CN219144112U - Novel penning ion source with leading-out hole shape - Google Patents
Novel penning ion source with leading-out hole shape Download PDFInfo
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Abstract
The penning ion source comprises an extraction hole, wherein the extraction hole comprises a rectangular area and a special-shaped area connected with the rectangular area, the width of the special-shaped area gradually decreases from one end connected with the rectangular area to the other end, and the symmetry axes of the rectangular area and the special-shaped area coincide; the ratio of the length to the width of the leading-out hole is 1-3.5:1. The penning ion source with the novel extraction hole shape adopts a novel special-shaped extraction hole structure, the longitudinal dimension of a seam is reduced, the transverse dimension is increased, the longitudinal emission width of extracted beam is reduced, the area of a beam emission surface is enlarged, and the intensity of extracted beam is increased.
Description
Technical Field
The utility model belongs to the technical field of cores, and relates to an ion source, in particular to a penning ion source with a novel extraction hole shape.
Background
The low-energy cyclotron can be widely applied to the fields of biology, medicine, physical basic research and the like. In the medical field, cyclotrons can be used for producing various radionuclides, and the radionuclides are involved in metabolism of human bodies by using an isotope labeling method, and are subjected to targeted radiodiagnosis and treatment. In recent years, the positron emission computed tomography technology is rapidly developed, and a small medical cyclotron with the energy of 10-20 MeV matched with the positron emission computed tomography technology is widely applied and developed. 11C, 13N and 15O are all life components, and the radioisotope FDG synthesized by 18F has glucose property, is easier to gather in tumor cells after being injected into a human body, and can capture and display images of cancerous regions through a X-ray tomography scanner.
Cyclotrons are usually operated under high vacuum (less than 1E-3 Pa). In operation, charged particles (and negative hydrogen ions) are first extracted from the initial ion source to accelerate and are confined to a circular path by a magnetic field. The radio frequency high voltage source rapidly alternates the type of electric field inside the cyclotron room, resulting in the ion source performing a cyclotron motion in the accelerator to obtain kinetic energy. After obtaining sufficient energy, the ions are directed to the target material, producing different radionuclides as desired.
In medical cyclotrons, a negative hydrogen ion source is an indispensable important component. The beam intensity and quality of the negative hydrogen ions generated by the method directly influence the beam parameters and production efficiency of the accelerator, but the extracted beam is seriously lost in the axial direction of the central area of the cyclotron, so that the final target loading beam intensity is greatly reduced. The design of the ion source extraction system is an important factor affecting the axial loss of the accelerator center region. The ion source extraction Kong Daduo is slit-shaped and increases the axial width of the beam to some extent, resulting in serious axial loss of the extracted beam in the central region. The ion source extraction system is a device for extracting ions in plasma generated by an ion source, a plasma emission surface is formed at an extraction hole of the extraction system, the ions generated by the ion source are emitted from the emission surface, and an ion beam is accelerated and extracted through a subsequent extraction voltage. The plasma emission surface affects the emittance of the beam, and the larger the emittance is, the more serious the beam loss is. The shape of the plasma emission surface is usually at a certain equipotential surface determined by space charge and extraction electric field, and the main factors determining the emission surface are the conductivity and the electrode geometry, which plays an important role in the formation of extraction electric field in the vicinity of the emission surface. Thus, the geometry of the aperture shape of the ion source extraction aperture is critical and important.
The penning ion source is mainly divided into axial extraction and radial extraction, and in the radial extraction surface of the penning ion source, in order to ensure that the ion source has larger air resistance and increase extraction beam current, the extraction hole is usually designed as an elongated rectangular slit, the length of the slit is 2-10mm, the width is 0.1-1.0mm, and the thickness is usually 0.05-0.5mm. Fig. 7 and 8 are prior art designs. The main disadvantages of such slit ion sources are:
1. the longitudinal distance of the extracted beam is large, a certain divergence angle exists after the beam is extracted from the emission surface, and the magnetic field and the electric field in the central area of the accelerator are difficult to axially focus the beam, so that the longitudinal loss of an acceleration gap in the central area of the accelerator is serious, the emission area of the extracted Kong Shu flow is small, and the intensity of the extracted beam is limited.
2. The shape of the straight hole electrode cannot better enable the extraction electric field to permeate into the emitter hole, and the extraction capacity is low. In addition, the aberration is aggravated and the emittance is increased due to the "fringe effect" of the inner wall (due to the weakening of the electric field near the wall, the edge of the emitting surface against the wall).
3. In the emission surface of the rectangular slit, some emission positions are different from the electric field formed by the extraction electrode, so that the loss rate of emitted beam current in a central area is higher, and in theory, the emission positions with lower loss rate in the central area are not in the emission surface of the rectangular slit. The elongated rectangular slot does not fully utilize the beam receiving capability of the accelerator, resulting in inefficient beam trapping by the accelerator.
