The long dead time and cathode erosion of the Rosenblum corona‐spark counter for heavily ionizing radiations have been overcome by forming only the streamer stage of the spark by the addition of a few percent of some diatomic gas to nitrogen‐contaminated argon in corona detectors of coaxial wire‐cylinder geometry. The amplitude of the streamer pulse at the anode wire is large (>10 v) and distinctly greater than background, with a risetime of about 1 &mgr;sec. The recovery of the anode potential is made rapid (typically 5 &mgr;sec) by a simple RC anode circuit. Efficiencies for streamer formation of 7.5% for U234&agr; particles, 1.5% for (n, B10) &agr;'s and 5% for (n, U235) fission fragments have been obtained in coated counters.