Beam buncher for heavy ions

An ion beam buncher has been developed for efficient pulsing of heavy ions into a tandem accelerator. The buncher consists of a single acceleration gap, with aligned grids, which is excited by an rf voltage with a sawtooth waveform. The sawtooth is generated by combining an rf sine wave with its first three higher harmonics. The amplitudes of the second, fourth and sixth harmonics induced by the pulsed beam in a resonant cavity provide an immediate indication of the pulse width. Time-of-flight measurements yielded pulses 0.6 and 0.9 ns wide (fwhm) for ¹H and ¹²C beams, respectively, with over 75% of the dc beam compressed into the pulses.