Technique for reducing a local thermal load on a surface that is struck by electrically charged particles

Abstract

The invention relates to a method and a device for reducing a local thermal load on a surface of a particle collection device that is struck by electrically charged particles. The electrically charged particles may correspond in particular to a fraction of non-neutralised ions from a particle beam of neutralised ions downstream of a neutraliser of a neutral beam injection device of a fusion reactor. The method comprises changing, preferably continuously, the point of impact (P) of the charged particles (8) on the surface (34) by exposing the charged particles (8) to at least one magnetic and / or electric field, the field lines of which are oblique or perpendicular to a flight direction of the charged particles and the field strength of which is varied, preferably continuously, in order to change the point of impact (P) so as to reduce a local thermal load on the surface (34), the surface (34) being designed as an area with an open cross-section.

Description

[0001] DESCRIPTION

[0002] Technique for reducing the local thermal load on a surface struck by electrically charged particles

[0003] Technical field

[0004] The invention relates to a method and a device for reducing the local thermal load on the surface of a particle capture device struck by electrically charged particles. The electrically charged particles can, in particular, correspond to a proportion of unneutralized ions from a particle beam of neutralized ions downstream of a neutralizer in a neutral injection device of a fusion reactor.

[0005] Technical background

[0006] To achieve the necessary high temperatures of several million Kelvin in a plasma within fusion reactors, neutral beam injection (NBI) has proven to be a highly efficient method. These high temperatures necessitate confining the plasma within the fusion reactor using very strong magnetic fields, thus preventing direct contact with the reactor wall. State-of-the-art devices for this purpose include tokamaks, stellarators, and mirror machines.

[0007] For neutral beam injection, a plasma, usually consisting of hydrogen, deuterium, and / or tritium, is generated using arc or RF sources. The ions formed are then accelerated to speeds of up to 1,000 IMeV via a grid system. However, since the charged particles cannot penetrate the magnetic field of the plasma enclosure due to the Lorentz force, they must be neutralized. This is done in the so-called neutralizer by adding neutral gas. Complete neutralization of the ions is usually not achieved, so the residual ions, i.e., the fraction of unneutralized ions, are subsequently guided out of the beam and onto a so-called ion sump using a magnetic or electric field (see also "Conceptual Design of Neutral Beam Injection System for EAST," HU Chundong, Plasma Science and Technology, Vol. 14, No. 6, Jun. 2012).

[0008] The particles striking the ion sumps heat the surface(s) onto which they are deflected. Since all these processes preferentially occur in a vacuum, cooling of the surface(s) due to convection is negligible, resulting in a relatively high temperature increase in the components. Furthermore, it has been shown that the power density of the particles on the surface(s) is not constant due to space charge effects and the superposition of high- and low-energy ions and electrons. Instead, so-called hot spots (local heat zones) form, in which the power density can reach up to 50 MW / m². 2 The heat output can be high within the hot spot, while outside the hot spot it is only a few dozen kilowatts per square meter. This leads to a strong, local thermal overload of the surface(s) and consequently to local damage due to overheating.

[0009] From US patent 7,750,572 B2, a method is known in which electrons emitted from a microwave-induced electron gun are deflected by means of variable magnetic fields and subsequently strike cylindrical, tubular surfaces. The preferably continuous change in field strength alters the Larmor radius and thus the deflection of the electrons. This change in deflection shifts the point of impact of the hotspot on the surface, so that the heat load is distributed over a larger area. Due to the heat capacity of the surfaces, the temperature maximum is thereby reduced, thus preventing thermal damage to the surfaces. The change in field strength is achieved by periodic, sinusoidal changes in the current of electromagnets.According to US 7,750,572 B2, this leads to a longer residence time of the electron beam at the inflection points, resulting in temperature peaks at these points. US 7,750,572 B2 attempts to address this through superimposed modulation, but even this does not completely prevent local maxima. Furthermore, the control effort is significantly higher.

[0010] US 8,004,197 B2 describes a cylindrical electron sink. The electron beam is deflected in a spiral pattern within the electron sink using magnetic fields. The strength and / or frequency of these magnetic fields is modulated, thus altering the points where the electrons strike the inside of the cylinder. However, the cylindrical design necessitates that the magnetic fields penetrate the cylinder, requiring the coils to be positioned relatively far from the charged particles. This results in significant losses, necessitating the generation of strong magnetic fields and consequently high power consumption. Furthermore, two magnetic fields are required to variably deflect the electron beam: a transverse field that rotates the electron beam and a vertical field aligned with the electrons' main direction of travel.To generate the transverse, rotating magnetic field for imprinting the rotation (see column 2, line 22ff), several, but at least three, preferably six, variably controllable magnetic coils are necessary (Fig. 1B and column 6, line 40ff.), which is structurally complex and therefore disadvantageous.

