A method for measuring the transverse emittance of a specific energy beam of a wide-energy-band charged particle beam

Abstract

The application relates to a method for measuring the transverse emittance of a specific energy beam of a wide-energy-spectrum charged particle beam, which is based on a quadrupole scanning method in beam transverse emittance measurement, and realizes the transverse emittance measurement of a narrow-band beam in a specific energy range of a wide-energy-spectrum charged particle beam by adding a set of orthogonally arranged diodes as an auxiliary energy screening device. The method can meet the measurement requirements of the wide-energy-spectrum charged particle beam by using a set of systems, can reduce the additional measurement error of the multi-energy beam when the transverse emittance is measured by using the quadrupole scanning method, can further improve the emittance measurement precision, and provides a feasible solution for measuring the transverse emittance of the beam in the energy range of the wide-energy-spectrum charged particle.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of charged particle beam quality testing, in particular, to a method for measuring the transverse emittance of a specific energy beam of a wide energy spectrum charged particle beam. BACKGROUND

[0002] As a new type of physical detection, measurement and testing means, charged particle beam is no longer limited to the field of theoretical physics research, but is gradually applied to people's livelihood fields such as food production, medical diagnosis and treatment, as well as many scientific research fields such as material, biological imaging and radiation chemistry. In many application scenarios, beam transverse emittance is one of the important parameters for measuring beam quality. In the field of charged particle beam parameter measurement, quadrupole scanning method is a basic method for measuring the transverse emittance of charged particle beam. The principle is based on the spatial charged particle beam transport equation of Liouville theorem. By measuring the beam size change information of charged particle beam under different magnetic field transmission conditions multiple times, the characteristic parameters of the charged particle beam transport equation in the transport direction are obtained through the method of undetermined coefficients, and finally the transverse emittance of the charged particle beam is derived. In this process, the charged particle beam is transmitted in space. Each group of magnetic field size and direction, transmission distance and charged particle energy can uniquely determine the beam size of the charged particle beam downstream of the transmission. Multiple groups of magnetic fields correspond to multiple beam sizes, and each transmission process is described by a different transmission equation. When different transmission magnetic fields are generated by electromagnets and the beam size of the downstream charged particle beam is measured, multiple transmission equations can be obtained, thereby realizing the measurement of the transverse emittance of the charged particle beam.

[0003] At present, the quadrupole scanning method has the advantages of large measurable range, fast measurement speed and suitability for high-energy charged particle beam, etc. However, when calculating the transverse emittance, the transmission equation of the charged particle beam needs to be obtained according to the energy of the charged particle beam. Under ideal conditions, the charged particle beam is of single energy, and the derived transmission equation of the charged particle beam is applicable to all charged particles in the measurement process. Meanwhile, the transmission characteristics of the charged particle beam of single energy are consistent when passing through the quadrupole, and there is no chromatic aberration (i.e. imaging difference of the charged particle beam caused by energy difference) when measuring the beam size, so the measurement accuracy of the beam size is higher. However, in the usual measurement scene, the energy of the charged particle beam has a certain distribution range. When measuring the transverse emittance of the narrow energy spectrum charged particle beam with a small energy distribution range, the measurement error caused by the energy difference can be ignored. However, when measuring the transverse emittance of the wide energy spectrum charged particle beam with a large energy distribution range, the transmission equation error and the beam size measurement error caused by the energy difference will have a great influence, and the measurement accuracy of the quadrupole scanning method will be reduced. On the other hand, for the wide energy spectrum charged particle beam, it may be necessary to measure the transverse emittance of the particles in a certain energy range. This special requirement cannot be well achieved when using the traditional quadrupole scanning method. No matter how the nominal energy is selected, the measurement result of the traditional method is the statistical result of all energy charged particles, and it is impossible to distinguish the contribution and influence of each energy particle on the measurement result. SUMMARY

[0004] In order to overcome at least one deficiency in the prior art, the present application provides a method for measuring the transverse emittance of a specific energy beam of a wide energy spectrum charged particle beam.

