One-Millionth-Second Radiography and Its Applications

The making of ultraspeed radiographs using exposure times of the order of one-millionth of a second requires the passage of electron currents approaching 1000 amperes. Such currents are supplied by an electron source utilizing field emission from a cold-cathode electrode which degenerates into a metallic arc in a high vacuum. The recording of such high-speed transients is briefly reviewed. The development of this equipment has been greatly accelerated because of the war. Illustrations showing its applications to various radiographic problems requiring short exposure times which have recently been released by the War Department are included; among these are radiographs taken at Frankford Arsenal and Aberdeen Proving Grounds of exploding shells and bombs, and at Princeton University showing the wounding mechanism of high-velocity fragments.