Ion thermometer based on cold ion clusters

Abstract

The present invention discloses an ion thermometer based on a cold ion cluster, which relates to the field of temperature measurement technology and can be used for precise measurement and monitoring of ambient temperature in ultra-low temperature research. The thermometer uses a laser-cooled cold ion cluster as a temperature sensor. The motion temperature of the cold ion cluster is strongly coupled with the temperature of the gas in the vacuum chamber, and the temperature of the gas in the vacuum chamber is consistent with the ambient temperature when the temperature is balanced. By evaluating the increase in the motion temperature of the ion cluster caused by background gas collisions under different environments, the temperature of the background gas can be evaluated, thereby obtaining the measured ambient temperature. It includes a vacuum chamber, a camera, an ion trap, a metal target, a vacuum pump, an optical switch, cooling light, sputtering light, an optical fiber, a power supply and control system, an ultra-high vacuum electrode feedthrough, and an ultra-high vacuum optical fiber feedthrough; the thermometer measures the ambient temperature from a microscopic perspective and from the essence of heat exchange, has higher temperature measurement sensitivity and accuracy, and can be used for high-precision measurement and monitoring of the temperature in an ultra-low temperature environment.

Description

Technical Field

[0001] The present invention relates to the field of temperature measurement technology, and in particular to an ion thermometer based on cold ion clusters, which can be used for precise measurement and monitoring of ambient temperature in ultra-low temperature research. Background Art

[0002] The thermometer was invented in the late 16th century, over 400 years ago. Today, thermometers play a vital role not only in daily life but also in industrial production. More than a dozen thermometers are commonly used, meeting most temperature measurement needs. However, at ultra-low temperatures (below -150°C / 123K), many unique physical phenomena emerge, such as superconductivity and superfluidity. These phenomena have captured the attention of scientists and led to the rapid development of cryogenic technology. Currently, cryogenic technology has made significant progress in many fields, including transportation (magnetic levitation), medicine (nuclear magnetic resonance imaging), electronics (superconducting sensors), and scientific engineering (controlled thermonuclear ionization). To further promote research in cryogenic technology, precise measurement of ultra-low temperatures has become a crucial component of this research.

[0003] Currently, resistance thermometers, thermocouple thermometers, and gas thermometers are widely used in the low-temperature field. Resistance thermometers are nominally reliable for measuring temperatures down to -200°C / 73K, primarily leveraging the relationship between resistance and temperature. Platinum resistance thermometers are widely used in high-precision temperature measurement due to their highly stable resistance properties. However, since the relationship between resistance and temperature requires precise measurement, and the relationship between resistance and temperature varies across different temperature ranges, platinum resistance thermometers are currently limited to a temperature range of -200°C to 850°C. Thermocouple thermometers use the thermoelectric potential generated by the temperature difference between different metal materials to measure temperature. One material serves as the reference end, at a constant temperature, while the other serves as the measuring end. The thermoelectric potential generated between the two materials has a specific functional relationship with temperature, enabling temperature measurement. Therefore, thermocouples can measure temperatures over a wide range, even down to near absolute zero (-273.15°C / 0K). However, due to the need for temperature compensation at the reference end, their measurement accuracy is limited, with an error of approximately ±1°C. 3. Gas thermometers utilize the effect of temperature on gas pressure or volume, and are therefore divided into constant-pressure thermometers and constant-volume thermometers. Gas thermometers utilize helium or hydrogen, which have boiling points of -268.0°C / 4.3K and 252.8°C / 20.3K, respectively, at standard atmospheric pressure. Therefore, gas thermometers offer a wide measurement range and high accuracy, making them suitable for precision measurements. Since absolutely sealed gas does not exist, the amount of gas sealed within a gas thermometer gradually decreases. Therefore, for accurate measurements, gas thermometers require frequent calibration. Furthermore, if the measured temperature is below the boiling point of helium, the gas liquefies, and the gas thermometer will not function properly.

