A calibration device for a helix-based beam position detector

Abstract

The application relates to a particle accelerator beam diagnosis technology, and aims to solve the problem that an existing calibration device cannot calibrate the response of a beam position detector to non-relativistic beams, and provides a calibration device for a beam position detector based on a helix, which comprises a mounting table, a two-dimensional translation table, an electric rotating table, a first through pipe, a second through pipe, a helix assembly and a fixing support; a to-be-measured beam position detector is coaxially connected between the first through pipe and the second through pipe; the helix assembly is coaxially arranged in an internal space formed by the first through pipe, the to-be-measured beam position detector and the second through pipe; the helix assembly comprises a metal cylindrical inner core and an insulating sleeve, a helix is wound on the insulating sleeve, flange type SMA connectors are arranged at two ends of the metal cylindrical inner core, and the inner cores of the two flange type SMA connectors are electrically connected with the helix; one end of the flange type SMA connector is connected with an external signal generator, and the other end of the flange type SMA connector is connected with a matching load.

Description

Technical Field

[0001] This invention relates to particle accelerator beam diagnostic technology, and more specifically to a calibration device for a beam position detector based on a helical line. Background Technology

[0002] The beam position detector (BPM) is one of the most important unobstructed detectors in an accelerator, and the accuracy of its beam position measurement is crucial for the accelerator's commissioning and optimization. However, due to errors in manufacturing and assembly, each beam position detector (BPM) must undergo offline calibration before being installed on the test beamline to obtain its response coefficient to the beam position.

[0003] Currently, the beam position detector (BPM) is usually calibrated by using the wire drawing method or the antenna method to simulate the electromagnetic field generated by the beam at the speed of light.

[0004] However, simulation and experimental studies have revealed a correlation between the response of the beam position detector (BPM) and the relative velocity β of the beam. When the relative velocity β is small, the response of the BPM differs significantly from its response to a light-speed beam. Existing calibration devices cannot calibrate the response of the BPM to non-relativistic beams, thus failing to meet the requirements for high-precision position measurement. Therefore, accurately calibrating the response coefficient of the BPM installed in the low-energy band of the accelerator has become a major factor limiting the realization of high-precision position measurement for low-energy BPMs. Summary of the Invention

[0005] The purpose of this invention is to solve the problem that current calibration devices cannot calibrate the response of beam position detectors to non-relativistic beams, and to propose a calibration device for a beam position detector based on a spiral.

[0006] To achieve the above objectives, the technical solution proposed by this invention is as follows:

[0007] A calibration device for a beam position detector based on a helical line is characterized by comprising a mounting platform, a two-dimensional translation stage fixed on the mounting platform, an electric rotary stage fixed on the two-dimensional translation stage, a first through pipe and a second through pipe coaxially arranged from bottom to top on the electric rotary stage, as well as a helical line assembly and a fixing bracket.

[0008] The apertures of the first and second through-tubes are the same as the aperture of the beam position detector under test; the beam position detector under test is coaxially connected between the first and second through-tubes; the helical assembly is coaxially disposed within the internal space formed by the first through-tube, the beam position detector under test, and the second through-tube, and is used to simulate low-energy beams.

[0009] The helical assembly includes a metal cylindrical inner core and an insulating sleeve fitted on the metal cylindrical inner core. A helical wire is wound on the insulating sleeve. Both ends of the metal cylindrical inner core are provided with flange-type SMA connectors, and the inner cores of both flange-type SMA connectors are electrically connected to the helical wire. The flange-type SMA connector at one end of the metal cylindrical inner core is connected to an external signal generator, and the flange-type SMA connector at this end is mounted on the end of the second tube away from the position detector of the beam under test through the fixed bracket. The flange-type SMA connector at the other end of the metal cylindrical inner core is connected to a matching load for absorbing the electromagnetic waves transmitted by the helical assembly.

