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.
Design and test of a flat-top magnetic field system driven by capacitor banks.
An innovative method for generating a flat-top pulsed magnetic field by means of capacitor banks is developed at the Wuhan National High Magnetic Field Center (WHMFC). The system consists of two capacitor banks as they are normally used to generate a pulsed field. The two discharge circuits (the magnet circuit and the auxiliary circuit) are coupled by a pulse transformer such that the electromotive force (EMF) induced via the transformer in the magnet circuit containing the magnet coil is opposed to the EMF of the capacitor bank. At a certain point before the current pulse in the coil reaches its peak, the auxiliary circuit is triggered. With optimized parameters for charging voltage and trigger delay, the current in the magnet circuit can be approximately kept constant to obtain a flat-top. A prototype was developed at the WHMFC; the magnet circuit was energized by seven 1 MJ (3.2 mF/25 kV) capacitor modules and the auxiliary circuit by four 1 MJ modules. Fields up to 41 T with 6 ms flat-top have been obtained with a conventional user magnet used at the WHMFC.
Design installation and commissioning of the Los Alamos National Laboratory pulsed power generator
A 1430 MVA synchronous generator from a canceled nuclear power plant has been installed and commissioned at Los Alamos National Laboratory to provide pulsed power and energy for large physics experiments. The authors describe special studies, tests, and design modifications to enable a high-power, steady-state machine to operate as a pulsed, variable-speed generator. The generator rotor and stator core cooling have been changed from hydrogen to air to facilitate the operation. An all-solid-state drive system accelerates the generator rotor from standstill to the maximum operating speed of 2800 rpm and from 1260 rpm to 1800 rpm between load pulses. The excitation system has been modified to provide both the motor and generator mode of operation. The generator is mounted on a spring foundation to minimize the transmission of shaft vibrations into the subsoil. The springs also dampen shocks stemming from the pulsed loads. >