ABSTRACT
C. C. Lauritsen obtained his PhD in 1929, with a thesis on the study of electron emission from metals in intense electric fields. In his work on field-emission electrons, Lauritsen had need for an X-ray tube capable of producing highly penetrating rays. The maximum charge that can be deposited on a hollow conducting sphere is that which gives rise to an electric field equal to the electrical breakdown strength, or dielectric strength, of the surrounding medium—usually air. By 1928 the research at Round Hill had been reorganized, focusing on aerial navigation in fog and fog dissipation, and Edward Bowles of MIT’s Electrical Engineering Department, in overall charge of the project, arranged to borrow a dirigi-ble from the Goodyear Zeppelin Corporation for research purposes. The Round Hill installation was completed in 1936, and was described by Van de Graaff and his colleagues Lester and Chester van Atta and D. L. Northrup at MIT in the Physical Review that spring.
