MEASURING STRUCTURE OF SUPERCONDUCTING MAGNETIC SHIELD BRAIN FIELD MEASURING EQUIPMENT

摘要

A measuring structure of superconducting magnetic shield brain field measuring equipment is arranged in the enclosure outer wall while allowing the bottom of a first enclosure inner wall to oppose the ceiling of a second enclosure inner wall in a vacuum airtight body consisting of the first enclosure inner wall delimiting the enclosure outer wall and an upper space closed upward in the enclosure outer wall and the second enclosure inner wall delimiting a lower space opening downward. A first enclosure of high temperature superconductor and a second enclosure of high permeability magnetic body are arranged in an annular vacuum space between the enclosure outer wall and the first and second enclosure inner walls. Bottom of the first enclosure inner wall is allowed to oppose the ceiling of the second enclosure inner wall to form a head containing region in the hollow partition wall, and an SQUID magnetic sensor is arranged on the inner side of the upper space. The sensor is cooled with liquid helium in the upper space and the first enclosure is cooled with circulating helium gas. An adiabatic expansion chamber is provided in the upper space and helium gas supplied thereto is liquefied by adiabatic expansion and dripped onto liquid helium bath in the upper space thus replenishing loss of liquid helium during the operation. Alternatively, the adiabatic expansion chamber is connected with the sensor through a thermal conductor and the sensor is cooled indirectly with liquid helium.