Hideshi Fukumoto

Application of 3D eddy current analysis on magnetically levitated vehicles

The eddy currents induced on the superconducting magnet (SCM) vessels of magnetically levitated vehicles (MAGLEV) have been analyzed. A 3D eddy current analysis code, based on a finite-element method (FEM) with thin shell approximation, is developed and verified through a mock-up SCM experiment. Through a coupled electromagnetic and mechanical analysis under SCM vibration, a SCM structure with low-resistivity material coating on the inner vessel of SCM is found to be suitable for the significant reduction of helium evaporation due to eddy current loss. >

Experimental Study on Electromagnetic Interactions between Plasmas and a Vacuum Vessel during Disruptions in the Hitachi Tokamak HT-2

Electromagnetic interactions between plasmas and a vacuum vessel during disruptions are examined experimentally in the Hitachi tokamak HT-2. Eddy currents which flow in the toroidal direction and poloidal coil currents are determined from the measured magnetic data. The currents enable calculation of the electromagnetic force on the vacuum vessel and resistively dissipated magnetic energy. Eddy currents and electromagnetic forces are mainly due to the plasma displacement (shell effect), not decay of the plasma current. Large plasma current quench rate -dIP/dt is associated with scraping of the plasma by the inner limiter through the rapid plasma radial movement, and the decay rate in circular plasma is twice as large as that in elongated plasma. The magnetic energy dissipation is mainly due to the eddy current of the net toroidal current mode which is induced by large current quench rate.

Magnetic analysis of ohmic discharges in the superconducting tokamak TRIAM-1M

A magnetic analysis to determine the plasma cross-sectional shape and equilibrium parameters in the superconducting tokamak TRIAM-1M is discussed using magnetic data obtained in ohmic discharges. First, it is shown that the eddy currents in the tokamak structures should be taken into account. Two magnetic analysis codes are applied. One is the SHP code in which the plasma current is replaced by several filamental loop currents and the other is the FITEQ code in which the plasma current density is consistent with the MHD equilibrium. The magnetic fields due to eddy currents are expanded into multipole fields. The central safety factor q(0) is fixed at 1.0. The eddy currents reduce the vertical field by 10%. Taking account of them, the accuracy of the magnetic analysis is improved and estimation of the stored thermal energy in a plasma becomes possible. The SHP code has the difficulty that the local plasma surface position can be distorted by the eddy current magnetic field. In addition, it is also noted that the pressure profile analysed by the FITEQ code is consistent with the Thomson scattering measurement and that the energy confinement characteristics are consistent with the neo-Alcator scaling

Application of dynamic behaviour analysis coupled with electromagnetic force to a superconducting magnet for magnetically levitated vehicles

Coupling behaviour is analyzed between structural vibration and eddy currents in a superconducting magnet for magnetically levitated vehicles. The complicated coupling behaviour between them is clarified using a new analysis method prepared previously. Calculations considering the coupling effect show that Joule losses in the inner vessel due to eddy currents induced by structural vibration in resonance are very different between the bending and torsion modes.

Inductance calculation of multiple arbitrary shaped planes using finite element integral equation method

An efficient technique to calculate inductance of multiple arbitrary shaped planes is developed based on voltage driven current distribution analysis by the finite element integral equation method. The comparison between calculated and experimental results proved that the present technique is fast and accurate enough for complicated multilayer packaging applications.

Simultaneous switching noise analysis on bus lines using coupled circuit and electromagnetic simulation

Simultaneous switching noise (SSN) on bus lines is calculated by accurately modeling printed circuit boards and LSI packages using coupled circuit and electromagnetic simulation. Contribution of crosstalk and ground bounce to SSN is qualitatively estimated. With relatively low inductance package such as BGA, the main cause of SSN is cross talk which results in increasing SSN voltage along the length of bus line. The results of simulation are compared with those of experiment, the both results agree within 10% difference at maximum peak of SSN.

Analysis of electromagnetic wave propagation considering continuity of polarization current by using vector facet elements

A method for calculating the electromagnetic wave propagation considering continuity of polarization current is presented. An electric field integral equation is used along with the moment method to develop an efficient procedure for numerical analysis of thin dielectric slabs such as the printed circuit boards (PCBs). In order to accurately treat the polarization charge and current conditions, the basic function of facet elements is used, by which it is possible for divergence of polarization current in a subdivided volume element to be exactly zero. The internal electric field of the dielectric sphere agrees with the theoretical value. The calculated impedance characteristic of the PCBs is in good agreement with prediction of the patch antenna theory.

Computational study on eddy current characteristics in a super conducting tokamak

Abstract Eddy currents in a super conducting (SC) tokamak were calculated in order to understand the characteristics of magnetic fields, electromagnetic (EM) forces and joule heat generations due to those currents. The SC tokamak with plasma current of 10 MA and an elongated shaped plasma with a major radius of 4.8 m was taken for the study. The characteristics other than those on the vacuum vessel (VV) were studied. The magnetic fields due to eddy currents on the cryostat as well as the VV could not be ignored. The cryostat eddy current produced a 5×10−3 T vertical field. The EM force on the cryostat was on the order of 10 kPa, much less than atmospheric pressure. The TFC structures experienced joule heat of 2.2 MJ due to eddy currents in a normal discharge, but 10 times more joule heat was calculated in a disruption. A large amount of joule heat generation was calculated in the case of TFC SC quench, which would halt running of experiments for several days.

Analysis of Electromagnetic-Structural Coupling Behavior using Lumped Parameter Model.

This paper concerns the dynamic behavior of a structure coupled with an electromagnetic field. We study the coupling behavior between vibration and eddy current using the lumped parameter model of a superconducting magnet for magnetically levitated vehicles (MAGLEV). This is a simple model with multidegrees of freedom which consists of mass, spring, resistance, inductance, and differentiation of inductance. We calculate the frequency response of vibration, eddy current, and Joule loss. These results show that the dynamic behavior of a structure in a strong magnetic field is different from the dynamic behavior without the magnetic field. For example, an antiresonance point which does not appear in the structure system appears in the coupling system. We also show the modeling method to understand the vibration behavior under the magnetic field.

Magnetic Analysis of Plasma Configuration in Tokamak Experiment Using Boundary Element Method

A method of magnetic analysis has been developed for experimental study of tokamak plasma configuration. The boundary element method has been applied to the determination of the magnetic flux distribution in a region bounded by magnetic sensors. The plasma cross-sectional shape is obtained without the difficulties that arise in the evaluation of the effects of the iron core of the transformer or of the eddy currents if they are excluded from the poloidal region encircled by magnetic sensors. The accuracy and validity of this method is checked by means of a comparison with numerically obtained MHD equilibria. The results have shown that the location of the plasma surface positions have been identified with an error of several percent of the plasma minor radius. This method has been applied to the analysis of the HT-2 experiment. Fairly good agreement is obtained between the magnetic analysis and limiter potential measurements.