Top Magnetic Field Attained Using almost 10 per cent of the entire City of Cambridge's electric generating capacity, scientists and engineers at the National Magnet Laboratory there have attained the world's highest sustained magnetic field. Like Atom Smasher Their feat, Laboratory officials said in a press briefing Thursday, is a major development "in sense, a breakthrough," in terms of physical research. It should open whole new vistas to scientists studying the basic nature of matter, magnetism and fundamental phenomena. The Laboratory director, Dr. Benjamin Lax, compared the D. Bruce Montgomery stands beside magnet he and staff designed and built at National Magnet Laboratory, Cambridge.