The PTB single ion microbeam for irradiation of living cells

At the PTB's ion accelerators, a new microbeam facility is now in operation that is capable of delivering single ions, for example, to the nuclei of individual living cells. The wide range of proton and 4He2+ ion energies affords LET-values between 3 and 200 keV/μm. A beam diameter of less than 2 μm outside the vacuum system has been measured and a targeting accuracy of better than 2 μm has been determined. In contrast to other microbeam facilities operated for radiobiological research using mechanical collimators in front of the target to define the beam, the PTB facility utilises beam focusing by quadrupole magnets. The microbeam has a unique ion optical design that incorporates a 90 deg. bending magnet in the beam transport system. This design has the advantage of providing a microbeam basically without scattered particles. Every ion reaching the target is detected by a thin scintillating foil and a photomultiplier tube with efficiency close to 100%. Presently up to 1500 single cells per hour can be automatically irradiated with a chosen number of particles. Procedures and results of first cell irradiations are described as an example