A hydrogen atomic frequency standard with a heating adsorption pump

Abstract

The present invention provides a hydrogen atomic frequency standard with a heating adsorption pump, which includes an adsorption pump and a hydrogen atomic clock main body that communicate with each other, and a high-frequency heating coil arranged around the outer wall of the adsorption pump; an adsorbent is arranged in the adsorption pump, and the material of the adsorbent is metal; the high-frequency heating coil is connected to an alternating current power supply to inject an induced current on the high-frequency heating coil to achieve electromagnetic induction heating. The high-frequency induction heating adsorption pump of the hydrogen atomic frequency standard of the present invention adopts a high-frequency induction heating method, and the internal and external efficiencies are close, so the heating gradient is small, the heating efficiency is high, the requirement for the heating temperature is greatly reduced, the heat dissipation requirement for the hydrogen clock main body is reduced, and objectively the activation temperature required by the adsorbent is reduced, increasing the overall activation efficiency.

Description

Technical Field

[0001] The invention belongs to the field of hydrogen atomic clocks, and in particular relates to a hydrogen atomic frequency standard with a heating adsorption pump. Background Art

[0002] A frequency standard is a device that can provide a single frequency reference with high accuracy. In the field of hydrogen atomic clocks, the use of adsorbents in conjunction with other vacuum pumps, such as molecular pumps and titanium pumps, to achieve ultra-high vacuum is a common technical approach in the current industrial field. Specifically, titanium or zirconium can be used as a single metal adsorbent, or an alloy (usually composed of element A with strong hydrogen absorption capacity and element B with weak or essentially no hydrogen absorption capacity, and elements C or even D can also be added to consider other physical factors) can be used as an adsorbent. Usually, these adsorbents are made into a geometric shape that matches the shape of the pump (they can also be coated) and placed inside the pump body. The adsorbent is then heated in a vacuum environment to dissolve the oxide film on its surface. After the adsorbent is exposed to its fresh surface, it becomes active and has the ability to adsorb gas. Different adsorbents require different heating temperatures, ranging from 200-725°C depending on the alloy composition and the thickness of the oxide layer.

[0003] The hydrogen clock adsorption pump is an important component for maintaining the internal vacuum of the hydrogen clock. The function of the adsorption pump to maintain vacuum is mainly achieved by adsorbing hydrogen by pure titanium or alloy adsorbents.

[0004] Currently, hydrogen atomic frequency standards utilize two main types of adsorption pumps: a main pump and a split pump. The main pump itself serves as the main structure of the hydrogen clock, providing mechanical support and adsorbing gas. The split pump is independent of the main structure and connected via a flange, solely responsible for adsorbing gas. Both methods utilize heat transfer from an electric heating wire to activate the adsorbent within the pump.

[0005] The adsorption pump currently used on the hydrogen clock is mainly used as the main structure of the hydrogen clock, responsible for supporting and connecting other physical parts of the hydrogen clock and used as an air suction. The activation of the adsorbent adopts internal and external heating methods.

[0006] The internal heating method mainly places the heating tungsten wire, insulating components, and thermal shielding components into the vacuum chamber. The heating wire is buried in the adsorbent, and then the heating electrode is led out to raise the temperature through the heating wire to reach the activation temperature to achieve the activation process. The advantage of this method is that the internal heating insulation shield can play a good role in heat insulation and oxidation prevention for the outer shell. However, if the electric heating wire heating conduction method is placed inside the pump body (the pump structure limits the cross-sectional area of the electric heating wire), its heating rate is limited by the power consumption and thermal stress of the heating wire. The former affects the oxidation rate of the heating wire, and the latter affects the shear force of the thermal stress brought by the pump structure on the heating wire. The overall time consumed to heat to the activation temperature pad is long (more than 24 hours), which poses additional requirements for the power supply and heat dissipation facilities. In addition, there is also the stress caused by machining, which makes the heating rate of this kind of internal heating method low and the heating wire is prone to breakage and failure, increasing the cost and reducing the overall mechanical reliability.

