Tomoyuki Semba

Design of a Superconducting Wiggler for the Saga Light Source Storage Ring

A hybrid three-pole wiggler for generating hard X-rays in the range 4-40 keV was designed for the 1.4-GeV storage ring of a synchrotron radiation facility, i.e., the Saga Light Source. The wiggler consists of a superconducting main pole with a peak field of 4 T and two normal-conducting side poles with peak fields of 1 T. The normal-conducting side poles were used to reduce the heat load on the cryogenic system for the wiggler. A cryogen-free system was used to ensure long-term operational stability of the wiggler system. The superconducting coil and iron poles of the main pole are cooled by a Gifford-McMahon cryocooler via mechanical contact. To suppress the first and second field integrals of the main pole, we designed the main pole with relatively large field clamps and with no transverse return yoke. This pole structure was effective in suppressing beam displacement due to the wiggler field and in reducing the side pole volume. The beam effects due to the multipole fields of the wiggler were estimated and were found to be small or controllable. Based on these results, the storage ring with the designed wiggler is considered to be an effective hard-X-ray source.

Magnetic Field Design of a Superconducting Wiggler in the SAGA-LS Storage Ring

A magnetic field design for a superconducting (SC) wiggler system, which has been installed in the Saga light source storage ring, was described. The wiggler is a three-pole type, consisting of a 4.0-T SC center magnet and two normal-conducting side magnets; thus, each pole forms a magnet. Since the wiggler consists of isolated magnets, reduction of the first field integral of the center SC magnet was important from the viewpoint of suppression of the orbit displacement. For this purpose, the center SC magnet was designed to have a separated iron core with field clamps and no transverse return yoke. This concept made magnetic field negative regions near the center peak magnetic field on the electron beam orbit to reduce the first field integral and beam meandering. Heat generations due to eddy currents and the magnetic field due to supporting structures were calculated to have ignorable effects. The appropriateness of the design has been confirmed through daily stable operation at the light source.

Fabrication Process Qualification of TF Insert Coil Using Real ITER TF Conductor

JAEA is fabricating the toroidal field insert coil (TFIC) in cooperation with Hitachi, Ltd. This solenoidal coil has about 50 m of ITER TF conductor wound in a 1.44-m diameter. In preparation for fabricating the TFIC, fabrication trials of windings, removal of Cr plating of the cable and welding of the terminal sleeve were performed for process qualification. The winding trials were accomplished without breaking any of the superconducting strands. In the trials to remove the Cr plating from the cable, HCl-soaked unwoven cloth was used, and the surface of a strand selected from the cable was confirmed by magnification to be free of Cr plating. In trials to fabricate termination, using electron beam welding (of OFHC copper and SS316LN) and fillet-welding (of SS316LN and SS316LN using JK2LB weld wire), tensile tests of the welds were conducted at room temperature and 4 K, and ultimate tensile strength values equivalent to that of the base metal of the weld were obtained. Also these welds passed test items of JIS Z3040 code, so the weld procedures were qualified. During fillet-welding the maximum temperature of the cable under the weld was 120 °C, not high enough to damage the cable. From the results obtained, the main processes involved in TFIC fabrication were established and qualified.

Fabrication and Testing of a Model Quadrupole Magnet for Linear Accelerators

A model of a quadrupole magnet for linear accelerators was designed, fabricated, and tested at KEK in order to gain fabrication experience and a better understanding of superconducting magnet characteristics. The assembly has a design field gradient of 56.5 T/m, an aperture of 92 mm, and a cold mass length of 680 mm. Furthermore, it is designed as a superferric magnet with four racetrack coils wound with a specially fabricated ribbon cable of eight superconducting strands. In this paper, we present details of the magnet design, fabrication, and the results of its cold tests. Data of the field measurements are also presented in brief.

Manufacture and assembly of the 6-meter-long cryomodules for superconducting RF Test Facility (STF) at KEK

A superconducting RF test facility (STF) is being constructed at KEK for R&D oriented toward the International Linear Collider (ILC). Under KEKs guidance, Hitachi, Ltd. has manufactured cryostat components at its factory and completed final assembly in the STF Linac Building at KEK. The STF cryomodule consists of two cryostats, each about six meters long based on the TESLA-TTF-type III design. Each cryostat can house four 9-cell cavities, each one meter in length. This report outlines the flow of manufacturing from the factory to final assembly, and describes the manufacturing of equipment, assembly precision, and other matters.

Design and Performance Test of Superconducting Transport Solenoid for D-Line at J-PARC Muon Science Facility

A superconducting transport solenoid for Decay Muon Line (D-line) at J-PARC Muon Science Facility was newly designed and manufactured. It was designed to generate a magnetic field in relatively large region (warm bore diameter 0.2 m), while keeping the same outer dimensions, connection interfaces to the existing refrigerator and the power supply of the previous machine [1-3]. Major changes of both solenoids are the reduction of the central magnetic field, the equipment of a warm bore and the adoption of the high Tc current leads. After the installation to the beam line, the initial cooling test, the excitation test and the emergency shutdown test at the rated current were conducted by KEK in order to confirm cryogenic and magnetic performance. These tests were successfully performed with no damege and indicated the solenoid was precisely manufactured and fulfilled the requirements. The solenoid has been under operation since July, 2015. This report describes the design, the manufacturing process, the magnetic field measurement at room temperature and the results of performance tests conducted by KEK.

Manufacture and Quality Control of Insert Coil With Real ITER TF Conductor

JAEA successfully completed the manufacture of the toroidal field (TF) insert coil (TFIC) for a performance test of the ITER TF conductor in the final design in cooperation with Hitachi, Ltd. The TFIC is a single-layer 8.875-turn solenoid coil with 1.44-m diameter. This will be tested for 68-kA current application in a 13-T external magnetic field. TFIC was manufactured in the following order: winding of the TF conductor, lead bending, fabrication of the electrical termination, heat treatment, turn insulation, installation of the coil into the support mandrel structure, vacuum pressure impregnation (VPI), structure assembly, and instrumentation. In this presentation, manufacture process and quality control status for the TFIC manufacturing are reported.

Recent activities in accelerator construction and STF cryomodule

Since being founded in 1910, Hitachi, Ltd. has been providing a wide lineup of products and services in fields ranging from consumer home electronics to social infrastructure. The corporation has conducted a wide range of activities in the field of particle accelerators as well. This paper describes Hitachis contributions to the history of accelerator construction, major devices recently handled by Hitachi, and its efforts in developing STF cryomodules as part of recent R&D oriented toward the International Linear Collider (ILC).