First Sub-Micron Targeting with Single Ions

Since 2003, we use the GSI heavy-ion microprobe to irradiate living cells with ions from the UNILAC [1]. Two specific properties of the microbeam method make it stand out among other, more conventional irradiation procedures: First, we precisely control the dose by counting and switching individual particles that are to be delivered to the target, down to the low-dose limit of a single ion per irradiated object. Secondly, the microprobe delivers each ion into a predefined and deliberately chosen location of the target. The deviation of the actual ion impact from the point targeted defines the absolute targeting accuracy of a particle microbeam experiment. To allow for selective irradiation of tiny cellular sub-structures of interest, we strive for the best possible targeting accuracy. Here, we report on the first in-situ measurement of the absolute targeting accuracy of the GSI microbeam setup and the first sub-micron targeting accuracy measured at any biological particle microbeam.