We have been developing a cyclotron accelerator for radioisotope production of medical use. The features of developed cyclotron system are compactness, light weight, and multi energy outputs. To achieve such features, coils are wound with rare-earth barium copper oxide (REBCO) tapes and the magnet has no iron core to generate an azimuthal varying field (AVF). To install the developed cyclotron accelerator into hospitals, an iron shield is needed for protection of leakage radiation and magnetic field. In this paper, to optimally design main coils with iron shield, a fast field computation method called “Model Order Reduction (MOR)” is adopted. Using MOR technique, the field computation is accelerated ∼50 times. The error of MOR field computation is sufficiently small. Hence, the MOR is effective in the optimal configuration design of coils with iron shield. The optimized configuration of a miniaturized cyclotron accelerator magnet is also shown.
Abstract The radiation‐stability of annealed and quenched polyethylene (PE) was estimated by gel, FTIR, and mechanical property (elongation at break) measurements. Although both types of PE showed an equal probability in gel and carbonyl formation, the resistance to γ‐ray irradiation as probed by elongation at break (%) was superior in quenched PE compared to annealed PE. This difference is discussed from the viewpoint of polymer structure, especially the number of the tie molecules, of annealed and quenched PE.
This paper deals with the cooling characteristics of a room-temperature magnetic refrigerator using an active magnetic regenerator (AMR): The AMR-based refrigeration cycle, which consists of a thermal storage process and a regeneration process, realizes a practical magnetic refrigerator running at temperatures close to room temperature. The AMR cycle has four sequential processes: adiabatic magnetization, fluid flow, adiabatic demagnetization, and fluid flow. We devise an appropriate simulation model of the cyclic heat transfer process inside the AMR particle bed. Then, the temperature profile inside the AMR bed and the cooling characteristics of the room-temperature magnetic regenerator are studied analytically. In addition, the validity of the analytical model is verified by comparing the experimental results with the analytical results. The results show that the larger the transferred fluid volume, the larger is the temperature difference between the hot and the cold ends.
A room temperature magnetic refrigerator deserves our attention as a refrigerator without having to use environmentally hazardous fluids. The refrigerator had produced a maximum COP of 2.6 when the temperature at the hot end of the AMR duct was 24 ℃ and the temperature span was 5 ℃. In order to increase the temperature span, the AMR duct has been modified to a cascade structure. The performance of the refrigerator using the hybrid magnetic materials is reported in this paper.
