James R. Sims

First 100 T non-destructive magnet

The first 100 T non-destructive (100 T ND) magnet and power supplies as currently designed are described. This magnet will be installed as part of the user facility research equipment at the National High Magnetic Field Laboratory (NHMFL) Pulsed Field Facility at Los Alamos National Laboratory. The 100 T ND magnet will provide a 100 T pulsed field of 5 ms duration (above 90% of full field) in a 15 mm diameter bore once per hour. Magnet operation will be nondestructive. The magnet will consist of a controlled power outer coil set which produces a 47 T platform field in a 225 mm diameter bore. Located within the outer coil set will be a 220 mm outer diameter capacitor powered insert coil. Using inertial energy storage a synchronous motor/generator will provide AC power to a set of seven AC-DC converters rated at 64 MW/80 MVA each. These converters will energize three independent coil circuits to create 170 MJ of field energy in the outer coil set at the platform field of 47 T. The insert will then be energized to produce the balance of the 100 T peak field using a 2.3 MJ, 18 kV (charged to 15 kV), 14.4 mF capacitor bank controlled with solid-state switches. The magnet will be the first of its kind and the first non-destructive, reusable 100 T pulsed magnet. The operation of the magnet will be described along with special features of its design and construction.

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.

Operating experience of the United States National High Magnetic Field Laboratory 60 T Long Pulse Magnet

The 60 T Long-Pulse (60 T LP) magnet system has provided controlled power magnetic field pulses to experimentalists since August 3, 1998. This magnet system is installed as part of the user facility research equipment at the National High Magnetic Laboratory (NHMFL) Pulsed Field Facility at Los Alamos National Laboratory. The 60 T LP magnet is the first of its kind in the United States and produces the highest field in its class, routinely providing a 60 T pulsed field of 100 ms flat-top duration in a 32 mm diameter bore. In addition, numerous other controlled pulse shapes at 60 T and lower fields have been provided. Since the start of commissioning on September 17, 1997 the magnet has been pulsed in excess of 800 times at various field levels. More than 600 magnet pulses have been provided to experiments and almost 400 of these were at 60 T. Operating statistics including coil system and inductance and resistance histories are presented. Operating and maintenance experience and issues are discussed as well as realizable improvements and upgrades to the magnet.

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.

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.

The U.S. NHMFL 60 T long pulse magnet

The 60 T long pulse magnet operated by the U.S. National High Magnetic Field Laboratory at Los Alamos National Laboratory, Los Alamos, New Mexico failed catastrophically on July 28, 2000. The failure was investigated and the cause was determined to be unusually low toughness in the nitrogen strengthened manganese stainless steel (Nitronic-40/spl trade/) reinforcing material. The source of the reduced toughness condition was a sigma phase conversion in the microstructure. The magnet failure, failure investigation and results of the investigation are described. Plans for the construction of the successor magnet, the 60 tesla long pulse Mark II, are described.

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.

The NHMFL long-pulse magnet system − 60–100 T

The National High Magnetic Field Laboratory (NHMFL) is now completing a long-pulse magnet that will sustain a constant field of 60 T for 100 ms in a 34 mm cold bore plus a wide range of other pulse shapes. The magnet consists of nine mechanically independent, nested coils, which are reinforced with outer steel shells. Three SCR rectifier and control units power sub-groups of coils. A field of 100 T could be reached non-destructively for millisecond periods by combining outer coils of this type with a capacitor-driven insert magnet.

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.

Fatigue Property Examinations of Conductors for Pulsed Magnets

Cu matrix composites are used as conductors for pulsed magnets that have potential to reach 100 T. The conductors are fabricated by cold drawing that introduces high densities of dislocations or interfaces and internal stress. The density of the dislocation and the interface affects the mechanical properties of the conductors, such as the tensile strength and fatigue endurance at 77 K of the composites. Understanding the performance of the conductors under cyclic loading, i.e. fatigue properties, helps one to make good use of them for pulsed magnets and to manufacture conductors to meet the requirements of the magnets, particularly when the magnetic stress reaches the limit of the mechanical strength of the conductors. The goal of this research is to understand the fatigue properties of a Cu-0.085wt%Ag conductor and to relate such properties to mechanical tensile strength, dislocation densities and interface structures. The fatigue test loading is either in stress-controlled or strain-controlled mode. This work sheds a new light on the correlation between the tensile and fatigue properties at 77 K by consideration of dislocation densities and precipitate in particle strengthened conductors.