A liquid metal jet target collection cooling filtration return device

Abstract

The application relates to a collecting, cooling and filtering backflow device of a liquid metal jet target, and belongs to the technical field of medium circulation and pollution control of a liquid metal jet anode target, which is used for solving the problem that after high-speed liquid metal jet is affected by an electron beam in a vacuum chamber, it is difficult to consider impact splash inhibition, anti-backflow, heat removal and particle clean recovery. The device comprises a vacuum chamber, a collecting chamber located below a jet drop point, and a check valve, a first cooler and a first filter which are sequentially communicated from the collecting chamber to a medium container; the collecting chamber adopts a circular arc surface or a plane which is inclined relative to a jet tangent line, the jet momentum is guided to a low-position backflow outlet; the check valve blocks reverse pressure on the medium container side; the first cooler removes backflow heat and the outlet temperature is kept above a solidification boundary; and the first filter intercepts solid particles before the liquid metal returns to the medium container. The device is mainly used for closed-loop medium circulation of a liquid metal target X-ray source.

Description

Technical Field

[0001] This invention relates to media circulation and contamination control technology for liquid metal jet anode targets, specifically to a reflux device and method for sequentially performing momentum redirection, pressure isolation, cooling, and particle filtration on liquid metal after electron beam action. Background Technology

[0002] The media recovery method for liquid metal jet anode targets has evolved from simple liquid receiving to closed-loop reflux. Early devices had an open receiving tray or a single drain pipe below the jet landing point, relying solely on gravity to draw the heated liquid metal out of the vacuum chamber. The media was collected once and then discarded or manually reinjected. Subsequent closed-loop circulation schemes connected a storage container to the end of the drain pipe, allowing the media to be reused. Further schemes incorporated heat exchange and filtration elements in series in the loop, forming a reflux chain with heat recovery and purification functions. These evolutions solved the problems of whether the media could be recovered and reused, but the order of the components of the reflux chain, the pressure boundaries, and the temperature boundaries were long considered engineering details that could be arbitrarily combined.

[0003] Existing solutions follow a modular assembly approach because the arrangement of pumps, valves, heat exchangers, and filters in ordinary liquid circulation systems has a limited impact on system performance. However, the recovery end of a liquid metal jet target directly bears the high-speed medium heated by the electron beam: taking gallium indium tin eutectic alloy as an example, the jet velocity is typically 20 to 80 meters per second, and the electron beam deposition power is 300 to 800 watts. The return medium simultaneously carries three loads: momentum, sensible heat, and solid particles. Changes in the order of components will directly affect the liquid accumulation position in the vacuum chamber, the heat exchange inlet temperature, and the propagation path of particles in the loop. Therefore, the design conventions of ordinary water-cooled circulation cannot be applied.

[0004] After absorbing energy in the electron beam region, the liquid metal jet needs to be reliably collected at the bottom of the vacuum chamber and returned to the supply side. If the return link is only equipped with a simple drain pipe, debris, oxide particles, or vapor condensate carried by the heated liquid metal will repeatedly enter the pump chamber, valve assembly, and nozzle.

[0005] Existing closed-loop liquid recovery schemes often treat liquid storage, heat exchange, and filtration as accessories that can be arbitrarily combined. However, the collection end of a high-speed jet target directly bears the medium heated by the electron beam, and the order of components will change the liquid accumulation in the vacuum chamber, the cooling inlet temperature, and the propagation position of particles in the loop.

[0006] Examining the existing technology from the perspective of the need for continuous resetting after energy exchange is completed along the high-speed jet within the vacuum cavity, the aforementioned prior art reveals the following numbered technical defects:

[0007] (1) Uncontrolled momentum dissipation at the receiving end leads to splashing, erosion, and stagnation. Existing collection structures are mostly simplified to a sufficiently large liquid receiving volume, without special design for the conversion of jet flow direction. When a liquid column with a velocity of 30 m / s to 60 m / s hits a flat bottom or straight wall, the stagnation point impact pressure can reach 2.9 MPa to 11.5 MPa, based on a gallium indium tin alloy with a density of about 6.4 g / cm³. The normal momentum is converted into splash droplets, film spreading, and local erosion. The droplets can re-enter the electron beam action area or adhere to the X-ray window and insulating parts. Long-term accumulation manifests as a decrease in window transmittance and deterioration of insulation withstand voltage.

[0008] High-speed liquid metal jets retain significant momentum and thermal load even after being subjected to an electron beam. If the liquid column directly impacts the bottom wall of the vacuum chamber, the normal momentum is converted into splashing, thin film spreading, and localized erosion. Droplets can then re-enter the electron beam zone or adhere to windows and insulating components. The primary challenge for the collection chamber is to address the momentum conversion, rather than simply providing a sufficiently large volume.

[0009] The flow state of the jet after entering the collection surface is affected by wettability, incident angle, surface curvature, and outlet position. An excessively steep receiving surface can cause rebound, while an excessively gentle surface may form a large-area thin layer and adhere to the walls. Improperly designed reflux outlets can create stagnant liquid pools in the vacuum chamber. Uneven liquid pool temperatures can lead to further blockage of the reflux due to solidification at lower levels.

[0010] Secondary splashes within the collection chamber can increase contamination of windows and electron beam channels. The curvature or angle of the impact surface should allow the liquid metal to exit the impact zone along a continuous surface, rather than bouncing and atomizing at acute angles.

[0011] (2) There is a lack of reliable reverse pressure isolation between the vacuum boundary and the container boundary. Ordinary drain pipes are designed only for forward flow and do not consider that the vacuum chamber and the medium container belong to different pressure boundaries: shutdown, abnormal vacuuming, or changes in the liquid level of the container may all create a reverse pressure difference at both ends of the link, pushing the medium backflow into the collection chamber. After the backflowing medium contaminates the electron beam action area, the equipment needs to be cleaned and vacuumed again, and the recovery time is measured in hours. Moreover, the backflowing medium often cannot be removed by conventional rinsing after it solidifies on the vacuum side.

[0012] If there is no check valve between the return line and the medium container, liquid metal on the high-pressure side or the container side may backflow into the vacuum chamber during shutdown, evacuation, or maintenance. Backflow not only contaminates the electron beam interaction area but also increases the time required for re-evacuation.

[0013] The pressure difference in the return path comes from the different operating conditions of the vacuum chamber, the medium container, and the supply pump. If the check valve is far from the collection chamber, the liquid metal in the pipeline section may still be pushed back into the vacuum chamber when the machine stops; therefore, the direction of the check valve and its position in the link need to be specified in the attached diagram.

[0014] The vacuum chamber and the medium container may be at different pressure boundaries. Pump stoppage, vacuum anomalies, or changes in the liquid level in the medium container may all push liquid metal back into the collection chamber. The opening pressure differential and closing delay of the check valve must take into account both normal low-pressure backflow and abnormal backflow prevention; static one-way seals alone are insufficient.

[0015] (3) Reflux thermal management only pursues cooling and ignores the solidification boundary. Most of the electron beam deposition energy eventually enters the liquid metal, and the reflux medium must be cooled; however, the liquidus of gallium indium tin eutectic alloy is about 10.5 degrees Celsius, and the liquidus of some bismuth-based alloys is even higher. If the cooling medium inlet temperature is controlled only or the lowest outlet temperature is pursued unilaterally, local overcooling during low flow and shutdown will cause the metal to solidify in the cooling coil, valve or filter element, forming a solid blockage that cannot be removed by conventional flushing, and even misleading maintenance personnel to replace components that have not yet failed.

[0016] Excessive reflow temperature alters the viscosity and vapor pressure of the medium, thereby affecting subsequent supply pressure and vacuum chamber contamination levels. For long-duration continuous exposure equipment, the slow accumulation of reflow temperature and impurity concentration is more easily overlooked than a single impact.

[0017] Most of the energy from electron beam deposition ultimately enters the liquid metal and its surrounding structure. The reflux cooler must remove this heat without cooling the metal to near the liquidus line. Controlling the heat transfer solely based on the inlet temperature of the cooling medium may result in localized undercooling during low flow rates or shutdowns. Therefore, the heat transfer intensity needs to be determined by considering both the liquid metal outlet temperature and flow rate.

[0018] The primary cooler must reduce the heat brought in by the electron beam without causing the liquid metal to solidify within the cooling coils or filters. The cooling target should be expressed as a set temperature higher than the melting point of the selected liquid metal, rather than simply pursuing the lowest possible outlet temperature.

[0019] (4) The position and accuracy of particle control lack matching with the link status. The return medium may carry nozzle wear particles, erosion products of the receiving surface, oxides and solidification and remelting fragments; if the filter is close to the collection end, the heat load of the filter material is large and the pressure drop fluctuates drastically under high temperature and high viscosity conditions; if the filter is canceled or the accuracy is too low, the particles will be deposited in the heat exchange channel or directly enter the medium pump and nozzle, making the nozzle with a diameter of hundreds of micrometers face the risk of blockage, which will eventually manifest as jet instability and scorch drift.

[0020] The order of cooling and filtration is not arbitrary. If precision filtration is performed directly at excessively high temperatures, the filter element is prone to clogging due to thermal shock or adhesion; if filtration is not performed at all, particles will accumulate in the cooling channels.

[0021] The refluxed liquid metal may contain nozzle wear particles, collection surface erosion products, oxides, or solidification-remelted fragments. Higher filtration precision results in stronger particle retention, but also increases the pressure drop of high-density, high-viscosity media. If the filter is located upstream of the cooler, higher temperatures may reduce viscosity but increase the heat load on the filter media; if located downstream of the cooler, it is easier to evaluate the pressure drop at a stable temperature.

[0022] The particle load on the filter changes with the wear of the jet impact surface and the condition of the nozzle. For long-cycle equipment, the reflux device needs to be able to inspect the filter media and impact surface without damaging the vacuum chamber's main positioning.

[0023] (5) The order and maintenance boundaries of each component in the return chain are treated as interchangeable modules. Existing closed-loop schemes often regard liquid storage, heat exchange and filtration as accessories that can be arbitrarily combined. However, the collection end directly receives the medium heated by the electron beam. The order of components will change the position of the liquid accumulation in the vacuum chamber, the cooling inlet temperature and the propagation position of particles in the loop. If the isolation and venting sequence is not arranged according to the medium flow direction during maintenance, a single shutdown and disassembly may cause the solidified medium to lock the filter element, or the valve may be disassembled when there is still a reverse pressure difference, causing backflow pollution.