[0005] In a first aspect, a device for measuring the transverse emittance of a specific energy beam of a wide energy spectrum charged particle beam is provided, comprising: a charged particle beam source, an adjustable quadrupole, an energy slit, a diode assembly, a fluorescent screen assembly and a beam junk can; the diode assembly comprises a horizontal diode and a vertical diode, and the fluorescent screen assembly comprises a first fluorescent screen and a second fluorescent screen; the beam junk can is used to collect the charged particle beam which does not participate in deflection;

[0006] The direction of the energy slit is determined according to the selected transverse emittance measurement direction of the beam to be measured; if the transverse emittance measurement direction is the horizontal direction, the direction of the energy slit is the horizontal direction; if the transverse emittance measurement direction is the vertical direction, the direction of the energy slit is the vertical direction;

[0007] The charged particle beam source continuously emits a to-be-tested charged particle beam current, and after the to-be-tested charged particle beam current passes through the adjustable quadrupole, if the transverse emittance measurement direction is a horizontal direction, the to-be-tested charged particle beam current passes through an energy slit and a vertical dipole to be imaged on a central part of a first fluorescent screen, and if the transverse emittance measurement direction is a vertical direction, the to-be-tested charged particle beam current passes through the energy slit and a horizontal dipole to be imaged on a central part of a second fluorescent screen.

[0008] The adjustable quadrupole is controlled by a bipolar adjustable direct current power supply to generate different gradient scanning magnetic fields, so as to realize regulation and control of horizontal and vertical direction performances of the charged particle beam current; the dipole assembly is used for energy spectrum broadening and energy screening, and the energy slit is used for eliminating the influence of the transverse size of the beam current before the energy spectrum broadening and the energy screening; the magnetic field gradient of the quadrupole is changed by changing the excitation current of the adjustable quadrupole, so that the beam spot size on the fluorescent screen assembly changes, and the beam spot size and the excitation current of the corresponding adjustable quadrupole are used to calculate the transverse emittance of the charged particle beam current.

[0009] In one embodiment, the transverse emittance of the charged particle beam current is calculated, comprising:

[0010] According to the recorded multiple sets of excitation currents of the adjustable quadrupole and the beam spot sizes, the least square fitting method is used to determine the coefficients A and C in the charged particle beam transmission relationship formula, and the charged particle beam transmission relationship formula is:

[0011]

[0012] f=k4I4

[0013] L d =L1+Rθ+L2

[0014] wherein, is the square of the beam spot size, A, B and C are coefficients, L d is the total distance of the free drift of the beam current after passing through the adjustable quadrupole, f is the magnetic focal length of the adjustable quadrupole, I4 is the excitation current of the adjustable quadrupole, k4 is a proportional coefficient, L1 is the distance from the adjustable quadrupole to the dipole assembly, Rθ is the deflection distance in the dipole assembly, R is the deflection radius, θ is the rotation angle, and L2 is the distance from the dipole assembly to the fluorescent screen.

[0015] The transverse emittance of the charged particle beam current is calculated by using the following formula:

[0016]

[0017] wherein, ε is the transverse emittance of the charged particle beam current.

[0018] In one embodiment, the first fluorescent screen and the second fluorescent screen are both rectangular.

[0019] In a second aspect, a method for measuring transverse emittance of a specific energy beam of a wide-energy-band charged particle beam is provided, comprising:

[0020] In step S1, the magnetic field induction strength of the required dipole component is determined according to the energy of the charged particle beam to be measured; the excitation current of the electromagnet is determined according to the magnetic field induction strength; and the excitation current of the dipole component is set according to the excitation current of the electromagnet.

[0021] In step S2, the transverse emittance measurement direction of the charged particle beam to be measured is selected, and the direction of the energy slit is determined according to the transverse emittance measurement direction; if the transverse emittance measurement direction is a horizontal direction, the direction of the energy slit is a horizontal direction; if the transverse emittance measurement direction is a vertical direction, the direction of the energy slit is a vertical direction.