[0007] The external heating method heats the adsorbent through the heat transfer method of the heating wire or heating rod through the outer shell. Theoretically, the external heating power can far exceed the required heating power. However, in reality, if the electric heating wire is placed outside the pump body, it must conduct heat through the pump body outer shell to the inside. The better the vacuum inside the pump body, the lower the conduction rate. Therefore, the outer shell needs to withstand a higher temperature to complete the internal heat conduction. The outer shell of the hydrogen clock pump body is made of titanium material. If the heat transfer temperature of the heating wire is too high during the external heating process and no oxidation protection is provided for the outer shell, the outer shell will oxidize, and the overall mechanical properties of the pump will decrease significantly. In addition, if it is an externally connected flange adsorption pump, the flange connection cannot withstand a temperature exceeding 250 °C. After all, the heat dissipation surface of the flange is limited. Therefore, restricted by the contact surface between the heater and the pump body, the internal heat path from the pump shell, and the heat resistance temperature of the pump body, the external electric heating wire heating power cannot be too high. It is necessary to use an adsorbent with a lower activation temperature to meet the reduction of the internal limit temperature of the pump body caused by the heat transfer loss from the outside to the inside and the influence of avoiding too high temperature on the reduction of the material mechanical properties of the outer shell. Due to the need for good heat transfer to the inside and no internal heat shield, the thermal gradient of the adsorption pump is very large, and the overall activation rate of the adsorbent is not so ideal. Summary of the Invention

[0008] The purpose of the present invention is to provide a hydrogen atomic frequency standard with a heating adsorption pump to achieve high heating efficiency and uniform overall temperature for the adsorbent.

[0009] To achieve the above object, the present invention provides a hydrogen atomic frequency standard with a heating adsorption pump, including an adsorption pump and a hydrogen atomic clock main body that are connected to each other, and a high-frequency heating coil disposed around the outer wall of the adsorption pump; an adsorbent is provided inside the adsorption pump, and the material of the adsorbent is metal; the high-frequency heating coil is connected to an AC power supply to inject an induced current on the high-frequency heating coil to achieve electromagnetic induction heating.

[0010] The diameter of the sorption pump is at most twice the current penetration depth of the induced current.

[0011] The current penetration depth d of the induced current is:

[0012]

[0013] Where μ is the metal magnetic permeability of the adsorbent, γ is the metal electrical conductivity of the adsorbent, and ω is the angular frequency of the induced current.

[0014] The frequency range of the induced current is 50 Hz-20 KHz.

[0015] The adsorption pump and the hydrogen atomic clock body are connected through a transition pipe.

[0016] The adsorption pump and the hydrogen atomic clock body are both cylindrical in shape, and the transition pipe is a rectangular pipe connected between the side walls of the adsorption pump and the hydrogen atomic clock body.

[0017] The length L of the transition duct is greater than 10 mm, and the cross-section S of the transition duct is at least 5 cm 2 .

[0018] The diameter D of the adsorption pump is greater than 2.5 cm and at most 7 cm, and the volume is greater than 35 cm 3 The width W of the transition pipe is greater than 7.1 mm, and the heights of the adsorption pump and the transition pipe are both 7 cm.

[0019] The high-frequency heating coil is a hollow copper tube with an inner diameter of 3 mm and an outer diameter of 6 mm, and the interior of the high-frequency heating coil is cooled by water.

[0020] The high-frequency heating coil is formed by a plurality of single-turn coils arranged in sequence from the outside to the inside, and each single-turn coil is composed of two U-shaped segments opposite to each other, a first straight line segment connected between the first top ends of the two U-shaped segments, and a second straight line segment connected between the second top end of one of the U-shaped segments and the second top end of one of the U-shaped segments of the next single-turn coil.

[0021] The surface of the adsorbent is covered with an oxide; the material of the adsorbent is titanium, and the oxide is at least one of TiO2 and TiO.

[0022] The high-frequency induction heating adsorption pump of the hydrogen atomic frequency standard of the present invention adopts a high-frequency induction heating method. The internal and external efficiencies are close, and there is no need for heat conduction in a similar conduction manner. Therefore, the heating gradient is small, the heating efficiency is high, the demand for heating temperature is greatly reduced, the heat dissipation demand for the main body of the hydrogen clock is reduced, and objectively the activation temperature required for the adsorbent is reduced, increasing the overall activation efficiency; compared with the existing heating methods, the activation heating time of the adsorption pump is greatly shortened and the overall temperature rise is uniform under the same power, and the heating device is simple; if the pump body needs to be activated again later, it can be processed without damage.

