Search

HTS coils designed to carry pulsed currents have been built and tested demonstrating fast charge and discharge times on the order of a second. Gaseous Helium from 40 to 80 K is used as a coolant. Losses due to ac, hysteresis, and transport currents associated with current entry into and exiting from HTS are small and do not produce thermal transients that induce current sharing or normal transitions for reasonable margins and operating temperatures. Short lengths of HTS and small coils show current sharing before normal transitions, whereas current sharing voltages are not identified in large coils since current sharing voltages are small compared to inductive and resistive voltages. Pulse shape, duration, and frequency are varied with no degradation in performance. [ABSTRACT FROM PUBLISHER]

The MgB2 coil wound with a parallel conductor composed of two MgB2 tapes with insulation has been developed. The tape is obtained by the rolling process from the round wire which is fabricated by in-situ method. The performances of tapes, such as critical current density and ac losses, are higher than that of round wires in case that the transverse magnetic fields are applied to the tape in direction of the parallel to the flat face of the tape. We proposed as a candidate of applying the tape to a conductor with large current capacity that the parallel conductor is composed of insulated tapes. We fabricated a tape with aspect ratio of two from a round wire with diameter of 0.8 mm as a strand for the conductor. The coil is composed of two coils that are jointed each other in series. At the joint, two strands are transposed to be identical the inductances of two strands. The inner and outer diameters of the coil are 65 mm and 107 mm, respectively. The length of the coil is 53 mm. The total turn number is 540 turn. The magnetic flux density at the center in the coil is 1.31 T when the transport current is 200 A. In this paper, the design and the test results of the MgB2 coil wound with the conductor are shown and the critical current properties and ac loss properties of the coil are discussed [ABSTRACT FROM AUTHOR]

Ceramic-silver composite conductors have been fabricated in lengths greater than 200 meters using both powder-in-tube and dip-coated methods. Progress has been made in conductor uniformity through control of process steps including powder packing, tape coating, deformation, and heat treatment. Critical current density (J/sub c/) in lengths up to 100 meters has been evaluated by measuring end to end current in coils, both pancake wound and solenoid wound. These coils were made using a wind-and-react technique. J/sub c/ values greater than 10/sup 5/ A/cm/sup 2/ have been attained over 17 m lengths of conductor in these coils in self field at 4.2 K. The magnetic field dependence of 4.2 K J/sub c/ in fields its high as 17 T will be reported for these coils. Microstructural factors affecting J/sub c/ are discussed. [ABSTRACT FROM PUBLISHER]

Long high critical current density Bi-2223/Ag tapes are required for the realization of cables and windings to be integrated in electric power devices. A cooperation agreement among CISE SpA, Europa Metalli and INFN, concerns the development of silver-sheathed multifilamentary Bi-2223/Ag tapes, over 100 meters long, produced by means of the Powder-In-Tube (PIT) technique. The Bi-2223/Ag tapes were thermomechanically processed and then wound into double pancakes by the React and Wind method. This article presents and discusses the electrical and magnetic characterization of the tapes, their degradation after winding as well as the performances of the pancakes tested after the final assembling. [ABSTRACT FROM PUBLISHER]

Wires of Pb/sub 1-x/Sn/sub x/Mo/sub 6/S/sub 8/ (PSMS) using the powder-in-tube process have been carefully drawn and the critical current density J/sub c/ has been measured on small coils wound with wires of 1.5 meter in length in magnetic fields up to 24 tesla. At 1.9 K, we achieved an overall critical current density J/sub co/, exceeding slightly 100 A/mm/sup 2/ at 20 tesla and 63 A/mm/sup 2/ at 24 tesla. Below 18 tesla, we always observed an abrupt occurrence of the resistive state, indicating that in this region J/sub c/ is limited by local defects, generally located at the ends of the coil. Nevertheless, at 15 tesla and 4.2 K, J/sub c/ reaches 550 A/mm/sup 2/. These very good results are the consequence of a better choice of the materials forming the wire and of a full control of the synthesis of the PSMS powder, The analysis of the field dependence of J/sub c/ shows that the grains are well connected, but that the critical field B/sub c2/ is still too low at 4.2 K (31 tesla instead of 50 tesla). An optimization of the annealing conditions is expected to considerably increase J/sub c/ at high magnetic fields. [ABSTRACT FROM PUBLISHER]

Bi-2212/Ag tapes have been produced using a continuous dip coating and partial melt processing technique. The role of the annealing and melt processing temperatures on the microstructure and current-carrying properties of the tapes are reported. In particular, the effect of a pre-anneal heat treatment on the residual carbon content from the organic binder has been investigated, in order to improve critical currents. These results have been used to optimise the temperature profile of a multiple-zone tube furnace through which continuous melt processing of the tape is possible. Multiple metre lengths of superconducting tape have been produced and wound into coils. Critical currents of 8.3 A in statically processed tapes and 1.9 A in continuously processed tapes have been achieved at 77 K, zero field. [ABSTRACT FROM PUBLISHER]

Superconducting solenoids developed for the Fermilab Mu2e require an extended R&D on superconductor cables performance, working in strong field in the critical currents range. To test these cables, the Mu2e Cable Test Solenoid was designed and fabricated at Fermilab. The solenoid contains three coils (two Main coils, and one Test coil), connected in series. The Main coils are wound with the well known SSC NbTi cable. They are permanently attached to the solenoid top and bottom carbon steel flanges. The Test coil is replaceable, and meant to be installed between two Main coils. This coil can be wound with any superconductor cable which needs to be tested (the first Test coil was wound with RIKEN heavy aluminum stabilized NbTi cable). The cables cross section ratio in the Main Coils and the Test coil ensures operating of Main coils in the current ranges well below the critical value for their cable, while the Test coil always works near its critical current range. The solenoid design and some cable splicing issues are presented. [ABSTRACT FROM AUTHOR]