A sectored Ge-Compton polarimeter for parity assignments in photon scattering experiments

Parities of nuclear levels excited in photon scattering experiments can be determined by measurements of the linear polarization of the scattered photons. The needed theoretical formalism is summarized. A fourfold sectored single crystal Ge-Compton polarimeter, its operation and performances are described. The compact polarimeter has an outstanding coincidence efficiency εcoinc of about 25% and a good energy resolution of 2.2 keV at 1.333 MeV. The polarization sensitivity of the device as determined in (γ, γ) polarization correlation measurements and several (p, p′γ) reaction studies amounts to about 20% at photon energies of 0.5 MeV and is about 10% at 4 MeV photon energies. The polarimeter has been successfully operated in systematic photon scattering experiments at the bremsstrahlung beam at the Stuttgart Dynamitron facility to investigate enhanced magnetic and electric dipole excitations in heavy deformed nuclei. Typical results are shown and discussed.