| Name: | Sreevaishnava Cherukuri |
| Affiliation: | Physical Research Laboratory |
| Conference ID : | ASI2023_571 |
| Title : | Experimental verification of off-axis polarimetry with cadmium zinc telluride detectors of AstroSat-CZT Imager |
| Authors : | C. S. Vaishnava, N. P. S. Mithun, Santosh V. Vadawale, Esakkiappan Aarthy, Arpit R. Patel, Hiteshkumar L. Adalja, Neeraj Kumar Tiwari, Tinkal Ladiya, Nilam Navale, Tanmoy Chattopadhyay, A. R. Rao, Varun Bhalerao, Dipankar Bhattacharya |
| Mode of Presentation: | Oral |
| Abstract Category : | Instrumentation and Techniques |
| Abstract : | The cadmium zinc telluride imager (CZTI) on board AstroSat consists of an array of 64 pixelated cadmium zinc telluride (CZT) detectors capable of measuring polarization of the incident radiation at energies above 100 keV. Polarimetric response of CZTI for on-axis sources was validated and investigated well before the launch of AstroSat through detailed experimental and simulation
studies which was paramount behind the tantalizing results obtained for Crab nebula and pulsar polarization in 100 to 380 keV. CZTI has also contributed to the measurement of prompt emission polarization for several gamma-ray bursts (GRBs). However, polarization measurement of off-axis sources such as GRBs is challenging and therefore it is important to experimentally calibrate the CZTI sensitivity to off-axis sources to enhance the credence of the measurements. In this context, we carried out the experimental verification for off-axis polarimetric capability of pixelated CZT detectors (identical to those used in CZTI). Our results show that the CZT
detectors can be used to measure polarization of bright GRBs with off-axis angles up to ∼60 degrees. However, at incidence angles between 45 deg and 60 degrees, there are some systematic effects that need to be taken into account when interpreting the measured polarization fraction. Here, we present the complete experimental procedure and the extensive Geant4 simulations used for verifying and inferring the experimental data. We also discuss the implications of our current results in the context of upcoming astronomical missions which plan to use pixelated CZT detectors. |
