Helium atom gas chamber capacitance testing method

Abstract

The invention provides a helium atom gas chamber capacitance test method, and relates to the technical field of magnetic field measurement, and the method comprises the following steps: analyzing the capacitance change condition of a helium atom gas chamber before and after radio frequency excitation, and laying a foundation for the precise measurement of capacitance parameters through a targeted scheme; aiming at the capacitance change condition before radio frequency excitation of the helium atom gas chamber, a network analyzer is adopted to realize precise measurement of the capacitance of the helium atom gas chamber after radio frequency excitation by measuring radio frequency reflection parameters; aiming at the capacitance change condition after radio-frequency excitation of the helium atom gas chamber, the optimal excitation radio-frequency frequency is determined by adopting a signal source matching excitation and quantum magnetic measurement system comprehensive analysis mode, so that accurate measurement of the capacitance of the helium atom gas chamber after radio-frequency excitation is realized.

Description

Technical Field

[0001] This invention relates to the field of magnetic field measurement technology, and in particular to a method for testing the capacitance of a helium atom gas chamber. Background Technology

[0002] The magnetic field is an inherent physical field of the Earth and certain objects with specific characteristics, effectively reflecting various information about the Earth's interior and exterior. With the deepening of research across various disciplines, the use of different technologies to monitor the characteristics and changing patterns of the geomagnetic field is becoming increasingly important for research in fields such as space science, military anti-submarine warfare, geomagnetic-assisted navigation, geological surveys, mineral and oil and gas resource exploration, earthquake precursor monitoring, biomedicine, and basic science.

[0003] Among existing magnetic measurement equipment, the helium optically pumped magnetometer boasts advantages such as high magnetic measurement sensitivity, high bandwidth, and high accuracy, making it widely applicable in geomagnetic exploration across various scenarios. In the helium optically pumped magnetometer, the helium atom chamber is its core component, and its internal parameters, including capacitance, atomic number density, and state parameters, directly affect measurement performance.

[0004] Because helium atoms are inert gases and chemically very stable under normal conditions, they need to be excited to a metastable state using radio frequency (RF) discharge before subsequent precision field measurements can be performed. During RF discharge, effective matching between the signal input and the excitation input (helium atom chamber) is necessary to ensure maximum signal transmission efficiency to the helium atom chamber, thereby improving excitation efficiency. The matching formula is shown below:

[0005]

[0006] Where f is the frequency of the radio frequency signal, L is the inductance of the matching circuit, and C is the capacitance of the matching circuit. Since the helium atom cell is a capacitive device, the accurate measurement of its capacitance parameters directly determines the efficiency of radio frequency matching.

[0007] Currently available publicly available information lacks reports on the precise measurement of capacitance within a helium atom chamber. If traditional capacitance testing methods for contact electronic devices are used, two problems arise:

[0008] (1) The helium atom chamber is a precision optical device. Traditional contact measurement will cause mechanical damage to the end face of the helium atom chamber, making it difficult to achieve in-situ measurement and affecting the subsequent magnetic measurement performance.

[0009] (2) The helium atom chamber is an optical device with ultra-low capacitance, generally at the pF level. Traditional contact measurement methods will generate parasitic capacitance (pF level) due to the fixture, lead wire and surrounding environment, which will reduce the measurement accuracy of the helium atom chamber. Summary of the Invention

[0010] To address the problems existing in the prior art, this invention designs a non-contact, high-precision measurement method. It adopts a radio frequency matched excitation measurement method, which achieves accurate measurement of the capacitance parameters of the helium atom cell before and after excitation by accurately measuring the matched excitation frequency. It has the advantages of zero damage to the helium atom cell and high measurement accuracy.

[0011] This invention provides a method for testing the capacitance of a helium atom gas chamber, comprising the following steps:

[0012] Analyze the capacitance changes in the helium atom gas chamber before and after radio frequency excitation;

[0013] To address the capacitance change of the helium atom chamber before radio frequency excitation, a network analyzer is used to accurately measure the capacitance of the helium atom chamber after radio frequency excitation by measuring the radio frequency reflection parameters.

[0014] To address the capacitance change of a helium atom chamber after radio frequency excitation, a combined analysis of signal source matching excitation and quantum magnetic measurement system is employed to determine the optimal excitation radio frequency, thereby enabling accurate measurement of the helium atom chamber capacitance after radio frequency excitation.

[0015] Optionally, the analysis of the capacitance change before and after radio frequency excitation of the helium atom gas chamber includes:

[0016] Before radio frequency excitation of the helium atom chamber, the helium atom chamber exhibits the characteristics of a pure capacitor, and the size of its capacitance Ccell is proportional to the volume of the helium atom chamber.

[0017] After the helium atom chamber is excited by radio frequency, a new capacitor Csh and a resistor Rb are connected in parallel to the existing capacitor Ccell.

[0018] Optionally, the precise measurement of the helium atom cell capacitance after radio frequency excitation is achieved by measuring radio frequency reflection parameters using a network analyzer, including:

[0019] The network analyzer generates a radio frequency excitation signal, which is then applied to the helium atom gas cell via a gas cell matching circuit.

