Charles A. Swenson

Assembly, Commissioning and Operation of the NHMFL 100 Tesla Multi-Pulse Magnet System

The U.S. National High Magnetic Field Laboratory 100 Tesla multi-pulse magnet system is now successfully commissioned. This magnet system is the result of a long-term partnership project jointly funded by the U. S. Department of Energy - Office of Basic Energy Science and the National Science Foundation. Science experimentation inside the magnet started in December 2006 at the NHMFL Pulsed Field Science Facility located at Los Alamos National Laboratory. Repeated, non-destructive operation of the system with original components is continuing in the 85 T to 90T range. The system will eventually combine a nominal 40 T platform field produced by a controlled-waveform generator-powered long-pulse magnet with a nominal 60 T field generated by a capacitor-bank powered pulsed insert magnet to produce the rated field. Milestone non-destructive operation to 88.9 T was achieved in October 2006. This paper will present an overview of the generator driven outsert magnet system together with the high-field pulsed insert magnets design and construction. We will review commissioning and performance data through summer of 2007. Criteria for increasing the systems maximum field performance will also be reviewed addressing the goal to increase operating field level (in support of experiments) to 95 T and then to 100 T.

Mechanical Properties of Zylon/Epoxy Composite at 295K and 77 K

Zylon fiber/epoxy composites are used at the National High Magnetic Field Laboratory for structural reinforcement of high field pulse magnet coils. Zylon fiber have been chosen to replace glass or carbon fibers primarily because of the fibers extremely high strength and elastic modulus. Although the fiber properties are well documented, there is limited data available with respect to its properties in fiber/epoxy composite form, especially at low temperatures. Here the mechanical properties pertinent to pulse magnet design are characterized and analyzed with respect to manufacturing variables. Specifically the elastic modulus, tensile strength, and fatigue life of the quasiunidirectional composite specimens, are measured at both 295 K and 77 K

Mechanical properties of MP35N as a reinforcement material for pulsed magnets

A cobalt multiphase alloy, MP35N, is studied as one of the reinforcement materials for pulsed magnets. The mechanical properties of this alloy at room temperature and 77 K are examined. The cold-rolled and aged MP35N produces a hardness of 5650 MPa and yield strength of 2125 MPa at room temperature. At 77 K, the yield strength reached 2500 MPa and the work hardening rate was higher than that at room temperature. The Youngs modulus increases about 6% upon cooling from 300 to 5 K. Therefore, the increase of the strength at low temperatures is attributed mainly to the increase of the work hardening rate rather than modulus. The potential for further increasing the strength of this alloy is discussed.

Mechanical properties of epoxy impregnated superconducting solenoids

The mechanical properties of epoxy impregnated coils are critical to proper stress analysis of high field superconducting magnets. In order to identify the engineering properties of coil composites, mechanical test specimens of epoxy impregnated coil windings are prepared. The samples consist of multiple layers of superconductor separated with interlayer insulation and are epoxy impregnated. Mechanical tests are performed at liquid nitrogen and liquid helium temperature. Orthotropic elastic properties are measured for the composite and used for mechanical analyses. Properties in a direction longitudinal to the conductor (hoop direction) are measured in tension. The compression modulus is measured for properties transverse to the conductor, representing radial and axial directions.

25 T high resolution NMR magnet program and technology

The program at the National High Magnetic Field Laboratory for the design and development of 1 GHz class NMR magnets is described. The parameters are given for a 1.066 GHz magnet incorporating an HTS inner coil. The design of the related wide bore 900 MHz conventional superconductor magnet is described. Aspects of the technology development program supporting these designs are presented.

Quench protection heater design for superconducting solenoids

The National High Magnetic Field Laboratory is responsible for the design and construction of a large bore 900 MHz NMR magnet. The magnets protection system consists of an active quench detector circuit controlling a persistent switch electrically in series with the magnet. The quench heater network is electrically in parallel with this persistent switch and powered when the switch is resistive. Heater network design entails a definition of the design constraints required to operate the 900 MHz magnet, a review of the material properties, and the developmental data to validate the design. Quench heater development will entail power testing and quench initiation studies. Heater power testing will establish the reliability of the epoxy heater interface. Quench initiation studies will measure the characteristic times required to induce quench in coils at design fields. This paper presents developmental progress on the power testing results, and a discussion of the power testing results on the heater network design for 900 MHz.

