Abstract:
A deflection plate having a non-planar shape, for deflecting charged particles is provided. An associated method is also provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to PCT Application No. PCT/EP2012/060279, having a filing date of May 31, 2012, the entire contents of which is hereby incorporated by reference. 
     
    
     FIELD OF TECHNOLOGY 
       [0002]    The following relates to a deflection plate for deflecting charged particles, and a deflection device for deflecting charged particles. 
       BACKGROUND 
       [0003]    The deflection of moving charged particles by electric and/or magnetic fields is known. The generation of electric fields by applying electric voltages to conductive plates is also known. 
       SUMMARY 
       [0004]    An aspect relates to an improved deflection plate for deflecting charged particles. According to another aspect, embodiments of the invention include providing an improved deflection device for deflecting charged particles. 
         [0005]    A deflection plate according to embodiments of the invention for deflecting charged particles has a non-planar shape. Advantageously, compared to a planar deflection plate, this deflection plate generates an electric field with an improved spatial profile. 
         [0006]    In a preferred embodiment of the deflection plate, the latter is curved about an axis oriented in a first spatial direction. Then, a component, perpendicular to the first spatial direction, of an electric field generated by the deflection plate advantageously has a flatter profile in a further spatial direction perpendicular to the first spatial direction than is the case in a planar deflection plate. Advantageously, this simplifies the deflection of individual bunches of charged particles from a beam with a plurality of successive particle bunches. 
         [0007]    In a particularly preferred embodiment of the deflection plate, the latter has an arced shape like a cylinder lateral surface. Advantageously, research has shown that an arced shape like a cylinder lateral surface generates a particularly advantageous profile of the electric field. A further advantage consists of it being relatively simple to produce a deflection plate with an arced shape like a cylinder lateral surface. 
         [0008]    In an expedient embodiment of the deflection plate, the latter comprises a conductive material, more particularly a metal. Advantageously, the deflection plate can then be charged to an electric potential. 
         [0009]    A deflection device according to embodiments of the invention for deflecting charged particles comprises a first deflection plate of the aforementioned type. Advantageously, this deflection device can be used for deflecting charged particles of a particle beam. As a result of the advantageously embodied deflection plate, the deflection device then can be used for selective deflection of individual particle bunches from a beam of successive bunches of charged particles. 
         [0010]    In a preferred embodiment of the deflection device, the latter comprises a second deflection plate of the aforementioned type. Advantageously, a potential difference then can be generated between the deflection plates of the deflection device. 
         [0011]    In a particularly preferred embodiment of the deflection device, the second deflection plate is disposed in a mirror-imaged manner in relation to the first deflection plate. Advantageously, a particularly expedient spatial profile of an electric field then emerges between the two deflection plates of the deflection device. 
         [0012]    In a particularly preferred embodiment of the deflection device, the two deflection plates are respectively curved about an axis oriented in a first spatial direction. Here, the first deflection plate and the second deflection plate are spaced apart in a second spatial direction perpendicular to the first spatial direction. Moreover, the first deflection plate and the second deflection plate are disposed in a mirror-imaged manner in relation to a plane perpendicular to the second spatial direction. Advantageously, in the case of this deflection device, a component of an electric field pointing in the second spatial direction extends in a flat manner in a spatial direction perpendicular to the first spatial direction and to the second spatial direction. 
         [0013]    Particularly preferably, the concave surfaces of the deflection plates face one another. Advantageously, the field profile of the component of the electric field pointing in the second spatial direction then is flat in a third spatial direction perpendicular to the first spatial direction and to the second spatial direction, without the deflection plates of the deflection device needing to have a great length in the third spatial direction. 
         [0014]    In an additional development of the deflection device, the latter comprises a third deflection plate and a fourth deflection plate. Here, the third deflection plate is displaced in relation to the first deflection plate in a third spatial direction perpendicular to the first spatial direction and to the second spatial direction. Moreover, the fourth deflection plate is displaced in relation to the second deflection plate in the third spatial direction. Advantageously, a different potential difference can be applied between the third deflection plate and the fourth deflection plate than between the first deflection plate and the second deflection plate. 
         [0015]    Preferably, the deflection device is embodied to deflect a charged particle moving in the third spatial direction into the second spatial direction. Advantageously, the deflection device can then be used to selectively deflect individual particles or bunches of particles from a particle beam. 