[0024] In the return flow chain, the vacuum chamber is located after the jet landing point and affects the collection chamber. If stagnation, supercooling, or reverse flow occurs in this area, it will gradually accumulate into nozzle blockage and vacuum contamination, rather than immediately causing the entire machine to shut down.

[0025] Liquid metal closed-loop circulation simultaneously obeys the laws of mass and energy conservation. If the collection end only pursues rapid drainage, high-temperature media and impact particles may be directly sent back to the supply end; if the heat exchange end only pursues low temperature, local solidification may occur. The loop sequence therefore directly affects the continuous operation capability.

[0026] Furthermore, the components in the reflux device operate at different pressure and temperature boundaries: the collection chamber is at the vacuum chamber boundary, the media container is typically at the supply side boundary, and the valves, heat exchangers, and filters between them must maintain the continuity of the liquid metal while preventing the ingress of external cooling media or ambient gases. These constraints prevent the direct replacement of ordinary open receiving trays or ambient temperature filtration circuits.

[0027] The liquid metal reflux chain comprises a collection chamber, a check valve, a first cooler, a first filter, and a medium container connected in sequence, and can employ an arc or inclined impact surface, a cooling coil, and temperature control above the melting point. Based on this, the present invention forms an independent technical subject of reflux device.

[0028] Maintenance conditions also differ from those of ordinary circulating water systems. Liquid metal may solidify after cooling, and residual media must be recovered and the appropriate temperature maintained before disassembling filters and valves; otherwise, a single shutdown may result in solid blockages that cannot be removed by routine flushing.

[0029] This case organizes the reflux chain in the order of receiving surface, check valve, cooler, filter and medium container, so that momentum dissipation, pressure isolation, heat removal and particle control occur in appropriate locations, and the shutdown venting and mass conservation verify that no new stagnant liquid or contamination source is generated in each link.

[0030] Therefore, the collection chamber, check valve, cooler, filter, media container, and maintenance interface need to be protected as a closed-loop device to ensure that the temperature and particle state of the liquid metal are reset before returning to the supply side.

[0031] Therefore, the engineering evaluation of the reflux device needs to simultaneously observe whether the collection is complete, whether the outlet temperature has a melting point margin, and whether the returned medium is clean.

[0032] In summary, the key technical challenge in this field is how to sequentially dissipate impact, isolate pressure, control heat exchange, and clean recovery of high-speed, high-temperature, particulate liquid metal subjected to electron beam action within a vacuum boundary, according to a defined material flow direction, so that the return medium can be simultaneously reset in three dimensions: temperature, pressure, and cleanliness. Furthermore, the failures of each stage can be measured and maintained independently, rather than being detected only after accumulating at the overall machine level as nozzle blockage, vacuum contamination, or scorch spot drift. Summary of the Invention

[0033] The technical problem to be solved by this invention is:

[0034] This invention addresses the problem of how to continuously recover a high-speed liquid metal jet after it has been irradiated with an electron beam within a vacuum chamber without disrupting the vacuum boundary. The jet possesses significant momentum and sensible heat at the collection point; if it falls directly into a narrow outlet, it is prone to splashing or becoming trapped. If it returns directly to the medium container, the heat and particles will be carried back to the high-pressure pump and nozzle.

[0035] The return path also bears the pressure difference between the vacuum chamber and the medium container. Shutdown, evacuation, or changes in supply pressure can cause the liquid metal on the low-pressure side to flow back into the vacuum chamber. Therefore, collection, cooling, and filtration cannot be regarded as arbitrarily arranged independent modules.

[0036] This invention aims to establish a unidirectional mass path and a step-by-step energy processing path from the jet landing point to the medium container, so that momentum redirection, backflow isolation, heat removal and particle interception occur sequentially, and ensure that all low-temperature risk areas are above the melting point of liquid metal.

[0037] To solve the above-mentioned technical problems, the present invention adopts the following complementary technical solutions:

[0038] The collection chamber is located directly below the high-pressure nozzle, and its receiving area covers the impact zone after the linear region of the jet. The impact area is made into an arc surface or a plane inclined relative to the jet tangent, so that the liquid metal changes direction and enters the return outlet.

[0039] A check valve is located downstream of the collection chamber to allow liquid metal to leave the vacuum chamber and prevent liquid metal from flowing back from the medium container side due to pressure difference. A first cooler is installed after the check valve to reduce the backflow temperature rise caused by the electron beam input.

[0040] The first cooler uses a cooling coil and circulating coolant for heat exchange, maintaining the outlet target temperature above the melting point of the liquid metal. The first filter, located downstream of the cooler, intercepts solid particles in the return flow before connecting to the media container.

[0041] Optionally, the receiving area of ​​the collection chamber covers the jet landing point envelope measured according to the minimum, rated and maximum allowable jet pressures and superimposed with the nozzle repeated installation deviation, and has a safety margin of not less than 5 mm in each direction; when the receiving surface is an arc surface, its radius of curvature is 5 to 20 times the nominal diameter of the jet; when the receiving surface is an inclined plane, its inlet contact angle with the tangent of the jet is 15 degrees to 75 degrees, so that the instantaneous impact pressure of the jet on the receiving surface is distributed along the wall-adhering flow path, and the secondary splash direction avoids the X-ray window and the electron beam inlet.

[0042] Optionally, the receiving area of ​​the collection chamber is provided with a replaceable erosion-resistant liner. The liner is made of diamond, sapphire, or ruby. The liner seams are arranged along the wall-mounted flow direction and do not form a transverse step at the jet injection point. The fasteners are located in a position that the main jet cannot reach directly. After replacing the liner, the relative position of the receiving surface and the jet axis is reproduced through the back positioning surface.

[0043] Optionally, the check valve is arranged close to the return outlet of the collection chamber, with an opening pressure difference of 3 kPa to 15 kPa, a reverse pressure bearing capacity of not less than 0.6 MPa, a closing response time from the occurrence of the reverse pressure difference to the valve core contacting the valve seat of not more than 80 milliseconds, and the valve core movement direction does not rely on gravity to maintain the opening under the normal installation posture of the equipment.

[0044] Optionally, the heat exchange capacity of the first cooler is designed to be 1.2 to 1.5 times the maximum electron beam deposition power, and the liquid metal outlet temperature is set to be 10 to 80 degrees Celsius higher than the liquidus line of the alloy used; a bypass or flow regulation is provided on the cooling medium side so that the lowest wall temperature on the liquid metal side is still higher than the solidification boundary under low return flow conditions, and a temperature measuring point is set at the cooler outlet to participate in the heat exchange intensity control.

[0045] Optionally, the equivalent particle size cutoff of the first filter is 5 micrometers to 25 micrometers, and is selected according to one-third to one-tenth of the nominal orifice diameter of the nozzle; a coarse filter protection element with an equivalent particle size cutoff of 100 micrometers to 200 micrometers can be provided upstream of the first cooler to protect the heat exchange channel, and the coarse filter protection element does not change the end particle control relationship of the first filter located in front of the media container.

[0046] Optionally, the total available differential pressure of the return chain from the collection chamber to the medium container is calculated based on the liquid column height and pumping conditions, and the sum of the pressure drops of the check valve, the first cooler, the first filter and the connecting pipeline does not exceed the available differential pressure; temperature control devices are set in the pipelines and components through which the liquid metal flows, so that the lowest measured temperature of the entire chain during the start-up, steady state and shutdown venting stages is more than 15 K higher than the liquidus line of the alloy used.

[0047] On the other hand, the present invention also provides a method for recovering liquid metal jet targets using the above-mentioned reflux device, which includes the following steps in sequence according to the material flow direction: causing the liquid metal jet under the action of the electron beam to fall into the receiving surface of the collection chamber and form a wall-adhering flow towards the reflux outlet; causing the liquid metal to enter the first cooler in the direction allowed by the check valve and isolating the reverse pressure on the medium container side by the check valve; removing heat according to the inlet temperature of the cooler and the reflux flow rate and keeping the outlet temperature above the solidification boundary; causing the cooled liquid metal to pass through the first filter to intercept solid particles; returning the filtered liquid metal to the medium container, and checking the residual amount and backflow status in the order of collection chamber, cooler and filter after shutdown.

[0048] The receiving area of ​​the collection chamber covers the nozzle's rated landing point and the landing point envelope formed by the allowable oscillation. The receiving surface can be an arc surface, a plane inclined relative to the jet tangent, or a continuous combination of both. Its normal does not directly point to the window and electron beam inlet, causing the liquid metal after the main jet impact to turn along the surface and flow back to the outlet.

[0049] Temperature control devices are installed at low-temperature risk areas where liquid metal passes through to prevent the cooler outlet, filter, or pipeline from falling below the melting point; materials in contact with liquid metal are selected based on corrosion resistance and impact resistance requirements.

[0050] The impact zone of the collection chamber and the temperature target of the first cooler are interconnected. The impact surface first converts the jet flow and guides the liquid out, and the cooler then removes the heat brought in by the electron beam; the filter is responsible for particle control, and does not use filtration pressure drop as a substitute for temperature control.

[0051] Before system startup, a vacuum is established and temperature control is activated to keep the reflux line, check valve, and filter above the melting point of the liquid metal. During shutdown, injection is stopped while maintaining reflux and temperature control until the liquid metal in the vacuum chamber and lines is fully recovered. These two stages prevent the liquid metal in the reflux chain from solidifying at low temperatures or returning to the vacuum chamber due to pressure differences.

[0052] The substrate material is selected based on its compatibility with the liquid metal, erosion resistance, and thermal conductivity. Suitable materials include diamond, sapphire, ruby, ceramic, or a metal substrate with a compatible coating. Material selection involves not only comparing room temperature hardness but also examining wetting, surface spalling, and contaminant formation at operating temperatures and representative jet velocities.

[0053] The collection chamber outlet is located at a low position after the liquid metal flows along the impact surface; no structure is installed before the outlet that would allow the liquid metal to cross the step. The vacuum side volume of the collection chamber and the medium volume in the return pipe both participate in the shutdown evacuation.

[0054] The check valve opens with a differential pressure lower than that provided by normal backflow, while remaining able to withstand pressure changes on the medium container side when closed. The valve core material and sealing surface are compatible with liquid metal at operating temperatures.

[0055] The first cooler and the first filter can be installed separately in space, but the flow direction should remain the same: controlled heat exchange should be completed before entering the final filtration. If a coarse particle protection device is installed, its function is to protect the cooling channel without changing the relationship of the first filter before the return medium container.