[0022] In step S3, the charged particle beam source continuously emits the charged particle beam to be measured, and after the charged particle beam to be measured passes through the adjustable quadrupole, if the transverse emittance measurement direction is a horizontal direction, the charged particle beam to be measured passes through the energy slit and the vertical dipole, and is imaged in the center of the first fluorescent screen; if the transverse emittance measurement direction is a vertical direction, the charged particle beam to be measured passes through the energy slit and the horizontal dipole, and is imaged in the center of the second fluorescent screen.

[0023] In step S4, the excitation current of the adjustable quadrupole is changed, and the beam spot size on the fluorescent screen assembly is recorded.

[0024] In step S5, the transverse emittance of the charged particle beam is calculated according to the beam spot size on the fluorescent screen assembly and the corresponding excitation current of the adjustable quadrupole.

[0025] In step S6, the transverse emittance measurement direction is changed, and step S2 is returned to until all transverse emittance measurement directions are measured.

[0026] In step S7, the energy of the charged particle beam to be measured is changed, and step S1 is returned to.

[0027] In one embodiment, the transverse emittance of the charged particle beam is calculated, comprising:

[0028] According to the recorded multiple sets of excitation current and beam spot size of the adjustable quadrupole, the least square fitting method is used to determine the coefficients A and C in the charged particle beam transmission relationship formula:

[0029]

[0030] f=k4I4

[0031] L d =L1+Rθ+L2

[0032] wherein, A, B, C are coefficients, L is the square of the beam spot size d is the total distance of the beam free drift after the adjustable quadrupole, f is the magnetic focal length of the adjustable quadrupole, I4 is the excitation current of the adjustable quadrupole, k4 is the proportional coefficient, L1 is the distance from the adjustable quadrupole to the dipole assembly, Rθ is the deflection distance in the dipole assembly, R is the deflection radius, θ is the rotation angle, and L2 is the distance from the dipole assembly to the fluorescent screen.

[0033] The transverse emittance of the charged particle beam is calculated using the following formula:

[0034]

[0035] wherein ε is the transverse emittance of the charged particle beam.

[0036] In one embodiment, the magnetic field induction strength of the dipole assembly required is determined according to the energy of the charged particle beam to be measured, using the following formula:

[0037]

[0038] wherein B2 is the magnetic field induction strength, E0 is the energy of the charged particle beam to be measured, m0 is the mass of the charged particle, c is the speed of light, e is the charge of the charged particle, and R is the deflection radius.

[0039] The excitation current of the electromagnet is determined according to the magnetic field induction strength, using the following formula:

[0040] I2 = B2 / k2

[0041] wherein I2 is the excitation current of the electromagnet, and k2 is the proportional coefficient.

[0042] Compared with the prior art, the present application has the following beneficial effects: the transverse emittance measurement method of the specific energy beam of the wide energy spectrum charged particle beam of the present application is based on the quadrupole scanning method in the beam transverse emittance measurement, and by adding a set of orthogonally arranged dipoles as an auxiliary energy screening device, the transverse emittance measurement of the narrow-band particle beam in a specific energy range in the wide energy spectrum charged particle beam is realized. Not only can the measurement requirements of the transverse emittance of the wide energy spectrum charged particle beam be met by using a set of systems, but also the additional measurement error of the multiple energy charged particle beams when the transverse emittance is measured by using the quadrupole scanning method can be reduced by using the screening effect of the dipole, and the measurement accuracy of the transverse emittance of the charged particle beam is further improved, thereby providing a feasible solution for the transverse emittance measurement of the wide energy spectrum charged particle beam. BRIEF DESCRIPTION OF DRAWINGS

[0043] The present application can be better understood with reference to the following description in conjunction with the accompanying drawings, in which:

[0044] Figure 1 A top view of a wide energy spectrum charged particle beam specific energy beam current lateral emittance measurement apparatus is shown;

[0045] Figure 2 A side view of a wide energy spectrum charged particle beam specific energy beam current lateral emittance measurement apparatus is shown;

[0046] Figure 3 A schematic view of an energy slit is shown;

[0047] Figure 4 A schematic view of a deflection of a charged particle beam current to be measured in a diode is shown;

[0048] Figure 5 A flow chart of a wide energy spectrum charged particle beam specific energy beam current lateral emittance measurement method is shown. DETAILED DESCRIPTION

[0049] In the following, exemplary embodiments of the present application will be described with reference to the drawings. In the description, not all features of a practical embodiment are described in order to keep the description clear and concise. It should be appreciated that during development of any such practical embodiment numerous implementation-specific decisions can be made in order to achieve the developer's specific goals, and these decisions can vary from one implementation to another.

