electromagnetic pump

Abstract

An apparatus is provided for providing a liquid metal jet in a vacuum environment. The apparatus includes a vacuum chamber, a nozzle configured to provide a liquid metal jet, a jet receiver configured within the vacuum chamber to receive liquid metal from the liquid metal jet, a first electromagnetic pump section including a first inlet and a first outlet, where the first inlet has a first diameter, a second electromagnetic pump section including a second inlet and a second outlet, and a pumping conduit connecting the second inlet to the second outlet, where the pumping conduit has a second diameter, and the first outlet is configured to provide liquid metal to the second inlet. The first diameter is at least 1.8 times greater than the second diameter. Corresponding methods are also provided.

Description

Cross-reference to related applications

[0001] The project leading to this application has received funding from the ECSEL Joint Undertaking (JU) under grant agreement No 826589. The JU receives support from the European Union's Horizon 2020 research and innovation programme and Austria, Belgium, France, Germany, Hungary, Israel, Italy, the Netherlands, Romania, Sweden.

Technical field

[0002] The present disclosure relates to a method for providing a liquid metal jet using an electromagnetic pump, particularly for use in a liquid metal jet radiation source such as an X-ray source.

Background art

[0003] Providing a liquid metal jet in a vacuum environment can be useful in many cases. A group of examples includes radiation sources where an energy beam interacts with a liquid metal jet in an interaction region to generate radiation. An example within this group is a liquid metal jet X-ray source where an electron beam interacts with a liquid metal jet to generate X-ray radiation. This interaction is typically carried out within a vacuum chamber to avoid oxidation of the liquid metal as well as scattering of the electrons. The X-ray radiation is conventionally emitted through an X-ray transmission window. Another example within this group is an EUV source where a laser beam is provided to interact with a liquid metal jet. Another group of examples relates to shielding and / or cooling applications. The liquid metal jet can be used, for example, to provide wall shielding in a fusion reactor.

[0004] The use of electromagnetic pumps to pump target material in liquid metal jet X-ray sources has been studied in the prior art and is a promising technique for improving jet uniformity in terms of speed, shape, and cross-sectional size, and for avoiding liquid metal leakage. By replacing conventional pumps with electromagnetic pumps to circulate the liquid metal and generate the liquid jet, the number of moving parts in the pumping system can be reduced or even eliminated.

[0005] An example of an X-ray source equipped with an electromagnetic pump for pumping a conductive liquid used as an electron impact target is disclosed in WO2020 / 225333, in which it is proposed to arrange the electromagnetic pumps in series to provide an increased final pressure.

[0006] To generate a liquid metal jet for use as a target in an electron beam collision X-ray source, the liquid typically needs to be pressurized to over 100 bar before being ejected through a nozzle to produce the liquid metal jet. The pressure increase in a conductive liquid metal can be achieved by a magnetic force arising from the interaction between a magnetic field and an electric current flowing through the liquid. The direction of the magnetic force is approximately perpendicular to a plane containing both the current and magnetic field directions, and by orienting this plane substantially perpendicular to the longitudinal direction of the conduit carrying the liquid metal, the liquid flow can be induced through the conduit. The magnetic force on a current-carrying conductor can be written as follows:

[0007]

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[0008] In other words, the resulting force is perpendicular to both the magnetic field and the current, and only the components of the magnetic field and current perpendicular to each other contribute to the resulting force. The resulting magnetic force, and therefore the flow of the liquid, is thus influenced by the strength of the magnetic field, the current flowing through the liquid, and the length of the conduit through which the magnetic force acts. Furthermore, the strength of the magnetic force is influenced by the angle the magnetic field makes with the direction of the current. Typically, the magnetic field is thus provided perpendicular to the direction of the current to provide the maximum magnetic force. [Overview of the project]

[0009] Conventional electromagnetic pumps are often designed to provide pressures in the range of tens of bar at most. However, in the case of liquid metal jet X-ray sources, pressures of several hundred bar, for example, 200 bar, 350 bar, or even 1000 bar, may be required. As is recognized, a liquid metal jet may comprise either a continuous jet of liquid or a spray of droplets forming a jet. A continuous liquid jet may also spontaneously break into droplets due to surface tension at a certain distance from the nozzle. The exact nature of the liquid jet is not essential to the teachings of the invention provided herein.