[0011] The invention is therefore based on the objective of creating an improved technique to reduce and / or better distribute the thermal stress on a surface struck by electrically charged particles, and which avoids the disadvantages of conventional techniques.

[0012] These tasks are solved by methods and devices with the features of the independent claims. Advantageous further developments are specified in the dependent claims and the description.

[0013] A first general aspect of the present disclosure relates to a method for reducing a thermal load, preferably a local thermal load, on the surface of a device struck by electrically charged particles. This device is hereinafter referred to as a particle capture device. The reduction of a local thermal load on the surface can also be understood as a distribution of the thermal load on the surface generated by the charged particles, preferably to avoid or at least reduce the concentration of the thermal load on a partial area, e.g., a hotspot, of the surface.

[0014] The method comprises, preferably continuously, changing the point of impact of the charged particles on the surface by exposing the charged particles to at least one magnetic and / or electric field whose field lines are inclined or perpendicular to the direction of travel of the charged particles. The charged particles are thus injected into the field lines at an angle greater than zero degrees, causing them to be deflected. The electrically charged particles are preferably injected into the magnetic and / or electric field as a particle beam or beams. Changing the point of impact of the charged particles on the surface corresponds to changing the position of the point of impact of the charged particles on the surface.

[0015] Furthermore, the field strength of the magnetic and / or electric field is varied, preferably continuously, to change the point of impact and / or the position of the point of impact in order to reduce a local thermal load on the surface. This, in particular continuous, variation of the point of impact can be described as temporal, particularly continuous, variation and / or as uninterrupted and steady variation of the point of impact over time. In other words, the method comprises, preferably continuously, adjusting and shifting the point of impact of the charged particles on the surface. Advantageously, the concentration of the thermal load on individual hot spots is avoided. The thermal load (heat load) is distributed over a larger area of ​​the surface.Due to the heat capacity of the surface, the maximum temperature is thus lowered, thereby avoiding thermal damage to the surface or at least reducing the risk thereof.

[0016] The surface of the particle collection device is designed as a surface with an open cross-section and / or as a surface with a non-cylindrical cross-section. The surface can be planar or mostly flat. Advantageously, it is possible to avoid guiding the particles onto a spiral path for deposition. This reduces the number of required magnetic coils or electrically charged plates. Furthermore, it is not necessary to position the particle collection device between the device for generating the magnetic and / or electric field and the beam of charged particles, thus reducing losses in the walls and those caused by large distances.The method thus enables a structurally simple and at the same time effective reduction of the local thermal load of the surface by, preferably continuously, shifting the point of impact on the surface, through the design of the surface with an open cross-section.

[0017] According to one embodiment, the charged particles are ions. These ions can be, for example, ions of isotopes of hydrogen, namely hydrogen, deuterium, and / or tritium. Alternatively, or in addition, the ions can be negative ions with a particle energy greater than 500 keV and / or positive ions with a particle energy greater than 50 keV. This is particularly advantageous for use in neutral injection devices for a fusion reactor.

[0018] In another embodiment, the electrically charged particles correspond to a fraction of non-neutralized ions from a particle beam of neutralized ions downstream of a neutralizer in a neutral injection device. The neutral injection device is preferably a neutral injection device of a fusion reactor. The particle collection device is preferably an ion sump that is part of the neutral injection device. This makes the method advantageously suitable for use in neutral injection, particularly in fusion reactors or neutron sources.

[0019] Preferably, the electrically charged particles form a particle beam or several individual beams of charged particles. The formation of such individual beams of charged particles is known, for example, in the field of neutral injection and can be achieved by individual openings in the plates of a grid system, between which an accelerating voltage is applied. The number of individual beams can be at least 10, at least 30, or at least 50.

[0020] For example, the at least one magnetic and / or electric field can comprise at least one magnetic field whose field strength is changed by changing the current of at least one electromagnet. Alternatively, or in addition, the at least one magnetic and / or electric field can comprise at least one electric field whose field strength is changed by changing an electrical voltage applied between two electrically conductive surfaces, preferably plates. The aforementioned change in current and / or voltage preferably occurs continuously and / or in such a way that a continuous change in the point of impact on the surface is generated.

[0021] Here, the current and / or voltage can be varied according to a periodic function. The periodic function can be, for example, a sine, sawtooth, step, and / or square wave. This enables a control-efficient and, with regard to the generated heat distribution, effective realization of the, preferably continuous, change in the position of the impact point. The method is preferably carried out in a vacuum.

[0022] In a further embodiment, the method also includes detecting a temperature distribution on the surface, wherein the position of the point of impact is changed depending on the detected temperature distribution.

