Y.M. Eyssa

An overview of the 45-T hybrid magnet system for the new National High Magnetic Field Laboratory

The new National High Magnetic Field Laboratory (NHMFL) at Tallahassee, Florida is committed to putting into operation in 1995 a 45-T Hybrid Magnet System to support research in steady, high magnetic fields. This facility will be accessible by qualified users world-wide on the basis of proposal and review. The more prominent components of this system will be a 24-MW resistive insert and a 120-MJ superconducting outsert. But successful achievement of the performance goals for the 45-T Hybrid System will depend on a number of unique, state-of-the-art subsystems and components. This paper describes the requirements and specifications on the individual subsystems and components in the context of the overall performance gears and reviews the plan for putting the whole together. >

A new concept in Bitter disk design

A new concept in cooling hole design in Bitter disks that allows for much higher power densities and results in considerably lower hoop stresses has been developed and successfully tested at the National High Magnetic Field Laboratory (NHMFL) in Tallahassee, FL. The new cooling hole shape allows for extreme power densities (up to 12 W/mm/sup 3/) at a moderate heat flux of only 5 W/mm/sup 2/. The new concept also reduces the hoop stress by about 30-50% by making a Bitter disk compliant in the radial direction through staggering small width and closely spaced elongated cooling holes. Finally, the design is optimized for equal temperature.

Design of a poly-Bitter magnet at the NHMFL

The worlds first 33 Tesla resistive magnet is being designed and built at the National High Magnetic Field Laboratory in Tallahassee, FL. Completion of the magnet is expected in the fourth quarter of 1995. It will produce a peak on-axis field greater than 33 Teslas in a 32 mm warm bore while consuming 20 megawatts of power. This magnet consists of two small concentric parallel coils (poly-Bitter) in series with two larger Bitter coils. Details of optimization calculations and the resulting magnet design and construction are presented.

The world's first 27 T and 30 T resistive magnets

We describe in detail a 30 Tesla, 32 mm warm bore, 15 MW resistive magnet which was put into operation at the National High Magnetic Field Laboratory in Tallahassee, FL in March 1995. The magnet consists of three concentric axially-cooled Bitter stacks connected electrically in series. This magnet employs a substantial new development in Bitter magnet technology which allows high current densities without the usually accompanying high stresses. Details of magnet optimization, design, construction, testing and operation are presented. We also report on operating experience with the 27 T magnets.

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.

Design and construction of 12-MW magnets at the NHMFL

The worlds first 12 megawatt resistive magnet will be available to users at NHMFL-FSU during the first quarter of 1994. The magnet will generate an on-axis field of 27 T in a 32 mm warm bore. The magnet consists of three concentric Bitter stacks with axial cooling. Optimal geometries, materials, and power distribution were determined by a constrained optimization program written by S. Prestemon. >

Design and analysis of a 25 T resistive NMR magnet

A 25 Tesla resistive magnet with homogeneity of 1 ppm over 10 nun diameter spherical volume is being designed at the National High Magnetic Field Laboratory in Tallahassee, FL. The magnet consists of three concentric axially cooled Bitter stacks connected electrically in series. It will produce a peak field of 24.1 T in a 50 mm warm bore while consuming 15 megawatts of power and 25 T at 16.3 MW. Each of the stacks is designed to have a high uniformity by itself so the tolerance in axial positioning is not critical. Details of the magnet design, sensitivity to manufacturing tolerances and current distribution between cooling rings is presented.

Design of a 20 T, 200 mm bore resistive magnet

A 20 tesla, three coil, 200 mm bare, 20 MW resistive magnet is being designed at the National High Magnetic Field Laboratory in Tallahassee, FL., USA, in cooperation with the High Magnetic Field Laboratory of Grenoble, France. The outer two coils are axially-cooled and are connected electrically in series producing a central field of 11.27 T in a 365 mm warm bore while consuming 13.5 MW of power. The 6.5 MW inner coil (insert) is a poly-Bitter design with two sub-cells connected electrically in parallel and they together are connected in series to the two outer coils. The field of the inner coil is 8.78 T resulting in a 20 T total field in a 200 mm warm bore. All four coils are made of hard copper.

Material and cooling requirements for poly-Bitter resistive magnets and hybrid inserts generating continuous fields up to 50 T

The new National High Magnetic Field Laboratory (NHMFL), equipped with a 40 MW DC power supply, will design and construct the next generation of high field resistive magnets and hybrid inserts generating DC fields up to 50 T. We present a study on the required materials and the necessary cooling characteristics, these magnets need. The configuration selected for this study consists of a combination of thin poly-Bitter and thick Bitter coils optimized in dimensions and power under constraint of maximum design stress and heat removal to obtain maximum field. The study shows that each design requires a different optimum ratio of conductor strength to electrical conductivity and that efficient cooling is only advantageous if strong copper alloys are used. For efficient use of the available power the development of new high strength, high conductivity materials will be necessary. Equally important are improvements in the heat transfer characteristics of these high power density magnets. >