[0010] Furthermore, the spiral is spirally wound onto the insulating sleeve at a fixed interval using epoxy resin adhesive.

[0011] Furthermore, the fixed bracket includes a support crossbar and two support vertical bars respectively disposed at both ends of the support crossbar, for fixing and supporting the spiral wire assembly, so that the spiral wire assembly is coaxial with the first through tube, the beam position detector to be measured, and the second through tube; the two support vertical bars are fixed on the mounting platform;

[0012] In the spiral assembly, one end of the flange-type SMA connector connected to the external signal generator is mounted on the end of the second tube away from the position detector of the beam under test via a support crossbar; the flange-type SMA connector at the other end of the metal cylindrical core is located in the internal space formed by the first tube, the position detector of the beam under test, and the second tube.

[0013] Furthermore, the characteristic impedance of the spiral assembly and the impedance of the matched load are both 50 ohms.

[0014] Furthermore, the flange-type SMA connector is connected to an external signal generator via an RF coaxial cable to feed in RF signals, thereby calibrating the response of the beam position detector under test to signals of different frequencies or waveforms.

[0015] Furthermore, the metal cylindrical core is a stainless steel cylindrical core;

[0016] The spiral is a spiral copper strip.

[0017] Furthermore, the propagation speed v of the spiral assembly p The characteristic impedance Z0 satisfies the following equation:

[0018]

[0019] Where: L0 is the equivalent inductance, C0 is the equivalent capacitance, and β z Where γ is the axial phase shift constant and γ is the propagation constant. ∈0 and μ0 are the vacuum permittivity and permeability, respectively, and ω is the angular frequency. rI is the relative permittivity of the insulating sleeve. m and K m Let be the m-th modified Bessel functions of the first and second kind, respectively; a be the outer radius of the insulating sleeve; b be the radius of the first conduit; d be the radius of the inner core of the metal cylinder; φ = atan(p / 2πa) be the helix angle of the helix; and p be the pitch of the helix.

[0020] Furthermore, the radius of the metal cylindrical inner core, the thickness of the insulating sleeve, the width of the helix, and the winding pitch of the helix in the helical assembly are determined based on the propagation speed of the electromagnetic wave along the helical assembly and its characteristic impedance.

[0021] The beneficial effects of this invention are:

[0022] [1] The calibration device for a beam position detector based on a spiral wire proposed in this invention can calibrate the accurate response of the beam position detector to beams of different speeds and frequencies. It has a wide range of applications and high calibration accuracy. The spiral wire component can achieve a propagation speed that matches the beam, realize slow wave propagation, and at the same time ensure that the basic characteristics remain unchanged in a large frequency range. It has good broadband characteristics and can effectively simulate the electromagnetic field generated by low-energy beams.

[0023] [2] The present invention uses a spiral slow wave structure composed of a metal cylindrical inner core, an insulating sleeve, a spiral and two flange-type SMA connectors. One flange-type SMA connector is connected to an external signal generator via an RF coaxial line to feed in RF signals and obtain the response of the beam position detector to signals of different frequencies or waveforms. The other flange-type SMA connector is connected to a matching load to achieve efficient absorption of electromagnetic waves transmitted by the spiral assembly, which can effectively reduce signal reflection and improve the bandwidth of the calibration device.

[0024] [3] The present invention can realize the translation of the device in two-dimensional space by means of a two-dimensional translation stage, and can realize the rotation of the beam position detector under test by means of an electric rotary stage, so that the measurement direction of the detector under test coincides with the movement direction of the two-dimensional translation stage, which can effectively improve the calibration accuracy; keeping the aperture of the first tube and the second tube consistent with the aperture of the beam position detector under test can effectively ensure the continuity of the boundary conditions of the calibration device.