[0023] Since the high-frequency induction heating adsorption pump of the hydrogen atomic frequency standard of the present invention greatly reduces the demand for heating temperature and shortens the heating time, the degree of oxidation of the outer shell is reduced or terminated, and the reliability of the adsorption pump is improved.

[0024] Furthermore, the high-frequency induction heating adsorption pump of the present invention does not serve as a support for the hydrogen clock. The adsorption pump and the main body of the hydrogen clock are connected through a transition rectangular groove, increasing the heat dissipation surface. While meeting the gas absorption efficiency, the heat dissipation demand of the main body of the hydrogen clock for heating activation is reduced, and the success rate of single-body activation of the adsorption pump is improved; on the other hand, pump bodies of different volumes can be switched to meet the demand for different gas absorption amounts without changing the main body structure. Brief Description of the Drawings

[0025] Figure 1 It is a three-dimensional structure schematic diagram of a hydrogen atomic frequency standard with a heating adsorption pump after removing the high-frequency heating coil according to an embodiment of the present invention.

[0026] Figure 2 It is a top view structure diagram of a hydrogen atomic frequency standard with a heating adsorption pump after removing the high-frequency heating coil according to an embodiment of the present invention.

[0027] Figure 3 As shown in Figure 1 the structure schematic diagram of the high-frequency heating coil of the hydrogen atomic frequency standard with a heating adsorption pump after removing the high-frequency heating coil.

[0028] Figure 4 It is a typical schematic diagram of induction heating principle.

[0029] Figure 5 It is the temperature distribution diagram of the adsorption pump of the hydrogen atomic frequency standard with a heating adsorption pump of the present invention. The Z direction is the axial direction of the adsorption pump, and the R direction is the radial direction of the adsorption pump.

[0030] Figure 6 It is the temperature distribution diagram of the Z axis at the center of the adsorption pump of the hydrogen atomic frequency standard with a heating adsorption pump of the present invention.

[0031] Figure 7It is the temperature distribution diagram of the R axis of the adsorption pump of the hydrogen atomic frequency standard with a heating adsorption pump according to the present invention. Detailed implementation manners

[0032] The following further describes the present invention in conjunction with specific embodiments. It should be understood that the following embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0033] The high-frequency induction heating adsorption pump of the hydrogen atomic frequency standard according to the present invention is based on the following principles:

[0034] 1) The high-frequency induction heating adsorption pump of the hydrogen atomic frequency standard according to the present invention adopts a high-frequency induction heating method, and the internal and external efficiencies are close. There is no need for heat conduction in a similar conduction manner, so the heating gradient is small, the heating efficiency is high, the demand for heating temperature is greatly reduced, the heat dissipation demand of the hydrogen clock main body is reduced, and objectively the activation temperature required by the adsorbent is reduced (the activation temperature of the pure titanium adsorbent is reduced from the original 800 °C to 450 °C), increasing the overall activation efficiency; compared with the existing heating methods, the activation heating time of the adsorption pump is greatly shortened and the overall temperature rise is uniform under the same power (the activation time is reduced from the original maximum of 28 hours to 1.5 hours, and the temperature gradient is reduced from the original 350 °C to 16 °C. The temperature gradient is the temperature difference between the highest temperature point and the lowest temperature point of the pump body during the activation heating steady state process), and the heating device is simple; if the pump body is activated again later, it can also be processed without damage.

[0035] 2) Since the high-frequency induction heating adsorption pump of the hydrogen atomic frequency standard according to the present invention greatly reduces the demand for heating temperature and shortens the heating time, the degree of oxidation of the outer shell is reduced or terminated, improving the reliability of the adsorption pump.

[0036] 3) Furthermore, the high-frequency induction heating adsorption pump of the present invention is not used as a support for the hydrogen clock. The adsorption pump and the hydrogen clock main body are connected through a transition rectangular groove, increasing the heat dissipation surface. While meeting the gas absorption efficiency, the heat dissipation demand of the hydrogen clock main body for heating activation is reduced (the surface temperature cannot be higher than 85 degrees Celsius. Above this temperature, the hydrogen clock will be irreversibly damaged), improving the success rate of the single activation of the adsorption pump; on the other hand, pump bodies of different volumes can be switched to meet the requirements of different gas absorption amounts without changing the main body structure.