[0004] With the advancement of atomic and molecular photophysics, microscopic atoms are demonstrating their exceptionally high intrinsic precision in applications such as atomic clocks and as sensors in magnetometers, gravimeters, gradiometers, and gyroscopes. Some studies have also clarified the nature of certain macroscopic phenomena from a microscopic perspective, resulting in more accurate measurements. As charged particles, ions possess unique properties. The interactions between charged particles cause them to exhibit certain plasma characteristics under certain conditions. In a vacuum environment, as the temperature of ion motion decreases, the ions undergo a phase transition from gas to liquid and then to solid. Ion clusters then adopt an ordered structure, forming cold ion clusters, whose motion temperature can be accurately assessed. The collision of vacuum background gas with cold ion clusters will affect their motion temperature. Even if the ambient temperature is -250℃, the gas speed is still tens of meters per second. The heat exchange with the cold ion clusters through collision is very fast. Therefore, the cold ion clusters are very sensitive to the temperature changes of the background gas, that is, a small amount of heat exchange will cause their motion temperature to change. The collision probability between gas and cold ion clusters is determined by the number and temperature of the gas. Therefore, the temperature of the background gas can be determined by heating the motion temperature of the cold ion clusters with isovolumetric gas at different temperatures, thereby obtaining the temperature of the surrounding measurement environment.

[0005] Using cold ion clusters as sensors to make thermometers has its natural advantages: First, the temperature of the ions after laser cooling is on the order of 0.01K, close to absolute zero. Therefore, as long as a gas with a higher thermal motion temperature collides with it, the energy exchange will increase its motion temperature. Since the background gas temperature is about 100 times higher than the temperature of the cold ion cluster even at -272°C, a few collisions will cause a considerable change in the motion temperature of the cold ion cluster, so the sensitivity to ambient temperature measurement is very high. Secondly, the motion temperature of the cold ion cluster can be actively controlled by the laser and can be prepared to any temperature higher than 0.01K. At present, laser control technology is very mature, and it is easy to prepare the motion temperature of the cold ion cluster in the phase change range, and adjust the temperature of the cold ion cluster for different measurement temperature ranges, so that it remains sensitive to different gas temperatures. In addition, the ion cluster is in a vacuum chamber, the main gas in the chamber is hydrogen, and the vacuum degree is 10 -8 Pascal order of magnitude, since the inverse of the boiling point of a gas is approximately proportional to the logarithm of the gas pressure, according to the Antony equation logP=AB / (tC) (where P is the gas pressure, A, B, C are Antony parameters, and t is the temperature), substitute the Antony parameters corresponding to the extremely low temperature range of hydrogen, and it can be obtained that under this vacuum degree, the boiling point of hydrogen is approximately around -272°C / 1K. As the vacuum degree increases, this value gets closer to absolute zero. Therefore, the ambient temperature that can be measured using cold ion clusters as thermometers can reach -272°C. Because it uses the principle of heat exchange caused by particle collisions at the microscopic level to measure gas temperature, the error is small and the accuracy is high. When the ambient temperature is lower than -272°C, due to 10 -8 After the hydrogen in the Pascal vacuum exchanges heat with the environment, it begins to liquefy, so the measurement of the ambient temperature begins to be inaccurate. However, with the gradual improvement of vacuum technology, the boiling point of hydrogen in higher vacuum environments will continue to decrease, making it possible to measure lower temperature environments.

[0006] In summary, the cold ion cluster can be used as a temperature sensor and become a new type of thermometer. It uses the residual hydrogen in the vacuum as an energy transfer medium to act on the cold ion cluster, making it sensitive to changes in ambient temperature. The temperature measurement range can be from room temperature to -272°C, or even lower, with high accuracy, and can be used for precise measurement and monitoring of ultra-low temperature environments. Summary of the Invention

[0007] The present invention aims to overcome the shortcomings and deficiencies of existing technologies and, in response to the need for ultra-low temperature measurements, provide a temperature sensor that uses cold ion clusters to measure ambient temperature with high accuracy, capable of measuring ultra-low ambient temperatures. The present invention utilizes collisions between trapped and laser-cooled ion clusters and the gas within a vacuum chamber to measure ambient temperature.