[0023] An optional further development of this principle provides that, if the temperature of a surface sub-area exceeds a temperature threshold, the position of the point of impact of the charged particles is changed in such a way that the temperature of the sub-area is reduced and / or the charged particles are directed to other sub-areas of the surface with a temperature below the temperature threshold. Additionally or alternatively, an embodiment may provide that the point(s) of impact of the charged particles are changed in such a way that the charged particles are directed to sub-areas of the surface with the lowest temperature. By monitoring the temperature and / or temperature distribution of the surface, the impact area of ​​the charged particles can be selectively shifted to areas with low or very low temperatures as needed.Advantageously, the formation of critical surface temperatures can be prevented even more reliably. Shifting the point of impact to areas of the surface with the lowest temperature, or with a temperature below the temperature threshold, is achieved by adjusting at least one magnetic and / or electric field so that the deflection force generated by the field deflects the charged particles towards the desired area of ​​the surface.

[0024] The temperature distribution is preferably captured using a camera, preferably an infrared-sensitive camera, and preferably with spatial resolution. Using a camera offers the advantage that it can be positioned at a distance and not in direct contact with the surface, thus avoiding the risk of damage from high-energy charged particles. The use of a camera is particularly advantageous if the particle collection device is cooled, for example, by means of a cooling device. The cooling device can be arranged on a side opposite the impact side of the charged particles. Preferably, the cooling device is arranged between the impact side and the opposite side. This is achieved by internal cooling channels through which a cooling medium flows.In principle, these active cooling methods can reduce the thermal load on the collection device caused by the charged particles; however, they also complicate the reliable placement of temperature sensors for measuring the temperature distribution and thus monitoring the temperatures. Here, the use of a camera, preferably an infrared camera, proves advantageous. However, it is also possible to measure the surface temperature and / or temperature distribution using other sensors, such as temperature sensors positioned on or near the surface.

[0025] In another embodiment, the point of impact is changed by means of a control device which is designed to change the field strength to change the point of impact, preferably continuously, preferably depending on the detected temperature distribution.

[0026] The method can further include deflecting the charged particles towards the surface. In another embodiment, the deflection of the charged particles towards the surface is achieved by the same electromagnet and / or the same electrical surfaces that also generate the at least one magnetic and / or electric field for changing the point of impact on the surface. For example, the function of the magnet for deflecting the charged particles towards and / or onto the surfaces of the particle-collecting device and the function of the magnet for changing the point of impact on the surface can be combined. This is achieved by changing the current strength of the magnet for deflection onto the surfaces, preferably continuously, such that an additional, preferably continuous, change in the point of impact is generated.Advantageously, no additional field-generating components, e.g., no additional magnetic coils, are necessary to deflect the charged particles onto the surface of the particle collection device. This embodiment is particularly preferred for neutral injection: Here, non-neutralized ions are deflected from the neutral beam onto the surface of the particle collection device by means of the magnet downstream of the neutralizer.

[0027] In a further embodiment, the at least one magnetic and / or electric field that generates the change in the point of impact is formed by two variable magnetic and / or electric fields whose field lines are not parallel and are preferably perpendicular to each other, wherein the point of impact can be changed and / or is changed independently along two different spatial directions. This allows for an even better distribution of the thermal load on the surface to avoid hot spots.

[0028] For example, the two variable magnetic and / or electric fields can be formed by two variable magnetic fields generated by two magnetic coils, by two variable electric fields, or by one electric and one magnetic field. Furthermore, it is possible that the change in field strength, preferably with regard to its magnitude, shape, frequency, and / or shift, is defined differently for each of the two variable magnetic and / or electric fields. Advantageously, this allows for the flexible and situation-adapted generation of a wide variety of impact distribution patterns.

[0029] In a further embodiment, where the point of impact can be changed independently of each other by means of two fields along two different spatial directions, the particle collection device is cooled by a cooling fluid. The cooling fluid can be guided through cooling channels located on a side facing away from the surface, or it can be internal cooling channels, i.e., cooling channels running inside a material or a particle collection device that forms the surface. Furthermore, the field strength of the two fields is varied according to periodic functions, the period frequencies of which are set differently such that the rate of change of the point of impact on the surface differs in a directional component parallel to a flow direction of the cooling fluid from that in a directional component perpendicular to the flow direction.For example, the velocity in the directional component parallel to the flow direction can be slower than in the directional component perpendicular to it. This allows for a particularly efficient distribution of the thermal load, since partial thermal relief is already achieved by the coolant flow itself. Perpendicular to the flow direction, this can then be compensated for, for example, by a faster change in the point of impact.

[0030] In a further embodiment, where the point of impact can be changed independently of each other by means of two fields along two different spatial directions, the field strength of the two fields is again varied according to periodic functions. Furthermore, the period frequencies for the two fields are set differently such that the change in the point of impact along a first spatial direction is slower than in the second. Optionally, the periodic function that generates the change in the point of impact along the first spatial direction can also have different slopes for the rising and falling edges of the field strength in order to execute back-and-forth movements in the first spatial direction at different speeds. This makes it possible to further improve the uniform distribution of the thermal load on the surface.This is advantageous when dealing with actively cooled surfaces, especially those with a preferred direction of the cooling medium.

