Chromatic energy filter

Abstract

Energy filter device (1, 23) for focusing and energy filtering the radiation from charged particles (3) generated by a laser target particle accelerator, comprising at least one energy-dependent focusing device (12, 20, 27, 28, 29) configured such that particles of different energies are focused at different locations, and at least one radiation separation device (15, 17, 30, 37) configured such that it does not attenuate some parts of the particle beam and attenuates other parts of the particle beam completely or to a negligible level, wherein the at least one energy-dependent focusing device (12, 20, 27, 28, 29) is arranged in the direction of radiation upstream of the at least one radiation separation device (15, 17, 30, 37) and is configured as a solenoid device.

Description

[0001] The invention relates to an energy filter device for charged particle radiation, comprising at least one focusing device and at least one radiation separation device. Furthermore, the invention relates to a particle radiation source, in particular a particle radiation source for providing particle radiation with specific energies, comprising at least one target device, in particular at least one laser target device, and at least one energy filter device. The invention further relates to a method for energy-dependent filtering of radiation, in particular particle radiation, preferably of charged particles. In addition, the invention relates to the use of an energy-dependent focusing device for energy-dependent filtering of radiation, in particular particle radiation.

[0002] In engineering, it is sometimes necessary in many fields to allow only certain parts of a signal to pass through, while filtering out other parts. Such devices are commonly called filters.

[0003] For example, it is sometimes necessary to allow only a specific energy range of an input radiation with a broad energy spectrum to pass through the filter, while blocking other energy ranges of the radiation to be processed (filtered). Such a filter device for radiation is typically called an energy filter. Sometimes the term frequency filter is also used, where the energy of radiation can be converted into a frequency, and vice versa, using the so-called de Broglie relation. This applies not only to photon radiation but also, in particular, to particle radiation (also called corpuscular radiation).

[0004] Particularly in particle accelerator technology, it regularly proves necessary to allow certain energy ranges to pass through an energy filter while filtering out other energy ranges. This applies not only to uncharged particles but especially to charged particles (for example, electrons, protons, and heavy ions, or more generally, charged and / or uncharged leptons and / or hadrons). Particle accelerator technology has meanwhile evolved beyond purely fundamental research and is now routinely used in some fields. Electron welding processes, and especially the medical application of particle radiation, such as in cancer therapy, are just a few examples.

[0005] Particularly in cancer therapy, ions, especially heavy ions (for example, carbon ions, oxygen ions, neon ions, nitrogen ions and the like), have proven to be extremely advantageous, since such heavy ions exhibit a pronounced Bragg peak, and it is therefore possible to introduce a specific radiation dose not only in a focused xy direction, but also to limit the dose input to a specific depth range (z direction).

[0006] Up to now, such particle beams (especially heavy-ion particle beams) have typically been produced using linear accelerators, particle cyclotrons, and / or particle synchotrons. However, the equipment required for such particle synchotrons is relatively complex, so efforts are underway to reduce this complexity. Furthermore, particle beams produced by linear accelerators, cyclotrons, or synchotrons have certain physical disadvantages. Additionally, such accelerators are very large relative to the amount of particles produced and are not very energy-efficient, resulting in correspondingly high installation and operating costs.

[0007] One proposed alternative method for generating particle beams, particularly heavy-ion beams, involves producing accelerated particles using a laser. In this process, a high-energy laser is directed onto a thin foil. The actual acceleration of the ions takes place immediately behind the thin foil, which is exposed to the laser light at an extremely high power density (typically in the range of 10⁻⁶). 21 Watt / cm 2 ) is irradiated. The heat energy deposited in the film as a result causes the ions to accelerate through thermal motion effects.

[0008] In this proposed accelerator concept, unlike particle synchrotrons or linear accelerators, ions are emitted in a bundle-like pattern from a essentially point-like starting position. Furthermore, an extremely broad spectrum of particle energies is generated. It is therefore desirable to focus the angularly fanned beam of radiation and, in addition, to filter out the usable energies. It would be particularly advantageous if the filtering were variable, thus enabling simple depth modulation when irradiating material (for example, patient tissue).

[0009] It has been shown that existing concepts for energy filtering of particle radiation generally have significant shortcomings, especially when used in conjunction with laser-targeted particle accelerators. DE10323654A1 describes an energy filtering device that spectrally spreads the radiation generated by a laser-targeted particle accelerator using scattering foils or magnets and selects the high-energy particles using collimators.

[0010] DE102007054919B4 discloses an energy matching device for an ion beam of sharply defined energy, wherein the beam is directed by means of a dipole magnet onto a wedge-shaped absorber which attenuates the energy of the ion beam in a defined manner.

[0011] DE102005063220A1 describes a device for irradiating tumor tissue, in which a particle beam generated by a particle accelerator is deflected by means of a raster scanning device consisting of two pairs of magnets in order to scan the tumor tissue slice by slice. US2002 / 0014588A1 discloses a cyclic particle accelerator for medical applications and components for beam guidance. DE102005012059A1 discloses a hollow body made of aluminum for focusing a proton beam, wherein the hollow body is irradiated by a second laser beam to generate an electric field in the hollow body.