[0008] The object of the present invention is achieved like this:

[0009] 1. An ion thermometer based on cold ion clusters

[0010] This thermometer uses laser-cooled cold ion clusters as temperature sensors. The motion temperature of the cold ion clusters is strongly coupled to the temperature of the gas in the vacuum chamber, which, when in equilibrium, is consistent with the ambient temperature. By evaluating the increase in the motion temperature of the ion clusters caused by collisions with background gas under different conditions, the background gas temperature can be estimated, thereby obtaining the measured ambient temperature.

[0011] Specifically:

[0012] The ion thermometer includes a vacuum chamber, a camera, an ion trap, a metal target, a vacuum pump, an optical switch, a cooling light, a sputtering light, an optical fiber, a power supply and a control system, an ultra-high vacuum electrode feedthrough, and an ultra-high vacuum optical fiber feedthrough;

[0013] Its location and connectivity are:

[0014] The vacuum pump is fixed on the rear panel of the vacuum chamber to maintain the vacuum degree in the vacuum chamber; the ion trap is placed in the middle of the bottom of the vacuum chamber and fixed at the bottom of the vacuum chamber to trap ions; the camera is fixed on the top of the vacuum chamber, facing the center of the ion trap to image the cold ion cluster; the metal target is fixed on the left side of the bottom of the vacuum chamber, with the target surface facing the ion trap, and ions are produced after being irradiated by sputtering light; the ultra-high vacuum electrode feedthrough and ultra-high vacuum fiber feedthrough are installed on the right panel of the vacuum chamber to provide electrical and optical connections inside and outside the vacuum chamber. The center of the ultra-high vacuum fiber feedthrough is consistent with the center of the ion trap. The cooling light and sputtering light are placed outside the vacuum chamber and introduced into the optical switch through the optical fiber. The optical switch controls the shutdown of the two lights. The optical fiber is then introduced into the center of the ion trap through the ultra-high vacuum fiber feedthrough and finally hits the metal target; the power supply and control system are placed outside the vacuum chamber and connected to the ultra-high vacuum electrode feedthrough, cooling light and sputtering light through cables to realize equipment power supply and program control, as well as data acquisition and display.

[0015] 2. A method for obtaining an ion thermometer based on cold ion clusters

[0016] The following steps are involved:

[0017] ①Place the vacuum chamber in the measured environment and wait for the temperature to reach equilibrium;

[0018] ② Turn on the photoelectric system, power supply and control system;

[0019] ③ Turn on the sputtering light, irradiate the metal target, and generate ions instantly;

[0020] ④ Turn off the sputtering light and turn on the cooling light to form a cold ion cluster;

[0021] ⑤ According to the measured temperature range and accuracy requirements, adjust the cooling light parameters to control the motion temperature of the cold ion cluster within the appropriate range;

[0022] ⑥ Obtain cold ion cluster imaging, calculate the background gas temperature by evaluating the cold ion cluster motion temperature and data processing, and display the measured ambient temperature.

[0023] Compared with the prior art, the present invention has the following advantages and positive effects:

[0024] ① The present invention uses a cold ion cluster as a temperature sensor and the gas in the vacuum chamber where the cold ion cluster is located as a temperature transfer medium to measure the ambient temperature of the environment where the ion thermometer is located.

[0025] ② The present invention is an ion thermometer using cold ions as temperature sensors. Since it mainly uses hydrogen as a temperature conduction medium, it can measure an extremely low temperature range of -272°C. This temperature limit will be further improved with the advancement of vacuum technology.