[0056] The effective volume of the collection chamber is used to accommodate short-term flow fluctuations and residual liquid during shutdown, but it does not form a long-term liquid pool. The return outlet is located at a low position where the flow converges along the wall, and a smooth transition is provided before the outlet to avoid abrupt contraction that could cause gas-liquid interface stagnation; the removable cover or inspection port is located in a position not directly impacted by the main jet.

[0057] The medium container receives the return flow and supplies liquid metal to the supply system. The container temperature control and the first cooler work together to maintain thermal balance, preventing return flow temperature fluctuations from directly entering the high-pressure pump.

[0058] Liquid metal enters the vacuum chamber from the jet landing point and flows into the collection chamber.

[0059] Liquid metal enters the first cooler through the check valve and flows towards the first filter. This lowers the temperature of the heated liquid metal, bringing the medium back to a range suitable for pumping and storage.

[0060] The check valve is positioned near the outlet of the collection chamber or at the pressure boundary. Its opening pressure differential is lower than the liquid column pressure differential provided by normal backflow, while its reverse pressure resistance is higher than the maximum pressure that may occur on the medium container side. The valve core movement direction should avoid gravity causing it to remain incorrectly open for extended periods in its normal installation position.

[0061] Liquid metal enters the first filter from the first cooler and flows into the media container. It intercepts particles, condensates, or nozzle wear products, protecting downstream valve assemblies and nozzles.

[0062] The collection chamber is located at the bottom of the vacuum chamber, and its receiving area covers the designed landing point and allowable deviation range of the high-pressure nozzle jet. When the receiving area is an arc surface, the jet changes direction along a continuous curvature; when an inclined plane is used, the plane forms an angle with the jet tangent, causing the liquid metal after impact to flow along the surface towards the low-level return outlet.

[0063] The receiving area can be formed of impact-resistant materials such as diamond, sapphire, or ruby ​​and is connected to the main body of the collection chamber. This area primarily handles momentum redirection, while the remaining space in the collection chamber is used to collect liquid metal; the filter is not required to withstand direct jet impact to avoid contaminating the entire circuit if the filter media breaks.

[0064] The primary cooler receives the continuous reflux after a check valve and can employ coils, jackets, plate channels, or dual-loop heat exchangers. The liquid metal side channel remains ventable and temperature-controlled, while the cooling medium side adjusts the heat transfer intensity via flow rate or bypass. Installing a temperature measuring point at the cooler outlet provides a more accurate assessment of the solidification risk than simply measuring the cooling water temperature.

[0065] A check valve is connected to the outlet of the collection chamber. The check valve opens in the forward direction from the vacuum chamber to the medium container. Backflow is allowed when there is a liquid column or pumping conditions on the collection chamber side sufficient to overcome the valve opening pressure difference. When the pressure on the medium container side is higher than that on the collection chamber side, the valve core presses against the valve seat and blocks backflow.

[0066] Downstream of the check valve is a first cooler. The first cooler may include a cooling coil through which liquid metal flows and a circulating coolant passage for heat exchange with the cooling coil; the two medium circuits are isolated from each other. The cooling load is determined based on the electron beam input, jet mass flow rate, and allowable reflux temperature rise.

[0067] The primary cooler's control objective is not to cool the liquid metal to ambient temperature, but rather to reduce the reflux temperature to a range suitable for the operation of the medium container and supply system, while maintaining a safety margin above the melting point. If the reflux medium is an alloy of different composition, the outlet temperature should be re-determined based on the actual melting point and pipeline heat dissipation.

[0068] The cooling target is limited by the upper limit of the allowable temperature of the upstream medium container and the supply pump, and the lower limit of the liquidus line of the alloy used plus a safety margin. In an feasible scenario, the outlet temperature is 10 to 80 degrees Celsius above the liquidus line; the specific margin is determined based on temperature measurement errors, pipeline heat dissipation, and alloy composition.

[0069] The first filter is located downstream of the first cooler and upstream of the medium container. After cooling, the viscosity and flow state of the liquid metal are relatively controllable, and solid particles are trapped before entering the medium container, reducing the probability of particles re-entering the medium pump, the second check valve assembly, or the high-pressure nozzle.

[0070] The medium container receives cooled and filtered liquid metal and provides a low-pressure medium source to the supply system. The container and return line can be equipped with temperature control devices to keep the check valve, first cooler outlet, first filter, and connecting pipes above their melting points during operation and shutdown recovery.

[0071] During startup, first establish a vacuum in the vacuum chamber and activate the temperature control of the reflux path. After confirming that the check valve can open in the forward direction and that the first cooler is circulating normally, then form the jet. During shutdown, first stop the electron beam and jet, and continue to maintain reflux and temperature control until the recoverable liquid metal in the collection chamber and pipeline enters the medium container.

[0072] The first filter is located downstream of the cooler and upstream of the media container, and its filter element has a detachable structure. The filtration area is determined based on the allowable pressure drop and contamination load, and an equivalent rejection range of 5 micrometers to 200 micrometers can be set as the prototype screening window. Fine filtration should not come at the expense of a stable liquid supply from the media pump.

[0073] The aforementioned ordered relationships form a functional chain that cannot be arbitrarily interchanged: the collection chamber first reduces the jet flow, the check valve then isolates the back pressure, the first cooler removes heat before filtration, and the first filter finally protects the media container and subsequent supply path. This sequence is the core difference between this solution and ordinary liquid recovery tanks or standalone heat exchange and filtration equipment.

[0074] The curvature or angle of the receiving area not only affects the splashing but also determines the residence time of the molten metal from the impact point to the return outlet. The design should ensure a continuous surface descent to avoid the formation of stagnant pools adjacent to the jet's heat load.

[0075] A check valve positioned near the collection chamber outlet can reduce the amount of reverse-moving medium between the vacuum chamber and the valve; if a connecting pipe is required due to space constraints, the pipe should also be kept above the melting point to avoid forming a high-point gas lock.

[0076] The return pipe and components are insulated or heat-traced to prevent the liquid metal from passing through uncontrollable cold points during startup, steady state, and shutdown venting. The active heat exchange zone of the cooler and the heat tracing zone of the pipeline are controlled separately to prevent the same temperature control action from simultaneously cooling and heating, thus avoiding loss of fault identifiability.

[0077] The heat exchange area of ​​the primary cooler is checked based on the most unfavorable electron beam power and minimum reflux flow rate. A lower reflux flow rate may increase the temperature rise per unit mass; therefore, the control system should limit the cooling outlet to a safety margin above the melting point.

[0078] The flow area of ​​the first filter is affected by both particle load and viscosity. The selection of filter media pore size should balance protecting downstream nozzles with not excessively increasing backflow resistance, and should be verified through actual liquid metal compatibility.

[0079] Before re-entering the supply system, the liquid metal in the media container passes through a coarse filter and a media pump. The first filter controls particles at the end of the reflux, while the coarse filter protects the supply inlet; their locations and filtration targets differ.

[0080] The device establishes mass and energy accounting through the inlet, cooler outlet, before and after the filter, and liquid level in the media container. Temperature difference and mass flow rate estimate the heat carried back by the flow, filter pressure difference and filter element inspection estimate the particle load, and liquid level changes and residue are used to detect splashing, wall adhesion, or leaks.

[0081] The sealing check of the return chain is divided into the vacuum side and the liquid metal side. The collection chamber and its vacuum connection are checked for leak rate, the cooler and filter are checked for liquid metal leakage, and the circulating coolant channel is checked separately for isolation from the liquid metal circuit.

[0082] The geometrical elevation differences of the collection chamber, check valve, and return pipe are determined in conjunction with the equipment's orientation. For variants that are not vertically installed, the liquid metal behind the receiving surface is still ensured to have a pressure differential or gravitational component pointing towards the outlet, and the check valve is guaranteed to open in the positive direction.

[0083] The temperature of the reflux medium after passing through the first cooler affects both the filtration pressure drop and the pumping conditions within the medium container. Temperature control is constrained by the lowest measured temperature across the entire reflux chain, rather than simply reading the temperature at the cooler outlet.

[0084] Maintenance boundaries are arranged according to the media flow direction: first isolate the vacuum chamber side and confirm that the check valve is closed, then release the pressure in the cooler and filter, and finally disassemble and inspect the filter element. After reassembly, first perform low-pressure flow and temperature homogenization, then restore vacuum jet to prevent the cold filter element from becoming a solidification point.

[0085] During maintenance of the first filter, the check valve and vacuum chamber boundary should be kept unaffected by reverse media. Before disassembly, recover any liquid metal inside the filter housing and maintain it at a suitable temperature to prevent solidification of the media from fixing the filter element inside the housing.

[0086] Claim 1 uses the location of the collection chamber and the sequential connection of the five components as the framework; the shape and material of the receiving surface, the structure of the cooler, the temperature control above the melting point and the filtering object respectively form a subordinate and defensive hierarchy.

[0087] A continuous liquid metal passage is maintained between the return outlet, check valve, and cooler inlet.

[0088] Based on the above structural relationships, parameter boundaries, and operating modes, the beneficial effects of the present invention are described below in numerical order, and each effect can be verified by the experimental methods in the accompanying drawings and embodiments:

[0089] (1) The receiving surface transforms the normal impact of the free jet into a wall-attached flow toward the return outlet. The instantaneous impact pressure is distributed along the wall-attached path through curvature or inclination. The secondary splash droplets are constrained in a direction away from the X-ray window and electron beam channel. According to the comparison of the test film, the deposition amount on the window side can be reduced by more than an order of magnitude compared with the flat bottom collection structure without surface optimization. No stagnant liquid pool adjacent to the jet heat load is formed in the collection chamber.

[0090] (2) The check valve is arranged close to the reflux start point. The opening pressure difference of 3 kPa to 15 kPa and the closing response time of no more than 80 milliseconds are calibrated in both directions for low flow reflux and abnormal back pressure. It can block the backflow channel when the machine is stopped, the vacuum is abnormal or the pressure of the medium container fluctuates, avoid liquid metal backflow into the vacuum chamber and shorten the vacuum recovery time after maintenance.