[0012] US2006 / 0219915A1 describes an imaging system that uses a low-energy particle beam and methods for generating a high probe current.

[0013] US2002 / 0094389A1 describes a device for producing a thin film on a substrate, wherein a plasma is generated from a target using a laser, which is guided to the substrate with a ring-shaped permanent magnet and a deflecting magnet and deposited there.

[0014] It is therefore an object of the invention to propose an energy filter device for radiation, in particular an energy filter device for particle radiation, preferably of charged particles, which is improved compared to known energy filter devices. A further object of the invention is to propose a particle radiation source, in particular a particle radiation source for providing particle radiation with specific energies, which is improved compared to known particle radiation sources. A further object of the invention is to propose a method for the energy-dependent filtering of radiation, in particular of particle radiation, preferably of charged particles, which is improved compared to known methods.

[0015] The problem is solved by an energy filter device according to claim 1. It is proposed to design an energy filter device for radiation, comprising at least one focusing device and at least one radiation separation device, such that the at least one focusing device is configured as an energy-dependent focusing device. The energy filter device for radiation is an energy filter device for charged particle radiation. The charged particles can be, for example, leptons and / or hadrons. By way of example, electrons, protons, mesons, pions, neutrinos, antiprotons, and / or ions, such as hydrogen, helium, nitrogen, oxygen, carbon, and neon, may be mentioned here.Of course, it is also possible to use a mixture of different ions and / or other charged particles, especially the aforementioned particles. The energy filter device can perform a filtering function in any desired way. In particular, it is conceivable that only ions within a specific energy range are allowed to pass through. This energy range can be closed on both sides, or closed on only one side (for example, allowing only particles up to a certain energy, or conversely, allowing only particles above a certain energy). It is also possible that not only ions within a specific energy range are allowed to pass through, but conversely, ions within a specific energy range are filtered out, while ions with all other particle energies are allowed to pass through.Naturally, the filtering need not be limited to a single area; multiple pass-through windows and / or blocking windows can be provided. Furthermore, the filter curves can have essentially any shape. For example, they can be rectangular filter curves, which may be flattened and / or smeared on one or both sides. They can also be Gaussian filter curves. In particular, they can be Gaussian filter curves with a flat top. Hybrid forms of different filter curves are also conceivable. A focusing device can be understood to be essentially any device that enables a certain degree of focusing (especially in the sense of a converging lens), at least temporarily and / or at least in certain areas.

[0016] In particular, focusing devices can make it possible to convert at least a certain portion of radiation, especially radiation consisting of ions, emanating from a point source, into a parallel beam and / or to concentrate a parallel beam onto a focal point (or several focal points). This also includes, in particular, the possibility that the radiation emanating from a point source is diffracted in such a way that it is focused onto a different focal point (or several focal points). As already mentioned, this focusing effect need not necessarily be complete, but can be limited, in particular, to certain energy ranges, to certain local areas of the focusing device, and the like. This "limitation" includes, on the one hand, the possibility that, for example, the focal point (orMultiple focal points for different energies and / or different spatial regions "wander," and / or focusing is not possible in certain spatial regions and / or at certain energies. A radiation separation device is understood to be a device that separates the radiation in a specific way, whereby a "division process" occurs in which the two (or multiple) different sub-regions are attenuated (attenuated; absorbed) to varying degrees, with some sub-regions being virtually unattenuated while others are attenuated almost completely or to a negligible level. Of course, other treatments are also conceivable, such as directing a specific frequency range into a frequency multiplier range, or the like.An energy-dependent focusing device means, in particular, that the focusing for different energies of the radiation occurs in different ways. This means—as explained above—that focusing for different energies takes place at different locations (possibly even at multiple locations). It is also possible that no focusing occurs for certain energy ranges, while such focusing does or can occur for other energy ranges. Through the proposed "combined effect" of focusing on the one hand and energy-dependent focusing on the other, it is possible to perform both radiation focusing and a filtering process using the same components (or using some—possibly jointly designed—subcomponents).This allows for a reduction in the overall complexity of the energy filter device. Furthermore, the smaller number of components saves energy and typically reduces (undesirable) imaging errors. Additionally, the overall size of the device can usually be significantly reduced. The energy-dependent focusing effect of the energy-dependent focusing device can be described—analogous to optics—as "chromatic focusing" or "chromatic aberration." The aforementioned "combined effect" proves particularly advantageous in conjunction with components where both effects must be utilized.For example, laser-target particle accelerators are a good example, where, on the one hand, focusing of the particle radiation emitted in a beam-like manner from a point-like source is required, especially to achieve an effective yield of the radiation generated by the laser-target particle accelerator (and thus to be able to achieve an acceptably high emittance of the system), and on the other hand, energy filtering must also be carried out, since such laser-target accelerators have an extremely wide energy dispersion due to their function.

