Polarization Measurements with Compton Telescopes

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Session 10 -- Remote Observing, Ground-Based Telescopes and Instruments
Display presentation, Monday, 9, 1995, 9:20am - 6:30pm

[10.14] Polarization Measurements with Compton Telescopes

A. Aky\"{u}z*, T. J. O'Neill, D. Bhattacharya, D. D. Dixon, T. O. T\"{u}mer, R. S. White and A. D. Zych (UC Riverside)

The response of the Tracking and Imaging Gamma-Ray Experiment (TIGRE) instrument to polarized celestial gamma rays above 300 keV is presented. TIGRE uses multilayers of silicon strip detectors both as a gamma-ray converter and to track Compton recoil electrons and positron-electron pairs up to 100 MeV. For Compton events, the direction and energy of the Compton scattered gamma ray are measured with arrays of small CsI(Tl)-photodiode detectors. A small balloon prototype instrument is being constructed that has a high absolute detection efficiency of 10\% and a sensitivity of 100 milliCrabs for an exposure of 12 hours. The prototype's sensitivity to polarized gamma radiation has been calculated with the MCNP detector simulation code which was modified to include the polarization dependence of the Klein-Nishina formula. Polarized events and unpolarized source events with background are combined to simulate an observation of the Crab Nebula and pulsar. TIGRE's polarization modulation factor varies from 0.17 to 0.42 depending on the energy and Compton scatter angle cuts that are used. With 12 hours of observation on the Crab, polarized gamma radiation can be detected down to the level of about 10\%. Potential celestial sources of polarized gamma-ray emission will be discussed. \hline *visiting from Cukurova University, Adana, Turkey

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