[0050] It is also to be noted that, in order to avoid obscuring the present application with unnecessary detail, only the structures closely related to the solution according to the present application are shown in the drawings, while other details not closely related to the present application are omitted.

[0051] It is to be understood that the present application is not limited to the embodiments described, which can be modified in many ways. In the description, the embodiments can be combined with each other, features can be replaced or borrowed between different embodiments, and one or more features can be omitted in an embodiment.

[0052] The embodiment of the present application provides a kind of wide energy spectrum charged particle beam specific energy beam flow transverse emission degree measuring device, it is based on the improvement of existing quadrupole scanning method technology, increase its measurement function to the transverse emission degree of specific energy beam flow in wide energy spectrum charged particle beam flow, while improve the measurement accuracy of quadrupole scanning method to charged particle beam transverse emission degree.The transverse emission degree measuring device of the present application is jointly constituted by increasing a group of magnetic field direction orthogonal in the vacuum drift section between quadrupole and fluorescent screen, and the two dipole placed in front and back as energy screening component of charged particle beam flow, and replacing the traditional small size fluorescent screen (most is circular) with size larger rectangular fluorescent screen, and being assisted with slit and other auxiliary components, the two important characteristics that whole device uses magnetic field to deflect charged particle do not change its energy and charged particle transverse emission degree measurement and energy screening are not interfered with each other.The change of different excitation current and charged particle beam flow cluster size in the direction to be measured (horizontal direction or vertical direction) is the basis for calculating the transverse emission degree of charged particle beam when using quadrupole scanning method, the regulation and control of quadrupole to charged particle beam flow horizontal or vertical direction performance is effective to all energy charged particles, and the size change degree is related to the size of its energy, therefore increase dipole as energy screening device in the process of charged particle beam flow drift, set specific dipole excitation current, only select the charged particle beam flow of specific energy range to pass through, and measure the beam spot size, finally combine the excitation current of quadrupole, the energy size of screened charged particle beam flow, the three parameters of obtained beam spot size, finally realize the transverse emission degree measurement of specific energy charged particle beam flow.Because transverse emission degree measurement has directionality, therefore a group of two orthogonal direction magnetic fields are needed to realize the measurement of two direction transverse emission degree.

[0053] Figure 1 The top view of the wide energy spectrum charged particle beam specific energy beam flow transverse emission degree measuring device is shown, Figure 2 The side view of the wide energy spectrum charged particle beam specific energy beam flow transverse emission degree measuring device is shown, referring to Figure 1 And Figure 2 The wide energy spectrum charged particle beam specific energy beam flow transverse emission degree measuring device includes: charged particle beam source, adjustable quadrupole, energy slit, dipole component, fluorescent screen component and beam flow garbage can;The dipole component includes horizontal dipole and vertical dipole, and the fluorescent screen component includes first fluorescent screen and second fluorescent screen;Beam flow garbage can is used for collecting charged particle beam flow not involved in deflection, and reducing the influence of radiation;

[0054] The direction of energy slit is determined according to the selected transverse emission degree measurement direction of selected beam flow;If the transverse emission degree measurement direction is horizontal direction, the direction of energy slit is horizontal direction;If the transverse emission degree measurement direction is vertical direction, the direction of energy slit is vertical direction; Figure 3 The schematic diagram of energy slit is shown.

