The Linear Accelerator, a device for accelerating electrons along straight lines, was the most powerful ever built at the time of its opening in 1961. The unit was obtained under an Atomic Energy Commission contract, with Rensselaer providing the site and building. Linac was formally dedicated on October 21, 1961 along with the Jonsson-Rowland Science Center.
A Nuclear Engineering and Science Building, funded in part by a $120,000 grant from the National Science Foundation, was announced in 1963. The two-story structure, built by Harrison and Mero of Troy, was placed between Linac and Tibbits Avenue . The building provided facilities for utilizing the linear accelerator and allowed for expanded graduate research in neutron and radiation studies.
Federal funding for the Atomic Energy Commission's research was reduced beginning in 1972. In order to save the linear accelerator program, Rensselaer purchased Linac in July 1974. In 1975, Linac was named the Gaerttner Linear Accelerator in memory of Dr. Erwin R. Gaerttner, the first director of Linac and the first chair of the Department of Nuclear Science. The American Nuclear Society designated Linac as a Nuclear Historic Landmark in 1998. During that year, Rensselaer received $1.1 million from Knolls Atomic Power Laboratory to refurbish the linear accelerator, which was completed in 2001.