Improvement of the modulation factor for a Compton scattering type polarimeter using subdivided scintillators

We are developing a Compton scattering type polarimeter, using plastic scintillators as scatterers and NaI(Tl) scintillators as detectors of scattered X rays. To improve the modulation factor keeping the good detection efficiency, we investigated the effect of subdivided plastic and NaI(Tl) scintillators for the modulation factor and the detection efficiency with basic tests and computer simulations. By measuring both x and y points of the scattering and the absorption with 1.4 cm accuracy by the subdivision, the modulation factor can go up to 38%, keeping the detection efficiency of 36%. As both positions are detected with 7 mm accuracy, this type of polarimeter will obtain modulation factor of 45%. By this improvement, the polarimeter call obtain about two times higher performance than that by the former design.