Triode were invented, Philipp Lenard used the principle of grid control while conducting photoelectric experiments in 1902. The first vacuum tube used in radio was the thermionic diode or Fleming valve, invented by John Ambrose Fleming in 1904 as a detector for radio receivers. It was an evacuated glass bulb containing two electrodes, a heated filament and a plate (anode). Triodes came about in 1906 when American engineer Lee De Forest and Austrian physicist Robert von Lieben independently patented tubes that added a third electrode, a grid, between the filament and plate to control current. Von Lieben's partially-evacuated three-element tube, patented
Don Carpenter (electrical engineer) dynamics and for development and use of whistler-mode waves as diagnostic probes of the magnetosphere". He was elected a Fellow of the American Geophysical Union in 2002. Don Carpenter (electrical engineer) Donald L. Carpenter is a Space Scientist, Professor (Research) Emeritus in the Electrical Engineering Department at Stanford University. He co-discovered the sharp dropoff in the plasmasphere surrounding Earth. Known as co-discoverer of the “knee,” or sharp dropoff (later called the plasmapause) in the radial profile of the dense plasma cloud (later called the plasmasphere) that surrounds the Earth to typical equatorial distances of several Earth radii. Carpenter was awarded