     
    
     
       BRIEF DESCRIPTION 
         [0016]    Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein: 
           [0017]      FIG. 1  shows a schematic illustration of a particle therapy instrument; 
           [0018]      FIG. 2  shows a schematic illustration of an embodiment of a deflection device; 
           [0019]      FIG. 3  show a first section through an embodiment of a plate pair of the deflection device; 
           [0020]      FIG. 4  shows a top view of an embodiment of the plate pair of the deflection device; 
           [0021]      FIG. 5  shows a second section through an embodiment of the plate pair of the deflection device; 
           [0022]      FIG. 6  shows a first graph of a field strength profile within the plate pair; and 
           [0023]      FIG. 7  shows a second graph of the field strength profile within the plate pair. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]      FIG. 1  shows, in a schematic illustration, a particle therapy instrument  100  as an exemplary application for a deflection device. However, deflection devices can also be used in a multiplicity of other fields of application. Embodiments of the invention are by no means restricted to the field of particle therapy instruments. 
         [0025]    The particle therapy instrument  100  can be used for performing particle therapy, in which a diseased body part of a patient is bombarded with charged particles. By way of example, the charged particles can be protons. By way of example, the disease of the patient can be a tumor. 
         [0026]    The particle therapy instrument  100  comprises an ion source  110 , a bunching device  120 , a deflection device  130 , a stop  140  and a particle accelerator  150 , which are disposed in succession in a z-direction  103 . The ion source  110  serves for generating a beam  115  of charged particles. By way of example, the particles of the particle beam  115  can be protons. The particles of the particle beam  115  leave the ion source  110  in the z-direction  103 . By way of example, when leaving the ion source  110 , the particles of the particle beam  115  can have an energy of 10 keV to 20 keV. 
         [0027]    The bunching device  120  serves for subdividing the continuous particle beam  115  into discrete particle bunches  125 . The particle bunches  125  leave the bunching device  120  in the z-direction  103 . The bunching device  120  can also be dispensed with. 
         [0028]    The deflection device  130  serves to selectively deflect individual particle bunches  125  (or individual particles from the continuous particle beam  115 ) in relation to the movement thereof extending in the z-direction  103  in a y-direction  102  perpendicular to the z-direction  103 . 
         [0029]    Particles and particle bunches  125  deflected by the deflection device  130  do not, or do not completely, pass the stop  140  which follows the deflection device  130 , while the non-deflected particles and particle bunches  125  pass the stop  140 . In alternative embodiments of the particle therapy instrument  100 , only particles and particle bunches  125  deflected in the y-direction  102  by the deflection device  130  completely pass the stop  140 . 
         [0030]    Particles and particle bunches  125 , which pass the stop  140 , reach the particle accelerator  150 , where they are accelerated to a higher kinetic energy of e.g. 80 MeV to 250 MeV. By way of example, the particle accelerator  150  can be a linear accelerator. In particular, the particle accelerator  150  can be an RF linear accelerator. 
         [0031]      FIG. 2  shows a schematic illustration of the deflection device  130 . In the embodiment shown in  FIG. 2 , the deflection device  130  comprises eight deflection plates for deflecting the particle bunches  125  of charged particles. In detail, the deflection device  130  in the shown embodiment comprises a first deflection plate  210 , a second deflection plate  220 , a third deflection plate  230 , a fourth deflection plate  240 , a fifth deflection plate  250 , a sixth deflection plate  260 , a seventh deflection plate  270  and an eight deflection plate  280 . 
         [0032]    The first deflection plate  210  and the second deflection plate  220  form a first plate pair  201 . The third deflection plate  230  and the fourth deflection plate  240  form a second plate pair  202 . The fifth deflection plate  250  and the sixth deflection plate  260  form a third plate pair  203 . The seventh deflection plate  270  and the eighth deflection plate  280  form a fourth plate pair  204 . In other embodiments, the deflection device  130  may also comprise fewer than four plate pairs  201 ,  202 ,  203 ,  204  or more than four plate pairs  201 ,  202 ,  203 ,  204 . 