[0010] To achieve such high pressures using a compact electromagnetic pump suitable for integration into liquid metal jet radiation sources such as X-ray sources, it is preferable that the conduit carrying the liquid metal through the electromagnetic pump be fairly narrow. In this case, a problem may arise in which gravity is insufficient to supply the liquid metal from the jet receiver vessel to the pump. In this context, it should be noted that the receiver for the liquid metal circulated in, for example, a liquid metal jet radiation source is typically located in a vacuum chamber, which means that there is no ambient pressure to help push the liquid metal into the pump. This disclosure provides a solution to this problem by using a two-stage pumping system in which a first-stage electromagnetic pump has an inlet large enough to be supplied from the receiver vessel by the available gravitational pressure, and a second-stage electromagnetic pump has a pumping conduit with an inner diameter small enough to reach the required pressure. The supply conduit of the first-stage electromagnetic pump is coupled to the pumping conduit of the second-stage electromagnetic pump. Thus, the first-stage electromagnetic pump supplies the second-stage electromagnetic pump, which may be supplied by the gravitational pressure provided from the jet receiver vessel.

[0011] This invention is based on an understanding of how gravity-induced pressure creates the flow of liquid metal into an electromagnetic pump. While an electromagnetic pump may be capable of substantially increasing pressure, the flow will be limited by the amount of liquid entering the pump. In a simple model, the pressure increase in the pump is proportional to 1 / conduit diameter, and therefore, those skilled in the art are encouraged to decrease the conduit diameter. On the other hand, as the conduit diameter decreases, the viscous pressure loss within the conduit increases. The design choice, therefore, will typically be a balance between these two effects to achieve the maximum effective pressure increase. Pressure can be controlled by increasing the current and / or magnetic field in the pump. To increase the jet velocity for a given nozzle diameter, the pressure must increase, as can be seen from the following equation (2), which shows that pressure is proportional to the square of the jet velocity. Increasing the jet velocity for a given nozzle diameter also implies an increase in liquid flow. However, the flow is limited by gravity-induced pressure and the pump inlet diameter. This means that despite efforts to increase the capacity to raise the pressure in the pump, the jet velocity may not increase.

[0012] To improve this situation, a prepump, or first-stage pump, is introduced. The inlet of the prepump should be designed to accommodate the required flow, taking into account the gravity-induced pressure acting on the front. The outlet diameter of the prepump should match the outlet diameter of the main pump inlet. The prepump may have a passive outlet section designed to match the inlet diameter of the main pump, where no pumping force is applied to the liquid metal. Alternatively, the prepump may seamlessly merge with the main pump by, for example, providing a tapered supply conduit whose first diameter matches the inlet diameter of the prepump and whose second diameter matches the inlet diameter of the pump conduit or main pump. A magnetic field and current may be applied along the entire length of the tapered supply conduit of the prepump, thereby eliminating any passive parts of the prepump.

[0013] As will be discussed below, it was found that the inlet diameter of the first-stage pump should be at least 1.8 times, for example 2.5 times, the diameter of the main (second-stage) pump's pressure conduit.

[0014] Thus, the apparatus described in claim 1 is provided. A corresponding method for pumping liquid metal in a radiation source is also provided. Dependent claims relate to various preferred embodiments.

[0015] The second-stage electromagnetic pump may have a pressurized conduit with a substantially constant inner diameter. The connection between the supply conduit of the first-stage electromagnetic pump and the pressurized conduit of the second-stage electromagnetic pump may be made using a connecting conduit that connects the outlet of the supply conduit to the inlet of the pressurized conduit. Alternatively, the supply conduit in the first-stage pump may gradually decrease in diameter, for example, by tapering continuously from its inlet to its outlet, so that the diameter at its outlet matches the diameter of the inlet of the second-stage pump.

