Condensing device and method for in-situ preparation of icicle shots

Abstract

According to the condensing device and method for in-situ preparation of the icicle projectiles, the size of a spallation projectile injection system can be reduced, the cold source utilization efficiency is improved, and the requirement of a future large fusion device for a plasma fracture relieving system is better met. The condensing device comprises: a condenser for desublimating the raw material gas into pellets in a condensing area; the precooler is used for precooling the raw material gas; the vacuum heat insulation shell provides a vacuum heat insulation environment for the condenser and the precooler; the intermediate temperature shielding part is in thermal contact with the precooler and is used for reducing radiation heat exchange between the condenser and the vacuum heat insulation shell, the intermediate temperature shielding part is provided with a cooling medium flow path and a raw material gas flow path, the upstream end of the raw material gas flow path is connected with a raw material gas supply source and reaches the condenser after flowing through the precooler, and the downstream end of the raw material gas flow path reaches the vacuum heat insulation shell after flowing through the precooler. The upstream end of the cooling medium flow path is connected with a cooling medium supply source and sequentially flows through the condenser and the precooler from the upstream to the downstream, and the downstream end of the cooling medium flow path is connected with a cooling medium recovery device.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of particle injection of nuclear fusion devices, in particular to the low-temperature condensation pellet injection technology, and more particularly to a condensing device and method for in-situ preparation of ice column pellets. BACKGROUND

[0002] Nuclear fusion energy, as a potential clean, safe and almost inexhaustible energy source, is the focus of global energy research. In the Tokamak device, which is widely studied as a magnetic confinement nuclear fusion device, solving the plasma disruption is a key challenge.

[0003] Plasma disruption is a phenomenon that the magnetic confinement is quickly lost and accompanied by the release of a large amount of plasma energy due to the sudden instability of the plasma. Due to the release of a large amount of plasma energy and current in a very short time, it may cause serious impact on the device components and shorten the service life of the Tokamak device. In order to alleviate the harm caused by the disruption, researchers have proposed a scheme of rapidly injecting impurity particles into the plasma to make it radiate energy.

[0004] As in Non-Patent Literature 1, the Shattered Pellet Injection (SPI) technology is to condense the pre-filled impurity gas into an ice pellet, accelerate the pellet with high-pressure gas, and make it into fragments by a fragmentation device before entering the plasma. This technology can achieve deeper core heat dissipation and can effectively alleviate the local thermal load, electromagnetic stress and escaped electrons caused by disruption, and has become one of the main technical routes for Tokamak device disruption mitigation (for example, see Non-Patent Literature 2).

[0005] However, the existing SPI system usually uses a separate low-temperature refrigerator (such as a G-M refrigerator) as a cold source to design the condensing device. The refrigerator is bulky and occupies a large space, resulting in a large volume and complex structure of the entire SPI system. For future fusion devices, the demand for SPI systems is large, and the space outside the vacuum chamber is limited. The over-bulky condensing and injection device is difficult to arrange in the ideal position. Secondly, the refrigeration efficiency and refrigeration power of the traditional refrigerator are limited, and the energy utilization rate is low during the pellet condensation process, making it difficult to provide sufficient cooling capacity to quickly prepare large-size pellets, affecting the efficiency of the device operation. In summary, the existing shattered pellet injection technology has deficiencies in equipment volume, installation space, and cold source utilization efficiency, and there is an urgent need for an improved condensing device with compact structure and high refrigeration efficiency to meet the application requirements of large Tokamak device disruption mitigation.

[0006] Non-Patent Literature 1: L.R. Baylor et al 2009 Nucl. Fusion 49 085013

[0007] Non-patent document 2: Y. Li et al 2021 Nucl. Fusion 61 126025 SUMMARY

[0008] To solve the problems of large structure and low cooling efficiency of the condensing device in the prior art, in the present application, supercritical helium is used as a cold source instead of a low-temperature refrigerator, and through a unique pre-cooling-condensing-recovery integrated process, low-temperature projectiles can be quickly prepared in situ. Thus, a small and high-efficiency condensing device and method for preparing ice column projectiles in situ are provided to meet the application requirements of impurity injection for future fusion device disruption mitigation.

