Search

High field pulsed magnets at the NHMFL use high strength conductor wires up to 90% of their ultimate tensile strength. Therefore it is very important to ensure that the wires are free of flaws. It is known that in the conductors cold drawing process, internal chevron crack could occur due to unsuitable drawing die schedule or inadequate lubrication. These internal cracks occurs infrequently along the wire, so tensile tests of short samples cut from the ends of a long length conductor often miss the problem. In addition, small inclusions on the wire surface can compromise wires fatigue properties. In this paper, we present results of our non-destructive testing (NDT) inspection of Glidcop AL60 wires using eddy current testing (ECT), ultrasonic testing (UT) and x-ray radiography (2D and 3D). Chevron cracks were found in some AL60 conductors by all three NDT techniques. Surface inclusions were found by ECT. We have developed a long length ECT wire inspection capability., 4 pages, 9 figures

The High Magnetic Field Laboratory in Nijmegen has been collaborating with the National High Magnetic Field Laboratory (NHMFL) in Florida on a 45 T hybrid magnet project. The primary scope of the collaboration was the design and manufacture of the hybrid magnet's superconducting cold mass. The 7.5 ton cold mass includes a single 13 T solenoid wound with high JC RRP Nb 3 Sn/Cu cable-in-conduit conductor. The coil will be forced flow supercritical helium and operated in parallel with a set of Bitter-disk resistive coils. Coil winding, reaction heat treatment, epoxy impregnation, and cold mass assembly has been completed at the NHMFL. The full cold mass has been delivered to Radboud University and will be assembled with the cryostat and interfaced with the system utilities.

The final assembly of the Series-Connected Hybrid magnet system for the Helmholtz-Zentrum Berlin for Materials and Energy (HZB) has occurred with the integration of the superconducting cold mass, cryostat, resistive Florida-Bitter coils, and the cryogenic, chilled water, power, and control subsystems. The hybrid magnet consists of a 13-T superconducting $\hbox{Nb}_{3}\hbox{Sn/CICC}$ coil and a set of 12-T resistive, water cooled coils at 4.4 MW. Much of the cryostat and cold mass functional requirements were dictated by the electromagnetic interactions between the superconducting and resistive coils. This includes the radial decentering and axial aligning forces from normal operations and a 1.1 MN fault load. The system assembly was an international achievement with the cold mass being completed at the NHMFL in the USA, cryostat to cold mass interfaces made at Criotec Impianti in Italy, and final assembly at the HZB in Germany.

Recent activities that were conducted on the Helmholtz Zentrum Berlin Series-Connected Hybrid outsert coil included the reaction heat treatment and vacuum-pressure impregnation. A thermocouple was wound into the windings for diagnostic purposes during processing of the coil. To maintain a reasonable temperature differential across the coil, the ramp rate was limited to approximately 2.7°C/hr. Epoxy impregnation was conducted with an epoxy developed in-house. The epoxy is transferred in vacuum but cured with one atmosphere gage pressure applied. Subsequently, the winding hardware was removed including the stainless steel mandrel through a machining operation. After assembly of voltage breaks and voltage taps, Paschen tests to 4 kV were conducted successfully that qualified the ground insulation. In addition, surge tests to qualified the internal insulation with 3 kV applied across the leads were conducted. Impedance measurements were conducted to confirm the internal insulation integrity.

Objectives Media effects research has generally ignored the possibility that popular films can affect political attitudes. This omission is puzzling for two reasons. First, research on public opinion finds the potential for persuasion is highest when respondents are unaware that political messages are being communicated. Second, multiple studies have found that entertainment media can alter public opinion. Together, this suggests that popular films containing political messages should possess the potential to influence attitudes. Methods We develop a laboratory experiment where subjects were randomly assigned to watch a control movie with no political messages, a movie with subtle political messages, or a movie with strong and explicit political messages. Results We find that popular movies possess the ability to change political attitudes, especially on issues that are unframed by the media. Furthermore, we show such influence persists over time and is not moderated by partisanship, ideology, or political knowledge. Conclusions Our key findings suggest that a renewed scholarly interest in the political influence of popular movies is clearly warranted.

The public opinion literature shows that cues about the policy positions of social groups influence citizens’ political attitudes. We assess whether cues about religious groups’ positions affect attitudes on three issues: protection of homosexuals in the workplace, improving the socio-economic conditions of African-Americans, and government-provided health insurance. We argue that such cues should shape issue attitudes and condition the impact of religious and political orientations on those attitudes. That should be especially true on issues closely connected to religion and for citizens with low levels of political awareness. We assess this argument with a survey experiment pitting pairs of religious groups on opposite sides of issues. We find that religious group cues matter primarily for cultural attitudes, among less politically-aware individuals, and for the religiously unaffiliated, Democrats, and liberals. The dominant effect is negative, moving these groups away from the positions of religious leaders and especially evangelical leaders.