[0016] The two electromagnetic pumps may have separate current sources. In such embodiments, the connecting conduit may be electrically insulated so that current cannot flow through it. In implementations where a common current source is used for both the first and second electromagnetic pumps, the path for current between the first and second electromagnetic pumps can be provided by the electrical connection between the two pumps (i.e., isolated from the conduit).

[0017] The two electromagnetic pumps may be equipped with permanent magnets, preferably NdFeB magnets, to provide a magnetic field. Furthermore, each pump may be provided with a yoke made of a ferromagnetic material such as iron, magnetic steel, etc. The design intent of such a yoke is to enclose the magnetic circuit and, from this, confine the magnetic field. This is advantageous in several respects, including the possibility of improved pump efficiency and the fact that the confined magnetic field does not interfere with the operation of the radiation source comprising the pumping device. In particular, in embodiments where an electron beam is provided for interaction with a liquid jet, avoiding a stray magnetic field provides better control of the electron beam. To achieve the confinement, the thickness of the yoke may be selected to be greater than the length of the permanent magnet along the direction parallel to the current passing through the electromagnetic pump, scaled by the ratio between the magnetic field strength of the magnet and the saturation magnetization of the material constituting the yoke. Furthermore, the yoke may be configured to provide mechanical support. In particular, the yoke may be configured to withstand the liquid metal pressure generated by the electromagnetic pump.

[0018] The pumping method of the present invention disclosed herein is appropriately applied to a liquid metal jet X-ray source comprising an electron source for providing an electron beam that interacts with a liquid metal jet to generate X-ray emission. However, the method of the present invention may also be applied to other radiation sources in which liquid metal is used as a target for generating radiation, such as laser-induced plasmas and the like. Another area of ​​application is, for example, shielding or cooling in a fusion reactor.

[0019] Within the scope of the present invention, several modified and variant forms are possible. In particular, radiation sources comprising more than one liquid metal jet or more than one energy beam are conceivable within the scope of the concept of the present invention. Further, X-ray sources of the type described herein may advantageously, but not limited to, be combined with X-ray optics and / or detectors tailored to specific applications exemplified by medical diagnostics, non-destructive inspection, lithography, crystal analysis, microscopy, materials science, microscopy surface physics, protein structure determination by X-ray diffraction, X-ray spectroscopy (XPS), critical dimension small-angle X-ray scattering (CD-SAXS), wide-angle X-ray scattering (WAXS), and X-ray fluorescence (XRF).

[0020] In the following detailed description, reference is made to the accompanying drawings.

Brief Description of the Drawings

[0021] [Figure 1] Schematically shows a radiation source incorporating the two-stage pumping method disclosed herein. [Figure 2] Schematically shows a first example of an electromagnetic pump device. [Figure 3] Schematically shows a second example of an electromagnetic pump device. [Figure 4] It is a flowchart outlining a method for pumping liquid metal in a radiation source.

Modes for Carrying Out the Invention

[0022] The following detailed description is provided to enable those skilled in the art to implement the teachings disclosed herein.

[0023] As an introduction, it may be useful to derive some equations / formulae that underlie the principles of the two-stage electromagnetic pumping method disclosed herein. First, some general equations related to the pressure increase that can be obtained under the constraint of mass continuity of the flow are presented. Then, more specific equations applicable to liquid metal jets are presented.

[0024] During operation, for example, the ambient pressure inside the vacuum chamber of an electron blast X-ray source is 10 -6 It may be less than or equal to mbar. The pressure p0 available to create the inflow into the first pump is then provided primarily (or, in fact, solely) by gravity and can be written as follows:

[0025]

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[0026] Here, ρ is the density of the liquid metal, g is the acceleration due to gravity, and h0 is the vertical height between the inlet to the first pump and the surface of the receiver container.

