Taper angle dependence of the focusing effect of high energy heavy ion beams by glass capillaries

The 6.4 MeV 15N2+ ion beams are focused using glass capillary optics. The transmitted beam includes ions which have suffered slight energy loss. The areal density of the transmitted beam is enhanced by approximately 10 times, and the enhancement factor does not depend on the incident beam current. The NRA spectrum intensity decreases with the increase of the capillary taper angle. These results all together suggest that the nuclear forward scattering is more significant in the focusing mechanism than the low energy ions case.