[0055] A charged particle beam source continuously emits a beam of charged particles to be measured. After passing through an adjustable quadrupole, if the transverse emittance measurement direction is horizontal, the beam passes through an energy slit and a vertical diode, and is imaged at the center of a first fluorescent screen. If the transverse emittance measurement direction is vertical, the beam passes through an energy slit and a horizontal diode, and is imaged at the center of a second fluorescent screen. Here, the beam is deflected after entering either the vertical or horizontal diode. Figure 4 A schematic diagram is shown showing the deflection of the beam of charged particles under test in a dipole.

[0056] The tunable quadrupole is controlled by a bipolar adjustable DC power supply to generate scanning magnetic fields with different gradients, thereby controlling the horizontal and vertical performance of the charged particle beam. The diode assembly is used for energy spectrum broadening and energy screening, and the energy slit is used to eliminate the influence of the beam's transverse size before energy spectrum broadening and energy screening. By changing the excitation current of the tunable quadrupole, the magnetic field gradient of the quadrupole is changed, which causes the beam spot size on the fluorescent screen assembly to change. The beam spot size and the corresponding excitation current of the tunable quadrupole are used to calculate the transverse emittance of the charged particle beam.

[0057] In this embodiment, the transverse emittance measurement device for a specific energy beam of a wide-spectrum charged particle beam uses a diode assembly, including two diodes: a horizontal diode and a vertical diode. The horizontal and vertical diodes can be respectively positioned in two branches of the vacuum tube. The horizontal diode is connected to a second fluorescent screen, and the vertical diode is connected to a first fluorescent screen. The two branches are used for measurements when the transverse emittance measurement direction is vertical and when it is horizontal, respectively. The orthogonal configuration of the magnetic field directions of the two diodes allows for simultaneous energy measurement and transverse emittance measurement in both directions without requiring reassembly of the equipment or compromising the integrity of the vacuum chamber, thus improving experimental measurement efficiency.

[0058] In addition, the adjustable quadrupole generates different gradient scanning magnetic fields to realize the regulation of the horizontal and vertical performance of the charged particle beam; the horizontal / vertical two groups of dipole provide uniform magnetic field to deflect the charged particle beam, and the deflection radius of the particles with different energies is proportional to the magnetic field strength. The dipole also uses electromagnet to change the magnetic field strength, thereby realizing the energy spectrum widening and energy selection. Through the energy selection of the dipole assembly, the energy of the charged particles imaged on the screen is basically uniform, which reduces the size deviation of the beam spot caused by the over-focusing or under-focusing of the non-nominal energy charged particles, and is beneficial to improve the measurement accuracy of the quadrupole scanning method. The screen assembly realizes the beam fluorescence imaging, and the formed beam spot is the basis for measuring the beam size of the charged particle beam. Other auxiliary devices include a vacuum pipeline for providing the ultra-high vacuum environment required for beam transmission; a quadrature slit for eliminating the influence of the transverse size of the beam spot before the energy spectrum widening and energy selection to ensure that only the beam center particles of the charged particle beam enter the subsequent measurement system; and a beam garbage can for collecting other non-deflected beams to reduce the radiation influence.

[0059] According to the beam transmission theory, the original size of the beam spot is The transverse emittance of the charged particle beam and the size of the beam spot on the screen There is a relationship as follows:

[0060]

[0061] wherein, is the square of the size of the beam spot, is the square of the original size of the beam spot, L d is the total distance of the free drift of the beam after passing through the quadrupole, L d =L1+Rθ+L2, L1 is the distance from the adjustable quadrupole to the dipole assembly, Rθ is the deflection distance in the dipole assembly, R is the deflection radius, θ is the rotation angle, and L2 is the distance from the dipole assembly to the screen; is the beam spot ellipse inclination direction and degree representation, f is the magnetic focal length of the adjustable quadrupole, and ε is the transverse emittance of the charged particle beam.

