Design of pulsed high-field magnets for pion/muon collection

Based on the potential for improving collection of negative-muons for standoff active-detection of fissile materials, we explore the design of pulsed high-field (15-20T) magnets that might be powered by the PHELIX capacitor bank and used in experiments with the 800 MeV proton beam at Line C of LANSCE. Experiments with pulsed high magnetic fields could include the placement of the pion-production target in or near the center of a pulsed solenoidal magnet and, with two such coils separated by several gyro-diameters, at the center of a magnetic mirror trap. As an alternative approach, we also consider the use of a pulsed, azimuthal magnetic field created around the pion target by a plurality of conductors forming a largely open, coaxial inductor. In all these approaches, the constraints on our design are the gyro-radius of pions with the highest angular momentum, the strength and thermal capacity of the pulsed magnet, and the circuit parameters of the PHELIX capacitor bank. Principal concerns are the mechanical and thermal stresses associated with operation at upwards of 20T, corresponding to a magnetic pressure of 1600 atm and a temperature rise of a few hundred C per shot. Approximate hand-calculations and detailed ANSYS simulations are used to address these concerns.