摘要 :
Superconducting undulators (SCUs) for advanced light sources are being developed rapidly to emit light with higher brightness and flux. The SCU consists of two superconducting magnets with a small gap, each with alternating poles....
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Superconducting undulators (SCUs) for advanced light sources are being developed rapidly to emit light with higher brightness and flux. The SCU consists of two superconducting magnets with a small gap, each with alternating poles. The SCU is invisible when operating in a Dewar or cryostat, so measuring the magnetic field in the narrow magnetic gap is a challenge in the development of the SCU. This paper presents a measurement system in vertical status for scanning the magnetic field of the SCU along the z-axis. The SCU is immersed vertically in 4.2K liquid helium in a Dewar and the scanning is powered by a servo motor at room temperature. The measurement system overcomes the temperature difference of 300K to drive the Hall probes to scan the magnetic field in the narrow magnetic gap of the SCU. In order to make the scanning area of the Hall probes coincide with the trajectory of the electron beam, a lot of detailed work on mechanical aspects has been done, such as controlling the positional accuracy of the Hall probes as they move, high precision machining and limiting the direction of movement. Unlike the currently reported magnetic field scans in the vertical status which are only available for SCU mock-ups of few periods, this system supports magnetic field measurements for SCUs up to 1.5m long. The measurement system was validated on a 20-period SCU prototype, and after modification, the magnetic field of a liquid helium-cooled 30.5-period SCU was scanned. When the excitation current of the SCU with a magnetic gap of 7mm is 450 A, the system measured a field distribution with a peak magnetic field of 1 T. The measurement system completed a full stroke trial run of 1750mm before the 1.5m SCU was machined. The results of magnetic field measurement from scanning in vertical status can be used as a reference for local shimming and correction of the magnetic poles of the SCU. This work establishes the SCU's ability to operate in cryostat horizontally.
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摘要 :
Superconducting undulators (SCUs) are crucial components for advanced photon sources and have broad applications. IHEP is currently developing SCU, which requires a vacuum chamber to provide a beam path and protect the superconduc...
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Superconducting undulators (SCUs) are crucial components for advanced photon sources and have broad applications. IHEP is currently developing SCU, which requires a vacuum chamber to provide a beam path and protect the superconducting magnets from image currents induced by the beams. However, due to the narrow magnetic gap and low temperature of the SCU, designing and processing its vacuum chamber presents challenges in terms of mechanical design, positioning, and intercepting synchrotron radiation that could damage the sensitive superconducting magnets. The SCU vacuum chamber is divided into three parts based on location and function: chamber inside the cryostat as well as upstream and downstream chambers outside it. The complex fit of the constant aperture vacuum chamber inside the cryostat with both magnets and cryostat ensures high-current operation while also safely managing dynamic heat loads imposed by beams. Using an SCU operating on HEPS as an example shows how smooth transitions between upstream/downstream and storage ring chambers effectively absorb synchrotron radiation to protect magnets and downstream equipment from damage caused by synchrotron radiation exposure. Simulations are performed to check the possible effects of synchrotron radiation on the mechanical properties, the ultimate vacuum of these chambers and to calculate the beam impedance. Finally, two solutions for using the vacuum chamber as a channel for measuring the magnetic field of the SCU in the operating state are discussed.
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摘要 :
The 1.5-m-long superconducting undulator (SCU) must have its magnetic field measured in a vertical Dewar to verify the field quality before the SCU is integrated into a horizontal cryostat. The magnetic field measurement mechanism...
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The 1.5-m-long superconducting undulator (SCU) must have its magnetic field measured in a vertical Dewar to verify the field quality before the SCU is integrated into a horizontal cryostat. The magnetic field measurement mechanism must ensure that the trajectory of the Hall probe scanning the magnetic field is in the center of the magnetic gap, that is, the trajectory of the beam passing through the SCU. The good field region of the SCU's magnetic field and the position of the Hall probe are given by Opera and the magnetic field distribution formula. Precise machining technology assists the positioning of the Hall probe. Due to the existence of mechanical errors, there is no guarantee that the peak magnetic field is also uniformly distributed under a uniform gap. The adjustment of the gap helps the SCU magnetic field distribution to be improved. The adjustment amount of the gap is obtained by comparing the measured data with the theoretical value. After the SCU returns to room temperature, keep the electrical connection, and adjust the gap on-line. Both peak magnetic field uniformity and phase error of the adjusted magnetic field are improved. This greatly reduces the difficulty of SCU's magnetic field correction and makes the subsequent SCU horizontal test meaningful.
