CN114828381A - Magnetic field structure for high-power accelerator lead-out area - Google Patents

Magnetic field structure for high-power accelerator lead-out area Download PDF

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CN114828381A
CN114828381A CN202210549127.3A CN202210549127A CN114828381A CN 114828381 A CN114828381 A CN 114828381A CN 202210549127 A CN202210549127 A CN 202210549127A CN 114828381 A CN114828381 A CN 114828381A
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magnetic
magnetic pole
section
magnetic field
accelerator
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边天剑
安世忠
冀鲁豫
付伟
周洪吉
魏素敏
管锋平
关镭镭
王飞
王哲
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China Institute of Atomic of Energy
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H13/00—Magnetic resonance accelerators; Cyclotrons
    • H05H13/005—Cyclotrons
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    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H7/00—Details of devices of the types covered by groups H05H9/00, H05H11/00, H05H13/00
    • H05H7/001—Arrangements for beam delivery or irradiation
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H7/00—Details of devices of the types covered by groups H05H9/00, H05H11/00, H05H13/00
    • H05H7/10—Arrangements for ejecting particles from orbits
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H7/00—Details of devices of the types covered by groups H05H9/00, H05H11/00, H05H13/00
    • H05H7/001—Arrangements for beam delivery or irradiation
    • H05H2007/005—Arrangements for beam delivery or irradiation for modifying beam emittance, e.g. stochastic cooling devices, stripper foils

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Abstract

The invention discloses a magnetic field structure for a lead-out area of a high-power accelerator, wherein the magnetic field structure of the lead-out area is distributed on a main magnetic pole of a multi-magnetic-circuit fan-shaped magnet, the magnetic field structure of the lead-out area distributed on the main magnetic pole of the multi-magnetic-circuit fan-shaped magnet is a composite two-section type magnetic pole structure, and the composite two-section type magnetic pole structure is used for enabling a magnetic air gap to start to rapidly descend when beam current is about to reach lead-out energy; the composite two-section magnetic pole structure divides the magnetic pole structure into two sections, an ab section and a bc section along the radial direction of the accelerator, the ab section close to the center of the accelerator is an isochronal magnetic pole section, the bc section close to the large radius of the accelerator is an unequal solidity section, a fine adjustment coil is installed on the magnetic pole at the unequal time interval, and a magnetic field generated by the coil is used for finely adjusting the average magnetic field
Figure DEST_PATH_IMAGE002
And the magnetic field gradient is finely adjusted, the invention combines the isochronism and the non-isochronism organically, increases the radial working point and gives consideration to enough axial focusing force, thereby meeting the requirements of the extraction area of the high-energy and high-power accelerator.

Description

Magnetic field structure for high-power accelerator lead-out area
Technical Field
The invention belongs to the technical field of high-power cyclotrons, and particularly relates to a magnetic field structure for a lead-out area of a high-power accelerator.
Background
The proton beam with high energy (GeV magnitude) and high average current intensity (mA magnitude) has important application in the fields of nuclear physics, public health, advanced energy, national defense safety and the like. In the field of leading edge fundamental research, a high-power accelerator is one of the main tools for researching mesoparticle physics, proton decay observation, muon physics and the like of physical strength leading edges. In the important fields of national economy such as public health, advanced energy and the like, fast neutrons generated by high-power proton targeting are ideal choices for nuclear waste treatment and rare isotope production. In the fields of national defense industry and homeland security, high-energy protons have extremely important and wide application in the aspects of shielding special nuclear materials by remote detection belts, preventing nuclear diffusion and nuclear threat, photographing high-Z materials in dynamic processes and the like.
The bottleneck problem of the circular accelerator which restricts high energy (GeV magnitude) and high average flow strength (mA magnitude) at the present stage is as follows:
1. the strong space charge effect of the high-energy and high-power accelerator causes beam halo to increase and beam quality to be poor, and the current average current is strong and is difficult to break through 3 mA. The particles are subjected to magnetic field force and repulsive force among the particles during movement, the strong space charge effect is the repulsive force among the particles, and the repulsive force is a nonlinear force between two charges, so that the beam group is enlarged in size. The loose particles at the cluster edge are called as the cluster halo, the stronger the space charge the more obvious the cluster halo is, and the more serious the cluster is, the worse the cluster quality is, i.e. the cluster size is large and the particle density at the cluster edge is small. The larger cluster size results in particles being lost during acceleration and during extraction: 1) during the acceleration process, because the quality of the beam cluster is poor, particles at the edge can be hit on the vacuum wall and lost, and the radiation dose is too large; 2) during extraction, the beam cloud quality is poor, causing particles in the beam cloud to strike the deflector plate, causing the deflector plate to ignite and damage. Therefore, the problem of beam loss caused by beam halo in the high-energy and high-power circular accelerator is a bottleneck problem of limited average flow strength.