[0020] The reflection coefficient S11 of the radio frequency signal reflected back through the gas cell matching circuit is measured by a network analyzer. The reflection coefficient S11 is minimized when the gas cell excitation end is matched with the network analyzer end.

[0021] By analyzing the reflection coefficient S11, the optimal excitation frequency f1 is determined at this time;

[0022] The capacitance Ccell before excitation of the helium atom gas chamber is accurately measured using the following formula:

[0023] .

[0024] Optionally, the method of determining the optimal excitation radio frequency by combining signal source matching excitation and quantum magnetic measurement system analysis, thereby achieving accurate measurement of the helium atom cell capacitance after radio frequency excitation, includes:

[0025] Radio frequency signals of different frequencies and amplitudes are generated by an adjustable signal source, and after being amplified by a signal amplifier, they are loaded onto the air cell matching circuit.

[0026] Radio frequency signals are applied to the helium atom chamber through a matching circuit, and the helium atom chamber is placed in a quantum magnetic measurement system. The optimal excitation parameters of the helium atom chamber are determined by analyzing the optimal sensitivity of the quantum magnetic measurement system.

[0027] Adjust the frequency of the adjustable signal source, analyze the sensitivity of the quantum magnetic measurement system at different frequencies, and determine the optimal excitation frequency f2 when the sensitivity is optimal.

[0028] The following formula is used to accurately measure the capacitance Csh that is added after excitation of the helium atom gas chamber:

[0029] .

[0030] The beneficial effects of the present invention are as follows:

[0031] (1) This invention proposes a method for high-precision measurement of the capacitance parameters of a helium atom cell using radio frequency matching excitation measurement. This method is a non-contact, high-precision measurement method with the advantages of zero damage to the helium atom cell and high measurement accuracy.

[0032] (2) The present invention also has the advantage of strong resistance to environmental interference. By matching the precise control of the excitation frequency, it effectively suppresses the influence of environmental electromagnetic noise (such as power frequency interference and radio frequency radiation) on the measurement, improves the measurement accuracy of device capacitance parameters, and provides parameter input for the design of high-precision helium optical pump magnetic measurement system.

[0033] It should be understood that the description in the foregoing summary section is not intended to limit the key or essential features of the embodiments of the present invention, nor is it intended to restrict the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 The following are analysis diagrams of the capacitance changes before and after radio frequency excitation of the helium atom chamber: (a) shows the capacitance changes before radio frequency excitation of the helium atom chamber, and (b) shows the capacitance changes after radio frequency excitation of the helium atom chamber.

[0036] Figure 2 A schematic diagram of a technical scheme for capacitance testing before radio frequency excitation in a helium atom chamber.

[0037] Figure 3 This is a schematic diagram of a technical scheme for capacitance testing after radio frequency excitation in a helium atom chamber.

[0038] The accompanying drawings have illustrated specific embodiments of this disclosure, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concepts of this disclosure to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0039] Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. While some embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the invention. It should be understood that the accompanying drawings and embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the invention.

[0040] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0041] This disclosure provides a method for testing the capacitance of a helium atom gas chamber, including the following steps:

[0042] Figure 1 The diagram shows the capacitance changes before and after RF excitation of the helium atom chamber. The excitation matching circuit for the entire helium atom chamber is an LCR loop.

[0043] Before radio frequency excitation in the helium atom chamber, the helium atom chamber exhibits pure capacitive characteristics, with a capacitance C. cell The size is directly proportional to the volume of the helium atom chamber.

[0044] After radio frequency excitation, helium atoms in the helium atom chamber transition from their ground state to a metastable state, changing the number density of metastable atoms within the chamber. Because metastable atoms have higher polarizability, this increases the dielectric constant of the entire helium medium, ultimately leading to an increase in the capacitance of the helium atom chamber. Simultaneously, the change in the state of the helium atoms within the chamber causes parasitic resistance to appear. At this point, the helium atom chamber is no longer a purely capacitive state; its resistance is expressed as a change in capacitance C. cell Based on this, a new capacitor C was connected in parallel. sh and resistance R b .

[0045] As can be seen from the above analysis, for LC matching, only the capacitance changes before and after the helium atom cell RF excitation, and the inductance does not change. Therefore, it is necessary to test the capacitance before and after the helium atom cell excitation.

[0046] Figure 2 This diagram illustrates a technical solution for capacitance testing before radio frequency (RF) excitation of a helium atom chamber. The core idea of ​​this solution is to use a network analyzer to accurately measure the capacitance of the helium atom chamber after RF excitation by measuring RF reflection parameters. The specific implementation process is as follows:

[0047] The network analyzer generates a radio frequency excitation signal, which is then applied to the helium atom gas cell via a gas cell matching circuit.

[0048] The reflection coefficient S11 of the radio frequency signal reflected back through the gas cell matching circuit is measured by a network analyzer. When the gas cell excitation end is matched with the network analyzer end, the reflection coefficient S11 is the smallest, which should generally be less than -25dB.

