The linear induction pump (76 laminations, 0.125-inch duct thickness, 0.319-inch air gap) can produce a maximum no-flow pressure of 0.734 psi and can pump 0.450 gpm against a 0.2 psi head. With an air gap of 0.443 inch and a pump section having a 0.250-inch duct thickness, the maximum no-flow pressure decreases to 0.551 psi, but the improved hydraulic efficiency of the larger duct permits circulation of 0.9 gpm against a 0.2 psi head. The improvement in magnetic field strength from 78 gauss/amp at 0.443 inch air gap to 103 gauss/amp at 0.310 inch air gap indicates the need for minimizing the pump air gap while maintaining a duct thickness consistent with good hydraulic efficiency.
Thompson, David H. and Fisher, Ray W., "Performance characteristics of an electromagnetic pump" (1960). Ames Laboratory Technical Reports. 26.