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A PrFeB-based cryogenic permanent-magnet undulator (CPMU) with a period length of 15 mm (CU15) is being constructed to provide high brilliant X-rays for the Taiwan Photon Source (TPS) nano-probe beamline. Field measurements of this undulator will be performed with a Hall probe in a vacuum environment. The in-situ Hall probe measurement system (Yang et al. , 2014) was improved (Yang et al. , 2016) to allow measurement and tuning of the CU15 magnetic field. A field strength and temperature dependent calibration of the Hall probe was done to obtain realistic field distributions. By tuning the differential adjusters and spring modules, we can correct magnetic field errors caused by assembly tolerances and temperature gradients along the magnetic arrays, thus lowering phase errors to reach our design goals. This paper describes details of improvements in the measurement system, field tuning methods, and measurement results at cryogenic temperatures.

An undulator composed of an electromagnet (EM) and a permanent magnet (PM) has been developed to switch rapidly the right- or left-circularly polarized radiation. The polarization switching is achieved using the rapid change of polarity of excitation currents in the EM, which provides a vertical field in a fixed gap. A horizontal field is generated with a PM; the field strength is adjusted on altering its horizontal gaps. In addition to circularly polarized radiation, the structure fulfills the needs of horizontal and vertical linear polarization. In this paper, we discuss the compact structure and show a design to provide soft X-rays for TPS. The design considerations for this magnet include the design concept, magnetic materials, mechanical and coil structure, all of which are discussed in this paper.

A method based on wave optics together with electron tracking is used to analyze synchrotron radiation from a segmented undulator in a double or multi mini-β function lattice storage ring. Radiation brilliance and transverse coherence features are investigated, where the former is calculated with the Wigner distribution function and the latter is evaluated by integrating the photon flux and cross-spectral density to exhibit the coherent flux and overall degree of coherence. To be specific, radiation properties for a single undulator in a typically single mini-β function and a tandem undulator in a double mini-β y lattice are compared in this work. As a result, both, brilliance and coherent flux can be enhanced by a second tandem undulator at the Taiwan Photon Source.

Because of a strong demand for circularly polarized radiation, elliptically polarized undulators (EPU) are widely used in synchrotron light source nowadays. At Taiwan Photon Source (TPS) with a 3-GeV ring, the EPU plays an important role to fulfill the needs of the user community for EUV to soft X-ray. Up to phase II, in total five EPU have been installed. Because multiple operating modes are necessary, the EPU suffers changes in attractive and repulsive forces in three directions, in contrast to a general ID, which suffers only a vertical attraction. A mechanical structure of the EPU is required that can withstand multiple stresses and eliminate mechanical deformation. In addition, the EPU, a purely magnetic structure, is sensitive to high-permeability material, which makes the overall structure a heterogeneous material, resulting in a problem with uneven thermal expansion and contraction because of changes in ambient temperature. Here we discuss and propose solutions to resist force and temperature variations of EPU mechanical structures, which includes mechanical simulation and inspection.

Due to the strong demand for circularly polarized radiation, insertion devices (ID) have been used to provide elliptical fields since the late 1980s. The trend is to increase the degree of circular...

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-temperature-superconducting 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.

The design of a helical permanent magnet undulator with a period length of 24 mm for the production of circularly and linearly polarized radiation will be discussed. This undulator consists of four helically shaped magnet arrays, which is expected to produce adjustable helical fields in a cylindrical gap. The helical fields were calculated with the 3-D OPERA computer code producing vertical and horizontal peak fields of 1.29 T for a 24-mm-period length within a bore diameter of 5 mm. The sizes and location of the end poles were optimized to minimize the first and second field integrals. Furthermore, on-axis horizontal or vertical magnetic fields can be generated independently by shifting the relative positions of diagonal pairs of magnet arrays in this device. It leads to the generation of circular and linear polarized radiation in one undulator. The undulator phase shifter can be controlled by mechanical changes to adjust field strength and to tune the helical and linear photon energy. This paper describes magnetic field simulations and mechanical design of the short-period helical permanent magnet undulator.

