A. Bonito Oliva

Development of the Superconducting Outserts for the Series-Connected-Hybrid Program at the National High Magnetic Field Laboratory

The National High Magnetic Field Laboratory (NHMFL) has embarked on an innovative program to develop a number of Series-Connected-Hybrid magnetic systems. In this novel concept, a set of resistive coils (insert) and a set of superconducting cable-in-conduit conductor (CICC) coils (outsert) are electrically driven in series, rather than independently as in previous hybrid systems. Presently NHMFL is working on 3 different projects. The first, funded by the National Science Foundation (NSF) with an

Test result of full size 40 kA NET/ITER conductor in the FENIX test facility

11.7 million grant, is related to the construction of a cylindrical-bore Series-Connected Hybrid (SCH), for high field nuclear magnetic resonance (NMR), condensed matter physics, biology and chemistry, to be located at the Magnet Labs Tallahassee location. The second, funded by the Hahn-Meitner Institute (HMI) in Berlin, relates to the engineering design for a horizontal bore Series-Connected Hybrid to be used in a neutron diffraction experimental system. Finally, the third, also funded by NSF, is a conceptual and engineering study for an SCH that would be used for neutron scattering experiments at Oak Ridge National Laboratorys Spallation Neutron Source (SNS), similar to the HMI version. Because of the main points in common between the 3 different systems, our final goal is to develop a superconducting magnetic system suitable for the 3 applications. We believe this is possible for the magnet although, due to the different field/bore orientations, some differences in the mechanical design of the cryostat and resistive inserts will exist. In this paper we will give an overview of the R&D strategy devised to develop these superconducting magnetic systems, together with a report on the present status of such program.

Manufacture and preliminary tests of a 12 T "wind and react" coil

Three Nb/sub 3/Sn cable-in-conduit prototype conductors have been manufactured in the framework of the European conductor development program for NET. They have been tested in the FENIX test facility at the Lawrence Livermore National Laboratory, beyond their operating conditions, with current up to 40 kA, magnetic field up to 13.5 T, and supercritical helium up to 8 K. The testing procedure is described and the test results are discussed. The main objective of the test was the measurement of temperature margin under DC operation and the hydraulic pressure drop.<<ETX>>

Zeus thin solenoid: test results analysis

As already reported ENEA is engaged in the realization of a 12 T wind and react Nb/sub 3/Sn coil, a subsize magnet designed to simulate many technological problems to be faced in NET-ITER magnets. EM-LMI and Ansaldo are the industrial partners in this project. A preliminary winding has been built and successfully tested. This winding has been cut in pieces and carefully inspected to be sure that the impregnation process after the heat treatment works well. No particular flaws have been detected. Then manufacturing of the 12 T magnet has been started and completed in about three months. Heat treatment, impregnation and electrical tests at 300 K have been successfully performed and the magnet is now ready for final tests. In order to obtain the most significant scientific and technological informations from this magnet, the original test programme (insertion of the coil in the SULTAN facility) has been modified according to a decision of the Fusion Technology Steering Committee (FTSC) of EURATOM. Details of the new test programme are given in the paper. >

Zeus Magnets Construction Status Report

The thin solenoid for the Zeus detector has been installed and tested in HERA (Hadron Electron Ring Accelerator) at DESY. The coil reached the design magnetic field (1.8 T in the center) without training. During the test some measurements were made in order to investigate the cooling system and the quench-back behavior. No spontaneous quenches occurred. Several induced fast discharges showed the evidence of a quench-back effect, and the quench-back starting time was less than 1 s. The cylinder temperature measurements during the coil discharge perfectly agree with adiabatic calculations. The indirect cooling efficiency was verified for the two-layer winding. The tests performed showed that the magnet can operate safely at the nominal field.