[0091] (3) The heat exchange intensity of the first cooler is determined by the liquid metal outlet temperature and the reflux flow rate. The heat exchange capacity is designed to be 1.2 to 1.5 times the maximum electron beam deposition power, which can remove more than 90% of the heat input by the electron beam. The outlet temperature is always 10 to 80 degrees Celsius higher than the liquidus of the alloy used. Local overcooling and solidification do not occur during low flow and shutdown stages. The viscosity and vapor pressure of the medium remain stable.

[0092] (4) The first filter intercepts particles of 5 to 25 micrometers at the end of the link after heat exchange stabilization. The coarse filter protection component and the fine filter element are arranged in stages. The pressure drop in the clean state accounts for only a part of the available pressure difference for return. The wear and blockage probability of nozzles, valve groups and piston chambers are significantly reduced. The filter element can also trace the wear source according to the particle type of the material trapped.

[0093] (5) The collection, check valve, cooling and filtration are connected in series according to the direction of media flow to form a functional chain that cannot be arbitrarily exchanged. The reverse pressure, heat load and particle load fall on the chain segments that can be measured and maintained independently. The combined changes of the three types of signals, namely the liquid level in the collection chamber, the temperature difference of the cooler and the pressure difference of the filter, can directly distinguish the fault location of the check valve, the cooling channel and the filter element without the need for the whole machine to be shut down and disassembled.

[0094] (6) The reflux chain is jointly accepted by the cooler outlet temperature, filtration pressure difference and mass conservation. After the reflux medium is reset in three dimensions of temperature, pressure and cleanliness, it returns to the medium container. The supply viscosity and vapor pressure remain stable, providing thermal-mass closed-loop protection for the continuous operation of liquid metal anode target for thousands of hours and the stable position of micron-level scorch spots.

[0095] Through the above-described structure or control relationship, a mass-energy closed loop is formed by jet flow redirection, reverse pressure isolation, sensible heat removal, and particle retention. The technical features are interconnected and verifiable by the accompanying drawings and embodiments, rather than being independent modules listed side by side. Attached Figure Description

[0096] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments are briefly introduced below; all drawings are drawn with black lines on a white background, and the reference numerals in the drawings correspond one-to-one with the main text of the specification and the reference numeral table at the end of the document.

[0097] Figure 1 A longitudinal cross-sectional view of the collection chamber at the bottom of the vacuum chamber receiving the jet is shown. The vacuum chamber 101, high-pressure nozzle 102, liquid metal jet 103, collection chamber 104, and return outlet 105 are marked in the figure, showing that the free jet turns into a wall-attached flow moving towards the return outlet after falling into the receiving surface.

[0098] Figure 2 A comparison diagram of a circular arc receiving surface and an inclined plane receiving jet is shown. The diagram is marked with the circular arc receiving surface 201, the inclined receiving surface 202, the jet tangent 203, the changed flow direction 204, and the impact-resistant region 205. The effects of the two receiving geometries on the impact direction, secondary splash, and impact-resistant region are compared.

[0099] Figure 3 The diagram shows the sequential reflux of the collection check, cooling filter, and media container. The diagram is marked with the collection chamber 301, check valve 302, first cooler 303, first filter 304, and media container 305. The check, heat exchange, particle interception, and container recovery are marked sequentially along the media return direction.

[0100] Figure 4 The diagram shows the heat exchange between the cooling coil and the circulating coolant in the first cooler. The diagram marks the liquid metal inlet 401, the cooling coil 402, the circulating coolant channel 403, the liquid metal outlet 404, and the heat exchange direction 405. The high-temperature reflux side and the circulating coolant side are separated, and cross-wall heat exchange is indicated by arrows.

[0101] Figure 5 The diagram shows a connection where the first filter is located upstream of the media container. The diagram marks the first cooler outlet 501, the first filter 502, the filter medium 503, the media container 504, and the supply system interface 505. It highlights that the filter element is located in a maintainable position downstream of the cooler and upstream of the media container.

[0102] Figure 6 The diagram shows the state of the check valve blocking the backflow of the medium container into the vacuum chamber. The diagram is marked with the vacuum chamber side 601, check valve 602, medium container side 603, allowed backflow direction 604, and reverse blocking state 605. The vacuum chamber anti-backflow function is explained by the two valve core states of forward opening and reverse closing. Detailed Implementation

[0103] The recycling cycle is described below along the common direction of mass flow and heat flow. The parameters in the examples were determined by material compatibility, design calculations, and prototype testing; unverified fixed values ​​are not considered universally necessary conditions.

[0104] The following four embodiments are organized in sequence according to the material flow direction of liquid metal: Embodiment 1 corresponds to jet impact dissipation and bearing surface design; Embodiment 2 corresponds to heat management of collected liquid and heat exchange of cooler; Embodiment 3 corresponds to filtration cleanliness classification and backflow prevention; Embodiment 4 corresponds to the whole machine matching of reflux and recirculation. The engineering data of each embodiment are interconnected on the same prototype platform and can be combined into a complete reflux device without changing the order of components.

[0105] Example 1: Impact dissipation of jet flow and design of the bearing surface (combined with...) Figure 1 , Figure 2 )

[0106] This embodiment first describes the jet receiving geometry at the bottom of the vacuum chamber. The high-pressure nozzle is located at the top of the vacuum chamber, and the collection chamber is arranged below its axis; the electron beam's point of application is located in the linear region of the jet between the nozzle and the collection chamber.

[0107] The inlet of the collection chamber covers the range of jet oscillation that may occur during startup. The impact zone uses an arc surface to change the direction of the jet tangentially; in another configuration, a plane at an angle to the jet tangent is used to allow the liquid metal to flow along this plane towards the drain port.

[0108] In this embodiment, the nozzle axis is first determined using a low-pressure jet under electron beam-free conditions, and then the landing points are recorded above and below the rated pressure. The landing point envelope is formed by superimposing nozzle manufacturing deviation, thermal drift, and allowable oscillation. The receiving surface of the collection chamber extends beyond this envelope in all directions, and the edge is provided with an inward-facing liquid-retaining transition rather than a vertical hard wall.

[0109] The landing envelope was measured according to three levels of injection pressure: taking a gallium indium tin alloy jet with a nominal aperture of 100 micrometers to 300 micrometers and a jet velocity of 20 meters per second to 80 meters per second as an example, the landing point dispersion diameter under rated working conditions is about 2 mm to 5 mm. After superimposing the starting swing, thermal drift and nozzle repeated installation deviation, the landing point envelope diameter is taken as 8 mm to 15 mm; the inlet contour of the receiving surface extends beyond the envelope by no less than 5 mm in each direction, and the edge is set with an inward smooth liquid-blocking transition, so that under extreme swing conditions, the liquid metal still contacts the receiving surface first rather than the vacuum chamber sealing edge or the return pipe port.

[0110] When diamond is selected as the impact surface material, its hardness and thermal conductivity can withstand continuous impacts; sapphire or ruby ​​can also be used. The material block is embedded in the collection chamber in a manner that does not form a step in front of the flow path.

[0111] The check valve is located immediately adjacent to the outlet of the collection chamber, with its permissible direction pointing towards the first cooler. After installation, the closing direction of the valve disc or valve core is checked under conditions of low pressure on the vacuum chamber side and pressure variation on the medium container side.

[0112] The initial validation of the collection geometry employed a low-flow-rate test to observe the redirection of liquid metal on the collection impact surface and the continuity of its entry into the return outlet. Subsequently, the jet flow rate was gradually increased to confirm that the impact surface did not cause the liquid metal to bounce back into the X-ray window or electron beam channel.

[0113] The receiving surface adopts an arc with a larger inlet curvature and a gradually decreasing curvature near the outlet. The jet first contacts the surface at an oblique incidence, and the normal momentum is distributed over a longer path; the liquid metal then enters the outlet tank tangentially. The free surface is observed through a transparent equivalent liquid test, and the wetting difference is verified using actual liquid metal at low power.

[0114] The seal between the collection chamber and the vacuum chamber body is not located in the direct impact zone. When the impact surface needs to be replaced, the geometry of the high-pressure nozzle and electron beam system should be kept unchanged to minimize realignment after maintenance.

[0115] When the circular impact surface has a continuous curvature, the injection point is not located at the material joint; the inclined plane configuration ensures that there is no reverse slope between the injection point and the drainage direction. Both configurations confirm wetting and drainage paths at low flow rates.

[0116] The sidewalls of the collection chamber cover the initiation oscillation but do not obstruct the effective paths of the electron beam and X-rays. The top edge of the sidewalls has a smooth profile to reduce the re-entry of splashed droplets into the action zone after impact.

[0117] The inlet contact angle was selected from 15 to 75 degrees. Smaller angles reduced splashing but increased spread length, while larger angles shortened the device but increased the risk of bounce. The final angle was evaluated based on three factors: the number of droplets on the window side, the outlet recovery rate, and the temperature rise of the receiving surface.

[0118] Impact pressure is estimated based on jet stagnation conditions: With a gallium-indium-tin alloy density of approximately 6.4 g / cm³ and a velocity of 30-60 m / s, the head-on stagnation pressure is approximately 2.9 MPa to 11.5 MPa. The bearing surface distributes the normal momentum along a wall-attached path with a length 2 to 4 times the width of the bearing surface through curvature and tilt angle, reducing the local pressure peak to less than 30% of the stagnation value. The bearing component and support structure are checked for an instantaneous pressure margin of not less than 20 MPa, taking into account jet pulsations caused by short-term electron beam overpower.

[0119] The pipe section between the drain outlet and the check valve should be kept heated and as short as possible. If the temperature of this pipe section is below its melting point, the check valve will not be able to form a backflow even if it is functioning normally.

[0120] When the impact surface is replaceable, a repeatable positioning structure is used to ensure that the jet landing point remains within the designed area after reassembly. The sealing surface of the maintenance interface is kept away from direct impact and high-temperature areas.

[0121] The reflux outlet is located at the lowest potential energy position on the receiving surface and is aligned with the tangential flow direction. The outlet cross-sectional area is larger than the area required for steady-state reflux to prevent the main impact zone from being submerged after the liquid level rises; at the same time, rounded corners are provided to prevent localized cooling and slag buildup at sharp corners.

[0122] The collection chamber capacity should be sufficient to accommodate short-term liquid metal flow during start-up and shutdown transitions, and capacity verification should also consider liquid accumulation when the check valve is not fully open.

[0123] Acceptance of the collection chamber is based on the jet landing point envelope. Liquid is passed through the rated landing point and the allowable sway boundary, respectively. It is observed whether the receiving surface can convert the impact momentum into wall-attached flow towards the outlet, and whether secondary splashing occurs on the chamber wall that crosses the liquid-blocking boundary.

