Polarimeter for high-energy gamma-ray astrophysics

Paper number

IAC-19,A7,3,6,x53710

Author

Prof. Branislav Vlahovic, United States, North Carolina Central University

Coauthor

Dr. Bogdan Wojtsekhowski, United States, Jefferson National Laboratory

Year

2019

Abstract

Photon polarimetry is important for understanding the nature of the emission mechanisms responsible for blazars, GRBs, X-ray binaries, pulsars, and magnetars as demonstrated by recent space exploration missions devoted to gamma-ray astronomy, AGILE, FERMI-LAT, and EGRET, and recent theoretical and experimental publications.  However, no polarization measurements are available in the medium and high-energy regions because of the instrumental challenges.

A high-energy photon polarimeter for astrophysics studies in the energy range from 10 MeV to 2 GeV is considered. It is based on pair production and Si microstrip detectors and a prototype that was already developed and tested (40 MeV in Duke, 300 MeV in Brookhaven, and 2.4 GeV in the Osaka-Spring-8 laboratory) and sucessfully used as part of a Jlab 6 GeV experiment. It acheived the highest analyzing power recorded at energies above 50 MeV [1]. The proposed concept for the space polarimetry based on that prototype uses a stack of silicon microstrip detectors where they play the roles of both a converter and a tracker. The purpose of this presentation is to outline the parameters of such a polarimeter and to estimate the productivity of measurements. 

The prototype is based on our original design [2], experiments, and Monte Carlo simulations used to optimize the polarimeter for 30 layers of cells. It will provide 11-15\% photon efficiency and 1 mrad angular resolution. In a yearlong observation, the polarization of the photons from the Crab pulsar will be measured to 5.5\% accuracy at an energy cut of 100 MeV and 15\% accuracy at an energy cut of 1,000 MeV, which would be a significant advance relative to the currently explored energy range of a few MeV. The proposed polarimeter design could easily be adjusted to the specific photon energy range to maximize efficiency if needed.

[1] A Polarimeter for Linearly Polarized High Energy Photons, B. Wojtsekhowski, D Tedeschi, and B. Vlahovic, Nuclear Instruments and Methods, 515 (3), (2003) 605-613. 

[2] Maxim Eingorn, Lakma Fernando, Branislav Vlahovic, Cosmin Ilie, Bogdan Wojtsekhowski, Guido Maria Urciuoli, Fulvio De Persio, Franco Meddi, and Vladimir Nelyubing, A high energy photon polarimeter for astrophysics, Journal of Astronomical Telescopes, Instruments, and Systems 4 (1), 011006 (2018).

Abstract document

IAC-19,A7,3,6,x53710.brief.pdf

Manuscript document

IAC-19,A7,3,6,x53710.pdf (🔒 authorized access only).

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