AC losses in superconducting Nb/sub 3/Sn and NbTi CIC conductors

The construction progress status of the superconducting magnets for the ZEUS detector, commissioned by INFN Frascati and to be installed in the HERA e- p+ring (DESY, Hamburg), is reported. The first one is a double layer, two densities, aluminum stabilized coil 1849 mm in inner dia., 2487 mm in length and 32.6 mm thick, with a central field of 1.8 T and high particle transparency. The second one is a compensating magnet, wound by a copper stabilized Nb-Ti cable. Its coil has a central field of 5 T, inner dia. 370 mm, a length of 1200 mm and is inserted into a cold iron yoke. The main problems encountered during the large coil construction and the geometrical accuracy obtained are reported. Four splices among the high purity aluminum stabilized cable length were made. An outer support cylinder, 18 mm thick, was shrink fitted around the coil and then the temporary inner mandrel was removed. The distribution of mechanical stresses was measured in the different configurations. A large aluminum alloy vacuum chamber with high radiation transparency was built. The compensating coil is ready to be installed inside its stainless steel cryostat. The cryostat critical features are the high design pressure (20 bar) and the heavy cold mass.

Development and tests of electrical joints and terminations for CICC Nb/sub 3/Sn 12 Tesla solenoid

AC losses measurements and calculation on large scale Cable-in-Conduit (CIC) conductors have been carried out at NHMFL In particular samples of the Nb/sub 3/Sn and NbTi conductors developed for the NHMFL 45-T Hybrid Magnet superconducting outsert have been tested. A calorimetric technique involving superfluid helium (He II) has been used. The samples have been tested with applied field variation rates varying in the range between 0.01 T/s to 30 T/s. From results it appears that for most of the samples, at high field variation rates, the coupling currents are so intense to locally saturate the superconducting strands. As no theories describing the saturation regime in CIC conductors exist, we tried to extend the theories developed for monolithic conductors to the more complicated CICC geometry. It emerges by defining an effective coupling time constant and an effective radius for the conductor that it is possible to fit the data with good accuracy. Effective coupling time constants between 3 ms and 200 ms, depending on the strands surface condition and the cable void fraction, have been measured for the Nb/sub 3/Sn conductors, while a time constant of 16 ms has been determined for the NbTi sample. The experimental results and the theoretical analysis are reported in the paper.

AC loss measurement of the SMES/CIC conductor

Ansaldo Componenti, under a contract with ENEA, has developed the interlayer electrical points and coil terminations for a 12-T solenoid, 0.6-m bore, Nb/sub 3/Sn, wound with the wind and react technique with a cable-in-conduit (CIC) conductor. Both the interlayer joints and terminations under the coils operating conditions, will be subjected to a magnetic field of about 8-10 T with a 6-kA current. Tests on shorter length interlayer joints and terminations, at different magnetic fields and currents, were carried out. The resistance of a 140-mm-long interlayer joint at magnetic field B=8 T and I=6 kA was 2.4*10-9 Omega . The measured resistance for a joint between two terminations, under the same conditions, was 1.5*10-8 Omega .<<ETX>>

Quench Behaviour of a Thin Solenoid Model

Abstract We have performed a calorimetric measurement of the AC loss in a Cable-in-Conduit (CIC) conductor for the superconductive magnetic energy storage (SMES) application. A new technique is used based on the temperature rise in the He II in contact with the conductor. The sample is located in a cryostat and placed in the bore of a superconducting dipole magnet. A change in the transverse field produces an easily measurable temperature increase. The approach is used to measure the loss in a length of conductor developed as part of the Bechtel SMES-ETM project. The time constant measured for this sample is found to be 8.5 s, which is in the range of values estimated from a simple coupling current model.

Zeus Magnet Tests

A thin superconducting solenoid of 0.76 m in internal diameter and 0.8 m in length has been manufactured and tested by Ansaldo under the ZEUS project contract with Istituto Nazionale di Fisica Nucleare (INFN). It is a model of the ZEUS detector magnet. The coil has two layers and it is wound with a Rutheford cable stabilized with high purity aluminium (bare dimensions 15 × 4.3 mm) manufactured by EUROPA METALLI, Florence. The coil has an external aluminium cylinder with helium circulating in an aluminium pipe welded around it. The quench propagation velocity and the minimum quench energy have been measured during the tests. The quench back behaviour has been analyzed. In this paper we present the measurements and the results obtained from the data analysis.