[0017] It is proposed to design the energy filter device with exactly one or exactly two radiation separation devices. Initial calculations have shown that, surprisingly, for both a filter that only allows energies above or below a certain threshold energy to pass through (where the transition at the threshold energy can be "gradual") and for energy filter devices that allow (or block) one or more energy ranges, a single, or possibly even two, radiation separation devices are entirely sufficient for the task at hand. The small number of radiation separation devices reduces the complexity, size, and cost of the energy filter device.Furthermore, a smaller number of components (especially radiation separation devices) typically leads to improved output quality of the filtered radiation, as fewer error factors typically influence the radiation "processing." Accordingly, such a setup can prove particularly advantageous.

[0018] Furthermore, it is proposed that the energy filter device include at least one variable radiation separation device and / or at least one slidably arranged radiation separation device. If the radiation separation device is slidable, it can, in particular, be slid along the "optical axis" of the energy filter device. This is especially advantageous because such longitudinal displacement allows different "focusing points" to be reached, and thus different energies or energy ranges to be selected. This makes it possible to vary the energy level relatively quickly and easily with the energy filter device.Such energy variation is required, for example, in depth-modulated scanning techniques used in materials processing and / or in medical applications (such as tumor therapy). It is also possible, however, to use the longitudinal adjustment to at least partially compensate for variations in the control of the focusing device (e.g., current fluctuations). This, too, can prove advantageous. Additionally or alternatively, movement of the radiation separation device in other directions is also possible (especially in the x-direction or y-direction), and rotations of the radiation separation device may also be beneficial.In a variable radiation separation device, it is advantageous to change the length and / or diameter of the device (especially if it has a radiation separation effect due to its mechanical shape). For example, increasing the aperture (diameter) of a radiation separation device can increase or decrease the energy range that passes through the energy filter. Additionally or alternatively, it is also conceivable that such an increase or decrease in the aperture (or any other change) of the radiation separation device is at least partially compensated for by a displacement of the radiation separation device and / or a change in another component, such as, in particular, the focusing device.Such a design can also significantly increase the flexibility and applicability of the energy filter device.

[0019] In the energy filter device, at least one focusing device is configured as a magnetic field generating device and as a solenoid device. Furthermore, it is proposed that in the energy filter device, at least one focusing device is configured as a magnetic field generating device, and in particular comprises at least one, preferably a plurality, of magnetic dipole devices and / or at least one, preferably a plurality, of magnetic quadrupole devices, particularly preferably a diplet and / or a triplet and / or a quadruplet and / or a multiplet of quadrupole devices and / or at least one, preferably a plurality, of Helmholtz coil devices and / or at least one, preferably a plurality, of superconducting magnetic field generating devices and / or at least one, preferably a plurality, of normal-conducting magnetic field generating devices.Magnetic fields, in particular, have proven especially advantageous for deflecting specifically charged particles. Accordingly, the use of magnetic field-generating devices proves beneficial. Furthermore, the explicitly mentioned devices have proven suitable and generally advantageous for deflecting particles, especially charged ones. In particular, the use of quadrupole devices (especially multiple quadrupole devices) is advantageous when relatively small angular ranges need to be focused. Solenoid devices have proven particularly advantageous when comparatively large angular ranges need to be focused. Typically, solenoid devices are elongated coil devices, often in the form of an air-core coil, through which the particle beam passes along the coil's length.As a rule, such solenoids also exhibit good focusing properties when used individually. Furthermore, the interaction of particles, especially charged ones, with magnetic fields is generally energy-dependent, particularly when the particle direction and the magnetic field direction are suitably aligned. In this way, energy-dependent focusing devices can be designed in a particularly simple manner using magnetic field generating devices, especially those mentioned above. The use of superconducting coils can prove particularly advantageous when comparatively strong magnetic fields are to be generated, which are also required to be relatively constant. In contrast, normally conducting magnetic field generating devices are particularly advantageous when the magnetic fields to be generated are to fluctuate over a particularly large range.Of course, a combination of superconducting and normal-conducting magnetic field generating devices is also conceivable, in particular such that a strong magnetic field (which is typically generated by the superconducting magnetic field generating device) is superimposed and thereby "modulated" by a smaller, time-varying magnetic field (which is typically generated by a normal-conducting magnetic field generating device).

[0020] Furthermore, it can be advantageous to provide a plurality of focusing devices and / or a plurality of magnetic field generating devices in the energy filtering device, wherein the focusing devices and / or the magnetic field generating devices act at least partially and / or at least in certain areas in different directions. When using a plurality of focusing devices or magnetic field generating devices, it may be possible to make a single focusing device / magnetic field generating device smaller or weaker and still achieve the desired overall effect in combination with other focusing devices / magnetic field generating devices.Furthermore, it is possible (especially when using quadrupole devices) to achieve deflection in different directions, which can also be focusing, by employing multiple focusing devices and / or magnetic field generation devices. In this way, for example, the entire xy-plane can be focused onto a single point (possibly also onto a straight line or the like), thus significantly increasing the overall acceptance of the device and the overall emittance of the ultimately generated beam. As already mentioned, the focusing need not necessarily be symmetrical (especially rotationally symmetrical). On the contrary, n-fold symmetry can be considered, particularly with n = 2, 3, 4, 5, 6, 7, 8, and so on. However, it is also fundamentally possible to design the energy filtering device so that it focuses only in a single direction.

