A novel ion beam focusing technique

tapered glass capillary

has interested many groups.Compared to conventional way of obtaining micro ion beams

its advantages are cheap

simple compacted

and convenient. However

mechanisms of the tapered glass capillary in focusing MeV ions are not clear yet.In this work

2 MeV He~+ ion microbeams were obtained with tapered glass capillaries in outlet diameter of 35

75 and 110μm.The current intensity

beam crosssection

and energy spectra were measured at various tilt angles of the capillary.The results suggested that the MeV ions outgoing from capillary outlet might undertake at least two of three kinds of interactions: deflection by the electrical field of statistic charges deposited on the capillary wall

small angle scattering by continuously surface potential

and small angle Rutherford scattering.