Transverse profile shaping of a charged-particle beam using multipole magnets - Formation of hollow beams -

The use of multipole magnets enables us to transform the transverse profile of a charged-particle beam into various ones that can never be formed through linear beam optics. To date, the formation of a large-area beam with a uniform transverse intensity distribution has been realized using octupole magnets for uniform beam irradiation. Here, we report the first demonstration of the hollow-beam formation using multipole magnets in a beam transport line. Results of beam-formation experiments and tracking simulations are shown. The hollow beam has a steep peak at the edge of the beam and thus has a high contrast between the edge peak and the intensity near the beam center.