[0037] 4) Secondly, a U-shaped heating coil is designed to match the structure of the pump. The magnetic field distribution inside the coil is uniform. The metal conductor placed inside the coil has the same magnetic field change trend in each part during the heating process, making the temperature rise uniform in each part (avoiding the skin effect); the characteristics that eddy currents are generated inside the metal in the high-frequency field enable the rapid and uniform temperature rise of the pump body by adjusting the high-frequency induction power of the coil, and by changing the power of the U-shaped coil, it can adapt to the activation work of pump bodies of different volumes.

[0038] In summary, the present invention solves the disadvantages of the prior art such as complex pump body structure, long heating time, and large thermal gradient during the heating process, reduces the system's requirement for heat dissipation conditions, objectively reduces the activation temperature required for the adsorbent, and increases the overall activation efficiency. In addition, it also reduces or terminates the oxidation degree of the outer shell and does not serve as a support for the hydrogen clock, increasing the mechanical reliability of the system.

[0039] As Figures 1 - 3 shown is a schematic structural diagram of a hydrogen atomic frequency standard with a heated adsorption pump according to an embodiment of the present invention. As Figures 1 - 3 shown, the hydrogen atomic frequency standard with a heated adsorption pump includes an adsorption pump 10 and a hydrogen atomic clock main body 20 that communicate with each other, and a high-frequency heating coil disposed around the outer wall of the adsorption pump 10.

[0040] Among them, the material of the adsorption pump 10 can be selected from ultra-low outgassing rate and high-strength metal materials such as stainless steel and titanium alloy to maintain high vacuum and sealing. The high-frequency heating coil is connected to an AC power supply, so that an induced current is injected into the high-frequency heating coil to achieve electromagnetic induction heating.

[0041] Specifically, a high-frequency magnetic field is generated by the current on the coil, and when the magnetic force lines of this magnetic field cut through the heated component (i.e., the adsorption pump 10) placed therein, an induced eddy current is generated, thereby bringing a heating effect to the heated component and achieving electromagnetic induction heating.

[0042] An adsorbent is provided inside the adsorption pump 10. The material of the adsorbent is metal and has a plate-like structure, and the surface of the adsorbent is covered with an oxide. In this embodiment, the material of the adsorbent plate is titanium, and the oxide is at least one of TiO2 and TiO.

[0043] The shapes of both the adsorption pump 10 and the hydrogen atomic clock main body 20 are cylinders to meet the requirements of mechanical design and volume.

[0044] 1. Selection of pump body size

[0045] As Figure 4 shown is a schematic diagram of a typical electromagnetic induction heating principle. As Figure 4 shown, for a heated component and a high-frequency heating coil surrounding it, a high-frequency magnetic field can be generated by the current on the coil. When the magnetic force lines of this magnetic field cut through the heated component (i.e., the adsorption pump 10) placed therein, an induced eddy current is generated, thereby bringing a heating effect to the heated component and achieving electromagnetic induction heating.

[0046] Among them, the high-frequency current I1 injected into the heated component is expressed as:

[0047] I1 = Asinωt,

[0048] Among them, A is the current amplitude constant, ω is the angular frequency of the high-frequency current, and t is the time.

[0049] The induced magnetic field B inside the high-frequency heating coil can be approximately written as:

[0050] B = I1 × μ0 × N / L,

[0051] where N is the number of turns of the high-frequency heating coil, I1 is the high-frequency current, μ0 is the permeability of free space, and L is the length of the high-frequency heating coil.

[0052] Then, the induced current I2 is:

[0053]

[0054] where ε is the induced electromotive force generated by the heated component, R 体 is the bulk resistance of the heated component, is the magnetic flux in the space occupied by the heated component, t is the time, B is the magnetic induction intensity, S is the cross-sectional area of the heated component (perpendicular to B), and r is the cross-sectional radius.

[0055] The average power of the induced current within one cycle is:

[0056]

[0057] where ε is the induced electromotive force generated by the heated component, R 体 is the bulk resistance of the heated component, is the magnetic flux in the space occupied by the heated component, t is the time, B is the magnetic induction intensity, S is the cross-sectional area of the heated component (perpendicular to B), r is the cross-sectional radius, and T is the integration time period.

[0058] The Joule heat Q generated by the induced current I2 within the integration time period T is:

[0059]

[0060] As the frequency of the electromagnetic field increases, the induced current I2 increasingly tends to the surface of the heating body, and the current penetration depth d of the induced current can be expressed as:

[0061]

[0062] where μ is the magnetic permeability of the adsorbent metal, γ is the electrical conductivity of the adsorbent metal, and ω is the angular frequency of the induced current.