[0009] Specifically, the first aspect of the present application provides a condensing device for preparing ice column projectiles in situ, characterized in that it comprises: a condenser for sublimating raw gas into projectiles in a condensing area; a pre-cooler for pre-cooling the raw gas; a vacuum adiabatic shell for providing a vacuum adiabatic environment for the condenser and the pre-cooler; and an intermediate temperature shielding part in thermal contact with the pre-cooler for reducing the radiation heat exchange between the condenser and the vacuum adiabatic shell, wherein the condensing device is provided with a cooling medium flow path, a raw gas flow path and a propellant gas flow path, the propellant gas flow path is connected with a propellant gas supply source, and after the raw gas sublimates into projectiles, the propellant gas is supplied to push the projectiles out, the upstream end of the raw gas flow path is connected with a raw gas supply source, and after passing through the pre-cooler, it reaches the condenser, the upstream end of the cooling medium flow path is connected with a cooling medium supply source, the cooling medium flow path sequentially passes through a flow regulating valve, the condenser and the pre-cooler from upstream to downstream, and the downstream end is connected with a cooling medium recovery device, the cooling medium first exchanges heat with the raw gas pre-cooled by the pre-cooler in the condenser, the cooling medium after the first heat exchange is pre-cooled by exchanging heat with the raw gas supplied from the raw gas supply source and not pre-cooled by the pre-cooler in the pre-cooler, and the cooling medium after the first heat exchange also cools the intermediate temperature shielding part through the thermal contact between the pre-cooler and the intermediate temperature shielding part.

[0010] The second aspect of the present application provides a condensing device for preparing ice column projectiles in situ, characterized in that in the above condensing device, the cooling medium supplied from the cooling medium supply source is supercritical helium, and the cooling medium after the first heat exchange becomes cold gas helium.

[0011] The third aspect of the present application provides a condensing device for in-situ preparation of ice column projectiles, characterized in that in the condensing device, the condenser comprises a condensing gun tube and a cold head installed on the condensing gun tube in a heat-conducting manner, a flow channel for the cooling medium to flow through is formed in the cold head, the cooling medium cools the cold head and forms the condensing area on the condensing gun tube by the cold head to condense the raw material gas, and thus the first heat exchange occurs between the cooling medium and the raw material gas.

[0012] The fourth aspect of the present application provides a condensing device for in-situ preparation of ice column projectiles, characterized in that in the condensing device, a heater and a low-temperature sensor are arranged on the cold head, and the temperature of the condensing area is controlled by adjusting the heating power of the heater in real time based on the detection result of the low-temperature sensor to meet the requirements of different material projectiles for condensing temperature.

[0013] The fifth aspect of the present application provides a condensing device for in-situ preparation of ice column projectiles, characterized in that in the condensing device, the cooling medium flow path is provided with a first heat exchanger at a position downstream of the condenser and upstream of the precooler, the first heat exchanger comprises a heat sink, a heater and a low-temperature sensor, and the heating power of the heater is adjusted in real time based on the detection result of the low-temperature sensor, so that the temperature of the cooling medium entering the precooler meets the following conditions: one is that the raw material gas will not be liquefied in the precooler, and the other is that the temperature of the cooling medium discharged from the precooler does not exceed the maximum recoverable temperature required by the recovery device.

[0014] The sixth aspect of the present application provides a condensing device for in-situ preparation of ice column projectiles, characterized in that in the condensing device, the precooler forms a cavity structure, and two spiral coiled raw material gas pipelines are arranged inside the cavity structure, the raw material gas flows in opposite directions in the two raw material gas pipelines, the cooling medium after the first heat exchanger flows in the cavity outside the pipelines of the precooler, and the raw material gas is precooled.

[0015] The seventh aspect of the present application provides a condensing device for in-situ preparation of ice column projectiles, characterized in that in the condensing device, a second heat exchanger and a third heat exchanger are arranged upstream and downstream of the condensing area of the condensing gun tube respectively, the second heat exchanger and the third heat exchanger each comprise a heat sink, a heater and a low-temperature sensor, the heating power of the heater is adjusted in real time based on the detection result of the low-temperature sensor according to the type of the raw material gas, and thus the temperature variation gradient near the condensing area of the condensing gun tube is adjusted, so that the projectiles can be shaped into a cylindrical shape.

[0016] The eighth aspect of the present application provides a condensing device for in-situ preparation of ice cylinder projectiles, characterized in that in the condensing device, the raw material gas is H2, D2, Ne, Ar or a mixture of any two thereof.

[0017] The ninth aspect of the present application provides a condensing device for in-situ preparation of ice cylinder projectiles, characterized in that in the condensing device, the propellant gas is He or H2, and the propellant gas flow path is capable of adjusting the pressure of the propellant gas to adjust the launch speed of the projectiles.

