has an obvious response.

[0016] Furthermore, in step 3, the number of quasiparticles at the corresponding detector bath temperature is calculated as:

[0017]

[0018] N 0 is the electron single spin state density at the Fermi surface of the superconductor of the superconductor dynamic inductance detector absorber, V is the volume of the superconducting dynamic inductance detector absorber, k B is the Boltzmann constant, T bath is the detector bath temperature, Δ 0 It is the superconductor energy gap of the superconducting dynamic inductance detector absorber.

[0019] Furthermore, in step 5, the ambient temperature should not exceed 1 / 10 of the superconducting critical temperature of the absorber part of the superconducting dynamic inductance detector, and the temperature of the black body source is gradually increased from the lowest until the detector has an obvious response.

[0020] Furthermore, in step 7, the radiation power of the low-temperature blackbody source is calculated as follows:

[0021] N qp =η pb η opt Pτ qp Δ 0

[0022] N qp is the number of quasiparticles calculated in step 6, η pb is the Cooper pair breaking efficiency of the absorber part of the superconducting dynamic inductance detector, η opt is the optical efficiency, and P is the radiation power of the low-temperature blackbody source.

[0023] Furthermore, in step 8, the radiation efficiency of the low-temperature blackbody source is calculated as follows:

[0024]

[0025] P is the radiation power of the low-temperature blackbody source radiated to the detector calculated in step 7, ∈ is the radiation efficiency of the low-temperature blackbody source, Ω is the solid angle of the superconducting dynamic inductance detector relative to the low-temperature blackbody source, A is the radiation window area of ​​the low-temperature blackbody source, ν l is the lower limit of frequency integration, ν h is the upper limit of frequency integration, T is the transmittance of the filter group, and I is the radiation emittance of the low-temperature blackbody source.

[0026] Furthermore, in step 8, the radiation power of the low-temperature blackbody source complies with Planck's blackbody radiation law, and the radiation power of the actual blackbody source is obtained by multiplying the radiation efficiency by the ideal blackbody radiation power, thereby realizing the calibration of the radiation power of the low-temperature blackbody source.

[0027] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: the radiation power of a low-temperature blackbody source can be directly calibrated in extremely low-temperature conditions, without the need to test at room temperature and extend to low temperatures, thereby reducing the complexity of the operation; the calibration can be achieved directly using a low-temperature terahertz detector characterization system, without the need to build an additional test system; extremely low-power radiation calibration can be achieved, without the need to calibrate the detector, thereby avoiding expensive equipment and testing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the structure of the test system of the present invention.

[0029] Figure 2 It is a schematic diagram of the method flow of the present invention.

[0030] Figure 3 It is a diagram of the calibration data and fitting data of the low-temperature blackbody source of the present invention.

[0031] Among them, 1. 4K cold plate; 2. distillation cold plate; 3. 300mK cold plate; 4. mixing chamber cold plate; 5. low-temperature blackbody source; 6. terahertz filter; 7. superconducting dynamic inductance detector. DETAILED DESCRIPTION

[0032] like Figure 2As shown, a method for calibrating the radiation power of a low-temperature blackbody source comprises the following steps:

[0033] Step 1. Press Figure 1 The test system is built as shown. The built test system includes: a low-temperature blackbody source, a terahertz filter and a superconducting dynamic inductance detector; the low-temperature blackbody source is fixedly installed on the 4K cold plate of the refrigerator, and the detector is fixed on the cold plate of the mixing chamber of the refrigerator; the low-temperature blackbody source is the radiation source and also the object of calibration, the terahertz filter is used to filter the electromagnetic waves radiated by the low-temperature blackbody source to obtain electromagnetic waves in a narrow frequency band, and the superconducting dynamic inductance detector is used to detect the radiation of the low-temperature blackbody source. The center frequency of the filter in the figure is 1.6THz, the distance between the superconducting dynamic inductance detector and the low-temperature blackbody source is 315mm, and the solid angle is 2.3×10 -7 sr;

[0034] Step 2: lower the temperature of the low-temperature blackbody source to 4K, change the ambient temperature range to 60mK-120mK, test the superconducting dynamic inductance detector curve under different ambient temperatures, and extract the amplitude;

[0035] Step 3: According to the formula Calculate the number of quasiparticles at the corresponding ambient temperature; N 0 is the electron single spin state density at the Fermi surface of the superconductor of the superconductor dynamic inductance detector absorber, V is the volume of the superconducting dynamic inductance detector absorber, k B is the Boltzmann constant, T bath is the detector bath temperature, Δ 0 It is the superconductor energy gap of the superconducting dynamic inductance detector absorber.

