Utilization of superconducting permanent magnets is now under investigation at SPring-8 for future development of synchrotron radiation sources, and several concepts has been reported so far. In one of them, ring-shaped bulk superconductors (ring SCs) will be used for enhancement of the undulator field strength. In the previous work, it was reported that the mechanical property of the ring SCs were so poor that the magnetic performance degraded during experiments. In this work, several methods are proposed to enhance the mechanical property of the ring SCs and results of experiments performed to investigate the effects of them are reported. Resin impregnation with a pole piece inserted into the ring SCs is found to be effective.

A new concept of synchrotron radiation (SR) sources with ring-shaped high-Tc superconducting bulk (bulk ring) magnets have been proposed at the SPring-8, a SR facility in Japan. During the proof-of-principle experiments, it was found that the magnetic field generated by the bulk ring gradually decreased, due to mechanical damages in the bulk ring. In order to improve the mechanical property of the bulk ring toward realization of this concept, two methods of reinforcement, i.e., resin impregnation and iron ribbing, were proposed. The effects of these methods were investigated with four bulk ring samples and it was found that combination of the two methods significantly improved the mechanical property.

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.

A novel synchrotron radiation source is proposed that utilizes bulk-type high-temperature superconductors (HTSCs) as permanent magnets (PMs) by in situ magnetization. Arrays of HTSC blocks magnetized by external magnetic fields are placed below and above the electron path instead of conventional PMs, generating a periodic magnetic field with an offset. Two methods are presented to magnetize the HTSCs and eliminate the field offset, enabling the HTSC arrays to work as a synchrotron radiation source. An analytical formula to calculate the peak field achieved in a device based on this scheme is derived in a two-dimensional form for comparison with synchrotron radiation sources using conventional PMs. Experiments were performed to demonstrate the principle of the proposed scheme and the results have been found to be very promising.

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.