[0027] The flow velocity v related to the pressure drop p can be obtained from the following, for the first approximation (neglecting viscosity):

[0028]

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[0029] From this, keeping in mind that in the case of a circular conduit, the flow rate is equal to the flow velocity multiplied by the cross-sectional area, the following equation can be obtained for the flow rate Q (volume per unit time):

[0030]

number

[0031] Here, d is the inner diameter of the conduit. Subsequently, the flow rate Q0 that can be driven through a circular aperture of diameter d0 by gravity-induced pressure from a liquid column of height h0 can be written as follows:

[0032]

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[0033] Since the flow rate must be the same through both pumps due to continuity (there is no supply or absorption source for the liquid metal along the pump conduit), the pressure p1 at the inlet of the second pump can be expressed in terms of the gravity-induced flow rate Q0 and the inner diameter d1 of the conduit of the second pump:

[0034]

number

[0035] From this, under the constraint of flow continuity, the available flow of liquid metal supplied by gravity at the inlet to the first pump limits the pressure that can be obtained at the inlet to the second pump according to equation (5). The pressure that can be obtained at the inlet to the second pump is the gravity-induced inlet pressure of the first pump amplified by the ratio of the conduit diameter to the fourth power. Having a sufficiently high column of liquid metal to increase this inlet pressure for the second pump is often impractical or even impossible. For example, 1 decimeter of gallium corresponds to a pressure of only about 58 mbar. From this, it can be concluded that the gravity-induced pressure is too small for most practical applications where the second pump must be able to raise the pressure above 100 bar. Therefore, according to the teachings disclosed herein, the pressure should be amplified by at least one order of magnitude in order to provide sufficient pressure to supply the second pump. In other words, the diameter of the inlet to the first conduit should be at least the diameter of the inlet to the second conduit

[0036]

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[0037] It should be double.

[0038] In an apparatus for providing a liquid metal jet in a vacuum environment, the situations arising from the constraints discussed in the above overview can be illustrated by several basic mathematical relationships. Given a nozzle diameter d nand the desired jet speed v jet In contrast, the flow rate throughout the entire system can be calculated by noting that the flow rate Q is equal to the flow velocity multiplied by the cross-sectional area:

[0039]

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[0040] The same flow must enter the electromagnetic pump to maintain continuity. Therefore, assuming the inlet diameter of the pump system is d0, the following equation is obtained:

[0041]

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[0042]

number

[0043] Here, v0 is the flow velocity at the pump inlet. The relationship between the pressure p0 and the flow velocity v0 at the pump inlet can be approximated as follows, according to equation (2) above, for the inviscid case:

[0044]

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[0045] Here, ρ is the density of the liquid metal. The pressure available at the pump inlet is the gravity-induced pressure created by the liquid metal material collected by the jet receiver. Combining equations (1) and (9) above, we derive the following equation for the flow velocity:

[0046]

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[0047] By inserting this into equation (8) for the pump inlet diameter, the equation for the pump inlet diameter can be obtained as follows:

[0048]

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[0049] This represents a lower bound for the pump inlet diameter. If the inlet is made smaller, the available flow into the pump becomes a limiting factor, and the desired jet velocity will not be reached regardless of the pumping capacity. Therefore, the lower bound for the pump inlet diameter can be written as follows:

[0050]

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[0051] The pressure increase generated by an electromagnetic pump powered by a current I and a magnetic flux density B across a cross-section of dimension d1 can be written as follows:

[0052]

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[0053] Here, C is a geometric constant determined by the pump design. In the pump according to the embodiment disclosed in WO2020 / 225333, C may represent the number of turns in the pressure conduit, i.e., how many times the cross product of current and magnetic field should be applied. In the nozzle, the achieved pressure p1 is used to create the desired jet velocity according to the following:

[0054]

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[0055] From this, the upper bound of the pump conduit diameter d1 can be obtained as follows:

[0056]

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[0057] Given the value on the right-hand side of the above relationship, d1 must be smaller than this limit in order for the pump to reach the pressure required to achieve the desired jet velocity.

