A tapered undulator beamline BL36XU was constructed at SPring-8 to conduct structural and electronic analysis of dynamic events on polymer electrolyte fuel cell (PEFC) cathode catalysts for the development of next-generation PEFCs. BL36XU provides various time and spatially resolved XAFS techniques in an energy range from 4.5 to 35 keV for investigating PEFCs under the operating conditions. In addition, we developed in-situ complementary measurement systems, such as in-situ time-resolved XAFS/XRD and ambient pressure HAXPES systems. This report describes the performance and present status of the BL36XU.

This paper describes the development of a phase shifter that can be used in cross undulators for fast polarization switching. The phase shifter is composed of a pair of cut-core coils and a thin-walled stainless steel duct. Evaluation of the magnetic fields of the phase shifter indicates that the switching frequency of this simple and low-cost device can exceed 30Hz.

The newly installed BL28XU beamline at SPring-8 is dedicated to in situ structural and electronic analysis of rechargeable batteries. It supports the time range (1 ms to 100 s) and spatial range (1 µm to 1 mm) needed for battery analysis. Electrochemical apparatus for battery charging and discharging are available in experimental hutches and in a preparation room. Battery analysis can be carried out efficiently and effectively using X-ray diffraction, X-ray absorption fine-structure analysis and hard X-ray photoelectron spectroscopy. Here, the design and performance of the beamline are described, and preliminary results are presented.

We are currently constructing a new X-ray absorption fine structure (XAFS) beamline BL36XU at SPring-8 dedicated for the structural and electronic analysis of the dynamic events on polymer electrolyte fuel cell (PEFC) cathode catalysts for the development of next-generation PEFCs. To investigate the cathode catalyst nanoparticles in PEFCs under the operating conditions, the beamline is designed to provide time- and spatially resolved XAFS techniques having a time resolution of 100 μs, spatial resolution of 200 nm, and depth resolution of 1 μm. We report the outline and design of the new beamline.

Permanent magnets decrease their magnetic field under severe radiation environment. This radiation damage, radiation-induced demagnetization, is a great concern especially for the devices that requires very precise uniform magnetic field such as undulators. The evaluation of this field degradation is difficult because the mechanism of the radiation–induced demagnetization is not clear. Several approaches to clarify this mechanism have been made. For example, (1) the approach to examine the relations between the field degradation and the environmental factors like magnet shape, temperature and so on, (2) the approach to examine the changes of the microstructures and the properties of the magnet after irradiation, (3) the approach to compare and examine the experiments of the demagnetization and the computer simulations of the radiation. This paper reviews and summarizes these approaches and models briefly. The new point of view to consider the mechanism is presented as well.

Permanent magnets Nd2Fe14B are the main component of the insertion devices of the synchrotron radiation facilities and used at other accelerators. The radiation induced demagnetization of permanent magnets, becomes one of the most important issues of the next generation light sources. To investigate the radiation damage the magnetic field change of Nd2Fe14B magnet exposed to a 2.5 GeV electron beam has been measured. The radiation field near the magnet and the distribution of energy deposition in the magnet are studied with Monte Carlo code FLUKA. The radiation induced demagnetization is analyzed and a fitted formula is proposed to estimate the relative reduction of remanence.

The measurements of high-energy and high dose mixed radiation from high-energy electron accelerator are carried out using a radiation damage monitor. It consists of two Radiation-Sensing Field-Effect Transistors (RADFETs) for total absorbed dose from mainly gamma ray and other charged particles and a Si PIN diode for neutron fluence. This is a part of the demagnetization study of rare earth permanent magnet irradiated by 2.5-GeV electron beam. The sensitivities of damage detectors are measured using 65-MeV quasi-monoenergic neutron, 14-MeV D-T neutron, (252)Cf neutron for Si PIN diode and (60)Co and (137)Cs gamma ray for RADFETs. Measured sensitivities are in acceptable range in the comparison of producer's proposed values. The dose and fluence measurements are carried out for the same target condition, Cu and Ta, as that for the demagnetization study. The 5 x 5 cm(2) cross-sectional and 5.5-cm-thick Pb target is also used for the general comparison with photoneutron yields. All measured dose and fluence are compared with the calculated results using the FLUKA code and agree well each other. The application of this kind of radiation damage monitor to high-level dosimetry at high-energy electron accelerator has been discussed.

