A terraced cyclotron strip shimming structure

Abstract

The present invention discloses a terraced cyclotron strip shimming structure, which is characterized in that: the terraced cyclotron strip shimming structure adopts a double layer, the upper strip structure is used for magnetic field shimming and is processed during the shimming process, and the lower strip structure is not used for magnetic field shimming and is not processed during the shimming process; the distance of the upper strip structure extending inward from the small radius to the large radius along the strip width direction and the distance of the upper strip structure extending downward along the height direction are a set distance. The shimming strip of the present invention can modify both the width shimming magnetic field and the height shimming magnetic field; it avoids the problem of lack of high-frequency cavity shell flange space caused by too small local shimming amount; the screw holes and pin holes are placed on the bottom layer that will not be shimmed, avoiding the processing of the strip side passing through the screw and pin holes during the shimming process, which can improve the accuracy of the shimming magnetic field calculation; it can prevent the problem of screws and pins protruding due to excessive processing width.

Description

Technical Field

[0001] The invention belongs to the technical field of shimming of a main magnetic field of a cyclotron, and in particular relates to a terraced shimming structure of a cyclotron. Background Art

[0002] Magnetic field shimming is a key step in adjusting the magnetic field to meet the physical design requirements in the design and manufacture of cyclotron accelerators. Figure 2 The method of cutting the vertically penetrating strips shown in the figure is to process the shim strips, and finely adjust the magnetic field by processing the size of the shim strips. Due to the fine adjustment of the magnetic field, the cutting amount of the strip shape is very small or even "negligible", so that the strips are too close to the high-frequency cavity shell at the corners adjacent to the high-frequency cavity, such as Figure 1 As shown, due to the close distance, there is not enough space left for the high-frequency cavity at the corner, which does not meet the design requirements of the high-frequency cavity. The reason why the inlay is too close to the high-frequency cavity at the corner is that, on the one hand, the high-frequency cavity is required to be close to the main magnet pole and the inlay on the side of the main magnet, and the heat generated by the high-frequency cavity is dissipated through the magnet. In this way, the inlay is close to the high-frequency cavity from top to bottom in the height space. When the padding cutting amount at the corner is "minimal", the high-frequency cavity and the inlay are naturally too close at the corner; on the other hand, the high-frequency cavity and the inlay are also required to be fixed. The fixing method is to turn the high-frequency cavity shell outward at the top, and then press it on the upper surface of the inlay to form the corner of the high-frequency cavity. The design requires that the inlay at the corner and the high-frequency cavity cannot be close but must leave a set distance. If the traditional cutting and padding is performed on the side of the inlay, when the cutting amount is very small or almost no cutting amount, the inlay and the high-frequency cavity shell will be too close at the corner.

[0003] Prior art Patent number: 202311111671 Patent name: A guide angle shimming structure for angle changes of a desktop cyclotron, such as Figure 3 As shown in the figure, in order to solve the problem of the "corner" being too close, the method of cutting the chamfer at the upper oblique side of the insert is adopted. This method is too complicated to implement. The key is that the processing of the mold used for cutting and shimming is particularly complicated, because the mold processing is generally performed by the tool cutting from top to bottom along the curve at the lower cutting position, that is, according to the following Figure 2 The curve shape cuts from top to bottom, but Figure 3 The chamfer padding structure shown is not an inclined surface but a curved surface with a continuously changing angle on the inclined surface. As you can imagine, it is extremely difficult. On the other hand, since it is an inclined curved surface with a changing angle, the calculation of the padding amount is also quite complicated.

[0004] In summary, the prior art Figure 2 , Figure 3The strip shimming methods mentioned above cannot satisfy the requirement of leaving a certain space for the high-frequency cavity at the corner of the high-frequency cavity, or the distance between the strip and the high-frequency cavity is too close at the corner, or the processing of the strip shimming mold is too complicated. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention proposes a terraced cyclotron strip filling structure, aiming to solve the problems that the prior art strip filling methods cannot meet the requirement of leaving a certain space for the high-frequency cavity at the corner of the high-frequency cavity, or the distance between the strip and the high-frequency cavity at the corner is too close, or the processing of the strip filling mold is too complicated.

[0006] The present invention adopts the following technical solutions to solve the technical problems:

[0007] A terraced cyclotron strip shimming structure is characterized in that: the terraced cyclotron strip shimming structure adopts a double layer, the upper strip structure is used for magnetic field shimming and is processed during the shimming process, and the lower strip structure is not used for magnetic field shimming and is not processed during the shimming process; the distance that the upper strip structure extends inward from the small radius to the large radius along the strip width direction and the distance that the upper strip structure extends downward along the height direction are a set distance.