[0031] In addition, or alternatively, the periodic function that generates the change of the point of impact along the second spatial direction can also have different amplitudes, preferably to exclude predetermined areas of the surface that are less coolable than other areas of the surface.

[0032] It has already been established that the surface of the particle collection device can be flat. Furthermore, the particle collection device can comprise a flat collection plate, preferably a copper collection plate. According to one embodiment, the particle collection device comprises two collection plates, for example copper plates, arranged in a V-shape relative to each other. Preferably, the two V-shaped collection plates are arranged relative to the particle beam and / or the direction of impact of the charged particles such that the charged particles first strike a first of the two plates, and a portion of the particles rebounding from the first plate then strikes the second plate. This allows even rebounding particles to be effectively captured.

[0033] It has already been stated above that the particle collection device can be cooled on a side facing away from the surface and / or through internal cooling channels using a cooling fluid, for example by a cooling plate through which a cooling fluid flows.

[0034] A second general aspect of the present disclosure relates to a device for reducing the local thermal load on the surface of a particle capture device struck by charged particles. The device comprises a particle capture device having a surface with an open cross-section. The device further comprises a deflection device configured to generate at least one magnetic and / or electric field, the field lines of which are oblique or perpendicular to a direction of travel of the charged particles, in order to change, preferably continuously and / or over time, the point of impact of the charged particles on the surface, and to change the field strength of this field in order to change the point of impact, preferably continuously, in order to reduce the local thermal load on the surface.The deflection device may include a preferably electronic control unit designed to control and / or regulate the change in the point of impact by controlling the magnetic and / or electric field.

[0035] To avoid repetition, features disclosed purely by way of procedure shall also be deemed disclosed by way of device and be claimable. The aforementioned aspects and features of the invention, in particular with regard to the design of the particle collection device and with regard to the modification of the at least one electric and / or magnetic field, thus also apply to the device, e.g., as functional or design features of the particle collection device, the deflection device, or the control device of the deflection device.

[0036] Accordingly, for example, in a preferred embodiment of the device, the particle collection device can comprise a flat collection plate or two collection plates arranged in a V-shape relative to each other, as described above. Furthermore, in a preferred embodiment, the deflection device of the device can comprise: two magnetic coils for generating the at least one magnetic and / or electric field; a camera for detecting a temperature distribution on the surface; and an electronic control device configured to change the point of impact of the charged particles, preferably continuously, by controlling the current in the magnetic coils depending on the detected temperature distribution.

[0037] Another general aspect of the present disclosure relates to a neutral injection device for a fusion reactor, comprising a neutralizer for ions of isotopes of hydrogen, namely hydrogen, deuterium and / or tritium; and a device arranged downstream of the neutralizer for reducing a local thermal load on the surface of a particle capture device, as described herein.

[0038] The previously described preferred embodiments and features of the invention can be combined with one another in any way.

[0039] Brief description of the characters

[0040] Further details and advantages of the invention are described below with reference to the accompanying drawings. These show:

[0041] Figure 1 schematically shows the structure of a device for reducing a local thermal load on the surface of a particle capture device, using the example of a neutral injection device for a fusion reactor according to an exemplary embodiment;

[0042] Figure 2 shows the point of impact and the thermal load on a surface according to the prior art;

[0043] Figure 3 shows a time course of a magnetic field for continuously changing the point of impact according to an exemplary embodiment;

[0044] Figure 4 shows a change in the point of impact and the thermal load on a surface according to an exemplary embodiment;

[0045] Figure 5 shows a change in the point of impact and the thermal load on a surface according to a further embodiment; and

[0046] Figures 6 to 11 show the time courses of two magnetic fields for the continuous change of the point of impact according to further embodiments.

[0047] The embodiments shown in the figures are at least partially identical, so that similar or identical parts are provided with the same reference numerals and, to avoid repetition, reference is also made to the description of the other embodiments or figures for their explanation.

[0048] Detailed en

[0049] To illustrate the method and apparatus according to the invention, Figure 1 shows an exemplary setup of a device for reducing the local thermal load on the surface of a particle collection device. The particle collection device in the embodiment shown in Figure 1 is a particle collection device (here an ion sump) of a neutral injection device for a fusion reactor. However, it is emphasized that the method and apparatus according to the invention are not limited to application in neutral injection devices.

[0050] In a fusion reactor 1, a plasma 100 is heated to several million Kelvin. The plasma 100 is contained within a vacuum vessel 102. Very strong magnetic fields are generated by means of magnetic coils 101 to confine the plasma 100, preventing it from having direct contact with the reactor wall. State-of-the-art devices in this context include tokamaks, stellarators, and mirror machines.

