Dr. Liang Li [from PHMFF, Wuhan, China]
Title: The Construction, Operation and Application of Wuhan Pulsed High Magnetic Field Facility
Time: 9:00 - 10:00am, April 19, Sunday
Place: Auditorium room 410, Building 6, HPSTAR (Shanghai)
Host: Bin Chen
Abstract:
The Pulsed High Magnetic Field Facility (PHMFF) at Wuhan National High Magnetic Field Center (WHMFC) has passed the final evaluation by the Chinese government and is open to the external users since 2014. The measurement stations of transport, magnetization, magneto-optics, ESR and NMR have carried out experiments on HTS superconductors, topological insulators, Wyle semi-metals, semiconductors and so on. Magnets of short pulse (less than 100 ms), long pulse and the combination of both have been developed with bore sizes from 12 to 34 mm, and are operational for experiments at temperatures in the range from 100 mK to 350 K. Fast cooling channels are inserted in the magnets. For a typical 60 T capacitor bank driven pulsed magnetic field with pulse duration of 40 ms, the cooling time between subsequent pulses is 35 min. This time for a 50 T magnet with 300 ms pulse duration is 65 min. The power supplies for these magnets consist of a capacitor bank with 12 modules of 1 MJ/25 kV each and 2 modules of 0.8 MJ/25 kV each, a 100 MVA/100 MJ flywheel pulse generator and a 771 V/180 kAh battery bank. A dual-coil magnet driven by the capacitor banks has successfully generated 90.6 T field with total pulse duration over 350 ms in a 12-mm bore. A dual-coil long pulse magnet wound from soft copper wire energized by the flywheel generator produces 50 T peak field with a 100 ms flat-top and a total 1.1 s pulse duration in a 22 mm bore. A battery bank driven long pulse magnet composed by the series connection of two nested coils generates 32 T peak field with the pulse duration of 1.5 s in a 21-mm bore. By introducing in the main circuit a passive IGBT bypass circuit that can regulate current up to tens of thousands amperes, with the same magnet we can generate a 25 T/200 ms flat-top pulsed magnetic field with a ripple of 250 ppm. An innovative method for generating a flat-top pulsed magnetic field by means of capacitor banks is developed. Fields up to 52 T with 7 ms flat-top with no ripples have been obtained with a conventional user magnet. A three stage 100 T magnet is under development with the inner two coils energized by two different capacitor banks and the outer coil by the rectifier of the pulse generator connected in series with the battery bank.
Biography of the Speaker:
Liang Li received the B.Sc. degree in Electrical Engineering from the University of Science and Technology (HUST), Wuhan, China, in 1985 and the M.Eng. degree in Fusion engineering from the Plasma Physics Institute, Chinese Academy of Science, in 1988. He received the Ph.D. degree from Kathlieke University Leuven, Belgium in 1997.
From 1997 to 2000, he was an associate researcher with the National High Magnetic Field Laboratory (NHMFL) at Tallahassee, Florida, where he engaged in high field pulsed magnet development and made a few record high pulsed magnetic fields. From October 2000 to April 2007, he was a senior electrical engineer with the Electromagnetic and Superconductivity laboratory of GE Global Research Center (GRC). His research areas were pulsed magnets, Permanent magnetic (PM) and superconducting MRI, high temperature superconducting generator and wind generator. In April 2007, he joined HUST as the director of the pulsed high magnetic field laboratory and the general manager of the national “Big Science Project” of Pulsed High Magnetic Field Facility. He is a Yangtze river Scholar, the winner of the distinguished young scientist of CNF.