Rare-earth permanent magnets such as Nd2Fe14B and Sm2Co17 are the main components of the insertion devices of synchrotron radiation facilities and are used at other particle accelerators. Due to radiation safety concern the induced radioactivity in permanent magnets at a 2.5GeV electron accelerator were studied with Monte Carlo simulations and experiments. The saturated activity of each radioactive isotope was estimated with FLUKA code (2005 version) and compared with measurement results. Three models of NEOMAX Nd2Fe14B magnets and one trivial Sm2Co17 magnet were chosen as the test magnets. The remnant dose rate at 1m from the magnet and its cooling time dependence are calculated with the induced activities from the view of radiation protection. These are investigated under unique radiation environments due to different target conditions. The transverse distributions of induced radioactivities of several representative isotopes, which were measured at different target conditions, agree well with the electromagnetic shower characteristics at different target conditions as well as the spatial distributions of photon and neutron fluences.

Most of radiation damages in materials are structural changes (radiation-induced defects), but the origins of radiation-induced demagnetization of permanent magnets can be explained by a magnetization reversal caused by a thermal process. We propose a model for the mechanism of radiation-induced demagnetization and suggest some protections strategies.

Sintered Nd2Fe14B permanent magnets are damaged (demagnetized) by strong radiation, though some techniques of the magnets can reduce the sensitivity to radiation. High coercivity magnets show strong resistance to radiation, while they have a manufacturing dependence. Using magnets at very low temperature is effective. Stabilization under the appropriate annealing conditions enhances the radiation resistance successfully. Stabilizing by reverse field also increases the resistance. Combination of these techniques is much more effective, for example, annealed high coercivity magnets indicate very strong resistance.

A new application of high-temperature superconducting (HTS) bulk magnets to synchrotron radiation (SR) sources, i.e., magnetic devices that generate a periodic field to produce highly brilliant SR, is presented. Utilization of HTS bulk magnets brings two advantages over the existing SR sources: much stronger field than that of conventional SR sources with rare-earth permanent magnets (REPMs) and higher feasibility than existing superconducting SR sources with low-temperature superconducting coils. Two schemes for the application of HTS bulk magnets to SR sources are presented. In the first scheme, HTS bulk rings are mounted on REPMs to enhance the magnetic field. In the second one, HTS bulk magnets are arranged in line instead of REPMs. Principles and recent demonstration experiments are described.

The cryogenic permanent magnet undulator (CPMU) is an insertion device in which permanent magnets (PMs) are cooled to a cryogenic temperature to improve magnetic performances in terms of remanence and coercivity. Operation of CPMUs is expected to be much easier than that of existing superconductive undulators (SCUs) with low-temperature superconducting coils, since the operating temperature can be much higher than that of liquid helium. In addition to pure PMs, high-permeability pole pieces and/or high-temperature superconductors (HTSCs) can be exploited to enhance the magnetic field of the CPMU. Towards realization of this concept, a number of R&Ds are in progress at SPring-8: field measurement under a cryogenic environment and reinforcement of HTSC samples. Encouraging results have been obtained from preliminary studies.

SCSS or “SPring-8 Compact SASE Source” is an XFEL facility proposed at the SPring-8 and aims at an angstrom laser, whose facility scale is much smaller than other XFEL facilities. R&Ds of accelerator components such as the low-emittance electron gun, high-gradient C-band accelerator, and short-period in-vacuum undulator, which enable the SCSS concept, have been carried out from 2001. Construction of a 250-MeV prototype accelerator has been started that is composed of these components. It not only examines feasibility of each accelerator component but is also expected to give perspectives for construction and operation of the XFEL facility.

The effect of the thermal stabilization on the radiation sensitivity of neodymium‐iron‐boron (Nd2Fe14B) undulator magnets to high‐energy electron irradiation was investigated. The sample magnets were baked in an oven for 24 hours before irradiation, and the temperatures of this thermal treatment were varied from 142 °C to 240 °C. All of the thermally stabilized magnets showed higher resistance to irradiation with 2.0 GeV electrons than unbaked sample. Their demagnetization curves decreased linearly with respect to the number of electrons, and with a demagnetization rate remarkably smaller than that of the unbaked magnets. Though, when the stabilizing temperature exceeded some point, the resistance showed small decrease.

