Heavy-ion postaccelerator at the University of Tsukuba

Abstract A linear rf accelerator of the interdigital-H type has been constructed as a heavy-ion postaccelerator for the 12 UD Pelletron tandem accelerator. The high effective shunt impedance of the accelerating cavity resulted in the generation of a total accelerating voltage of 1.77 MV with an rf power of only 8 kW at 100 MHz. By means of this postaccelerator, the energy of 35 Cl 15+ ions delivered by the tandem accelerator at 110 MeV increased up to a final energy of 136.5 MeV. A new method of the determination of drift-tube lengths has also been developed. In this method, the gaps between the drift tubes are adjusted by using an empirical formula in order to obtain a uniform distribution of accelerating fields as well as to satisfy the synchronous condition for ions to be accelerated. The present postaccelerator has been successfully used for nuclear spectroscopy as a simple, low-cost and powerful apparatus.