[0051] To achieve the necessary high temperatures of several million Kelvin in the plasma 100, a neutral injection or a neutral injection device 2 can be used. Here, ions are generated using an ion source 3. For example, a plasma can be generated using arc or RF sources, usually consisting of hydrogen, deuterium, and / or tritium. The ions 6 formed are then accelerated to up to 1 MeV via an accelerator grid or grid system 4. A high-speed vacuum pump 9 is provided to carry out the process in a vacuum. However, since the charged particles / ions 6 cannot penetrate the magnetic field of the plasma enclosure 102 due to the Lorentz force, they must first be neutralized. This is done in the so-called neutralizer 5 by adding neutral gas. The neutralized ions are labeled Ho 7 in Fig. 1.However, complete neutralization of the ions is usually not achieved, so the residual ions, labeled H+ 8 in Figure 1, are subsequently diverted from the beam using a magnetic and / or electric field and directed onto a particle collection device 30, also referred to here as an ion sump. The fast neutralized ions Ho 7 remaining in the particle beam are then directed into the plasma 100, where they transfer their energy to the plasma electrons and ions through collisions, thus heating the plasma. A calorimeter 60 may also be provided. To divert and deflect the residual ions 8, i.e., the fraction of non-neutralized ions 8 from the particle beam of neutralized ions 7 downstream of the neutralizer 5, magnetic coils 22 are provided, which generate a magnetic field by which the residual ions 8 (or, more generally, the electrically charged particles 8) are deflected onto a surface 34 of the particle collection device 30.

[0052] If the point of impact of the charged particles 8 on the particle collection device 30 were not changed, a situation as shown in Figure 2 (prior art) would result. The point of impact P of the charged particles on the surface of the particle collection device 30 would be concentrated in a narrow circular area 36, ​​i.e., a so-called hot spot. In this area, the power density can reach up to 50 MW / m² and lead to a strong, local thermal overload of the surface 34 in this area, resulting in local damage due to overheating.

[0053] To avoid this, according to the invention the position of the point of impact P of the charged particles on the surface 34 of the particle collection device is changed, preferably continuously.

[0054] Simultaneously, the surface 34 of the particle collection device 30 is designed as a surface with an open cross-section. This is also illustrated in Figure 1. The neutral injection device 2 is equipped with a device 10 for reducing a local thermal load on a surface 34 of a particle collection device that is struck by charged particles 8.

[0055] The device 10 comprises a particle collection device 30, having a surface 34 with an open cross-section. In the illustrated embodiment, the particle collection device 30 has two flat collection plates 32 arranged in a V-shape relative to each other, e.g., two V-shaped copper plates, onto whose surface 34 the charged particles 8 are directed. The charged particles are thereby directed onto the rear plate. The V-shaped arrangement offers the advantage that charged particles 8, which rebound from the rear plate, then strike the front plate and are thus captured by it.

[0056] The device 10 further comprises a deflection device 20, which is configured to generate at least one magnetic and / or electric field B, the field lines of which are inclined or perpendicular to a direction of travel of the charged particles, in order to change the position of the point of impact P of the charged particles 8 on the surface 34, and to preferably continuously change the field strength of which to change the point of impact P in order to reduce a local thermal load on the surface. For this purpose, the deflection device 20 comprises magnetic coils 22 and a control unit 50 for controlling the magnetic coils 22. The magnetic coils 22 are used in a dual function in this case.The control unit 50 controls the magnetic coils 22 such that they generate a magnetic field which, on the one hand, causes charged particles 8 to be deflected from the particle beam of the neutralized ions 7 and directed towards the surface 34 of the particle capture device 30, and, on the other hand, causes the point of impact P of the charged particles 8 on the surface 34 to be changed, preferably continuously. Advantageously, no additional field-generating components, e.g., no additional magnetic coils, are necessary to deflect the charged particles onto the surface of the particle capture device.

[0057] In contrast to known approaches where charged particles are guided onto a surface with a cylindrical cross-section to reduce thermal stress, the non-cylindrical design of the surface, in particular the planar or plate-shaped design of the surface 34, enables an implementation in which both the diversion of the charged particles 8 from the particle beam of neutralized ions 7 and the, preferably continuous, change of the point of impact can be achieved with only two magnets 22. Furthermore, if required, any desired distribution pattern of the point of impact P on the surface 34 can be realized, as will be explained below with reference to Figures 5 to 11.

[0058] Figure 3 illustrates a possible embodiment. Here, the control device 50 is configured to control the magnetic coils 22 such that the current and / or voltage is varied according to a periodic function, preferably a sine, sawtooth, and / or square wave function. Figure 3 shows such control according to a sawtooth or zigzag function.