[0008] Further, the set distance is at least 5 mm, that is, the upper strip structure extends inward at least 5 mm along the width direction away from the side of the high-frequency cavity housing, and the upper strip structure extends downward at least 5 mm along the height direction away from the top of the high-frequency cavity housing.

[0009] Furthermore, the lower strip structure is not used for magnetic field shimming and is not processed during the shimming process, that is, the lower strip structure does not participate in the calculation of magnetic field shimming, and the strip shimming calculation of the upper strip structure covers the shimming calculation of the lower strip structure.

[0010] Furthermore, the padding calculation of the upper-layer padding structure includes the padding calculation of the lower-layer padding structure, that is, when the padding amount of the upper-layer padding structure is insufficient, it can continue to extend inward in a direction of not less than 5 mm in the width direction of the padding, and can continue to extend downward in a direction of not less than 5 mm in the height direction of the padding.

[0011] Furthermore, the lower layer of the inlay structure is provided with pins, and the inlay is precisely fixed on the main magnet through the pins.

[0012] Furthermore, when the upper strip structure satisfies the requirement that the inward extension in the width direction and the downward extension in the height direction are not less than 5 mm, the distance inward extension in the width direction and the distance downward extension in the height direction may not be equal.

[0013] Advantages and effects of the present invention

[0014] 1. The new shimming strip can modify both the width shimming magnetic field and the height shimming magnetic field, thus avoiding the problem of lack of high-frequency cavity shell flange space due to too small local shimming amount.

[0015] 2. Placing the screw holes and pin holes on the bottom layer that will not be shimmed can avoid the side edges of the processing strip passing through the screw and pin holes during the shimming process, which can improve the accuracy of the shimming magnetic field calculation; it can also prevent the problem of screws and pins protruding due to excessive processing width. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the layout of the cyclotron main magnet, high-frequency cavity housing, and inlay strips;

[0017] Figure 2 It is a schematic diagram of the main magnet shim of the side-cut cyclotron accelerator in the prior art;

[0018] Figure 3 It is a schematic diagram of the main magnet shim of the prior art guide angle cyclotron accelerator;

[0019] Figure 4 Schematic diagram of the main magnet shim of the terraced cyclotron accelerator of the present invention; DETAILED DESCRIPTION

[0020] Design principle of the present invention

[0021] 1. Innovation of the present invention: The innovation lies in that compared with the various strip shimming structures in the prior art, a strip shimming structure that is the simplest to implement and meets the design requirements of the high-frequency cavity is adopted. The terraced double-layer strip structure of the present invention takes the upper strip structure as the basic condition that the upper strip structure is not less than 5mm horizontally inward and vertically downward at the corner of the high-frequency cavity. When this basic condition is met, the upper strip structure can continue to extend inward and downward, thereby meeting various magnetic field shimming requirements. Compared with the prior art Figure 2 , Figure 3 In comparison, it retains Figure 2 The advantages of the side-cutting type of insert processing mold are simple processing, and it also takes into account Figure 3 The advantage of cutting the chamfer at the upper side of the inlay strip is that it can avoid the crowded space at the corner of the high-frequency cavity; and because the cutting surface is not at a variable angle, compared with Figure 3 The padding algorithm is much simpler.

[0022] 2. The upper strip structure of the present invention extends inwards by at least 5mm and downwards by 5mm, which can fully meet the precision requirements. In this embodiment, the total height of the double-layer strip structure is generally 50mm. The present invention is an improvement on the situation where the sideways and upwards through-type cutting strips extend inwards by 1-2mm. Figure 2For side through-cutting, assuming the inward cutting is 1mm, the height of the cut strip is 50mm, and the cross section of the cut strip is 50mm. 2 , and the present invention adopts the upper strip structure for cutting. When extending inward (cutting) 5mm and extending downward (cutting) 5mm, the cross section of the cut strip is 25mm 2 , compared to the existing technology of 50mm 2 The minimum cutting section can fully meet the accuracy requirements.

[0023] 3. Summary: The present invention adopts a double-layer inlay strip shimming structure. The curve of the upper inlay strip structure will be modified according to the magnetic measurement results to adjust the magnetic field to meet the physical design requirements. When the conditions of extending (cutting) inward by at least 5 mm and extending (cutting) downward by at least 5 mm are met, various precision requirements are met by increasing the inward extension width and downward extension depth of the upper inlay strip structure; the lower inlay strip structure is not processed during the shimming process, and the screws and positioning pin holes used to fix the inlay strip are used to accurately fix the inlay strip on the main magnet.

[0024] 4. Difference from the prior art: The original inlay strip adopts a single-layer shimming structure. In the shimming process after magnetic measurement, the inlay strip will be processed as a whole in the entire height direction according to the shimming curve, and the side of the inlay strip is also used to fix the inlay strip and install pins. Since the pin hole and the cutting surface of the inlay strip are on the same plane, not only is the processing amount too large, but there is also a risk of screws and pins being exposed on the side of the inlay strip.

