Research and development of Nb 3 Al strands and cables for a high field accelerator magnet is ongoing under the framework of the CERN-KEK collaboration. In this program, new Ta-matrix Nb 3 Al strands ...were developed and their mechanical properties and superconducting properties were studied. The non-Cu J c values of these strands were 750 ~ 800 A/mm 2 at 15 T and 4.2 K. Using these strands, test fabrication of 27-strand Rutherford cable was carried out in collaboration with NIMS and Fermilab. The properties of the strands extracted from the cable were examined and it was found that there was no degradation of the superconducting properties of the strands. In this paper, we report the fabrication of the strands and the cable in brief and present some of the results obtained by studying their properties.
In this experiment, we designed, constructed and tested a 21 T superconducting magnet to be operated at 4.2 K, consisting of a Nb 3 Al inner coil with an exclusive power supply, and a series of Nb 3 ...Al middle, Nb 3 Sn outer-1 and Nb-Ti outer-2 coils with a common power supply. The flux jumps of the Nb 3 Al middle coil occurred in low magnetic fields and caused frequent shutdowns of an overvoltage-sensitive common power supply; however, we discovered this could be avoided by reducing the current ramp rate. The outer-middle coil unexpectedly quenched at 17.7 T, which was less than the expected 19.3 T. Simultaneous excitation of the inner coil was scarcely effective in increasing the quench current of the outer-middle coil, indicating that the Ic degraded location is relatively far from the inner coil. However, energization of the inner coil to a quench, in a backup field of 17.6 T by the outer-middle coil generated a central field of 20 T in a 25.4 mm clear bore at 4.2 K.
A polymer solid-electrolyte (PSE) switch has been embedded in a 90-nm-node CMOS featuring a forming-less programming and extremely high on/off ratio of 105. A fast programming of 10 ns is also ...demonstrated for 50-nmΦ 1 k-b array by introducing the PSE switches integrated with a fully logic compatible process below 350°C. A high free volume in the PSE is supposed to result in the smooth formation of the Cu bridge without destroying the electrolyte, thereby also resulting in forming-less programming and high breakdown voltage. High disturbance reliability (T 50 ; 50% fail) is extracted to be over 10 years at operation condition. The improved switching characteristics enable us to accurately program the crossbar circuit in a practical scale (32 × 32) without cell transistors. The developed switch is a strong candidate for realizing a low-power and low-cost nonvolatile programmable logic.
We have succeeded in making a superconducting Nb-Zr and V-Ti alloy multifilament wire using the diffusion reaction between constituent pure-metal subelements, which can omit the melt-and-casting step ...and may reduce the fabrication cost. A third element addition was also performed by replacing the constituent subelements with the third pure-metal subelement in the monofilament; Nb-Zr-V, Nb-Zr-Ti and V-Ti-Ta. Three kinds of heat treatment were investigated; (1) an alloying heat treatment (HTalloy) which is carried out at the final size ('fs-HTalloy '), (2) HTalloy is followed by cold-working (W) down to the final size ('HTalloy+W '), and (3) an intermediate precipitation heat treatment (HTprec) is carried out during the W stage coming after the HTalloy stage ('HTalloy+W+HTprec+W' ). The 'HTalloy+W+HTprec+W'treatment was found to be most effective in enhancing the critical current densities for both Nb-68 at.% Zr and V-60 at.% Ti-9 at.% Ta alloys, despite the HTprec treatment having slightly degraded the critical magnetic field.
