| 摘要 |
Operation signals of a compressor 21 for a helium refrigerator 20 are inputted to a correction magnetic field power source 13, so as to generate a current in synchronism with mechanical vibration of the helium refrigerator 20. The current generated by the correction magnetic field power source 13 drives a magnetic field correction coil 14 combined with the static magnetic field generation magnet 2 so as to generate a correction magnetic field of which amplitude is equal to that of the magnetic field variation component caused by the mechanical vibration of the helium refrigerator 20 and of which phase is inverted thereto. Thereby, an open type MRI apparatus employing a super conducting magnet which eliminates a magnetic field variation due to mechanical vibration of the helium refrigerator 20 and always maintains a stable magnetic field, is realized.
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