2. The beam extraction of the high-energy and high-power accelerator is difficult. The types of ions to be accelerated are generally selected from the group consisting of a negative hydrogen ion H- (which is stripped to form a proton), an H2+ ion (which is stripped to form 2 protons), and a proton. Since electromagnetic stripping (electromagnetic stripping phenomenon occurs in a 0.3 Tesla magnetic field) is very easy to occur when the H-energy of the negative hydrogen ions is in GeV magnitude, so that a large amount of beam current loss is caused, only H2+ ions or protons can be selected to accelerate.
High-energy and high-power accelerators for accelerating H2+ ions all adopt a mode of multi-stage accelerator combination, the combination mode of the multi-stage accelerator combination is three-stage extraction as shown in figure 3, and the extraction modes from the upper stage to the lower stage are divided into two types: 1) stripping and leading out; 2) the electrostatic deflection plate is led out. The extraction of the last stage generally adopts a stripping extraction mode, because the stripping extraction mode has simple structure and high extraction efficiency. The difficulty is that the leading-out of the first stages is taken as an example, if the leading-out mode of the first stage and the second stage adopts an electrostatic deflector, the beam power deposited on the deflector cannot be larger than 200 watts, because the deflector is arranged between the first circle and the second circle of the leading-out area of each stage of accelerator, and the distance between the two circles is about 1 cm generally. If the electrostatic deflection plate is adopted for leading out, the particles in the beam halo can be bombarded on the deflection plate due to the small ring distance, so that the problems of large radiation dose, ignition of the deflection plate, short service life and the like are caused. If the first-stage and second-stage extraction modes adopt a stripping extraction mode, H2+ ions are stripped and then changed into 2 protons, the number of protons in a beam group is doubled, at the moment, a strong space charge effect is more easily generated, so that beam halo is increased, the quality of the beam group led out to a second-stage accelerator by the first stage is poor or the quality of the beam group led out to a third-stage accelerator by the second stage is poor, when the beam of the third-stage accelerator is led out, because electrons in the beam group are stripped in the first stages, even if the beam halo is increased, the stripping extraction mode cannot be adopted, and only a deflection plate is adopted for extraction, so that the beam quality of the extracted particles of the third stage is poor.
In summary, when the multi-stage extraction method is adopted, the difficulties of the previous extraction stages are: either of the conventional two extraction methods is used alone: 1) stripping and leading out; 2) the static deflection plates are difficult to make the flow intensity reach more than 3 mA: if the electrostatic deflection plate is adopted for leading out, beam corona is large due to the strong space charge effect of high-power beam current, and ignition is caused on the deflection plate; if stripping extraction is adopted, the strong space charge effect becomes strong because the number of protons of the stripped cluster is doubled; since the peel-off lead-out can only be used once, only a deflection plate lead-out can be used in the third stage.
In the prior art, in order to solve the problem of small ring spacing of a beam extraction deflector, particles are injected in a non-centering oscillation mode, the oscillation is carried out until the beam extraction deflector of an accelerator, and the ring spacing is enlarged through the amplitude generated during the oscillation. Although the circle spacing can be enlarged, the non-centered injection mode cannot cross the integer resonance, and the non-centered injection mode adopts a method of reducing a local magnetic field and reducing a radial working point to be close to a half-integer resonance point in an integer resonance region, for example, the radial working point is retreated from a position adjacent to an integer resonance line vr equal to 2 to a position of the half-integer resonance with a radial working point of 1.5, and the method causes the beam to be in a longitudinal defocusing phase of a high-frequency acceleration cavity, so that the beam is longitudinally stretched.
Disclosure of Invention
The invention provides a magnetic field structure for a high-power accelerator lead-out area, which aims to solve the problem that the beam longitudinal stretching is caused by the fact that the beam is in the longitudinal defocusing phase of a high-frequency acceleration cavity only by reducing a local magnetic field in the prior art.
