Mitsuru Saeki

Cryostat and nuclear magnetic resonance imaging apparatus including a cryostat

A magnetically shielded cryostat, e.g. in a MRI imaging apparatus, has a heat-insulating tank having an outer wall. A magnetic shield is spaced from the tank, covers at least partly the outer wall of the tank and is not supported by the tank. A refrigerator having a cooled member extends into the tank. In order to avoid direct transmission of vibration of the refrigerator to a center region of the shield, the refrigerator is supported on the magnetic shield by at least one elongate support member connected to the shield only at or close to the ends of the shield.

Three Dimensional Harmonic Field and Eddy Current Analysis for Rotor End Region of Turbine Generator

In this paper, we report eddy current loss distribution in retaining rings of a turbine generator rotor end region. Main causes of the eddy current are harmonic fluxes in a steady state. Although the calculation required full model in three dimensional analysis, we used two different models. One is to analyze eddy current loss due to the magneto-motive force harmonic flux and another is to analyze the loss due to the slot harmonic flux. This enabled us to acquire results in reasonable times. By the analysis, distributions of eddy current loss caused by each harmonic flux are well studied. In addition, we propose a harmonic flux distribution analysis method based on a Fourier series expansion. We were able to clarify the higher harmonic flux and eddy current loss distributions.