In order to obtain high magnetic fields in a short period undulator, superconductive undulators have been actively investigated in recent years. In this paper, however, we propose a new approach, the cryogenic permanent magnet undulator (CPMU) design, using permanent magnets at the cryogenic temperature of liquid nitrogen or higher. This cryogenic scheme can be easily adapted to currently existing in-vacuum undulators and it improves the magnetic field performance by 30%-50%. Unlike superconductive undulators operating around the liquid helium temperature, there is no big technological difficulty such as the thermal budget problem. In addition, existing field correction techniques are applicable to the CPMUs. Since there is no quench in the CPMUs, the operation of the CPMUs has the same reliability as conventional permanent magnet undulators.

Synchrotron X-ray diffraction measurements on a spin-Peierls material CuGeO3 in applied magnetic fields, H, up to 15 T are made. We find that the temperature, T, dependence of the incommensurate Bragg peak at a lower H is quite different from that at a higher H. At sufficiently high fields, we find that the lattice incommensurability, deltal, is almost independent of T, while at H slightly above the critical field = 12.25 T for the commensurate to incommensurate transition, deltal decreases with increasing T. We interpret that this finding is due to a stabilization of the incommensurate state by a strong magnetic field which suppresses thermal fluctuations.

The concept and plan of the in-vacuum type revolver undulator has been presented in a previous paper [1]. Since then, it has been developed, tested and improved. This device can select an undulator by rotating the magnet beam, on which there is four undulators with different period length. The magnet beams are placed inside the vacuum chamber, so the magnetic gap can be reduced to size smaller than that of out-vacuum type undulators without any limitation from the chamber wall. This small magnetic gap size realizes a short magnetic period using small-size magnet blocks [2, 3]. The mechanisms for rotating magnet beams in vacuum bring several technical difficulties compared to other standard in-vacuum type undulators. In this paper, several exotic and typical mechanisms of the in-vacuum revolver undulator are reported. A schematic drawing of this revolver undulator is shown in Fig. 1.This revolver undulator has been installed in the storage ring at the Pohang Accelerator Laboratory in South Korea during summer shut down in 2003.

A simple scheme for field enhancement in synchrotron radiation sources such as undulators and wigglers is proposed, which is based on the fundamental nature of the superconducting loop where the magnetic flux is preserved. A superconductor ring placed to enclose the magnetic pole works as a kind of permanent magnet. The magnetization is performed by electromagnetic induction brought by the opening movement of the magnetic gap. Since neither additional external power supplies nor current leads are necessary, high-temperature bulk superconductors can easily be implemented in this scheme. Calculations to check the effectiveness of the new concept show that the critical current density of the superconductor is crucial to the performance of the synchrotron radiation sources based on this concept. Experiments were performed to verify the principle of the proposed scheme, which gave promising results to strongly support it.

One direction of the recent insertion device development is the pursuit of short periodicity. After the advent of in-vacuum undulators, short period undulators have been widely used at small gaps in many synchrotron radiation facilities. In order to pursue shorter periodicity, however, further improvement of the magnetic performance is needed. Although a superconductive device is a prospective candidate, there still remains technological R&Ds such as the thermal budget problem and new magnetic field correction methods. In this paper, we propose a new approach for the construction of a high performance short period undulator, in which the permanent magnets are used at cryogenic temperatures. In this so-called cryogenic permanent magnet undulator (CPMU), the magnetic field performance is improved by roughly 30 % compared with the current invacuum undulators. Since the CPMUs are operated at the temperature of liquid nitrogen or higher, a cryocooler with sufficient cooling capacity (several hundred watts) is available and the thermal budget is no more a problem. Moreover, there is no quench in the CPMUs and stable operation of the undulator can be expected. Design examples and expected performance of the CPMUs are given in the paper.

One of the neodymium-iron-boron (Nd2Fe14B) magnet with high coercivity was found to show very high resistance to irradiation. The sample was irradiated with 2.0 GeV electrons. The radiation-induced demagnetization of this Nd2Fe14B magnet was as small as that of the samarium-cobalt (Sm2Co17) magnets, known as to show high radiation resistance, irradiated under same experimental conditions for comparison.