  The investigation of beam halo transverse distributions is important for the
understanding of beam losses and the control of backgrounds in Future Linear
Colliders (FLC). A novel in vacuum diamond sensor (DSv) scanner with four
strips has been designed and developed for the investigation of the beam halo
transverse distributions and also for the diagnostics of Compton recoil
electrons after the interaction point (IP) of ATF2, a low energy (1.3 GeV)
prototype of the final focus system for the ILC and CLIC linear collider
projects. Using the DSv, a dynamic range of $\sim10^6$ has been successfully
demonstrated and confirmed for the first time by simultaneous beam core
($\sim10^9$ electrons) and beam halo ($\sim10^3$ electrons) measurements at
ATF2. This report presents the characterization, performance studies and tests
of the diamond sensors using an $\alpha$ source as well as using the electron
beams at PHIL, a low energy ($< 10$ MeV) photo-injector at LAL, and at ATF2.
First beam halo measurement results using the DSv at ATF2 with different beam
intensities and vacuum levels are also presented. Such measurements not only
allow one to evaluate the different sources of beam halo generation but also to
define the requirements for a suitable collimation system to be installed at
ATF2, as well as to optimize its performance during future operation.
