Studies on halo formation in a long magnetic quadrupole FODO channel. First experimental results

A study is progress to prepare an experiment on the transport of an intense proton beam, with high optical qualities, through a periodic magnetic quadrupole FODO channel (29 periods). It is intended to provide a better understanding of how halo develops and can be controlled as a crucial issue for the design of high-intensity linear accelerators. Simulations were done showing that this experiment can be performed with a high-brightness proton beam produced by a duoplasmatron source, with an energy of 500 keV and a current of tens of mA. Beam pulse length will be less than 1 ms and normalized emittance better than 1./spl pi/ mm.mrad (90% of total beam). Thus, transverse tune can be sufficiently depressed in the transport channel to allow instabilities to grow and halo to develop or stay under control. The overall experiment is divided in two phases. Phase 1, the subject of this paper, is dedicated to precise measurements on initial beam conditions, such as emittance, for the beam entering the FODO channel. Phase 2, concerning the halo formation phenomena will be carried on latter, if results of phase 1 are satisfactory.