Masaru Iwamatsu

Development of a high rigidity superconducting magnet for the Maglev system

A high rigidity type superconducting magnet (SCM) is developed and tested by an electromagnetic vibration simulator which simulates the actual running conditions. To reduce the increase in heat load due to the vibration of the cryostat, several kinds of design concepts are chosen. It is recognized from the experiment result that the most effective design concept is to increase the characteristic frequency in twisting mode of the inner vessel with the high rigidity outer vessel.

Bi2212 superconducting tubular conductors prepared by the diffusion process for current lead

Bi2212 HTS conical tubular conductors have been prepared by the diffusion process for current lead application. The Bi2212 HTS layers are synthesized through the diffusion reaction between a Sr-Ca-Cu oxide substrate and a Bi-Cu oxide coating with Ag addition. Highly oriented HTS diffusion layers about 150μm in thickness are formed around both outside and inside of the conical tube 34/29mm in outside/inside diameter at larger end, 24/19mm in outside/inside diameter at smaller end, and 100mm in length. The transport current has been measured using two cryocoolers between 12 K at cold end and 40–70 K at warm end under 0.5 T. The transport current of 1,000 A was stably passed for 10 minutes at 50 K. The joint voltage of cold end was as low as 30μV at 50 K during 1,000 A running. The low voltage results from the low contact resistance between Bi2212 grains and Ag precipitated on the surface. Heat leakage conducted through the specimen has been newly evaluated using heat flux meter by steady-state heat flow method.

Heat load characteristics of superconducting magnet in the electromagnetic vibration test

Abstract Japanese maglev system consists of on-board superconducting magnets(SCMs) and ground coils. When SCMs vibrate due to magnetic fluctuation from ground coils, the heat load of SCMs increases not a little. To estimate this heat load of SCMs with different structures, we have done electromagnetic vibration tests by changing the inner structures of the SCMs. And then, we have tried to measure the eddy current on the inner vessel, and we got available knowledge. As a result, we have found that the increase of the heat load is influenced by vibration characteristics and resistivity of structures.