[0063] For the heating of the adsorbent, it is necessary to achieve overall temperature rise as much as possible and avoid the occurrence of such skin effects. From formulas (1) and (2), the design idea can be obtained. On the premise of ensuring the heating power (i.e., A is large enough), the frequency ω of the induced current should be set lower.

[0064] In this embodiment, taking the adsorbent plate made of titanium as an example, the surface of the 4-mm-thick adsorbent plate is covered with oxides such as TiO2 and Ti0 within 10 nm, and its conductivity is about 10 4 (S / m), and the magnetic permeability is the vacuum magnetic permeability μ0 = 4 * π × 10 -7 (H / m). Calculated with the frequency of the common 20-kHz induced current, the current penetration depth d is 3.56 cm. Then, the width of the pump filled with titanium adsorbent should not exceed 7 cm. In other embodiments, according to the characteristic of uniform heating, the frequency range of the induced current can be set from 50 Hz to 20 kHz.

[0065] This is because in order to achieve the uniformity of the pump body temperature, it is necessary to avoid the skin effect and ensure that the induced current can penetrate the entire pump body. The calculated penetration depth is 3.56 cm, so the radius of the pump body less than 3.56 cm can meet the requirements; here, the diameter of the adsorption pump 10 is simply set to be at most 7 cm. In addition, considering that the total amount of adsorbed hydrogen within the life of the hydrogen clock should be greater than 10 L (under standard atmospheric pressure), according to the requirement of the mass of the filled titanium adsorbent, the volume of the adsorption pump 10 should be greater than 35 cm 3 (with a 50% redundancy).

[0066] In other embodiments, the diameter of the adsorption pump 10 is at most twice the current penetration depth d of the induced current.

[0067] The thickness of the adsorption pump 10 can be given as 1 - 1.5 mm according to the design value of the non-load-bearing parts by experience.

[0068] 2. Selection of the structure and size of the transition pipeline

[0069] The position where the hydrogen atomic clock main body 20 is placed is the hydrogen clock beam optics L2 part (the area with the highest efficiency of adsorbing the remaining ionized particles of the hydrogen atomic frequency standard). The height of this part is about 12 cm. Considering the heat dissipation during pump body activation and the installation of connectors, the height of the hydrogen atomic clock main body 20 cannot exceed 9 cm. Considering that the diameter of the state selection part of the hydrogen clock is not less than 5 cm, if it is similar to the existing technology and an adsorption pump with a diameter of 7 cm is used as the main pump of the hydrogen atomic clock, it is impossible to fill enough mass of adsorbent. Specifically, the existing hydrogen clock state selector is nested inside the adsorption pump (the two are concentrically distributed), and the diameter of the state selector is about 5 cm; if the state selector is placed in a pump with a diameter of 7 cm, the gap between the state selector and the pump housing is only 1 cm. Considering the heat insulation gaps required by the adsorbent and the state selector, and the adsorbent and the pump housing during the activation process, there is no space to place the adsorbent.

[0070] Therefore, in this embodiment, as Figure 1 and Figure 2 shown, the adsorption pump 10 and the hydrogen atomic clock main body 20 are connected through a transition pipeline 40, so as to ensure that enough mass of adsorbent can be filled and the influence of heating on the magnetism of the state selector can be avoided as much as possible. The hydrogen atomic clock main body 20 refers to the hydrogen clock state selector.

[0071] The transition pipeline 40 is a channel for hydrogen and other particles of the hydrogen atomic clock main body 20 to diffuse into the adsorption pump 10, and it is also a channel for the pump body to convect and dissipate heat to the outside world, used to reduce the thermal diffusion effect on the main hydrogen clock during the activation and heating process; the uniformity of heating improves the number of successfully activated adsorbents in disguise, and reduces the amount of adsorbent used in disguise.

[0072] In this embodiment, the transition pipeline 40 is a rectangular pipeline and is connected between the side walls of the adsorption pump 10 and the hydrogen atomic clock main body 20. The length L of the transition pipeline 40 is greater than 10 mm to ensure that the thermal diffusion effect of the pump body heating on the hydrogen clock main body is small.