To measure the magnetic fields with a Hall probe, accurate alignment needs to be considered. Therefore, we present improvements to the Hall probe measurement system, including cone magnets and a zero-field shield as simulated by the OPERA. The design of the cone magnets of the North-face-North type is greatly helpful to monitor the magnet alignment. The accurate location of the Hall probe doping area should be determined before doing any measurements. In addition, a zero-field shielding tube is used to reset the probe to zero. The results of simulations are reported in this paper.

A permanent-magnet (PM) phase shifter has been constructed for tandem elliptically polarizing undulators at the Taiwan photon source. To increase the magnetic field reproducibility and to allow installation in a limited space, a robust mechanical structure is desired. To decrease multipole errors and optimize the magnetic field, algorithms for magnet sorting were used and magnetic field shimming was done. The start-to-end construction of a PM phase shifter will be discussed and explained in detail.

In an in-vacuum undulator, the dynamic phase error, which is a kind of systematic phase errors, is increased because the out-of-vacuum girder is deformed with a strong magnetic force. As a result, the spectral performance of synchrotron radiation is deteriorated. A recommended solution for a problem of this kind is to adopt a spring system to compensate the magnetic force, but a conventional spring system has a problem in that the mechanical frame of the undulator is deformed by a reaction force from the springs. The new force-compensating spring module shown in this paper is a self-contained type that can treat the spring reaction force within the module, therefore, the side effects of the spring operation can be minimized. Three in-vacuum undulators with a length of 2–4 m are equipped with the spring modules of new type, so a small rms phase error of 1.7°–2.2° is obtained under the highest magnetic force at the minimum gap.

To enhance the flux density or to control polarization, a phase shifter was designed and used to modulate the phase matching between segmented undulators. A larger hysteresis loop causes, however, a repeatability issue in the phase matching; the fringe field of the phase shifter creates an extra magnetic-field error. The design of the phase shifter must therefore minimize the hysteresis loop and fringe field to maintain the phases exact and to ignore the crosstalk effect. Two critical issues are the hysteresis-loop problem and the fringe-field effect, which determine the radiation performance and the stability of the ring. To investigate these issues, a phase shifter was constructed to operate in accordance with electromagnetic- and permanent-type magnets; the results from the field measurements and shims are discussed here. The shimming algorithm and a compact permanent-magnet phase shifter that eliminates the issues are also presented.

The TPS 13A biological small-angle X-ray scattering (BioSAXS) beamline under construction is equipped with 4-m IU24 undulator for X-rays in the energy range of E = 4-23 keV (covering the K-edge absorptions from Ca to Ru). The beamline aims for cutting-edge researches in biomacromolecular structures and kinetics, in solid and solution, covering a wide length scale from atomic to micrometer scale and time resolution down to μs. To achieve the goals, the beamline integrates double-multilayer and double-crystal monochromators (DMM/DCM) to have an option of high flux of 4 × 1014 photons/s or a high energy resolution of ΔE/E = 1.5×10−4. The DCM together with a horizontal four-bounce crystal collimator (4BCC) will be implanted for low beam divergence to perform 2D ultra-SAXS (USAXS). To keep a common X-ray beam path of the operation modes, DMM and DCM are integrated into one rotating cradle in a same chamber for a common beam exit. Microbeam with reasonable beam divergence for SAXS/WAXS structural mapping will be realized with a virtual source defined by a set of high precision/stability slits and another set of K-B mirrors for a focus at the sample position with a demagnification close to 1.3:1. Two beam position monitors, with intensity and position feedbacks respectively to the virtual source slits and the 4BCC and a vertical deflection mirror, are used mainly to stabilize microbeam intensity and position within 1 μm in the vertical and horizontal directions. This TPS 13A BioSAXS beamline will be commissioning at the end of 2019.

