Investigation of the Effect of Beam Space-charge on Electron Trajectories in Ionization Profile Monitors

The correct measurement of beam size using an ionization profile monitor relies on the confinement of electron trajectories from their source to the electron-sensitive detector. This confinement is provided by a magnetic field aligned with electric extraction field. As the initial electron velocities are boosted by the presence of a high-charge density beam, the value of the magnetic field depends on both the beam size and on the charge density. If the magnetic field is not strong enough a deformation of the observed beam profile occurs. In this paper the results of a study of electron trajectories in the presence of high charge density beams is presented along with an estimation of the required magnetic field for various scenarios. A correction procedure for compensating any residual distortions in the measured profile is also discussed.