[0124] The collection chamber is equipped with a removable erosion-resistant liner. The liner is fixed by a back positioning surface, and the fasteners are located in areas inaccessible to the main jet. After replacing the liner, the relationship between the curved surface and the nozzle axis is re-measured to prevent thickness differences from altering the landing point. The liner seams are arranged along the flow direction to avoid the formation of transverse steps.

[0125] In Example 1, the vacuum chamber is arranged vertically, with the high-pressure nozzle at the top and the collection chamber below it. The nozzle axis passes through the middle of the receiving area of ​​the collection chamber, ensuring that the jet falls into the receiving area within the allowable positional fluctuation range, without directly impacting the vacuum chamber wall or the return pipe port.

[0126] Record the temperatures at the front, middle, and rear of the receiving section at the rated flow rate. If the highest temperature zone is far from the main impact point and concentrated near the outlet, it indicates that the flow adhering to the wall is stagnating before the outlet; this should be corrected by expanding the outlet or reducing the local curvature, rather than simply increasing the overall cooling.

[0127] The first type of receiving component has an arc-shaped working surface. The arc surface smoothly transitions to the jet direction near the injection point, allowing the molten metal to leave the impact zone tangentially along the arc and flow into the lower part of the collection chamber. The back of the working surface is supported by the main body of the collection chamber to withstand the long-term impact of the jet.

[0128] The second type of receiving component uses an inclined plane. The plane forms a non-zero angle with the jet tangent, and the incident liquid metal changes direction and flows along the plane towards the outlet. The inclination angle should prevent the liquid metal from being reflected near the vacuum chamber window or nozzle, while ensuring that gravity or pressure difference can push the liquid metal away from the receiving surface.

[0129] Splash evaluation involves placing detachable witness sheets within the vacuum chamber, positioned at the window direction, electron beam inlet direction, and non-sensitive direction. After a specified running time, the deposition area is compared to confirm that the receiving surface guides secondary droplets to a low-risk region. The witness sheets are for verification purposes only and are not essential components of the device.

[0130] Splash quantification was evaluated using a combination of witness sheet weighing and microscopic counting: two witness sheets were placed in the window direction, the electron beam inlet direction, and the non-sensitive direction. After running continuously for 2 hours, the deposition amount in the window direction corresponding to the optimized receiving surface was controlled to be below 0.5 micrograms per square centimeter, while the deposition amount in the flat-bottomed, formless reference structure was 5 to 20 micrograms per square centimeter. The temperature rise of the receiving surface was recorded simultaneously, and the matching relationship between curvature and flow rate was verified when the temperature rise in the main impact zone exceeded 30 K.

[0131] The outlet size of the collection chamber is calculated based on the maximum return flow rate and viscosity at the operating temperature to ensure that the receiving area will not experience continuous liquid accumulation due to an insufficiently small outlet. Furthermore, the outlet is not directly exposed to the jet impact to prevent impact pressure from being transmitted to the check valve.

[0132] The inlet size of the receiving surface is determined by the safety margin of the jet impact envelope. The impact envelope is measured at the minimum, rated, and maximum permissible injection pressures, respectively, and the positional deviation caused by repeated nozzle installation is added; the edge of the receiving surface must not fall on the direct impact line under any operating condition. In this way, even if the jet velocity changes, the liquid metal will first contact the continuous receiving surface and will not hit the vacuum chamber sealing edge or the return pipe port.

[0133] The curvature of the contact surface was selected by observing the secondary splashing after impact and the continuity of the adhering layer. If the curvature is too small, the jet will almost collide head-on and generate rebound droplets, while if the curvature is too large, the liquid film will detach at the turning point. The flow direction of the sample was confirmed in transparent equivalent medium tests and hot liquid metal tests, and the final acceptance criteria were no out-of-bounds splashing in the vacuum chamber and no periodic gas ingestion at the return outlet.

[0134] The radius of curvature of the arc-shaped receiving surface is taken as 5 to 20 times the nominal diameter of the jet: when the jet diameter is 200 micrometers, the radius of curvature is taken as 1 mm to 4 mm, the thickness of the wall-attached flow layer is about 0.2 mm to 0.8 mm, and the flow velocity along the surface is reduced to 1 m / s to 3 m / s; the inlet contact angle of the inclined plane configuration is selected within the range of 15 degrees to 75 degrees. The splash amount, spreading length and drainage time are most balanced near 45 degrees. The final angle is determined by weighting three factors: the number of microdroplets on the window side, the outlet recovery ratio and the temperature rise of the receiving surface.

[0135] The effective volume of the collection chamber covers the amount of liquid in transit during the jet's operation from normal operation to the cessation of supply, the amount of liquid in the return pipe before the check valve closes, and the liquid level fluctuation margin. The return outlet is located at the point where the flow naturally converges along the wall and avoids the formation of a high-level weir; the maintenance vent is located at a lower position and is closed during normal operation, thereby separating the responsibilities of the operational return path and the maintenance vent path.

[0136] The connection between the collection chamber and the vacuum chamber is checked according to the maximum liquid metal mass and instantaneous impact load. When the receiving component is detachably fixed, the fasteners are not directly exposed in the main impact area, and the joint direction is offset from the flow direction against the wall; after disassembly and assembly, the position of the receiving surface relative to the jet axis is reproduced by the positioning surface, rather than relying on visual adjustment based on the gap of the fastening holes.

[0137] The lifespan of erosion-resistant liners is assessed based on erosion depth: the erosion rate of diamond liners under continuous jet impact of 60 m / s is less than 0.1 micrometers per thousand hours, while that of sapphire and ruby ​​liners is approximately 3 to 5 times higher, both meeting the requirement of more than 2000 hours without replacement; the liner replacement cycle is linked to particle monitoring, and when there is a sudden increase in the count of hard particles after filtration, priority is given to checking the liner surface gaps and seam steps, rather than directly attributing it to nozzle wear.

[0138] The verification of the receiving chain segment first involves a low-flow test to observe the turning of the liquid metal on the collection impact surface and the continuity of its entry into the return outlet. After confirming that there is no rebound splashing and no periodic air swallowing, the jet flow rate is gradually increased to the rated value.

[0139] Once the vacuum chamber reaches the working vacuum, the high-pressure nozzle begins to form a jet from a low flow rate. When the jet reaches the receiving area, observe whether it enters the low-position outlet along the predetermined direction. If significant splashing occurs, first check the nozzle axis and the angle of the receiving surface, rather than trying to cover up the landing point error by increasing backflow suction.

[0140] When collecting and replacing impact surface materials, record the wetting state, surface damage, and particle generation. High hardness does not necessarily mean low contamination; liquid metal compatibility must also be checked.

[0141] The comparison of the receiving surface materials also records wetting, erosion, and thermal response. After the candidate materials are subjected to the same jet flow rate, the changes in surface notches, adhesion layers, and outlet flow are examined; usability cannot be determined solely by room temperature hardness.

[0142] The bonding area can be made of diamond, sapphire, or ruby. The material sample is exposed to liquid metal at the operating temperature and subjected to equivalent jet impact or thermal cycling; surface spalling, cracking, and reaction with the liquid metal are observed to determine the materials and fixing methods used in the actual equipment.

[0143] The comparative test of the receiving surface configuration kept the nozzle, flow rate and landing point unchanged, and recorded the proportion of liquid metal entering the return outlet, the splash range and the temperature rise of the receiving surface under the two structures of arc receiving surface and inclined plane. The structure that can stably guide the flow within the allowable space of the vacuum cavity and has smaller maintenance size was selected as the final configuration.

[0144] Example 2: Heat management of collected liquid and heat exchange matching of the first cooler (in combination) Figure 3 , Figure 4 )

[0145] The primary cooler is verified based on heat load, not on whether it is flowing. Record the inlet and outlet temperatures and the state of the cooling medium, confirming that the outlet temperature is below the upper limit allowed by the supply side and always above the risk boundary of liquid metal solidification, while also checking that there is no local stagnation in the heat exchange channels.

[0146] The collection chamber outlet is connected to a check valve, and the first cooler and the first filter are arranged sequentially after the check valve. Figure 3 The arrow shown always points from the vacuum chamber to the medium container. During installation, check the flow direction markings on the valve body, the inlet and outlet of the cooler, and the flow direction of the filter one by one to avoid reversing the direction due to similar pipe shapes.

[0147] The primary cooler uses a coil-type refrigeration coil, where liquid metal flows inside the coil, while circulating coolant flows outside the coil or in an adjacent channel. Independent pressure checks are performed on both circuits to ensure that coolant does not enter the liquid metal circuit and that the liquid metal does not contaminate the cooling system.

[0148] The heat exchange structure of the coil-type refrigeration coil is designed with dual-loop isolation: the liquid metal side is a corrosion-resistant metal coil with an inner diameter of 4 mm to 8 mm and a wall thickness of 0.5 mm to 1 mm, with a single coil length of 0.8 m to 2 m; the circulating coolant side is deionized water with a flow rate of 2 liters per minute to 6 liters per minute and an inlet temperature of 15 degrees Celsius to 25 degrees Celsius; the two loops are physically isolated by heat conduction through the wall surface, and pressure resistance and mutual leakage tests are performed at 1.5 times their respective maximum working pressure.

[0149] This embodiment describes the continuous process of cooling, filtering, and returning the medium to the container, starting from the outlet of the collection chamber. The first cooler and the first filter are located outside the vacuum chamber for easy supply of coolant and replacement of filter elements.

[0150] Under the condition of confirming the landing point, confirm that the collection chamber is located below the landing point of the jet and that the return outlet is unobstructed before spraying.

[0151] In this embodiment, a check valve, a coil-type first cooler, and a cylindrical first filter are installed sequentially after the collection chamber outlet. Temperature measuring points are set at the liquid metal inlet, cooler outlet, and filter outlet, and differential pressure measuring points are set before and after the filter. The liquid level is recorded in the medium container.

[0152] In the heat tracing preparation condition, a vacuum is established and temperature control is activated to keep the return pipeline, check valve and filter above the melting point of liquid metal.

[0153] Under low-flow recovery conditions, low-flow injection begins, causing the liquid metal to fall into the collection chamber and flow to the first cooler via the check valve.

[0154] Under heat exchange regulation conditions, the circulating coolant is started and the heat exchange capacity is adjusted so that the outlet temperature of the first cooler reaches the set temperature.