The invention provides the following technical scheme for solving the technical problems.
A magnetic field structure for a high-power accelerator lead-out area is arranged on a main magnetic pole of a multi-magnetic-circuit fan-shaped magnet, and the multi-magnetic-circuit fan-shaped magnet is uniformly arranged in an accelerator annular vacuum chamber along the upper layer and the lower layer of the central plane of the accelerator; each magnetic pole cover plate of the multi-magnetic loop fan-shaped magnet is provided with a plurality of magnetic poles which can form a plurality of magnetic field loops, and the magnetic field directions of two adjacent magnetic poles of the plurality of magnetic poles are opposite; the multi-magnetic loop fan-shaped magnet comprises a back yoke at the position of a magnetic pole with large radius, a magnetic pole cover plate with one end connected with the back yoke and the other end extending to the center of an accelerator, and a plurality of raised fan-shaped magnetic poles on the lower surface or the upper surface of the magnetic pole cover plate; the plurality of raised fan-shaped magnetic poles comprise a main magnetic pole and more than one non-main magnetic pole, a coil is wound on the main magnetic pole, a coil is not wound on the more than one non-main magnetic pole, and the volume of the main magnetic pole is larger than that of the non-main magnetic pole; the return yoke and the main magnetic pole and the non-main magnetic pole respectively form a magnetic field loop;
the magnetic field structure of the leading-out area is based on an integer resonance suppressor, the integer resonance suppressor consists of a plurality of suppressor coil groups, and the plurality of suppressor coil groups are uniformly distributed in a drift section area which is free from magnet and high-frequency cavities along the circumferential direction of the accelerator; the resonance suppressor for suppressing integer resonance is characterized in that 4n resonance suppression coil groups are distributed along the circumferential direction of the accelerator according to the requirement of generating an n-th harmonic magnetic field with an adjustable phase, and the 4n suppressor coil groups are surrounded and uniformly distributed at the large radius of the annular vacuum chamber of the accelerator; each suppressor coil group is provided with a first coil and a second coil, the phases of the first coil and the second coil have a certain difference, and the difference in the magnetic field phase is determined by the coil current;
it is characterized in that the fan is arranged on a plurality of magnetic loopsThe magnetic field structure of the leading-out area on the main magnetic pole of the magnet is a composite two-section type magnetic pole structure, and the composite two-section type magnetic pole structure is used for enabling a magnetic air gap to start to rapidly descend when beam current is about to reach leading-out energy; the composite two-section magnetic pole structure divides the magnetic pole structure into two sections, an ab section and a bc section along the radial direction of the accelerator, the ab section close to the center of the accelerator is an isochronal magnetic pole section, the bc section close to the large radius of the accelerator is an unequal solidity section, a fine adjustment coil is installed on the magnetic pole at the unequal period, and a magnetic field generated by the fine adjustment coil is used for finely adjusting an average magnetic field B av And finely adjusting the magnetic field gradient to achieve the purpose of finely adjusting the radial working point.
The ab segment of the two-segment magnetic pole is used for realizing isochronism, and the average magnetic field must satisfy B av
B av ＝γ·B 0
Gamma is Lorentz factor and is in direct proportion to beam energy, B 0 For central field strength, it is necessary to gradually decrease the ab-segment field gap slowly from h1 to h2 for increasing the average field.
When the beam current is about to reach the extraction energy, the bc section of the two-section magnetic pole generally enters the bc section in 5-10 circles before the extraction, the bc section is different from the ab section, and the bc section does not satisfy the isochronism relational expression B any more av ＝γ·B 0 To increase the magnetic field gradient
Figure BDA0003653806380000051
The radial operating point is brought quickly closer to half-integer resonance, and the magnetic air gap of the bc segment begins to fall quickly from h2 to h3, at which time B av ＞γ·B 0 。
The extent of the magnetic air gap descent depends on the desired magnetic field gradient, radial operating point:
vr＝1-n
Figure BDA0003653806380000052
the magnetic air gap is rapidly reduced from h2 to h3
Figure BDA0003653806380000053
Increasing, directing vr to increase to near half an integer.
The radial length of the fine adjustment coil is slightly smaller than the radial length of the bc section, and the width of the fine adjustment coil is slightly smaller than the width of the magnetic pole.