[0049] By analyzing the reflection coefficient S11, the optimal excitation frequency f1 is determined at this time;

[0050] According to the following formula, the capacitance C before the excitation of the helium atom gas chamber... cell To perform precise measurements:

[0051] .

[0052] Figure 3 This diagram illustrates a technical scheme for capacitance testing after radio frequency (RF) excitation of a helium atom chamber. Because the state of the helium atoms inside the chamber changes after RF excitation, they exist in different states at different excitation frequencies. Measuring capacitance parameters under the optimal excitation state of the helium atom chamber is more meaningful and can provide accurate parameter input for the subsequent design of a helium optical pump magnetometry system. The capacitance after RF excitation of the helium atom chamber includes C. cell and C sh Two parts, due to Ccell Since the measurement was completed before excitation, this part of the technical solution can accurately measure the capacitance inside the helium atom chamber after radio frequency excitation. The core idea of ​​this technical solution is to determine the optimal excitation radio frequency by using a combination of signal source matching excitation and quantum magnetic measurement system analysis, thereby achieving accurate measurement of the capacitance of the helium atom chamber after radio frequency excitation. The specific implementation process is as follows:

[0053] Radio frequency signals of different frequencies and amplitudes are generated by an adjustable signal source, and after being amplified by a signal amplifier, they are loaded onto the air cell matching circuit.

[0054] Radio frequency signals are applied to the helium atom chamber through a matching circuit, and the helium atom chamber is placed in a quantum magnetic measurement system. The optimal excitation parameters of the helium atom chamber are determined by analyzing the optimal sensitivity of the quantum magnetic measurement system.

[0055] Adjust the frequency of the adjustable signal source, analyze the sensitivity of the quantum magnetic measurement system at different frequencies, and determine the optimal excitation frequency f2 when the sensitivity is optimal.

[0056] According to the following formula, the newly added capacitance C after the excitation of the helium atom gas chamber... sh To perform precise measurements:

[0057] .

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for testing the capacitance of a helium atom gas chamber, characterized in that, Includes the following steps: Analyze the capacitance changes in the helium atom chamber before and after radio frequency excitation; To address the capacitance change of the helium atom chamber before radio frequency excitation, a network analyzer is used to accurately measure the capacitance of the helium atom chamber after radio frequency excitation by measuring the radio frequency reflection parameters. To address the capacitance change of a helium atom chamber after radio frequency excitation, a combined analysis of signal source matching excitation and quantum magnetic measurement system is employed to determine the optimal excitation radio frequency, thereby enabling accurate measurement of the helium atom chamber capacitance after radio frequency excitation.

2. The method for testing the capacitance of a helium atom gas chamber according to claim 1, characterized in that, The analysis of capacitance changes before and after radio frequency excitation of the helium atom gas chamber includes: Before radio frequency excitation of the helium atom chamber, the helium atom chamber exhibits the characteristics of a pure capacitor, and the size of its capacitance Ccell is proportional to the volume of the helium atom chamber. After the helium atom chamber is excited by radio frequency, a new capacitor Csh and a resistor Rb are connected in parallel to the existing capacitor Ccell.

3. The method for testing the capacitance of a helium atom gas chamber according to claim 2, characterized in that, The method of using a network analyzer to accurately measure the capacitance of the helium atom gas cell after radio frequency excitation by measuring radio frequency reflection parameters includes: The network analyzer generates a radio frequency excitation signal, which is then applied to the helium atom gas cell via a gas cell matching circuit. The reflection coefficient S11 of the radio frequency signal reflected back through the gas cell matching circuit is measured by a network analyzer. The reflection coefficient S11 is minimized when the gas cell excitation end is matched with the network analyzer end. By analyzing the reflection coefficient S11, the optimal excitation frequency f1 is determined at this time; The capacitance Ccell before excitation of the helium atom gas chamber is accurately measured using the following formula: 。 4. The distance zero-value self-calibration method based on an RF agile transceiver chip according to claim 3, characterized in that, The method employs a combination of signal source matching excitation and quantum magnetic measurement system analysis to determine the optimal excitation radio frequency, thereby enabling precise measurement of the helium atom gas cell capacitance after radio frequency excitation. This includes: Radio frequency signals of different frequencies and amplitudes are generated by an adjustable signal source, and after being amplified by a signal amplifier, they are loaded onto the air cell matching circuit. Radio frequency signals are applied to the helium atom chamber through a matching circuit, and the helium atom chamber is placed in a quantum magnetic measurement system. The optimal excitation parameters of the helium atom chamber are determined by analyzing the optimal sensitivity of the quantum magnetic measurement system. Adjust the frequency of the adjustable signal source, analyze the sensitivity of the quantum magnetic measurement system at different frequencies, and determine the optimal excitation frequency f2 when the sensitivity is optimal. The following formula is used to accurately measure the capacitance Csh that is added after excitation of the helium atom gas chamber: 。

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