A 5 MV Tesla coil built by pioneering accelerator physicists Merle Tuve and Gregory Breit at the Carnegie Institution in 1928 for use as an early particle accelerator. It consists of a cylindrical secondary coil one meter long of 800 turns of fine wire on a pyrex tube, with spherical metal corona caps attached to each end, with a spiral primary of 5 turns of thick wire around the center. The pyrex secondary coil form was evacuated and used as the acceleration tube within which the electrons were accelerated. It was operated immersed in a tank of insulating oil pressurized to 500 psi to prevent air breakdown to reach high voltages. The coil reached voltages of 5.2 MV but did not work well as a particle accelerator because the high frequency AC voltage left only a small interval of time at the peak of each cycle to accelerate the particles.