A PrFeB-based cryogenic permanent magnet undulator (CPMU) is under construction at the Taiwan Photon Source (TPS) to provide high brilliant X-rays. When magnets are cooled to 80 K, a CPMU with a period length of 15 mm and a gap of 4 mm can generate an effective magnetic field of 1.30 T. The main goals of TPS CPMU developments are low-intrinsic-phase errors and high thermal stability against diverse heat loads. Low-intrinsic-phase errors can be obtained by force-compensation modules on the out-of-vacuum girders in a four-support-point configuration. Furthermore, adjustments of the spring settings can lead to even lower undulator phase errors. Two cryo-coolers, each with a cooling capacity of 200W at 80 K, allow a high beam-induced heat load with external heat transfer of up to a few hundred watts. An in-situ and vacuum compatible field measurement system has been developed to characterize the magnetic field at cryogenic temperatures and allowing corrections of gap errors due to temperature variations. In this paper, the relevant technology and test results for the TPS-CPMU will be discussed including some CPMU observations associated with phase errors, magnetic field quality at cryogenic temperature.A PrFeB-based cryogenic permanent magnet undulator (CPMU) is under construction at the Taiwan Photon Source (TPS) to provide high brilliant X-rays. When magnets are cooled to 80 K, a CPMU with a period length of 15 mm and a gap of 4 mm can generate an effective magnetic field of 1.30 T. The main goals of TPS CPMU developments are low-intrinsic-phase errors and high thermal stability against diverse heat loads. Low-intrinsic-phase errors can be obtained by force-compensation modules on the out-of-vacuum girders in a four-support-point configuration. Furthermore, adjustments of the spring settings can lead to even lower undulator phase errors. Two cryo-coolers, each with a cooling capacity of 200W at 80 K, allow a high beam-induced heat load with external heat transfer of up to a few hundred watts. An in-situ and vacuum compatible field measurement system has been developed to characterize the magnetic field at cryogenic temperatures and allowing corrections of gap errors due to temperature variations. In t...

A Robinson wiggler is designed to decrease the emittance within 1 nm · rad for Taiwan Photon Source. According to an analysis of the beam dynamics, decreasing the emittance with a multiperiod Robinson wiggler is more efficient than a single-period traditional Robinson wiggler. This wiggler consists of a dipole field and a strong gradient field, which creates a strong dynamic field integral multipole error. To enhance the gradient field and to have also a small dynamic field integral multipole error, a compensated side-pole design and an edge-pole shape in each pole are proposed in this paper. After optimization of the magnet, the dipole and gradient fields are 0.82 T and -37 T/m, respectively. The concept of the design of the magnetic circuit and the results of an analysis of the magnetic field are discussed herein.

A 4.77-T wavelength shifter is designed for extending the X-ray spectrum beyond 50 keV in the 3-GeV storage ring of the Taiwan Photon Source. The compact 400-mm-long wavelength shifter is designed by using the PrFeB-based cryogenic permanent magnets to generate 4.77 T at a 5-mm magnet gap. The 0.1% field uniformity on the transverse 40 mm is calculated. A cryocooler system that is cryogen free is designed to cool the magnets and to maintain the temperature of the magnets at 77 K in a vacuum chamber. Numerical simulation shows that the cooling system can cool the magnet array from 300 K to 77 K. In this paper, we present the high-magnetic-field performance and the cooling system for the wavelength shifter.

A recent trend toward building an undulator for a mid-energy storage ring is a small period length and a large magnetic field, which typically requires a vacuum and cryogenic environment. To measure the magnetic field of such undulators, we designed and fabricated a Hall-probe measurement system in vacuum. All components of this system are installed in a vacuum chamber and are compatible with a high-vacuum and a low-temperature environment; the deployment of all parts is designed to fit a cryogenic permanent-magnet undulator that is now under construction at the National Synchrotron Radiation Research Center. The details of the design, completed fabrication, and test results are presented in this paper.