[0026] ③This thermometer measures the ambient temperature from a microscopic perspective and based on the essence of heat exchange. It has higher temperature measurement sensitivity and accuracy and can be used for high-precision measurement and monitoring of the temperature in ultra-low temperature environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of the present invention, in which:

[0028] 1—vacuum chamber;

[0029] 2—Camera;

[0030] 3—ion trap;

[0031] 4—metal target;

[0032] 5—vacuum pump;

[0033] 6—Optical switch;

[0034] 7—Cooling light;

[0035] 8—Sputtering light;

[0036] 9—Optical fiber;

[0037] 10—Power supply and control system;

[0038] 11—Ultra-high vacuum electrode feedthrough;

[0039] 12—Ultra-high vacuum fiber feedthrough.

[0040] Figure 2These are images of two-dimensional plane simulations of ionic crystals at different temperatures, where a, b, c, d, e, and f correspond to the temperatures of beryllium ions at approximately 20℃ / 293K, 7℃ / 280K, -123℃ / 190K, -213℃ / 100K, -263℃ / 10K, and -272℃ / 1K, respectively.

[0041] Figure 3 This is a simulated image of the precise measurement of the temperature using ion clusters when the temperature is below -253℃ / 20K. Among them, g, h, and i correspond to the temperature of beryllium ions at -253.15℃ / 20K and -253.77℃

[0042] / 19.38K, -254.00℃ / 19.15K. DETAILED DESCRIPTION

[0043] In order to facilitate ordinary technicians in this field to understand and implement the present invention, the present invention is further described in detail below in conjunction with specific implementation examples. It should be understood that the specific implementation examples described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0044] 1. Structure of ion thermometer

[0045] 1. Overall

[0046] like Figure 1 As shown, an ion thermometer based on cold ion clusters includes a vacuum chamber 1, a camera 2, an ion trap 3, a metal target 4, a vacuum pump 5, an optical switch 6, a cooling light 7, a sputtering light 8, an optical fiber 9, a power supply and control system 10, an ultra-high vacuum electrode feedthrough 11, and an ultra-high vacuum optical fiber feedthrough 12;

[0047] Its location and connectivity are:

[0048] The vacuum pump 5 is fixed on the rear panel of the vacuum chamber 1 to maintain the vacuum degree in the vacuum chamber; the ion trap 3 is placed in the middle of the bottom of the vacuum chamber 1 and fixed at the bottom of the vacuum chamber 1 to trap ions; the camera 2 is fixed on the top of the vacuum chamber and faces the center of the ion trap 3 to image the cold ion cluster; the metal target 4 is fixed on the left side of the bottom of the vacuum chamber 1, with the target surface facing the ion trap 3, and ions are generated after being irradiated by the sputtering light 8; the ultra-high vacuum electrode feedthrough 11 and the ultra-high vacuum fiber feedthrough 12 are installed on the right panel of the vacuum chamber to provide electrical and Optical connection, in which the center of the ultra-high vacuum fiber feedthrough 12 is consistent with the center of the ion trap 3, the cooling light 7 and the sputtering light 8 are placed outside the vacuum chamber 1, and are introduced into the optical switch 6 through the optical fiber 9. The optical switch 6 controls the shutdown of the two lights, and then the optical fiber 9 passes through the ultra-high vacuum fiber feedthrough 12 and is introduced into the center of the ion trap 3, and finally hits the metal target 4; the power supply and control system 10 is placed outside the vacuum chamber and is connected to the ultra-high vacuum electrode feedthrough 11, the cooling light 7 and the sputtering light 8 through cables to realize power supply and program control of the equipment, as well as data acquisition and display.

[0049] 2. Functional components

[0050] 01) Vacuum chamber 1

[0051] It is a rectangular container made of non-magnetic metal, used to maintain a vacuum sealed space.

[0052] 02) Camera 2

[0053] It is a commonly used component used for imaging.

[0054] 03) Ion Trap 3

[0055] It is a device that traps charged particles through a combination of radio frequency electric field and electrostatic field. The structure shown in this figure is a linear segmented ion trap. Ion traps with other structures do not affect its function.

