A high field superconducting magnet, 4-5T in central magnetic filed, is required for magnetic resonance spectroscopic imaging (MRSI) on 31P, essential nuclei for energy metabolism of human body. This paper reviews superconducting magnets for high field MRSI systems. Examples of the cross-sectional image and the spectrum of living animals are shown in the paper.
A brief review is presented of the recent space cryogenic applications. There are many potential space missions requiring cryogenic cooling, some of which are in progress and others are still under consideration. Techniques for cryogenic cooling in space are discussed with emphasis on the temperature range and the refrigeration load. A He II cooled onboard infrared telescope which is indeed the highlight of the application of current space cryogenic technology is described by taking the IRTS as an example. Several new techniques required for the utilization of He II in space have been developed prior to the practical design studies of onboard IR telescopes. Some other projects, in addition to IR telescopes, requiring He II cooling are also briefly described. Finally, a prospect of future space cryogenics is discussed for further development of space cryogenics.
The strain effect on the critical current density, Jc, of NbN tapes has been investigated in 4.2K and 9T. Superconducting films of NbN have been prepared on metal tapes of Hastelloy B and 304 Stainless steel by reactive sputtering in an argon-nitrogen atmosphere. The strain dependences of Jc are influenced by the substrate material and NbN film thickness. The NbN tapes with Hastelloy B substrate maintains constant values of Jc up to strain values of above 1%. However, those with 304 Stainless steel substrate show a gradual decrease in Jc from 0.3 to 0.9% and exhibit a marked decrease in the range of above -0.9%. The value of the irreversible strain limit εirrev. where each NbN tape is permanently damaged, is in good agreement with the ratio between the proportional limit and Young's modulus in an investigated stress-strain curve. The maximum value of εirrev. reaches -1.4% and has been obtained in the tape consisting of the Hastelloy B substrate and a 3, 000Å NbN film. In tapes thickly coated with NbN, which have been measured up to above their εirrev. values, some cracks are found and films of NbN are frequently peeling off their substrates.