Ko Agatsuma

Fabrication and test of a forced cooled Nb 3 Sn superconducting coil

The forced cooled Nb 3 Sn superconducting magnet has been manufactured and tested in a high field test facility(HFTF). It consists of 4 double pancake coils by wind & react process. The magnet has been successfully tested under 4T of the back up field of HFTF this August. The test results appear that the quench of the magnet has occurred under the conditions of 8,000A, 6T and 10.3K. Those results have proved the good performances of the conductor and its magnet.

Ti added Nb 3 Sn wires by new fabrication processes

The new fabrication processes for Ti addition to Nb 3 Sn have been developed. Using the pure Ti around Nb cores and sufficient Sn by internal plating, we have been able to get the good workability during drawing to a final diameter and the high critical current density at a higher field than 14 T. Several characteristics of both Ti foil and Ti rod processes have been discussed about the effect of Ti addition to Nb 3 Sn.

High resolution cryogenic quartz thermometer and application towireless measurement

Abstract The high quality synthetic single crystal quartz resonator mounted in a casing of 3 mm diameter with 8 mm length has been developed for the cryogenic temperature sensor covering with the wide range from 400 K to 4.2 K under thickness shear mode operation about 28 MHz through either extended cable connection or wireless radio echo telemetric transmission from the resonator. A wireless echo sensor system of quartz cryogenic temperature sensor system has been constructed and tested for an application to cryogenic temperature control.

Cryogenic microstrain measurement using laser light interference

Abstract A new system which makes it possible to measure an absolute value of cryogenic microstrain and cryogenic creep has been developed. The system adopts a method of counting He-Ne laser light interference pulses to detect the microstrain in a sample specimen at cryogenic temperature. This laser method is superior to the conventional strain gauge method in three main respects (1) it is calibration free: (2) it does not need temperature compensation; and (3) there is no limitation on the maximum measurable value of a strain. The cryogenic creep test facility developed is presented in detail. Preliminary test results and typical cryogenic creep testing results on polytetrafluoroethylene (Teflon) are also presented.

The forced cooled Nb 3 Sn superconductor and its magnet

The coil is a 0.6 m outer diameter solenoid, made up of eight double pancakes which will be tested in a forced cooled test facility that has been already constructed. The hollow conductor consists of a couple of Nb 3 Sn flattened cable in the center, a couple of Oxygen Free Copper stabilizer and the outside welded sheath. Some features of this conductor are as follows; the cooling mechanism by forced cooled supercritical helium and the high current capacity. The experimental results of this conductor and its magnet will be presented in this paper.

Investigation of mixed convection caused by centrifugal acceleration

Abstract In this paper, the influence of a macro-flow, which is some kind of natural convection caused by heat-in leak in rotational cryostats, has been investigated. A cooling channel unit which has a main flow counter to the buoyancy direction has been made to simulate the macroflow influence. A high-speed camera have been used to observe the transient local convection. Also a thin film thermometer has been used to detect the transient temperature variation. As the result, some fluctuation caused by the macro-flow has been observed in the transient convection. The degradation of the transient temperature variation and steady heat transfer have been measured.

AN ACOUSTIC MONITORING METHOD FOR SUPERCONDUCTING MAGNET

By monitoring acoustic signals, we could pick up the states which have not been observed by voltage measurement such as AE from Nb3Sn conductor carrying no transport current, and such in the case of AE from the magnet in persistent current mode both in NbTi and Nb Sn magnets. The large scale superconducting magnet3was also monitored. The results of these experiments had shown that minute super-to-normal transition had been detected by knowing the time constant of AE counting rates during the charging of themagnet.

Boundary layers of oxide superconductors films pasted on Al/sub 2/O/sub 3/, MgO, SrTiO/sub 3/ and YSZ

Energy-dispersive X-ray analysis, wavelength-dispersive X-ray analysis, and scanning microscopy examinations have been performed for annealed Y-Ba-Cu-O(YBCO) and Bi-Sr-Ca-Cu-O(BSCCO) films which will be adopted for future superconducting devices. Relatively thin films pasted on various substrates and cross sections were tested. The influence of the annealing on the substrate and superconducting films has been investigated. The results show the formation of boundary layers of intermediate products, which consists of Ba compounds between the YBCO layer and substrate (Al/sub 2/O/sub 3/, SrTiO/sub 3/, and ZrO/sub 2/) and Sr and Bi compounds between the BSCCO layer and substrate (SrTiO/sub 3/, MgO, and ZrO/sub 2/). >

Stainless steel sheathed forced internally cooled Nb 3 Sn superconductor and its coil test

Forced cooled Nb 3 Sn superconducting coil with the stainless steel sheathed conductor has been manufactured and tested in a High Field Test Facility (HFTF). Some properties of the sheath material and the conductor with stainless steel sheath have been investigated. A 316L stainless steel sheathed conductor (the outer dimension of 13 × 23 mm2) was fabricated, and one coil was completed by the wind and react method using this conductor. The coil was connected with 8 pancake coils made of copper sheathed conductor. The forced cooled magnet of 9 double pancake coils was tested under 5.9 T of the back up field in HFTF and generated 8.8 T under 7.6 kA of transport current. Experimental results show that the Nb 3 Sn strand in the copper sheathed conductor near the connector was degraded due to handling through reconnecting the conductor for several times.

Stability of a force-cooled superconducting magnet made from hollow conductor

A hollow superconductor test magnet cooled by forced-flow supercritical helium has been tested. The steady state stability of this magnet has been studied analytically in order to get a basis for design of a big superconducting magnet. The results suggest that the magnet would be quite stable if the transport current is held constant below a certain value given by the simple equation we proposed.