LINEAR PARTICLE ACCELERATORS
United States Patent 3796906
Linear particle accelerator of compact dimensions, intended for industrial or medical applications, comprising, in a vacuum enclosure, a particle source and an accelerating structure having an input coupler connected to a waveguide extending along the lateral and end walls of said accelerating structure, the waveguide portion located against the end wall of said structure being provided with two holes located along the beam path for the passage of accelerated particles; a hood arrangement groups all parts of the accelerating device (accelerator, UHF electromagnetic power source, voltage supplies).
US Patent References:
Waveguide structure for microwave linear electron accelerator
Kelliher et al. - July 1961 - 2993143
Traveling-wave tube having a comb delay line formed on a ridge in a first waveguideand a plurality of connecting ridge waveguides
Kato et al. - November 1967 - 3353057
Linear particle accelerator with collinear termination
Haimson - May 1967 - 3319109
Travelling wave tube, in which an electron beam interacts with a helical delay line, having spurious oscillation suppressing means
Decherino et al. - May 1966 - 3250946
/2899598.html
Ginzton - August 1959 - 2899598
Waveguide structure for microwave linear electron accelerator
Kelliher et al. - July 1961 - 2993143
Traveling-wave tube having a comb delay line formed on a ridge in a first waveguideand a plurality of connecting ridge waveguides
Kato et al. - November 1967 - 3353057
Linear particle accelerator with collinear termination
Haimson - May 1967 - 3319109
Travelling wave tube, in which an electron beam interacts with a helical delay line, having spurious oscillation suppressing means
Decherino et al. - May 1966 - 3250946
/2899598.html
Ginzton - August 1959 - 2899598
Inventors:
Henry-bezy, Georges (Paris, FR)
Leboutet, Hubert P. (Paris, FR)
Leboutet, Hubert P. (Paris, FR)
Application Number:
05/247346
Publication Date:
03/12/1974
Filing Date:
04/25/1972
View Patent Images:
Export Citation:
Assignee:
Thomson-csf (Paris, FR)
Primary Class:
Other Classes:
315/3.500, 315/5.420
International Classes:
H05H9/00; H05H9/02; H01J25/10
Field of Search:
315/5.41,5.42,3.5X,39.3X
US Patent References:
Primary Examiner:
Lieberman, Eli
Assistant Examiner:
Chatmon Jr., Saxfield
Attorney, Agent or Firm:
Cushman, Darby & Cushman
Claims:
1. A linear particle accelerator comprising a vacuum tight enclosure in which is located a source producing a particle beam, an accelerating structure, means for loading said accelerating structure and injecting means to inject hyperfrequency energy in said structure, said injecting means comprising at least a folded waveguide entirely located within said enclosure, along said accelerating structure ; said structure being formed with a succession of cylindrical elements provided with notches , said
2. A linear accelerator as claimed in claim 1, wherein said structure, having notches, carries at least a waveguide having a shape adapted
3. A linear accelerator as claimed in claim 2, wherein said accelerating structure, having a cylindrical shape, is provided with notches comprising substantially radial walls, said waveguide having lateral planar walls
4. A linear accelerator as claimed in claim 3, wherein said bent walls are
5. A linear accelerator as claimed in claim 3, wherein said bent walls are
6. A linear accelerator as claimed in claim 1, further comprising another waveguide into said vacuum enclosure and extending along said accelerating structure, said waveguide being coupled thereto to the last element of said structure, said waveguide including said high-frequency absorbing
7. A linear accelerator as claimed in claim 1, wherein the portion of said waveguide extending in front of the end wall of said structure is provided with two holes located along the beam path and facing one another.
2. A linear accelerator as claimed in claim 1, wherein said structure, having notches, carries at least a waveguide having a shape adapted
3. A linear accelerator as claimed in claim 2, wherein said accelerating structure, having a cylindrical shape, is provided with notches comprising substantially radial walls, said waveguide having lateral planar walls
4. A linear accelerator as claimed in claim 3, wherein said bent walls are
5. A linear accelerator as claimed in claim 3, wherein said bent walls are
6. A linear accelerator as claimed in claim 1, further comprising another waveguide into said vacuum enclosure and extending along said accelerating structure, said waveguide being coupled thereto to the last element of said structure, said waveguide including said high-frequency absorbing
7. A linear accelerator as claimed in claim 1, wherein the portion of said waveguide extending in front of the end wall of said structure is provided with two holes located along the beam path and facing one another.
Description:
The present invention relates to linear particle accelerators, in particular electron accelerators, and relates more particularly to accelerators of compact design.
Compact linear accelerators of this kind are generally intended for medical applications such as gamma radiography or radiotherapy, in which the high-energy particles bombard a target made of a metal having a high atomic number which metal emits X-rays or gamma-rays under the influence of said bombardment. The compact design of the accelerator is even more important where the equipment has to be spatially mobile, that is to say to be capable of being aligned in order that the radiation emitted by the target can be directed to the desired location (organ being irradiated).