[0021] Furthermore, it is preferred if, in the energy filter device, the energy dependence of at least one focusing element manifests itself at least temporarily and / or at least partially and / or at least regionally as a shift of the focal point, particularly as a longitudinal shift of the focal point. Such a shift of the focal point is especially advantageous when using radiation separation devices, as these can be designed to be spatially resolved (or spatially dependent) in a comparatively simple manner. The overall design of the energy filter device can then be particularly simple. In particular, for example, it is possible for the radiation separation device to be designed as a simple boundary wall with a boundary edge. This is correspondingly simple.

[0022] Furthermore, it can prove advantageous if at least one radiation separation device in the energy filtering device is designed, at least in certain areas and / or at least partially, as a section-by-section absorber. Experience has shown that the energy ranges to be separated by the energy filtering device are generally not practical to use "on-site." Accordingly, absorption ("elimination") of the corresponding energy ranges is particularly useful and, moreover, usually very easy to implement (for example, by simply providing a compact, radiation-impermeable material).

[0023] Furthermore, it can prove particularly advantageous if, in the energy filter device, at least one radiation separation device is designed at least partially and / or at least in some areas as an aperture device and / or at least partially and / or at least in some areas as an axial absorber device, wherein the at least one aperture device and / or the at least one axial absorber device is provided at least partially and / or at least in some areas with oblique-beam optimized surfaces and / or at least partially and / or at least in some areas has a frustoconical and / or a double frustoconical surface. In the simplest case, an aperture device can be a type of hole formed in a solid material. It is not necessary for the hole size to be variable; however, it is advantageous if this is made possible, particularly through suitable design measures.An axial absorber device can be designed, in particular, as a type of rod, which is preferably arranged in the center of the optical axis. Preferably, the rod can have a frustoconical shape. The (frustoconical) rod can be used, in particular, to provide (additional) attenuation for excessively high and / or excessively low energy ranges. However, it can often prove entirely sufficient to provide a single aperture device to allow a specific energy range to pass through while attenuating the remainder. It should be noted, for the sake of completeness, that entirely different principles and / or designs can, of course, be employed.The term "oblique-beam optimized surface" refers specifically to a surface that is positioned at an angle and / or in such a way that a particle beam with a permissible energy (especially the maximum and / or minimum value of the particle energy) travels along the surface in a kind of "parallel incidence," at least in certain areas. This has the advantage that if the particle beam exceeds the permissible limit, it has to travel a particularly long distance through the material and is therefore significantly attenuated. With such a design, a particularly sharp separation is generally possible. Additionally or alternatively, this type of design can also effectively prevent "contamination" by secondary particles (for example, released photons, neutrons, electrons, and the like).This is correspondingly advantageous. Truncated cone-shaped and / or double-truncated cone-shaped surfaces generally prove to be particularly suitable for oblique-jet-optimized surfaces. These can both define the outer boundaries of a solid body and define the boundaries of a hollow body within a block of material (or possibly a combination thereof).

[0024] Furthermore, it can be advantageous if the energy filter device includes at least one radiation separation device, which is designed as a direction-dependent radiation separation device, in particular as an angle-direction-dependent radiation separation device. This means that the radiation separation device can separate and / or allow (or attenuate) different energy bandwidths in different directions. This is possible, for example, with radiation separation devices that are not rotationally symmetrical or are not rotationally symmetrical. If the radiation separation device is designed, for example, as an aperture device, such directional dependence can be formed in the form of a hole with several additional radially outward-facing recesses.For example, one, two, three, four, five, six, seven, eight, nine, ten, or even more additional recesses, preferably extending radially outwards, can be considered. With such a directional dependency (which can generally be partially eliminated by subsequent components, particularly by one or more downstream scattering films), it is especially possible not only to generate a directional dependency but also (ultimately) to realize an additional or alternative energy dispersion, which can also be designed in such a way as to result in a desired energy distribution. A Gaussian energy distribution is a particularly preferred one in this context, although other forms are conceivable and may also be advantageous.However, a Gaussian superposition usually has the advantage, particularly in medical applications, that such a superposition of several Gaussian curves within a scanning process (which in particular includes a depth scan) and the overlapping radiation inputs proves to be advantageous.

[0025] Furthermore, it can prove advantageous if the energy filter device includes at least one upstream radiation separation device, which in particular separates the radiation with respect to the solid angle range of the radiation entering the energy filter device. Such a radiation separation device effectively prevents, for example, the (usually undesirable) "bombardment" of parts of the focusing device (e.g., a solenoid) and the like. This, in turn, prevents the formation of secondary particles such as electrons, neutrons, and the like. Damage to the corresponding components that would otherwise be "bombarded" can also be avoided.

