Time-resolved measurements of the compensation process have been performed at the (high-intensity light ion source)-low-energy beam transport test stand (CEA-Saclay) using an 92 kV; 73 mA proton beam. A residual gas ion energy analyzer was used to measure the potential distribution as a function of time. To measure the radial density profile of the ion beam a charge coupled device camera has been used to perform time-resolved measurements and to estimate the rise time of compensation. Both measurements in combination allow an investigation of the space-charge compensation process due to the residual gas ionization and the experimental study of the rise of compensation. A numerical simulation of selfconsistent equilibrium states [J. Pozimski, Il Nuovo Cimento 106, A.N.11 (1993)] of the ion beam has been used to determine plasma parameters such as the density and the temperature of the electrons from the measured data. An interpretation of the acquired data and the achieved results is given.

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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 le ss th an 1 ms an d no rmal ize d em itta nce be tter th an 1. π 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.