         [0033]    The plate pairs  201 ,  202 ,  203 ,  204  are disposed in succession in the z-direction  103 . The two respective deflection plates of each plate pair  201 ,  202 ,  203 ,  204  are situated at a respectively common position in the z-direction  103  and in an x-direction  101  perpendicular to the y-direction  102  and to the z-direction  103 , and are spaced apart in the y-direction  102 . The particle bunches  125  pass between the two respective deflection plates of the plate pairs  201 ,  202 ,  203 ,  204  in the z-direction  103 . 
         [0034]    The deflection plates  210 ,  220 ,  230 ,  240 ,  250 ,  260 ,  270 ,  280  consist of an electrically conductive material, preferably a metal, or at least comprise an electrically conductive material, for example in the form of a coating. 
         [0035]    A potential difference, and hence an electric field, can respectively be generated between the deflection plates of the plate pairs  201 ,  202 ,  203 ,  204  in order to deflect the particles of the particle bunches  125  moving in the z-direction  103  in the y-direction  102 . By way of example, a positive voltage could be applied to the first deflection plate  210  of the first plate pair  201  and a negative voltage with the same magnitude could be applied to the second deflection plate  220  of the first plate pair  201 . The potential differences generated in the various plate pairs  201 ,  202 ,  203 ,  204  can differ from one another. In order only to deflect individual particle bunches  125  of the particle bunches  125  following one another in quick time succession into the y-direction  102 , it is necessary to apply short-term voltage pulses to the deflection plates  210 ,  220 ,  230 ,  240 ,  250 ,  260 ,  270 ,  280 . 
         [0036]    A component pointing in the y-direction  102  of an electric field generated in a plate pair  201 ,  202 ,  203 ,  204  has a Gaussian profile in the z-direction  103  if the deflection plates  210 ,  220 ,  230 ,  240 ,  250 ,  260 ,  270 ,  280  are embodied as plane plates. However, it is more expedient if the profile of the component of the electric field pointing in the y-direction  102  has an approximate rectangle function in the z-direction  103  within a plate pair  201 ,  202 ,  203 ,  204 . In order to approximate this preferred spatial profile of the component of the electric field pointing in the y-direction  102 , the deflection plates  210 ,  220 ,  230 ,  240 ,  250 ,  260 ,  270 ,  280  of the deflection device  130  in each case have a non-planar geometry. This will be explained below on the basis of  FIGS. 3 to 5 , which show representations of the first plate pair  201 . The remaining plate pairs  202 ,  203 ,  204  preferably have an identical design to that of the first plate pair  201 . 
         [0037]      FIG. 3  shows a first section through the first plate pair  201 . Here, the section extends perpendicular to the z-direction  103 . The first deflection plate  210  and the second deflection plate  220  of the first plate pair  201  have a width  301  in the x-direction  101 . By way of example, the width  301  can be 4 mm. The deflection plates  210 ,  220  respectively have a thickness  302  in the y-direction  102 . By way of example, the thickness  302  can be 0.1 mm. In the y-direction  102 , the first deflection plate  210  and the second deflection plate  220  have a distance  312  from one another. By way of example, the distance  312  can be 6 mm. 
         [0038]      FIG. 4  shows a top view of the first deflection plate  210  of the first plate pair  201  in a viewing direction opposing the y-direction  102 . The first deflection plate  210  has a length  303  in the z-direction  103 , which may be e.g. 4 mm. The second deflection plate  220  of the first plate pair  201  preferably has the same length  303  in the z-direction  103  as the first deflection plate  210 . 
         [0039]      FIG. 5  shows a second section through the deflection plates  210 ,  220  of the first plate pair  201 . In  FIG. 5 , the section is perpendicular to the x-direction  101 . Each one of the deflection plates  210 ,  220  is curved about an axis parallel to the x-direction  101 . Here, the curvature preferably follows a circular arc, such that the deflection plates  210 ,  220  have a design that is arc shaped like a cylinder lateral surface. Here, the deflection plates  210 ,  220  each have a radius of curvature  313 . By way of example, the radius of curvature  313  may lie between 1 mm and 4 mm. The curved deflection plates  210 ,  220  each have a concave surface  510  and a convex surface  520 . The concave surfaces  510  of the deflection plates  210 ,  220  face one another. 
         [0040]      FIG. 6  shows, in a first graph  600 , spatial field strength profiles which emerge in the case of different radii of curvature  313  of the deflection plates  210 ,  220 ,  230 ,  240 ,  250 ,  260 ,  270 ,  280 . The z-direction  103  in the region of a plate pair  201 ,  202 ,  203 ,  204  is plotted on a horizontal axis of the first graph  600 . A component  601  of an electric field strength pointing in the y-direction  102  is plotted on a vertical axis of the first graph  600 . 
