Metallic bellows are today used for a variety of application in wide range of fields from fusion reactors to simple vacuum components. These are mainly two types (1) welded bellows and (2) formed bellows, each of which are designed with different characteristics for different application. In this report the design of such bellows is described. In particular a new method of life-time calculation given by combination of examination and theoretical consideration will be explained. The usefulness of such calculations in terms of suitable bellows design and product standardization will also be outlined. New materials for the production increased life-time bellows will be looked at and finally we will show the application of metallic bellows in such areas as paticle-free gate valves for semiconductor production/processing equipment which require life-time >106 cycles, fusion reactors, particle accelerators and power electronic devices.
High stress arising from thermal and electromagnetic force is generated during energizing the superconducting magnet. The effect of this stress must be noted especially for large magnet. In addition to this, stress distribution has been found to be irregular and complicated, thus it is important to evaluate the rigidity of superconducting magnet. Each spacer between the conductor bears higher compressive force than the conductor, which have great concern with the rigidity of the magnet. In this report we evaluate the behavior of the magnet in totality by means of homogeneous doughnut disk model and equivalent elastic module's. In the meanwhile there is one other thing that is important for superconducting magnet. One of the most effective factors to deteriorate the stability of the magnet is mechanical disturbance, for example, the behavior of the friction. In this report we are concerned with the movement of the conductor arising from electromagnetic force. We calculated the force of the conductor and between the conductor and spacer. It was found that heating which is cause of Quench occurs most easily in inner layer, which is nearest axis, of the magnet. The possibility of heating was found to depend on the location of conductor and spacer. Hence it is important to evaluate the location of spacer.
A commercial pressure sensor is studied to assess the applicability of the poly-crystalline silicon gauges at cryogenic temperatures under magnetic fields. Its pressure sensitivity and resistance of the gauges are studied down to 5K under the magnetic fields of up to 8T. Its performance is compared with that of previously reported commercial pressure sensor with the crystalline silicon gauges. Its dependence of pressure sensitivity on temperature change from room temperature down to 6K is smaller than 4% as long as the sensor is operated in the constant voltage mode. The change in the sensitivity under magnetic fields is also as small as 2% under the same mode. However, its zero point shift due to the temperature change is larger than 20% of the full span. The zero point shift also shows an anomalous dependence on the magnetic fields, which is about 10% of the full span and independent of temperature. Some means to improve its performance are discussed.
We have developed a fully automated measurement system of thermal conductivity combining a helium refrigerator and a data acquisition, processing and control system (NEC-9800 series) with RS 232 C-GPIB lines. The thermal conductivity is measured by a conventional steady-state heat flow method in the range of 15-200K. It is found that a measurement of a NIST standard reference material ensures high accuracy of 3% for this apparatus. Furthermore, the measured thermal conductivity of high-Tc oxide superconductor (BPSCCO) agrees with the typical data reported by a number of groups, and shows a clear enhancement below Tc.