[0036] Step 4, interpolating the response amplitude obtained in step 2 and the quasiparticle number obtained in step 3 to obtain a function of the quasiparticle number of the superconducting dynamic inductance detector with respect to the response amplitude;

[0037] Step 5, lower the ambient temperature to 60mK, change the temperature range of the low-temperature blackbody source to 4K-30K, test the curves of the superconducting dynamic inductance detector at different low-temperature blackbody source temperatures, and extract the amplitude;

[0038] Step 6: Substitute the amplitude obtained in step 5 into the fourth step to calculate the corresponding number of quasiparticles;

[0039] Step 7: According to formula N qp =η pb Pτ qp Δ, calculate the radiation power of the low-temperature blackbody source from the number of quasiparticles in step 6, such as Figure 3 As shown in the figure, the test data is the radiation power of the low-temperature blackbody source received by the detector; N qp is the number of quasiparticles calculated in step 6, η pbis the Cooper pair breaking efficiency of the superconducting dynamic inductance detector absorber, η opt is the optical efficiency, and P is the radiation power of the low-temperature blackbody source. ;

[0040] Step 8: According to the formula Calculate the radiation efficiency of a low-temperature blackbody source, Figure 3 is the radiation power of the low-temperature blackbody source received by the detector, wherein the fitting result is the result of Planck blackbody radiation fitting of the radiation power of the low-temperature blackbody source, and the radiation efficiency of the low-temperature blackbody source obtained by fitting is ∈=0.9, thereby realizing the calibration of the radiation power of the low-temperature blackbody source.

[0041] The present invention can realize extremely low-power radiation power calibration at extremely low temperatures, without the need to calibrate the detector, thus avoiding expensive equipment and testing costs.

Claims

1. A method for calibrating the radiation power of a low-temperature blackbody source, characterized in that: The steps include: Step 1: Build a low temperature test system; Step 2: Lower the blackbody source temperature to below 4K, change the detector bath temperature, and test the superconducting dynamic inductance detector S at different detector bath temperatures. 21 curve and extract the response amplitude; Step 3, calculate the number of quasiparticles at the corresponding detector bath temperature; Step 4, fitting the response amplitude obtained in step 2 and the number of quasiparticles obtained in step 3 to obtain a function of the number of quasiparticles of the superconducting dynamic inductance detector with respect to the response amplitude; Step 5: Lower the detector bath temperature to below 100 mK, change the blackbody source temperature, and test the S of the superconducting dynamic inductance detector at different blackbody source temperatures. 21 curve and extract the amplitude; Step 6, substituting the amplitude obtained in step 5 into step 4 to calculate the corresponding number of quasiparticles; Step 7, calculating the radiation power radiated from the low-temperature blackbody source to the detector based on the number of quasiparticles in step 6; Step 8: Calculate the radiation efficiency of the low-temperature blackbody source.

2. The low-temperature blackbody source radiation power calibration method according to claim 1, characterized in that: In step 1, the test system built includes: a low-temperature blackbody source, a terahertz filter and a superconducting dynamic inductance detector; the low-temperature blackbody source is fixed on the 4K cold plate of the refrigerator, and the detector is fixed on the cold plate of the mixing chamber of the refrigerator; the low-temperature blackbody source is a radiation source and is also an object to be calibrated. The terahertz filter is used to filter the electromagnetic waves radiated by the low-temperature blackbody source to obtain electromagnetic waves in a narrower frequency band for easy calculation; the superconducting dynamic inductance detector is used to detect the radiation of the low-temperature blackbody source.

3. The low-temperature blackbody source radiation power calibration method according to claim 1, characterized in that: In step 2, the temperature of the blackbody source should not exceed 4K, and the residual temperature of the detector increases gradually from the lowest temperature until the detector has an obvious response.

4. The low-temperature blackbody source radiation power calibration method according to claim 1, characterized in that: In step 3, the number of quasiparticles at the corresponding detector bath temperature is calculated as: N0 is the electron single spin state density at the Fermi surface of the superconductor of the superconductor dynamic inductance detector absorber, V is the volume of the superconducting dynamic inductance detector absorber, k B is the Boltzmann constant, T bath is the detector bath temperature and Δ0 is the superconductor energy gap of the superconducting dynamic inductance detector absorber.

5. The low-temperature blackbody source radiation power calibration method according to claim 1, characterized in that: In step 5, the detector bath temperature should not exceed 1 / 10 of the superconducting critical temperature of the superconducting dynamic inductance detector absorber, and the temperature is gradually increased from 4K until the detector has an obvious response.

6. The low-temperature blackbody source radiation power calibration method according to claim 1, characterized in that: In step 7, the radiation power of the low-temperature blackbody source is calculated as follows: N qp =the pb or opt Pt qp D0 N qp is the number of quasiparticles calculated in step 6, η pb is the Cooper pair breaking efficiency of the absorber part of the superconducting dynamic inductance detector, η opt is the optical efficiency, and P is the radiation power of the low-temperature blackbody source.

7. The low-temperature blackbody source radiation power calibration method according to claim 1, characterized in that: In step 8, the radiation efficiency of the low-temperature blackbody source is calculated as: P is the power radiated from the low-temperature blackbody source to the detector calculated in step 7, ∈ is the radiation efficiency of the low-temperature blackbody source, Ω is the solid angle of the superconducting dynamic inductance detector relative to the low-temperature blackbody source, A is the radiation window area of ​​the low-temperature blackbody source, ν l is the lower limit of frequency integration, ν h is the upper limit of frequency integration, T is the transmittance of the filter group, and I is the radiation emittance of the low-temperature blackbody source.

8. The low-temperature blackbody source radiation power calibration method according to claim 1, characterized in that: In step 8, the radiation power of the low-temperature blackbody source complies with Planck's blackbody radiation law. The radiation power of the actual blackbody is obtained by multiplying the radiation efficiency by the ideal blackbody radiation power, thereby realizing the calibration of the radiation power of the low-temperature blackbody source.

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