A new facility using 6 MeV/nheavy‐ion beams is described along with preliminary results of its applications to biophysical investigations. The beams are obtained at the terminal of the injector linac installed in the heavy‐ion medical accelerator in Chiba. Various ion species (He–Xe) having different charge states are accelerated to the same velocity, which is suitable for comparing the charge effects of heavy ions. An attempt has been made for investigations of the track structure by using pBR322 plasmid DNA and spores as targets. Newly constructed equipment with the molecular beam source (H2O) placed on this beam line is also described. ©1996 American Institute of Physics.