American physicist who independently discovered the powder method of X-ray analysis of crystals, which permits the study of crystalline materials in a finely divided microcrystalline, or powder, state. He also invented a number of electron tubes that have found wide application as components in electronic circuits.

After he received his Ph.D. from Yale University (1909) and had taught for a few years, Hull began work as a research physicist for General Electric Company (1914) and served (1928–50) as assistant director of its research laboratory in Schenectady.

Hull devised the powder method in 1917, unaware that this technique had been discovered the previous year by Peter Debye and Paul Scherrer; he was the first to determine the crystal structure of iron and most of the other common metals. After completing his crystallographic work, he returned to research in electronics with great success. His inventions included the thyratron, a gas-filled tube used to control high-power circuits, and the magnetron, an oscillator used to generate microwaves.