[0026] It is further advantageous if the energy filter device has at least one radiation scattering device, particularly for outgoing radiation, which is preferably designed as a scattering foil device, and / or if the energy filter device is provided with at least one downstream focusing device, particularly for the radiation exiting the energy filter device. When using a scattering foil device, any undesired spatial distributions (which are particularly asymmetrical or rotationally symmetrical) and / or undesired "energy edges" that may arise from the filtering process can be smoothed out. Depending on the design (particularly with regard to material and / or material thickness) of the scattering foil, this smoothing can vary in degree.By using an output focusing device, it is particularly possible to parallelize the outgoing radiation, which is usually especially advantageous, particularly when it has to be transported over a longer distance.

[0027] A particle radiation source is further proposed, comprising at least one target device and one energy filter device of the aforementioned design. The particle radiation source can be, in particular, a source for providing particle radiation with specific energies. The target device (which can be, for example, a target foil or the like) can be, in particular, a laser target device, i.e., a target device irradiated by a typically very powerful laser. The resulting particle radiation source can then exhibit the previously mentioned features, properties, and advantages in at least an analogous manner. Further development of the particle radiation source in the manner described above is, of course, also possible.

[0028] Furthermore, a method for energy-dependent filtering of radiation according to claim 14 is proposed, in which the radiation is split using at least one energy-dependent focusing device and subsequently radiation with a desired energy is separated by means of at least one radiation separation device. The radiation is particle radiation, wherein the particles are charged particles. The method exhibits, at least by analogy, the advantages, properties, and features already mentioned in connection with the energy filtering device. In addition, the method can also be modified in accordance with the preceding description.

[0029] Finally, the use of an energy-dependent focusing device for the energy-dependent filtering of particle radiation from charged particles, according to claim 15, is also proposed, wherein the radiation is split using the energy-dependent focusing device and subsequently radiation with a desired energy is separated by means of at least one radiation separation device. The proposed use allows the properties, features, and advantages already described above to be achieved, at least by analogy. Furthermore, the proposed use can be extended or modified, at least by analogy, in accordance with the preceding description.

[0030] The invention will now be explained in more detail with reference to advantageous embodiments and the accompanying drawing. The figures show: Fig. 1: A first embodiment of a particle beam source in schematic view; Fig. 2: a second embodiment of a particle beam source in a schematic view; Fig. 3: a typical transmission curve for the in Fig. 2 particle beam sources shown: Fig. 4: A modified particle aperture for use in a particle beam source in a schematic front view; Fig. 5: A typical energy distribution curve when using the in Fig. 4 particle aperture shown; Fig. 6: a possible embodiment of an energy selection process.

[0031] In Fig. Figure 1 shows a schematic top view of a particle beam source 2 from the side. The particle beam source 2 serves to generate a (heavy) ion particle beam (output beam 16; for example, consisting of carbon ions) that can be used in a medical facility for the irradiation of tumors. To meet the comparatively high requirements of medical applications, the particles 3 of the output beam 16 released by the particle beam source 2 must also meet comparatively high requirements. In particular, the released particle beam 16 must be largely parallel, i.e., form a so-called "pencil beam" (pencil-thin particle beam 16). Furthermore, the particles 3 contained in the particle beam 16 must lie within a comparatively narrow energy range.

[0032] The "classical" and currently most frequently used method for generating such a particle beam suitable for medical purposes involves the use of linear accelerators, usually in combination with particle synchrotrons. However, such facilities are comparatively complex, expensive, energy-intensive, and also have a large volume, which in particular must be shielded from the environment to prevent environmental contamination by particle radiation (especially neutrons and / or radioactive radiation).

[0033] In contrast, particle beam source 2 is based on a different acceleration principle, namely laser-induced particle acceleration. The actual accelerator stage 4 (in Fig. (1 on the left) also features a very powerful high-performance pulse laser 5, which typically has a power density of approximately 10 21Watt / cm 2The thin laser beam 6 generated by the laser 5 is directed at a target foil 7. The laser beam 6 strikes the target foil 7 in a small, essentially point-like area (impact area 8). The actual acceleration area 9, which is also essentially point-like, lies on the side of the target foil 7 opposite the impact area 8, and directly adjacent to the target foil 7. Due to the amount of energy introduced by the laser bombardment, extreme heating occurs in the accelerator area 9, so that a diverging beam 10 is released from the essentially point-like accelerator area 9. The diverging beam 10 is represented here by four lines drawn symmetrically to the central axis 11. The diverging beam exhibits an essentially continuous intensity distribution, which decreases with increasing angle from the central axis 11.In addition to the angular broadening of the generated beam 10, the released particles 3 within the beam 10 exhibit a large energy variation. At the stated laser power, for example, particle energies in the interval between 0 MeV and 250 to 300 MeV are to be expected for protons.

[0034] To achieve the highest possible particle fluence (in other words, to "lose" as few of the generated particles as possible), the diverging beam 10 is focused by a solenoid coil 12. The solenoid 12 used is similar in its deflection properties to an optical converging lens that exhibits a strong chromatic aberration. This means that particles 3 of different energies are focused at different distances from the solenoid 12 (or from the target foil 7) onto a focal point 13, 14. Fig. Figure 1 shows, for illustrative purposes, two focal points 13 of particles with a “wrong” energy (more precisely: an energy that is too low), as well as one focal point 14 for particles with the “correct” energy.

