Production of long pulse high magnetic fields using chemical double-layer capacitor banks

The application of CDLs (chemical double-layer capacitors) for the production of high magnetic fields is described. From a knowledge of the internal parameters of the individual CDL units, scaling laws are developed which allow the specification of a capacitor bank which can produce an arbitrary magnetic field. Bank designs are presented using both commercially available and laboratory prototype units capable of producing fields greater than 1 T for several seconds. A laboratory unit was built which operated at a voltage of 21 V, had an equivalent series resistance (ESR) of approximately 7 mΩ, and a capacitance of about 30 F. In practice, the limiting field is governed by material parameters such as magnet wire size, dynamic stresses, and system heating which limits the current on the time scale for discharge of the bank. To test the scaling relations, a capacitor bank was constructed from commercially available products. Bank designs based on commercial products are contrasted with those which could be realized with laboratory prototypes