[0018] The tenth aspect of the present application provides a method for preparing ice cylinder projectiles using the condensing device, characterized in that the method comprises: a first step of drawing the vacuum adiabatic shell to a certain vacuum, then supplying the cooling medium from the cooling medium supply source, adjusting the flow regulating valve, and cooling the condenser, the precooler and the intermediate temperature shield to the lowest temperature; a second step of adjusting the temperature of the cooling medium before entering the precooler by using the first heat exchanger; a third step of adjusting the temperature of the condensing region and its upstream and downstream according to the type of raw material gas and the size of the projectiles to be prepared; a fourth step of supplying the raw material gas from the upstream and downstream of the condensing region after precooling by the precooler, and condensing the projectiles from both sides of the upstream and downstream of the condensing region; and a fifth step of injecting the propellant gas from the upstream of the condensing region to push out the projectiles after the projectiles are formed.

[0019] Based on the above-mentioned aspects, compared with the prior art, the condensing device of the present application has significant beneficial effects and technical progress.

[0020] Firstly, the system has a small overall volume and a compact structure, which breaks away from the limitations of the large volume and numerous peripheral devices of traditional G-M refrigerators, and is convenient for integration and deployment in the limited installation space of a tokamak device.

[0021] Secondly, the cold source utilization efficiency is high and the cooling capacity is sufficient. The supercritical helium cold source provides a refrigeration power much higher than that of ordinary refrigerators, which can quickly condense the raw material gas into projectiles; at the same time, through the precooling-recovery closed loop design, the cold helium generated by the evaporation of supercritical helium is fully utilized, which greatly reduces the waste of cold energy and improves the energy utilization efficiency.

[0022] In addition, the miniaturization and high-efficiency condensation of the device enable multiple injection systems to be installed on the same tokamak device as needed to meet the needs of different locations for disruption mitigation, thereby improving the reliability and adaptability of the system as a whole.

[0023] In summary, the scheme of the present application is superior to the traditional pellet injection system in volume, efficiency and the like, and can better meet the technical requirements of the plasma disruption mitigation system of future large fusion devices, thereby providing an important guarantee for the safe and efficient operation of the magnetic confinement fusion device. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a schematic diagram of the structure of the condensing device of the present application.

[0025] Figure 2 is a schematic diagram of the flow of the condensing method in the condensing device of the present application.

[0026] BRIEF DESCRIPTION OF DRAWINGS:

[0027] 1: gas supply device, 2: condenser dewar, 3: cold shield, 4: pre-cooler, 5: helium recovery device, 6: first low-temperature sensor, 7: second low-temperature sensor, 8: cold head, 9: first heater, 10: first heat sink, 11: second heater, 12: third low-temperature sensor, 13: helium supply device, 14: flow regulating valve, 15: condensing gun tube, 16: fourth low-temperature sensor, 17: second heat sink, 18: third heater, 19: fifth low-temperature sensor, 20: pellet, 21: sixth low-temperature sensor, 22: third heat sink, 23: fourth heater, 24: seventh low-temperature sensor, 25: condenser, 26: first gas flow path, 27: second gas flow path, 28: cooling medium flow path, 29: first gas supply port, 30: second gas supply port, 31: first heat exchanger, 32: second heat exchanger, 33: third heat exchanger, 34: propellant gas flow path, 101: condensing device. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Of course, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort fall within the protection scope of the present application.

[0029] For example, the size, material, quantity and the like of each structural component described in the specification are not limited, and other alternatives can be adopted by those skilled in the art according to technical common sense.

[0030] Before the condensing device of the present application is described, the general structure of the SPI system for in-situ preparation of pellets is briefly introduced.

[0031] Generally, the SPI system utilizes the principle of a pipe gun, in which low-pressure gas is introduced into the interior of a barrel, and a condensing region cooled by a cold source is provided in the barrel, in which the inner wall temperature is much lower than the condensation point of the gas, and the gas directly condenses from gas to solid after contacting the cooled inner wall in the condensing region, forming a cylindrical solid projectile. Once the projectile is formed, it can be directly pushed out of the barrel in situ by high-pressure gas and accelerated, and after being pulverized by a fragmentation device, it enters the plasma.

[0032] As described above, the existing SPI technology uses a separate low-temperature refrigerator such as a G-M refrigerator as a cold source, and has the problem of resulting in a large SPI system and limited refrigeration efficiency.

[0033] In this regard, the inventors have found that by replacing the low-temperature refrigerator with supercritical helium as a cold source, and using a unique pre-cooling-condensing-recovery integrated process, ice column projectiles can be prepared in situ in a small and high cooling efficiency compared with the prior art.

[0034] The structure of the condensing device 101 of the present application will be described in detail below with reference to the accompanying drawings.

[0035] Figure 1 is a schematic view showing the structure of the condensing device of the present application.