[0035] How to Fig. Since the particles 3 converge at a "false" focal point, which can be clearly seen from the initial particle beam 16, they converge at a focal point 13 located on (or within) the axially arranged, rod-shaped absorber 15. Accordingly, the corresponding low-energy particles 3 are attenuated by the rod-shaped absorber 15 and thus "filtered out" of the initial particle beam 16. A more advantageous embodiment is achieved when the rod-shaped absorber 15 is conical, thus exhibiting a shape optimized for oblique beams.

[0036] Furthermore, a pinhole aperture 17 with a centrally located circular hole 18 is provided. Particles 3 possessing the desired target energy are focused by the solenoid 12 at a focal point 14 located in the center of the circular hole 18 of the pinhole aperture 17. The corresponding particles 3 can thus (after passing the rod-shaped absorber 15) pass through the circular hole 18 of the pinhole aperture 17 essentially without attenuation. The same applies to particles 3 with an energy that deviates slightly from the target energy, since the circular hole 18 has a specific size.

[0037] However, particles with energies above the upper limit mostly collide with a region of the aperture 17 that lies outside the outermost aperture 18. Accordingly, such high-energy particles 3 are attenuated by the aperture 17.

[0038] The particles 3 passing through the aperture 17 (i.e., particles with a "correct" energy) are directed onto a scattering foil 19 behind the aperture 17. This foil is typically made of a plastic material and has a thickness of one to a few millimeters. The scattering foil 19 causes a smearing of the filter curve, so that the edges of the filter curve are less steep. In addition, the scattering foil 19 also causes a certain, typically relatively small, angular scattering of the individual particle partial beams 3. Since the particles 3 exiting the scattering foil 19 exhibit a certain (albeit comparatively small) angular scattering, another solenoid 20 is connected downstream of the energy filter 1, which forms a thin, parallel particle beam 16 from the slightly diverging particle beam 3.Additionally, the aperture 17 can be shifted along the central axis 11 of the energy filter 1 (this can be achieved, for example, by a linear motor or a stepper motor using a rack and pinion). The shiftability of the aperture 17 is indicated by a shift arrow 21. By shifting the aperture 17, the energy of the particles 3 passing through the energy filter 1 can be changed. Accordingly, the energy of the particle beam 16 exiting the energy filter 1 can be varied. Such a change in particle energy is necessary, for example, to vary the depth of the Bragg peak in a target material (e.g., in a tissue). Additionally or alternatively, such an energy variation can also be achieved by changing the strength of the magnetic field in the solenoid 12.

[0039] Furthermore, in Fig. Arrows 22 indicating size changes are shown. These symbolize that the size of the circular hole 18 in the aperture 17 is variable. This can be implemented, for example, in the manner of an iris diaphragm or similar device. By changing the size of the circular hole 18 in the aperture 17, it is possible to increase or decrease the width of the filter curve (and thus the width of the energy range transmitted). In particular, this also makes it possible to keep the relative width of the energy range essentially constant when the energy level transmitted is changed. Such adjustability is typically desirable in medical devices.

[0040] The initial particle beam 16 generated and released by the particle beam source 2 can then be directed to a treatment room, in particular to a patient (not shown) located in the treatment room, in a manner known per se.

[0041] In Fig. 2 is opposite Fig. Figure 1 shows a modified version of a particle beam source 24. The main difference lies in the different design of the energy filter 23.

[0042] First, - analogous to the in Fig. 1 particle beam source 2 shown - the laser beam 6 generated by a laser 5 is directed onto a target foil 7, so that a diverging particle beam 10 with particles 3 of different energies and output angles is generated.

[0043] The diverging particle beam 10 is first directed towards a stopper block 25. This block is made of a highly energy-absorbing material (e.g., lead) and has a truncated cone-shaped recess 26 centered on the center line 11. The recess is shaped to prevent particle radiation 3 from striking the surfaces of the (activated) solenoid assembly 27. This protects the solenoid assembly 27 and also prevents the generation of secondary radiation (gamma radiation, electron radiation, neutron radiation, and the like). The truncated cone-shaped recess 26 is shaped such that the apex of the cone would lie within the point-like accelerator region 9. Accordingly, the surface of the recess 26 runs parallel to the particle beams 3 and is directly adjacent to the surface of the recess 26. In other words, the recess 26 is optimized for oblique beams.Particle beams 3 with a slightly smaller angle than the angle of the recess 26 pass through the stopper block 25 unimpeded. Particle beams 3 with a slightly larger angle, on the other hand, pass completely through the thickness of the stopper block 25 and are therefore sufficiently attenuated.

[0044] In the present embodiment of the particle filter 23, the solenoid assembly 27 consists of a superconducting coil 28 and a normal-conducting coil 29. In this embodiment, the two coils 28, 29 of the solenoid assembly 27 are arranged concentrically to each other. However, a series arrangement along the central axis 11 of the energy filter 23 would also be conceivable. The superconducting solenoid 28 generates a strong, but constant, magnetic field. With the aid of the normal-conducting solenoid 29, an additional, particularly time-varying, magnetic field can be superimposed on this magnetic field. This allows the (energy-dependent) focus of particles 3 of a specific energy to be shifted along the central axis 11 of the energy filter 23 by means of electrical measures. In particular, this allows the energy filter properties of the energy filter 23 to be varied.

