Upgrading of the 4.5 MV Dynamitron accelerator at Tohoku University for microbeam and nanobeam applications

Abstract To improve the beam brightness and the stability of the accelerator for nanobeam and microbeam applications, the Dynamitron accelerator was upgraded. Although the microbeam system at Tohoku University can focus the beam to several hundred square micrometers, its beam currents were insufficient for analyses of sub-micrometer resolution because of the lack of the accelerator brightness. For this upgrade, an ion source, with lenses in the terminal, and an acceleration tube were replaced with new ones. A control system for the ion source and lens system was also newly developed. Beam brightness of 2.6 and 0.44 pA μm −2  mrad −2  MeV −1 is currently obtained for H 2 + and H 1 + beams at half divergence of 0.07 mrad. The voltage stability of the accelerator was improved by adjusting the voltage stabilizing system, thereby improving the beam current stability. The Dynamitron accelerator has been operated routinely for various experiments without a serious problem.