Wide field compact detector for hard x-ray polarization measurements

W. Hajdas; N. Produit; E. Suarez-Garcia; F. Barao; C. Casella; K. Deiters; S. Deluit; C. Leluc; A. Mchedlishvilli; M. Pohl; D. Rapin; Ch. Tao; J.-P. Vialle; R. Walter; C. Wigger; A. Zehnder

doi:10.1117/12.672067

18 July 2006 Wide field compact detector for hard x-ray polarization measurements

W. Hajdas, N. Produit, E. Suarez-Garcia, F. Barao, C. Casella, K. Deiters, S. Deluit, C. Leluc, A. Mchedlishvilli, M. Pohl, D. Rapin, Ch. Tao, J.-P. Vialle, R. Walter, C. Wigger, A. Zehnder

Author Affiliations +

Proceedings Volume 6266, Space Telescopes and Instrumentation II: Ultraviolet to Gamma Ray; 62662W (2006) https://doi.org/10.1117/12.672067
Event: SPIE Astronomical Telescopes + Instrumentation, 2006, Orlando, Florida , United States

Abstract

The polarization data in hard X-ray and gamma-ray energy regimes remain until now very scarce. Having in mind very large importance of the polarization information provided by astrophysical objects we propose a novel compact polarimeter POLAR. It utilizes Compton scattering process and is based on the detector array made of low-Z, fast scintillators. As the instrument with its relatively small dimensions and mass will be a non-intrusive one, it can be installed on any typical satellite platform. It has a sensitivity peak in the energy range from tens to several hundreds keV and a wide viewing angle covering almost a third of the sky. The main objects to be observed by POLAR will be Gamma Ray Bursts and X-Ray Flashes but also X-ray pulsars (Crab). The instrument response and measurement accuracy were intensively modeled and optimized in series of Monte Carlo simulations. It resulted in laboratory design that consists of 2304 plastic scintillator bars with dimension 6x6x200 mm³. The scintillator light is converted by an array of multi-anode photomultipliers. This arrangement assures both a large effective area for Compton scattering as well as a big polarization modulation factor. Moreover, both quantities keep large values also for gammas coming off the detector axis. Currently, a sequence of laboratory tests is performed using polarized photon sources of different energies and various experimental setups. The first experiment consists of small (8x8) array of nominal scintillators while the other one will utilize a large array (1536) of smaller bars (4x4x20 mm³) from the existing high energy project. The goal of these two measurements is to optimize the design, validate simulation results and test the prototype.

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W. Hajdas, N. Produit, E. Suarez-Garcia, F. Barao, C. Casella, K. Deiters, S. Deluit, C. Leluc, A. Mchedlishvilli, M. Pohl, D. Rapin, Ch. Tao, J.-P. Vialle, R. Walter, C. Wigger, and A. Zehnder "Wide field compact detector for hard x-ray polarization measurements", Proc. SPIE 6266, Space Telescopes and Instrumentation II: Ultraviolet to Gamma Ray, 62662W (18 July 2006); https://doi.org/10.1117/12.672067

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