[0062] The variable substitution is made to the above transmission relationship to obtain:

[0063]

[0064] wherein, A, B and C are all coefficients,

[0065] Specifically, the calculation of the transverse emittance of the charged particle beam includes:

[0066] According to the recorded multiple groups of excitation currents of the adjustable quadrupole and the size of the beam spot, the least square fitting method is used to determine the coefficients A and C in the charged particle beam transmission relationship, and the charged particle beam transmission relationship is:

[0067]

[0068] f=k4I4

[0069] L d =L1+Rθ+L2

[0070] wherein, is the square of the beam spot size, A, B, C are coefficients, L d is the total distance of the beam free drift after passing through the adjustable quadrupole, f is the magnetic focal length of the adjustable quadrupole, I4 is the excitation current of the adjustable quadrupole, k4 is the proportional coefficient, L1 is the distance from the adjustable quadrupole to the dipole assembly, Rθ is the deflection distance in the dipole assembly, R is the deflection radius, θ is the rotation angle, and L2 is the distance from the dipole assembly to the fluorescent screen;

[0071] The transverse emittance of the charged particle beam is calculated using the following formula:

[0072]

[0073] wherein, ε is the transverse emittance of the charged particle beam.

[0074] The embodiment of the present application also provides a method for measuring the transverse emittance of a specific energy beam of a wide-energy-spectrum charged particle beam, Figure 5 The flow chart of the method for measuring the transverse emittance of a specific energy beam of a wide-energy-spectrum charged particle beam is shown in FIG. 1, and the method comprises the following steps. Figure 5

[0075] In step S1, the magnetic field induction intensity of the required dipole assembly is determined according to the energy of the to-be-measured charged particle beam, the excitation current of the electromagnet is determined according to the magnetic field induction intensity, the excitation current of the dipole assembly is set according to the excitation current of the electromagnet, and the charged particle beam is emitted for a short time to ensure that the beam can be correctly imaged in the center of the fluorescent screen.

[0076] Specifically, in order to ensure that the to-be-measured charged particle beam is deflected to the center of the fluorescent screen, the magnetic field induction intensity of the required dipole assembly is determined according to the action of the Lorentz force and the relativistic effect, and the following formula is used:

[0077]

[0078] wherein, B2 is the magnetic field induction intensity, E0 is the energy of the to-be-measured charged particle beam, m0 is the mass of the charged particle, c is the speed of light, e is the charge amount of the charged particle, and R is the deflection radius.

[0079] The excitation current of the electromagnet is determined according to the magnetic field induction intensity, and the following formula is used:

[0080] ​I2 = B2 / k2

[0081] Wherein, I2 is the electromagnet excitation current, k2 is the proportional coefficient, and the proportional coefficient k2 is related to the design of the measurement system.

[0082] Step S2, select the transverse emittance measurement direction of the to-be-measured beam, and determine the direction of the energy slit according to the transverse emittance measurement direction; if the transverse emittance measurement direction is the horizontal direction, the direction of the energy slit is the horizontal direction; if the transverse emittance measurement direction is the vertical direction, the direction of the energy slit is the vertical direction.

[0083] Step S3, the charged particle beam source continuously emits the to-be-measured charged particle beam, and after the to-be-measured charged particle beam passes through the adjustable quadrupole, if the transverse emittance measurement direction is the horizontal direction, the to-be-measured charged particle beam passes through the energy slit and the vertical dipole, and is imaged in the center of the first fluorescent screen; if the transverse emittance measurement direction is the vertical direction, the to-be-measured charged particle beam passes through the energy slit and the horizontal dipole, and is imaged in the center of the second fluorescent screen.

[0084] Step S4, change the excitation current of the adjustable quadrupole, and record the beam spot size on the fluorescent screen assembly.

[0085] Step S5, according to the beam spot size on the fluorescent screen assembly and the excitation current of the corresponding adjustable quadrupole, calculate the transverse emittance of the charged particle beam.