[0059] The effect on the displacement of the impact point P on the surface 34 is illustrated in Figure 4. The impact point P is continuously shifted back and forth along the displacement direction V. This increases the impact area 36 of the impact points P on the surface, which is elongated in the direction of V. Advantageously, the concentration of the thermal load on a single small hot spot is avoided. The thermal load (heat load) is distributed over a larger area of ​​the surface. Due to the heat capacity of the surface, the temperature maximum is thus lowered, thereby preventing thermal damage to the surface or at least reducing the risk thereof. Figure 5 illustrates another embodiment.In this case, the magnetic coils 22 and their control by the control device 50 are designed such that two variable magnetic Bl, B2 are generated, whose field lines are not parallel and which are preferably perpendicular to each other, wherein the point of impact can be changed and is changed independently of each other along two different spatial directions X, Y.

[0060] The magnetic field Bl can, for example, generate a displacement of the impact point along an X-direction of the surface 34, while the magnetic field B2, for example, generates a displacement of the impact point along a Y-direction of the surface 34 that is perpendicular to the X-direction. This allows for an even better distribution of the thermal load on the surface 34. The impact area 36 in Figure 5 is expanded two-dimensionally compared to Figure 4; that is, the impact area 36 is continuously distributed along two spatial directions instead of just one, so that a good planar distribution of the impact points P can be achieved.

[0061] Figure 6 shows a possible control of the magnetic coils 22 according to two periodic functions for generating the magnetic fields Bl and B2 along the spatial directions X and Y. The field strength of the magnetic field Bl is inversely proportional to the field strength of the magnetic field B2, i.e., when one field strength increases, the other decreases, and vice versa. This allows the point of impact P to be distributed on the surface 34 in order to cover this surface 34 as completely as possible.

[0062] Figure 7 shows another embodiment to illustrate that the magnetic fields Bl and B2 do not have to be of equal strength. Here, the amplitude of B2 is, for example, smaller than that of Bl. Such generation of magnetic fields Bl, B2 for deflecting the charged particles 8 is advantageous, for example, if the surface 34 of the particle collection device 30 is not symmetrical or its projection is not symmetrical. This is the case, for example, if the charged particles 8 strike at an angle, such as when the collection plate 32 of the particle collection device 30 is tilted relative to the direction of impact of the charged particles 8. In this case, the control method shown in Figure 7 deflects the impact points P more strongly in one direction (X-axis) than in the other direction (Y-axis).

[0063] Figure 8 shows another embodiment to illustrate that the magnetic fields Bl and B2 do not have to be opposite (i.e., shifted by half a vibration), but can have any phase shift.

[0064] Figure 9 shows another embodiment in which the point of impact can again be changed independently of each other by means of two fields, e.g., two magnetic fields Bl and B2, along two different spatial directions. The orientation of the magnetic fields Bl and B2 shown in Figure 9 for changing the point of impact can be particularly advantageous, for example, if the particle collection device 30 is cooled on a side facing away from the surface 34 and / or by means of a cooling fluid via internal cooling channels. In the example of Figure 9, the field strength of the two magnetic fields Bl and B2 is again changed according to periodic functions. Here, the period frequencies for the two fields are defined differently such that the rate of change of the point of impact on the surface 34 differs in a directional component parallel to a flow direction of the cooling fluid from the directional component perpendicular to the flow direction.For example, the velocity in the directional component parallel to the flow direction (here, for example, the X-direction) can be slower than in the directional component (Y-direction) perpendicular to it. This allows for a particularly efficient distribution of the thermal load, since in the flow direction of the coolant, partial thermal relief already occurs due to the coolant itself. Perpendicular to the flow direction, this can then be compensated for, for example, by a faster change in the point of impact.

[0065] Figure 10 shows another embodiment in which the point of impact can again be changed independently of each other along two different spatial directions by means of two fields, e.g., two magnetic fields Bl and B2. In this embodiment as well, the field strength of the two fields is changed according to periodic functions. The period frequencies for the two fields Bl and B2 are set differently such that the change in the point of impact along a first spatial direction (here, e.g., the X-direction) is slower than in the second spatial direction (Y-direction). The periodic function that generates the change in the point of impact along the first spatial direction has different slopes for the rising edges of the field strength compared to the falling edges, in order to execute back-and-forth movements in the first spatial direction at different speeds.

[0066] According to the magnetic field Bl in Figure 10, the point of impact P can be slowly shifted from left to right along an X-axis. The magnetic field B2, with its higher period frequency, causes the point of impact P to be shifted back and forth along the Y-direction when shifted along the X-axis. After reaching the maximum shift position to the right along the X-axis, the point of impact P is shifted back in the opposite direction of the X-axis (from right to left), but now more quickly, since the downward slope of the Bl field is steeper than its upward slope. This allows for a faster return to the area to the left, which has already cooled down, thus enabling a better distribution of the thermal load across the surface.