         [0041]    A first field profile  610  specifies the profile of the electric field strength in the y-direction  102  in the case of a very large radius of curvature  313  of 1000 mm, which is selected in an exemplary manner. Such a large radius of curvature  313  constitutes an approximation to planar deflection plates  210 ,  220 ,  230 ,  240 ,  250 ,  260 ,  270 ,  280 . The first field profile  610  therefore approximately specifies a field profile which emerges in the case of using planar deflection plates  210 ,  220 ,  230 ,  240 ,  250 ,  260 ,  270 ,  280 . A second field profile  620  specifies the profile of the field component pointing in the y-direction  102  when using a radius of curvature  313  of 4 mm. A third field profile  630  specifies the profile of the field strength when using a radius of curvature  313  of 3 mm. A fourth field profile  640  specifies the profile of the component of the electric field pointing in the y-direction  102  when using a radius of curvature of 2.5 mm. The field profiles  610 ,  620 ,  630 ,  640  are in this case specified in each case at a position situated in the center in the y-direction  102  between the deflection plates of the plate pairs  201 ,  202 ,  203 ,  204 . What can be identified is that the profile of the field strength  601  the y-direction  102  becomes increasingly rectangular, as a smaller radius of curvature  313  is selected, i.e. as the deflection plates  210 ,  220 ,  230 ,  240 ,  250 ,  260 ,  270 ,  280  are curved more strongly. The first graph  600  in  FIG. 6  moreover depicts a fifth field profile  650 , a sixth field profile  660 , a seventh field profile  670  and an eighth field profile  680 . The fifth field profile  650  emerges when using a radius of curvature  313  of 1000 mm. The sixth field profile  660  emerges when using a radius of curvature  313  of 4 mm. The seventh field profile  670  emerges when using a radius of curvature  313  of 3 mm. The eighth field profile  680  emerges when using a radius of curvature  313  of 2.5 mm. The field profiles  650 ,  660 ,  670 ,  680  in each case emerge at a position in the y-direction  102  which is not situated precisely between the two plates of the respective plate pair  201 ,  202 ,  203 ,  204 , but which is disposed closer to one of the plates of the respective plate pair  201 ,  202 ,  203 ,  204 . What can be identified is that each one of the field profiles  650 ,  660 ,  670 ,  680  has a convex embodiment in the z-direction  103  in the region around the center of the plate pair  201 ,  202 ,  203 ,  204 . The convexity in this case increases as the radius of curvature  313  is selected to be smaller. Since such a convexity of the profile of the component pointing in the y-direction  102  of the electric field in the z-direction  103  may be connected with disadvantages, the radius of curvature  313  should not be selected to be too small. 
         [0042]      FIG. 7  shows a second graph  700  of the profile of the component pointing in the y-direction  102  of the electric field along the z-direction  103 . Once again, the z-direction  103  in the region of a plate pair  201 ,  202 ,  203 ,  204  is plotted on the horizontal axis of the second graph  700 . A normalized field strength  701  of a component of the electric field pointing in the y-direction  102  is plotted on a vertical axis of the second graph  700 . A first field profile  710 , a second field profile  720 , a third field profile  730  and a fourth field profile  740  specify the profile of the component pointing the y-direction  102  of the electric field along the z-direction  103  in the center between the two deflection plates of the respective plate pair  201 ,  202 ,  203 ,  204 . Here, the radius of curvature  313  is 1000 mm in the first field profile  710 , 4 mm in the second field profile  720 , 3 mm in the third field profile  730  and 2.5 mm in the fourth field profile  740 . It can be seen even more clearly from the normalized representation of the second graph  700  that the profile of the component of the electric field pointing in the y-direction  102  becomes ever more rectangular in the z-direction  103 , the smaller the radius of curvature  313  of the deflection plates  210 ,  220 ,  230 ,  240 ,  250 ,  260 ,  270 ,  280  is selected to be. 
         [0043]    Although the invention was illustrated and described in detail by the preferred exemplary embodiments, the invention is not restricted by the disclosed examples. Other variations can be derived therefrom by a person skilled in the art, without departing from the scope of protection of the invention.