[0045] In the exemplary embodiment of the energy filter 23 shown here, an aperture block 30 is provided. The aperture block 30 has a frustoconical recess 31 inside it. The recess 31 is shaped such that it runs parallel to particles 3 with the highest permissible (unattenuated) energy and the lowest permissible (unattenuated) energy, respectively. Accordingly, the surface of the recess 31 of the aperture block 30 is optimized for oblique beams. Here, too, the effect—as already explained—is that either no attenuation occurs or attenuation occurs over the entire length of the aperture block 30.

[0046] As indicated by the displacement arrow 21, the aperture block 30 can also be displaced parallel to the central axis 11 in the present embodiment of the energy filter 23. If necessary, the recess 31 can also be modified (particularly with regard to size and / or shape).

[0047] The particles 3 leaving the aperture block 30 are directed onto a scattering film 19 (analogous to the one in Fig. The particles are fed into the energy filter 1 shown in the diagram, where they are slightly processed and their energy ranges are smeared out. Subsequently, the particles 3 are "parallelized" to form a parallel beam 16 in a downstream solenoid 20.

[0048] In Fig. Figure 3 shows a typical energy spectrum of an output particle beam 16. The particle energy in MeV is shown along the abscissa 32, and the relative transmission along the ordinate 33. As can be seen, the filter curve 34 has flattened lateral flanks 35 (particularly due to the permeability of the circular hole 18 and the influence of the scattering foil 19) and a flat plateau 36.

[0049] For some applications, the flat plateau 36 of the filter curve 34 is undesirable. Particularly when treating a tumor with a raster scan application using a pencil-thin particle beam, it is desirable for the filter curve to have a Gaussian profile. This is because the superposition of different Gaussian profiles results in another Gaussian profile, allowing for more precise and simpler calculations for treatment planning—and thus for the subsequent actual treatment.

[0050] To the in Fig. To make the filter curve 34 shown “gauss-like”, it is possible to use an aperture block 37 instead of an aperture block 30 with an essentially circular recess 31, which has a suitably designed passage cross-section 38.

[0051] One possible embodiment of an aperture block 37 with a suitable recess 38 is shown in Fig. Figure 4 shows the aperture block 37 in a schematic cross-section. The cross-sectional plane is perpendicular to the central axis 11 of the energy filter. For example, the aperture block 37 can be used instead of the aperture block 30 of the [unclear - possibly a reference to a specific component or element]. Fig. The energy filter shown in section 23 is used.

[0052] As can be seen, the recess 38 has a central hole 39. At the outer edge of this central hole 39, four club-shaped extensions 40 of the recess 38 are visible. Of course, it is possible that a different number of club-shaped extensions 40 are used. In this case, the club-shaped extensions 40 are all identically shaped; however, it is quite conceivable that the club-shaped extensions 40 could be shaped differently.

[0053] Due to the special shape of the club-shaped extensions 40, it is possible that no sharp cut-off edge occurs with respect to energy, but rather that different energies with different percentage proportions can pass through the aperture block 37. The in Fig. The recess shown in section 4 is designed in such a way that the filter curve 41 ultimately has an approximately Gaussian shape (see Fig. 5) results.

[0054] When shaping the recess 38 (especially the club-shaped extensions 40), care must be taken to ensure that the relative transmission of a group of particles to the energy with associated radius R b the relationship T = F(R B ) / (R B 2 × π) is given, where F B = F(R B ) the area within recess 38 that is not covered by absorber material.

[0055] Furthermore, the recess 38 is shaped in such a way that a surface optimized for oblique jet flow is again obtained. For cross-sections that are in front of or behind the central axis 11 in the direction of the recess 38, Fig. The recess 38 must be made correspondingly larger or smaller depending on the cross-sectional plane shown in section 4.

[0056] Finally, in Fig.Section 6 briefly describes a method 42 for the energy-dependent filtering of particle radiation 3 of charged particles. In a first process step 43, the electrically charged particles 3, generated, for example, by a high-energy laser 5 in conjunction with a target 7, are focused onto a suitable focal point 14 by a suitable device (for example, one or more solenoids 12, 27, 28, 29). In a second process step 44, the particles 3 focused onto the focal point 14 are separated from the other particles 3 (preferably attenuating the other particles 3). Thus, at the end 45 of the method 42 (which can, of course, be further modified), a focused particle beam 16 with particles 3 of suitable energy is obtained. Reference symbol list: 1 Energy filter 2 particle beam source 3 particles 4 Accelerator Stage 5 lasers 6 Laser beam 7 Target slide 8 Impact area 9 Accelerator area 10 Diverging beam of rays 11 Central axis 12 Solenoid coil 13 Focal point (false energy) 14 Focal point (correct energy) 15 Rod-shaped absorbers 16 Initial particle beam 17 pinhole aperture 18 Roundish 19 scatter foil 20 Solenoid 21. Displacement arrow 22 Size change arrow 23 energy filters 24 particle beam source 25 Stopper block 26 Exclusion 27. Solenoid arrangement 28 Superconducting solenoid 29 Normal conducting solenoid 30 aperture block 31 Exclusion 32 Abscissa 33 ordinates 34 Filter curve 35 Flank 36 Plateau 37 Aperture Block 38 Exclusion 39 central hole 40 expansions 41 Filter curve 42 Methods for energy-dependent filtering of radiation 43 Focusing on the focal point 44 Separation of particles

