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A strong field and short period undulator can be a desirable light source device in a storage ring or a free-electron laser. Bulk YBCO can be used to construct a high-temperaturesuperconducting undulator in a staggered array structure. The YBCO material in form of 32 mm diameter and 2.5 mm thick was used to assemble a staggered magnet array. The period length is 5 mm and the magnet gap is 4 mm. To estimate the strength of a sinusoidal field and to optimize the end-pole design to minimize the first (i.e., electron angle) and second field integral (electron position), an energy-minimization method (EM-method) based on Bean's model to simulate the field trapped in the HTS-Block is introduced. In this paper, we focus on promoting the practical value of the EM-method simulation. Combining the experimental experience of a YBCO staggered undulator and the simulation experience based on the EM-method, we address some issues to enhance the efficacy of this undulator design. [ABSTRACT FROM AUTHOR]

For the study of high-temperature superconductors and for the application of superconductivity, a superconducting high-field magnetization system with a hybrid superconducting coil was designed. This coil is composed of superconducting wires of three kinds—HTS YBCO 2G-wire, high-field and low-field NbTi wires. Three principal purposes of building this system are to inspect the characteristics of disk-shape bulk YBCO, to develop a HTS-bulk undulator, and to magnetize a portable HTS-bulk high-field magnet for application to a resonant X-ray scattering experiment. With four steps of temperature decrease, a two-stage GM-type cryocooler and liquid nitrogen provide cooling for the magnetization system. The hybrid superconducting coil, two cryogenic systems for the magnetization system and the portable HTS-bulk magnet, and the control and monitor systems that were designed are discussed. [ABSTRACT FROM PUBLISHER]

A 130-pole superconducting undulator with NbTi wires was wound and tested at National Synchrotron Radiation Research Center (NSRRC). The magnetic field was measured with a cryogenic mini-Hall sensor in a vertical dewar. The difference of total length between the nominal design and that measured experimentally with the Hall probe is approximately 1.2 mm; this discrepancy arises from the thermal contribution during the field measurement in the test dewar. The reliability of the measurement system is confirmed, and is discussed in terms of the field-mapping spectrum. The measurement of the field strength revealed a non-uniform distribution of the field in the 1 m long arrays. An iron pole piece was used to shim the on-axis field strength of the undulators. We discuss the thermal effect of the measurement system, a useful shimming method and its results for the superconducting undulator. [ABSTRACT FROM AUTHOR]

The wire windings and magnetic performance of the mini-pole superconducting undulator (SCU) at the National Synchrotron Radiation Research Center (NSRRC) are being improved. NbTi superconducting (SC) wire with a rectangular cross section 0.51 mm x 0.77 mm was wound on a racetrack iron pole. The designed field strength was 1.4 T at excitation current 510 A. The bath LHe-cryostat cools the SC wire directly and uniformly using LHe. A stainless-steel (SS) beam duct (thickness 0.3 mm) is designed to separate the ultra-high vacuum (UHV) from the storage ring and the LHe. The SS beam duct is glued to the dummy arrays with resin epoxy. The dummy arrays provide a strong support for the beam duct, providing against deformity from a pressure differential. A vacuum test was performed with a short version of a beam duct (length 400 mm) at low temperature. This paper describes the construction of the magnet, the measurement of the field and the testing of the SS beam duct. [ABSTRACT FROM AUTHOR]

A prototype of an Apple-II elliptically polarized undulator (EPU4.6), of length 0.46 m, has been constructed to test the performance of the newly designed magnet block, which was magnetized at a tilt angle 10°. The magnet design and various mechanism analysis are performed to clarify the error source of multipole field components. Good end pole design in the EPU4.6 revealed the variation of the first integral field strength as function of gap and phase is minimized. Shimming algorithm had been used to improve the field quality and phase error. We report here the scheme of the magnetized block arrangement, an analysis of the design mechanism, the end pole design, field shimming and the final test performance using the Hall-probe mapping system. [ABSTRACT FROM AUTHOR]