The applicability of the double-undulator concept for an electron storage ring of 3-GeV class is evaluated based on the parameters of Taiwan Photon Source. In the soft X-ray case, the fundamental harmonic is mainly used, the interference effect is preserved at some level, which means that the brilliance from a double-undulator is expected to be much greater than that of a single undulator. In the hard X-ray case, harmonics number greater than five are generally used, the interference effect cannot, however, be preserved, which means that a double undulator configuration can be assumed to comprise two independent and uncorrelated sources. The total coherent flux obtained from a double-undulator configuration is found to be much less than twice that of a single undulator. The double-undulator concept is hence inapplicable in the hard X-ray region from the viewpoint of high coherent flux performance.

A gasket-type standard leak element with a microfluidic channel was developed and measured. The microfluidic channel with a diameter of several micrometers and a length of one hundred micrometers was fabricated by using femtosecond laser micromachining. The conductances (

An undulator magnet design is described consisting of four electromagnet arrays to produce arbitrarily polarized photon beams including a linear inclined mode. Polarization changes are effected by a current switch rather than mechanical longitudinal translations. The capability of choosing a variety of current excitations in each double coil of the structure can produce any desired polarization mode. This concept exhibits an advantage over mechanical designs especially for superconducting design versions of this undulator. In this paper, we will discuss the magnet structure concept, the current distribution in each double coil and magnetic field features for various polarizing modes. In addition, the concept of current switching will be discussed, which allows to reduce the number of individual current sources from eight to one.

To minimize unwanted beam dynamics effects in a storage ring, multipole errors in an undulator are normally reduced by sorting and shimming methods. Nonetheless, an investigation of the error source is worth pursuing and interesting. Our work focuses on multipole errors introduced by mechanical deformations of an APPLE-II type undulator, which undergoes complicated forces during operation. Our results give guidelines for mechanical specifications derived from quantitative analyses., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

A spatially periodic magnetic field is essential to cause an electron beam to wiggle and to emit electromagnetic radiation in a synchrotron (SR) source of radiation, and to provide fully coherent light in free electron lasers (FEL). To create this field, permanent magnets (PM) or electromagnets are patterned in a device commonly called an insertion device for SR and a radiator or modulator for FEL. In reality, magnet blocks or iron poles are not identical, in terms of geometry and magnetic properties, even with progressive manufacture. Compensatory methods are thus desired to recover the magnetic field and also to decrease the duration of construction. Magnet sorting is a pre-process that aims to eliminate the effect of manufacturing error. Before assembly of an insertion device, data of each component, especially the magnetic properties of each magnet block and the gap variation of mechanical structure, are organized to optimize the performance of the magnetic field. After that process, there is sometime...

For hard X-rays users in a synchrotron radiation source, the development of an in-vacuum mini-gap undulator with a short period is a recent trend. The performance of the undulator can become degraded by large beam-induced heat load that arises from both the synchrotron radiation (SR) and the image current. SR is responsible for avalanche meltdown of the magnet foil, whereas the image current mainly decreases the threshold of power to cause an avalanche meltdown. To maximize the performance of the in-vacuum undulator, we hence consider the most appropriate conditions for the beam in a storage ring, such as a long bunch length or a small bunch current. An appropriate strategy to utilize the undulator is also important, for example, operating a collinear double in-vacuum undulator or a canted in-vacuum undulator with a small canting angle may result in avalanche meltdown of the magnet foil. In this paper, we present methods to calculate the linear power density of SR and the resistive wall heating on a conductive magnet foil. The beam-induced heat load of a double undulator in Taiwan Photon Source (TPS) is presented as an example.

An in-vacuum undulator (IVU) provides a means to reach high-brilliance x rays in medium energy storage rings. The development of short period undulators with low phase errors creates the opportunity for an unprecedented brilliant light source in a storage ring. Since the spectral quality from cryogenic permanent magnet undulators (CPMUs) has surpassed that of IVUs, NdFeB or PrFeB CPMUs have been proposed for many new advanced storage rings to reach high brilliance x-ray photon beams. In a low emittance ring, not only the performance of the undulator but also the choice of the lattice functions are important design considerations. Optimum betatron functions and a zero-dispersion function shall be provided in the straight sections for IVU/CPMUs. In this paper, relevant factors and design issues for IVUs and CPMUs are discussed together with many technological challenges in short period undulators associated with beam induced--heat load, phase errors, and the deformation of support girders.

