R. Van de Graaf, Phys. Rev. Vol.38,1931, p.1919 According to a 1831 patent application, it had two 60-cm-diameter charge-accumulation spheres mounted on borosilicate glass columns 180 cm high; the apparatus cost only $90 in 1931.
R. Van de Graaf, Phys. Rev. Vol.38,1931, p.1919 a version able to produce 1,000,000 volts was described in a patent disclosure. This version had two 60-cm-diameter charge-accumulation spheres mounted on borosilicate glass columns 180 cm high; the apparatus cost only $90 in 1931.