Disclosure of Invention
In order to overcome the technical defects in the prior art, the utility model discloses a novel penning ion source with a leading-out hole shape.
The penning ion source with the novel extraction hole shape comprises an extraction hole, and is characterized in that the extraction hole comprises a rectangular area and a special-shaped area connected with the rectangular area, the width of the special-shaped area gradually decreases from one end connected with the rectangular area to the other end, and the symmetry axes of the rectangular area and the special-shaped area are coincided;
the ratio of the length to the width of the leading-out hole is 1-3.5:1, wherein the length is the length of the rectangular area, and the width is the sum of the maximum widths of the rectangular area and the special-shaped area.
Preferably, the cross section at the boundary of the leading-out hole is wedge-shaped, and the wedge-shaped angle is more than 10 degrees and less than 90 degrees.
Preferably, the special-shaped area is an isosceles triangle.
Preferably, the special-shaped area comprises an isosceles trapezoid area connected with the rectangular area and an isosceles triangle connected with the isosceles trapezoid area.
Preferably, the isosceles trapezoid area and the isosceles triangle are the same in height.
Preferably, the inflection point in the profiled region is a rounded corner.
The penning ion source with the novel extraction hole shape adopts a novel special-shaped extraction hole structure, the longitudinal dimension of a seam is reduced, the transverse dimension is increased, the longitudinal emission width of extracted beam is reduced, the area of a beam emission surface is enlarged, and the intensity of extracted beam is increased; the electric field formed from the emitting surface to the extraction electrode in the extraction hole structure area is beneficial to improving the capture efficiency of the beam in the central area, fully improving the beam receiving capacity of the accelerator, reducing the beam loss rate in the central area and effectively improving the target flow intensity of the accelerator.
Drawings
FIG. 1 is a schematic view of one embodiment of a novel exit aperture according to the present utility model;
FIG. 2 is a schematic cross-sectional view taken along the direction A-A in FIG. 1;
FIG. 3 is an enlarged schematic view of FIG. 1 at C2;
FIG. 4 is an enlarged schematic view at B2 in FIG. 2;
FIG. 5 is a schematic view of another shape of the novel exit hole of the present utility model;
FIG. 6 is a schematic view of another shape of the novel exit hole of the present utility model;
FIG. 7 is a prior art lead-out hole schematic;
FIG. 8 is a schematic cross-sectional view taken along the direction A1-A1 in FIG. 7;
FIG. 9 is a beam loss rate contour plot according to one embodiment of the present utility model;
FIG. 10 is a comparative schematic diagram of the distribution of electric field lines near the boundaries of extraction holes according to the prior art and described herein;
FIG. 11 is a comparative schematic diagram of beam boundaries near the exit aperture boundaries of the prior art and described herein.
Detailed Description
The following describes embodiments of the present utility model in further detail with reference to fig. 1 to 8.
The penning ion source with the novel extraction hole shape comprises an extraction hole, wherein the extraction hole comprises a rectangular region and a special-shaped region connected with the rectangular region, the width of the special-shaped region gradually decreases from one end connected with the rectangular region to the other end, and the symmetry axes of the rectangular region and the special-shaped region are coincided;
the ratio of the length to the width of the leading-out hole is 1-3.5:1, wherein the length is the length of the rectangular area, and the width is the sum of the maximum widths of the rectangular area and the special-shaped area.
Compared with the prior art, the utility model has the advantages that the longitudinal size of the extraction hole is reduced, the transverse size is increased, and the longitudinal emission width of the extraction beam is reduced. The special-shaped surface enlarges the area of the beam emission surface, and the intensity of the extracted beam is greatly increased. According to beam research in the central area of the cyclotron, the electric field formed from the emitting surface to the extraction electrode in the special-shaped structure area is beneficial to improving the capture efficiency of the beam in the central area, fully improving the beam receiving capacity of the accelerator, reducing the beam loss rate in the central area and effectively improving the target flow intensity on the accelerator.
Fig. 9 shows a contour diagram obtained by using a COMSOL (multi-physical simulation software) particle tracking module to perform simulation and calculating the beam loss rate of the accelerator central area by scanning a small range of the extraction surface, wherein in fig. 9, the x and y axes respectively represent the coordinate positions of the extraction plane, the color depth represents the loss rate of the central area, the loss rate of the special-shaped seam in the central area is less than 40% as can be seen from the contour diagram, and the loss rate of the central area of the extraction seam in the prior art is about 54%, so that the loss rate of the beam in the central area can be effectively reduced by using the extraction hole.