[0086] Specifically, the transverse emittance of the charged particle beam is calculated, including:

[0087] According to the recorded multiple sets of excitation currents of the adjustable quadrupole and the beam spot size, the least square fitting method is used to determine the coefficients A and C in the charged particle beam transmission relationship formula:

[0088]

[0089] f = k4I4

[0090] L d = L1+Rθ+L2

[0091] Wherein, is the square of the beam spot size, A, B, and C are coefficients, L d is the total distance of the free drift of the beam after passing through the adjustable quadrupole, f is the magnetic focal length of the adjustable quadrupole, I4 is the excitation current of the adjustable quadrupole, k4 is the proportional coefficient, L1 is the distance from the adjustable quadrupole to the dipole assembly, Rθ is the deflection distance in the dipole assembly, R is the deflection radius, θ is the deflection angle, and L2 is the distance from the dipole assembly to the fluorescent screen.

[0092] The transverse emittance of the charged particle beam is calculated using the following formula:

[0093]

[0094] wherein ε is the transverse emittance of the charged particle beam.

[0095] Step S6, change the transverse emittance measurement direction, return to step S2 until all transverse emittance measurement directions are measured;

[0096] Step S7, change the energy of the measured charged particle beam, return to step S1. Here, the above measurement steps are performed according to the new energy of the measured charged particle beam.

[0097] Compared with the prior art, the present application has the following technical effects:

[0098] The present application is based on the quadrupole scanning method in the measurement of the transverse emittance of the charged particle beam. By adding a set of orthogonally arranged diodes as auxiliary energy screening devices, the transverse emittance of the narrow-band charged particle beam in a specific energy range in the wide-energy-spectrum charged particle beam is measured. It can not only meet the measurement requirements of the transverse emittance of the wide-energy-spectrum charged particle beam with one set of system, but also reduce the additional measurement error of the multiple-energy charged particle beam when using the quadrupole scanning method to measure the transverse emittance, further improve the measurement accuracy of the transverse emittance of the high-energy charged particle beam, and provide a feasible solution for the measurement of the transverse emittance of the wide-energy-spectrum charged particle beam.

[0099] The above is only various embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An apparatus for measuring the transverse emittance of a specific energy beam current of a broad energy spectrum charged particle beam, characterized by, The apparatus comprises: a charged particle beam source, an adjustable quadrupole, an energy slit, a dipole assembly, a fluorescent screen assembly and a beam dump; the dipole assembly comprises a horizontal dipole and a vertical dipole, the fluorescent screen assembly comprises a first fluorescent screen and a second fluorescent screen; the beam dump is used for collecting charged particle beams which do not participate in deflection; the direction of the energy slit is determined according to the selected transverse emission measurement direction of the to-be-measured beam; if the transverse emission measurement direction is a horizontal direction, the direction of the energy slit is a horizontal direction; if the transverse emission measurement direction is a vertical direction, the direction of the energy slit is a vertical direction; the charged particle beam source continuously emits a to-be-measured charged particle beam, after the to-be-measured charged particle beam passes through the adjustable quadrupole, if the transverse emission measurement direction is a horizontal direction, the to-be-measured charged particle beam passes through the energy slit and the vertical dipole and is imaged in the center of the first fluorescent screen, if the transverse emission measurement direction is a vertical direction, the to-be-measured charged particle beam passes through the energy slit and the horizontal dipole and is imaged in the center of the second fluorescent screen; the adjustable quadrupole is controlled by a bipolar adjustable direct current power supply and is used for generating different gradient scanning magnetic fields to realize the regulation and control of the horizontal and vertical direction performance of the charged particle beam; the dipole assembly is used for energy spectrum broadening and energy screening, and the energy slit is used for eliminating the influence of the transverse size of the beam before energy spectrum broadening and energy screening; by changing the excitation current of the adjustable quadrupole, the magnetic field gradient of the quadrupole is changed, so that the beam spot size on the fluorescent screen assembly changes, and the beam spot size and the corresponding excitation current of the adjustable quadrupole are used to calculate the transverse emission of the charged particle beam.