[0036] Figure 1 The supply device 1, the condenser Dewar 2, the cold shield 3, the pre-cooler 4, the helium recovery device 5, the first low-temperature sensor 6, the second low-temperature sensor 7, the cold head 8, the first heater 9, the first heat sink 10, the second heater 11, the third low-temperature sensor 12, the helium supply device 13, the flow regulating valve 14, the condensing barrel 15, the fourth low-temperature sensor 16, the second heat sink 17, the third heater 18, the fifth low-temperature sensor 19, the projectile 20, the sixth low-temperature sensor 21, the third heat sink 22, the fourth heater 23, the seventh low-temperature sensor 24, the first gas flow path 26, the second gas flow path 27, the cooling medium flow path 28, and the propellant gas flow path 34 are shown in FIG.

[0037] Among them, the supply device 1, the helium recovery device 5, and the helium supply device 13 can be considered as components of the condensing device 101 of the present application, but can also be considered as peripheral components, and are not particularly limited. For example, the condensing device 101 can be considered to have only components, flow paths, etc. mainly for realizing the condensing function, and other parts belong to other devices (for example, sensing devices, launching devices, gas / fluid supply sources, etc.).

[0038] Among the above components, each of the low temperature sensors 6, 7, 12, 16, 19, 21, 24 and each of the heaters 9, 11, 18 can employ those commonly used in the art, and their structure and principle of implementation are not particularly limited. For example, in one embodiment, each of the low temperature sensors 6, 7, 12, 16, 19, 21, 24 is capable of measuring temperature in the range of 3.5-300 K, and has an accuracy of ±0.25 K in the temperature range of 8-80 K. Each of the heaters 9, 11, 18 is a non-inductive constant resistance capable of being used stably at low temperature, and has a resistance of 10-50 Ω. Each of the flow paths is formed by connecting various pipes, and the material and size of the pipes are appropriately selected according to the actual situation.

[0039] In the present application, the main components of the condensing device 101 are the condenser 25, the pre-cooler 4, the cold shield 3 constituting the intermediate temperature shield, the condenser Dewar 2 constituting the vacuum adiabatic housing, and each of the flow paths.

[0040] In the condensing device 101, the raw material gas supplied from the gas supply device 1 is pre-cooled by the pre-cooler 4, and the pre-cooled raw material gas is condensed into pellets 20 by the condenser 25, and the pellets 20 are directly detached in situ and pushed out by the high-pressure propellant gas.

[0041] The above components will be described in detail below.

[0042] The condenser 25 functions to condense (i.e., to sublimate) the supplied raw material gas into pellets, and also provides a channel for launching the pellets. The condenser 25 mainly includes a cold head 8 and a condenser gun tube 15.

[0043] The condenser gun tube 15 is a pipe member such as a cylindrical pipe, formed of a material having good thermal conductivity and sufficient strength, and has a certain roughness on the inner surface to enhance the sublimation effect, and the inner diameter thereof can be replaced according to the size requirement of the pellets for breakage mitigation. In one embodiment, the condenser gun tube 15 is, for example, a seamless stainless steel pipe having a wall thickness of 1 mm and an inner diameter of 10-20 mm.

[0044] The cold head 8 functions to form a condensing area on the condenser gun tube 15, and is made of a material having high thermal conductivity, such as oxygen-free copper, and includes, for example, a main body portion and a mounting portion formed integrally. The main body portion is in the form of a block, and has a cooling medium flow channel formed therein. Cooling medium (in one embodiment, supercritical helium) from the outside flows into the flow channel inlet and flows out of the flow channel outlet, thereby exchanging heat with the main body portion to lower its temperature. The flow channel can have a commonly used shape and structure, such as a spiral shape, and the present application is not limited thereto. As an example, the flow channel inlet is shown to be located on the lower side of the main body portion, and the flow channel outlet is shown to be located on the upper side of the main body portion.

[0045] The mounting portion plays a role of fixing the cold head 8 on the condensing barrel 15, for example, in a cylindrical shape corresponding to the outer shape of the condensing barrel 15 and in a two-half structure, and can be connected and fixed to the condensing barrel in good thermal conduction after being fastened. For example, by brazing or connecting through a pad of soft thermal conduction metal and then fastening through a bolt, a condensing area with good thermal conduction is formed on the condensing barrel 15. The first heater 9, the second low-temperature sensor 7 and the fifth low-temperature sensor 19 can be provided on the cold head 8 as needed, and the temperature control of the condensing area is realized by adjusting the heating power of the first heater 9 in real time through the PID control logic, so as to meet the requirements of the condensing temperature of the projectiles of different materials. For example, when the projectiles are prepared by using Ne raw gas, the temperature control of the cold head 8 is 12K.