[0025] [4] The present invention can change the propagation speed of electromagnetic waves along the spiral assembly by adjusting the radius of the inner core of the metal cylinder on the spiral assembly, the thickness of the insulating sleeve, the width of the spiral and the winding pitch of the spiral, thereby simulating beams of different speeds and obtaining the response of the beam position detector to beams of different speeds, which greatly improves the measurement accuracy and measurement range of the beam position detector. Attached Figure Description

[0026] Figure 1This is a schematic diagram of the structure of a calibration device for a beam position detector based on a spiral wire according to the present invention.

[0027] Figure 2 This is a schematic diagram of the spiral assembly in an embodiment of the present invention;

[0028] Figure 3 This is a cross-sectional view of the spiral assembly in an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram showing the change of phase velocity and characteristic impedance of the helix with frequency in an embodiment of the present invention;

[0030] Where: (a) is a schematic diagram of the phase velocity of the helix changing with frequency, and (b) is a schematic diagram of the characteristic impedance changing with frequency;

[0031] Figure 5 This is a schematic diagram of the radial electric field distribution generated by the helix and the low-energy beam in an embodiment of the present invention;

[0032] Figure 6 This is a schematic diagram comparing the beam position detector response calibrated by the calibration device with the theoretically calculated beam position detector response in an embodiment of the present invention.

[0033] Figure label:

[0034] 1- Mounting platform, 2- Two-dimensional translation stage, 3- Electric rotary stage, 4- First through pipe, 5- Second through pipe, 6- Fixed bracket, 7- Beam position detector, 8- Metal cylindrical inner core, 9- Insulating sleeve, 10- Helical wire, 11- Flange type SMA connector, 12- Matching load, 13- Supporting crossbar, 14- Supporting vertical bar. Detailed Implementation

[0035] like Figure 1 As shown, a calibration device for a beam position detector based on a spiral includes a mounting platform 1, a two-dimensional translation stage 2 fixed on the mounting platform 1, an electric rotary stage 3 fixed on the two-dimensional translation stage 2, a first through pipe 4 and a second through pipe 5 coaxially arranged from bottom to top on the electric rotary stage 3, as well as a spiral assembly and a fixing bracket 6.

[0036] Among them, the calibration device can be translated in the xoy plane by the two-dimensional translation stage 2, and the electric rotary stage 3 is adjusted so that the measurement direction of the detector under test coincides with the movement direction of the two-dimensional translation stage.

[0037] The apertures of the first tube 4 and the second tube 5 are the same as the aperture of the beam position detector 7 under test; the beam position detector 7 under test is coaxially connected between the first tube 4 and the second tube 5, ensuring the continuity of the boundary conditions of the calibration device; the end of the first tube 4 away from the beam position detector 7 under test is fixedly connected to the drive end of the electric rotary table 3 by bolts.

[0038] The spiral assembly is coaxially arranged within the internal space formed by the first tube 4, the beam position detector 7, and the second tube 5 to simulate low-energy beams.

[0039] like Figure 2 and Figure 3 As shown, the spiral assembly includes a metal cylindrical inner core 8 and an insulating sleeve 9 fitted on the metal cylindrical inner core 8. A spiral wire 10 is tightly spirally wound on the insulating sleeve 9 at a fixed interval using epoxy resin. Both ends of the metal cylindrical inner core 8 are provided with flange-type SMA connectors 11. The inner cores of the two flange-type SMA connectors 11 are electrically connected to the spiral wire 10 by soldering. The metal cylindrical inner core 8 is a stainless steel cylindrical inner core, the spiral wire 10 is a spiral copper strip, and the insulating sleeve 9 is a polyetheretherketone insulating sleeve.

[0040] A flange-type SMA connector 11 at one end of the metal cylindrical inner core 8 is connected to an external signal generator via an RF coaxial cable to feed in RF signals and obtain the BPM's response to signals of different frequencies or waveforms. This flange-type SMA connector 11 is mounted on the end of the second conduit 5 away from the beam position detector 7 via a mounting bracket 6. A matching load 12 is connected to the flange-type SMA connector 11 at the other end of the metal cylindrical inner core 8 to absorb electromagnetic waves transmitted by the helical assembly. The impedance of both the helical assembly and the matching load 12 is 50 ohms.

