Measuring the linear polarization of $\gamma$s in 20-170 GeV range
  The Na59 collaboration aims to measure the linear polarization of its photon beam in the 20-170 GeV range, using an aligned thin crystal. The tracks of $e^-/e^+$ pairs created in two different crystal targets, germanium and diamond, are reconstructed to obtain the photon spectrum. Using the polarization dependence of the pair production cross section in an aligned crystal, photon polarization is obtained to be 55% at the vicinity of 70 GeV. 
G. Unel (for the Na59 Collaboration)