[0046] As shown in Figure 1 , the first heater 9 can be arranged on the main body portion of the cold head 8 on the side of the mounting portion (i.e., on the side of the barrel), and the second low-temperature sensor 7 and the fifth low-temperature sensor 19 are arranged at positions away from each other, for example, the second low-temperature sensor 7 is arranged at the upper end of the main body portion of the cold head 8 and is suitable for monitoring the temperature of the cooling medium flowing through the cold head 8, and the fifth low-temperature sensor 19 is arranged at the lower end of the mounting portion and is suitable for monitoring the temperature of the condensing area of the condensing barrel 15 cooled by the cold head.

[0047] The gas supply device 1 integrates a raw gas supply source and a high-pressure propellant gas supply source, is connected with the first gas flow path 26, the second gas flow path 27 and the propellant gas flow path 34, and can supply raw gas and propellant gas. The first gas flow path 26 and the second gas flow path 27 are respectively connected to the condensing barrel 15 of the condenser 25 via the pre-cooler 4, and the condensing barrel 15 is respectively provided with a first gas supply port 29 and a second gas supply port 30 on the upstream and downstream of the condensing area, which are respectively communicated with the first gas flow path 26 and the second gas flow path 27. Thus, the gas supply device 1 supplies the raw gas pre-cooled via the pre-cooler 4 to the condensing barrel 15 of the condenser 25, and by supplying from the upstream and downstream of the condensing area respectively, the projectiles can be formed symmetrically. In addition, the type and flow of the raw gas can be adjusted according to the gas demand of the projectile preparation and launching, so as to meet the pressure required by the raw gas on the upstream and downstream of the condensing area in the projectile preparation process. The required type of raw gas is generally H2, D2, Ne, Ar and any two mixed gases, and the pressure range is 10-1000 mbar.

[0048] The propellant gas flow path 34 is connected at one end with the gas supply device 1 and at the other end with the upstream end (left end in the figure) of the condensing barrel 15, and the flow path can adjust the pressure of the propellant gas to meet the regulation of the projectile launching speed. The required type of propellant gas is generally He, H2, etc., and the pressure range is 20-100 Bar.

[0049] Further, the source of the raw material gas and the propellant gas is shown as one gas supply device 1, but is not limited to this, and separate sources can be used to supply the raw material gas and the propellant gas separately.

[0050] The helium supply device 13 functions as a source of the cooling medium, and supplies a cooling medium fluid that serves as a cold source. In the present application, supercritical helium at a temperature of 4.5 K is used. The helium supply device 13 is connected to the upstream end of the cooling medium flow path 28, which is provided with the flow rate adjustment valve 14, the cold head 8, the first heat sink 10, the pre-cooler 4 in that order from the upstream to the downstream, and is finally connected to the helium recovery device 5. In this way, the cooling medium, i.e., the supercritical helium, exchanges heat with the cold head 8 to cool it and produce the projectile (indirectly exchanges heat with the raw material gas that has been pre-cooled), and after the heat exchange, the cooling medium, i.e., the supercritical helium, evaporates and changes into cold gas helium. The residual cold of the cold gas helium can be used to pre-cool the raw material gas using the cold source of the pre-cooler 4 (as described later, also used to cool the cold shield), and the helium gas discharged from the pre-cooler 4 is recovered by the helium recovery device 5.

[0051] The pre-cooler 4 pre-cools the raw material gas supplied from the gas supply device 1 using the residual cold of the cold gas helium, and as described later, also cools the cold shield 3. In one embodiment, the pre-cooler 4 is a hollow structure made of a highly heat-conductive material (e.g., oxygen-free copper), and two raw material gas pipes are arranged inside the pre-cooler in a spiral shape along the length direction of the pre-cooler. The inlets of the two pipes are respectively connected to the raw material gas supply source in the gas supply device 1, and the outlets are respectively connected to the condenser gun pipes 15, and each pipe constitutes a part of the first gas flow path 26 and the second gas flow path 27. The hollow inside the pre-cooler 4 outside the pipes is a passage for the cooling medium (the cold gas helium that has exchanged heat with the cold head 8), and therefore the hollow has a cooling medium inlet at the upstream and a cooling medium outlet at the downstream, the cooling medium inlet is connected to the downstream end of the first heat sink 10, and the cooling medium outlet is connected to the helium recovery device 5. Further, the inlets of the raw material gas pipes are respectively located at both ends in the length direction of the pre-cooler, and the outlets are respectively located at the opposite ends, and thus the raw material gas flows in different directions in the two pipes, and exchanges heat well with the cold gas helium in the hollow. Further, the pre-cooler 4 can be provided with the first low-temperature sensor 6 for monitoring the temperature to facilitate temperature control.