[0041] The fixed bracket 6 includes a support crossbar 13 and two support vertical bars 14 respectively disposed at both ends of the support crossbar 13, for fixing and supporting the spiral assembly, so that the spiral assembly is coaxial with the first through tube 4, the beam position detector 7 to be measured and the second through tube 5; the other ends of the two support vertical bars 14 are fixed on the mounting platform 1.

[0042] In the spiral assembly, one end of the flange-type SMA connector 11, which is connected to the external signal generator, is mounted on the end of the second tube 5 away from the beam position detector 7 via a support crossbar 13; the flange-type SMA connector 11 at the other end of the metal cylindrical inner core 8 is located in the internal space formed by the first tube 4, the beam position detector 7, and the second tube 5.

[0043] The propagation speed v of the spiral component p The characteristic impedance Z0 satisfies the following equation:

[0044]

[0045] Where: L0 is the equivalent inductance, C0 is the equivalent capacitance, and β z Where γ is the axial phase shift constant and γ is the propagation constant. ∈0 and μ0 are the vacuum permittivity and permeability, respectively, and ω is the angular frequency. r I is the relative permittivity of insulating sleeve 9. m and K m Let a be the first and second type of modified Bessel functions of the mth order, b be the outer radius of the insulating sleeve 9, b be the radius of the first through pipe 4, d be the radius of the inner core 8 of the metal cylinder, φ = atan(p / 2πa) be the helix angle of the helix 10, and p be the pitch of the helix 10.

[0046] By adjusting the radius of the inner core 8 of the metal cylinder on the helical assembly, the thickness of the insulating sleeve 9, the width of the helical 10, and the winding pitch of the helical 10, the propagation speed of electromagnetic waves along the helical assembly can be changed. This can effectively simulate the electromagnetic field generated by beams of different energy levels, and directly measure the accurate response of the beam position detector 7 to low-energy beams, which can significantly improve the measurement accuracy and measurement range of the beam position detector 7.

[0047] Through the above formula derivation and calculation, combined with three-dimensional electromagnetic field simulation, a spiral assembly structure can be derived, which has a metal cylindrical inner core 8 with a radius of 2.4 mm, an insulating sleeve 9 with a thickness of 0.9 mm and a relative permittivity of 3.2, and a metal spiral 10 with a line width of 2.9 mm, a thickness of 0.1 mm, and a pitch of 4 mm.

[0048] like Figure 4 As shown in (a) and (b), the axial propagation velocity and characteristic impedance of the helical component structure are simulated. It can be seen that the helical component structure can not only realize slow wave propagation, but also maintains its characteristics basically unchanged in a large frequency range, thus exhibiting broadband characteristics.

[0049] By feeding a Gaussian pulse signal into the helical assembly structure, such as Figure 5 As shown, the electric field distribution at the inner surface of the beam position detector electrode obtained by simulation of the calibration device of the present invention is compared with the electric field distribution generated by a beam with the same velocity obtained by theoretical calculation. It can be seen that the two match well, and the calibration method of the present invention can effectively simulate the electric field generated by a low-energy beam; furthermore, as Figure 6 As shown, the response of the BPM under excitation by a spiral structure at different positions was calculated and compared with the response characteristics of the actual BPM to low-energy beams. Within 60% of the aperture (21.6 mm), the relative deviation between the two is within 1%, indicating that the present invention can calibrate the response of the BPM to low-energy beams with high accuracy.