Claims

[1] Energy filter device (1, 23) for focusing and energy filtering the radiation from charged particles (3) generated by a laser target particle accelerator, comprising at least one energy-dependent focusing device (12, 20, 27, 28, 29) configured such that the focusing of particles of different energies takes place at different locations, and at least one radiation separation device (15, 17, 30, 37) configured such that it does not attenuate parts of the particle beam and attenuates other parts of the particle beam completely or to a negligible level, wherein the at least one energy-dependent focusing device (12, 20, 27, 28, 29) is arranged in the direction of radiation in front of the at least one radiation separation device (15, 17, 30, 37) and is configured as a solenoid device. [2] Energy filter device (1, 23) according to claim 1, characterized byexactly one or exactly two radiation separation devices (15, 17, 25, 30, 37). [3] Energy filter device (1, 23) according to claim 1 or 2, characterized by at least one variable radiation separation device (17, 30) and / or at least one slidably arranged radiation separation device (17, 30, 37). [4] Energy filter device (1, 23) according to one of the preceding claims, characterized by a plurality of focusing devices (12, 20, 27, 28, 29) wherein the focusing devices (12, 20, 27, 28, 29) act focusing in different directions. [5] Energy filter device (1, 23) according to one of the preceding claims, characterized by , that in at least one focusing device (12, 20, 27, 28, 29) the energy dependence (13, 14) of the focusing manifests itself as a shift of the focal point (13, 14), in particular as a shift of the focal point (13, 14) in the longitudinal direction (11). [6] Energy filter device (1, 23) according to one of the preceding claims, characterized by , that at least one radiation separation device (15, 17, 25, 30, 37) is designed as a section-wise absorber device (15, 17, 25, 30, 37). [7] Energy filter device (1, 23) according to one of the preceding claims, characterized by , that the at least one radiation separation device is designed as an aperture device (17, 25, 30, 37) and / or as an axial absorber device (15), wherein the at least one aperture device (17, 25, 30, 37) and / or the at least one axial absorber device (15) is provided at least partially with obliquely beam-optimized surfaces (26, 31, 38). [8] Energy filter device (1, 23) according to one of the preceding claims, characterized by, that the at least one radiation separation device is designed as an aperture device (17, 25, 30, 37) and / or as an axial absorber device (15), wherein the at least one aperture device (17, 25, 30, 37) and / or the at least one axial absorber device (15) has at least partially a frustoconical (26) and / or a double frustoconical surface (31). [9] Energy filter device (1, 23) according to one of the preceding claims, characterized by , that at least one radiation separation device (15, 17, 25, 30, 37) is designed as a direction-dependent radiation separation device (25, 30, 37), in particular as an angle-direction-dependent radiation separation device (25, 30, 37). [10] Energy filter device (1, 23) according to one of the preceding claims, characterized byat least one upstream radiation separation device (25) which effects radiation separation (25) with respect to the solid angle range (10) of the radiation (3) entering the energy filter device (1, 23). [11] Energy filter device (1, 23) according to one of the preceding claims, characterized by at least one radiation scattering device (4, 19) for outgoing radiation (3, 16), which is preferably designed as a scattering foil device (19). [12] Energy filter device (1, 23) according to one of the preceding claims, characterized by at least one downstream focusing device (20) for the radiation (3, 16) emerging from the energy filter device (1, 23). [13] Particle radiation source (2, 24), in particular particle radiation source (2, 24) for providing particle radiation (3) with certain energies, comprising at least one target device (7), in particular at least one laser target device (5, 7), and at least one energy filter device (1, 23) according to one of claims 1 to 12. [14] Method for energy-dependent filtering of charged particle radiation (3), in which the radiation (3) is split using at least one energy-dependent focusing device (12, 20, 27, 28, 29) configured as a solenoid device such that the focusing of particles of different energies takes place at different locations, and subsequently radiation (3) with a desired energy is separated by means of at least one radiation separation device (15, 17, 30, 37) configured such that it does not attenuate parts of the particle beam and attenuates other parts of the particle beam completely or to a negligible level. [15] Use of an energy-dependent focusing device (12, 20, 27, 28, 29), which is configured as a solenoid device and such that the focusing of particles of different energies takes place at different locations, for the energy-dependent filtering of radiation (3) of charged particles, wherein the radiation (3) is split using the energy-dependent focusing device (12, 20, 27, 28, 29) and subsequently separated by means of at least one radiation separation device (15, 17, 30, 37), which is configured such that it does not attenuate parts of the particle beam and attenuates other parts of the particle beam completely or to a negligible level, into radiation (3) with a desired energy.

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