[0073] 3. Detailed dimensions of the adsorption pump and the transition pipeline

[0074] To ensure that the internal vacuum degree of the hydrogen clock is maintained at the level of 10-5 pa, the pumping speed of the adsorption pump must ensure that it can pump out the hydrogen particles entering the adsorption pump of the hydrogen clock. The hydrogen flow entering the adsorption pump can be expressed as:

[0075]

[0076] Among them, n is the number of particles per unit volume, is the average speed of hydrogen, I is the hydrogen flow entering the adsorption pump, and S is the cross-section of the transition area between the adsorption pump and the main body connection.

[0077] At 10 -5Under the vacuum condition of pa, the number of particles per unit volume n = 2.69x10 11 (calculated based on the total vacuum volume within 0.1L), the average velocity of hydrogen (at 25°C); calculated based on the level of 1L of hydrogen consumed by the hydrogen clock in one year, the hydrogen flow rate I entering the internal vacuum chamber per second is 8.5x10 14 / s. Substituting into the above formula, the cross-sectional area S of the transition pipeline 40 connecting the adsorption pump and the main body can be calculated to be at least 5 cm 2 .

[0078] As Figure 2 shown, combining the diameter and volume of the adsorption pump 10 described above, the specific dimensions of the adsorption pump 10 and the transition pipeline 40 are as follows:

[0079] According to the above description, the diameter D of the adsorption pump is at most 7 cm, and the volume is greater than 35 cm 3 , and the cross-sectional area of the transition pipeline 40 is at least 5 cm 2 . Taking the height of the adsorption pump 10 and the transition pipeline 40 as 7 cm for calculation (the height refers to the length along the central axis direction of the adsorption pump 10), it can be obtained that: the diameter D of the adsorption pump 10 is greater than 2.5 cm, and the width W of the transition pipeline 40 is greater than 7.1 mm.

[0080] Figure 2 Shows a top view structure diagram of an adsorption pump with the diameter D of the adsorption pump 10 = 3 cm and the width W of the transition pipeline 40 = 8 mm.

[0081] 4. Design parameters of the high-frequency heating coil

[0082] The predicted output power of the coil is greater than 1000 w (based on the power required for traditional internal and external heating assumptions). When a power of 1000 w acts on the coil, the temperature of the coil will gradually get out of control (the air convection heat dissipation power is too small), which will cause the copper coil to soften and lead to irreversible deformation of the structure. Therefore, heat dissipation is required. According to a power conversion rate of 90%, it can be obtained that the heat dissipation power required by the coil should be greater than 100 w. It is obviously impossible to achieve such a large heat dissipation power through the natural convection heat dissipation of the coil itself, and it can only be achieved through water-cooled heat dissipation.

[0083] The water-cooled heat dissipation power P per unit volume 散热 is expressed as:

[0084] P heat dissipation = M × C p × (T in - T out )

[0085] Among them, T in is the water temperature entering the coil, T out is the water temperature leaving the coil, and C pC is the specific heat capacity of water, and M is the water flow rate per unit time.

[0086] The specific heat capacity C of water p is 4.2 kJ / kg*°C. With a temperature difference of 5 °C (a typical value for the temperature difference between the inlet and outlet water pipes of the cooler), the water flow rate M per unit time is calculated to be 4.2x10 -3 kg / s. Calculated with a water flow velocity of 1 m / s, the cross-sectional area required for the water flow is 4.2 mm 2 , and through conversion, it can be obtained that the diameter of the cooling water pipe at the center of the high-frequency coil is 2.4 mm.

[0087] Considering the mechanical properties of the coil and the capacitance value of the coil, in this embodiment, a hollow copper tube with an inner diameter of 3 mm and an outer diameter of 6 mm is used as the high-frequency heating coil, and the inside of the high-frequency heating coil is cooled by water.

[0088] According to the coupling relationship with the power supply, as Figure 3 shown, the high-frequency heating coil is formed by connecting in series multiple single-turn coils arranged in sequence from the outside to the inside. Each single-turn coil is composed of two U-shaped line segments 31 facing each other, a first straight line segment 32 connecting the first tops of the two U-shaped line segments, and a second straight line segment 33 connecting the second top of one of the U-shaped line segments and the second top of one of the U-shaped line segments of the next single-turn coil. The outer wall of the adsorption pump 10 fits the arc surface formed by the two U-shaped line segments.