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The superconducting undulator (SCU) is a type of insertion device with great development potential. SCU can generate higher peak field than permanent magnet undulator at the same period length and vacuum gap. In the early stage of...
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The superconducting undulator (SCU) is a type of insertion device with great development potential. SCU can generate higher peak field than permanent magnet undulator at the same period length and vacuum gap. In the early stage of SCU development, it is necessary to test various winding schemes and coil parameters. A reliable cryogenic system is the precondition for superconductivity. To test SCU short prototypes in a compatible way, a convenient low-temperature platform is in high demand. In addition, due to the high cost and unpredictable availability of liquid helium, a helium-free platform is beneficial. In this paper, a successful low-temperature platform for the SCU short module test is introduced. It is compatible with different coil structures. Comprehensive design ingredients, such as the current leads, cold mass, thermal shield, etc., are described in detail. The platform performances in the module test are recorded and analyzed as well. The cold mass was cooled to about 2.9 K, and the maximum current of the superconductor was approximately 500 A.
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An Nb
3
Sn/NbTi subscale dipole magnet named LPF1 with graded coil design and common-coil configuration has been designed, assembled, and tested at the Institute of High Energy Physics, Beijing, China. Compared to the previously p...
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An Nb
3
Sn/NbTi subscale dipole magnet named LPF1 with graded coil design and common-coil configuration has been designed, assembled, and tested at the Institute of High Energy Physics, Beijing, China. Compared to the previously proposed FECD1, LPF1 is designed with a longer outer NbTi racetrack coil to reduce the peak field in the coil end. The computed bore field and peak coil field of LPF1 is 12.0 T and 12.1 T, if it works at 6100 A with a safety margin of 17\% at 4.2 K. The horizontal and vertical directions of the coil packs are preloaded by using bladder and key technology while the axial direction of the coil packs is preloaded by pretightening four aluminum rods. Before assembly, we tested the electron-beam welded bladders in a subscale shell-support structure and verified the strain measurement system. During assembly, we preloaded the coil packs gradually by referring to the measured shell strain after inserting stainless steel keys and removing the bladders. After assembly, we started to test the subscale dipole magnet vertically at 4.2 K. LPF1 reached a bore field of 10.2 T after 13 training quenches and then it reached a stable quench current without detraining. This paper presents the updated design parameters, the stress analysis, the magnet assembly, and test of LPF1.
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Using the conventional coil manufacturing method, the iron core of a small aperture quadrupole magnet needs to be divided into four or more segments to install the excitation coils, which brings assembly errors and generates high-...
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Using the conventional coil manufacturing method, the iron core of a small aperture quadrupole magnet needs to be divided into four or more segments to install the excitation coils, which brings assembly errors and generates high-order magnetic field harmonics. In this paper, the development of a high-precision small-aperture quadrupole magnet named HQ22 using copper plate coils is described. The magnet has a bore aperture of 22 mm, a gradient of 90 T/m, and an effective length of 0.36 m. Its coil is mainly composed of a number of U-shaped copper plates, electrical connection sheets, and insulating sheets, which are directly assembled and connected on the pole. Outside the coil, water box with cooling water channel inside is installed to provide indirect cooling to the coil. Using copper plate coil, one-piece or two-piece structure can be adopted for the iron core, so the assembly error is reduced and magnetic field quality can be improved. The research provides an attractive technical scheme for small aperture quadrupole magnets in future light sources. The detailed magnet design, magnetic field calculation and measurement results of HQ22 are presented, and the application prospect of copper plate coil is discussed.
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A batch superconducting solenoid magnet for the ADS proton linear accelerator has been designed, fabricated, and tested in a vertical dewar in Sept. 2013. A total of ten superconducting magnets will be installed into two separate ...
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A batch superconducting solenoid magnet for the ADS proton linear accelerator has been designed, fabricated, and tested in a vertical dewar in Sept. 2013. A total of ten superconducting magnets will be installed into two separate cryomodules. Each cryomodule contains six superconducting spoke RF cavities for beam acceleration and five solenoid magnets for beam focusing. The multifunction superconducting magnet contains a solenoid for beam focusing and two correctors for orbit correction. The design current for the solenoid magnet is 182 A. A quench performance test shows that the operating current of the solenoid magnet can reach above 300 A after natural quenching on three occasions during current ramping (260 A, 268 A, 308 A). The integrated field strength and leakage field at the nearby superconducting spoke cavities all meet the design requirements. The vertical test checked the reliability of the test dewar and the quench detection system. This paper presents the physical and mechanical design of the batch magnets, the quench detection technique, field measurements, and a discussion of the residual field resulting from persistent current effects.
