Experimental study of photon beam polarimetry based on nuclear e+e-e+e- pair production in an amorphous target

The degree of linear polarization of a coherent bremsstrahlung (CB) was measured using an azimuthal asymmetry of incoherent e+e-e+e- pair production. The measurement was carried out in the γγ-2 photon beam line of the Yerevan synchrotron, using a 2.55 GeV electron beam and a diamond radiator oriented to position the primary coherent peak in the interval 0.9–1.1 GeV. The polarization at the peak was measured to be 0.56±0.060.56±0.06, in good agreement with the value computed from CB spectral shape analysis.