[0058] For these constraints to be satisfied in an electromagnetic pump having a certain cross-sectional conduit diameter, i.e., a diameter where d0 is equal to d1, the upper limit of the conduit diameter must be greater than the lower limit of the inlet diameter. Given the jet requirements with respect to jet velocity, nozzle diameter, and liquid metal density, this translates to the pump input requirements with respect to product CBI, which can be written as follows:

[0059]

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[0060] From the above relationship, it is clear that the requirements of the electromagnetic pump will increase as the desired jet velocity or the desired jet width (i.e., nozzle diameter) increases. Of particular importance is the jet velocity at which the pump input (CBI) must increase to the power of 2.5, as with the jet velocity. This is impractical for many applications. This recognition led to the present invention, which provides a two-stage electromagnetic pump. In the embodiment, two pumps are provided in series, where the inlet of the first pump is selected to satisfy the lower bound calculated above, and the diameter of the pressurized conduit of the second pump is selected to satisfy the upper bound calculated above. The ratio of these two diameters must be greater than the fraction given by:

[0061]

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[0062] Nozzle diameter 100 μm, jet speed 100 m / s, liquid metal density 6000 kg / m³ 3 For typical values ​​such as a liquid metal available height of 0.1m, magnetic flux density of 1T, current of 100A, and number of turns of 100, a lower bound of approximately 2.5 for the diameter ratio is obtained. Increasing the desired jet velocity to 200m / s and the available current to 300A yields a lower bound of approximately 4.8. It should be noted that viscosity losses in the electromagnetic pump are ignored in the above discussion. In practice, this may mean that using only the derived lower bound of the diameter ratio as a design criterion may be insufficient. However, generally, for any value of various parameters, the diameter ratio in embodiments of the present invention is at least 1.8, which provides a 10-fold pressure increase, as can be derived by referring to equations (1) to (5) above.

[0063] A radiation source 100 according to the principle disclosed herein is schematically shown in Figure 1. An energy source 102, a jet receiver having a nozzle 104 for generating a liquid metal jet 106, a container 108, and pumping devices 110a and 110b for pumping liquid metal from the container 108 to the nozzle 104 are all located within a vacuum chamber 112. The energy source 102 may be, for example, an electron source that generates an electron beam 114 that interacts with the liquid metal jet 106 to generate X-ray radiation 116 emitted from the vacuum chamber through an X-ray transmission window 118. In other embodiments, the energy source may comprise a laser that generates a laser beam that interacts with the liquid metal jet to generate extreme ultraviolet (EUV) radiation. The pumping device comprises a first electromagnetic pump 110a and a second electromagnetic pump 110b, as schematically shown in Figure 1. The first pump 110a receives liquid metal from the container 108 and supplies the liquid metal to the second pump 110b.

[0064] The second (main) pump 110b may, advantageously, be of the type disclosed in WO2020 / 225333, which is incorporated herein by reference. Such a pump may comprise at least first and second sections. A first permanent magnet may be located in the first section, and a second permanent magnet may be located in the second section, with the first and second permanent magnets arranged in opposite magnetic field orientations. In order to achieve the same pumping force along the liquid metal in both sections of the main pump, the winding direction of the conduit in the first section may be opposite to that of the conduit in the second section. In this way, the current can flow in the same direction throughout the entire apparatus. It should be noted that such an apparatus can be extended to any number of sections, and the magnetic field orientation and the winding direction of the conduit can be switched between each section as appropriate.

[0065] The above explanation and derivation assume that the conduit of the second pump has a constant inner diameter, but please understand that the second pump conduit may be tapered or may have a tapered section.