[0052] The condenser Dewar 2 functions as a vacuum heat-insulated housing, and in one embodiment, it is a vacuum chamber made of stainless steel, and has an ultimate vacuum degree of <10 -5 Pa, and a total leak rate of <10 -9 Pa·m 3 / s. The condenser Dewar 2 is provided with openings through which various flow paths and the gun pipes pass.

[0053] The cold shield 3 is an intermediate temperature shield between the condenser dewar 2 and the condenser 25, the pre-cooler 4, etc., for reducing the radiation heat exchange between the condenser and the dewar. The cold shield 3 encloses the above-mentioned parts of the condenser 25, the pre-cooler 4, etc., and is made of a metal material having high thermal conductivity. Also, the cold shield 3 is in good thermal contact with the pre-cooler 4, so that it can be cooled to a certain low temperature (close to the temperature of the pre-cooler) by the cold gaseous helium in the pre-cooler 4. In one embodiment, the cold shield 3 is made of a box body of 2 mm thick high thermal conductivity oxygen-free copper, and its surface is covered with an aluminum foil to reduce heat leakage. The cold shield 3 can be provided with a seventh low temperature sensor 24 for detecting the temperature of the cold shield to facilitate temperature control.

[0054] The first heat sink 10, the second heat sink 17 and the third heat sink 22 have similar structures, and each of the main bodies has a two-part structure made of a high thermal conductivity material, the two parts sandwiching the condenser gun tube 15 or the pipe constituting the cooling medium flow path 28, the contact surfaces being filled with a soft metal having thermal conductivity and being fastened to each other by fasteners such as bolts, so as to be in good thermal contact with the condenser gun tube 15 or the pipe constituting the cooling medium flow path 28.

[0055] The first heat sink 10 is arranged on the cooling medium flow path 28 downstream of the cold head 8 and upstream of the pre-cooler 4, and is provided with the second heater 11 and the third low temperature sensor 12, which together constitute a first heat exchanger 31. By means of the first heat exchanger 31, the second heater 11 can be adjusted as appropriate according to the detection result of the low temperature sensor 12 to adjust the temperature of the cooling medium (cold gaseous helium) flowing in the cooling medium flow path 28 after heat exchange with the cold head 8 and before entering the pre-cooler 4. Specifically, the temperature adjustment here needs to be made according to the type of the raw material gas, so that the temperature of the cold gaseous helium entering the pre-cooler 4 meets the following conditions: one is to ensure that the raw material gas does not liquefy when pre-cooled, and the other is to ensure that the temperature of the waste helium discharged from the pre-cooler 4 can meet the requirements of the helium recovery device 5 (not higher than the maximum recoverable temperature). The temperature of the cold gaseous helium set here is different for different raw material gases. In one example, when preparing Ne pellets, the temperature of the cold gaseous helium entering the pre-cooler 4 is 30-40 K, and the temperature of the waste helium discharged is less than 80 K.

[0056] The second heat sink 17 and the third heat sink 22 are respectively arranged upstream and downstream of the condensing region of the condensing gun tube 15, and are closer to the condensing region than the first gas supply port 29 and the second gas supply port 30 on the condensing gun tube 15. The fourth low-temperature sensor 16, the third heater 18, the sixth low-temperature sensor 21 and the fourth heater 23 are respectively arranged on the second heat sink 17 and the third heat sink 22, and constitute the second heat exchanger 32 and the third heat exchanger 33. The second and third heat exchangers can appropriately adjust the heaters according to the detection results of the sensors, appropriately heat the temperatures of the upstream and downstream portions of the condensing region of the condensing gun tube 15, thereby adjusting the temperature variation gradient near the condensing region on the condensing gun tube 15, and ensuring that the condensed pellets have a good cylindrical shape. For example, when the pellets are prepared by using Ne raw gas, the temperatures of the second heat sink 17 and the third heat sink 22 on the condensing gun tube are controlled to be 100 K.

[0057] In addition to the structures shown in the figure, various flow meters, flow / flow rate adjusting valves and the like can be arranged on the first gas flow path 26, the second gas flow path 27 and the cooling medium flow path 28 as needed, and the description thereof is omitted here.