[0155] During startup, the return pipe, valve body, liquid metal side of the cooler, and filter housing should be preheated uniformly. Once the temperature reaches a safe margin above the alloy liquidus line, fill with a low flow rate of liquid metal; at this time, the cooling medium should bypass most of its flow to avoid localized overcooling before a continuous return flow is formed.

[0156] As the electron beam power is increased, the heat removal is estimated based on the temperature difference between the liquid metal inlet and the cooler outlet, as well as the reflux mass flow rate. The cooling medium is gradually increased until the inlet temperature of the medium container is within the allowable range of the supply pump, while maintaining a solidification margin sufficient to cover measurement errors and ambient heat dissipation.

[0157] The heat load is calculated based on the electron beam deposition power: when the electron beam power is 300 W to 800 W, more than 90% of the energy enters the jet, and the jet carries about 270 W to 760 W of heat; the return mass flow rate is 40 kg / h to 120 kg / h based on the jet diameter and velocity, the specific heat capacity of gallium indium tin alloy is about 0.34 kJ / kg K, and the corresponding return sensible heat temperature rise is about 40 K to 150 K; the heat exchange capacity of the first cooler is selected as 1.2 to 1.5 times the maximum heat carrying capacity, and the temperature rise of the circulating cooling water is controlled at 3 K to 8 K.

[0158] Heat exchangers are prone to overcooling under low flow conditions. In this embodiment, the cooling medium flow rate is reduced as the return flow rate decreases, while a bypass path is maintained; if the outlet temperature drops close to the lower limit, active cooling is reduced first rather than increasing the heat tracing power to counteract the cooling.

[0159] The low-flow overcooling prevention adopts a cooling medium follow-up strategy: when the return flow rate is lower than 40% of the rated value, the cooling medium flow rate is simultaneously reduced to less than 30% of the rated value and the bypass is opened, so that the lowest wall temperature on the liquid metal side is not lower than 15 degrees above the solidification boundary; the response time of the outlet temperature measuring point is no more than 2 seconds, and the adjustment is completed before the temperature drops to the set lower limit, avoiding power waste and unidentifiable faults caused by the mutual opposition between heat tracing and cooling.

[0160] The circulating coolant flow rate is gradually increased from a low value, aiming to stabilize the outlet temperature of the first cooler above its melting point. If periodic fluctuations in the outlet temperature are observed, check whether the jet power and cooling control oscillate synchronously.

[0161] When the outlet temperature of the first cooler is close to the solidification boundary of the alloy used, reduce the flow rate of the cooling medium or increase the heating power to prevent the liquid metal from solidifying in the filter or valve port. When handling this, first stop or reduce the injection to put the return chain in a controllable thermal state before checking it in sections.

[0162] In Example 2, the collection chamber, check valve, first cooler, first filter, and medium container are first heated or kept at a constant temperature above the melting point of the liquid metal used. Then, the circulating coolant is started, but the flow rate or temperature is adjusted to maintain a safety margin at the melting point of the liquid metal.

[0163] After the electron beam is activated, the temperature of the liquid metal rises in the active zone. The heated medium enters the first cooler through the collection chamber and check valve, where the cooling coil transfers heat to the circulating coolant. The coolant inlet temperature and flow rate are adjusted according to the return temperature to prevent the outlet temperature from approaching the solidification boundary.

[0164] The heat load is balanced by electron beam deposition power, jet sensible heat variation, and pipeline heat dissipation. During operation, the equivalent heat input before entering the collection chamber and the temperature difference between the inlet and outlet of the first cooler are obtained, and the heat removed is estimated by combining the circulating mass flow rate. If the temperature difference increases but the flow rate decreases, it cannot be simply concluded that the cooling capacity has increased. Instead, the filter resistance or narrowing of the return channel should be checked.

[0165] The minimum wall temperature of the primary cooler is higher than the solidification boundary of the liquid metal while maintaining a control margin, and the maximum outlet temperature meets the allowable range of the medium container, medium pump, and sealing materials. Before starting the machine, the cooler is established to a thermal state before receiving high-temperature reflux. After shutdown, the controlled temperature is maintained until all liquid metal en route is drained to prevent localized pre-cooling and blockage.

[0166] Temperature settings are determined based on the boundaries of the medium and components: the liquidus of the gallium indium tin eutectic alloy is approximately 10.5 degrees Celsius, and the outlet of the first cooler is set to 60 to 90 degrees Celsius, with a margin of approximately 50 to 80 K on the liquidus. The entire heat tracing process is independently controlled by each zone, with a heat tracing power density of 30 to 80 watts per meter for the return pipe, check valve body, and filter housing. The temperature control accuracy is ±2 K, and the lowest measured temperature of the entire process under the most unfavorable operating conditions is no less than 15 K above the liquidus.

[0167] Table 1. Heat exchange design parameters for the first cooler (Example 2)

[0168]

[0169] If the equipment is used for high-power, long-duration exposure, it can increase the long-term recording of coolant temperature and medium container temperature; if used for intermittent laboratory exposure, it can be used to confirm that the liquid metal does not solidify in the first cooler or filter after shutdown.

[0170] The cooler is emptied in the co-current direction, allowing the liquid metal to return to the medium container while maintaining heat tracing. After evacuation, the cooler mass is compared or the residue is estimated using specified testing methods; if the residue is concentrated at the low point of the coil, the installation slope is adjusted or a controllable discharge port is added.

[0171] Before filter maintenance, record the differential pressure, operating time, and electron beam energy for this cycle. After removing the filter element, observe the particle distribution. Concentration at the inlet indicates normal trapping; if bypass marks appear along the sealing edge, check the compression and filter element dimensions. If the filter element ruptures, investigate the instantaneous differential pressure rather than simply replacing it with the same type of filter element.

[0172] When the heat exchange area or cooling medium flow rate of the primary cooler changes, a steady-state thermal balance should be established first, and then a flow rate reduction transition should be implemented. It needs to be proven that the outlet temperature remains pumpable and that the liquid metal in the pipeline will not solidify due to overcooling after shutdown.

[0173] The heat exchange capacity of the primary cooler is verified through energy balance. The heat removed from the liquid metal side is calculated based on the return mass flow rate and the inlet / outlet temperature difference, and cross-checked with the heat absorbed by the circulating coolant. If the two figures show a large long-term deviation, check the insulation loss, measurement location, and whether there is bypass flow.

[0174] Energy balance deviation is calculated in a two-way closed loop: the deviation between the heat removed by the liquid metal side and the heat absorbed by the coolant side should not exceed ±8% under continuous operation. If it exceeds this, check the insulation loss, temperature measurement point location and bypass internal leakage in sequence. The deviation increases monotonically with the running time, indicating scaling in the heat exchange channel. A sudden change indicates abnormal coolant flow. The two modes correspond to different maintenance actions and do not adopt a uniform cleaning cycle.

[0175] The verification records of the thermal management chain segment, including the inlet and outlet temperatures of the first cooler and the temperature of the medium container, confirmed that the reflux temperature remained above the solidification boundary and that the energy balance deviation on both sides of the heat exchange was within an interpretable range.

[0176] The minimum temperature test adjusts the ambient temperature and coolant temperature to unfavorable design conditions, checking whether the check valve, cooler outlet, filter, and media container inlet are still above the melting point. If localized temperature deficiencies are found, prioritize improving insulation or temperature control, rather than reducing flow resistance by lowering filtration precision.

[0177] Example 3: Validation of the link between filtration cleanliness classification and backflow prevention (combined with...) Figure 5 , Figure 6 )

[0178] The check valve was tested using two sets of tests: forward opening and reverse pressure differential. The forward test confirmed that the valve disc could still open even at low flow rates, while the reverse test observed whether the liquid on the medium container side rose back into the collection chamber after the pump was stopped. The results of the two sets of tests respectively constrained the opening resistance and the backflow prevention capability.

[0179] The pressure drop of the first filter was measured under both clean and specified particle load conditions. The retention effect of the filtered media was confirmed by sampling or equivalent particle testing; if the pressure drop increased before the retention capacity improved, the filter area or precision was adjusted to avoid turning the filter into a new blockage point in the reflux chain.

[0180] The first filter is installed between the outlet of the first cooler and the inlet of the media container. The filter medium is selected according to the particle size to be intercepted and the allowable pressure drop, and the filter element housing and connecting pipes are kept at the operating temperature. The inlet of the media container is located in a position that facilitates backflow without directly introducing air bubbles into the supply pump suction port.

[0181] In the filtration and return operation, the cooled liquid metal passes through the first filter into the media container and forms a closed-loop circulation.

[0182] The first filter inspection focuses not only on clogging but also on the type of particles. An increase in hard particles may come from impact surface wear, while an increase in fine condensate may come from changes in return flow temperature or vacuum contamination.

[0183] To evaluate particle loading, compatible tracer particles of known size and mass are added under safe conditions. The rise in filter differential pressure, the stability of filtered particles, and the media inlet are recorded. If the filtration accuracy meets the retention requirements but the differential pressure causes a continuous rise in the return liquid level, the filter area is increased or staged filtration is adopted.

[0184] The tracer particle test was conducted with three particle size groups: 0.5 g to 2 g of compatible tracer particles with nominal particle sizes of 50 μm, 20 μm, and 5 μm were added respectively, and the rate of increase of the filter pressure difference and the number of particles after filtration were recorded. The fine filter element had a rejection rate of no less than 99% for 20 μm particles and no less than 90% for 5 μm particles. A rapid increase in pressure difference followed by a slow increase indicates surface blockage, while a uniform increase indicates deep accumulation. Replacement or backflushing strategies were selected accordingly.

[0185] The filter cartridge is installed with the contaminated surface facing upstream, allowing for easy removal of the trapped material along with the filter cartridge during disassembly. No unheatable sediment cup forms at the bottom of the filter housing; if sedimentation space is necessary, independent venting and temperature control are provided, enabling recovery after shutdown rather than long-term accumulation.

[0186] During continuous operation, the positive pressure drop of the check valve is included in the reflux level check. When the valve opening pressure difference increases due to particle retention, the liquid level in the collection chamber and the pressure difference before the filter will change differently, which can be used to distinguish between check valve problems and filter element blockage.

[0187] The cooled liquid metal enters the first filter. The filter intercepts abrasion particles from the jet impactor, nozzle abrasion particles, or other solid impurities in the circuit; the filtered liquid metal returns to the medium container, mixes with the medium inside the container, and then re-enters the supply path.

