| 摘要 |
PURPOSE:To obviate the generation of eddy currents in a radiant heat shielding plate and to miniaturize a superconducting magnet by installing a cancel gradient coil between the outermost peripheral radiant heat shielding plate enclosing the superconducting coil and ordinary-temp. pore and installing a main gradient coil in the ordinary-temp. core. CONSTITUTION:The cancel gradient coil 25 is disposed between the ordinary- temp. pore 7 and the 80K radint heat shielding plate 22 in the superconducting magnet concentrically with the superconducting coil 19. The main gradient coil 24 is disposed in the ordinary-temp. pore 76 concentrically with the cancel gradient coil 25. An iron shim 27 is stuck to the inside surface of the ordinary- temp. pore 7. The external magnetic field generated by the main gradient coil 24 are canceled by the gradient coil 25 and, therefore, pulse magnetic fields do not act in the 80K radiant heat shielding plate 22 and the eddy currents are not generated therein. Since the iron shim 27 is disposed between the main gradient coil and the cancel gradient coil, the electrical coupling of the gradient coil and the iron shim 27 does not arise. |