While emitting low energy photons from a medium or high energy storage ring, the on-axis heat load on the beam line optics can become a critical issue. In addition, the heat load in the bending magnet chamber, especially in the vertical and circular polarization mode of operation may cause some concern. In this work, we compare the heat loads for the APPLE-II and the Knot-APPLE, both optimized to emit 10 eV photons from the 3 GeV TPS. Under this constraint the heat load analysis, synchrotron radiation performance and features in various polarization modes are presented. Additional consideration is given to beam dynamics effect., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

A staggered undulator with high-temperature superconducting bulks might be a solution to achieve an undulator with an extremely short period for a synchrotron light source. YBCO bulk was thus selected to investigate the feasibility. This bulk (diameter 32 mm, thickness 2.5 mm) was used to build a staggered-magnet array structure and a mock-up staggered undulator of period 5 mm and fixed gap 4 mm was designed for this test. The potential generation of a sinusoidal field was tested in a 3-T magnetization system with field-cooling magnetization (FCM). The practicability of a HTS undulator is discussed in regard to the possibility of correction of the local field, repetition of field trapping and long-term stability. In addition, a field simulation concept was developed for designing the staggered undulator with YBCO bulks.

Two in-vacuum undulators (length 2 m) with period 22 mm (IU22) are constructed to be installed in the Taiwan Photon Source (TPS, 3 GeV) to provide a highly brilliant light source at hard X-ray energies. To verify ultimately the magnetic fields of these IU before installation in the storage ring, we have developed a system to measure the magnetic field in vacuum. To avoid contamination of the vacuum chambers, all components of the system are compatible with high vacuum. During actuation along the longitudinal direction, the positions of the Hall probe are monitored with optical devices and corrected with three two-axis stages. The deviations of position of the Hall probe with dynamic correction are less than 5 μm. The phase error reproducibility of this system is 0.15° and the first integral reproducibility is 13 G·cm. We applied this system to measure the magnetic performance of our in-vacuum undulators at varied gaps of the magnet array. The results of those measurements show no significant difference after assembly of the magnet arrays inside the chamber. The details of design and construction of this system are described, together with the results of measuring the magnetic field of the IU22.

Taiwan Photon Source (TPS) is a synchrotron radiation facility of medium energy, 3 GeV, and low emittance, under construction at National Synchrotron Radiation Research Center (NSRRC). The multipole errors of lattice magnets were rigorously examined and corrected so as to maintain the dynamic aperture of the electron beam in the storage ring. The lattice magnets were fully inspected at both the vendor and vendee sites. The multipole errors of the lattice magnets were tested and corrected. In particular, the sextupole magnets have the pole position adjusted to correct the multipole errors so as to conform to the specification. The yoke cutting is to correct the octupole error of the long-quadrupole magnets. The shimming of the magnetic center and the final examination of the magnets will be undertaken at NSRRC. In this paper, we report the methods of correcting the multipole errors, the magnetic center, and the performance of the TPS lattice magnets.

An effective initial sorting of permanent magnets can decrease the adverse effects of magnetic inhomogeneities and the imperfect geometry of blocks on the performance of an undulator. A sorting algorithm, based on simulated annealing, for the TPS EPU is implemented. The algorithm takes into account the magnetization of the blocks and the interactions between magnets. The field quality, including multipole, phase error, and particle trajectory, was optimized to within the specified tolerance. In this paper, we describe the sorting procedure and demonstrate the optimization results.

The plan for beamlines in Phase II at Taiwan Photon Source is to construct two new BioSAXS and nano-ARPES beamlines. A highly brilliant light source can be produced with a cryogenic undulator, and many synchrotron facilities have been developed and operated with these in their storage rings. The development of a cryogenic undulator became a target for a light source in TPS phase II. A cryogenic undulator with period of length 15 mm will be made in a hybrid magnetic structure, and use PrFeB permanent-magnet materials. A maximum magnetic field 1.31 T is estimated at gap 4 mm and temperature about 100 K. The spectral performance of a TPS cryogenic undulator is presented in this paper.