[0025] Compared with the single-layer shimming structure, the double-layer shimming structure of the present invention is mainly different in that it is divided into two layers in the height direction. The upper-layer shimming structure retains the ability of the original solution to adjust the magnetic field by modifying the side curve of the shimming strip, and increases the middle layer in the height direction of the shimming strip to make up for the part of the upper layer where the local shimming amount is too small. The lower-layer shimming strip structure plays the role of fixing the shimming strip. Since the upper-layer shimming strip structure of the present invention does not require the processing of screws and pin holes, the problem of simultaneous processing of pin holes and shimming strips affecting the calculation accuracy of the shimming magnetic field is avoided. Because the hole positions on the shimming strips are difficult to model in theoretical calculations, their influence on the magnetic field is ignored. The new shimming solution avoids the location of the hole positions, which can greatly improve the calculation accuracy of the shimming.

[0026] Based on the above invention principle, the present invention designs a terraced cyclotron shimming structure as follows Figure 4 As shown, its characteristics are: the terraced cyclotron strip shimming structure adopts a double layer, the upper strip structure is used for magnetic field shimming and is processed during the shimming process, and the lower strip structure is not used for magnetic field shimming and is not processed during the shimming process; the distance that the upper strip structure extends inward from the small radius to the large radius along the strip width direction and the distance that the upper strip structure extends downward along the height direction are a set distance.

[0027] Further, the set distance is at least 5 mm, that is, the upper strip structure extends inward at least 5 mm along the width direction away from the side of the high-frequency cavity housing, and the upper strip structure extends downward at least 5 mm along the height direction away from the top of the high-frequency cavity housing.

[0028] Furthermore, the lower strip structure is not used for magnetic field shimming and is not processed during the shimming process, that is, the lower strip structure does not participate in the calculation of magnetic field shimming, and the strip shimming calculation of the upper strip structure covers the shimming calculation of the lower strip structure.

[0029] Furthermore, the padding calculation of the upper-layer padding structure includes the padding calculation of the lower-layer padding structure, that is, when the padding amount of the upper-layer padding structure is insufficient, it can continue to extend inward in a direction of not less than 5 mm in the width direction of the padding, and can continue to extend downward in a direction of not less than 5 mm in the height direction of the padding.

[0030] Furthermore, the lower layer of the inlay structure is provided with pins, and the inlay is precisely fixed on the main magnet through the pins.

[0031] Furthermore, when the upper strip structure satisfies the requirement that the inward extension in the width direction and the downward extension in the height direction are not less than 5 mm, the distance inward extension in the width direction and the distance downward extension in the height direction may not be equal.

[0032] It should be emphasized that the above specific embodiments are merely explanations of the present invention, and they are not limitations of the present invention. After reading this specification, those skilled in the art can make modifications to the above embodiments without any creative contribution as needed, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A terraced cyclotron strip shimming structure, characterized in that: The terraced cyclotron strip shimming structure adopts a double layer, the upper strip structure is used for magnetic field shimming and is processed during the shimming process, and the lower strip structure is not used for magnetic field shimming and is not processed during the shimming process; the distance of the upper strip structure extending inward from the small radius to the large radius along the strip width direction and the distance of the upper strip structure extending downward along the height direction are a set distance; The set distance is at least 5 mm, that is, the upper strip structure extends inward at least 5 mm along the width direction away from the side of the high-frequency cavity housing, and the upper strip structure extends downward at least 5 mm along the height direction away from the top of the high-frequency cavity housing.

2. The terraced cyclotron strip shimming structure according to claim 1, characterized in that: The lower strip structure is not used for magnetic field shimming and is not processed during the shimming process, that is, the lower strip structure does not participate in the calculation of magnetic field shimming, and the strip shimming calculation of the upper strip structure covers the shimming calculation of the lower strip structure.

3. The terraced cyclotron strip shimming structure according to claim 2, characterized in that: The padding calculation of the upper-layer padding structure includes the padding calculation of the lower-layer padding structure, that is, when the padding amount of the upper-layer padding structure is insufficient, it can continue to extend inward in a direction of not less than 5 mm in the width direction of the padding, and can continue to extend downward in a direction of not less than 5 mm in the height direction of the padding.

4. The terraced cyclotron strip shimming structure according to claim 1, characterized in that: The lower strip structure is installed with pins, and the strip is accurately fixed on the main magnet through the pins.

5. The terraced cyclotron shimming structure according to claim 1, characterized in that: When the upper strip structure satisfies the requirement that the inward extension in the width direction and the downward extension in the height direction are not less than 5 mm, the distance of the inward extension in the width direction and the distance of the downward extension in the height direction may not be equal.

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