Beam HALO Monitoring at CTF3

In high intensity accelerators, the knowledge of the beam halo distribution and its generation mechanisms are important issues. In order to study these phenomena, dedicated beam diagnostics must be foreseen. In circular machines, beam halo is monitored by using scrapers and beam loss detectors. In the framework of the CLIC project, a beam halo monitor is currently under development. The proposed device is based on an imaging system and a masking technique, which suppresses the core of the beam to allow direct observation of the halo. A first test was performed on the CLIC Test Facility 3 in 2003. We discuss the performances and the limitations of this technique pointing out our plans for future developments.