Author/Authors :
Mizuno، نويسنده , , T. and Kanai، نويسنده , , Y. and Kataoka، نويسنده , , J. and Kiss، نويسنده , , M. and Kurita، نويسنده , , K. and Pearce، نويسنده , , M. and Tajima، نويسنده , , H. and Takahashi، نويسنده , , H. and Tanaka، نويسنده , , T. and Ueno، نويسنده , , M. and Umeki، نويسنده , , Y. and Yoshida، نويسنده , , H. and Arimoto، نويسنده , , M. and Axelsson، نويسنده , , M. and Marini-Bettolo، نويسنده , , C. and Bogaert، نويسنده , , G. and Chen، نويسنده ,
Abstract :
The energy response of plastic scintillators (Eljen Technology EJ-204) to polarized soft gamma-ray photons below 100 keV has been studied, primarily for the balloon-borne polarimeter, PoGOLite. The response calculation includes quenching effects due to low-energy recoil electrons and the position dependence of the light collection efficiency in a 20 cm long scintillator rod. The broadening of the pulse-height spectrum, presumably caused by light transportation processes inside the scintillator, as well as the generation and multiplication of photoelectrons in the photomultiplier tube, were studied experimentally and have also been taken into account. A Monte Carlo simulation based on the Geant4 toolkit was used to model photon interactions in the scintillators. When using the polarized Compton/Rayleigh scattering processes previously corrected by the authors, scintillator spectra and angular distributions of scattered polarized photons could clearly be reproduced, in agreement with the results obtained at a synchrotron beam test conducted at the KEK Photon Factory. Our simulation successfully reproduces the modulation factor, defined as the ratio of the amplitude to the mean of the distribution of the azimuthal scattering angles, within ∼ 5 % (relative). Although primarily developed for the PoGOLite mission, the method presented here is also relevant for other missions aiming to measure polarization from astronomical objects using plastic scintillator scatterers.
