Proposed laser ion source for the Columbia University microbeam

A laser ion source is scheduled as an upgrade for the 4 MV Van de Graaff accelerator at the Columbia University's Radiological Research Accelerator Facility (RARAF). The source has been designed for use with the RARAF single-particle single-cell microbeam, though it will be used also for broad-beam irradiations. The operating principle, laser ablation, can produce heavy-ions with high charge states so that their energies will be high enough to provide sufficient range - at least 20 μm - for irradiating cells on a thin surface at atmospheric pressure. The laser ion source being implemented at RARAF consists of three main components: a high-power 100 Hz Nd:YAG laser, a source vacuum chamber and a 24 deg. spherical electrostatic analyzer and a double focusing element with point-to-point focusing in both the horizontal and vertical planes. We expect that the laser ion source will enable us to use ions of sufficient range from hydrogen to iron, providing a range of linear energy transfer from about 10 to 4500 keV/μm