A one‐turn coil of 20 cm diameter and 30 cm length produces a field up to 1.7 kG with a rise time of 30 ns. The rate of rise of field, nearly 6 T/&mgr;s, is faster than for any other coil of this size. Powering the coil is a transformer‐charged pulse‐forming line machine operating at up to 28 kA, 280 kV without deleterious arcing. The field is uniform to 5% over the coil length, focusing an electron beam passing along its axis.