[0066] According to the embodiment shown in Figure 2, the first pump (pre-pump) comprises a substantially straight metal tube 210 of a first diameter having a first inlet 211. As shown in Figure 2B, a magnetic field is provided perpendicular to the cross-section of the tube by a pair of permanent magnets. Current is provided perpendicular to the cross-section of the tube and the magnetic field by two electrodes (not shown) brazed or otherwise attached to the outside of the tube, for example, by soldering or welding. The first diameter tube 210 is connected to the inlet of a second main tube 220 by a diameter limiter 212 attached (e.g., welded) to the tube and the inlet of the second pump. The second pump (main pump) is preferably of the type described above. A first current source 240a is connected to a pair of electrodes brazed to the pre-pump tube. A second current source 240b is connected to an electrode located on the end of the second pump. The current flowing through the second pump is indicated by arrow I in Figure 2. To further improve the efficiency of the first pump, an external magnetic yoke (not shown) may be provided to close the magnetic circuit between the two permanent magnets. Alternative embodiments, for example, having one permanent magnet and a suitable yoke designed to close the magnetic circuit and provide a magnetic field as shown in B, are also within the scope of the invention. The flow direction of the liquid metal is shown by P in Figure 2, and the winding direction of the conduit is reversed in the section of the pump, as shown in 230, where the magnetic field is reversed so that the flow direction matches the magnetic field. The outlet of the second pump is shown in 234 in Figure 2.

[0067] According to the embodiment of Figure 3, the first pump 110a is realized as the first section of the pump according to WO2020 / 225333, which has been briefly discussed above. Liquid from the jet receiver is supplied into an inlet 310 of a first diameter. A first conduit 312 connected to the first inlet 310 is wound around a core 314 made of iron (or some other suitable magnetic material). A permanent magnet (or a number of permanent magnets) provides a magnetic field in the radial direction of the core perpendicular to the cross-section of the conduit. An electric current is applied to the conduit in a direction along the longitudinal axis of the core, and thus substantially perpendicular to the cross-section of the conduit 312. The first conduit is connected to a second conduit 316 of a second diameter, wound around the same core 314 in a number of sections having alternating winding directions. These sections are equipped with permanent magnets arranged such that the magnetic field direction of neighboring sections is reversed, as indicated by the arrows in Figure 3B, and the flow direction P of the liquid metal is reversed accordingly, as shown in 330. In this embodiment, the first pump 110a corresponds to the first section, and the second pump 110b corresponds to the subsequent section. In this example, the first reversal of the flow direction at 330a corresponds to the transition from the first pump 110a to the second pump 110b. A single current source 340 is configured to provide a current I through all segments in series. Neighboring windings of the conduit are electrically connected to each other. Electrical connections are provided between sections to provide a low-resistance path for the current from one section to the next. The first diameter is at least 1.8 times the second diameter. To accommodate this, the inner diameter of the outer magnet is larger in the first section compared to the subsequent section. The connection between the conduit in the first section and the conduit in the second section includes a diameter reduction from the first diameter to the second diameter. In Figure 3, the outlet of the second pump is shown at 334.

[0068] A method for pumping liquid metal in a liquid metal jet radiation source is outlined in Figure 4. While pumping methods are understood to involve circulating liquid metal in a loop, this method can be described as beginning with step 401, collecting liquid metal in a receiver located in a vacuum chamber. The liquid metal is then pumped from the receiver to a second electromagnetic pump using a first electromagnetic pump 402. The second electromagnetic pump then pumps the liquid metal to a nozzle to generate a liquid metal jet 403. The first electromagnetic pump has an inlet of a first diameter for receiving liquid metal from the receiver, and the second electromagnetic pump has a pumping conduit of a second diameter. According to the principle disclosed herein, the first diameter is at least 1.8 times, e.g., 2.5 times, the second diameter. A common current source can be used to provide current to both the first and second electromagnetic pump sections. However, it is also conceivable that the first and second electromagnetic pumps have separate current sources.

[0069] In conclusion, an apparatus for providing a liquid metal jet in a vacuum environment is disclosed. To achieve sufficient pressure and liquid flow to generate a jet using an electromagnetic pump, the apparatus includes a first electromagnetic pump that receives liquid metal from a container and pumps this metal to the inlet of a second electromagnetic pump. The inlet pressure to the first pump is provided by gravity due to the height difference between the container and the inlet of the first pump, while the inlet pressure to the second pump is provided by the first pump. Sufficient pressure increase under the constraint of flow continuity is provided by the apparatus of the present invention by making the inlet diameter of the first pump at least 1.8 times the diameter of the pumping conduit of the second pump.