[0067] Furthermore, the periodic function of the magnetic field B2, which generates the change in the point of impact P along the second spatial direction (Y-direction), can have different amplitudes, as also shown in Figure 10, here exemplified in the region of negative currents for the y-axis or the field Bl. This optional embodiment is advantageous if, for example, the surface 34 has areas that are difficult to cool and should therefore not be approached. For example, this could be an area of ​​the surface 34 where a screw is located. This area can then be selectively excluded during approach by appropriately defining different amplitudes, in order to prevent the point of impact from falling on the screw area or another area that is difficult to cool.

[0068] Figure 11 illustrates another embodiment in which the current and / or voltage for generating the electric and / or magnetic fields (in Figure 11, only the example using magnetic fields Bl, B2 is shown) for changing the point of impact are not generated according to a periodic function. Instead, the location on the surface 34 to which the point of impact should currently be directed is determined, and depending on this, the fields are then selectively generated by the control device 50 in order to direct the point of impact to the desired position.

[0069] Firstly, this can be achieved using models stored in the control unit 50. Such models can be determined experimentally, for example, by appropriately adjusting the models, e.g., values ​​of model parameters, so that the resulting temperature distribution on the surface is as optimal as possible, e.g., as uniformly distributed as possible while avoiding hotspots.

[0070] Advantageously, an infrared-sensitive camera 40 (see Figure 1) can also be provided, which determines the temperature distribution on the surface 34 with spatial resolution. The control unit 50 is connected to the camera 40 via a signal input and is configured to control and / or regulate the change in the position of the point of impact depending on the spatially resolved temperature distribution detected by the camera 40. For example, if the temperature of a sub-area of ​​the surface exceeds a temperature threshold, the point of impact P of the charged particles 8 can be changed such that the temperature of the sub-area is reduced and / or the charged particles are directed to other sub-areas of the surface with a temperature below the temperature threshold.In addition or alternatively, the points of impact of the charged particles can be changed in such a way that the charged particles are directed onto sub-areas of the surface which have the lowest temperature within the surface 34.

[0071] The invention is not limited to the preferred embodiments described above. Rather, a multitude of variants and modifications are possible, which also make use of the inventive concept and therefore fall within the scope of protection. In particular, the invention also claims protection for the subject matter and features of the dependent claims independently of the referenced claims. In particular, the individual features of independent claim 1 are each disclosed independently of one another.

[0072] Reference symbol list

[0073] 1 fusion reactor

[0074] 2 Neutral injection device

[0075] 3 ion source

[0076] 4 Acceleration grids

[0077] 5 Neutralizer

[0078] 6 H+ ions

[0079] 7 Neutralized ions

[0080] 8 electrically charged particles, e.g. H+ ions

[0081] 9 High-speed vacuum pump

[0082] 10 Device for reducing a local thermal load

[0083] 20 Deflection device

[0084] 22 Magnetic coil

[0085] 30 particle collection device

[0086] 32 Plane drip tray

[0087] 34 surface

[0088] 36 Impact area

[0089] 40 cameras for temperature measurement

[0090] 50 Control unit

[0091] 60 calorimeters

[0092] P Point of impact

[0093] V, X, Y Direction of displacement or change in the point of impact

[0094] B Magnetic field

[0095] First magnetic field

[0096] B2 Second magnetic field

[0097] 100 Plasma

[0098] 101 Magnetic coil for plasma

[0099] 102 Plasma Housings

Claims

REQUIREMENTS 1. Method for reducing a local thermal load on a surface (34) of a particle capture device (30) struck by electrically charged particles (8), comprising: Changing, preferably continuously changing, an impact point (P), preferably a position of the impact point (P), of the charged particles (8) on the surface (34) by exposing the charged particles (8) to at least a magnetic and / or electric field, the field lines of which are oblique or perpendicular to a direction of flight of the charged particles and the field strength of which is changed to change the impact point (P), preferably continuously, in order to reduce a local thermal load on the surface (34), wherein the surface (34) is designed as a surface with an open cross-section.

2. Method according to claim 1, wherein the charged particles (8) correspond to a proportion of non-neutralized ions from a particle beam of neutralized ions (7) downstream of a neutralizer (5) of a neutral injection device (2) of a fusion reactor, and wherein the particle collection device (30), preferably an ion sump, is part of the neutral injection device (2).

3. Method according to one of the preceding claims, wherein the at least one magnetic and / or electric field comprises a) at least one magnetic field whose field strength is changed by changing, preferably continuously changing, the current strength of at least one electromagnet; and / or b) at least one electric field whose field strength is changed by changing, preferably continuously changing, an electric voltage applied between two electrically conductive surfaces, preferably plates.

4. Method according to claim 3, wherein the current and / or voltage is varied according to a periodic function, preferably according to a sine, sawtooth, and / or square wave function.

5. A method according to any of the preceding claims, further comprising: Detecting a temperature distribution on the surface, wherein the changing, preferably continuous, of the point of impact is dependent on the detected temperature distribution.

