Construction and implementation of the DAGATA-polarimeter

In this work the calibration of a highly segmented HPGe-detector, the DAGATA-detector (DArmstadt GAmma-ray Tracking Assembly), as a Compton polarimeter and a method for (quasi-)continuous angle Compton polarimetry are presented. A polarization-directional correlation experiment with a 60Co source with an activity of 680 kBq using the DAGATA-polarimeter and two conventional coaxial germanium detectors (external detectors) was performed to obtain the polarization sensitivity. A quantization axis for polarized photons was defined by the detection of one of the two photons with the energies 1173 and 1332 keV from the 4+ - 2+ - 0+-cascade in 60Ni in one of the external detectors in coincidence with a Compton-scattered photon in the DAGATA-polarimeter. The maximum degree of linear polarization can be obtained at a relative angle 90 between DAGATA-polarimeter and one of the external detectors. The degree of polarization for this setup is 1/6. In this work the theoretical treatment of polarization have been discussed and the most important observables are derived. The analysis of the experiment was done on the information provided by segments of the DAGATApolarimeter. The centers of gravity of the DAGATA segments were used to analyze the experimental data. These centers of gravity were obtained from the simulations. The required angles for analysis of the experiment were also calculated from the centers of gravity of the DAGATA segments. The ratio of the intensities for Compton-scattered events from polarized and unpolarized γ-rays can be used to define an angle-dependent asymmetry. Using this asymmetry the polarization sensitivity of the DAGATA polarimeter can be defined. From the Experiment the polarization sensitivities of 21(3)% at 1173 keV and 19(1)% at 1332 keV have been achieved. In comparison with four-fold segmented polarimeters, the DAGATA-polarimeter has higher polarization sensitivities.