[0070] Although the present invention has been described with reference to several specific embodiments, it should be understood that various modifications and alternative implementations are possible within the scope of the appended claims. The following is a direct reproduction of the claims as originally filed. [1] Apparatus for providing a liquid metal jet in a vacuum environment, Vacuum chamber and A nozzle configured to provide the aforementioned liquid metal jet, A jet receiver is provided within the vacuum chamber and configured to receive liquid metal from the liquid metal jet, A first electromagnetic pump section comprising a first inlet and a first outlet, wherein the first inlet has a first diameter, A second electromagnetic pump section comprising a second inlet and a second outlet, and a pressure conduit connecting the second inlet to the second outlet, wherein the pressure conduit has a second diameter, In an apparatus comprising, wherein the first outlet is configured to supply liquid metal to the second inlet, The apparatus is characterized in that the first diameter is at least 1.8 times larger than the second diameter. [2] The apparatus according to [1], further comprising a supply conduit connecting the first inlet to the second inlet, wherein the supply conduit has a diameter that decreases along the supply conduit from a first diameter at the first inlet to a second diameter at the second inlet. [3] The apparatus according to [2], wherein the supply conduit is continuously tapered from the first inlet to the second inlet. [4] The apparatus according to any one of [1] to [3], further comprising a connecting conduit connecting the first outlet to the second inlet. [5] The apparatus according to any one of [1] to [4], further comprising a current source for supplying current to both the first electromagnetic pump section and the second electromagnetic pump section. [6] The apparatus according to [5], further comprising an electrical connection between the first electromagnetic pump section and the second electromagnetic pump section providing a path for the current. [7] The apparatus according to any one of [1] to [4], further comprising a first current source for supplying current to the first electromagnetic pump section and a second current source for supplying current to the second electromagnetic pump section. [8] The apparatus according to any one of [1] to [7], wherein the first diameter is at least 2.5 times larger than the second diameter. [9] A liquid metal jet radiation source, The apparatus described in any one of items [1] to [8], An energy source for providing an energy beam that interacts with the liquid metal jet in an interaction region so as to generate radiation, A liquid metal jet radiation source comprising the jet receiver positioned downstream of the interaction region in the flow direction of the liquid metal jet.

[10] The liquid metal jet radiation source according to [9], wherein the liquid metal jet radiation source is an X-ray source, and the energy source is an electron source for providing an electron beam that interacts with the liquid metal jet to generate X-ray emission.

[11] A method for providing a liquid metal jet in a vacuum environment, The liquid metal is collected in a receiver, and the receiver is placed in a vacuum chamber. Using the first electromagnetic pump section, liquid metal is pumped from the receiver to the second electromagnetic pump section. The second electromagnetic pump section is used to pump liquid metal to a nozzle for generating a liquid metal jet. A method comprising: the first electromagnetic pump section comprising a first inlet and a first outlet, the first inlet having a first diameter; the second electromagnetic pump section comprising a second inlet and a second outlet, and a pressure conduit connecting the second inlet to the second outlet, the pressure conduit having a second diameter; A method characterized in that the first diameter is at least 1.8 times larger than the second diameter.

[12] The method of

[11] , wherein pumping liquid metal from the receiver to the second electromagnetic pump section using the first electromagnetic pump section comprises pumping the liquid metal through a supply conduit connecting the first inlet to the second inlet, the supply conduit having a diameter that decreases along the supply conduit from the first diameter at the first inlet to the second diameter at the second inlet.

[13] The method according to

[11] or

[12] , wherein a common current source is used to supply current to both the first electromagnetic pump section and the second electromagnetic pump section.