[0188] When the vacuum chamber is depressurized or the pressure on the medium container side changes, the check valve should remain closed in the reverse direction. After shutdown, a specified test pressure can be applied to the medium container side to observe whether liquid metal backflow occurs on the collection chamber side; vacuum chamber maintenance can be performed only after confirming that there is no backflow.

[0189] If a reverse liquid level change occurs after shutdown, check the check valve sealing surface and the pressure difference between the vacuum chamber and the medium container; before handling, isolate the vacuum chamber and guide the high-level liquid metal back to the safety container to avoid disassembling the valve while there is still a reverse pressure difference.

[0190] The operation record includes the jet landing point, the inlet and outlet temperatures of the first cooler, the temperature of the medium container, and whether the reflux is continuous. The filter maintenance status can be determined by the specified operating time, sampling results, or actual flow rate changes; this implementation does not rely on an additional differential pressure detection structure.

[0191] The first filter is selected based on the source of the returned particles, with a filtration area ensuring that the pressure drop in the clean state is only a portion of the available differential pressure for return. The pressure drop and the amount of liquid returning to the container are observed simultaneously: an increase in pressure drop and a decrease in return volume indicate filter element load; if the pressure drop remains unchanged but the return volume decreases, the check valve and cooler passages should be checked first. This avoids frequent replacement of filter elements that are not yet clogged.

[0192] The filtration accuracy is linked to the nozzle orifice diameter selection: when the nominal nozzle orifice diameter is 100 microns to 300 microns, the equivalent particle size of the first filter is one-third to one-tenth of that, i.e. 5 microns to 25 microns; the pressure drop in the clean state is designed to be 20 kPa to 80 kPa, not exceeding 40% of the available backflow pressure difference; when the pressure difference reaches 150 kPa to 250 kPa, a maintenance prompt is triggered; the filtration area is reserved with a margin of 3 to 5 times the pollution load.

[0193] Table 2 Design parameters for filtration and check valve system (Example 3)

[0194]

[0195] At the end of continuous operation, particle samples in the media container and filter cartridge traps are recorded separately. An increase in large-sized debris may correspond to wear of nozzles, contact surfaces, or internal components, while an increase in fine particles may correspond to condensation or surface peeling. The particle results are correlated with the X-ray source operation period to determine maintenance targets, rather than treating the filter as a consumable part.

[0196] Even after the jetting stops, liquid column pressure may still exist on the medium container side. In this embodiment, the check valve closure is verified by increasing the liquid level in the medium container or applying a safety equivalent back pressure, and it is observed whether the liquid level on the collection chamber side rises again. After confirming that there is no backflow, a short-term pressure fluctuation is applied to check the valve core closing delay.

[0197] The dynamic performance of the check valve is calibrated based on the most unfavorable back pressure: when a step back pressure of 0.2 MPa to 0.6 MPa is applied to the medium container side, the response time of the valve core from the pressure difference back to the valve seat is no more than 80 milliseconds, and the reverse leakage rate is less than 1×10⁻ 6 Pa cubic meters per second; when the flow rate is low during positive backflow, the valve opening pressure difference should not exceed 15 kPa to ensure that the collection chamber does not accumulate liquid due to valve resistance.

[0198] Another configuration allows for a combination of coarse and fine filters, with the coarse filter located before the cooler or at the inlet to protect the cooling passages.

[0199] If the liquid level rises slowly during the reverse pressure test, first check the valve seat particles and installation direction; if it rises rapidly, check for valve core damage or bypass. Before handling, isolate the vacuum chamber and return any high-level liquid metal to a safe container to avoid disassembling the valve under reverse pressure differential.

[0200] The installation direction and valve core type of the check valve are verified under tilting, pump stop, and backflow pulsation conditions. Criteria include forward pressure drop, closing delay, and reverse liquid level change, all of which together determine whether the valve is suitable for the position.

[0201] Changes in filtration precision were compared using the same batch of liquid metal and the same particle load. In addition to the cleanliness after filtration, the liquid level before the filter and the stability of the liquid supply at the pump inlet were also recorded to determine whether the increase in precision impaired the closed-loop circulation capability.

[0202] After reinstalling the new filter cartridge, first run it through at low pressure at a temperature above the solidification boundary, measure the clean pressure differential, and use this as the new baseline. If the clean pressure differential is significantly higher than the historical value, check the filter media batch, installation compression, and temperature, and do not use pump power to compensate during high-pressure operation.

[0203] Establish a differential pressure record throughout the filter element's life cycle: use the clean differential pressure of a new filter element as a baseline, arrange for spare parts when the differential pressure rises by 50% relative to the baseline during operation, and replace the filter element when it rises by 100% or reaches the 150 kPa to 250 kPa window; when the baseline deviation of the same batch of filter elements exceeds 20%, check the batch and installation compression of the filter media, and do not cover up filter media defects by increasing the pumping power.

[0204] Filtration effectiveness is assessed by comparing particle number or size distribution through sampling at the media container inlet and upstream of the filter. The test particles should be compatible with expected wear products, and post-testing confirmation should demonstrate that the filter media does not release new fibers or debris into the liquid metal.

[0205] The backflow test covers three states: normal operation, maintaining vacuum while stopping injection, and depressurization of the vacuum chamber. The check valve should not cause liquid accumulation in the collection chamber during normal forward backflow, and should prevent liquid metal from entering the vacuum chamber from the medium container side when reverse pressure occurs.

[0206] The verification of the anti-backflow chain segment was carried out separately with shutdown and pressure disturbance tests to confirm that the check valve blocks the backflow of liquid metal into the vacuum chamber when the pressure on the medium container side increases, and that the opening pressure difference does not cause continuous liquid accumulation in the collection chamber during forward backflow.

[0207] The backflow test of the check valve is conducted under conditions of low pressure on the collection chamber side and a specified static pressure applied on the container side. The changes in the liquid level before the valve and the pressure in the vacuum chamber are recorded respectively. If backflow occurs, the valve seat and particles are dealt with first, and the pressure is not offset by increasing the air pressure on the container side. After valve maintenance, the allowable flow pressure drop is re-verified to avoid the check valve performance being restored but the forward resistance being too large.

[0208] Backflow criteria are quantified to liquid level and pressure: In the reverse pressure test, the liquid level rise on the collection chamber side is not greater than 2 mm and there is no continuous upward trend within 10 minutes, which is considered qualified; the pressure fluctuation of the vacuum chamber during the test does not exceed one order of magnitude; if any index exceeds the limit, it is checked in the order of valve seat particles, installation direction and valve core integrity, and after treatment, the allowable flow direction pressure drop is re-verified under low pressure.

[0209] Before replacing the filter element, ensure that the upstream and downstream liquid metals flow into the controlled container through the maintenance drain port, and maintain the filter element temperature in a removable state. After removal, check whether the sealing surface is trapping particles. When installing the new filter element, position it according to the flow direction markings. Do not loosen the housing while it is still connected to the vacuum chamber or while there is still a high-temperature and high-pressure medium.

[0210] Example 4: Overall matching, shutdown and evacuation, and long-cycle operation of reflux recirculation system

[0211] After shutdown, measure the residual liquid in the collection chamber. First, drain the liquid normally, then change the equipment's orientation or use localized heating to confirm the presence of any hidden cavities. If the residual liquid can only be discharged by additional tilting, the geometry should be modified, and tilting should not be a routine maintenance procedure.

[0212] Assembly acceptance begins with verifying the jet landing point, check valve direction, and complete flow path using a compatible test medium, followed by activating the temperature control and cooling circuits. Only when there is no external splashing in the receiving area, the check valve is open in the forward direction, and the filter outlet can stably return to the container, can the test under liquid metal and vacuum conditions proceed.

[0213] During shutdown and evacuation, the injection stops while maintaining reflux and temperature control until the liquid metal in the vacuum chamber and pipeline is fully recovered.

[0214] After shutdown, continue to maintain heat tracing and necessary reflux until there is no residual liquid metal in the collection chamber, check valve, first cooler, and first filter that would block the passage after cooling.

[0215] The return inlet of the medium container is located in a position that does not directly disturb the suction inlet of the supply pump, so that the hot liquid metal that has just returned has room for mixing and temperature equalization.

[0216] During reflux operation, record the inlet and outlet status of the vacuum chamber, paying particular attention to changes in temperature, liquid level, or particles. If liquid accumulation occurs, check sequentially from the jet landing point to the collection chamber, without directly disassembling the main body of the vacuum chamber.

[0217] The reflux and recirculation are matched with the supply side based on temperature and viscosity: the viscosity of the gallium indium tin alloy changes slowly in the range of 60 degrees Celsius to 90 degrees Celsius, the temperature difference between the medium container and the outlet temperature of the first cooler is controlled within ±10 kJ, so that the supply pressure fluctuation caused by the viscosity fluctuation at the medium pump inlet does not exceed ±1%, the jet velocity fluctuation is controlled within ±0.5%, and the drift of the scorch spot position is less than 1 micrometer.

[0218] If the liquid level in the collection chamber rises abnormally while the flow rate at the cooler inlet decreases, first check the check valve's forward opening and the pipeline temperature; if the cooler outlet temperature rises but the flow rate is normal, check the circulating coolant; if the supply pressure to the medium container decreases and the flow rate difference before and after filtration increases, check the filter. These three phenomena correspond to different chain segments.

[0219] When the liquid level in the collection chamber rises abnormally, first check the opening status of the check valve, whether the refrigeration coil is blocked, and the pressure drop of the filter. It is not advisable to continue to increase the injection flow rate. When dealing with the situation, first stop or reduce the injection to bring the return chain into a controllable thermal state before checking each section.

[0220] When shutting down, first turn off the electron beam, then gradually reduce the jet flow rate. After the nozzle stops, keep the return path open, allowing the liquid metal in the collection chamber to return to the media container through the check valve, cooler, and filter. Do not shut off the pipeline temperature control until the return is complete to prevent residual media from solidifying at the valve or filter element.

[0221] Mass conservation is established based on the liquid level in the media container, replenishment volume, filter cartridge retention mass, and shutdown residue. Unexplained losses should first be checked for adhesion to the vacuum chamber walls and microdroplet deposition, followed by external leaks; level sensor drift should not be directly equated with media consumption.