The known accelerators of this type generally have a relatively substantial bulk and are therefore difficult to manipulate.
The acclerator in accordance with the invention enables these drawbacks to be overcome. In this accelerator, in other words, the essential elements are arranged along the accelerator section and rotated inside a cylinder of reduced dimensions.
In accordance with the invention,a linear particle accelerator comprises a vacuum enclosure in which is located a source producing a particle beam, an accelerating structure and means to inject hyperfrequency energy in said structure, said means comprising at least a folded waveguide entirely located within said enclosure, along said accelerating structure ; said structure being formed with a succession of cylindrical elements provided with notches ; said waveguide being located within said notches.
For a better understanding of the invention and to show how the same may be carried into effect, reference will be made to the drawings, given solely by way of example, which accompanies the following description and wherein :
FIG. 1 illustrates a longitudinal section of an accelerator in accordance with the invention.
FIGS. 2, 3 and 4 illustrate a partial transversal section of an accelerator in accordance with the invention.
FIGS. 5 and 6 respectively illustrate two embodiments of the waveguide used in the accelerator.
FIGS. 7 and 8 illustrate two variant embodiments of the accelerator in accordance with the invention.
In all these figures, identical references indicate identical elements.
FIG. 1 shows a partial longitudinal section of a particle accelerator in accordance with the invention. This accelerator comprises a vacuum enclosure 1 in which is located a particle source 2 (electron gun for example), an accelerating structure 3 and means for injecting the hyperfrequency energy into said structure 3 which is constituted with elements e 1 , e 2 ... e n , each comprising a cylindrical portion 5 provided with a diaphragm 6 which is in the form of a thin disc having a central opening 7 for the passage of the beam. The assembly of these elements makes up the cylindrical resonant cavities of the accelerating structure 3.
Each of these elements e 1 , e 2 ... e n , comprises a certain number of notches 8 and fixing lugs 9, provided with a cylindrical hole, so that they can be assembled by means of rods 11. The neighbouring elements e 1 ... e n assembled on the rod 11 are then welded together along an annular surface 4.
The two ends of an accelerator section thus assembled, are respectively equipped with conventional input and output. The first element e 1 of the accelerating structure 3 is coupled to a first junction or input coupler 13. The input coupler 13 is designed to provide a matched junction between a waveguide 14 and the cylindrical accelerator element e 1 and to excite at the latter a TM-mode wave (preferably TM 01 ). This waveguide 14 can be a rectangular section waveguide as shown in FIG. 2 or another waveguide as shown in FIG. 3 and 5 or FIG. 4 and 6. The FIG. 6 illustrates an arcuate section waveguide and the FIG. 5 a vee-shaped waveguide.
In FIG. 1, in order on the one hand to achieve a minimum bulk and on the other hand to group together the parts which carry high voltages (the electron-gun 2 and the magnetron 24), the waveguide supplying UHF power to an input coupler 13 is arranged parallel to the longitudinal axis of the structure 3.
The magnetron 24, here located close to the electron-gun 2, supplies in series an isolator 25 and a flexible waveguide 26, arranged parallel to the accelerating structure 3, and a flat elbow terminating in the sealed window 22 which is, in this case, located at the level of the exit of the accelerating structure.
Inside the enclosure 1, the UHF power has to be supplied to the input coupler 13 through a waveguide 14 of low height. The standard section window 22 is connected to the waveguide 14 of low height, through a matching section or coupler 20 whose dimensions reduce gradually.
The waveguide 14 is arranged, at the output of the accelerating structure 3, perpendicularly to the axis of said accelerating structure 3 and is equipped with two openings 18 and 19 to pass the accelerated electrons towards the target.
A flat elbow 16 permits to the waveguide 14 to be parallel to the accelerating structure and arranged between the cylindrical parts 5 of the elements e 1 ...e n, and the internal face of the enclosure 1. The notches 8 of the elements e 1 ...e n enable the waveguide 14 to pass along it.
The waveguide 14 is connected to the input coupler 13 through an elbow 15.
It should be pointed out that in order to gain space, it is possible to replace a rectangular waveguide 14 as shown in FIG. 2 to a waveguide having a vee-shaped cross section 41 cross-section, (see FIG. 5) or an arcuate cross section 40 (see FIG. 6).
In this case, the elbows 15 and 16 which respectively connect the waveguide 14, extending along the accelerating structure 3, with the input coupler 13 and the other coupler 16 having rectangular cross-sections, have special shapes to match the UHF power channel.