The U.S. NHMFL 100 Tesla multi-shot magnet

The design, analysis and fabrication progress of the 100 T Multi-Shot Magnet is described. The description includes the structural analysis of the outer coil set, the fabrication of the 100 T prototype coil 1, the fabrication of a coil 1 test shell, and the analysis of the electrical busbar assembly. Fabrication issues and their solutions are presented. This magnet will be installed as part of the user facility research equipment at the U.S. National High Magnetic Field Laboratory (NHMFL) Pulsed Field Facility at Los Alamos National Laboratory.

Measurement of thermal contraction properties for NbTi and Nb/sub 3/Sn composites

Accurate knowledge of winding composite thermal contraction properties is critical to the design of large epoxy impregnated Nb/sub 3/Sn and NbTi coils. Measurement of thermal contraction properties allows the reliable design prediction of cold coil dimensions, the state of the coil form interface, resulting mechanical stresses from cool-down, and the correct locations of coils in an assembly. NbTi and Nb/sub 3/Sn epoxy glass winding composites have been built to precisely model the material, packing factors, and processing steps consistent with coil fabrication. Thermal contraction properties are measured using a strain gage measurement technique where gage signals are compared to known reference samples. Composites are inherently anisotropic. Gages are placed on each sample to measure the thermal contraction along each principal axis of the composite. This paper reports these measurement results.

Low-Noise Pulsed Pre-Polarization Magnet Systems for Ultra-Low Field NMR

A liquid cooled, pulsed electromagnet of solenoid configuration suitable for duty in an ultra-low field nuclear magnetic resonance system has been designed, fabricated and successfully operated. The magnet design minimizes Johnson noise, minimizes the hydrogen signal and incorporates minimal metal and no ferromagnetic materials. In addition, an acoustically quiet cooling system permitting 50% duty cycle operation was achieved by designing for single-phase, laminar flow, forced convection cooling. Winding, conductor splicing and epoxy impregnation techniques were successfully developed to produce a coil winding body with integral cooling passageways and adequate structural integrity. Issues of material compatibility, housing, coolant flow system and heat rejection system design will be discussed. Additionally, this pulsed electromagnet design has been extended to produce a boiling liquid cooled version in a paired solenoid configuration suitable for duty in an ultra-low field nuclear magnetic resonance system. This pair of liquid nitrogen cooled coils is currently being tested and commissioned. Issues of material compatibility, thermal insulation, thermal contraction, housing and coolant flow design are discussed.

80 T Magnet Operational Performance and Design Implications

The US National High Magnetic Field Laboratory constructed and tested a stand-alone 80 T prototype magnet. The activity was in support of the insert magnet development project for the US-DOE-NSF 100 Tesla Multi-Pulse Magnet Program. The 80 T magnet assembly was developed to simulate the physical conditions an insert magnet would encounter during peak field operations at 105 T... The design incorporated further improvements to the engineering template developed from the 65 T and 75 T pulsed magnets now in use at the NHMFL Pulsed Field Facility at Los Alamos National Laboratory. Two coaxially nested solenoid coils comprised the 80 T prototype magnet design. The windings are in series electrically. The inner coil is constructed with materials & techniques identical to those in use for the 100 T insert program. The outer coil is a conventional winding. The prototype was successfully trained to a peak field of ~80.4 T. 80 T pulsed operations were repeated until the coil assembly faulted after 10 full-field pulses. Post-fault inspection of the magnet assembly indicated that the outer magnet winding failed structurally. This paper will present an overview of the 80 T prototypes design, construction, and performance. A review of the magnets failure mode will be presented. Additionally, we will discuss new design criteria for stand alone high-field pulsed magnet based upon the 80 T prototype experience.