High-field magnetic resonance imaging (MRI) is highlighted where the effects of increasing magnetic fields include drastic improvements in imaging and analyzing resolutions in space, quantity and time. The most remarkable outcome of high-field MRI may be found in conducting the imaging and real-time analysis of carbon (13C). We can then examine the metabolism by detecting biochemical reactions in the human body. For such purpose, an 11.7 Tesla superconducting magnet with a bore of 900 mm is required. This is a great challenge in terms of magnet technology. Furthermore, high-field MRI may open up a new market for the application of superconductivity in the area of education. Due to its non-invasive nature to the human body, high-field MRI may be regarded as an ultimate diagnostic tool that can contribute to the so-called aging society, which is progressing due to the dwindling birthrate.
Part V of this study covers the basic characteristics of pulse tube coolers. In the first section, energy flow consepts are reviewed using graphical representations. Three different categories of the cooling effect obtaines by flow oscilations without having a solid expansion piston are described based on the phase difference between the pressure and gas displacement within the system. In the second section, numerical calculations for different types of pulse tube coolers are performed to clarify the loss mechanisms. Consequently, the method of thermodynamic efficiency improvement is discussed.
Hoop stress is a very important factor in the design of multi-solenoid magnets. Designs of high-field magnets in the range of 23.5 T to 30.5 T were researched. It was confirmed that the designs were strongly limited by the design criteria of hoop stress. A modeling magnet consisting of multi-coils has been assumed for the calculation of several properties under the condition that the maximum hoop stress of every coil has the same value. The calculation results show that there are certain relationships among the central magnetic field B0, the magnet volume, and the stored energy. The results show that these values correlate with the exponential of B02.