The NHMFL Series Connected Hybrid (SCH) magnet will provide an energy-efficient 36 T to the DC user facility by employing a 20 kA superconducting outsert coil in series with a resistive insert. The magnet outsert consists of three concentric layer-wound sub-coils using three different grades of Nb3Sn Cable-in-Conduit Conductors (CICC). The electrical joints in the superconducting outsert require low DC resistance to minimize the refrigeration requirement at the operational 4.5 K temperatures and low AC losses to ensure good stability against ramping operation required by the users. There are four internal splice joints in the outsert, which are Nb3Sn to Nb3Sn joints with the same design configuration. There are another two terminal joints between the Nb3Sn outsert and the two NbTi buslines, which connect the outsert terminals to the two current leads. The two Nb3Sn to NbTi terminal joints are of identical configurations. All of the joints will be praying-hands configuration with an operation current of 20 kA. The R&D for the joins has been carried out at the NHMFL. The joints design and test results are discussed in this article.

The National High Magnetic Field Laboratory (NHMFL) has designed and is constructing a Series-Connected Hybrid (SCH) magnet system in Tallahassee, FL. Before the construction of the magnet system can begin many obstacles have to be solved through hardware design and winding practices. The hardware has to have the strength to handle the stresses of winding as well as retaining maximum functionality. The NHMFL will overcome these issues by running several analysis calculations and by producing three model coils for practicing functionality. Two model coils have been built and necessary changes to design and winding procedures have occurred through the practices. These changes will be presented and have been implemented into our winding procedures.

The National High Magnetic Field Laboratory (NHMFL) in Tallahassee, Florida has designed and is now constructing two Series Connected Hybrid (SCH) magnets, each connecting a superconducting outsert coil and a resistive Florida Bitter insert coil electrically in series. The SCH to be installed at the NHMFL will produce 36 T and provide 1 ppm maximum field inhomogeneity over a 1 cm diameter spherical volume. The SCH to be installed at the Helmholtz Center Berlin (HZB) in combination with a neutron source will produce 25 T to 30 T depending on the resistive insert. The two magnets have a common design for their cable-in-conduit conductor (CICC) and superconducting outsert coils. The CICC outsert coil winding packs have an inner diameter of 0.6 m and contribute 13.1 T to the central field using three grades of CICC conductors. Each conductor grade carries 20 kA and employs the same type of Nb3Sn superconducting wire, but each grade contains different quantities of superconducting wires, different cabling patterns and different aspect ratios. The cryostats and resistive insert coils for the two magnets are different. This paper discusses the progress in CIC conductor and coil fabrication over the last year including specification, qualification and production activities for wire, cable, conductor and coil processing.

Here, we report the development of the CICC joint design for the 36-T Series-Connected Hybrid Magnet. A novel solder-less single-box praying-hands joint has been designed to meet the mission of the SCH. A prototype sample joint, Florida Solder-less Joint A (FSJ-A), was manufactured and tested. The low DC resistance confirmed the feasibility of the concept design. In addition, a simple model describing the current transient behavior of the pray-hand joint is presented. A comparison with the experimental data is also included.

The development of the semi-retractable current leads for a 21 T Fourier transform ion cyclotron resonance (FT-ICR) superconducting magnet system is presented. The semi-retractable current leads are composed of a normal metal element, conducting the current from room temperature to intermediate temperature, and an HTS element, conducting the current down to liquid helium temperature. An HTS element is partly immersed in liquid helium and the joint between the normal metal and HTS element is continuously refrigerated by a cryocooler. After magnet energization the metal element is disengaged from the HTS element without breaking vacuum to the insulating vacuum space. In the paper, the optimized dimensions of the leads are presented in order to minimize the thermal heat load when carrying operational current with some margin. The intermediate block with a lockable set point and the insulating vacuum system are fabricated and the adaptability and reliability are tested during engage and disengage performance. The effects of vacuum level and performance cycle on the electrical contact resistance in a lockable set are also investigated.

The series-connected hybrid magnets for the National High Magnetic Field Laboratory and the Helmholtz Zentrum Berlin (HZB) that are under construction utilize three grades of cable-in-conduit conductor (CICC). Each coil contains over 5000 kg of Nb3Sn/Cu CICC in five piece-lengths. Fabrication of the coils has commenced with the winding of the outsert coil for HZB first. Work on both coils will proceed in parallel as the winding for the HZB coil is completed and is prepared for reaction heat treatment. Aspects of the coil fabrication process and quality controls will be discussed with attention given to the coil winding and joint assembly.

The inter-strand contact resistance (RC) of Nb3Sn cable-in-conduit conductors (CICCs) is a very important parameter which strongly correlates with ac losses and current redistribution behavior of the CICCs. One way to obtain the desired RC is to apply a layer of hydrocarbon oil on the Nb3Sn strands before the CICC Nb3Sn reaction heat treatment. In this paper, we measured RC for a Nb3Sn CICC sample fabricated with hydrocarbon oil. The measurements were performed using an apparatus designed to apply transverse load and load cycling on CICCs at 4.2 K. Resistances RC between strands of different cabling stages were measured with transverse load up to 188 kN m−1 and load cycles up to 10 000. The results show that RC of the sample increases almost linearly with the first loading. With load cycling, RC increases rapidly at first, but becomes saturated after ~100 cycles. After 10 000 load cycles, RC decreases with increasing load at a decreasing rate. These behaviors are comparable to observations for CICC with Cr plated strands reported in the literature. Therefore from the RC point of view, Nb3Sn CICCs with hydrocarbon oil on strands may be used as a low cost alternative to CICCs with Cr plated strands.