[0058] The structure of the condensing device 101 of the present application is described above. According to the above structure, the present application uses a fluid such as supercritical helium as a cold source to prepare raw gas pellets, and the cooling medium fluid (supercritical helium) supplied from the cooling medium supply source is first subjected to first heat exchange (indirect heat exchange via the cold head) with the pre-cooled raw gas in the condenser 25, then subjected to second heat exchange with the raw gas at normal temperature in the pre-cooler 4, and then recovered by the recovery device. Thus, the raw gas is first subjected to second heat exchange (pre-cooling) with the cooling medium after the first heat exchange in the pre-cooler 4, and then the raw gas after the second heat exchange (pre-cooling) is condensed into pellets by the first heat exchange in the condenser.

[0059] Further, the pre-cooler 4 uses the residual cooling of the cold gas helium for both pre-cooling of the raw gas and cooling of the cold shield 3. Therefore, in the present application, the cold gas helium flowing out of the condenser can pre-cool the raw gas at normal temperature and cool the cold shield, greatly reducing the consumption of supercritical helium.

[0060] Thus, the condensing device of the present application has the characteristics of small overall volume and compact structure, and is free from the limitations of the large volume and numerous peripheral devices of the conventional G-M refrigerator, and is convenient to integrate and deploy in the limited installation space of the tokamak device. Secondly, the supercritical helium cold source provides a much higher refrigeration power than ordinary refrigerators, and can quickly condense the raw gas into pellets; at the same time, through the pre-cooling-recovery closed loop design, the residual cooling of the cold gas helium generated by the evaporation of supercritical helium is fully utilized, the waste of cold energy is greatly reduced, and the energy utilization efficiency is improved.

[0061] In addition, the miniaturization of the device and the high-efficiency condensation enable multiple sets of SPI injection systems to be installed on the same tokamak device as needed to cope with the disruption mitigation requirements at different positions, thereby improving the reliability and adaptability of the system as a whole.

[0062] The preparation method of the condensing projectile in the condensing device of the present application is briefly described below.

[0063] Figure 2 is a schematic diagram of the flow of the condensing method in the condensing device of the present application. The specific working process is as follows:

[0064] 1. Cooling medium supply

[0065] First, the condenser Dewar 2 is pumped to a certain vacuum, for example, 10 -3 Pa, after which the helium supply device 13 is opened, and the flow regulating valve 14 on the cooling medium flow path is adjusted to the appropriate position. In the case where the heaters of the heat exchangers are not working, the condensing device, including the condenser, the pre-cooler and the cold shield, is cooled to the lowest temperature by using supercritical helium at 4.5 K.

[0066] 2. Temperature adjustment

[0067] Next, the temperature of the cold gas helium flowing out of the cold head 8 is adjusted by using the first heat exchanger 31 (including the first heat sink 10, the second heater 11 and the third low-temperature sensor 12), the temperature of the pre-cooler 4 and the cold shield 3 is regulated to the required temperature, and according to the material and the expected size of the projectile 20, the temperature of the cold head 8 and the temperatures of the second heat exchanger 32 and the third heat exchanger 33 on the condensing gun tube are regulated to the required process parameters by using the PID control logic. The values of the temperatures depend on the material of the projectile to be prepared, for example, when preparing Ne projectiles, the temperature of the pre-cooler and the cold shield is <60 K, the temperature of the cold head is 12 K, and the temperature of the condensing gun tube heat exchanger is 100 K.

[0068] 3. Raw gas supply and projectile preparation

[0069] Then, the raw gas is supplied to the condensing gun tube 15 in two paths according to a certain flow rate by using the gas supply device 1, the raw gas flows in opposite directions along the two pipelines in the pre-cooler 4 and is pre-cooled by the cold gas helium in the pre-cooler 4, and then enters the condensing gun tube 15, where it is condensed from the upstream and downstream sides by the cooled cold head 8 to form the projectile.

[0070] 4. Projectile ejection

[0071] Finally, after the projectile 20 is formed, the propellant gas is injected into the upstream of the condensing gun tube 15 by using the gas supply device 1 to accelerate the projectile 20 to leave the condensing gun tube 15.

[0072] According to the condensing method of the present application, the cold helium generated by the supercritical helium evaporation is fully utilized by the pre-cooling-recovery closed loop design, so as to greatly reduce the waste of cold energy and improve the energy utilization efficiency.

[0073] The above specific embodiments are only illustrative but not restrictive, and those skilled in the art can make many modifications under the inspiration of the present application without departing from the purpose of the present application, which all belong to the protection scope of the present application.

