MIRROR-FIELD MAGNET FOR STRIPPED ELECTRON SWEEPING

Multi-turn injection of H- by foil stripping into an accumulator ring produces metastable neutrals that contribute to machine activation. Pl acing the foil in a magnetic field has been shown to greatly reduce su ch losses. However, the electrons associated with the H- repeatedly an d destructively pass through the foil under the influence of the magne tic field, The electrons can be swept off the foil by a small circular coil placed on the surface of the injection dipole's pole face, cente red on the electron's trajectory. The coil, in a ''magnetic-mirror'' c onfiguration, will exert a downward force on the electrons causing the m to be swept off the foil, limiting the electron foil interactions to one or two. Beam dynamics simulations indicate that the effect an the stored beam is minimal and that such effects can be corrected by smal l correction magnets in the ring. As a test of this concept a full sca le prototype has been fabricated and mapped in the ''magnetic-mirror'' configuration. The measured and calculated results were found to be i n good agreement.