The Columbia University single-ion microbeam

A single-ion microbeam facility has been constructed at the Columbia Univer sity Radiological Research Accelerator Facility. The system was designed to deliver defined numbers of helium or hydrogen ions produced by a van de Gr aaff accelerator, covering a range of LET from 30 to 220 keV/mum, into an a rea smaller than the nuclei of human cells growing in culture on thin plast ic films. The beam is collimated by a pair of laser-drilled apertures that form the beam-line exit. An integrated computer control program locates the cells and positions them for irradiation. We present details of the microb eam facility including descriptions of the collimators, hardware, control p rogram, and the various protocols available. Various contributions to targe ting and positioning precision are discussed along with our plans for futur e developments. Beam time for outside users is often available (see www.rar af.org). (C) 2001 by Radiation Research Society.