[0056] 04) Metal Target 4

[0057] It is a target material bombarded by high-speed particles;

[0058] In this ion thermometer, the target material corresponds to a material that can trap ions, such as beryllium, magnesium, calcium, strontium, barium, etc. This target material is in sheet form, and other shapes of target materials do not affect its function.

[0059] 05) Vacuum pump 5

[0060] It is a commonly used component used to improve the vacuum degree of a closed space. In this ion thermometer, an ion pump is used to maintain ultra-high vacuum.

[0061] 06) Optical switch 6

[0062] is an optical device having one or more selectable transmission ports;

[0063] Its function is to perform physical switching or logical operations on optical signals in optical transmission lines or integrated optical circuits.

[0064] 07) Cooling Light 7

[0065] It is a laser device that can generate a frequency consistent with that of ion laser cooling, in the form of continuous light.

[0066] 08) Sputtering Light 8

[0067] It is a device that can generate high-energy lasers that can produce ions after bombarding the target material. It can be in the form of pulses or continuous light.

[0068] 09) Fiber 9

[0069] It is a commonly used component that can be used as a light-transmitting device. Its principle is total reflection of light.

[0070] 10) Power supply and control system 10

[0071] It is a device that integrates components and its functions are power supply, timing control of each component, data calculation and temperature display.

[0072] 11) Ultra-high vacuum electrode feedthrough 11

[0073] It is a vacuum device used to transmit voltage and current signals inside and outside an ultra-high vacuum cavity.

[0074] 12) Ultra-high vacuum fiber feedthrough 12

[0075] It is a vacuum device used to realize laser transmission inside and outside the ultra-high vacuum cavity.

[0076] 2. The following are examples for two different usage scenarios:

[0077] 1. Scenario 1

[0078] When a large low-temperature range (~100°C) needs to be measured, the laser parameters need to be set to control the sensitivity of the ion cluster to changes in ambient temperature. When the temperature measurement range is large, the ion cluster movement temperature in the high-temperature range to be measured needs to be relatively high, making it less sensitive to changes in ambient temperature. In specific implementation, the ion thermometer vacuum chamber is placed in the measured environment. After the temperature is fully transferred, the ion trap electronic system is turned on, and the sputtering light, cooling light, and camera are turned on at the same time. Then the optical switch turns on the sputtering light, sputtering the metal target, forming metal ions, which are trapped in the ion trap. The sputtering light only needs to act on the target instantaneously, because the sputtering light is immediately turned off after it is turned on. The cooling light is turned on, cooling the ions in the ion trap to form cold ion clusters, which are observed through the camera. At this time, the ion cluster is less sensitive to environmental changes, and an ambient temperature change of the order of 0.1°C can cause an observable change in the movement temperature of the ion cluster. Figure 2 This is a two-dimensional image of a cold ion cluster that simulates a temperature range from room temperature to -272°C. Specific parameters are as follows: the ions are beryllium ions, the number of particles is 62; the vacuum degree is 2*10 -8 Pascal (at room temperature); the ion trap's RF voltage is 320V, the axial voltage is 1.5V, the distance from the pole to the trap center is 3.5mm, and the length of the intermediate pole is 6mm; the camera resolution is 0.83 microns per pixel, and the imaging time is 180 milliseconds; the average motion temperatures of the six imaged ions in groups a, b, c, d, e, and f are: 2.05K, 0.62K, 0.10K, 0.49K, 0.25K, and 0.02K, corresponding to air temperatures of approximately 20°C / 293K, 7°C

[0079] / 280K, -123℃ / 190K, -213℃ / 100K, -263℃ / 10K, -272℃ / 1K. It can be seen that the background gas temperature has a very obvious influence on the movement of ions in the ion cluster, so the ambient temperature can be accurately evaluated.