2. The apparatus of claim 1, wherein, The calculation of the transverse emission of the charged particle beam comprises: According to the recorded groups of excitation current of the adjustable quadrupole and the beam spot size, the least square fitting method is used to determine the coefficients in the charged particle beam current transmission relationship formula , , the charged particle beam current transmission relationship formula is: wherein is the square of the beam spot size, , , are coefficients, is the total distance of the free drift of the beam after the adjustable quadrupole, is the magnetic focal length of the adjustable quadrupole, is the excitation current of the adjustable quadrupole, is the proportionality coefficient, is the distance of the adjustable quadrupole to the dipole assembly, is the deflection distance in the dipole assembly, is the deflection radius, is the turning angle, is the distance of the dipole assembly to the screen; The calculation of the transverse emission of the charged particle beam adopts the following formula: wherein is the transverse emittance of the charged particle beam.

3. The apparatus of claim 1, wherein, The first fluorescent screen and the second fluorescent screen are both rectangular.

4. A method of measuring the transverse emittance of a beam of charged particles of a specific energy of a wide energy spectrum of charged particles, based on the device for measuring the transverse emittance of a beam of charged particles of a specific energy of a wide energy spectrum of charged particles according to any one of claims 1 to 3, characterized in that, The apparatus comprises: Step S1, determining the magnetic field induction intensity of the required dipole assembly according to the energy of the to-be-measured charged particle beam; determining the electromagnetic excitation current according to the magnetic field induction intensity; setting the excitation current of the dipole assembly according to the electromagnetic excitation current; Step S2, selecting a transverse emission measurement direction of the to-be-measured beam, and determining the direction of the energy slit according to the transverse emission measurement direction; if the transverse emission measurement direction is a horizontal direction, the direction of the energy slit is a horizontal direction; if the transverse emission measurement direction is a vertical direction, the direction of the energy slit is a vertical direction; Step S3, the charged particle beam source continuously emits a to-be-measured charged particle beam, after the to-be-measured charged particle beam passes through the adjustable quadrupole, if the transverse emission measurement direction is a horizontal direction, the to-be-measured charged particle beam passes through the energy slit and the vertical dipole and is imaged in the center of the first fluorescent screen, if the transverse emission measurement direction is a vertical direction, the to-be-measured charged particle beam passes through the energy slit and the horizontal dipole and is imaged in the center of the second fluorescent screen; Step S4, changing the exciting current of the adjustable quadrupole, recording the beam spot size on the fluorescent screen assembly; Step S5, calculating the charged particle beam current transverse emittance according to the beam spot size on the fluorescent screen assembly and the corresponding exciting current of the adjustable quadrupole; Step S6, changing the transverse emittance measurement direction, returning to Step S2 until all the transverse emittance measurement directions are measured; Step S7, changing the energy of the charged particle beam to be measured, returning to Step S1.

5. The method of claim 4, wherein, The calculation of the charged particle beam current transverse emittance comprises: According to the recorded groups of excitation current of the adjustable quadrupole and the beam spot size, the least square fitting method is used to determine the coefficients in the charged particle beam current transmission relationship formula , , the charged particle beam current transmission relationship formula is: wherein is the square of the beam spot size, , , are coefficients, is the total distance of the free drift of the beam after the adjustable quadrupole, is the magnetic focal length of the adjustable quadrupole, is the excitation current of the adjustable quadrupole, is a proportionality coefficient, is the distance of the adjustable quadrupole to the dipole assembly, is the deflection distance in the dipole assembly, is the deflection radius, is the turning angle, is the distance of the dipole assembly to the screen; The calculation of the charged particle beam current transverse emittance comprises the following formula: wherein is the transverse emittance of the charged particle beam.

6. The method of claim 4, wherein, Wherein, According to the energy of the charged particle beam to be measured, the magnetic field induction intensity of the required dipole assembly is determined by the following formula: wherein, B 2is the magnetic field induction, E 0is the energy of the charged particle beam to be measured, m 0is the mass of the charged particle, c is the speed of light, e is the charge of the charged particle, R is the deflection radius; According to the magnetic field induction intensity, the electromagnet exciting current is determined by the following formula: According to the magnetic field induction intensity, the electromagnet exciting current is determined by the following formula: I 2= B 2 / k 2 wherein I 2 is the electromagnetic excitation current, k 2 is a proportionality factor.

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