In a Van de Graaff generator, invented in 1929 by Robert J. Van de Graaff, an endless rubber or fabric belt carries electric charges from a roller at the base of the device and deposits them inside a hollow metal electrode at the top. This causes a high voltage to develop between electrodes at the top and bottom of the apparatus. In the Westinghouse machine, two high-speed belts traveled up a 47-foot shaft to a mushroom-shaped electrode near the top of the bulb-shaped enclosure, where electric charges were accumulated . Various ions, like those generated from hydrogen gas or helium gas, were injected into the upper part of an accelerator tube. The high electrostatic potential between the top and bottom of the tube then caused these subatomic particles to accelerate to extremely high velocities as they traveled down a 17-inch-diameter evacuated cylinder 40 feet in height, which was a sealed stack of many individual glass segments that collectively composed the largest vacuum tube in the world at the time of construction. The accelerator tube ran between and parallel to the whirling belts to the base of the machine, where the accelerated particles bombarded experimental targets placed inside the tube, inducing various nuclear reactions. The energy of the particles was measured through the gamma rays that the beam produced when its particles hit a fluorinetarget, which was directly related to the voltage potential between the machine's electrodes. The maximum voltage that a Van de Graaff generator can produce is limited by leakage of the charge off the upper electrode due to corona discharge and arcing. At atmospheric pressure, a Van de Graaff machine is generally limited to around 1 megavolt. Thus this instrument was installed inside a pear-shaped 65-foot tall, 30-foot diameter air tank which was pressurized during operation to 120 pounds per square inch. High pressure improved the insulating qualities of the air and reduced charge leakage, allowing the machine to achieve a voltage potential of 5 megavolts. This allowed a beam energy of 5 MeV, although it was originally hoped to reach 10 MeV.
Preservation efforts
In 2012, the property surrounding the atom smasher was purchased by P&L Investments, LLC. The company was run by Gary Silversmith, a developer who intended to build apartments and expressed an interest in saving the smasher. In 2013, the Young Preservationists Association of Pittsburgh named it as one of the city’s top 10 preservation opportunities. During 2013, plans had been discussed of the Woodland Hills School District establishing a STEM educational facility with the atom smasher as the centerpiece, but the $4 to $5 million cost was prohibitive and the project never moved forward. By 2015, the structure was in significant disrepair and was dislodged from its supports, due to vandalism and age. On January 20, 2015, Silversmith had the atom smasher removed from its supports and laid on its side. Workers laid bricks to brace the fall, and tipped it over. In an email to the Pittsburgh Post-Gazette, Silversmith pronounced his continuing commitment to refurbishing and restoring the atom smasher, saying "The iconic Atom Smasher bulb survives."