[0080] 2. Scenario 2

[0081] When you need to measure the ambient temperature with a small range (~℃) and high precision, set the temperature of the cold ion group to the phase transition temperature range by laser. Turn on the device as in scenario 1. Figure 3 To simulate a two-dimensional image of a cold ion cluster at -253°C / 20K, the parameters g, h, and i were adjusted to correspond to temperatures of -253.15°C / 20K, -253.77°C / 19.38K, and -254.00°C / 19.15K, respectively. The ion cluster image can clearly discern changes resulting from a temperature difference of 0.01°C. The specific parameters are the same as those for Scenario 2. With these settings, the cold ion cluster's sensitivity to ambient temperature changes is approximately four times higher than in Scenario 1.

[0082] The laser sputtering, ion trapping, laser cooling, and ion crystal simulation imaging and evaluation described herein are all general technologies, and their control has reached a high level. During the temperature measurement process, the suppression of the impact of temperature changes on devices other than the cold ion cluster, as well as the evaluation and calibration, will not be detailed here, as the details do not affect the implementation of the principles. The ion species and number, as well as other parameters used in the implementation scenario, are provided solely to facilitate understanding and do not constitute limitations of the present invention.

Claims

1. An ion thermometer based on cold ion clusters, characterized in that: It includes a vacuum chamber (1), a camera (2), an ion trap (3), a metal target (4), a vacuum pump (5), an optical switch (6), a cooling light (7), a sputtering light (8), an optical fiber (9), a power supply and control system (10), an ultra-high vacuum electrode feedthrough (11), and an ultra-high vacuum optical fiber feedthrough (12); Its location and connectivity are: The vacuum pump (5) is fixed on the rear panel of the vacuum chamber (1) to maintain the vacuum degree in the vacuum chamber; the ion trap (3) is placed in the middle of the bottom of the vacuum chamber (1) and fixed on the bottom of the vacuum chamber (1) to trap ions; the camera (2) is fixed on the top of the vacuum chamber to image the center of the ion trap (3) and to image the cold ion group; the metal target (4) is fixed on the left side of the bottom of the vacuum chamber (1) with the target surface facing the ion trap (3) to generate ions after irradiation with sputtering light (8); the ultra-high vacuum electrode feedthrough (11) and the ultra-high vacuum fiber feedthrough (12) are installed on the right panel of the vacuum chamber to provide electrical and optical communication inside and outside the vacuum chamber (1). The invention relates to a device for manufacturing a metal target. The device comprises a power supply and control system (10). The power supply and control system (10) is connected to the ultra-high vacuum fiber feedthrough (12), wherein the center of the ultra-high vacuum fiber feedthrough (12) is consistent with the center of the ion trap (3); the cooling light (7) and the sputtering light (8) are placed outside the vacuum chamber (1), and are introduced into the optical switch (6) through the optical fiber (9); the optical switch (6) controls the shutoff of the two lights, and then the optical fiber (9) passes through the ultra-high vacuum fiber feedthrough (12) and is introduced into the center of the ion trap (3), and finally hits the metal target (4); the power supply and control system (10) is placed outside the vacuum chamber, and is connected to the ultra-high vacuum electrode feedthrough (11), the cooling light (7) and the sputtering light (8) through cables, so as to realize power supply and program control of the equipment, as well as data acquisition and display.

2. The method for obtaining an ion thermometer based on a cold ion cluster according to claim 1, characterized in that: ①Place the vacuum chamber in the measured environment and wait for the temperature to reach equilibrium; ② Turn on the photoelectric system, power supply and control system; ③ Turn on the sputtering light, irradiate the metal target, and generate ions instantly; ④ Turn off the sputtering light and turn on the cooling light to form a cold ion cluster; ⑤ According to the measured temperature range and accuracy requirements, adjust the cooling light parameters to control the motion temperature of the cold ion cluster within the appropriate range; ⑥ Obtain cold ion cluster imaging, calculate the background gas temperature by evaluating the cold ion cluster motion temperature and data processing, and display the ambient temperature to be measured.

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