[14] The method of any one of

[11] to

[13] , further comprising directing the energy beam onto the liquid metal jet to generate radiation from the interaction between the energy beam and the liquid metal jet.

[15] The method according to

[14] , wherein the energy beam is an electron beam that interacts with the liquid metal jet to generate X-ray emission.

Claims

1. Apparatus for providing a liquid metal jet in a vacuum environment, Vacuum chamber and A nozzle configured to provide the aforementioned liquid metal jet, A jet receiver is provided within the vacuum chamber and configured to receive liquid metal from the liquid metal jet, A first electromagnetic pump section comprising a first inlet and a first outlet, wherein the first inlet has a first diameter, A second electromagnetic pump section comprising a second inlet and a second outlet, and a pressure conduit connecting the second inlet to the second outlet, wherein the pressure conduit has a second diameter, In an apparatus comprising, wherein the first outlet is configured to supply liquid metal to the second inlet, The apparatus is characterized in that the first diameter is at least 1.8 times larger than the second diameter.

2. The apparatus according to claim 1, further comprising a supply conduit connecting the first inlet to the second inlet, wherein the supply conduit has a diameter that decreases along the supply conduit from a first diameter at the first inlet to a second diameter at the second inlet.

3. The apparatus according to claim 2, wherein the supply conduit is continuously tapered from the first inlet to the second inlet.

4. The apparatus according to any one of claims 1 to 3, further comprising a connecting conduit for connecting the first outlet to the second inlet.

5. The apparatus according to any one of claims 1 to 3, further comprising a current source for supplying current to both the first electromagnetic pump section and the second electromagnetic pump section.

6. The apparatus according to claim 5, further comprising an electrical connection between the first electromagnetic pump section and the second electromagnetic pump section that provides a path for the current.

7. The apparatus according to any one of claims 1 to 3, further comprising: a first current source for supplying current to the first electromagnetic pump section; and a second current source for supplying current to the second electromagnetic pump section.

8. The apparatus according to any one of claims 1 to 3, wherein the first diameter is at least 2.5 times larger than the second diameter.

9. A liquid metal jet radiation source, The apparatus according to any one of claims 1 to 3, An energy source for providing an energy beam that interacts with the liquid metal jet in an interaction region so as to generate radiation, A liquid metal jet radiation source comprising the jet receiver positioned downstream of the interaction region in the flow direction of the liquid metal jet.

10. The liquid metal jet radiation source according to claim 9, wherein the liquid metal jet radiation source is an X-ray source, and the energy source is an electron source for providing an electron beam that interacts with the liquid metal jet to generate X-ray emission.

11. A method for providing a liquid metal jet in a vacuum environment, The liquid metal is collected in a receiver, and the receiver is placed in a vacuum chamber. Using the first electromagnetic pump section, liquid metal is pumped from the receiver to the second electromagnetic pump section. The second electromagnetic pump section is used to pump liquid metal to a nozzle for generating a liquid metal jet. A method comprising: the first electromagnetic pump section comprising a first inlet and a first outlet, the first inlet having a first diameter; the second electromagnetic pump section comprising a second inlet and a second outlet, and a pressure conduit connecting the second inlet to the second outlet, the pressure conduit having a second diameter; A method characterized in that the first diameter is at least 1.8 times larger than the second diameter.

12. The method according to claim 11, wherein pumping liquid metal from the receiver to the second electromagnetic pump section using the first electromagnetic pump section comprises pumping the liquid metal through a supply conduit connecting the first inlet to the second inlet, the supply conduit having a diameter that decreases along the supply conduit from the first diameter at the first inlet to the second diameter at the second inlet.

13. The method according to claim 11 or 12, wherein a common current source is used to provide current to both the first electromagnetic pump section and the second electromagnetic pump section.

14. The method according to claim 11 or 12, further comprising directing the energy beam onto the liquid metal jet in order to generate radiation from the interaction between the energy beam and the liquid metal jet.

15. The method according to claim 14, wherein the energy beam is an electron beam that interacts with the liquid metal jet to generate X-ray emission.

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