Advantageous effects of the invention
The invention overcomes the traditional prejudice, organically combines the isochronism and the non-isochronism, increases the radial working point and gives consideration to enough axial focusing force, finds an optimal combination point between the isochronism and the non-isochronism, finds an optimal combination point between the increased radial working point and the given consideration to the axial focusing force, organically combines the technologies of the isochronism, the non-isochronism, the increased radial working point, the increased axial focusing force and the integer resonance line crossing, is mutually dependent and interdependent, and meets the requirement of a high-energy and high-power accelerator lead-out area.
Drawings
FIG. 1 is a perspective view of a magnetic field configuration for a high power accelerator extraction region;
FIG. 2 is a schematic diagram of a magnetic field configuration for a high power accelerator extraction region;
FIG. 3 is a schematic diagram of increasing the average magnetic field at the takeoff to bring the radial operating point vr rapidly close to a half integer;
FIG. 4-1 is a diagram of an integer resonance suppressor layout structure;
FIG. 4-2 is a schematic diagram of an integer resonance suppressor coil set;
4-3 are schematic diagrams of integer resonance suppressor current distribution;
in the figure, 1-1: back yoke; 1-2: a magnetic pole cover plate; 1-3: a main magnetic pole; 1-4: a non-main magnetic pole; 1-5: a field coil; 1-6: fine tuning the coil;
2-1: a suppressor coil set; 2-2: a suppressor coil set; 2-3: a suppressor coil set; 2-4: a suppressor coil set; 2-5: a suppressor coil set; 2-6: a suppressor coil set; 2-7: a suppressor coil set; 2-8: a suppressor coil set; 2-9: a suppressor coil set; 2-10: a suppressor coil set; 2-11: a suppressor coil set; 2-12: a suppressor coil set;
Detailed Description
Design principle of the invention
In order to obtain larger ring spacing and increase the average magnetic field at the leading-out part, the invention leads the radial working current vr to be quickly close to a half integer, and the ring spacing can be enlarged to be close to three times by matching with the optimization of the leading-out ring spacing. The adopted technical means is as follows: the magnetic field structure of an extraction area distributed on the main magnetic pole of the multi-magnetic loop fan-shaped magnet is a composite two-section type magnetic pole structure, and the composite two-section type magnetic pole structure is used for enabling a magnetic air gap to start to rapidly descend when beam current reaches extraction energy; the composite two-section magnetic pole structure divides the magnetic pole structure into two sections, an ab section and a bc section along the radial direction of the accelerator, the ab section close to the center of the accelerator is an isochronous magnetic pole section, the bc section close to the large radius of the accelerator is a non-isochronous section, a fine adjustment coil is installed on the non-isochronous magnetic pole, and a magnetic field generated by the coil is used for finely adjusting an average magnetic field B av And finely adjusting the magnetic field gradient to achieve the purpose of finely adjusting the radial working point.
The technical characteristics represent organic combination of 3 aspects:
1. isochronous and non-isochronous combinations: the invention overcomes the traditional prejudice that the magnetic field intensity is increased and the partial deviation is isochronism when the last 5-10 circles are dared. This is because the destructive isochronism is a phase mismatch between the beam and the high frequency cavity only when the isochronism is destroyed for a long time (multiple turns). The invention achieves the purpose of enlarging the circle distance by destroying the isochronism when the beam is led out for a plurality of circles, and the condition of serious mismatch is not developed due to small mismatching degree of the beam and the high-frequency cavity and local destroyed isochronism, so that the invention is allowable.
2. The combination of increasing the radial working point and taking into account sufficient axial focusing force: increasing the radial working point requires increasing the radial focusing force, which inevitably reduces the axial focusing force at the same time, which is a pair of contradictions. Too low a local axial focusing force also leads to beam divergence. The invention adopts that before the local magnetic field is enhanced to enhance the radial focusing force, the axial focusing force is made enough: the multi-magnetic circuit fan-shaped magnet is used for strengthening the axial focusing force, and although the axial focusing force is reduced while the local radial focusing force is strengthened, the axial focusing force is reduced a little bit because the axial focusing force is high enough. The multi-magnetic-circuit fan-shaped magnet and the magnetic field structure of the extraction area support mutual dependence. If only the multi-magnetic-circuit fan-shaped magnet improves the axial focusing force and does not have a magnetic field structure of the lead-out area, the radial focusing force of the lead-out area cannot be improved sufficiently, and the radial working point cannot be increased and is close to the half-integer resonance point; if only the radial focusing force of the extraction area is strengthened, but the axial focusing force has insufficient foundation, when the radial focusing force is strengthened, the beam current is dispersed due to the fact that the axial focusing force is too low, and at the moment, even if the radial working point is close to a half-integer resonance point, the circle distance of the extraction area is enlarged, the beam current is greatly lost due to the fact that the beam current dispersion degree is increased, the beam halo is enlarged or the beam group is widened.