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Superconducting undulators (SCUs) are developing fast around the world. An R&D project is undergoing at Institute of High Energy Physics (IHEP) in China to produce a prototype of 15 mm period length planar undulator with superconducting technology. For undulators, the first and second magnetic field integrals along the longitudinal axis should be zero to avoid disturbing the beam trajectory. By using the finite element program OPERA-3D, we built the SCU model to study the magnetic field distribution on axis. We designed two correction coil pack on each end of the SCU core. The end-field can be adjusted flexibly with different correction currents. Our study in this paper reveals that the magnetic field integrals are highly dependent on the end-field. The relationship between the end-field integrals and the correction currents are given based on polynomial fitting. The optimal correction currents are obtained via numerical analysis....
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Superconducting undulators (SCUs) are developing fast around the world. An R&D project is undergoing at Institute of High Energy Physics (IHEP) in China to produce a prototype of 15 mm period length planar undulator with superconducting technology. For undulators, the first and second magnetic field integrals along the longitudinal axis should be zero to avoid disturbing the beam trajectory. By using the finite element program OPERA-3D, we built the SCU model to study the magnetic field distribution on axis. We designed two correction coil pack on each end of the SCU core. The end-field can be adjusted flexibly with different correction currents. Our study in this paper reveals that the magnetic field integrals are highly dependent on the end-field. The relationship between the end-field integrals and the correction currents are given based on polynomial fitting. The optimal correction currents are obtained via numerical analysis.
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An R&D project aiming to develop superconducting undulators (SCUs) is in progress at the Institute of High Energy Physics (IHEP) in China. The insertion device group has produced a 1.5-m-long NbTi planar superconducting undulator prototype recently. This SCU prototype has a period length of 15 mm and a magnetic gap of 9.5 mm. The SCU was fabricated in a frame to be trained vertically in a Dewar submerged by liquid helium. After dozens of quenches, the maximum current in the superconducting coils reached 450 A. The magnetic field along the axis at different currents were obtained by a measurement system to characterize the local magnetic field distribution. We applied a gap adjustment method to improve the magnetic field quality. A cryostat has been specially designed for this 1.5-m-long SCU prototype. The SCU was installed in the cryostat to be cooled to 4.2 K successfully. A series of cryogenic tests for the SCU prototype in the cryostat are in progress....
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An R&D project aiming to develop superconducting undulators (SCUs) is in progress at the Institute of High Energy Physics (IHEP) in China. The insertion device group has produced a 1.5-m-long NbTi planar superconducting undulator prototype recently. This SCU prototype has a period length of 15 mm and a magnetic gap of 9.5 mm. The SCU was fabricated in a frame to be trained vertically in a Dewar submerged by liquid helium. After dozens of quenches, the maximum current in the superconducting coils reached 450 A. The magnetic field along the axis at different currents were obtained by a measurement system to characterize the local magnetic field distribution. We applied a gap adjustment method to improve the magnetic field quality. A cryostat has been specially designed for this 1.5-m-long SCU prototype. The SCU was installed in the cryostat to be cooled to 4.2 K successfully. A series of cryogenic tests for the SCU prototype in the cryostat are in progress.
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Introduction The circular electron-positron collider (CEPC) with a circumference about 100 km, a beam energy up to 120 GeV is proposed by the Institute of High Energy Physics. The heart of the CEPC is a double-ring collider with t...
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Introduction The circular electron-positron collider (CEPC) with a circumference about 100 km, a beam energy up to 120 GeV is proposed by the Institute of High Energy Physics. The heart of the CEPC is a double-ring collider with two interaction points. In each side of the collision point, superconducting double-aperture quadrupole magnets based on cos2θ design which is named QD0 and QF1 separately are required. Such kind of superconducting magnet is designed first time in domestic. Mechanical stability analysis is very important for superconducting magnet before manufacture. This paper mainly focused on the mechanical analysis of the prototype for QD0. Materials and methods A 2D 2-layers model was developed using ANSYS to simulate the stress distribution in the coil from collaring process at room temperature to low temperature excitation. Conclusion As part of the CEPC project, a 40 mm bore diameter superconducting double-aperture quadrupole magnet named QD0 is being designed and the physical calculation has been completed. This paper introduces the mechanical design, simulation model of prototype for QD0, and mainly expounds on stress analysis. The stress distribution during 4 stages including collaring (load application), collaring (inserting keys), cooling down and excitation is described in detail.
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