The Taiwan Photon Source (TPS) has been successfully commissioned. However, the minimum emittance in the TPS lattice is 1.6 nm rad. In the existing TPS storage ring lattice, it is imperative to reduce the emittance to below 1 nm rad. Therefore, a feasibility study for reducing the effective emittance of the TPS storage ring by using a Robinson wiggler was launched; the reduction is necessary to enhance the photon brilliance. In this study, a permanent-magnet multiperiod Robinson wiggler (MRW) was developed for use instead of the single-period Robinson wiggler. In general, the quadruple field of a combined function magnet in the storage ring is approximately few tesla per meter. According to beam dynamic analysis, we found that it is necessary to adopt a high gradient (40 T/m) combined-function MRW magnet to reduce the emittance effectively. Therefore, a high gradient field strength is required in the combined function MRW magnet. In this study, the quadrupole field strength of the MRW magnet was allowed to be approximately 40T/m at a magnet gap of 20 mm. The period length of the MRW magnet was 300 mm and the period number was 16. The of MRWs is discussed in regard to the possibility of increasing the photon brilliance from IU22.

Ten years ago, an elliptically polarized undulator (EPU) with a periodic length of 56 mm was constructed at the Taiwan Light Source. It was the longest EPU at that time. An electron beam of energy 1.5 GeV and current 300 mA passes through the undulator gap and radiates variously polarized light in the soft X-ray spectral domain. This EPU was extensively used in a wide range of research fields, including inelastic scattering, spin-polarized photoemission spectroscopy, photoelectron emission microscopy, and soft X-ray scattering. In response to increased demand by users with differing experimental requirements and applications, the construction of an EPU with a period of length 46 mm is under way. This investigation describes many aspects of the magnetic design, the structural engineering, and the control system. As magnetic technology is undergoing dramatic advances, advanced mechanical devices, and mechanisms have been included in the new EPU design; this design and its differences from the earlier design...

In material research, the characteristics of novel materials vary greatly with the environment. A magnet with a strong field will be developed for an experimental station for resonant X-ray scattering to investigate the magnetic properties of materials. This magnet will be developed with high-temperature superconductor (HTS) bulk YBa2Cu3O7 and magnetized with a HTS coil magnet wound with 2G HTS wire. HTS (RE) BCO will be selected to construct the coil of this magnet. Both the bulk and coil magnets will be assembled on the same movable system. The bulk HTS magnet will provide flux density greater than 4 T with a gap 34 mm that can accommodate the sample holder of the experimental station. The bulk magnet will be cooled with cryocoolers to 29 K and the coil magnet to 4.2 K; the coil magnet is separable from the bulk magnet after the field is trapped. We describe the concept of the magnetic-field calculation, the overall design of these magnets, and the cooling algorithm for the bulk HTS magnet system.

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.

In 1983, the Taiwan government established the Synchrotron Radiation Research Center to begin the planning of a national synchrotron facility for soft X-ray and vacuum ultraviolet research. After several years of preparation, the Taiwan Light Source (TLS), a 1.3-GeV storage ring, became commissioned for user operation in October 1993. Since then, synchrotron radiation research has grown to become a major field of research in Taiwan. In May 2003, the synchrotron organization formally became one of seven national laboratories and was given the name National Synchrotron Radiation Research Center (NSRRC). This institutional establishment ensures continuous support by the government in terms of annual budget and future development of the Center. In December 2007, the government approved a new synchrotron project to construct a small-emittance 3-GeV storage ring, the Taiwan Photon Source (TPS). In this report, we briefly discuss in two parts the development of accelerator facilities, and the growth of user rese...