The accelerating structure 3 illustrated in FIG. 1, has no external matched load to dissipate the residual UHF energy. This load is here constituted by a material 29 of a high - resistivity alloy, covering the internal surfaces of the elements (e n -2 , e n -1 , e n ) which are located at the exit extremity of the structure 3. This kind of material can be produced by means of an alloy of iron, chromium, cobalt and aluminium which is available commercially under the name of KANTHAL, or better an alloy of nickel, chromium and aluminium which is commercially marketed under the name TOPHET H, for example. This latter alloy contains no ferromagnetic elements (Fe) which is avantageous because the presence of the magnetic field generated, for example, by the coils used to focus the electron beam and surrounding the accelerating structure (these coils have not been shown).
It should be pointed out that by reducing the number of cut-outs 8 and fixing lugs 9 in the elements e 1 ... e n , to three (instead of four), it is possible to arrange into cut-outs 8 having substantially radial walls, a waveguide 14 of greater width, whose cut-off frequency is lower than that which it is possible to obtain with a waveguide of the kind shown in FIG. 2.
The embodiment illustrated in FIG. 7, comprises a matched load within a waveguide 30. An output coupler 42 is matched to the waveguide 30 and to the last element e n of the accelerating structure 3. The waveguide 30 will preferably have a cross-section identical to the section of the waveguide 14 which supplies UHF power to the input coupler 13 (FIG. 1). The waveguide 30 is terminated in a matched load 31. This matched load can be replaced by the waveguide section which is internally covered with a resistive material and closed by a short-circuiting plate. The resistive material used can be constituted by one of the aforementioned materials.
FIG. 8 illustrates another variant embodiment of the accelerator in accordance with the invention.
In this embodiment, the input waveguide 32 is provided with three elbows 33, 34 and 35 and is coupled on the one hand to the magnetron 24 and on the other hand to the first element e 1 of the accelerating structure 3 by means couplers 38 and 39.
A modulator assembly 50 supplies the cathodes of the magnetron 24 and the particle source 2, (FIG. 1).
The accelerator in accordance with the present invention is a device of reduced dimensions in order to make it easy to manipulate, and groups together the parts carried to very high voltages (cathodes), thus facilitating the protection of the user. The modulator 30, the accelerating structure 3, the magnetron 24 are including within a hood 44.
Linear electron accelerators of this kind are intended primarily for medical application such as gamma radiography or radiotherapy, for example.
Compact linear accelerators of this kind are generally intended for medical applications such as gamma radiography or radiotherapy, in which the high-energy particles bombard a target made of a metal having a high atomic number which metal emits X-rays or gamma-rays under the influence of said bombardment. The compact design of the accelerator is even more important where the equipment has to be spatially mobile, that is to say to be capable of being aligned in order that the radiation emitted by the target can be directed to the desired location (organ being irradiated).
The known accelerators of this type generally have a relatively substantial bulk and are therefore difficult to manipulate.
The acclerator in accordance with the invention enables these drawbacks to be overcome. In this accelerator, in other words, the essential elements are arranged along the accelerator section and rotated inside a cylinder of reduced dimensions.
In accordance with the invention,a linear particle accelerator comprises a vacuum enclosure in which is located a source producing a particle beam, an accelerating structure and means to inject hyperfrequency energy in said structure, said means comprising at least a folded waveguide entirely located within said enclosure, along said accelerating structure ; said structure being formed with a succession of cylindrical elements provided with notches ; said waveguide being located within said notches.
For a better understanding of the invention and to show how the same may be carried into effect, reference will be made to the drawings, given solely by way of example, which accompanies the following description and wherein :
FIG. 1 illustrates a longitudinal section of an accelerator in accordance with the invention.
FIGS. 2, 3 and 4 illustrate a partial transversal section of an accelerator in accordance with the invention.
FIGS. 5 and 6 respectively illustrate two embodiments of the waveguide used in the accelerator.
FIGS. 7 and 8 illustrate two variant embodiments of the accelerator in accordance with the invention.
In all these figures, identical references indicate identical elements.
FIG. 1 shows a partial longitudinal section of a particle accelerator in accordance with the invention. This accelerator comprises a vacuum enclosure 1 in which is located a particle source 2 (electron gun for example), an accelerating structure 3 and means for injecting the hyperfrequency energy into said structure 3 which is constituted with elements e 1 , e 2 ... e n , each comprising a cylindrical portion 5 provided with a diaphragm 6 which is in the form of a thin disc having a central opening 7 for the passage of the beam. The assembly of these elements makes up the cylindrical resonant cavities of the accelerating structure 3.
Each of these elements e 1 , e 2 ... e n , comprises a certain number of notches 8 and fixing lugs 9, provided with a cylindrical hole, so that they can be assembled by means of rods 11. The neighbouring elements e 1 ... e n assembled on the rod 11 are then welded together along an annular surface 4.