Meanwhile, the shape of an external cutting-out electrode near the leading-out hole is improved, the shape of a straight hole electrode in the prior art as shown in fig. 8 is designed to be wedge-shaped and concave inwards, and the angle alpha of a wedge-shaped cutting-out is 10-90 degrees as shown in fig. 4; the structure can better enable the extraction field to permeate into the emitter hole, effectively avoid aberration caused by excessive bending of the equipotential surface at the edge of the hole, enable the vicinity of the emission surface to obtain uniform equipotential surface curvature, and reduce the beam emittance. As shown in fig. 10 and fig. 11, the electric field line distribution and the beam boundary contrast schematic diagrams of the prior art and the wedge-shaped cross section adopted by the leading-out hole boundary are shown, the right side in fig. 10 and fig. 11 is the flat-mouth cross section of the prior art, the left side is the wedge-shaped cross section adopted by the application, the obvious difference of the distribution of the electric lines around the flat-mouth shape in the prior art can be seen to be larger, the inclination angle of the beam boundary is larger, and after the electrode with the wedge-shaped cross section is adopted, the distribution of the electric lines is more uniform, and the beam boundary is more gentle.
In a specific embodiment shown in fig. 3, the lead-out hole is approximately equal to a rectangle and an isosceles triangle, two sides of the isosceles triangle can be designed into two straight sides, and more preferably can be designed to be concave inwards, namely, the special-shaped area comprises an isosceles trapezoid area connected with the rectangle area and an isosceles triangle connected with the isosceles trapezoid area, as shown in fig. 5; the recess location may be near the midpoint location on the edge, for example within 0.5mm of the midpoint, most preferably the recess location and the apex of the isosceles triangle are designed to be circular arc shaped, as shown in fig. 6.
External cutting design of the edge of the extraction hole: the angle alpha of the cut is 10 deg. -90 deg., and the specific shape is referred to in fig. 2.
The penning ion source with the novel extraction hole shape adopts a novel special-shaped extraction hole structure, the longitudinal dimension of a seam is reduced, the transverse dimension is increased, the longitudinal emission width of extracted beam is reduced, the area of a beam emission surface is enlarged, and the intensity of extracted beam is increased; the electric field formed from the emitting surface to the extraction electrode in the extraction hole structure area is beneficial to improving the capture efficiency of the beam in the central area, fully improving the beam receiving capacity of the accelerator, reducing the beam loss rate in the central area and effectively improving the target flow intensity of the accelerator.
The foregoing description of the preferred embodiments of the present utility model is not obvious contradiction or on the premise of a certain preferred embodiment, but all the preferred embodiments can be used in any overlapped combination, and the embodiments and specific parameters in the embodiments are only for clearly describing the utility model verification process of the inventor and are not intended to limit the scope of the utility model, and the scope of the utility model is still subject to the claims, and all equivalent structural changes made by applying the specification and the content of the drawings of the present utility model are included in the scope of the utility model.
Claims (6)
1. The penning ion source with the novel extraction hole shape comprises an extraction hole, and is characterized in that the extraction hole comprises a rectangular area and a special-shaped area connected with the rectangular area, the width of the special-shaped area gradually decreases from one end connected with the rectangular area to the other end, and the symmetry axes of the rectangular area and the special-shaped area are coincided;
the ratio of the length to the width of the leading-out hole is 1-3.5:1, wherein the length is the length of the rectangular area, and the width is the sum of the maximum widths of the rectangular area and the special-shaped area.
2. The penning ion source of claim 1, wherein the cross-section at the boundary of the extraction aperture is wedge-shaped, the wedge angle being greater than 10 degrees and less than 90 degrees.
3. The penning ion source of claim 1, wherein the shaped region is an isosceles triangle.
4. The penning ion source of claim 1, wherein the shaped region comprises an isosceles trapezoid region connected to the rectangular region and an isosceles triangle connected to the isosceles trapezoid region.
5. The penning ion source of claim 4, wherein the isosceles trapezoid region and isosceles triangle are the same height.
6. A penning ion source according to any one of claims 3 to 5, wherein the inflection point in the profiled region is a rounded corner.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202223295606.1U CN219144112U (en) | 2022-12-09 | 2022-12-09 | Novel penning ion source with leading-out hole shape |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202223295606.1U CN219144112U (en) | 2022-12-09 | 2022-12-09 | Novel penning ion source with leading-out hole shape |
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| CN219144112U true CN219144112U (en) | 2023-06-06 |
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| CN202223295606.1U Active CN219144112U (en) | 2022-12-09 | 2022-12-09 | Novel penning ion source with leading-out hole shape |
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- 2022-12-09 CN CN202223295606.1U patent/CN219144112U/en active Active
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Inventor after: Chen Yuhang Inventor after: Wang Dan Inventor after: Ma Ruili Inventor after: Du Yang Inventor after: Li Jie Inventor before: Chen Yuhang Inventor before: Wang Dan Inventor before: Ma Ruili Inventor before: Du Yang Inventor before: Li Jie Inventor before: Shi Jinshui Inventor before: Ding Hengsong |