At the National Synchrotron Radiation Research Center (NSRRC), which operates a 1.5 GeV storage ring, a dedicated small-angle X-ray scattering (SAXS) beamline has been installed with an in-achromat superconducting wiggler insertion device of peak magnetic field 3.1 T. The vertical beam divergence from the X-ray source is reduced significantly by a collimating mirror. Subsequently the beam is selectively monochromated by a double Si(111) crystal monochromator with high energy resolution (DeltaE/E approximately 2 x 10(-4)) in the energy range 5-23 keV, or by a double Mo/B4C multilayer monochromator for 10-30 times higher flux ( approximately 10(11) photons s(-1)) in the 6-15 keV range. These two monochromators are incorporated into one rotating cradle for fast exchange. The monochromated beam is focused by a toroidal mirror with 1:1 focusing for a small beam divergence and a beam size of approximately 0.9 mm x 0.3 mm (horizontal x vertical) at the focus point located 26.5 m from the radiation source. A plane mirror installed after the toroidal mirror is selectively used to deflect the beam downwards for grazing-incidence SAXS (GISAXS) from liquid surfaces. Two online beam-position monitors separated by 8 m provide an efficient feedback control for an overall beam-position stability in the 10 microm range. The beam features measured, including the flux density, energy resolution, size and divergence, are consistent with those calculated using the ray-tracing program SHADOW. With the deflectable beam of relatively high energy resolution and high flux, the new beamline meets the requirements for a wide range of SAXS applications, including anomalous SAXS for multiphase nanoparticles (e.g. semiconductor core-shell quantum dots) and GISAXS from liquid surfaces.

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 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.

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.

This study describes the design and testing of a superconducting solenoid magnet for soft X-ray magnetic circular dichroism (SXMCD) experiments at the National Synchrotron Radiation Research Center (NSRRC). The superconducting solenoid magnet provides an uniform field of up to 8 T in a bore of 55 mm in diameter and 0.5 m long. The superconducting solenoid is operated in a 4.5-K liquid helium bath for reducing the vibration level during the experiments. The magnet and its cryostat are optimized to prevent magnet quenching and lower liquid helium consumption. The magnet quench test and magnetic field measurements are also performed.

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

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

A 3.2 T superconducting wiggler with a periodic length of 6 cm and 32 poles was designed and fabricated as an X-ray source. The beam duct of this magnet is a semi-cold, ultra-high vacuum chamber that consists of an aluminum and stainless steel taper. The number of poles in this magnet design is even, to minimize the integral strengths of the multipole components. Two measurement systems—involving room-temperature and cryogenic Hall probes—were set up to measure the field of the superconducting wiggler. A cryogenic plant that supplied liquid helium and nitrogen to the superconducting wiggler has already been established. The performance of magnet construction is good and the commissioning of the superconducting wiggler in the storage ring has been successful. No trim coil compensation on the magnet is required to adjust the electron beam orbit. Furthermore, the electron beams exhibit no loss and remain highly stable after the superconducting wiggler has been quenched.

The Taiwan Light Source (TLS) is the first third-generation light source in Asia. The storage ring has six straight sections one section for injection, one for the RF cavities and diagnostic instrumentation and four sections for insertion devices, which are U5, U9, EPU and W20. Generating high-energy X-ray photons is a high priority at TLS. A single hybrid type wiggler is associated with three beam lines to serve X-ray users. The installed Superconducting Wavelength Shifter (SWLS) is very compact in size and can produce very high-energy photons. The injection section at TLS can barely accommodate the SWLS. The expected multipole components of the SWLS are strong, shrink the dynamic aperture; perturb the beta function, and reduce the beam lifetime. The increase in the synchrotron radiation by the SWLS also changes beam emittance and increases the energy spread. The influence of SWLS on the low-energy, 1.5 GeV, storage-ring should not be neglected. The downstream kicker with the water-cooled copper mask must be modified to prevent a potential meltdown of the welding junction of the ceramic chamber because the heat load is high. The 1.2 μs half-sine pulse field of the kicker is then altered by the copper-made radiation mask, which is installed inside the ceramic chamber. The operating capability of cryogenic system is established to ensure the smooth commissioning of the SWLS. The magnetic field mapping, the dynamic aperture simulation data and commissioning results will be presented and discussed herein.