Claims

1. A condensation apparatus for in-situ preparation of icicle pellets, characterized in that, include: A condenser is used to condense raw gas into pellets in a condensation zone. A precooler is used to precool the raw material gas; A vacuum-insulated housing that provides a vacuum-insulated environment for the condenser and the precooler; and The intermediate temperature shield, which is in thermal contact with the precooler, is used to reduce radiative heat transfer between the condenser and the vacuum insulation shell. The condensation device is equipped with a cooling medium flow path, a raw material gas flow path, and a propulsion gas flow path. The propulsion gas flow path is connected to the propulsion gas supply source, and after the raw material gas sublimates into a projectile, the propulsion gas is supplied to detach and eject the projectile. The upstream end of the raw material gas flow path is connected to the raw material gas supply source, and after passing through the precooler, it reaches the condenser. The upstream end of the cooling medium flow path is connected to the cooling medium supply source. The cooling medium flow path passes sequentially from upstream to downstream through the flow regulating valve, the condenser, and the precooler, and the downstream end is connected to the cooling medium recovery device. The cooling medium first undergoes a first heat exchange with the raw material gas, which has been precooled by the precooler, in the condenser. After the first heat exchange, the cooling medium undergoes a second heat exchange with the raw material gas supplied from the raw material gas supply source and which has not been precooled by the precooler in the precooler for precooling. Furthermore, the cooling medium after the first heat exchange also cools the intermediate temperature shield through thermal contact between the precooler and the intermediate temperature shield.

2. The condensation device as described in claim 1, characterized in that: The cooling medium supplied from the cooling medium supply source is supercritical helium, and the cooling medium becomes cold helium gas after a first heat exchange.

3. The condensation device as described in claim 1 or 2, characterized in that: The condenser includes a condenser tube and a cold head thermally mounted on the condenser tube. The cold head has a flow channel for the cooling medium to flow through. The cooling medium cools the cold head and the cold head forms a condensation area on the condensation gun tube to condense the raw material gas, thereby the cooling medium and the raw material gas undergo the first heat exchange.

4. The condensation device as described in claim 3, characterized in that: The cold head is equipped with a heater and a low-temperature sensor. Based on the detection results of the low-temperature sensor, the heating power of the heater is adjusted in real time to control the temperature of the condensation zone to meet the condensation temperature requirements of different material projectiles.

5. The condensation device as described in claim 1 or 2, characterized in that: The cooling medium flow path includes a first heat exchanger located downstream of the condenser and upstream of the precooler. The first heat exchanger includes a heat sink, a heater, and a low-temperature sensor. Based on the detection results of the low-temperature sensor, the heating power of the heater is adjusted in real time so that the temperature of the cooling medium entering the precooler meets the following conditions: Firstly, the raw material gas will not liquefy in the precooler. Secondly, the temperature of the cooling medium discharged from the precooler does not exceed the maximum recyclable temperature required by the recycling device.

6. The condensation device as described in claim 5, characterized in that: The precooler forms a cavity structure, inside which are arranged two spirally coiled raw material gas pipes. The raw material gas flows in opposite directions within these two raw material gas pipes. The cooling medium, after passing through the first heat exchanger, flows in the cavity outside the pipe of the precooler to precool the raw material gas.

7. The condensation device as described in claim 3, characterized in that: A second heat exchanger and a third heat exchanger are respectively installed upstream and downstream of the condensation zone of the condensation gun tube. The second heat exchanger and the third heat exchanger each include a heat sink, a heater, and a low-temperature sensor. Based on the detection results of the low-temperature sensor, the heating power of the heater is adjusted in real time according to the type of raw material gas, thereby adjusting the temperature change gradient near the condensation area of ​​the condensation gun tube, so that the projectile can be formed into a cylindrical shape.

8. The condensation device as described in claim 1, characterized in that: The raw material gas is H2, D2, Ne, Ar, or a mixture of any two.

9. The condensation device as described in claim 1, characterized in that: The propellant gas is He or H2. The propulsion gas flow path can adjust the pressure of the propulsion gas to adjust the launch velocity of the projectile.

10. A method for preparing icicle pellets using the condensation apparatus of claim 1, characterized in that, include: The first step is to evacuate the vacuum insulation shell to a certain vacuum, supply the cooling medium from the cooling medium supply source, and adjust the flow regulating valve to cool the condenser, precooler and intermediate temperature shield to the lowest temperature. The second step is to use the first heat exchanger to adjust the temperature of the cooling medium before it enters the precooler; The third step is to adjust the temperature of the condensation zone and its upstream and downstream areas according to the type of raw material gas and the size of the projectile to be prepared. The fourth step involves supplying the raw material gas from upstream to downstream to the condensation zone after precooling it in the precooler, where it is condensed from both upstream and downstream sides to form projectiles. and The fifth step involves injecting the propulsion gas upstream of the condensation zone after the projectile has been formed, causing the projectile to detach and be ejected.

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