This exhibit attempts to show, in a simple way, what happens inside the dermatologist's x-ray machine when a treatment is given.
Thomas A. Edison, while experimenting with the filament lamp, discovered that when a piece of wire was placed in a vacuum and heated by electricity, electrons were evaporated, forming a cloud around its surface. This phenomenon, called "thermionic emission" was utilized years later by Dr. William David Coolidge, who designed the modern x-ray tube. Into a highly evacuated glass tube containing less than one-billionth of an atmosphere of pressure, he introduced a wire filament which was heated by a low-voltage circuit to supply electrons. He then introduced a separate, high-voltage circuit into the tube, with a tungsten anode (target). When the high voltage was applied to the filament, the liberated electrons were propelled at high speed to the positive anode, where their sudden deceleration produced x-rays. The flow of
PAUL M. CROSSLAND. Inside X-Ray. AMA Arch Derm. 1960;82(1):80–89. doi:10.1001/archderm.1960.01580010086013