A cryogen-free cryostat for a superconducting undulator with a period of 15 mm (SU15) was developed at the National Synchrotron Radiation Research Center (NSRRC). A 0.44 mm-thin superconducting NbTi wire was wound on iron pole with a racetrack profile. The design field strength of SU15 was 1.4 T and the coil had 148 turns/pole at 230 A; the magnet gap was 5.6 mm. The liquid helium (LHe) recondensation cryostat was designed for SU15. The cryostat provides the advantage of uniform cooling and reduces the amount of LHe consumed. A 0.3 mm-thick stainless steel (SS) beam duct was formed to separate the vacuum in the storage ring from the magnet. Therefore, all of dirty material is produced out of storage ring vacuum. Most of the heat leaked from the LHe vessel leaks from the LHe-fill port heat leak and the 300 K-4.2 K beam duct or was associated with image current power dissipation (ICPD) and bending magnet power dispersion (BMPD). The leaking of heat from the main coil was prevented by the high-temperature superconducting current leads (HTSC). The beam duct was coated with a copper layer with a high-RRR ratio to reduce image current heating. The heat loads on the magnet were cooled using two 1.5 W Gifford-MacMahon (GM) type cryocoolers via LHe medium. [ABSTRACT FROM AUTHOR]

A mini-pole planar vertically-wound racetrack coil undulator was studied to determine its potential for use as a hard X-ray source in a 3 GeV storage ring. A field strength of 1.4 T can be obtained for a superconducting undulator with a periodic length of 1.5 cm and a fixed magnetic gap of 5.6 mm. The magnetic circuit was optimized and a current density of 1090 A/mm², at 80% of the critical current, meets the field strength requirement. A prototype with 40 poles was constructed to verify the design of the magnet and the performance of NbTi superconductor. Additionally, the magnetic field shimming method was developed for spectrum shimming. This study discusses the design of the magnetic circuit and the structure of the magnetic array, the field shimming technique, and the test results of the prototype magnet. [ABSTRACT FROM AUTHOR]

A superconducting wiggler with a magnetic period of 6.0 cm (SW6) and a peak field of 3.2 T has been designed and fabricated in the National Synchrotron Radiation Research Center (NSRRC). The beam duct separates the electron beam from the cryogenic system of the magnet. The heat load on the beam duct should be low to stabilize the operation of the superconducting magnets. However, outgassing caused by synchrotron radiation at an electron energy of 1.5 GeV and a current of 200 mA must be reduced. Accordingly, operating the system at a higher temperature can minimize the adsorption of molecules on the beam duct. Therefore, the beam duct system and its connection by finite element analysis are designed to optimize the operating temperature of the beam duct at between 100 and 120 K. Performance of the beam duct is established to comply with specifications during the operation of magnet. [ABSTRACT FROM AUTHOR]

Mini-pole (short period) in-vacuo superconducting undulators, a vert5ical-winding racetrack coil structure, a horizontal-winding racetrack coil structure and a staggered array structure, were studied for use in the X-ray source in a 1.5 GeV or a medium-energy 3 GeV storage ring. The magnetic arrays are all installed in the ultra-high vacuum environment, required for passing electron beams. In a periodic length of 15 mm and a gap of 5 mm, field strengths of 1.5 T, 1.5 T and 0.7 T can be generated in the three different structures, respectively. Additionally, the staggered undulator with variable-period length or a translator structure with different periodic length can yield various deflection parameters k, by driving a longitudinal solenoid field of 0.8 T. Accordingly, this study addresses the magnet structure of and mechanism of the magnet, and the advantages and disadvantages of the structures of these undulators. The spectral characteristics and the magnetic field features of these undulators are also studied. [ABSTRACT FROM AUTHOR]

A 0.96 m with 16 poles superconducting wiggler is fabricated in-house at NSRRC. The wiggler produced a magnetic field of 3.1 T for a 61 mm period with a pole gap of 19 mm. Three 5-pole prototype magnets using various pole materials from low carbon steel, vanadium permendure steel and holmium are tested and measured to verify the magnetic field performance in the testing dewar. This work describes the design and construction of a magnet and cryostat system. Furthermore, this work presents the results of magnet tests and the field performance of the compact superconducting wiggler. [ABSTRACT FROM AUTHOR]