Claims

1. A calibration device for a beam position detector based on a helical coil, characterized in that: It includes a mounting platform (1), a two-dimensional translation stage (2) fixed on the mounting platform (1), an electric rotary stage (3) fixed on the two-dimensional translation stage (2), a first through pipe (4) and a second through pipe (5) coaxially arranged from bottom to top on the electric rotary stage (3), as well as a spiral assembly and a fixing bracket (6); The apertures of the first tube (4) and the second tube (5) are the same as the aperture of the beam position detector (7) to be tested; the beam position detector (7) to be tested is coaxially connected between the first tube (4) and the second tube (5); the spiral assembly is coaxially arranged in the internal space formed by the first tube (4), the beam position detector (7) to be tested and the second tube (5) to simulate low-energy beams; The spiral assembly includes a metal cylindrical inner core (8) and an insulating sleeve (9) sleeved on the metal cylindrical inner core (8). A spiral wire (10) is wound on the insulating sleeve (9). Both ends of the metal cylindrical inner core (8) are provided with flange-type SMA connectors (11). The inner cores of the two flange-type SMA connectors (11) are electrically connected to the spiral wire (10). The flange-type SMA connector (11) at one end of the metal cylindrical inner core (8) is connected to an external signal generator, and the flange-type SMA connector (11) at this end is mounted on the end of the second tube (5) away from the beam position detector (7) through the fixed bracket (6). The flange-type SMA connector (11) at the other end of the metal cylindrical inner core (8) is connected to a matching load (12) for absorbing the electromagnetic waves transmitted by the spiral assembly. The fixed bracket (6) includes a support crossbar (13) and two support vertical bars (14) respectively set at both ends of the support crossbar (13), which are used to fix the support spiral assembly so that the spiral assembly is coaxial with the first through tube (4), the beam position detector (7) to be measured and the second through tube (5); the two support vertical bars (14) are fixed on the mounting platform (1); The flange-type SMA connector (11) of the spiral assembly, which is connected to the external signal generator, is mounted on the end of the second tube (5) away from the beam position detector (7) via a support crossbar (13); the flange-type SMA connector (11) at the other end of the metal cylindrical inner core (8) is located in the internal space formed by the first tube (4), the beam position detector (7), and the second tube (5). The propagation speed v of the helical assembly p The characteristic impedance Z0 satisfies the following equation: Where: L0 is the equivalent inductance, C0 is the equivalent capacitance, and β z Where γ is the axial phase shift constant and γ is the propagation constant. ∈0 and μ0 are the vacuum permittivity and permeability, respectively, and ω is the angular frequency. r I is the relative permittivity of the insulating sleeve (9). m and K m Let a be the first and second type of modified Bessel functions of the mth order, b be the outer radius of the insulating sleeve (9), b be the radius of the first through pipe (4), d be the radius of the inner core (8) of the metal cylinder, φ = atan(p / 2πa) be the helix angle of the helix (10), and p be the pitch of the helix (10).

2. The calibration device for a helical beam position detector according to claim 1, characterized in that: The spiral (10) is spirally bonded to the insulating sleeve (9) at a fixed interval using epoxy resin adhesive.

3. The calibration device for a helical beam position detector according to claim 2, characterized in that: The characteristic impedance of the spiral assembly and the impedance of the matching load (12) are both 50 ohms.

4. The calibration device for a helical beam position detector according to claim 3, characterized in that: The flange-type SMA connector (11) is connected to an external signal generator via an RF coaxial line to feed in RF signals, thereby calibrating the response of the beam position detector (7) to different frequencies or waveform signals.

5. The calibration device for a helical beam position detector according to claim 4, characterized in that: The metal cylindrical inner core (8) is a stainless steel cylindrical inner core; The spiral (10) is a spiral copper strip.

6. The calibration device for a helical beam position detector according to claim 5, characterized in that: The radius of the metal cylindrical inner core (8), the thickness of the insulating sleeve (9), the width of the helix (10), and the winding pitch of the helix (10) in the helical assembly are determined based on the propagation speed of the electromagnetic wave along the helical assembly and the characteristic impedance.

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