An apparatus designed for nuclear studies at energies up to somewhat in excess of 300 kv is described. The potentials are derived from a voltage quadrupling circuit using laboratory constructed rectifiers and condensers. The accelerating tube, of the cascaded type, and its accompanying ion source furnish steady, well‐focused proton beams. Effective proton intensities of 12, 40, and 60 microamperes are available in the beams of ionic masses 1, 2, and 3 respectively. Voltages are measured by a resistance voltmeter which has been calibrated to an accuracy of a few tenths of one percent. Certain peculiarities of the ion source which affect the homogeneity of the ion energies are discussed.