A positron source using an axially oriented crystal associated to a granular amorphous converter

Submitted to Chinese Physics C; A non conventional positron source using the intense γ radiation from an axially oriented monocrystal which materialize into e+e- pairs in a granular amorphous converter is described. The enhancement of photon radiation by multi-GeV electrons crossing a tungsten crystal along its axis is reported. The resulting enhancement of pair production in an amorphous converter placed 2 meters downstream, is also reported. Sweeping off the charged particles from the crystal by a bending magnet upstream of the converter allows a significant reduction of the deposited energy density. Substituting a granular target made of small spheres to the usual compact one, makes easier the energy dissipation. The deposited energy and corresponding heating are analyzed and solutions for cooling are proposed. The configurations studied here for this kind of positron source allow its consideration for unpolarized positrons for the ILC.