ИСТИНА

Gas cluster ion beams and their interaction with solid surface is a rapidly developing area during the last years. In this work gas cluster ion beam accelerator is described. Clusters are formed by supersonic expansion of gas through Laval nozzle. The gas passes through a valve operating in pulsed regime to reduce gas load on the pumping system and to support pressure below 10-2 Torr in the expansion chamber. Neutral clusters are ionized by an originally designed ionizer; electrostatic field accelerating cluster ions can be set up to 20 kV. Magnetic field is used to remove monomers, and then focused beam is directed onto a sample. In the experiments, argon was employed as the working gas. Using variable homogeneous magnetic field it was shown that ArN+ clusters with N>500 are there in the beam when the stagnation pressure is above 2,5 bar. Time of flight technique was applied to measure argon cluster size distribution; the spectra obtained are in good agreement with literature [1]. Cluster sizes are in a range from 200 to a few thousands of atoms in a cluster. Surface relief and structure of different materials after cluster irradiation was investigated.