The two ends of an accelerator section thus assembled, are respectively equipped with conventional input and output. The first element e 1 of the accelerating structure 3 is coupled to a first junction or input coupler 13. The input coupler 13 is designed to provide a matched junction between a waveguide 14 and the cylindrical accelerator element e 1 and to excite at the latter a TM-mode wave (preferably TM 01 ). This waveguide 14 can be a rectangular section waveguide as shown in FIG. 2 or another waveguide as shown in FIG. 3 and 5 or FIG. 4 and 6. The FIG. 6 illustrates an arcuate section waveguide and the FIG. 5 a vee-shaped waveguide.
In FIG. 1, in order on the one hand to achieve a minimum bulk and on the other hand to group together the parts which carry high voltages (the electron-gun 2 and the magnetron 24), the waveguide supplying UHF power to an input coupler 13 is arranged parallel to the longitudinal axis of the structure 3.
The magnetron 24, here located close to the electron-gun 2, supplies in series an isolator 25 and a flexible waveguide 26, arranged parallel to the accelerating structure 3, and a flat elbow terminating in the sealed window 22 which is, in this case, located at the level of the exit of the accelerating structure.
Inside the enclosure 1, the UHF power has to be supplied to the input coupler 13 through a waveguide 14 of low height. The standard section window 22 is connected to the waveguide 14 of low height, through a matching section or coupler 20 whose dimensions reduce gradually.
The waveguide 14 is arranged, at the output of the accelerating structure 3, perpendicularly to the axis of said accelerating structure 3 and is equipped with two openings 18 and 19 to pass the accelerated electrons towards the target.
A flat elbow 16 permits to the waveguide 14 to be parallel to the accelerating structure and arranged between the cylindrical parts 5 of the elements e 1 ...e n, and the internal face of the enclosure 1. The notches 8 of the elements e 1 ...e n enable the waveguide 14 to pass along it.
The waveguide 14 is connected to the input coupler 13 through an elbow 15.
It should be pointed out that in order to gain space, it is possible to replace a rectangular waveguide 14 as shown in FIG. 2 to a waveguide having a vee-shaped cross section 41 cross-section, (see FIG. 5) or an arcuate cross section 40 (see FIG. 6).
In this case, the elbows 15 and 16 which respectively connect the waveguide 14, extending along the accelerating structure 3, with the input coupler 13 and the other coupler 16 having rectangular cross-sections, have special shapes to match the UHF power channel.
The accelerating structure 3 illustrated in FIG. 1, has no external matched load to dissipate the residual UHF energy. This load is here constituted by a material 29 of a high - resistivity alloy, covering the internal surfaces of the elements (e n -2 , e n -1 , e n ) which are located at the exit extremity of the structure 3. This kind of material can be produced by means of an alloy of iron, chromium, cobalt and aluminium which is available commercially under the name of KANTHAL, or better an alloy of nickel, chromium and aluminium which is commercially marketed under the name TOPHET H, for example. This latter alloy contains no ferromagnetic elements (Fe) which is avantageous because the presence of the magnetic field generated, for example, by the coils used to focus the electron beam and surrounding the accelerating structure (these coils have not been shown).
It should be pointed out that by reducing the number of cut-outs 8 and fixing lugs 9 in the elements e 1 ... e n , to three (instead of four), it is possible to arrange into cut-outs 8 having substantially radial walls, a waveguide 14 of greater width, whose cut-off frequency is lower than that which it is possible to obtain with a waveguide of the kind shown in FIG. 2.
The embodiment illustrated in FIG. 7, comprises a matched load within a waveguide 30. An output coupler 42 is matched to the waveguide 30 and to the last element e n of the accelerating structure 3. The waveguide 30 will preferably have a cross-section identical to the section of the waveguide 14 which supplies UHF power to the input coupler 13 (FIG. 1). The waveguide 30 is terminated in a matched load 31. This matched load can be replaced by the waveguide section which is internally covered with a resistive material and closed by a short-circuiting plate. The resistive material used can be constituted by one of the aforementioned materials.
FIG. 8 illustrates another variant embodiment of the accelerator in accordance with the invention.
In this embodiment, the input waveguide 32 is provided with three elbows 33, 34 and 35 and is coupled on the one hand to the magnetron 24 and on the other hand to the first element e 1 of the accelerating structure 3 by means couplers 38 and 39.
A modulator assembly 50 supplies the cathodes of the magnetron 24 and the particle source 2, (FIG. 1).
The accelerator in accordance with the present invention is a device of reduced dimensions in order to make it easy to manipulate, and groups together the parts carried to very high voltages (cathodes), thus facilitating the protection of the user. The modulator 30, the accelerating structure 3, the magnetron 24 are including within a hood 44.
Linear electron accelerators of this kind are intended primarily for medical application such as gamma radiography or radiotherapy, for example.