6. The method of claim 5, wherein a) if the temperature of a sub-region of the surface exceeds a temperature threshold, the point of impact of the charged particles is changed such that the temperature of the sub-region is reduced and / or the charged particles are directed to other sub-regions of the surface with a temperature below the temperature threshold; and / or b) the points of impact of the charged particles are changed such that the charged particles are directed to sub-regions of the surface having the lowest temperature.

7. Method according to claim 5 or 6, wherein the temperature distribution is spatially resolved by means of a camera (4), preferably an infrared-sensitive camera.

8. Method according to claims 5 to 7, wherein the change of the point of impact is effected by means of a control device (50) which is configured to change the field strength to change the point of impact (P) depending on the detected temperature distribution, preferably continuously.

9. A method according to any of the preceding claims, further comprising: Deflection of the charged particles towards the surface by the same electromagnet (22) and / or the same electric surfaces, which also generate the at least one magnetic and / or electric field to change, preferably continuously change, the point of impact on the surface.

10. Method according to one of the preceding claims, wherein the at least one magnetic and / or electric field is formed by two variable magnetic and / or electric fields (B1, B2) whose field lines not running parallel and preferably perpendicular to each other, wherein the point of impact can be changed and / or is changed independently of each other along two different spatial directions.

11. Method according to claim 10, wherein the two variable magnetic and / or electric fields are formed by two variable magnetic fields (Bl, B2) generated by two magnetic coils, by two variable electric fields or by an electric and a magnetic field.

12. Method according to claim 10 or 11, wherein a change in the field strengths, preferably with regard to their strength, shape, frequency and / or displacement, is defined differently for the two variable magnetic and / or electric fields.

13. A method according to any one of claims 10 to 12, wherein the particle collection device is cooled on a side facing away from the surface by a cooling liquid; and wherein the field strength of the two fields is changed according to periodic functions, wherein the period frequencies for the two fields are set differently such that the rate of change of the point of impact on the surface differs in a directional component parallel to a flow direction of the cooling liquid from that in a directional component perpendicular to the flow direction.

14. A method according to any one of claims 9 to 12, wherein the field strength of the two fields is varied according to periodic functions, wherein the period frequencies for the two fields are set differently such that the change of the point of impact along a first spatial direction is slower than in the second spatial direction, a) wherein the periodic function that generates the change of the point of impact along the first spatial direction has different slopes of the rising edges of the field strength compared to the falling edges in order to execute back-and-forth movements in the first spatial direction at different speeds; and / or b) wherein the periodic function that generates the change of the point of impact along generated in the second spatial direction, exhibiting different amplitudes, preferably for the purpose of excluding predetermined areas of the surface (34) which are less coolable than other areas of the surface (3).

15. Method according to any of the preceding claims, wherein the charged particles (8) are ions, preferably a) ions of isotopes of hydrogen, namely hydrogen, deuterium and / or tritium; and / or b) negative ions with a particle energy greater than 500 keV and / or positive ions with a particle energy greater than 50 keV.

16. Method according to any of the preceding claims, wherein the charged particles (8) form several individual beams of charged particles, wherein the number of individual beams is at least 10, at least 30 or at least 50.

17. Method according to one of the preceding claims, wherein the surface (34) of the particle collection device (30) is planar.

18. Method according to one of the preceding claims, wherein the particle collection device (34) comprises a) a flat collection plate (32), preferably a copper collection plate; and / or b) two collection plates (32) arranged in a V-shape relative to each other; and / or c) is cooled on a side facing away from the surface by a cooling liquid.

19. Device (10) for reducing a local thermal load on a surface (34) of a particle capture device struck by charged particles (8), comprising: a particle capture device (30) having a surface (34) with an open cross-section; and a deflection device (20) configured to change, preferably continuously change, an impact point (P), in particular the Po- The aim is to generate at least one magnetic and / or electric field (B) at the point of impact (P) of the charged particles (8) on the surface (34), the field lines of which are oblique or perpendicular to a direction of flight of the charged particles, and to change the field strength of which to change the point of impact (P), preferably continuously, in order to reduce a local thermal load on the surface.

20. Device according to claim 19, wherein the particle collection device (30) comprises a flat collection plate (32) or two collection plates (32) arranged in a V-shape relative to each other; wherein the deflection device (30) comprises: Magnetic coils (22) for generating the at least one magnetic and / or electric field (B); a camera (40) for detecting a temperature distribution on the surface; and an electronic control device (50) configured to change the point of impact (P) of the charged particles (8), preferably continuously, by controlling the current strength of the magnetic coils (22) depending on the detected temperature distribution.

21. Neutral injection device (2) for a fusion reactor (1), comprising a neutralizer (5) for ions of isotopes of hydrogen, namely hydrogen, deuterium and / or tritium; and a device (10) arranged downstream of the neutralizer according to claim 19 or 20. * * * *

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