3. The forward crossing of integer resonance combined with increasing the radial operating point: if the integer resonance line cannot be traversed forward, the radial operating point can only be chosen to be lowered to near half an integer in order to bring the radial operating point close to half an integer. Just because the beam can pass through the integer resonance line in the forward direction, the method of increasing the radial working point to be close to a half integer is realized. If the integer resonance is only passed through in the forward direction without increasing the radial working point to be close to a half integer, the spacing between the leading-out rings cannot be maximized. The two support interdependence.
Based on the inventive principle, the invention designs a magnetic field structure for the lead-out region of a high-power accelerator,
a magnetic field structure for a lead-out area of a high-power accelerator is shown in figures 1 and 2, and the magnetic field structure of the lead-out area is distributed on main poles 1-3 of a multi-magnetic-circuit fan-shaped magnet; the multi-magnetic loop fan-shaped magnets are uniformly distributed in the annular vacuum chamber of the accelerator along the upper layer and the lower layer of the central plane of the accelerator; each magnetic pole cover plate of the multi-magnetic loop fan-shaped magnet is provided with a plurality of magnetic poles which can form a plurality of magnetic field loops, and the magnetic field directions of two adjacent magnetic poles of the plurality of magnetic poles are opposite; the multi-magnetic-circuit fan-shaped magnet comprises a back yoke 1-1 at the position of a magnetic pole with large radius, a magnetic pole cover plate 1-2 with one end connected with the back yoke 1-1 and the other end extending to the center of an accelerator, and a plurality of raised fan-shaped magnetic poles on the lower surface or the upper surface of the magnetic pole cover plate; the plurality of raised fan-shaped magnetic poles comprise a main magnetic pole 1-3 and more than one non-main magnetic pole 1-4, a coil 1-5 is wound on the main magnetic pole 1-3, no coil is wound on the more than one non-main magnetic pole 1-4, and the volume of the main magnetic pole 1-3 is larger than that of the non-main magnetic pole 1-4; the main magnetic pole 1-3, the return yoke 1-1 and the non-main magnetic pole 1-4 form a magnetic field loop respectively;
the magnetic field structure of the leading-out area is based on an integer resonance suppressor, the integer resonance suppressor consists of a plurality of suppressor coil groups, and the plurality of suppressor coil groups are uniformly distributed in a drift section area which is free from magnet and high-frequency cavities along the circumferential direction of the accelerator; the resonance suppressor for suppressing integer resonance is characterized in that 4n resonance suppression coil groups are distributed along the circumferential direction of the accelerator according to the requirement of generating an n-th harmonic magnetic field with an adjustable phase, and the 4n suppressor coil groups are surrounded and uniformly distributed at the large radius of the annular vacuum chamber of the accelerator; each suppressor coil group is provided with a first coil and a second coil, the phases of the first coil and the second coil have a certain difference, and the difference in the magnetic field phase is determined by the coil current;
the magnetic field structure of the lead-out area arranged on the main magnetic pole of the multi-magnetic loop fan-shaped magnet is a composite two-section type magnetic pole structure as shown in fig. 1 and fig. 2, and the composite two-section type magnetic pole structure is used for enabling a magnetic air gap to start to rapidly descend when beam current reaches lead-out energy; the composite two-section magnetic pole structure divides the magnetic pole structure into two sections, an ab section and a bc section along the radial direction of the accelerator, the ab section close to the center of the accelerator is an isochronous magnetic pole section, the bc section close to the large radius of the accelerator is a non-isochronous section, fine adjustment coils 1-6 are installed on the non-isochronous magnetic poles, and magnetic fields generated by the fine adjustment coils 1-6 are used for finely adjusting an average magnetic field Bav and finely adjusting the magnetic field gradient, so that the purpose of finely adjusting the radial working point is achieved.
