• A. Feschenko, V.A. Moiseev
  RAS/INR, Moscow

Bunch shape monitors with low energy secondary electrons transverse modulation have found a use for measurements of longitudinal distribution of charge in bunches for ion linear accelerators. Temporal bunch structure is coherently transformed into the spatial distribution through transverse rf scanning. The fields of the analyzed beam can influence the trajectories of the secondary electrons thus resulting in a distortion of the transformation and hence to a deterioration of measurement accuracy revealed in worsening of a phase resolution and in appearance of an error of phase reading. The first error component aggravates observation of the bunch fine structure. The second one distorts the measured shape of the bunch as a whole. Two models have been used for the effect analysis. In the first model a target potential of the bunch shape monitor is supposed to be undistorted by the analyzed beam space charge. In the second model a target potential is completely defined by the potential of the analyzed beam bunch. The applicability of the two models is discussed. The results of simulations for typical beam parameters are presented for the latest bunch shape monitor elaborations.