[0089] Experimental results:

[0090] Using comsol software to simulate and calculate the high-frequency heating adsorption pump, the temperature of the adsorbent inside the pump reaches above 450 °C after 18 minutes, as Figure 5 shown.

[0091] Figure 6 And Figure 7 are the temperature distributions in the Z direction and R direction of the adsorption pump after heating for 18 minutes: the temperature difference in the Z direction of the whole pump does not exceed 16 °C, the radial temperature difference does not exceed 1 °C, and the temperature difference between the pump shell and the adsorbent itself does not exceed 5 °C. The above data shows that the hydrogen atomic frequency standard with a heating adsorption pump of the present invention has the effect of quickly and uniformly heating the adsorbent.

[0092] In addition, the technical solution of the present invention reduces the activation temperature of the adsorption pump, increases the overall activation success rate of the adsorbent, and can ensure the gas adsorption efficiency and achieve the minimum filling rate of the adsorbent quality on the premise of greatly reducing the activation time. The following table is the comparison result with the current existing technology:

[0093] Titanium adsorbent Getter filling amount Activation temperature Activation time Pump housing material selection The present invention 50g 450℃ 1.2h TA2 External heating technology 90g 800℃ 6h Stainless steel 310 Internal heating 100g 800℃ >24h TA2

[0094] The above are only the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Various changes can be made to the above embodiments of the present invention. That is, all simple, equivalent changes and modifications made in accordance with the claims and the content of the specification of the present invention application fall within the scope of protection of the claims of the present invention patent. Those not described in detail in the present invention are all conventional technical contents.

Claims

1. A hydrogen atomic frequency standard with a heating adsorption pump, characterized in that, It includes an adsorption pump and a hydrogen atomic clock body that are connected to each other, and a high-frequency heating coil disposed around the outer wall of the adsorption pump; an adsorbent is provided in the adsorption pump, and the material of the adsorbent is metal; the high-frequency heating coil is connected to an AC power supply to inject an induced current into the high-frequency heating coil to achieve electromagnetic induction heating; The diameter of the adsorption pump is at most twice the current penetration depth of the induced current; The current penetration depth d of the induced current is: ， where μ is the magnetic permeability of the adsorbent and γ is the electrical conductivity of the adsorbent, is the angular frequency of the induced current; The adsorption pump and the hydrogen atomic clock body are connected through a transition pipeline.

2. The hydrogen atomic frequency standard with a heating adsorption pump according to claim 1, characterized in that, The frequency range of the induced current is 50 Hz - 20 KHz.

3. The hydrogen atomic frequency standard with a heating adsorption pump according to claim 1, characterized in that, The adsorption pump and the hydrogen atomic clock body are both in the shape of a cylinder, the transition pipeline is a rectangular pipeline, and is connected between the side walls of the adsorption pump and the hydrogen atomic clock body.

4. The hydrogen atomic frequency standard with a heating adsorption pump according to claim 3, characterized in that, The length L of the transition pipeline is greater than 10 mm, and the cross-section S of the transition pipeline is at least 5 cm 2 ; the diameter D of the adsorption pump is greater than 2.5 cm and at most 7 cm, and the volume is greater than 35 cm 3 , the width W of the transition pipeline is greater than 7.1 mm, and the heights of both the adsorption pump and the transition pipeline are 7 cm.

5. The hydrogen atomic frequency standard with a heating adsorption pump according to claim 1, characterized in that, The high-frequency heating coil is a hollow copper tube with an inner diameter of 3 mm and an outer diameter of 6 mm, and the inside of the high-frequency heating coil is cooled by water.

6. The hydrogen atomic frequency standard with a heating adsorption pump according to claim 1, characterized in that, The high-frequency heating coil is formed by connecting in series a plurality of single-turn coils arranged in sequence from the outside to the inside. Each single-turn coil is composed of two U-shaped line segments facing each other, a first straight line segment connecting the first tops of the two U-shaped line segments, and a second straight line segment connecting the second top of one of the U-shaped line segments and the second top of one of the U-shaped line segments of the next single-turn coil.

7. The hydrogen atomic frequency standard with a heating adsorption pump according to claim 1, characterized in that, The surface of the adsorbent is covered with an oxide; the material of the adsorbent is titanium, and the oxide is at least one of TiO2 and TiO.

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