Supplementary explanation on the integer resonance suppressor:4n resonance suppression coil sets are required to generate the nth harmonic magnetic field; the 4n resonance suppression coil groups are arranged along the circumferential direction of the acceleratorEvenly distributed at equal intervals; and are numbered 1-4 n in sequence.
When generating n-th harmonic magnetic field with adjustable phase, the n-th harmonic magnetic field is composed of n resonance suppression coil groups 1 st The general expression of the serial number is 4i +1, and an n-th harmonic magnetic field with a fixed phase is formed; in order to ensure that the average magnetic field is not changed, n other resonance suppression coil compositions 2 with opposite currents are also needed nd The general formula of group number is 4i +3, 1st group and 2 nd The group resonance suppression coil forms an n-th harmonic magnetic field forming a fixed phase, and the average magnetic field is unchanged; in order to generate 3 rd harmonic magnetic field with adjustable phase, another two groups and 1 are needed st Group, 2 nd Set orthogonal resonance suppression coil 3 rd Group, resonance suppression coil 4 th Set of resonance suppression coils 3 rd The general formula of the number of the group is 4i +2, and the resonance suppression coil 4 th The general formula of the group is 4i +4, the value range of i is 0 to n-1, and four groups of resonance suppression coil units are formed.
As shown in fig. 4-1, in this embodiment, in order to distinguish the labels, the number of the suppression coil group in fig. 4-1 is divided into two parts, a prefix part and a general formula part, where the prefix part can be changed by itself as required, and the following general formula is not changed. In this embodiment, 4 general formulas: 4i +1, 4i +2, 4i +3, 4i +4 are preceded by prefix 2_, and the coil groups are numbered as 2_4i +1, 2_4i +2, 2_4i +3, 2_4i + 4;
the current distribution of the 1st group is shown in FIGS. 4-3 as
Figure BDA0003653806380000091
Current distribution of the 2nd group is
Figure BDA0003653806380000092
3 rd Current distribution of the group is
Figure BDA0003653806380000093
4 th Group current distribution of
Figure BDA0003653806380000094
The position of the first coil is the position before integer resonance, the position of the second coil is the position after integer resonance, and the radial range covered by the first coil is about the track width of 5-10 turns before integer resonance; the radial range covered by the second coil is about the track width of 5-10 circles after integral resonance.
As shown in FIG. 2, the ab-segment of the two-segment magnetic pole is used to achieve isochronism, and the average magnetic field must satisfy B av
B av ＝γ·B 0
Gamma is Lorentz factor and is in direct proportion to beam energy, B 0 For central field strength, it is necessary to gradually decrease the ab-segment field gap slowly from h1 to h2 for increasing the average field.
When the beam current is about to reach the extraction energy, the bc section of the two-section magnetic pole generally enters the bc section in 5-10 circles before the extraction, the bc section is different from the ab section, and the bc section does not satisfy the isochronism relational expression B any more av ＝γ·B 0 For increasing the magnetic field gradient, as shown in FIG. 3
Figure BDA0003653806380000101
The radial operating point is brought quickly closer to the half-integer resonance 3.5, as shown in FIG. 2, and the magnetic air gap of the bc segment begins to fall quickly from h2 to h3, at which time B av ＞γ·B 0 。
The extent to which the magnetic air gap is reduced depends on the desired magnetic field gradient, radial operating point:
(reference: Zengtian Jazz of cyclotron physics and engineering technology, written by Fan Mingwu atomic energy Press)
Figure BDA0003653806380000104
Figure BDA0003653806380000102
As shown in FIG. 3, the magnetic air gap rapidly decreases from h2 to h3, resulting in
Figure BDA0003653806380000103
Increasing, directing vr to increase to near half an integer.
The radial length of the fine adjustment coil is slightly smaller than the radial length of the bc section, and the width of the fine adjustment coil is slightly smaller than the width of the magnetic pole.
It should be emphasized that the above-described embodiments are merely illustrative and not restrictive of the current invention, and that those skilled in the art, after reading this specification, may make modifications to the embodiments as required without any inventive contribution, but that they fall within the scope of the appended claims.

