Yoshikado Hosoda

NIJI-III Compact Superconducting Electron Storage Ring

The NIJI-III is a compact superconducting electron storage ring for industrial applications. Features of the ring include four strongly curved large-bore superconducting bending magnets utilizing quadrupole coils with a circular cross section surrounded by an air core and a cold bore. The circumference of the ring is 15.54 m with a critical wavelength of 13 A. Development of the NIJI-III is near completion. This report examines the design and performance of the NIJI-III.

Adjustable focusing force undulator

Abstract Several types of permanent magnet undulators for FELs have been developed that have a focusing force on the electron beam to avoid the spread of the beam in the undulator. However, the focusing force of these undulators cannot be changed after fabrication. To vary the focusing force, the undulator must be used with an electric quadrupole magnet, which requires additional space and the maintenance of a separate power supply. To solve this problem, an adjustable focusing force undulator has been developed. This undulator was designed using magnetic field analysis and electron beam tracking. The permanent magnets for this undulator have the same shape as those of a conventional Halbach-type undulator. The magnets whose magnetization direction is perpendicular to the electron beam axis in the upward and downward directions are offset horizontally to the right and left respectively. The strength of the focusing force is determined by the offset distance. This undulator has been fabricated and its magnetic field measured. Electron beam tracking using this measured data has confirmed the focusing effect of the undulator. The measured results agree with the results obtained by simulation.

Development of High Tc Superconducting Wire by Powder Method

Ag-sheathed high Tc superconducting wires of YBa2Cu3O7-x and Bi0.8Pb0.2SrCaCU1.5Ox were developed. Improvements in the density and the orientation of crystals brought about by press processing have been investigated, and by adopting adequate processing procedures the critical current densities were increased up to 4140A/ cm2 and 4400A/ cm2 for Ag-sheathed YBa2Cu3O7-x and Bi0.8Pb0.2SrCaCu1.5Ox superconductors, respectively.

Development of 2kA-Class High-Tc Superconducting Current Lead

We made and practically used 350A current lead for SMES magnet, and developed the lead into a large current carrying lead. The leads were made by stacking the Bi-based silver-sheathed wires thick in a high temperature region and thin in a low temperature region to reduce the heat conduction through the silver sheath. They were fixed on a FRP by a resin to improve the mechanical properties. The overall Jc at 77K was about 5,000–6,000A/cm 2 showing that the compactness can be achieved. The heat leak was 0.14W/lead when the lead carried 500A. For a large current carrying lead, 4 units were connected in parallel to increase the current capacity. The heat leak of the large current carrying lead was 0.345–0.412W/(kA•lead) when the lead carried 2.5kA. This proves that the high-Tc current leads using the Bi-2223 silver-sheathed wire are available even for a large current carrying lead, and has low heat leak property.

Development of High-Tc Superconducting Current Lead

We made the current lead using a silver-sheathed Bi-based superconducting wire. The structure was thick in a high temperature region and thin in a low temperature region to reduce the heat conduction through the silver sheath. The number of stacked wires and the Ic at 77.3 K of each part from a high temperature region to a low temperature region is 10 wires (210 A), 5 wires (110 A), 4 wires (90 A) and 3 wires (70 A). The loss of liquid He from one current lead was 0.14 W in a current from 0 A to 500 A. This represents about 60∼70% reduction of liquid He consumption of Cu lead.

GaAs Concentrator Solar Cells Using Aluminum-Cored Printed Circuit Bases

An effective cooling method is essential for GaAs concentrator solar cells operated under highly concentrated sunlight, because the conversion efficiencies of the cells decrease at high temperature. We fabricated aluminum-cored printed circuit bases which consist of an aluminum core, anodic oxide layer of aluminum, polymer layer such as polyimide, and metal layer. In this paper we report that this aluminum-cored printed circuit base is effective and that on this base a higher conversion efficiency can be obtained than on a conventional alumina ceramic base. Cell conversion efficiencies of 23.9%, 23.7%, and 22.6% were obtained at 96 suns, 186 suns, and 327 suns, respectively, from the GaAs concentrator solar cell mounted on the aluminum-cored printed circuit base.

GaAs Solar Cell Test Facility

A hybrid type (electricity and heat) GaAs solar cell test facility has been made to evaluate total characteristics of GaAs cell and to study the energy conversion system. The size of solar collector is 3.4 m ×2.1 m and 60 GaAs cells with Fresnel lenses are attached on it. The solar collector is controlled by a microcomputer to track up the sun. Electric energy produced by the cells is stored in a lead-acid battery and then supplied to the load through a DC-AC inverter. The microcomputer also controls the data acquisition in parallel with tracking. This paper presents an overview of our facility and experimental results of power generation obtained to date.