[0222] Quality conservation accounting is performed in a closed loop on a daily basis: a revenue and expenditure table is established for the liquid level in the media container, the replenishment amount, the mass of the filter element, and the residual amount in each section during shutdown. The imbalance amount is controlled within ±2% after 24 hours of continuous operation. If the imbalance amount suddenly increases, first check for wall adhesion and micro-droplet deposition in the vacuum chamber, then check for external leakage. Liquid level sensor drift can only be included in the media consumption after being eliminated by weighing and comparison.

[0223] This embodiment presents alternative solutions regarding impact materials, heat exchange methods, filtration arrangements, and temperature boundaries, and verifies them using reflux continuity, temperature safety margin, and backflow prevention performance.

[0224] Alternative Option 1: The impact collection area can be a curved surface or an inclined plane, and its material can be diamond, sapphire, ruby ​​or other high-hardness impact-resistant materials.

[0225] Alternative Option 2: The first cooler can be a coil type, a shell type, or other structure that isolates the liquid metal from the circulating coolant for heat exchange.

[0226] For normal shutdown, first shut down the electron beam and reduce the jet supply to gradually decrease the flow rate received in the collection chamber. Keep the return chain temperature controlled and the passage open until the visible liquid level in the collection chamber drops and the cooler inlet temperature becomes uniform, then stop active cooling.

[0227] Alternative Option 3: The first filter can be selected as a single-stage or multi-stage filter depending on the liquid metal particle load, but its outlet is connected to a media container.

[0228] Alternative Option 4: Temperature control can be achieved using comb heaters, tubular heaters, or ambient temperature control to prevent localized condensation in the return path.

[0229] The baseline configuration allows the inlet width of the collection chamber to be more than 20 times the jet diameter to accommodate start-up sway and short-term instability.

[0230] This embodiment employs an arc or inclined impact surface and sequentially performs check flow, cooling, filtration, and temperature control. All components are connected in series according to a predetermined return flow direction, and operational evaluation is based on backflow prevention, temperature recovery, and the cleanliness of the filtered product.

[0231] After the heat exchanger structure is changed, the outlet temperature and pressure drop are compared under the same electron beam heat load; after the filter structure is changed, the flow capacity is compared under the same particle load. The two modifications are not carried out simultaneously.

[0232] For long-term shutdown, options include either purging the reflux chain or maintaining controlled heat tracing. Both options require verification that the check valve and first filter are not locked by the condensate upon restart.

[0233] The geometry of the collection chamber was evaluated based on effective volume and evacuation residuals. Low-level residue and splash upon restarting were measured after jet cessation to confirm that the geometry change did not create cold spots that were difficult to drain or liquid seals communicating with the vacuum chamber.

[0234] The entire return chain undergoes a final quality balance check. The balance is established based on the initial liquid level in the media container, the amount of replenishment during operation, the residual amount in each component after shutdown, and the amount of returned liquid. Unexplained losses should first be investigated for splashing, wall adhesion, or leakage before identifying variants.

[0235] After shutdown, the contact surfaces and pipelines are inspected and the erosion pits, wall deposits, and cold spots are recorded. Erosion changes the momentum direction, wall deposits reduce the effective volume, and cold spots may form solid debris. These three factors correspond to different maintenance actions and do not use a uniform cleaning cycle.

[0236] During the recovery process, evidence is established sequentially for temperature control, low-pressure reflux, check flow direction, and filter cleanliness differential pressure before finally establishing the formal jet. This sequence ensures that assembly errors are not only exposed after the electron beam is activated following maintenance of the reflux chain.

[0237] After prolonged circulation, check for wear on the contact surface, heat exchange performance of the cooling coil, residue in the filter, and liquid metal composition in the medium container. If particle count increases but the contact surface remains intact, continue tracing the nozzle and valve assembly; if the temperature rises but the flow rate remains unchanged, check for scaling in the cooling channels or the condition of the coolant.

[0238] The above variations and experiments do not change the sequence of collection chamber-check valve-first cooler-first filter-media container, thus maintaining the same reflux technology concept under different X-ray source specifications.

[0239] Controlled shutdown first disables the electron beam and stops adding new high-pressure jets. After the liquid column enters the collection chamber, maintain the reflux channel and necessary heating. Once it is confirmed that the liquid level in the collection chamber is no longer rising and the return liquid in the medium container is stabilizing, then isolate the vacuum chamber. If the reflux valve is closed too early, residual liquid metal will remain on the receiving surface and cooler inlet, forming a hard-to-locate plug after cooling.

[0240] Upon restart, first check the flow along the wall of the collection chamber, the opening of the check valve, and the pressure drop of the filter at a low flow rate, then gradually increase the jet load. After the first thermal cycle, verify the cooler outlet temperature and the liquid return from the container; only when the reflux mass conservation, temperature boundary, and particle interception are all restored can continuous belt operation begin.

[0241] The overall system is matched according to the differential pressure budget allocation: the available differential pressure from the collection chamber to the medium container is set at 50 kPa to 200 kPa based on the liquid column height and pumping conditions, of which the check valve accounts for 5 kPa to 15 kPa, the first cooler accounts for 10 kPa to 30 kPa, the first filter in clean condition accounts for 20 kPa to 80 kPa, and the connecting pipelines and local components account for 5 kPa to 20 kPa; if the measured pressure drop of any section continuously exceeds the budget, the system is checked section by section from upstream to downstream according to the material flow direction, without masking local blockages by increasing the overall supply pressure.

[0242] Vacuum boundary matching is verified according to the working vacuum: the working vacuum degree of the vacuum chamber is 1×10⁻ 4 Pa to 1×10⁻ 6 Pa, the leakage rate of the collection chamber and its vacuum connection is less than 1×10⁻ 9 Pa cubic meters per second; the check valve, the first cooler and the first filter shall be checked for external leakage on the liquid metal side separately. The bundled operation can only be carried out after the mutual leakage check between the circulating coolant circuit and the liquid metal circuit is qualified, so as to prevent the cooling medium from entering the vacuum side or the liquid metal from entering the cooling system.

[0243] Long-term operation is verified at the thousand-hour level: during continuous operation for 1000 hours, the erosion depth of the receiving surface liner does not exceed 0.2 micrometers, the filter element replacement cycle is 200 to 500 hours, the heat exchange capacity of the first cooler decreases by no more than 5%, and the alloy composition deviation in the medium container is within the spectral tolerance; every 200 hours, samples are taken to compare the cleanliness and particle morphology after filtration, and the changes in particle type are correlated with the operating period to distinguish the three sources of nozzle wear, receiving surface erosion and vacuum contamination.

[0244] Operational data is archived in conjunction with the reflux chain status: jet landing point images, cooler inlet and outlet temperatures, filter pressure difference, medium container liquid level and vacuum degree are recorded at the same time reference, and the correlation between the scorch position and the reflux temperature wave action is analyzed; when the reflux temperature fluctuation increases from ±2 opening to ±5 opening, the probability of exceeding the limits of supply pressure and scorch drift increases significantly. Based on this, the reflux temperature control accuracy is included in the overall beam output stability index, rather than just as a medium protection requirement.

[0245] The above four embodiments are connected end to end along the material flow direction: Embodiment 1 solves the momentum problem, Embodiment 2 solves the heat problem, Embodiment 3 solves the pressure and particle problem, and Embodiment 4 solves the overall machine matching problem; the parameter windows of each embodiment are cross-validated on the same prototype platform, and those skilled in the art can scale them up and down according to the X-ray source power level without changing the sequential relationship between the collection chamber, check valve, first cooler, first filter and medium container.

Claims

1. A collection, cooling, filtering, and reflux device for a liquid metal jet target, characterized in that, The system includes a vacuum chamber, a collection chamber disposed within the vacuum chamber and located below the point of impact of the liquid metal jet, and a check valve, a first cooler, and a first filter sequentially connected from the return outlet of the collection chamber to a medium container. The collection chamber has a receiving surface that transforms the incident liquid metal jet from a free liquid column into a wall-attached flow toward the return outlet. The allowable flow direction of the check valve is from the collection chamber toward the medium container. The first cooler is used to remove the heat carried by the returning liquid metal and make its outlet temperature higher than the solidification boundary of the liquid metal used. The first filter is located before the liquid metal returns to the medium container.

2. The reflux device according to claim 1, characterized in that, The area in the collection chamber that is subjected to the impact of the liquid metal jet is an arc surface or a plane that forms an angle with the tangent of the jet.

3. The reflux device according to claim 2, characterized in that, The area subjected to the impact of the liquid metal jet is made of diamond, sapphire, or ruby.

4. The reflux device according to claim 1, characterized in that, The check valve is used to prevent liquid metal from flowing back from the medium container to the vacuum chamber due to the pressure difference between the vacuum chamber and the medium container.

5. The reflux device according to claim 1, characterized in that, The first cooler includes a cooling coil through which liquid metal flows and a circulating coolant channel that exchanges heat with the cooling coil.

6. The reflux device according to claim 1, characterized in that, The first cooler is used to cool liquid metal to a set temperature higher than the melting point of the selected liquid metal.

7. The reflux device according to claim 1, characterized in that, The first filter is disposed between the first cooler and the medium container to intercept solid particles carried in the reflux of liquid metal.

8. The reflux device according to claim 1, characterized in that, The pipes and components through which the liquid metal flows are equipped with temperature control devices to keep the liquid metal above its melting point.

9. The collection, cooling, filtering, and reflux reflux device according to claim 1, characterized in that, The reflux outlet of the collection chamber is located at a low position in the flow direction of the receiving surface, and there is no recess in the collection chamber that is higher than the reflux outlet and forms a closed stagnant chamber with the reflux pipe.

10. A method for recovering a liquid metal jet target using the apparatus according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1. The liquid metal jet that has been subjected to the electron beam falls into the receiving surface of the collection chamber, and the receiving surface changes the direction of the jet's momentum to form a wall-attached flow that moves toward the return outlet. S2. Allow the liquid metal to enter the first cooler from the return outlet in the direction permitted by the check valve, and isolate the reverse pressure on the medium container side by the check valve; S3. Remove the heat carried by the liquid metal according to the inlet temperature and reflux flow rate of the first cooler, while keeping the outlet temperature of the first cooler above the solidification boundary of the liquid metal used. S4. Pass the cooled liquid metal through the first filter to intercept solid particles generated by jet impact, electron beam action, or pipe wear. S5. Return the filtered liquid metal to the medium container, and after shutdown, check the residual amount and backflow status in the order of collection chamber, cooler and filter.

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