Claims (5)

1. A magnetic field structure for a high-power accelerator lead-out area is arranged on a main magnetic pole of a multi-magnetic-circuit fan-shaped magnet, and the multi-magnetic-circuit fan-shaped magnet is uniformly arranged in an accelerator annular vacuum chamber along the upper layer and the lower layer of the central plane of the accelerator; each magnetic pole cover plate of the multi-magnetic loop fan-shaped magnet is provided with a plurality of magnetic poles which can form a plurality of magnetic field loops, and the magnetic field directions of two adjacent magnetic poles of the plurality of magnetic poles are opposite; the multi-magnetic loop fan-shaped magnet comprises a back yoke at the position of a magnetic pole with large radius, a magnetic pole cover plate with one end connected with the back yoke and the other end extending to the center of an accelerator, and a plurality of raised fan-shaped magnetic poles on the lower surface or the upper surface of the magnetic pole cover plate; the plurality of raised fan-shaped magnetic poles comprise a main magnetic pole and more than one non-main magnetic pole, a coil is wound on the main magnetic pole, a coil is not wound on the more than one non-main magnetic pole, and the volume of the main magnetic pole is larger than that of the non-main magnetic pole; the main magnetic pole, the return yoke and the non-main magnetic pole form a magnetic field loop respectively;
the magnetic field structure of the leading-out area is based on an integer resonance suppressor, the integer resonance suppressor consists of a plurality of suppressor coil groups, and the plurality of suppressor coil groups are uniformly distributed in a drift section area which is free from magnet and high-frequency cavities along the circumferential direction of the accelerator; the resonance suppressor for suppressing integer resonance is characterized in that 4n resonance suppression coil groups are distributed along the circumferential direction of the accelerator according to the requirement of generating an n-th harmonic magnetic field with an adjustable phase, and the 4n suppressor coil groups are surrounded and uniformly distributed at the large radius of the annular vacuum chamber of the accelerator; each suppressor coil group is provided with a first coil and a second coil, the phases of the first coil and the second coil have a certain difference, and the difference in the magnetic field phase is determined by the coil current;
the magnetic field structure of the lead-out area arranged on the main magnetic pole of the multi-magnetic loop fan-shaped magnet is a composite two-section type magnetic pole structure, and the composite two-section type magnetic pole structure is used for enabling a magnetic air gap to start to rapidly descend when beam current reaches lead-out energy; the composite two-section magnetic pole structure divides the magnetic pole structure into two sections, an ab section and a bc section along the radial direction of the accelerator, the ab section close to the center of the accelerator is an isochronal magnetic pole section, the bc section close to the large radius of the accelerator is an unequal solidity section, a fine adjustment coil is installed on the magnetic pole at the unequal time interval, and a magnetic field generated by the coil is used for finely adjusting an average magnetic field B av And finely adjusting the magnetic field gradient to achieve the purpose of finely adjusting the radial working point.
2. The magnetic field structure for the extraction region of a high power accelerator as claimed in claim 1, wherein: the ab segment of the two-segment magnetic pole is used for realizing isochronism, and the average magnetic field must satisfy B av
B av ＝γ·B 0
Gamma is Lorentz factor and is in direct proportion to beam energy, B 0 For central field strength, it is necessary to gradually decrease the ab-segment field gap slowly from h1 to h2 for increasing the average field.
3. The magnetic field structure for the extraction region of a high power accelerator as claimed in claim 1, wherein: when the beam current is about to reach the extraction energy, the bc section of the two-section magnetic pole generally enters the bc section in 5-10 circles before the extraction, the bc section is different from the ab section, and the bc section does not satisfy the isochronism relational expression B any more av ＝γ·B 0 To increase the magnetic field gradient
Figure FDA0003653806370000021
The radial operating point is brought quickly closer to half-integer resonance, and the magnetic air gap of the bc segment begins to fall quickly from h2 to h3, at which time B av >γ·B 0 。
4. The magnetic field structure for the extraction region of a high power accelerator as claimed in claim 1, wherein: the extent of the magnetic air gap descent depends on the desired magnetic field gradient, radial operating point:
Figure FDA0003653806370000022
Figure FDA0003653806370000023
the magnetic air gap is rapidly reduced from h2 to h3
Figure FDA0003653806370000024
Increasing until vr increases to near a half integer.
5. The magnetic field structure for the extraction region of a high power accelerator as claimed in claim 1, wherein: the radial length of the fine adjustment coil is slightly smaller than the radial length of the bc section, and the width of the fine adjustment coil is slightly smaller than the width of the magnetic pole.
CN202210549127.3A 2022-05-20 2022-05-20 Magnetic field structure for high-power accelerator lead-out area Pending CN114828381A (en)

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